US3216084A - Semiconductor process control technique - Google Patents

Semiconductor process control technique Download PDF

Info

Publication number
US3216084A
US3216084A US271867A US27186763A US3216084A US 3216084 A US3216084 A US 3216084A US 271867 A US271867 A US 271867A US 27186763 A US27186763 A US 27186763A US 3216084 A US3216084 A US 3216084A
Authority
US
United States
Prior art keywords
molecular sieve
devices
ratio
moisture
level
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 - Lifetime
Application number
US271867A
Inventor
Steward S Flaschen
Preston J Heinle
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motorola Solutions Inc
Original Assignee
Motorola Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Motorola Inc filed Critical Motorola Inc
Priority to US271867A priority Critical patent/US3216084A/en
Priority to GB11015/64A priority patent/GB1060541A/en
Priority to NL6402955A priority patent/NL6402955A/xx
Priority to FR968283A priority patent/FR1389848A/en
Priority to CH409764A priority patent/CH422999A/en
Priority to DEN24762A priority patent/DE1283968B/en
Application granted granted Critical
Publication of US3216084A publication Critical patent/US3216084A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/16—Fillings or auxiliary members in containers or encapsulations, e.g. centering rings
    • H01L23/18—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device
    • H01L23/26—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device including materials for absorbing or reacting with moisture or other undesired substances, e.g. getters
    • 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

