Electro-optical device and electronic device

• US 7,642,559 B2
• Filed: 10/27/2005
• Issued: 01/05/2010
• Est. Priority Date: 06/04/1999
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Konuma, Toshimitsu, Yamamoto, Kunitaka, Koyama, Jun, Yamazaki, Shunpei
• Primary Examiner(s): Nguyen; Dao H
• Application Number:
  US11/258,933
• Publication Number:
  US 20060097256A1
• Time in Patent Office: 1,531 Days
• Field of Search: 257/79, 257/88, 313/500, 313/504
• US Class Current: 257/88
• CPC Class Codes: H01L 27/1218 with a particular composition or structure of the substrate
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H01L 29/78627 with a significant overlap between the lightly doped drain and the gate electrode, e.g. GOLDD
• CPC Class Codes: H01L 29/78645 with multiple gate
• 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
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H10K 2102/3026 Top emission
• CPC Class Codes: H10K 50/84 Passivation; Containers; Encapsulations
• CPC Class Codes: H10K 50/841 Self-supporting sealing arrangements
• CPC Class Codes: H10K 50/8426 Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 50/846 comprising getter material or desiccants
• CPC Class Codes: H10K 50/87 Arrangements for heating or cooling
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]
• CPC Class Codes: H10K 59/8722 : Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 59/874 : including getter material or desiccant
• CPC Class Codes: H10K 59/8794 : Arrangements for heating and cooling

Abstract

An object of the present invention is to provide an EL display device having a high operation performance and reliability.

The switching TFT 201 formed within a pixel has a multi-gate structure, which is a structure which imposes an importance on reduction of OFF current value. Further, the current control TFT 202 has a channel width wider than that of the switching TFT to make a structure appropriate for flowing electric current. Morever, the LDD region 33 of the current control TFT 202 is formed so as to overlap a portion of the gate electrode 35 to make a structure which imposes importance on prevention of hot carrier injection and reduction of OFF current value.

Claims

1. A light emitting device comprising:

a substrate;

a source wiring over the substrate;

a gate wiring intersecting with the source wiring, over the substrate;

a switching element, wherein a gate electrode of the switching element is electrically connected to the gate wiring and a first electrode of the switching element is electrically connected to the source wiring;

a current control element comprising at least two thin film transistors, and electrically connected to an electric current supply line; and

an electroluminescence element electrically connected to the current control element,

wherein the at least two thin film transistors and the electroluminescence element are connected in series, and

wherein gate electrodes of the at least two thin film transistors are electrically connected to a second electrode of the switching element.

2. A light emitting device according to claim 1, wherein an equation of W2/L2≧

5×

W1/L1 establishes under such conditions that a channel length of the switching element is L1, a channel width of the switching element is W1, a channel length of the current control element is L2, and a channel width of the current control element is W2.

3. A light emitting device according to claim 1, wherein the current control element comprises an LDD region and at least a part of the LDD region is overlapped with a gate electrode of the current control element.

4. A light emitting device according to claim 1, wherein the switching element comprises an LDD region and the LDD region is not overlapped with a gate electrode of the switching element.

5. A light emitting device according to claim 1, wherein the light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a personal computer, a mobile computer, a mobile telephone, an electronic book, and an image playback device using a recording medium.

6. A light emitting device according to claim 1, wherein the substrate comprises a material selected from the group consisting of glass, glass ceramic, quartz, silicon, ceramic, a metal, and a plastic.

7. A light emitting device according to claim 1, wherein each gate electrode of the switching element and the current control element has a single layer structure, a two-layer structure or a three-layer structure and includes at least one material selected from the group consisting of tantalum, titanium, molybdenum, tungsten, chromium, a tantalum nitride film, a tungsten nitride film, and a titanium nitride.

8. A light emitting device according to claim 1, wherein channel width of the current control element is lager than that of the switching element.

9. A light emitting device according to claim 1, wherein the light emitting device further comprises a capacitor over the substrate, and the capacitor is electrically connected to a gate electrode of the current control element and a source or a drain region of the switching element.

10. A light emitting device comprising:

a substrate;

a source wiring over the substrate;

a gate wiring intersecting with the source wiring, over the substrate;

a switching element, wherein a gate electrode of the switching element is electrically connected to the gate wiring and a first electrode of the switching element is electrically connected to the source wiring;

a current control element comprising at least two thin film transistors, and electrically connected to an electric current supply line; and

an electroluminescence element electrically connected to the current control element,

wherein the switching element comprises at least two thin film transistors connected in series,

wherein the at least two thin film transistors of the current control element and the electroluminescence element are connected in series, and

wherein gate electrodes of the at least two thin film transistors of the current control element are electrically connected to a second electrode of the switching element.

11. A light emitting device according to claim 10, wherein an equation of W2/L2≧

5×

W1/L1 establishes under such conditions that a channel length of the switching element is L1, a channel width of the switching element is W1, a channel length of the current control element is L2, and a channel width of the current control element is W2.

12. A light emitting device according to claim 10, wherein the current control element comprises an LDD region and at least a part of the LDD region is overlapped with a gate electrode of the current control element.

13. A light emitting device according to claim 10, wherein the switching element comprises an LDD region and the LDD region is not overlapped with a gate electrode of the switching element.

14. A light emitting device according to claim 10, wherein the light emitting device is incorporated into an electronic device selected from the group consisting of a video camera, a digital camera, a goggle type display, a car navigation system, a personal computer, a mobile computer, a mobile telephone, an electronic book, and an image playback device using a recording medium.

15. A light emitting device according to claim 10, wherein the substrate comprises a material selected from the group consisting of glass, glass ceramic, quartz, silicon, ceramic, a metal, and a plastic.

16. A light emitting device according to claim 10, wherein each gate electrode of the switching element and the current control element has a single layer structure, a two-layer structure or a three-layer structure and includes at least one material selected from the group consisting of tantalum, titanium, molybdenum, tungsten, chromium, a tantalum nitride film, a tungsten nitride film, and a titanium nitride.

17. A light emitting device according to claim 10, wherein channel width of the current control element is lager than that of the switching element.

18. A light emitting device according to claim 10, wherein the light emitting device further comprises a capacitor over the substrate, and the capacitor is electrically connected to a gate electrode of the current control element and a source or a drain region of the switching element.