Thin film transistor having lightly doped regions

• US 6,399,988 B1
• Filed: 03/22/2000
• Issued: 06/04/2002
• Est. Priority Date: 03/26/1999
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Le, Bau T
• Application Number:
  US09/533,040
• Time in Patent Office: 804 Days
• Field of Search: 257/59, 257/72, 257/296, 257/344, 257/350, 257/392, 257/408
• US Class Current: 257/344
• CPC Class Codes: G02F 1/13454 Drivers integrated on the active matrix substrate G02F1/136277 takes precedence
• CPC Class Codes: H01L 2029/7863 with an LDD consisting of more than one lightly doped zone or having a non-homogeneous dopant distribution, e.g. graded LDD
• CPC Class Codes: H01L 21/02107 Forming insulating materials on a substrate
• CPC Class Codes: H01L 21/316 composed of oxides or glassy oxides or oxide based glass
• 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 27/127 with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
• 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 59/12 Active-matrix OLED [AMOLED] displays

Abstract

By appropriately selecting the structure of top gate type or staggered type TFTs disposed in the respective circuits of a semiconductor device depending on the function of the circuits, the operating characteristics and the reliability of the semiconductor device is improved. An LDD region (107) the whole of which overlaps a gate electrode is provided in a first n-channel type TFT of a controlling circuit. LDD regions (111) and (112) at least part of which overlaps a gate electrode are provided in a second n-channel type TFT of the control circuit. LDD regions (117) to (120) which do not overlap a gate electrode through offset regions are provided in an n-channel type TFT of a pixel matrix circuit. By making different the concentration of LDD regions of the control circuit and the concentration of the pixel matrix circuit, optimized circuit operation is obtained.

Claims

1. A semiconductor device comprising a pixel portion and a driver circuit for driving said pixel portion formed over a same substrate, said pixel portion comprising:

an n-channel type thin film transistor over said substrate, said n-channel type thin film transistor comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region is disposed so as not to overlap said insulating gate electrode, and an offset region is formed between said channel forming region and said lightly doped region, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor is disposed so as to overlap said gate electrode of said first n-channel type thin film transistor,

wherein said lightly doped region of said second n-channel type thin film transistor is disposed so as to at least partly overlap said gate electrode of said second n-channel type thin film transistor.

2. A semiconductor device according to claim 1, wherein an n-type impurity element contained in said lightly doped regions of said first and of said second n-channel type thin film transistor of said driver circuit is larger than that contained in said lightly doped region of said n-channel type thin film transistor of said pixel portion.

3. A semiconductor device according to claim 1, wherein an n-type impurity element contained in said lightly doped regions of said first and said second n-channel type thin film transistor of said driver circuit is two to ten times as large as that contained in said lightly doped region of said n-channel type thin film transistor of said pixel portion.

4. A semiconductor device according to claim 1, wherein a concentration of n-type impurity element contained in said lightly doped regions of said first and said second n-channel type thin film transistor of said driver circuit is from 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³ and a concentration of n-type impurity element contained in said lightly doped region of said n-channel type thin film transistor of said pixel portion is from 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

5. A semiconductor device according to claim 1, wherein said offset region is formed of a semiconductor film having the same composition as that of said channel forming region abutting against said offset region.

6. A semiconductor device according to claim 1, wherein a p-type impurity element is contained in said offset region at a concentration from 1×

10¹⁵ to 1×

10¹⁸ atoms/cm³.

7. A semiconductor device according to claim 1, wherein a storage capacitance is formed from a semiconductor layer connected with said n-channel type thin film transistor of said pixel portion and containing an n-type impurity element, capacitance wirings, and an insulating film between said semiconductor layer and said capacitance wirings in said pixel portion.

8. A semiconductor device according to claim 1, wherein said semiconductor device is an electro-luminescence display device.

9. A semiconductor device according to claim 1, wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

10. A semiconductor device according to claim 1, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

11. A semiconductor device according to claim 1, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

12. A semiconductor device comprising a pixel portion and a driver circuit for driving said pixel portion formed over a same substrate, said pixel portion comprising:

an n-channel type thin film transistor over said substrate, said n-channel type thin film transistor comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region is disposed so as not to overlap said gate electrode, and an offset region is formed between said channel forming region and said lightly doped region, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor is disposed so as to entirely overlap said gate electrode of said first n-channel type thin film transistor,

wherein said lightly doped region of said second n-channel type thin film transistor is disposed so as to partly overlap said gate electrode of said second n-channel type thin film transistor.