Definitions

  • This invention relates to semiconductor devices and particularly to a method of adjusting certain specifications of transistors by controlling the nature of the ambient atmosphere in which they are sealed.
  • an object of the present invention is to provide a method of adjusting transistor characteristics that is inexpensive, easy and rapidly accomplished.
  • the invention features encapsulating the transistors with varying mixtures of drying agents and moistening agents to that the moisture level of the ambient atmosphere is maintained at appropiate levels according to the distribution of transistor characterisitics desired.
  • This invention permits shifting of important device parameters such as current gain, saturation currents or storage time at will within rather broad limits determined by device design and previous process variables. This is accomplished by controlling the moisture level within the ambient atmosphere.
  • controlled ambient atmospheres is well-known to the semiconductor industry to stabilize and optimize transistor parameters but such systems in the past have provided a rigidly controlled moisture level whereas the present invention provides any desired useful moisture level, and changes from one level to another may be easily carried out.
  • the invention provides for adjusting the moisture level by adjusting the ratio of a reversible adsorbent such as molecular sieve in combination with varying amounts either of drying agents such as barium oxide (BaO) or moistening agents such as calcium sulfate hemihydrate (CaSO /zI-I O) and encapsulating these powders so formed with the transistors.
  • a reversible adsorbent such as molecular sieve in combination with varying amounts either of drying agents such as barium oxide (BaO) or moistening agents such as calcium sulfate hemihydrate (CaSO /zI-I O) and encapsulating these powders so formed with the transistors.
  • the reversible adsorbent is prepared in any convenient manner. For example, it is convenient to store opened containers of molecular sieve powder in ovens at or near 200 C. After cooling in a dry atmosphere, the adsorbent is mixed with drying or moistening agents in the desired ratio.
  • the drier will be the ambient atmosphere.
  • drier ambient atmospheres result in lower current and power gains, higher saturation currents, and lower storage times in switching applications.
  • a ratio is selected which will provide relatively more moistening agent than would be used with the adsorbent if lower current gains were de sired.
  • a dry atmosphere is obtained for this purpose by using adsorbent and drying agent together.
  • Other characteristics, such as breakdown voltages, are not so strongly affected by the moisture level, though some difference may appear.
  • the purpose of the moistening or drying agents is primarily to vary the amount of moisture contained in the reversible adsorbent. It is postulated that this amount of moisture determines the water vapor content of the encapsulated atmosphere in equilibrium with the powder in the encapsulation, which in turn affects the device parameters.
  • the moisture content of the adsorbent may be controlled at any preselected level, so that a continuous spectrum of controlled ambient materials is available.
  • the powder is applied as one of the last steps in device production. If a need develops for more devices within a given range of parameters, a change in ratio may be used to shift the parameter distribution and thus provide the needed devices. All the devices, however, contain the same materials; they are merely present in different ratios. Possibly "because the powders contain the same materials, the devices, unles sther parameters are widely different, have about the same aging characteristics at temperatures as high as 125 C.
  • a power transistor In normal production, industrial power transistors are electrolytically etched after assembly. After etching, rinsing and drying, they are stored in hot ovens until just before canning (encapsulation). The canning operation is performed on a large welding press. The cup-like can or lid for the transistor is placed in the lower electrode of the welder and a charge of the ambient atmosphere controlling materials is dispensed into it. The partial transistor assembly is then completed by placing it on the can, and the can is then welded to it.
  • Two alternate methods of dispensing the powder are used.
  • a charge of hot (and therefore dry) molecular sieve is dispensed into the can.
  • a charge of cold calcium sulfate hemihydrate (CaSO /2H O) is dispensed into the can.
  • the ratio between the two components is determined by controlling the sizes of the respective charges.
  • the components are premixed in the proper ratio and placed in the dispenser. No heating need be used, but the chamber of the dispenser containing the mixture is flushed with a slow stream of dry, clean gas such as nitrogen or air to keep the powder from absorbing excess moisture.
  • the appropriate volume of powder is dispensed into the can.
  • the second or preferred method provides better ratio control, more uniform'composition of powder, and it is easier to change from one ratio to another.
  • the application of calcium sulfate hemihydrate-molecular sieve to a product line of industrial power transistors gave results as follows.
  • the ratios used were (a) molecular sieve, (b) 0.5 part calcium sulfate hemihydrate to 1 part molecular sieve, (c) 3.5 parts calcium sulfate hemihydrate to 1 part molecular sieve and (d) 5.0 parts calcium sulfate hemidydrate to 1 part molecular sieve.
  • the parameter measured was 1 with 10 amps collector current (1 and 2 volts collector voltage, as a measure of the DC.
  • cur-rent gain h since they are related by Specifications for the device required an k to be within the limits to 30 which corresponds toamaximurn I of 1000 milliamps and a minimum of 333 milliamps.
  • Groups of ten transistors were canned each day for five consecutive days using each of the four listed-compositions giving a total of fifty devices for each composition or treatment.
  • the median values of 1 to reach group were as follows:
  • Group Ratio Thus, if one wishes to produce from a single lot of transistors, a certain percentage of the production having levels of k higher than those produced by using barium oxide (BaO) alone, but lower than those produced by the use of the molecular sieve alone, one would employ the group 3 or group 4 material (having a ratio of, 50:50 or 25:75 BaOzmolecular sieve). The relative level of the parameter h therefore, can be preselected by the selection of the proper ratio of the two materials.
  • BaO barium oxide
  • the invention is not limited to just one or a few types of transistors'but operate on a great variety of device's 4 v using radically dissimilar technologies. It is an inexpensive non-critical process which is easy to apply where ever transistors are to be encapsulated in an ambient atmosphere.
  • a method of controlling the electrical paraments of hermetically sealed semiconductor devices by establishing a desired level of gaseous moisture in the atmosphere within the devices including the steps of, mixing a reversible adsorbent material and a chemically reactive moisture controlling material in a predetermined ratio to provide a mixture capable of establishing a preselcted moisture level in said devices when sealed, placing said mixture in said devices, and sealing said devices.
  • a method of controlling the electrical parameters of hermetically sealed semiconductor devices by establishing a desired level of gaseous moisture in the atmosphere within the devices including the steps of placing in said devices a mixture, comprised of a predetermined ratio of a reversible adsorbent material and a chemically active moisture controlling material capable of adjusting the moisture level in saiddevices when sealed to a level which establishes the electrical parameters of the devices at the desired values, and sealing said devices with said mixture therein.
  • the method of establishing a particular moisture level within an encapsulated semiconductor device including the steps of, mixing a reversible adsorbent material and a moistening agent in a predetermined ratio to provide the particular moisture level, placing said mixture within said device, and sealing said device.
  • the method of establishing a particular moisture level within an encapsulated semiconductor device including the steps. of, mixing molecular sieve with calcium sulfate hemihydrate (CaSO /2H OD in a predetermined ratio to provide the particular moisture level, placing said mixture within said device, and sealing said device.

