Electronic device and electronic apparatus

• US 6,512,504 B1
• Filed: 04/18/2000
• Issued: 01/28/2003
• Est. Priority Date: 04/27/1999
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Fukunaga, Takeshi, Yamauchi, Yukio
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): Kovalick, Vincent E.
• Application Number:
  US09/551,866
• Time in Patent Office: 1,015 Days
• Field of Search: 345/87, 345/76, 345/77, 345/92, 315/169.1, 315/169.3, 349/42, 349/43, 349/46
• US Class Current: 345/87
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1251 comprising TFTs having a different architecture, e.g. top- and bottom gate TFTs
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 27/13 combined with thin-film or thick-film passive components
• CPC Class Codes: H01L 29/66757 Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate
• 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: H10K 2102/3026 Top emission
• 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 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]

Abstract

An EL display having high operating performance and reliability is provided. LDD regions 15a through 15d of a switching TFT 201 formed in a pixel are formed such that they do not overlap gate electrodes 19a and 19b to provide a structure which is primarily intended for the reduction of an off-current. An LDD region 22 of a current control TFT 202 is formed such that it partially overlaps a gate electrode 35 to provide a structure which is primarily intended for the prevention of hot carrier injection and the reduction of an off-current. Appropriate TFT structures are thus provided depending on required functions to improve operational performance and reliability.

Claims

1. An electronic device having at least one pixel, said pixel comprising:

a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;

wherein an LDD (lightly-doped-drain) region formed in said first TFT does not overlap a gate electrode of said first TFT with a gate insulating film interposed,

wherein an LDD region formed in said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulating film interposed.

2. An electronic device according to claim 1 wherein a length of the LDD region overlapping said gate electrode of said second TFT is in the range from 1 to 3 μ

m.

3. An electronic device according to claim 1 wherein an n-type impurity element is contained in the LDD region of said second TFT at a concentration 2 to 10 times higher than that of the LDD region of said first TFT.

4. An electronic device according to claim 1 wherein the LDD region of said second TFT contains an n-type impurity element at a concentration 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³.

5. An electronic device according to claim 1 wherein the LDD region of said first TFT contains an n-type impurity element at a concentration 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

6. An electronic device according to claim 1 wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggle type display, a navigation systems, a sound reproduction device, a note type personal computer, a game machine, a portable information terminal, and an image projection device.

7. An electronic device having at least one pixel, said pixel comprising:

a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;

wherein an LDD (lightly-doped-drain) region of said first TFT partially overlaps a gate electrode of said first TFT with a gate insulation film interposed,

wherein an LDD region of said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulation film interposed.

8. An electronic device according to claim 7 wherein a length of the LDD region overlapping said gate electrode of said second TFT is in the range from 1 to 3 μ

m.

9. An electronic device according to claim 7 wherein an n-type impurity element is contained in the LDD region of said second TFT at a concentration 2 to 10 times higher than that of the LDD region of said first TFT.

10. An electronic device according to claim 7 wherein the LDD region of said second TFT contains an n-type impurity element at a concentration 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³.

11. An electronic device according to claim 7 wherein the LDD region of said first TFT contains an n-type impurity element at a concentration 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

12. An electronic device according to claim 7 wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggle type display, a navigation systems, a sound reproduction device, a note type personal computer, a game machine, a portable information terminal, and an image projection device.

13. An electronic device having a pixel portion and a driving circuit portion formed on an insulating surface,

said driving circuit portion comprising:

at least one n-channel type TFT having an LDD (lightly-doped-drain) region partially or entirely overlapping a gate electrode with a gate insulation film interposed, and

said pixel portion comprising;

a pixel including a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;

wherein an LDD region of said first TFT does not overlap a gate electrode of said first TFT with a gate insulation film interposed; and

wherein an LDD region of said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulation film interposed.

14. An electronic device according to claim 13 wherein a length of the LDD region overlapping the gate electrode of said second TFT is in the range from 1 to 3 μ

m.

