CA1192669A - Vertical igfet with internal gate and method of making same - Google Patents
Vertical igfet with internal gate and method of making sameInfo
- Publication number
- CA1192669A CA1192669A CA000429823A CA429823A CA1192669A CA 1192669 A CA1192669 A CA 1192669A CA 000429823 A CA000429823 A CA 000429823A CA 429823 A CA429823 A CA 429823A CA 1192669 A CA1192669 A CA 1192669A
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- Prior art keywords
- silicon
- source
- accordance
- insulated gate
- drain
- Prior art date
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Links
- 238000004519 manufacturing process Methods 0.000 title description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 25
- 239000010703 silicon Substances 0.000 claims abstract description 25
- 238000000151 deposition Methods 0.000 claims abstract description 19
- 239000000758 substrate Substances 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 14
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims abstract description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 20
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 11
- 235000012239 silicon dioxide Nutrition 0.000 claims description 10
- 239000000377 silicon dioxide Substances 0.000 claims description 10
- 230000008021 deposition Effects 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 3
- 208000012868 Overgrowth Diseases 0.000 abstract description 2
- 239000004065 semiconductor Substances 0.000 description 18
- 238000005530 etching Methods 0.000 description 12
- 239000007789 gas Substances 0.000 description 7
- 210000000746 body region Anatomy 0.000 description 6
- 239000002019 doping agent Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000005669 field effect Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 238000005468 ion implantation Methods 0.000 description 2
- 239000003607 modifier Substances 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 102000001324 CD59 Antigens Human genes 0.000 description 1
- 108010055167 CD59 Antigens Proteins 0.000 description 1
- 229910003818 SiH2Cl2 Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000005137 deposition process Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000002513 implantation Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- XUIMIQQOPSSXEZ-IGMARMGPSA-N silicon-28 atom Chemical compound [28Si] XUIMIQQOPSSXEZ-IGMARMGPSA-N 0.000 description 1
Classifications
-
- 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
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/7801—DMOS transistors, i.e. MISFETs with a channel accommodating body or base region adjoining a drain drift region
- H01L29/7802—Vertical DMOS transistors, i.e. VDMOS transistors
- H01L29/7813—Vertical DMOS transistors, i.e. VDMOS transistors with trench gate electrode, e.g. UMOS transistors
-
- 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
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66666—Vertical transistors
-
- 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
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/7827—Vertical transistors
-
- 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
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/7827—Vertical transistors
- H01L29/7828—Vertical transistors without inversion channel, e.g. vertical ACCUFETs, normally-on vertical MISFETs
-
- 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
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
- H01L29/423—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions not carrying the current to be rectified, amplified or switched
- H01L29/42312—Gate electrodes for field effect devices
- H01L29/42316—Gate electrodes for field effect devices for field-effect transistors
- H01L29/4232—Gate electrodes for field effect devices for field-effect transistors with insulated gate
- H01L29/42356—Disposition, e.g. buried gate electrode
- H01L29/4236—Disposition, e.g. buried gate electrode within a trench, e.g. trench gate electrode, groove gate electrode
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Ceramic Engineering (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Manufacturing & Machinery (AREA)
- Insulated Gate Type Field-Effect Transistor (AREA)
- Electrodes Of Semiconductors (AREA)
Abstract
VERTICAL IGFET WITH INTERNAL GATE
AND METHOD FOR MAKING SAME
Abstract A vertical IGFET device comprising a substantially planar silicon wafer with a source electrode on one major surface and a drain electrode on the opposite major surface is disclosed. An insulated gate electrode, which includes a conductive finger-like portion surrounded by an insulating layer, is internally disposed in the silicon wafer such that a predetermined voltage applied to the gate electrode will regulate a current flow between the source and drain electrodes. The IGFET device is fabricated utilizing an epitaxial lateral overgrowth (ELO) technique for depositing a monocrystalline silicon layer over the insulated gate electrode which is disposed on a silicon substrate.
AND METHOD FOR MAKING SAME
Abstract A vertical IGFET device comprising a substantially planar silicon wafer with a source electrode on one major surface and a drain electrode on the opposite major surface is disclosed. An insulated gate electrode, which includes a conductive finger-like portion surrounded by an insulating layer, is internally disposed in the silicon wafer such that a predetermined voltage applied to the gate electrode will regulate a current flow between the source and drain electrodes. The IGFET device is fabricated utilizing an epitaxial lateral overgrowth (ELO) technique for depositing a monocrystalline silicon layer over the insulated gate electrode which is disposed on a silicon substrate.
Description
6~
-1- RCA 76,695 VERTICAL IGFET WITH INTERNAL GATE
AND METHOD FOR MAKING SAME
The present invention relates to insulated gate field effect transis-tors (IGFETs). More par-ticularly, it relates to vertical IGFETs which are substantially planar in structure and which are used in power switching applications.