Landscapes

  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Drying Of Gases (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Description

United States Patent Office Patented Nov. 9, 1965 3,216,084 SEMICONDUCTOR PROCESS CONTROL TECHNIQUE Steward S. Flaschen and Preston J. Heinle, Phoenix, Ariz.,
assignors to Motorola, Inc., Chicago, 111., a corporation of Illinois No Drawing. Filed Apr. 10, 1963, Ser. No. 271,867
6 Claims. (Cl. 2925.3)
This invention relates to semiconductor devices and particularly to a method of adjusting certain specifications of transistors by controlling the nature of the ambient atmosphere in which they are sealed.
In the manufacture of transistors it is often desirable to adjust certain of the device characteristics to meet the specified needs of particular customers as well as to maintain the distribution of certain types of devices within the limits of their specifications. Such adjustments are usually made by using semiconductor material of different characterisitics, adjusting geometric factors such as the base width of the device, or by altering major processing operations such as etching operations. These methods are troublesome, expensive and often rather slow since the feedback of information to optimize the processing adjustments may take from several hours to several days.
Accordingly, an object of the present invention is to provide a method of adjusting transistor characteristics that is inexpensive, easy and rapidly accomplished.
The invention features encapsulating the transistors with varying mixtures of drying agents and moistening agents to that the moisture level of the ambient atmosphere is maintained at appropiate levels according to the distribution of transistor characterisitics desired.
This invention permits shifting of important device parameters such as current gain, saturation currents or storage time at will within rather broad limits determined by device design and previous process variables. This is accomplished by controlling the moisture level within the ambient atmosphere. The use of controlled ambient atmospheres is well-known to the semiconductor industry to stabilize and optimize transistor parameters but such systems in the past have provided a rigidly controlled moisture level whereas the present invention provides any desired useful moisture level, and changes from one level to another may be easily carried out.
The invention provides for adjusting the moisture level by adjusting the ratio of a reversible adsorbent such as molecular sieve in combination with varying amounts either of drying agents such as barium oxide (BaO) or moistening agents such as calcium sulfate hemihydrate (CaSO /zI-I O) and encapsulating these powders so formed with the transistors. The reversible adsorbent is prepared in any convenient manner. For example, it is convenient to store opened containers of molecular sieve powder in ovens at or near 200 C. After cooling in a dry atmosphere, the adsorbent is mixed with drying or moistening agents in the desired ratio. The ratio used determines the average value of the desired device parameter which will be obtained. The greater the proportion of drying agent, the drier will be the ambient atmosphere. As a general rule, in PNP germanium transistors, drier ambient atmospheres result in lower current and power gains, higher saturation currents, and lower storage times in switching applications. Thus, if high current gain is desired, a ratio is selected which will provide relatively more moistening agent than would be used with the adsorbent if lower current gains were de sired. Or, if a lower storage time is desired, a dry atmosphere is obtained for this purpose by using adsorbent and drying agent together. Other characteristics, such as breakdown voltages, are not so strongly affected by the moisture level, though some difference may appear.
The purpose of the moistening or drying agents is primarily to vary the amount of moisture contained in the reversible adsorbent. It is postulated that this amount of moisture determines the water vapor content of the encapsulated atmosphere in equilibrium with the powder in the encapsulation, which in turn affects the device parameters.
The advantages of this invention are:
(1) The moisture content of the adsorbent may be controlled at any preselected level, so that a continuous spectrum of controlled ambient materials is available.
(2) The powder is applied as one of the last steps in device production. If a need develops for more devices within a given range of parameters, a change in ratio may be used to shift the parameter distribution and thus provide the needed devices. All the devices, however, contain the same materials; they are merely present in different ratios. Possibly "because the powders contain the same materials, the devices, unles sther parameters are widely different, have about the same aging characteristics at temperatures as high as 125 C.
. (3) The use of a good adsorbent, particularly molecular sieve, represents an attractive aspect in relation to reliability. While many adsorbents react only or primarily with water, molecular sieve, for example, can adsorb many other molecular and ionic species which may be present and may tend to degrade the device.
The manner of application of this process to a typical device, a power transistor, is as follows: In normal production, industrial power transistors are electrolytically etched after assembly. After etching, rinsing and drying, they are stored in hot ovens until just before canning (encapsulation). The canning operation is performed on a large welding press. The cup-like can or lid for the transistor is placed in the lower electrode of the welder and a charge of the ambient atmosphere controlling materials is dispensed into it. The partial transistor assembly is then completed by placing it on the can, and the can is then welded to it.
