Method of building a 3d functional optical material layer stacking structure

Abstract

Embodiments herein describe a sub-micron 3D diffractive optics element and a method for forming the sub-micron 3D diffractive optics element. In a first embodiment, a method is provided for forming a sub-micron 3D diffractive optics element on a film stack disposed on a substrate without planarization. The method includes forming a hardmask on a top surface of a film stack. Forming a mask material on a portion of the top surface and a portion of the hardmask. Etching the top surface. Trimming the mask. Etching the top surface again. Trimming the mask a second time. Etching the top surface yet again and then stripping the mask material.

What is claimed is: 
     
         1 . A method for forming a sub-micron one sided symmetrical 3D optical material structure into a film stack disposed on a substrate without planarization, the method comprising:
 forming a hardmask on a top surface of the film stack;   forming a mask material onto a portion of the top surface of the film stack and a portion of the hardmask, the mask material having a plurality of sides;   etching the top surface of the film stack a depth of less than one micron revealing a second top surface and forming a first material level under the mask material;   trimming the sides of the mask material by less than one micron to reveal a second side surface of the mask material and a first upper surface of the first material level;   etching the second top surface of the film stack and the first upper surface of the first material level by a depth of less than one micron forming a second material level under the first material level and revealing a third top surface for the film stack and a second upper surface for the second material level;   trimming the second sides of the mask material by less than one micron to reveal a third side surface of the mask material and the first upper surface of the first material level;   etching the third top surface of the film stack, the first upper surface of the first material level and the second upper surface of the second material level all by a depth of less than one micron forming a third material level under the second material level and revealing a fourth top surface for the film stack and a third upper surface for the third material level; and   stripping the mask material from the film stack to reveal the sub-micron symmetrical 3D optical material structure.   
     
     
         2 . The method of  claim 1  further comprising:
 removing the hardmask; 
 forming a second mask material on the sub-micron symmetrical 3D optical material structure and the fourth top surface of the film stack; 
 etching the top surface of the film stack to the depth of the fourth top surface; and 
 stripping the second mask material from the film stack to reveal a sub-micron one sided symmetrical 3D optical material structure. 
 
     
     
         3 . The method of  claim 1  further comprising:
 imprinting the inverse shape of the one sided symmetrical 3D optical material structure in an optical material or stack. 
 
     
     
         4 . The method of  claim 1  wherein the depth of the etch is about 200 nm. 
     
     
         5 . The method of  claim 1  wherein trimming the second sides of the mask material a desired distance corresponding to a lateral step size. 
     
     
         6 . The method of  claim 5  wherein the lateral step size is the same as the depth. 
     
     
         7 . The method of  claim 5  further comprising:
 directional etching the mask material. 
 
     
     
         8 . The method of  claim 1  wherein the second top surface is closer to the mask material than the third top surface. 
     
     
         9 . The method of  claim 1  further comprising:
 skipping the trimming of one or more of the sides of the mask material for one or more etching operations. 
 
     
     
         10 . The method of  claim 1  further comprising:
 imprinting the inverse shape of the 3D optical material structure in an optical material or stack. 
 
     
     
         11 . A sub-micron 3D optical material structure on a diffractive optics element, the 3D optical material structure comprising:
 a substrate having a top surface;   a first material level formed on the top surface of the substrate, wherein the first material level has a first top surface and comprises:
 a plurality of first unit pieces of material, each first unit piece of material having a height, a width and a length, all of which are less than about one micron; 
   a second material level formed on the first top surface of the first material level, wherein the second material level has a second top surface and comprises:
 a plurality of second unit pieces of material, wherein each second unit piece of material is disposed on one of the first unit pieces of material and each second unit piece of material having a second height, a second width and a second length, comparable to the height, the width and the length of the first unit piece of material; and 
   a third material level formed on the second top surface of the second material level, wherein the third material level comprises:
 a plurality of third unit piece of material, wherein each third unit piece of material is disposed on one of the second unit piece of material and each third unit piece of material having a third height, a third width and a third length, comparable to that of the second unit piece of material. 
   
     
     
         12 . The 3D optical material structure of  claim 11  wherein the first material level further comprises:
 a plurality of first vias, wherein the first vias are devoid of any of the plurality of first unit pieces. 
 
     
     
         13 . The 3D optical material structure of  claim 12  wherein each via of the plurality of first vias is substantially similar in size to that of the first unit piece. 
     
     
         14 . The 3D optical material structure of  claim 12  wherein each second unit piece is disposed on a first unit piece and not on or in any of the plurality of first vias. 
     
     
         15 . The 3D optical material structure of  claim 12  wherein the second material level further comprises:
 a plurality of second vias, wherein the second vias are devoid of any of the plurality of second unit pieces and disposed on the plurality of first vias. 
 
     
     
         16 . The 3D optical material structure of  claim 15  wherein one or more of the plurality of second vias is additionally disposed on one or more of the first unit pieces. 
     
     
         17 . The 3D optical material structure of  claim 16  wherein a multitude of layers are be stacked to form the 3D optical material structure having four (4), eight (8), sixteen (16), thirty two (32) or more layers of material. 
     
     
         18 . A method of fabricating a sub-micron 3D optical diffractive optics element, the method comprising:
 A) depositing an optical material stack to be patterned into a diffractive optics element on a substrate;   B) depositing and patterning a mask material on a portion of the material stack;   C) etching the material stack down one level;   D) directionally etch one or more side portions of the mask material laterally by a desired distance;   E) vertically etching the material stack down vertically a 2 nd  level;   F) repeating D and E; and   G) stripping the mask material.   
     
     
         19 . The method of  claim 18  further comprising:
 depositing a blocking layer that is resistant to etch to a blocked area and patterned with lithography a non-blocked area; 
 removing the blocking layer; and 
 adding a mask material covering the non-blocked area and etching down the optical material stack to a lower step level.