JP2008300514A - Laser annealing method and laser annealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a polycrystalline semiconductor film having a uniform crystal grain size by generating homogeneous nucleuses in a crystallizing process for a semiconductor film. <P>SOLUTION: A photocatalyst layer 4 is formed as a base layer or a cap layer of the semiconductor film. While the photocatalyst layer 4 is irradiated with excitation light 8 having such a wavelength that it is absorbed by the photocatalyst layer 4, the semiconductor film 5 is irradiated with a laser beam 1 and the semiconductor film 5 is fused and solidified to be crystallized. In this method, the wettability of semiconductor melt is improved by the super-hydrophilic operation of the photocatalyst layer 4. Consequently, crystal nucleuses can be generated almost at the fusion point of the semiconductor film 5 on the interface between the semiconductor film 5 and photocatalyst layer 4 and then the polycrystalline semiconductor film can be formed which has the uniform crystal grain size. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser annealing method and a laser annealing apparatus for crystallizing a semiconductor film by irradiating a semiconductor film formed on a substrate with laser light.

  Laser annealing is performed by irradiating an amorphous semiconductor film (usually amorphous silicon film) formed on a substrate made of low-melting glass (usually non-alkali glass) with laser light to melt and solidify it for recrystallization. This is a technique for forming polycrystalline silicon. Hereinafter, the amorphous silicon film is referred to as an a-Si film. Since the crystallized silicon film has better electrical characteristics than the a-Si film, it is used for a transistor that drives a liquid crystal display such as a mobile phone or a digital still camera that requires high-definition display.

FIG. 7 is a diagram showing a cross-sectional structure of a glass substrate with an a-Si film used in, for example, a thin film transistor (TFT) (in addition, such a structure is disclosed in, for example, Patent Document 1 below). . In FIG. 7, a SiO ₂ film 33 is formed on a glass substrate 32 (non-alkali glass or the like), and an a-Si film 35 is formed thereon. The a-Si film 35 is irradiated with a laser beam 31 to melt and then solidified, whereby the a-Si film 35 is crystallized to become polycrystalline silicon.

As shown in Table 1 below, for example, the contact angle of the silicon melt with respect to the SiO ₂ film is 93 degrees or more, and the wettability is poor. Further, the contact angles of other semiconductors such as Ge (germanium) and InP (indium phosphide) with respect to the SiO ₂ film are 120 degrees or more and 130 degrees or more in the above order. Because of this poor wettability, the interfacial energy between the SiO ₂ film and the silicon melt is high. For this reason, crystal nuclei are not formed in the vicinity of the above-mentioned interface even when the temperature is below the melting point, resulting in supercooling (a phenomenon in which crystal nuclei are not generated even when the temperature is below the melting point). A large amount of small nuclei are generated in the position, that is, in the film, and there is a problem that homogeneous nuclei cannot be generated and polycrystalline silicon having a uniform crystal grain size cannot be obtained. The following Patent Document 2 describes matters relating to wettability and the degree of supercooling.

JP 2001-60551 A JP 2005-257244 A

  The present invention has been made in view of the above problems, and a laser annealing method capable of forming a polycrystalline semiconductor film having a uniform crystal grain size by generating homogeneous nuclei in a crystallization process of a semiconductor film, and It is an object to provide a laser annealing apparatus.

In order to solve the above problems, the laser annealing method and laser annealing apparatus of the present invention employ the following means.
(1) The present invention is a laser annealing method for crystallization by irradiating a semiconductor film formed on one side of a substrate with laser light to melt and solidify the semiconductor film, and the one side of the substrate Forming a photocatalyst layer on the side, forming the semiconductor film directly on the photocatalyst layer, and irradiating the photocatalyst layer with excitation light having a wavelength that is absorbed by the photocatalyst layer; And crystallizing the semiconductor film by melting and solidifying the semiconductor film.

According to the above method, since the photocatalyst layer is irradiated with excitation light having a wavelength absorbed by the photocatalyst layer, carriers (electrons / holes) are formed at the interface between the semiconductor film and the photocatalyst layer. Improves the wettability when melted by laser light irradiation. That is, the wettability of the semiconductor melt is improved by the superhydrophilic action of the photocatalyst layer. For this reason, crystal nuclei can be generated at the interface between the semiconductor film and the photocatalytic layer in the vicinity of the melting point of the semiconductor film, whereby a polycrystalline semiconductor film having a uniform crystal grain size can be formed.
In addition, since the photocatalyst layer is formed as an underlayer of the semiconductor film, it is not necessary to remove the photocatalyst layer for processing performed after the crystallization process.

(2) In the method of (1), the absorption edge wavelength of the photocatalyst layer is longer than the absorption edge wavelength of the substrate, and the substrate is made of a material that transmits the excitation light, from the other surface side of the substrate. The photocatalyst layer is irradiated with the excitation light through the substrate.

