Semiconductor display device and manufacturing method thereof

• US 6,909,117 B2
• Filed: 03/11/2003
• Issued: 06/21/2005
• Est. Priority Date: 09/22/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Ohnuma, Hideto
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): Soward, Ida M.
• Application Number:
  US10/386,257
• Publication Number:
  US 20030155594A1
• Time in Patent Office: 833 Days
• Field of Search: 257/291, 257/359, 257/72, 257/69, 257/204, 257/257
• US Class Current: 257/72
• 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 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask
• 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 29/4908 for thin film semiconductor, e.g. gate of TFT
• 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 29/78675 with normal-type structure, e.g. with top gate

Abstract

A semiconductor display device which includes the polycrystalline silicon TFTs is constructed by a pixel region and a peripheral circuit and TFT characteristics required for each circuit are different. For example, an LDD structure TFT having a large off-current suppressing effect is suitable for the pixel region. Also, a GOLD structure TFT having a large hot carrier resistance is suitable for the peripheral circuit. When the performance of the semiconductor display device is improved, it is suitable that difference TFT structures are used for each circuit. In the case where the GOLD structure TFT having both Lov regions and Loff regions is formed, ion implantation into the Lov regions is independently performed using a negative resist pattern formed in a self alignment by a rear surface exposure method as a mask, and thus impurity concentrations of the Lov regions and the Loff regions can be independently controlled. Therefore, the GOLD structure TFT having both the hot carrier resistance and the off-current suppressing effect can be formed and the simplification of a manufacturing process of the semiconductor display device and the improvement of performance thereof are compatible with each other.

Claims

1. A semiconductor device comprising a plurality of thin film transistors formed over a transparent insulating substrate, each of said thin film transistors comprising:

a semiconductor layer, a gate insulating film, and a gate electrode being laminated in order from a side near the transparent insulating substrate, and a source region and a drain region being formed in the semiconductor layer outside the gate electrode,

wherein the gate electrode comprises a first layer gate electrode and a second layer gate electrode located over the first layer gate electrode wherein the first layer gate electrode extends beyond a side edge of the second layer gate electrode,

wherein a first impurity region is formed in the semiconductor layer below the extending portion of the first layer gate electrode,

wherein a second impurity region and the source region or the drain region are formed adjacent to each other from a side near the gate electrode in the semiconductor layer being the outside of a side edge of the first gate electrode, and

wherein an impurity concentration of the first impurity region is higher than that of the second impurity region and lower than that of the source region or the drain region.

2. A device according to claim 1, wherein the first impurity region, the second impurity region, and the source region or the drain region are the same conductivity type impurity regions and have one of an n-type and a p-type as a conductivity type.

3. A device according to claim 1, wherein the first layer gate electrode and the second layer gate electrode comprise different high melting metals.

4. A device according to claim 1, wherein the first layer gate electrode comprises a TaN film as a compound containing high melting metal and the second layer gate electrode comprises a W film as the high melting metal.

5. A device according to claim 1, wherein the semiconductor layer comprises one of a polycrystalline silicon film and a crystalline silicon film formed using a catalyst element.

6. An electronic equipment having a device according to claim 1, wherein the electronic equipment is selected from the group consisting of a video camera, a digital camera, a rear type projector, a front type projector, a head mounted display, a goggle type display, a game machine, a car navigation system, a personal computer, a mobile computer, a mobile telephone, an electronic book, a personal computer, and a recording medium.

7. A semiconductor device comprising a plurality of n-channel thin film transistors formed over a transparent insulating substrate, each of the n-channel thin film transistors comprising:

a semiconductor layer, a gate insulating film, and a gate electrode being laminated in order from a side near the transparent insulating substrate, and a source region and a drain region being formed in the semiconductor layer outside the gate electrode,

wherein the gate electrode comprises a first layer gate electrode and a second layer gate electrode located over the first layer gate electrode wherein the first layer gate electrode extends beyond a side edge of the second layer gate electrode,

wherein a first impurity region is formed in the semiconductor layer below the extending portion of the first layer gate electrode,

wherein a second impurity region and the source region or the drain region are formed adjacent to each other from a side near the gate electrode in the semiconductor layer being the outside of a side edge of the first gate electrode, and

wherein an impurity concentration of the first impurity region is higher than that of the second impurity region and lower than that of the source region or the drain region.

