JP7632873B2 - Laser Annealing Equipment - Google Patents

Description

The present invention relates to a laser annealing device and a laser annealing method for modifying an amorphous silicon film on a TFT substrate into a pseudo single crystal silicon film.

Flat panel displays (FPDs) such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs) are becoming larger and more precise.

FPDs are equipped with a TFT substrate on which thin film transistors (TFTs) are 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.

To increase the mobility of the channel region in a TFT, a laser annealing method is known in which pseudo-single crystal silicon is grown laterally on an amorphous silicon film. In this laser annealing method, crystal grains of a microcrystalline silicon film formed by excimer laser annealing are used as seed crystals. With this laser annealing method, lateral crystal growth is performed starting from the seed crystal in the scanning direction of the continuous wave laser light, forming a pseudo-single crystal silicon film with high mobility.

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).

JP 2020-119913 A

However, as mentioned above, if a dehydrogenation treatment device is used to remove hydrogen contained in the amorphous silicon film, and then the TFT substrate is transferred to a laser annealing device to perform laser annealing of the amorphous silicon film, there is a problem that production efficiency decreases. In addition, the dehydrogenation treatment device requires space to accommodate the TFT substrate. Therefore, the above-mentioned laser annealing method has a problem that high costs are required before the amorphous silicon film is transformed into a crystallized film (pseudo single crystal silicon film).

The present invention has been made in consideration of the above problems, and aims to provide a laser annealing device and a laser annealing method that improve the production efficiency up to the point where an amorphous silicon film is converted into a crystallized film by laser annealing, and that also enables space saving and cost reduction.

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 beam 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 the most convergent spot portion of the crystallization laser beam located inside the amorphous silicon film to modify the region to be modified in the amorphous silicon film into a crystallized film, and includes a dehydrogenation optical head that 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 to dehydrogenate the amorphous silicon film.

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

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 from the beam spot of the crystallization laser beam irradiated onto the surface of the amorphous silicon film, and 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.

In the above 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.

In the above embodiment, it is preferable that the crystallization optical head and the dehydrogenation optical head are a single shared optical head.

In the above embodiment, it is preferable that the crystallization optical head and the dehydrogenation optical head are a single shared optical head, laser light is guided from a light source to the optical head 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, the crystallization laser beam is emitted from the crystallization opening, and the dehydrogenation laser beam is emitted from the dehydrogenation opening.

In the above embodiment, it is preferable that the output side of the optical fiber has a shape that expands so that the diameter dimension increases toward the output end face.

In the above embodiment, the region to be modified is preferably the channel semiconductor layer of a thin-film transistor.

Another aspect of the present invention is a laser annealing method in which a crystallization laser beam, which is processed so that the continuous oscillated laser light 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 the most convergent spot portion of the crystallization laser beam located inside the amorphous silicon film to modify 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.

The laser annealing device 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 of realizing a laser annealing device and a laser annealing method that enable space saving and cost reduction.

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. FIG. 2 is a schematic diagram showing the configuration of a laser annealing apparatus according to a first embodiment of the present invention. 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. 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. 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. 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. FIG. 7A is a plan view illustrating a laser annealing method using the laser annealing apparatus according to the first embodiment of the present invention. FIG. 7B is a plan view illustrating the method for manufacturing a TFT array, showing 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. 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. 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. FIG. 9 is a plan view showing the beam spot of a crystallization laser beam and the beam spot of a 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. FIG. 11 is an explanatory diagram of an optical head of a laser annealing apparatus according to the third embodiment of the present invention. FIG. 12 is an explanatory diagram showing an optical head of a laser annealing apparatus according to the fourth embodiment of the present invention. FIG. 13 is a schematic diagram showing the configuration of a laser annealing apparatus according to the fifth embodiment of the present invention. FIG. 14 is a schematic diagram showing the configuration of a laser annealing apparatus according to the sixth embodiment of the present invention. FIG. 15 is a schematic diagram showing the configuration of a laser annealing apparatus according to the seventh embodiment of the present invention. FIG. 16 is a side view showing a main part of a laser annealing apparatus according to the seventh embodiment of the present invention. FIG. 17 is a schematic diagram showing the configuration of a laser annealing apparatus according to an eighth embodiment of the present invention. FIG. 18 is a schematic diagram showing the configuration of a laser annealing apparatus according to a ninth embodiment of the present invention. FIG. 19 is a diagram showing the configuration of an imaging optical system in a laser annealing apparatus according to the ninth embodiment of the present invention. FIG. 20 is a schematic diagram showing the configuration of a laser annealing apparatus according to a tenth embodiment of the present invention. 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. FIG. 22A 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. FIG. 22B 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. 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. 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. 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.

