US20190067335A1

US20190067335A1 - Manufacturing method of pixel structure

Info

Publication number: US20190067335A1
Application number: US16/178,606
Authority: US
Inventors: Hsi-Ming Chang; Yen-Yu Huang
Original assignee: Chunghwa Picture Tubes Ltd
Current assignee: Chunghwa Picture Tubes Ltd
Priority date: 2015-08-18
Filing date: 2018-11-02
Publication date: 2019-02-28
Also published as: US10153302B2; CN106469739A; US20170053945A1

Abstract

A method for manufacturing a pixel structure is provided. A patterned semiconductor material layer, an insulation material layer, and a gate electrode material layer are formed in sequence on a substrate to form a stacked structure. A patterned photoresist layer is formed on the stacked structure by using a photomask. A portion of the stacked structure is removed to pattern the patterned semiconductor material layer into a patterned semiconductor layer by using the patterned photoresist layer as a mask. Another portion of the stacked structure is etched by using a portion of the patterned photoresist layer as a mask until a portion of the semiconductor layer in the stacked structure is exposed. Then, an exposed portion of the semiconductor layer is modified to increase a conductivity of the exposed portion of the semiconductor layer. Finally, the patterned photoresist layer is removed. A pixel structure manufactured by the method is provided.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser. No. 14/829,179, filed on Aug. 18, 2015, now allowed. The entirety of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Field of the Invention

The invention relates to a pixel structure and a manufacturing method thereof. In particular, the invention relates to a pixel structure with a patterned oxide semiconductor layer.

Description of Related Art

In general, the conventional manufacturing process of a pixel structure having an oxide semiconductor layer substantially involves six masking steps. With the first masking step, a gate electrode is formed on a substrate. Then, a gate insulating layer is comprehensively formed on the substrate for covering the gate electrode. Next, with the second masking step, an oxide semiconductor layer is formed on the gate insulating layer above the gate electrode. Furthermore, with the third masking step, an etching stop layer is formed on a portion of the oxide semiconductor layer. Afterward, a metal layer is formed on the etching stop layer; and with the fourth masking step, a source electrode and a drain electrode, which are electrically insulated with each other, are separately defined on two sides of the etching stop layer. Then, an insulating layer is formed on the substrate for covering the source electrode and the drain electrode. After that, with the fifth masking step, a contact window is formed on the insulating layer in order to expose the drain electrode. Finally, with the sixth masking step, a pixel electrode is formed on the substrate, and this pixel electrode fills up the contact window and is electrically connected with the drain electrode. At this point, the manufacturing of the pixel structure having the oxide semiconductor layer is completed. Nevertheless, the abovementioned manufacturing process of the pixel structure is complicated, and has high production costs.

