Flow sensor using a heat element and a resistance temperature detector formed of a metal film

Abstract

The present invention provides a technology capable of achieving a highly-sensitive flow sensor, by forming a metal film having a relatively high TCR on a semiconductor substrate via an insulating film. A measurement device which is a thermal fluid flow sensor includes a heat element, resistance temperature detectors (upstream-side resistance temperature detector and downstream-side resistance temperature detector), and a resistance temperature detector for air which are all formed of a first metal film. The first metal film is formed of an α-Ta film having a resistivity lower than three times the resistivity of a Ta ingot and obtained by deposition through sputtering on an amorphous film containing metal.

1. A flow sensor, which includes a heat element and a resistance temperature detector formed above a semiconductor substrate with an insulating film in-between and measures a fluid or gas flow,
 wherein at least said resistance temperature detector is formed of a metal film which is directly formed on an amorphous film, said amorphous film contains metal and is provided on said insulating film, and 
 a resistivity of said metal film is lower than three times the resistivity of an ingot, which is made of a main metal element forming said metal film. 
 
     
     
       2. The flow sensor according to  claim 1 , wherein said metal film is any one of a Ta film, a Mo film, a Ti film, a W film, a Co film, a Ni film, a Nb film, a Hf film, a Cr film, a Zr film, and an Fe film. 
     
     
       3. The flow sensor according to  claim 1 , wherein said metal film is a Ta film, and a Ta crystal having a body-centered cubic crystal structure accounts for 50% or more of said Ta film. 
     
     
       4. The flow sensor according to  claim 3 , wherein said Ta film includes a plurality of Ta crystal grains, and said plurality of crystal grains have a relation in which a crystal lattice arrangement in the grains forms a twin crystal or a relation of a small angel grain boundary in which a lattice plane angle is within 20 degrees. 
     
     
       5. The flow sensor according to  claim 4 , wherein said plurality of crystal grains having an adjacent grain-boundary contact such as the relation in which a crystal lattice arrangement in the grains forms a twin crystal or the relation of a small angle grain boundary in which a lattice plane angle is within 20 degrees account for approximately 30% of a polycrystal region. 
     
     
       6. The flow sensor according to  claim 1 , wherein said metal film is a polycrystal in which crystal grains having a particle diameter of 100 nm or more account for 50% or more of said metal film. 
     
     
       7. The flow sensor according to  claim 1 , wherein said amorphous film containing metal has a thickness of 50 nm or smaller. 
     
     
       8. The flow sensor according to  claim 1 , wherein said amorphous film containing metal is any one of a TaOx film, an AlOx film, a TiOx film, a MoOx film, and an AlNx film. 
     
     
       9. The flow sensor according to  claim 1 , wherein an oxidized compound containing metal is formed on said metal film. 
     
     
       10. The flow sensor according to  claim 9 , wherein said oxidized compound containing metal is any one of AlOx, MoOx, TaOx, and TiOx. 
     
     
       11. The flow sensor according to  claim 1 , wherein a nitrided compound containing metal is formed on said metal film. 
     
     
       12. The flow sensor according to  claim 11 , wherein said nitrided compound containing metal is any one of MoN, TiN, TaN, WN, and NiN. 
     
     
       13. The flow sensor according to  claim 1 , wherein said flow sensor is mounted in a thermal air flowmeter together with a support member and an external circuit and measures an air flow. 
     
     
       14. A flow sensor, which includes a heat element and a resistance temperature detector formed above a semiconductor substrate with an insulating film in-between and measures a fluid or gas flow,
 wherein at least said resistance temperature detector is formed of a metal film which is directly formed on a reforming film layer, said reforming film layer has bonds of a composition element of said insulating film and is provided on a surface of said insulating film, and 
 a resistivity of said metal film is lower than three times the resistivity of an ingot, which is made of the main metal element forming said metal film. 
 
     
     
       15. The flow sensor according to  claim 14 , wherein said reforming layer is formed by either one of sputter-etching and ion implantation. 
     
     
       16. The flow sensor according to  claim 14 , wherein said insulating film is either one of a SiOx film and a SiNx film. 
     
     
       17. The flow sensor according to  claim 14 , wherein said metal film is any one of a Ta film, a Mo film, a Ti film, a W film, a Co film, a Ni film, a Nb film, a Hf film, a Cr film, a Zr film, and a Fe film. 
     
