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HWAHAK KONGHAK,
Vol.31, No.6, 675-682, 1993
Vol.31, No.6, 675-682, 1993
CF4/O2 식각 가스계를 사용한 텅스텐 박막의 건식 식각 연구
Dry Etching of Tungsten Films in CF4/O2 Gas System
CF4/O2 반응가스계를 사용하여 저압화학증착된 텅스텐 박막의 플라즈마 식각 및 반응성 이온 식각을 수항하고 산소분율, 압력 및 RF 출력에 따른 텅스텐의 식각속도와 SiO2에 대한 식각선택성을 조사하였다. 플라즈마 식각 및 반응성 이온 식각 모드에서 텅스텐의 식각속도는 반응가스중의 산소분율이 각각 40%와 50%일 때 최대속도를 나타내었다. SiO2에 대한 텅스텐의 식각선택성은 플라즈마 모드에서 약 16이었으며 반응성 이온 식각에서는 2.3의 낮은 값을 나타내었다. 산소분율에 따른 텅스텐의 식각속도 측정과 질량분석기 및 분광분석기에 의한 플라즈마상의 식각성분을 분석한 결과, WF6 뿐만 아니라 WOF4의 생성에 의한 텅스텐식각이 중요한 반응경로로 판단된다. 압력이 증가함에 따라 플라즈마 mode에서는 0.6torr에서 RIE mode에서는 200mtorr에서 텅스텐의 최대식각속도를 보였다. RF출력의 증가에 따라 식각속도는 크게 증가하지만 W/SiO2의 식각선택성은 감소하였다.
Dry etching of LPCVD tungsten film was performed using CF4/O2 plasma in both reactive ion etching(RIE) and plasma etching(PE) modes. The etch rate of tungsten and the selectivity of tungsten to SiO2 were examined as a function of oxygen content in feed gas, pressure and RF power. The maximum etch rate in PE and RIE modes were observed at 40 and 50% O2 in feed gas, respectively. The maximum selectivities of tungsten to SiO2 in both modes were about 16 and 2.3, respectively. Mass spectroscopy(MS) and optical emission spectroscopy (OES) were used to identify the reactive species in CF4/O2 plasma. The results of MS and OES analyses in measuring the etch rate as a function of O2 percent suggest that WOF4 and WF6 are main etch products for tungsten etching. The maximum etch rate was obtained at 0.6 torr for PE mode and 200 mtorr for RIE mode. With the increase of RF power, the etch rates of both tungsten and SiO2 increased, but the selectivity of tungsten to SiO2 decreased.
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