CA1161970A - Diode and rom device using same - Google Patents
Diode and rom device using sameInfo
- Publication number
- CA1161970A CA1161970A CA000430398A CA430398A CA1161970A CA 1161970 A CA1161970 A CA 1161970A CA 000430398 A CA000430398 A CA 000430398A CA 430398 A CA430398 A CA 430398A CA 1161970 A CA1161970 A CA 1161970A
- Authority
- CA
- Canada
- Prior art keywords
- region
- rom device
- conductors
- diode
- amorphous alloy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000004020 conductor Substances 0.000 claims abstract description 63
- 239000000463 material Substances 0.000 claims abstract description 59
- 229910000808 amorphous metal alloy Inorganic materials 0.000 claims abstract description 32
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 27
- 239000010703 silicon Substances 0.000 claims abstract description 27
- 229910052751 metal Inorganic materials 0.000 claims abstract description 16
- 239000002184 metal Substances 0.000 claims abstract description 16
- 230000004888 barrier function Effects 0.000 claims abstract description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 12
- 239000001257 hydrogen Substances 0.000 claims abstract description 12
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 10
- 239000011737 fluorine Substances 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 7
- 229910001092 metal group alloy Inorganic materials 0.000 claims abstract description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 5
- 239000000758 substrate Substances 0.000 claims description 23
- 239000010409 thin film Substances 0.000 claims description 16
- 239000002019 doping agent Substances 0.000 claims description 15
- 238000012856 packing Methods 0.000 claims description 10
- 239000011810 insulating material Substances 0.000 claims description 7
- 239000012212 insulator Substances 0.000 claims description 7
- 238000002955 isolation Methods 0.000 claims description 4
- 238000007736 thin film deposition technique Methods 0.000 claims description 2
- 238000000427 thin-film deposition Methods 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 abstract description 10
- 239000000956 alloy Substances 0.000 abstract description 10
- 239000011159 matrix material Substances 0.000 abstract description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 24
- 238000000034 method Methods 0.000 description 14
- 239000010408 film Substances 0.000 description 12
- 239000013078 crystal Substances 0.000 description 11
- 239000004065 semiconductor Substances 0.000 description 11
- 229910021417 amorphous silicon Inorganic materials 0.000 description 10
- 238000000151 deposition Methods 0.000 description 9
- 229910052732 germanium Inorganic materials 0.000 description 9
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 9
- 230000000737 periodic effect Effects 0.000 description 9
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 229910000077 silane Inorganic materials 0.000 description 8
- 235000012431 wafers Nutrition 0.000 description 8
- 101001034843 Mus musculus Interferon-induced transmembrane protein 1 Proteins 0.000 description 7
- 229910052782 aluminium Inorganic materials 0.000 description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 239000002178 crystalline material Substances 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 230000002441 reversible effect Effects 0.000 description 5
- 229910052714 tellurium Inorganic materials 0.000 description 5
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 5
- ZXEYZECDXFPJRJ-UHFFFAOYSA-N $l^{3}-silane;platinum Chemical group [SiH3].[Pt] ZXEYZECDXFPJRJ-UHFFFAOYSA-N 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 4
- 229910052796 boron Inorganic materials 0.000 description 4
- 230000008021 deposition Effects 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 4
- 239000011733 molybdenum Substances 0.000 description 4
- 235000016768 molybdenum Nutrition 0.000 description 4
- 229910021339 platinum silicide Inorganic materials 0.000 description 4
- 238000004544 sputter deposition Methods 0.000 description 4
- 229910001080 W alloy Inorganic materials 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 3
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 229960001866 silicon dioxide Drugs 0.000 description 3
- 235000012239 silicon dioxide Nutrition 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 2
- 238000001459 lithography Methods 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- SDTHIDMOBRXVOQ-UHFFFAOYSA-N 5-[bis(2-chloroethyl)amino]-6-methyl-1h-pyrimidine-2,4-dione Chemical compound CC=1NC(=O)NC(=O)C=1N(CCCl)CCCl SDTHIDMOBRXVOQ-UHFFFAOYSA-N 0.000 description 1
- 241000905957 Channa melasoma Species 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 241000257303 Hymenoptera Species 0.000 description 1
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 1
- 101100409194 Rattus norvegicus Ppargc1b gene Proteins 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- 229910017817 a-Ge Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 150000004770 chalcogenides Chemical class 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 230000002939 deleterious effect Effects 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- QUZPNFFHZPRKJD-UHFFFAOYSA-N germane Chemical compound [GeH4] QUZPNFFHZPRKJD-UHFFFAOYSA-N 0.000 description 1
- 229910052986 germanium hydride Inorganic materials 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- KRTSDMXIXPKRQR-AATRIKPKSA-N monocrotophos Chemical compound CNC(=O)\C=C(/C)OP(=O)(OC)OC KRTSDMXIXPKRQR-AATRIKPKSA-N 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 239000012782 phase change material Substances 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
- H01L23/525—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body with adaptable interconnections
- H01L23/5252—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body with adaptable interconnections comprising anti-fuses, i.e. connections having their state changed from non-conductive to conductive
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/04—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body
- H01L27/06—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being a semiconductor body including a plurality of individual components in a non-repetitive configuration
- H01L27/0688—Integrated circuits having a three-dimensional layout
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/04—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/16—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table
- H01L29/167—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table further characterised by the doping material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/685—Hi-Lo semiconductor devices, e.g. memory devices
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/861—Diodes
- H01L29/8615—Hi-lo semiconductor devices, e.g. memory devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/20—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having two electrodes, e.g. diodes
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
- H10B63/80—Arrangements comprising multiple bistable or multi-stable switching components of the same type on a plane parallel to the substrate, e.g. cross-point arrays
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/30—Resistive cell, memory material aspects
- G11C2213/35—Material including carbon, e.g. graphite, grapheme
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/12—Passive devices, e.g. 2 terminal devices
- H01L2924/1204—Optical Diode
- H01L2924/12044—OLED
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/20—Multistable switching devices, e.g. memristors
- H10N70/231—Multistable switching devices, e.g. memristors based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/821—Device geometry
- H10N70/826—Device geometry adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N70/00—Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
- H10N70/801—Constructional details of multistable switching devices
- H10N70/881—Switching materials
- H10N70/882—Compounds of sulfur, selenium or tellurium, e.g. chalcogenides
- H10N70/8828—Tellurides, e.g. GeSbTe
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Ceramic Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Semiconductor Memories (AREA)
- Read Only Memory (AREA)
- Bipolar Transistors (AREA)
- Non-Volatile Memory (AREA)
Abstract
ABSTRACT
A diode has at least a first region and a second region with the regions abutting each other to form a junction therebetween and with the first region being made of an amorphous alloy including silicon and fluorine. Such a diode finds particular usefulness in closed cells in a ROM or in a EEPROM
device having a memory circuit at each cross over point of a conductor of a first group of conductors in a memory matrix extending in a first direction over a conductor of a second group of conductors extending in a second direction traversing the first direction. The first group of conductors is insulated from the second group of conductors and each memory circuit is coupled to and between a pair of crossing over conductors at one of the cross over points and includes a memory region and the diode. Preferably, the amorphous alloy also contains hydrogen and such alloy is a-Sia:Fb:Hc, where a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 atomic percent. me first and second alloy regions of can be oppositely P and N doped. Alternately, one of the regions can be a metal, metal alloy or a metallic like material to form a Schottky barrier with the other region or MIS junctions can be utilized.
A diode has at least a first region and a second region with the regions abutting each other to form a junction therebetween and with the first region being made of an amorphous alloy including silicon and fluorine. Such a diode finds particular usefulness in closed cells in a ROM or in a EEPROM
device having a memory circuit at each cross over point of a conductor of a first group of conductors in a memory matrix extending in a first direction over a conductor of a second group of conductors extending in a second direction traversing the first direction. The first group of conductors is insulated from the second group of conductors and each memory circuit is coupled to and between a pair of crossing over conductors at one of the cross over points and includes a memory region and the diode. Preferably, the amorphous alloy also contains hydrogen and such alloy is a-Sia:Fb:Hc, where a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 atomic percent. me first and second alloy regions of can be oppositely P and N doped. Alternately, one of the regions can be a metal, metal alloy or a metallic like material to form a Schottky barrier with the other region or MIS junctions can be utilized.
Description
~ ~ ` 7 Ig~9~ Ca~e 556.~
This is a division of copending Canadian P~tent ~pplicat:ion Serial Number 366,713, filed December 12, lg80.
The present invention rela~tes to a diode and a ROM or EEPROM device utilizing sameO More specif-ically~ the present invention rela~es to a dlode which utilizes an amorphous alloy including silicon and fluorineO In thîs respect, reference is made to UOSo Patent ~oO 4~217~374 Stanford Ro Ovshinsky and Masatsugu Izu entitled: ~MORP~OUS SEMICO~-DUCTORS EQUIVALENT TO CRYSTALLINE SE~ICO~DUCTORS
and U.SO Patent No. 4~226,898 Stanford R. Ovshinsky and Arun Madan, of the same titleO
Silicon is the basis of thé huge crystalline semiconductor industry and is the material which is utilized in substantiall.~ all the commerc.ial inte-grated circuits now producedO When crystalline semiconductor technology reached a commercial state it became the foundation of the present huge semî-conductor device manufacturing industryO This was ~ue to the abili~y of the scientist to grow suh-stantially defect~free germanium and particularly silicon crystals, and then turn them into extrinsic materials with p~type and n-type conductivity re-gions thereinO This was accomplished by diffusing into such crystalline material parts per million of donor (n) or acceptor (p) dopant materlals intro-.. ; ' ~, " . !
, ~ , .
" I lB197() duced as substitutional impurities into the sub-stantially pure crystalline materials, to increase their electrical conductivi~y and to control their being either of a p or n conduction type.
The semiconductor fabrication processes for making p-n junction crystals involve exkremely complex, time con~uming, and expensive procedures as well as high pxocessing temperatures. Thus, these crystalline materials used in rectifying and other current control devices are produced under very carefully controlled conditions by growing individual single silicon or germanium crystals, and where p-n junctions are required, by doping such single crystals with extremely small and crit-ical amounts of dopants. These crystal growingprocesses produce relatively small crystal wafers upon which the integrated memory circuits are form-ed.