  When excitation light is irradiated from one side (semiconductor film side) of the substrate, the excitation light is absorbed by the semiconductor film, and the photocatalyst layer cannot be irradiated with excitation light, but transmits the excitation light as described above. By using the substrate made of the material to be irradiated and irradiating the photocatalyst layer with excitation light from the substrate side, the photocatalyst layer can be efficiently and reliably irradiated with excitation light.

(3) In the method (2), gas is blown out from the upper surfaces of the first stage and the second stage that are arranged in a horizontal direction with a predetermined gap in between with the one surface of the substrate facing upward. The substrate is levitated, and the levitated substrate is conveyed horizontally from one of the first stage and the second stage to the other across the gap, and in parallel with the conveyance of the substrate, the gap and The semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light from the upper surface side of the substrate toward the gap while irradiating the photocatalyst layer with the excitation light from the lower surface side of the substrate through the substrate. Irradiate with laser light.

  According to the above method, since the gap is formed between the first stage and the second stage, it is possible to easily irradiate the photocatalytic layer with excitation light from the other surface (lower surface) side of the substrate through the gap. it can.

(4) In the method of (2), the substrate is supported by a substrate stage made of a material that transmits the excitation light, with the other surface facing the substrate stage, and is passed through the substrate stage and the substrate. While irradiating the photocatalyst layer with the excitation light from the other surface side of the substrate, the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light is irradiated with laser light from the one surface side of the substrate, Laser light is scanned in the surface direction of the substrate.

  According to the above method, since the substrate stage is made of the material that transmits the excitation light, the photocatalytic layer can be easily irradiated with the excitation light from the other surface side of the substrate through the substrate stage.

(5) The present invention is also a laser annealing method for crystallization by irradiating a semiconductor film formed on one side of a substrate with laser light to melt and solidify the semiconductor film, The semiconductor film is formed on one side, a photocatalyst layer is formed directly on the semiconductor film, and a laser is applied to the semiconductor film while irradiating the photocatalyst layer with excitation light having a wavelength that is absorbed by the photocatalyst layer. Crystallization is performed by irradiating light to melt and solidify the semiconductor film.

  According to the above method, similarly to the method (1), crystal nuclei can be generated at the interface between the semiconductor film and the photocatalytic layer in the vicinity of the melting point of the semiconductor film. A semiconductor film can be formed.

(6) In the method of (5), the photocatalyst layer is made of a material that transmits the laser beam, and the substrate is supported by the substrate stage with the other surface facing the substrate stage. While irradiating the photocatalyst layer with the excitation light from one side of the substrate, the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light is irradiated with laser light from the one side of the substrate, Scan in the surface direction of the substrate.

  According to the above method, since the photocatalyst layer is made of a material that transmits laser light, the semiconductor film can be irradiated with laser light from one side of the substrate in the same manner as in ordinary laser annealing. In addition, since the photocatalytic layer is irradiated with excitation light from one side of the substrate, it is not necessary to add any special device to the substrate stage.

(7) Further, in the method of the above (1) to (6), the photocatalytic layer _consists of _{TiO 2, ZnO 2, MgO,} SnO 2, SrTiO 3, WO 3, Bi 2 O 3 or _Fe 2 _{O 3.}

Thus, various photocatalysts can be applied as the photocatalyst layer. In particular, TiO ₂ (titanium dioxide) is harmless, chemically stable, and available at low cost.

(8) Further, the present invention is a laser annealing apparatus for crystallizing a semiconductor film formed on one side of a substrate by irradiating a laser beam to melt and solidify the semiconductor film, The substrate has a photocatalyst layer formed on one side, the semiconductor film is formed directly on the photocatalyst layer, and the absorption edge wavelength of the photocatalyst layer is longer than the absorption edge wavelength of the substrate. And a first stage and a second stage arranged in a horizontal direction with a predetermined gap interposed therebetween, and gas is blown out from the upper surfaces of the first stage and the second stage to float the substrate with the one surface facing upward A gas levitation device, a horizontal feeding device for horizontally sending the substrate levitated by the gas levitation device from one of the first stage and the second stage to the other across the gap, and an upper surface side of the substrate Before A laser irradiation device that irradiates the semiconductor film with laser light toward the gap, and an excitation light irradiation device that irradiates the photocatalyst layer with excitation light having a wavelength that is absorbed by the photocatalyst layer. The excitation light irradiation device irradiates the excitation light to the photocatalyst layer through the gap and the substrate from the lower surface side of the substrate, and the laser irradiation device transmits the excitation light. The semiconductor film adjacent to the irradiated photocatalyst layer is irradiated with laser light.

According to the above configuration, since the photocatalyst layer is irradiated with excitation light having a wavelength that is absorbed by the photocatalyst layer, carriers (electrons / holes) are formed at the interface between the semiconductor film and the photocatalyst layer. Improves the wettability when melted by laser light irradiation. That is, the wettability of the semiconductor melt is improved by the superhydrophilic action of the photocatalyst layer. For this reason, crystal nuclei can be generated at the interface between the semiconductor film and the photocatalytic layer in the vicinity of the melting point of the semiconductor film, whereby a polycrystalline semiconductor film having a uniform crystal grain size can be formed.
In addition, since a gap is formed between the first stage and the second stage, the photocatalyst layer can be easily irradiated with excitation light from the other surface (lower surface) side of the substrate through the gap.

