TFT substrate manufacturing method and TFT substrate

Abstract

The present invention provides a TFT substrate manufacturing method and a TFT substrate. The TFT substrate manufacturing method of the present invention applies etching to source and drain contact zones of an active layer to have heights thereof lower than a height of a channel zone in the middle and configures the source and drain contact zones in a stepwise form so that charge carriers are affected by an electric field (Vds electric field) that is deviated in a direction away from a poly-silicon / gate insulation layer interface and the migration path thereof is caused to shift away from the poly-silicon / gate insulation layer interface thereby reducing the injection of high energy carriers into the gate insulation layer. Further, due to the formation of the steps in the drain contact zone, the peak intensity of the lateral electric field (Vds electric field) around the drain contact zone and the intensity of a longitudinal electric field (Vgs electric field) of the drain contact zone are both reduced, making a pinch-off point shifted toward an edge of the drain contact zone, reducing drifting of threshold voltage, and improving TFT reliability.

Description

BACKGROUND OF THE INVENTION1. Field of the Invention[0001]The present invention relates to the field of display technology, and in particular to a thin-film-transistor (TFT) substrate manufacturing method and a TFT substrate.2. The Related Arts[0002]Thin-film transistors (TFTs) are currently the primary driving device of liquid crystal displays (LCDs) and active matrix organic light-emitting diodes (AMOLEDs) and are directly related to the development of high performance flat panel display devices. The TFTs have various structures and there are various materials that are used to make the corresponding ones of the TFT structures. Low temperature poly-silicon (LTPS) material is one of the preferred materials. The regular arrangement of atoms of LTPS makes the mobility of charge carriers high. For the liquid crystal displays that are driven by voltage, due to the relatively high mobility that a poly-silicon thin-film transistor may have, driving liquid crystal molecules to rotate can b...

AI Technical Summary

Benefits of technology

The present invention provides a method for manufacturing a thin-film transistor (TFT) substrate by etching the source and drain contact zones of an active layer to have lower heights than the channel zone in the middle and to have a stepwise form. This reduces the peak intensity of the lateral electric field around the drain contact zone and the intensity of the longitudinal electric field, which improves the TFT's reliability and alleviates the hot carrier effect. The resulting TFT substrate also reduces drifting of the threshold voltage and improves its reliability.

Problems solved by technology

Hot carrier effect is an important mechanism of failure of metal oxide semiconductor (MOS) devices and with the size of the MOS devices being increasingly reduced, the hot carrier injection effect becomes increasingly severe.

The hot carriers may cause breaking of energy bonds at the silicon substrate and silicon oxide gate oxide interface and generate an interface state between the silicon substrate and the silicon oxide gate oxide interface, leading to deterioration of device performance, such as threshold voltage, transconductance and linear zone / saturation zone currents, and eventually resulting in failure of the MOS device.

The failure of the MOS device generally occurs at the drain terminal first.

Consequently, the hot carrier injection phenomenon is more severe at the drain terminal.

For LTPS TFTs, the charge carrier mobility is around 20-100 times of that of amorphous silicon (a-Si) TFTs and they are readily susceptible to hot carrier injection phenomenon.

The charge carriers, when moving in an intense electric field (>4E10̂4V / cm), may acquire an amount of energy from the electric field that is greater than an amount of energy lost by interaction with the crystal lattice so that the speed of the charge carriers may get higher and higher, eventually resulting in the occurrence of hot carrier injection.

These solutions, however, are complicated and are readily susceptible to doping deviation to result in failure.

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