8. A device according to claim 7, wherein the first impurity region, the second impurity region, and the source region or the drain region are n-type impurity regions.

9. A device according to claim 7, wherein an n-type impurity concentration of the first impurity region is 2×

10¹⁶ to 2.7×

10¹⁹ atoms/cm³, preferably, about 1×

10¹⁷ to 5.3×

10¹⁸ atoms/cm³.

10. A device according to claim 7, wherein an n-type impurity concentration of the second impurity region is 4.7×

10¹⁵ to 2.7×

10¹⁸ atoms/cm³, preferably, about 4.7×

10¹⁷ to 5.3×

10¹⁷ atoms/cm³.

11. A device according to claim 7, wherein an n-type impurity concentration of the source region or the drain region is about 3×

10¹⁸ to 5×

10²¹ atoms/cm³, preferably, about 1.7×

10¹⁹ to 2.7×

10²⁰ atoms/cm³.

12. A device according to claim 7, wherein the first layer gate electrode and the second layer gate electrode comprise different high melting metals.

13. A device according to claim 7, wherein the first layer gate electrode comprises a TaN film as a compound containing high melting metal and the second layer gate electrode comprises a W film as the high melting metal.

14. A device according to claim 7, wherein the semiconductor layer comprises one of a polycrystalline silicon film and a crystalline silicon film formed using a catalyst element.

15. An electronic equipment having a device according to claim 7, wherein the electronic equipment is selected from the group consisting of a video camera, a digital camera, a rear type projector, a front type projector, a head mounted display, a goggle type display, a game machine, a car navigation system, a personal computer, a mobile computer, a mobile telephone, an electronic book, a personal computer, and a recording medium.

16. A semiconductor device comprising:

a substrate;

a semiconductor layer formed over the substrate;

a gate insulating film formed over the semiconductor layer;

a gate electrode formed over the semiconductor layer with the gate insulating film interposed therebetween, said gate electrode including a first conductive layer and a second conductive layer formed on the first conductive layer wherein the first conductive layer extends beyond side edges of the second conductive layer;

a pair of first impurity regions formed in the semiconductor layer below the extending portions of the first conductive layer;

a channel region formed in the semiconductor layer between the pair of first impurity regions;

source and drain regions formed in the semiconductor layer;

a pair of second impurity regions formed in the semiconductor layer between the pair of first impurity regions and the source and drain regions,

wherein an impurity concentration of the first impurity region is higher than that of the second impurity region and lower than that of the source and drain regions.

17. A device according to claim 16, wherein the substrate is transparent.

18. A device according to claim 16, wherein the first impurity region, the second impurity region, and the source and drain regions are the same conductivity type impurity regions and have one of an n-type and a p-type as a conductivity type.

19. A device according to claim 16, wherein the first layer gate electrode and the second layer gate electrode comprise different high melting metals.

20. A device according to claim 16, wherein the first conductive layer comprises a TaN film as a compound containing high melting metal and the second layer gate electrode comprises a W film as the high melting metal.

21. A device according to claim 16, wherein the semiconductor layer comprises one of a polycrystalline silicon film and a crystalline silicon film formed using a catalyst element.

22. An electronic equipment having a device according to claim 16, wherein the electronic equipment is selected from the group consisting of a video camera, a digital camera, a rear type projector, a front type projector, a head mounted display, a goggle type display, a game machine, a car navigation system, a personal computer, a mobile computer, a mobile telephone, an electronic book, a personal computer, and a recording medium.