Performance of four-terminal low-temperature polycrystalline-silicon thin-film transistors and their application in CMOS inverters on glass substrates

Abstract

High-performance and low-power-operation CMOS circuits comprising low-temperature (LT) polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) are indispensable for integrated circuits on glass substrate. The fabrication of high-quality poly-Si films with large grains can enhance the on-current of TFTs on glass substrates owing to low carrier scattering. In this study, we used continuous-wave laser lateral crystallization (CLC) to fabricate high-quality thin poly-Si films on a glass substrate. To achieve low-power operation, precise threshold voltage (Vth) control is most important, and four-terminal (4T) TFT is one attractive approach to achieve it. We fabricated a CMOS inverter comprising 4T CLC LT poly-Si TFTs on a glass substrate and confirmed nearly identical controllability of Vth, subthreshold swing, and mobility of n- and p-channel TFTs in CMOS inverter as compared with TFTs fabricated on different glass substrates with their own processes. By using the high controllability of 4T CLC LT poly-Si TFTs, we successfully operated the CMOS inverter with Vdd = 1.0 V.

Four-terminal polycrystalline-silicon vertical thin-film transistors on glass substrates

“…[19][20][21] Among multigate structures, our group has investigated planar DG and planar four-terminal (4 T) polycrystalline silicon (poly-Si) TFTs on glass substrates. [22][23][24][25][26][27] 4 T TFTs have the advantage that the top gate (TG) and bottom gate (BG) are separated and operate independently of each other. This enables the control of the threshold voltage (V th ) by using one gate for the switching operation and another as a control gate.…”

“…This enables the control of the threshold voltage (V th ) by using one gate for the switching operation and another as a control gate. [24][25][26][27] The advantage of V th control in an n-channel 4 T drive is as follows, in the case where the TG is the drive gate and the BG is the control gate. When a positive voltage is applied to the BG, the threshold voltage shifts in the negative direction.…”

“…It was fabricated via continuous-wave laser lateral crystallization (CLC). [24][25][26][27] The other method was the Ni-MIC used in this experiment. The cross-sectional structures of the planar CLC 4 T and Ni-MIC 4 T poly-Si TFTs are shown in Figs.…”

Poly-Si Thin-Film Transistors with N-Type Line-Array Doping Channels Fabricated by Nanoimprint Lithography

“…Polycrystalline-silicon thin-film transistors (poly-Si TFTs) are potential devices for various applications, including active-matrix organic light-emitting diodes (AMOLEDs), active-matrix liquid crystal displays (AMLCDs), [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] nonvolatile memories, [17][18][19] sensors, 20 and three-dimensional (3D) integrated circuits (ICs). [21][22][23][24][25] Poly-Si TFTs with the modified channels, such as the nanowire (NW), [9][10][11][12] multigate, 24 finlike, 15,16 and bridge-grain (BG) TFTs, 13,14 have been proposed to improve electrical performance. In these methods, dense and/or periodic nanoscale patterns must be introduced on the poly-Si TFTs channels.…”

“…The related concept is proposed and studied for the p-type channel poly-Si TFTs. 13,14 However, for the 3D IC applications, [21][22][23][24][25] high-performance CMOS circuits with n-and p-type channel poly-Si TFTs are required. Moreover, the n-channel poly-Si TFT circuit that can reduce the supply voltage of drivers, is an alternative candidate for the low-power and high performance pixel circuits of AMOLED displays.…”