Active matrix substrate for liquid crystal display and its fabrication

• US 20020176032A1
• Filed: 05/20/2002
• Published: 11/28/2002
• Est. Priority Date: 05/18/2001
• Status: Active Grant

• Current Assignee: Vista Peak Ventures LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: NEC Corporation
• Inventors: Kimura, Satoshi, Tanaka, Hiroaki, Kimura, Shigeru, Maeda, Akitoshi
• Granted Patent: US 6,894,311 B2
• Time in Patent Office: Days
• US Class Current: 349/43
• CPC Class Codes: G02F 1/13458 Terminal pads
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/13629 Multilayer wirings
• CPC Class Codes: G02F 1/136295 Materials; Compositions; Manufacture processes
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• 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 29/458 for thin film silicon, e.g. source or drain electrode
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT

Abstract

An active matrix substrate comprises a matrix array of TFTs. A double-layered film includes an under-layer of aluminum-neodymium (Al—Nd) alloy and an over-layer of high melting point metal. The double-layered film forms first interconnection lines for connection to the TFTs. A triple-layered film includes an under-layer of said high melting point metal, a middle-layer of said Al—Nd alloy and an over-layer of the high melting point metal. The triple-layered film forms second interconnection lines for connection to the TFTs.

Claims

1. An active matrix substrate, comprising:

a substrate;

a matrix array of thin film transistors (TFTs) disposed within a display area on said substrate;

a double-layered film including an under-layer of aluminum-neodymium (Al—

Nd) alloy and an over-layer of high melting point metal, said double-layered film forming first interconnection lines for connection to said TFTs; and

a triple-layered film including an under-layer of said high melting point metal, a middle-layer of said Al—

Nd alloy and an over-layer of said high melting point metal, said triple-layered film forming second interconnection lines for connection to said TFTs.

2. The active matrix substrate as claimed in claim 1, wherein said high melting point metal is selected from a group consisting of chromium (Cr), titanium (Ti), tantalum (Ta), niobium (Nb), chromium alloy, titanium alloy, tantalum alloy, and niobium alloy;

and wherein said Al—

Nd alloy contains 0.01 wt % to 1.00 wt % neodymium (Nd).

3. The active matrix substrate as claimed in claim 1, wherein said high melting point metal is selected from a group consisting of molybdenum (Mo), tungsten (W), titanium nitride (TiN), molybdenum alloy, tungsten alloy, and titanium nitride alloy;

and wherein said Al—

Nd alloy contains 0.5 wt % to 1.0 wt % neodymium (Nd).

4. A method of fabricating a active matrix substrate including a substrate, a matrix array of thin film transistors (TFTs) disposed within a display area on the substrate, scanning lines for connection to the TFTs, and signal lines for connection to the TFTs, said method comprising:

forming a double-layered film including an under-layer of aluminum-neodymium (Al—

Nd) alloy and an over-layer of high melting point metal; and

removing portions of said double-layered film to form the scanning lines.

6. The method as claimed in claim 4, wherein the step of removing includes wet etching;

and wherein said high melting point metal is one of molybdenum (Mo) and molybdenum alloy.

8. The method as claimed in claim 6, wherein the step of removing includes wet etching using, as an etchant, a mixture selected from a group consisting of a first mixture that contains phosphoric acid (H₃PO₄), nitric acid (HNO₃) and acetic acid (CH₃—

COOH) at the ratio, in mass percent, that 72;

4.4 to 5.4;

8, and a second mixture that contains phosphoric acid (H₃PO₄), nitric acid (HNO₃) and acetic acid (CH₃—

COOH) at the ratio, in mass percent, that 74;

4.2 to 5.2;

6.

10. The method as claimed in claim 6, wherein the step of removing includes wet etching using, as an etchant, a mixture that contains phosphoric acid (H₃PO₄), nitric acid (HNO₃) and acetic acid (CH₃—

COOH); and

wherein the sub-step of wet etching is applied in shower mode with or without one of puddle mode and dip mode.

12. The method as claimed in claim 4, wherein the step of removing includes at least dry etching.

26. The method as claimed in any one of the preceding claims 12 to 15, wherein the step of removing is the step of dry etching.

31. The method as claimed in any one of the preceding claims 12, 13, 27 and 28, wherein the step of removing is the step of dry etching.

36. The method as claimed in any one of the preceding claims 12, 13, 32, 33, 34 and 35, wherein the step of removing is the step of dry etching.

37. The method as claimed in claim 4, further comprising:

depositing a transparent conductive film;

wet etching said transparent conductive film, using an etchant, oxalic acid (C₂H₂O₄) to form electrodes.

