Patent Application
20200168642
This disclosure relates to formation of a thin film transistor, and particularly relates to a laser irradiation device, a projection mask, a laser irradiation method, and a program for irradiating an amorphous silicon thin film with laser light to form a polysilicon thin film.
There is a technique in which, in an image display area of a TFT panel, a predetermined region of an amorphous silicon thin film is instantaneously heated by laser light to be polycrystallized, a polysilicon thin film having high electron mobility is formed, and the polysilicon thin film is used for a channel region of a thin film transistor.
For example, Japanese Unexamined Patent Application Publication No. 2016-100537 discloses that an amorphous silicon thin film is formed on a glass substrate and, thereafter, the amorphous silicon thin film is irradiated with laser light such as an excimer laser to be subject to a laser annealing so that the amorphous silicon thin film is crystallized as a polysilicon thin film by melting and solidifying in a short time. Japanese Unexamined Patent Application Publication No. 2016-100537 discloses that the processing makes it possible to form the channel region between a source and a drain of the thin film transistor as a polysilicon thin film having high electron mobility, and to improve a response time of the transistor.
In the TFT panel, a gate driver serves as a driving circuit that drives a thin film transistor of an image display area. In this regard, the TFT panel manufactured by using the technique disclosed in Japanese Unexamined Patent Application Publication No. 2016-100537 requires externally mounting the gate driver after creating the image display area, which is a factor in an increase in the manufacturing cost of the TFT panel.
It could therefore be helpful to provide a laser irradiation device, a projection mask, a laser irradiation method, and a program that can reduce the manufacturing cost of the TFT panel by eliminating the need of externally mounting of a gate driver in the TFT panel.
I thus provide:
A laser irradiation device may include: a light source that generates laser light; and a projection lens that irradiates a predetermined region of an amorphous silicon thin film deposited on a substrate with the laser light, in which the projection lens includes a first projection lens that irradiates first regions corresponding to a channel region of a thin film transistor with the laser light and being a part of the predetermined regions and a second projection lens that irradiates second regions corresponding to predetermined elements included in a gate driver with the laser light and being a part of the predetermined regions.
The second projection lens may be a microcylindrical lens that irradiates the second regions with the laser light.
The second projection lens may irradiate each of the second regions with the laser light two or more times using a plurality of cylindrical lenses included in the microcylindrical lens.
The laser irradiation device may further include a projection mask pattern arranged on the projection lens, and causes the laser light to transmit in a predetermined projection pattern, and in which the projection mask pattern includes first opening portions corresponding to the first regions and second opening portions corresponding to the second regions.
The first projection lens may be a microlens array that irradiates the first regions included in the substrate with the laser light, and an irradiation energy of the laser light with which the second projection lens irradiates the second region may be greater than an irradiation energy of the laser light with which the first projection lens irradiates the first regions.
The projection mask may be a projection mask arranged on a projection lens that radiates laser light generated from a light source, and includes: first opening portions that cause the laser light to transmit from a first projection lens included in the projection lens in first regions corresponding to a channel region of a thin film transistor and being a part of the amorphous silicon thin films that are deposited on the substrate, and second opening portions that cause the laser light to transmit from a second projection lens included in the projection lens in second regions corresponding to predetermined elements included in a gate driver and being a part of the amorphous silicon thin films.
In the projection mask, the second projection lens may be a microcylindrical lens capable of irradiating the second regions with the laser light, and the second opening portions cause the laser light from the microcylindrical lens to transmit in the second regions.
The laser irradiation method may include: generating step of generating laser light; and irradiating step of irradiating predetermined regions of an amorphous silicon thin film deposited on the substrate with the laser light; and in which in the irradiating step, first regions corresponding to a channel region of a thin film transistor and second regions corresponding to predetermined elements included in a gate driver are irradiated with the laser light, and the first regions and the second regions are parts of the predetermined regions.
In the laser irradiation method, in the irradiating step, each of the second regions may be irradiated with the laser light by using a microcylindrical lens.
The program stored in a computer readable non-transitory storage medium may cause a computer to execute: a generating function to generate laser light; and an irradiating function to irradiate predetermined regions of an amorphous silicon thin film deposited on a substrate with the laser light, in which, in the irradiating function, first regions corresponding to a channel region of a thin film transistor and second regions corresponding to predetermined elements included in a gate driver are irradiated with the laser light, and the first regions and the second regions are parts of the predetermined regions.
