Low-Resistive Source/Drain Formation Using Nitrogen Plasma Treatment in Self-Aligned In-Ga-Zn-Sn-O Thin-Film Transistors

Abstract

In this work, we demonstrate the effectiveness of nitrogen plasma treatment on the formation of low-resistive source/drain (S/D) in self-aligned (SA) oxide thin-film transistors (TFTs) using a high-mobility oxide semiconductor (OS), In-Ga-Zn-Sn-O (IGZTO). The nitrogen plasma treatment was more effective at reducing the sheet resistance (Rsheet) of IGZTO films than the commonly used argon plasma treatment. Furthermore, Rsheet for nitrogen-plasma-treated IGZTO films remained low, even when the RF power and radiation time during the plasma treatment were increased when the minimum Rsheet was achieved. The same trends were also observed in OS films with different compositions, such as In-Ga-Zn-O and In-Sn-Zn-O. These results indicate that nitrogen plasma treatment is effective for achieving a reduction of Rsheet for various OS films with a wide process window regarding plasma processing parameters. The advantages could be attributed to the smaller sputtering effect on the OS films due to the lower mass of nitrogen ions than argon ions, which was verified by X-ray reflectivity and X-ray photoelectron spectroscopy analyses. For further validation, SA IGZTO TFTs with a channel length (L) of 3 to 100 m were fabricated with nitrogen or argon plasma treatment. The width-normalized parasitic SD resistance (RSDW) with the nitrogen plasma treatment was determined to be 11.3 •cm, which was ca. 40% lower than that with the argon plasma treatment. This improvement in RSDW resulted in higher mobility () in the nitrogen-plasma-treated SA IGZTO TFTs. A nitrogen-plasma-treated SA IGZTO TFT with L=10 m exhibited a high  of 27.2 cm 2 /Vs.

High Performance Amorphous In0.5Ga0.5O Thin‐Film Transistor Embedded with Nanocrystalline In2O3 Dots for Flexible Display Application

“…There are several material compositions for TAOS for active semiconductors using indium (In) and tin (Sn) as carrier enhancers and gallium (Ga), and zinc (Zn) as a stabilizer. Popular oxide semiconductors like InGaO, [18][19][20][21][22][23][24] InSnO, [25][26][27][28] InZnO, [29][30][31][32] ZnSnO, [33][34][35][36] InGaZnO, [1,2,[7][8][9][10] InGaSnO, [37][38][39][40] InZnSnO, [41][42][43] and InGaZnSnO [44][45][46][47] are widely studied. The choice of the materials in the periodic table suggests the atoms with spherically symmetric s-orbitals with a comparatively large ionic radius tends to show high mobility.…”

Impact of the Source/Drain Electrode Process on the Mobility-Threshold Trade-Off for InSnZnO Thin-Film Transistors

“…Amorphous oxide semiconductor thin-film transistors (AOS TFTs), which serve as the pixel switch/drive devices, have attracted extensive attention in the active-matrix flat panel display (FPD) area nowadays. 1,2 FPDs with high resolution and a high refresh rate demand great improvement in TFTs' μ FE, 3,4 which drives researchers to explore various novel AOS materials, such as In 2 O 3 :H, 5 InZnO, 6 InWZnO, 7 AlInSnZnO, 8 InGaZnSnO, 9 and InSnZnO. 10 However, it is generally a challenge to lower the intrinsic electron density (N e ) of AOS materials to achieve a small threshold voltage (V th ) of their TFTs and simultaneously maintain a high μ FE.…”

“…Amorphous oxide semiconductor thin-film transistors (AOS TFTs), which serve as the pixel switch/drive devices, have attracted extensive attention in the active-matrix flat panel display (FPD) area nowadays. , FPDs with high resolution and a high refresh rate demand great improvement in TFTs’ μ FE, , which drives researchers to explore various novel AOS materials, such as In 2 O 3 :H, InZnO, InWZnO, AlInSnZnO, InGaZnSnO, and InSnZnO …”

Hydrogen-Doping-Enabled Boosting of the Carrier Mobility and Stability in Amorphous IGZTO Transistors

“…For this reason, various strategies have been reported to improve the carrier mobility of oxide TFTs. A classic approach was based on process optimization, looking at variables like the cation composition, deposition conditions, postannealing, surface treatment, etc. − Recently, novel cation combinatorial compositions, − channel crystallization, − smart channel/device designs (such as heterojunctions), − superlattice structures, − and dual gate architectures have been researched to boost the carrier mobility of oxide TFTs. − Among the many promising channel materials, including indium gallium oxide (IGO), − indium zinc oxide (IZO), , indium gallium tin oxide (IGTO), indium zinc tin oxide (IZTO), etc., − the a -IGZTO system is regarded as a front-runner for achieving high mobility; this material is a strong alternative to a -IGZO. − The addition of Sn 4+ in a-IGZO substance facilitates a formation of more efficient percolation conduction pathway due to its identical electron configuration ([Kr]­4 d 10 5 s 0 ) to the In 3+ ion leading to a lower effective electron mass and thus enhanced carrier mobility in TFT. , Studies investigating the combinatorial approach in a -IGZTO, however, are limited even though promising performance has been reported for specific cation compositions. − In addition, hydrogen (H) is a representative ubiquitous impurity acting as either a shallow donor or complex defect depending on its concentration in a semiconducting oxide materials such as ZnO and a -IGZO. The physical role of H in the Sn-containing a -IGZTO system has not yet been studied in detail. , …”