Method of selective gas etching on a silicon nitride layer

Claim 1

A method of gas etching a silicon nitride layer deposited on a semiconductor body of silicon by immercing said semiconductor body having said silicon nitride layer thereon in a plasma produced by way of high frequency glow discharge of a glass atmosphere containing carbon tetrafluoride and oxygen, the improvement comprising: etching in a first stage at a first oxygen concentration and at a first high frequency power range; and etching in a second stage at a second oxygen concentration and at a second high frequency power range, wherein the first oxygen concentration is lower than the second oxygen concentration.

Claim 2

A method of gas etching a silicon nitride layer deposited on a semiconductor body of silicon by immercing said semiconductor body having said silicon nitride layer thereon in a plasma produced by way of high frequency glow discharge of a glass atmosphere containing carbon tetrafluoride and oxygen, the improvement comprising: etching in a first stage at a first oxygen concentration and at a first high frequency power range; and etching in a second stage at a second oxygen concentration and at a second high frequency power range, wherein the first oxygen concentration is lower than the second oxygen concentration.

Claim 5

A method of etching a silicon nitride layer deposited on a semiconductor body of silicon wherein said silicon nitride layer is exposed to a plasma produced by way of a high frequency glow discharge of a gas containing carbon tetrafluoride and oxygen, the improvement comprising: pre-etching the silicon nitride layer wherein 0-6 Vol. % oxygen is mixed to the carbon tetrafluoride at a total pressure between 0.5 and 1.5 torr and at a frequency power of 300-800 watts; and main etching the silicon nitride layer wherein 50 Vol. % oxygen is mixed to the carbon tetrafluoride at a total pressure between 0.5 and 1.5 torr and at a frequency power of 100-400 watts.

Claim 6

A method of etching a silicon nitride layer deposited on a semiconductor body of silicon wherein said silicon nitride layer is exposed to a plasma produced by way of a high frequency glow discharge of a gas containing carbon tetrafluoride and oxygen, the improvement comprising: pre-etching the silicon nitride layer wherein 0-6 Vol. % oxygen is mixed to the carbon tetrafluoride at a total pressure between 0.5 and 1.5 torr and at a frequency power of 300-800 watts; and main etching the silicon nitride layer wherein 50 Vol. % oxygen is mixed to the carbon tetrafluoride at a total pressure between 0.5 and 1.5 torr and at a frequency power of 100-400 watts.