(9) In the present invention, the laser beam is scanned in the surface direction of the substrate, the semiconductor film formed on one surface side of the substrate is irradiated with the laser beam, and the semiconductor film is melted and solidified. A laser annealing apparatus for crystallization, wherein the substrate to be processed has a photocatalyst layer formed on one side, the semiconductor film is formed directly on the photocatalyst layer, and an absorption edge wavelength of the photocatalyst layer Is longer than the absorption edge wavelength of the substrate, a substrate stage that supports the substrate from the other surface side of the substrate, and a laser irradiation device that irradiates the semiconductor film with laser light from the one surface side of the substrate; An excitation light irradiation device that irradiates the photocatalyst layer with excitation light having a wavelength that is absorbed by the photocatalyst layer, wherein the substrate and the substrate stage are made of a material that transmits the excitation light, and the excitation light Irradiation device The photocatalytic layer is irradiated with the excitation light from the other surface side of the substrate through the substrate stage and the substrate, and the laser irradiation apparatus applies laser light to the semiconductor film adjacent to the photocatalytic layer irradiated with the excitation light. It is characterized by irradiating.

According to the above configuration, similarly to the device of (8) above, crystal nuclei can be generated at the interface between the semiconductor film and the photocatalytic layer in the vicinity of the melting point of the semiconductor film. A semiconductor film can be formed.
Moreover, since the substrate stage is made of a material that transmits the excitation light, the photocatalyst layer can be easily irradiated with the excitation light from the other side of the substrate through the substrate.

(10) Further, the present invention scans the laser beam in the surface direction of the substrate, irradiates the semiconductor film formed on one side of the substrate with the laser beam, and melts and solidifies the semiconductor film. A laser annealing apparatus for crystallizing, wherein the substrate to be processed has a semiconductor film formed on one side, a photocatalytic layer is formed directly on the semiconductor film, and the photocatalytic layer emits the laser beam. A substrate stage that supports the substrate from the other surface side of the substrate, a laser irradiation device that irradiates the semiconductor film with laser light from the one surface side of the substrate, and An excitation light irradiation device that irradiates the photocatalyst layer with the excitation light from one side, and the laser irradiation device irradiates the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light with laser light. That And butterflies.

According to the above configuration, similarly to the device of (8) above, crystal nuclei can be generated at the interface between the semiconductor film and the photocatalytic layer in the vicinity of the melting point of the semiconductor film. A semiconductor film can be formed.
In addition, since the photocatalytic layer is irradiated with excitation light from one side of the substrate, it is not necessary to add any special device to the substrate stage.

  According to the present invention, it is possible to form a polycrystalline semiconductor film having a uniform crystal grain size by generating homogeneous nuclei in the semiconductor film crystallization process.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

[Laser annealing method according to first embodiment]
FIG. 1 is an explanatory diagram of a laser annealing method according to the first embodiment of the present invention.
In this laser annealing, the semiconductor film 5 formed on one surface side of the substrate 2 is irradiated with the laser beam 1 to melt and solidify the semiconductor film 5 to be crystallized. Hereinafter, in the substrate 2, the surface on which the semiconductor film 5 is formed is referred to as “one surface”, and the opposite surface is referred to as “the other surface”.

In FIG. 1, a barrier layer 3 is formed on one surface (upper surface in the drawing) of a substrate 2. The substrate 2 is a glass substrate for a liquid crystal panel, a PDP panel, or the like. As the glass substrate, alkali-free glass is often used, but other glass substrates such as quartz glass, Pyrex (registered trademark) glass, and Vycor glass may be used. The barrier layer 3 is made of a SiO ₂ film or the like.

A photocatalyst layer 4 made of a photocatalyst is formed on the barrier layer 3. The photocatalyst layer 4 can be formed by using a film forming method such as CVD or PVD. The photocatalyst has a “superhydrophilic action” in which the surface is superhydrophilic by absorbing light. As the photocatalyst, TiO ₂ , ZnO ₂ , MgO, SnO ₂ , SrTiO ₃ , WO ₃ , Bi ₂ O ₃ or Fe ₂ O ₃ can be used, but other photocatalysts may be used. Of the above photocatalysts, TiO ₂ (titanium dioxide) is harmless, chemically stable, and available at low cost.

A semiconductor film 5 is formed directly on the photocatalyst layer 4. The semiconductor film 5 can be formed using a film forming method such as CVD or PVD. The semiconductor film 5 is an amorphous semiconductor film (for example, an a-Si film).
Hereinafter, a structure in which the barrier layer 3, the photocatalytic layer 4, and the semiconductor film 5 are formed on the substrate 2 is referred to as a substrate 6 with a semiconductor film.

