Heat Transport Analysis for Flash Lamp Annealing

Abstract

The silicon wafer temperature change during flash lamp annealing is theoretically evaluated. A calculation model is developed on the basis of a finite difference method taking into account various heat transport phenomena, such as heat radiation from a lamp to a silicon surface, reflection at the silicon surface, heat radiation from a hot silicon surface, light absorption in silicon, and thermal conduction. The effect of the light absorption in a silicon wafer on the temperature profile is negligible at the position of ultrashallow junction formation. The largest temperature slope is shown to be formed by flash lamp annealing because of the agreement of the temperature slope obtained by taking into account heat absorption in silicon with that obtained by assuming heat absorption only at the surface, without accounting for the light absorption in silicon. This study further concludes that the surface reflectivity strongly affects the silicon temperature.

Variation of crystallization mechanisms in flash-lamp-irradiated amorphous silicon films

“…Detailed deposition conditions of a-Si films have been summarized elsewhere [17]. Only one shot of flash lamp light, with a broad spectrum mainly in the visible range [11], was irradiated for each sample. Irradiance of flash lamp light was tuned around 18-25 J/cm 2 in order to obtain as large an area of poly-Si as possible and to avoid the peeling of the Si film.…”

“…Flash lamp annealing (FLA), which is flash discharge from a xenon lamp array, can realize an annealing duration in the order on milliseconds [10,11], corresponding to the thermal diffusion lengths of a-Si and glass of several tens of mm. This means that a precursor a-Si film of a few mm thickness, required for c-Si for the effective absorption of sunlight, can be fully heated and crystallized, while a glass substrate of $ 1 mm thickness is not entirely heated.…”

Polycrystalline Si films with unique microstructures formed from amorphous Si films by non‐thermal equilibrium flash lamp annealing

“…The flash lamp light has a broad spectrum mainly in visible range, which is therefore absorbed in a-Si films, resulting in increasing film temperature. The typical spectrum of the flash lamp light is seen elsewhere [7]. FLA was performed under pulse durations of 1 or 5 ms with various irradiances on the order of several tens of J/cm 2 .…”

“…Flash lamp annealing (FLA) is an annealing technique with millisecond-order pulse light [5][6][7]. This annealing duration corresponds to the thermal diffusion length of glass and a-Si of approximately 50 µm, meaning sufficient heating of a-Si films a few µm thick, while avoiding thermal damage to glass substrates.…”

Carrier recombination mechanisms in solar cells fabricated using flash-lamp-crystallized polycrystalline silicon films

“…Of a variety of methods to form poly-Si films, we have investigated FLA, millisecondorder discharge from a Xe lamp array [5][6][7]. Due to its proper pulse duration, a few µm-thick a-Si films can be sufficiently heated and crystallized by a single pulse of FLA without heating entire glass substrates.…”