JP2005276996A - Flat display device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of alignment mark processing step during the formation of an active layer of a silicon film in a crystalline state, which is necessary for various circuits, on an insulating substrate that constitutes a flat display device, and thereby to achieve a high throughput and a low cost. <P>SOLUTION: An L-pattern 20 is formed on a photomask 17, and pattern matching is performed using the L-pattern 20 and a straight line or a nearly straight line (side) around a pseudo monocrystal region 11 on a substrate. At this time, the photomask 17 is driven relative to three axes XYθ together with the substrate so that the distance ΔX between the side 22 of the L-pattern 20, and the side 24 of the pseudo mnocrystal region 11 becomes equal to the distance ΔY between the side 23 of the L-pattern 20 and the side 25 of the pseudo monocrystal region 11, thus making the photomask and the substrate coincide with each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a flat panel display device, and in particular, irradiates an amorphous or polycrystalline semiconductor film formed on an insulating substrate with a laser beam to improve film quality, enlarge crystal grains, or make a single crystal. This is suitable for manufacturing a flat display device including an active substrate having a thin film transistor formed in a semiconductor film formed by the above method.

  A liquid crystal display device or an organic EL display device is an active substrate having a pixel circuit composed of a thin film transistor formed on an amorphous silicon thin film (also referred to as an amorphous silicon thin film) formed on an insulating substrate such as glass or fused silica. (Hereinafter also referred to as a display panel, or simply a panel or a substrate). As the circuit arranged on the substrate, the pixel circuit constituting the display area by forming pixels at the intersection of the scanning lines and the signal lines arranged in a matrix directly on the substrate, and arranged outside the display area. A driving circuit (also referred to as a driver) for driving the pixels and other circuits (peripheral circuits) are arranged as necessary. The driving circuit includes a scanning line driving circuit that selects a pixel and a signal line driving circuit that supplies a display signal to the selected pixel. The pixel circuit is selected by the scanning line driving circuit, and forms an image by turning on or off the pixel by switching of the selected thin film transistor (pixel transistor). At present, the scanning line driving circuit and the signal line driving circuit are mounted on a substrate as so-called semiconductor chips.

  If it becomes possible to simultaneously form a scanning line driving circuit for driving a pixel transistor and a so-called driver circuit constituting a signal line driving circuit on this substrate, a drastic reduction in manufacturing cost and improvement in reliability can be expected. However, under the present circumstances, since the silicon thin film forming the active layer of the transistor has poor crystallinity, the performance of the thin film transistor represented by mobility is low, and it is difficult to manufacture a circuit that requires high speed and high function. In order to manufacture these high-speed and high-function circuits, a high-mobility thin film transistor is required, and in order to realize this, it is necessary to improve the crystallinity of the silicon thin film.

As a method for improving the crystallinity, excimer laser annealing has been conventionally employed. In this method, an amorphous silicon thin film (mobility of 1 cm ² / Vs or less) formed on an insulating substrate such as glass is irradiated with an excimer laser, and the amorphous silicon thin film is converted into a polycrystalline silicon thin film (polysilicon thin film). In other words, the mobility is improved. The polycrystalline thin film obtained by excimer laser irradiation has a crystal grain size of about several hundreds of nanometers and a mobility of about 150 cm ² / Vs, which is sufficient for driving a transistor of a pixel circuit. Insufficient performance to apply to a high mobility transistor such as a driver circuit for driving the transistor.

  In addition, protrusions of several tens of nm to 100 nm are formed at the crystal grain boundary, which causes a reduction in the breakdown voltage of the transistor. In addition, excimer lasers have a large process variation due to large variations in energy between pulses, and because toxic gases are used, equipment costs are high, and expensive oscillators need to be replaced periodically. There are also disadvantages such as extremely high costs.

As a method for solving these problems, Patent Document 1 discloses that a second harmonic of a continuous wave solid laser pulsed by an EO modulator (electro-optic element) at an arbitrary time width is linearly collected, and a glass substrate. A method of irradiating a laser beam while scanning the silicon thin film formed thereon is disclosed. The invention disclosed in this publication promotes the extension of the melting time of silicon and the reduction of the cooling rate to increase the number of crystal grains.
JP 2003-124136 A

In the above prior art, the second harmonic of an LD (laser diode) pumped continuous wave solid-state laser is scanned on an amorphous silicon thin film formed on a substrate to grow a crystal in the scanning direction of the laser beam, and the thickness is 500 cm. ^A mobility exceeding ² / Vs is obtained. The resulting polycrystalline thin film has no protrusions, and when a silicon thin film with such a degree of mobility is obtained, a drive circuit with sufficient performance can be formed, and the drive circuit can be formed into a flat panel display substrate (panel). A system-on-panel formed directly on can be realized.

