Laser Annealing Equipment

Abstract

To provide a laser annealing apparatus capable of improving production efficiency until a film is reformed into a film for crystallization, and enabling space saving and cost reduction.SOLUTION: A laser annealing apparatus includes an optical head for dehydrogenation that emits laser beam for dehydrogenation, the optical head for dehydrogenation irradiates at least a region to be modified in an amorphous silicon film with a laser beam for dehydrogenation prior to a laser beam for crystallization, and the optical head for dehydrogenation is moved relative to the amorphous silicon film in the scanning direction so as to dehydrogenate the amorphous silicon film.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a laser annealing apparatus and a laser annealing method for modifying an amorphous silicon film into a pseudo single-crystalline silicon film on a TFT substrate. [Background technology]

[0002] 2. Description of the Related Art Flat panel displays (FPDs) such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs) are becoming larger and more highly detailed.

[0003] FPDs are equipped with a thin film transistor (TFT) substrate on which a TFT is formed. The TFT substrate is a substrate on which minute TFTs are formed to actively drive each of the pixels arranged in a matrix. For example, in the case of a display with a full HD (1920 x 1080 dots) resolution and a 120 Hz drive, more than 10 million pixels are formed.

[0004] A laser annealing method is known that grows pseudo single crystal silicon laterally on an amorphous silicon film to increase the mobility of the channel region in a TFT. In this laser annealing method, crystal grains of a microcrystalline silicon film formed by excimer laser annealing are used as seed crystals. In this laser annealing method, the seed crystal is used as a starting point for lateral crystal growth in the scanning direction of a continuous wave laser beam, forming a pseudo single crystal silicon film with high mobility.

[0005] In the above-mentioned method for laser annealing an amorphous silicon film, a dehydrogenation process is required as a pre-processing step to remove hydrogen contained in the amorphous silicon film. A known device for carrying out this dehydrogenation process is a dehydrogenation process device that includes a dehydrogenation furnace that houses a TFT substrate and heats it at a dehydrogenation temperature, and a current generating unit that generates a current in the gate wiring of the TFT substrate to heat the gate wiring (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-119913 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, as described above, when the TFT substrate is transferred to a laser annealing apparatus to perform laser annealing of the amorphous silicon film after using a dehydrogenation treatment apparatus that removes hydrogen contained in the amorphous silicon film, there is a problem that the production efficiency is reduced. In addition, the dehydrogenation treatment apparatus requires a space to accommodate the TFT substrate. Therefore, the above-mentioned laser annealing method has a problem that it requires high costs to reform the amorphous silicon film into a crystallized film (quasi-single crystal silicon film).

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a laser annealing apparatus and a laser annealing method that improve the production efficiency up to the point where an amorphous silicon film is modified into a crystallized film by laser annealing, and that also enables space saving and cost reduction. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, an aspect of the present invention is a laser annealing device that includes a crystallization optical head that emits a crystallization laser beam that is processed so that a continuous oscillated laser light converges toward a region to be modified in an amorphous silicon film formed on a substrate, and the crystallization optical head is moved along a scanning direction relative to the amorphous silicon film with a spot portion where the crystallization laser beam is most converged located inside the amorphous silicon film, thereby modifying the region to be modified in the amorphous silicon film into a crystallized film, and is characterized in that the dehydrogenation optical head emits a dehydrogenation laser beam, and the dehydrogenation optical head is moved along the scanning direction relative to the amorphous silicon film so that the dehydrogenation laser beam irradiates at least the region to be modified prior to the crystallization laser beam, thereby dehydrogenating the amorphous silicon film.

[0010] In the above aspect, it is preferable that the dehydrogenation optical head emits a dehydrogenation laser beam that is processed so that continuous oscillated laser light converges, and that the most convergent spot portion of the dehydrogenation laser beam is located inside the amorphous silicon film.

[0011] In the above aspect, it is preferable that the beam spot of the dehydrogenation laser beam irradiated onto the surface of the amorphous silicon film is positioned upstream in the scanning direction of the beam spot of the crystallization laser beam irradiated onto the surface of the amorphous silicon film, and that the width dimension of the beam spot of the dehydrogenation laser beam is set longer than the width dimension of the beam spot of the crystallization laser beam.

[0012] In the above-mentioned aspect, it is preferable that the crystallization optical head guides laser light from a crystallization light source via a crystallization optical fiber, and the dehydrogenation optical head guides laser light from a dehydrogenation light source via a dehydrogenation optical fiber.

[0013] In the above aspect, it is preferable that the crystallization optical head and the dehydrogenation optical head are formed as a single common optical head.

[0014] In the above-mentioned aspect, it is preferable that the crystallization optical head and the dehydrogenation optical head are formed as a single common optical head, laser light is guided to the optical head from a light source via a single optical fiber, an aperture formed with a crystallization opening and a dehydrogenation opening spaced apart is arranged on the output end face of the optical fiber so that the crystallization opening and the dehydrogenation opening face face each other, and the crystallization laser beam is emitted from the crystallization opening, and the dehydrogenation laser beam is emitted from the dehydrogenation opening.

[0015] In the above aspect, it is preferable that the emission side of the optical fiber has a shape expanding so that the diameter dimension increases toward the emission end face.

[0016] In the above aspect, the intended modification region is preferably a channel semiconductor layer of a thin film transistor.

