Micro-fabrication method and equipment thereby

Abstract

An SrTiO 3 monocrystal substrate having a crystallographic plane (100) or (110) is anisotropically etched in an H 3 PO 4 solution using an SiO 2 thin film as an etching mask. The H 3 PO 4 solution is maintained at a boiling point of approximately 150 deg. C. for increasing an etching rate and enhancing selectivity for protection with the SiO 2 thin film mask.

What is claimed is:  
     
         1 . A microfabrication method, comprising the steps of: 
 (a) providing an SrTiO 3  monocrystal substrate having a (100) plane on a surface thereof;    (b) forming an SiO 2  film on said (100) plane of said SrTiO 3  monocrystal substrate;    (c) removing a part of said SiO 2  film according to a predetermined pattern;    (d) providing an H 3 PO 4  solution maintained at a predetermined temperature;    (e) immersing said SrTiO 3  monocrystal substrate in said H 3 PO 4  solution for a predetermined period of time; and    (f) taking said SrTiO 3  monocrystal substrate out of said H 3 PO 4  solution.    
     
     
         2 . A microfabrication method as claimed in  claim 1 , further comprising the steps of: 
 (a) removing said SiO 2  film from said (100) plane on the surface of said SrTiO 3  monocrystal substrate; and    (b) epitaxially growing a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film on said (100) plane on the surface of said SrTiO 3  monocrystal substrate.    
     
     
         3 . A microfabrication method as claimed in  claim 1 , further comprising the step of: 
 (a) epitaxially growing a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film on a (100) plane on the back side of said SrTiO 3  monocrystal substrate.    
     
     
         4 . A microfabrication method, comprising the steps of: 
 (a) providing an SrTiO 3  monocrystal substrate having (100) planes on mutually opposed surfaces thereof;    (b) epitaxially growing a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film on one of said (100) planes of said SrTiO 3  monocrystal substrate;    (c) forming an SiO 2  film on said YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film;    (d) forming an SiO 2  film on the other one of said (100) planes of said SrTiO 3  monocrystal substrate;    (e) removing a part of said SiO 2  film from each of said (100) planes of said SrTiO 3  monocrystal substrate according to a predetermined pattern;    (f) forming a protective material on said SiO 2  film on said YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film;    (g) providing an H 3 PO 4  solution maintained at a predetermined temperature;    (h) immersing said SrTiO 3  monocrystal substrate in said H 3 PO 4  solution for a period of time required for etching said SrTiO 3  monocrystal substrate according to the predetermined pattern corresponding to the removed part of said SiO 2  film; and    (i) taking said SrTiO 3  monocrystal substrate out of said H 3 PO 4  solution.    
     
     
         5 . A microfabrication method, comprising the steps of: 
 (a) providing an SrTiO 3  monocrystal substrate having at least one (110) plane on a surface thereof;    (b) forming an SiO 2  film on said (110) plane of said SrTiO 3  monocrystal substrate;    (c) removing a part of said SiO 2  film according a predetermined pattern;    (d) providing an H 3 PO 4  solution maintained at a predetermined temperature;    (e) immersing said SrTiO 3  monocrystal substrate in said H 3 PO 4  solution for a predetermined period of time; and    (f) taking said SrTiO 3  monocrystal substrate out of said H 3 PO 4  solution.    
     
     
         6 . A microfabrication method as claimed in  claim 5 , further comprising the steps of: 
 (a) removing said SiO 2  film from said (110) plane on the surface of said SrTiO 3  monocrystal substrate; and    (b) epitaxially growing a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film on said (110) plane on the surface of said SrTiO 3  monocrystal substrate.    
     
     
         7 . A microfabrication method as claimed in  claim 5 , further comprising the step of: 
 (a) epitaxially growing a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film on a (110) plane on the back side of said SrTiO 3  monocrystal substrate.    
     
     
         8 . A microfabrication method, comprising the steps of: 
 (a) providing an SrTiO 3  monocrystal substrate having (110) planes on mutually opposed surfaces thereof;    (b) epitaxially growing a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film on one of said (110) planes of said SrTiO 3  monocrystal substrate;    (c) forming an SiO 2  film on said YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film;    (d) forming an SiO 2  film on the other one of said (110) planes of said SrTiO 3  monocrystal substrate;    (e) removing a part of said SiO 2  film from each of said (110) planes of said SrTiO 3  monocrystal substrate according to a predetermined pattern;    (f) forming a protective material on said SiO2 film on said YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film;    (g) providing an H 3 PO 4  solution maintained at a predetermined temperature;    (h) immersing said SrTiO 3  monocrystal substrate in said H 3 PO 4  solution for a period of time required for etching said SrTiO 3  monocrystal substrate according to the predetermined pattern corresponding to the removed part of said SiO 2  film; and    (i) taking said SrTiO 3  monocrystal substrate out of said H 3 PO 4  solution.    
     
     
         9 . A microfabrication method as claimed in  claim 1 , further comprising the steps of: 
 (a) applying a part to be molded to said (100) plane of said SrTiO 3  monocrystal substrate taken out of said H 3 PO 4  solution; and    (b) separating said part thus molded from said SrTiO 3  monocrystal substrate.    
     
     
         10 . A microfabrication method as claimed in  claim 5 , further comprising: 
 (a) applying a part to be molded to said (110) plane of said SrTiO 3  monocrystal substrate taken out of said H 3 PO 4  solution; and    (b) separating said part thus molded from said SrTiO 3  monocrystal substrate.    
     
     
         11 . A superconducting quantum interference device using a Josephson junction, comprising: 
 (a) a monolithic SrTiO 3  monocrystal substrate having one of (100) and (110) planes on a surface thereof, said SrTiO 3  monocrystal substrate having a step difference part formed to provide areas which are different in height; and    (b) a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film epitaxially grown on the surface of said SrTiO 3  monocrystal substrate including said step difference part, said YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film being patterned to form a closed loop circuit.    
     
     
         12 . A magnetic field sensor, comprising: 
 (a) an SrTiO 3  monocrystal substrate having one of (100) and (110) planes on a surface thereof, a center area thereof being formed to have a cutout part; and    (b) a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film epitaxially grown on the surface of said SrTiO 3  monocrystal substrate including said cutout part.    
     
     
         13 . A magnetic field sensor as claimed in  claim 12 , further comprising: 
 (a) a photoreflective film formed on the external surface of said YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film.    
     
     
         14 . A electric field sensor, comprising: 
 an SrTiO 3  monocrystal substrate having one of (100) and (110) planes, a center area thereof being formed to provide a self-supporting film which is thinner than the other areas.    
     
     
         15 . A electric field sensor as claimed in  claim 14 , further comprising: 
 a photoreflective film formed on one side of said self-supporting film.    
     
     
         16 . A probe for a magnetic force microscope, comprising: 
 an SrTiO 3  monocrystal substrate structured to contain two continuous parts having different thicknesses, each of said parts having the same one of (100) and (110) planes;    a holder attached to one of said parts which has a larger dimension in thickness in said substrate; and    a stylus formed out of a YBa 2 Cu 3 O 7-δ  high-temperature superconductor thin film at the tip end of the other one of said parts which has a smaller dimension in thickness in said substrate.    
     
     
         17 . A probe for a magnetic force microscope as claimed in  claim 16 , further comprising: 
 a photoreflective film formed on the side opposite from where said stylus is formed.