Silicon nitride etch process with critical dimension gain

• US 6,593,245 B1
• Filed: 08/01/1996
• Issued: 07/15/2003
• Est. Priority Date: 11/18/1994
• Status: Expired due to Fees

• Current Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Original Assignee: Advanced Micro Devices SDN Berhad (Advanced Micro Devices, Inc.)
• Inventors: Chan, Maria
• Primary Examiner(s): Bowers, Charles
• Assistant Examiner(s): WHIPPLE, MATTHEW LAVERNE
• Application Number:
  US08/690,848
• Time in Patent Office: 2,539 Days
• Field of Search: 438/724, 438/744
• US Class Current: 438/724
• CPC Class Codes: H01L 21/31116 by dry-etching

Abstract

A method for plasma etching of silicon nitride using a mixture of trifluoromethane and oxygen in a ratio of approximately 8 to 1 to selectively etch silicon nitride in preference to silicon dioxide and photoresist, resulting in critical dimension gain.

Claims

1. A method for etching a silicon nitride layered on a silicon substrate, comprising the steps of:

(a) growing a layer of oxide on the substrate;

(b) depositing a layer of silicon nitride on the oxide layer;

(c) creating a patterned photoresist layer on the silicon nitride layer, said patterned photoresist layer having a plurality of photoresist lines with a developed inspection critical dimension (DICD);

(d) plasma etching the patterned photoresist and silicon nitride layers in a single wafer plasma etcher with one step process conditions with a gas mixture of trifluoromethane and oxygen in a flow ratio of between 6;

1 and 10;

1 at a pressure between 20 and 60 millitorr, thereby selectively removing the silicon nitride which is not covered by photoresist; and

(e) removing the photoresist to uncover silicon nitride underlying the photoresist, said underlying silicon nitride having a final inspection critical dimension (FICD) which exceeds the DICD of the patterned photoresist, whereby a critical dimension gain from the patterned photoresist to the underlying silicon nitride is achieved.

2. The method of claim 1, further comprising the step of growing a field oxide layer over areas of exposed oxide after the photoresist removal step is completed.

3. The method of claim 1, wherein the power density in the etching step is in the range of 0.6 to 1.1 W/cm².

4. The method of claim 2, further comprising the step of growing a field oxide layer over areas of exposed oxide after the photoresist removal step is completed.