Ⅰ号液在MEMS晶圆级封装中的应用研究

Study on application of liquid No.1 in wafer-level packaging for MEMS

Ⅰ号液是H_(2)O_(2),NH_(3)·H_(2)O和H_(2)O的混合物。通过研究微机电系统(MEMS)晶圆级封装钛(Ti)粘附层在Ⅰ号液中的腐蚀特性,为新工艺开发和在线工艺维护提供数据支持。研究表明:1)Ti的腐蚀速率与H_(2)O_(2)含量成正比关系,其原因在于腐蚀Ti的有效基团OOH-离子浓度随H_(2)O_(2)含量的增加而增大;2)Ti的腐蚀速率随NH_(3)·H_(2)O含量的增加而减小,这是由于NH_(3)·H_(2)O促进了H_(2)O_(2)的分解与电离,降低了H_(2)O_(2)浓度,促使亚稳态、溶解性较强的Ti(OH)_(2)O_(2)向难溶的Ti(OH)_(4)或氧化物沉淀转变,这些难溶物附着在Ti表面阻碍了反应的进行;3)由于H_(2)O_(2)的不断电离并逐步衰减,Ti的腐蚀速率随着Ⅰ号液放置时间的延长而减小;4)由于自然氧化层的存在,刚开始时,Ti腐蚀速率较慢,自然氧化层被清洗掉以后,Ti的腐蚀速率明显增加。

Liquid No.1 is a mixture of hydrogen peroxide,ammonia and water.In order to provide data supports for new process development and on-line process maintenance,corrosion characteristics of titanium adhesion layer of wafer-level packaging for MEMS in liquid No.1 is studied.The results show that corrosion rate of titanium is proportional to the content of hydrogen peroxide,due to the concentration of OOH-ion,the effective group for titanium corrosion,increases with the increasing content of hydrogen peroxide.Corrosion rate of titanium decreases with the increasing content of ammonia,because ammonia can promote the decomposition and ionization of hydrogen peroxide,reduces concentration content of hydrogen peroxide,promotes metastable and highly soluble Ti(OH)_(2)O_(2)to transform into insoluble Ti(OH)_(4)or oxide precipitation,which hinders the reaction through adhering to the surface of titanium.The corrosion rate of titanium decreases with the placing time of liquid No.1,due to the continuous ionization and gradual attenuation of hydrogen peroxide.Because of the existence of natural oxide layer,the corrosion rate of titanium is slowly at the beginning and then increases obviously after the natural oxide layer is washed away.