In the program, in the irradiating function, each of the second regions may be irradiated with the laser light by using a microcylindrical lens.
A gate driver may be formed on a substrate, and thus the need of externally mounting of a gate driver in a TFT panel is eliminated, thereby enabling provision of the laser irradiation device and others that can reduce a manufacturing cost of the TFT panel.
Hereinafter, examples will be specifically described with reference to the attached drawings.
In a first example, in a laser irradiation device with which an annealing treatment is performed to a substrate, in addition to a microlens array, a microcylindrical lens is provided (included) in a projection lens that radiates laser light, whereby an annealing treatment to first regions corresponding to a gate driver and an annealing treatment to second regions corresponding to a channel region of a thin film transistor are simultaneously performed.
The TFT panel 100 includes a thin film transistor for each pixel of a liquid crystal, and voltage of the TFT panel 100 is controlled for each pixel to change the amount of transmissions of light and a direction of the light that transmits in each pixel. As illustrated in
The liquid crystal display 101 includes a plurality of pixels each having a thin film transistor 20. In addition, the gate driver 102 is a circuit that scans (drives) the plurality of pixels included in the liquid crystal display 101 per one row (one line). In addition, the source driver 103 is a circuit that gives image data (voltage according to information, including lightness and darkness, for example) to each pixel included in one row (one line) scanned by the gate driver 102. Thus, voltage of the thin film transistor 20 included in each of the plurality of pixels is controlled by the gate driver 102 and the source driver 103 to change the amount of transmission of each light of the pixel and the direction of light that transmits. Accordingly, the color of the TFT panel 100 can be changed for each pixel, and a predetermined image can be displayed on the entire TFT panel 100.
As illustrated in
The laser irradiation device 10 is used, for example, when forming the thin film transistor of pixels such as a peripheral circuit of a liquid crystal display. When forming such a thin film transistor, pattern formation of a gate electrode which includes of metal membranes such as aluminum, on a substrate 30 is first carried out by sputtering. Then, a gate dielectric film that includes a SiN film is formed on the entire surface of the substrate 30 by a low temperature plasma CVD method. Thereafter, an amorphous silicon thin film 21 is formed on the gate dielectric film with a plasma CVD method, for example That is, the amorphous silicon thin film 21 is formed (deposited) on the entire surface of the substrate 30 Finally, a silica dioxide (SiO2) film is formed on the amorphous silicon thin film 21. Then, the laser irradiation device 10 illustrated in
As shown in
Then, the laser light 14 transmits first opening portions 151 of a projection mask pattern 15 provided on a projection lens 13, is separated into a plurality of laser lights 14, and the predetermined regions of the amorphous silicon thin film 21 are irradiated with the plurality of laser lights 14. A projection mask pattern 15 is provided in the projection lens 13, and predetermined regions are irradiated with the laser lights 14 through the projection mask pattern 15. Then, the predetermined regions of the amorphous silicon thin film 21 are instantaneously heated and melted, and a part of the amorphous silicon thin film 21 becomes a polysilicon thin film 22.
Predetermined regions are first regions 25 corresponding to a channel region of the thin film transistor 20 and second regions 26 corresponding to predetermined elements included in the gate driver 102. That is, the laser irradiation device 10 irradiates the first regions 25 corresponding to the channel region of the thin film transistor 20 on the substrate 30, and the second regions 26 corresponding to the predetermined elements included in the gate driver 102 with the laser lights 14 emitted from the laser light source 11 through the projection lens 13. As a result, the first regions 25 corresponding to the channel region of the thin film transistor 20 on the substrate 30 and the second regions 26 corresponding to the predetermined elements included in the gate driver 102 becomes the polysilicon thin film 22.
The polysilicon thin film 22 has higher electron mobility than that of the amorphous silicon thin film 21, and can be used as the channel region of the thin film transistor 20 and predetermined elements (TFT elements) of the gate driver in the TFT panel.