  However, experiments have revealed that this method has the following problems. The output of a continuous wave solid-state laser is small. Therefore, when the silicon thin film is irradiated and melted and recrystallized (so-called laser annealing), the laser irradiation width is reduced to several hundred microns in order to increase the power density on the laser irradiation surface to such an extent that the silicon thin film is melted. Is required. That is, the width that can be crystallized in one scan is very small. Therefore, in order to form a gate region of a transistor, that is, a channel region in the crystallization region after selectively irradiating a laser to a desired region in the panel and performing crystallization, a photoresist process (photo-etching process, (Also referred to as a photolithography process), it is required to realize a precise alignment technique between a photomask and a substrate.

  As a solution to this problem, the following method is disclosed in Patent Document 1 described above. As a first method, the alignment mark for the alignment is formed on the amorphous silicon thin film in the photoresist process provided between the amorphous silicon thin film forming process and the laser annealing process. As a second method, a laser used for crystallization or an alignment mark forming laser is mounted on a manufacturing apparatus, and the silicon thin film is subjected to laser processing to form an alignment mark. However, in these methods, the throughput decreases due to an increase in the number of steps. In addition, in the laser processing method, the manufacturing cost increases due to an increase in optical system components.

  An object of the present invention is to provide a method of manufacturing a flat display device that improves the throughput in the manufacturing process and reduces the manufacturing cost.

  In the method for manufacturing a flat display device according to the present invention, the planar shape of the quasi-single crystal region formed by irradiating time-modulated continuous wave solid-state laser light is used as an alignment mark in a photoresist process for forming a gate portion, that is, a channel portion. Thus, the above object is achieved.

That is, the manufacturing method of the flat display device of the present invention to obtain an active substrate by making a circuit composed of thin film transistors on an insulating substrate,
A silicon thin film forming step of forming a silicon thin film on an insulating substrate constituting an active substrate of a flat display device;
A lateral crystal growth step of selectively forming a laterally grown polycrystalline silicon thin film on the substrate by irradiating the silicon thin film with time-modulated continuous wave laser light while scanning at the same speed;
A polycrystalline silicon thin film patterning step of forming an active layer of a thin film transistor by patterning the laterally grown polycrystalline silicon thin film formed in the lateral crystal growth step by a photolithography technique using a photomask on the insulating substrate;
Including
A part or all of the planar shape of the laterally grown polycrystalline region formed in the polycrystalline silicon thin film patterning step (for example, a corner of the planar shape) is used as one alignment mark, and the other alignment of the photomask. It is characterized in that alignment with a mark is performed.

  Note that the present invention is not limited to the above-described configuration and the configuration described in the embodiments described later, and it goes without saying that various modifications can be made without departing from the technical idea of the present invention.

  According to the method for manufacturing a flat panel display device of the present invention, time-modulated, that is, a high-mobility pseudo single beam selectively formed on a large substrate by focusing continuous-wave solid-state laser light whose laser intensity is modulated by time into a line shape. By adopting the crystal formation area as an alignment mark when performing the photoresist process, it is possible to reduce the alignment mark formation process, and the required high-performance silicon film can be applied to the desired area with high throughput and low manufacturing cost. Can be obtained at

  Embodiments of the present invention will be described below in detail with reference to the drawings of the embodiments.

  First, a configuration of a panel constituting a flat display device manufactured by the manufacturing method of the present invention and a method for forming a quasi-single crystal silicon thin film that becomes an active layer of a thin film transistor will be described. The quasi-single crystal means one having a strip shape (laterally grown polycrystal) in which one direction of the crystal is longer than the other direction orthogonal to the one direction.

FIG. 1 is a diagram showing a configuration of a large substrate and a crystallization region in the display device in the method for manufacturing a flat display device of the present invention. FIG. 1 (a) is an overall plan view of the large substrate, and FIG. FIG. 2 is an enlarged plan view of one of a number of panels configured on the large substrate of FIG. Note that the large substrate is a substrate having a size finally separated into a plurality of panels, and is also referred to as a base substrate or a mother substrate. This large substrate is generally glass, and the substrate in the following description assumes a glass substrate. However, a substrate formed of another similar material may be used. In FIG. 1, as a large substrate, SiO ₂ or SiN having a film thickness of 50 nm to 200 nm or a composite film thereof (underlayer, not shown) is formed on one main surface of a glass substrate having a thickness of about 0.3 mm to 1.0 mm. Then, an amorphous silicon thin film having a thickness of 30 nm to 150 nm is formed.