     
       18. The flow sensor according to  claim 14 , wherein said metal film is a Ta film, and a Ta crystal having a body-centered cubic crystal structure accounts for 50% or more of said Ta film. 
     
     
       19. The flow sensor according to  claim 18 , wherein said Ta film includes a plurality of Ta crystal grains, and said plurality of crystal grains have a relation in which a crystal lattice arrangement in the grains forms a twin crystal or a relation of a small angle grain boundary in which a lattice plane angle is within 20 degrees. 
     
     
       20. The flow sensor according to  claim 19 , wherein said plurality of crystal grains having an adjacent grain-boundary contact such as the relation in which a crystal lattice arrangement in the grains forms a twin crystal or the relation of a small angle grain boundary in which a lattice plane angle is within 20 degrees account for approximately 30% of a polycrystal region. 
     
     
       21. The flow sensor according to  claim 14 , wherein said metal film is a polycrystal in which crystal grains having a particle diameter of 100 nm or more account for 50% or more of said Ta film. 
     
     
       22. The flow sensor according to  claim 14 , wherein an oxidized compound containing metal is formed on said metal film. 
     
     
       23. The flow sensor according to  claim 22 , wherein said oxidized compound containing metal is any one of AlOX, MoOX, TaOX, and TiOX. 
     
     
       24. The flow sensor according to  claim 14 , wherein a nitrided compound containing metal is formed on said metal film. 
     
     
       25. The flow sensor according to  claim 24 , wherein said nitrided compound containing metal is any one of MoN, TiN, TaN, WN, and NiN. 
     
     
       26. The flow sensor according to  claim 14 , wherein said flow sensor is mounted in a thermal air flowmeter together with a support member and an external circuit, and measures an air flow. 
     
     
       27. A flow sensor, which includes a heat element and a resistance temperature detector formed above a semiconductor substrate with an insulating film in-between and measures a fluid or gas flow,
 wherein said heat element and said resistance temperature detector are formed of a metal film which is directly formed on an amorphous film, said amorphous film contains metal and is provided on said insulating film, 
 a resistivity of said metal film is lower than three times the resistivity of an ingot, which is made of a main metal element forming said metal film, and 
 a temperature coefficient of resistance of said metal film is 2000 ppm/° C. or more. 
 
     
     
       28. The flow sensor according to  claim 27 , wherein said metal film is a Mo film. 
     
     
       29. The flow sensor according to  claim 27 , wherein said metal film is a Ta film, and said temperature coefficient of resistance of said Ta film is 2500 ppm/° C. or more. 
     
     
       30. A flow sensor, which includes a heat element and a resistance temperature detector formed above a semiconductor substrate with an insulating film in-between and measures a fluid or gas flow,
 wherein said heat element and said resistance temperature detector are formed of a metal film which is directly formed on a reforming film layer, said reforming film layer has bonds of a composition element of said insulating film and is provided on a surface of said insulating film, 
 a resistivity of said metal film is lower than three times the resistivity of an ingot, which is made of a main metal element forming said metal film, and 
 a temperature coefficient of resistance of said metal film is 2000 ppm/° C. or more. 
 
     
     
       31. The flow sensor according to  claim 30 , wherein said metal film is a Mo film. 
     
     
       32. The flow sensor according to  claim 30 , wherein said metal film is a Ta film, and said temperature coefficient of resistance of said Ta film is 2500 ppm/° C. or more. 
     
     
       33. A flow sensor which measures a fluid or gas flow comprising:
 a measurement device which comprises:   a semiconductor substrate;   a heat element and a resistance temperature detector formed above said semiconductor substrate with an insulating film in-between, and   a control circuit,   wherein at least said resistance temperature detector is formed of a metal film which is formed on a reformed layer of said insulating film, said reformed layer has bonds of a composition element of said insulating film and is provided on a surface of said insulating film, and   wherein said control circuit receives a signal from said measurement device that is based on a temperature of said heat element.    
     