  In the laser annealing method of the present embodiment, a photocatalyst layer 4 is formed on one side of the substrate 2, a semiconductor film 5 is formed directly on the photocatalyst layer 4, and has a wavelength that is absorbed by the photocatalyst layer 4. While irradiating the photocatalyst layer 4 with the excitation light 8, the semiconductor film 5 is irradiated with the laser beam 1, and the semiconductor film 5 is melted and solidified to be crystallized. FIG. 1A shows a state in which the laser light 1 is irradiated to the semiconductor film 5 while irradiating the photocatalyst layer 4 with the excitation light 8, and FIG. The semiconductor film 5 is melted, solidified, and crystallized. Reference numeral 5 a in FIG. 1B indicates a crystallized region of the semiconductor film 5.

  The “wavelength absorbed by the photocatalyst layer 4” is 380 nm when the photocatalyst layer 4 is, for example, titanium dioxide. In addition, the “wavelength absorbed by the photocatalyst layer 4” can be rephrased as “wavelength of energy larger than the band gap of the photocatalyst layer 4”.

  The excitation light 8 is emitted from the excitation light irradiation device 9. When the photocatalyst layer 4 is titanium dioxide, the excitation light 8 is ultraviolet light, and the excitation light irradiation device 9 is an ultraviolet irradiation lamp (black light). The excitation light 8 may be laser light. In this case, the excitation light irradiation device 9 is a laser device.

  As shown in FIG. 1A, excitation light 8 is irradiated to the photocatalyst layer 4 through the substrate 2 from the other surface (lower surface in the drawing) side of the substrate 2. For this reason, the absorption edge wavelength of the photocatalyst layer 4 is longer than the absorption edge wavelength of the substrate 2, and the substrate 2 needs to be made of a material that transmits the excitation light 8.

  The semiconductor film 5 is irradiated with the laser beam 1 by scanning the laser beam 1 in the surface direction of the substrate 2. Normally, the scanning is performed by fixing the position of the laser beam 1 and moving the substrate 2 in the surface direction. Conversely, the position of the substrate 2 is fixed and the irradiation position of the laser beam 1 is set to the surface of the substrate 2. The scanning may be performed by moving in the direction.

The laser beam 1 is irradiated to the semiconductor film 5 at an energy density sufficient to melt the semiconductor film 5 by being shaped into a linear beam, similarly to the normal laser annealing.
The laser beam 1 may be either a continuous wave or a pulse wave. However, since the crystal grain size of the semiconductor film 5 increases according to the number of times of melting and solidification, that is, the number of incidences of the laser beam 1, a pulse wave is used. By scanning the laser beam 1 in the surface direction of the substrate 2 so that the number of times of irradiation of the pulsed light per region is plural, crystal grains having a large grain size can be obtained efficiently.

According to the laser annealing method of the present embodiment, when the semiconductor film 5 is irradiated with the laser beam 1, the photocatalyst layer 4 is irradiated with the excitation light 8 having a wavelength that the photocatalyst layer 4 absorbs, whereby the semiconductor film Since carriers (electrons / holes) are formed at the interface between the photocatalyst layer 5 and the photocatalyst layer 4, the wettability when the semiconductor film 5 is melted by irradiation with the laser beam 1 is improved. That is, the wettability of the semiconductor melt is improved by the superhydrophilic action of the photocatalyst layer 4. For this reason, crystal nuclei can be generated at the interface between the semiconductor film 5 and the photocatalytic layer 4 in the vicinity of the melting point of the semiconductor film 5, thereby forming the polycrystalline semiconductor film 5 having a uniform crystal grain size.
In addition, since the photocatalyst layer 4 is formed as a base layer of the semiconductor film 5, it is not necessary to remove the photocatalyst layer 4 for processing performed after the crystallization process.

  Further, when the excitation light 8 is irradiated from one surface side (semiconductor film 5 side) of the substrate 2, the excitation light 8 is absorbed by the semiconductor film 5, and the photocatalyst layer 4 cannot be irradiated with the excitation light 8. As described above, the photocatalyst layer 4 has an absorption edge wavelength longer than the absorption edge wavelength of the substrate 2 and the substrate 2 is made of a material that transmits the excitation light 8. By irradiating the layer 4 with the excitation light 8, the excitation light 8 can be efficiently and reliably irradiated to the photocatalyst layer 4. In addition, glass substrates, such as a non-alkali glass used normally, satisfy | fill said conditions.

  FIG. 2 is a diagram schematically showing a crystallized region 35a that is melted, solidified and crystallized by laser light irradiation, and a solid phase region 35b that is not irradiated with laser light and is not crystallized. It is. The semiconductor melted by the laser beam and its solid phase have good wettability, and the conventional laser annealing method that does not use the photocatalyst layer 4 does not use the photocatalyst layer 4 as shown in FIG. The portion in the vicinity of the solid-liquid interface of the liquid reaches the surface, and the surface unevenness increases. Japanese Patent No. 2,710,670 describes the phenomenon that the melt reaches the surface when the wettability is good.

  On the other hand, according to the laser annealing method of the present embodiment, the wettability of the semiconductor melt with respect to the photocatalyst layer 4 is good, so that the energy of wetting at the solid-liquid interface between the photocatalyst layer 4 and the semiconductor melt is It can be expected that the above-described phenomenon that the melt reaches the surface and the surface unevenness is reduced.

