US3765962A - Method of making a charge storage device - Google Patents

Method of making a charge storage device Download PDF

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Publication number
US3765962A
US3765962A US00201551A US3765962DA US3765962A US 3765962 A US3765962 A US 3765962A US 00201551 A US00201551 A US 00201551A US 3765962D A US3765962D A US 3765962DA US 3765962 A US3765962 A US 3765962A
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United States
Prior art keywords
making
charge storage
storage device
target
diodes
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Expired - Lifetime
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US00201551A
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English (en)
Inventor
M Poleshuk
A Milch
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Philips North America LLC
US Philips Corp
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US Philips Corp
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    • H10P95/00—
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
    • H01L21/3063—Electrolytic etching
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10D—INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
    • H10D99/00—Subject matter not provided for in other groups of this subclass
    • H10P50/613—

Definitions

  • This invention relates to charge storage devices having a charge storage target scanned by a reading means and particularly concerns a target of the type comprising an array of diodes which are scanned by an electron beam.
  • Germanium vidicon camera tubes find application for image forming at long infrared wavelengths at which wavelengths the silicon vidicon camera tubes become ineffective.
  • a typical germanium vidicon camera tube target comprises a wafer of germanim material having an array of discrete photosensitive diodes comprising p-n junctions on the surface of the target facing the electron gun. It has been found that the most practical means of forming p-n junctions in the germanium wafer with characteristics desirable for vidicon camera tube operation has been by means of the indium alloy process.
  • the electron beam sweeps repetitively across the target surface and charges each diode up to cathode potential. Photoconduction and consequent discharge occurs at each of the p-n junctions in accordance with an infrared image projected onto the reverse surface of the target.
  • the recharging current constitutes the electrical signal output of the vidicon camera tube.
  • An insulating layer on the portions of the target between diodes prevents the electron beams from hitting the germanium wafer so that the so-called dark current is minimized.
  • the insulating layer is usually deposited in moats around each of the diodes for best performance.
  • One of the major problems of the prior art methods of forming the electron beam target surface for the vidicon camera tube is in forming an insulating layer in moats around each of the diodes without leaving insulating material on the diodes therealso and thereby degrade the electrical performance of the target.
  • Another problem of prior art configurations is the possibility of forming an incidental insulating coating, usually an oxide, on the indium metal remaining on top of the indium alloy diodes subsequent to their formation. In such cases, during operation of the vidicon camera tube a charge builds up on the insulating coatings which charge repels the electron beam away from the diode thereby degrading the performance of the camera tube.
  • One prior art method for making a vidicon camera tube employs a photolithographic process for the deposition of the insulating material into the moats around each of the diodes of the target.
  • a mask is prepared and placed on the beam target surface so that during the deposition of insulating material into the moats around each of the diodes, no insulating material settles on top of the diodes.
  • the removal of the insulating material which happens to settle on the diodes is accomplished by etching. The oxidation of the indium metal remaining on the diodes is not avoided by this method.
  • Another prior art method for making a vidicon camera tube involves simply depositing magnesium oxide over the entire beam target surface including all of the diodes and then removing the insulating material from the diodes by abrading the surface.
  • An alternate method used for exposing the diodes is to place pressure sensitive tape on the insulating layer on the target and then to remove the tape. Removal of the tape also carries away the insulating material lying on top of the diodes.
  • the present invention is particularly directed on an improved method of making a vidicon camera tube simply and economically with the resulting vidicon camera tube having electrical characteristics greatly improved over prior art vidicon camera tubes.
  • an array of alloy indium p-n junction diodes and moats around each of the diodes on a germanium wafer are formed by known procedures.
  • mercury is placed on the beam target surface so that the residual indium metal on each of the diodes forms a liquid amalgam therewith which dissolves in and is removed with the liquid mercury. Removal of the amalgam exposes each of the diode surfaces completely since both the deposited insulating material and the incidental insulating coatings are also swept away mechanically with the liquid mercuryand dissolved indium amalgam.
  • the exposed diode surface is germanium doped with indium metal and will not oxidize easily under ordinary conditions.
  • the resulting target is then incorporated into a vidicon camera tube by known methods.
  • an object of the present invention is to provide an improved method for making a charge de: vice having a charge storage target comprising an array of p-n junction diodes.
  • Another object of the present invention is to provide a method for making vidicon camera tube having an improved target comprising an array of p-n junction diodes.
  • Another object of the present invention is to provide an improved method for making a germanium vidicon camera tube.
  • the germanium vidicon camera tube 1 shown in FIG. 1 comprises an evacuated envelope 2 having a transparent faceplate 3 at one end with an adjacent germanium target 4.
  • Means for accelerating, focusing and deflecting the electron beam to cause it to scan target 4 are of well known form and are not shown for the sake of simplification.
  • the target 4 a portion of which is shown in greater detail in FIG. 5, comprises a plurality of diodes 7 having surfaces 18 and p-n junctions 8 formed, as later to be more fully described, on the surface of bulk germanium region 6.
  • the bulk germanium region 6 is biased by a potential, V,,, a few volts positive with respect to the cathode potential of electron gun 5.
  • the scanning electron beam impinges on each of the diode surfaces 18 and since each p-n junction 8 is reversed biased, the electrons accumulate on surfaces 18 until surfaces 18 reach cathode potential and repel the electron beam. In the absence of incident radiation, a good p-n junction 8 can retain most of its accumulated change a considerable time.
  • FIG. 2 shows typical alloy indium p-n junctions 8 formed by a known method in an n-type bulk germanium region 6 having a wafer shape.
  • One method for making p-n junctions 8 comprises the deposition of indium metal onto portion surface 15 through a mechanical mask.
  • the next steps are depositing a silicon oxide layer on surface 15 and the surface of insulating coating 12, alloying the indium metal into germanium region 6 through heating, and then removing the silicon oxide layer by etching with an HF and HNO; solution.
  • silicon oxide layer The function of silicon oxide layer is to keep the low-melting indium metal at each diode site during the heating process.
  • the indium metal 10 not used up in the doping of the p+ region 1 l and insulating coating 12 remain on top of the p+ region 11.
  • moats 13 are etched around each of the p+ regions 11 by a known method.
  • the target surface 15 is immersed in a 4 percent KOH solution and used as an anode with a germanium rod used as a cathode; the reverse side of the target 4 is illuminated during the etching process. It is preferable to permit undercutting 14 of indium metal 10 during this step.
  • a suitable material is deposited in the moats 13 to form an insulating layer 17 and incidentally on top of insulating coating 12 to form an insulating layer 16.
  • One of the commonly used methods for the deposition of insulating material which is suitable here employs the evaporation of silicon monoxide from a source at about 1000 C in a low pressure oxygen environment.
  • the insulating layers 16 and 17 comprise silicon dioxide for this case.
  • the target 4 is then immersed in liquid mercury at,
  • the mercury amalgamates with indium metal 10 whereupon merely shaking target 4 and lightly brushing the beam target surface is sufficient to remove the amalgam with both the insulating layer 16 and the insulating coating 12, thereby exposing each of the diode surfaces 18.
  • Germa nium is insoluble in mercury and at room temperatures mercury does not even wet germanium so that the mercury does not adversely affect the electrical properties of target 4.
  • FIG. 5 illustrates a section view of a finished target 4.
  • the invention is also useful for the manufacture of targets in which other metals such as tin, lead, bismuth, gold, thallium, silver, zinc, and gallium are used in combination with a germanium target which other metals also amalgamate with mercury.
  • the procedure for these other metals would not vary substantially from the procedure for indium metal.
  • the invention is suitable for targets in which silicon is substituted for germanium since silicon is also insoluble in mercury and is also not wet by mercury at room temperature.
  • a method of making a charge storage device comprising the steps of providing a semiconductor wafer, forming an array of alloy p-n junction diodes on a major surface of said wafer with a metal which amalgamates with mercury, depositing an insulating material on said major surface and said alloy p-n junction diodes, and removing a residual portion of said metal from the top of at least one of said diodes using liquid mercury whereby a portion of the insulating layer on top of the diode is also removed.
  • a method of making a charge storage device further comprising the step of forming moats around each of said diodes and depositing said insulating material in said moats.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Light Receiving Elements (AREA)
  • Formation Of Insulating Films (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US00201551A 1971-11-23 1971-11-23 Method of making a charge storage device Expired - Lifetime US3765962A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US20155171A 1971-11-23 1971-11-23