The laser annealing apparatus and the laser annealing method according to the embodiment of the present invention will be described in detail below with reference to the drawings. However, it should be noted that the drawings are schematic, and the number of components, the dimensions of each component, the dimensional ratios, shapes, etc. differ from the actual ones. In addition, the drawings include parts with different dimensional relationships, ratios, and shapes.

[First embodiment]
(Configuration of laser annealing device)
As shown in Figures 1 and 2, the laser annealing apparatus 1 according to 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).

The light source unit 2 comprises 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.

As shown in FIG. 2, the crystallization light source unit 2A includes multiple semiconductor lasers LD (LD1 to LDn) as light sources that emit continuous wave laser light (CW laser light). Here, continuous wave laser light (CW laser light) is a concept that includes so-called pseudo-continuous wave, in which laser light is continuously irradiated onto the target area. 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 it solidifies). As the laser light source, various lasers such as semiconductor lasers, solid-state lasers, liquid lasers, and gas lasers can be used.

In this embodiment, for example, semiconductor lasers LD100 to LDn are provided as spare semiconductor lasers R.

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 semiconductor laser LD.

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

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 output 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 output end surface of the crystallization fiber array 31A.

The dehydrogenation light source unit 2B shown in FIG. 1 is connected to a dehydrogenation optical head 3B 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.

The other ends of the dehydrogenation optical fibers 22B are connected to the dehydrogenation fiber array 31B. As shown in FIG. 4, the output 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 output end surface of the dehydrogenation fiber array 31B.

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 Figures 2 and 3, the imaging optical system 32A receives the laser light emitted from the crystallization fiber array 31A. As shown in Figure 1, the crystallization optical head 3A processes the laser light downstream (rear side) to become a crystallization laser beam LB1 that converges at a spot portion F.

In this embodiment, as shown in FIG. 7-1, on the exit 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 below. 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 below.

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. The dehydrogenation optical head 3B also processes the laser light toward the downstream side (rear side) to become a dehydrogenation laser beam LB2 that converges at a spot portion.

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

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.

The substrate transport means (not shown) has a mechanism for transporting the substrate 10 to be subjected to laser annealing in the scanning direction (one direction of the X direction in this embodiment) at any 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 relative to the substrate 10.

In this embodiment, as shown in FIG. 3, the beam spot of the crystallization laser beam LB1 irradiated onto the surface of the amorphous silicon film 15a (described later) is positioned downstream in the scanning direction S from the beam spot of the dehydrogenation laser beam LB2 irradiated onto the surface of the amorphous silicon film 15a. 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.

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, which will be described later.

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 (Si ₃ N ₄ ) 13, a silicon oxide film (SiO ₂ ) 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 so as to be parallel to each other. As described above, the pitch between the gate lines 12 is set to the above-mentioned pitch P1.

The gate line 12 includes a portion that will become the gate electrode of a TFT formed for each pixel region (not shown). By way of 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.

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. In addition, it is preferable to set the beam diameter of the beam spot of the dehydrogenation laser beam LB2 to be larger than the beam diameter of the beam spot of the crystallization laser beam LB1. The range of the beam diameter of the beam spot of the crystallization laser beam LB1 is a size that allows the irradiation surface of the crystallization laser beam LB1 to be accommodated in the semiconductor active region (region to be modified) of the TFT. In addition, it is preferable that the diameter of the irradiation surface of the laser beam LBcw is between 10 μm and 100 μm.