[0017] Another aspect of the present invention is a laser annealing method in which a crystallization laser beam, which is processed so that a continuous oscillated laser beam converges, is emitted toward a region to be modified in an amorphous silicon film formed on a substrate, and the crystallization laser beam is moved relative to the amorphous silicon film in a scanning direction with a spot portion where the crystallization laser beam is most converged located inside the amorphous silicon film, thereby modifying the region to be modified in the amorphous silicon film into a crystallized film, characterized in that a dehydrogenation laser beam is moved relative to the amorphous silicon film in the scanning direction so as to irradiate at least the region to be modified in the amorphous silicon film prior to the crystallization laser beam to perform dehydrogenation. Effect of the Invention

[0018] The laser annealing apparatus and the laser annealing method according to the present invention have the effect of improving the production efficiency up to the stage of reforming an amorphous silicon film into a crystallized film by laser annealing, and also realizing a laser annealing apparatus and a laser annealing method that enable space saving and cost reduction. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view illustrating a method for manufacturing a TFT array using a laser annealing apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of a laser annealing apparatus according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is an explanatory diagram showing the crystallization optical head and the dehydrogenation optical head of the laser annealing apparatus according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a bottom view showing the crystallization fiber array and the dehydrogenation fiber array in the laser annealing apparatus according to the first embodiment of the present invention as viewed from below. [Diagram 5] FIG. 5 is a plan view showing the beam spot of the crystallization laser beam and the beam spot of the dehydrogenation laser beam irradiated onto the surface of an amorphous silicon film in the laser annealing apparatus according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a plan view illustrating a method for manufacturing a TFT array using the laser annealing apparatus according to the first embodiment of the present invention. [Figure 7-1] FIG. 7-1 is a plan view illustrating a laser annealing method using the laser annealing apparatus according to the first embodiment of the present invention. [Figure 7-2] FIG. 7-2 is a plan explanatory view showing the method for manufacturing a TFT array, illustrating a state in which the crystallization optical head is rotated to change the beam pitch in the laser annealing apparatus according to the first embodiment of the present invention. [Figure 8]FIG. 8 is an explanatory diagram showing an optical head provided in a laser annealing apparatus according to the second embodiment of the present invention. [Figure 9] FIG. 9 is a bottom view showing the emission end surface of a fiber array in an optical head of a laser annealing apparatus according to the second embodiment of the present invention. [Figure 10] FIG. 9 is a plan view showing the beam spot of the crystallization laser beam and the beam spot of the dehydrogenation laser beam irradiated onto the surface of an amorphous silicon film in a laser annealing apparatus according to the second embodiment of the present invention. [Figure 11] FIG. 11 is an explanatory diagram of an optical head of a laser annealing apparatus according to the third embodiment of the present invention. [Figure 12] FIG. 12 is an explanatory diagram showing an optical head of a laser annealing apparatus according to the fourth embodiment of the present invention. [Figure 13] FIG. 13 is a schematic diagram showing the configuration of a laser annealing apparatus according to the fifth embodiment of the present invention. [Figure 14] FIG. 14 is a schematic diagram showing the configuration of a laser annealing apparatus according to the sixth embodiment of the present invention. [Figure 15] FIG. 15 is a schematic diagram showing the configuration of a laser annealing apparatus according to the seventh embodiment of the present invention. [Figure 16] FIG. 16 is a side view showing a main part of a laser annealing apparatus according to the seventh embodiment of the present invention. [Figure 17] FIG. 17 is a schematic diagram showing the configuration of a laser annealing apparatus according to the eighth embodiment of the present invention. [Figure 18] FIG. 18 is a schematic diagram showing a configuration of a laser annealing apparatus according to a ninth embodiment of the present invention. [Figure 19] FIG. 19 is a configuration diagram of an imaging optical system in a laser annealing apparatus according to the ninth embodiment of the present invention. [Figure 20] FIG. 20 is a schematic diagram showing the configuration of a laser annealing apparatus according to the tenth embodiment of the present invention. [Figure 21]FIG. 21 is an explanatory diagram showing a region A including the focal point and the vicinity of the focal point of a laser beam in a laser annealing apparatus according to an eleventh embodiment of the present invention, where the energy density profile maintains a top hat shape. [Figure 22-1] FIG. 22-1 is an explanatory diagram showing the relationship between the radial position of the laser beam and the power density in the region (4) in FIG. [Figure 22-2] FIG. 22-2 is an explanatory diagram showing the relationship between the radial position of the laser beam and the power density in the region (2) in FIG. [Figure 22-3] FIG. 22-3 is an explanatory diagram showing the relationship between the radial position of the laser beam and the power density in the region (1) in FIG. [Figure 22-4] FIG. 22-4 is an explanatory diagram showing the relationship between the radial position of the laser beam and the power density in the region (3) in FIG. [Figure 22-5] FIG. 22-5 is an explanatory diagram showing the relationship between the radial position of the laser beam and the power density in the region (5) in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The details of the laser annealing apparatus and the laser annealing method according to the embodiment of the present invention will be described below with reference to the drawings. However, it should be noted that the drawings are schematic, and the number of each member, the size of each member, the dimensional ratio, the shape, etc. are different from the actual ones. In addition, there are parts in which the dimensional relationships, ratios, and shapes are different between the drawings.

[0021] [First embodiment] (Configuration of laser annealing device) As shown in Figures 1 and 2, the laser annealing apparatus 1 of this embodiment includes a light source unit 2, an optical head 3, a substrate transport means (not shown) for transporting a substrate 10, and a displacement meter (not shown).

[0022] The light source unit 2 includes a crystallization light source unit 2A and a dehydrogenation light source unit 2B. Since the crystallization light source unit 2A and the dehydrogenation light source unit 2B have the same configuration, the configuration of the crystallization light source unit 2A will be described here, and a detailed description of the configuration of the dehydrogenation light source unit 2B will be omitted.

[0023] As shown in FIG. 2, the crystallization light source unit 2A includes a plurality of semiconductor lasers LD (LD1 to LDn) as light sources that oscillate continuous wave laser light (CW laser light). Here, the continuous wave laser light (CW laser light) is a concept that includes so-called pseudo-continuous wave in which a target region is continuously irradiated with laser light. In other words, the laser light may be a pulsed laser or a pseudo-continuous wave laser in which the pulse interval is shorter than the cooling time of the silicon thin film (amorphous silicon film) after heating (the next pulse is irradiated before the film solidifies). As the laser light source, various lasers such as a semiconductor laser, a solid-state laser, a liquid laser, and a gas laser can be used.

[0024] In this embodiment, for example, semiconductor lasers LD100 to LDn are provided as spare semiconductor lasers R for the semiconductor lasers LD.

