JP4477333B2 - Thin film transistor substrate manufacturing method and laser annealing apparatus used therefor - Google Patents

Description

  The present invention relates to a method for manufacturing a thin film transistor substrate and a laser annealing apparatus used therefor, and more particularly to a method for manufacturing a thin film transistor substrate comprising a polycrystalline silicon thin film transistor and constituting a liquid crystal display device and a laser annealing apparatus used therefor.

  In recent years, liquid crystal display devices are used for various purposes, and demands for higher definition and higher performance are increasing. In order to realize this requirement, a polycrystalline semiconductor (polysilicon (p-Si)) is used instead of a conventional amorphous semiconductor (amorphous silicon (a-Si)) as an operation layer of a thin film transistor (TFT). ) Is becoming more active. In order to achieve higher performance, studies have been made to increase the crystal grain size of polysilicon using a technique such as lateral crystallization.

  Recently, an excimer laser or a continuous wave (CW) laser is irradiated only on a specific position of the a-Si film formed on the substrate, thereby forming a p-Si film having a large crystal grain size. There is a method for manufacturing a TFT substrate that is formed only in a desired region (for example, a peripheral circuit portion that requires high-speed operation). However, in this case, a p-Si film having a large particle size is formed in the island formation process in which the Si film (a-Si film and p-Si film) is patterned into an island shape in order to form an operation layer of the TFT. It must be possible to accurately recognize the position of the region. If there is a large alignment tolerance when forming the TFT in the region where the p-Si film is formed, a mechanical alignment method can be employed. However, in recent years when high definition has advanced, the tolerance for alignment has become smaller. Therefore, it is necessary to form alignment marks in order to improve alignment accuracy. Usually, the alignment mark is formed through a photolithography process and an etching process. For this reason, the manufacturing cost of the TFT substrate increases by these steps.

  As a method for forming an alignment mark at a low cost, Patent Document 1 describes a technique for forming an alignment mark by removing a thin film by laser processing. As another method, in Patent Document 2, a mask having an alignment mark-shaped light transmission region is installed in the path of the laser optical system, and the thin film is not removed but the Si film of the portion irradiated with the laser light is removed. A technique for forming an alignment mark on a substrate by changing optical characteristics is described.

  FIG. 6 shows a configuration of a conventional laser annealing apparatus (exposure apparatus) described in Patent Document 2. As shown in FIG. 6, the laser annealing apparatus 101 includes a stage 152 on which the glass substrate 110 is placed, and a laser beam irradiation unit 144 for forming alignment marks on the glass substrate 110. A peripheral circuit section 160 is arranged around each display area of the six-chamfered glass substrate 110. The stage 152 can relatively move the irradiation position of the laser beam with respect to the placed glass substrate 110. The laser beam irradiation unit 144 includes a light source unit 140 that oscillates an excimer laser, and a laser optical system 142 that guides the laser beam to a predetermined irradiation position. The laser optical system 142 includes a mirror, an optical lens, and the like. Further, a mask 150 having a light transmission region having a predetermined shape is disposed on the laser light path. When the alignment mark 162 is formed, the alignment mark forming region of the a-Si film on the substrate is irradiated with laser light through the mask 150. As a result, the a-Si film on the glass substrate 110 is irradiated with the laser light transmitted through the light transmission region of the mask 150, and the alignment mark 162 made of the p-Si film is formed.

  However, in the technique described in Patent Document 1, the thin film removed by laser light irradiation evaporates, and the annealing window on the laser light path is contaminated. For this reason, the maintenance for removing the contaminant adhering to the annealing window is required. In the technique described in Patent Document 2, since the laser beam is irradiated through the mask 150, the metal layer or the dielectric multilayer film formed on the mask 150 as a light shielding pattern evaporates, and the laser beam path The upper optical lens is contaminated. For this reason, maintenance for removing contaminants attached to the optical lens is required. There is a problem that the manufacturing cost of the TFT substrate increases due to the part cost and labor cost necessary for the maintenance, or the reduction in the operating rate of the laser annealing apparatus due to the maintenance.