[Laser annealing method according to second embodiment]
FIG. 3 is an explanatory diagram of a laser annealing method according to the second embodiment of the present invention. In the description of the present embodiment, items not mentioned are the same as in the first embodiment.

  In the laser annealing method of this embodiment, a semiconductor film 5 is formed on one side of the substrate 2, a photocatalyst layer 4 is formed directly on the semiconductor film 5, and excitation light 8 having a wavelength that is absorbed by the photocatalyst layer 4. The semiconductor film 5 is irradiated with the laser beam 1 while the photocatalyst layer 4 is irradiated, and the semiconductor film 5 is melted and solidified to be crystallized. FIG. 3A shows a state where the semiconductor film 5 is irradiated with the laser light 1 while irradiating the photocatalyst layer 4 with the excitation light 8, and FIG. The semiconductor film 5 is melted, solidified, and crystallized. Reference numeral 5 a in FIG. 3B indicates a crystallized region of the semiconductor film 5.

In the first embodiment described above, the photocatalyst layer 4 is formed as a base layer of the semiconductor film 5, but in this embodiment, the photocatalyst layer 4 is formed as a cap layer of the semiconductor film 5.
Hereinafter, the structure in which the barrier layer 3, the semiconductor film 5, and the photocatalyst layer 4 are formed on the substrate 2 is referred to as a substrate 7 with a semiconductor film.

  When the excitation light 8 is irradiated from the other surface side of the substrate 2, it is blocked by the semiconductor film 5 and cannot be irradiated to the photocatalyst layer 4. In this embodiment, the excitation light 8 is applied to the photocatalyst layer 4 from the one surface side of the substrate 2. Irradiate. In this case, in order to irradiate the semiconductor film 5 with the laser beam 1, the laser beam 1 must pass through the photocatalyst layer 4. Therefore, the photocatalyst layer 4 needs to be made of a material that transmits the laser beam 1.

According to the laser annealing method of the present embodiment, the wettability of the semiconductor melt is improved by the superhydrophilic action of the photocatalyst layer 4 as in the first embodiment. Crystal nuclei can be generated at the interface of the photocatalyst layer 4, whereby a polycrystalline semiconductor film 5 with a uniform crystal grain size can be formed.
Further, since the photocatalyst layer 4 is made of a material that transmits the laser light 1, the semiconductor film 5 can be irradiated with the laser light 1 from the one surface side of the substrate 2 in the same manner as normal laser annealing.

  Hereinafter, a configuration example of a laser annealing apparatus for performing the above-described laser annealing method will be described.

[First configuration example]
FIG. 4 is a diagram illustrating a schematic configuration of a laser annealing apparatus 10A according to a first configuration example for performing the laser annealing method of the first embodiment.
The laser annealing apparatus 10A includes a laser irradiation apparatus 16, a gas levitation apparatus 12, a horizontal feeding apparatus 14, and an excitation light irradiation apparatus 9, and the semiconductor film with the semiconductor film 6 shown in FIG. 5 is irradiated with the laser beam 1 to melt and solidify the semiconductor film 5 to be crystallized.

  The laser irradiation device 16 is a device for irradiating the semiconductor film 5 on the substrate 2 with the laser light 1 from the upper surface side of the substrate 2. The laser oscillator 17 that oscillates the laser light 1 and the laser light from the laser oscillator 17. Beam homogenizer 18 for uniformizing 1 into a linear beam, mirror 19 for reflecting laser beam 1 from beam homogenizer 18 in the direction of substrate 2, and semiconductor film 5 on substrate 2 for laser beam 1 from mirror 19 And a projection lens 20 for condensing the light.

Examples of the laser oscillator 17 include excimer lasers, solid lasers such as YAG, YLF, and YVO ₄ , semiconductor lasers, and CO ₂ lasers. More specifically, an excimer laser having a wavelength of 248 nm or 308 nm, a YAG laser having a wavelength of 1064 nm, 532 nm or 355 nm, a semiconductor laser (laser diode) having a wavelength of 600 nm to 1000 nm, and a CO ₂ laser having a wavelength of 10.6 μm are exemplified. Further, as described above, the laser beam 1 may be either a continuous wave or a pulse wave.

  The gas levitation device 12 includes a first stage 12a and a second stage 12b arranged in a horizontal direction (left and right in the figure) with a predetermined gap therebetween, and gas is supplied from the upper surfaces of the first stage 12a and the second stage 12b. Is blown out to float the substrate 2 with one surface (the surface on which the semiconductor film 5 is formed) facing upward. A number of holes for blowing out gas are provided on the upper surfaces of the first stage 12a and the second stage 12b, and the holes are connected to a gas supply device (not shown) through a gas pipe (not shown).

  The horizontal feeding device 14 sends the substrate 2 levitated by the gas levitation device 12 in the horizontal direction from one of the first stage 12a and the second stage 12b to the other across the gap. Hereinafter, the horizontal direction from one of the first stage 12a and the second stage 12b to the other is referred to as a “feeding direction”. FIG. 4 shows only the gripping mechanism that grips the end portion of the substrate 2 in the horizontal feeding device 14, and the gripping mechanism moves horizontally in the feeding direction by driving of a gripping mechanism moving device (not shown).