43. The method as claimed in claim 4, further comprising:

forming a semiconductor layer;

dry etching said semiconductor layer partially to separate source and drain electrodes of the TFTs, wherein the step of dry etching uses, as etchant gas, one selected from a family of fluoride-based gas or a mixture of one selected from the family of fluoride-based gas and another selected from a family of chloride-based gas excluding hydrochloric acid (HCl).

5. A method of fabricating a active matrix substrate including a substrate, a matrix array of thin film transistors (TFTs) disposed within a display area on the substrate, scanning lines for connection to the TFTs, and signal lines for connection to the TFTs, said method comprising:

forming a triple-layered film including an under-layer of high melting point metal, a middle-layer of Al—

Nd alloy and an over-layer of said high melting point metal; and

removing portions of said triple-layered film to form the signal lines.

7. The method as claimed in claim 5, wherein the step of removing includes wet etching;

and wherein said high melting point metal is one of molybdenum (Mo) and molybdenum alloy.

9. The method as claimed in claim 7, wherein the step of removing includes wet etching using, as an etchant, a mixture selected from a group consisting of a first mixture that contains phosphoric acid (H₃PO₄), nitric acid (HNO₃) and acetic acid (CH₃—

COOH) at the ratio, in mass percent, that 72;

4.4 to 5.4;

8, and a second mixture that contains phosphoric acid (H₃PO₄), nitric acid (HNO₃) and acetic acid (CH₃—

COOH) at the ratio, in mass percent, that 74;

4.2 to 5.2;

6.

11. The method as claimed in claim 7, wherein the step of removing includes wet etching using, as an etchant, a mixture that contains phosphoric acid (H₃PO₄), nitric acid (HNO₃) and acetic acid (CH₃—

COOH); and

wherein the sub-step of wet etching is applied in shower mode with or without one of puddle mode and dip mode.

13. The method as claimed in claim 5, wherein the step of removing includes at least dry etching.

14. The method as claimed in claim 12, wherein said high melting point metal is one of chromium (Cr) and chromium alloy;

and wherein said Al—

Nd alloy contains 0.01 wt % to 1.00 wt % neodymium (Nd).

15. The method as claimed in claim 13, wherein said high melting point metal is one of chromium (Cr) and chromium alloy;

and wherein said Al—

Nd alloy contains 0.01 wt % to 1.00 wt % neodymium (Nd).

16. The method as claimed in claim 12, wherein said high melting point metal is one of chromium (Cr) and chromium alloy;

wherein the step of removing also includes wet etching; and

wherein said wet etching is applied to etch said over-layer of said melting point metal, and said dry etching is applied to etch said under-layer of said Al—

Nd alloy.

17. The method as claimed in claim 14, wherein the step of removing also includes wet etching;

and wherein said wet etching is applied to etch said over-layer of said melting point metal, and said dry etching is applied to etch said under-layer of said Al—

Nd alloy.

18. The method as claimed in claim 13, wherein said high melting point metal is one of chromium (Cr) and chromium alloy;

wherein the step of removing also includes wet etching; and

wherein said wet etching is applied to etch said over-layer of said melting point metal and said middle-layer of said Al—

Nd alloy, and said dry etching is applied to etch said under-layer of said high melting point metal.

19. The method as claimed in claim 15, wherein the step of removing also includes wet etching;

and wherein said wet etching is applied to etch said over-layer of said melting point metal and said middle-layer of said Al—

Nd alloy, and said dry etching is applied to etch said under-layer of said high melting point metal.

20. The method as claimed in claim 18, wherein the step of removing includes depositing a photoresist on said triple-layered film and baking said photoresist until it has a sidewall tapered at an angle ranging from 30°

to 55°

.

21. The method as claimed in claim 19, wherein the step of removing includes depositing a photoresist on said triple-layered film and baking said photoresist until it has a sidewall tapered at an angle ranging from 30°

to 55°

.

22. The method as claimed in claim 18, wherein the step of removing includes depositing a photoresist on said triple-layered film, wherein said dry etching is applied using, as an etchant, chlorine (Cl₂) and oxygen (O₂) to etch said under-layer of said high melting point metal and, in the process of said dry etching, said photoresist due to ashing thereby to expose an overhang portion of said over-layer of said high melting point metal to allow removal of said overhang portion by etching.

23. The method as claimed in claim 19, wherein the step of removing includes depositing a photoresist on said triple-layered film, wherein said dry etching is applied using, as an etchant, chlorine (Cl₂) and oxygen (O₂) to etch said under-layer of said high melting point metal and, in the process of said dry etching, said photoresist due to ashing thereby to expose an overhang portion of said over-layer of said high melting point metal to allow removal of said overhang portion by etching.

24. The method as claimed in claim 20, wherein said dry etching is applied using, as an etchant, chlorine (Cl₂) and oxygen (O₂) to etch said under-layer of said high melting point metal and, in the process of said dry etching, said photoresist loses volume due to ashing thereby to expose an overhang portion of said over-layer of said high melting point metal to allow removal of said overhang portion by etching.

