Piezoelectric mems actuator for compensating unwanted movements and manufacturing process thereof

Abstract

A method of making a MEMS actuator with a monolithic body of semiconductor material includes forming a supporting portion of semiconductor material, orientable with respect to first and second rotation axes, the first rotation axis being transverse with respect to the second rotation axis, and forming a first frame of semiconductor material. The method further includes forming first deformable elements, of semiconductor material, coupled to the first frame, and configured to control a rotation of the supporting portion about the first rotation axis. The method also includes forming a second frame of semiconductor material, and forming second deformable elements, of semiconductor material, coupled to the first frame and to the second frame, and configured to control a rotation of the supporting portion about the second rotation axis. The first and second deformable elements are formed to carry respective first and second piezoelectric actuation elements.

1 . A method of making a MEMS actuator comprising a monolithic body of semiconductor material, the method comprising:
 forming a supporting portion of semiconductor material;   forming a first frame of semiconductor material;   forming first deformable elements, of semiconductor material, coupled to the first frame;   forming a second frame of semiconductor material; and   forming second deformable elements, of semiconductor material, coupled to the first frame and to the second frame;   wherein the first and second deformable elements are formed to carry respective first and second piezoelectric actuation elements.   
     
     
         2 . The method according to  claim 13 , further comprising:
 forming, on a first surface of a first wafer of semiconductor material, a first insulating layer;   forming, on the first insulating layer, a membrane layer of semiconductor material;   forming, on the membrane layer, a second insulating layer;   forming, on the second insulating layer, a first electrode;   forming, on the first electrode, a piezoelectric region;   forming, on the piezoelectric region, a second electrode;   forming an opening in the second insulating layer, thereby exposing a first portion of the membrane layer;   removing selective portions of the first wafer, thereby forming the supporting portion, the first and second frames, and the first and second deformable elements;   forming an adhesive layer coating the first electrode, the piezoelectric region, the second electrode, and the second insulating layer;   coupling a second wafer to the adhesive layer, thereby forming a third wafer;   removing portions of the first wafer and of the first insulating layer from a second surface of the first wafer, thereby forming substrate portions laterally delimiting a cavity, delimiting membrane portions of the first and second deformable elements; and   detaching the second wafer by removing the adhesive layer.   
     
     
         3 . The method according to  claim 1 , further comprising:
 forming a first insulating layer fon a first surface of a first wafer of semiconductor material via thermal growth;   epitaxially growing a membrane layer on the first insulating layer;   forming a second insulating layer on the membrane layer; and   forming a first stack of layers extending over the first surface of the first wafer.   
     
     
         4 . The method according to  claim 3 , wherein forming the first stack of layers is formed by forming a layer from which a first electrode is formed, a layer from which a piezoelectric region is formed, and a layer from which a second electrode is formed. 
     
     
         5 . The method according to  claim 4 , wherein the first stack of layers is etched to form a first electrode on the second insulating layer, a piezoelectric region on the first electrode, and a second electrode on the piezoelectric region. 
     
     
         6 . The method according to  claim 5 , further comprising etching the second insulating layer to form an opening, thereby exposing a portion of the membrane layer. 
     
     
         7 . The method according to  claim 6 , further comprising forming, over the first stack of layers, a second stack of layers via deposition and definition to include a first passivation layer and a second passivation layer on the first passivation layer. 
     
     
         8 . The method according to  claim 7 , further comprising defining first and second contact openings in the first and second passivation layers to expose respective portions of the first and second electrodes. 
     
     
         9 . The method according to  claim 8 , wherein the second stack of layers is further formed to include a first metallization layer on the second passivation layer and extending through the first contact opening to contact the second electrode, and to include a second metallization layer on the second passivation layer and extending through the second contact opening to contact the first electrode. 
     
     
         10 . The method according to  claim 9 , wherein the second stack of layers is further formed to include a third passivation layer on the second passivation layer and first and second metallization layers, with a third contact opening being formed in the third passivation layer to expose at least in part the first metallization layer. 
     
     
         11 . The method according to  claim 10 , further comprising depositing and defining a contact layer over the second stack of layers, and etching the membrane layer to define the first and second deformable elements and to define trenches in the membrane layer. 
     
     
         12 . The method according to  claim 11 , further comprising depositing an adhesive layer on the third passivation layer and the contact layer, and coupling a carrier wafer to the adhesive layer to obtain a second wafer and delimited by a top surface and a bottom surface. 
     
     
         13 . The method according to  claim 12 , further comprising flipping the second wafer and etching the second wafer from its bottom surface to form first, second, and third substrate portions, a cavity being delimited between the first and second substrate portions, wherein the etching exposes a back side of the membrane layer. 
     
     
         14 . The method according to  claim 13 , further comprising etching the first insulating layer to define first and second connections arms and the first and second frames, then removing the adhesive layer via thermal release to thereby detach the carrier wafer from the first wafer. 
     
     
         15 . The method according to  claim 13 , further comprising dicing the first wafer. 
     
     
         16 . A method of making a MEMS actuator comprising a monolithic body of semiconductor material, the method comprising:
 forming a supporting portion of semiconductor material, orientable with respect to first and second rotation axes, the first rotation axis being transverse with respect to the second rotation axis;   forming a first frame of semiconductor material;   forming first deformable elements, of semiconductor material, coupled to the first frame, and configured to control a rotation of the supporting portion about the first rotation axis;   forming a second frame of semiconductor material; and   forming second deformable elements, of semiconductor material, coupled to the first frame and to the second frame, and configured to control a rotation of the supporting portion about the second rotation axis,   wherein the first and second deformable elements are formed to carry respective first and second piezoelectric actuation elements.   
     
     
         17 . The method according to  claim 16 , wherein the first frame is formed to have an elongated hexagonal shape, with two first sides parallel to a first symmetry axis and four end sides extending transverse to the first symmetry axis and a second symmetry axis, wherein the first symmetry axis and the second symmetry axis are parallel to the first and second rotation axis, wherein the first deformable elements extend perpendicularly to the first symmetry axis. 
     
     
         18 . The method according to  claim 17 , wherein the second frame is formed to have a regular quadrangular shape with sides parallel to the end sides of the first frame, and wherein the second deformable elements extend parallel to the first symmetry axis. 
     
     
         19 . The method according to  claim 18 ,
 wherein forming the first deformable elements is accomplished by forming first and second elastic elements of the first deformable elements on opposite sides of the supporting portion and extending transversely to the first symmetry axis; and   wherein forming the second deformable elements is accomplished by forming first and second elastic elements of the second deformable element on opposite sides of the first frame and extending transversely to the second symmetry axis.   
     
     
         20 . The method according to  claim 19 , wherein the first and second elastic elements of the first deformable elements are formed as respective first and second deformable arms carrying the first piezoelectric actuation elements and respective first and second connection arms, connecting opposite ends of respective successive ones of the first and second deformable arms, thereby forming a serpentine shape. 
     
     
         21 . The method according to  claim 20 , wherein the first and second elastic elements of the second deformable elements are formed as respective third and fourth deformable arms carrying the second piezoelectric actuation elements and respective third and fourth connection arms, connecting opposite ends of respective successive third and fourth deformable arms, thereby forming the serpentine shape.