In wafer scale integration technology the small area crystal wafer limits the overall size of the integrated circuits which can be formed there-on~ In applications requiring large scale areas, such as in the display technology, the crystal wafers can not be manu~actured with as large areas
This is a division of copending Canadian P~tent ~pplicat:ion Serial Number 366,713, filed December 12, lg80.
The present invention rela~tes to a diode and a ROM or EEPROM device utilizing sameO More specif-ically~ the present invention rela~es to a dlode which utilizes an amorphous alloy including silicon and fluorineO In thîs respect, reference is made to UOSo Patent ~oO 4~217~374 Stanford Ro Ovshinsky and Masatsugu Izu entitled: ~MORP~OUS SEMICO~-DUCTORS EQUIVALENT TO CRYSTALLINE SE~ICO~DUCTORS
and U.SO Patent No. 4~226,898 Stanford R. Ovshinsky and Arun Madan, of the same titleO
Silicon is the basis of thé huge crystalline semiconductor industry and is the material which is utilized in substantiall.~ all the commerc.ial inte-grated circuits now producedO When crystalline semiconductor technology reached a commercial state it became the foundation of the present huge semî-conductor device manufacturing industryO This was ~ue to the abili~y of the scientist to grow suh-stantially defect~free germanium and particularly silicon crystals, and then turn them into extrinsic materials with p~type and n-type conductivity re-gions thereinO This was accomplished by diffusing into such crystalline material parts per million of donor (n) or acceptor (p) dopant materlals intro-.. ; ' ~, " . !
, ~ , .
" I lB197() duced as substitutional impurities into the sub-stantially pure crystalline materials, to increase their electrical conductivi~y and to control their being either of a p or n conduction type.
The semiconductor fabrication processes for making p-n junction crystals involve exkremely complex, time con~uming, and expensive procedures as well as high pxocessing temperatures. Thus, these crystalline materials used in rectifying and other current control devices are produced under very carefully controlled conditions by growing individual single silicon or germanium crystals, and where p-n junctions are required, by doping such single crystals with extremely small and crit-ical amounts of dopants. These crystal growingprocesses produce relatively small crystal wafers upon which the integrated memory circuits are form-ed.
In wafer scale integration technology the small area crystal wafer limits the overall size of the integrated circuits which can be formed there-on~ In applications requiring large scale areas, such as in the display technology, the crystal wafers can not be manu~actured with as large areas
-2-g 7 ~
as required or desiredO The devices are formed, at least in part, by diffusing p or n-type dopants into the substrate~ Furtherl each device is formed between isolation channels which are diffused into the substrate. Packing density tthe number of devices per unit area of wafer surace) is also limited on the silicon wafers, because of ~he leak-age current in each device and the power necessary to operate the devices, each of which generate heat which is undesirable. The silicon wafers do not readily dissipate heat. Also, the leakage current adversely affects the batt~ry or power cell life~
! time in portable applicatiQns.
Further~ the packing density is extremely important because the ~ell size is exponentially related to the cost of each device. For instance, a decrease in die size by a factor of two results in a decrease in cost on the order of a factor of six. A conventional crystalline ROM utilizing two micron lithrography has a bipolar cell size of about ~3 to .5 mil2 or a MOS cell size of about .2 to O3 mil2.
In summaryg crystal silicon rectifiers and integrated circuit parameters are not variable as desired, require large amounts of material, high processing temperatures, are only producible only on relatively small area wafers and are expensi~e and time consuming to produce. Devices baserl upon amorphous silicon can eliminate these crystal sil-icon disadvantages. Amorphous silicon can be made faster, easier, at lower temperatures and in larger areas than can crystal silicon.
Accordingly, a considerable effort has been made to develop processes for readily depositing amorphous semiconductor alloys or films each of which can encompass relatively large areas, if desired, limited only by the size of the deposition , . . .
equipment, and which couid be doped to form p-type and n~type materials to form p-n junction rec-ti~iers and devices superior in cost and/or opera~
tion to those produced by their crystalline coun-terparts. For many years such work was substan-tially unproductive. Amorphous silicon or ger- ¦
manium (Group IV) films are normally four-fold coordinated and were found to have microvoids and dangling bonds and other defects which produce a high density of localized states in the energy gap thereof. The presence of a high density of local-~4~
`, ,'~ ' ' 1 lB197() 'I
ized states in the energy gap of amorphous siliconsemiconductor films resulted in such films not being successfully doped or o~herwise modified ~o shift the Fermi level close to the conduction or valence bands making them unsuitable for making p-n junction rectifiers and other current control de-vice applications.
In an at~empt to minimize the aforementioned problems involved with amorphous silicon and germa-~lium, W.E. Spear and P. G. Le Comber of CarnegieLaboratory of Physics, University of Dundee, in Dundee, Sco~land did some work on "Substitutional Doping of Amorphous Siliconi'I as reported in a paper published in Solid State Communications, Vol.
17, pp. 1193~1196, 1975, toward the end of reducing the localized states in the energy gap in amorphous silicon or germanium to make the same approximate more closely intrinsic'crystalline silicon or ger-manium and of substitutionally doping the amorphous materials with suitable classic dopants, as in doping crystalline materials, to make them ex-trinsic and of p or n conduction types.
The reducticrl of the localized states was accomplished by glow discharge deposition or amor-~ `
7 t~
, phous silicon films wherein a ~as o~ silane (SiH4) was passed through a reactivn tube where the gas was decomposed by an r.f. glow discharge and de-posited on a substrate at a substrate temperature of about 500-600X (227-327C). The material so deposited on ~he subs~rate was an intrinsic amor-phous material consisting of silicon and hydrogen~
To produce a doped amorphous material a gas of phosphine (PH3) for n-type conduction or a gas of ~iborane ~B2H6) for p-type conduction were premixed with the silane gas and passed through the glow discharge reaction tube under the same operating ~l conditions. The gaseous concentration of the dop- I
ants used was between about 5 x 10~6 and 10-2 parts per volume. The material so deposited included supposedly substitutional phosphorus or boron dop- !
ant and was shown to be extrinsic and of n or p conduction type.
While it was not known by these researchers, it is now known by the work of others that the hydrogen in the silane combines at an optimum tem- ¦
perature with many of the dangling bonds of the silicon during the glow discharge deposition, to substantially reduce the density of the localized ' --'' '' 1 l6ls~n states in the energy gap toward the end of making the electronic properties of the amorphous ma~erial approximate more nearly those of the corresponding crystalline material.
DoI~ Jones, W.E. Spear, P~G. LeComber, S. r,i, and R. Martins also worked on preparing a-Ge:H form GeH4 using similar deposition techniques. The material obtained gave evidence of a high density of localized states in ~he energy gap thereof.
Although the material could be doped the efficiency was substantially reduced from that obtalnable with a-Si:E~. In this work reported in Philsophical Maga-zine B, Vol. 39y p. 147 (1979~ the authors conc7ude that because of the large density of gap states the material obtained is". . . a less attractive mate-rial than a-Si or doping experiments and possible applications."
The incorporation of hydrogen in the above silane method not only has limitations based upon the fixed ratio of hydrogen to silicon in silane, but, most importantly, various Si:H bonding confi gurations introduce new antibonding states which can have deleterious consequences in these mate-rials. Therefore, there are basic limitations in 1 16 L9~7~) ,--reducing the density of localized states in these materials which are particularly harmful in terms of ef~ective p as well as n doping. The resulting density of states o the silane deposited materials s leads ~o a narrow depletion width which in turn limits the efficiencies of devices whose operation depends on the drift of free carriersO The method of making these materials by the use of only sil-icon and hydrogen also results in a high density of surface states which affects all the above para-meters.
After the development of the glow discharge deposition of silicon from silane gas was carried out t work was done on the sputter deposition of amorphous silicon films in the atmosphere of a mixture of argon (required by the sputtering de-position process~ and molecular hydrogen, to deter-mine the results of such molecular hydrogen on the characteristics of the deposited amorphous silicon film. This research indicated that the hydrogen acted as a compensating agent which bonded in such a way as to reduce the localized states in the energy gap. However, the degree to which the lo-calized states in the energy gap were reduced in l I6197~
the sputter deposition process was much less than that achieved by the silane deposition process described above~ rrhe above described p and n dop-ant materials also were introduced in the sput-tering process to produce p and n doped materials.These materials had a lower doping efficiency than the materials produced in the glow discharge pro-cess. Neither process produced efficient p-doped materials with sufficiently high acceptor concen-trations for producing commercial p-n junction devices. The n-doping efficiency was below desir-able acceptable commercial levels and the p-doping was particularly undesirable since it increased the number of localized states in the band gap.
Heretofore various semiconductor materials, both crystalline and amorphous, have been proposed for utilization in rectifying type devices such as a diode. Also it has been proposed to make a semi-conductor or a photoconductive rectifier utilizing an amorphous alloy including silicon and fluoride.
U.S. Patent No. 4,217,374 r issued August 12, 1980 for Amorphous Semiconductor Equilvalent to Cry~-talline Semiconductor, Stanford R. Ovshinksy and Masatsugu Izu and U.S. Patent No. 4,226,898, issued 19~n .
Qctober 7, 1980 of the same title, Stanford R~
Ovshinsky and Arun Madan.
As will be described in greater detail here-inafter, the diode of ~he present invention con-tains the amorphous al~oy including silicon andfluorine disclosed in the applications indentified a~ove in a specific construction of a diode having at least two regions with at least one region con-taining the amorphous alloy in combination with ROM
or ~EPROM device construc~ions.
A typical ROM device includes a matrix o~ X
and Y axis conductors which are insulated from each other and which have a memory circuit at and cou-pled between each cross over of an X axis conductor over a Y axis conductor. Each memory circuit in-cludes a memory region and an isolating device such as a transistor or a diode. Typically, such tran-sistors and diodes have been formed in semicon-ductor substrates with permanently open contact points or permanently closed contact points for establishing logic 1 or logic 0 bits of information which are stored in the ROM device. Such a ROM
device is programmed during the manufacture there-of.
,, 7 () EEPROM (electrically erasible programmable read only memory) devices have been proposed where-in a vertically disposed memory region or cell in the memory circuit is vertically coupled at and between an upper X axis conductor and a lower Y
axis conductor in a memory matrix~ These devices follow from the storing of information with phase change switch devices first invented by Stanford R.