SUMMARY OF THE INVENTION

The invention is to provide a pixel structure and a manufacturing method thereof, capable of reducing production costs and simplifying the manufacturing process by reducing the number of masks.
The invention provides a method of forming a pixel structure. The method includes the following steps. A patterned semiconductor material layer, an insulation material layer, and a gate electrode material layer are formed in sequence on a substrate to form a stacked structure. Next, a patterned photoresist layer is formed on the stacked structure by using a photomask. The patterned photoresist layer comprises a first thickness portion covering a first portion of the stacked structure and a second thickness portion covering a second portion of the stacked structure, and the patterned photoresist layer exposes a third portion of the stacked structure. The third portion of the stacked structure is removed to pattern the patterned semiconductor material layer into a patterned semiconductor layer by using the patterned photoresist layer as a mask. The first thickness portion of the patterned photoresist layer is then removed and the second thickness portion of the patterned photoresist layer is thinned to expose the first portion of the stacked structure previously covered by the first thickness portion of the patterned photoresist layer. Next, the first portion of the stacked structure is etched by using the thinned second thickness portion of the patterned photoresist layer as a mask until an exposed portion of the patterned semiconductor layer in the first portion of the stacked structure is exposed. The gate electrode material layer is patterned into a gate electrode layer, and the insulation material layer is patterned into an insulation layer having a shape substantially conformal to the gate electrode layer and covering a covered portion of the patterned semiconductor layer. Then, the exposed portion of the patterned semiconductor layer is modified to increase a conductivity of the exposed portion of the patterned semiconductor layer. The thinned second thickness portion of the patterned photoresist layer is then removed. The covered portion of the patterned semiconductor layer includes a channel, and the exposed portion of the patterned semiconductor layer includes a source and a drain. The gate electrode layer includes a gate above the channel, and the gate, the channel, the source and the drain form a thin film transistor structure.
In an embodiment of the invention, the method further includes forming a patterned metal layer on the substrate prior to forming the stacked structure. The patterned metal layer includes a data line electrically connected to the source.
In an embodiment of the invention, the patterned semiconductor material layer has an opening exposing a portion of the data line and the patterned semiconductor layer patterned from the patterned semiconductor material layer includes a semiconductor portion and has a separating gap corresponding to the opening, such that the insulation layer patterned from the insulation material layer has a insulation portion filling the separating gap and contacting the portion of the data line and the semiconductor portion is electrically insulating to the data line.
In an embodiment of the invention, removing the first thickness portion of the patterned photoresist layer and the thinning the second thickness portion of the patterned photoresist layer includes performing an ashing process.
In an embodiment of the invention, the forming the patterned photoresist layer on the stacked structure includes using one half-tone photomask or one gray-tone photomask to form the first thickness portion and the second thickness portion.
In an embodiment of the invention, modifying the exposed portion of the patterned semiconductor layer includes performing a plasma treatment, an ion implanting, or a combination thereof.
In an embodiment of the invention, a processing gas of the plasma treatment includes hydrogen gas.
In an embodiment of the invention, removing the second thickness portion includes performing a stripping process.
In an embodiment of the invention, the method further includes forming a pixel electrode electrically connected to the drain.
In an embodiment of the invention, the formation of the pixel electrode is simultaneous to the formation of the source and the drain.
In an embodiment of the invention, the pixel electrode is formed by modifying the exposed portion of the patterned semiconductor layer.
The invention further provides a pixel structure. The pixel structure includes a pixel electrode, disposed on a substrate, a thin film transistor structure, and an insulation layer. The thin film transistor structure is disposed on the substrate and connected to the pixel electrode. The thin film transistor structure includes a source, a drain and a channel formed by a patterned semiconductor layer and a gate formed by a gate electrode layer. The source and the drain are located on two opposite sides of the channel, and the gate is located above the channel. The insulation layer is interposed between the patterned semiconductor layer and the gate electrode layer and has a shape substantially conformal to the gate electrode layer. The insulation layer covers an covered portion of the patterned semiconductor layer to form the channel and exposes an exposed portion of the patterned semiconductor layer to form the source and the drain.
In an embodiment of the invention, a material of the patterned semiconductor layer includes an oxide semiconductor material.
In an embodiment of the invention, the covered portion of the patterned semiconductor layer has a first conductivity type and the exposed portion of the patterned semiconductor layer has a second conductivity type more conductive than the first conductivity type.
In an embodiment of the invention, the exposed portion of the patterned semiconductor layer further includes the pixel electrode.
In an embodiment of the invention, the pixel structure further includes a data line disposed on the substrate, located between the patterned semiconductor layer and the substrate, and electrically connected to the source of the thin film transistor structure.
In an embodiment of the invention, the gate electrode layer further includes a gate line electrically connected to the gate of the thin film transistor structure. The insulation layer includes an insulation portion underlying the gate line. The patterned semiconductor layer further includes a semiconductor portion underlying the gate line, and the gate line, the insulation portion and the semiconductor portion form a gate line structure crossing over the data line.
In an embodiment of the invention, the patterned semiconductor layer has a separating gap exposing a portion of the data line, and the insulation portion fills the separating gap and contacts the portion of the data line. In addition, the semiconductor portion is electrically insulating to the data line.
In an embodiment of the invention, a portion of the source is in direct contact with the data line to electrically connect to the data line.
In an embodiment of the invention, the pixel structure further includes a patterned metal portion disposed on the substrate, located and electrically connected between the drain and the pixel electrode. A material of the patterned metal portion and the data line is the same.
Based on the above, in the manufacturing process of the pixel structure of the invention, the patterned photoresist layer is patterned to have a first thickness portion and a second thickness portion by using a photomask, and the following processes of forming the pixel structure use the patterned photoresist layer as a mask for forming multiple elements, such as the channel, the source, the drain, the gate and the gate insulation layer. Therefore, this allows the manufacture of the pixel structure of the invention to reduce the amount of photomasks required. Thus, the manufacturing cost of the pixel structure of the invention can be effectively lowered. Furthermore, in the pixel structure, the source and drain are electrically contacted with the channel without contact holes. In addition, the drain is electrically contacted with the pixel electrode without contact holes. The pixel structure according to the embodiment of the present invention has an improved resolution or aperture ratio. In addition, not requiring contact holes also saves space in the thin film transistor layout that utilizes the pixel structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1A to FIG. 12A are schematic top views illustrating the manufacture process of a pixel structure according to an embodiment of the invention.

FIG. 1B to FIG. 12B are schematic cross-sectional views respectively taken along line A-A′ in the corresponding FIG. 1A to FIG. 12A.

FIG. 12C is a schematic cross-sectional view taken along line B-B′ in the corresponding FIG. 12A.

FIG. 13A to FIG. 24A are schematic top views illustrating the manufacture process of a pixel structure according to another embodiment of the invention.

FIG. 13B to FIG. 24B are schematic cross-sectional views respectively taken along line A-A′ in the corresponding FIG. 13A to FIG. 24A.