There is also a method in which an alignment mark is formed in advance prior to the island formation step using another laser marking device. However, in this case, a dedicated laser marking device is newly required, and a laser annealing device for crystallizing the a-Si film needs to have a function of aligning the substrate by reading the alignment mark. For this reason, a problem arises that the manufacturing apparatus becomes expensive and the manufacturing cost of the TFT substrate increases.
Japanese Patent Laid-Open No. 7-161627 JP 2001-28440 A

  An object of the present invention is to provide a method of manufacturing a thin film transistor substrate capable of reducing the manufacturing cost and a laser annealing apparatus used therefor.

  The above object is a method of manufacturing a thin film transistor substrate having a crystallization step of crystallizing at least part of an amorphous silicon film formed on a substrate to form a polysilicon film, wherein the crystallization step includes the amorphous silicon film. This is achieved by a method of manufacturing a thin film transistor substrate, comprising the step of selectively crystallization by irradiating a laser beam without passing through a mask to form an alignment mark made of the polysilicon film.

  According to the present invention, the manufacturing cost of the thin film transistor substrate can be reduced.

  A method of manufacturing a thin film transistor substrate and a laser annealing apparatus used therefor according to an embodiment of the present invention will be described with reference to FIGS. First, the configuration of the laser annealing apparatus according to the present embodiment will be described. FIG. 1 is a diagram schematically showing the configuration of the laser annealing apparatus according to the present embodiment, and FIG. 2 is a block diagram showing the configuration of the laser annealing apparatus according to the present embodiment. As shown in FIGS. 1 and 2, the laser annealing apparatus 1 includes an XY stage 52 on which a glass substrate 10 is placed, and a first laser light irradiation unit for forming alignment marks on the glass substrate 10. 44 and a second laser light irradiation unit 50 for crystallizing the a-Si film in the TFT formation region. In the present embodiment, for example, the a-Si film of the peripheral circuit unit 60 disposed around each display region of the six-chamfered glass substrate 10 is crystallized. The XY stage 52 is movable in the XY plane, and the irradiation position of the laser beam on the placed glass substrate 10 can be relatively moved. The XY stage 52 has a substrate fixing jig for fixing the placed glass substrate 10. The laser beam irradiation unit 44 includes a light source unit 40 that oscillates a laser beam (for example, a CW laser) and a laser optical system 42 that guides the laser beam to a predetermined irradiation position. Similarly, the laser beam irradiation unit 50 includes a light source unit 46 that oscillates a laser beam (for example, a CW laser) and a laser optical system 48 that guides the laser beam to a predetermined irradiation position. The laser optical systems 42 and 48 are configured by mirrors, optical lenses, and the like. The laser beam irradiation units 44 and 50 may be fixed with respect to the laser annealing apparatus 1 or may be movable in the XY plane. The laser annealing apparatus 1 includes a control unit 56 that moves the XY stage 52 (and the laser beam irradiation units 44 and 50) to a predetermined position, and a laser beam irradiation position confirmation CCD camera 54 described later. Yes.

  Here, when positioning the laser beam irradiation positions of the laser beam irradiation units 44 and 50 with respect to the glass substrate 10, the alignment mark is not used, and the coordinate data set in the laser annealing apparatus 1 is used. It has become. As coordinate data, the absolute coordinates of the position of the XY stage 52 with respect to the apparatus origin of the laser annealing apparatus 1 and the absolute coordinates of the laser light irradiation positions of the laser light irradiation units 44 and 50 with respect to the apparatus origin are set. The position of the glass substrate 10 placed on the XY stage 52 is acquired as relative coordinates with respect to the XY stage 52 based on the position of the substrate fixing jig. As a result, when the laser beam irradiation units 44 and 50 are fixed to the laser annealing apparatus 1, the laser beam is irradiated by setting the relative coordinates with respect to the glass substrate 10 at the position where the laser beam should be irradiated. The absolute coordinates of the position of the XY stage 52 for arranging the glass substrate 10 at the power position can be obtained. In addition, when the laser beam irradiation units 44 and 50 are movable with respect to the laser annealing apparatus 1, the laser beam irradiation unit can be set by setting the relative coordinates with respect to the glass substrate 10 at the position where the laser beam is to be irradiated. 44 and 50 relative coordinates with respect to the XY stage 52 can be obtained. Therefore, when the laser annealing apparatus 1 of the present embodiment is used, the control unit 56 reads the alignment mark by setting absolute coordinates of the laser beam irradiation positions of the XY stage 52 and the laser beam irradiation units 44 and 50. A desired position on the glass substrate 10 can be irradiated with laser light without any problem.

