JP2012243818A - Laser processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing apparatus which can accelerate laser processing, e.g. annealing, for modifying an a-Si film to a polysilicon film while shortening the tact time.SOLUTION: By means of a cylindrical lens array 2a having a plurality of cylindrical lenses 12, eight planar laser beams 4 are shaped, for example, and an a-Si film on a substrate 1 is irradiated with the laser beams 4 thus shaped. The substrate 1 is then moved at a pitch of a gap G between the irradiation regions 5, and elongated irradiation regions 5 are formed on the substrate at a pitch of the gap G. When this gap G is set as a pixel pitch, only a region in which a pixel transistor is to be formed becomes the irradiation region 5 in the pixel region.

Description

  The present invention is used to crystallize a-Si into polycrystalline silicon (hereinafter referred to as polysilicon) by irradiating an amorphous silicon film (hereinafter referred to as a-Si film) with laser light and annealing. In particular, the present invention relates to a laser processing apparatus using a plurality of cylindrical lenses.

  As a thin film transistor having an inverted stagger structure, a gate electrode is formed of a metal layer such as Cr or Al on an insulating substrate, and then, for example, a SiN film is formed as a gate insulating film on the substrate including the gate electrode. A hydrogenated amorphous silicon (hereinafter referred to as a-Si: H) film is formed on the entire surface, and the a-Si: H film is patterned in an island shape in a predetermined region on the gate electrode. There is an amorphous silicon transistor in which a drain electrode is formed.

  However, since this amorphous silicon transistor uses an a-Si: H film for the channel region, there is a drawback that the mobility of charges in the channel region is small. Therefore, an amorphous silicon transistor can be used as a pixel transistor in a pixel portion of a liquid crystal display device, for example. However, as a drive transistor in a peripheral drive circuit that requires high-speed rewriting, the charge mobility in the channel region is high. It is too small and difficult to use.

  On the other hand, when a polycrystalline silicon film is formed directly on a substrate, it is formed by LPCVD (Low Pressure Chemical Vapor Deposition), which is a high temperature process of about 1500 ° C. A polycrystalline silicon film cannot be directly formed on a transparent glass substrate (softening point is 400 to 500 ° C.).

  Therefore, once an a-Si: H film is formed in the channel region, and then this a-Si: H film is irradiated with a laser beam such as a YAG excimer laser to perform laser annealing, thereby melting in an extremely short time. Due to the solidification phase transition, a low-temperature polysilicon process for crystallizing an a-Si: H film into a polysilicon film has been adopted. As a result, the channel region on the glass substrate can be formed of a polysilicon film that has high charge mobility and can speed up the transistor operation (Patent Document 1).

  Further, in this type of laser annealing apparatus, the pulse laser beam is shaped by one cylindrical lens so that the irradiation area on the substrate becomes a band-shaped beam, and the laser optical system or the substrate is relatively irradiated. In some cases, the a-Si: H film is crystallized into a polysilicon film by moving in the width direction of the region and scanning the entire region on the substrate with a laser beam.

JP-A-5-63196

  However, the above-described conventional laser processing technique has a narrow beam length of, for example, 750 mm and a beam width of, for example, 350 μm in the irradiation region on the substrate, and scans the laser beam in the width direction. Since laser processing is performed by scanning the entire area, there are problems that the processing time is long and the tact time is long.

  The present invention has been made in view of such problems, and is capable of speeding up laser processing such as annealing processing for modifying an a-Si film into a polysilicon film and capable of shortening tact time. An object is to provide an apparatus.

  A laser processing apparatus according to the present invention includes a laser light source that emits pulsed laser light, and a plurality of cylindrical lenses that shape the pulsed laser light from the laser light source so that an irradiation region on the substrate has a plurality of bands. A control device that controls the substrate and the cylindrical lens to move relative to each other in the width direction and the longitudinal direction of the irradiation region, and the cylindrical lens is fixed in a direction perpendicular to the longitudinal direction. Arranged in parallel with each other at a lens pitch, the control device irradiates a pulse laser beam in the first region on the substrate so that the band-shaped irradiation region has a first pitch in the width direction; In the second region, the laser light source emits light so that the belt-shaped irradiation region emits pulsed laser light at a second pitch smaller than the first pitch in the width direction. Serial and controlling the relative movement of the substrate and the cylindrical lens.