15. An electronic device according to claim 13 wherein an n-type impurity element is contained in the LDD region of said second TFT at a concentration 2 to 10 times higher than that of the LDD region of said first TFT.

16. An electronic device according to claim 13 wherein the LDD region of said second TFT contains an n-type impurity element at a concentration 2×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

17. An electronic device according to claim 13 wherein the LDD region of said first TFT contains an n-type impurity element at a concentration 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

18. An electronic device according to claim 13 wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggle type display, a navigation systems, a sound reproduction device, a note type personal computer, a game machine, a portable information terminal, and an image projection device.

19. An electronic device having a pixel portion and a driving circuit portion formed on an insulating surface,

said driving circuit portion comprising:

at least one n-channel type TFT having an LDD (lightly-doped-drain) region partially or entirely overlapping a gate electrode with a gate insulation film interposed, and

said pixel portion comprising;

a pixel including a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;

wherein an LDD region of said first TFT overlaps a gate electrode of said first TFT with a gate insulation film interposed; and

wherein an LDD region of said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulation film interposed.

20. An electronic device according to claim 19 wherein a length of the LDD region overlapping the gate electrode of said second TFT is in the range from 1 to 3 μ

m.

21. An electronic device according to claim 19 wherein an n-type impurity element is contained in the LDD region of said second TFT at a concentration 2 to 10 times higher than that of the LDD region of said first TFT.

22. An electronic device according to claim 19 wherein the LDD region of said second TFT contains an n-type impurity element at a concentration 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³.

23. An electronic device according to claim 19 wherein the LDD region of said first TFT contains an n-type impurity element at a concentration 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

24. An electronic device according to claim 19 wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggle type display, a navigation systems, a sound reproduction device, a note type personal computer, a game machine, a portable information terminal, and an image projection device.

25. An electronic device having at least one pixel, said pixel comprising:

a switching TFT;

a current-control TFT connected to said switching TFT;

an EL element connected to said current-control TFT,

wherein an LDD (lightly-doped-drain) region formed in said switching TFT does not overlap a gate electrode of said switching TFT with a gate insulating film interposed,

wherein an LDD region formed in said current-control TFT partially or entirely overlaps a gate electrode of said current-control TFT with a gate insulating film interposed,

wherein an n-type impurity element is contained in the LDD region of said current-control TFT at a higher concentration higher than that of the LDD region of said switching TFT.

26. An electronic device according to claim 25 wherein the LDD region of said current-control TFT contains an n-type impurity element at a concentration of 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³.

27. An electronic device according to claim 25 wherein the LDD region of said switching TFT contains an n-type impurity element at a concentration of 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

28. An electronic device according to claim 25 wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggle type display, a navigation systems, a sound reproduction device, a note type personal computer, a game machine, a portable information terminal, and an image projection device.

29. An electronic device having at least one pixel, said pixel comprising:

a switching TFT;

a current-control TFT connected to said switching TFT;

an EL element connected to said current-control TFT;

wherein an LDD (lightly-doped-drain) region formed in said switching TFT does not overlap a gate electrode of said switching TFT with a gate insulating film interposed,

wherein an LDD region formed in said current-control TFT partially or entirely overlaps a gate electrode of said current-control TFT with a gate insulating film interposed,

wherein a length of the LDD region overlapping the gate electrode of said current-control TFT is in the range from 1 to 3 μ

m.

30. An electronic device according to claim 29 wherein the LDD region of said current-control TFT contains an n-type impurity element at a concentration of 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³.

31. An electronic device according to claim 29 wherein the LDD region of said switching TFT contains an n-type impurity element at a concentration of 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

32. An electronic device according to claim 29 wherein said electronic device is selected from the group consisting of a video camera, a digital camera, a goggle type display, a navigation systems, a sound reproduction device, a note type personal computer, a game machine, a portable information terminal, and an image projection device.