  Further, the laser annealing apparatus 1 can confirm the position where the laser light is actually irradiated and the a-Si film is crystallized. When confirming the position irradiated with the laser beam, first, the control unit 56 of the laser annealing apparatus 1 performs predetermined irradiation on the XY stage 52 and the laser camera for confirming the laser beam irradiation position. A laser beam irradiation position confirmation instruction signal designating the position is transmitted. The XY stage 52 moves so that the laser beam irradiation position confirmation CCD camera 54 is disposed in the vicinity of the designated position. When the CCD camera 54 for confirming the laser beam irradiation position senses the position where the laser beam is irradiated and the a-Si film is crystallized based on the difference in reflectance between a-Si and p-Si, Information to that effect is transmitted to the control unit 56. The control unit 56 that has received the information indicating that the position irradiated with the laser light has been sensed acquires the coordinate data at that time from the XY stage 52. Thereby, the coordinate data of the position where the laser beam is actually irradiated can be obtained. The control unit 56 compares the preset coordinate data of the laser beam irradiation position with the coordinate data of the position where the laser beam is actually irradiated. If there is an error between these coordinate data due to a deviation of the optical axis of the laser beam due to a change with time, the control unit 56 moves the XY stage 52 at the time of the next laser beam irradiation based on the error, for example. Correct the amount. Note that, in this example, the laser beam irradiation position confirmation CCD camera 54 is fixed to the laser annealing apparatus 1, but it may be movable in the XY plane.

Next, the manufacturing method of the TFT substrate according to the present embodiment will be described with reference to FIGS. 3 and 4 are process cross-sectional views illustrating a method for manufacturing a TFT substrate according to the present embodiment. 3 and 4, the formation region of the alignment mark 62 is shown on the right side, and the TFT formation region of the peripheral circuit section 60 is shown on the left side. First, as shown in FIG. 3A, a silicon nitride film (SiN film) 12 having a thickness of 50 nm and a silicon oxide film (SiO ₂ film) 14 having a thickness of 200 nm are formed on a glass substrate 10 by using, for example, a CVD method. The a-Si film 16 having a thickness of 80 nm is continuously formed in this order. Next, annealing is performed at 400 ° C., and a hydrogen removal process for removing hydrogen from the a-Si film 16 is performed.

  Next, the a-Si film 16 in the TFT formation region of the peripheral circuit section 60 and the alignment mark 62 formation region is crystallized using the laser annealing apparatus 1 according to the present embodiment. The TFT formation region of the peripheral circuit unit 60 is irradiated with a CW laser under irradiation conditions of, for example, an output of 5.0 W and a scanning speed of 20 cm / sec by the laser beam irradiation unit 50, and the p-Si film 19 shown in FIG. Is formed. The alignment mark 62 formation region is irradiated with a CW laser from the laser light irradiation unit 44 under irradiation conditions of, for example, an output of 5.0 W and a scanning speed of 20 cm / sec. Thereby, the first alignment mark 62 made of the p-Si film 18 is formed. Here, when positioning the laser beam irradiation positions of the laser beam irradiation units 44 and 50, coordinate data set in the laser annealing apparatus 1 is used instead of using alignment marks.

  The alignment mark 62 is formed by directly irradiating the a-Si film 16 with laser light without passing through a mask and drawing it in a predetermined shape (for example, a cross shape having a size of about 50 to 100 μm). Since the a-Si film 16 is present around the alignment mark 62 made of p-Si, the CCD camera and the UV are affected by the difference in optical characteristics such as reflectance and transmittance between the p-Si and the a-Si. The alignment mark 62 can be recognized using a reflection device or the like.

