Method of etching ferroelectric material

Abstract

A method of etching a ferrolectric material is disclosed whereby a single layer of ions is implanted into a surface of the film and then, without first annealing the substrate, the material between that surface and the layer of ion implantation is etched away. Such a method has the benefit of being faster and much less costly as compared to prior art methods. A single ion implantation of sufficient energy causes a high level of electronic damage near the surface of the material and a high level of crystalline damage at the ion implant level. While it is well known that crystalline damage greatly increases the etch rate of a ferroelectric material, the inventors have discovered that the aforementioned electronic damage also substantially increases the etch rate of the material. Since damaged lithium niobate etches at a much faster rate then undamaged lithium niobate, no annealing is necessary to create an etch stop. Additionally, since there is sufficient damage, either electronic or nuclear, continuously from the surface of the material to the implant layer, multiple ion layer implantations are not necessary.

What is claimed is:  
     
         1 . A method for use in etching structures in a substrate, said method comprising the steps of: 
 implanting a single layer of ions into a substrate top surface using an energy sufficient to drive the ions a predetermined depth into said substrate; and    without performing a preceding annealing step, etching with a chemical wet etchant the substrate through said top surface of the substrate until reaching the layer of ions at said predetermined depth from said surface.    
     
     
         2 . The method of  claim 1  wherein said substrate is a lithium niobate (LiNbO 3 ) substrate.  
     
     
         3 . The method of  claim 1  wherein said top surface is the +z crystal surface.  
     
     
         4 . The method of  claim 1  wherein said top surface is the −z crystal surface.  
     
     
         5 . The method of  claim 1  further comprising, prior to said etching step, implanting at least a second layer of ions into said substrate top surface using an energy sufficient to drive the ions to a level of minimum combined electronic and nuclear damage within said substrate.  
     
     
         6 . The method of  claim 1  wherein at least one portion of said top surface of said substrate is masked in such a way that the ions do not penetrate into the substrate underlying said mask.  
     
     
         7 . The method of  claim 6  wherein said etching step comprises exposing said top surface to a chemical wet etchant for a length of time necessary to etch away at least a portion of the lithium niobate to form a predetermined structure in said lithium niobate.  
     
     
         8 . The method of  claim 7  wherein said structure is a ridge.  
     
     
         9 . The method of  claim 1  wherein said implanting step comprises tilting the substrate in such a way that the ions form reentrant angles between the base and the side walls of said substrate.