[0025] The crystallization light source unit 2A includes the above-mentioned multiple semiconductor lasers LD, a drive circuit 20, and multiple coupling lenses 21. The drive circuit 20 is connected to each of the multiple semiconductor lasers LD, and drives each of the semiconductor lasers LD.

[0026] The coupling lens 21 is connected to the output side of each semiconductor laser LD. One end of a crystallization optical fiber 22A serving as a waveguide is connected to each coupling lens 21. In this embodiment, a multimode fiber is used as the crystallization optical fiber 22A.

[0027] The optical head 3 includes a crystallization optical head 3A and a dehydrogenation optical head 3B. The crystallization optical head 3A includes a crystallization fiber array 31A and an imaging optical system 32A. The other end of the crystallization optical fiber 22A is connected to the crystallization fiber array 31A. As shown in FIG. 4, the emission ends of the crystallization optical fibers 22A connected to the crystallization fiber array 31A are arranged in a row at equal intervals along a straight line on the emission end surface of the crystallization fiber array 31A.

[0028] A dehydrogenation optical head 3B is connected to the dehydrogenation light source unit 2B shown in Fig. 1 via a dehydrogenation optical fiber 22B as shown in Fig. 3. As shown in Fig. 3, the dehydrogenation optical head 3B includes a dehydrogenation fiber array 31B and an imaging optical system 32B.

[0029] The other end of the dehydrogenation optical fiber 22B is connected to the dehydrogenation fiber array 31B. As shown in Fig. 4, the emission ends of the dehydrogenation optical fibers 22B connected to the dehydrogenation fiber array 31B are arranged in a row at equal intervals along a straight line on the emission end face of the dehydrogenation fiber array 31B.

[0030] The imaging optical system 32A includes at least a first lens 33A on the incident side and a second lens 34A on the exit side. As shown in Fig. 2 and Fig. 3, the laser light emitted from the crystallization fiber array 31A is incident on the imaging optical system 32A. As shown in Fig. 1, the crystallization optical head 3A processes the laser light toward the downstream side (rear side) to become a crystallization laser beam LB1 that converges at a spot portion F.

[0031] In this embodiment, as shown in Fig. 7-1, on the emission side of the crystallization optical head 3A, the crystallization laser beam LB1 is emitted from positions arranged at a pitch P1 along a straight line. This pitch P1 is set to be the same as the pitch of the gate lines 12 described later. In this embodiment, the direction in which the crystallization laser beam LB1 is arranged is set to be perpendicular to the extension direction of the gate lines 12 described later.

[0032] The imaging optical system 32B has the same configuration as the imaging optical system 32A, and includes at least a first lens 33B on the incident side and a second lens 34B on the exit side. As shown in Fig. 3, the laser light emitted from the dehydrogenation fiber array 31B is incident on the imaging optical system 32B. In the dehydrogenation optical head 3B, the laser light is also processed to be a dehydrogenation laser beam LB2 that converges at a spot portion toward the downstream side (rear side).

[0033] A displacement meter (not shown) is provided on the side of the crystallization optical head 3A to correct the positional deviation between the crystallization optical head 3A and the substrate 10. An autofocus function is provided to automatically adjust the focus of the crystallization laser beam LB1 emitted from the crystallization optical head 3A based on data of the positional deviation between the crystallization optical head 3A and the substrate 10 detected by this displacement meter. In this embodiment, a displacement meter is used as a means for autofocusing, but the present invention is not limited to this, and various known techniques can be used. A similar displacement meter may be provided on the side of the dehydrogenation optical head 3B to provide an autofocus function to automatically adjust the focus of the dehydrogenation laser beam LB2 emitted from the dehydrogenation optical head 3B based on data of the positional deviation between the dehydrogenation optical head 3B and the substrate 10.

[0034] In this embodiment, the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 have top-hat shaped characteristics and have a square cross-sectional shape in a direction perpendicular to the optical axis. The cross-sectional shapes of the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 may be rectangular, hexagonal, etc. In order to make the cross-sectional shapes of the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 into such shapes, the cross-sectional shapes of the cores of the crystallization optical fiber 22A and the dehydrogenation optical fiber 22B may be set to a square, rectangular, hexagonal, etc.

[0035] The substrate transport means (not shown) includes a mechanism for transporting the substrate 10 to be subjected to the laser annealing treatment in the scanning direction (one direction of the X direction in this embodiment) at an arbitrary speed. Therefore, by transporting the substrate 10 side with the crystallization optical head 3A and the dehydrogenation optical head 3B in a fixed position, the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 are scanned relatively to the substrate 10.

[0036] 3, in this embodiment, the beam spot of the crystallization laser beam LB1 irradiated onto the surface of the amorphous silicon film 15a described below is located downstream of the beam spot of the dehydrogenation laser beam LB2 irradiated onto the surface of the amorphous silicon film 15a in the scanning direction S. Therefore, the region to be modified in the amorphous silicon film 15a is irradiated with the dehydrogenation laser beam LB2 prior to irradiation with the crystallization laser beam LB1.

[0037] As shown in FIG. 5, the width dimension (length in the Y direction) of the beam spot of the dehydrogenation laser beam LB2 is set to be longer than the width dimension (length in the Y direction) of the beam spot of the crystallization laser beam LB1 irradiated onto the surface of the amorphous silicon film 15a described later.

[0038] The structure of the substrate 10 will be described below. As shown in FIG. 1, the substrate 10 as a substrate to be laser annealed has a glass substrate 11 as a main body. On the glass substrate 11, a plurality of gate lines 12 patterned with copper (Cu), other metal wiring patterns, a silicon nitride film (Si3N4) 13, a silicon oxide film (SiO2) 14, an amorphous silicon film 15a as a film to be laser annealed, and the like are sequentially laminated. The plurality of gate lines 12 are arranged to be parallel to each other. As described above, the pitch between the gate lines 12 is set to the above-mentioned pitch P1.

