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如果低电阻率的硅钛栅被用于按比例缩小的MOS器件,硅化钛的各向异性腐蚀是必要的。CCl_4、CF_4等离子体以及离子铣都可用来腐蚀硅化钛/多晶硅复合膜,每一种方法都表现于一些缺点。由于硅化物含氧量高及CCl_4等离子腐蚀的腐蚀选择比大(对二氧化硅的腐蚀速率低),因而CCl_4等离子腐蚀时会产生残留物并且腐蚀表面粗糙。CF_4反应离子腐蚀和离子铣刻蚀是光洁的腐蚀,但存在对下面的薄栅SiO_2膜的过腐蚀问题。然而,综合这些方法就能成功地加工出上述结构的各向导性图形。首先用腐蚀选择性差的CF_4反应离子腐蚀的光洁腐蚀刻透氧化物,随后用具有较高腐蚀选择比的Cl_2等离子腐蚀刻透硅化物下的多晶硅层至薄栅SiO_2层。
Anisotropic etching of titanium silicide is necessary if a low-resistivity SiN gate is used for a scaled-down MOS device. CCl_4, CF_4 plasma and ion milling can be used to etch titanium silicide / polycrystalline silicon composite film, each of the methods are shown in some disadvantages. Due to the high oxygen content of silicide and the large corrosion selectivity of CCl_4 plasma etching (the corrosion rate to silicon dioxide is low), the residue of CCl_4 plasma corrosion and the corrosion of the surface are roughened. The reactive ion etching and ion milling of CF 4 reactive etching is smooth and clean, but there is an overcorrosion problem for the underlying thin gate SiO 2 film. However, by combining these methods, the anisotropic patterns of the above structures can be successfully processed. Firstly, the etchant was cleaned with a mildly corroded selective CF_4 reactive ion etch followed by etching of the polysilicon layer under the silicide to a thin gate SiO_2 layer with a Cl_2 plasma having a higher etch selectivity.