  Next, as shown in FIG. 3C, for example, using an inline coater / developer apparatus, a resist is applied to the entire surface of the substrate on the p-Si film 19 and patterned to form a resist pattern 24 in the TFT formation region. Then, a resist pattern 25 in the second alignment mark formation region is formed. In this step, the first alignment mark 62 is read using a CCD camera or the like, the glass substrate 10 and the exposure mask are aligned based on the alignment mark 62, and resist patterns 24 and 25 are formed at predetermined positions. The

Next, as shown in FIG. 4A, dry etching is performed on the p-Si films 18 and 19 and the a-Si film 16 using a mixed gas of SF ₆ and O ₂ using the resist patterns 24 and 25 as a mask. Then, the island-shaped p-Si film 20 in the TFT formation region and the second alignment mark 64 are formed (islandization step). The second alignment mark 64 is used for alignment between the glass substrate 10 and the exposure mask in a step after the islanding step. The alignment mark 64 is recognized by detecting unevenness formed on the surface of the thin film formed on the alignment mark 64 with a CCD camera or the like. In this example, the first alignment mark 62 and the second alignment mark 64 are formed at different positions. However, the second alignment mark 64 is formed so as to overlap the first alignment mark 62. Also good. Subsequently, the resist patterns 24 and 25 are peeled off.

  Next, as shown in FIG. 4B, the insulating film (gate insulating film) 26 made of, for example, a 100 nm-thickness SiO film is disposed on the p-Si film 20, and the insulating film 26. A gate electrode 28 made of an Al film having a thickness of 300 nm is formed. Next, as illustrated in FIG. 4C, for example, an n-type impurity is implanted into the p-Si film 20 using the gate electrode 28 as a mask, and a source region 32 and a drain region 34 are formed in regions other than the channel region 30. Form.

  Next, a SiN film having a film thickness of 400 nm, for example, is formed on the entire surface of the substrate on the gate electrode 28 to form an interlayer insulating film 36. Next, the interlayer insulating film 36 on the source region 32 and the drain region 34 is removed to form a contact hole. Next, on the entire surface of the interlayer insulating film, for example, a Ti film with a thickness of 100 nm, an Al film with a thickness of 200 nm, and a Ti film with a thickness of 100 nm are formed and patterned in this order, and the source electrode 38 and the drain electrode 39 are formed. Form. The source electrode 38 and the drain electrode 39 are connected to the source region 32 and the drain region 34, respectively. A TFT is formed by the above process. Note that the manufacturing method and structure of the TFT are not limited to the above. In this example, the a-Si film 16 in the pixel drive TFT formation region in the display region is not crystallized. However, for example, the a-Si film 16 in the pixel drive TFT formation region at a higher scanning speed than the peripheral circuit unit 60. May be irradiated with a CW laser and crystallized to a particle size smaller than that of the peripheral circuit portion 60. Further, a low concentration impurity region (LDD (Lightly Doped Drain) region) may be formed between the channel region 30, the source region 32, and the drain region 34 in the pixel driving TFT in the display region. . Thereafter, an interlayer insulating film is further formed on the source electrode 38 and the drain electrode 39, and a pixel electrode electrically connected to the source electrode 38 is formed for each pixel region in the display region, thereby completing the TFT substrate.

  In the present embodiment, the first alignment mark 62 is formed not by removing the a-Si film 16 but by selectively crystallizing the a-Si film 16. Further, when forming the alignment mark 62, the laser beam is directly irradiated without using a mask. Therefore, the laser optical system is not contaminated, and maintenance for removing the contaminant is not required. Further, in the present embodiment, the positioning of the alignment mark 62 and the position where the a-Si film 16 is crystallized to form the p-Si film 19 are determined using absolute coordinates in the laser annealing apparatus 1. Therefore, it is not necessary to form an alignment mark before these steps. In the island formation step, alignment is performed using an alignment mark 62 formed by crystallizing the a-Si film 16. Therefore, the process for forming the alignment mark can be reduced, and the laser annealing apparatus does not need to have an alignment mark reading function, so that the manufacturing cost of the TFT substrate can be reduced. Furthermore, in this embodiment, since the CW laser is used instead of the excimer laser in the crystallization, the p-Si film 19 having a larger particle size can be formed.

