Forming a print head with a thin membrane

Abstract

A microfabricated device and method for forming a microfabricated device are described. A thin membrane including silicon is formed on a silicon body by bonding a silicon-on-insulator substrate to a silicon substrate. The handle and insulator layers of the silicon-on-insulator substrate are removed, leaving a thin membrane of silicon bonded to a silicon body such that no intervening layer of insulator material remains between the membrane and the body. A piezoelectric layer is bonded to the membrane.

1 . A method of forming a microfabricated device, comprising:
 etching an upper surface of a substrate to form at least one etched feature;   bonding a multilayer substrate to the upper surface of the substrate so that the etched feature on the upper surface is covered to form a chamber, the multilayer substrate including a silicon layer and a handle layer, wherein the bonding forms a silicon-to-silicon bond between the upper surface of the substrate and the silicon layer; and   removing the handle layer from the multilayer substrate to form a membrane including the silicon layer over the chamber.   
     
     
         2 . The method of  claim 1 , wherein:
 the multilayer substrate is a silicon-on-insulator substrate including an oxide layer.   
     
     
         3 . The method of  claim 2 , further comprising:
 removing the oxide layer from the silicon-on-insulator substrate to form the membrane.   
     
     
         4 . The method  claim 1 , further comprising:
 forming a conductive layer on the membrane.   
     
     
         5 . The method of  claim 1 , further comprising:
 bonding a piezoelectric layer to the membrane.   
     
     
         6 . The method of  claim 1 , wherein:
 bonding a multilayer substrate to the upper surface of the substrate includes fusion bonding silicon of the first layer to silicon of the upper surface.   
     
     
         7 . The method of  claim 1 , wherein:
 removing the handle layer from the multilayer substrate includes grinding the handle layer.   
     
     
         8 . The method of  claim 1 , wherein:
 removing the handle layer from the multilayer substrate includes etching the handle layer.   
     
     
         9 . The method of  claim 1 , wherein:
 the membrane is less than 15 microns thick.   
     
     
         10 . The method of  claim 9 , wherein:
 the membrane is less than 5 microns thick.   
     
     
         11 . The method of  claim 1 , further comprising:
 forming a metal mask on the upper surface of the substrate prior to etching the upper surface.   
     
     
         12 . The method of  claim 11 , wherein:
 the metal mask includes nickel and chromium.   
     
     
         13 . The method of  claim 1 , further comprising:
 forming a metal stop layer on a bottom surface of the substrate prior to etching.   
     
     
         14 . The method of  claim 13 , wherein:
 the metal stop layer includes at least one metal from a group consisting of nickel, chromium, aluminum, copper, tungsten and iron.   
     
     
         15 . The method of  claim 1 , wherein:
 the handle layer includes silicon.   
     
     
         16 . The method of  claim 1 , further comprising:
 removing oxide from the upper surface of the substrate prior to bonding the multilayer substrate.   
     
     
         17 . The method of  claim 16 , further comprising:
 removing oxide from the silicon layer of the multilayer substrate prior to bonding the multilayer substrate.   
     
     
         18 . The method of  claim 17 , wherein:
 removing the oxide includes a hydrofluoric acid etch.   
     
     
         19 . A method of forming a printhead, comprising:
 etching an upper surface of a substrate to have at least one etched feature;   bonding a multilayer substrate to the upper surface of the substrate so that the etched feature on the upper surface is covered to form a chamber, the multilayer substrate including a first layer and a handle layer;   removing the handle layer from the multilayer substrate to form a membrane; and   bonding a piezoelectric layer to the membrane.   
     
     
         20 . The method of  claim 19 , further comprising:
 bonding a nozzle layer to a lower surface of the substrate, wherein the nozzle layer includes at least a portion of one or more nozzles for ejecting a fluid.   
     
     
         21 . The method of  claim 20 , wherein:
 etching the upper surface of the substrate forms at least a portion of an ink flow path.   
     
     
         22 . The method of  claim 1 , wherein etching an upper surface of a substrate includes etching a substrate consisting essentially of silicon.