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硅局部氧化(LOCOS)工艺之后生长薄栅(500)氧化层,发现在整个栅区以及沿 LO-COS 图样边缘各处都分布着缺陷。同时发现缺陷密度强烈地依赖于 LOCOS 工艺的各种工艺条件,尤其是场氧化的环境气体。提出了一个缺陷诱生的新模型,并已被一些实验所证实。模型的依据是:1)氮化硅(Si_3N_4)顶部由于 Si_3N_4与 H_2O 反应生成的 NH_3气体穿通过 Si_3N_4—SiO_2界面扩散至 SiO_2—Si 界面;2)扩散入的 NH_3与衬底硅反应形成氮化物。通过予氧化处理和栅氧化之前付去氧化物就能有效地克服由于 LOCOS 工艺在 SiO_2—Si 界面产生的氮化物。
Growth of the thin gate (500) oxide layer after the LOCOS process revealed defects throughout the gate region and along the edges of the LO-COS pattern. It is also found that the defect density strongly depends on the various process conditions of the LOCOS process, in particular the field-oxidized ambient gas. A new model of defect induction is proposed and has been confirmed by some experiments. The model is based on the following: 1) NH3 gas generated at the top of silicon nitride (Si3N4) diffuses to the SiO2-Si interface through the interface of Si3N4-SiO2 through reaction with Si3N4 and H2O2; 2) NH3 diffused into the substrate reacts with the substrate silicon to form nitride . Nitrides generated at the SiO 2-Si interface due to the LOCOS process can be effectively overcome by oxide removal prior to pre-oxidation and gate oxidation.