고순도 플라즈마 형성을 위한 카보레인 박막 특성 및 불순물 제거 효율 연구

Abstract

카보레인 (C2B10H12) 박막의 물리적 특성을 분석하기 위해 카보레인 분말을 기화시켜 기판과 전극의 거리, 카보레인 질량, 플라즈마 발생 시간을 변경하며 실리콘 기판에 증착하였다. 최적의 박막을 얻기 위해 3개의 실리콘 기판을 전극으로부터 각각 6.5, 16.5, 36.5 cm 떨어진 위치에 배치하여 제작한 시료를 X-선 회절계 (XRD), 투과 전자현미경 (TEM), 전계 방출-주사 전자현미경 (FE-SEM)으로 분석하였다. 카보레인 분말을 80 ℃ 이상으로 가열하여 기화된 카보레인을 주입하였고 900W (전압 150V, 전류 6A) 의 직류전력으로 2시간 동안 증착하였다. 카보레인 질량과 플라즈마 발생 시간을 변경하며 제작한 시료를 XRD와 TEM으로 분석한 결과 카보레인 박막은 비정질로 증착 되었으며, 박막의 두께는 FE-SEM으로 측정한 결과 카보레인 질량을 증가 시킬수록 두께 또한 증가한 반면 플라즈마 발생 시간과는 무관하였다. 카보레인 주입구에서 가까운 위치에서 가장 두꺼운 353 nm의 박막을 얻었으며, 주입구에서 멀수록 얇은 두께를 나타냈다. 이는 주입구에서 멀수록 기화된 카보레인의 밀도가 낮아지기 때문이다. 진공용기 안의 불순물 제거 효율을 측정하기 위해 주입해주는 기체의 종류와 주입량, 카보레인 가열온도를 변경하며 시료를 제작 분석 하였다. 카보레인 증착 후 진공용기 안의 기체 분압과 카보레인 박막의 원자량을 측정하여 불순물 제거 효율을 분석하였고, 이차이온 질량분석 (SIMS)으로 중수소와 수소의 치환율을 측정하였다. 잔류 기체 분석기 (RGA)로 카보레인 증착 전후의 기체 분압을 측정하여 비교 분석한 결과 증착 전보다 증착 후 물 분압이 낮아졌으며, 산소와 질소의 분압은 변화가 적었고, 150 ℃로 가열한 카보레인을 중수소 기체가 차있는 진공용기에 주입 하였을 경우 가장 효과적인 불순물 제거 효율을 보였다. X-선 광전자 분광법 (XPS)으로 측정 한 결과 카보레인 박막에 산소와 질소의 원자량은 중수소 기체를 주입해 주었을 때 가장 높게 측정되었다. 이는 불순물을 제거함에 있어 중수소 기체를 사용하여 카보레인을 증착 시켰을 때 가장 효과적이라는 것을 의미한다.| Carborane (C2B10H12) powders were evaporated and deposited on a silicon substrate by using a glow discharge method and the physical properties of the evaporated films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma pulse. To obtain the optimum thickness of the films, three silicon substrates were placed at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using an X-ray diffractometer (XRD), a transmission electron microscope (TEM), and a field emission scanning electron microscope (FE-SEM). For the deposition, the carborane powder was warmed to 80 oC in 10 minutes and was applied a DC-power pulse of 900 W for 2 hours. The mass of flown carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the FE-SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 nm was achieved from the samples was placed closest to the carborane inlet and the thickness became thinner as farther from the source which suggests that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet. To reduce the impurity levels in a chamber, the effects on degrees of reduction as functions of the carborane temperature and the rates of flowing gases of deuterium and helium were investigated. The reduced amount of impurities after boronization was estimated by measuring the partial pressures of the gases in the chamber and concentrations of nitrogen and oxygen in a deposited carborane film. The ratio of deuterium to hydrogen in the films was analyzed by using a secondary ion mass spectrometry. When carborane powders were evaporated under deuterium atmosphere, results of a residual gas analyzer showed a significant decreasing in a partial pressure of water while less change was noted from the ones of nitrogen and oxygen. The most efficient removal rate for water was obtained when carborane powder was flown under deuterium atmosphere at carborane heating temperature of 150 oC. The X-ray photoelectron spectroscopy data show higher concentrations of nitrogen and oxygen in the carborane films deposited on a Si substrate flown under deuterium atmosphere demonstrating that boronization under deuterium atmosphere is an effective method to remove impurities.; Carborane (C2B10H12) powders were evaporated and deposited on a silicon substrate by using a glow discharge method and the physical properties of the evaporated films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma pulse. To obtain the optimum thickness of the films, three silicon substrates were placed at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using an X-ray diffractometer (XRD), a transmission electron microscope (TEM), and a field emission scanning electron microscope (FE-SEM). For the deposition, the carborane powder was warmed to 80 oC in 10 minutes and was applied a DC-power pulse of 900 W for 2 hours. The mass of flown carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the FE-SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 nm was achieved from the samples was placed closest to the carborane inlet and the thickness became thinner as farther from the source which suggests that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet. To reduce the impurity levels in a chamber, the effects on degrees of reduction as functions of the carborane temperature and the rates of flowing gases of deuterium and helium were investigated. The reduced amount of impurities after boronization was estimated by measuring the partial pressures of the gases in the chamber and concentrations of nitrogen and oxygen in a deposited carborane film. The ratio of deuterium to hydrogen in the films was analyzed by using a secondary ion mass spectrometry. When carborane powders were evaporated under deuterium atmosphere, results of a residual gas analyzer showed a significant decreasing in a partial pressure of water while less change was noted from the ones of nitrogen and oxygen. The most efficient removal rate for water was obtained when carborane powder was flown under deuterium atmosphere at carborane heating temperature of 150 oC. The X-ray photoelectron spectroscopy data show higher concentrations of nitrogen and oxygen in the carborane films deposited on a Si substrate flown under deuterium atmosphere demonstrating that boronization under deuterium atmosphere is an effective method to remove impurities.