Wavelike hard nanomask on a topographic feature and methods of making and using

Abstract

An array of nanowires with a period smaller than 150 nm can be used for optoelectronics and semiconductor electronics applications. A hard nanomask is registered to a lithographically defined feature and can be used to manufacture such structures. This nanomask includes a substantially periodic array of substantially parallel elongated elements having a wavelike cross-section. The fabrication method of the nanomask may be contactless and uses ion beams.

1 . A hard nanomask, comprising:
 a first layer formed of a first material and having a surface, a topographic feature, and two opposing sidewalls defining the topographic feature; and   a substantially periodic array of substantially parallel, elongated elements formed on the surface of the first layer and having a wavelike cross-section and being oriented along a first direction, at least some of the elements having the following structure in cross-section
 an inner region of the first material, and 
 a first outer region of a second material covering a first portion of the inner region, 
   wherein the second material is formed by modifying the first material using an ion flow;   wherein the substantially parallel, elongated elements having the wavelike cross-section are positioned on the topographic feature between the two opposing sidewalls of the topographic feature and wherein the sidewalls of the topographic feature are oriented substantially parallel along the first direction.   
     
     
         2 . The nanomask of  claim 1 , wherein a wavelength of the substantially periodic array is in a range from 20 to 150 nm. 
     
     
         3 . The nanomask of  claim 1 , wherein the first material is silicon, amorphous silicon, silicon oxide, gallium arsenide, epitaxial gallium arsenide, gallium aluminum arsenide, epitaxial gallium aluminum arsenide, germanium, or silicon-germanium. 
     
     
         4 . The nanomask of  claim 1 , wherein the thickness of the first outer region is at least 2 nm. 
     
     
         5 . The nanomask of the  claim 1 , further comprising a second outer region of the second material covering a second portion of the inner region connected to the first outer region at a wave crest, wherein the first outer region is substantially thicker than the second outer region. 
     
     
         6 . The nanomask of the  claim 5 , wherein a thickness of the second outer region is no more than 1.5 nm. 
     
     
         7 . The nanomask of  claim 5 , wherein the second material is silicon nitride, silicon-germanium nitride, silicon oxide, gallium nitride, gallium oxide, aluminum nitride, aluminum oxide, gallium aluminum nitride, or gallium aluminum oxide. 
     
     
         8 . The nanomask of  claim 5 , wherein the ion flow is N 2   + , N + , NO + , NH m   + , O 2   + , Ar + , Kr + , Xe + , or a mixture of Ar +  and N 2   + . 
     
     
         9 . The nanomask of  claim 1 , wherein the topographic feature a raised topographic feature. 
     
     
         10 . The nanomask of  claim 1 , wherein the topographic feature is a recessed topographic feature. 
     
     
         11 . The nanomask of  claim 1 , wherein the sidewalls of the topographic feature are sloped with respect to the surface of the topographic feature between the sidewalls. 
     
     
         12 . The nanomask of  claim 1 , wherein the periodic array includes N elongated elements where N is a positive integer. 
     
     
         13 . The nanomask of  claim 12 , wherein N is 2, 3, 4, 5, 6, 7 or 8. 
     
     
         14 . A method of forming a hard nanomask for transferring a substantially periodic pattern into a thin film, the method comprising:
 forming a first layer of a first material;   forming a topographic feature in a surface of the first layer, wherein the topographic feature is defined by two opposing sidewalls, wherein the sidewalls are oriented substantially parallel along a first direction; and   irradiating the surface of the topographic feature with a flow of ions directed alternatively towards the opposite sidewalls of the topographic feature to form a hard nanomask, the nanomask comprising a substantially periodic array of substantially parallel elongated elements having a wavelike cross-section and being oriented substantially parallel along the first direction, at least some of the elements having the following structure in cross-section: an inner region of first material, a first outer region of a second material covering a first portion of the inner region, and a second outer region of the second material covering a second portion of the inner region and connecting with the first outer region at a wave crest, wherein the first outer region is substantially thicker than the second outer region, and wherein the second material is formed by modifying the first material by the ion flow, wherein a plane of incidence of the ion flow is substantially perpendicular to the first direction and wherein the substantially parallel, elongated elements having the wavelike cross-section are positioned on the surface of the topographic feature between the two opposing sidewalls defining the topographic feature.   
     
     
         15 . The method of  claim 14 , wherein a wavelength of the substantially periodic array is in a range from 20 to 150 nm. 
     
     
         16 . The method of  claim 14 , wherein the first material is silicon, amorphous silicon, silicon oxide, gallium arsenide, epitaxial gallium arsenide, gallium aluminum arsenide, epitaxial gallium aluminum arsenide, germanium, or silicon-germanium. 
     
     
         17 . The method of  claim 14 , wherein the ion flow comprises a flow of N 2   + , N + , NO + , NH m   + , Ar + , Xe + , or a mixture of Ar +  and N 2   + . 
     
     
         18 . The method of  claim 14 , wherein a thickness of the first outer region is at least 4 nm. 
     
     
         19 . The method of  claim 14 , wherein a thickness of the second outer region is no more than 2 nm. 
     
     
         20 . The method of  claim 14 , wherein the second material is silicon nitride, silicon-germanium nitride, silicon oxide, gallium nitride, gallium oxide, aluminum nitride, aluminum oxide, gallium aluminum nitride, or gallium aluminum oxide. 
     
     
         21 . The method of  claim 14 , wherein the topographic feature is a raised topographic feature. 
     
     
         22 . The method of  claim 21 , further comprising after forming the topographic feature depositing a second layer of a first material to compensate for narrowing of the topographic feature due to ion sputtering during irradiating the surface of the topographic feature by a flow of ions. 
     
     
         23 . The method of  claim 14 , wherein the topographic feature is a recessed topographic feature. 
     
     
         24 . The method of  claim 14 , wherein the sidewalls of the topographic feature are sloped. 
     
     
         25 . The method of  claim 14 , wherein the periodic array includes N elongated elements where N is a positive integer. 
     
     
         26 . The method of  claim 25 , wherein N is 2, 3, 4, 5, 6, 7 or 8. 
     
     
         27 . (canceled)