薄膜制备中的微蚀孔问题

Micro-Etching Holes in the Thin Film Fabrication

研究了自终止腐蚀停法制备浓硼重掺杂硅薄膜的腐蚀孔问题.许多MEMS结构需要进行2次或2次以上的深刻蚀,有些需要在多次深刻蚀后释放超薄的悬空薄膜结构,这时薄膜表面极易出现微小的腐蚀孔.分析可知,微蚀孔并不完全在第2次腐蚀的过程中形成,而是从第1次深腐蚀过程中对掩膜层的钻蚀开始的.对掩膜层的钻蚀,导致硅表面出现轻微腐蚀,形成细小的凹坑,并在浓硼扩散和第2次深腐蚀中被放大,最终在成膜过程中形成小孔.分析了微蚀孔的成因,提出了工艺上的解决方法,形成了一套重复性好的成膜工艺.

The problem of etching holes was researched during the fabrication of boron-doped p^＋ -silicon freehanding diaphragm using anisotropic wet etching techniques. Many MEMS structures need twice deep etching or even more, and usually the free-handing diaphragm is achieved after several deep etching. In this case, it is likely that some micro-etching holes can be found on the surface of the film. Researches show that the formation of the etching holes does not begin in the second deep etching, but begin with the destroy of the mask in the first deep etching. The destroy of the mask leads to a slight etching of the Si film, and some slight concaves are formed. These concaves are magnified during the boron doping and the second deep etching. Finally, the micro-etching holes are formed on the Si film. The reason for the formation of etching holes was analyzed, and solutions were proposed, then a repeatable film fabrication process was formed.