Background of the Invention Vertical IGFETs are so named because they incorporate source and drain electrodes on opposite surfaces o~ a semiconductor wafer. When a preZetermined voltage is applied to a gate electrode, a vertical current flow between the source and drain electrodes is established. The gate electrode is typically insulated from the semiconductor surface by a silicon dioxide layer, such IGFETs being referred to as metal-oxide-semiconductor ~MOS) FETs. Conventionally, the insulated gate electrode is disposed on the same semiconductor surface as the source electrode, as disclosed in U.S. ~atent 4,145,700, POWER FIELD EFFECT TRANSISTORS, issued March 20~ 1979, to C. G. Jambotkar, or it is disposed in a groove in a major semiconductor surface, as disclosed in U.S. Patent 4,145,703, HIGH POWER MOS DEVICE AND FABRICATION MET~OD
THEREFO~, issued March 20, 1979, to R. A. Blanchard e-t al.
Vertical IGFETs wherein the gate electrode is disposed on a major semiconductor surface are referred to as planar, vertical IGFETs herein, and are commonly referred to in the semiconductor industry as VDMOS
(vertical, double-diffused MOS) devices. Grooved, vertical IGFETs are commonly referred to in the semiconductor industry as VMOS devices. Being insulated gate structures, both VMOS and VDMOS devices are typically operated in the enhancement mode, and, being vertical devices, they are commonly used in power switching applications. When the predetermined voltage is applied to the gate electrode, a channel is formed in the semiconductor area immediately beneath the oxide of the insulated gate and provides a path for current flow .~
-1- RCA 76,695 VERTICAL IGFET WITH INTERNAL GATE
AND METHOD FOR MAKING SAME
The present invention relates to insulated gate field effect transis-tors (IGFETs). More par-ticularly, it relates to vertical IGFETs which are substantially planar in structure and which are used in power switching applications.
Background of the Invention Vertical IGFETs are so named because they incorporate source and drain electrodes on opposite surfaces o~ a semiconductor wafer. When a preZetermined voltage is applied to a gate electrode, a vertical current flow between the source and drain electrodes is established. The gate electrode is typically insulated from the semiconductor surface by a silicon dioxide layer, such IGFETs being referred to as metal-oxide-semiconductor ~MOS) FETs. Conventionally, the insulated gate electrode is disposed on the same semiconductor surface as the source electrode, as disclosed in U.S. ~atent 4,145,700, POWER FIELD EFFECT TRANSISTORS, issued March 20~ 1979, to C. G. Jambotkar, or it is disposed in a groove in a major semiconductor surface, as disclosed in U.S. Patent 4,145,703, HIGH POWER MOS DEVICE AND FABRICATION MET~OD
THEREFO~, issued March 20, 1979, to R. A. Blanchard e-t al.
Vertical IGFETs wherein the gate electrode is disposed on a major semiconductor surface are referred to as planar, vertical IGFETs herein, and are commonly referred to in the semiconductor industry as VDMOS
(vertical, double-diffused MOS) devices. Grooved, vertical IGFETs are commonly referred to in the semiconductor industry as VMOS devices. Being insulated gate structures, both VMOS and VDMOS devices are typically operated in the enhancement mode, and, being vertical devices, they are commonly used in power switching applications. When the predetermined voltage is applied to the gate electrode, a channel is formed in the semiconductor area immediately beneath the oxide of the insulated gate and provides a path for current flow .~
2~
-2- RCA 76,695 between the source and drain electrodes. Thus, in a VDMOS
device, the channel is formed at a major semiconductor surface, and in a VMOS device the channel is formed along the surface of the groove in the major semiconductor surface. In both cases, the gate electrode is externally disposed on the semiconductor wafer and therefore necessarily consumes a certain amount of surface area.
Summary of the Inven-tion A novel vertical IGFET and method for fabrication are disclosed herein. A silicon wafer with first and second opposing major surfaces has a source electrode on the first surface and a drain electrode on the second surface. The gate elec-trode is internally disposed in the silicon wafer, and includes a finger portion which is surrounded by an insulating layer such as silicon dioxide. A predetermined voltage applied to the gate electrode finger portion will regulate current flow between the source and drain electrodes.
Brief Description of the Drawing FIGURE l is a cross-sectional view of a depletion-type vertical IGFET incorporating the present nventlon .
FIGURE 2 is a cross-sectional view of an enhancement-type vertical IGFET incorporating the present invention.
FIGURES 3 through 6 illustrate the basic processing sequence used to fa~ricate a vertical IGFET of the present invention.
FIGURE 7 illustrates an exemplary configuration of the gate electrode in devices of the present invention.
It illustrates the view taken through cross-sectional line 7-7 of FIGURES l and 2.