  This laser processing apparatus is particularly effective for an annealing process for modifying an a-Si film into a polysilicon film. In addition, it is particularly effective when applied to manufacturing a plurality of panels of a liquid crystal display device from a single glass substrate.

  Therefore, as one aspect of the present invention, the substrate is a glass substrate for manufacturing one or a plurality of liquid crystal display panels, the first region is a pixel region, and the second region forms a driving circuit. In the case of the peripheral area of the panel, for example, in the first area on the glass substrate, the control apparatus irradiates the pulse laser light so that the irradiation area of the pulse laser light coincides with the pixel pitch of the pixel area. Then, in the second region on the glass substrate, control is performed so that the pulse laser light is irradiated at a pitch equal to or less than the width so that the irradiation regions of the pulse laser light are connected to each other in the width direction. In addition, a plurality of alignment marks are formed on the substrate at a pixel pitch G, and a camera for imaging the alignment marks is provided, and the control device performs a pulse each time the camera detects the alignment marks on the substrate. It can also be controlled to irradiate laser light.

  In the present invention, for example, when used for manufacturing a panel of a liquid crystal display device, since the pixels are arranged at a predetermined pixel pitch, by setting the first pitch of the irradiation region to be the same as the pixel pitch, In the pixel region (first region), the control device can irradiate the band-shaped pulsed laser light at the same pitch as the pixel pitch. As a result, it is possible to perform a modification process to polysilicon by laser processing at a position where a pixel in the pixel area is to be formed, and since the area between them is not laser-processed, the entire process is highly efficient. , Tact time can be shortened. On the other hand, in the drive circuit formation region (second region) disposed in the peripheral portion of the panel, the laser processing region is formed in the first region by irradiating the pulsed laser light with a pitch smaller than the pixel pitch. By making the area wider than the region, it is possible to increase the optionality of the formation position of the drive circuit and widen the selection range of the formation position of the drive circuit. At this time, in the second region, by setting the second pitch to be the same as the width of the pulsed laser beam, the irradiated region of the pulsed laser beam can be connected in the width direction. Can be laser treated (polysiliconized).

  Therefore, according to the present invention, in the first region, the laser processing is not performed on the entire area of the substrate because the laser beam is thinned out so as not to irradiate the laser beam on the portion where the laser processing is unnecessary. Thus, the laser processing can be performed, and the tact time of the processing can be shortened.

1 is a perspective view showing a laser processing apparatus according to a first embodiment of the present invention. It is a figure which shows the annealing aspect of a 1st area | region (pixel area | region). It is a figure which shows the annealing aspect of a 2nd area | region (peripheral area | region). It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the next process of FIG. It is a figure which shows the laser irradiation aspect on a glass substrate. FIG. 10 is a diagram showing a step subsequent to that in FIG. 9. FIG. 11 is a diagram showing a step subsequent to FIG. 10. It is a graph which shows the effect of this invention.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. As shown in FIG. 1, two cylindrical lens arrays 2a and 2b are arranged in parallel above a substrate 1 to be laser-processed. In each of the cylindrical lens arrays 2a and 2b, for example, eight cylindrical lenses 12 are formed in parallel with each other at a predetermined lens pitch. Pulse laser light is controlled and output from a suitable pulse laser light source (not shown) by a suitable control device. The pulsed laser light emitted from the laser light source is shaped into a flat plate-like laser beam by the two cylindrical lens arrays 2a and 2b and irradiated onto the substrate. Therefore, on the substrate, the irradiation region 5 of each beam 4 of the laser light has a band shape and is parallel to each other. For example, the irradiation region 5 of the laser beam 4 has a width of 250 μm and a length of 50 mm. Further, the pitch at the irradiation position of the laser beam 4 is the same as the pixel pitch, for example, 750 μm. Alternatively, the pitch of the laser beams 4 may be 2 or an integer multiple of the pixel pitch. The pitch of the laser beam 4 is made the same as the arrangement pitch (lens pitch) of the cylindrical lenses 12 of the cylindrical lens arrays 2a and 2b by adjusting the optical characteristics of the cylindrical lens arrays 2a and 2b and other optical systems. Can do. Therefore, the cylindrical lens arrays 2a and 2b are prepared in advance so that the lens pitch of the cylindrical lenses corresponds to the pixel pitch of the liquid crystal display panel, and the panel to be processed from these cylindrical lens arrays 2a and 2b. By selecting the cylindrical lens arrays 2a and 2b to be used according to the pixel pitch, it is possible to easily configure the optical system.

