Process for manufacturing a nozzle plate and fluid-ejection device provided with the nozzle plate

Abstract

A nozzle plate for a fluid-ejection device, comprising: a first substrate made of semiconductor material, having a first side and a second side; a structural layer extending on the first side of the first substrate, the structural layer having a first side and a second side, the second side of the structural layer facing the first side of the first substrate; at least one first through hole, having an inner surface, extending through the structural layer, the first through hole having an inlet section corresponding to the first side of the structural layer and an outlet section corresponding to the second side of the structural layer; a narrowing element adjacent to the surface of the first through hole, and including a tapered portion such that the inlet section of the first through hole has an area larger than a respective area of the outlet section of the first through hole.

1 . A process for manufacturing a nozzle plate for a fluid-ejection device, the method comprising:
 forming a structural layer over a first side of a first substrate of semiconductor material, the structural layer having a respective first side and second side, the second side of the structural layer facing the first side of the first substrate;   forming a first through hole in the structural layer by removing a portion of the structural layer, said first through hole having an inner surface, an inlet section at the first side of the structural layer, and an outlet section at the second side of the structural layer;   forming a narrowing element on the inner surface of the first through hole;   tapering the narrowing element so that the inlet section of the first through hole has an area larger than a respective area of the outlet section of the first through hole; and   removing the first substrate, the removing rendering accessible the first through hole.   
     
     
         2 . The process according to  claim 1 , further comprising forming, in a position corresponding to the second side of the structural layer, a recess configured to at least partially surround the outlet section of the first through hole. 
     
     
         3 . The process according to  claim 2 , wherein said recess has a perimeter having a shape that is one of a polygonal, polygonal with rounded corners, circular, oval, circular with rounded corners, and oval with rounded corners. 
     
     
         4 . The process according to  claim 2 , wherein forming the first through hole comprises forming said outlet section of the first through hole in said recess. 
     
     
         5 . The process according to  claim 2 , wherein the forming said recess comprises forming a trench path, and forming the first through hole comprises forming said outlet section of the first through hole enclosed by said trench path. 
     
     
         6 . The process according to  claim 1 , wherein:
 forming the narrowing element comprises depositing, in the first through hole, a narrowing layer; and   tapering the narrowing element comprises etching the narrowing layer in an etching direction that is substantially parallel to the surface of the first through hole.   
     
     
         7 . The process according to  claim 1 , further comprising forming a surface-modification layer inside the first through hole that covers and protects the narrowing element. 
     
     
         8 . The process according to  claim 7 , wherein forming the surface-modification layer comprises depositing, on the narrowing element, a material that includes at least one of silicon carbide, alumina, hafnium oxide, titanium, tantalum, tungsten, and alloys thereof. 
     
     
         9 . The process according to  claim 7 , wherein forming the surface-modification layer comprises forming the surface-modification layer on portions of the narrowing element and of the structural layer facing the first substrate. 
     
     
         10 . The process according to  claim 1 , further comprising:
 forming an intermediate layer over the first side of the first substrate;   wherein forming the structural layer comprises forming said structural layer over the intermediate layer; and   wherein forming the recess comprises:
 etching the intermediate layer in a region corresponding to the inlet section of said first through hole; and 
 removing a portion of the intermediate layer extending between the narrowing element and the first substrate, and between a portion of the structural layer adjacent to the narrowing element and the first substrate by further etching the intermediate layer. 
   
     
     
         11 . The process according to  claim 1 , further comprising:
 forming an intermediate layer over the first side of the first substrate; and   forming a sacrificial island on the intermediate layer; and   wherein:
 forming the structural layer comprises forming said structural layer on the intermediate layer and over the sacrificial island; 
 forming the first through hole comprises forming said first through hole on the sacrificial island, and in such a way that the first through hole is contained by the sacrificial island; and 
 forming the recess comprises forming a cavity extending partially between the first substrate and the structural layer, and between the first substrate and the narrowing element by selectively etching the sacrificial island and a portion of the intermediate layer extending underneath the sacrificial island. 
   
     
     
         12 . The process according to  claim 11  further comprising forming a surface-modification layer inside the first through hole that covers and protects the narrowing element, and wherein forming the surface-modification layer comprises forming the surface-modification layer in surface portions of the narrowing element and of the structural layer facing said cavity. 
     