Ovshinsky, as for example, disclosed in U.S. Patent
as required or desiredO The devices are formed, at least in part, by diffusing p or n-type dopants into the substrate~ Furtherl each device is formed between isolation channels which are diffused into the substrate. Packing density tthe number of devices per unit area of wafer surace) is also limited on the silicon wafers, because of ~he leak-age current in each device and the power necessary to operate the devices, each of which generate heat which is undesirable. The silicon wafers do not readily dissipate heat. Also, the leakage current adversely affects the batt~ry or power cell life~
! time in portable applicatiQns.
Further~ the packing density is extremely important because the ~ell size is exponentially related to the cost of each device. For instance, a decrease in die size by a factor of two results in a decrease in cost on the order of a factor of six. A conventional crystalline ROM utilizing two micron lithrography has a bipolar cell size of about ~3 to .5 mil2 or a MOS cell size of about .2 to O3 mil2.
In summaryg crystal silicon rectifiers and integrated circuit parameters are not variable as desired, require large amounts of material, high processing temperatures, are only producible only on relatively small area wafers and are expensi~e and time consuming to produce. Devices baserl upon amorphous silicon can eliminate these crystal sil-icon disadvantages. Amorphous silicon can be made faster, easier, at lower temperatures and in larger areas than can crystal silicon.
Accordingly, a considerable effort has been made to develop processes for readily depositing amorphous semiconductor alloys or films each of which can encompass relatively large areas, if desired, limited only by the size of the deposition , . . .
equipment, and which couid be doped to form p-type and n~type materials to form p-n junction rec-ti~iers and devices superior in cost and/or opera~
tion to those produced by their crystalline coun-terparts. For many years such work was substan-tially unproductive. Amorphous silicon or ger- ¦
manium (Group IV) films are normally four-fold coordinated and were found to have microvoids and dangling bonds and other defects which produce a high density of localized states in the energy gap thereof. The presence of a high density of local-~4~
`, ,'~ ' ' 1 lB197() 'I
ized states in the energy gap of amorphous siliconsemiconductor films resulted in such films not being successfully doped or o~herwise modified ~o shift the Fermi level close to the conduction or valence bands making them unsuitable for making p-n junction rectifiers and other current control de-vice applications.
In an at~empt to minimize the aforementioned problems involved with amorphous silicon and germa-~lium, W.E. Spear and P. G. Le Comber of CarnegieLaboratory of Physics, University of Dundee, in Dundee, Sco~land did some work on "Substitutional Doping of Amorphous Siliconi'I as reported in a paper published in Solid State Communications, Vol.
17, pp. 1193~1196, 1975, toward the end of reducing the localized states in the energy gap in amorphous silicon or germanium to make the same approximate more closely intrinsic'crystalline silicon or ger-manium and of substitutionally doping the amorphous materials with suitable classic dopants, as in doping crystalline materials, to make them ex-trinsic and of p or n conduction types.
The reducticrl of the localized states was accomplished by glow discharge deposition or amor-~ `
7 t~
, phous silicon films wherein a ~as o~ silane (SiH4) was passed through a reactivn tube where the gas was decomposed by an r.f. glow discharge and de-posited on a substrate at a substrate temperature of about 500-600X (227-327C). The material so deposited on ~he subs~rate was an intrinsic amor-phous material consisting of silicon and hydrogen~
To produce a doped amorphous material a gas of phosphine (PH3) for n-type conduction or a gas of ~iborane ~B2H6) for p-type conduction were premixed with the silane gas and passed through the glow discharge reaction tube under the same operating ~l conditions. The gaseous concentration of the dop- I
ants used was between about 5 x 10~6 and 10-2 parts per volume. The material so deposited included supposedly substitutional phosphorus or boron dop- !
ant and was shown to be extrinsic and of n or p conduction type.
While it was not known by these researchers, it is now known by the work of others that the hydrogen in the silane combines at an optimum tem- ¦
perature with many of the dangling bonds of the silicon during the glow discharge deposition, to substantially reduce the density of the localized ' --'' '' 1 l6ls~n states in the energy gap toward the end of making the electronic properties of the amorphous ma~erial approximate more nearly those of the corresponding crystalline material.
DoI~ Jones, W.E. Spear, P~G. LeComber, S. r,i, and R. Martins also worked on preparing a-Ge:H form GeH4 using similar deposition techniques. The material obtained gave evidence of a high density of localized states in ~he energy gap thereof.
Although the material could be doped the efficiency was substantially reduced from that obtalnable with a-Si:E~. In this work reported in Philsophical Maga-zine B, Vol. 39y p. 147 (1979~ the authors conc7ude that because of the large density of gap states the material obtained is". . . a less attractive mate-rial than a-Si or doping experiments and possible applications."
The incorporation of hydrogen in the above silane method not only has limitations based upon the fixed ratio of hydrogen to silicon in silane, but, most importantly, various Si:H bonding confi gurations introduce new antibonding states which can have deleterious consequences in these mate-rials. Therefore, there are basic limitations in 1 16 L9~7~) ,--reducing the density of localized states in these materials which are particularly harmful in terms of ef~ective p as well as n doping. The resulting density of states o the silane deposited materials s leads ~o a narrow depletion width which in turn limits the efficiencies of devices whose operation depends on the drift of free carriersO The method of making these materials by the use of only sil-icon and hydrogen also results in a high density of surface states which affects all the above para-meters.
After the development of the glow discharge deposition of silicon from silane gas was carried out t work was done on the sputter deposition of amorphous silicon films in the atmosphere of a mixture of argon (required by the sputtering de-position process~ and molecular hydrogen, to deter-mine the results of such molecular hydrogen on the characteristics of the deposited amorphous silicon film. This research indicated that the hydrogen acted as a compensating agent which bonded in such a way as to reduce the localized states in the energy gap. However, the degree to which the lo-calized states in the energy gap were reduced in l I6197~
the sputter deposition process was much less than that achieved by the silane deposition process described above~ rrhe above described p and n dop-ant materials also were introduced in the sput-tering process to produce p and n doped materials.These materials had a lower doping efficiency than the materials produced in the glow discharge pro-cess. Neither process produced efficient p-doped materials with sufficiently high acceptor concen-trations for producing commercial p-n junction devices. The n-doping efficiency was below desir-able acceptable commercial levels and the p-doping was particularly undesirable since it increased the number of localized states in the band gap.
Heretofore various semiconductor materials, both crystalline and amorphous, have been proposed for utilization in rectifying type devices such as a diode. Also it has been proposed to make a semi-conductor or a photoconductive rectifier utilizing an amorphous alloy including silicon and fluoride.
U.S. Patent No. 4,217,374 r issued August 12, 1980 for Amorphous Semiconductor Equilvalent to Cry~-talline Semiconductor, Stanford R. Ovshinksy and Masatsugu Izu and U.S. Patent No. 4,226,898, issued 19~n .
Qctober 7, 1980 of the same title, Stanford R~
Ovshinsky and Arun Madan.
As will be described in greater detail here-inafter, the diode of ~he present invention con-tains the amorphous al~oy including silicon andfluorine disclosed in the applications indentified a~ove in a specific construction of a diode having at least two regions with at least one region con-taining the amorphous alloy in combination with ROM
or ~EPROM device construc~ions.
A typical ROM device includes a matrix o~ X
and Y axis conductors which are insulated from each other and which have a memory circuit at and cou-pled between each cross over of an X axis conductor over a Y axis conductor. Each memory circuit in-cludes a memory region and an isolating device such as a transistor or a diode. Typically, such tran-sistors and diodes have been formed in semicon-ductor substrates with permanently open contact points or permanently closed contact points for establishing logic 1 or logic 0 bits of information which are stored in the ROM device. Such a ROM
device is programmed during the manufacture there-of.
,, 7 () EEPROM (electrically erasible programmable read only memory) devices have been proposed where-in a vertically disposed memory region or cell in the memory circuit is vertically coupled at and between an upper X axis conductor and a lower Y
axis conductor in a memory matrix~ These devices follow from the storing of information with phase change switch devices first invented by Stanford R.
Ovshinsky, as for example, disclosed in U.S. Patent
3,271,591 We have found that these disadvantages may be overcome by providing a diode having at least first and second abutting regions forming a junction ., therebetween wherein the first region is made from an amorphous alloy including silicon and fluorine.
We also provide ROM and EEPRQM devices utilizing these diodes as isolating means for coupling the memory regions thereof to the cross over points of a memory matrix. The packing density of the ROM
and EEPROM devices, utilizing two micron lithog-raphy for reference, i,5 on the order of .1 mil~ per cell. Also, the devices and diodes are all thin film deposited and have low leakage currents allow-ing the structure to be stacked upon one another to ` 25 further increase the packing density.
;
., .
-~ 7 lgl97n Further, according to ~he inven~ion, there is provided in a RO~ device havin~ memory circui~
means at each cross over point of a conductor of a first group of conductors extending in a first direction over a conductor of a second group of conductors extending in a second direction trav-ersing the first direction, the first group of conductors being insulated from the second group of condu tors~ and each memory circuit being couple~
to and between a pair of crossing over conductors . at one of ~he cross over points and including iso~
. i lating means, the improvement residing ;n the iso-l~ting means including a diode having at least a first region and a second region, the regions abut-ting each other ~o form a junction therebetween and - :
the first region being made of the amorphous alloy including silicon and fluorine, 11 ~ 7 ~
Preferahl~" the amorphous alloy also contai n.
hydrogen and such amorphous alloy i5 a-Sia~E~h Hc"
where a is }: ewteen 80 and 98 atomic percent, b i5 between 0 and 10 a~omit:: perc:ent an~ c is ~e'cween 0 and lQ atomic per-cent~ -The first alloy region is doped with an ~
dopan~c ma~erial chose~ from an element o~ G~oup Y
, ~ 13 --, ~ ~3.97~
of the Periodic Table, e~g., phosphorous, arsenic or others by an amount constituting between a few parts per million (ppm) and five atomic percent and preferably between 10 to 1000 parts per million.
The second region can be a metal, metal alloy, a metallic like material having a high barrier height on the first region so as to create a Schottky barrier.
