Silicon substrate comprising positive etching profiles with a defined slope angle, and production method

Abstract

The invention relates to a silicon substrate comprising positive etching profiles with defined slope angle. Said silicon substrate is obtained by etching the silicon substrate that is covered with a mask and by carrying out the following steps: a) the silicon substrate is isotropically etched, the undercut u of the mask being approximately identical to the etching depht A t ; b) the etching depth is increased by means of anisotropic etching in alternating etching steps and polynerization steps during which the undercut of the mask remains constant and the etching front follows a new course, the sidewalls of the structure being coated with a polymer in said step; c) the polymer is removed from the structure; and d) steps a) to c) are repeated until the predefined etching profile has been obtained. Also disclosed is a method.

1 . Silicon substrate with positive etching profiles having a defined slope angle, obtained by etching of the silicon substrate, wherein the silicon substrate is covered by a mask and the following steps 
 a) iso-tropic etching of the silicon substrate, wherein the mask under etching u is approximately equal to the etching depth A t ,    b) enlargement of the etching depth by iso-tropic etching with alternating, successively following etching steps and polymerization steps, wherein the mask under etching remains constant and wherein the etching front obtains a new course, and wherein the side walls of structure are covered with a polymer with this step,    c) removal of the polymer from the structure, and    d) repeating the steps a) through c) until the predetermined etching profile has been reached.    
   
   
       2 . Method for plasma etching for generating positive etched profiles with defined slope angle in silicon substrates, wherein this silicon substrate is covered with a mask and wherein 
 a) silicon substrate is initially iso-tropically etched such that the mask under etching u is approximately equal to the etching depth At,    b) following thereto the etching depth becomes enlarged by aniso-tropic etching with alternatingly successively following etching steps and polymerization steps, such that the mask under etching remains constant and the etching frowned obtains a new course, wherein the side walls of the structure are covered with a polymer in this step,    c) thereupon the polymer is removed at the side walls of the structure, and    d) the steps a) through c) and I repeated as many times until the predetermined etched profile has been reached.    
   
   
       3 . Method according to  claim 2  characterized in that the silicon substrate is iso-tropically etched in a SF 6 -plasma.  
   
   
       4 . Method according to  claim 2  characterized in that the enlargement of the etching depth is performed by an aniso-tropic etching process, wherein the pressures for the process gases are from 1.0 to 5.3 Pa and the interval times amount to 3 to 12 seconds in the aniso-tropic etching process.  
   
   
       5 . Method according to one of the  claim 2  characterized in that the removal of the polymer is performed by way of an O 2 -plasma.  
   
   
       6 . Method according to one of  claim 2  characterized in that the slope angle β in the etching profile is determined by adjustment of a time ratio between the steps a) and b).  
   
   
       7 . Method according to  claim 6  characterized in that the step b) is prolonged and that the time ratio is therefrom determined.  
   
   
       8 . Method according to  claim 6  characterized in that the step a) is prolonged and that the time ratio is therefrom determined.