25. The method as claimed in claim 21, wherein said dry etching is applied using, as an etchant, chlorine (Cl₂) and oxygen (O₂) to etch said under-layer of said high melting point metal and, in the process of said dry etching, said photoresist loses volume due to ashing thereby to expose an overhang portion of said over-layer of said high melting point metal to allow removal of said overhang portion by etching.

27. The method as claimed in claim 12, wherein said high melting point metal is one of molybdenum (Mo) and molybdenum alloy;

and wherein said Al—

Nd alloy contains 0.5 wt % to 1.0 wt % neodymium (Nd).

28. The method as claimed in claim 13, wherein said high melting point metal is one of molybdenum (Mo) and molybdenum alloy;

and wherein said Al—

Nd alloy contains 0.5 wt % to 1.0 wt % neodymium (Nd).

29. The method as claimed in claim 13, wherein said high melting point metal is one of molybdenum (Mo) and molybdenum alloy;

wherein the step of removing also includes wet etching; and

wherein said wet etching is applied to etch said over-layer of said melting point metal and said middle-layer of said Al—

Nd alloy halfway to remove a portion thereof, and said dry etching is applied to etch the remaining portion of said middle-layer and said under-layer of said high melting point metal.

30. The method as claimed in claim 28, wherein the step of removing also includes wet etching;

wherein said wet etching is applied to etch said over-layer of said melting point metal and said middle-layer of said Al—

Nd alloy halfway to remove a portion thereof, and said dry etching is applied to etch the remaining portion of said middle-layer and said under-layer of said high melting point metal.

32. The method as claimed in claim 12, wherein said high melting point metal is selected from a group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), titanium alloy, tantalum alloy, and niobium alloy;

and wherein said Al—

Nd alloy contains 0.01 wt % to 1.00 wt % neodymium (Nd).

33. The method as claimed in claim 13, wherein said high melting point metal is selected from a group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), titanium alloy, tantalum alloy, and niobium alloy;

and wherein said Al—

Nd alloy contains 0.01 wt % to 1.00 wt % neodymium (Nd).

34. The method as claimed in claim 12, wherein said high melting point metal is selected from a group consisting of tungsten (W), titanium nitride (TiN), tungsten alloy, and titanium nitride alloy;

and wherein said Al—

Nd alloy contains 0.5 wt % to 1.0 wt % neodymium (Nd).

35. The method as claimed in claim 13, wherein said high melting point metal is selected from a group consisting of tungsten (W), titanium nitride (TiN), tungsten alloy, and titanium nitride alloy;

and wherein said Al—

Nd alloy contains 0.5 wt % to 1.0 wt % neodymium (Nd).

38. The method as claimed in claim 5, further comprising:

depositing a transparent conductive film;

wet etching said transparent conductive film, using an etchant, oxalic acid (C₂H₂O₄) to form electrodes.

39. The method as claimed in claim 37, wherein said transparent conductive film is an indium tin oxide (ITO) film that is deposited at room temperature within the atmosphere of inert gas containing water at partial pressure ranging from 2×

10<sup>−

3</sup> pa to 5×

10<sup>−

2</sup> pa.

40. The method as claimed in claim 38, wherein said transparent conductive film is an indium tin oxide (ITO) film that is deposited at room temperature within the atmosphere of inert gas containing water at partial pressure ranging from 2×

10<sup>−

3</sup> pa to 5×

10<sup>−

2</sup> pa.

41. The method as claimed in claim 37, wherein said transparent conductive film is an indium zinc oxide (IZO) film.

42. The method as claimed in claim 38, wherein said transparent conductive film is an indium zinc oxide (IZO) film.

44. The method as claimed in claim 5, further comprising:

forming a semiconductor layer;

dry etching said semiconductor layer partially to separate source and drain electrodes of the TFTs, wherein the step of dry etching uses, as etchant gas, one selected from a family of fluoride-based gas or a mixture of one selected from the family of fluoride-based gas and another selected from a family of chloride-based gas excluding hydrochloric acid (HCl).

45. The method as claimed in claim 13, further comprising:

forming a semiconductor layer underlying said triple-layered film;

wherein the step-step of dry etching for removing said triple-layered film uses, as etchant gas, one selected from a family of fluoride-based gas or a mixture of one selected from the family of fluoride-based gas and another selected from a family of chloride-based gas excluding hydrochloric acid (HCl), and

dry etching said semiconductor layer partially to separate source and drain electrodes of the TFTs, wherein the step of dry etching uses, as etchant gas, one selected from a family of fluoride-based gas or a mixture of one selected from the family of fluoride-based gas and another selected from a family of chloride-based gas excluding hydrochloric acid (HCl).