Alternately, the second region also can be an amorphous alloy including silicon and fluorine and preferably also containing hydrogen. The second alioy region is doped with a P dopant material chosen from an element of Group III of the Periodic Table, e.g., boron, aluminum or others by an amount constituting between a few parts per million and five atomic percent, and preferably between 10 and 1000 parts per millionO Alsot the first region could be a P type region with the second region being an N type region.
The packing density utilizing two micron li-thrography for reference in the thin film ROM and all thin film EEPROM is on the order of .1 mil2 per cell. Further, due to the all thin ilm deposited structure and the low leakage current the devices can be stacked upon one another to further increase n the packing density. The devices can be formed on various substrates including insulated metal which is utilized as a heat sink for the devices.
The preferred embodiments of this invention will now be described, by way of example~ with reference to the drawings accompanying this speci-fication in which:
Fig~ 1 is a fragmentary plan view of the de-posited film side of a substrate which forms a support for an all deposited film ROM device in-cluding a diode made in accordance with the teach-ings of the present invention.
Fig.-2 is a sectional view through the memory circuits of the ROM device shown in Fig. 1 and is taken along line 2-2 of Fig. 1.
FigO 3 is a schematic circuit diagram of the memory circuit shown in Fig. 2.
Fig. 4 is a fragmentary plan view o the de-posited film side of a substrate forming a support for an all deposited thin film EEPROM device in-cluding memory circuits, each of which include a diode constructed according to the teachings of the present invention.
g~
Fig. 5 is a sectional view through two memory circuits shown in Fig. 4 and is take~ along line 5-5 of FigO 4.
Fig. 6 is a schematic circuit diagram of the memory circuit shown in Fig. 5~
Fig~ 7 is a sectional view through a second .
embodiment of deposited thin film ROM device in-cluding a Schottky diode device made in accordance with the teachings of the present invention.
Fig~ 8 is a schematic circuit diagram of t~e memory circuit shown in Fig. 7.
Referrin~ to Figs. 1 and 2 there is illus-trated therein a ROM device 10 including two dedi~
cated memory circuits ll and 12 each of which in-cludes a thin ilm d70de or rectifying device 14(Fig. 2) constructed in accordance with the teach~
in~s of the present inventionO The memory circuit 11 is a closed circuit which includes the diode 14 which is coupled through an ohmic contact region such as a platinum silicide region 16 to an upper X
axis conductor 18 and to a lower Y axis conductor 20.
The memory circuit 12 also includes a diode 14 which is connected on one side to another Y axis s~n conductor 20' and on the other side is open cir-cuited by reason of a re~ion of insulating material 21 disposed between the upper surface of diode 14 and the X axis conductor 18 as will be described in greater detail below~
In the construc~ion oE the ROM device 10, there is deposited on any suitable substrate 22 having an insulating top surface 25, parallel con-ductors 20 and 20' which form the Y axis conductors ~nd which form a compat'kle interface with the diode 14. The conductors or bands 20 of conductive material may be made of aluminum, chromium, molyb-denum, an alloy of titanium and tungsten (Ti-W) or the like. Also, the conductive bands 20 may in-clude a bottom layer 23 oE a highly conductivematerial like aluminum and an upper layer 24 of a refractory barrier-forming material like molybdenum or Ti-W. The conductive layers 23 and 24 may be formed by conventional vacuum deposition, photo resist masking and etchant techniques.
Next, spaced layers 26 and 28 of amorphous semiconductor alloy including silicon and fluorine are deposited over the conductor bands 20 to ~orm the thin film diodes 14 at each cross over ~oint in 7 n the matrix of X and Y axis conductors 18 and 20 in the ROM device 10. Each such P~~ junction diode 14 may be formed from doped N~ and P~ amorphous alloy layers 26 and 28 as shown.
An insulating layer 30, such as silicon diox-ide, is applied over the entire substrate 22 so as to form the insulating region 21 above the diode 14 in th~ memory circuit 12. However, wherever it is desired to store a data bit which will be indicated by a low resistance condition coupled through the diode 14~ an opening 31 i~ formed in the insulating layer of silicon dioxide.
The platinum silicide or ohmic contact region ! 16 can be formed on the outermost amorphous silicon layer 28, where the opening 31 had been formed in the insulating layer 30C such as by applying plati-. num over the exposed portions of the amorphousalloy layer 28. The rectifier diodes 14 then can have a conductor band 32 formed thereover of a barrier-forming material such as molybdenum or the Ti-W alloy. Subsequently, a band of aluminum is deposited over the conductor band 32 to form the X
axis conductor 18. Alternately, the conductor 18 can be depo6ited over the layer 28 and the in-~s sulator 30 without the barrier 32.
~; .;
l~.as7n From the foregoing description, it will be seen that the memory region of each memory circuit 11 and 12 is a prede~ermined conductive path or a predetermined insulator path between the Y axs conductor 20 through the diode 14 to the X axis conductor 18.
A150 o it will be apparent that the memor~
regions are formed by depositing a thin film of insulating material 30 on one region 28 of each diode 14 followed by depositing a thin film band (band 32 and/or 18) of conductive material to form the X axis conductor 18. For a conductive path memory region, the insulating film layer 30 is cut or etched away such as at 31 in the area above the one region 28 of a selected diode 14 before the thin film conductive band is deposited so that the conductive path is a direct contact of the con-ductive band 18 with the first region 28 of the selected diode 14.
Alsor it is apparent, that each memory circuit 11 or 12 coupled to and between a pair of crossing over conductors 18 and 20 includes not only a con-ductive path or insulator path memory region but also the diode 14 having a first region 26 and a 7~ ' second region 28 which abut each other to form a junction therebetween and with at least the first region 26 beiny made of the amorphous alloy in-cluding silicon and fluorine. In the illustrated embodiment in Fig~ 2 the second region 28 is also formed of amorphous alloy including silicon and fluorine.
Also, in each memory circuit 11 and 12, the memory region is aligned with the regions 26 and 28 Of the diode 14 and all of the regions are juxta-posed and are situated on a line substantially perpendicular to, and extending between each pair of cross-over conductors 18 and 20 at the cross-over thereof to provide a very small center-to-center distance between adjacent memory circuits 11and 12 thereby to provide a very high packing den-sity of memory circuits ll and 12 in the ROM device 10 on the order of ~l mil2.
In accordance with the teachings of the pre-sent invention, th~ amorphous alloy including sil-icon and fluorine also preferably contains hydrogen and is preferably an a-Sia:Fb:Hc alloy, where a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 . ` ' ~ s ~ n atomic percent.
The alloy layers 26 and 2# can be between 500 ; and 20,000 angstroms, one thickness utilized being 1000 angstroms.
The first region or layer 26 can be doped with an N type dopant material chosen from an element of Group V of the Periodic Table such as phosphorous or arsenic in an amount between a few parts per million and 5 atomic percent and preferably in an amount constituting 10 to 1000 parts per million.
Alternatively, the first region 26 can be doped with a P type dopant material chosen from an ele-ment of Group III of the Periodic Table such as boron or aluminum in an amount constituting between a few parts per million and 5 atomic percent and is preferably doped in an arnount constituting 10 to 1000 parts per million~
Alternatively, the second region 28 can be a metal, a metal alloy or a metallic like material having a high barrier height on the first region 26 so as to create a Schottky barrier. There also can be an insulator layer forming an MIS (metal insu-lator semiconductor) interface.
i . 1 ~6197() Further, as another alternative, the second region 28 can be doped with a material chosen from an element of Group III of the Periodic Table or with an element of Group V of the Periodic Table.
Still further, one of the regions could be made of a material dissimilar to the amorphous alloy such as to form a heterojunction rectifying device.
In any event~ with ~he thin film diode 14 having at least one region made of ~he amorphous alloy included in the momory circuit 11 a ROM de-vice 10 is provided which has a low resistance and high conductivity in the forward biased direction and a very high resistance in the reverse biased direction.
A schematic circuit diagram of the closed memory circuit 17 and the open memory circuit 12 is shown in E'igO 3 of the drawing.
Referring now to Figs. 4 and 5, there is il-lustrated therein an EEPROM device 50 and more specifically, two memory circuits 52 thereof which are made in accordance with the teachings of the present invention. As shown, each memory circuit 52 includes a memory region 56 made of a reversible resettable memory material as will be described in I .l6I97() . .
more detail hereafter connected in series with a thin film diode 58 between an upper X axis con-ductor 60 and lower Y axis conductors 62 and 62'.
Referring to Fig. 5~ it will be readily appar-ent that the memory region 56 and the diode 58 are juxtaposed to each other on a line substantially perpendicular to the crossing over conductors 60 and 62 suzh that the memory circuit 52 formed by each of the memory region 56 and diode 58 have a ~inimum cell area thereby to provide 2 maximum packing density of memory cells or memory circuits 56 in the EEPROM device 50O
In the construction of the EEPROM device 50, a !
substrate 64 such as a metal substrate is provided on which a layer of insulating material 66 is de-posited such as hy thin film depositing technique.
Then parallel bands of conductive material such as --metal are laid down to form the Y axis conductors 6~.
In accordance with the teachings of the pre-sent invention, the P-N junction diode 58 is made of layers of amorphous alloy conductive film 68 and 70 deposited on top of the Y axis conductor bands 60. The isolating diode 58 is formed from success--~3-.i ~ . 7 1~1~7f) ., fully doped N+ and P~ layers or regions 68 and 7U
of amorphous alloy~ After these layers have been deposited a layer 72 of insulating material such as silicon dioxide material is deposited over the substrate 66 and the layers 62, 68 and 70 thereon~
Next, an open space 74 is cut or etched out of the layer of insulating material in the area above the upper layer 70 of the diode 58. Preferably, a platinum silicide or ohmic contact region 76 is formed in the upper layer 70 which is exposed through the opening 74 in the manner described above for forming region 16 in ROM device 10~
Then, a thin film of phase change reversible amorphous material is deposited to form memory region 56. Next a thin layer 80 of refractory barrier-forming material like molybdenum or a Ti-W
alloy is deposited on the insulating layer 72 and over the memory region 560 Next, a thicker layer 60 of conductive material such as aluminum is de-posited in a band over the refractory barrier-forming layer 80 to form the X axis conduc~or 60~
The platinum silicide region 76 can form an ohmic contact or a Schottky barrier interface with the doped outer layer 70.