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US3765962A true US3765962A (en) 1973-10-16

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US (1) US3765962A (enExample)
CA (1) CA966590A (enExample)
DE (1) DE2256763C3 (enExample)
FR (1) FR2160956B1 (enExample)
GB (1) GB1407438A (enExample)
IT (1) IT975786B (enExample)
NL (1) NL158651B (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4096511A (en) * 1971-11-29 1978-06-20 Philip Gurnell Photocathodes

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2823148A (en) * 1953-03-02 1958-02-11 Rca Corp Method for removing portions of semiconductor device electrodes
US3011089A (en) * 1958-04-16 1961-11-28 Bell Telephone Labor Inc Solid state light sensitive storage device
US3419746A (en) * 1967-05-25 1968-12-31 Bell Telephone Labor Inc Light sensitive storage device including diode array
US3548233A (en) * 1968-11-29 1970-12-15 Rca Corp Charge storage device with pn junction diode array target having semiconductor contact pads
US3687745A (en) * 1971-03-15 1972-08-29 Bell Telephone Labor Inc Light-sensitive storage device including diode array and method for producing the array

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1515869A (fr) * 1966-06-21 1968-03-08 Electronique & Physique Procédé de réalisation de mosaïques de diodes

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2823148A (en) * 1953-03-02 1958-02-11 Rca Corp Method for removing portions of semiconductor device electrodes
US3011089A (en) * 1958-04-16 1961-11-28 Bell Telephone Labor Inc Solid state light sensitive storage device
US3419746A (en) * 1967-05-25 1968-12-31 Bell Telephone Labor Inc Light sensitive storage device including diode array
US3548233A (en) * 1968-11-29 1970-12-15 Rca Corp Charge storage device with pn junction diode array target having semiconductor contact pads
US3687745A (en) * 1971-03-15 1972-08-29 Bell Telephone Labor Inc Light-sensitive storage device including diode array and method for producing the array

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4096511A (en) * 1971-11-29 1978-06-20 Philip Gurnell Photocathodes

Also Published As

Publication number Publication date
DE2256763B2 (de) 1979-02-15
FR2160956B1 (enExample) 1977-08-26
FR2160956A1 (enExample) 1973-07-06
IT975786B (it) 1974-08-10
NL7215650A (enExample) 1973-05-25
DE2256763A1 (de) 1973-05-30
CA966590A (en) 1975-04-22
NL158651B (nl) 1978-11-15
GB1407438A (en) 1975-09-24
DE2256763C3 (de) 1979-10-11

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