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

In this embodiment, prior to irradiation with the crystallization laser beam LB1, the region to be modified in the amorphous silicon film 15a is irradiated with the dehydrogenation laser beam LB2 along the direction in which the gate line 12 extends, thereby partially dehydrogenating the amorphous silicon film 15a. By irradiating the dehydrogenated region to be modified with the crystallization laser beam LB1 in this manner, as shown in FIG. 6, the film can be modified into a high-quality pseudo single-crystal silicon film 15La without being damaged by the action of hydrogen.

According to the laser annealing device 1 of this embodiment, the spot portion F with high power density in the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 is located inside the amorphous silicon film 15a, so a large amount of heat is supplied to the amorphous silicon film 15a in a focused manner. Then, most of the heat from the spot portion F is transmitted to the side (in the direction of the arrow h in FIG. 1) inside the amorphous silicon film 15a. Because the beam is diffused on the rear side (lower side) of the spot portion F, the power density of the light reaching the underlying silicon oxide film 14, etc. is lowered, and overheating of the lower layer side of the amorphous silicon film 15a can be suppressed. Therefore, according to the laser annealing device 1 of this embodiment, damage to the gate line 12, other wiring patterns, the glass substrate 11, etc. due to overheating can be avoided.

In particular, in this embodiment, since there is no need to dehydrogenate the amorphous silicon film in a separate process, production efficiency is improved up to the stage of laser annealing to convert the amorphous silicon film 15a into a pseudo single crystal silicon film (crystallized film), and space saving and cost reduction are also possible.

With the laser annealing device 1 according to this embodiment, it is only necessary to irradiate the dehydrogenation laser beam LB2 and the crystallization laser beam LB1 to the region to be modified that is to become the channel semiconductor layer of the TFT, thereby improving energy efficiency.

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 in the amorphous silicon film 15a is maintained. The range in which the power density in the spot portion F maintains the top hat shape characteristics will be described later in the eighth embodiment.

In addition, 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 decreases rapidly outside the flat part of the top hat shape in the crystallization laser beam LB1 and the dehydrogenation laser beam LB2, it is possible to avoid thermal damage and improve energy utilization efficiency at the same time.

Furthermore, if an amorphous silicon film 15a is formed over 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 conventional annealing processing using a line beam. Here, a beam diameter 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.

Figure 7-2 shows an example in which the crystallization optical head 3A of the laser annealing device 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 when the pitch P2 between the gate lines 12 is shorter than the pitch P1 of the gate lines 12 shown in Figure 7-1. As shown in Figure 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 area of the amorphous silicon film 15a above the gate line 12.

When the crystallization optical head 3A is rotated and moved obliquely as shown in FIG. 7-2 and 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.

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 device can be realized that can be applied even when the pitch of the gate lines 12 on the substrate is changed. Similarly, the dehydrogenation optical head 3B can also be rotated so that it can be applied when the pitch of the gate lines 12 is changed.

[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 to be modified on a substrate 10 using a laser annealing apparatus 1.

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 one another 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 the gate lines 12.

Next, while the substrate 10 is moved relatively in the scanning direction S by a substrate transport means (not shown), the 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.

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 that is to become the channel semiconductor layer of the TFT can be modified into a pseudo single crystal silicon film 15La.

The laser annealing method of this embodiment can form the pseudo single crystal silicon film 15La only in the region where the channel semiconductor layer of the TFT is to be formed, so that annealing can be performed with good energy efficiency. Therefore, this laser annealing method improves the production efficiency up to the stage of reforming the amorphous silicon film 15a into a crystallized film by laser annealing, and furthermore, does not require a furnace as in the past, realizing space saving and cost reduction.

In addition, the laser annealing method of this embodiment does not thermally damage the gate lines 12, the glass substrate 11, etc., making it possible to manufacture TFT substrates with a high yield.

[Second embodiment]
8 shows the 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 by 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 by a laser beam guided from a dehydrogenation light source (not shown) through a dehydrogenation optical fiber 22B having a relatively large cross-sectional area.

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

As shown in FIG. 8, in this embodiment, both the crystallization laser beam LB1 and the dehydrogenation laser beam LB2 are processed 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.

In this embodiment, the fiber array 31, the first lens 33, and the second lens 34 that make up the optical head 3 are each single, making it possible to make the device compact.

[Third embodiment]
11 shows a main part of a laser annealing apparatus according to a third embodiment of the present invention. In this embodiment, as in 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 long optical fiber 22 having a long diameter.

