Microstructure and manufacturing process thereof

Abstract

It is an object of the present invention to attain a microstructure having a miniature continuous structure which has high throughput and has been processed with high accuracy. To achieve this, provided is a microstructure having a column-shaped structure and a slit-forming portion which extends in a side-face direction from a side face of the column-shaped structure, wherein the slit-forming portion has a plurality of slits aligned in parallel at an interval from 20 to 1,000 nm in a direction along a center axis of the column-shaped structure.

1 . A microstructure comprising a column-shaped structure and a slit-forming portion which extends in a side-face direction from a side face of the column-shaped structure, wherein the slit-forming portion has a plurality of slits aligned in parallel at intervals from 20 to 1,000 nm in a direction along a center axis of the column-shaped structure.  
   
   
       2 . An optical element comprising the microstructure according to  claim 1 .  
   
   
       3 . The optical element according to  claim 2 , wherein a surface is covered with a metal layer.  
   
   
       4 . The optical element according to  claim 2  or  3 , wherein the intervals of the slit in a direction along a center axis of the column-shaped structure are constant.  
   
   
       5 . An optical filter using the optical element according to any of claims  2  or  3 .  
   
   
       6 . A branching filter comprising the optical filter according to  claim 5 .  
   
   
       7 . The optical element according to  claim 2  or  3 , wherein the slit-forming portion comprises slits aligned in parallel at a first interval and slits aligned in parallel at a second interval in a direction along a center axis of the column-shaped structure.  
   
   
       8 . The optical element according to  claim 7 , wherein a ratio of the first interval to the second interval is from 1:5 to 1:20.  
   
   
       9 . A polarized beam splitter using the optical element according to  claim 8 .  
   
   
       10 . A process for manufacturing a microstructure which comprises a column-shaped structure and a slit-forming portion which extends in a side-face direction from a side face of the column-shaped structure, wherein the slit-forming portion has a plurality of slits aligned in parallel in a direction along a center axis of the column-shaped structure, the process comprising the steps of: 
 (1) preparing a substrate which has a thickness greater than a height of the column-shaped structure;    (2) providing a mask extending in a prescribed direction of an upper face of the substrate which comprises a narrow-width portion in a direction which intersects with the extending direction for defining a portion to serve as the slit-forming portion and a broad-width portion in a direction which intersects with the extending direction for defining a portion to serve as the column-shaped portion;    (3) forming two facing grooves by carrying out isotropic etching on an upper face of the substrate by a reactive ion etching method using SF6 gas using the mask as a etching mask, and excavating in a thickness direction at least a portion of both sides opposing the extending direction of the mask of the upper face of the substrate;    (4) covering the upper face of the substrate forming the grooves with a passivation film formed by plasma reaction using C4F8 gas;    (5) providing apertures for connecting between grooves which are faced sandwiching the narrow-width portion of the mask at least below the narrow-width portion of the mask, by carrying out isotropic etching on the upper face of the substrate covered with the passivation film by a reactive ion etching method using SF6 gas; and    (6) repeating the steps (3) to (5) for aligning in parallel the apertures in a thickness direction below the narrow-width portion of the mask, to thereby attain the microstructure as well as extending the grooves in a thickness direction of the substrate.    
   
   
       11 . The process for manufacturing a microstructure according to  claim 10 , wherein the mask comprises a portion extending from one end to another end which is on an upper face of the substrate, and the ends are the broad-width portions.  
   
   
       12 . The process for manufacturing a microstructure according to  claim 11 , wherein the mask further comprises the broad-width portion on a portion other than on the end.  
   
   
       13 . The process for manufacturing a microstructure according to any of  claims 10  to  12 , wherein the mask extends in a branched manner in a plurality of prescribed directions.  
   
   
       14 . The process for manufacturing a microstructure according to any of  claims 10  to  12 , wherein the substrate is an SOI substrate.  
   
   
       15 . The process for manufacturing a microstructure according to any of  claims 10  to  12 , wherein the steps (3) to (5) are finished prior to the grooves penetrating as far as a lower face of the substrate.