Thin film transistor, display device including the same, and method of manufacturing the display device

• US 8,258,510 B2
• Filed: 02/20/2009
• Issued: 09/04/2012
• Est. Priority Date: 02/25/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Joo-Han, Shim, Seung-Hwan
• Primary Examiner(s): Valentine, Jami M
• Application Number:
  US12/390,020
• Publication Number:
  US 20090212288A1
• Time in Patent Office: 1,292 Days
• Field of Search: 257/57, 257/59, 438/158
• US Class Current: 257/57
• CPC Class Codes: H01L 27/1229 with different crystal properties within a device or between different devices
• CPC Class Codes: H01L 27/1251 comprising TFTs having a different architecture, e.g. top- and bottom gate TFTs
• CPC Class Codes: H01L 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask
• CPC Class Codes: H01L 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/66765 Lateral single gate single channel transistors with inverted structure, i.e. the channel layer is formed after the gate
• CPC Class Codes: H01L 29/7866 Non-monocrystalline silicon transistors
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621

Abstract

A display device including the thin film transistor, and a method of manufacturing the display device are provided. The thin film transistor comprising a first gate electrode, a second gate electrode formed on the first gate electrode, a first semiconductor formed on the first gate electrode and including a polycrystalline semiconductor, a second semiconductor formed on the second gate electrode and including an amorphous semiconductor.

Claims

1. A thin film transistor comprising:

a first gate electrode;

a second gate electrode formed on the first gate electrode;

a first semiconductor formed on the first gate electrode and including a polycrystalline semiconductor; and

a second semiconductor formed on the second gate electrode and including an amorphous semiconductor, the second gate electrode being disposed between the second semiconductor and the first gate electrode,

wherein the first gate electrode is formed of a transparent conductive layer, and the second gate electrode is formed of a metal layer.

2. The thin film transistor of claim 1, wherein the first semiconductor and the second semiconductor are formed on the same layer.

3. The thin film transistor of claim 1, wherein a width of the second semiconductor is the substantially same as a width of the second gate electrode.

4. The thin film transistor of claim 1, wherein a width of the second gate electrode is smaller than a width of the first gate electrode and the second gate electrode does not overlap the first semiconductor.

5. The thin film transistor of claim 1, wherein a portion of the first semiconductor overlaps a source electrode or a drain electrode.

6. The thin film transistor of claim 5, wherein a distance between the second semiconductor and the source electrode or a distance between the second semiconductor and the drain electrode is between 1 and 40 μ

m.

16. The thin film transistor of claim 1, wherein the second semiconductor is disposed between a first portion of the first semiconductor and a second portion of the first semiconductor.

7. A display device comprising:

a first thin film transistor including a first circuit gate electrode, a second circuit gate electrode formed on the first circuit gate electrode, a first circuit semiconductor, a second circuit semiconductor, a circuit source electrode, and a circuit drain electrode; and

a second thin film transistor including a first pixel gate electrode, a second pixel gate electrode formed on the first pixel gate electrode, a pixel semiconductor, a pixel source electrode, and a pixel drain electrode,

wherein the first circuit semiconductor includes a polycrystalline semiconductor, and the second circuit semiconductor and the pixel semiconductor includes an amorphous semiconductor.

8. The display device of claim 7, wherein the first circuit semiconductor, the second circuit semiconductor, and the pixel semiconductor are formed on the same layer.

9. The display device of claim 7, wherein a width of the second circuit semiconductor is the substantially same as a width of the second circuit gate electrode.

10. The display device of claim 7, wherein the first circuit gate electrode and the first pixel gate electrode are formed of a transparent conductive layer, and the second circuit gate electrode and the second pixel gate electrode are formed of a metal layer.

11. The display device of claim 7, further comprising a storage upper electrode and a storage lower electrode.

12. The display device of claim 11, wherein at least one of the storage upper electrode and the storage lower electrode is formed of a transparent conductive layer.

13. The display device of claim 7, wherein the first thin film transistor is positioned in at least one of a gate driver and a data driver, and the second thin film transistor is positioned in a pixel unit.

14. The display device of claim 7, wherein a portion of the first circuit semiconductor overlaps the circuit source electrode or the circuit drain electrode.

15. The display device of claim 14, wherein a distance between the second circuit semiconductor and the circuit source electrode or a distance between the second circuit semiconductor and the circuit drain electrode is between 1 and 40 μ

m.

17. A thin film transistor comprising:

a first gate electrode including a first conductive material;

a second gate electrode overlapping the first gate electrode and including a second conductive material that is different from the first conductive material;

a first semiconductor disposed on the first gate electrode and including a first semiconductor material; and

a second semiconductor disposed on the second gate electrode and including a second semiconductor material that is different from the first semiconductor material,

wherein the second gate electrode and the second semiconductor are completely overlapped by the first gate electrode.

18. The thin film transistor of claim 17, wherein the second gate electrode contacts the first gate electrode.

19. The thin film transistor of claim 17, wherein the second gate electrode is disposed between the second semiconductor and the first gate electrode.