Detailed Description of the Preferred Em~odimen-t Illustrated in FIGURE l is an exemplary vertical, depletion-type IGFET device 10 incorporating the present invention. The device 10 comprises a substantially planar monocrystalline silicon wafer 12 having first and second opposing major surfaces 14 and 16,
-2- RCA 76,695 between the source and drain electrodes. Thus, in a VDMOS
device, the channel is formed at a major semiconductor surface, and in a VMOS device the channel is formed along the surface of the groove in the major semiconductor surface. In both cases, the gate electrode is externally disposed on the semiconductor wafer and therefore necessarily consumes a certain amount of surface area.
Summary of the Inven-tion A novel vertical IGFET and method for fabrication are disclosed herein. A silicon wafer with first and second opposing major surfaces has a source electrode on the first surface and a drain electrode on the second surface. The gate elec-trode is internally disposed in the silicon wafer, and includes a finger portion which is surrounded by an insulating layer such as silicon dioxide. A predetermined voltage applied to the gate electrode finger portion will regulate current flow between the source and drain electrodes.
Brief Description of the Drawing FIGURE l is a cross-sectional view of a depletion-type vertical IGFET incorporating the present nventlon .
FIGURE 2 is a cross-sectional view of an enhancement-type vertical IGFET incorporating the present invention.
FIGURES 3 through 6 illustrate the basic processing sequence used to fa~ricate a vertical IGFET of the present invention.
FIGURE 7 illustrates an exemplary configuration of the gate electrode in devices of the present invention.
It illustrates the view taken through cross-sectional line 7-7 of FIGURES l and 2.
Detailed Description of the Preferred Em~odimen-t Illustrated in FIGURE l is an exemplary vertical, depletion-type IGFET device 10 incorporating the present invention. The device 10 comprises a substantially planar monocrystalline silicon wafer 12 having first and second opposing major surfaces 14 and 16,
-3- RCA 76,695 respectively. A source electrode 18 is disposed on the first surface 14, an a drain electrode 20 is disposed on the second surface 16. Portions of the wafer 12 adjacent to the major surfaces 14 and 16 are doped with N or P type conductivity modifiers so as to provide source and drain regions 22 and 24 in ohmic con-tact with -the source and drain electrodes 18 and 20, respectively. With the exception of the insula-ted gate electrode, which will be described subse~uently, the bulk of the silicon wafer 12, i.e., the volume be-tween the source and drain regions 22 and 24, is of similar conductivity type to the source and drain regions, but of relatively low conductivity. For example, as illustrated, both the source and drain regions 22 and 24 might be of N~ type conductivity, having relatively high carrier concentrations of about 1019 cm 3, whereas the bulk of the wafer 12 might be of N- type conductivity, having a carrier concentration of about 1~15 cm It should be noted that although the FIGURE 1 illustration shows the source and drain regions 22 and 24 to be present only near the wafer surface 14 and 16, the structure is not so limited. In that the regions 22 and 24 serve to reduce source-to-drain resistance, it may be desirable, for example, to have these regions extend more deeply into the wafer. Such an example will be shown subsequently, in a description of enhancement-type device 40 of FIGURE 2.
In the preferred embodiment shown in FIGURE 1, a plurality of insulated gate fingers 26 are disposed along a plane which is internal to the wafer 12 and which is substan-tially parallel to the major surfaces 1~ and 16.
It should be noted, however, that a functional device could also be formed utilizing a single gate finger 26.
In the preferred embodiment, the fingers 26 are arranged in a ladder-shaped pattern, as further illustrated in FIGURE 7, although it should be recognized that the finger like configuration is not limited to this pattern.
Each finger 26 incorporates a gate electrode 28 of, for ~L~ 3
In the preferred embodiment shown in FIGURE 1, a plurality of insulated gate fingers 26 are disposed along a plane which is internal to the wafer 12 and which is substan-tially parallel to the major surfaces 1~ and 16.
It should be noted, however, that a functional device could also be formed utilizing a single gate finger 26.
In the preferred embodiment, the fingers 26 are arranged in a ladder-shaped pattern, as further illustrated in FIGURE 7, although it should be recognized that the finger like configuration is not limited to this pattern.
Each finger 26 incorporates a gate electrode 28 of, for ~L~ 3
-4- RCA 76,695 example, relatively heavily doped polycrystalline silicon, and is surrounded by an insulating layer 30 of, for example, silicon dioxide. External electrical connection to the insulated gate fingers 26 is made by a gate electrode contact 32 in direct ohmic contact with a portion of the gate electrode 28.
The design spacing between opposing fingers is determined by the si~e of the depletion region which each finger will generate in the semiconductor region 29 therebetween when the gate electrode 28 is appropriately biased. Thus, in the depletion-type device 10, wherein it is desirable to pinch off a "normally on" source-to~drain current, the maximum spacing between opposing insulated gate fingers 26 should be approximately twice the distance that the depletion region of each finger 26 extends into the semiconductor region 29 between fingers.