The first projection lens 130 is a microlens array 16, for example. Using a plurality of microlenses 160 included in the microlens array 16 one by one, the laser irradiation device 10 irradiates the first regions 25 of the amorphous silicon thin film 21 with the laser lights 14 and the first regions 25 form the polysilicon thin film 22. The number of the microlenses 160 included in one line of the microlens array 16 is twenty. Therefore, the predetermined regions of the amorphous silicon thin film 21 formed (deposited) on the substrate 30 are irradiated with the laser lights 14 using twenty microlenses 160. The number of the microlenses 160 included in one row of the microlens array 16 is not limited to twenty, but may be any number. In addition, the number of the microlenses 160 included in one row (one line) of the microlens array 16 is eighty-three, for example, but it is not limited to this, but may be any number.
Annealing the predetermined regions by the first projection lens 130 forms the polysilicon thin film 22 and, thereafter, a source 23 and a drain 24 are formed at both ends of formed polysilicon thin film 22, whereby the thin film transistor 20 is created. The laser irradiation device 10 irradiates one thin film transistor 20 with the laser lights 14 using, for example, twenty microlenses 160 included in one column (or one row) of the microlens array 16. That is, the laser irradiation device 10 irradiates one thin film transistor 20 with twenty shots of the laser lights 14. As a result, in the thin film transistor 20, the predetermined regions of the amorphous silicon thin film 21 are instantaneously heated, melted and become a polysilicon thin film 22. In the laser irradiation device 10, the number of microlenses 160 included in one column (or one row) of the microlens array 16 is not limited to twenty, but may be any number as long as the number of microlenses 160 is plural.
The first projection lens 130 does not necessarily need to be a microlens array, and may radiate the laser lights 14 using one projection lens.
The second projection lens 131 is a microcylindrical lens 17, for example. A large amount of current is necessary for the predetermined elements (TFT element parts) of the gate driver 102 since the plurality of thin film transistors 20 included in one row (one line) of the liquid crystal display 101 are necessary to be scanned (driven). In addition, the current needs to be turned on and off at high speed to the predetermined elements (TFT elements) of the gate driver 102 since one column of the liquid crystal display 101 needs to be scanned for a short time. Therefore, the regions (the second regions 26) corresponding to the predetermined elements (TFT elements) of the gate driver 102 are greater than the channel region (the first regions 25) of the thin film transistor 20. Therefore, a problem arises that completion of the annealing treatment requires a long time if the annealing treatment of the second regions 26 is carried out with the microlens 160 included in the microlens array 16. Therefore, the annealing treatment cannot be carried out to the regions (the second regions 26) corresponding to the predetermined elements (TFT element parts) of the gate driver 102 simultaneously with the annealing treatment of the channel region of the thin film transistor 20, in the microlenses 160 included in the microlens array 16.
Accordingly, the annealing treatment of the second regions corresponding to the predetermined elements (TFT elements) of the gate driver 102 is carried out using a microcylindrical lens 17 including multiple cylindrical lenses 170 with a greater condensing degree of the laser lights 14 than that of the microlenses 160. Since the cylindrical lenses 170 are used, an irradiation energy of the laser lights 14 irradiated to the second regions corresponding to the predetermined elements (TFT elements) of the gate driver 102 is greater. Therefore, the time required for crystallization of the amorphous silicon thin film 21 in the second regions can be shortened and, thus, the annealing treatment can be carried out in a greater area, the annealing treatment can be carried out to the regions (the second regions) corresponding to the predetermined elements (TFT element parts) of the gate driver 102 simultaneously with the annealing treatment of the channel region of the thin film transistor 20.
The left side of
As illustrated in
Thereafter, the substrate 30 is moved by only a predetermined distance (interval of adjoining second regions 26). After movement of the substrate 30, the second region 26a is irradiated with the laser light 14 by the cylindrical lens 170b contiguous to the cylindrical lens 170a, and subject to an annealing treatment. In addition, in the same manner as the second region 26a, the second region 26b is irradiated with the laser light 14 by the cylindrical lens 170c contiguous to the cylindrical lens 170b, and subject to an annealing treatment. In the same manner as the second region 26a and the second region 26b, the second region 26c is irradiated with the laser light 14 by the cylindrical lens 170e and subject to an annealing treatment, and the second region 26d is irradiated with the laser light 14 by the cylindrical lens 170d. Thus, one second region 26 is irradiated with the laser light 14 by the number of the cylindrical lenses 170 included in the microcylindrical lens 17. As shown in
After the substrate 30 is moved by a predetermined distance, the laser irradiation device 10 may irradiate the substrate 30 which stopped once with the laser lights 14, and may continue to irradiate the substrate 30 that continues to be moved with the laser lights 14.