The amorphous silicon thin film is polycrystallized (granular crystallization) on the entire surface by excimer laser or solid laser irradiation, and then selectively using a crystallization technique using a continuous oscillation solid laser described in Patent Document 1. Pseudo single crystallization is applied. As the solid-state laser here, one that generates continuous-wave light of ultraviolet light or visible light wavelength is used, and in particular, laser diode excitation YVO ₄ laser or laser diode excitation from the viewpoint of output size, output stability, etc. The second harmonic (wavelength: 532 nm) of the YAG laser is optimal. However, the present invention is not limited to this, and it is possible to use a third or fourth harmonic of an argon laser, YVO ₄ or YAG laser, a plurality of semiconductor lasers coupled by a fiber, and the like.

  In the substrate 1, a plurality of panels 1, 2, 3, 4,... Are formed as indicated by broken lines. As an example, an enlarged view of the panel 3 in the substrate 1 of FIG. 1A is shown in FIG. All the other panels in the substrate 1 have the same configuration as the panel 3. The panel 3 includes a signal line driving circuit region 5, a scanning line driving circuit region 6, a pixel region (display region) 7, and a circuit forming region having thin film transistors such as other peripheral circuit regions 8 provided as necessary. The

Each region in the panel 3 has a high mobility silicon film having a mobility of 300 cm ² / Vs or more in the signal line driving circuit region 5 and the other peripheral circuit region 8, and a signal line in the scanning line driving circuit region 6. A silicon film having a mobility as high as that of the drive circuit region or a silicon film having a mobility lower than that (˜150 cm ² / Vs), and a silicon film having a lower mobility than the above two regions in the pixel region 7. Is required.

  In order to form the required silicon crystal film in each of the above regions, the amorphous silicon thin film is crystallized by laser light irradiation. In the signal line drive circuit region 5 and the other peripheral circuit regions 8, a continuous wave solid-state laser is pulsed with an EO modulator or an AO modulator in order to form a pseudo single crystal having high mobility performance. The quasi-single crystal having a high mobility is formed by focusing the light on the substrate 1 and scanning it relative to the substrate 1. Reference numeral 14 denotes a corner of the signal line driver circuit region 5.

  Similarly to the signal line drive circuit area 5, a pseudo single crystal is formed in the scanning line drive circuit area 6 by irradiation with a continuous wave solid laser, or an excimer laser or a solid laser (in this case, a continuous wave system, a pulse) Either method may be used) to form a polycrystal having a medium mobility.

  Whether the pixel region 7 is irradiated with an excimer laser or a solid-state laser (in this case, either a continuous oscillation method or a pulse oscillation method may be used) to form a medium or low mobility polycrystal. Alternatively, an amorphous film is used.

  Here, the formation method of the pseudo single crystal and the shape of the formed crystal region will be described. FIG. 2 is an explanatory view of the state of the silicon thin film before and after the formation of the pseudo single crystal by the irradiation of the linear laser beam in the method for manufacturing the flat display device of the present invention, and FIG. FIG. 2B shows the state after the formation of the pseudo single crystal. As shown in FIG. 2A, the quasi-single crystal region is formed on the substrate in a direction intersecting with the longitudinal direction (here, a direction orthogonal to the longitudinal direction) of the laser light 9 condensed linearly. Crystallization is performed by scanning relative to the silicon thin film 10 (in this case, the starting sample may be either an amorphous thin film or a polycrystalline thin film).

  In the process where the silicon film irradiated with the linear laser beam 9 is melted and re-solidified, the crystal grains grow in the scanning direction of the laser beam 9 indicated by the arrow, that is, in the lateral direction, and the crystal growth occurs at the end of the laser beam irradiation. Stop.

  When forming a transistor using this laterally grown crystal, as shown in FIG. 2 (b), parallel to the crystal grains grown in the laser scanning direction (any one direction, lateral direction in the figure) If the source region 60, the drain region 61, and the channel region 62 are set to be formed, a thin film transistor in which the grain boundary does not cross the channel can be formed, and the single crystal is used in terms of mobility and threshold voltage variation. Performance close to that of the formed thin film transistor can be obtained. As described above, the crystal region 11 grown in the laser scanning direction is called a pseudo single crystal region.

  Further, at the irradiation end point of the laser beam 9, that is, at the end point of the pseudo single crystal region, the melted silicon solidifies in a state where the wave collides with the quay, so that a linear protrusion 36 is formed. As a result, the formed pseudo single crystal region 11 has a rectangular shape as shown in FIG.

  FIG. 3 is a plan view showing a state of the large-sized substrate after forming the pseudo single crystal in the method for manufacturing a flat display device of the present invention. A continuous wave laser beam is shaped to an arbitrary time width by an EO modulator, an AO modulator, etc., and is irradiated from end to end of the large substrate 1 while being repeatedly turned on and off periodically. For example, as shown in FIG. 1, a pseudo single crystal region 11 having a rectangular shape or a shape close to a rectangular shape is periodically formed. The scanning start position in this case is set by driving the substrate to a coordinate position obtained by detecting the corner portion of the substrate 1 by pre-alignment and rough alignment as a reference point and adding an arbitrary offset amount from the reference point. To do.

