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Laser-induced removal of particles from surfaces was demonstrated. Such “laser cleaning” can be performed on the bare contaminated surface or with additional micronthickness liquid film coverage on the surface. With the latter “steam laser cleaning” we achieved removal of epoxy, alumina, silicon, and gold particles of size 0.1 μm to 10 μm from silicon surfaces. The proposed mechanism of particle ejection is described.

‘Liquid Film Enhanced Laser Cleaning” is a technique to remove particulate contamination from surfaces. A thin liquid film deposited onto the contaminated surface is flood irradiated with a short laser pulse. The resulting sudden evaporation of the liquid film leads to high transient explosive forces, large enough to expel even submicron particles from the surface. For instance 0.1μm alumina particles could efficiently be removed from a silicon surface with KrF excimer laser irradiation of 16 ns pulse length and 120 mJ/cm 2 energy density.

Following the trends in the semiconductor technology to higher density and smaller dimensions the light-optical tools get serious technical problems to solve the requirements on resolution, depth of focus and overlay. Besides exposure tools using DUV / excimer laser sources other technologies like e-beam and X-ray will follow. There are several requirements which have to be solved to demonstrate the capability of a lithography technique for the fabrication of ULSI circuits. Three of them, the 1. o mask technology. 2. o resolution of a high throughput exposure tool. 3. o registration capability for layer to layer overlay. will be addressed in this paper and will confirm that the Electron Beam Proximity Printing (EBP) technology can fulfill these requirements for the 64 Mbit and 256 Mbit chip generations with minimum linewidths of 0.35 and 0.25 micron respectively.

Laser cleaning was demonstrated to be a new, promising approach to efficiently remove particulate contamination of micron and submicron size from wafer surfaces as well as from the surface and trenches of thin silicon membrane stencil masks as used for e-beam projection lithography.

Mix-and-match lithography between Electron Proximity Printing (EBP) and optical lithography was demonstrated in processing nine levels of a 1Mbit device up to first metallization. High overlay accuracy was achieved. For the first time we produced a large membrane stencil mask with the high pattern density of a standard 1Mbit chip.