Method and apparatus for making ohmic and/or Schottky barrier contacts to semiconductor substrates

• US 4,545,115 A
• Filed: 12/23/1983
• Issued: 10/08/1985
• Est. Priority Date: 02/19/1980
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Garben, Bernd, Bauer, Hans J.
• Primary Examiner(s): Hearn, Brian E.
• Assistant Examiner(s): Auyang, Hunter L.
• Application Number:
  US06/565,080
• Time in Patent Office: 655 Days
• Field of Search: 29/590, 148/174, 204/192 C, 427/84, 427/88, 427/91, 427/93, 427/250
• US Class Current: 438/570
• CPC Class Codes: B64D 25/14 Inflatable escape chutes
• CPC Class Codes: C23C 14/56 Apparatus specially adapted for continuous coating; Arrangements for maintaining the vacuum, e.g. vacuum locks
• CPC Class Codes: Y10S 148/019 Contacts of silicides
• CPC Class Codes: Y10S 148/022 Controlled atmosphere
• CPC Class Codes: Y10S 148/158 Sputtering

Abstract

Disclosed is a method of making ohmic and/or Schottky barrier contacts to a silicon semiconductor substrate in which before depositing the metal on silicon semiconductor substrates containing integrated circuits which are covered by a mask having contact windows, the metal is initially deposited on freshly cleaned blank silicon semiconductor substrates mounted in the same vacuum chamber. In this manner any traces of oxygen present in the vacuum chamber are chemisorbed by the blank substrate resulting in deposition of a high quality oxide-free metal contacts on the device substrates.

The disclosed apparatus comprises a deposition chamber maintained at a predetermined low pressure, a substrate holder carrying a plurality of blank silicon substrates and silicon substrates containing integrated circuit structures covered by a mask having contact windows, a source of metal placed in the chamber for evaporation or sputtering and a shutter arranged in close proximity with said substrate holder for shielding selected substrates during the initial stages of metal deposition.

Claims

1. A low temperature method for fabricating a silicon dioxide-free conductive contact on a semiconductor substrate having integrated circuit devices thereon, said method comprising:

(a) placing a semiconductor substrate having integrated circuit devices (device substrate) and atleast one clean, blank silicon substrate in a deposition chamber maintained at a predetermined low pressure;

(b) heating said substrates to a low temperature in the range of 330°

C. to 550°

C.;

(c) shielding said device substrate by means of a shutter arranged in close proximity to said device substrate;

(d) depositing a conductive metal on said atleast one blank substrate at said low temperature and pressure for a short period of time to remove any trace of oxygen in said chamber by chemisorption of said oxygen by said atleast one blank substrate and thereby establishing an oxygen-free environment in said chamber;

(e) unshielding said device substrate by opening said shutter; and

(f) depositing on atleast a selected portion of said device substrate said conductive metal at said low temperature and pressure in said oxygen-free environment, whereby is formed on said atleast a selected portion of said device substrate a conductive metal contact free of an oxide layer.

2. The method as recited in claim 1 wherein said metal is selected from the group consisting of platinum, palladium, nickel, rhodium, zirconium, hafnium, aluminum, tantalum, titanium, tungsten and titanium-tungsten.

3. The method as recited in claim 2 wherein said device substrate exhibits N^- type conductivity and said contact is a Schottky barrier diode contact.

4. The method as recited in claim 2 wherein said contact is an ohmic contact.

5. The method as recited in claim 2 wherein said deposition steps are accomplished by E-beam evaporation.

6. The method as recited in claim 2 wherein said deposition steps are accomplished by high frequency cathode sputtering.

7. The method as recited in claim 5 or 6 wherein prior to placing said blank substrate in said chamber cleaning said blank substrate surface in a diluted hydrofluoric acid solution.

8. The method as recited in claim 5 or 6 wherein said predetermined low pressure is in the range 2.5×

10^-6 -4×

10^-7 torr.

9. The method as recited in claim 8 wherein said metal depositing on said blank substrate is accomplished for about 30 seconds.

10. A low temperature method of forming silicon dioxide-free metal silicide connecting contact on a semiconductor silicon substrate having integrated circuit structures thereon, said method comprising:

placing a semiconductor silicon substrate having integrated circuit structures which are covered with a mask having contact windows (device substrate) and atleast one clean, blank silicon substrate in a deposition chamber maintained at a predetermined low pressure;

heating said substrates to a low temperature in the range of 330°

C. to 550°

C.;

shielding said device substrate by a substrate shield arranged in close proximity to said device substrate;

depositing a metal on said atleast one blank substrate at said low temperature and pressure for a short period to remove any traces of oxygen in said chamber by chemisorption of said oxygen by said atleast one blank substrate and thereby establishing an oxygen-free environment in said chamber;

exposing said device substrate by removing said substrate shield;

depositing in said contact windows of said device substrate said metal at said low temperature and pressure in said oxygen-free environment; and

sintering said device substrate at a sufficient temperature and time in a suitable ambient to convert said metal in said contact windows to corresponding metal silicide.

11. The method as recited in claim 10 wherein said short period is about 30 seconds.

12. A low temperature method for forming a silicon dioxide-free platinum silicide contact on a semiconductor wafer having integrated circuit structures, said method comprising:

placing a silicon wafer having integrated circuit structures (device wafer) and atleast one clean, blank silicon wafer in a deposition chamber maintained at a low pressure;

heating said wafers simultaneously to a low temperature in the range of 330°

C.-550°

C.;

shielding said device wafer by means of a shutter arranged in close proximity to said device wafer;

depositing platinum metal on said at least one blank wafer at said low temperature and pressure for a period of about 30 seconds to remove any traces of oxygen present in said chamber by chemisorption of said oxygen traces by said atleast one blank wafer as the platinum is deposited and thereby establishing an oxygen-free environment in said chamber;

exposing said wafer substrate by removing said shutter;

depositing on at least a selected portion of said device wafer said platinum at said low temperature and pressure in said oxygen-free environment; and

sintering said device wafer at a sufficient temperature and time in a suitable ambient to react the deposited platinum with the silicon thereunder forming platinum silicide contact.