紫外光催化辅助SiC抛光过程中化学反应速率的影响

目的为了探究紫外光催化辅助抛光过程中,化学反应速率对SiC化学机械抛光的影响规律。方法通过无光照、光照抛光盘和光照抛光液3种光照方式,研究紫外光催化辅助作用对单晶SiC抛光过程中材料去除率的影响。测量不同条件下光催化反应过程中的氧化还原电位(ORP)值,来表征光催化反应速率,并进行了单晶SiC的紫外光催化辅助抛光实验,考察光催化反应速率对抛光效果的影响规律。结果实验表明,引入紫外光催化辅助作用后,材料去除率提高14%～20%,随着材料去除率的增加,光催化辅助作用对材料去除率的影响程度变小。光照射抛光液方式的材料去除率明显高于光照射抛光盘。不同条件下的抛光结果显示,化学反应速率越快,溶液的ORP值越高,材料去除率越大,表面粗糙度越低。在光照抛光液、H_2O_2体积分数4.5%、TiO_2质量浓度4 g/L、光照强度1500 mW/cm~2、pH=11的条件下,用W0.2的金刚石磨料对SiC抛光120 min后,能够获得表面粗糙度Ra=0.269 nm的光滑表面。结论在单晶SiC的紫外光催化辅助抛光过程中,光催化反应速率越快,溶液ORP值越高,抛光效率越高,表面质量越好。在H_2O_2浓度、TiO_2浓度、光照强度、pH等4个因素中,对抛光效果影响最大的是H_2O_2浓度,光照强度主要影响光催化反应达到稳定的时间。

Effect of Chemical Reaction Rate in Ultraviolet Photocatalytic Auxiliary SiC Polishing Process

The work aims to investigate the effect of chemical reaction rate on SiC chemical mechanical polishing (CMP) in the process of ultraviolet photocatalysis assisted polishing. The effect of ultraviolet catalysis on the material removal rate of (MRR) of polishing wafer was studied by three kinds of irradiation modes: no irradiation, polishing disc irradiation and polishing slurry irradiation. The Oxidation-reduction potential (ORP) value of photocatalytic reaction under different conditions was measured to characterize the photocatalytic reaction rate. The ultraviolet photocatalysis assisted polishing experiment of single crystal SiC wafer was carried out to investigate the effect of photocatalysis rate on polishing performance. From the experimental results, the material removal rate was increased by about 14%~20% with ultraviolet photocatalysis. With the increase of material removal rate, the effect of ultraviolet photocatalysis assistance on material removal rate became smaller. The material removal rate under polishing slurry irradiation was obviously higher than that under polishing disc irradiation. The polishing results under different conditions showed that as the the chemical reaction rate became faster, the ORP value of the solution became higher, the material removal rate became larger, and the surface roughness became lower. Under the conditions of polishing slurry irridation, H2O2 concentration of 4.5vol%, TiO2 concentration of 4 g/L, light intensity of 1500 mW/cm2 and pH11, the smooth surface with roughness of Ra 0.269 nm could be obtained after 120 min polishing with W0.2 diamond abrasive. In the process of ultraviolet photocatalysis assisted polishing of single crystal SiC, with the faster photocatalytic reaction rate, the solution ORP value is higher, the polishing efficiency is larger and the surface quality is better. Among the four factors such as H2O2 concentration, TiO2 concentration, light intensity and pH, H2O2 concentration has the greatest influence on the polishing effect, and the light intensity mainly affects the time for photocatalytic reaction to achieve stability.