13. A semiconductor device according to claim 12, wherein an n-type impurity element contained in said lightly doped regions of said first and of said second n-channel type thin film transistor of said driver circuit is larger than that contained in said lightly doped region of said n-channel type thin film transistor of said pixel portion.

14. A semiconductor device according to claim 12, wherein an n-type impurity element contained in said lightly doped regions of said first and said second n-channel type thin film transistor of said driver circuit is two to ten times as large as that contained in said lightly doped region of said n-channel type thin film transistor of said pixel portion.

15. A semiconductor device according to claim 12, wherein a concentration of n-type impurity element contained in said lightly doped regions of said first and said second n-channel type thin film transistor of said driver circuit is from 2×

10¹⁶ to 5×

10¹⁹ atoms/cm³ and a concentration of n-type impurity element contained in said lightly doped region of said n-channel type thin film transistor of said pixel portion is from 1×

10¹⁶ to 5×

10¹⁸ atoms/cm³.

16. A semiconductor device according to claim 12, wherein said offset region is formed of a semiconductor film having the same composition as that of said channel forming region abutting against said offset region.

17. A semiconductor device according to claim 12, wherein a p-type impurity element is contained in said offset region at a concentration from 1×

10¹⁵ to 1×

10¹⁸ atoms/cm³.

18. A semiconductor device according to claim 12, wherein a storage capacitance is formed from a semiconductor layer connected with said n-channel type thin film transistor of said pixel portion and containing an n-type impurity element, capacitance wirings, and an insulating film between said semiconductor layer and said capacitance wirings in said pixel portion.

19. A semiconductor device according to claim 12, wherein said semiconductor device is an electro-luminescence display device.

20. A semiconductor device according to claim 12, wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

21. A semiconductor device according to claim 12, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

22. A semiconductor device according to claim 12, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

23. A semiconductor device comprising a pixel portion and a driver circuit for driving said pixel portion formed over a same substrate, said pixel portion comprising:

an n-channel type thin film transistor over said substrate, said n-channel type thin film transistor comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region is disposed so as not to overlap said gate electrode, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor is disposed so as to entirely overlap said gate electrode of said first n-channel type thin film transistor,

wherein said lightly doped region of said second n-channel type thin film transistor is disposed so as to partly overlap said gate electrode of said second n-channel type thin film transistor.

24. A semiconductor device according to claim 23, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

25. A semiconductor device according to claim 23, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

26. A semiconductor device according to claim 23, wherein said semiconductor device is an electro-luminescence display device.

27. A semiconductor device according to claim 23, wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

28. A semiconductor device comprising a pixel portion and a driver circuit for driving said pixel portion formed over a same substrate, said pixel portion comprising:

an n-channel type thin film transistor over said substrate, said n-channel type thin film transistor comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region is disposed so as not to overlap said gate electrode, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region comprising an n-type impurity between 2×

10¹⁶ and 5×

10¹⁹ atoms/cm³; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor is disposed so as to entirely overlap said gate electrode of said first n-channel type thin film transistor,

wherein said lightly doped region of said second n-channel type thin film transistor is disposed so as to partly overlap said gate electrode of said second n-channel type thin film transistor.

29. A semiconductor device according to claim 28, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

30. A semiconductor device according to claim 28, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

31. A semiconductor device according to claim 28, wherein said semiconductor device is an electro-luminescence display device.

32. A semiconductor device according to claim 28, wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

33. A semiconductor device comprising a pixel portion and a driver circuit for driving said pixel portion formed over a same substrate, said pixel portion comprising:

an n-channel type thin film transistor over said substrate, said n-channel type thin film transistor comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region comprising an n-type impurity between 1×

10¹⁶ and 5×

10¹⁸ atoms/cm³; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region is disposed so as not to overlap said gate electrode, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a source region, a drain region, a channel forming region, and a lightly doped region comprising an n-type impurity between 2×

10¹⁶ and 5×

10¹⁹ atoms/cm³; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor disposed so as to entirely overlap said gate electrode of said first n-channel type thin film transistor,

wherein said lightly doped region of said second n-channel type thin film transistor is disposed so as to partly overlap said gate electrode of said second n-channel type thin film transistor.