Illustrated in FIGURE 2 is a vertical, enhancement-type IGFET device 40 incorporating -the present invention. The basic structure of the enhancement-type device 40 is similar to that of the depletion-type device 10. The device 40 also incorporates a silicon wafer 42, having first and second opposing major surfaces 44 and 46 respectively, with source and drain electrodes 48 and 50 respectively, disposed thereon. Source and drain regions 52 and 54, of first conductivity type, extend into the wafer from the firs-t and second surfaces 44 and 46, and a plurality of insulated gate fingers 56 are disposed along an internal plane of the wafer which is substantially parallel to the major surfaces. The source and drain regions 52 and 54 ex-tend to the plane on which the insulated gate fingers lie so as to define the body region 62 of second conductivity type, between each pair of ne.ighboring fingers 56. In the preferred embodiment, the source and drain regions 52 and 54 are of relatively high conductivity compared to the body regions. Additionally, the conductivity of the source and drain regions 52 and 54 might be graded, e.g., higher at the wafer surface(s) than near the body regions 62.
The design spacing between opposing fingers is determined by the si~e of the depletion region which each finger will generate in the semiconductor region 29 therebetween when the gate electrode 28 is appropriately biased. Thus, in the depletion-type device 10, wherein it is desirable to pinch off a "normally on" source-to~drain current, the maximum spacing between opposing insulated gate fingers 26 should be approximately twice the distance that the depletion region of each finger 26 extends into the semiconductor region 29 between fingers.
Illustrated in FIGURE 2 is a vertical, enhancement-type IGFET device 40 incorporating -the present invention. The basic structure of the enhancement-type device 40 is similar to that of the depletion-type device 10. The device 40 also incorporates a silicon wafer 42, having first and second opposing major surfaces 44 and 46 respectively, with source and drain electrodes 48 and 50 respectively, disposed thereon. Source and drain regions 52 and 54, of first conductivity type, extend into the wafer from the firs-t and second surfaces 44 and 46, and a plurality of insulated gate fingers 56 are disposed along an internal plane of the wafer which is substantially parallel to the major surfaces. The source and drain regions 52 and 54 ex-tend to the plane on which the insulated gate fingers lie so as to define the body region 62 of second conductivity type, between each pair of ne.ighboring fingers 56. In the preferred embodiment, the source and drain regions 52 and 54 are of relatively high conductivity compared to the body regions. Additionally, the conductivity of the source and drain regions 52 and 54 might be graded, e.g., higher at the wafer surface(s) than near the body regions 62.
-5- RCA 76,695 Each insulated gate finger 56 again includes a gate electrode 58 of, for example, relatively heavily doped polycrystalline silicon, and is surrounded by an insulating layer 60 of, for example, silicon dioxide. An external gate elec-trode contact 64 ohmically contacts the gate electrode 58.
A variety of configura-tions for the gate fingers 56 is also possible with the enhancement-type device, although in the preferred enbodiment, a laddex-shaped structure, as illustrated in FIGURE 7, is used. It should be noted, however, that in an enhancement-type device there are fewer restrictions on the configuration for the gate fin~ers 56. Since an enhancement-type device is normally off, there is no necessity for each gate finger 56 to be in pro~imity to a structure such as an opposing finger 56, against which source-to-drain current is pinched off. Operationally, the IGFET device 40 behaves as a typical enhancemen-t-type device. The device 40 is normally off, and current flow between the source and drain electrodes 48 and 50 is regulated by a voltage applied to the insulated ga-te fingers 56. When a predetermined voltage is applied to the gate electrodes 58 via gate electrode contact 64, a conductive channel region is created in each body region 62 in an area adjacent to the gate oxide 60.
The basic processing steps for fabricating -the devices 10 or 40 of FIGURES l and 2 are shown in FIGURES 3 through 6. As shown in FIGURE 3, the starting point for processing is a monocrystalline silicon substrate 70 having opposing major surfaces 72 and 74. Depending upon whether a depletion-type device or an enhancement-type device is being fabricated, the substrate 70 will be doped with an appropriate concentration of a particular conductivity modifier. A relatively heavy dopant concentration may be desirable so as to decrease power dissipation in the completed device. On the other hand, a relativley low concentration may be desirable for ease of device fabrication.
