Effective annealing and crystallization of si film for advanced TFT system
Abstract The effect of the crystallization and activated annealing of Si films using an excimer laser and the new CW blue laser are described and compared with furnace annealing for application in advanced TFTs and for future applications. Pulsed excimer laser annealing (ELA) is currently being used extensively as a low‐temperature poly‐silicon (LTPS) process on glass substrates as its efficiency is high in the ultra‐violet (UV) region for thin Si films with thickness of 40–60 nm. ELA enables extremely low resistivity relating to high crystallinity for both the n‐ and p‐type Si films. On the other hand, CW blue laser diode annealing (BLDA) enables the smooth Si surface to have arbitral crystal grains from micro‐grains to an anisotropic huge grain structure only by controlling its power density. Both annealing techniques are expected to be applied in the future advanced TFT systems.
High average power quasi-CW single-mode green and UV fiber lasers
Kilowatt-level narrow-linewidth SM ytterbium fiber laser operating in high-repetition-rate QCW regime was used to obtain 700 W average power at 532 nm with single-mode beam quality and wall-plug efficiency of over 23 %. To the best of our knowledge, this is ~60 % higher power than previously reported for single-mode green lasers based on other platforms, and also is ~30 % increase comparing to the previous result obtained by our group on the base of similar fiber laser platform. We have also experimentally proved that the same type of fiber laser can be used for generating of world-record levels of power at other wavelengths of visible and UV spectral ranges by employing cascaded non-linear frequency conversion. Thus, utilizing frequency tripling in 2 LBO crystals, we achieved over 160 W average power of nearly single-mode UV light at 355 nm with THG efficiency of more than 25 %. As far as we know, this is the highest output power ever reported for UV laser with nearly diffraction limited beam quality. We also conducted some preliminary experiments to demonstrate suitability of our approach for generating longer wavelengths of the visible spectrum. By pre-shifting fundamental emission wavelength in fiber Raman converter, followed by frequency doubling in NCPM LBO, we obtained average powers of 36 W at 589 nm and 27 W at 615 nm. These proof-of-concept experiments were performed with low-power pump laser and were not fully optimized with respect to frequency conversion. Our analysis indicates that employing kW-level QCW ytterbium laser with optimized SRS and SHG converters we can achieve hundreds of Watts of average power in red and orange color with single-mode beam quality.
Enhancement of lateral solid phase epitaxial growth in evaporated amorphous Si films by phosphorus implantation
Characteristics of lateral solid phase epitaxial (L‐SPE) growth and random crystallization in amorphous Si films, which were deposited on (100) Si substrates with SiO2 patterns at elevated substrate temperature and amorphized by subsequent Si+ or P+ ion implantation, were investigated. It was found from Nomarski optical microscopy that phosphorus doping is effective to enhance the L‐SPE growth rate and to reduce the random nucleation rate. Owing to these two effects, the maximum L‐SPE length of about 24 μm was obtained in the film doped with 3×1020 P atoms/cm3 after 8‐h annealing at 600 °C, which was about six times longer than that in the undoped films.