Micromachined mirror assembly having reflective layers on both sides

Abstract

Embodiments of the disclosure provide a micromachined mirror assembly having a mirror-base layer, a first reflective layer on a top surface of the mirror-base layer, and a second reflective layer on a bottom surface of the mirror-base layer. In an example, the first reflective layer is reflective to incident light of the micromachined mirror assembly, and the first reflective layer and the second reflective layer are made of a same material and have same dimensions.

1 .- 7 . (canceled) 
     
     
         8 . A method for forming a micromachined mirror assembly, comprising:
 forming an initial mirror-base layer on a first surface of a material substrate, the initial mirror-base layer exposing a first surface;   removing a portion of the material substrate to expose a second surface of the initial mirror-base layer and form a mirror-base layer that exposes a first surface and a second surface of the mirror-base layer; and   forming a first reflective layer on the first surface of the mirror-base layer and a second reflective layer on the second surface of the mirror-base layer, the first reflective layer and the second reflective layer being made of a same material and having same dimensions.   
     
     
         9 . The method of  claim 8 , wherein forming the first reflective layer on the first surface and the second reflective layer on the second surface of the mirror-base layer comprises respectively depositing at least one of a metal layer and a distributed Bragg reflector on the first surface and the second surface. 
     
     
         10 . The method of  claim 9 , wherein depositing the metal layer on the first surface and the second surface of the mirror-base layer comprises depositing, respectively on the first surface and the second surface of the mirror-base layer, aluminum, gold, or a combination thereof. 
     
     
         11 . The method of  claim 8 , wherein forming the initial mirror-base layer on the material substrate comprises patterning a silicon layer of a silicon on insulator (SOI) substrate to form the initial mirror-base layer. 
     
     
         12 . The method of  claim 11 , wherein removing the portion of the material substrate to expose the second surface of the initial mirror-base layer and form the mirror-base layer that exposes the first surface and the second surface of the mirror-base layer comprises:
 removing a portion of a base substrate of the material substrate under the initial mirror-base layer to expose an insulator layer and form a first initial cavity;   depositing an insulating layer over the first initial cavity to cover at least a sidewall of the first initial cavity and connect with the insulator layer; and   removing a portion of the insulator layer under the initial mirror-base layer to expose the second surface of the initial mirror-base layer, the first and second surfaces of the initial mirror-base layer respectively forming the first and second surfaces of the mirror-base layer.   
     
     
         13 . The method of  claim 12 , wherein removing the portion of the base substrate of the material substrate under the initial mirror-base layer to expose the insulator layer to form the first initial cavity comprises:
 depositing a mask layer to cover the initial mirror-base layer and a second surface of the material substrate;   patterning the mask layer to expose a portion of the base substrate under the initial mirror-base layer, a location of the portion of the base substrate being corresponding to a location of the initial mirror-base layer;   performing an anisotropic etch to remove the portion of the base substrate to expose a portion of the insulator layer under the initial mirror-base layer; and   removing the mask layer over the initial mirror-base layer and the second surface of the material substrate.   
     
     
         14 . A method for forming a micromachined mirror assembly, comprising:
 forming an initial mirror-base layer on a first surface of a material substrate, a first surface of the initial mirror-base layer being exposed;   bonding the material substrate with another material substrate, the other material substrate having a cavity that exposes the first surface of the initial mirror-base layer;   removing a top portion of the material substrate to expose a second surface of the initial mirror-base layer and form a mirror-base layer that exposes a first surface and a second surface of the mirror-base layer; and   forming a first reflective layer on the first surface of the mirror-base layer and a second reflective layer on the second surface of the mirror-base layer, the first reflective layer and the second reflective layer being made of a same material and having same dimensions.   
     
     
         15 . The method of  claim 14 , wherein forming the first reflective layer on the first surface and the second reflective layer on the second surface of the mirror-base layer comprises respectively depositing at least one of a layer of metal and a distributed Bragg reflector on the first surface and the second surface of the mirror-base layer. 
     