  FIG. 5 shows a modification of the laser annealing apparatus according to this embodiment. As shown in FIG. 5, the laser annealing apparatus 1 ′ according to the present modification includes one laser beam irradiation unit 84 that serves both as alignment mark formation and TFT formation region crystallization. In this modification, the laser annealing apparatus 1 ′ is less expensive than the configuration provided with the laser beam irradiation unit 44 for forming the alignment mark and the laser beam irradiation unit 50 for crystallizing the TFT formation region, and the TFT substrate. The manufacturing cost can be further reduced.

The manufacturing method of the thin film transistor substrate according to the present embodiment described above and the laser annealing apparatus used therefor can be summarized as follows.
(Appendix 1)
A method of manufacturing a thin film transistor substrate comprising a crystallization step of crystallizing at least part of an amorphous silicon film formed on a substrate to form a polysilicon film,
The crystallization step includes a step of selectively crystallization by irradiating the amorphous silicon film with a laser beam without using a mask to form an alignment mark made of the polysilicon film. A method for manufacturing a substrate.
(Appendix 2)
In the method for manufacturing a thin film transistor substrate according to appendix 1,
After the crystallization step, the method includes an island formation step of patterning the polysilicon film into an island shape,
The island formation step includes a step of recognizing the alignment mark based on a difference in optical characteristics between the polysilicon film and the amorphous silicon film, and aligning the substrate based on the alignment mark. A method of manufacturing a thin film transistor substrate.
(Appendix 3)
In the method for manufacturing a thin film transistor substrate according to appendix 1 or 2,
The method of manufacturing a thin film transistor substrate, wherein the alignment mark is formed at a predetermined position based on preset coordinate data.
(Appendix 4)
In the method for manufacturing a thin film transistor substrate according to any one of appendices 1 to 3,
A method of manufacturing a thin film transistor substrate, wherein a continuous wave laser is used as the laser light.
(Appendix 5)
In the method for manufacturing a thin film transistor substrate according to any one of appendices 1 to 4,
The island forming step includes a step of patterning the polysilicon film or the amorphous silicon film to form a second alignment mark,
The method after the island formation step includes aligning the substrate on the basis of the second alignment mark.
(Appendix 6)
An alignment mark forming laser beam irradiation unit including a light source that oscillates a laser beam for forming an alignment mark made of a polysilicon film, and a laser optical system that guides the laser beam to a predetermined irradiation position;
A stage capable of moving the irradiation position relative to the placed substrate;
The irradiation position is moved based on preset coordinate data, and the laser beam is irradiated to a predetermined position of the amorphous silicon film formed on the substrate without passing through a mask to selectively crystallize, And a control unit for forming alignment marks.
(Appendix 7)
In the laser annealing apparatus according to appendix 6,
The alignment mark forming laser light irradiation unit further has a function of irradiating the thin film transistor forming region of the amorphous silicon film with the laser light to crystallize the laser annealing apparatus.
(Appendix 8)
In the laser annealing apparatus according to appendix 6,
A thin film transistor formation region crystallization laser light irradiation part for crystallization by irradiating the thin film transistor formation region of the amorphous silicon film with the laser beam;
The control unit moves the irradiation position of the laser beam irradiation unit for crystallizing a thin film transistor formation region based on preset coordinate data.
(Appendix 9)
In the laser annealing apparatus according to any one of appendices 6 to 8,
An optical property detector that detects an optical property of a predetermined detection position on the substrate;
The laser annealing apparatus, wherein the stage is capable of moving the detection position relative to the substrate.
(Appendix 10)
In the laser annealing apparatus according to appendix 9,
The laser annealing apparatus, wherein the optical property detection unit detects reflectance or transmittance at the detection position.
(Appendix 11)
In the laser annealing apparatus according to appendix 9 or 10,
The controller is configured to identify a position where the amorphous silicon film is irradiated with the laser light based on optical characteristics of the detection position.
(Appendix 12)
In the laser annealing apparatus according to appendix 11,
The laser annealing apparatus, wherein the control unit has a function of comparing preset coordinate data with coordinate data of a position irradiated with the laser light and correcting an error.
(Appendix 13)
In the laser annealing apparatus according to any one of appendices 6 to 12,
The laser annealing apparatus, wherein the laser beam is a continuous wave laser.