  The excitation light irradiation device 9 irradiates the photocatalyst layer 4 with excitation light 8 having a wavelength absorbed by the photocatalyst layer 4 from the other surface (lower surface) side of the substrate 2 through the gap. As described above, the excitation light irradiation device 9 is an ultraviolet irradiation lamp (black light) when the excitation light 8 is ultraviolet light. Further, the excitation light irradiation device 9 may be a laser device.

  In order to improve the wettability of the semiconductor melt by the superhydrophilic action of the photocatalyst layer 4, the irradiation region of the laser beam 1 in the semiconductor film 5 is adjacent to the photocatalyst layer 4 irradiated with the excitation light 8. It is necessary to be. Therefore, the laser irradiation device 16 irradiates the laser beam 1 toward the gap, and irradiates the semiconductor film 5 adjacent to the photocatalyst layer 4 irradiated with the excitation light 8 with the laser beam 1.

  Using the laser annealing apparatus 10A, the substrate 2 is levitated by the gas levitation stage with the one surface of the substrate 2 facing upward, and the levitated substrate 2 straddles the gap between the first stage 12a and the first stage 12a. The substrate 2 is transported by sending it horizontally from one of the two stages 12b to the other. In parallel with the transport of the substrate 2, the excitation light is directed from the upper surface side of the substrate 2 toward the gap while irradiating the photocatalyst layer 4 with the excitation light 8 from the lower surface side of the substrate 2 through the gap and the substrate 2. The semiconductor film 5 adjacent to the photocatalyst layer 4 irradiated with 8 is irradiated with the laser beam 1.

As described above, according to the laser annealing apparatus 10A of the first configuration example, the photocatalyst layer 4 is irradiated with the excitation light 8 having a wavelength that is absorbed by the photocatalyst layer 4, so that the semiconductor catalyst is melted by the superhydrophilic action of the photocatalyst layer 4. Improves liquid wettability. For this reason, crystal nuclei can be generated at the interface between the semiconductor film 5 and the photocatalyst layer 4 in the vicinity of the melting point of the semiconductor film 5, thereby forming a polycrystalline semiconductor film 5 having a uniform crystal grain size. In addition, by irradiating the photocatalyst layer 4 with the excitation light 8 from the substrate 2 side, the excitation light 8 can be efficiently and surely applied to the photocatalyst layer 4.
Further, since a gap is formed between the first stage 12a and the second stage 12b, the excitation light 8 can be easily irradiated from the other surface (lower surface) side of the substrate 2 to the photocatalyst layer 4 through the gap. Can do.

[Second configuration example]
FIG. 5 is a diagram showing a schematic configuration of a laser annealing apparatus 10B according to a second configuration example for implementing the laser annealing method of the first embodiment.
The laser annealing apparatus 10B includes a laser irradiation apparatus 16, a substrate stage 22, and an excitation light irradiation apparatus 9, and irradiates the semiconductor film 5 with the laser light 1 on the substrate 6 with a semiconductor film shown in FIG. Then, the semiconductor film 5 is crystallized by melting and solidifying.

  The second configuration example is different from the first configuration example described above in that the gas levitation device 12 and the horizontal feeding device 14 in the first configuration example are replaced with a substrate stage 22 made of a material that transmits the excitation light 8. is there. Examples of the material that transmits the excitation light 8 include glass materials such as non-alkali glass and quartz glass. In addition, the “material that transmits the excitation light 8” can be rephrased as “a material whose absorption edge wavelength is shorter than the wavelength of the excitation light 8”.

  The substrate stage 22 supports the substrate 2 from the other surface side of the substrate 2. In the present configuration example, the substrate stage 22 moves in a direction intersecting the incident direction of the laser beam 1 with respect to the substrate 2 (left and right direction in the figure). By moving the substrate stage 22, the laser beam 1 can be scanned in the surface direction of the substrate 2. The position of the substrate stage 22 may be fixed, and the laser light 1 may be scanned in the surface direction of the substrate 2 by moving the irradiation direction of the laser light 1.

  Using the laser annealing apparatus 10B of this configuration example, the substrate 2 is supported by the substrate stage 22 with the other surface facing the substrate stage 22, and the photocatalyst layer 4 is formed from the other surface side of the substrate 2 through the substrate stage 22 and the substrate 2. While irradiating the excitation light 8, the semiconductor film 5 adjacent to the photocatalyst layer 4 irradiated with the excitation light 8 is irradiated with the laser light 1 from one side of the substrate 2, and the laser light 1 is directed in the surface direction of the substrate 2. Scan.

According to the laser annealing apparatus 10B of this configuration example, crystal nuclei can be generated at the interface between the semiconductor film 5 and the photocatalyst layer 4 in the vicinity of the melting point of the semiconductor film 5, as in the first configuration example. A polycrystalline semiconductor film 5 having a uniform grain size can be formed.
In addition, since the substrate stage 22 is made of a material that transmits the excitation light 8, the excitation light 8 can be easily irradiated onto the photocatalyst layer 4 through the substrate 2 from the other surface side of the substrate 2.

