Investigation on surface smoothing of silicon-on-insulator with gas phase hydrogen chloride etching

Silicon-on-insulator (SOI) substrates are widely used in integrated circuit manufacture because of the advantages of SOI devices. To obtain smooth and uniform top silicon layer, the process of smoothing and thinning becomes more and more critical. Surface smoothing and thinning of top silicon layer of SOI are achieved by applying gas phase hydrogen chloride etching. In this work, gas mixture with HCl proportion below 1% is used to etch the top silicon layer at various conditions. Etch rate is influenced by HCl proportion and gas flow, however, the etch rate almost keeps constant at the temperature range between 1000 degrees C and 1100 degrees C. Root mean square roughness value of etched sample can be lower than 0.2 nm, which is close to the value of bare silicon substrate, and could satisfy the requirements of CMOS applications.

Automated summary

Gas phase hydrogen chloride etching can achieve surface smoothing and thinning of the top silicon layer of SOI, with etch rate being influenced by HCl proportion and gas flow. The etch rate remains constant within a certain temperature range, and the root mean square roughness value of the etched sample can meet the requirements of CMOS applications.