As shown in FIG. 11, an aperture 40 is formed on the output end face of the optical fiber 22, with a relatively small crystallization opening 40A and a relatively large dehydrogenation opening 40B spaced apart from each other, and is arranged so 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.

In this embodiment, the optical head 3 is also made up of a single fiber array 31, first lens 33, and second lens 34, making it possible to make the device compact.

[Fourth embodiment]
Fig. 12 shows the 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 that expands so that the diameter increases toward the output end face of the fiber array 31.

As shown in FIG. 12, an aperture 40 is formed on the output end face of the optical fiber 22, with a relatively small crystallization opening 40A and a relatively large dehydrogenation opening 40B spaced apart from each other, and is arranged so 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.

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

[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.

This embodiment is characterized by including a light intensity sensor D1 that detects the light intensity of each of the multiple crystallization laser beams LB1. The other configuration of this embodiment is the same as that of the laser annealing device 1 according to the first embodiment described above, so a description thereof will be omitted.

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.

In this embodiment, the data detected by the light quantity sensor D1 is fed back to the drive circuit 20 to adjust the output of the semiconductor laser LD, which serves as the light source of the crystallization laser beam LB1.

In this embodiment, the light intensity of each crystallization laser beam LB1 can be adjusted before performing the laser annealing process, thereby making the output (light intensity) of these crystallization laser beams LB1 uniform. Therefore, with the laser annealing device 1A according to this embodiment, it is possible to make the electrical characteristics of the channel semiconductor layers of the TFTs uniform. Similarly, the light intensity of the dehydrogenation laser beam LB2 can be detected by a light intensity sensor (not shown) to adjust the output of the semiconductor laser LD (not shown).

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, 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 a description of the dehydrogenation optical head 3B will be omitted.

The laser annealing apparatus 1B according to this embodiment includes a beam splitter 35 in the optical path within the imaging optical system 32A, and a side lens 36 and a light quantity sensor D2 are arranged to the side 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. The other configurations of the laser annealing apparatus 1B according to this embodiment are substantially similar to those of the first embodiment described above.

In this embodiment, the 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 device 1B is operating.

[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. In this embodiment, the apparatus is provided 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.

In the laser annealing apparatus 1C according to this embodiment, the laser light emitted from the crystallization fiber array 31A passes through the 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.

According to this embodiment, the height dimension of the device can be shortened, making the device compact. In addition, 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.

[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.

This embodiment includes an imaging optical system 32D configured by placing 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. The 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.

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. This embodiment also includes the light intensity sensor D1, so that the light intensity of each of the crystallization laser beams LB1 whose patterns have been changed can be detected by the light intensity sensor D1.

[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 crystallization optical head 3A and the dehydrogenation optical head 3B (not shown) are provided, but since the crystallization optical head 3A and the dehydrogenation optical head 3B (not shown) have the same configuration, the crystallization optical head 3A will be described and the description of the dehydrogenation optical head 3B will be omitted.

As shown in FIG. 18, the laser annealing apparatus 1E according to this embodiment includes a crystallization optical head 3A, which is a crystallization fiber array 31A and an imaging optical system 38, in the same manner as in 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 surface of the crystallization fiber array 31A.

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 by the actuator 39. In this embodiment, during autofocusing of the laser annealing device 1E, the actuator 39 moves only the crystallization fiber array 31A along the optical axis. At this time, the crystallization light source unit 2A and the imaging optical system 38 do not move.

As shown in FIG. 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 with 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.

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

As the actuator 39, a piezoelectric actuator, which is a positioning element that utilizes the piezoelectric effect, can be used. A 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. In this embodiment, a piezoelectric actuator is used as the actuator 39, but it is of course possible to use other driving means such as a linear motor.

In this laser annealing device 1E, only the lightweight crystallization fiber array 31A needs to be moved, so the load on the actuator 39 is small and a rapid autofocus function can be provided.

[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.

The semiconductor laser LD oscillates continuous wave laser light (CW laser light) as in each of the above embodiments. The coupling lens 21 is connected to the output side of the semiconductor laser LD. One end of the crystallization optical fiber 22A, which serves as a waveguide, is connected to the coupling lens 21. In this embodiment, for example, a square fiber is used as the crystallization optical fiber 22A.

