Metrology for Implanted Si Substrate and Dopant Loss Studies

Abstract

Spectroscopic ellipsometry (SE) model was developed to study substrate loss of shallow implanted silicon substrate following photoresist strip. Model is based on different optical properties of silicon oxide (SiO2) and implanted silicon (i-Si) layers and silicon substrate, and is used to characterize relevant layers, i-Si and SiO2, before and after plasma treatment. The increase in SiO2 and decrease in i-Si layer was observed after plasma exposure. Changes in i-Si layer are the result of two phenomena, oxidation and heating induced re-growth of i-Si layer, while changes in SiO2 thickness represent direct measure of substrate loss due to oxidation. Good agreement between TEM and SE measurements confirms that SE model can distinguish between crystalline (c-Si) substrate and i-Si, regardless if i-Si is only damaged, d-Si (crystalline) or amorphized, a-Si after implantation. We have also found consistency in SIMS dopant profiles and substrate losses extracted from SE measurements for plasma processes studied.