The microlens array 16 radiates the laser lights 14 by contracting the projection mask pattern 15 to ⅕. As a result, the laser lights 14 that transmit the projection mask pattern 15 is contracted to a width of about 10 μm in the channel region. In addition, the laser lights 14 that transmit the projection mask pattern 15 are contracted to a length of about 20 μm in the channel region. The contraction percentage of the microlens array 16 may not be limited to ⅕, but may be any scale. In addition, the projection mask patterns 15, as illustrated in
On the other hand, the laser lights 14 transmit the second opening portions 152 of the projection mask pattern 15, and the second regions 26 that are regions corresponding to the predetermined elements (TFT elements) of the gate driver 102 are irradiated with the laser lights 14. The width (the length of a shorter side), and the length of the longer side of the second opening portions 152 of the projection mask pattern 15 are substantially same as the size of the microcylindrical lens 17. The size of the second opening portions 152 is a mere example, and may be any size.
Next, a method of producing a TFT panel 100 in the first example using the laser irradiation device 10 will be described.
First, the laser irradiation device 10 irradiates the first regions 25 (a portion to be the channel region, that are predetermined regions of the amorphous silicon thin film 21 formed (deposited) on the substrate 30) that are to be a channel region of the thin film transistor 20 and the second regions 26 that are regions corresponding to the predetermined elements (TFT elements) of the gate driver 102 by using the projection lens 13 illustrated in
The substrate 30 is moved by a predetermined distance every time when the microlens array 16 and the microcylindrical lens 17 radiate the laser lights 14. The predetermined distance is a distance between a plurality of the thin film transistors 20 on the substrate 30. The laser irradiation device 10 stops irradiation of the laser lights 14 while moving the substrate 30 by the predetermined distance. The laser irradiation device 10 may stop irradiation of the laser lights 14, while moving the substrate 30.
After the substrate 30 is moved by a predetermined distance, the laser irradiation device 10 irradiates the first regions 25 irradiated with the laser lights 14 with one microlens 160 again using another microlens 160 included in the microlens array 16. In addition, the laser irradiation device 10 irradiates the second regions 26 irradiated with one cylindrical lens 170 again using another cylindrical lens 170 included in the microcylindrical lens 17. Since the microlens array 16 includes twenty rows of the microlenses 160, for example, the first regions 25 are irradiated with the laser lights 14 at least twenty times. In addition, the microcylindrical lens 17 includes five cylindrical lenses 170, for example, and thus the second regions 26 are irradiated with the laser lights 14 at least five times.
While repeating the above-mentioned process and irradiating the first regions 25 to be the channel regions of the thin film transistor 20 with twenty shots of the laser lights 14, using each of twenty microlenses 160 one by one, and the second regions 26 that are regions corresponding to the predetermined elements (TFT elements) of the gate driver 102 are irradiated using each of the five cylindrical lenses 170 one by one. As a result, while the polysilicon thin film 22 is formed in the first regions 25 on the substrate 30, the polysilicon thin film 22 is formed in the second regions 26 on the substrate 30.
Thereafter, in another process, a source 23 and a drain 24 are formed and, consequently, the thin film transistor 20 is formed.
As described above, in the first example to the projection lens 13, in addition to the microlens array 16 which is the first projection lens 130, the microcylindrical lens 17 which is the second projection lens 131 is provided and, thus, the first regions 25 corresponding to the channel region of thin film transistor 20 is subject to the annealing treatment, and simultaneously the second regions 26 corresponding to the gate driver 102 can be subject to the annealing treatment. Therefore, the gate driver 102 can be formed on the substrate and, thus, the need of externally mounting of the gate driver 102 in the TFT panel 100 is eliminated, and the laser irradiation device which can reduce the manufacturing cost of the TFT panel 100, for example, can be provided.
In addition, as illustrated in
As illustrated in
In contrast, use of the projection lens 13 and the projection mask pattern 15 as illustrated in
A second example includes using one projection lens 18 instead of the microlens array 16 as the first projection lens 130 of the projection lens 13.
