Fabrication of oxynitride frontside microstructures

• US 5,164,339 A
• Filed: 05/28/1991
• Issued: 11/17/1992
• Est. Priority Date: 09/30/1988
• Status: Expired due to Fees

• Current Assignee: Siemens-Bendix Automotive Electronics LP
• Original Assignee: Siemens-Bendix Automotive Electronics LP
• Inventors: Gimpelson, George E.
• Primary Examiner(s): WILCZEWSKI, MARY A
• Application Number:
  US07/707,931
• Time in Patent Office: 539 Days
• Field of Search: 437/226, 437/228, 437/194, 437/238, 437/921, 437/235, 437/944, 437/901, 437/966, 73/715, 73/719, 73/720, 73/721, 73/725, 73/726, 73/727, 73/754, 73/304 C, 357/26, 148/DIG. 159, 148/33.2
• US Class Current: 438/52
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: Y10S 148/159 Strain gauges

Abstract

Method for producing a low stress silicon oxynitride microstructure on a semiconductor substrate at temperatures not higher than 500° C. The method is particularly adapted for forming integrated silicon sensors where the oxynitride microstructure is fabricated on a substrate under conditions which do not harm the integrated circuit electronics.

Claims

1. A method for producing a low stress free-standing microstructure, said method comprising the steps of:

providing a silicon substrate;

forming a spacer layer on said silicon substrate;

etching a pattern in said spacer layer to produce an etched spacer layer;

forming a silicon oxynitride layer on said etched spacer layer; and

etching said spacer layer to remove said spacer layer without removing portions of said oxynitride layer formed on said spacer layer to form said low stress free-standing oxynitride microstructure on said substrate.

2. A method according to claim 1, wherein said step of forming said oxynitride layer is carried out at a temperature of not more than 500°

C.

3. A method according to claim 2, wherein said temperature is in the range of 150°

C. to 300°

C.

4. A method according to claim 1, wherein said microstructure is in the form of a bridge.

5. A method according to claim 1, wherein said microstructure is in the form of a cantilever.

6. A method according to claim 1, wherein said microstructure has a stress of less than 5×

10⁸ dyne/cm².

7. A method according to claim 6, wherein said stress is in the region of 5×

10⁶ to 1×

10⁸ dyne/cm².

8. A method according to claim 1, wherein said spacer layer is formed of aluminum.

9. A method according to claim 1, wherein said oxynitride layer is formed by a plasma-enhanced chemical vapor deposition of oxynitride from a mixture comprising silane, nitrous oxide and nitrogen.

10. A method according to claim 9, wherein said silane, nitrous oxide and nitrogen are present in a volume ratio of 0.5 to 2 (silane):

3 to 12 (nitrous oxide);

5 to 20 (nitrogen).

11. A method according to claim 10, wherein said volume ratio of silane to nitrous oxide to nitrogen is about 1:

6;

10.

12. A method according to claim 9, wherein said chemical vapor deposition is carried out at a temperature of about 300°

C. for a time period of about 25 minutes and at a power level of about 45 watts and a pressure of about 300 mtorr.

13. A method according to claim 9, wherein said oxynitride layer has a thickness of about 1000 to about 25000 Angstroms.

14. A method for forming an integrated silicon sensor comprising a low stress free-standing oxynitride microstructure, said method comprising the steps of:

providing a substrate having at least one integrated circuit on the major surface thereof;

forming a spacer layer on said substrate;

etching a pattern in said spacer layer to produce an etched spacer layer;

forming a silicon oxynitride layer on said major surface under conditions which do not adversely affect said integrated circuit; and

etching said spacer layer to remove said spacer layer without removing portions of said oxynitride layer formed on said spacer layer to form said low stress free-standing oxynitride microstructure on said substrate.

15. A method according to claim 14, wherein said step of forming said oxynitride layer is carried out at a temperature not higher than 500°

C.

16. A method according to claim 15, wherein said temperature is in the region of 150°

to 300°

C.

17. A method according to claim 14, wherein said oxynitride microstructure comprises a metal layer disposed between two oxynitride layers.

18. A method according to claim 17, wherein said metal is selected from the group consisting of aluminum, platinum, nickel, titanium, tungsten, gold, chromium, silver, palladium, titanium-tungsten, titanium-platinum, aluminum-silicon, and aluminum-silicon-copper.

19. A method according to claim 18, wherein said metal is aluminum and is encapsulated between said layers of oxynitride.