STI CMP 공정에서 산화규소와 다결정규소 막질의 선택적 연마 메커니즘에 관한 연구

Abstract

Shallow trench isolation (STI) is a key technology for high packing density of the device in ultra-large-scale integration (ULSI) fabrication. In order to fabricate the STI structure, (1) the trenches are formed via etching process, (2) SiO2 film is deposited on the trenches, (3) chemical mechanical planarization (CMP) process is performed to remove the step height of SiO2, and it is stopped on the poly-Si. After these processes, the defect-free surface is essential for the high density and high performance of devices. As pattern sizes of transistors reduced from 50 to 30nm, the control of defects such as dishing and erosion becomes be more important. Thus, there are requirements on understanding the mechanism of removal selectivity between SiO2 and Poly-Si film. The pH value is a dominant factor affecting adsorption behavior of chemical additives and surface chemistry of the films. To elucidate the mechanism of removal selectivity between SiO2 and poly-Si films, we have investigated the adsorption behaviors of passivation agent for removal selectivity between SiO2 and Poly-Si films. The adsorption data were fitted using Langmuir and Freundlich models. Plyethylene glycol (PEG), a water-soluble nonionic polymer, has been widely used as passivation agent for removal selectivity between SiO2 and Poly-Si films in the STI CMP. Adsorption isotherm data of PEG on poly-Si are better fitted with the Freundlich isotherm model, which means that the PEG is adsorbed on poly-Si film by heterogeneous systems. Additionally, we observed that amount of adsorption PEG on the films is increased with lower pH value due to the increase in the hydrophobic interaction between PEG and film. The CMP results are in good agreement with the result of adsorption isotherm. As a result, we provide researchers, studying the removal selectivity in the STI CMP, with guidelines on the detail mechanism of the removal selectivity between SiO2 and Poly-Si films.