7 ~
As provided in ~he construction of the P~OM
device 10 described above and in accordance with ~he teachings of the present in~ention, the diode 58 has at least the first region or layer 68 and a second region or layer 70 which abut each other to form a junction therebetween with the first region 68 being made of the amorphous alloy.
The second region or layer 70 can also be made of the amorphous alloy and which can be doped with a different dopant material than the material with which the layer 68 is doped. Alternatively, region 70 could be made of a metal, a metal alloy or a metallic like material having a high barrier height on the first region 68 so as to create a Schottky barrier, when the first region 68 is doped with a dopant material chosen from an element of Group V
of the Periodic Table. Such a metal can be from the group consisting of gold, platinum, palladium or chromium.
Also, the second region 70 can be made of a material dissimilar to the amorphous material of the first region 68 such as to form a heterojunc-tion. The first region can be N or P doped and the second region can be P or N doped.
7 n A preferred amorphous alloy is a-Sia Fb:~c, : wherein a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 atomîc percent. The dopant material also can be chosen from elements of Group V of the Peri-odic Table such as phosphorus or arsenic and can constitute between a few parts per million and 5 atomic percent o~ the region 68 or 70 and prefer ably 10 to 1000 parts per million~
The second region or layer 70 can then be the amorphous alloy as is the first region 68. Then, such material can be doped with a dopant material chosen from an element of Group III of ~he Periodic Table and can constitute between a few parts per million and 5 atomic percent of the region 70.
Such a dopant mat~rial can be boron or aluminum and constitute 10 to 1000 parts per million of the region 70. It will be apparentl of course that the doping of the regions 68 and 70 can be reversed if desired. Also, in accordance with the teachings of the present invention, the regions are laid down as deposited thin films~
The memory regions 56 are aligned with the regions 68 and 70 of the diode 58 and all of these g 7 (~
.
regions are juxtaposed and situated on a line sub-stantiall~ perpendicular to and extending between a pair of cross-over conductors 60 and 62 at a cross~
over thereo~ to provide a very small center-to-center distance between adjacent memory circuits 52there~y to provide a very high packing density of such memeory circuits 52 in the EEPROM device 50.
Also, both the memory region and the diode region are thin film depositions.
Further, the memory regions 56 comprise a reversible, phase change material which can be set in a highly conductive state or a highly non-con-ductive state. More specifically~ the memory re-gion 56 is formed of a material which is initially amorphous and which can be changed by a set voltage and current to a crystalline conductive state and then reset by a reset voltage and current to an amorphous insulator state. One preferred material from which memory region 56 can be made includes germanium and tellurium such as Ge20Tego. This material has a good reversibility of up to 106 cycles, a maximum processing temperature of approx-imately 200C, a maximum storage temperature of 100C, a threshold voltage of 8 volts, a SET resis--27~
lg7~
tance of 300 ohms and OFF resistance (at 175C~ of approximately 104 ohms.
The memory region can comprise a memory struc-ture situated between one of the conductors 60 and 62 and one region 68 or 70 of the diode 58 with the memory structure comprising first, second and third regions~ The first region is adjacent to the one conductor 60 or 62 or to the one region 70 or 68, whichever is adapted to be coupled ts a positive voltage source.
The second region is situated between the first and third regions and the third region is adjacent the one region 70 or 68 or the one con-ductor 62 or 60, whichever is adapted to be coupled to a negative ~ine of the voltage source and com-pletely separates the second region from the con-nection to the negative line.
The second region is formed of a tellurium based chalcogenide which has higher electrical resistance in its amorphous state and lower elec-trical resistance in its crystalline state and can be switched from one state to another upon appli-cation to the conductors of an electrical signal of appropriate valuec . ; , 7 ~
- ` The first region is formed of a material hav-ing a higher percentage of tellurium than the sec-ond region. The third region is formed of a mate~
rial having between 25 and 46 atomic percent ger-manium with the remaining material being substan-tially tellurium.
Preferably, the third region contains approx~
imately 33 atomic percent germanium and the second region can contain between 10 and 25 atomic percent germanium and preferably between 15 and 17 percent germanium.
Also, preferably, the first region contains at least 90 atomic percent tellurium.
. . .
A schematic circuit diagram of the EEPROM
memory circuits 52 is illustrated in Fig. 6 of the drawing~
FigO 7 illustrates a ROM device 100 similar to that illustrated in Fig. 2 with a 5chottky barrier rectifying device in a closed cell 102~ An open cell 104 can be formed substantially indentical to the cell 12 except for the diode 14 as shown in Fig. 8. The device 100 is formed on a substrate 106 which has an insulating layer 108 formed there-on. Bottom or Y axis conductors 110 are formed on ~ o ~ n the layer 108 as before described.
Referring to the cell 102, a heavily doped amorphous alloy contact layer 112 is formed on the conductor 110. An intrinsic or slightly doped alloy layer 114 of the same conductivity type is formed on the layer I lZo An insulator layeL 116 is then formed over the cells 102 and 104 with an opening 118 etched or cut through the layer 116 for each closed cell 102. A
Schottky barrier 120 is then formed on the alloy 114, such as the barrier 15 described in Fig. 2. A
top X axis conductor 122 is formed over the cells 102 and 104 as previously described. The Schottk~
barrier 120 then forms the cell rectifying device instead of the P-N junction described in Figs. 2 or A schematic circuit diagram of the ROM closed cell 102 and open cell 104 is illustrated in Fig. 8 of the drawing. The open cell 104 does not have a rectifying device 120 since the insulating material 116 is de~osited on the alloy layers.
Both the ROM device 10 and the EEPROM device 50 can be deposited on an insulating layer of mate-rial which has first been deposited on a metal ~30-r7 . l substrate~ which metal substrate can form a heat sink and facilitate stacking and heat dissipation of one ROM device on top of another ROM device or an EEPROM device on top of another EEPROM device.
Also, if desired, the edges of the metal substrate ox substrates can have a heat radiating fin for~
mation thereon for further facilitating heat dis-sipation~
Of course, metal substrates are not essential and ~he ROM device 10 or E~PROM device 50 utilizir.g same have a number of advantages, some of which have been described above and others of which are inherent in the invention. Such diodes and memory regions that form memory circuits in a ROM or EEPROM
device can be easily deposited by thin film de-position techniques on a substrate and the devices can be stacked to make a three dimensional memory system. Also, a diode made of two regions of this material, one N doped and one P doped, has a low forward bias resistance and a high reverse bias resistance.
The diode takes up a minimum of space in that it is made by thin film deposition techniques with the amorphous alloy. Such a diode in combination 1 ~1(37~
, --with a memory region in a ROM device or an EEPROM
devi~e takes up a very small space such that the memory circuit or memory cell density can be as low as 0.1 mil2 with a center-to-center distance be-tween adjacent memory cells or circuits of 8 mi-crons utiliæing two micron lithography. In conven-tional bipolar ROM's, each cell is isolated between a pair of junction diffusion channels. Material to be diffused is deposited two microns wide, but the high temperature process diffuses the material into the substrate. As a result the channels are from four to six microns wide; have a rectifier width of about two microns with six to eight microns allowed between the channels and the rectifier. This re-sults in a bipolar ROM center-to-center distance of about eighteen microns and a cell density of about . S mil2 .
Utiliæing oxide isolation the rectifiers can be formed, in a best case, adjacent or overlapping the channel's; however, the channels are eight to ten microns wide. This results in a center-to-center distance of about twelve microns and a best cell density o about o25 mil2O
- . . . 1 ~6~7n , The decrease irl cell density ~rom .25 m;l2 to .1 mil2 is a very significant cost reduction. Al~
though the conventional junction and oxide isola-tion ROM's can be reduced in size as phstolithog~-raphy techniques are improved, the correspondingreduction will also take place in the ROM's and EEPROM's utilizing ~he thin ilm diode of ~he in-vention.
Certain embodiments disclQsed i~ this app~iGati.on ~re also disclosed an~ claimed in. the parent application filed under Serial Number 366~713 ana a fu~ther di~isional application filed on even date O
- .
-33~
We also provide ROM and EEPRQM devices utilizing these diodes as isolating means for coupling the memory regions thereof to the cross over points of a memory matrix. The packing density of the ROM
and EEPROM devices, utilizing two micron lithog-raphy for reference, i,5 on the order of .1 mil~ per cell. Also, the devices and diodes are all thin film deposited and have low leakage currents allow-ing the structure to be stacked upon one another to ` 25 further increase the packing density.
;
., .
-~ 7 lgl97n Further, according to ~he inven~ion, there is provided in a RO~ device havin~ memory circui~
means at each cross over point of a conductor of a first group of conductors extending in a first direction over a conductor of a second group of conductors extending in a second direction trav-ersing the first direction, the first group of conductors being insulated from the second group of condu tors~ and each memory circuit being couple~
to and between a pair of crossing over conductors . at one of ~he cross over points and including iso~
. i lating means, the improvement residing ;n the iso-l~ting means including a diode having at least a first region and a second region, the regions abut-ting each other ~o form a junction therebetween and - :
the first region being made of the amorphous alloy including silicon and fluorine, 11 ~ 7 ~
Preferahl~" the amorphous alloy also contai n.
hydrogen and such amorphous alloy i5 a-Sia~E~h Hc"
where a is }: ewteen 80 and 98 atomic percent, b i5 between 0 and 10 a~omit:: perc:ent an~ c is ~e'cween 0 and lQ atomic per-cent~ -The first alloy region is doped with an ~
dopan~c ma~erial chose~ from an element o~ G~oup Y
, ~ 13 --, ~ ~3.97~
of the Periodic Table, e~g., phosphorous, arsenic or others by an amount constituting between a few parts per million (ppm) and five atomic percent and preferably between 10 to 1000 parts per million.
The second region can be a metal, metal alloy, a metallic like material having a high barrier height on the first region so as to create a Schottky barrier.
Alternately, the second region also can be an amorphous alloy including silicon and fluorine and preferably also containing hydrogen. The second alioy region is doped with a P dopant material chosen from an element of Group III of the Periodic Table, e.g., boron, aluminum or others by an amount constituting between a few parts per million and five atomic percent, and preferably between 10 and 1000 parts per millionO Alsot the first region could be a P type region with the second region being an N type region.