A variety of configura-tions for the gate fingers 56 is also possible with the enhancement-type device, although in the preferred enbodiment, a laddex-shaped structure, as illustrated in FIGURE 7, is used. It should be noted, however, that in an enhancement-type device there are fewer restrictions on the configuration for the gate fin~ers 56. Since an enhancement-type device is normally off, there is no necessity for each gate finger 56 to be in pro~imity to a structure such as an opposing finger 56, against which source-to-drain current is pinched off. Operationally, the IGFET device 40 behaves as a typical enhancemen-t-type device. The device 40 is normally off, and current flow between the source and drain electrodes 48 and 50 is regulated by a voltage applied to the insulated ga-te fingers 56. When a predetermined voltage is applied to the gate electrodes 58 via gate electrode contact 64, a conductive channel region is created in each body region 62 in an area adjacent to the gate oxide 60.
The basic processing steps for fabricating -the devices 10 or 40 of FIGURES l and 2 are shown in FIGURES 3 through 6. As shown in FIGURE 3, the starting point for processing is a monocrystalline silicon substrate 70 having opposing major surfaces 72 and 74. Depending upon whether a depletion-type device or an enhancement-type device is being fabricated, the substrate 70 will be doped with an appropriate concentration of a particular conductivity modifier. A relatively heavy dopant concentration may be desirable so as to decrease power dissipation in the completed device. On the other hand, a relativley low concentration may be desirable for ease of device fabrication.
-6- RCA 76,695 A first silicon dioxide layer 76 is formed across the subs-trate surface 74. A first oxide layer 76 might have a thickness of approximately lO00 Angstroms and it can be formed, for example, by thermal oxidation. A
polycrystalline silicon layer 78 is then formed across the first oxide layer 76. The thickness of the polycrystalline silicon layer 78 will ul-timately determine gate length and it might have a value in the approximat~
range of 5000-20,000 Angstroms. ~s is illustrated, the polycrystalline silicon layer 78 is relatively heavily doped -to a particular conductivity type. This doping can be performed either during the polycrystalline s1licon deposition or following the deposition by conventional doping or ion implantation procedures.
The doped polycrystalline silicon layer 78 is next photolithographically defined so as to form a pattern, comprising a plurality of fingers 80, and each of the fingers 80 is oxidized so as to form a surrounding second silicon dioxide layer 82, as illustrated in FIGURE
4. The first silicon dioxide layer 76 is then removed from areas of the substrate surface 74 between the oxidized fingers 80, as illustrated in FIGURE 5. This may be accomplished photolithographically, for example, by first protectin~ the oxidized fingers 80 with photoresist and then etching the first silicon dioxide layer 76.
As shown in FIGURE 6, an epitaxial silicon layer 84 is next grown from the exposed surface 74 such that it fills the space between the oxidized fingers 80 and forms a layer 84 of monocrystalline material over all of the oxidized fingers 80. The surface of this epitaxial layer 84 is identified at 86 in FIGURE 6, and it will ultimately form the first wafer surface 14 or 44 illustrated in FIGURES l or 2, respectively. The epi-taxial layer 84 can be formed by what is now referred to as the epitaxial lateral overgrowth (ELO) technique.
Basically, the ELO process involves a repetitious, two-phase, depositing/etch cycle whereby monocrystalline silicon is grown from a monocrystalline 6~
polycrystalline silicon layer 78 is then formed across the first oxide layer 76. The thickness of the polycrystalline silicon layer 78 will ul-timately determine gate length and it might have a value in the approximat~
range of 5000-20,000 Angstroms. ~s is illustrated, the polycrystalline silicon layer 78 is relatively heavily doped -to a particular conductivity type. This doping can be performed either during the polycrystalline s1licon deposition or following the deposition by conventional doping or ion implantation procedures.
The doped polycrystalline silicon layer 78 is next photolithographically defined so as to form a pattern, comprising a plurality of fingers 80, and each of the fingers 80 is oxidized so as to form a surrounding second silicon dioxide layer 82, as illustrated in FIGURE
4. The first silicon dioxide layer 76 is then removed from areas of the substrate surface 74 between the oxidized fingers 80, as illustrated in FIGURE 5. This may be accomplished photolithographically, for example, by first protectin~ the oxidized fingers 80 with photoresist and then etching the first silicon dioxide layer 76.
As shown in FIGURE 6, an epitaxial silicon layer 84 is next grown from the exposed surface 74 such that it fills the space between the oxidized fingers 80 and forms a layer 84 of monocrystalline material over all of the oxidized fingers 80. The surface of this epitaxial layer 84 is identified at 86 in FIGURE 6, and it will ultimately form the first wafer surface 14 or 44 illustrated in FIGURES l or 2, respectively. The epi-taxial layer 84 can be formed by what is now referred to as the epitaxial lateral overgrowth (ELO) technique.
Basically, the ELO process involves a repetitious, two-phase, depositing/etch cycle whereby monocrystalline silicon is grown from a monocrystalline 6~
-7- RC~ 76,695 silicon surface which is exposed within the apertures of an overlying silicon dioxide mask. When the silicon which is being epitaxially deposited grows through the apertures to a thickness greater than that of the mask, the epitaxial growth proceeds laterally, across the surface of the mask, as well as vertlcally. Ul-timately, a continuous monocrystalline silicon layer overlying the aper-tured mask is formed.