[0039] The gate line 12 includes a portion that becomes a gate electrode of a TFT formed for each pixel region (not shown). For example, the thickness of the gate line 12 is 200 to 700 nm, the thickness of the silicon nitride film 13 is about 300 nm, the thickness of the silicon oxide film 14 is 50 to 100 nm, and the thickness of the amorphous silicon film 15a is about 50 nm.

[0040] In this embodiment, the beam diameter of the beam spot of the crystallization laser beam LB1 irradiated on the surface of the amorphous silicon film 15a is set to any dimension, for example, between 5 μm and 300 μm. The beam diameter of the beam spot of the dehydrogenation laser beam LB2 is preferably set to be larger than the beam diameter of the crystallization laser beam LB1. The beam diameter of the beam spot of the crystallization laser beam LB1 is within a range such that the irradiated surface of the crystallization laser beam LB1 can be accommodated in the semiconductor active region (region to be modified) of the TFT. The diameter of the irradiated surface of the laser beam LBcw is preferably between 10 μm and 100 μm.

[0041] In this embodiment, the scanning speed at which the crystallization laser beam LB1 scans the amorphous silicon film 15a relatively is preferably 200 mm to 500 mm / sec, but is not limited to this. The distance between the beam spot of the crystallization laser beam LB1 and the beam spot of the dehydrogenation laser beam LB2, which are arranged on the upstream and downstream sides along the scanning direction S, may be equal to or greater than the diffraction limit of light.

[0042] In this embodiment, prior to the irradiation with the crystallization laser beam LB1, the amorphous silicon film 15a can be partially dehydrogenated by irradiating the region to be modified in the amorphous silicon film 15a with the dehydrogenation laser beam LB2 along the extending direction of the gate line 12. By irradiating the dehydrogenated region to be modified with the crystallization laser beam LB1 in this manner, the film can be modified into a good quality pseudo single crystal silicon film 15La without being damaged by the action of hydrogen, as shown in FIG.

[0043] According to the laser annealing apparatus 1 of the present embodiment, the spot portion F with high power density of the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 is located inside the amorphous silicon film 15a, so that a large amount of heat is supplied to the amorphous silicon film 15a in a focused manner. Then, most of the heat is transferred from the spot portion F to the side (the direction of the arrow h in FIG. 1) inside the amorphous silicon film 15a. At the rear (lower) side of the spot portion F, the beam is diffused, so that the power density of the light reaching the underlying silicon oxide film 14 and the like is lowered, and overheating of the lower layer side of the amorphous silicon film 15a can be suppressed. Therefore, according to the laser annealing apparatus 1 of the present embodiment, it is possible to prevent the gate line 12, other wiring patterns, the glass substrate 11, and the like from being damaged by overheating.

[0044] In particular, in this embodiment, since there is no need to dehydrogenate the amorphous silicon film in a separate process, the production efficiency up to the point where the amorphous silicon film 15a is modified into a pseudo single-crystal silicon film (crystallized film) by laser annealing is improved, and furthermore, space saving and cost reduction are possible.

[0045] According to the laser annealing apparatus 1 of this embodiment, it is only necessary to irradiate the dehydrogenation laser beam LB2 and the crystallization laser beam LB1 onto the region to be modified that is to become the channel semiconductor layer of the TFT, thereby improving energy efficiency.

[0046] The spot portion F may have a finite width (margin) in the optical axis direction as a range in which the power density maintains the top hat shape characteristics. This is because within such a range, uniform annealing is possible and the state in which energy is concentrated on the amorphous silicon film 15a is maintained. The range in which the power density at the spot portion F maintains the top hat shape characteristics will be described later in the eighth embodiment.

[0047] In the present invention, the beam diameter of the crystallization laser beam LB1 can be considered as the diameter dimension of the flat part of the top hat shape. This is because it is sufficient to perform a uniform annealing treatment on the region to be modified, and since the power density of the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 decreases rapidly outside the flat part of the top hat shape, it is possible to avoid thermal damage and improve the energy utilization efficiency at the same time.

[0048] Furthermore, if the amorphous silicon film 15a is formed on the entire surface of the substrate and the beam diameter (width of the irradiated area) is sufficiently smaller than the distance between the gate lines, the beam diameter may be larger than the area to be modified. This is because heat generation is concentrated in the amorphous silicon film 15a, and energy utilization efficiency is greatly improved compared to the conventional annealing process using a line beam. Here, the beam diameter being sufficiently smaller than the distance between the gate lines means, for example, that the beam diameter is 1 / 10 or less of the distance between the gate lines.

[0049] Fig. 7-2 shows an example in which the crystallization optical head 3A of the laser annealing apparatus 1 according to the first embodiment of the present invention is set to be rotatably driven by a rotary drive unit (not shown). In this case, the crystallization optical head 3A can be applied to a case in which the pitch P2 between the gate lines 12 is shorter than the pitch P1 between the gate lines 12 shown in Fig. 7-1. As shown in Fig. 7-2, by rotating and adjusting the crystallization optical head 3A so that the crystallization laser beam LB1 corresponds to the multiple gate lines 12, it becomes possible to accurately irradiate the crystallization laser beam LB1 to the intended modification region of the amorphous silicon film 15a above the gate line 12.

[0050] In addition, when the crystallization optical head 3A, which is rotated and moved obliquely as shown in Figure 7-2, is scanned relative to the substrate 10, the timing at which the crystallization laser beam LB1 is irradiated onto the appropriate intended modification area shifts sequentially for each gate line 12, so the drive circuit 20 can be set to sequentially delay the output timing to the semiconductor laser LD.

[0051] According to this embodiment, the pitch between the rows irradiated with the crystallization laser beam LB1 can be changed by rotating the crystallization optical head 3A. Therefore, a laser annealing apparatus that can be applied even when the pitch of the gate lines 12 on the substrate is changed can be realized. Similarly, the dehydrogenation optical head 3B may also be rotated so that it can be applied when the pitch of the gate lines 12 is changed.

[0052] [Laser annealing method] Next, a laser annealing method according to the present embodiment will be described. The laser annealing method is a laser annealing processing method for forming a pseudo single crystal silicon film 15La in a region of a substrate 10 to be modified by using a laser annealing apparatus 1.

