학술논문
SF6 gas대체를 위한 NF3, COF2 gas의 SiNx 와 a-Si Dry Etch Rate 특성비교 / A Comparison of SiNx and a-Si dry etch characteristics using NF3, COF2 and SF6
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
SF6 Gas는 반도체 및 디스플레이 제조공정 중 Dry etch과정에서 널리 사용되는 Gas로 자연적으로 존재하는 것이 아닌 사용 목적에 맞춰 인위적으로 제조된 Gas이다. 디스플레이 산업 및 반도체 산업이 활성화됨에 따라 SF6 Gas의 소비가 급격히 늘었다. 디스플레이 산업에서 SF6 gas가 사용되는 Dry etch공정은 주로 a-Si, n+ a-si, passivation 등 Si계열의 박막을 etch하는데 사용된다. 이러한 Si 계열의 박막을 식각하기 위해서는 fluorine, chlorine등이 사용된다, fluorine계열의 gas로는 SF6 Gas, CF4 Gas등이 있으며, 주로 SF6 Gas를 사용한다. 하지만 SF6 Gas는 대표적인 온실가스로 지구 온난화이 주범으로 주목 받고 있다. 세계적으로 온실가스의 규제에 대한 움직임이 활발하고, 대한민국은 2020년까지 온실가스 감축목표를 ‘배출전망치(BAU)대비 30% 감축으로’ 발표하였다. 따라서 디스플레이 및 반도체 공정에는 GWP(Global warming Potential)에 적용 가능한 대체 가스의 연구가 필요한 상황이다. 본 논문에서는 대표적인 온실가스인 SF6를 대체하기 위한 방법으로 NF3, COF2의 건식 식각 특성을 확인하였다.PECVD(Plasma Enhanced Chemical Vapor Deposition)으로 증착한 a-Si 박막과 SiNx 박막을 CCP-RIE(Capacitively - Coupled - Plasma Reactive Ion Etching)를 이용하여 식각하였다. 각각의 gas를 사용하여 SiNx와 a-Si의 etch rate과 특성을 파악하고자 Power, Pressure, Gas flow rate을 변화시켜 비교하였다. 식각 특성 결과를 토대로 식각 Gas 대체시 고려사항 및 가능성을 파악하고자 하였다.
In thin film transistor liquid crystal display (TFT-LCD) manufacturing industry, dry etch process used for etching thin films such as a-Si, n+a-si, passivation, SiNx etc. Si based films are etched using fluorine, chlorine based gases. Among fluorine gases, SF6 gas is mainly used.According to The second IPCC (Intergovernmental Panel on Climate Change) report, SF6 have been estimated to have an atmospheric lifetimes of 3,200 years and GWP (Global Warming Potential) is 23,900 times comparing CO2. While NF3 has not only shorter atmospheric lifetimes (740 years) but also lower GWP (17000) than SF6. For this reason, the use of NF3 is one of the alternatives for reducing greenhouse gas. Therefore, display process needs alternative gas for applicable GWP. If a similar or predominant process by using NF3 can be obtained, it will be beneficial for the environ-ment. In this paper, dry etching characteristics of SiNx and a-Si thin film using SF6 and NF3 gas chemistries were investigated using dual frequency CCP-RIE. We studied alternative possibility after comparing etching characteristics of SF6 and NF3.Dry etching characteristics of SiNx and a-Si thin film using SF6 and NF3 gas chemistry were investigated with dual frequency RIE. Dry etching characteristics were studied by varying the power ratio, pressure and gas flow rate.In SiNx film, etch rate using NF3/O2 were relatively higher than those using SF6/O2 in various power ratio, pressure and gas flow rate conditions. As the pressure was increased etch rate both NF3/O2 and SF6/O2 cases were increased. In the same condition, the maximum etch rate of SiNx using NF3/O2(1280nm/min) was higher than that using SF6/O2(872nm/min).For the a-Si film, the etch rate was similar for various power and pressure conditions both SF6/Cl2 and NF3/Cl2 gas chemistry. In the gas flow rate condition, slight increase of the etch rate was found up to about 50% Cl2 then continuous decrease was observed at SF6/Cl2. But increasing the ratio of Cl2 gas, etch rate of a-Si was decreased in NF3/Cl2 chemistry. The maximum etch rate was 200 nm/min in the SF6/Cl2 chemistry and about 346 nm/min in the NF3/Cl2 chemistry.
In thin film transistor liquid crystal display (TFT-LCD) manufacturing industry, dry etch process used for etching thin films such as a-Si, n+a-si, passivation, SiNx etc. Si based films are etched using fluorine, chlorine based gases. Among fluorine gases, SF6 gas is mainly used.According to The second IPCC (Intergovernmental Panel on Climate Change) report, SF6 have been estimated to have an atmospheric lifetimes of 3,200 years and GWP (Global Warming Potential) is 23,900 times comparing CO2. While NF3 has not only shorter atmospheric lifetimes (740 years) but also lower GWP (17000) than SF6. For this reason, the use of NF3 is one of the alternatives for reducing greenhouse gas. Therefore, display process needs alternative gas for applicable GWP. If a similar or predominant process by using NF3 can be obtained, it will be beneficial for the environ-ment. In this paper, dry etching characteristics of SiNx and a-Si thin film using SF6 and NF3 gas chemistries were investigated using dual frequency CCP-RIE. We studied alternative possibility after comparing etching characteristics of SF6 and NF3.Dry etching characteristics of SiNx and a-Si thin film using SF6 and NF3 gas chemistry were investigated with dual frequency RIE. Dry etching characteristics were studied by varying the power ratio, pressure and gas flow rate.In SiNx film, etch rate using NF3/O2 were relatively higher than those using SF6/O2 in various power ratio, pressure and gas flow rate conditions. As the pressure was increased etch rate both NF3/O2 and SF6/O2 cases were increased. In the same condition, the maximum etch rate of SiNx using NF3/O2(1280nm/min) was higher than that using SF6/O2(872nm/min).For the a-Si film, the etch rate was similar for various power and pressure conditions both SF6/Cl2 and NF3/Cl2 gas chemistry. In the gas flow rate condition, slight increase of the etch rate was found up to about 50% Cl2 then continuous decrease was observed at SF6/Cl2. But increasing the ratio of Cl2 gas, etch rate of a-Si was decreased in NF3/Cl2 chemistry. The maximum etch rate was 200 nm/min in the SF6/Cl2 chemistry and about 346 nm/min in the NF3/Cl2 chemistry.