CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Taiwan Patent Application No. 104117270 filed on May 29, 2015, the contents of which are incorporated by reference herein.
FIELD
The subject matter herein generally relates to a thin film transistor liquid crystal display (TFT LCD), and in particular to a method for manufacturing a thin film transistor substrate for the TFT LCD.
BACKGROUND
A TFT LCD includes a TFT substrate, a color filter over the TFT LCD and a liquid crystal layer between the TFT substrate and the color filter. By controlling rotations of liquid crystals in the liquid crystal layer by the TFT substrate, a picture can be displayed through the color filter. The TFT substrate includes electronic components such as thin film transistors, capacitors, connection pads and connection lines. After the electronic components are formed, an electrically insulating cover is formed to cover the electronic components. Thereafter, the electrical insulating cover is subjected to light exposure through a mask. The light exposure causes the electrically insulating cover to have a rugged top surface after development, which adversely affects a performance and reliability of the TFT substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is a flowchart showing a method for manufacturing a TFT substrate in accordance with a first embodiment of the present disclosure.
FIG. 2 is a cross-sectional view of a part of a TFT substrate corresponding to a first block of the method of FIG. 1.
FIG. 3 is a cross-sectional view of a part of a TFT substrate corresponding to a second block of the method of FIG. 1.
FIG. 4 is a cross-sectional view of a part of a TFT substrate corresponding to a third block of the method of FIG. 1.
FIG. 5 is a cross-sectional view of a part of a TFT substrate corresponding to a fourth block of the method of FIG. 1.
FIG. 6 is a cross-sectional view of a part of a TFT substrate corresponding to a fifth block of the method of FIG. 1.
FIG. 7 is a flowchart showing a method for manufacturing a TFT substrate in accordance with a second embodiment of the present disclosure.
FIG. 8 is a cross-sectional view of a part of a TFT substrate corresponding to a first block of the method of FIG. 7.
FIG. 9 is a cross-sectional view of a part of a TFT substrate corresponding to a second block of the method of FIG. 7.
FIG. 10 is a cross-sectional view of a part of a TFT substrate corresponding to a third block of the method of FIG. 7.
FIG. 11 is a cross-sectional view of a part of a TFT substrate corresponding to a fourth block of the method of FIG. 7.
FIG. 12 is a cross-section view of a part of a TFT substrate corresponding to a fifth block of the method of FIG. 7.
FIG. 13 is a cross-sectional view of a part of a TFT substrate corresponding to a sixth block of the method of FIG. 7.
DETAILED DESCRIPTION
It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features. The description is not to be considered as limiting the scope of the embodiments described herein.
Several definitions that apply throughout this disclosure will now be presented.
The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising” means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in a so-described combination, group, series and the like.
The present disclosure is described in relation to a method for manufacturing a TFT substrate.
Referring to FIG. 1, a flowchart is presented in accordance with an example embodiment. The example method 200 is provided by way of example, as there are a variety of ways to carry out the method. The method 200 described below can be carried out using the configurations illustrated in FIGS. 2-6, for example, and various elements of these figures are referenced in explaining example method 200. Each block shown in FIG. 1 represents one or more processes, methods or subroutines, carried out in the example method 200. Furthermore, the illustrated order of blocks is illustrative only and the order of the blocks can change according to the present disclosure. Additional blocks can be added or fewer blocks may be utilized, without departing from this disclosure. The example method 200 can begin at block 202.
Also referring to FIG. 2, at block 202, a substrate 100 is provided. A buffer layer 105 is formed on the substrate 100, and a connection pad 118 is formed on the buffer layer 105. Although only one connection pad 118 is shown in FIG. 2, it can be understood that in reality there is a plurality of connection pads 118 formed on the substrate buffer layer 105.
In more detail, block 202 includes forming the buffer layer 105 on the substrate 100 and then forming a metal layer on the buffer layer 105. The metal layer is then patterned through photolithography under a yellow light environment to form the connection pad 118.
According to this embodiment, the substrate 100 can be made of transparent material such as glass, quartz or organic polymer. The buffer layer 105 can be made of transparent, electrically insulating material such as silicon oxide, silicon nitride, or silicon oxide nitride. The connection pad 118 can be made of metal such as aluminum, titanium, molybdenum, tantalum, or copper. It can be understood that the buffer layer 105 can be omitted; then the connection pad 118 is directly formed on the substrate 100.
Also referring to FIG. 3, at block 204, an electrically insulating layer 122 is formed to cover the buffer layer 105 and the connection pad 118. A connection hole 172 is defined in electrically insulating layer 122 at a position corresponding to the connection pad 118 whereby the connection pad 118 is exposed through the connection hole 172. The connection hole 172 is formed through photolithography to the electrically insulating layer 122 in a yellow light environment.
In this embodiment, the electrically insulating layer 122 can be made of transparent, insulating material such as aluminum oxide, silicon oxide, silicon nitride or silicon oxide nitride.
