Defect Termination of Flash-Lamp-Crystallized Large-Grain Polycrystalline Silicon Films by High-Pressure Water Vapor Annealing

Abstract

High-pressure water-vapor annealing (HPWVA) is performed on 3-µm-thick polycrystalline silicon (poly-Si) films formed on glass substrates by crystallizing electron-beam (EB)-evaporated precursor amorphous Si (a-Si) films by flash lamp annealing (FLA). HPWVA at higher temperature and pressure tends to result in a lower defect density of FLC poly-Si films. The defect density of FLC poly-Si films can be reduced from ∼3×1017 to ∼2×1016/cm3 when the HPWVA temperature is 500 °C and the pressure is more than 8 MPa, which is sufficiently of device grade. The annealing of flash-lamp-crystallized (FLC) poly-Si films under inert-gas atmosphere does not lead to sufficient reduction in their defect density, indicating the necessity of water vapor during annealing.

Effect of starting point formation on the crystallization of amorphous silicon films by flash lamp annealing

“…The pulse light emitted from the Xe lamp has a broad spectrum mainly in the visible region, as reported previously. 25) Only one flash lamp pulse was irradiated for each sample. The surfaces of Si films after FLA were observed by optical microscopy.…”

“…[1][2][3][4][5][6][7][8][9] There are many methods used to form poly-Si on glass substrates, such as the crystallization of precursor amorphous Si (a-Si) films and the direct deposition of microcrystalline Si (µc-Si) films. Among these methods, we have focused on the crystallization of a-Si by flash lamp annealing (FLA), [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] millisecond-order annealing using pulse light from xenon lamps. [29][30][31] FLA can crystallize µmorder-thick a-Si films without serious thermal damage to glass substrates with poor thermal tolerance because of the thermal diffusion length being several tens of µm both for a-Si and glass.…”

Effect of antireflection coating on the crystallization of amorphous silicon films by flash lamp annealing

“…The thickness of the SiN x films was determined for application to antireflection films in solar cells. Since flash-lamp light has a similar spectrum to sunlight, 29) the SiN x films can also have an antireflection effect for flash-lamp pulse light. We measured the optical reflectance spectra of these a-Si structures to estimate the energies actually reaching a-Si films.…”

“…[10][11][12][13][14][15] We have thus far investigated FLA as a method of crystallizing micrometer-order-thick a-Si films. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] In particular, the utilization of electron-beam (EB)-evaporated a-Si films results in the formation of poly-Si films consisting of grains with a length of >10 µm owing to the occurrence of liquid-phase explosive crystallization during FLA. [26][27][28][29][30] Although this feature is favorable for the application of flash-lamp-crystallized (FLC) poly-Si to solar cells, EB-evaporated a-Si films need a higher fluence for crystallization than a-Si films prepared by other methods. [26][27][28][29][30] The fluence of a flash pulse may be reduced if the loss of a flash-lamp pulse light is minimized by suppressing optical reflection.…”

Photoluminescent Si/SiO2 Core/Shell Quantum Dots Prepared by High-Pressure Water Vapor Annealing for Solar Concentrators, Light-Emitting Devices, and Bioimaging

“…High-pressure water vapor annealing (HWA) is another passivation method that has been shown to both reduce defect densities and provide long-term stability in air for various types of silicon, including porous silicon, − polycrystalline silicon, − SiO x /Si films, − and silicon nanowires . Generally, the termination of defects is due to the formation of thermally relaxed, high-quality Si–O–Si bonds.…”