[0053] First, in this laser annealing method, as shown in FIG. 1, a substrate 10 is prepared in which a plurality of gate lines 12 parallel to each other are formed on a glass substrate 11, and an amorphous silicon film 15a is formed on top of the plurality of gate lines 12 so as to entirely cover these gate lines 12.

[0054] Next, while the substrate 10 is moved relatively in the scanning direction S by a substrate transport means (not shown), a dehydrogenation laser beam LB2 is irradiated toward the region to be modified in the amorphous silicon film 15a prior to the crystallization laser beam LB1, as shown in FIG. 3.

[0055] Here, the most convergent spot F of the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 is maintained inside the amorphous silicon film 15a. As a result, as shown in FIG. 6, the region to become the channel semiconductor layer of the TFT can be modified into a pseudo single crystal silicon film 15La.

[0056] In the laser annealing method of the present embodiment, the pseudo single crystal silicon film 15La can be formed only in the region where the channel semiconductor layer of the TFT is to be formed, so that the annealing can be performed with good energy efficiency. Therefore, in this laser annealing method, the production efficiency up to the point where the amorphous silicon film 15a is reformed into a crystallized film by laser annealing is improved, and further, a furnace as in the conventional method is not required, so that space saving and cost reduction can be realized.

[0057] Furthermore, in the laser annealing method of the present embodiment, the gate lines 12, the glass substrate 11, and the like are not thermally damaged, and therefore it is possible to realize the manufacture of TFT substrates with a high yield.

[0058] [Second embodiment] 8 shows a main part of a laser annealing apparatus according to a second embodiment of the present invention. In this embodiment, the crystallization fiber array 31A and the dehydrogenation fiber array 31B in the first embodiment are integrated into a single fiber array 31. The crystallization laser beam LB1 is formed of a laser beam guided from a crystallization light source (not shown) through a crystallization optical fiber 22A having a relatively small cross-sectional area. The dehydrogenation laser beam LB2 is formed of a laser beam guided from a dehydrogenation light source (not shown) through a dehydrogenation optical fiber 22B having a relatively large cross-sectional area.

[0059] As shown in FIG. 9, in this embodiment, the ends of a plurality of crystallization optical fibers 22A and a plurality of dehydrogenation optical fibers 22B can be arranged on the output end face of a single fiber array 31.

[0060] 8, in this embodiment, both the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 are processed so as to converge by a common first lens 33 and second lens 34. Also in this embodiment, as shown in FIG 10, the width dimension (length in the Y direction) of the beam spot of the dehydrogenation laser beam LB2 is set to be longer than the width dimension (length in the Y direction) of the beam spot of the crystallization laser beam LB1 irradiated onto the surface of the amorphous silicon film 15a described later.

[0061] In this embodiment, the optical head 3 is made up of a single fiber array 31, a single first lens 33, and a single second lens , so that the device can be made compact.

[0062] [Third embodiment] 11 shows a main part of a laser annealing apparatus according to a third embodiment of the present invention. In this embodiment, similar to the second embodiment, the crystallization fiber array 31A and the dehydrogenation fiber array 31B are configured as a single common fiber array 31. Laser light is guided from a light source to the fiber array 31 via a single optical fiber 22 having a long diameter.

[0063] 11, an aperture 40 having a relatively small crystallization opening 40A and a relatively large dehydrogenation opening 40B formed at a distance from each other is disposed on the output end face of the optical fiber 22 such that the crystallization opening 40A and the dehydrogenation opening 40B face the output end face of the optical fiber 22. A crystallization laser beam LB1 is emitted from the crystallization opening 40A, and a dehydrogenation laser beam LB2 is emitted from the dehydrogenation opening 40B. In this embodiment, as in the second embodiment, both the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 are processed to converge by the common first lens 33 and second lens 34.

[0064] In the present embodiment as well, the optical head 3 is made up of a single fiber array 31, a single first lens 33, and a single second lens 34, so that the device can be made compact.

[0065] [Fourth embodiment] Fig. 12 shows a main part of a laser annealing apparatus according to a fourth embodiment of the present invention. In this embodiment, as in the second embodiment, a single fiber array 31 is used as both a crystallization fiber array 31A and a dehydrogenation fiber array 31B. Laser light is guided from a light source to the fiber array 31 through a single optical fiber 22 having a small diameter. As shown in Fig. 12, the optical fiber 22 is formed with an expanded diameter portion 22E having a shape expanding so that the diameter increases toward the output end face of the fiber array 31.

[0066] 12, an aperture 40 having a relatively small crystallization opening 40A and a relatively large dehydrogenation opening 40B formed at a distance from each other is disposed on the output end face of the optical fiber 22 such that the crystallization opening 40A and the dehydrogenation opening 40B face the output end face of the optical fiber 22. A crystallization laser beam LB1 is emitted from the crystallization opening 40A, and a dehydrogenation laser beam LB2 is emitted from the dehydrogenation opening 40B. In this embodiment, as in the second embodiment, both the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 are processed to converge by the common first lens 33 and second lens 34.

[0067] In this embodiment, a thin optical fiber 22 is used, but since the end of the optical fiber 22 is formed with an expanded diameter section 22E having a large diameter dimension toward the output end surface, the distance between the crystallization opening 40A and the dehydrogenation opening 40B in the aperture 40 can be secured.

[0068] [Fifth embodiment] 13 is a schematic diagram showing a laser annealing apparatus 1A according to a fifth embodiment of the present invention. In this embodiment, a crystallization optical head 3A and a dehydrogenation optical head 3B (not shown) are provided, but since they have the same configuration, only the crystallization optical head 3A will be described and the description of the dehydrogenation optical head 3B will be omitted.

[0069] The present embodiment is characterized by including a light intensity sensor D1 for detecting the light intensity of each of the crystallization laser beams LB1. The other configurations of the present embodiment are the same as those of the laser annealing apparatus 1 according to the first embodiment, and therefore the description thereof will be omitted.

