一种改善内部高速振荡器低温良率的工艺方法  

A process method to improve low temperature yield of internal high speed oscillator

作　　者：魏代龙 WEI Dai-long(Product Engineering Department,Xiaohua Semiconductor Co.)

机构地区：[1]小华半导体有限公司

出　　处：《中国集成电路》2022年第6期74-77,共4页China lntegrated Circuit

摘　　要：MCU芯片内部高速振荡器(HRC)的低温度敏感性对其在控制领域的应用至关重要,通过优化晶圆制造工艺来降低温度敏感性提升良率具有重要的意义。通常晶圆上有源区的图形密度差异会引起大块浅沟槽隔离区域的碟形化,在后续的多晶硅蚀刻步骤中引入有源区损伤,进而使器件的实际电性参数偏离预期值,最后使低温条件下HRC频率精度降低。本文通过在晶圆的制作工艺中,增加浅沟槽隔离化学机械研磨步骤后氮化硅剩余厚度来减少大块浅沟槽隔离区域的碟形化,同时在多晶硅光刻步骤中减少抗反射涂层厚度去改善抗反射涂层厚度的均一性,最后在多晶硅蚀刻步骤中相应的减少蚀刻时间去避免过蚀刻,进而可以有效地改善有源区损伤。通过这种工艺优化方式,低温晶圆级探针(CP)测试时HRC频率精度分布更集中并且接近目标频率,有效提升了在低温条件下HRC的频率精度,晶圆边缘HRC良率提升可以达到1%。The low temperature sensitivity of internal high-speed oscillator(HRC)in MCU chip is very important for its applications in the control field.It is significant to reduce the temperature sensitivity and improve yield by optimizing the wafer manufacturing process.In general,the pattern density difference of OD layer in chip will cause the dishing for large STI region,and OD DAMAGE will be introduced in the subsequent POLY ETCH step,which will make the actual electrical parameters of device deviate from the expected value,and finally reduce the HRC frequency accuracy at low temperature.This paper,in the wafer fabrication process,the SiN remain thickness after STI CMP step was increased to reduce STI Dishing,and BARC thickness was decreased during POLY PHOTO step to improve BARC thickness uniformity.Finally,the ETCH time was reduced to avoid over-etching in the POLY ETCH step,thus effectively improving OD DAMAGE.Through this process optimization,the HRC frequency precision distribution in low-temperature CP test is more concentrated and close to the target frequency,which effectively improves the HRC frequency accuracy under low-temperature conditions,and the HRC yield at the wafer edge can be improved about 1%.

关 键 词：内部高速振荡器 温度敏感性 浅沟槽隔离化学机械研磨 有源区损伤 多晶硅光刻 

分 类 号：TN752[电子电信—电路与系统]