Stable high temperature heater system with tungsten heating layer

Abstract

A sensor system has an AlN substrate, a W layer on the substrate, a signal source adapted to apply an electrical actuating signal to the W layer, and a sensor adapted to sense the response of the W layer. The W layer can comprise a thin film, with various types of optional protective layers over the film. Applications include sensing temperature, fluid flow rates, fluid levels, pressure and chemical environments. For a planar heater, the W layer comprises a plurality of conductive strands distributed on the substrate, with the strands generally parallel and serpentine shaped for a rectangular substrate, and extending along respective lines of longitude that merge at opposite poles of the substrate for a circular substrate.

1 . A heater system, comprising: 
 an AlN substrate,    a W layer on said substrate,    a signal source connected to apply a current or a voltage actuating signal to heat said W layer, and    a sensor connected to sense the voltage across said W layer in the case of a current actuating signal, or the current through said W layer in the case of a voltage actuating signal, as an indication of the temperature of said W layer, said W layer having a resistance which varies with the W layer's temperature.    
   
   
       2 . The system of  claim 1 , said W layer comprising a thin film.  
   
   
       3 . The system of  claim 1 , further comprising an oxidation resistant protective layer on said W layer.  
   
   
       4 . The system of  claim 3 , said protective layer comprising gold.  
   
   
       5 . The system of  claim 3 , said protective layer comprising B 2 O 3 —SiO 2 .  
   
   
       6 . The system of  claim 3 , said protective layer comprising an Au—Pt alloy.  
   
   
       7 . The system of  claim 6 , said protective layer further comprising W on said Au—Pt alloy.  
   
   
       8 . The system of  claim 6 , said protective layer further comprising B 2 O 3 —SiO 2  on said Au—Pt alloy.  
   
   
       9 . The system of  claim 3 , said protective layer comprising Pt.  
   
   
       10 . The system of  claim 9 , said protective layer comprising B 2 O 3 —SiO 2  on said Pt.  
   
   
       11 . The system of  claim 3 , further comprising an AlN cap on said protective layer.  
   
   
       12 . The system of  claim 1 , said W layer comprising a plurality of conductive strands distributed on said substrate.  
   
   
       13 . The system of  claim 12 , wherein said strands are generally parallel and serpentine shaped.  
   
   
       14 . The system of  claim 13 , wherein said substrate is rectangular.  
   
   
       15 - 18 . (canceled)  
   
   
       19 . The system of  claim 1 , further comprising an additional AlN substrate with an additional W layer thereon, said signal source connected to apply a substantially non-heating current or voltage signal to said additional W layer, and a sensor connected to sense the voltage across said additional W layer in the case of a non-heating current signal, or the current through said additional W layer in the case of a non-heating voltage signal, as an indication of its temperature, 
 said additional substrate and additional W layer disposed downstream of said substrate and W layer in a fluid flow path, with the difference in temperature between said W and additional W layers corresponding to the fluid flow rate.    
   
   
       20 . The system of  claim 1 , said substrate and W layer disposed in a fluid flow path, said response sensed by said sensor corresponding to a fluid flow rate along said path.  
   
   
       21 - 23 . (canceled)  
   
   
       24 . A heater system, comprising: 
 an AlN substrate,    a conductive layer on said substrate which, over a predetermined temperature operating range, has an expansion coefficient within 1.00+/−0.07 of said substrate, is substantially non-reactive with said substrate, and exhibits substantially no solid-solubility or interdiffusivity with said substrate,    a signal source connected to apply a current or a voltage actuating signal to heat said conductive layer, and    a sensor connected to sense the voltage across said conductive layer in the case of a current actuating signal, or the current through said conductive layer in the case of a voltage actuating signal, as an indication of the temperature of said conductive layer, said conductive layer having a resistance which varies with the conductive layer's temperature.    
   
   
       25 . The system of  claim 24 , said conductive layer comprising a thin film.  
   
   
       26 . The system of  claim 24 , further comprising an oxidation resistant protective layer on said conductive layer.  
   
   
       27 . The system of  claim 26 , further comprising an AlN cap on said protective layer.  
   
   
       28 . The system of  claim 24 , said conductive layer comprising a plurality of conductive strands distributed on said substrate.  
   
   
       29 . The system of  claim 28 , wherein said strands are generally parallel and serpentine shaped.  
   
   
       30 . The system of  claim 29 , wherein said substrate is rectangular.  
   
   
       31 - 34 . (canceled)  
   
   
       35 . The system of  claim 24 , further comprising an additional AlN substrate with an additional conductive layer thereon, said signal source connected to apply a substantially non-heating current or voltage actuating signal to said additional conductive layer, and an additional sensor connected to sense the voltage across said additional conductive layer in the case of a non-heating current actuating signal, or the current through said additional conductive layer in the case of a non-heating voltage actuating signal, as an indication of its temperature, 
 said additional substrate and additional conductive layer disposed downstream of said substrate and conductive layer in a fluid flow path, with the difference in temperature between said conductive layer and additional conductive layer corresponding to the fluid flow rate.    
   
   
       36 . The system of  claim 24 , said substrate and conductive layer disposed in a fluid flow path, said voltage or current sensed by said additional sensor corresponding to a fluid flow rate along said path.  
   
   
       37 - 39 . (canceled)  
   
   
       40 . A heater system, comprising: 
 an insulative substrate,    a W conductive layer on said substrate which, over a predetermined temperature operating range, has an expansion coefficient within 1.00+/−0.07 of said substrate, is substantially non-reactive with said substrate, and exhibits substantially no solid-solubility or interdiffusivity with said substrate,    a signal source connected to apply a current or a voltage actuating signal to heat said W layer, and    a sensor connected to sense the voltage across said W layer in the case of a current actuating signal, or the current through said W layer in the case of a voltage actuating signal, as an indication of the temperature of said W layer, said W layer having a resistance which varies with the W layer's temperature.    
   
   
       41 . The system of  claim 40 , said W layer comprising a thin film.  
   
   
       42 . The system of  claim 40 , further comprising an oxidation resistant protective layer on said W layer to inhibit oxidation of said conductive layer.  
   
   
       43 . The system of  claim 42 , further comprising an AlN cap on said protective layer.  
   
   
       44 . The system of  claim 40 , said W layer comprising a plurality of conductive strands distributed on said substrate.  
   
   
       45 . The system of  claim 44 , wherein said strands are generally parallel and serpentine shaped.  
   
   
       46 . The system of  claim 45 , wherein said substrate is rectangular.  
   
   
       47 - 50 . (canceled)  
   
   
       51 . The system of  claim 40 , further comprising an additional insulative substrate with an additional W conductive layer thereon, said signal source connected to apply a substantially non-heating current or voltage actuating signal to said additional conductive layer, and an additional sensor connected to sense the voltage across said additional conductive layer in the case of a non-heating current actuating signal, or the current through said additional conductive layer in the case of a non-heating voltage actuating signal, as an indication of its temperature, 
 said additional substrate and additional conductive layer disposed downstream of said substrate and conductive layer in a fluid flow path, with the difference in temperature between said conductive layer and additional conductive layer corresponding to the fluid flow rate.    
   
   
       52 . The system of  claim 40 , said substrate and conductive layer disposed in a fluid flow path, said voltage or current sensed by said sensor corresponding to a fluid flow rate along said path.  
   
   
       53 - 69 . (canceled)