US3222216A - Process for affixing ohmic contacts to photoconductor elements - Google Patents

Process for affixing ohmic contacts to photoconductor elements Download PDF

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Publication number
US3222216A
US3222216A US199799A US19979962A US3222216A US 3222216 A US3222216 A US 3222216A US 199799 A US199799 A US 199799A US 19979962 A US19979962 A US 19979962A US 3222216 A US3222216 A US 3222216A
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photoconductor
electrodes
elements
affixing
ohmic
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US199799A
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English (en)
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Berkenblit Melvin
Cheroff George
Hochberg Frederick
Reisman Arnold
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International Business Machines Corp
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International Business Machines Corp
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Priority to US199799A priority Critical patent/US3222216A/en
Priority to JP2772163A priority patent/JPS4017411B1/ja
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/20—Electrodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass

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  • This invention relates to a process for afiixing ohmic contacts to photoconductor elements. More particularly, it relates to afiixing ohmic contacts to cadmium selenide photoconductor elements. Prior to this time ohmic contacts could not be reproducibly afiixed to sintered layer photoconductors.
  • the process of the invention produces an electroded sintered layer which exhibits a minimum of non-linear current-voltage behavior.
  • An object of the invention is to affix ohmic contacts to photoconductor elements.
  • Another object of the invention is to aflix silver paste electrodes to cadmium selenide photoconductor elements.
  • a further object of the invention is to remove the barrier layers formed during the sintering process prior to afiixing electrodes to the photoconductor element.
  • Still another object of the invention is to remove the cadmium oxide barrier layer prior to affixing the electrodes to the photoconductor elements with nitric acid.
  • a further object of the invention is the preparation of ohmic contacts of photoconductor elements so that re producible photoconductors can be prepared.
  • Another object of the invention is to enable scaling of electrode spacing.
  • Still another object of the invention is to increase the sensitivity of photoconductor elements to a lower value than is normally obtained by a given process.
  • An additional object of the invention is preparing the surface of a photoconductor for electrodes so that the electrodes thus aflixed are ohmic in nature.
  • FIGURE 1 shows oscilliscope curves of a current (I) vs. voltage (V) plot for cadmium selenide photoconductor elements illustrating behavior with ohmic and non-ohmic electrodes.
  • Curve A demonstrates the linear behavior 3,222,216 Patented Dec. 7, 1965 of a photoconductor element which has been subjected to the process of the invention and thus has electrodes which are ohmic in nature.
  • Curve B is that obtained for a photoconductor element which has non-ohmic electrodes (Le. has not been subjected to the process of the invention).
  • FIGURE 2 compares the distribution curves of reproducibility of cadmium selenide photoconductor elements prepared according to the process of the invention (Curve II) and those elements prepared without using the process of the invention (Curve 1). It is evident from inspection of FIGURE 2 that photoconductors prepared by the process of the invention have a lower average resistance and therefore a greater sensitivity and exhibit a much smaller absolute resistance spread than those not incorporating the process of the invention.
  • the phenomenon known as scaling is understood to mean that when an electrode separation is reduced to a fraction of its previous value, the light resistance of the element will be reduced by the same value.
  • a single parameter which aifects both of these properties markedly is the ohmicity of the photoconductor-electrode junction.
  • the photoconductor elements having electrodes afiixed thereto which are ohmic in nature are used in machine logic of computer mechanisms.
  • EXAMPLE 1 A sintered cadmium selenide activated photoconductor element containing parts per million of Cu is washed in triple distilled water until the Wash water fails to reveal any traces of cadmium chloride flux used in the sintering process. The photoconductor is then treated with a 0.7 N HNO solution for 30 minutes at room temperature and washed six times in triple distilled water. The photoconductor is then dried at C. in air for 10 minutes and cooled to room temperature. Silver paste electrodes are affixed by a standard silk screening process and these electrodes are dried in air at 165 C. for 2 hours. Electrical measurements of the finished electroded sintered layer show the linear current-voltage characteristics as depicted in curve A of FIGURE 1.
  • EXAMPLE 2 A sintered cadmium selenide activated photoconductor element containing approximately 100 parts per million of Cu is washed in triple distilled water until the wash fails to reveal any traces of cadmium chloride flux used in the sintering process. The photoconductor is then dried at 125 C. in air for 10 minutes and cooled to room temperature. Silver paste electrodes are aflixed by a silk screening process and these electrodes are dried at 165 C. for 2 hours in air. Electrical measurements of the finished electroded sintered layer photoconductor show non-linear current-voltage characteristics as shown in curve B of FIGURE 1.
  • Example 3 The process of Example 1 is repeated except that 3 N HNO is used for 10 minutes instead of 0.7 N HNO for 30 minutes. The results are identical to those of curve A of FIGURE 1 (i.e. linear).
  • EXAMPLE 4 The process of Example 1 is repeated except that 5 N HNO is used for 2 minutes instead of 0.7 N HNO for 30 minutes. The results are identical to curve A of FIGURE 1 (i.e. linear).
  • EXAMPLE 5 The process of Examples 1, 3 or 4 is repeated except that after the final distilled water rinsing the sintered photoconductors are dried in a vacuum desiccator for 2 hours at room temperature under a pressure of 13 mm. of Hg. The results are identical to those of curve A of FIGURE 1 (i.e. linear).
  • Photoconductors are prepared as in Example 2 with an electrode separation of 10 mils and an electrode length of 150 mils exhibit an average resistance in the light of 3 kilohms under a 1000 microwatt per square centimeter incident neon light source.
  • EXAMPLE 7 A set of 438 photoconductors are prepared which have a 30 mil electrode separation and 120 mils long according to Example 2. They exhibit a distribution of light resistance value shown in FIGURE 2, Curve I. Another set of 259 photoconductors having the same electrode geometry is prepared according to the process of Example 1. They exhibit a distribution of light resistance value shown in FIGURE 2, Curve II.
  • the process of the invention enables the preparation of photoconductors which exhibit linear current-voltage characteristics which are reproducible and which exhibit the phenomenon of electrical characteristic scaling.
  • this is accomplished by making the surface receptive to the affixing of contacts through treatment of processed (sintered) photoconductors in 0.7 N to 5 N HNO for 2 to 30 minutes at room temperature.
  • a process for preparing the surface layer of a cadmium selenide photoconductor element so that electrodes afiixed thereto define an ohmic contact between the surface of the electrode and the photoconductor element which comprises washing the photoconductor element with distilled Water to remove excess cadmium chloride flux used in said sintering process; treating the washed photoconductor element with nitric acid; washing the nitric acid treated photoconductor element with distilled water; and then drying the photoconductor element.
  • a process for electrically integrating electrodes to photoconductor elements which comprises treating the photoconductor element with nitric acid; affixing electrodes to the treated photoconductor element by a screening process to produce thereby photoconductor elements having electrodes which are ohmic in nature.
  • a process for affixing electrodes to cadmium selenide photoconductor elements which comprises treating the photoconductor element with nitric acid and afiixing silver paste electrodes to the treated photoconductor element by a screening process to produce thereby cadmium selenide photoconductor elements having silver paste electrodes which are ohmic in nature.
  • a process for atfixing electrodes to photoconductor elements which comprises washing the photoconductor element in distilled water until the wash water fails to reveal any traces of the flux used in the sintering process; treating the photoconductor element with 0.7 N to 5 N HNO solution for 2 to 30 minutes at room temperature; washing the thus treated photoconductor element in triple distilled water; drying the photoconductor element for 10 minutes at C. in air and cooling to room temperature; affixing electrodes by screening to the surface of the photoconductor element and drying this assembly in air at C. for 2 hours to produce thereby a photoconductor element having ohmic electrodes.
  • a process for afiixing silver paste electrodes to cadmium selenide photoconductor elements which comprises washing cadmium selenide photoconductor elements in triple distilled water until the wash water fails to reveal traces of cadmium chloride flux used in the sintering process; treating the photoconductor element with 0.7 N to 5 N HNO solution for 2 to 30 minutes at room temperature; washing the nitric acid treated photoconductor element with triple distilled water; drying the photoconductor element at 125 C. in air for 10 minutes and cooling to room temperature; afiixing silver paste electrodes by screening to the surface of the photoconductor element and drying this assembly in air at 165 C. for 2 hours to produce thereby a photoconductor element having an ohmic contact between the surface of the electrode and the photoconductor element.
  • a process for aflixing silver paste electrodes to a cadmium selenide photoconductor element which comprises:

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US199799A 1962-06-04 1962-06-04 Process for affixing ohmic contacts to photoconductor elements Expired - Lifetime US3222216A (en)

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US199799A US3222216A (en) 1962-06-04 1962-06-04 Process for affixing ohmic contacts to photoconductor elements
JP2772163A JPS4017411B1 (cs) 1962-06-04 1963-05-30

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4155155A (en) * 1977-01-19 1979-05-22 Alsthom-Atlantique Method of manufacturing power semiconductors with pressed contacts

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB556718A (en) * 1942-04-15 1943-10-19 William Julius Syplie Peschard Process for manufacturing soft impervious bodies, sheets and films such as edible bodies useful for imitation soft fruit and the like
US2784121A (en) * 1952-11-20 1957-03-05 Bell Telephone Labor Inc Method of fabricating semiconductor bodies for translating devices
CA563340A (en) * 1958-09-16 Western Electric Company, Incorporated Surface treatment of germanium circuit elements
US2879182A (en) * 1956-05-31 1959-03-24 Rauland Corp Photosensitive devices
CA573246A (en) * 1959-03-31 Radio Corporation Of America Sintered photoconducting layers
US2880119A (en) * 1956-10-01 1959-03-31 Dresser Ind Procedure for producing a photoconductive device
CA620009A (en) * 1961-05-09 Herczog Andrew Art of producing electroconductive films on a refractory ceramic base
US2999240A (en) * 1957-11-01 1961-09-05 Frederick H Nicoll Photovoltaic cells of sintered material

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA563340A (en) * 1958-09-16 Western Electric Company, Incorporated Surface treatment of germanium circuit elements
CA573246A (en) * 1959-03-31 Radio Corporation Of America Sintered photoconducting layers
CA620009A (en) * 1961-05-09 Herczog Andrew Art of producing electroconductive films on a refractory ceramic base
GB556718A (en) * 1942-04-15 1943-10-19 William Julius Syplie Peschard Process for manufacturing soft impervious bodies, sheets and films such as edible bodies useful for imitation soft fruit and the like
US2784121A (en) * 1952-11-20 1957-03-05 Bell Telephone Labor Inc Method of fabricating semiconductor bodies for translating devices
US2879182A (en) * 1956-05-31 1959-03-24 Rauland Corp Photosensitive devices
US2880119A (en) * 1956-10-01 1959-03-31 Dresser Ind Procedure for producing a photoconductive device
US2999240A (en) * 1957-11-01 1961-09-05 Frederick H Nicoll Photovoltaic cells of sintered material

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4155155A (en) * 1977-01-19 1979-05-22 Alsthom-Atlantique Method of manufacturing power semiconductors with pressed contacts

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JPS4017411B1 (cs) 1965-08-07

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