[0070] The light intensity sensor D1 is disposed behind the crystallization optical head 3A and is capable of moving sequentially to the spot portion F of the crystallization laser beam LB1. Furthermore, this light intensity sensor D1 is set so that when detecting the light intensity of one crystallization laser beam LB1, an adjacent crystallization laser beam LB1 is not incident on it.

[0071] In this embodiment, data detected by the light amount sensor D1 is fed back to the drive circuit 20, and the output of the semiconductor laser LD serving as the light source of the crystallization laser beam LB1 is adjusted.

[0072] In this embodiment, the light intensity of each of the crystallization laser beams LB1 is adjusted before the laser annealing process is performed, and the output (light intensity) of these crystallization laser beams LB1 can be made uniform. Therefore, the laser annealing device 1A according to this embodiment can make the electrical characteristics of the channel semiconductor layers of the TFTs uniform. Similarly, the light intensity of the dehydrogenation laser beam LB2 may be detected by a light intensity sensor (not shown) to adjust the output of the semiconductor laser LD (not shown).

[0073] [Sixth embodiment] 14 is a schematic diagram of a laser annealing apparatus 1B according to a sixth embodiment of the present invention. In this embodiment, an optical head for crystallization 3A and an optical head for dehydrogenation 3B (not shown) are provided, but since they have the same configuration, only the optical head for crystallization 3A will be described, and a description of the optical head for dehydrogenation 3B will be omitted.

[0074] The laser annealing apparatus 1B according to this embodiment includes a beam splitter 35 in the optical path in the imaging optical system 32A, and a side lens 36 and a light quantity sensor D2 are arranged on the sides of the beam splitter 35. In this embodiment, the crystallization laser beam LB1 reflected by the beam splitter 35 is set to enter the light quantity sensor D2 through the side lens 36. Other configurations of the laser annealing apparatus 1B according to this embodiment are substantially similar to those of the first embodiment.

[0075] In this embodiment, data detected by the light quantity sensor D2 is fed back to the drive circuit 20 to adjust the output of the semiconductor laser LD serving as the light source of the crystallization laser beam LB1. In this embodiment, the output of each semiconductor laser LD can be adjusted while the laser annealing apparatus 1B is operating.

[0076] [Seventh embodiment] Fig. 15 is a schematic diagram showing a laser annealing apparatus 1C according to a seventh embodiment of the present invention, and Fig. 16 is a side view of the main part of the laser annealing apparatus 1C. This embodiment includes a crystallization optical head 3A and a dehydrogenation optical head 3B (not shown), but since the crystallization optical head 3A and the dehydrogenation optical head 3B (not shown) have substantially the same configuration, only the crystallization optical head 3A will be described, and a description of the dehydrogenation optical head 3B will be omitted.

[0077] In the laser annealing apparatus 1C according to the present embodiment, the laser light emitted from the crystallization fiber array 31A passes through a first lens 33A and is reflected downward (to the side) by a scan mirror SM such as a galvanometer mirror. The crystallization laser beam LB1 reflected by the scan mirror SM is irradiated to the substrate side through a second lens 34 arranged below. As shown in FIG. 16, the scan mirror SM is set to be rotatable in the direction of the arrow B so that the degree of inclination can be changed.

[0078] According to this embodiment, the height dimension of the device can be reduced to make the device compact. Also, by adjusting the rotation of the scan mirror SM, it is possible to adjust the irradiation position of the crystallization laser beam LB1 and the depth position of the spot portion F in the film thickness direction from the surface of the amorphous silicon film 15a.

[0079] [Eighth embodiment] 17 is a schematic diagram of a laser annealing apparatus 1D according to an eighth embodiment of the present invention. In this embodiment, the apparatus is equipped with a crystallization optical head 3A and a dehydrogenation optical head 3B (not shown), but since the crystallization optical head 3A and the dehydrogenation optical head 3B (not shown) have substantially the same configuration, only the crystallization optical head 3A will be described, and a description of the dehydrogenation optical head 3B will be omitted.

[0080] This embodiment includes an imaging optical system 32D configured by arranging a mask 37 having an opening 37A at the pupil position in the imaging optical system 32 of the laser annealing apparatus 1A according to the fifth embodiment. Other configurations of the laser annealing apparatus 1D according to this embodiment are substantially similar to those of the laser annealing apparatus 1A according to the fifth embodiment.

[0081] According to this embodiment, the pattern of the crystallization laser beam LB1 passing through the imaging optical system 32D can be changed by the mask 37. In this embodiment as well, since the light intensity sensor D1 is provided, the light intensity sensor D1 can detect the light intensity of each of the crystallization laser beams LB1 whose pattern has been changed.

[0082] [Ninth embodiment] Fig. 18 is a schematic diagram of a laser annealing apparatus 1E according to a ninth embodiment of the present invention. Fig. 19 is a schematic diagram of an imaging optical system 38 in the laser annealing apparatus 1E. In this embodiment, the apparatus is provided with a crystallization optical head 3A and a dehydrogenation optical head 3B (not shown). However, since the crystallization optical head 3A and the dehydrogenation optical head 3B (not shown) have the same configuration, only the crystallization optical head 3A will be described, and a description of the dehydrogenation optical head 3B will be omitted.

[0083] 18, the laser annealing apparatus 1E according to this embodiment includes a crystallization optical head 3A including a crystallization fiber array 31A and an imaging optical system 38, similar to the first embodiment. The other ends of the crystallization optical fibers 22A are connected to the crystallization fiber array 31A. The emission ends of the crystallization optical fibers 22A are arranged in a row along a straight line on the emission end face of the crystallization fiber array 31A.

[0084] In this embodiment, the imaging optical system 38 is configured as a telecentric optical system. The crystallization fiber array 31A is displaced along the optical axis direction by an actuator 39. In this embodiment, during autofocusing of the laser annealing apparatus 1E, only the crystallization fiber array 31A is moved along the optical axis by the actuator 39. At this time, the crystallization light source unit 2A and the imaging optical system 38 are not moved.

