Silicon penetration device with increased fracture toughness and method of fabrication

Abstract

A silicon penetration device with increased fracture toughness and method of fabrication thereof are provided. The method comprises strengthening silicon penetration devices by thermally growing a silicon oxide layer on the penetration device and then subsequently stripping the silicon oxide. The method also includes strengthening silicon penetration devices through the sputtering of thin film coatings on the silicon penetration devices.

We claim as our invention  
     
         1 . A method of forming a silicon penetration device having increased fracture toughness, the method comprising: 
 cleaning the surface of the silicon penetration device;    heating the cleaned silicon penetration device;    exposing the silicon penetration device to a reactive environment at elevated temperature to form an adherent film on the surface of the penetration device, the reactive environment containing one or more of the following reactants at one time, or in a sequence: oxygen, ozone, steam, hydrogen, ammonia, nitrous oxide, nitric oxide, nitrogen;    cooling the silicon penetration device; and    etching the silicon penetration device to remove at least a part of the adherent film.    
     
     
         2 . The method of  claim 1  wherein, during the cleaning step, the silicon penetration device is RCA cleaned.  
     
     
         3 . The method of  claim 1  wherein the heating step is accomplished by a Tylan oxide furnace.  
     
     
         4 . The method of  claim 1  wherein during the heating step the temperature of the device is raised to 1100 degrees Celsius.  
     
     
         5 . The method of  claim 1  wherein the cooling step begins when the silicon penetration device has approximately one (1) micrometer of film has grown on the surface of the silicon substrate.  
     
     
         6 . The method of  claim 1  wherein during the etching step the silicon penetration device is placed in a 6:1 solution of water and hydrofluoric acid.  
     
     
         7 . The method of  claim 1  wherein during the etching step the silicon penetration device is placed in a buffered oxide etchant (BOE) for approximately thirty (30) minutes such that the thermally grown surface layer is removed and the smoothened surface of the silicon substrate is exposed.  
     
     
         8 . A method of forming a penetration device having increased fracture toughness, the method comprising: 
 cleaning the surface of the silicon penetration device;    heating the cleaned silicon penetration device;    exposing the silicon penetration device to a dry oxygen environment at elevated temperature to form an adherent film on the surface of the penetration device;    introducing a wet steam into the oxygen environment;    further exposing the silicon penetration device to a dry oxygen environment;    cooling the silicon penetration device; and    etching the silicon penetration device to remove at least a part of the oxide film.    
     
     
         9 . The method of  claim 8  wherein the first exposure of the silicon penetration device to a dry oxygen environment is for about five (5) minutes;  
     
     
         10 . The method of  claim 8  wherein the wet steam is introduced into the furnace for a variable predetermined time such that silicon oxide growth rate on the silicon substrate is approximately forty (40) Angstroms per minute;  
     
     
         11 . The method of  claim 8  wherein the cooling step begins when approximately one (1) micrometer of silicon oxide has grown on the surface of the silicon substrate.  
     
     
         12 . A method of forming a penetration device having increased fracture toughness, the method comprising: cleaning the silicon penetration device; and depositing a nickel film on the silicon substrate.  
     
     
         13 . The method of  claim 12  wherein during the cleaning step the silicon penetration device is submerged into methylene chloride (CH 2 Cl 2 ).  
     
     
         14 . The method of  claim 13  wherein during the cleaning step the silicon penetration device is cleaned for approximately ten (10) minutes.  
     
     
         15 . The method of  claim 12  wherein during the depositing step the nickel film is sputtered on the silicon substrate to a thickness of approximately one (1) micrometer.  
     
     
         16 . The method of  claim 12  wherein during the depositing step the nickel film is deposited on the substrate at a power of approximately five-hundred (500) watts and at a rate of approximately four hundred and ninety-five (495) Angstroms per minute.  
     
     
         17 . A penetration device with increased fracture toughness, comprising: 
 an unprocessed silicon penetration device; and    an adherent film comprising silicon reacted with one or more of the following: oxygen, ozone, steam, hydrogen, ammonia, nitrous oxide, nitric oxide, nitrogen on the silicon substrate, at least a portion of which is removed by an etchant.    
     
     
         18 . A penetration device with increased fracture toughness, comprising: 
 an unprocessed silicon substrate;    a silicon oxide layer on the silicon substrate, at least a portion of which is removed by an etchant.    
     
     
         19 . The penetration device of  claim 18  wherein the device is RCA cleaned.  
     
     
         20 . The penetration device of  claim 18  wherein the silicon oxide layer is formed in a Tylan oxide furnace having a temperature of approximately 1100 degrees Celsius.  
     
     
         21 . The penetration device of  claim 18  wherein wet steam is introduced into a furnace.  
     
     
         22 . The penetration device of  claim 18  wherein the silicon oxide layer has a growth rate on the silicon substrate of approximately forty (40) Angstroms per minute;  
     
     
         23 . The penetration device of  claim 18  wherein the silicon oxide layer has a thickness of approximately one (1) micrometer.  
     
     
         24 . The penetration device of  claim 18  wherein the etchant used to remove at least a portion of the silicon oxide layer is a buffered oxide etchant.  
     
     
         25 . A penetration device with increased fracture toughness, the device comprising; 
 an unprocessed silicon penetration device; and    a nickel film deposited on the silicon substrate of the penetration device.    
     
     
         26 . The penetration device of  claim 23  wherein the nickel film is sputtered on the silicon substrate to a thickness of approximately one (1) micrometer.  
     
     
         27 . The penetration device of  claim 24  wherein the nickel film is deposited on the substrate at a power of approximately five-hundred (500) watts and at a rate of approximately four hundred and ninety-five (495) Angstroms per minute.