     
         16 . The method of  claim 15 , wherein depositing the layer of metal on the first surface and the second surface of the mirror-base layer comprises depositing, respectively on the first surface and the second surface of the mirror-base layer, aluminum, gold, or a combination thereof. 
     
     
         17 . The method of  claim 14 , wherein forming the initial mirror-base layer on the first surface of the material substrate comprises:
 forming a first mirror-forming structure on a silicon on insulator (SOI) substrate;   bonding a second SOI substrate with the SOI substrate to form a second mirror-forming structure from the first mirror-forming structure, the second SOI substrate being over the SOI substrate and a base substrate of the second SOI substrate being on top of a silicon layer of the second SOI substrate;   removing the base substrate and an insulator layer of the second SOI substrate to expose the second mirror-forming structure; and   patterning the second mirror-forming structure to form the initial mirror-base layer over an insulator layer of the SOI substrate.   
     
     
         18 . The method of  claim 14 , further comprising:
 forming an initial cavity in other material substrate, resulting in a remaining first surface of the other material substrate after the initial cavity is formed;   depositing an insulating layer to cover a sidewall of the initial cavity and the remaining first surface of the other material substrate and form the cavity; and   bonding the material substrate over the remaining first surface of the other material substrate, a base substrate of the material substrate being over a silicon layer of the material substrate, and the cavity exposing the first surface of the initial mirror-base layer.   
     
     
         19 . The method of  claim 18 , wherein forming the cavity in the other material substrate comprises:
 forming a mask layer over a first surface and a second surface of the other material substrate;   patterning the mask layer over the first surface of the other material substrate to expose a portion of the other material substrate, a location of an exposed portion of the other material substrate being corresponding to a location of the initial mirror-base layer along a direction perpendicular to the first surface of the other material substrate;   performing an anisotropic etch to remove the portion of the other material substrate to form the initial cavity; and   removing the mask layer over the first and second surfaces of the other material substrate.   
     
     
         20 . The method of  claim 19 , wherein exposing the second surface of the initial mirror-base layer to form the mirror-base layer that exposes the first surface and the second surface of the mirror-base layer comprises removing the base substrate of the material substrate to expose a second surface of the initial mirror-base layer, the first surface of the initial mirror-base layer forming the second surface of the mirror-base layer and the second surface of the initial mirror-base layer forming the first surface of the mirror-base layer. 
     
     
         21 . A method for forming a micromachined mirror assembly, comprising:
 forming a mirror-base layer over a base structure, a first surface of the mirror-base layer facing away from the base structure and a second surface of the mirror-base layer being exposed by the base structure; and   forming a first reflective layer on the first surface of the mirror-base layer and a second reflective layer on the second surface of the mirror-base layer, the first reflective layer and the second reflective layer being made of a same material and having same dimensions.   
     
     
         22 . The method of  claim 21 , wherein the base structure is formed by:
 patterning a base substrate to form a cavity that at least partially overlaps with the mirror-base layer in a vertical direction; and   forming an insulating layer over the base substrate to cover side surfaces of the cavity.   
     
     
         23 . The method of  claim 21 , wherein the base substrate is attached to the mirror-base layer. 
     
     
         24 . The method of  claim 22 , further comprising:
 bonding the base structure with the mirror-base layer after the insulating layer is formed.   
     
     
         25 . The method of  claim 21 , wherein forming the first reflective layer on the first surface and the second reflective layer on the second surface of the mirror-base layer comprises respectively depositing at least one of a metal layer or a distributed Bragg reflector on the first surface and the second surface of the mirror-base layer. 
     
     
         26 . The method of  claim 25 , wherein depositing the metal layer on the first surface and the second surface of the mirror-base layer comprises depositing, respectively on the first surface and the second surface of the mirror-base layer, aluminum, gold, or a combination thereof. 
     
     
         27 . The method of  claim 21 , wherein forming the mirror-base layer comprises patterning a silicon layer of a silicon on insulator (SOI) substrate.