FIG. 24C is a schematic cross-sectional view taken along line B-B′ in the corresponding FIG. 24A.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
FIG. 1A to FIG. 12A are schematic top views illustrating the manufacture process of a pixel structure according to an embodiment of the invention. FIG. 1B to FIG. 12B are schematic cross-sectional views respectively taken along line A-A′ in the corresponding FIG. 1A to FIG. 12A. It should be noted that in FIG. 1A to FIG. 12A, if a boundary of a layer substantially overlaps with another layer, the schematic top views only label the top most layer. Thus, FIG. 1A to FIG. 12A have omitted the references for some of the components. Please refer to the corresponding schematic cross-sectional views (i.e., FIG. 1B to FIG. 12B) at the same time. The following uses FIG. 1A to FIG. 12A and FIG. 1B to FIG. 12B to describe the manufacture process of the pixel structure of an embodiment of the invention.
Referring to FIG. 1A and FIG. 1B, a metal layer (not shown) is first formed on a substrate 110. Next, the metal layer is patterned to form a patterned metal layer 120 on the substrate 110. The patterned metal layer includes a first metal portion 120 a, a second metal portion 120 b, and a data line 120 c. The first metal portion 120 a branches off of the data line 120 c. A material of the patterned metal layer 120 is, for example, molybdenum, aluminum, titanium, indium tin oxide, or a combination thereof. However, the invention is not limited thereto.
Referring to FIG. 2A and FIG. 2B, a patterned semiconductor material layer 130 is formed on the substrate 110. Particularly, the patterned semiconductor material layer 130 has an opening 130A exposing a portion of the data line 120 c. A material of the patterned semiconductor material layer 130 is an oxide semiconductor material. For example, the material of the patterned semiconductor material layer 130 may be indium gallium zinc oxide, indium zinc oxide, indium gallium oxide, zinc oxide, tin oxide, gallium zinc oxide, zinc tin oxide, or indium tin oxide. However, the invention is not limited thereto. In addition, the opening 130A can be formed by performing a lithography-etching process.
Referring to FIG. 3A and FIG. 3B, an insulation material layer 140 is formed on the patterned semiconductor material layer 130. A material of the insulation material layer 140 is for example, silicon dioxide. However, the invention is not limited thereto.
Referring to FIG. 4A and FIG. 4B, a gate electrode material layer 150 is formed on the insulation material layer 140. A material of the gate electrode material layer 150 is for example, molybdenum, aluminum, titanium, or a combination thereof. However, the invention is not limited thereto.
Thus, it can be seen that the patterned semiconductor material layer 130, the insulation material layer 140, and the gate electrode material layer 150 are formed in sequence on the substrate 110 to form a stacked structure 152.
Referring to FIG. 5A and FIG. 5B, a photoresist layer 160 is formed on the gate electrode material layer 150 by using a photosensitive material.
Referring to FIG. 6A and FIG. 6B, a photomask 162 is used to pattern the photoresist layer 160. The photomask 162 includes a first mask pattern 162 a, a second mask pattern 162 b, and a third mask pattern 162 c with different transparencies. The transparency of the second mask pattern 162 b is, for example, between the transparencies of the first mask pattern 162 a and the third mask pattern 162 c. In further detail, the first mask pattern 162 a is, for example, completely transparent, the third mask pattern 162 c is, for example, not transparent, and the second mask pattern 162 b has a transparency between the first mask pattern 162 a and the third mask pattern 162 c. The photomask 162 may be a half-tone photomask or a gray-tone photomask. However, the invention is not limited thereto. Any suitable type of photomask to pattern the photoresist layer 160 can be utilized.
Referring to FIG. 7A and FIG. 7B, the photoresist layer 160 is patterned to form a patterned photoresist layer 164. The patterned photoresist layer 164 includes a first thickness portion 164 a and a second thickness portion 164 b. The first thickness portion 164 a corresponds to the second mask pattern 162 b of the photomask 162 and covers a first portion 152 a of the stacked structure 152. The second thickness portion 164 b corresponds to the third mask pattern 162 c of the photomask 162 and covers a second portion 152 b of the stacked structure 152. A third portion 152 c of the stacked structure 152 is exposed by the patterned photoresist layer 164, wherein the third portion 152 c of the stacked structure 152 corresponds to the first mask pattern 162 a of the photomask 162. In the present embodiment, owing to transparency difference of the second mask pattern 162 b and the third mask pattern 162 c, the second thickness portion 164 b is thicker than the first thickness portion 164 a.
Referring to FIG. 8A and FIG. 8B, the third portion 152 c of the stacked structure 152 is removed to pattern the patterned semiconductor material layer 130 into a patterned semiconductor layer 132 by using the patterned photoresist layer 164 as a mask. The patterned semiconductor layer 132 has the same shape as the first thickness portion 164 a and the second thickness portion 164 b of the patterned photoresist layer 164. The third portion 152 c of the stacked structure 152 is removed by etching from the gate electrode material layer 150 until the patterned metal layer 120 is exposed. Thus, parts of the first metal portion 120 a, the second metal portion 120 b, and the data line 120 c are exposed.
