Defect Etching of Germanium

Abstract

The present invention provides an etching solution for revealing defects in a germanium layer, a method for revealing defects in a germanium layer using such an etching solution and to a method for making such an etching solution. The etching solution according to embodiments of the present invention is able to exhibit an etch rate of between 4 nm·min −1 and 450 nm·min −1 , which makes it suitable to be used for revealing defects in a thin layer of germanium, i.e. in a layer of germanium with a thickness of between 20 nm and 10 μm, for example between 20 nm and 2 μm, between 20 nm and 1 μm or between 20 nm and 200 nm.

1 . An etching solution for revealing defects in a germanium layer, the solution consisting of:
 an oxidizing agent comprising Ce 4+  or MnO 4   − , and   a solvent.   
     
     
         2 . An etching solution according to  claim 1 , wherein the etching solution exhibits, when in use, an etch rate of between 4 nm·min −1  and 450 nm·min −1 . 
     
     
         3 . An etching solution according to  claim 2 , wherein the etch rate is between 4 nm·min −1  and 200 nm·min −1 . 
     
     
         4 . An etching solution according to  claim 1 , wherein the solvent is water. 
     
     
         5 . An etching solution according to  claim 1 , wherein the etching solution comprises Ce 4+ . 
     
     
         6 . An etching solution according to  claim 5 , wherein Ce 4+  is present in a concentration of between 0.01 mol·L −1  and 1 mol·L −1 . 
     
     
         7 . An etching solution according to  claim 6 , wherein the Ce 4+  concentration is lower than 0.4 mol·L −1 . 
     
     
         8 . An etching solution according to  claim 1 , wherein the etching solution comprises MnO 4   − . 
     
     
         9 . An etching solution according to  claim 8 , wherein MnO 4   −  is present in a concentration of between 0.01 mol·L −1  and 0.6 mol·L −1 . 
     
     
         10 . An etching solution according to  claim 9 , wherein the etching solution further comprises HF. 
     
     
         11 . An etching solution according to  claim 10 , wherein HF is present in a concentration of between 0 mol·L −1  and 5 mol·L −1 . 
     
     
         12 . An etching solution according to  claim 1 , wherein the etching solution has a selectivity towards the defects of 1, the selectivity being defined as the ratio of a width of an etched figure to an etch depth of the etched figure. 
     
     
         13 . A method for revealing defects in a thin germanium layer, the method comprising immersing the thin germanium layer in an etching solution consisting of an oxidizing agent comprising Ce 4+  or MnO 4   − , and a solvent, wherein the thin germanium layer has a thickness between 20 nm and 2 μm. 
     
     
         14 . A method for making an etching solution for revealing defects in a germanium layer, the etching solution being able to exhibit an etch rate of between 4 nm·min −1  and 450 nm·min −1 , the method comprising:
 providing an oxidizing agent comprising Ce 4+  or MnO 4   −  in a container and   adding a solvent.   
     
     
         15 . A method according to  claim 14 , wherein the oxidizing agent comprises Ce 4+ . 
     
     
         16 . A method according to  claim 15 , wherein Ce 4+  is provided in a concentration of between 0.01 mol·L −1  and 1 mol·L −1 . 
     
     
         17 . A method according to  claim 14 , wherein the oxidizing agent comprises MnO 4   − . 
     
     
         18 . A method according to  claim 17 , wherein MnO 4   −  is provided in a concentration of between 0.01 mol·L −1  and 0.6 mol·L −1 . 
     
     
         19 . A method according to  claim 18 , wherein the method further comprises adding HF to the etching solution. 
     
     
         20 . A method according to  claim 19 , wherein HF is provided in a concentration of between 0 mol·L −1  and 5 mol·L −1 . 
     
     
         21 . An etching solution for revealing defects in a germanium layer prepared according to  claim 14 . 
     
     
         22 . A method for revealing defects in a germanium layer, the method comprising immersing a substrate comprising the germanium layer in an etching solution consisting of an oxidizing agent comprising Ce 4+  or MnO 4   − , and a solvent, the etching solution being able to exhibit an etch rate of between 4 nm·min −1  and 450 nm·min −1 . 
     
     
         23 . A method according to  claim 22 , wherein immersing the substrate comprising the germanium layer in the etching solution is performed during a time period of between 1.5 minutes and 10 minutes.