34. A semiconductor device according to claim 33, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

35. A semiconductor device according to claim 33, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

36. A semiconductor device according to claim 33, wherein said semiconductor device is an electro-luminescence display device.

37. A semiconductor device according to claim 33, wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

38. A semiconductor device comprising:

a pixel thin film transistor and a driver circuit for driving said pixel thin film transistor over a substrate, said pixel thin film transistor comprising;

a semiconductor layer having at least a pair of impurity regions, a channel forming region, and a lightly doped region interposed between at least one of said pair of impurity regions and said channel forming region, said lightly doped region having a length of 3.5 μ

m or less along said channel forming region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region does not overlap said gate electrode, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a pair of impurity regions, a channel forming region, and a lightly doped region interposed between at least one of said of impurity regions and said channel forming region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor entirely overlaps said gate electrode of said first n-channel type thin film transistor, and

wherein said lightly doped region of said second n-channel type thin film transistor partially overlaps said gate electrode of said second n-channel type thin film transistor.

39. A semiconductor device according to claim 38 wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

40. A semiconductor device according to claim 38 wherein said second n-channel type thin transistor is incorporated in a sampling circuit.

41. A semiconductor device according to claim 38 wherein said semiconductor device is an electro-luminescence display device.

42. A semiconductor device according to claim 38 wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

43. A semiconductor device comprising:

a pixel thin film transistor and a driver circuit for driving said pixel thin film transistor over a substrate, said pixel thin film transistor comprising;

a semiconductor layer having at least a pair of impurity regions, a channel forming region, and a lightly doped region interposed between at least one of said pair of impurity regions and said channel forming region, said lightly doped region having a length of 3.5 μ

m or less along said channel forming region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region does not overlap said gate electrode, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and said second n-channel type thin film transistors comprising;

a semiconductor layer having at least a pair of impurity regions, a channel forming region, and a lightly doped region interposed between at least one of said pair of impurity regions and said channel forming region, said lightly doped region containing an n-type impurity between 2×

10¹⁶ and 5×

10¹⁹ atoms/cm³; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor entirely overlaps said gate electrode of said first n-channel type thin film transistor, and

wherein said lightly doped region of said second n-channel type thin film transistor partially overlaps said gate electrode of said second n-channel type thin film transistor.

44. A semiconductor device according to claim 43, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

45. A semiconductor device according to claim 43, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

46. A semiconductor device according to claim 43, wherein said semiconductor device is an electro-luminescence display device.

47. A semiconductor device according to claim 43, wherein said semiconductor device is one selected from the group consisting of portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.

48. A semiconductor device comprising:

a pixel thin transistor and a driver circuit for driving said pixel thin film transistor over a substrate, said pixel thin film transistor comprising;

a semiconductor layer having at least a pair of impurity regions, a channel forming region, and a lightly doped region interposed between at least one of said pair of impurity regions and said channel forming region, said lightly doped region having a length of 3.5 μ

m or less along said channel forming region, and containing an n-type impurity between 1×

10¹⁶ and 5×

10¹⁸ atoms/cm³; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region does not overlap said gate electrode, and

said driver circuit comprising;

a first and a second n-channel type thin film transistors over said substrate, each of said first and second n-channel type thin film transistors comprising;

a semiconductor layer having at least a pair of impurity regions, a channel forming region, and a lightly doped region interposed between at least one of said pair of impurity regions and said channel forming region; and

a gate electrode adjacent to said channel forming region with a gate insulating film interposed therebetween,

wherein said lightly doped region of said first n-channel type thin film transistor entirely overlaps said gate electrode of said first n-channel type thin film transistor, and

wherein said lightly doped region of said second n-channel type thin film transistor partially overlaps said gate electrode of said second n-channel type thin film transistor.

49. A semiconductor device according to claim 48, wherein said first n-channel type thin film transistor is incorporated in at least one selected from the group consisting of a shift register circuit, a level shifter circuit, and a buffer circuit.

50. A semiconductor device according to claim 48, wherein said second n-channel type thin film transistor is incorporated in a sampling circuit.

51. A semiconductor device according to claim 48, wherein said semiconductor device is an electro-luminescence display device.

52. A semiconductor device according to claim 48, wherein said semiconductor device is one selected from the group consisting of a portable telephone, a video camera, a mobile computer, a goggle type display, a projector, a portable book, a digital camera, a car navigation system, and a personal computer.