  After passing through the quasi-single crystallization step by the laser light irradiation, rectangular quasi-single crystal regions 11 are periodically arranged in parallel on the substrate 1 as shown in FIG. When this crystallization process is completed, an impurity diffusion process is performed, followed by a photoresist process for forming a silicon thin film island (semiconductor island) in the gate region (channel region). In this step, unnecessary silicon thin films other than the gate region of the transistor are removed. At this time, the circuit pattern of the photomask is accurately transferred into the pseudo single crystal region 11 selectively crystallized as shown in FIG. 3, and the channel region of the thin film transistor is formed of a desired crystal. There must be. Patent Document 1 described above discloses a method in which an alignment mark is formed in advance in a photoresist process before a crystallization process by laser irradiation, and a method in which a mark is formed by laser processing. From the viewpoint of cost, it is desirable that the mark forming step can be omitted as much as possible.

  Therefore, in this embodiment, in order to omit the alignment mark (positioning mark) forming process for forming the gate region, an arbitrary pseudo single crystal region formed in the silicon film crystallization process is used as the alignment mark. As shown in FIG. 2B, the quasi-single crystal region 11 includes two sides 63 and 64 parallel to the scanning direction, sides of the linear protrusion 36 (laser irradiation end region) at the end of scanning, and a crystal. It is surrounded by the growth starting point (the left side of the pseudo single crystal region 11 in FIG. 2B, that is, the laser irradiation start region... Polycrystalline grain row (side formed by fine uneven curves)). Therefore, the crystal region 11 has a rectangular shape or a shape surrounded by at least these three sides and one uneven curve side. That is, the surroundings always include corners 65 and 66 where two sides are orthogonal or intersect. The corners 65 and 66 are used for alignment with the photomask.

  FIG. 4 is a view for explaining an example of an exposure apparatus in the method for manufacturing a flat display device of the present invention. This apparatus includes an exposure light source 70, a mirror 71 that turns back light from the light source, a projection optical system 72, a substrate stage 74 on which a glass substrate 73 is mounted, a mask stage 76 on which a photomask 17 is mounted, and alignment mark detection cameras 77 and 78. 79, an image processing device 80 for performing binarization processing on the image captured by the camera and calculating the reference point and the mark coordinates, and the mark on the substrate and the mark on the mask calculated by the image processing device 80 A driver 81 or the like that drives the mask stage 76 so as to match the coordinates is configured.

  FIG. 5 is a schematic diagram illustrating an example of a method for aligning a photomask and a substrate. An observation optical system (not shown) including an objective lens, a CCD camera, and the like captures an image of a point where two sides of the pseudo single crystal region 15 intersect, that is, a corner 16 of the pseudo single crystal region 11, and an image processing apparatus. Image coordinates such as a binarization process are performed as necessary (not shown) to calculate the position coordinates of the corner 16. Thereafter, the substrate and the photomask are driven with respect to the three axes XYθ, and the corner 16 and the arbitrary reference coordinate point 18 of the photomask 17 are made to coincide. In this way, the pseudo single crystal region corner (intersection of two sides) is detected for at least three arbitrary points in the substrate, and is made to coincide with the reference coordinate point of the photomask 17, and the relative position of the substrate and the photomask is determined. Determine exactly.

  As another example of the method for aligning the photomask and the substrate, there is the following method. FIG. 6 is a schematic diagram showing another example of the alignment method between the photomask and the substrate, FIG. 6A is a perspective view showing the arrangement of the photomask and the substrate, and FIG. 6B is FIG. 6A. It is the top view to which the principal part of was expanded. That is, instead of aligning the coordinates calculated as described above, an L-shaped pattern 20 as shown in FIG. 6 is provided on the photomask 17, and the L-shaped pattern 20 and the periphery of the pseudo single crystal region 11 on the substrate are provided. Pattern matching may be performed with a straight line or a substantially straight line (side). In this case, as shown in FIG. 6, the distance ΔX between the side 22 of the L-shaped pattern 20 and the side 24 of the pseudo single crystal region 11 and the distance between the side 23 of the L-shaped pattern 20 and the side 25 of the pseudo single crystal region 11. Both the photomask 17 and the substrate are driven and matched with respect to the three axes of XYθ so that the distance ΔY is equal.

  In this embodiment, the L-shaped pattern 20 as shown in FIG. 6 is used for alignment with the pseudo single crystal region 11, but the pattern as the alignment mark provided on the photomask is not limited to the L-shaped pattern. Any shape can be used as long as it can detect the positional relationship between the photomask and the pseudo single crystal region on the substrate in the XYθ direction, such as a square pattern. The alignment using this alignment mark is performed for an arbitrary number of points on the substrate, and the alignment operation is completed.