The depositing/etching cycle can be performed within a conventional reactor at atmospheric or reduced pressure. During the depositing phase of the cycle, the substrate is exposed to a gas mixture which comprises a silicon-source gas such as SiH2Cl2 and a carrier gas such as hydrogen. Additionally, it may be desirable to include a silicon-etching gas such as HCl during the depositing phase. During the etching phase of the cycle, the substrate is exposed to a gas mixture comprising an etching gas such as HCl and a carrier gas such as hydrogen.
During the depositing phase, silicon deposits from the silicon-source gas onto exposed surfaces of the substrate and mask. The silicon that deposits onto the surface of the monocrystalline substrate follows the monocrystalline lattice structure at that site, whereas the silicon which precipitates onto the mask deposits in the form of isolated, non-single-crystalline aggregates.
The gas composition and duration of the etching phase is designed so as to completely remove all of the non-single-crystalline aggregates which were formed on the mask following the depositing phase. Although this etching also removes some of the monocrystalline silicon growing from the exposed area of the monocrystalline substrate, the etch rate of this monocrystalline silicon is relatively low compared to the etch rate of the non-single-crystalline aggregates. Thus, after a single depositing/etching cycle, more silicon is deposited on exposed silicon surfaces during the depositing phase than
The depositing/etching cycle can be performed within a conventional reactor at atmospheric or reduced pressure. During the depositing phase of the cycle, the substrate is exposed to a gas mixture which comprises a silicon-source gas such as SiH2Cl2 and a carrier gas such as hydrogen. Additionally, it may be desirable to include a silicon-etching gas such as HCl during the depositing phase. During the etching phase of the cycle, the substrate is exposed to a gas mixture comprising an etching gas such as HCl and a carrier gas such as hydrogen.
During the depositing phase, silicon deposits from the silicon-source gas onto exposed surfaces of the substrate and mask. The silicon that deposits onto the surface of the monocrystalline substrate follows the monocrystalline lattice structure at that site, whereas the silicon which precipitates onto the mask deposits in the form of isolated, non-single-crystalline aggregates.
The gas composition and duration of the etching phase is designed so as to completely remove all of the non-single-crystalline aggregates which were formed on the mask following the depositing phase. Although this etching also removes some of the monocrystalline silicon growing from the exposed area of the monocrystalline substrate, the etch rate of this monocrystalline silicon is relatively low compared to the etch rate of the non-single-crystalline aggregates. Thus, after a single depositing/etching cycle, more silicon is deposited on exposed silicon surfaces during the depositing phase than
-8- RCA 76,695 is etched during the etching phase, and all of the deposited material is monocrystalline in nature.
The monocrystalline silicon deposited by the ELO
process can also be simultaneously doped as it is ~eing deposited. For e~ample, in the deple-tion-type device 10, arsenic or some other N -type conduc-tivity modifer can be introduced during the depositing phase of the depositing/etching cycle. Additionally, when this is done, the dopant concentration can optionally be varied during the deposition so as to yield a conductivity gradient in the deposited layer. When fabricating the enhancement-type device 40, a P type dopant such as boron can be introduced during the initial phase of the depositing cycle so as to form the P type body regions 6~.
The P type dopant can then be replaced with an N type dopant after the epitaxial deposit has achieved a thickness approximately equal to that of the oxidized fingers 80. Thus, the depth of the N+ source region 22 in the depletion-type device 10, and the depth of the N-~
source region 52 in the enhancement-type device 40 can be readily varied during the ELO deposition process.
Alternatively, high-conductivity source regions 22 and 52 can be fabricated by a process such as ion implanation after the ELO layer is formed. Such an ion implanation might also be used to form high-conductivity drain regions 24 and 54.
In the case of both the depletion-type device 10 and the enhancement-type device 40, a contact opening through the epitaxial layer 84 can be made next so as to expose an area of heavily doped polycrystalline silicon 28 or 58 where the external gate electrode contact will be formed. External source, gate and drain electrode contacts 18, 32 and 20, or 48, 64 and 50 can then be formed in a conventional manner, such as evaporation, using a conventional electrode ma-terial, such as aluminum.
In addition to being a novel structure, devices of the present invention provide several advantages over `` conventional VDMOS and ~MOS devices. The source electrode ~2~
The monocrystalline silicon deposited by the ELO
process can also be simultaneously doped as it is ~eing deposited. For e~ample, in the deple-tion-type device 10, arsenic or some other N -type conduc-tivity modifer can be introduced during the depositing phase of the depositing/etching cycle. Additionally, when this is done, the dopant concentration can optionally be varied during the deposition so as to yield a conductivity gradient in the deposited layer. When fabricating the enhancement-type device 40, a P type dopant such as boron can be introduced during the initial phase of the depositing cycle so as to form the P type body regions 6~.