[0085] 19, in this embodiment, the imaging optical system 38 is a telecentric optical system made up of optical members L1 to L14, such as lenses, arranged in sequence along the optical axis direction. By providing the imaging optical system 38 made up of such a telecentric optical system, when focusing on the substrate 10, the actuator 39 only needs to move the lightweight crystallization fiber array 31A, and therefore autofocus performance with rapid response can be obtained.

[0086] Furthermore, since the imaging optical system 38 is a telecentric optical system, there is an advantage that there is no image shift with respect to the substrate 10, and the pitch of the irradiation positions of the multiple crystallization laser beams LB1 on the surface of the substrate 10 does not change.

[0087] As the actuator 39, a piezoelectric actuator, which is a positioning element that utilizes the piezoelectric effect, can be used. The piezoelectric actuator can perform accurate positioning from an extremely small range of about nanometers to several hundred micrometers. Furthermore, since the piezoelectric actuator is made of ceramic, it is very hard and can generate a large force. Furthermore, the piezoelectric actuator can perform compact and energy-saving driving. Although the piezoelectric actuator is used as the actuator 39 in this embodiment, it is of course possible to use other driving means such as a linear motor.

[0088] In this laser annealing apparatus 1E, since it is only necessary to move the lightweight crystallization fiber array 31A, the load on the actuator 39 is small, and a rapid autofocus function can be provided.

[0089] [Tenth embodiment] 20 is a schematic diagram showing a laser annealing apparatus 1F according to a tenth embodiment of the present invention. This embodiment includes a semiconductor laser LD as a single light source, a coupling lens 21, a single optical fiber 22, a single crystallization optical head 3A, and a substrate transport means (not shown) for transporting the substrate 10. This embodiment also includes a dehydrogenation optical head 3B (not shown), but the description thereof will be omitted.

[0090] The semiconductor laser LD oscillates a continuous wave laser beam (CW laser beam) in the same manner as in each of the above-mentioned embodiments. The coupling lens 21 is connected to the emission side of the semiconductor laser LD. One end of the crystallization optical fiber 22A as a waveguide is connected to the coupling lens 21. In this embodiment, for example, a square fiber is applied as the crystallization optical fiber 22A.

[0091] The crystallization optical head 3A includes a first lens 33A on the entrance side and a second lens 34A on the exit side as an imaging optical system. As shown in Fig. 20, the laser light emitted from the other end of the crystallization optical fiber 22A is incident on the crystallization optical head 3A. The crystallization optical head 3A processes the laser light toward the downstream side (rear side) to become a crystallization laser beam LB1 that converges at a spot portion F. In this embodiment as well, the spot portion F is set to be located inside the amorphous silicon film (inside in the depth direction).

[0092] In this embodiment, the crystallization laser beam LB1 also has top-hat shaped characteristics and has a square cross-sectional shape in a direction perpendicular to the optical axis. The cross-sectional shape of the crystallization laser beam LB1 may be rectangular, hexagonal, or the like. To make the cross-sectional shape of the crystallization laser beam LB1 into such a shape, the cross-sectional shape of the core of the crystallization optical fiber 22A may be set to a square, rectangular, hexagonal, or the like.

[0093] The substrate conveying means (not shown) is provided with a mechanism for conveying the substrate 10 to be subjected to the laser annealing treatment in the scanning direction at an arbitrary speed, as in the above-mentioned embodiments. Therefore, by conveying the substrate 10 side with the crystallization optical head 3A in a fixed position, the crystallization laser beam LB1 is scanned relatively to the substrate 10.

[0094] According to the laser annealing apparatus 1F of this embodiment, the spot portion F of the crystallization laser beam LB1 with high power density is located inside the amorphous silicon film, so that a large amount of heat is supplied to the amorphous silicon film in a focused manner. Then, most of the heat is transferred from the spot portion F to the side inside the amorphous silicon film. At the rear (lower) side of the spot portion F, the beam is diffused, so that the power density of the light reaching the underlying silicon oxide film or the like is lowered, and overheating of the lower layer side of the amorphous silicon film can be suppressed. Therefore, according to the laser annealing apparatus 1F, damage to the gate line, other wiring patterns, glass substrate, and the like due to overheating can be avoided.

[0095] [Eleventh embodiment] FIG. 21 shows the basic principle of a laser annealing apparatus and a laser annealing method according to an eleventh embodiment of the present invention.

[0096] In the above first to tenth embodiments, the crystallization laser beam LB1 is scanned in a state where the most convergent spot F of the crystallization laser beam LB1 is located inside the amorphous silicon film 15a in the region to be modified. In contrast, in this embodiment, as shown in Fig. 21, the crystallization laser beam LB1 is scanned in the region to be modified in a state where a region A including the focal point and the vicinity of the focal point in the crystallization laser beam LB1 and where the beam profile maintains a top hat shape overlaps with a region inside the amorphous silicon film 15a. That is, in the laser annealing apparatus according to this embodiment, it is sufficient that the amorphous silicon film 15a overlaps with the region A of the crystallization laser beam LB1 shown in Fig. 21.

[0097] As shown in FIG. 21, region A includes (1), (2), and (3) in the crystallization laser beam LB1. FIG. 22-3 shows the relationship between the radial position of the laser beam and the power density in the range of (1) in FIG. 21. As shown in FIG. 21, region (1) is a region of approximately the focal depth, and shows a typical top-hat beam profile as shown in FIG. 22-3. Region (2) in FIG. 21 is located in front of the focal point compared to region (1), but is a region where the laser profile can be considered to be top-hat shaped as shown in FIG. 22-2. Region (3) in FIG. 21 is located behind the focal point compared to region (1), but is a region where the laser profile can be considered to be top-hat shaped as shown in FIG. 22-4.

[0098] The area (4) in Fig. 21 is located in front of the area (2), and as shown in Fig. 22-1, the laser profile has a shape that cannot be regarded as a top hat type. The area (5) in Fig. 21 is located behind the area (3), and as shown in Fig. 22-5, the laser profile has a shape that cannot be regarded as a top hat type. Therefore, in this embodiment, the area A shown in Fig. 21 is defined as the area where the beam profile maintains a top hat shape. Note that this area A may be set appropriately depending on the conditions of the optical head 3, etc.

