US20120033166A1

US20120033166A1 - Pixel array substrate

Info

Publication number: US20120033166A1
Application number: US12/958,408
Authority: US
Inventors: Kai-Hung Huang; Li-Wen Wang
Original assignee: Chunghwa Picture Tubes Ltd
Current assignee: Chunghwa Picture Tubes Ltd
Priority date: 2010-08-03
Filing date: 2010-12-02
Publication date: 2012-02-09
Also published as: US20120034719A1; TW201207526A; US8293549B2

Abstract

A pixel array substrate is disclosed. The reflective pixel array substrate can be made by utilizing five photo masks only. The reflective pixel array substrate includes a substrate, a thin film transistor, a reflective electrode, an insulating layer and numerous protruding bumps. The step between the protrusion bump and the substrate cause the reflective electrode thereon to have a corrugated structure. The gate electrode of the thin film transistor and the protruding bumps are made of a same conductive layer. The drain electrode connects the reflective electrode, and the drain electrode and the reflective electrode are made of a same conductive layer.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a pixel array substrate, and more particularly to a reflective pixel array substrate.
2. Description of the Prior Art
Reflection liquid crystal display devices are commonly used for portable cellular phones or intelligent terminals. In a reflection liquid crystal display, an externally entered incident light is reflected by a reflector disposed within the back light module and the reflected light is used as a display illumination light. As a result, reflection type liquid crystal display devices are more effective at achieving reduction in power consumption, thickness and weight compared with a transmitting type liquid crystal display device.
A reflection liquid crystal display device should have a display performance for displaying a bright and white display when the liquid crystal is in the light transmitting state. In order to realize this display performance, it is necessary to effectively reflect back the incident light from various directions. To achieve this, the reflection electrode on the reflective pixel array substrate is formed with a convex/concave structure.
To form a reflective pixel array substrate in the reflection liquid crystal display device requires too many fabricating steps, however. A simplified production procedure is required in order to reduce the production cost and production time.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide a reflective pixel array substrate to solve the above mentioned problems.
According to a preferred embodiment of the present invention, a reflective pixel array substrate is provided. The reflective pixel array substrate includes a substrate having at least a pixel region, the pixel region having a reflective region and an element region, a thin film transistor disposed within the element region, wherein the thin film transistor comprises: a gate electrode disposed on the substrate, a gate insulating layer covering the gate electrode and extending to the reflective region, a semiconductive layer disposed on the gate insulating layer and overlapping the gate electrode, a source electrode and a drain electrode disposed on the semiconductive layer and the gate insulating layer and a plurality of protruding bumps disposed on the substrate within the reflective region and the gate insulating layer covering the protruding bumps, wherein the protruding bumps are floating, a reflective electrode disposed on the gate insulating layer, and connecting to the drain electrode, the reflective electrode extending from the drain electrode to the reflective region, wherein the reflective electrode within the reflective region overlaps with the protruding bumps so that the surface of the reflective electrode forms a corrugated structure, an insulating layer covering the reflective region and a plurality of first openings disposed in the insulating layer, wherein the reflective electrode disposed directly above each of the protruding bumps is exposed through the first openings.
The reflective pixel array substrate of the present invention is compatible with current processes. Furthermore, the reflective pixel array substrate has protruding bumps to make corrugated structure on the surface of the reflective electrode. Therefore, the light reflected from the reflective electrode can become uniform.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 4C show a method of fabricating a reflective pixel array substrate according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION

FIGS. 1A to 4C show a method of fabricating a reflective pixel array substrate according to a first preferred embodiment of the present invention. FIG. 1A shows a top view of a first preferred embodiment of the present invention. FIG. 1B is a sectional view of FIG. 1A taken along the line G-G′. FIG. 1C is a sectional view of FIG. 1A taken along the line K-K′.
As shown in FIGS. 1A, 1B and 1C, first a substrate 10 having an active region 12 and at least one peripheral circuit region 14 is provided. The peripheral circuit region 14 is disposed at an edge of the active region 12. At least one pixel region 16 is disposed in the active region 12. The pixel region 16 can be divided into a reflective region 18 and an element region 20. For the sake of brevity, only one pixel region 16 is described in the detailed description. Please note, however, that there could be numerous pixel regions in the active region 12, and each of the pixel regions can be divided into an element region and a reflective region. The substrate 10 can be glass, plastic, quartz or other suitable materials.
Next, a conductive layer 22 is formed on the substrate 10. Then, a first photo mask (not shown) is utilized to perform a lithography and development process and the conductive layer 22 is patterned to form a gate line 24, a gate electrode 26, a common line 28, and protruding bumps 30 on the substrate 10. The gate electrode 26 and the common line 28 are disposed within the element region 20 of the pixel region 16. The protruding bumps 30 are disposed within the reflective region 18 of the pixel region 16. Additionally, the gate line 24 extends from the element region 20 to the peripheral circuit region 14.
The conductive layer 22 may be a metal layer made of Al, Cr, Mo, W, Ta, Cu or an alloy of the combination thereof. The conductive layer 22 may be a non metal layer such as indium tin oxide (ITO) or zinc oxide (ZnO). Furthermore, each of the protruding bumps 30 is individual and separate from each other. Each of the protruding bumps 30 is floating. Moreover, the shape of each of the protruding bumps 30 may be polygonal, circular or oval-shaped, but is not limited to these shapes. It is noteworthy that the gate line 24, the gate electrode 26, the common line 28 and the protruding bumps 30 are formed by utilizing one photo mask.
Please refer to FIGS. 2A, 2B and 2C. FIG. 2A shows a top view of a first preferred embodiment of the present invention. FIG. 2B is a sectional view of FIG. 2A taken along the line G-G′. FIG. 2C is a sectional view of FIG. 2A taken along the line K-K′. As shown in FIGS. 2A, 2B, and 2C, a gate insulating layer 32 is formed to cover the element region 20, the reflective region 18, and the peripheral circuit region 14 entirely. The gate insulating layer 32 conformally covers the substrate 10, the gate line 24, the gate electrode 26, the common line 28 and each of the protruding bumps 30. Because the gate insulating layer 32 covers each protruding bump 30 conformally, the surface of the gate insulating layer 32 will go up and down with the protruding bumps 30. The gate insulating layer 32 may be silicon oxide, silicon nitride, or silicon oxynitride, but is not limited to these materials. Then, a semiconductive layer 34 is formed on the gate insulating layer 32. After that, a second photo mask (not shown) is utilized during a lithographic and development process, and is followed by an etching process to pattern the semiconductive layer 34. After these processes, the patterned semiconductive layer 34 is positioned corresponds to the gate electrode 26.
Please refer to FIGS. 3A to 3B. FIG. 3A shows a top view of a first preferred embodiment of the present invention. FIG. 3B is a sectional view of FIG. 3A taken along the line G-G′. As shown in FIG. 3A to FIG. 3B. a conductive layer 36 is formed on the substrate 10 to cover the active region 12 and the peripheral circuit region 14. The conductive layer 36 covers the semiconductive layer 34 and the gate insulating layer 32 conformally. Then, a third photo mask (not shown) is utilized during a lithographic and development process, which is followed by an etching process to pattern the conductive layer 36. After the etching process, the conductive layer 36 within the peripheral region 14 is removed, and a source line 38, a source electrode 40, a drain electrode 42 and a reflective electrode 44 are formed. The source line 38, the source electrode 40 and the drain electrode 42 are disposed within the element region 20. The reflective electrode 44 connects to the drain electrode 42 and the reflective electrode 44 extends from the element region 20 to the reflective region 18.
It is noteworthy that the reflective electrode 44 within the reflective region 18 overlaps with each of the protruding bumps 30. The surface of the gate insulating layer 32 below the reflective electrode 44 goes up and down because a step is between each of the protruding bumps 30 and the substrate 10. Therefore, the surface of the reflective electrode 44 in the reflective region 18 forms a corrugated structure 46, or a convex/concave structure. The corrugated structure 46 can thereby reflect an incident light illuminating the corrugated structure in a plurality of reflective angles. This allows the reflected light to be a uniform light source for a back light module. In addition, the reflective electrode 44, the source line 38, the source electrode 40 and the drain electrode 42 are formed by the same photo mask.
Please refer to FIGS. 4A, 4B and 4C. FIG. 4A shows a top view of a first preferred embodiment of the present invention. FIG. 4B is a sectional view of FIG. 4A taken along the line G-G′. FIG. 4C is a sectional view of FIG. 4A taken along the line K-K′. As shown in FIGS. 4A, 4B and 4C, an insulating layer 48 is formed to cover the pixel region 16 and the peripheral circuit region 14. That is, the insulating layer 48 covers the entire substrate 10. Then, a fourth photo mask (not shown) is utilized during a lithographic and development process, which is followed by an etching process to pattern the insulating layer 48 within the reflective region 18 so as to form numerous openings 52. The reflective layer 44 directly above each protruding bump 30 within the reflective region 18 is exposed through the openings 52. After utilizing the fourth photo mask, the insulating layer 32 and the gate insulating layer 48 are patterned to form an opening 54 exposing part of the gate line 24.
