Method of producing electrooptical device and method of producing driving substrate for driving electrooptical device

• US 6,492,190 B2
• Filed: 03/02/2001
• Issued: 12/10/2002
• Est. Priority Date: 10/05/1998
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sato, Yuuichi, Yamoto, Hisayoshi, Yagi, Hajime, Yamanaka, Hideo
• Primary Examiner(s): Booth, Richard
• Application Number:
  US09/798,832
• Publication Number:
  US 20020006681A1
• Time in Patent Office: 648 Days
• Field of Search: 438/151-166, 438/30
• US Class Current: 438/30
• CPC Class Codes: C30B 13/00 Single-crystal growth by zone-melting; Refining by zone-melting C30B17/00 takes precedence; by changing the cross-section of the treated solid C30B15/00; under a protective fluid C30B27/00; for the growth of homogeneous polycrystalline material with defined structure C30B28/00
• CPC Class Codes: C30B 29/06 Silicon
• CPC Class Codes: G02F 1/13454 Drivers integrated on the active matrix substrate G02F1/136277 takes precedence
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02625 using melted materials
• CPC Class Codes: H01L 21/02628 using solutions
• 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 29/78603 characterised by the insulating substrate or support H01L29/78657 takes precedence
• CPC Class Codes: H01L 29/78609 for preventing leakage current H01L29/78618 takes precedence
• 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 29/78648 arranged on opposing sides of the channel

Abstract

A single-crystal silicon layer is formed by graphoepitaxy from a low-melting-point metal layer which contains dissolved polycrystalline or amorphous silicon, or from a melt of a silicon-containing low-melting-point metal, using step differences formed on a substrate as a seed for the epitaxial growth. This single-crystal silicon layer is used as dual-gate MOSTFTS, or bottom-gate MOSTFTS, of an electrooptical device such as an LCD integrating a display section and a peripheral-driving-circuit section. This process enables production of a uniform single-crystal silicon thin-film having high electron/hole mobility at a relatively low temperature. The display section includes LDD-nMOSTFTs or pMOSTFTs having high switching characteristics and a low leakage current. The peripheral-driving-circuit section includes cMOSTFTs, nMOSTFTs, pMOSTFTs, or a combination thereof, having high driving ability.

Claims

1. A method of producing an electrooptical device having a first substrate carrying a display section provided with pixel electrodes and a peripheral-driving-circuit section provided on a periphery of the display section, a second substrate, and an optical material disposed between the first substrate and the second substrate;

the method comprising the steps of;

a gate-forming step for forming a gate portion including a gate electrode and a gate insulating film on one face of said first substrate;

a step-forming step for forming a step difference on said one face of the first substrate;

a layer-forming step for forming a polycrystalline or amorphous silicon layer having a predetermined thickness on the first substrate having the gate portion and the step difference and then forming a low-melting-point metal layer on or under the polycrystalline or amorphous silicon layer, or of forming a low-melting-point metal layer containing silicon on the first substrate having the step difference;

a heating step for dissolving silicon of the polycrystalline or amorphous layer or of the low-melting-point metal layer into said low-melting-point metal layer by heating;

a deposition step for depositing on said first substrate a single-crystal silicon layer by allowing the silicon of said polycrystalline or amorphous silicon layer or of the low-melting-point metal layer to grow by graphoepitaxy by a cooling treatment using as a seed the step difference on the substrate;

a step for effecting a predetermined treatment on said single-crystal silicon layer, thereby forming a channel region, a source region and a drain region; and

a step for forming a first thin-film transistor of dual-gate type having the gate portions on the above and below said channel region and constituting at least part of said peripheral-driving-circuit section.

2. A method of producing an electrooptical device according to claim 1, wherein the step difference is formed as an indented section so that a cross-sectional side face is perpendicular to the bottom face or slanted to the bottom face, and the step difference is used as a seed for graphoepitaxy of the single-crystal silicon layer.

3. A method of producing an electrooptical device according to claim 1, wherein the polycrystalline or amorphous silicon layer is formed by a low-temperature deposition process and the low-melting-point metal layer is deposited thereon or thereunder, or the low-melting-point metal layer containing the silicon is deposited, followed by the heating and cooling steps.

4. A method of producing an electrooptical device according to claim 1, wherein the first substrate comprises one of a glass substrate and a heat-resistant organic substrate, and the low-melting-point metal layer comprises at least one metal selected from the group consisting of indium, gallium, tin, bismuth, lead, zinc, antimony, and aluminum.