Referring to FIG. 9A and FIG. 9B, the first thickness portion 164 a of the patterned photoresist layer 164 is then removed and the second thickness portion 164 b of the patterned photoresist layer 164 is thinned to expose the first portion 152 a of the stacked structure 152 previously covered by the first thickness portion 164 a of the patterned photoresist layer 164. In the embodiment, an ashing process is performed to remove the first thickness portion 164 a of the patterned photoresist layer 164 and thin the second thickness portion 164 b of the patterned photoresist layer 164.
Referring to FIG. 10A and FIG. 10B, the first portion 152 a of the stacked structure 152 is etched by using the thinned second thickness portion 164 b of the patterned photoresist layer 164 as a mask until an exposed portion 132J of the patterned semiconductor layer 132 in the first portion 152 a of the stacked structure 152 is exposed. The gate electrode material layer 150 is patterned into a gate electrode layer 154, and the insulation material layer 140 is patterned into an insulation layer 142 having a shape substantially conformal to the gate electrode layer 154 and covering a covered portion 1321 of the patterned semiconductor layer 132.
Referring to FIG. 11A and FIG. 11B, the exposed portion 132J of the patterned semiconductor layer 132 is then modified to increase a conductivity of the exposed portion 132J of the patterned semiconductor layer 132. The process for modifying the exposed portion 132J of the patterned semiconductor layer 132 includes performing a plasma treatment, an ion implanting, or a combination thereof. Particularly, in the plasma treatment, a processing gas includes hydrogen gas. However, the invention is not limited thereto. Other suitable method of modifying the exposed portion 132J of the patterned semiconductor layer 132 can be performed for increasing the conductivity of the exposed portion 132J of the patterned semiconductor layer 132.
By modifying the exposed portion 132J of the patterned semiconductor layer 132 by the insulation layer 142 to increase conductivity, the modified portion of the patterned semiconductor layer 132 includes and forms a pixel electrode 132 a, a drain 132 b, and a source 132 c. The pixel electrode 132 a is electrically connected to the drain 132 b through the second metal portion 120 b. That is to say the pixel electrode 132 a is electrically connected to the second metal portion 120 b, and the second metal portion 120 b is electrically connected to the drain 132 b.
In the embodiment, the pixel electrode 132 a is formed simultaneously with the formation of the source 132 c and the drain 132 b by using the same film layer. In addition, the covered portion 1321 of the patterned semiconductor layer 132, that was covered by the insulation layer 142 and not modified to increase conductivity, forms a channel 132 d.
Referring to FIG. 12A and FIG. 12B, the thinned second thickness portion 164 b of the patterned photoresist layer 164 is then removed. The process for removing the second thickness portion 164 b includes performing a stripping process. However, the invention is not limited thereto. Other suitable method of removing the second thickness portion 164 b can also be selected. After removing the second thickness portion 164 b, the gate electrode layer 154 is exposed, and a pixel structure 100 of the embodiment is completely manufactured. In the present embodiment, the gate electrode layer 154 includes a gate 154 a above the channel 132 d, and a gate line 154 b electrically connected to the gate 154 a. The gate 154 a, the channel 132 d, the source 132 c and the drain 132 b form a thin film transistor structure 134. Based on the method described above, it can be seen that the thin film transistor structure 134 is self-aligned during formation, wherein the channel 132 d and the gate 154 a are defined by using the thinned second thickness portion 164 b of the patterned photoresist layer 164. Thus, the thin film transistor structure 134 is a self-aligned thin film transistor structure. Particularly, in the present embodiment, the channel 132 d, the source 132 c, the drain 132 b and the gate 154 a are formed by using the same patterned photoresist layer 160 and the patterned photoresist layer 160 is formed by using one photomask. Therefore, the required amount of photomask for forming the thin film transistor structure 134 is reduced for saving the manufacture cost.
FIG. 12C is a schematic cross-sectional view taken along line B-B′ in the corresponding FIG. 12A. Referring to FIG. 12A, FIG. 12B, and FIG. 12C, the pixel structure 100 includes the pixel electrode 132 a disposed on a substrate 110, the thin film transistor structure 134, and the insulation layer 142. The thin film transistor structure 134 is disposed on the substrate 110 and connected to the pixel electrode 132 a. The thin film transistor structure 134 includes the source 132 c, the drain 132 b and the channel 132 d formed by the same patterned semiconductor layer 132 and the gate 154 a formed by the gate electrode layer 154. The source 132 c and the drain 132 b are located at two opposite sides of the channel 132 d, and the gate 154 a is located above the channel 132 d. The insulation layer 142 is interposed between the patterned semiconductor layer 132 and the gate electrode layer 154 and has a shape substantially conformal to the gate electrode layer 154. The insulation layer 142 covers a portion of the patterned semiconductor layer 132 to form the channel 132 d and exposes another portion of the patterned semiconductor layer 132 to form the source 132 c and the drain 132 b.
According to the step depicted in FIG. 11A and FIG. 11B, the covered portion 1321 of the patterned semiconductor layer 132 has a first conductivity type and the exposed portion 132J of the patterned semiconductor layer 132 has a second conductivity type more conductive than the first conductivity type. Therefore, the exposed portion 132J of the patterned semiconductor layer 132 can form the source 132 c, the drain 132 b and the pixel electrode 132 a which are the elements predetermined to be electrically conductive.