Two alternate methods of dispensing the powder are used. In the first method, a charge of hot (and therefore dry) molecular sieve is dispensed into the can. Then a charge of cold calcium sulfate hemihydrate (CaSO /2H O) is dispensed into the can. The ratio between the two components is determined by controlling the sizes of the respective charges. In the second method, which is preferred, the components are premixed in the proper ratio and placed in the dispenser. No heating need be used, but the chamber of the dispenser containing the mixture is flushed with a slow stream of dry, clean gas such as nitrogen or air to keep the powder from absorbing excess moisture. The appropriate volume of powder is dispensed into the can.
The second or preferred method provides better ratio control, more uniform'composition of powder, and it is easier to change from one ratio to another.
The application of calcium sulfate hemihydrate-molecular sieve to a product line of industrial power transistors gave results as follows. The ratios used were (a) molecular sieve, (b) 0.5 part calcium sulfate hemihydrate to 1 part molecular sieve, (c) 3.5 parts calcium sulfate hemihydrate to 1 part molecular sieve and (d) 5.0 parts calcium sulfate hemidydrate to 1 part molecular sieve. The parameter measured was 1 with 10 amps collector current (1 and 2 volts collector voltage, as a measure of the DC. cur-rent gain h since they are related by Specifications for the device required an k to be within the limits to 30 which corresponds toamaximurn I of 1000 milliamps and a minimum of 333 milliamps. Groups of ten transistors were canned each day for five consecutive days using each of the four listed-compositions giving a total of fifty devices for each composition or treatment. The median values of 1 to reach group were as follows:
An analysis of variance shows with 99% confidence that groups (c) and (d) are not significantly different from each other and that groups (a) and (b) are dilferent from each other and from groups (c) and (d). Thus, in order to produce a maximum number of high h units (low 1 a ratio of 3.5:1 or 5.0:1 should be used. If treatment (a) were used, about a third could be expected to be outside specification for low gain while on the other hand powder (c) or ((1) would yield essentially 100% good units for this parameter.
Other parameters were also affected but usually to a lesser extent. Diiferences between averages for breakdown voltages as measured from collector-to-base and emitter-to-base were not significant. The colector or emit ter reverse currents varied with I but the difference was generally less noticeable than the differences in I If still drier ambients than those produced by the molecular sieve alone are desired, to establish lower h values (higher I a mixture of the molecular sieve and a dehydrating material such as barium oxide (BaO), in the proper ratio, can be used within the device enclosure. The system 'barium oxide (BaO)-molecular sieve was applied to a germanium mesa production line. Sixteen units were canned in each of five groups listed below, and the median values h were calculated.
Group Ratio Thus, if one wishes to produce from a single lot of transistors, a certain percentage of the production having levels of k higher than those produced by using barium oxide (BaO) alone, but lower than those produced by the use of the molecular sieve alone, one would employ the group 3 or group 4 material (having a ratio of, 50:50 or 25:75 BaOzmolecular sieve). The relative level of the parameter h therefore, can be preselected by the selection of the proper ratio of the two materials.
The invention is not limited to just one or a few types of transistors'but operate on a great variety of device's 4 v using radically dissimilar technologies. It is an inexpensive non-critical process which is easy to apply where ever transistors are to be encapsulated in an ambient atmosphere.
We claim:
1. A method of controlling the electrical paraments of hermetically sealed semiconductor devices by establishing a desired level of gaseous moisture in the atmosphere within the devices, said method including the steps of, mixing a reversible adsorbent material and a chemically reactive moisture controlling material in a predetermined ratio to provide a mixture capable of establishing a preselcted moisture level in said devices when sealed, placing said mixture in said devices, and sealing said devices.
2. A method of controlling the electrical parameters of hermetically sealed semiconductor devices by establishing a desired level of gaseous moisture in the atmosphere within the devices, said method including the steps of placing in said devices a mixture, comprised of a predetermined ratio of a reversible adsorbent material and a chemically active moisture controlling material capable of adjusting the moisture level in saiddevices when sealed to a level which establishes the electrical parameters of the devices at the desired values, and sealing said devices with said mixture therein. Y
3. The method of establishing a particular moistur level within an encapsulated semiconductor device, said method including the steps .of, mixing a reversible adsorbent material with a drying agent in a predetermined ratio to provide the particular moisture level, placing said mixture within said device, and sealing said device.
4. The method of establishing a particular moisture level within an encapsulated semiconductor device, said method including the steps of, mixing a reversible adsorbent material and a moistening agent in a predetermined ratio to provide the particular moisture level, placing said mixture within said device, and sealing said device.
5. The method of establishing a particular moisture level within an encapsulated semiconductor device, said method including the steps. of, mixing molecular sieve with calcium sulfate hemihydrate (CaSO /2H OD in a predetermined ratio to provide the particular moisture level, placing said mixture within said device, and sealing said device.
6. The method of establishing a particular moisture .level within an encapsulated semiconductor device, said method including the steps of, mixing molecular sieve with barium oxide (BaO) in a predetermined ratio to provide the particular moisture level, placing said mixture within said device, and sealing said device.
References Cited by the Examiner UNITED STATES PATENTS RICHARD H. EANES, JR., Printary Examiner.

