4-羟基苯甲酸对DSTI化学机械抛光SiO_(2)/Si_(3)N_(4)去除选择性的影响

Effect of 4-hydroxybenzoic acid on removal selectivity of SiO_(2)/Si_(3)N_(4) during chemical mechanical polishing of direct shallow trench isolation

针对直接浅沟槽隔离(DSTI)化学机械抛光(CMP)过程中SiO_(2)/Si_(3)N_(4)去除速率选择比难以控制的问题,采用CeO_(2)(平均粒径300 nm)为磨料、4-羟基苯甲酸(4-HBA)为抑制剂,以及柠檬酸和四乙基氢氧化铵为pH调节剂,对SiO_(2)晶圆和Si_(3)N_(4)晶圆进行CMP。研究了抛光液的CeO_(2)质量分数、4-HBA质量分数和pH对SiO_(2)/Si_(3)N_(4)去除速率选择比的影响,得到较优的抛光液组成为:CeO_(2)0.5%(质量分数,后同),4-HBA 0.04%,pH=4.5。采用较优抛光液时,SiO_(2)/Si_(3)N_(4)的去除速率选择比达到97∶1,并且CMP后Si O_(2)晶圆和Si_(3)N_(4)晶圆的表面粗糙度(Sq)分别降至0.612 nm和0.226 nm,获得较好的表面品质。

Aiming at the difficult control of the removal rate selectivity ratio of SiO_(2) to Si_(3)N_(4) during chemical mechanical polishing(CMP)of direct shallow trench isolation(DSTI),a slurry using CeO_(2) with an average size of 300 nm as abrasive,4-hydroxybenzoic acid(4-HBA)as inhibitor,and citric acid and tetraethylammonium hydroxide as pH regulator was used for the CMP of SiO_(2) wafer and Si_(3)N_(4) wafer.The effects of mass fractions of CeO_(2) and inhibitor and pH of slurry on the removal rate ratio of SiO_(2) to Si_(3)N_(4) were studied.The slurry composition was optimized as follows:CeO_(2)0.5%(mass fraction),4-HBA 0.04%(mass fraction),and pH=4.5.The removal rate ratio of SiO_(2) to Si_(3)N_(4) reached 97:1 when CMP with the optimized slurry,and the surface roughness(Sq)of SiO_(2) wafer and Si_(3)N_(4) wafer after CMP were decreased to 0.612 nm and 0.226 nm respectively,indicating that the surface quality of the wafers were improved.