초임계이산화탄소를 이용한 실리카 희생막 에칭 및 실리카-폴리스티렌 코어셀 나노입자 제조에 관한 연구

Abstract

실험을 통해 TLIRP 시스템을 통해 SiO₂@PS 코어셀 콜로이드 입자 제조하였다. 하이브리드 콜로이드의 잘 정렬된 코어셀 구조물을 높은 수율과 분자량으로 얻을 수 있었다. 하이브리드 입자는 유기 용매 내에서 좋은 분산도를 보여주었고 얇은 필름에서 정열된 구조로 형성되었다. 본 새로운 기술은 무기물-유기물 하이브리드 물질의 제조를 위한 손쉽고 유용한 기술로 고려될 수 있을 것으로 기대된다.

Aqueous etchants used in traditional wet etching for the production of integrated circuits and MEMS devices hinder the processes and pose environmental difficulties. To resolve these issues, a dry etching method with anhydrous HF/pyridine in supercritical carbon dioxide (scCO₂) was developed. Etch rates of BPSG, P-TEOS, Thermal SiO₂ and SiN with dry etching method were several times higher than those in wet etching. Etch rates were found to be a function of temperature, HF concentration, and the kind of co-solvents. The presence of alcoholic co-solvents, especially IPA with HF/Pyridine etchant greatly increased the etch rate of BPSG. Etch selectivity could be controlled with the etchant concentration. A wafer composed of poly-Si cantilevers with various lengths and widths, and a sacrificial oxide P-TEOS were used to determine the longest cantilever without stiction. While stiction occurred over the 10 μm beams (gap to beam length, 1:20) in wet etching, no stiction was observed after scCO₂ dry etching. Residue SiF₄·2py was produced as a byproduct during the dry etching, which was attributed to the reaction between SiF₄ and pyridine. However, it could be removed completely from the wafer by subsequent flowing of a 10 wt % bis(2-methoxyethyl)ether solution in scCO₂. Consequently, Poly-Si cantilevers with high aspect ratios (1:150) were successfully released using this technique. On the other side, It is reported here that a novel synthesis of structurally well-defined silica-polystyrene (SiO₂@PS) core-shell nanoparticles using Thiol-Lactam Initiated Radical Polymerization (TLIRP) techniques. The TLIRP technique turns out to be a simple and effective method for inorganic-organic hybrid materials. In this method, thiols functionalized on SiO₂ particles are used as an initiator for the polymerization of styrene in the presence of lactams. It is easy to manipulate the PS shell size (the molecular weight of grafted PS) by controlling a polymerization variable such as reaction time.