     
       34. The flow sensor according to claim 33,
 wherein a first resistance temperature detector formed of said metal film is provided closer to said heat element than a second resistance temperature detector formed of said metal film, and   wherein said control circuit receives a first signal corresponding to said first resistance temperature detector and a second signal corresponding to said second resistance temperature detector, and   wherein said control circuit controls said measurement device so that a temperature of said first resistance temperature detector based on said first signal is higher than a temperature of said second resistance temperature based on said second signal by a predetermined value.    
     
     
       35. The flow sensor according to claim 34, further comprising:
 a transistor supplying a current to said heat element,   wherein when said temperature of said first resistance temperature detector is lower than a set value, said control circuit controls said transistor to turn on, and   wherein when said temperature of said first resistance temperature detector is higher than the set value, said control circuit controls said transistor to turn off.    
     
     
       36. The flow sensor according to claim 35,
 wherein the control circuit monitors said fluid or gas flow based on said current.    
     
     
       37. The flow sensor according to claim 33,
 wherein said control circuit is formed on a different substrate from said semiconductor substrate.    
     
     
       38. The flow sensor according to claim 33,
 wherein said control circuit is formed on said semiconductor substrate.    
     
     
       39. A flow sensor which measures a fluid or gas flow comprising:
 a semiconductor substrate; and   a heat element and a resistance temperature detector formed above said semiconductor substrate with an insulating film in-between,   wherein at least said resistance temperature detector is formed of a metal film which is formed on a reformed layer of said insulation film so that an orientation of said metal film is improved, said reformed layer has bonds of a composition element of said insulating film and is provided on a surface of said insulating film.   
     
     
       40. The flow sensor according to claim 39,
 wherein said reformed layer is formed by performing either one of sputter-etching and ion implantation.   
     
     
       41. The flow sensor according to claim 39,
 wherein said insulating film is either one of a SiOx film and a SiNx film.   
     
     
       42. The flow sensor according to claim 39,
 wherein said metal film is any one of a Ta film, a Mo film, a Ti film, a W film, a Co film, a Ni film, a Nb film, a Hf film, a Cr film, a Zr film and a Fe film.   
     
     
       43. The flow sensor according to claim 39,
 wherein a nitrided compound containing metal is formed on said metal film and said nitrided compound containing metal is any one of MoN, TiN, TaN, WN and NiN.   
     
     
       44. The flow sensor according to claim 39,
 wherein an oxidized compound containing metal is formed on said metal film and said oxidized compound containing metal is any one of AlOx, MoOx, TaOx and TiOx.   
     
     
       45. A flow sensor which measures a fluid or gas flow comprising:
 a measurement device which comprises:   a semiconductor substrate; and   a heat element and a resistance temperature detector formed above said semiconductor substrate with an insulating film in-between; and   a control circuit,   wherein at least said resistance temperature detector is formed of a metal film which is directly on an amorphous film, said amorphous film contains metal and is provided or said insulating film, and   wherein said control circuit receives a signal from said measurement device that is based on a temperature of said heat element.   
     
     
       46. The flow sensor according to claim 45,
 wherein a first resistance temperature detector formed of said metal film is provided closer to said heat element than a second resistance temperature detector formed of said metal film, and   wherein said control circuit receives a first signal corresponding to said first resistance temperature detector and a second signal corresponding to said second resistance temperature detector, and   wherein said control circuit controls said measurement device so that a temperature of said first resistance temperature detector based on said first signal is higher than a temperature of said second resistance temperature based on said second signal by a predetermined value.   
     
     
       47. The flow sensor according to claim 46, further comprising:
 a transistor supplying a current to said heat element,   wherein when said temperature of said first resistance temperature detector is lower than a set value, said control circuit controls said transistor to turn on, and   wherein when said temperature of said first resistance temperature detector is higher than the set value, said control circuit controls said transistor to turn off.   
     
     
       48. The flow sensor according to claim 47,
 wherein the control circuit monitors said fluid or gas flow based on said current.   
     
     
       49. The flow sensor according to claim 45,
 wherein said control circuit is formed on a different substrate from said semiconductor substrate.   
     
     
       50. The flow sensor according to claim 45,
 wherein said control circuit is formed on said semiconductor substrate.