Mask blank for charged particle beam exposure, method of forming mask blank and mask for charged particle beam exposure
The present invention provides a mask blank used for the charged particle beam exposure made by employing an SOI substrate having a silicon membrane higher reliability in quality, without the problem of deformation due to the compression stress of a silicon oxide film as an intermediate layer of the SOI substrate, and provides a method for forming a mask blank and a mask used for the charged particle beam exposure. The mask blank used for the charged particle beam exposure made by employing an SOI substrate having a front-side silicon membrane and a back-side silicon layer with a silicon oxide layer interposed therebetween is characterized in that the back-side silicon layer and the silicon oxide film of said SOI substrate are partially removed to form an opening to be an exposed region and an etching stop layer having lower stress is formed in the opening.
1. A mask blank used for a stencil mask comprising a silicon membrane defining through-holes for transmitting charged particle beams, which is made by employing an SOI substrate having a front-side silicon membrane and a back-side silicon layer with a silicon oxide film having a first internal stress interposed therebetween, wherein the back-side silicon layer of said SOI substrate and the silicon oxide film are partially removed to form an exposed region opening in which an etching stop layer having lower internal stress than said first internal stress is formed, and wherein said etching stop layer, which is removed at the time of mask processing, is made of any one selected from the group consisting of Cr, Ta, Mo, W, and Zr and nitrides, oxides, and oxynitrides of these metals.
2. A mask blank used for the charged particle beam exposure as claimed in claim 1 , wherein a hard mask layer made of any one selected from a group consisting of Cr, Ti, Ta, Mo, W, and Zr and oxides, nitrides, and oxynitrides of these metals is formed on the front-side silicon membrane of said mask blank used for the charged particle beam exposure.
3. A mask blank used for the charged particle beam exposure as claimed in claim 2 , wherein said etching stop layer and said hard mask layer are made of the same material.