Low‐Temperature Polysilicon Oxide Thin‐Film Transistors with Coplanar Structure Using Six Photomask Steps Demonstrating High Inverter Gain of 264 V V⁻¹

Abstract

The low-temperature polysilicon oxide (LTPO) complementary metal-oxidesemiconductor (CMOS) thin-film transistors (TFTs) is fabricated by p-type lowtemperature polysilicon (LTPS) TFT and n-type amorphous indium-gallium-zinc oxide (a-IGZO) TFT using coplanar structure. A double-stack SiO 2 layer deposited by high temperature first and then low-temperature process is used as a gate insulator for LTPS TFT, leading to reduce the number of photomask steps. The p-channel LTPS TFT of the fabricated LTPO circuits exhibits the field-effect mobility (μ FE) and threshold voltage (V TH) of 89.9 cm 2 (V s) À1 and À5.5 V, respectively. However, the a-IGZO TFT exhibits the μ FE of 22.5 cm 2 (V s) À1 and V TH of À1.3 V. Both the LTPS TFT and a-IGZO TFT show excellent bias stability (ΔV TH of <0.1 V) and zero hysteresis voltage, which reveals the excellent interface between gate insulator and semiconductor. The LTPO CMOS inverter exhibits a gain of 264.5 V V À1 and a high noise margin of 4.29 V, and a low noise margin of 3.69 V at V DD of 8 V. Therefore, the LTPO TFT technology developed in this work can be a promising candidate for low cost, large-area manufacturing of display, and TFT electronics.

25‐2: LTPO TFT Technology for Level Shifter Integrated Gate Driver in UHD 4K Displays

“…Details of the coplanar single gate and dual gate TFT process are studied in our previous reports [8]- [9]. More details of the 6-mask LTPO fabrication process described in [2], [4]- [5]. The electrical properties of the TFTs were measured at room temperature using the Agilent 4156C semiconductor analyzer.…”

“…By integrating these two TFT technologies it is possible to crisscross the disadvantages and take the advantages from both sides. The performance enhancement with the LTPO TFT technology has been reported with various circuits like pixel circuits [1], level shifter [2], inverter [4]- [5], operational amplifier [6], and TFTs array [7]. However, gate drive circuits with this technology not yet realized to the best of our knowledge.…”

39‐3: Distinguished Student Paper: In‐Pixel Temperature Sensor for High‐Luminance Active‐Matrix Micro‐LED Display using LTPO TFTs

“…LTPO TFTs with p-type BLA LTPS TFTs using coplanar structure and n-type a-IGZO TFTs using dual-gate back channel etch (BCE) structure have been fabricated with the detailed process described in [8][9][10]. Fig.…”

7‐4: High Mobility Hydrogenated Polycrystalline In‐Ga‐O (IGO:H) Thin‐Film Transistors formed by Solid Phase Crystallization

“…Furthermore, in recently, hybrid TFTs technology, named as low-temperature processed poly-Si and OS (LTPO) TFTs, is used for mobile displays in order to satisfy the requirements of high-mobility LTPS TFTs for peripheral drivers and the OS TFTs with extremely low-off current for pixel drivers. 7) However, the LTPO process is complicated and required additional mask steps. Therefore, the development of high-mobility OS TFTs is of great importance to achieve simple and cost-effective TFT array for future displays.…”