Manufacturing Optical MEMS with Thin-Film Anti-Reflective Layers

Abstract

In accordance with the teachings of one embodiment of the present disclosure, a method for manufacturing a semiconductor device includes forming a support structure outwardly from a substrate. The support structure has a first thickness and a first outer sidewall surface that is not parallel with the substrate. The first outer sidewall surface has a first minimum refractive index. A first anti-reflective layer is formed outwardly from the support structure and outwardly from the substrate. A second anti-reflective layer is formed outwardly from the first anti-reflective layer. The first and second anti-reflective layers each includes respective compounds of at least two elements selected from the group consisting of: silicon; nitrogen; and oxygen.

1 . A method for manufacturing an optical microelectrical mechanical system (MEMS), comprising:
 forming a support structure outwardly from a substrate, the support structure having a first thickness and a first outer sidewall surface that is not parallel with the substrate, the first outer sidewall surface having a first minimum refractive index;   forming a first anti-reflective layer outwardly from the first outer sidewall surface, the first anti-reflective layer capable of resisting the flow of electric current and having:
 a second outer sidewall surface that is not parallel with the substrate; 
 a second refractive index that is greater than the first minimum refractive index; 
 a second thickness that is less than the first thickness; and 
   forming a second anti-reflective layer outwardly from the first anti-reflective layer, the first and second anti-reflective layers each comprising respective compounds of at least two elements selected from the group consisting of:
 silicon; 
 nitrogen; and 
 oxygen. 
   
   
   
       2 . The method of  claim 1 , wherein the second thickness is less than 1 micron. 
   
   
       3 . The method of  claim 1 , wherein the first outer sidewall surface and the second outer sidewall surface are substantially parallel. 
   
   
       4 . The method of  claim 1 , wherein the second refractive index is greater than approximately 1.5. 
   
   
       5 . The method of  claim 1 , wherein the support structure comprises material selected from the group consisting of aluminum or an aluminum alloy, copper, silver, gold, tungsten, titanium, titanium nitride (TiN), silicon, polysilicon, carbon, chromium, and nickel. 
   
   
       6 . The method of  claim 1 , wherein the support structure comprises a plurality of layers. 
   
   
       7 . An optical microelectrical mechanical system (MEMS), comprising:
 a MEMS base disposed outwardly from a first substrate, the MEMS base coupled to a MEMS superstructure and having a first thickness and a first outer sidewall surface that is not parallel with the substrate, the first outer sidewall surface having a first minimum refractive index;   at least two anti-reflective layers each disposed outwardly from the MEMS base, outwardly from the first outer sidewall surface, and inwardly from the MEMS superstructure, the at least two anti-reflective layers each capable of resisting the flow of electric current and having:
 a second outer sidewall surface that is not parallel with the substrate; 
 a second refractive index that is greater than the first minimum refractive index; and 
 a second thickness that is less than the first thickness; and 
   wherein the at least two anti-reflective layers each comprise respective compounds of at least two elements selected from the group consisting of silicon, nitrogen, and oxygen, the respective compound of a first anti-reflective layer of the at least two anti-reflective layers different from the respective compound of a second anti-reflective layer of the at least two anti-reflective layers.   
   
   
       8 . The optical microelectrical mechanical system (MEMS) of  claim 7 , wherein the MEMS superstructure comprises:
 a plurality of micromirrors disposed outwardly from the first substrate;   a plurality of hinges, each hinge coupled to respective ones of the plurality of micromirrors and operable to pivot the respective ones of the plurality of micromirrors about at least one axis;   a plurality of support posts disposed outwardly from the support structure, at least two of the plurality of support posts operable to suspend at least one of the plurality of hinges; and   further comprising a transparent substrate disposed outwardly from the plurality of micromirrors, the transparent substrate and the first substrate at least partially defining an enclosed cavity.   
   
   
       9 . The optical microelectrical mechanical system (MEMS) of  claim 8 , wherein one or more chemical compounds disposed within the enclosed cavity are more chemically reactive with titanium nitride (TiN) than with the respective compounds of the first and second anti-reflective layers. 
   
   
       10 . The optical microelectrical mechanical system (MEMS) of  claim 7 , wherein the MEMS superstructure comprises a support post electrically coupled to the MEMS base. 
   
   
       11 . The optical microelectrical mechanical system (MEMS) of  claim 7 , wherein the anti-reflective layer is less than 1 micron thick. 
   
   
       12 . The optical microelectrical mechanical system (MEMS) of  claim 7 , wherein the first outer sidewall surface and the second outer sidewall surface are substantially parallel. 
   
   
       13 . The optical microelectrical mechanical system (MEMS) of  claim 7 , wherein the second refractive index is greater than approximately 1.5. 
   
   
       14 . A method for manufacturing a semiconductor device comprising:
 forming a support structure outwardly from a substrate, the support structure forming a supportive base for a microelectromechanical systems (MEMS) element, the support structure having a first thickness and a first outer sidewall surface that is not parallel with the substrate, the first outer sidewall surface having a first minimum refractive index;   forming a first anti-reflective layer outwardly from the support structure and outwardly from the substrate; and   forming a second anti-reflective layer outwardly from the first anti-reflective layer, the first and second anti-reflective layers each comprising respective compounds of at least two elements selected from the group consisting of:
 silicon; 
 nitrogen; and 
 oxygen. 
   
   
   
       15 . The method of  claim 14 , further comprising forming a second dielectric layer outwardly from the anti-reflective layer. 
   
   
       16 . The method of  claim 14 , wherein the anti-reflective layer has an index of refraction greater than the first minimum refractive index. 
   
   
       17 . The method of  claim 14 , wherein the anti-reflective layer is less than 1 micron thick. 
   
   
       18 . The method of  claim 14 , wherein the first outer sidewall surface and the second outer sidewall surface are substantially parallel. 
   
   
       19 . The method of  claim 14 , wherein anti-reflective layer has a refractive index greater than approximately 1.5. 
   
   
       20 . The method of  claim 14 , wherein the first anti-reflective layer is capable of resisting the flow of electric current.