In the second example, when using the projection lens 18 instead of the microlens array 16 as the first projection lens 130, laser light 14 is converted by a magnification of the optical system of the projection lens 18. That is, the pattern of the projection mask pattern 15 is converted by the magnification of the optical system of the projection lens 18, and the first regions 25 of an amorphous silicon thin film 21 formed (deposited) on a substrate 30 are subject to an annealing treatment. The microcylindrical lens 17 irradiates the second regions 26 that are regions corresponding to the predetermined elements (TFT elements) of the gate driver 102 with the laser lights 14 in the same manner as the first example.
In the second example, the projection mask pattern 15 is a projection mask pattern 15 illustrated in
The projection mask pattern 15 is converted by the magnification of the optical system of the projection lens 18, and the first regions 25 of the amorphous silicon thin film 21 formed (deposited) on the substrate 30 are subject to annealing treatment. For example, when the magnification of the optical system of the projection lens 18 is about twice, the mask pattern of projection mask pattern 15 is multiplied by ½ (0.5), and the predetermined regions of the substrate 30 are subject to an annealing treatment. The magnification of the optical system of the projection lens 18 is not limited to about twice, but may be any magnification. The projection mask pattern 15 is changed according to the magnification of the optical system of projection lens 18, and the predetermined regions on the substrate 30 are subject to an annealing treatment. For example, if the magnification of the optical system of the projection lens 18 is four, the mask pattern of projection mask pattern 15 is multiplied by about ¼ (0.25), and the first regions 25 of the amorphous silicon thin film 21 formed (deposited) on the substrate 30 are subject to an annealing treatment.
In addition, when the projection lens 18 forms an inverted image, the contracted image of the projection mask pattern 15 which the amorphous silicon thin film 21 formed (deposited) on the substrate 30 is irradiated forms a pattern obtained by rotation of 180 degrees along an optic axis of a lens of the projection lens 18. On the other hand, when the projection lens 18 forms an erection image, the contracted image of the projection mask pattern 15 in which the amorphous silicon thin film 21 formed (deposited) on the substrate 30 is irradiated remains the projection mask pattern 15 as it is.
Also in the second example, the laser irradiation device 10 radiates the laser lights 14 with a predetermined cycle, the substrate 30 is moved while the laser lights 14 are not radiated, and the first regions 25 and the second regions 26 of the amorphous silicon thin film 21 deposited on the substrate 30 are allowed to be irradiated with the laser lights 14.
As described above, in the second example, one projection lens 18 that serves as the first projection lens 130 of the projection lens 13 instead of microlens array 16 and the microcylindrical lens 17 that serves as the second projection lens 131 are included. Therefore, the first regions 25 corresponding to the channel region of the thin film transistor 20 are subject to the annealing treatment, and simultaneously the second region corresponding to the gate driver 102 can be subject to the annealing treatment. Therefore, since the gate driver 102 can be formed on the substrate, the need of externally mounting of the gate driver 102 in the TFT panel 100 is eliminated, and thus a laser irradiation device, for example, which can reduce manufacturing cost of the TFT panel 100 can be provided.
In the above description, when there is a description such as “vertical”, “parallel”, “planar”, “orthogonal”, or the like, the description do not indicate strict meaning of such terms. That is, the words “vertical”, “parallel”, “planar” and “orthogonal” allow tolerances and errors in design, manufacturing, or the like, and the words “vertical”, “parallel”, “plane” and “orthogonal” mean “substantially vertical”, “substantially parallel”, “substantially plane” and “substantially orthogonal”. The tolerance or error means a unit within a range which does not deviate from the configuration, operation and desired effect.
Further, in the above description, when there is a description such as “same”, “equal”, “different”, or the like in a dimension and a size of external shape, the descriptions do not indicate strict meaning of such terms. That is, the words “same”, “equal” and “different” allow tolerances and errors in design, manufacturing, or the like and may mean “substantially same”, “substantially equal” and “substantially different”. The tolerance or error means a unit within a range which does not deviate from the configuration, operation and desired effect.
Although my devices, masks, methods and programs have been described with reference to the drawings or examples, those skilled in the art can easily make various changes and corrections based on this disclosure. Therefore, the changes and corrections are included in the scope of the disclosure. For example, functions included in each means, each step, and the like can be rearranged not to be logically inconsistent, and a plurality of means, steps, and the like can be combined into one or divided. Further, the configurations described in the above-described examples may combined as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-155870 | Aug 2017 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2018/027990 | Jul 2018 | US |
| Child | 16779978 | US |
