Patent ID: 7247247
Filing Date: 2007-07-24
Classification: B81B,B81C,H02N,Y10S

Abstract:
1. A selective etching method, comprising steps of: (a) providing a substrate; (b) forming a first mask layer having plural openings on said substrate; (c) forming a second mask layer on said first mask layer and forming said second mask layer in at least one of said openings for covering at least one part of said substrate; (d) forming a photoresist layer on said second mask layer and said part of said substrate so as to form plural etching windows directly on said substrate; (e) etching downwards said substrate through said plural etching windows by a first etching process so as to extend said plural etching windows downwards into said substrate; (f) removing said photoresist layer and etching said substrate through said plural openings by a second etching process so as to form plural tunnels with different depths; (g) forming a lateral strengthening structure at a peripheral wall of said plural tunnels with different depths; (h) removing said second mask layer, a portion of said lateral strengthening structure below said second mask layer, and a part of said substrate by a third etching process so as to form a lower structure and expose an unstrengthened structure; (i) etching said unstrengthened structure laterally so as to form an upper structure.