The packing density utilizing two micron li-thrography for reference in the thin film ROM and all thin film EEPROM is on the order of .1 mil2 per cell. Further, due to the all thin ilm deposited structure and the low leakage current the devices can be stacked upon one another to further increase n the packing density. The devices can be formed on various substrates including insulated metal which is utilized as a heat sink for the devices.
The preferred embodiments of this invention will now be described, by way of example~ with reference to the drawings accompanying this speci-fication in which:
Fig~ 1 is a fragmentary plan view of the de-posited film side of a substrate which forms a support for an all deposited film ROM device in-cluding a diode made in accordance with the teach-ings of the present invention.
Fig.-2 is a sectional view through the memory circuits of the ROM device shown in Fig. 1 and is taken along line 2-2 of Fig. 1.
FigO 3 is a schematic circuit diagram of the memory circuit shown in Fig. 2.
Fig. 4 is a fragmentary plan view o the de-posited film side of a substrate forming a support for an all deposited thin film EEPROM device in-cluding memory circuits, each of which include a diode constructed according to the teachings of the present invention.
g~
Fig. 5 is a sectional view through two memory circuits shown in Fig. 4 and is take~ along line 5-5 of FigO 4.
Fig. 6 is a schematic circuit diagram of the memory circuit shown in Fig. 5~
Fig~ 7 is a sectional view through a second .
embodiment of deposited thin film ROM device in-cluding a Schottky diode device made in accordance with the teachings of the present invention.
Fig~ 8 is a schematic circuit diagram of t~e memory circuit shown in Fig. 7.
Referrin~ to Figs. 1 and 2 there is illus-trated therein a ROM device 10 including two dedi~
cated memory circuits ll and 12 each of which in-cludes a thin ilm d70de or rectifying device 14(Fig. 2) constructed in accordance with the teach~
in~s of the present inventionO The memory circuit 11 is a closed circuit which includes the diode 14 which is coupled through an ohmic contact region such as a platinum silicide region 16 to an upper X
axis conductor 18 and to a lower Y axis conductor 20.
The memory circuit 12 also includes a diode 14 which is connected on one side to another Y axis s~n conductor 20' and on the other side is open cir-cuited by reason of a re~ion of insulating material 21 disposed between the upper surface of diode 14 and the X axis conductor 18 as will be described in greater detail below~
In the construc~ion oE the ROM device 10, there is deposited on any suitable substrate 22 having an insulating top surface 25, parallel con-ductors 20 and 20' which form the Y axis conductors ~nd which form a compat'kle interface with the diode 14. The conductors or bands 20 of conductive material may be made of aluminum, chromium, molyb-denum, an alloy of titanium and tungsten (Ti-W) or the like. Also, the conductive bands 20 may in-clude a bottom layer 23 oE a highly conductivematerial like aluminum and an upper layer 24 of a refractory barrier-forming material like molybdenum or Ti-W. The conductive layers 23 and 24 may be formed by conventional vacuum deposition, photo resist masking and etchant techniques.
Next, spaced layers 26 and 28 of amorphous semiconductor alloy including silicon and fluorine are deposited over the conductor bands 20 to ~orm the thin film diodes 14 at each cross over ~oint in 7 n the matrix of X and Y axis conductors 18 and 20 in the ROM device 10. Each such P~~ junction diode 14 may be formed from doped N~ and P~ amorphous alloy layers 26 and 28 as shown.
An insulating layer 30, such as silicon diox-ide, is applied over the entire substrate 22 so as to form the insulating region 21 above the diode 14 in th~ memory circuit 12. However, wherever it is desired to store a data bit which will be indicated by a low resistance condition coupled through the diode 14~ an opening 31 i~ formed in the insulating layer of silicon dioxide.
The platinum silicide or ohmic contact region ! 16 can be formed on the outermost amorphous silicon layer 28, where the opening 31 had been formed in the insulating layer 30C such as by applying plati-. num over the exposed portions of the amorphousalloy layer 28. The rectifier diodes 14 then can have a conductor band 32 formed thereover of a barrier-forming material such as molybdenum or the Ti-W alloy. Subsequently, a band of aluminum is deposited over the conductor band 32 to form the X
axis conductor 18. Alternately, the conductor 18 can be depo6ited over the layer 28 and the in-~s sulator 30 without the barrier 32.
~; .;
l~.as7n From the foregoing description, it will be seen that the memory region of each memory circuit 11 and 12 is a prede~ermined conductive path or a predetermined insulator path between the Y axs conductor 20 through the diode 14 to the X axis conductor 18.
A150 o it will be apparent that the memor~
regions are formed by depositing a thin film of insulating material 30 on one region 28 of each diode 14 followed by depositing a thin film band (band 32 and/or 18) of conductive material to form the X axis conductor 18. For a conductive path memory region, the insulating film layer 30 is cut or etched away such as at 31 in the area above the one region 28 of a selected diode 14 before the thin film conductive band is deposited so that the conductive path is a direct contact of the con-ductive band 18 with the first region 28 of the selected diode 14.
Alsor it is apparent, that each memory circuit 11 or 12 coupled to and between a pair of crossing over conductors 18 and 20 includes not only a con-ductive path or insulator path memory region but also the diode 14 having a first region 26 and a 7~ ' second region 28 which abut each other to form a junction therebetween and with at least the first region 26 beiny made of the amorphous alloy in-cluding silicon and fluorine. In the illustrated embodiment in Fig~ 2 the second region 28 is also formed of amorphous alloy including silicon and fluorine.
Also, in each memory circuit 11 and 12, the memory region is aligned with the regions 26 and 28 Of the diode 14 and all of the regions are juxta-posed and are situated on a line substantially perpendicular to, and extending between each pair of cross-over conductors 18 and 20 at the cross-over thereof to provide a very small center-to-center distance between adjacent memory circuits 11and 12 thereby to provide a very high packing den-sity of memory circuits ll and 12 in the ROM device 10 on the order of ~l mil2.
In accordance with the teachings of the pre-sent invention, th~ amorphous alloy including sil-icon and fluorine also preferably contains hydrogen and is preferably an a-Sia:Fb:Hc alloy, where a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 . ` ' ~ s ~ n atomic percent.
The alloy layers 26 and 2# can be between 500 ; and 20,000 angstroms, one thickness utilized being 1000 angstroms.
The first region or layer 26 can be doped with an N type dopant material chosen from an element of Group V of the Periodic Table such as phosphorous or arsenic in an amount between a few parts per million and 5 atomic percent and preferably in an amount constituting 10 to 1000 parts per million.
Alternatively, the first region 26 can be doped with a P type dopant material chosen from an ele-ment of Group III of the Periodic Table such as boron or aluminum in an amount constituting between a few parts per million and 5 atomic percent and is preferably doped in an arnount constituting 10 to 1000 parts per million~
Alternatively, the second region 28 can be a metal, a metal alloy or a metallic like material having a high barrier height on the first region 26 so as to create a Schottky barrier. There also can be an insulator layer forming an MIS (metal insu-lator semiconductor) interface.
i . 1 ~6197() Further, as another alternative, the second region 28 can be doped with a material chosen from an element of Group III of the Periodic Table or with an element of Group V of the Periodic Table.
Still further, one of the regions could be made of a material dissimilar to the amorphous alloy such as to form a heterojunction rectifying device.
In any event~ with ~he thin film diode 14 having at least one region made of ~he amorphous alloy included in the momory circuit 11 a ROM de-vice 10 is provided which has a low resistance and high conductivity in the forward biased direction and a very high resistance in the reverse biased direction.
A schematic circuit diagram of the closed memory circuit 17 and the open memory circuit 12 is shown in E'igO 3 of the drawing.
Referring now to Figs. 4 and 5, there is il-lustrated therein an EEPROM device 50 and more specifically, two memory circuits 52 thereof which are made in accordance with the teachings of the present invention. As shown, each memory circuit 52 includes a memory region 56 made of a reversible resettable memory material as will be described in I .l6I97() . .
more detail hereafter connected in series with a thin film diode 58 between an upper X axis con-ductor 60 and lower Y axis conductors 62 and 62'.
Referring to Fig. 5~ it will be readily appar-ent that the memory region 56 and the diode 58 are juxtaposed to each other on a line substantially perpendicular to the crossing over conductors 60 and 62 suzh that the memory circuit 52 formed by each of the memory region 56 and diode 58 have a ~inimum cell area thereby to provide 2 maximum packing density of memory cells or memory circuits 56 in the EEPROM device 50O
In the construction of the EEPROM device 50, a !
substrate 64 such as a metal substrate is provided on which a layer of insulating material 66 is de-posited such as hy thin film depositing technique.
Then parallel bands of conductive material such as --metal are laid down to form the Y axis conductors 6~.
In accordance with the teachings of the pre-sent invention, the P-N junction diode 58 is made of layers of amorphous alloy conductive film 68 and 70 deposited on top of the Y axis conductor bands 60. The isolating diode 58 is formed from success--~3-.i ~ . 7 1~1~7f) ., fully doped N+ and P~ layers or regions 68 and 7U
of amorphous alloy~ After these layers have been deposited a layer 72 of insulating material such as silicon dioxide material is deposited over the substrate 66 and the layers 62, 68 and 70 thereon~
Next, an open space 74 is cut or etched out of the layer of insulating material in the area above the upper layer 70 of the diode 58. Preferably, a platinum silicide or ohmic contact region 76 is formed in the upper layer 70 which is exposed through the opening 74 in the manner described above for forming region 16 in ROM device 10~
Then, a thin film of phase change reversible amorphous material is deposited to form memory region 56. Next a thin layer 80 of refractory barrier-forming material like molybdenum or a Ti-W
alloy is deposited on the insulating layer 72 and over the memory region 560 Next, a thicker layer 60 of conductive material such as aluminum is de-posited in a band over the refractory barrier-forming layer 80 to form the X axis conduc~or 60~
The platinum silicide region 76 can form an ohmic contact or a Schottky barrier interface with the doped outer layer 70.
7 ~
As provided in ~he construction of the P~OM
device 10 described above and in accordance with ~he teachings of the present in~ention, the diode 58 has at least the first region or layer 68 and a second region or layer 70 which abut each other to form a junction therebetween with the first region 68 being made of the amorphous alloy.
