AVS 52nd International Symposium
    Thin Films Monday Sessions
       Session TF+NS-MoA

Paper TF+NS-MoA4
Reduction of Laser-Induced Roughness in a-Si:H Surfaces for Vacuum Compatible Lithography

Monday, October 31, 2005, 3:00 pm, Room 306

Session: Focused Beam Processing & Fabrication
Presenter: R.N. Jacobs, US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate
Authors: R.N. Jacobs, US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate
E.W. Robinson, US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate
A.J. Stoltz, US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate
J.H. Dinan, US Army RDECOM CERDEC Night Vision and Electronic Sensors Directorate
L.G. Salamanca-Riba, University of Maryland, College Park
Correspondent: Click to Email
A vacuum compatible lithography technique has recently been demonstrated, whereby amorphous hydrogenated silicon (a-Si:H) films are used as a resist. Following plasma deposition of the a-Si:H film, poly-Si patterns are generated on the surface by excimer laser exposure through a projection mask. Development is then carried out by hydrogen plasma etching for which etch selectivities of over 1000:1 have been achieved for a-Si:H and poly-Si regions.@footnote 1@ However the rms roughness induced by excimer laser irradiation can be well over 10 times that of the as-deposited a-Si:H surface. This is problematic because the roughness may be transferred to underlying device layers during subsequent pattern transfer plasma etching. We have developed a step-wise laser irradiation procedure that results in a reduction of surface roughness by an order of magnitude to a level of ~1 nm (rms). This value is approximately equal to the surface roughness in the as-deposited a-Si:H film. The irradiation procedure uses multiple pulses with progressive increases in the energy density, in contrast to single high energy density pulses used previously. Transmission electron microscopy and Fourier transform infrared spectroscopy are used to understand and confirm the mechanism behind this process. Our data suggests that the observed reduction in roughness is due both to smaller grain sizes and to a slow rate of H removal from the film surface. While useful for a-Si:H vacuum-lithography processing, our results also hold significance for other applications of laser processed a-Si:H, even where different film properties may be desired. @FootnoteText@ @footnote 1@R.N. Jacobs, A.J. Stoltz, J.H. Dinan, and L. Salamanca-Riba, J. Vac. Sci. Technol. B, 22 1071 (2004).