LED用蓝宝石衬底抛光后湿法清洗研究

Study on the Post Chemical Mechanical Polishing Wet Cleaning of Sapphire Substrate Used for LED

LED被认为是下一代主要照明工具,其以高质量的衬底基片外延GaN层,目前主要用化学机械抛光后的蓝宝石晶片作为衬底,但抛光后的衬底表面布满杂质,这些杂质会导致外延层缺陷,降低发光率甚至使器件失效。探讨了在蓝宝石衬底清洗过程中,HF、表面活性剂、氧化剂的作用。得出HF溶液对衬底表面的SiO2颗粒有很好的清除效果,不会造成蓝宝石衬底表面质量恶化,表面活性剂可以形成覆盖层降低衬底表面能,同时防止被去除杂质的再次附着,强氧化剂可以腐蚀衬底表面去除附着力较强的颗粒。在试验中通过不同清洗顺序发现表面活性剂形成的覆盖层也会对杂质产生保护作用。在使用表面活性剂后再使用HF溶液清洗,衬底表面颗粒数从18降为10,但表面存在腐蚀坑样的污染,在以表面活性剂、浓硫酸、HF溶液的清洗顺序清洗后发现表面颗粒数从20降至8,没有腐蚀坑样的污染存在,因此采用表面活性剂、浓硫酸、HF溶液的清洗顺序可以得到好的效果。

Light Emitting Diode is thought as the primary illumination, which needs high-quality substrates to grow a film of GaN. Now it adopts sapphire as the substrates usually which must be processed by chemical mechanical polishing. However the substrate is covered with impurity that causes flow in epitaxial layer,reducing luminous efficiency and even destroy the tool.lt talks about work of HF, surfactant and oxidant during the wet cleaning. It is found that the solution of HF can wipe off the particle adhered to substrate well and do not worsen the surface. Suofactant can form a film on the substrate and stop particles in solution adhering to it again, and the oxidant can corrode sapphire and wipe off impurity, which has strong anchoring strength. It finds suoractant can protect pollution not to be dislodged by form a film. HF is used after the surfactant in cleaning, and the number of particle is reduced from 18 to 10 and there is pollution like etch pit on the surface. As it cleans the wafer with the order of surfactant, H2SO4,HF,and the etch pit disappears and the number is reduced from 20 to 8, so the order of surfactant,H2SO4,HF is better than others and get a good result.