It is a figure which shows the typical structure of the laser annealing apparatus by one embodiment of this invention. It is a block diagram which shows the structure of the laser annealing apparatus by one embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the TFT substrate by one embodiment of this invention. It is process sectional drawing which shows the manufacturing method of the TFT substrate by one embodiment of this invention. It is a figure which shows the modification of a structure of the laser annealing apparatus by one embodiment of this invention. It is a figure which shows the structure of the conventional laser annealing apparatus.

Explanation of symbols

1, 1 ′ Laser annealing apparatus 10 Glass substrate 12 SiN film 14 SiO ₂ film 16 a-Si films 18, 19, 20 p-Si film 24, 25 Resist pattern 26 Insulating film 28 Gate electrode 30 Channel region 32 Source region 34 Drain Region 36 Interlayer insulating film 38 Source electrode 39 Drain electrodes 40, 46 Light source unit 42, 48 Laser optical system 44 First laser beam irradiation unit 50 Second laser beam irradiation unit 52 XY stage 54 For laser beam irradiation position confirmation CCD camera 56 Control unit 60 Peripheral circuit unit 62 First alignment mark 64 Second alignment mark 70, 72 Contact hole

Claims (10)

A method of manufacturing a thin film transistor substrate comprising a crystallization step of crystallizing at least part of an amorphous silicon film formed on a substrate to form a polysilicon film,
The crystallization step includes a step of selectively crystallization by irradiating the amorphous silicon film with a laser beam without passing through a mask to form a first alignment mark made of the polysilicon film. A method for manufacturing a thin film transistor substrate. In the manufacturing method of the thin-film transistor substrate of Claim 1,
After the crystallization step, the method includes an island formation step of patterning the polysilicon film into an island shape,
The island forming step recognizes the first alignment mark based on a difference in optical characteristics between the polysilicon film and the amorphous silicon film, and aligns the substrate based on the first alignment mark. A process for producing a thin film transistor substrate, comprising the step of: In the manufacturing method of the thin-film transistor substrate of Claim 2 ,
The island forming step includes a step of patterning the polysilicon film or the amorphous silicon film to form a second alignment mark,
The method after the island formation step includes aligning the substrate on the basis of the second alignment mark. In the manufacturing method of the thin-film transistor substrate of any one of Claims 1 thru | or 3 ,
The method of manufacturing a thin film transistor substrate, wherein the first alignment mark is formed at a predetermined position based on preset coordinate data. An alignment mark forming laser beam irradiation unit including a light source that oscillates a laser beam for forming an alignment mark made of a polysilicon film, and a laser optical system that guides the laser beam to a predetermined irradiation position;
A stage capable of moving the irradiation position relative to the placed substrate;
The irradiation position is moved based on preset coordinate data, and the laser beam is irradiated to a predetermined position of the amorphous silicon film formed on the substrate without passing through a mask to selectively crystallize, And a control unit for forming alignment marks. The laser annealing apparatus according to claim 5, wherein
The alignment mark forming laser light irradiation unit further has a function of irradiating the thin film transistor forming region of the amorphous silicon film with the laser light to crystallize the laser annealing apparatus. The laser annealing apparatus according to claim 5, wherein
A thin film transistor formation region crystallization laser light irradiation part for crystallization by irradiating the thin film transistor formation region of the amorphous silicon film with the laser beam;
The control unit moves the irradiation position of the laser beam irradiation unit for crystallizing a thin film transistor formation region based on preset coordinate data. The laser annealing apparatus according to any one of claims 5 to 7,
An optical property detector that detects an optical property of a predetermined detection position on the substrate;
The laser annealing apparatus, wherein the stage is capable of moving the detection position relative to the substrate. The laser annealing apparatus according to claim 8, wherein
The controller is configured to identify a position where the amorphous silicon film is irradiated with the laser light based on optical characteristics of the detection position. The laser annealing apparatus according to claim 9, wherein
The laser annealing apparatus, wherein the control unit has a function of comparing preset coordinate data with coordinate data of a position irradiated with the laser light and correcting an error.

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