Advanced process control for poly-Si gate etching using integrated CD metrology

Advanced integrated metrology capability is actively being pursued in several process areas, including etch, to shorten process cycle times, enable wafer-level advanced process control (APC), and improve productivity. In this study, KLA-Tencor's scatterometry-based iSpectra Spectroscopic CD was integrated on a Lam 2300 Versys Star silicon etch system. Feed-forward control techniques were used to reduce critical dimension (CD) variation. Pre-etch CD measurements were sent to the etch system to modify the trim time and achieve targeted CDs. CDs were brought to within 1 nm from a starting CD spread of 25 nm, showing the effectiveness of this process control approach together with the advantages of spectroscopic CD metrology over conventional CD measurement techniques.