  The substrate to be laser-processed has an a-Si film formed on a glass substrate. The a-Si film is irradiated with laser light, melted once, and then solidified to form a polycrystal. It can be modified into a silicon film. The glass substrate has a width of 1 m or 2 m, for example. Usually, a plurality of panels are formed on a single glass substrate 1, and then pixel transistors and driving circuit transistors are formed by photolithography on all these panels, and then the panels are cut and separated. Thus, a plurality of display panels are manufactured at the same time.

  Next, the operation of this embodiment will be described together with the control mode of the control device. The laser light source is, for example, a Nd: YAG laser light having a wavelength of 1064 nm and a third harmonic of 355 nm and a frequency of, for example, 200 Hz. The pulsed laser light emitted from the laser light source is incident on the cylindrical lens arrays 2 a and 2 b shown in FIG. 1 and is shaped into a flat beam 4 by the cylindrical lens 12. Thereby, the surface of the substrate 1 is irradiated with the laser beam 4 having the irradiation region 5 in a band shape.

  FIG. 9 shows a six-piece glass substrate on which six liquid crystal display panels are formed on the glass substrate 20. Each display panel includes a pixel region 21 in which pixels as first regions are formed, and a peripheral region 22 in which drive circuits as second regions are formed.

For example, when a pixel driving transistor is formed as a peripheral circuit of a liquid crystal display device, a gate electrode made of a metal film such as Al is formed on a glass substrate by sputtering. Then, a gate insulating film made of a SiN film is formed on the entire surface by low-temperature plasma CVD at 250 to 300 ° C. using silane and H ₂ gas as source gases. Thereafter, an a-Si: H film is formed on the gate insulating film by, for example, a plasma CVD method. This a-Si: H film is formed using a gas obtained by mixing silane and H ₂ gas as a source gas. Using the region on the gate electrode of the a-Si: H film as a channel formation planned region, the channel formation planned region is annealed by irradiating laser light, and the channel formation planned region is polycrystallized to form a polysilicon channel region. Form.

  In this laser processing, FIG. 2 shows a laser irradiation mode of the pixel region, and FIGS. 3 to 8 show a laser irradiation mode of the peripheral region. First, in the pixel region shown in FIG. 2, for example, eight laser beams 4 are irradiated onto the substrate 1 at the same pitch as the pixel pitch G by, for example, eight cylindrical lenses 12 of the cylindrical lens arrays 2a and 2b. The Then, the control device relatively moves the substrate 1 or the laser irradiation system in the width direction (arrow a direction) of the irradiation region 5 of the laser beam 4. At this time, for example, when the substrate 1 is moved in the direction a, the control device irradiates the laser beam when the substrate 1 is moved by the pixel pitch G. This is because, for example, a plurality of alignment marks are formed on the substrate 1 with a pixel pitch G, the alignment marks are imaged by a camera (not shown), the substrate 1 moves in the direction a, and the alignment marks are formed by the camera. The substrate 1 may be irradiated with a pulsed laser beam 4 each time it is detected. Thereby, the substrate 1 is irradiated with eight laser beams 4 at intervals of the pixel pitch G in one shot. Each time the substrate 1 is relatively moved by the pixel pitch G, a pulse laser beam is shot. Thereby, in a steady state, the laser shot is received 8 times at the position where the laser beam irradiation is performed on the substrate, and the a-Si film on the substrate is subjected to the laser treatment 8 times. As a result, a-Si is modified into polysilicon in the irradiated region 5 subjected to this laser treatment. As described above, for example, the width of the irradiation region 5 of the pulse laser beam is 250 μm, the length is 50 mm, the pixel pitch G is 750 μm, and the size of one pixel transistor is 30 μm square. 5 is an area that sufficiently covers all the pixel transistors arranged in a line in a 50 mm long area. By forming an irradiation area 5 for each pixel pitch G and scanning the substrate with laser light, The amorphous silicon in all pixel transistor formation regions can be modified to polysilicon. On the other hand, since the pixel pitch is 750 μm, the region of 500 μm is not irradiated with laser light. For this reason, the laser processing can be made efficient and quick, and the tact time can be shortened.