For transmitting the electric signals, the pixel structure 100 further includes the data line 120 c disposed on the substrate 110, and electrically connected to the source 132 c of the thin film transistor structure 134, wherein the first metal portion 120 a of the data line 120 c is located between the semiconductor layer 132 and the substrate 110. In addition, the gate electrode layer 154 further includes the gate line 154 b electrically connected to the gate 154 a of the thin film transistor structure 134. The gate line 154 b and the data line 120 c extends in different directions for respectively transmitting a control signal to the gate 154 a and transmitting a data signal to the source 132 c. Therefore, the thin film transistor structure 134 can be turned on by the control signal and the data signal can be transmitted to the pixel electrode 132 a through the turned-on thin film transistor structure 134.
In the present embodiment, the gate line 154 b is formed by using the same method of forming the gate 154 a. Therefore, the insulation layer 142 includes an insulation portion 142 a underlying the gate line 154 b. The insulation portion 142 a conforms in shape to the gate line 154 b. The patterned semiconductor layer 132 further includes a semiconductor portion 132 e underlying the gate line 154 b and has a separating gap SG corresponding to the opening 130A shown in FIG. 2A and exposing a portion of the data line 120 c. The semiconductor portion 132 e partially conforms in shape to the gate line 154 b. The gate line 154 b, the insulation portion 142 a and the semiconductor portion 132 e form a gate line structure 156, where the gate line 154 b and the insulation portion 142 a of the gate line structure 156 cross over the data line 120 c at the separating gap SG such that the semiconductor portion 132 e is not in contact with the data line 120 c and the insulation portion 142 a of the insulation layer 142 fills in the separating gap SG and contacts the data line 120 c for isolating the data line 120 c from the gate line 154 b. In other words, the semiconductor portion 132 e of the gate line structure 156 is electrically insulating to the data line 120 c so that a short circuit would not generate between the semiconductor portion 132 e and the data line 120 c.
In the embodiment, a portion of the source 132 c is in direct contact with the data line 120 c by being in direct contact with the first metal portion 120 a that branches off of the data line 120 c, to electrically connect to the data line 120 c. In addition, the pixel structure 100 further includes the second metal portion 120 b disposed on the substrate 110, located and electrically connected between the drain 132 b and the pixel electrode 132 a. A material of the second metal portion 120 b and the data line 120 c is the same. However, in an alternative embodiment, the first metal portion 120 a and the second metal portion 120 b can be selectively omitted.
FIG. 13A to FIG. 24A are schematic top views illustrating the manufacture process of a pixel structure according to another embodiment of the invention. FIG. 13B to FIG. 24B are schematic cross-sectional views respectively taken along line A-A′ in the corresponding FIG. 13A to FIG. 24A. It should be noted that in FIG. 13A to FIG. 24A, if a boundary of a layer substantially overlaps with another layer, the schematic top views only label the top most layer. Thus, FIG. 13A to FIG. 24A have omitted the references for some of the components. Please refer to the corresponding schematic cross-sectional views (i.e., FIG. 13B to FIG. 24B) at the same time. The following uses FIG. 13A to FIG. 24A and FIG. 13B to FIG. 24B to describe the manufacturing process of the pixel structure of another embodiment of the invention.
The difference between the embodiment of FIG. 13A to FIG. 24A, FIG. 13B to FIG. 24B, and FIG. 24C and the embodiment of FIG. 1A to FIG. 12A, FIG. 1B to FIG. 12B, and FIG. 12C, is that the second metal portion 120 b is not included in the embodiment of FIG. 13A to FIG. 24A, FIG. 13B to FIG. 24B, and FIG. 24C. Similar elements will use the same names, and processes that are the same both embodiments will not be repeated herein. The materials used are also similar in both embodiments, and the description will not be repeated herein.
Referring to FIG. 13A and FIG. 13B, a metal layer (not shown) is first formed on a substrate 210. Next, the metal layer is patterned to form a patterned metal layer 220 on the substrate 210. The patterned metal layer includes a first metal portion 220 a and a data line 220 c. The first metal portion 220 a branches off of the data line 220 c.
Referring to FIG. 14A and FIG. 14B, a patterned semiconductor material layer 230 is formed on the substrate 210. Particularly, the patterned semiconductor material layer 230 has an opening 230A exposing a portion of the data line 220 c. Referring to FIG. 15A and FIG. 15B, an insulation material layer 240 is formed on the patterned semiconductor material layer 230. Referring to FIG. 16A and FIG. 16B, a gate electrode material layer 250 is formed on the insulation material layer 240. Thus, it can be seen that the patterned semiconductor material layer 230, the insulation material layer 240, and the gate electrode material layer 250 are formed in sequence on the substrate 210 to form a stacked structure 252.
Referring to FIG. 17A and FIG. 17B, a photoresist layer 260 is formed on the gate electrode material layer 250 by using a photosensitive material. Referring to FIG. 18A and FIG. 18B, a photomask 262 is used to pattern the photoresist layer 260. The photomask 262 includes a first mask pattern 262 a, a second mask pattern 262 b, and a third mask pattern 262 c with different transparencies. The description of the photomask 262 is similar to the photomask 162, and will not be repeated herein.
