Process for manufacturing high-sensitivity accelerometric and gyroscopic integrated sensors, and sensor thus produced

Abstract

A movable mass forming a seismic mass is formed starting from an epitaxial layer and is covered by a weighting region of tungsten which has high density. To manufacture the mass, buried conductive regions are formed in the substrate. Then, at the same time, a sacrificial region is formed in the zone where the movable mass is to be formed and oxide insulating regions are formed on the buried conductive regions so as to partially cover them. An epitaxial layer is then grown, using a nucleus region. A tungsten layer is deposited and defined and, using a silicon carbide layer as mask, the suspended structure is defined. Finally, the sacrificial region is removed, forming an air gap.

1. A process for manufacturing an accelerometric and gyroscopic integrated sensor, comprising the steps of:
 forming a sacrificial region on  in a substrate of semiconductor material;  
 growing an epitaxial layer on said substrate and said sacrificial region; and  
 removing selective portions of said epitaxial layer and said sacrificial region to form a movable mass surrounded at the sides and separated from fixed regions by trenches and separated from said substrate by an air gap, the movable mass supported by anchorage zones only at the sides; and  
 forming a weighting region of tungsten  at said movable mass.  
 
     
     
       2. The process according to  claim 1 , wherein said step of forming a weighting region comprises a step of depositing and defining a tungsten layer over said epitaxial layer to have a shape corresponding to a shape of the movable mass. 
     
     
       3. The process according to  claim 2  wherein said step of depositing and defining a tungsten layer is carried out before said step of removing selective portions of said epitaxial layer. 
     
     
       4. The process according to  claim 2  wherein after said step of depositing and defining said tungsten layer, a step of masking the epitaxial layer and said weighting regions through a protective layer resistant to etching of said sacrificial region is performed. 
     
     
       5. The process according to  claim 4  wherein said sacrificial region is a silicon oxide and said protective layer comprises silicon carbide. 
     
     
       6. The process according to  claim 2 , comprising, before said step of depositing said tungsten layer, the steps of:
 forming electronic components in said epitaxial layer;  
 depositing a dielectric layer over said electronic components; and  
 forming contact openings in said dielectric layer, and wherein said step of defining said tungsten layer further comprises the step of forming tungsten contact electrodes for said electronic components and for said accelerometric and gyroscopic sensor.  
 
     
     
       7. The process according to  claim 2  wherein before said step of depositing and defining a tungsten layer, a step of depositing an adhesive titanium nitride layer is performed. 
     
     
       8. The process according to  claim 1  wherein a step of forming a nucleus region of non-single-crystal semiconductor material on said sacrificial region is earned out before said step of growing an epitaxial layer and wherein said step of growing an epitaxial layer comprises the step of growing a multi-crystal region on said nucleus region and growing a single-crystal region on said substrate, and wherein said suspended mass is formed in said multi-crystal region and wherein the process comprises the step of forming electronic components in said single-crystal region. 
     
     
       9. The process according to  claim 8  wherein said substrate has a first conductivity type; wherein, before said step of forming a sacrificial region, a step of forming buried conductive regions of a second conductivity type in said substrate is carried out, wherein, at the same time as said step of forming a sacrificial layer, electrically insulating material regions are formed, extending on said buried conductive regions and delimiting therebetween portions of selective contact of said buried conductive regions; and wherein, after said step of growing an epitaxial layer, a step of forming deep contact regions extending from a surface of said epitaxial layer as far as said buried conductive regions to form deep contacts is performed. 
     
     
       10. A method for producing an integrated sensor comprising the steps of:
 forming a sacrificial support layer on  in a semiconductor substrate;  
 forming an epitaxial layer on the sacrificial support layer and on the semiconductor substrate;  
 depositing a tungsten layer  weighting region on the epitaxial layer;  
 removing the sacrificial support layer; and  
 forming a movable mass from portions of the epitaxial layer and tungsten layers  the weighting region by forming trenches to separate the movable mass from fixed regions of the epitaxial layer and tungsten layers  weighting region and separated from said substrate by an air gap, the movable mass thereby supported by anchorage zones only at the sides.  
 