  In the present embodiment, as the alignment mark for alignment, it is most preferable to perform alignment using linear protrusions formed at the end of the pseudo single crystal region (side of the laser irradiation end). However, alignment may be performed using a corner portion of the laser irradiation start side as long as it is linear.

  Next, an embodiment of a method for manufacturing a display device according to the present invention will be described. FIG. 7 is a diagram for explaining a quasi-single crystal crystallization step in the method for manufacturing a flat display device of the present invention. FIG. 8 is a diagram for explaining an example of an alignment process between a pseudo single crystal region of a substrate having a pseudo single crystal silicon thin film and a photomask. FIG. 7A shows two adjacent panels as representatives among a plurality of panels manufactured from a large substrate (usually several tens to several hundreds of panels are formed). Here, a substrate in which an amorphous silicon thin film was formed on one main surface of a glass substrate via an insulator thin film was used as a sample.

  As described with reference to FIG. 1, the display area (pixel area) 7, the scanning line driving circuit area 5, and the signal line driving circuit area 6 are formed on each panel. In this embodiment, a pixel transistor whose gate region is formed of a polycrystalline silicon film is formed in the display region, and the gate region is formed of a pseudo single crystal in the signal line driving circuit region 5 and the scanning line driving circuit region 6. An example of forming a thin film transistor capable of high-speed driving will be described. In this embodiment, an example in which only the above three regions are polycrystallized to form a thin film transistor is shown, but a circuit region may be provided in addition to the above three regions. As shown in FIG. 7A, a large substrate 27 on which an amorphous silicon thin film 26 is formed is mounted on a stage (not shown), and excimer laser light 28 is scanned in the direction indicated by the arrow to By irradiating the amorphous silicon thin film 26 over the entire surface, it is converted into a polycrystalline silicon thin film 29.

  Next, as shown in FIG. 7B, the solid-state laser light 30 condensed linearly is scanned relative to the substrate 27 in the direction indicated by the arrow while being time-modulated by the EO modulator. A pseudo single crystal having the performance necessary for formation is selectively formed only in desired regions 31 and 32. This scanning is generally performed by moving the substrate 27 on the stage, but the laser beam may be moved.

  When the quasi-single crystallization by laser annealing of the signal line driving circuit region is completed over the entire surface of the substrate 27, the substrate 27 is rotated by 90 ° in the plane, and as shown in FIG. For this purpose, a time-modulated linear laser beam 30 is irradiated to selectively form pseudo single crystals only in desired regions 34 and 35. In this case, the substrate 27 may be discharged once from the stage, rotated 90 °, and then returned to the stage again to perform this pseudo single crystallization, that is, laser annealing, or the laser light may be rotated 90 ° by rotating the optical system. It may be rotated. Note that, although an example has been described in which the laser light is repeatedly turned on and off at a constant cycle or an arbitrary cycle when scanning is performed, the laser light may be constantly scanned in an ON state. In this way, scanning is repeated, and all the scanning line driving circuit regions 5 in the panel are pseudo-single-crystallized, and irradiation is completed.

  In this embodiment, the example in which the power density of the laser beam is set to the power density for forming the pseudo single crystal and the crystallization is performed has been described. However, the crystal required in the scanning line driver circuit region is polycrystalline. In some cases, the crystallization may be performed by setting the laser light to a power density suitable for forming polycrystalline grains.

  In this embodiment, an example in which an excimer laser is used for crystallization of the display portion is described. However, a continuous wave solid-state laser or a pulsed oscillation solid laser that is time-modulated may be used for crystallization of the display portion. Furthermore, the polycrystallization by excimer laser irradiation and the selective quasi-single crystallization process by solid laser irradiation may be performed in separate annealing chambers for the excimer laser and the solid laser, or the excimer laser optical system and the solid laser. Laser light from the laser optical system may be guided to one annealing chamber.

By repeating the above operation, the entire surface of the substrate is scanned to complete laser annealing. Thereby, each panel in the substrate 27 has a polycrystalline silicon film whose pixel portion has a mobility of about 150 cm ² / Vs, a scanning line driving circuit region and a signal line driving circuit region (including other peripheral circuit regions). is converted mobility 300cm ² / Vs~400cm ² / Vs crystallized silicon laterally strip to (pseudo single crystal silicon) film.

  After all of the laser annealing steps of the substrate 27 are completed, photoetching is performed to form a so-called island by removing a region other than the silicon thin film in a region necessary for forming the thin film transistor by a photoresist step (photolithography process). In this step, after a photosensitive resin (photoresist) is dropped on the substrate 27 loaded in the exposure apparatus to form a resist film (not shown), a circuit pattern is drawn as shown in FIG. The exposed photomask 37 is placed on the substrate 27 after the photoresist film is formed, and exposure is performed.