The P type dopant can then be replaced with an N type dopant after the epitaxial deposit has achieved a thickness approximately equal to that of the oxidized fingers 80. Thus, the depth of the N+ source region 22 in the depletion-type device 10, and the depth of the N-~
source region 52 in the enhancement-type device 40 can be readily varied during the ELO deposition process.
Alternatively, high-conductivity source regions 22 and 52 can be fabricated by a process such as ion implanation after the ELO layer is formed. Such an ion implanation might also be used to form high-conductivity drain regions 24 and 54.
In the case of both the depletion-type device 10 and the enhancement-type device 40, a contact opening through the epitaxial layer 84 can be made next so as to expose an area of heavily doped polycrystalline silicon 28 or 58 where the external gate electrode contact will be formed. External source, gate and drain electrode contacts 18, 32 and 20, or 48, 64 and 50 can then be formed in a conventional manner, such as evaporation, using a conventional electrode ma-terial, such as aluminum.
In addition to being a novel structure, devices of the present invention provide several advantages over `` conventional VDMOS and ~MOS devices. The source electrode ~2~
-9- RCA 76,695 contacts 18 and 48 are substantially planar structures.
In addition to providing greater contact area to the corresponding source regions 22 and 52, there planar ohmic contacts are rela-tively easy to fabricate. The large contact area between the source electrode contac-t and the source region also lowers the contact resistance at that interface.
The fabrication process for making the devices
In addition to providing greater contact area to the corresponding source regions 22 and 52, there planar ohmic contacts are rela-tively easy to fabricate. The large contact area between the source electrode contac-t and the source region also lowers the contact resistance at that interface.
The fabrication process for making the devices
10 and 40 is also relatively simple. Conventional VDMOS
and VMOS devices re~uire single or multiple ion implantations so as to define source and body regions.
These implantations are not re~uired in devices of the present invention. There is only a single critical photolithographic step in the fabrication sequence for devices of the present invention, i.e., the patterning of the gate electrode. In contrast, conventional devices require several critical photolithographic steps for fabricating both internal semiconductor regions and external electrode contacts. Furthermore, the need for an insulating layer between conventional multilevel source and gate electrode contacts on the semiconductor surface is eliminated by the source and gate electrode contact configuration described herein. Lastly, the structure and fabrication process described herein provide a readily manufacturable depletion device. The fabrication of conventional depletion-type devices requires etching deep grooves into the semiconductor and deep diffusions for doping the sides of these grooves. The present invention eliminates the need for deep etchings and diffusions, as well as the need for depositing electrode material on the walls of the semiconductor grooves.
and VMOS devices re~uire single or multiple ion implantations so as to define source and body regions.
These implantations are not re~uired in devices of the present invention. There is only a single critical photolithographic step in the fabrication sequence for devices of the present invention, i.e., the patterning of the gate electrode. In contrast, conventional devices require several critical photolithographic steps for fabricating both internal semiconductor regions and external electrode contacts. Furthermore, the need for an insulating layer between conventional multilevel source and gate electrode contacts on the semiconductor surface is eliminated by the source and gate electrode contact configuration described herein. Lastly, the structure and fabrication process described herein provide a readily manufacturable depletion device. The fabrication of conventional depletion-type devices requires etching deep grooves into the semiconductor and deep diffusions for doping the sides of these grooves. The present invention eliminates the need for deep etchings and diffusions, as well as the need for depositing electrode material on the walls of the semiconductor grooves.
Claims (11)
1. A vertical IGFET device, comprising:
a silicon wafer having first and second opposing major surfaces;
a source electrode disposed on the first surface;
a drain electrode disposed on the second surface;
an insulated gate electrode having a conductive finger-like portion surrounded by an insulating layer, said insulated gate electrode being internally disposed within the silicon wafer, such that a predetermined voltage applied to the insulated gate electrode will regulate a current flow between the source and drain electrodes.
a silicon wafer having first and second opposing major surfaces;
a source electrode disposed on the first surface;
a drain electrode disposed on the second surface;
an insulated gate electrode having a conductive finger-like portion surrounded by an insulating layer, said insulated gate electrode being internally disposed within the silicon wafer, such that a predetermined voltage applied to the insulated gate electrode will regulate a current flow between the source and drain electrodes.
2. A device in accordance with Claim 1, wherein the insulated gate electrode comprises a plurality of conductive finger-like portions.
3. A device in accordance with Claim 2, wherein said finger-like portions are disposed on a plane substantially parallel to the major wafer surfaces.
