VLSI中双层多晶硅结构的剖面研究

Investigation on the Cross-Section Profile of Double Layer Polysilicon Structure in VLSI

本文对VLSI中双层多晶硅结构的剖面及用于结构成形的干法腐蚀技术进行了研究,获得了优化的剖面结构.研究分析表明,多晶硅Ⅰ的侧墙越倾斜,则双层多晶硅结构越佳.改变刻蚀条件可以有效地调节横向对纵向的刻蚀速率比δ,满意地获得多晶硅Ⅰ侧墙倾角α为49°左右;多晶硅Ⅱ采用二步刻蚀工艺.结果既消除了3μm工艺中用各向异性的RIE刻蚀易出现的多晶硅Ⅱ沿多晶硅Ⅰ侧墙的残留造成的相邻字线短路现象,又保证了线宽的精确控制,对下层SiO_2只有轻微的侵蚀.为VLSI制造提供了适用的工艺结构设计和加工技术,成功地研制出了64K DRAM合格样品.

The cross-section profile of double layer polysilicon structure and dry etching technique forpatterning structure are investigated.The optimum profile of cross-section structure is obtain-ed.The study and analysis show that the sloper the sidewall of the polysilicon-1,the better isthe double polysilicon structure. σ,the ratio of horizontal to vertical etching rate,can be ad-justed effectually by changing etching conditions.The slope angle a of sidewall of polysilicon-I, around 49°, is got successfully and satisfactorily.The polysilicon-2 is etched by two steps.The troubles of short-circuit between adjacent wordlines caused by the residue of the polysilicon-2along the polysilicon-I sidewall, which is easy to come across with anisotropic RIE in 3μmtechnology,are eliminated,and the precise control of the linewidth is guaranteed and the SiO_2substrate is etched slightly,it is suitable for the requirement of the technical structure designand the process of VLSI, and the typical samples of 64kDRAM are fabricated successfully.