Excimer laser crystallization and doping of silicon films on plastic substrates

Abstract

We report the pulsed laser recrystallization and doping of thin film amorphous silicon deposited on oxide-coated polyester substrates. Although our heat-flow simulation of the laser recrystallization process indicates that the plastic is briefly subjected to temperatures above its softening point, we see no evidence of damage to the plastic or film delamination from the substrate. Film grain size is found to vary up to ∼0.1 μm. Electrical characteristics obtained from simple strip line resistors and thin film transistors indicate that device-quality silicon films have been produced on an inexpensive flexible plastic substrate.

Multiple pulse thermal damage thresholds of materials for x-ray free electron laser optics investigated with an ultraviolet laser

“…16 A fraction of the incoming photon beam is absorbed through photoionization within 10 nm of the surface. Photoelectrons are ejected primarily in the direction of the electric field vector of the incoming radiation, 17 which is nearly normal to the mirror surface at LCLS. The inward directed electrons and electrons reflected by space-charge effects back to the mirror deposit their energy within 1000 nm of the mirror surface through electron impact ionization.…”

“…To compare the XFEL and UV cases, we have calculated temperature profiles using a Monte Carlo technique for the XFEL case 20 and a one-dimensional heat-flow model for the UV case. 17 We consider two limiting cases for the LCLS optics. For the HOMS irradiated at 8267 eV, the depth at which the temperature rise drops to 1 / e of the surface value of 37 K is 0.40 m, while for the SOMS at 827 eV, the surface temperature rise is 34 K and the depth is 0.025 m. We compare these values to the heat penetration depths for UV irradiation at the end of the laser pulse ͑when the temperature is highest͒.…”

“…The beam was shaped into a 4 ϫ 4 mm 2 square focal spot, and the exposure rate was 50 Hz. 17 We measured the reflectivity of the irradiated spot using a 650 nm laser and a photodiode with a time resolution of better than 1 ns. This allowed us to detect the onset of melting in the Si samples because the reflectivity of molten silicon is substantially higher than for crystalline Si.…”

Organic semiconductors for device applications: current trends and future prospects

“…Laser annealing produces large-grain poly-Si and is compatible with lowtemperature substrates, despite raising the temperature above Si melting point. For instance, 30 ns excimer laser pulse take < 1 ms [742] for heating/cooling cycle for each pulse. Thus, having an appropriate barrier layer beneath the Si film, the molten Si cools back to room temperature before enough heat diffuses into the substrate causing damage.…”

Deposited low temperature silicon GHz modulator

“…Due to the very short duration and confinement of heat close to the surface, underlying device structures receive a minimal increase in the total thermal budget, while the a-Si film heats up enough to melt and re-solidify, crystallizing into polysilicon. In fact, the thermal impact is so small that ELA has been successfully performed even on a plastic substrate with 120 ˚C thermal processing limit 17 .…”