     
     
       11. The method of  claim 10  wherein the step of depositing a weighting region comprises depositing a tungsten layer is performed  before the step of forming a movable mass to have a shape corresponding to a shape of the movable mass. 
     
     
       12. The method of  claim 10  wherein the step of forming a moveable mass comprises:
 forming a protective layer on the tungsten layer  weighting region;  
 masking a pattern on the protective layer; and  
 etching trenches through the protective layer, tungsten, and  epitaxial layers  layer, and the weighting region.  
 
     
     
       13. The method of  claim 10 , further including the steps of:
 forming electronic components in the epitaxial layer;  
 depositing a dielectric layer over the components; and  
 forming contact openings in the dielectric layer.  
 
     
     
       14. A process for manufacturing an accelerometric and gyroscopic integrated sensor, comprising the steps of:
   forming a sacrificial region in a substrate of semiconductor material;        growing an epitaxial layer on said substrate and said sacrificial region; and        removing selective portions of said epitaxial layer and said sacrificial region to form a movable mass surrounded at the sides and separated from fixed regions by trenches and separated from said substrate by an air gap, the movable mass supported by anchorage zones only at the sides; and        forming a weighting region of a metal at said movable mass.     
     
     
       15. The process according to  claim 14  wherein said step of forming a weighting region comprises a step of depositing and defining a tungsten layer over said epitaxial layer to have a shape corresponding to a shape of the movable mass. 
     
     
       16. A method for producing an integrated sensor comprising the steps of:
   forming a sacrificial support layer in a semiconductor substrate;        forming an epitaxial layer in the sacrificial support layer and on the semiconductor substrate;        depositing a metal layer on the epitaxial layer;        removing the sacrificial support layer; and        forming a movable mass from portions of the epitaxial layer and the metal layer by forming trenches to separate the movable mass from fixed regions of the epitaxial layer and weighting region and separated from said substrate by an air gap, the movable mass thereby supported by anchorage zones only at the sides.     
     
     
       17. The process according to  claim 16  wherein the step of depositing a metal layer comprises depositing a tungsten layer to have a shape corresponding to a shape of the movable mass. 
     
     
       18. A process for manufacturing an accelerometric and gyroscopic integrated sensor, comprising the steps of:
   forming a sacrificial region on a substrate of semiconductor material;        growing an epitaxial layer on said substrate and said sacrificial region;        removing selective portions of said epitaxial layer and said sacrificial region to form a movable mass surrounded at the sides and separated from fixed regions by trenches and separated from said substrate by an air gap, the movable mass supported by anchorage zones only at the sides; and        forming a weighting region at said movable mass,        wherein a step of forming a nucleus region of non - single - crystal semiconductor material on said sacrificial region is carried out before said step of growing an epitaxial layer and wherein said step of growing an epitaxial layer comprises the step of growing a multi - crystal region on said nucleus region and growing a single - crystal region on said substrate, and wherein said suspended mass is formed in said multi - crystal region and wherein the process comprises the step of forming electronic components in said single - crystal region.     
     
     
       19. The process according to  claim 18  wherein said substrate has a first conductivity type; wherein, before said step of forming a sacrificial region, a step of forming buried conductive regions of a second conductivity type in said substrate is carried out, wherein, at the same time as said step of forming a sacrificial layer, electrically insulating material regions are formed, extending on said buried conductive regions and delimiting therebetween portions of selective contact of said buried conductive regions; and wherein, after said step of growing an epitaxial layer, a step of forming deep contact regions extending from a surface of said epitaxial layer as far as said buried conductive regions to form deep contacts is performed. 
     
     
       20. The process of  claim 18  wherein forming the weighting region comprises forming the weighting region over the movable mass to have a shape corresponding to a shape of the movable mass.