The crystallization optical head 3A is equipped with a first lens 33A on the input side and a second lens 34A on the output 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, the spot portion F is also set to be located inside the amorphous silicon film (inside in the depth direction).

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, etc. 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, rectangle, hexagon, etc.

The substrate transport means (not shown) is equipped with a mechanism for transporting the substrate 10 to be subjected to laser annealing in the scanning direction at an arbitrary speed, as in each of the above-mentioned embodiments. Therefore, by transporting the substrate 10 side with the crystallization optical head 3A in a fixed position, the crystallization laser beam LB1 is scanned relative to the substrate 10.

According to the laser annealing apparatus 1F of this embodiment, the spot portion F of the crystallization laser beam LB1, which has a 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 transmitted from the spot portion F to the side through the inside of the amorphous silicon film. Because the beam is diffused behind (below) the spot portion F, the power density of the light reaching the underlying silicon oxide film, etc. is reduced, 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, etc. due to overheating can be avoided.

[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.

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 of the crystallization laser beam LB1, which includes the focus and the vicinity of the focus 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 device 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.

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 (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.

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

As shown in Figure 22-3, region (1) in Figure 21 has sufficient energy density to anneal the amorphous silicon film 15a and has a flat width dimension that allows the necessary regions to be annealed. Regions (2) and (3) in Figure 21 are similar to the characteristics of region (1) as shown in Figures 22-2 and 22-4, but regions (4) and (5) are not suitable for local annealing of the amorphous silicon film 15a because they have insufficient energy density and the flat width for annealing the necessary regions is narrow as shown in Figures 22-1 and 22-5.

The above describes the eleventh embodiment of the present invention, but the other configurations are the same as those of the laser annealing apparatus and the laser annealing method according to the first embodiment described above.

In this embodiment, for example, when the 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 the amorphous silicon film 15a, but since most of the light is absorbed by the amorphous silicon film 15a, there is no thermal damage to the substrate or wiring below the amorphous silicon film 15a. Therefore, according to this embodiment, it is easy to set the conditions of the optical head 3, etc., and it is possible to reduce the cost of the device.

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.

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 irradiate the dehydrogenation laser beam LB2 onto the surface of the amorphous silicon film.

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 laser annealing method of the present invention can also be applied to cases where no gate line is formed below the amorphous silicon film. In other words, the laser annealing device and laser annealing method of 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 without a gate line.

D1, D2 Light quantity sensor F Spot portion LD Semiconductor laser 1, 1A, 1B, 1C, 1D, 1E, 1F Laser annealing device 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 Dehydrogenation optical fiber 22E Expanded diameter section 31 Fiber array 31A Crystallization fiber array 31B Dehydrogenation fiber array 32, 32A, 32B Imaging optical system 33, 33A, 33B First lens 34, 34A, 34B Second lens 35 Beam splitter 36 Side lens 37 Mask 37A Aperture 38 Imaging optical system 39 Actuator 40 Aperture 40A Crystallization opening 40B Dehydrogenation opening

Claims (7)

a laser annealing apparatus including a crystallization optical head that emits a crystallization laser beam, the continuous oscillated 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 to dehydrogenate 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 disposed such that the crystallization opening and the dehydrogenation opening face each other on the output end face;
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 comprising: the dehydrogenation optical head emits the dehydrogenation laser beam, which is processed so that a continuous oscillated laser beam converges, and a most convergent spot portion of the dehydrogenation laser beam is located inside the amorphous silicon film;
2. The laser annealing apparatus according to claim 1. a beam spot of the dehydrogenation laser beam irradiated onto the surface of the amorphous silicon film is disposed upstream of a beam spot of the crystallization laser beam irradiated onto the surface of the amorphous silicon film in the scanning direction;
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. 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. the crystallization optical head and the dehydrogenation optical head are a single shared optical head;
5. The laser annealing apparatus according to claim 4. The output side of the optical fiber has a shape expanding so that the diameter dimension increases toward the output end surface.
The laser annealing apparatus according to any one of claims 1 to 5 . 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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