Apparatus for detecting an amount of strain and method for manufacturing same

Abstract

An apparatus for detecting an amount of strain comprises a strain generating part, an electrical insulating layer and sensing elements. The strain generating part is a member to which strain is to be applied. The electrical insulating layer is formed on the strain generating part. The sensing elements are formed on the electrical insulating layer. Each of the sensing elements is made of a silicon film. The silicon film comprises a poly-crystalline main layer and a poly-crystalline interface-layer, which comes into contact with the electrical insulating layer.

What is claimed is:  
     
         1 . An apparatus for detecting an amount of strain comprising: 
 a strain generating part to which strain is to be applied;    an electrical insulating layer formed on the strain generating part; and    sensing elements formed on the electrical insulating layer, each of said sensing elements being made of a silicon film, said silicon film comprising a poly-crystalline main layer and a poly-crystalline interface-layer, which comes into contact with the electrical insulating layer.    
     
     
         2 . The apparatus as claimed in  claim 1 , wherein: 
 said silicon film is subjected, after formation thereof, to an annealing process at a temperature of from 540° C. to 590° C.    
     
     
         3 . The apparatus as claimed in  claim 1 , wherein: 
 said strain generating part has a main body made of martensitic precipitation hardened stainless steel, which comprises from 3 to 5 wt. % Ni, from 15 to 17.5 wt. % Cr and from 3 to 5 wt. % Cu.    
     
     
         4 . The apparatus as claimed in  claim 2 , wherein: 
 said silicon film contains an impurity as added in such a manner that specific resistance of the silicon film before said annealing process is within a range of from 7×10 −3  Ω·cm to 3.3×10 −2  Ω·cm and the specific resistance of the silicon film after said annealing process is within a range of from 3×10 −3  Ω·cm to 1.7×10 −2  Ω·cm.    
     
     
         5 . The apparatus as claimed in  claim 4 , wherein: 
 said impurity is boron.    
     
     
         6 . A method for manufacturing an apparatus for detecting an amount of strain, comprising the steps of: 
 (a) preparing a strain generating part to which strain is to be applied,;    (b) forming an electrical insulating layer on said strain generating part;    (c) preparing material for a silicon film; and    (d) forming the silicon film on said electrical insulating layer, utilizing said material to provide sensing elements thereon, said silicon film comprising a polycrystalline main layer and an interface-layer, which comes into contact with the electrical insulating layer,    characterized in that: 
 said step (a) is carried out, utilizing martensitic precipitation hardened stainless steel, which comprises from 3 to 5 wt. % Ni, from 15 to 17.5 wt. % Cr and from 3 to 5 wt. % Cu, to form a main body of said strain generating part;  
 said step (c) comprises adding boron as an impurity to said material for the silicon film so that specific resistance of the silicon film is within a range of from 7×10 −3  Ω·cm to 3.3×10 −2  Ω·cm; and  
 said method further comprises (e) subjecting, after said step (d), said silicon film to an annealing process at a temperature of from 540° C. to 590° C. so that the specific resistance of the silicon film is within a range of from 3×10 −3  Ω·cm to 1.7×10 −2  Ω·cm, thus crystallizing said interface-layer.  
   
     
     
         7 . The method as claimed in  claim 6 , wherein: 
 said step (e) is carried out in plasma into gas.