According to a preferred embodiment, the insulating layer 48 may be silicon nitride. Additionally, the insulating layer 48 surrounding the reflective electrode 44 within the reflective region 18 can reflect the light illuminating the insulating layer 48 toward the reflective electrode 44. Next, a conductive layer 56 is formed entirely within the active region 12 and the peripheral region 14. Then, a fifth photo mask (not shown) is utilized during a lithographic and development process, and followed by an etching process to pattern the conductive layer 56 for removing the conductive layer 56 within the active region 12 and removing part of the conductive layer 56 within the peripheral circuit region 14. Only the conductive layer 56 in the opening 54 and around the opening 54 remains. This enables the conductive layer 56 within the peripheral region 14 to connect to the gate line 24 electrically. Moreover, the gate line 24 covered by the conductive layer 56 can be kept from being oxidized. The conductive layer 56 preferably is ITO. At this point, the reflective pixel array substrate is completed.
The present invention also provides a reflective pixel array substrate. Please refer to FIGS. 4A and 4B, FIG. 4A depicts a top view of a reflective pixel array substrate according to a second preferred embodiment of the present invention. FIG. 4B is a sectional view of FIG. 4A taken along the line G-G′. FIG. 4C is a sectional view of FIG. 4A taken along the line K-K′. As shown in FIGS. 4A, 4B and 4C, the reflective pixel array substrate 100 includes a substrate 10 having an active region 12 and at least one peripheral circuit region 14. The peripheral circuit region 14 is disposed on at least one edge of the active region 12. At least one pixel region 16 is disposed in the active region 12. The pixel region 16 is divided into a reflective region 18 and an element region 20. For the sake of brevity, only one pixel region 16 is described in the detailed description. Please note, however, that there could be numerous pixel regions in the active region 12, and each of the pixel regions 16 can be divided into an element region 20 and a reflective region 18. The substrate 10 can be glass, plastic, quartz or other suitable material.
In addition, a thin film transistor 58 is disposed within the element region 20, wherein the thin film transistor 58 includes a gate electrode 26 disposed on the substrate 10. A gate insulating layer 32 covers the gate electrode 26 and extends from the element region 20 to the reflective region 18 and the peripheral circuit region 14. A semiconductive layer 34 is disposed on the gate insulating layer 32 and overlaps with the gate electrode 26. A source electrode 40 and a drain electrode 42 are both disposed on the semiconductive layer 34 and on the gate insulating layer 32. Moreover, a gate line 24 connects to the gate electrode 26 and extends from the element region 20 to the peripheral circuit region 14. The gate insulating layer 32 extends from the element region 20 to the peripheral region 14 and covers the gate line 24. A common line 28 is disposed in the element region 20.
The reflective pixel array substrate 100 further includes numerous protruding bumps 30 disposed within the reflective region 18 of the substrate 10. The gate insulating layer 32 extends from the element region 20 to the reflective region 18 and covers each of the protruding bumps 30. Each of the protruding bumps 30 is floating and is disposed individually. That is, the protruding bumps 30 do not connect with each other. A reflective electrode 44 is disposed on the gate insulating layer 32 and connects to the drain electrode 42. The reflective electrode 44 extends from the element region 20 to the reflective region 18. It is noteworthy that a step is between each protruding bump 30 and the substrate 10 so that the gate insulating layer 32 on the protruding bumps 30 and the substrate 10 goes up and down with the step profile. The reflective electrode 44 covering on the gate insulating layer 32 therefore forms a corrugated structure 46. The light illuminated on the corrugated structure 46 can be reflected into numerous reflective angles so the reflected light can form a uniform light source. Additionally, please refer to FIG. 1A, which shows each of the protruding bumps 30, the gate line 24, the gate electrode 26 and the common line 28 are formed by the same conductive layer 22. Moreover, please refer to FIGS. 4A and 4B, which shows an insulating layer 48 covers the pixel region 16 including the thin film transistor 58 and the reflective electrode 44 therein. The insulating layer 48 also covers the peripheral circuit region 14 including the gate insulating layer 32 therein. The insulating layer 48 within the reflective region 18 has numerous openings 52 that expose the reflective electrode 44 directly above each protruding bump 30. At least one opening 54 is disposed in the gate insulating layer 32 and the insulating layer 48 within the peripheral circuit region 14. Part of the gate line 24 is exposed through the opening 54. A conductive layer 56 fills in the opening 54. The conductive layer 56 also covers the insulating layer 48 within the peripheral circuit region 14 and covers the gate line 24 exposed through the opening 54. The conductive layer 56 could be ITO.
To sum up, the method of fabricating the reflective pixel array substrate is compatible with current fabricating processes. The gate electrode and the protruding bumps of the reflective pixel array substrate are formed by utilizing the same photo mask. The reflective electrode, the source electrode, and the drain electrode are formed by using the same photo mask. Therefore, the fabricating process of the reflective pixel array substrate only needs five photo masks so the process is simplified and the production cost can be reduced.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.