[Third configuration example]
FIG. 6 is a diagram showing a schematic configuration of a laser annealing apparatus 10C according to a third configuration example for carrying out the laser annealing method of the second embodiment.
This laser annealing apparatus 10C includes a laser irradiation apparatus 16, a substrate stage 24, and an excitation light irradiation apparatus 9, and irradiates the semiconductor film 5 with the laser beam 1 for the substrate 7 with a semiconductor film shown in FIG. Then, the semiconductor film 5 is crystallized by melting and solidifying.

The laser irradiation device 16 irradiates the semiconductor film 5 with the laser beam 1 from one side of the substrate 2. The configuration of the laser irradiation device 16 is the same as that of the first configuration example.
The excitation light irradiation device 9 irradiates the photocatalyst layer 4 with excitation light 8 having a wavelength absorbed by the photocatalyst layer 4 from one surface side of the substrate 2. The configuration of the excitation light irradiation device 9 is the same as that of the first configuration example except that the position with respect to the substrate 2 is different.

  The substrate stage 24 of this configuration example is the same as the substrate stage 22 of the second configuration example in that the substrate 2 is supported from the other surface side of the substrate 2, but from a material that transmits the excitation light 8. This is different from the substrate stage 22 of the second configuration example in that it does not need to be.

  Similarly to the second configuration example, the substrate stage 24 of this configuration example moves in a direction intersecting the incident direction of the laser beam 1 with respect to the substrate 2 (left and right in the drawing), and the movement of the substrate stage 24 causes the laser beam to move. 1 can be scanned in the plane direction of the substrate 2, but the position of the substrate stage 24 is fixed and the irradiation direction of the laser beam 1 is moved to scan the laser beam 1 in the plane direction of the substrate 2. May be.

  Using the laser annealing apparatus 10C of this configuration example, the substrate 2 is supported by the substrate stage 24 with the other surface facing the substrate stage 24, and the photocatalyst layer 4 is irradiated with the excitation light 8 from the one surface side of the substrate 2. The semiconductor film 5 adjacent to the photocatalyst layer 4 irradiated with the excitation light 8 is irradiated with the laser light 1 from the one surface side of the substrate 2, and the laser light 1 is scanned in the surface direction of the substrate 2.

According to the laser annealing apparatus 10C of this configuration example, crystal nuclei can be generated at the interface between the semiconductor film 5 and the photocatalyst layer 4 in the vicinity of the melting point of the semiconductor film 5, as in the first configuration example. A polycrystalline semiconductor film 5 having a uniform grain size can be formed.
In addition, since the photocatalyst layer 4 is irradiated with the excitation light 8 from the one surface side of the substrate 2, it is not necessary to add a special device to the substrate stage 24.

  In the third configuration example, the substrate stage 24 may be replaced with the gas levitation device 12 and the horizontal feed device 14 of the second configuration example, and the substrate 2 may be moved by the gas levitation device 12 and the horizontal feed device 14.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. For example, in the above embodiment, an a-Si film is targeted as an amorphous semiconductor film, but other amorphous semiconductor films (for example, compound semiconductor films having an amorphous structure such as an amorphous silicon germanium film). May be targeted. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

It is a figure explaining the laser annealing method concerning 1st Embodiment of this invention. It is the figure which showed typically the crystallization area | region which melted and solidified by the laser beam irradiation of the semiconductor film, and the solid phase area | region which is not irradiated with the laser beam but is not crystallized. It is a figure explaining the laser annealing method concerning 2nd Embodiment of this invention. It is a figure which shows schematic structure of the laser annealing apparatus concerning the 1st structural example for enforcing the laser annealing method of 1st Embodiment. It is a figure which shows schematic structure of the laser annealing apparatus concerning the 2nd structural example for enforcing the laser annealing method of 1st Embodiment. It is a figure which shows schematic structure of the laser annealing apparatus concerning the 3rd structural example for enforcing the laser annealing method of 2nd Embodiment. It is a figure which shows the cross-section of the conventional glass substrate with an a-Si film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser beam 2 Substrate 3 Barrier layer 4 Photocatalyst layer 5 Semiconductor films 6 and 7 Substrate with semiconductor film 8 Excitation light 9 Excitation light irradiation apparatus 10A, 10B, 10C Laser annealing apparatus 12 Gas levitation apparatus 12a First stage 12b Second stage 14 Horizontal feed device 16 Laser irradiation device 17 Laser oscillator 18 Beam homogenizer 19 Mirror 20 Projection lenses 22 and 24 Substrate stage

Claims (10)

