Light emitting device and fabricating method thereof

• US 20020048829A1
• Filed: 04/19/2001
• Published: 04/25/2002
• Est. Priority Date: 04/19/2000
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Inukai, Kazutaka, Fukunaga, Takeshi, Koyama, Jun, Yamazaki, Shunpei
• Granted Patent: US 6,706,544 B2
• Time in Patent Office: Days
• US Class Current: 438/16
• 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 27/127 with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
• 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 29/66757 Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate

Abstract

The present invention provides an inexpensive light emitting device and an inexpensive electric appliance. By reducing the number of photolithography steps in the fabrication of TFTs, the yield of the light emitting devices can be enhanced and the manufacturing period can be shortened. The present invention is substantially characterized in that a gate electrode is formed of a conductive film made of a plurality of layers and the concentration of impurity regions formed in the inside of an active layer can be adjusted by making use of the selection ratio at the time of etching these layers.

Claims

1. A light emitting device having pixels each of which is provided with an n-channel type TFT, a light emitting element, a passivation film which covers the light emitting element and a coloring layer disposed over the passivation film, the n-channel type TFT comprising:

an active layer which includes a channel forming region, an n-type impurity region (c) being in contact with the channel forming region, an n-type impurity region (b) being in contact with the n-type impurity region (c) and an n-type impurity region (a) being in contact with the n-type impurity region (b); and

a gate electrode which includes a first gate electrode and a second gate electrode having a contour smaller than a contour of the first gate electrode,

wherein the first gate electrode is superposed over the channel forming region and the n-type impurity region (c) while sandwiching a gate insulation film therebetween, and the second gate electrode is superposed over the channel forming region while sandwiching the gate insulation film therebetween.

2. A device according to claim 1, wherein the first gate electrode is made of tantalum nitride or titanium nitride and the second gate electrode is made of tungsten or aluminum alloy.

3. A device according to claim 1, wherein the n-type impurity region (a) contains an n-type impurity element at the concentration of 1×

10²⁰-1×

10²¹ atoms/cm³, the n-type impurity region (b) contains an n-type impurity element at the concentration of 2×

10¹⁶-5×

10¹⁹ atoms/cm³, and the n-type impurity region (c) contains an n-type impurity element at the concentration of 1×

10¹⁶-1×

×

10¹⁸ atoms/cm³.

4. A device according to claim 1, wherein the gate electrode is covered with an insulation film which is laminated with a silicon oxide nitride film and a resin film.

5. A device according to claim 1 wherein the gate electrode is covered with an insulation film which is laminated with a silicon nitride film and a resin film.

6. A device according to claim 1, wherein an outermost surface of a wiring which is connected to the n-channel type TFT is made of a metal film including an element selected from a group 1 or a group 2 of the periodic table or a bismuth film.

7. A light emitting device having pixels each of which is provided with an n-channel type TFT, a light emitting element electrically connected to the n-channel type TFT, a passivation film which covers the light emitting element and a coloring layer disposed over the passivation film, the n-channel type TFT comprising:

an active layer which includes a channel forming region, an n-type impurity region (c) being in contact with the channel forming region, an n-type impurity region (b) being in contact with the n-type impurity region (c) and an n-type impurity region (a) being in contact with the n-type impurity region (b); and

a gate electrode which includes a first gate electrode and a second gate electrode having a contour smaller than a contour of the first gate electrode,

wherein the first gate electrode is superposed over the channel forming region and the n-type impurity region (c) while sandwiching a gate insulation film therebetween, and the second gate electrode is superposed over the channel forming region while sandwiching the gate insulation film therebetween.

8. A device according to claim 7, wherein the first gate electrode is made of tantalum nitride or titanium nitride and the second gate electrode is made of tungsten or aluminum alloy.

9. A device according to claim 7, wherein the n-type impurity region (a) contains an n-type impurity element at the concentration of 1×

10²⁰-1×

10²¹ atoms/cm³, the n-type impurity region (b) contains an n-type impurity element at the concentration of 2×

10¹⁶-5×

10¹⁹ atoms/cm³, and the n-type impurity region (c) contains an n-type impurity element at the concentration of 1×

10¹⁶-1×

10¹⁸ atoms/cm³.