[0099] The region (1) in Fig. 21 has sufficient energy density to anneal the amorphous silicon film 15a, and has a flat width dimension that can anneal the required region, as shown in Fig. 22-3. The regions (2) and (3) in Fig. 21 are similar to the characteristics of the region (1), as shown in Fig. 22-2 and Fig. 22-4, but the regions (4) and (5), as shown in Fig. 22-1 and Fig. 22-5, have insufficient energy density and are narrow in the flat width for annealing the required region, making them unsuitable for local annealing of the amorphous silicon film 15a.

[0100] The eleventh embodiment of the present invention has been described above, but other configurations are similar to those of the laser annealing apparatus and the laser annealing method according to the first embodiment described above.

[0101] In this embodiment, for example, when amorphous silicon film 15a is located in the region (2) shown in Fig. 21, the focal position appears to be on the substrate or wiring below amorphous silicon film 15a, but most of the light is absorbed by amorphous silicon film 15a, so there is no thermal damage to the substrate, wiring, etc. below amorphous silicon film 15a. Therefore, according to this embodiment, it is easy to set the conditions of optical head 3, etc., and it is possible to reduce the device cost.

[0102] (Other embodiments) Although the embodiment of the present invention has been described above, the description and drawings forming a part of the disclosure of the embodiment should not be understood as limiting the present invention. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art.

[0103] In the above embodiment, the dehydrogenation laser beam LB2 is processed to have a converging spot portion, and this spot portion is positioned inside the amorphous silicon film, but this is not limited to this, and the configuration may simply be such that the dehydrogenation laser beam LB2 is irradiated onto the surface of the amorphous silicon film.

[0104] In the above embodiment, annealing was performed on the amorphous silicon film 15a formed on the gate line 12 so as to cover the gate line 12, but the laser annealing device and the laser annealing method according to the present invention can also be applied to a case where no gate line is formed below the amorphous silicon film. That is, the laser annealing device and the laser annealing method according to the present invention can be applied to the manufacture of TFTs having a bottom gate type (inverse staggered type) structure and TFTs having a top gate type (staggered type) structure. In addition, the present invention can also be applied to laser annealing of an amorphous silicon film formed on a substrate on which no gate line is provided. [Explanation of symbols]

[0105] D1, D2 Light sensor F Spot section LD Semiconductor Laser 1, 1A, 1B, 1C, 1D, 1E, 1F Laser annealing equipment 2 Light source unit 2A Crystallization light source unit 2B Dehydrogenation light source unit 3 Optical Head 3A Crystallization Optical Head 3B Dehydrogenation Optical Head 10 Substrate (substrate to be laser annealed) 11 Glass substrate (substrate) 12 Gate Line 13 Silicon nitride film 14 Silicon oxide film 15a Amorphous silicon film 21 Coupling Lens 22 Optical Fiber 22A Crystallization Optical Fiber 22B Optical fiber for dehydrogenation 22E Expanded diameter part 31 Fiber Array 31A Fiber array for crystallization 31B Fiber array for dehydrogenation 32, 32A, 32B Imaging optical system 33, 33A, 33B First lens 34, 34A, 34B Second lens 35 Beam splitter 36 Lateral Lens 37 Mask 37A aperture 38 Imaging Optical System 39 Actuator 40 Aperture 40A crystallization opening 40B Dehydrogenation opening

Claims

1. a laser annealing apparatus comprising a crystallization optical head that emits a crystallization laser beam, the continuous wave laser beam being processed to converge, toward a region to be modified in an amorphous silicon film formed on a substrate, the crystallization optical head being moved along a scanning direction relative to the amorphous silicon film with a spot portion where the crystallization laser beam is most converged being located inside the amorphous silicon film, thereby modifying the region to be modified in the amorphous silicon film into a crystallized film; a dehydrogenation optical head that emits a dehydrogenation laser beam; the dehydrogenation optical head is moved relative to the amorphous silicon film along the scanning direction so that the dehydrogenation laser beam irradiates at least the intended modification region prior to the crystallization laser beam, thereby dehydrogenating the amorphous silicon film; the crystallization optical head and the dehydrogenation optical head are a single common optical head, a laser beam is guided from a light source to the optical head through a single optical fiber; an aperture formed with a crystallization opening and a dehydrogenation opening spaced apart from each other on an output end face of the optical fiber, the aperture being arranged so that the crystallization opening and the dehydrogenation opening face each other; the crystallization laser beam is emitted from the crystallization opening, and the dehydrogenation laser beam is emitted from the dehydrogenation opening; A laser annealing apparatus characterized by:

2. the dehydrogenation optical head emits the dehydrogenation laser beam, which is processed so that continuous wave laser light converges, and the most convergent spot of the dehydrogenation laser beam is located inside the amorphous silicon film; 2. The laser annealing apparatus according to claim 1.

3. a beam spot of the dehydrogenation laser beam irradiated onto the surface of the amorphous silicon film is disposed upstream in the scanning direction of a beam spot of the crystallization laser beam irradiated onto the surface of the amorphous silicon film; a width dimension of the beam spot of the dehydrogenation laser beam is set to be longer than a width dimension of the beam spot of the crystallization laser beam; 3. The laser annealing apparatus according to claim 1 or 2.

4. The crystallization optical head guides laser light from a crystallization light source through a crystallization optical fiber, the dehydrogenation optical head guides laser light from a dehydrogenation light source through a dehydrogenation optical fiber; The laser annealing apparatus according to any one of claims 1 to 3.

5. the crystallization optical head and the dehydrogenation optical head are a single common optical head; 5. The laser annealing apparatus according to claim 4.

6. The output side of the optical fiber has a shape that expands so that the diameter dimension increases toward the output end surface. The laser annealing apparatus according to any one of claims 1 to 5.

7. The modification target region is a channel semiconductor layer of a thin film transistor. The laser annealing apparatus according to any one of claims 1 to 6.

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