Referring to FIG. 19A and FIG. 19B, the photoresist layer 260 is patterned to form a patterned photoresist layer 264. The patterned photoresist layer 264 includes a first thickness portion 264 a and a second thickness portion 264 b. The first thickness portion 264 a corresponds to the second mask pattern 262 b of the photomask 262 and covers a first portion 252 a of the stacked structure 252. The second thickness portion 264 b corresponds to the third mask pattern 262 c of the photomask 262 and covers a second portion 252 b of the stacked structure 252. A third portion 252 c of the stacked structure 252 is exposed by the patterned photoresist layer 264. The third portion 252 c of the stacked structure 252 that is exposed by the patterned photoresist layer 264 corresponds to the first mask pattern 262 a of the photomask 262. In the present embodiment, owing to transparency difference of the second mask pattern 262 b and the third mask pattern 262 c, the second thickness portion 264 b is thicker than the first thickness portion 264 a.
Referring to FIG. 20A and FIG. 20B, the third portion 252 c of the stacked structure 252 is removed to pattern the patterned semiconductor material layer 230 into a patterned semiconductor layer 232 by using the patterned photoresist layer 264 as a mask. The patterned semiconductor layer 232 has the same shape as the first thickness portion 264 a and the second thickness portion 264 b of the patterned photoresist layer 264 in the top view as shown in FIG. 20A. The third portion 252 c of the stacked structure 252 is removed by etching from the gate electrode material layer 250 until the patterned metal layer 220 is exposed. Thus, parts of the first metal portion 220 a and the data line 220 c are exposed.
Referring to FIG. 21A and FIG. 21B, the first thickness portion 264 a of the patterned photoresist layer 264 is then removed and the second thickness portion 264 b of the patterned photoresist layer 264 is thinned to expose the first portion 252 a of the stacked structure 252 previously covered by the first thickness portion 264 a of the patterned photoresist layer 264. In the embodiment, an ashing process is performed to remove the first thickness portion 264 a of the patterned photoresist layer 264 and thin of the second thickness portion 264 b of the patterned photoresist layer 264.
Referring to FIG. 22A and FIG. 22B, the first portion 252 a of the stacked structure 252 is etched by using the thinned second thickness portion 264 b of the patterned photoresist layer 264 as a mask until an exposed portion 232J of the patterned semiconductor layer 232 in the first portion 252 a of the stacked structure 252 is exposed. The gate electrode material layer 250 is patterned into a gate electrode layer 254, and the insulation material layer 240 is patterned into an insulation layer 242 having a shape substantially conformal to the gate electrode layer 254 and covering a covered portion 2321 of the patterned semiconductor layer 232.
Referring to FIG. 23A and FIG. 23B, the exposed portion 232J of the patterned semiconductor layer 232 is then modified to increase a conductivity of the exposed portion 232J of the patterned semiconductor layer 232. This step is similar to the description of the step in FIG. 11A and FIG. 11B, and will not be repeated herein.
By modifying the exposed portion 232J of the patterned semiconductor layer 232 exposed by the insulation layer 242 to increase conductivity, the modified exposed portion 232J of the patterned semiconductor layer 232 includes and forms a pixel electrode 232 a, a drain 232 b, and a source 232 c. The pixel electrode 232 a is electrically connected to the drain 232 b. In the embodiment, there is no a metal portion to electrically connect the pixel electrode 232 a and the drain 232 b. Rather, the pixel electrode 232 a and the drain 232 b are of the same patterned semiconductor layer 232, and branch off of each other to be in direct contact and electrically connected.
In the embodiment, the pixel electrode 232 a is formed simultaneously with the formation of the source 232 c and the drain 232 b by using the same film layer. In addition, the covered portion 2321 of the patterned semiconductor layer 232 covered by the insulation layer 242 that was not modified to increase conductivity forms a channel 232 d. Accordingly, in the present embodiment, the pixel electrode 232 a, the source 232 c, the drain 232 b and the channel 232 d can be formed by using the same film layer, the patterned semiconductor material layer 230.
Referring to FIG. 24A and FIG. 24B, the thinned second thickness portion 264 b of the patterned photoresist layer 264 is then removed. The process for removing the second thickness portion 264 b includes performing a stripping process. However, the invention is not limited thereto. Any suitable method of removing the second thickness portion 264 b can be used. After removing the second thickness portion 264 b, the gate electrode layer 254 is exposed, and a pixel structure 200 of the embodiment is completely manufactured. In the present embodiment, the gate electrode layer 254 includes a gate 254 a above the channel 232 d, and a gate line 254 b electrically connected to the gate 254 a. The gate 254 a, the channel 232 d, the source 232 c and the drain 232 b form a thin film transistor structure 234. Based on the method described above, it can be seen that the thin film transistor structure 234 is self-aligned during formation, wherein the channel 232 d and the gate 254 a are defined by using the thinned second thickness portion 264 b of the patterned photoresist layer 264. Thus, the thin film transistor structure 234 is a self-aligned thin film transistor structure. Particularly, in the present embodiment, the channel 232 d, the source 232 c, the drain 232 b and the gate 254 a are formed by using the same patterned photoresist layer 260 and the patterned photoresist layer 260 is formed by using one photomask. Therefore, the required amount of photomask for forming the thin film transistor structure 234 is reduced for saving the manufacture cost.