4. A device in accordance with Claim 2, wherein said finger-like portions are arranged in a ladder-shaped pattern.
5. A device in accordance with Claim 2, comprising a depletion-type device, wherein the silicon wafer is relatively lightly doped material of a first conductivity type and includes relatively heavily doped source and drain regions, of the first conductivity type, adjacent to the first and second major surfaces.
6. A device in accordance with Claim 1, wherein the conductive finger-like portion comprises doped polycrystalline silicon.
7. A device in accordance with Claim 1, wherein the insulating layer surrounding the conductive finger-like portion comprises silicon dioxide.
8. A device in accordance with Claim 1, comprising an enhancement-type device, wherein:
the silicon disposed between the finger-like portion and each of the major surfaces is of a first conductivity type, so as to form a source region at the first surface and a drain region at the second surface;
and the silicon disposed adjacent to the finger-like portion and between the source and drain regions is of a second conductivity type.
the silicon disposed between the finger-like portion and each of the major surfaces is of a first conductivity type, so as to form a source region at the first surface and a drain region at the second surface;
and the silicon disposed adjacent to the finger-like portion and between the source and drain regions is of a second conductivity type.
9. A method for fabricating a vertical IGFET
device, comprising:
providing a monocrystalline silicon substrate having first and second opposing major surfaces;
forming a first oxide layer across the first surface;
forming a pattern of doped polycrystalline silicon on the oxide layer;
forming a second oxide layer on all exposed portions of the polycrystalline silicon so as to form an insulated gate;
removing the first oxide layer from the first substrate surface in areas not covered by the insulated gate;
depositing epitaxial silicon on the first substrate surface and the insulated gate, and terminating said epitaxial deposition after a surface which is substantially parallel to the first surface is formed; and providing source, drain and gate electrodes in ohmic contact with the epitaxial silicon surface, the second substrate surface, and the polycrystalline silicon, respectively.
device, comprising:
providing a monocrystalline silicon substrate having first and second opposing major surfaces;
forming a first oxide layer across the first surface;
forming a pattern of doped polycrystalline silicon on the oxide layer;
forming a second oxide layer on all exposed portions of the polycrystalline silicon so as to form an insulated gate;
removing the first oxide layer from the first substrate surface in areas not covered by the insulated gate;
depositing epitaxial silicon on the first substrate surface and the insulated gate, and terminating said epitaxial deposition after a surface which is substantially parallel to the first surface is formed; and providing source, drain and gate electrodes in ohmic contact with the epitaxial silicon surface, the second substrate surface, and the polycrystalline silicon, respectively.
10. A method in accordance with Claim 9, further comprising:
doping the epitaxial silicon during the epitaxial silicon deposition.
doping the epitaxial silicon during the epitaxial silicon deposition.
11. A method in accordance with Claim 9, further comprising:
doping the epitaxial silicon and the substrate prior to providing the source, drain and gate electrodes.
doping the epitaxial silicon and the substrate prior to providing the source, drain and gate electrodes.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8218283 | 1982-06-24 | ||
GB8218283 | 1982-06-24 | ||
US06/439,563 US4546375A (en) | 1982-06-24 | 1982-11-05 | Vertical IGFET with internal gate and method for making same |
US439,563 | 1982-11-05 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1192669A true CA1192669A (en) | 1985-08-27 |
Family
ID=26283173
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000429823A Expired CA1192669A (en) | 1982-06-24 | 1983-06-07 | Vertical igfet with internal gate and method of making same |
Country Status (2)
Country | Link |
---|---|
CA (1) | CA1192669A (en) |
GB (1) | GB2122420B (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4546375A (en) * | 1982-06-24 | 1985-10-08 | Rca Corporation | Vertical IGFET with internal gate and method for making same |
FR2613537B1 (en) * | 1987-03-30 | 1990-03-09 | Pfister Jean Claude | PERMEABLE-BASED TRANSISTOR AND MANUFACTURING METHOD |
US5291050A (en) * | 1990-10-31 | 1994-03-01 | Fuji Electric Co., Ltd. | MOS device having reduced gate-to-drain capacitance |
US5183769A (en) * | 1991-05-06 | 1993-02-02 | Motorola, Inc. | Vertical current flow semiconductor device utilizing wafer bonding |
US5323040A (en) * | 1993-09-27 | 1994-06-21 | North Carolina State University At Raleigh | Silicon carbide field effect device |
US7927975B2 (en) | 2009-02-04 | 2011-04-19 | Micron Technology, Inc. | Semiconductor material manufacture |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2926741C2 (en) * | 1979-07-03 | 1982-09-09 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Field effect transistor and process for its manufacture |
-
1983
- 1983-06-07 CA CA000429823A patent/CA1192669A/en not_active Expired
- 1983-06-22 GB GB08316909A patent/GB2122420B/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
GB8316909D0 (en) | 1983-07-27 |
GB2122420B (en) | 1986-07-16 |
GB2122420A (en) | 1984-01-11 |
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