Dry multilayer inorganic alloy thermal resist for lithographic processing and image creation

Abstract

A thermal inorganic resist for lithographic processes and image creation is disclosed. In one embodiment an In layer of 15 nm is deposited, followed by a Bi layer of 15 nm. Upon exposure to a optical light pulse of sufficient intensity the optical absorption heats the film above the eutectic melting point (110° C. for BiIn) and the resist forms an alloy in the exposed area, replicating patterns projected on its surface. Optical characteristics of the alloyed layers are in these resists typically different from the unexposed layers creating a visual image of the exposure pattern before the development etch aiding in exposure control. The resist layer is then stripped, leaving the pattern layer on the substrate. In resists showing significant optical differences (such as BiIn) after exposure this same material can be used to create images for data storage, and, when transparent, photomasks for optical lithography.

What is claimed is:  
     
         1 . A photomask material comprising at least two layers of thin inorganic coatings, said coatings changing from opaque to transparent when heated.  
     
     
         2 . The photomask of  claim 1  comprising a transparent protective overcoat.  
     
     
         3 . The photomask of  claim 2  wherein the overcoat comprises a cross-linked polymer.  
     
     
         4 . A photomask according to  claim 1  made by a method comprising: 
 depositing a first layer of an inorganic thin film on a substrate, the first layer consisting of a layer of a single element metal;  
 depositing one or more subsequent layers of another inorganic material or materials; and,  
 imagewise exposing said layers, said exposing creating a resultant material with different etching characteristics from said first and subsequent layers.  
 
     
     
         5 . A photomask according to  claim 1  made by a method comprising: 
 depositing on a substrate a first layer of an inorganic thin film comprising a first inorganic material;  
 depositing one or more subsequent layers of one or more second inorganic materials; and,  
 imagewise exposing said first and subsequent layers, said exposing creating in exposed areas a contiguous layer of a resultant material having a melting point below melting points of said first and subsequent layers.  
 
     
     
         6 . A photomask according to  claim 5  wherein said resultant material is a eutectic alloy of said first and second materials.  
     
     
         7 . A photomask according to  claim 1  made by a method comprising: 
 depositing on a substrate a first layer of an inorganic thin film comprising a first inorganic material;  
 depositing one or more subsequent layers of one or more second inorganic materials; and  
 imagewise exposing said first and subsequent layers, said exposing causing one or more reactions with surrounding gases to create one or more oxides, nitrides or hydrides of an alloy of materials of said first and subsequent layers, said reactions creating a resultant material having different etching characteristics from any of said materials of said first and subsequent layers.  
 
     
     
         8 . A photomask according to  claim 4  wherein said resultant material has optical transmission characteristics different from optical transmission characteristics of the inorganic materials of the first and subsequent layers.  
     
     
         9 . A photomask according to  claim 1  made by a method comprising: 
 providing on the substrate a first layer of a first material and a second layer of a second material, the first and second materials each having a melting point higher than a melting point of an alloy of the first and second materials;  
 imagewise exposing the substrate by heating selected adjoining portions of the first and second layers to imaging temperatures exceeding the melting point of the alloy and thereby causing the first and second layers to melt together to form the alloy in the selected adjoining portions.  
 
     
     
         10  A photomask comprising first and second areas having different optical characteristics from one another, the first areas comprising a plurality of layers of different inorganic materials, the second areas comprising contiguous regions of an alloy of the inorganic materials, the alloy having a melting temperature lower than melting temperatures of the inorganic materials.  
     
     
         11 . A photomask according to  claim 10  wherein the first and second areas have different etching characteristics.  
     
     
         12 . A photomask according to  claim 10  wherein the different inorganic materials comprise different metals.  
     
     
         13 . A photomask according to  claim 10  wherein the alloy has optical characteristics different from optical characteristics of a topmost one of the inorganic materials, thus creating a visible image on a surface of the resist which can be viewed by illumination with optical radiation.  
     
     
         14 . A photomask according to  claim 10  wherein the alloy has a melting point below 300 degrees Celsius.  
     
     
         15 . A photomask according to  claim 14  wherein the alloy contains at least 5 percent of one of the inorganic materials.  
     
     
         16 . A photomask according to  claim 10  wherein the alloy comprises a binary alloy selected from the group consisting of: AsPb, BiCd, BiCo, BiIn, BiPb, BiSn, BiZn, CdIn, CdPb, CdSb, CdSn, CdTl, CdZn, GaIn, GaMg, GaSn, GaZn, InSn, InZn, MgPb, MgSn, MgTl, PbPd, PbPt, PbSb, PbSn, SbTl, SeTl, SnTl, and, SnZn.