FIG. 24C is a schematic cross-sectional view taken along line B-B′ in the corresponding FIG. 24A. Referring to FIG. 24A, FIG. 24B, and FIG. 24C, the pixel structure 200 includes the pixel electrode 232 a disposed on the substrate 210, the thin film transistor structure 234, and the insulation layer 242. The thin film transistor structure 234 is disposed on the substrate 210 and connected to the pixel electrode 232 a. The thin film transistor structure 234 includes the source 232 c, the drain 232 b and the channel 232 d formed by a patterned semiconductor layer 232 and a gate 254 a formed by a gate electrode layer 254. The source 232 c and the drain 232 b are located on two opposite sides of the channel 232 d, and the gate 254 a is located above the channel 232 d. The insulation layer 242 is interposed between the patterned semiconductor layer 232 and the gate electrode layer 254 and has a shape substantially conformal to the gate electrode layer 254. The insulation layer 242 covers a portion of the patterned semiconductor layer 232 to form the channel 232 d and exposes another portion of the patterned semiconductor layer 232 to form the source 232 c and the drain 232 b.
According to the step depicted in FIG. 23A and FIG. 23B, the covered portion 2321 of the patterned semiconductor layer 232 has a first conductivity type and the exposed portion 232J of the patterned semiconductor layer 232 has a second conductivity type more conductive than the first conductivity type. Therefore, the exposed portion 232J of the patterned semiconductor layer 232 can from the source 232 c, the drain 232 b, and the pixel electrode 232 a which are elements predetermined to be electrically conductive.
For transmitting the electric signals, the pixel structure 200 further includes the data line 220 c disposed on the substrate 210, located between the patterned semiconductor layer 232 and the substrate 210, and electrically connected to the source 232 c of the thin film transistor structure 234. In addition, the gate electrode layer 254 further includes the gate line 254 b electrically connected to the gate 254 a of the thin film transistor structure 234. The gate line 254 b and the data line 220 c extends in different directions for respectively transmitting a control signal to the gate 254 a and transmitting a data signal to the source 232 c. Therefore, the thin film transistor structure 234 can be turned on by the control signal and the data signal can be transmitted to the pixel electrode 232 a through the turned-on thin film transistor structure 234.
In the present embodiment, the gate line 254 b is formed by using the same method of forming the gate 254 a. Therefore, the insulation layer 242 includes a insulation portion 242 a underlying the gate line 254 b. The insulation portion 242 a conforms in shape to the gate line 254 b. The patterned semiconductor layer 232 further includes a semiconductor portion 232 e underlying the gate line 254 b and has a separating gap SG corresponding to the opening 230A shown in FIG. 14A and exposing a portion of the data line 220 c. The semiconductor portion 232 e partially conforms in shape to the gate line 154 b. The gate line 254 b, the insulation portion 242 a and the semiconductor portion 232 e form a gate line structure 256, where the gate line 254 b and the insulation portion 242 a of the gate line structure 256 cross over the data line 220 c at the separating gap SG such that the semiconductor portion 232 e is not in contact with the data line 220 c and the insulation portion 242 a of the insulation layer 242 fills in the separating gap SG and contacts the data line 220 c for isolating the data line 220 c from the gate line 254 b. In other words, the insulation layer 242 patterned from the insulation material layer 240 fills the separating gap SG such as the semiconductor portion 232 e of the gate lines structure 256 is electrically insulating to the data line 220 c for preventing the short circuit between the data lines 220 c and the semiconductor portion 232 e of the gate lines structure 256. In the embodiment, a portion of the source 232 c is in direct contact with the data line 220 c by being in direct contact with the first metal portion 220 a that branches off of the data line 220 c, to electrically connect to the data line 220 c. In addition, the pixel structure 200 is different from the pixel structure 100 in that it does not further include a second metal portion between the drain 232 b and the pixel electrode 232 a. The drain 232 b and the pixel electrode 232 a are connected to each other and made from the same patterned semiconductor layer 232.
Based on the above, it should be noted that, in the manufacturing process of the pixel structure of the embodiments, the photoresist layer is patterned by the photomask to form the patterned photoresist layer that includes the first thickness portion and the second thickness portion. This allows that patterned photoresist layer to act as a mask when etching different portions of the stacked structure. This further allows the manufacture of the pixel structure to require fewer masks. Thus, the manufacturing cost of the pixel structure of the invention can be effectively lowered.
In addition, when performing etching to expose the source and the drain, the channel is covered by the insulation layer. Thus, the channel of the semiconductor layer will not be damaged during the etching process. This allows the thin film transistor structure to have better reliability.
Furthermore, it can be seen that since the source, the drain, and the channel are of the same patterned semiconductor layer, the source, the drain, and the channel are electrically connected without requiring contact holes. In addition, the drain is electrically contacted with the pixel electrode without contact holes. This improves resolution or aperture ratio of the pixel structure. In addition, not requiring contact holes also saves space in the layout of the thin film transistor structure.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.

