Thermal Characteristics of Scattering Stencil Reticle for Electron Beam Stepper

Abstract

We are developing an electron beam (EB) stepper as one of the next-generation lithography systems for feature sizes of less than 100 nm. As a reticle for the EB stepper using a high-power EB (accelerating voltage:100 kV, current on reticle:100 µA), a scattering stencil reticle with a grid-grillage structure is investigated. We evaluated the deformation of a scattering stencil reticle, due to thermal expansion and bending by gravity. These phenomena are computer simulated. Immediately after the EB is illuminated, the temperature of the 2-µm-thick membrane of the reticle increases about 4 K. The induced pattern distortion is about 2 nm and gravitational horizontal deformation is less than 1 nm. Thermal and gravitational vertical deformations are about 3 nm and about 6 nm, respectively. From these results, the induced image horizontal distortion is about 0.5 nm and vertical distortion is about 0.4 nm on the wafer for a demagnification(1/4) system, due to thermal expansion and bending by gravity. This shows that a scattering stencil reticle with a 2-µm-thick membrane is applicable to an EB stepper for high throughput and high resolution, and has advantages compared with a conventional EB lithography mask from the viewpoint of thermal problems.

Complementary splitting with stress emulation for stencil masks

“…The mechanical properties such as Young's modulus and Poisson ratio for the silicon membranes have been taken from the literature treating the FEM analysis of a stencil mask of the same type [7]. Namely, the Young's modulus of 63.9 GPa and the Poisson ratio of 0.2 have been used.…”