Fabrication of Novel Three-Step Drift-Doped Low-Temperature Polycrystalline Silicon Lateral Double-Diffusion Metal–Oxide–Semiconductor Using Excimer Laser Crystallization

Abstract

Low-temperature polycrystalline silicon (poly-Si) thin-film transistor lateral double-diffusion metal-oxide-semiconductor field-effect transistors (LTPS TFT LDMOSFETs) and lateral insulated-gate bipolar transistors (LIGBTs) were fabricated by combining a thin-film transistor with a power structure, three-step drift doping, and excimer laser annealing. The maximum breakdown voltage of the three-step drift-doped LTPS-LDMOS after excimer laser annealing is 286 V with a 35 mm drift region length (L drift). The specific on-resistance is low (approximately 9 cm 2) and the ON/OFF current ratio is about 1:28 Â 10 6 with L drift ¼ 15 mm. The subthreshold swing (SS) is about 1 V/ decade. Comparing the three-step drift-doped LDMOS with the three-step drift-doped LIGBT under the same processing conditions clearly indicates that the breakdown voltage and current capacity of LIGBT exceeds those of LDMOS.

Design and Analysis of Power Low-Temperature Polysilicon Lateral Double-Diffusion Metal Oxide Semiconductor Field Effect Transistors with Shielding-Trench Structure

“…However, the uniformity of the empirical LTPS-LDMOSFET results showed large distributions of breakdown voltage and specific on-resistance, showing different grain sizes (different mobilities) between devices. 25) In our simulation, the corresponding mobility of the poly-Si of these devices (Ref. 25) could range from 150 to 40 cm 2 V À1 s À1 .…”

“…Regarding the shielding-trench structure, increasing the drift-region length could increase breakdown voltage to about 7 V/m, which is larger than that of the LTPS-LDMOSFET with 4.8 V/m. 25) STO-LDMOSFETs also show a high breakdown voltage of 340 V (L drift ¼ 25 m) compared with that of the LTPS HVLDMOS at 300 V (L drift ¼ 25 m). 2) The STO structure was used to obtain SLG degree poly-Si and it largely reduced the dependence of laser conditions in its manufacture, improving the overall stability of the devices.…”

“…However, the low temperatureprocess limit and the degradation of excimer lasers result in a poor uniformity of thin-film crystallization and a high turn-on resistance of devices. 25) Therefore, in this study, a shielding trench oxide structure was adopted to limit the impact of these difficulties. The trench oxide effectively increases the device's breakdown voltage and improves the grain size of poly-Si to decrease the turn-on resistance.…”