Abstract
Channel shape dependency on device instability for amorphous indium–gallium–zinc oxide (a-IGZO) thin film transistors (TFTs) is investigated by using various channel shape devices along with systematic electrical characterization including DC I-V characeristics and bias temperature stress tests. a-IGZO TFTs with various channel shapes such as zigzag, circular, and U-type channels are implemented and their vertical and lateral electric field stress (E-field) effects are systematically tested and analyzed by using an experimental and modeling study. Source and drain (S/D) electrode asymmetry and vertical E-field effects on device instability are neglibible, whereas the lateral E-field effects significantly affect device instability, particularly for zigzag channel shape, compared to circular and U-type TFTs. Moreover, charge trapping time (τ) for zigzag-type a-IGZO TFTs is extracted as 3.8 × 104, which is at least three-times smaller than those of other channel-type a-IGZO TFTs, hinting that local E-field enhancement can critically affect the device reliability. The Technology Computer Aided Design (TCAD) simulation results reveal the locally enhanced E-field at both corner region in the channel in a quantitative mode and its correlation with hemisphere radius (ρ) values.
Highlights
The requirement on ultra-low power-based driving of thin film transistors has soared due to significant demand on IoT applications, in particular, mobile devices such as smart-phones, smart-watches, and others
Among a variety of candidates for active materials which could be immediately applied toward the backplanes for flat panel displays (FPDs), amorphous indium–gallium–zinc oxide (a-IGZO) thin film transistors (TFTs) have attracted tremendous attention because they have high current drivability for an ultra-high definition (UHD) flat panel display beyond the advanced a-Si:H TFT technology
Even though a-IGZO TFTs has been developed to such an extent that they can be applied to commercialized backplanes in flat panel displays such as active-matrix liquidcrystal display (AMLCD) and active-matrix organic light-emitting diode (AMOLED) [7,8], the reliability issues associated with electrical field, temperature, and light induced instabilities are still challenging issues for the mass production of reliable active-matrix flatpanel displays (AMFPDs) based on a-IGZO TFTs [9,10,11,12,13,14]
Summary
The requirement on ultra-low power-based driving of thin film transistors has soared due to significant demand on IoT applications, in particular, mobile devices such as smart-phones, smart-watches, and others. The newly conceived thin film transistors with high field effect mobility, along with the capability of mass production and full compatibility with the previously setup manufacturing lines, have been welcomed for fulfilling all requirements for the future electronic applications, including flat panel displays [1,2,3] In this perspective, among a variety of candidates for active materials which could be immediately applied toward the backplanes for flat panel displays (FPDs), amorphous indium–gallium–zinc oxide (a-IGZO) thin film transistors (TFTs) have attracted tremendous attention because they have high current drivability for an ultra-high definition (UHD) flat panel display beyond the advanced a-Si:H TFT technology. Among the various parameters that determine the reliability of a-IGZO TFTs, the geometrical shape of the channel for a-IGZO
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