United States Patent 3,545,076
December 8, 1970

Process of Forming Contacts on Electrical Parts, Particularly Silicon Semiconductors
Reinhard Schulten

Filed August 22, 1967
Image of US PATENT 3,545,076

Abstract of the Disclosure

 Contacts of defined configuration are formed on an electrical part which essentially consists of silicon and has a top surface of silicon dioxide by a combination of the following steps:
 (a) A photolacquer coating is applied to the part above the silicon dioxide layer;
 (b) The intended contact areas are covered;
 (c) The photolacquer coating is exposed and subsequently subjected to the action of a photographic developer, thereby dissolving the unexposed portions of the photolacquer and baring the silicon dioxide layer and the said contact areas;
 (d) The surface of said part is etched with an etching agent suited to remove the bared silicon dioxide portions while leaving the developed portions of the photolacquer portion in contact;
 (e) The remaining developed portions of the photolacquer coating are dissolving with the photolacqued solvent;
 (f) A layer of a silicide forming metal is applied over all of the surface of the said part;
 (g) The metal layer is subjected to a modifying treatment by tempering so as to partially embed it in and alloy it with the silicon in the surface of the said electrical part, thereby forming an acid insoluble silicide at said contact area; and
 (h) The metal layer is then removed from the remaining unmodified portions of the silicon dioxide layer by treatment with a solvent for metal.
 The process is particularly applicable to a silicon semiconductor where the metal applied is a nickel layer.
 Preferably another nickel layer is applied on top of the tempered nickel layer to form the contacts proper of the semiconductor.
Figure descriptions: cover graphic

  • Figure 1 shows the silicon wafer after application of the silicon dioxide coating, the photoresist coating and the photomask.
  • Figure 2 shows the wafer after treatment with the photographic developer.
  • Figure 3 shows the wafer after treatment with the etching solution.
  • Figure 4 shows the wafer after treatment with hot sulfuric acid.
  • Figure 5 shows the wafer after application of the nickel deposit.
  • Figure 6 shows the wafer after tempering and subsequent acid treatment.

 Citations [54]:
3,274,670 09/1966 Cepselter 3,281,915 11/1966 Schramm 3,328,216 06/1967 Brown et al. 3,362,851 01/1968 Dunster
National Museum of American History
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