  First, pre-alignment and rough alignment of the substrate loaded in the exposure apparatus are performed, and the corner portion 40 corresponding to the crystallization region corner portion 14 in the panel 3 in the substrate 1 shown in FIG. It detects through the observation optical system (not shown) comprised from these. Next, a region 39 (see FIG. 8B) including the corner portion 40 is imaged, and image processing such as binarization processing is performed as necessary by an image processing device (not shown), and the corner portion 40 is processed. The position coordinates of are calculated.

  On the basis of the calculated coordinates, as shown in FIG. 8B, a photo-coordinate is made so that an arbitrary reference coordinate point 38 on the photomask 37 whose position coordinates are known in advance and the corner 40 of the region 39 are matched. The mask 37 (or the substrate) is driven in the XYθ direction. After the coordinates match, the same processing is performed using the corners of the panel 4 on the substrate shown in FIG. 1, and the photomask 37 or the substrate 27 is driven in the XYθ direction, so that the substrate 27 and the photomask 37 are driven. Complete the alignment.

  In this embodiment, an example in which the alignment process, that is, the alignment of the substrate 27 and the photomask 37 is performed on two points on the substrate 27 is shown, but this alignment process may be performed any number of times. Thus, the alignment of the substrate 27 and the photomask 37 is completed, and after exposure and etching processes, as shown in FIG. 8C, a signal line drive circuit region 41, a scan line drive circuit region 42, and a pixel region 43 are formed on the panel. The gate region is formed.

  Next, another embodiment of the method for manufacturing a display device of the present invention will be described. FIG. 9 is a diagram for explaining another example of the alignment process between a substrate having a quasi-single-crystallized silicon thin film and a photomask. FIG. 9A shows two adjacent panels as representatives among a plurality of panels manufactured from a large substrate (usually several tens to several hundreds of panels are formed). Here, a substrate in which an amorphous silicon thin film is formed on one main surface of a glass substrate via an insulator thin film is used as a sample. As shown in FIG. 1, a display area (pixel area) 7, a scanning line driving circuit area 5, and a signal line driving circuit area 6 are formed on each panel.

  In this embodiment, the gate region of the thin film transistor of the pixel in the display region 7 shown in FIG. 1 is composed of a polycrystalline silicon thin film, and the gate region of the signal line driving circuit region 5 and the scanning line driving circuit region 6 is also a pseudo single crystal silicon thin film. An example of forming a thin film transistor that can be driven at high speed is shown. In this embodiment, an example in which only the above three regions are polycrystallized to form a transistor is shown, but other peripheral circuit portions may be provided in addition to the above three regions.

  As shown in FIG. 7A, a large substrate 27 on which an amorphous silicon thin film 26 is formed is mounted on a stage (not shown), and an excimer laser beam 28 is scanned in the direction indicated by the arrow. The amorphous silicon thin film 26 is converted into a polycrystalline silicon thin film 29 by irradiation over the entire surface. Next, as shown in FIG. 7 (b), the solid-state laser light 30 collected in a linear shape is scanned relative to the substrate 27 in the direction indicated by the arrow while being time-modulated by the EO modulator. A pseudo single crystal having a performance necessary for forming a drive circuit is selectively formed only in desired regions 31 and 32. This scanning is generally performed by moving the substrate on the stage, but the laser beam may be moved.

  When the quasi-single crystallization of the signal line driving circuit region 6 shown in FIG. 1B is completed over the entire surface of the substrate 27, the substrate is rotated by 90 °, and the scanning line driving is performed as shown in FIG. 6C. Irradiation with a time-modulated linear laser beam 30 is performed to form a circuit, and a pseudo single crystal is selectively formed only in desired regions 34 and 35. In this case, the substrate 27 may be discharged from the stage once and rotated by 90 °, and then the substrate may be returned to the stage again for annealing treatment, or the laser beam may be rotated by 90 ° by rotating the optical system. . Note that, although an example has been described in which the laser light is repeatedly turned on and off at a constant cycle or an arbitrary cycle when scanning is performed, the laser light may be constantly scanned in an ON state. Scanning is repeated in this manner, and all the scanning line driving circuit regions 5 in the panel shown in FIG.

  In this embodiment, the example in which the laser light is set to the power density for forming the pseudo single crystal and the crystallization is performed has been described. However, when the crystal required in the scanning line driving circuit region is a polycrystal, The crystallization may be performed by setting the power density to a power density suitable for forming polycrystalline grains.

  In the present embodiment, an example in which an excimer laser is used for crystallization of the display region 7 shown in FIG. 1B has been described. However, a continuous wave solid-state laser or a pulse oscillation time-modulated for crystallization of the display portion is described. A solid laser may be used. Further, the polycrystallization by excimer laser irradiation and the selective quasi-single crystallization process by solid laser irradiation may be performed in separate annealing chambers for the excimer laser and the solid laser, or the excimer laser optical system and the solid laser. Laser light from the laser optical system may be guided to one annealing chamber. By repeating the above operation, the entire surface of the substrate is scanned to complete the annealing.

