Enhancing Hot-Carrier Reliability of Dual-Gate Low-Temperature Polysilicon TFTs by Increasing Lightly Doped Drain Length

Suppression of Hot‐Carrier Effects Facilitated by the Multimodal Thin‐Film Transistor Architecture

“…Recently, there has been renewed interest in mature thin film silicon technologies for display backplanes and sensing applications, [ 16–19 ] however the presence of kink effect [ 13–15 ] remains a challenge for TFT design. [ 16 ] LTPS remains favoured for its high mobility and hence, on‐current, allowing for increased TFT switching speed.…”

“…Recently, there has been renewed interest in mature thin film silicon technologies for display backplanes and sensing applications, [ 16–19 ] however the presence of kink effect [ 13–15 ] remains a challenge for TFT design. [ 16 ] LTPS remains favoured for its high mobility and hence, on‐current, allowing for increased TFT switching speed. [ 16,19,20 ] This meets the requirements for increasingly higher resolution displays, [ 16 ] and the combined benefits of LTPO with low‐leakage n‐type IGZO TFTs deliver more cost‐effective large area CMOS applications.…”

“…[ 16 ] LTPS remains favoured for its high mobility and hence, on‐current, allowing for increased TFT switching speed. [ 16,19,20 ] This meets the requirements for increasingly higher resolution displays, [ 16 ] and the combined benefits of LTPO with low‐leakage n‐type IGZO TFTs deliver more cost‐effective large area CMOS applications. [ 21–23 ] This will likely continue until stable enhancement mode p‐type oxide TFTs with high mobility can be reliably manufactured.…”

“…This, in turn, further aggravates impact ionization. [ 13,15,16 ] These effects are observed and most pronounced where hot carriers can be generated. While kink effect is common in polysilicon TFTs, there have been reports of hot‐carrier effects in lower mobility materials, such as amorphous silicon (a‐Si), [ 32 ] nanocrystalline silicon (nc‐Si), [ 33 ] IGZO, [ 4,34 ] and are likely to manifest in future high mobility materials [ 7 ] as technologies continue to advance.…”

“…Numerous structural improvements have been proposed to supress kink effect, including: field plates [ 35,36 ] ; lightly doped drain (LDD) [ 37 ] ; gate overlapped LDD (GOLDD) [ 38,39 ] ; asymmetric fingered polysilicon [ 31 ] ; and extended LDD. [ 16 ] Aside from such optimizations, contact‐controlled architectures, such as the source‐gated transistor [ 40–42 ] (SGT, Figure 1b,c, Supporting Information), have the ability to supress the kink effect when designed correctly. [ 36,43 ] By implementing a deliberate energy barrier at the source contact to enable source pinch‐off, charge injection can be controlled entirely in the source region.…”