     
         13 . The process according to  claim 1 , further comprising:
 forming a recess in the second side of the structural that at least partially surrounds the outlet section of the first through hole;   forming an intermediate layer over the first face of the first substrate; and   forming a sacrificial island, defining a parameter of said recess, on the intermediate layer, the sacrificial island defining a region of the intermediate layer internal to said path and a region of the intermediate layer external to said path; and   wherein:
 forming the structural layer comprises forming said structural layer over the intermediate layer and on the sacrificial island; 
 forming the first through hole comprises forming said first through hole in the region of the intermediate layer internal to said path; and 
   wherein forming the recess comprises:
 selectively removing the first substrate and the intermediate layer; and 
 selectively etching the sacrificial island. 
   
     
     
         14 . The process according to  claim 1 , further comprising:
 providing a second substrate made of semiconductor material;   forming a second through hole through said second substrate by etching said second substrate; and   coupling the second substrate to the structural layer in such a way that the second through hole is aligned with the first through hole.   
     
     
         15 . A nozzle plate for a fluid-ejection device, the nozzle plate comprising:
 a structural layer having a first side and a second side;   a first through hole having an inner surface extending through the structural layer, said first through hole having an inlet section at the first side of the structural layer and an outlet section at the second side of the structural layer; and   a narrowing element adjacent to the inner surface of the first through hole, and including a tapered portion such that the inlet section of the first through hole has an area larger than a respective area of the outlet section of the first through hole, said through hole and said narrowing element forming an ejection nozzle of said nozzle plate.   
     
     
         16 . The nozzle plate according to  claim 15 , further comprising a recess extending in the structural layer and at least partially surrounding the outlet section of the first through hole. 
     
     
         17 . The nozzle plate according to  claim 16 , wherein said recess has a perimeter having a shape that is one of a polygonal, polygonal with rounded corners, circular, and oval. 
     
     
         18 . The nozzle plate according to  claim 16 , wherein the outlet section of the first through hole extends in the recess. 
     
     
         19 . The nozzle plate according to  claim 16 , wherein said recess comprises a trench, the outlet section of the first through hole being surrounded by said trench. 
     
     
         20 . The nozzle plate according to  claim 16 , wherein the recess extends in the structural layer to a depth of approximately 0.1 μm to approximately 10 μm. 
     
     
         21 . The nozzle plate according to  claim 16 , wherein a wall of said recess extends at a minimum distance from the outlet section of the ejection nozzle between approximately 3 μm and approximately 30 μm. 
     
     
         22 . The nozzle plate according to  claim 15 , further comprising a surface-modification layer that covers the narrowing element, said surface-modification layer comprising a material resistant to said fluid. 
     
     
         23 . The nozzle plate according to  claim 22 , wherein the surface-modification layer extends in the recess and covers the structural layer. 
     
     
         24 . The nozzle plate according to  claim 15 , wherein the narrowing element further comprises a substantially cylindrical portion, extending as a prolongation of said tapered portion between the tapered portion and the outlet section of the first through hole. 
     
     
         25 . The nozzle plate according to  claim 15 , further comprising a substrate made of semiconductor material provided with a second through hole,
 the substrate being coupled to the structural layer in such a way that the second through hole is aligned to the first through hole.   
     
     
         26 . A fluid-ejection device, comprising:
 a reservoir having an internal chamber configured to contain a fluid substance;   an actuator connected to the reservoir and configured to cause expulsion of the fluid substance from the reservoir; and   a nozzle plate in fluid communication with the reservoir to enable expulsion of the fluid substance through the nozzle, the nozzle plate including:
 a structural layer having a first side and a second side; 
 a through hole having an inner surface extending through the structural layer, said through hole having an inlet section at the first side of the structural layer and an outlet section at the second side of the structural layer; and 
 a narrowing element adjacent to the surface of the through hole, and including a tapered portion such that the inlet section of the through hole has an area larger than a respective area of the outlet section of the through hole, said through hole and said narrowing element forming an ejection nozzle of said nozzle plate. 
   
     
     
         27 . A printing machine comprising the fluid-ejection device according to  claim 26 . 
     
     
         28 . The fluid-ejection device according to  claim 26 , further comprising a recess extending in the structural layer and at least partially surrounding the outlet section of the through hole. 
     
     
         29 . The fluid-ejection device according to  claim 26 , wherein the outlet section of the first through hole extends in the recess.