P-7: High Performance LTPS Thin-film Transistors using Low Cost Polycrystalline Silicon by Blue Laser Annealing

Abstract

Crystallization of amorphous silicon (a-Si) to polycrystalline silicon (p-Si) by a continuous-wave blue laser diode of wavelength 445 nm is investigated for high throughput thin-film transistor applications (TFT). As the laser scan speed is changed at constant laser power, laser scanned p-Si films show three kinds of grain shape that can be distinguished according to grain growth mechanism: (1) solid phase crystallization (SPC), (2) partial melting growth (PMG), and (3) full melting growth (FMG). These three growth mechanisms are as a result of different laser irradiation time to a-Si and relative absorbed laser energy difference, therefore, they achieve different grain size and crystallinity. By using this blue laser annealing (BLA) system, we can obtain the high performance and low cost low temperature polycrystalline silicon (LTPS) TFTs with large grain size. Author KeywordsPolycrystalline silicon (p-Si); crystallization; thin-film transistor (TFT); blue laser annealing (BLA); super lateral growth (SLG); low temperature polycrystalline silicon (LTPS).

Extremely foldable LTPS TFT backplane using blue laser annealing for low‐cost manufacturing of rollable and foldable AMOLED display

“…First, a solution-processed carbon-nanotube (CNT): graphene-oxide (GO) mixed layer is spray-coated on carrier glass and cured at 290 C. Transparency of the fabricated CNT:GO backbone film is around 90% as shown in Figure 1B. Then, PI solution is spin-coated to a thickness of $10 μm, followed by curing at $470 C for 2 h. The CNT:GO layer reduces the adhesion of the PI on glass and thus can be used as a buffer for mechanical detachment, [13][14][15][16] which is shown in Figure 1A (iii). After the formation of PI substrate, a gas barrier consisting of SiO 2 /SiN x multilayer is deposited through plasma-enhanced chemical vapor deposition (PECVD).…”

“…The detailed fabrication process of the p-channel LTPS TFTs on PI substrate appears elsewhere. 11,13 A SiO 2 buffer layer is deposited on PI film, and then a-Si was formed by PECVD at the substrate temperature of 360 C with its thickness of 50 nm for ELA and 100 nm for BLA, respectively. After the dehydrogenation at 450 C, the a-Si layers are crystallized by BLA or ELA.…”

“…We fabricated coplanar LTPS TFTs on PI substrate as shown in Figure 3A. The detailed fabrication process of the p‐channel LTPS TFTs on PI substrate appears elsewhere 11,13 . A SiO 2 buffer layer is deposited on PI film, and then a‐Si was formed by PECVD at the substrate temperature of 360°C with its thickness of 50 nm for ELA and 100 nm for BLA, respectively.…”

Remarkable Improvement in Foldability of Poly‐Si Thin‐Film Transistor on Polyimide Substrate Using Blue Laser Crystallization of Amorphous Si and Comparison with Conventional Poly‐Si Thin‐Film Transistor Used for Foldable Displays

“…The crystallization of amorphous silicon (a‐Si) on glass substrate can be possible by using solid phase crystallization (SPC), metal‐induced crystallization (MIC), ELA, and continuous wave (CW) laser annealing. Because of no intradefects in the grains, the ELA poly‐Si is widely used for the manufacturing of AMOLED and active‐matrix liquid crystal display (AMLCD) .…”

“…Another important merit of BLA poly-Si is no protrusion in the TFT channel. [60][61][62][63] The grain boundary defects at the protrusion can degrade the TFT performance, [69][70][71][72][73] and also affect the bias stability and mechanical bending stability. [74,75] The flexibility of the ELA TFTs on PI substrates can be a big issue for the foldable and rollable AMOLED displays.…”