Pattern displacement measurements for Si stencil reticles

We have fabricated Si stencil reticles that are employed by a new type of e -beam projection lithography system (EB stepper). We applied a stress reduc tion technique to the Si membrane to improve the pattern placement accuracy . The residual stress of Si membranes which were fabricated by anisotropic etching of B-doped Si wafers in KOH aqueous solution was reduced by anneali ng at 1150 degrees C. We carried out pattern-displacement measurements fur a Si stencil reticle made of a Si membrane where the residual stress was re duced to 10 MPa, and we observed that the pattern displacement error was re duced to less than 20 Mm. Furthermore, the pattern displacement in the sten cil reticle had a high correlation with, the displacement determined from a simulation based on a finite element model. However in the same reticle, w e discovered additional, comparatively small displacements in random direct ions, which was not expected in a membrane that had a homogeneous tensile s tress. As a cause of the pattern displacement in random directions, we iden tified a pattern-width broadening ih the dry etching process. (C) 1999 Amer ican Vacuum Society. [S0734-211X(99)07606-4].