Claims (1)

  1. 3. THE METHOD OF ESTABLISHING A PARTICULAR MOISTURE LEVEL WITHIN AN ENCAPSULATED SEMICONDUCTOR DEVICE, SAID METHOD INCLUDING THE STEPS OF, MIXING A REVERSIBLE ADSORBENT MATERIAL WITH A DRYING AGENT IN A PREDETERMINED RATIO TO PROVIDE THE PARTICULAR MOISTURE LEVEL, PLACING SAID MIXTURE WITHIN SAID DEVICE, AND SEALING SAID DEVICE
US271867A 1963-04-10 1963-04-10 Semiconductor process control technique Expired - Lifetime US3216084A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US271867A US3216084A (en) 1963-04-10 1963-04-10 Semiconductor process control technique
GB11015/64A GB1060541A (en) 1963-04-10 1964-03-16 Semiconductor process control technique
NL6402955A NL6402955A (en) 1963-04-10 1964-03-19
FR968283A FR1389848A (en) 1963-04-10 1964-03-23 Method of controlling the ambient atomosphere in sealed envelopes of semiconductor devices
CH409764A CH422999A (en) 1963-04-10 1964-03-31 Method for establishing a determined degree of humidity of the atmosphere prevailing in an enclosure containing a semiconductor device
DEN24762A DE1283968B (en) 1963-04-10 1964-04-09 Method for stabilizing semiconductor components

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US271867A US3216084A (en) 1963-04-10 1963-04-10 Semiconductor process control technique

Publications (1)

Publication Number Publication Date
US3216084A true US3216084A (en) 1965-11-09

Family

ID=23037425

Family Applications (1)

Application Number Title Priority Date Filing Date
US271867A Expired - Lifetime US3216084A (en) 1963-04-10 1963-04-10 Semiconductor process control technique

Country Status (5)

