Real-Time Measurement of W, TiN, and TaSiN Thicknesses Comprising Full-Metal Gates during Plasma Etching by Optical Interference of Etching Plasma

Abstract

Film thicknesses of W, TiN, and TaSiN in a full-metal gate stack with photoresist masks were measured in real time during plasma etching with an in situ thickness monitor. The accuracy of such measurement was approximately AE1 nm. The monitor functions on the basis of the interference of plasma optical emission, reflected from the surface and base of the film. Although W and TiN have large absorption indexes, their thicknesses were more accurately measured when they became thinner. In particular, W thickness was estimated more accurately when it was smaller than approximately 10 nm.

Etch Profile Control of W/TiN/HfSiON and W/TaSiN/HfSiON Full-Metal Gates

“…The monitor functions on the basis of the interference of plasma optical emission reflected from the surface and the base of the film. 7) This monitor was used for determining the time to change the etching condition during plasma etching.…”

“…It was reported that an in situ thickness monitor was used to predict the appearance of TaSiN with an accuracy of AE1 nm. 7) We can change the etching condition immediately before the appearance of TaSiN by monitoring the depth of etched W if the thickness of W is known in advance. Figure 12 shows the etch profile obtained by the above-mentioned novel method.…”