TFT with body contacts
View Patent ↗A thin-film transistor (TFT) with body contacts is disclosed. It is used in polysilicon TFT LCD's. A body contact region for separating the gate electrode, a source region, and a drain region is made in the TFT. Through the dopants in the body contact region and different impurities in the source region and the drain region, a body-trigger bias is imposed on the body of the TFT. This method reduces the threshold voltage of the TFT driving circuit, thereby increasing the driving current.
1. A thin-film transistor (TFT) comprising:
an insulating body;
a polysilicon layer;
an insulating layer; and
a gate electrode;
and wherein the polysilicon layer containing a channel region, a source region, and a drain region, the source region and the drain region are doped with an appropriate first impurity and connected to the channel region, the channel region has a body contact region formed between the source region and the drain region and connecting the insulating body and the insulating layer, the surface of the body contact region has a contact layer penetrating through the insulating layer, the contact layer is not in contact with the gate electrode, and the body contact region is doped with a second impurity different from that doped in the source region and the drain region to provide a body-trigger bias on the insulating body.
2. The TFT of claim 1 , wherein when the first impurity is a group-V recipient the second impurity is a group-III donor.
3. The TFT of claim 1 , wherein when the first impurity is a group-III donor the second impurity is a group-V recipient.
4. The TFT of claim 1 , wherein the border of the gate electrode is formed with a groove extending over the channel region and an excavated region is established with the body contact region and the contact layer.
5. The TFT of claim 1 , wherein the gate electrode is made of a metal selected from Cr and Al.
6. A thin-film transistor (TFT) comprising:
an insulating body;
a polysilicon layer;
insulating layer; and a gate electrode;
and wherein the polysilicon layer containing a channel region, a source region, and a drain region, the source region and the drain region are doped with an appropriate first impurity and connected to the channel region, the channel region has a body contact region connecting the insulating body and the insulating layer, the surface of the body contact region has a contact layer penetrating through the insulating layer, the body contact region and the contact layer thereon are formed inside a region surrounded by the gate electrode, the contact layer is not in contact with the gate electrode, and the body contact region is doped with a second impurity different from that doped in the source region and the drain region to provide a body-trigger bias on the insulating body.
7. The TFT of claim 6 , wherein when the first impurity is a group-V recipient the second impurity is a group-III donor.
8. The TFT of claim 6 , wherein when the first impurity is a group-III donor the second impurity is a group-V recipient.
9. The TFT of claim 6 , wherein the border of the gate electrode is formed with a groove extending over the channel region and an excavated region is established with the body contact region and the contact layer.
10. The TFT of claim 6 , wherein the gate electrode is made of a metal selected from Cr and Al.
11. The TFT of claim 1 , wherein the body contact region and the contact layer thereon are formed inside a region surrounded by the gate electrode.
12. The TFT of claim 1 , wherein the body contact region and the contact layer thereon are formed in a region adjacent the gate electrode.
13. The TFT of claim 12 , wherein the body contact region and the contact layer thereon are formed in regions adjacent two sides of the gate electrode.
14. The TFT of claim 12 , wherein the body contact region and the contact layer thereon are formed within a excavated region defined at one side of the gate electrode.
15. A method of increasing driving current in a thin-film transistor (TFT), comprising:
forming a TFT of claim 1 ; and
providing a body-trigger bias on the insulating body.
16. The method of claim 15 , wherein the body-trigger bias is provided via the contact layer.
17. The method of claim 15 , wherein the body contact region and the contact layer thereon are formed inside a region surrounded by the gate electrode.
18. The method of claim 15 wherein the body contact region and the contact layer thereon are formed in a region adjacent the gate electrode.
19. The method of claim 18 , wherein the body contact region and the contact layer thereon are formed in regions adjacent two sides of the gate electrode.
20. The method of claim 18 , wherein the body contact region and the contact layer thereon are formed within a excavated region defined at one side of the gate electrode.