[low-temperature polysilicon thin film transistor and fabrication method thereof]

Abstract

An LTPS-TFT structure comprises a gate, a gate dielectric layer, a patterned silicon layer, a patterned insulating layer, an ohmic contact layer and a source / drain layer. The gate and the gate dielectric layer are disposed on the substrate. The patterned silicon layer and the patterned insulating layer are disposed on the gate dielectric layer over the gate. The patterned silicon layer comprises a polysilicon channel region and an amorphous silicon hot carrier restrain region. The ohmic contact layer is disposed on a portion of the patterned silicon layer other than the polysilicon channel region and the amorphous silicon hot carrier restrain region and a portion of the patterned insulating layer over the amorphous silicon hot carrier restrain region. The source / drain layer is disposed on the ohmic contact layer and the gate dielectric layer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the priority benefit of Taiwan application serial no. 93109432, filed Apr. 6, 2004. BACKGROUND OF INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a transistor and fabrication methods thereof, and more particularly to a low-temperature polysilicon thin film transistor (LTPS-TFT) and fabrication methods thereof. [0004] 2. Description of the Related Art [0005] Generally, devices use switches to control the operation thereof. For example, active matrix displays use thin film transistors (TFT) as driving components. According to the material of a channel layer of the TFT, the types of the TFT include amorphous silicon TFT and polysilicon TFT. Based on the position of the channel layer corresponding to that of the gate, the types of TFT also include top-gate TFT and bottom-gate TFT. The bottom-gate TFT has an insulating / amorphous silicon layer interface which is capable of preventing ...

AI Technical Summary

Benefits of technology

[0012] Accordingly, the present invention is directed to a low-temperature polysilicon thin film transistor (LTPS-TFT) to improve device performance by forming an amorphous silicon hot carrier restrain region.

[0013] The present invention is also directed to a method of fabricating a LTPS-TFT. The method is capable of reducing manufacturing costs as well as improving device performance by forming an amorphous silicon hot carrier restrain region.

[0014] The present invention discloses a LTPS-TFT. The LTPS-TFT comprises a gate, a dielectric gate, a patterned silicon layer, a patterned insulating layer, an ohmic contact layer, and a source / drain layer which are sequentially formed on a substrate. The patterned silicon layer is disposed on the gate dielectric layer and directly over the gate. The patterned silicon layer comprises a polysilicon channel region and an amorphous silicon hot carrier restrain region adjacent thereto. Also, the patterned silicon layer further comprises an edge portion (i.e. a portion of the patterned silicon layer other than the polysilicon channel region and the hot carrier restrain region) underneath the ohmic contact layer. The amorphous silicon hot carrier restrain region is capable of reducing hot carrier effect, preventing degradation of the transistor during the operation of the transistor. The patterned insulating layer covers the patterned silicon layer. The ohmic contact layer is disposed on the edge portion of the patterned silicon layer and a portion of the insulating layer over the amorphous silicon hot carrier restrain region to expose a portion of the patterned insulating layer and contacting the amorphous silicon hot carrier restrain region. The source / drain layer is disposed on the ohmic contact layer, or even on a portion of the substrate.

[0025] Compared with the prior art method of fabricating LTPS-TFT, the fabrication method of the present invention saves a lightly-doped drain (LDD) process and a LDD mask. The manufacturing cost, therefore, is reduced. Moreover, the LTPS-TFT of the present invention has the advantages of high driving current of polysilicon thin film transistors and low leakage current of amorphous thin film transistors.

Problems solved by technology

The prior art method of fabricating the polysilicon TFT requires a high temperature process up to 1000° C. Due to the high temperature requirement, the choice of the substrate material that can be applied to the process is limited.

The polysilicon TFT is easy to induce hot carrier effect at the drain region, causing device degradation.

In addition, the LDD process is so complicated that the method of fabricating the prior art LTPS-TFT has high manufacturing cost.

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