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Cu seed layer 표면의 플라즈마 전처리가 Cu 전기도금 공정에 미치는 효과에 관한 연구
오준환,이성욱,이종무,O, Jun-Hwan,Lee, Seong-Uk,Lee, Jong-Mu 한국재료학회 2001 한국재료학회지 Vol.11 No.9
Electroplating is an attractive alternative deposition method for copper with the need for a conformal and conductive seed layer In addition, the Cu seed layer should be highly pure so as not to compromise the effective resistivity of the filled copper interconnect structure. This seed layer requires low electrical resistivity, low levels of impurities, smooth interface, good adhesion to the barrier metal and low thickness concurrent with coherence for ensuring void-free fill. The electrical conductivity of the surface plays an important role in formation of initial Cu nuclei, Cu nucleation is much easier on the substrate with higher electrical conductivities. It is also known that the nucleation processes of Cu are very sensitive to surface condition. In this study, copper seed layers deposited by magnetron sputtering onto a tantalum nitride barrier layer were used for electroplating copper in the forward pulsed mode. Prior to electroplating a copper film, the Cu seed layer was cleaned by plasma H$_2$ and $N_2$. In the plasma treatment exposure tome was varied from 1 to 20 min and plasma power from 20 to 140W. Effects of plasma pretreatment to Cu seed/Tantalum nitride (TaN)/borophosphosilicate glass (BPSG) samples on electroplating of copper (Cu) films were investigated.
옥내 마이크로셀 개인휴대통신 시스템의 채널할당과 핸드오버를 위한 High quality reassignment 방식
오준환,홍대형 대한전자공학회 1996 전자공학회논문지-A Vol.33 No.2
In this paper, we studied channel assignment and handover schemes for the indoor microcell systems. For efficient frequency spectrum reuse we proposed the high quality reassignment (HQR) scheme. Proposed HQR scheme tries to keep the reuse distances small by monitoring C/I of channels being used. To assign a channel for a new or handove call, the scheme checks C/I of all available channels. Then HQR assigns the channel that has C/I near the threshold value, A_TH. The scheme also checks C/I of ongoing calls and continuously reassigns a new channel when needed. It attempts handover not only when C/I gets below a handover threshold value, HO_TH, but also when C/I becomes above a high quality reassignment threshold, H_TH. The performance of the proposed HQR scheme was analyzed by a computer simulation configuraed. The performance of the scheme was also analyzed for various threshold values selected and the results are presented in this paper. The results show that HQR scheme perfomrs better than the scheme adopted for DECT.
Relation of Firm's IOS with Future Profitability and Earnings Persistence
오준환,심충진,Amanda Flint 한국회계정보학회 2014 회계정보연구 Vol.32 No.2
This paper examines the effect of a firm's investment opportunity set (IOS) on future profitability and earnings persistence. Using the market to book value as a proxy for IOS, evidence has been obtained confirming the previous findings that IOS is positively related to future pre-tax earnings and earnings persistence. When adding earnings management as a new variable, the coefficient of interaction between future profitability and earnings management turns significantly (p<0.01) negative (-0.012, t= -2.34) and at the same time, the coefficient of interaction between earnings persistence and earnings management becomes insignificant (0.099, t=0.63) even at 10% level. This paper provides support for a hypothesis that with the presence of earnings management, the IOS is negatively related to future profitability and earnings persistence. The practical implication of this finding explains that a firm's value cannot be increased by earnings management regardless of the magnitude of IOS.