The second region or layer 70 can also be made of the amorphous alloy and which can be doped with a different dopant material than the material with which the layer 68 is doped. Alternatively, region 70 could be made of a metal, a metal alloy or a metallic like material having a high barrier height on the first region 68 so as to create a Schottky barrier, when the first region 68 is doped with a dopant material chosen from an element of Group V
of the Periodic Table. Such a metal can be from the group consisting of gold, platinum, palladium or chromium.
Also, the second region 70 can be made of a material dissimilar to the amorphous material of the first region 68 such as to form a heterojunc-tion. The first region can be N or P doped and the second region can be P or N doped.
7 n A preferred amorphous alloy is a-Sia Fb:~c, : wherein a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 atomîc percent. The dopant material also can be chosen from elements of Group V of the Peri-odic Table such as phosphorus or arsenic and can constitute between a few parts per million and 5 atomic percent o~ the region 68 or 70 and prefer ably 10 to 1000 parts per million~
The second region or layer 70 can then be the amorphous alloy as is the first region 68. Then, such material can be doped with a dopant material chosen from an element of Group III of ~he Periodic Table and can constitute between a few parts per million and 5 atomic percent of the region 70.
Such a dopant mat~rial can be boron or aluminum and constitute 10 to 1000 parts per million of the region 70. It will be apparentl of course that the doping of the regions 68 and 70 can be reversed if desired. Also, in accordance with the teachings of the present invention, the regions are laid down as deposited thin films~
The memory regions 56 are aligned with the regions 68 and 70 of the diode 58 and all of these g 7 (~
.
regions are juxtaposed and situated on a line sub-stantiall~ perpendicular to and extending between a pair of cross-over conductors 60 and 62 at a cross~
over thereo~ to provide a very small center-to-center distance between adjacent memory circuits 52there~y to provide a very high packing density of such memeory circuits 52 in the EEPROM device 50.
Also, both the memory region and the diode region are thin film depositions.
Further, the memory regions 56 comprise a reversible, phase change material which can be set in a highly conductive state or a highly non-con-ductive state. More specifically~ the memory re-gion 56 is formed of a material which is initially amorphous and which can be changed by a set voltage and current to a crystalline conductive state and then reset by a reset voltage and current to an amorphous insulator state. One preferred material from which memory region 56 can be made includes germanium and tellurium such as Ge20Tego. This material has a good reversibility of up to 106 cycles, a maximum processing temperature of approx-imately 200C, a maximum storage temperature of 100C, a threshold voltage of 8 volts, a SET resis--27~
lg7~
tance of 300 ohms and OFF resistance (at 175C~ of approximately 104 ohms.
The memory region can comprise a memory struc-ture situated between one of the conductors 60 and 62 and one region 68 or 70 of the diode 58 with the memory structure comprising first, second and third regions~ The first region is adjacent to the one conductor 60 or 62 or to the one region 70 or 68, whichever is adapted to be coupled ts a positive voltage source.
The second region is situated between the first and third regions and the third region is adjacent the one region 70 or 68 or the one con-ductor 62 or 60, whichever is adapted to be coupled to a negative ~ine of the voltage source and com-pletely separates the second region from the con-nection to the negative line.
The second region is formed of a tellurium based chalcogenide which has higher electrical resistance in its amorphous state and lower elec-trical resistance in its crystalline state and can be switched from one state to another upon appli-cation to the conductors of an electrical signal of appropriate valuec . ; , 7 ~
- ` The first region is formed of a material hav-ing a higher percentage of tellurium than the sec-ond region. The third region is formed of a mate~
rial having between 25 and 46 atomic percent ger-manium with the remaining material being substan-tially tellurium.
Preferably, the third region contains approx~
imately 33 atomic percent germanium and the second region can contain between 10 and 25 atomic percent germanium and preferably between 15 and 17 percent germanium.
Also, preferably, the first region contains at least 90 atomic percent tellurium.
. . .
A schematic circuit diagram of the EEPROM
memory circuits 52 is illustrated in Fig. 6 of the drawing~
FigO 7 illustrates a ROM device 100 similar to that illustrated in Fig. 2 with a 5chottky barrier rectifying device in a closed cell 102~ An open cell 104 can be formed substantially indentical to the cell 12 except for the diode 14 as shown in Fig. 8. The device 100 is formed on a substrate 106 which has an insulating layer 108 formed there-on. Bottom or Y axis conductors 110 are formed on ~ o ~ n the layer 108 as before described.
Referring to the cell 102, a heavily doped amorphous alloy contact layer 112 is formed on the conductor 110. An intrinsic or slightly doped alloy layer 114 of the same conductivity type is formed on the layer I lZo An insulator layeL 116 is then formed over the cells 102 and 104 with an opening 118 etched or cut through the layer 116 for each closed cell 102. A
Schottky barrier 120 is then formed on the alloy 114, such as the barrier 15 described in Fig. 2. A
top X axis conductor 122 is formed over the cells 102 and 104 as previously described. The Schottk~
barrier 120 then forms the cell rectifying device instead of the P-N junction described in Figs. 2 or A schematic circuit diagram of the ROM closed cell 102 and open cell 104 is illustrated in Fig. 8 of the drawing. The open cell 104 does not have a rectifying device 120 since the insulating material 116 is de~osited on the alloy layers.
Both the ROM device 10 and the EEPROM device 50 can be deposited on an insulating layer of mate-rial which has first been deposited on a metal ~30-r7 . l substrate~ which metal substrate can form a heat sink and facilitate stacking and heat dissipation of one ROM device on top of another ROM device or an EEPROM device on top of another EEPROM device.
Also, if desired, the edges of the metal substrate ox substrates can have a heat radiating fin for~
mation thereon for further facilitating heat dis-sipation~
Of course, metal substrates are not essential and ~he ROM device 10 or E~PROM device 50 utilizir.g same have a number of advantages, some of which have been described above and others of which are inherent in the invention. Such diodes and memory regions that form memory circuits in a ROM or EEPROM
device can be easily deposited by thin film de-position techniques on a substrate and the devices can be stacked to make a three dimensional memory system. Also, a diode made of two regions of this material, one N doped and one P doped, has a low forward bias resistance and a high reverse bias resistance.
The diode takes up a minimum of space in that it is made by thin film deposition techniques with the amorphous alloy. Such a diode in combination 1 ~1(37~
, --with a memory region in a ROM device or an EEPROM
devi~e takes up a very small space such that the memory circuit or memory cell density can be as low as 0.1 mil2 with a center-to-center distance be-tween adjacent memory cells or circuits of 8 mi-crons utiliæing two micron lithography. In conven-tional bipolar ROM's, each cell is isolated between a pair of junction diffusion channels. Material to be diffused is deposited two microns wide, but the high temperature process diffuses the material into the substrate. As a result the channels are from four to six microns wide; have a rectifier width of about two microns with six to eight microns allowed between the channels and the rectifier. This re-sults in a bipolar ROM center-to-center distance of about eighteen microns and a cell density of about . S mil2 .
Utiliæing oxide isolation the rectifiers can be formed, in a best case, adjacent or overlapping the channel's; however, the channels are eight to ten microns wide. This results in a center-to-center distance of about twelve microns and a best cell density o about o25 mil2O
- . . . 1 ~6~7n , The decrease irl cell density ~rom .25 m;l2 to .1 mil2 is a very significant cost reduction. Al~
though the conventional junction and oxide isola-tion ROM's can be reduced in size as phstolithog~-raphy techniques are improved, the correspondingreduction will also take place in the ROM's and EEPROM's utilizing ~he thin ilm diode of ~he in-vention.
Certain embodiments disclQsed i~ this app~iGati.on ~re also disclosed an~ claimed in. the parent application filed under Serial Number 366~713 ana a fu~ther di~isional application filed on even date O
- .
-33~
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A ROM device including open and closed cells with memory circuit means at each closed cell cross over point of a conductor of a first group of conductors extending in a first direction over a conductor of a second group of conductors extending in a second direction traversing the first direction, the first group of conductors being insulated from the second group of conductors, and each memory circuit being coupled to and between a pair of crossing over conductors at one of the cross over points and including isolating means, said isolating means including a diode having at least a first region and a second region said regions abutting each other to form a junction therebetween and said first region being made of amorphous alloy.
2. The ROM device according to claim 1 wherein said amorphous alloy contains at least silicon, fluorine and/or hydrogen.
3. The ROM device according to claim 2 wherein said amorphous alloy is SiaFbHc wherein a is between 80 and 98 atomic percent, b is between 0 and 10 atomic percent and c is between 0 and 10 atomic percent.
4. The ROM device according to any one of claims 1 to 3 wherein said first region of amorphous alloy is doped with an n-type dopant material.
5. The ROM device according to claim 1 wherein said second region is a metal, a metal alloy or a metallic like material having a high barrier height on said first region so as to create a Schottky barrier.
6. The ROM device according to claim 1 wherein said second region is made of an amorphous alloy including silicon and fluorine and/or hydrogen.
7. The ROM device according to Claim 6 wherein said second region of amorphous alloy is doped with a p-type dopant material.
8. The ROM device according to claim 1 wherein said second region is made of a material dissimilar to said amorphous alloy such as to form a heterojunction.
9. The ROM device according to claim 1 wherein said first region is N or P doped and said second region is P or N doped.
10. The ROM device according to claim 1 wherein at least said first region is a deposited thin film.
11. The ROM device according to claim 1 wherein said memory circuit means include a memory region which is aligned with said regions of said diode and all of said regions being juxtaposed and being situated on a line substantially perpendicular to and extending between a pair of cross over conductors at the cross over with deposited oxide isolation being between each cross over thereof to provide a very small center-to-center distance between adjacent memory circuit means thereby to provide a very high packing density of cells in said ROM device.
12. The ROM device according to claim 11 wherein said memory region and said diode are thin film depositions.
13. The ROM device according to claim 1 or 12 wherein at least some of said cells are stacked one above the other.
14. The ROM device according to any one of claims 1, 6 or 11 wherein said first and second regions have an insulator therebetween.