Thereby, in each panel in the substrate 27, a polycrystalline silicon film having a mobility of about 150 cm ² / Vs is moved in the pixel area, and the scanning line driving circuit area and the signal line driving circuit area (including other peripheral circuit areas) are moved. is converted to a pseudo-single crystal silicon thin film in degrees 300cm ² / Vs~400cm ² / Vs. After all the laser annealing steps are completed, the regions other than the silicon thin film in the region necessary for transistor formation are removed by a photoresist step.

  First, after a photosensitive resin (photoresist) is dropped on the substrate 27 to form a resist film (not shown), a photomask on which a circuit pattern is drawn is placed on the substrate 27 after the resist film is formed, Perform exposure. Here, an example in which alignment is performed using an L-shaped pattern on a photomask and a pseudo single crystal region will be described. The alignment of the corners 14 of the signal line driver circuit formation region 5 of the panel 3 in the substrate 1 shown in FIG. 1 and the photomask pattern is performed.

  As shown in FIG. 9A, pre-alignment and rough alignment of the substrate 27 loaded on the stage are performed, and the signal line driving circuit on the loaded substrate 27 is within the field of view of the observation optical system (not shown). The substrate 27 and the photomask 37 are driven until the region 45 and the pattern 47 on the photomask 37 are in a position where they can be observed simultaneously. When the state observed from the observation optical system is represented, the relationship is as shown in FIG. While monitoring this state, the distance ΔX between one side 48 of the signal line driver circuit region 11 and one side 49 of the pattern 47 of the photomask 37, and the pattern of one side 50 of the signal line driver circuit region 11 and the photomask 37 The substrate is driven in the XYθ direction so that the distances ΔY between the one side 51 of 47 are equal to each other, and ΔX and ΔY are made to coincide. After the coincidence, the same scanning is performed using the corners of other arbitrary pseudo single crystal regions on the substrate 11 to complete the alignment.

  In this embodiment, the alignment process is completed by performing alignment at two arbitrary points on the substrate 11, but it is needless to say that alignment may be performed at an arbitrary number of points on the substrate. The alignment is thus completed, and the gates of the signal line driving circuit region 41, the scanning line driving circuit region 42, and the pixel region 43 are formed on the panel through exposure and etching steps as shown in FIG. 8C.

  Here, a manufacturing process of the display device including the above-described annealing process will be described. FIG. 10 is a diagram illustrating the entire process of the method for manufacturing a flat display device according to the present invention. As shown in FIG. 10, first, an insulating film (underlying film) is formed on a glass substrate. An amorphous silicon (amorphous silicon: a-Si) thin film is formed thereon, and laser annealing is performed. According to the embodiment described above, alignment is performed at the corners of the substrate, and the target crystal is grown by irradiating the pixel region and the peripheral circuit region with time-modulated solid-state oscillation laser light. When the necessary annealing is completed, the substrate is unloaded from the laser annealing apparatus and sent to the next process.

  After laser annealing, island formation that leaves only the silicon foil film necessary for thin film transistor formation is performed by photoetching process, gate insulating film formation, gate electrode formation, impurity diffusion, activation, interlayer edge film formation, source / drain electrode formation Then, an active substrate (thin film transistor substrate, TFT substrate) is completed through formation of a protective film (passivation film). Thereafter, an alignment film is formed on the TFT substrate, the TFT substrate that has undergone the rubbing process is used as one substrate, the color filter substrate that is the other substrate is stacked, and the liquid crystal is sealed between the color filter substrate and the TFT substrate. Liquid crystal in which high-speed drive circuits and high-speed circuits such as interface circuits as necessary are formed on a glass substrate through LCD (panel) processes, module processes that are connected to the case together with backlights after connecting signal and power terminals. A display device (so-called system on panel) is completed.

  FIG. 11 is a diagram illustrating an equivalent circuit of a panel constituting a liquid crystal display device which is an example of a flat display device to which the present invention is applied. Most of the active substrate (TFT substrate) which is a panel is occupied by a pixel region (display region) 7, and a signal line driver circuit region 5 is provided on one side of the outer periphery and a scanning line driver circuit region 6 is provided on the other side. doing. In the pixel area 7, a large number of pixels including thin film transistors 200, liquid crystal cells 201, and additional capacitors 202 are arranged in a matrix. Here, one color pixel is composed of three sub-pixels formed by the liquid crystal cells R, G, and B of three colors.

  A scanning line driving circuit for supplying selection signals to the scanning lines G-1, G0,..., Gend, Gend + 1 is formed in the signal line driving circuit region 6, and the signal line driving circuit region 5 has signal lines. A signal line driving circuit for applying a video signal to DiR, DiG, DiB, Di + 1R, Di + 1G, Di + 1B,.

