Oliver Kirch

Ion projection lithography below 70 nm: tool performance and resist process

Abstract Ion projection lithography (IPL) uses electrostatic ion-optics for reduction printing of stencil mask patterns to wafer substrates. The IPL process development tool (PDT) prints field sizes of 12.5 mm×12.5 mm (wafer) at a demagnification factor of 4. First printing results demonstrating different aspects such as resolution, linearity, exposure schemes with stencil masks and image stabilization are available. As an integral part of IPL a resist process suitable for 50 nm minimum feature size has been established using the IMS 1:1 ion beam proximity exposure tool. This resist process has been transferred successfully to the PDT. Compared to previous experiments, sensitivity and contrast have been determined for a larger number of resist materials and with higher precision. Improved resist patterns, better CD linearity and higher stability with respect to pattern collapse have been achieved by optimizing the process parameters. For a Shipley resist, system input parameters for simulations have been determined. Results for the quantum efficiency obtained by Szmanda’s titration method will be presented.

Comparison of resist outgassing at wavelengths from 193 nm to 13 nm

Corresponding to the ITRS roadmap, EUV Lithography will in the not-too-far future reach the point, where critical resist dimensions are in the same order of magnitude as polymer chains and acid diffusion lengths, while photon energies will largely exceed the binding energies of all organic molecules. Especially in EUV, where secondary electron side reactions may lead to a higher outgassing of polymer fragments than in 157nm and 193nm lithography, outgassing is agreed to be a critical issue for resist development. In this paper EUV, 193nm and 157nm outgassing is characterized using an online mass spectrometer attached to several different outgassing setups (i.e. synchrotron, laser). The total outgassing and the time dependent outgassing of resist fragments has been characterized for a number of resist polymer platforms. The results are compared and discussed in terms of the applied photon energies and differences in EUV, 157nm and 193nm exposures. Time dependent scanning of selected mass channels was used to differentiate if an outgassing fragment had its origin from the photoacid generator (PAG) or from a photolytic or a photochemical reaction of the polymer matrix. For EUV, correlations are given between resist outgassing and high dose crosslinking and scissioning behaviour of EUV resists.