  On the other hand, in the formation region of the driving circuit in the peripheral region 22, as shown in FIG. 3, after one shot of the laser beam 4 is irradiated to form one irradiation region 5, as shown in FIG. The substrate 1 is moved (shifted) in the width direction (direction a) by the width of the irradiation region 5 relatively, and then one shot of the laser beam 4 is irradiated. Thereby, the two-shot laser irradiation region 5 is formed continuously.

  Next, as shown in FIG. 5, the substrate 1 is relatively moved by the width of the irradiation region 5 in this width direction, and then one shot of the laser beam 4 is irradiated. Thereby, the three-shot laser irradiation region 5 is formed continuously.

  Next, as shown in FIG. 6, the substrate 1 is relatively moved in the width direction by the width of the irradiation region 5, and thereafter, one shot of the laser beam 4 is irradiated. As a result, four-shot laser irradiation regions 5 are formed continuously.

  Next, as shown in FIG. 7, the substrate 1 is relatively moved in the width direction by the width of the irradiation region 5, and then one shot of the laser beam 4 is irradiated. As a result, a 5-shot laser irradiation region 5 is formed continuously.

  Next, as shown in FIG. 8, the substrate 1 is relatively moved by the width of the irradiation region 5 in the width direction, and thereafter the operation of irradiating one shot of the laser beam 4 is repeated, whereby the peripheral circuit is The laser irradiation area 5 is connected in all areas 22, and the entire area 22 is subjected to laser processing.

  In this way, in the first region (for example, a pixel region) where the laser processing can be speeded up by thinning out the laser processing, only the region requiring the laser processing, such as the pixel transistor formation scheduled region, is subjected to laser processing. In the second region (for example, the peripheral region) where the formation region does not have periodicity and may be formed at an arbitrary position like the driving transistor, the entire region is subjected to laser processing. Thereby, laser processing can be speeded up compared with the past, and tact time can be shortened.

  Next, the laser irradiation mode of the first region and the second region will be described. As shown in FIG. 9, the glass substrate 20 includes a pixel region 21 in which pixels are formed and a peripheral region 22 in which driver circuits and the like are formed in the formation regions of the display panels (six in the illustrated example). First, an optical system including the cylindrical lens array 2 a is positioned in accordance with the peripheral region 22, and the irradiation region 5 of the laser beam 4 is positioned on the peripheral region 22. That is, the cylindrical lens array 2 a is installed so that the longitudinal direction of the irradiation region 5 of the laser beam 4 straddles the width direction of the peripheral region 22. Then, as shown by an arrow b in FIG. 10, the substrate 1 is moved in the width direction of the irradiation region 5 relative to the cylindrical lens array 2a, and laser shot is performed by the steps shown in FIGS. By linking the irradiation regions 5, the entire peripheral region 22 is laser-treated as shown in FIG. At this time, the laser processing region shown in FIG. 10 is a band-like region having a width of 50 mm (the length of the irradiation region 5), and a part of the pixel region 21 is also laser-processed beyond the peripheral region 22. The laser processing in the steps shown in FIGS. 3 to 8 is finally shifted in a direction (arrow c direction) orthogonal to the laser scanning direction as shown in FIG. That is, at the end of the step shown in FIG. 10, the cylindrical lens array 12a is shifted by the length of the irradiation region 5 in the direction (arrow c direction) perpendicular to the scanning direction shown by the arrow b in FIG.

  Thereafter, as shown in FIG. 11, the laser shot is scanned in the reverse direction (arrow d direction) of FIG. 10. At this time, the irradiation region 5 is formed in the pixel region 21 according to the mode shown in FIG. 2. Go. Accordingly, in the pixel region 21, an irradiation region 5 having a pixel pitch G (750 μm) and a width of 250 μm is formed. The intermediate region of the irradiation region 5 is not laser processed. As a result, the region including the channel region of the pixel transistor in the pixel region 21 is laser-processed and modified into a polysilicon film. A plurality of display panels (eight in the illustrated example) can be obtained from one glass substrate 20, but when the laser scanning moves from the pixel region 21 to the pixel region 21 of another panel, the display panel Therefore, the entire peripheral region 23 is also laser-treated in the steps shown in FIGS. Thereafter, the same process is repeated, and the entire glass substrate is subjected to laser processing by a process of laser-shoting at a pixel pitch G and a process of laser-shoting so that the irradiation areas are continuous.