5. A method of producing an electrooptical device according to claim 4, wherein, when the low-melting-point metal layer comprises indium, the heating step is performed in a hydrogen atmosphere at a temperature of 850 to 1,100°

C. and, when the low-melting-point metal layer comprises an indium-gallium alloy, at a temperature of 300 to 1,100°

C., whereas, when the low-melting-point metal layer comprises gallium, at a temperature of 400 to 1,100°

C.

6. A method of producing an electrooptical device according to claim 1, wherein a diffusion-barrier layer is formed on the first substrate, and the polycrystalline or amorphous silicon layer or the low-melting-point metal layer containing the silicon is formed on said diffusion barrier layer.

7. A method of producing an electrooptical device according to claim 1, wherein a Group III or V element is introduced into the polycrystalline or amorphous silicon layer or the low-melting-point metal layer containing the silicon material in the layer-forming step so as to control the type and the concentration of the impurity in the single-crystal silicon layer.

8. A method of producing an electrooptical device according to claim 1, wherein an upper gate portion having a gate insulating film and a gate electrode is formed on the deposited single-crystal silicon layer, and introducing the Group III or V element while using said upper gate portion as a mask, thereby forming said channel region, said source region and said drain region.

9. A method of producing an electrooptical device according to claim 1, wherein the step difference is formed in said first substrate and/or a film formed on the first substrate, and the first thin-film transistor is formed on at least one of the interior and the exterior of the indented section formed by the step difference.

10. A method of producing an electrooptical device according to claim 1, wherein the step difference is formed along at least one side of a device region including the channel region, the source region and the drain region of the first thin-film transistor.

11. A method of producing an electrooptical device according to claim 1, wherein said gate electrode underlying said single-crystal silicon layer is tapered at its side edges so as to form a trapezoidal shape.

12. A method of producing an electrooptical device according to claim 1, wherein the single-crystal silicon layer deposited in the depositing step is doped with a Group III or V impurity to form the channel region, the source region, and the drain region.

13. A method of producing an electrooptical device according to claim 1, wherein the peripheral-driving-circuit section further comprises at least one of a top-gate thin-film transistor, a bottom-gate thin-film transistor and a dual-gate thin-film transistor, each having a channel region of a polycrystalline or amorphous silicon layer and a gate region formed above or below the channel region, or comprises at least one of a diode, a resistor, a capacitor and an inductor, each comprising the single-crystal, polycrystalline or amorphous silicon layer.

14. A method of producing an electrooptical device according to claim 1, further comprising a switching device provided on said first substrate for switching the pixel electrodes of said display section.

15. A method of producing an electrooptical device according to claim 14, wherein the first thin-film transistor comprises at least the dual-gate type among a top-gate type having a gate section above the channel region, a bottom-gate type having a gate section below the channel region, and a dual-gate type having one gate section above and one below the channel region, and the switching device comprises one of a top-gate second thin-film transistor, a bottom-gate second thin-film transistor and a dual-gate second thin-film transistor.

16. A method of producing an electrooptical device according to claim 15, wherein when the second thin-film transistor is a bottom-gate or dual-gate type, a lower electrode of a heat-resistant material is provided below the channel region, and a gate insulating film is formed on the gate electrode to form a lower gate section, and the second thin-film transistor is formed by the same process including the step-forming step as that for the first thin-film transistor.

17. A method of producing an electrooptical device according to claim 15, wherein after the single-crystal silicon layer is formed on the lower gate section, the single-crystal silicon layer is doped with a Group III or V impurity to form the source region and the drain region, followed by an activation treatment.

18. A method of producing an electrooptical device according to claim 15, wherein source and drain regions of the first and second thin-film transistors are formed by ion implantation of the impurity through a resist mask after forming the single-crystal silicon layer, the activation treatment is performed, a gate insulating film is formed, and then a gate electrode of the first thin-film transistor and optionally an upper gate electrode of the second thin-film transistor are formed.

19. A method of producing an electrooptical device according to claim 15, wherein, when the second thin-film transistor is a top-gate type, the source region and the drain region of each of the first thin-film transistor and the second thin-film transistor are formed by ion implantation of an impurity element through a resist mask after the formation of the single-crystal silicon layer, an activation treatment is performed, and then gate sections including gate insulating films and gate electrodes of the first thin-film transistor and the second thin-film transistor are formed.

20. A method of producing an electrooptical device according to claim 15, wherein, when the thin-film transistor is the top-gate type, gate sections including gate insulating films and gate electrodes of the first thin-film transistor and the second thin-film transistor are formed after the formation of the single-crystal silicon layer, the source regions and the drain regions of the first thin-film transistor and the second thin-film transistor are formed by ion implantation of an impurity element through the gate sections and resists as masks, and then an activation treatment is performed.

