Wet and dry etching process on <110> silicon and resulting structures

Abstract

A method of producing smooth sidewalls on a micromachined device is described. A portion of the wafer is dry etched, forming a dry etched sidewall. The sidewall is covered with a mask. An area adjacent to the dry etched area is wet etched, forming a wet etched sidewall. The mask may optionally be removed after wet etching. The wafer substrate has a <110> orientation, which allows the wet etched area to have nearly vertical wet etched sidewalls.

What is claimed as new and desired to be protected by Letters Patent of the United States is:  
     
         1 . A method of forming an anisotropically wet etched sidewall adjacent to a dry etched sidewall in a <110> substrate, said method comprising: 
 directionally dry etching into an area of a <110> oriented substrate to form a dry etched sidewall;  
 coating the dry etched sidewall with a mask material resistant to an anisotropic wet etchant; and  
 anisotropically wet etching an area adjacent to the dry etched sidewall to form a wet etched sidewall.  
 
     
     
         2 . The method of  claim 1 , further comprising removing the mask material after said anisotropically wet etching.  
     
     
         3 . The method of  claim 1 , wherein said anisotropically wet etching forms a <111> sidewall at an angle of between ten and thirty degrees from a surface of the <110> substrate.  
     
     
         4 . The method of  claim 1 , wherein the substrate comprises silicon.  
     
     
         5 . The method of  claim 1 , wherein the mask material comprises one or more of the group consisting of silicon dioxide, silicon nitride, and tantalum oxide.  
     
     
         6 . The method of  claim 1 , wherein the dry etched sidewall and the wet etched sidewall are disposed on a flexure.  
     
     
         7 . The method of  claim 6 , wherein the area being anisotropically wet etched extends a distance greater than the width of the wet etched sidewall.  
     
     
         8 . The method of  claim 7 , wherein the wet etched sidewall is disposed on a pedestal.  
     
     
         9 . The method of  claim 7 , wherein the pedestal is of greater width than the flexure.  
     
     
         10 . The method of  claim 1 , further comprising removing remaining wedges after said anisotropically wet etching.  
     
     
         11 . A micromachined device formed in a <110> crystal substrate, comprising: 
 a dry etched sidewall; and  
 an anisotropically wet etched sidewall adjacent to said dry etched sidewall.  
 
     
     
         12 . The micromachined device of  claim 11 , wherein said wet etched sidewall is formed from a larger wet etched area.  
     
     
         13 . The micromachined device of  claim 11 , wherein said wet etched sidewall is located on a pedestal.  
     
     
         14 . The micromachined device of  claim 13 , wherein said pedestal is located on a structure.  
     
     
         15 . The micromachined device of  claim 14 , wherein said pedestal comprises a second wet etched sidewall opposite said wet etched sidewall.  
     
     
         16 . The micromachined device of  claim 14 , wherein said wet etched sidewall is located on an expanded portion of said pedestal, said pedestal being wider than said structure.  
     
     
         17 . The micromachined device of  claim 16 , wherein said structure is a stationary portion.  
     
     
         18 . The micromachined device of  claim 16 , wherein said structure is a flexure.  
     
     
         19 . The micromachined device of  claim 18 , wherein said pedestal is located at an end of said flexure.  
     
     
         20 . The micromachined device of  claim 18 , wherein said pedestal is located in the middle of said flexure.  
     
     
         21 . The micromachined device of  claim 18 , further comprising an electrostatic actuator for moving said flexure.  
     
     
         22 . The micromachined device of  claim 21 , wherein said electrostatic actuator comprises a comb drive.  
     
     
         23 . The micromachined device of  claim 21 , wherein said electrostatic actuator comprises a cantilever.  
     
     
         24 . The micromachined device of  claim 18 , further comprising a stationary portion spaced apart from said flexure.  
     
     
         25 . The micromachined device of  claim 24 , wherein a space between said flexure and said stationary portion may be altered.  
     
     
         26 . The micromachined device of  claim 24 , wherein said flexure may be rotated relative to said stationary portion.  
     
     
         27 . The micromachined device of  claim 24 , wherein said stationary portion comprises a second pedestal, said second pedestal being wider than said stationary portion.  
     
     
         28 . The micromachined device of  claim 27 , wherein said second pedestal comprises a second wet etched sidewall spaced apart from said wet etched sidewall.  
     
     
         29 . The micromachined device of  claim 11 , wherein said wet etched sidewall is defined by a nearly vertical <111> plane.  
     
     
         30 . The micromachined device of  claim 11 , wherein said wet etched sidewall comprises an optical quality sidewall.  
     
     
         31 . The micromachined device of  claim 11 , wherein said substrate is a single crystal silicon substrate.