低应力PECVD氮化硅薄膜的制备

Low Stress Silicon Nitride Thin Film Deposition by PECVD

研究了等离子增强化学气相淀积(PECVD)工艺中射频条件(功率和频率)对氮化硅薄膜应力的影响。对于不同射频条件下薄膜的测试结果表明:低频(LF)时氮化硅薄膜处于压应力,高频(HF)时处于张应力,且相同功率时低频的沉积速率和应力分别为高频时的两倍左右;在此基础上采用不同高低频时间比的混频工艺实现了对氮化硅薄膜应力的调控,且在高低频时间比为5∶1时获得了应力仅为10MPa的极低应力氮化硅薄膜。

SiN film stress under different radio frequency （RF） condition （RF power and frequency） of plasma enhanced chemical vapor deposition （PECVD） was studied. Thickness and stress of SiN films deposited under different RF conditions were measured by ellipsometer and stress instrument. Results show that high-frequency （HF） SiN film exihibit tensile stress, while low-frequency （LF） one compressive stress, and with the same RF power, deposition rate and stress value of film at LF are both 2 times of those at HF. According to above results, mixed frequency （MF） technique was successfully applied to control stress of SiN film just by altering time ratio of HF to LF during deposition; at the same time, SiN film with very low stress （-10 MPa） was achieved when time ratio of HF ： LF=5 ： 1.