15. The ROM device according to claim 1 formed by thin film deposition technique on a thin layer of insulating material which in turn has been deposited on a metal substrate such that heat generated by the active components of the ROM device can be transferred by conduction to the metal substrate which serves as a heat sink for dissipating such heat.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10301179A | 1979-12-13 | 1979-12-13 | |
US06/103,011 | 1979-12-13 | ||
US20827480A | 1980-11-19 | 1980-11-19 | |
US208,274 | 1980-11-19 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1161970A true CA1161970A (en) | 1984-02-07 |
Family
ID=26799984
Family Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000366713A Expired CA1155239A (en) | 1979-12-13 | 1980-12-12 | Diode and rom or eeprom device using same |
CA000430399A Expired CA1162327A (en) | 1979-12-13 | 1983-06-14 | Diode and eeprom device using same |
CA000430398A Expired CA1161970A (en) | 1979-12-13 | 1983-06-14 | Diode and rom device using same |
Family Applications Before (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000366713A Expired CA1155239A (en) | 1979-12-13 | 1980-12-12 | Diode and rom or eeprom device using same |
CA000430399A Expired CA1162327A (en) | 1979-12-13 | 1983-06-14 | Diode and eeprom device using same |
Country Status (15)
Country | Link |
---|---|
JP (3) | JPS56115571A (en) |
KR (2) | KR830004681A (en) |
AU (1) | AU543740B2 (en) |
BE (1) | BE886631A (en) |
CA (3) | CA1155239A (en) |
DE (1) | DE3046701A1 (en) |
FR (1) | FR2475295A1 (en) |
GB (1) | GB2066566B (en) |
IL (1) | IL61671A (en) |
IT (1) | IT1194001B (en) |
MX (1) | MX150800A (en) |
NL (1) | NL8006771A (en) |
SE (1) | SE8008739L (en) |
SG (1) | SG72784G (en) |
ZA (3) | ZA807762B (en) |
Families Citing this family (29)
Publication number | Priority date | Publication date | Assignee | Title |
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DE3277665D1 (en) * | 1981-08-07 | 1987-12-17 | British Petroleum Co Plc | Non-volatile electrically programmable memory device |
JPS5867066A (en) * | 1981-10-16 | 1983-04-21 | Semiconductor Energy Lab Co Ltd | Insulating gate type field-effect semiconductor device |
JPS59501988A (en) * | 1982-11-11 | 1984-11-29 | ハイドリル カンパニ− | Safety valve device and method |
US4545111A (en) * | 1983-01-18 | 1985-10-08 | Energy Conversion Devices, Inc. | Method for making, parallel preprogramming or field programming of electronic matrix arrays |
AU562641B2 (en) * | 1983-01-18 | 1987-06-18 | Energy Conversion Devices Inc. | Electronic matrix array |
US4677742A (en) * | 1983-01-18 | 1987-07-07 | Energy Conversion Devices, Inc. | Electronic matrix arrays and method for making the same |
US4569121A (en) * | 1983-03-07 | 1986-02-11 | Signetics Corporation | Method of fabricating a programmable read-only memory cell incorporating an antifuse utilizing deposition of amorphous semiconductor layer |
US4569120A (en) * | 1983-03-07 | 1986-02-11 | Signetics Corporation | Method of fabricating a programmable read-only memory cell incorporating an antifuse utilizing ion implantation |
JPS60153552U (en) * | 1984-03-24 | 1985-10-12 | 沖電気工業株式会社 | PN junction semiconductor device |
US4667217A (en) * | 1985-04-19 | 1987-05-19 | Ncr Corporation | Two bit vertically/horizontally integrated memory cell |
US4914055A (en) * | 1989-08-24 | 1990-04-03 | Advanced Micro Devices, Inc. | Semiconductor antifuse structure and method |
GB9113795D0 (en) * | 1991-06-26 | 1991-08-14 | Philips Electronic Associated | Thin-film rom devices and their manufacture |
GB9117680D0 (en) * | 1991-08-16 | 1991-10-02 | Philips Electronic Associated | Electronic matrix array devices |
JP3501416B2 (en) * | 1994-04-28 | 2004-03-02 | 忠弘 大見 | Semiconductor device |
JP2500484B2 (en) * | 1994-07-11 | 1996-05-29 | ソニー株式会社 | Thin film transistor manufacturing method |
US6646912B2 (en) * | 2001-06-05 | 2003-11-11 | Hewlett-Packard Development Company, Lp. | Non-volatile memory |
US6599796B2 (en) * | 2001-06-29 | 2003-07-29 | Hewlett-Packard Development Company, L.P. | Apparatus and fabrication process to reduce crosstalk in pirm memory array |
JP3948292B2 (en) | 2002-02-01 | 2007-07-25 | 株式会社日立製作所 | Semiconductor memory device and manufacturing method thereof |
WO2004027877A1 (en) * | 2002-09-19 | 2004-04-01 | Sharp Kabushiki Kaisha | Variable resistance functional body and its manufacturing method |
JP4541651B2 (en) * | 2003-03-13 | 2010-09-08 | シャープ株式会社 | Resistance change function body, memory, manufacturing method thereof, semiconductor device, and electronic apparatus |
JP4634014B2 (en) * | 2003-05-22 | 2011-02-16 | 株式会社日立製作所 | Semiconductor memory device |
KR100504700B1 (en) * | 2003-06-04 | 2005-08-03 | 삼성전자주식회사 | Phase random access memory with high dencity |
JP4767653B2 (en) * | 2004-10-22 | 2011-09-07 | 株式会社半導体エネルギー研究所 | Semiconductor device and wireless chip |
CN101044624A (en) | 2004-10-22 | 2007-09-26 | 株式会社半导体能源研究所 | Semiconductor device |
JP2008118108A (en) * | 2006-08-25 | 2008-05-22 | Qimonda Ag | Information storage element and method of manufacturing the same |
JP2007019559A (en) * | 2006-10-23 | 2007-01-25 | Hitachi Ltd | Semiconductor storage device and its manufacturing method |
US7915603B2 (en) * | 2006-10-27 | 2011-03-29 | Qimonda Ag | Modifiable gate stack memory element |
CN101689603B (en) * | 2007-06-20 | 2015-08-12 | 台湾积体电路制造股份有限公司 | Electronic component and manufacture method thereof |
US9716225B2 (en) | 2014-09-03 | 2017-07-25 | Micron Technology, Inc. | Memory cells including dielectric materials, memory devices including the memory cells, and methods of forming same |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS51122382A (en) * | 1975-04-18 | 1976-10-26 | Fujitsu Ltd | Semiconductor device |
US4064521A (en) * | 1975-07-28 | 1977-12-20 | Rca Corporation | Semiconductor device having a body of amorphous silicon |
JPS5819138B2 (en) * | 1977-01-11 | 1983-04-16 | 日本電信電話株式会社 | semiconductor equipment |
JPS53144274A (en) * | 1977-05-23 | 1978-12-15 | Hitachi Ltd | Semiconductor device and its manufacture |
JPS5457879A (en) * | 1977-10-15 | 1979-05-10 | Cho Lsi Gijutsu Kenkyu Kumiai | Semiconductor |
US4177475A (en) * | 1977-10-31 | 1979-12-04 | Burroughs Corporation | High temperature amorphous memory device for an electrically alterable read-only memory |
DE2909197A1 (en) * | 1978-03-20 | 1979-10-04 | Texas Instruments Inc | PROCESS FOR PRODUCING A FIXED MEMORY AND FIXED STORAGE MATRIX |
-
1980
- 1980-12-09 IL IL61671A patent/IL61671A/en unknown
- 1980-12-10 GB GB8039611A patent/GB2066566B/en not_active Expired
- 1980-12-10 MX MX185133A patent/MX150800A/en unknown
- 1980-12-11 ZA ZA00807762A patent/ZA807762B/en unknown
- 1980-12-11 DE DE19803046701 patent/DE3046701A1/en not_active Withdrawn
- 1980-12-11 JP JP17520080A patent/JPS56115571A/en active Pending
- 1980-12-11 ZA ZA00807761A patent/ZA807761B/en unknown
- 1980-12-11 ZA ZA00807763A patent/ZA807763B/en unknown
- 1980-12-11 JP JP17519980A patent/JPS56100464A/en active Pending
- 1980-12-12 FR FR8026401A patent/FR2475295A1/en active Pending
- 1980-12-12 NL NL8006771A patent/NL8006771A/en not_active Application Discontinuation
- 1980-12-12 JP JP17568280A patent/JPS56103474A/en active Pending
- 1980-12-12 KR KR1019800004729A patent/KR830004681A/en unknown
- 1980-12-12 CA CA000366713A patent/CA1155239A/en not_active Expired
- 1980-12-12 KR KR8004727A patent/KR850001045B1/en active
- 1980-12-12 AU AU65315/80A patent/AU543740B2/en not_active Withdrawn - After Issue
- 1980-12-12 IT IT26643/80A patent/IT1194001B/en active
- 1980-12-12 SE SE8008739A patent/SE8008739L/en not_active Application Discontinuation
- 1980-12-12 BE BE0/203148A patent/BE886631A/en not_active IP Right Cessation
-
1983
- 1983-06-14 CA CA000430399A patent/CA1162327A/en not_active Expired
- 1983-06-14 CA CA000430398A patent/CA1161970A/en not_active Expired
-
1984
- 1984-10-17 SG SG727/84A patent/SG72784G/en unknown
Also Published As
Publication number | Publication date |
---|---|
BE886631A (en) | 1981-04-01 |
ZA807762B (en) | 1981-12-30 |
NL8006771A (en) | 1981-07-16 |
GB2066566B (en) | 1984-07-04 |
KR830004681A (en) | 1983-07-16 |
DE3046701A1 (en) | 1981-10-15 |
IL61671A0 (en) | 1981-01-30 |
IL61671A (en) | 1984-04-30 |
CA1155239A (en) | 1983-10-11 |
SG72784G (en) | 1985-03-29 |
GB2066566A (en) | 1981-07-08 |
KR850001045B1 (en) | 1985-07-19 |
JPS56115571A (en) | 1981-09-10 |
FR2475295A1 (en) | 1981-08-07 |
ZA807761B (en) | 1981-12-30 |
CA1162327A (en) | 1984-02-14 |
SE8008739L (en) | 1981-06-14 |
ZA807763B (en) | 1981-12-30 |
JPS56103474A (en) | 1981-08-18 |
AU6531580A (en) | 1981-06-18 |
KR830004679A (en) | 1983-07-16 |
IT1194001B (en) | 1988-08-31 |
JPS56100464A (en) | 1981-08-12 |
IT8026643A0 (en) | 1980-12-12 |
AU543740B2 (en) | 1985-05-02 |
MX150800A (en) | 1984-07-19 |
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