抛光液pH值、温度和浓度对蓝宝石抛光效率的影响

Effect of Slurry pH, Temperature and Concentration on Removal Efficiency of Sapphire Material

目的研究抛光液pH值、温度和浓度对化学机械抛光蓝宝石去除率的影响,以提高抛光效率。方法采用CP4单面抛光试验机对直径为50.8 mm C向蓝宝石晶元进行化学机械抛光,通过电子分析天平对蓝宝石抛光过程中的材料去除率进行了分析,采用原子力显微镜(AFM)对蓝宝石晶元抛光前后的表面形貌和粗糙度(Ra)进行了评价。结果蓝宝石在化学机械抛光过程中的材料去除率均随抛光液pH值和温度的升高呈先增大后减小趋势。当抛光原液与去离子水按1:1的体积比混合配制抛光液,KOH调节pH值为12.2,水浴加热抛光液35℃时,蓝宝石抛光的材料去除率(MRR)达到1.119μm/h,Ra为0.101 nm。结论随着pH的增大,化学作用逐渐增强,而机械作用逐渐减弱,在pH为12.2的时候能达到平衡点,此时的MRR最佳;随着温度的升高,化学作用逐渐增强,而机械作用保持不变,抛光液温度为35~40℃时,化学作用与机械作用达到平衡,MRR最佳,当温度高于40℃后,抛光液浓度明显增大,而过高的浓度会导致MRR的减小。抛光液的相关性能优化后,化学机械抛光蓝宝石的MRR较优化前提高了71.4%。

The work aims to study effects of slurry PH, temperature and concentration on removal rate of sapphire material to improve polishing efficiency. Chemical mechanical polishing （CMP） for C-plane sapphire wafer with diameter of 50.8 mm was performed by using CP-4 single-sided tester. The removal rate of material during sapphire polishing was analyzed by using electronic analytical balance. Surface topography and roughness （Ra） were both evaluated with atomic force microscopy （AFM）. The effect of different SiO2 slurry （different pH, temperature and concentration） on the material removal rate （MRR） was investigated. MRR first increased and then decreased as slurry pH （10.4 to 12.2） and temperature （20 ℃ to 45 ℃） increased. The MRR and Ra were 1.119 μm/h and 0.101 nm respectively provided with KOH adjusted pH of 12.2, water-bath heating slurry temperature of 35 ℃ and volume ratio of original slurry： DI water of 1：1. Chemical effect is enhanced and mechanical effect is weakened as pH increases. Equilibrium point and optimal MRR are available when the pH value is 12.2; chemical effect is enhanced and mechanical effect remains unchanged as the temperature increases. The two effects achieve a balance and optimal MRR is available at the slurry temperature of 35～40 ℃. Concentration of the slurry increases significantly if the temperature exceeds 40 ℃. Too high concentration may lead to decrease of MRR; MRR of the sapphire subject to chemico-mechanical polishing increased by 71.4% af-ter relevant properties of the slurry have been optimized.