Amorphous silicon films are often laser treated to induce crystallinity with the resultant crystalline structure used for microelectronic devices. Existing methods are limited in their applicability because the surface roughness of the silicon film becomes unacceptably high. This technology uses an excimer laser in combination with a rigid cap layer that is formed on the outer surface of the amorphous thin film to create crystalline structures of reduced surface roughness. Laser pulses of controlled energy and spatial overlap are scanned across the surface, causing a precise amount of melting and resolidification. Thus, this technology presents a method for potentially improving the performance of silicon film-based devices.
This technology overcomes the issue of surface roughness that arises during laser crystallization of amorphous silicon. Rough surfaces are detrimental to the performance of the microelectronic devices that such films are often implemented in. It can be applied either as a post-processing step to a previously processed film, or simultaneously with the crystallization step. A homogenized excimer laser pulse with energy ranging from 25% to 75% induces partial melting, and multiple pulses are incident on each region to ensure uniformity. When used simultaneously with the crystallization step, a cap layer made of silicon oxide prevents the grains from protruding from the surface and is removed via wet or dry etching, resulting in a smooth surface finish.
Direct measurements have found that post processing a previously crystallized surface results in a 100% decrease of the surface roughness.
Patent Issued (US 7220660)
Tech Ventures Reference: IR MS99/04/26E