Claims

1. A reflective pixel array substrate, comprising:

a substrate having at least a pixel region, the pixel region having a reflective region and an element region;

a thin film transistor disposed within the element region, wherein the thin film transistor comprises:

a gate electrode disposed on the substrate;

a gate insulating layer covering the gate electrode and extending to the reflective region;

a semiconductive layer disposed on the gate insulating layer and overlapping the gate electrode;

a source electrode and a drain electrode disposed on the semiconductive layer and the gate insulating layer; and

a plurality of protruding bumps disposed on the substrate within the reflective region and the gate insulating layer covering the protruding bumps, wherein the protruding bumps are floating;

a reflective electrode disposed on the gate insulating layer, and connecting to the drain electrode, the reflective electrode extending from the drain electrode to the reflective region, wherein the reflective electrode within the reflective region overlaps with the protruding bumps so that the surface of the reflective electrode forms a corrugated structure;

an insulating layer covering the reflective region; and

a plurality of first openings disposed in the insulating layer, wherein the reflective electrode disposed directly above each of the protruding bumps is exposed through the first openings.

2. The reflective pixel array substrate of claim 1, wherein the gate electrode and the protruding bumps are formed by a same layer of a conductive layer.

3. The reflective pixel array substrate of claim 1, wherein the substrate further comprises:

a peripheral circuit region;

a gate line connecting to the gate electrode, the gate line extending from the element region to the peripheral circuit region, wherein the gate insulating layer and the insulating layer cover the gate line in sequence;

a second opening disposed in the gate insulating layer and the insulating layer, wherein the gate line within the peripheral circuit region is exposed through the second opening; and

a conductive layer filling in the second opening and covering the insulating layer within the peripheral circuit region and covering the gate line exposed through the second opening.

4. The reflective pixel array substrate of claim 1, wherein the shape of each of the protruding bumps comprises polygonal, circular or oval-shaped.

5. The reflective pixel array substrate of claim 1, wherein the protruding bumps are floating.

6. The reflective pixel array substrate of claim 1, wherein each of the protruding bumps is separate from each other.

7. The reflective pixel array substrate of claim 1, wherein the reflective electrode connects to the drain electrode electrically.

8. The reflective pixel array substrate of claim 1, wherein light illuminates the corrugated structure, and is reflected in a plurality of reflective angles.