21. A method of producing an electrooptical device according to claim 15, wherein thin-film transistors in the peripheral-driving-circuit section and the display section comprise n-channel, p-channel or complementary insulating-gate field-effect transistors.

22. A method of producing an electrooptical device according to claim 21, wherein the thin-film transistors in the peripheral-driving-circuit section are formed by a combination of a complementary type and an n-channel type, a combination of a complementary type and a p-channel type, or a combination of a complementary type, an n-channel type and a p-channel type thin-film.

23. A method of producing an electrooptical device according to claim 15, wherein at least a part of the thin-film transistors in the peripheral-driving-circuit section and the display section has a lightly-doped drain (LDD) structure of a single type having a LDD section between the gate and the source or drain or of a double type having LDD sections between the gate and source and between the gate and the drain.

24. A method of producing an electrooptical device according to claim 23, wherein the resist mask used when the LDD structure is formed is left unremoved and the ion implantation for forming the source region and the drain region is performed through a resist mask that covers the remaining resist mask.

25. A method of producing an electrooptical device according to claim 15, wherein the step difference is formed on one surface of the first substrate, a single-crystal, polycrystalline, or amorphous silicon layer is formed on the surface having the step difference, and the second thin-film transistor is formed to have a channel region, a source region, and a drain region constituted by the single-crystal, polycrystalline, or the amorphous silicon layer, with at least one gate section provided above and/or below the single-crystal, polycrystalline, or the amorphous silicon layer.

26. A method of producing an electrooptical device according to claim 25, wherein the thin-film transistor of said peripheral-drive-circuit section is constituted by said first thin-film transistor of the n-channel type, p-channel type or complementary type, while said thin-film transistor of said display section is of the n-channel type, p-channel type or the complementary type when said single-crystal silicon layer is used as the channel region, n-channel type, p-channel type or the complementary type when said polycrystalline silicon layer is used as the channel region, and n-channel type, p-channel type or the complementary type when said amorphous silicon layer is used as the channel region.

27. A method of producing an electrooptical device according to claim 25, wherein the step difference forms an indented section having a cross-section in which a side face is perpendicular to or slanted to the bottom face, and the step difference functions as a seed for graphoepitaxy of the single-crystal silicon layer.

28. A method of producing an electrooptical device according to claim 24, wherein source or drain electrodes of the first and/or second thin-film transistors are formed in a region including the step difference.

29. A method of producing an electrooptical device according to claim 25, wherein the step difference is formed on at least one of the first substrate and a film formed on the first substrate, and the second thin-film transistor is formed on at least one of the interior and the exterior of the indented section formed by the step difference.

30. A method of producing an electrooptical device according to claim 25, wherein at least one of the type and the concentration of a Group III or V impurity in the single-crystal, polycrystalline or amorphous silicon layer is controlled.

31. A method of producing an electrooptical device according to claim 25, wherein the step difference is formed along at least one side of a device region including the channel region, the source region and the drain region of the second thin-film transistor.

32. A method of producing an electrooptical device according to claim 25, wherein a gate electrode below the single-crystal, polycrystalline or amorphous silicon layer is tapered at its side edges to have a trapezoidal form.

33. A method of producing an electrooptical device according to claim 25, wherein a diffusion-barrier layer is provided between the first substrate and the single-crystal, polycrystalline or amorphous silicon layer.

34. A method of producing an electrooptical device according to claim 1, wherein the first substrate is one of a glass substrate and a heat-resistant organic substrate.

35. A method of producing an electrooptical device according to claim 1, wherein the first substrate is optically opaque or transparent.

36. A method of producing an electrooptical device according to claim 1, wherein the pixel electrodes are provided for a reflective or transmissive display.

37. A method of producing an electrooptical device according to claim 1, wherein the display section comprises a laminated configuration having the pixel electrodes and a color filter layer.

38. A method of producing an electrooptical device according to claim 1, wherein, when the pixel electrodes are reflective electrodes, unevenness is formed on a resin film and said pixel electrodes are provided on said resin having the unevenness and, when the pixel electrodes are transparent electrodes, the surface is planarized by a transparent planarization film and the pixel electrodes are formed on the planarized plane.

39. A method of producing an electrooptical device according to claim 14, wherein the display section is illuminated or dimmed by driving the switching device.

40. A method of producing an electrooptical device according to claim 14, wherein a plurality of the pixel electrodes are arranged in a matrix in the display section and a switching device is connected to each of the plurality of pixel electrodes.

41. A method of producing an electrooptical device according to claim 1, wherein the display section comprises one of a liquid crystal display, an electroluminescent display, a field emission display, a light-emitting polymer display, and a light-emitting diode display.