  In this manner, the channel regions of the pixel transistor and the drive transistor are modified from amorphous silicon to polysilicon, and high-speed transistor operation is ensured. On the other hand, the region where the transistor is not formed remains amorphous silicon. As a result, the laser processing can be speeded up and speeded up, and the tact time of the laser processing can be shortened.

  FIG. 12 is a graph showing the effect of the present invention with the panel size on the horizontal axis and the tact time on the vertical axis. In the figure, ▪ indicates the tact time when the entire surface of the substrate is laser processed using an excimer laser having a wavelength of 308 nm and a frequency of 600 Hz. Further, ▲ is the tact time when the entire surface of the substrate is laser processed using an Nd: YAG laser having a wavelength of 355 nm + 1064 nm and a frequency of 200 Hz. In contrast, ♦ is an embodiment of the present invention, and is a tact time when a substrate is laser-treated as shown in FIG. 11 using an Nd: YAG laser having a wavelength of 355 nm + 1064 nm and a frequency of 200 Hz. As is apparent from FIG. 12, when the panel size is 20 inches, there is not much effect, but as the panel size is changed from 40 inches to 70 inches, the tact time is significantly shortened. The larger the panel size, the greater the effect of the present invention because the larger the panel size, the larger the area of the pixel region compared to the area of the peripheral region.

  The present invention is effective not only for manufacturing a liquid crystal display panel but also for improving the tact time in a technical field that requires laser processing. Further, the number of cylindrical lenses 12 formed in one cylindrical lens array 2a, 2b is eight in the above embodiment, but the present invention is not limited to this and can be variously set. In the process shown in FIG. 2, the laser processing portion of the substrate 1 is usually subjected to the same number of laser processing according to the number of the cylindrical lenses 12, but one movement of the cylindrical lenses 2a and 2b is performed in the pixel. By setting the pitch G twice or more, the number of times of laser processing at the laser processing location on the substrate can be reduced to ½ or less of the number of cylindrical lenses 2a and 2b.

  INDUSTRIAL APPLICABILITY The present invention is useful for a technical field that requires laser processing such as film modification, such as a display panel of a liquid crystal display device.

1: Substrate 2a, 2b: Cylindrical lens array 4: Laser beam 5: Irradiation region 12: Cylindrical lens 20: Glass substrate 21: Pixel region 22: Peripheral region 23: Peripheral region

Claims (3)

A laser light source that emits pulsed laser light, a plurality of cylindrical lenses that shape the irradiation region of the pulse laser light from the laser light source into a plurality of strips, and the substrate and the cylindrical lens. And a control device for controlling the relative movement in the width direction and the longitudinal direction of the irradiation region, and the cylindrical lenses are arranged in parallel to each other at a constant lens pitch in a direction perpendicular to the longitudinal direction. The control device irradiates the first region on the substrate with the pulsed laser light so that the band-shaped irradiation region has a first pitch in the width direction, and the second region irradiates the band-shaped irradiation. The emission of the laser light source, the substrate, and the cylindrical so that the region is irradiated with pulsed laser light at a second pitch smaller than the first pitch in the width direction The laser processing apparatus characterized by controlling the relative movement of the lens. The substrate is a glass substrate for manufacturing one or a plurality of liquid crystal display panels, the first region is a pixel region, the second region is a peripheral region of the panel forming a driving circuit, and the control The apparatus irradiates the pulsed laser light in the first region on the glass substrate so that an irradiation region of the pulsed laser light coincides with a pixel pitch of a pixel region, and in the second region on the glass substrate. 2. The laser processing apparatus according to claim 1, wherein the laser processing apparatus is controlled to irradiate the pulsed laser light at a pitch equal to or less than the width so that the irradiation regions of the pulsed laser light are connected to each other in the width direction. A plurality of alignment marks are formed on the substrate at a pixel pitch G, and a camera for imaging the alignment marks is provided. The control device detects a pulse laser beam each time the camera detects an alignment mark on the substrate. The laser processing apparatus according to claim 1, wherein the laser processing apparatus is irradiated.

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