Country Link
US (1) US3216084A (en)
CH (1) CH422999A (en)
DE (1) DE1283968B (en)
GB (1) GB1060541A (en)
NL (1) NL6402955A (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1785975A (en) * 1926-07-27 1930-12-23 Leland A Phillips Humidor for inked ribbons
US2341310A (en) * 1941-07-01 1944-02-08 Remington Arms Co Inc Ammunition
US2807514A (en) * 1955-03-01 1957-09-24 Williams David John Humidor package
US2960639A (en) * 1958-07-02 1960-11-15 English Electric Valve Co Ltd Semi-conductor rectifier assemblies
US2998554A (en) * 1957-04-05 1961-08-29 Philips Corp Semi-conductor barrier layer system
US2998556A (en) * 1958-03-04 1961-08-29 Philips Corp Semi-conductor device
US3056074A (en) * 1960-11-03 1962-09-25 Philco Corp Miniature desiccator and production of units thereof

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE538791A (en) * 1951-06-08 1900-01-01

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1785975A (en) * 1926-07-27 1930-12-23 Leland A Phillips Humidor for inked ribbons
US2341310A (en) * 1941-07-01 1944-02-08 Remington Arms Co Inc Ammunition
US2807514A (en) * 1955-03-01 1957-09-24 Williams David John Humidor package
US2998554A (en) * 1957-04-05 1961-08-29 Philips Corp Semi-conductor barrier layer system
US2998556A (en) * 1958-03-04 1961-08-29 Philips Corp Semi-conductor device
US2960639A (en) * 1958-07-02 1960-11-15 English Electric Valve Co Ltd Semi-conductor rectifier assemblies
US3056074A (en) * 1960-11-03 1962-09-25 Philco Corp Miniature desiccator and production of units thereof

Also Published As

Publication number Publication date
DE1283968B (en) 1968-11-28
NL6402955A (en) 1964-10-12
GB1060541A (en) 1967-03-08
CH422999A (en) 1966-10-31

Similar Documents

Publication Publication Date Title
KR940004800A (en) Semiconductor memory device and manufacturing method thereof
FR2334201A1 (en) Non reversible semiconductor switching element - consists of resistance of polycrystalline silicon with high specific resistance
US3216084A (en) Semiconductor process control technique
US3748520A (en) Electric discharge lamp having a fill including niobium pentaiodide complexed with an inorganic oxo-compound as the primary active component
GB1403087A (en) High voltage current limiting fuse
US3953375A (en) Non-linear voltage titanium oxide resistance element
US2989424A (en) Method of providing an oxide protective coating for semiconductors
Lecomte et al. Non‐stoichiometry and electrical conductivity of strontium niobates with perovskite structure
Takamasu et al. Effect of finite electric field on the quantum Hall effect
Jones et al. Clustering in ternary III–V semiconductors
US2018815A (en) Liberation of alkali metals
US3571669A (en) Current controlling device utilizing sulphur and a transition metal
US3571671A (en) Switching device including boron and rare earth metal
Schock et al. Electrical Conductivity of AgI to 100 kbar
US2291864A (en) Electric discharge device
US3395445A (en) Method of making solid state relay devices from tellurides
US3241217A (en) Desiccation of electronic enclosures using boron nitride hot sealing method
Rogers et al. The electrical properties and band structure of doped LaInO3
US3713898A (en) PROCESS FOR PREPARING HIGH-TRANSITION-TEMPERATURE SUPERCONDUCTORS IN THE Nb-Al-Ge SYSTEM
Porowski et al. On the existence of two non-equivalent lattice positions of donors in n-type InSb
US3071708A (en) Electroluminescent screen
Arijs et al. The influence of surface donor states on the chemisorption kinetics of oxygen at the surface of ZnO single crystals. II. Experimental results
Vanselow Field electron emission from an aluminum oxide covered tungsten {112} plane at temperatures up to 1700° K
US3092733A (en) Four zone transistor having integral diode formed on base remote from transistor
JPH01294560A (en) Production of compound oxide superconducting material