Also referring to FIG. 4, at block 206, a connection line 146 is formed on the electrically insulating layer 122. The connection line 146 extends through the connection hole 172 to electrically connect with the connection pad 118. In this embodiment, the connection line 146 is formed by firstly applying a metal layer on the electrically insulating layer 122. Then the metal layer is processed by photolithography under a yellow light environment to form the connection line 146. The connection line 146 occupies an area which is larger than an area occupied by the connection pad 118. The connection line 146 can be made of aluminum, titanium, molybdenum, tantalum, or copper which can reflect light impinges thereon.
Also referring to FIG. 5, at block 208, an electrically insulating cover 152 is formed on the electrically insulating layer 122 and the connection line 122. The electrically insulating cover 152 is a passivation layer and can be made of organic material such as polycarbonate (PC) or benzocyclobutene (BCB).
Also referring to FIG. 6, at block 210, the electrically insulating cover 152 is exposed to light irradiation, for example, ultraviolet light irradiation, through a mask 220. The mask 220 has a first translucent region 222 located corresponding to a region of the electrically insulating cover 152 in which the connection line 146 is formed, and a second translucent region 224 located corresponding to a region of the electrically insulating cover 152 beside the connection line 146. A transmittance of the first translucent region 222 is lower than a transmittance of the second translucent region 224. The first translucent region 222 can have a transmittance between 5% and 90%. Moreover, the first translucent region 222 can have a transmittance between 20% and 80%. The second translucent region 224 can have a transmittance which is 5%-10% more than that of the first translucent region 222. For example, when the first translucent region 222 has a transmittance of 20%, the second translucent region 224 has a transmittance of 25%-30%.
After being irradiated by light which can be ultraviolet light, a photoresist developer (not shown) is used to develop the electrically insulating cover 152. The region of the electrically insulating cover 152 corresponding to the second translucent region 224 of the mask 220 is passivated to increase its transmittance. The region of the electrically insulating cover 152 corresponding to the first translucent region 222 of the mask 220 has less light irradiated thereon. Accordingly, even when the connection line 146 is made of metal and can reflect light impinging thereon, there is no intensive light reflected by the connection line 146 through a part of the electrically insulating cover 152 above the connection line 146. Thus no overexposure to light irradiation will happen to the electrically insulating cover 152 at a position thereof corresponding to the connection line 146, whereby a depression in a top face of the electrically insulating cover 152 over the connection line 146 can be avoided after the electrically insulating cover 152 is developed by the photoresist developer. Thus, the top face of the electrically insulating cover 152 can be prevented from being rugged, but be kept flat and smooth to ensure the reliability and performance of the TFT substrate.
Referring to FIG. 7, a flowchart is presented in accordance with another example embodiment. The example method 300 is provided by way of example, as there are a variety of ways to carry out the method. The method 300 described below can be carried out using the configurations illustrated in FIGS. 8-13, for example, and various elements of these figures are referenced in explaining example method 300. Each block shown in FIG. 7 represents one or more processes, methods or subroutines, carried out in the example method 300. Furthermore, the illustrated order of blocks is illustrative only and the order of the blocks can change according to the present disclosure. Additional blocks can be added or fewer blocks may be utilized, without departing from this disclosure. The example method 300 can begin at block 302.
Also referring to FIG. 8, at block 302, a substrate 100 is provided. Then a buffer layer 105 is formed on the substrate 100 and a gate electrode 114 and a connection pad 118 are formed on the buffer layer 105. The gate electrode 114 and the connection pad 118 are formed by first applying a metal layer on the buffer layer 105 and then processing (i.e., patterning) the metal layer by photolithography under a yellow light environment. Although only one gate electrode 114 and one connection pad 118 are shown in FIG. 8, it can be understood that in fact there are a plurality of gate electrodes 118 and connection pads 114 formed on the buffer layer 105.
According to this embodiment, the substrate 100 can be made of transparent material such as glass, quartz, or organic polymer. The buffer layer 105 can be made of transparent, electrically insulating material such as silicon oxide, silicon nitride, or silicon oxide nitride. The gate electrode 114 and the connection pad 118 can be made of metal such as aluminum, titanium, molybdenum, tantalum, or copper. It can be understood that the buffer layer 105 can be omitted, whereby the gate electrode 114 and the connection pad 118 are directly formed on the substrate 100.
Also referring to FIG. 9, at block 304, an electrically insulating layer 122 is formed to cover the buffer layer 105, the gate electrode 114 and the connection pad 118. A channel layer 132 is formed on the electrically insulating layer 122 at a location corresponding to the gate electrode 114. A connection hole 172 is defined in the electrically insulating layer 122 at a location corresponding to the connection pad 118 whereby the connection pad 118 is exposed through the connection hole 172.
To form the channel layer 132 and the connection hole 172, first a semiconductor layer is applied on the electrically insulating layer 122. Then the semiconductor layer is processed by photolithography under a yellow light environment to form the channel layer 132. The photolithography also patterns the electrically insulating layer 122 to form the connection hole 172.
