Thin film transistor substrate and method for manufacturing the same

• US 10,050,059 B2
• Filed: 09/01/2016
• Issued: 08/14/2018
• Est. Priority Date: 07/07/2014
• Status: Active Grant

• Current Assignee: Trivale Technologies, LLC (Vector Capital Corporation)
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Inoue, Kazunori, Oda, Koji, Tsumura, Naoki
• Primary Examiner(s): Sandvik, Benjamin
• Assistant Examiner(s): ASSOUMAN, HERVE-LOUIS Y
• Application Number:
  US15/254,636
• Publication Number:
  US 20160372501A1
• Time in Patent Office: 712 Days
• Field of Search: None
• CPC Class Codes: G02F 1/134372 for fringe field switching [FFS] where the common electrode is not patterned
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/136231 for reducing the number of lithographic steps
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• CPC Class Codes: H01L 21/441 Deposition of conductive or insulating materials for electrodes
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• 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 29/24 including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22 including organic materials H10K99/00
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

A thin film transistor substrate includes: a gate insulating film that covers a gate electrode and a common electrode; a transparent oxide film selectively disposed on the gate insulating film; a source electrode and a drain electrode that are spaced from each other on the transparent oxide film; and a light transmissive pixel electrode electrically connected to the drain electrode. The transparent oxide film includes a conductive region and a semiconductor region. The conductive region is disposed in a lower portion of the source electrode and the drain electrode and disposed in a portion that continues from the lower portion of the drain electrode, extends to part of an upper portion of the common electrode, and forms the pixel electrode. The semiconductor region is disposed in a portion corresponding to a lower layer in a region between the source electrode and the drain electrode.

Claims

1. A method for manufacturing a thin film transistor substrate including a plurality of pixels arranged in matrix, said method comprising the steps of:

(a) selectively forming a gate electrode and a common electrode on a substrate;

(b) forming a gate insulating film to cover said gate electrode and said common electrode;

(c) selectively forming a transparent oxide film on said gate insulating film; and

(d) forming a source electrode and a drain electrode spaced from each other on said transparent oxide film, forming a light transmissive pixel electrode electrically connected to said drain electrode, and oxidizing a portion of said transparent oxide film corresponding to a lower layer in a region between said source electrode and said drain electrode to form a semiconductor region that serves as a channel region of a thin film transistor, wherein said step (d) includes the step of forming said source electrode, said drain electrode, and said pixel electrode using a plurality of resist patterns that are formed in one photolithography process and include a complex resist pattern having a plurality of different film thicknesses, said complex resist pattern has a pattern in which a film thickness in a portion where said source electrode and said drain electrode are formed is larger than a film thickness in a portion where said pixel electrode is formed, and wherein said step (d) includes a step of performing ashing with O2 gas plasma on said plurality of resist patterns to reduce the film thickness of said plurality of resist patterns, and oxidizing the portion of said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region.

2. The method for manufacturing a thin film transistor substrate according to claim 1, wherein said step (d) includes the steps of:

(d-1) forming a conductive film on an entire surface of said substrate including on said transparent oxide film and forming the plurality of resist patterns including the complex resist pattern that has the plurality of different film thicknesses on said conductive film by halftone exposure;

(d-2) performing first patterning on said conductive film using said plurality of resist patterns and removing said conductive film that contains an upper portion of a portion corresponding to said channel region and is not covered with said plurality of resist patterns;

(d-3) performing said ashing with said O2 gas plasma on said plurality of resist patterns to reduce the film thicknesses of said plurality of resist patterns and said oxidizing the portion of said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region after the step (d-2); and

(d-4) performing second patterning on said conductive film using said plurality of resist patterns after the ashing to form said source electrode and said drain electrode and removing said conductive film on said transparent oxide film continuing from a lower portion of said drain electrode to form said pixel electrode.

3. A method for manufacturing a thin film transistor substrate including a plurality of pixels arranged in matrix, said method comprising the steps of:

(a) selectively forming a gate electrode and a common electrode on a substrate;

(b) forming a gate insulating film to cover said gate electrode and said common electrode;

(c) forming a transparent oxide film on said gate insulating film; and

(d) forming a source electrode and a drain electrode spaced from each other on said transparent oxide film, patterning said transparent oxide film to form a light transmissive pixel electrode electrically connected to said drain electrode, and oxidizing a portion of said transparent oxide film corresponding to a lower layer in a region between said source electrode and said drain electrode to form a semiconductor region that serves as a channel region of a thin film transistor, wherein said step (d) includes the step of forming said source electrode, said drain electrode, and said pixel electrode using a plurality of resist patterns that are formed in one photolithography process and include a complex resist pattern having a plurality of different film thicknesses, said complex resist pattern has a pattern in which a film thickness in a portion where said source electrode and said drain electrode are formed is larger than a film thickness in a portion where said pixel electrode is formed, and wherein said step (d) includes a step of performing ashing with O2 gas plasma on said plurality of resist patterns to reduce the film thickness of said plurality of resist patterns, and oxidizing the portion of said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region.