Claims

What is claimed is:

1. A manufacturing method of a pixel structure, the method comprising:

forming a patterned semiconductor material layer, an insulation material layer, and a gate electrode material layer in sequence on a substrate to form a stacked structure;

forming a patterned photoresist layer on the stacked structure by using a photomask, wherein the patterned photoresist layer comprises a first thickness portion covering a first portion of the stacked structure and a second thickness portion covering a second portion of the stacked structure, and the patterned photoresist layer exposes a third portion of the stacked structure;

removing the third portion of the stacked structure to pattern the patterned semiconductor material layer into a patterned semiconductor layer by using the patterned photoresist layer as a mask;

removing the first thickness portion of the patterned photoresist layer and thinning the second thickness portion of the patterned photoresist layer to expose the first portion of the stacked structure previously covered by the first thickness portion of the patterned photoresist layer;

etching the first portion of the stacked structure by using the thinned second thickness portion of the patterned photoresist layer as a mask until an exposed portion of the patterned semiconductor layer in the first portion of the stacked structure is exposed, wherein the gate electrode material layer is patterned into a gate electrode layer, and the insulation material layer is patterned into an insulation layer having a shape substantially conformal to the gate electrode layer and covering a covered portion of the patterned semiconductor layer;

modifying the exposed portion of the patterned semiconductor layer to increase a conductivity of the exposed portion of the patterned semiconductor layer; and

removing the thinned second thickness portion of the patterned photoresist layer, wherein the covered portion of the patterned semiconductor layer comprises a channel, the exposed portion of the patterned semiconductor layer comprises a source and a drain, the gate electrode layer comprises a gate above the channel, and the gate, the channel, the source and the drain form a thin film transistor structure.

2. The method as claimed in claim 1, further comprising forming a patterned metal layer on the substrate prior to forming the stacked structure, wherein the patterned metal layer comprises a data line electrically connected to the source.

3. The method as claimed in claim 2, wherein the patterned semiconductor material layer has an opening exposing a portion of the data line and the patterned semiconductor layer patterned from the patterned semiconductor material layer comprises a semiconductor portion and has a separating gap corresponding to the opening, such that the insulation layer patterned from the insulation material layer comprises an insulation portion filling the separating gap and contacting the portion of the data line and the semiconductor portion is electrically insulating to the data line.

4. The method as claimed in claim 1, wherein the removing the first thickness portion of the patterned photoresist layer and the thinning the second thickness portion of the patterned photoresist layer comprises performing an ashing process.

5. The method as claimed in claim 1, wherein the forming the patterned photoresist layer on the stacked structure comprises using one half-tone photomask or one gray-tone photomask to form the first thickness portion and the second thickness portion.

6. The method as claimed in claim 1, wherein the modifying the exposed portion of the patterned semiconductor layer comprises performing a plasma treatment, an ion implanting, or a combination thereof.

7. The method as claimed in claim 6, wherein the plasma treatment uses hydrogen gas as a processing gas.

8. The method as claimed in claim 1, wherein the removing the second thickness portion comprises performing a stripping process.

9. The method as claimed in claim 1, further comprising forming a pixel electrode electrically connected to the drain.

10. The method as claimed in claim 9, wherein the formation of the pixel electrode is simultaneous to the formation of the source and the drain.

11. The method as claimed in claim 9, wherein the pixel electrode is formed by modifying the exposed portion of the patterned semiconductor layer.