Jung-kyu Lee

Study on electrical characteristics of HfO 2 treated by Nf 3 plasma

Summary form only given. Plasma process was used widely to manufacture semiconductor device due to low temperature and good performance. In particular, capacitively coupled plasma (CCP) and inductively coupled plasma (ICP) system were commonly used for dry etch, deposition and plasma treatment process in semiconductor device. In this paper, the fluorine plasma treatment process on high-k dielectric HfO2 was studied for improvement of dielectric performance. Fluorine can recover the trap due to passivation into oxygen vacancy of HfO2 dielectric. Plasma treatment is one of promising candidates to inject the ionized fluorine atom into oxygen vacancy of HfO2 effectively. Both CCP system with low density plasma (LDP, ~0.01%) and ICP system with high density plasma (HDP, ~1%) with NF3 gas were used for fluorine ionization. Composition and structure of the fluorinated-HfO2 treated by plasma were analyzed with TEM, XPS and Tof-SIMS. Electrical characteristics of I-V and C-V were measured with semiconductor device analyzer. Interfacial layer (IL) thickness of the fluorinated-HfO2 increasingly increased under the condition of ICP system, which led to the decrease of capacitance and degradation of dielectric. Also, crystallization and agglomeration of HfO2 was observed at TEM image. These result from fluorine ion bombardment and high temperature induced by plasma with high energy. Fluorine ionized by ICP system collides with HfO2. Bombardment of ionized fluorine can convert from HfO bond to Hf-F bond partially due to thermal energy and ion bombardment. Dissociated oxygen diffuses out surface or into silicon substrate, and then oxygen piled up on silicon substrate is combined with silicon. This results in the increase of IL thickness. Also, High thermal energy (>;550°C) generated from ion bombardment by ICP system can crystallize and agglomerate HfO2 dielectric sufficiently. Based on this model, we suggest that the fluorine treatment with low temperature and low density plasma can incorporate fluorine into oxygen vacancy of HfO2 without the damage of HfO2 and the increase of IL thickness on substrate silicon. We improved electrical characteristics of fluorinated-HfO2 without degradation of dielectric at the condition of low temperature (>;250°C) and low power with HFRF in CCP system. VBD (breakdown voltage) and IG (gate leakage current) of fluorinated-HfO2 were sharply improved about 10% and 50% compared to that of conventional HfO2. Stress induced leakage current (SILC) of fluorinated-HfO2 was improved in terms of dielectric reliability.

Temperature Dependence of Polar Anchoring Strength of Nematic Liquid Crystal Aligned on Rubbed Side Chain Liquid Crystalline Polymer

Abstract We have investigated the temperature dependence of the polar anchoring strength of nematic liquid crystal aligned homogeneously on glass substrates treated with side chain liquid crystalline polymer poly (4-cyanophenyl-4′-ethoxybenzoyloxy) acrylate (LCP100). The polar anchoring strength of rubbed LCP100 films is seen to be quite strong and comparable to that of rubbed polyimide films. The temperature dependence of orientational extrapolation length failed to show a critical divergence instead a very small increase on approaching the N-I transition. This indicates that the surface order parameter is quite strong and hence the polar anchoring energy weakens quite gradually.

Temperature Dependence of the Pretilt Angle Generated on the Rubbed Surface of a Side Chain Liquid Crystalline Polymer

Abstract While a wealth of data is available on the pretilt angle measurements at room temperature, there exist only a few reports on the temperature dependence of the pretilt angle. The present investigation is on the thermal variation of the pretilt angle of nematic liquid crystal molecules aligned on treated substrates. Glass substrates are coated with side chain-liquid crystalline polymer poly (4-cyanophenyl-4′-ethoxyben-zoyloxy) acrylate (LCP100). An unusual temperature behavior is seen in way of two stable values for the pretilt angle (θ). As the temperature is increased θ changed from one stable value to another. On cooling the sample from the isotropic phase θ increased from zero to a second stable value and thereafter remained as a temperature invariant.