硅片背面铜污染的清洗

Si Wafer Backside Cleaning of Cu Contamination

H2SO4/H2O2/H2O、HNO3/HF和HF/H2O2/H2O为半导体芯片生产过程中三种去除硅片背面铜污染的化学清洗液。在单片湿法清洗机上采用这三种化学液对直径300 mm具有类似于实际生产中铜污染的硅片进行了清洗,结果发现H2SO4/H2O2/H2O在清洗过程中不对硅片表面的Si3N4膜产生损伤,但铜污染的去除效率较低;HNO3/HF和HF/H2O2/H2O对Si3N4膜产生微量刻蚀,从而去除扩散至硅片内部铜污染,从而显示出较佳的去除效果。通过比较HF/H2O2/H2O中HF体积分数与Si3N4膜刻蚀深度和清洗后铜原子浓度,HF的体积分数为1.5%时,可以使硅片表面铜原子浓度降至1010cm-2以下,并且Si3N4膜厚的损失小于1 nm。

H2SO4H2 O2/H2O、 HNO3/HF 和 HF/H2O2/H2O are three typical cleaning chemicals to remove Cu contamination from Si wafer backside in mass semiconductor line with Cu process. These chemicals were used to clean the Cu contaminated wafers which like the ones in real production line in single wafer wet clean tool. The results show that H2SO4/H202/H20 can not remove Cu well and almost does not etch Si3N4 film; HNO3/HF and HF/H2O2/H2O can etch Si3N4 film slightly to remove the Cu atoms which diffused into the film, thus these two chemicals have better cleaning results than HESO4/H2O2/H2O. In HF/ H2OE/H2O, increasing HF concentration can etch SiaN4 film deeper and have less final Cu concentration. As HF is 1.5% , Cu concentration is less than 10^10 cm-2 and Si3N4 film loss is also less than 1 nm.