  A selection signal and a video signal are supplied from the interface circuit board 100 to the scanning line driving circuit and the signal line driving circuit, respectively. The interface circuit board 100 includes a display control circuit 101 including a timing controller, a power supply circuit 102, and the like, and generates the selection signal and the video signal based on a display signal input from a signal source (host) (not shown).

  In the present invention, each liquid crystal of a known method such as a method in which a color filter is formed on the TFT substrate as described above and a counter electrode and an alignment film are formed on the other substrate, or a method in which a counter electrode is also formed on the TFT substrate. The present invention can be similarly applied to a display device, an organic electroluminescence display device, and other flat display devices using an active substrate.

It is a figure which shows the structure of the large sized substrate in the manufacturing method of the flat display apparatus of this invention, and the crystallization area | region in a display apparatus. It is explanatory drawing of the state of the silicon thin film before and after formation of the pseudo single crystal by irradiation of the linear laser beam in the manufacturing method of the flat display device of the present invention. It is a top view which shows the state of the large sized substrate after pseudo | simulation single crystal formation in the manufacturing method of the flat display apparatus of this invention. It is a figure explaining an example of the exposure apparatus in the manufacturing method of the flat display apparatus of this invention. It is a schematic diagram which shows an example of the alignment method of a photomask and a board | substrate. It is a schematic diagram which shows the other example of the alignment method of a photomask and a board | substrate. It is a figure explaining the crystallization process of the pseudo single crystal in the manufacturing method of the flat display apparatus of this invention. It is a figure explaining an example of the alignment process of the quasi-single-crystal area | region of a board | substrate which has a quasi-single-crystallized silicon thin film, and a photomask. It is a figure explaining the other example of the alignment process of the board | substrate which has a quasi-single-crystallized silicon thin film, and a photomask. FIG. 3 is a diagram illustrating a complete process of a method for manufacturing a flat display device according to the present invention. It is a figure explaining the equivalent circuit of the panel which comprises the liquid crystal display device which is an example of the flat display device to which this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ..... Substrate, 2, 3, 4 ..... Panel, 5 ..... Signal line drive circuit area, 6 ..... Scan line drive circuit area, 7 ........ Pixel area, 8 ... ......... Other peripheral circuits, 9 ......... Linearly focused laser beam, 10 ......... Amorphous silicon thin film, 11 ......... Pseudo single crystal region, 14 ......... Signal line Corners of drive circuit region, 17 ............ Photomask, 18 ............ Reference coordinates, 20 ............ L-shaped pattern, 26 ............ Amorphous silicon thin film, 28 ............ Excimer laser Light, 29... Polycrystalline silicon thin film, 30... Continuous oscillation solid laser light, 36.

Claims (5)

A silicon thin film forming step of forming a silicon thin film on an insulating substrate constituting an active substrate of a flat display device;
A lateral crystal growth step of selectively forming a laterally grown polycrystalline silicon thin film on the substrate by irradiating the silicon thin film with time-modulated continuous wave laser light while scanning at the same speed;
A polycrystalline silicon thin film patterning step of patterning the laterally grown polycrystalline silicon thin film formed in the lateral crystal growth step to form an active layer of a thin film transistor;
Including
A method of manufacturing a flat panel display device by which a circuit having a thin film transistor is formed by a photolithography technique using a photomask on the insulating substrate to obtain an active substrate,
A part or all of the planar shape of the laterally grown polycrystalline region formed in the polycrystalline silicon thin film patterning step is used as one alignment mark, and the other alignment mark in the photomask is used as the lateral direction of the insulating substrate. A method of manufacturing a flat display device, comprising aligning a grown polycrystalline region and the photomask. The planar shape is a substantially rectangular shape composed of two parallel sides in the lateral direction of the laterally grown polycrystalline region and another parallel side intersecting the two sides in the lateral direction,
2. The method of manufacturing a flat display device according to claim 1, wherein the alignment is performed based on a relative position between at least one corner of the substantially rectangular planar shape and an arbitrary coordinate on the photomask. .   The side of the substantially rectangular shape is a boundary between the silicon thin film formed in the silicon thin film formation step and the laterally grown polycrystalline region at the scanning start position of the continuous wave laser light. 3. A method for producing a flat display device according to 2.   The side of the substantially rectangular shape is a boundary between the silicon thin film formed in the silicon thin film forming step and the laterally grown polycrystalline region at the scanning end position of the continuous wave laser light. 3. A method for producing a flat display device according to 2. The silicon thin film formed on the insulating substrate as a starting sample of the laterally grown polycrystalline silicon thin film is either an amorphous silicon thin film or a polycrystalline silicon thin film. A method of manufacturing a flat display device.

Images