Etch apparatus

Abstract

An etch apparatus. The etch apparatus includes a tank coupled to a recirculating path that includes a dissolver. The dissolver includes a porous carbon matrix filter coated with silicon nitride. An etchant from the tank circulates through the recirculating path and performs a selective etching of a structure in the tank in contact with the etchant. The structure includes silicon nitride on a pad layer that includes silicon dioxide. The selective etching is characterized by the silicon nitride on the pad layer being selectively etched by the etchant relative to an etching by the etchant of the silicon dioxide. The etch apparatus further includes: means for dissolving the silicon nitride coated on the filter into the etchant at a controlled dissolution rate sufficient to cause the selective etching; and means for coating the silicon nitride onto the filter to facilitate the selective etching.

1 . An etch apparatus, comprising: 
 an etching tank comprising an etchant, said etchant configured to perform a selective etching of a structure in the tank in contact with the etchant, wherein the structure comprises silicon nitride on a pad layer comprising silicon dioxide, wherein said selective etching is characterized by the silicon nitride on the pad layer being selectively etched by the etchant relative to an etching by the etchant of the silicon dioxide of the pad layer;    a recirculating path coupled to the tank, wherein the recirculating path comprises a dissolver, wherein the dissolver comprises a porous carbon matrix filter coated with silicon nitride, and wherein the recirculating path is configured to receive the etchant from the tank and to circulate the etchant from the tank through the recirculating path, including through the dissolver, and back into the tank;    means for dissolving the silicon nitride coated on the filter into the etchant at a controlled dissolution rate sufficient to cause the selective etching to decrease an etch rate of the silicon dioxide of the pad layer in the etchant in a controlled manner such that an etch rate of silicon nitride of the silicon nitride structure is substantially unchanged; and    means for coating the silicon nitride onto the filter to configure the coated silicon nitrate to facilitate said selective etching.    
   
   
       2 . The etch apparatus of  claim 1 , wherein the silicon nitride coated on the filter has a different spatial distribution on the filter than would silicon nitride coated on the filter by being precipitated from the etchant onto the filter while the etchant is passing through the filter.  
   
   
       3 . The etch apparatus of  claim 1 , wherein the tank comprises a heating element for heating and adjusting a temperature of the etchant, and wherein the heater is immersed in the etchant.  
   
   
       4 . The etch apparatus of  claim 1 , further comprising an etchant temperature controller adjacent said dissolver, said etchant temperature controller adjusting a temperature of the etchant flowing through said dissolver.  
   
   
       5 . The etch apparatus of  claim 1 , wherein the etchant comprises a phosphoric acid solution;  
   
   
       6 . The etch apparatus of  claim 1 , wherein the recirculating path further comprises a chamber in contact with the tank, a filtering system, a first conduit, and a second conduit comprising the dissolver, 
 wherein the chamber is in direct mechanical contact with the tank,    wherein a first end of the first conduit is connected to an outlet of the chamber,    wherein an inlet of the filtering system is connected to a second end of the first conduit, wherein an outlet of the filtering system is connected to a first end of the second conduit,    wherein a second end of the second conduit is connected to the tank or the chamber,    wherein the recirculating path is configured to receive the etchant from the tank into the chamber and to flow the etchant from the chamber through the first conduit, the filtering system, the second conduit, and back into the tank.    
   
   
       7 . The etch apparatus of  claim 6 , further comprising a spout for providing deionized water to the tank to adjust the concentration of the etchant in the tank, wherein the spout is directly connected to the chamber.  
   
   
       8 . The etch apparatus of  claim 6 , wherein a permeable sidewall is disposed between the tank and the chamber, and wherein the etchant flows from the tank to the chamber by flowing through the permeable sidewall and/or by overflowing the permeable sidewall.  
   
   
       9 . The etch apparatus of  claim 8 , wherein the etchant flows from the tank to the chamber by flowing through the permeable sidewall.  
   
   
       10 . The etch apparatus of  claim 8 , wherein the etchant flows from the tank to the chamber by overflowing the permeable sidewall.  
   
   
       11 . The etch apparatus of  claim 6 , wherein the second end of the second conduit is connected to the chamber, and wherein the etch apparatus further includes: 
 a split valve within the first conduit; and    a bypass conduit external to the first conduit, wherein a first end of the bypass conduit is connected to the split valve and a second end of the bypass conduit is connected to a merge location in the first conduit, wherein the dissolver is disposed within the first conduit between the split valve and the merge location, wherein the split valve is configured to split the etchant flowing into the split valve from the first end of the first conduit into a first etchant component flowing through the filter and a second etchant component flowing through the bypass conduit, and wherein the second etchant component merges with the first etchant at the merge location into a merged etchant flowing into the second end of the first conduit and into the inlet of the filtering system.    
   
   
       12 . The etch apparatus of  claim 6 , wherein the etch apparatus further includes: 
 a split valve within the second conduit;    a merge valve within the second conduit, wherein the dissolver is disposed within the second conduit between the split valve and the merge valve, wherein the merge valve is closer to the second end of the second conduit than is the split valve, and wherein the second end of the second conduit is connected to the tank; and    a bypass conduit connecting the split valve to the merge valve, wherein the bypass conduit is external to the second conduit, wherein the split valve is configured to split the etchant flowing into the split valve from the first end of the second conduit into a first etchant component flowing through the filter and a second etchant component flowing through the bypass conduit, and wherein the merge valve is configured to merge the first etchant component flowing through the filter and the second etchant component flowing through the bypass conduit into a merged etchant flowing into the second end of the second conduit and into the tank.