10. A device according to claim 7, wherein the gate electrode is covered with an insulation film which is laminated with a silicon oxide nitride film and a resin film.

11. A device according to claim 7 wherein the gate electrode is covered with an insulation film which is laminated with a silicon nitride film and a resin film.

12. A device according to claim 7, wherein an outermost surface of a wiring which is connected to the n-channel type TFT is made of a metal film including an element selected from a group 1 or a group 2 of the periodic table or a bismuth film.

13. A device according to claim 7, wherein the passivation film is made of an insulation film selected from a group including a carbon film, a silicon nitride film and a silicon nitride-oxide film.

15. A method according to claim 14, wherein the conductive film is formed by laminating a tungsten film or an aluminum alloy film over a tantalum nitride film or a titanium nitride film.

16. A method according to claim 14, wherein the insulation film formed in the eighth step is made of a silicon nitride film or a silicon nitride-oxide film and a resin film.

17. A method according to claim 14, wherein the passivation film includes a carbon film, a silicon nitride film or a silicon nitride-oxide film.

18. A method according to claim 14, wherein an outermost surface of the wiring is made of a metal film including an element selected from a group 1 or a group 2 of the periodic table or a bismuth film.

19. A method according to claim 14, wherein the gate electrode formed in the fourth step has a tapered shape.

14. A method for fabricating a light emitting device comprising:

a first step of forming a semiconductor film over an insulation body;

a second step of forming an insulation film which covers the semiconductor film;

a third step of forming a conductive film formed by laminating two or more conductive films over the insulation film;

a fourth step of forming a gate electrode by etching the conductive film;

a fifth step of doping the semiconductor film with an n-type impurity element using the gate electrode as a mask;

a sixth step of selectively etching a portion of the gate electrode after a side surface of the gate electrode is etched;

a seventh step of doping an n-type impurity element into the semiconductor film using a portion of the gate electrode on which the conductive films are laminated in two or more layers as a mask after completing the sixth step, by allowing the n-type impurity element to pass through a portion of the gate electrode;

an eighth step of forming an insulation film which covers the gate electrode;

a ninth step of forming a wiring which is brought into contact with the semiconductor film over the insulation film formed in the eighth step;

a tenth step of forming a light emitting element over the insulation film formed in the eighth step; and

an eleventh step of forming a passivation film over the light emitting element.

20. A method for fabricating a light emitting device comprising:

a first step of forming a semiconductor film over an insulation body;

a second step of forming an insulation film which covers the semiconductor film;

a third step of forming a conductive film formed by laminating a first conductive film and a second conductive film over the insulation film;

a fourth step of forming a first gate electrode made of the first conductive film and a second gate electrode made of the second conductive film are formed by etching the first and second conductive films;

a fifth step of doping the semiconductor film with an n-type impurity element using the first gate electrode and the second gate electrode as masks;

a sixth step of etching the first gate electrode and the second gate electrode to narrow a line width thereof and thereafter selectively etching the second gate electrode;

a seventh step of doping an n-type impurity element into the semiconductor film using the second gate electrode as a mask after completing the sixth step, by allowing the n-type impurity element to pass through a portion of the first gate electrode;

an eighth step of forming an insulation film which covers the gate electrodes;

a ninth step of forming a wiring which is brought into contact with the semiconductor film over the insulation film formed in the eighth step;

a tenth step of forming a light emitting element over the insulation film formed in the eighth step; and

an eleventh step of forming a passivation film over the light emitting element.

21. A method according to claim 20, wherein a tantalum nitride film or a titanium nitride film is used as the first conductive film and a tungsten film or an aluminum alloy film is used as the second conductive film.

22. A method according to claim 20, wherein the first gate electrode and the second gate electrode formed in the fourth step have a tapered shape.

23. A method according to claim 20, wherein the insulation film formed in the eighth step is made of a silicon nitride film or a silicon nitride-oxide film and a resin film.

24. A method according to claim 20, wherein the passivation film includes a carbon film, a silicon nitride film or a silicon nitride-oxide film.

25. A method according to claim 20, wherein an outermost surface of the wiring is made of a metal film including an element selected from a group 1 or a group 2 of the periodic table or a bismuth film.