Application of Optical Combined Methods to Control of Shallow Etching Process
Production CMOS technology node shallow trench isolation (STI) etching process control has been discussed in the present paper. It has been shown that optical scatterometry can be adopted for that in order to increase throughput and informativity of the control. In addition, it has been shown that scatterometry can replace a number of currently used techniques. The process of model suitable for the STI application creation has been discussed. A number of cross-control techniques is used to enable scatterometry for the discussed application. The application limits of the optical scatterometry are developed and techniques for control of the nodes beyond these limits have been discussed. In particular, process of CD control beyond 20 nm node has been discussed. The model created enables the control of not only the width of the trench but also its depth and sidewall angle. Those additional parameters were not controlled in-line previously and it helped to reduce production cost and increase the IC reliability. The control process has been tested on the CMOS 180 nm technology node, but its adoption to smaller nodes has been discussed.