4. The method for manufacturing a thin film transistor substrate according to claim 3, wherein said step (d) includes the steps of:

(d-1) forming a conductive film on an entire surface of said substrate including on said transparent oxide film and forming the plurality of resist patterns including the complex resist pattern that has the plurality of different film thicknesses on said conductive film by halftone exposure;

(d-2) patterning said conductive film and said transparent oxide film using said plurality of resist patterns and removing said conductive film and said transparent oxide film that are not covered with said plurality of resist patterns;

(d-3) performing first ashing with O₂ gas plasma on said plurality of resist patterns to reduce the film thicknesses of said plurality of resist patterns and to remove a portion with the thinnest film thickness of said complex resist pattern on a portion corresponding to said channel region after said step (d-2);

(d-4) patterning said conductive film using said plurality of resist patterns after said first ashing and removing said conductive film on the portion corresponding to said channel region;

(d-5) performing said ashing as second ashing with the O2 gas plasma on said plurality of resist patterns to further reduce the film thicknesses of said plurality of resist patterns, and said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region; and

(d-6) patterning said conductive film using said plurality of resist patterns after said second ashing to form said source electrode and said drain electrode and removing said conductive film on said transparent oxide film continuing from a lower portion of said drain electrode to form said pixel electrode.

5. The method for manufacturing a thin film transistor substrate according to claim 4, wherein said step (d-1) forms said plurality of resist patterns such that a source wiring extending from said source electrode and said transparent oxide film below the source wiring are left.

6. A method for manufacturing a thin film transistor substrate including a plurality of pixels arranged in matrix, said method comprising the steps of:

(a) selectively forming a gate electrode and a common electrode on a substrate;

(b) forming a gate insulating film to cover said gate electrode and said common electrode;

(c) forming a laminated film of a transparent oxide film and an n-type Si film containing an n-type impurity on said gate insulating film; and

(d) forming a source electrode and a drain electrode spaced from each other on said n-type Si film, forming a light transmissive pixel electrode electrically connected to said drain electrode, and oxidizing a portion of said transparent oxide film corresponding to a lower layer in a region between said source electrode and said drain electrode to form a semiconductor region that serves as a channel region of a thin film transistor,

wherein said step (d) includes the step of forming said source electrode, said drain electrode, and said pixel electrode using a plurality of resist patterns that are formed in one photolithography process and include a complex resist pattern having a plurality of different film thicknesses,

said complex resist pattern has a pattern in which a film thickness in a portion where said source electrode and said drain electrode are formed is larger than a film thickness in a portion where said pixel electrode is formed, and

wherein said step (d) includes a step of performing ashing with O2 gas plasma on said plurality of resist patterns to reduce the film thickness of said plurality of resist patterns, and oxidizing the portion of said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region.

7. The method for manufacturing a thin film transistor substrate according to claim 6, wherein said step (d) includes the steps of:

(d-1) forming a conductive film on an entire surface of said substrate including on said n-type Si film and forming the plurality of resist patterns including the complex resist pattern that has the plurality of different film thicknesses on said conductive film by halftone exposure;

(d-2) patterning said conductive film, said n-type Si film, and said transparent oxide film using said plurality of resist patterns and removing said conductive film, said n-type Si film, and said transparent oxide film that are not covered with said plurality of resist patterns;

(d-3) performing first ashing with O₂ gas plasma on said plurality of resist patterns to reduce the film thicknesses of said plurality of resist patterns and to remove a portion with the thinnest film thickness of said complex resist pattern on a portion corresponding to said channel region after said step (d-2);

(d-4) patterning said conductive film and said n-type Si film using said plurality of resist patterns after said first ashing and removing said conductive film and said n-type Si film on the portion corresponding to said channel region;

(d-5) performing said ashing as second ashing with the O2 gas plasma on said plurality of resist patterns to further reduce the film thicknesses of said plurality of resist patterns, and said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region; and

(d-6) patterning said conductive film and said n-type Si film using said plurality of resist patterns after said second ashing to form said source electrode and said drain electrode and removing said conductive film and said n-type Si film on said transparent oxide film continuing from a lower portion of said drain electrode to form said pixel electrode.

8. The method for manufacturing a thin film transistor substrate according to claim 7, wherein said step (d-1) forms said plurality of resist patterns such that a source wiring extending from said source electrode and said n-type Si film and said transparent oxide film below the source wiring are left.

9. The method for manufacturing a thin film transistor substrate according to claim 6, wherein

said step (c) includes the step of selectively forming the laminated film of said transparent oxide film and said n-type Si film, and

said step (d) includes the steps of:

(d-1) forming a conductive film on an entire surface of said substrate including on said n-type Si film and forming the plurality of resist patterns including the complex resist pattern that has the plurality of different film thicknesses on said conductive film by halftone exposure;

(d-2) performing first patterning on said conductive film and said n-type Si film using said plurality of resist patterns and removing said conductive film and said n-type Si film that include an upper portion of a portion corresponding to said channel region and are not covered with said plurality of resist patterns;

(d-3) performing said ashing with said O2 gas plasma on said plurality of resist patterns to reduce the film thicknesses of said plurality of resist patterns, and said oxidizing the portion of said transparent oxide film corresponding to the lower layer in the region between said source electrode and said drain electrode to form said semiconductor region after said step (d-2); and

(d-4) performing second patterning on said conductive film and said n-type Si film using said plurality of resist patterns after the ashing to form said source electrode and said drain electrode and removing said conductive film and said n-type Si film on said transparent oxide film continuing from a lower portion of said drain electrode to form said pixel electrode.