Polymers caused by CF4 plasma etching trimming process and its effects on SAW device characteristics

This paper investigates residual polymers caused by the CF₄ plasma etching trimming process on narrow bandwidth surface acoustic wave devices. Experimental results show that a small quantity of residuals remain even under the trimming conditions used in production. When the devices are exposed to water vapor, a systematic frequency shift occurs in the device-center-frequency. We report the experimental results of studies on physical and chemical features of residuals. We also show that this phenomenon applies to the recovery process of slightly over-trimmed devices