According to this embodiment, the electrically insulating layer 122 can be made of transparent, electrically insulating material such as aluminum oxide, silicon oxide, silicon nitride or silicon oxide nitride. The channel layer 132 can be made of semiconductor material such as metal oxide, amorphous silicon, or polycrystalline silicon (also called polysilicon).
Also referring to FIG. 10, at block 306, a source electrode 142, a drain electrode 144 and a connection line 146 are formed on the electrically insulating layer 122. The source electrode 142 and the drain electrode 144 are formed on the electrically insulating layer 122 over two opposite ends of the channel layer 132 whereby the source and drain electrodes 142, 144 are electrically coupled with the channel layer 132. The connection line 146 is formed on the electrically insulating layer 122 and extends downwardly thorough the connection hole 172 to electrically couple with the connection pad 118. The connection line 146 occupies a real estate larger than a real estate occupied by the connection pad 118. An area occupied by the channel layer 132, the source electrode 142 and the drain electrode 144 in combination is larger than an area occupied by the gate electrode 114. The source and drain electrodes 142, 144 and the connection line 146 are formed by first applying a metal layer on the electrically insulating layer 122 and then processing the metal layer by photolithography. The source and drain electrodes 142, 144 and the connection line 146 can be made of metal such as aluminum, titanium, molybdenum, tantalum, or copper.
Also referring to FIG. 11, at block 308, an electrically insulating cover 152 is formed to cover the source electrode 142, the channel layer 132, the drain electrode 144, the connection line 146 and the electrically insulating layer 122. The electrically insulating cover 152 is a passivation layer and can be made of organic material such as polycarbonate (PC) or benzocyclobutene (BCB).
Also referring to FIG. 12, at block 310, the electrically insulating cover 152 is exposed to light irradiation through a mask 320. The mask 320 has a first translucent region 322 located corresponding to a region of the electrically insulating cover 152 in which the connection line 146, the source electrode 142 and the drain electrode 144 are formed, and a second translucent region 324 located corresponding to a region of the electrically insulating cover 152 beside the connection line 146, the source electrode 142 and the drain electrode 144. The mask 320 further has a third region 326 located corresponding to a part of the electrically insulating cover 152 in which a foot portion of the drain electrode 144 is formed. The third region 326 is used for forming a contact hole 174 (FIG. 13) in the electrically insulating cover 152. A transmittance of the second translucent region 324 is lower than a transmittance of the third region 326, while a transmittance of the first translucent region 322 is lower than that of the second translucent region 324. The first translucent region 322 can have a transmittance between 5% and 90%. Moreover, the first translucent region 322 can have a transmittance between 20% and 80%. The second translucent region 324 can have a transmittance which is 5%-10% more than that of the first translucent region 322. The third region 326 can have a transmittance of 100%. In other words, the third region 326 can be transparent.
After being irradiated by light which can be ultraviolet light, the part of the electrically insulating cover 152 which corresponds to the third region 326 and can absorb the highest intensity of light irradiation can be removed by a photoresist developer (not shown) to define the contact hole 174 (FIG. 13). The region of the electrically insulating cover 152 corresponding to the second translucent region 324 of the mask 320 is passivated to increase its transmittance. The region of the electrically insulating cover 152 corresponding to the first translucent region 322 of the mask 320 has less light irradiated thereon since the first translucent region 322 has the least transmittance. Accordingly, even that the connection line 146, the source electrode 142 and the drain electrode 144 which are made of metal and can reflect light impending thereon, there is no intensive light reflected by the connection line 146, the source electrode 142 and the drain electrode 144, whereby a rugged top face of the electrically insulating cover 152 over the connection line 146, the source electrode 142 and the drain electrode 144 due to an overexposure thereof to the light irradiation can be avoided by the present disclosure after the electrically insulating cover 152 is developed by the photoresist developer (not shown). Thus, the top face of the electrically insulating cover 152 can be kept flat and smooth to ensure the performance and reliability of the TFT substrate.
Also referring to FIG. 13, at block 312, the photoresist developer (not shown) is applied to the top face of the electrically insulating cover 152 after the electrically insulating cover 152 has been subjected to the light irradiation through the mask 320. By the photoresistor developer, the contact hole 174 is formed in the electrically insulating cover 152 to expose the foot portion of the drain electrode 144. Then, a pixel electrode 162 is formed on the electrically insulating layer 152 and extends into the contact hole 174 to electrically couple with the drain electrode 144. The pixel electrode 162 is formed by applying a transparent, electrically conductive layer on the electrically insulating cover 152 and then patterning the transparent, electrically conductive layer by photolithography to obtain the pixel electrode 162. The pixel electrode 162 can be made of indium tin oxide (ITO).
The embodiments shown and described above are only examples. Even though numerous characteristics and advantages of the present technology have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in the detail, including in particular the matters of shape, size and arrangement of parts within the principles of the present disclosure, up to and including the full extent established by the broad general meaning of the terms used in the claims.
Patent Application
20160351718
