Method for rapidly etching material on a semiconductor device

Abstract

Apparatus and methods for precise processing of thin materials in a process chamber by the use of ellipsometer monitoring is disclosed. The process includes rapidly etching a layer 42 of material covering a semiconductor device. The process includes placing the semiconductor wafer 14 into a processing chamber 10. In a typical operation, the wafer 14 will include a selected substrate 32 having a first thin layer 30 of material covering the substrate 32 and then a second layer 42 of a different material covering the first layer 30. A process such as reactive ion anisotropic etching which rapidly etches the second layer 42 is initiated and this etching is monitored in situ by an ellipsometer in combination with a controller 28 to determine the thickness of the second layer 42' which has been achieved. Once the desired amount of second layer 42 remains, the rapid etching process stops to leave a residual layer 42' such as about 250 .ANG. or in a preferred embodiment a thickness equivalent to about one molecular layer. A second chemical isotropic etching process step then starts which may be substantially ineffective at etching the first layer 30 of material and which etching process consequently is typically substantially slower than the first etching process. Since only a very thin layer remains, the slow speed or isotropic nature of the second etching process does not take an unacceptable amount of time or cause other problems, such as loss of critical dimension.