Development of line-shaped optical system for green laser annealing used in the manufacture of low-temperature poly-Si thin-film transistors

Abstract

We have developed a new optical system that transforms the circle profile beam generated with near-Gaussian intensity distribution by a pulse green laser (YAG2omega laser; second harmonics of a Q-switched Nd:YAG laser) into a line-profile beam. For homogenization in the longitudinal direction, we employed a waveguide plate-type homogenizer. We successfully reduced interference fringes. In the width direction, the laser beam was focused up to the limited M2 value. This transformed beam has a uniform distribution to within 5% in the longitudinal direction, and it is approximately 100 mm long and 40 microm wide.

Laser Beam Shaping Using Hollow Optical Fiber and Its Application in Laser Induced Thermal Printing

“…In such devices, the beam shaping optics is usually placed between the beam expander and the Galvanomirror. Various optics such as lens set [6], micro lens array [7], diffractive optical elements [8], random phase plate [9], light guiding plate [10], and acousto-optic modulator (AOM) [4] have been used for beam shaping. The lens set method is frequently employed in commercially developed marking systems.…”

“…When the ring-shaped beam is focused and scanned on the donor film surface, the energy distribution becomes similar to the result obtained when the dithered beam by an AOM was used. Beam shaping optics using light guiding was also employed in the display industry for the laser annealing of polysilicon [10]. Compared to the other beam shaping methods, the device using light guiding is less affected by the spatial fluctuation of the input beam.…”

Electronic devices fabricated at CMOS backend-compatible temperatures

“…This ensures a larger penetration depth of ≈ 49 nm for a-Si and near 200 nm for the crystallized poly-Si film [103], leading to a more homogeneous melting of the silicon layer [102] [ 104,105]. This widens the process window for the re-crystallization in terms of the laser power and pulse duration [104][105][106]. Additionally, the use of the green laser reduces the maintenance expenses and assures a higher safety processing conditions [107].…”