A laser annealing method for crystallization by irradiating a semiconductor film formed on one side of a substrate with laser light to melt and solidify the semiconductor film,
Forming a photocatalyst layer on one side of the substrate, forming the semiconductor film directly on the photocatalyst layer;
The semiconductor film is irradiated with laser light while irradiating the photocatalyst layer with excitation light having a wavelength absorbed by the photocatalyst layer, and the semiconductor film is melted and solidified to be crystallized. Laser annealing method. The absorption edge wavelength of the photocatalyst layer is longer than the absorption edge wavelength of the substrate, and the substrate is made of a material that transmits the excitation light,
The laser annealing method according to claim 1, wherein the excitation light is irradiated to the photocatalyst layer through the substrate from the other surface side of the substrate. With the one surface of the substrate facing upward, a gas is blown out from the upper surfaces of the first stage and the second stage arranged in a horizontal direction with a predetermined gap interposed therebetween, and the substrate that has floated is Transport across the gap in the horizontal direction from one of the first stage and the second stage toward the other,
In parallel with the transport of the substrate, the excitation light is irradiated from the upper surface side of the substrate toward the gap while irradiating the photocatalyst layer with the excitation light from the lower surface side of the substrate through the gap and the substrate. The laser annealing method according to claim 2, wherein the semiconductor film adjacent to the irradiated photocatalytic layer is irradiated with laser light. Supporting the substrate in a state in which the other surface faces the substrate stage by a substrate stage made of a material that transmits the excitation light;
While irradiating the photocatalyst layer from the other surface side of the substrate through the substrate stage and the substrate, the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light from one surface side of the substrate. The laser annealing method according to claim 2, wherein the laser beam is irradiated and the laser beam is scanned in the surface direction of the substrate. A laser annealing method for crystallization by irradiating a semiconductor film formed on one side of a substrate with laser light to melt and solidify the semiconductor film,
Forming the semiconductor film on one side of the substrate, forming a photocatalytic layer directly on the semiconductor film,
While irradiating the photocatalyst layer with excitation light having a wavelength that is absorbed by the photocatalyst layer, the semiconductor film is irradiated with laser light, and the semiconductor film is melted and solidified to be crystallized. Laser annealing method. The photocatalytic layer is made of a material that transmits the laser beam,
The substrate is supported by the substrate stage with the other surface facing the substrate stage,
While irradiating the photocatalyst layer with the excitation light from one side of the substrate, the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light is irradiated with laser light from the one side of the substrate, and the laser The laser annealing method according to claim 5, wherein light is scanned in a surface direction of the substrate. The laser annealing method according to claim 1, wherein the photocatalyst layer is made of TiO ₂ , ZnO ₂ , MgO, SnO ₂ , SrTiO ₃ , WO ₃ , Bi ₂ O _3, or Fe ₂ O ₃ . A laser annealing apparatus for crystallization by irradiating a semiconductor film formed on one side of a substrate with laser light to melt and solidify the semiconductor film,
The substrate to be processed has a photocatalyst layer formed on one side, the semiconductor film is formed directly on the photocatalyst layer, and the absorption edge wavelength of the photocatalyst layer is longer than the absorption edge wavelength of the substrate, Is,
A first stage and a second stage arranged in a horizontal direction across a predetermined gap are provided, and gas is blown out from the upper surfaces of the first stage and the second stage to float the substrate with the one surface facing upward. A gas levitation device;
A horizontal feeding device for sending the substrate levitated by the gas levitation device in a horizontal direction from one of the first stage and the second stage to the other across the gap;
A laser irradiation apparatus for irradiating the semiconductor film with laser light from the upper surface side of the substrate toward the gap;
An excitation light irradiation device for irradiating the photocatalyst layer with excitation light having a wavelength absorbed by the photocatalyst layer,
The substrate is made of a material that transmits the excitation light, the excitation light irradiation device irradiates the photocatalyst layer through the gap and the substrate from the lower surface side of the substrate, and the laser irradiation device A laser annealing apparatus, wherein the semiconductor film adjacent to the photocatalyst layer irradiated with excitation light is irradiated with laser light. A laser annealing apparatus for performing crystallization by scanning a laser beam in a surface direction of a substrate, irradiating the semiconductor film formed on one side of the substrate with the laser beam, and melting and solidifying the semiconductor film. ,
The substrate to be processed has a photocatalyst layer formed on one side, the semiconductor film is formed directly on the photocatalyst layer, and the absorption edge wavelength of the photocatalyst layer is longer than the absorption edge wavelength of the substrate, Is,
A substrate stage for supporting the substrate from the other side of the substrate;
A laser irradiation apparatus for irradiating the semiconductor film with laser light from one side of the substrate;
An excitation light irradiation device for irradiating the photocatalyst layer with excitation light having a wavelength absorbed by the photocatalyst layer,
The substrate and the substrate stage are made of a material that transmits the excitation light, and the excitation light irradiation device irradiates the excitation light to the photocatalyst layer through the substrate stage and the substrate from the other surface side of the substrate, The laser annealing apparatus irradiates the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light with a laser beam. A laser annealing apparatus for performing crystallization by scanning a laser beam in a surface direction of a substrate, irradiating the semiconductor film formed on one side of the substrate with the laser beam, and melting and solidifying the semiconductor film. ,
The substrate to be processed has a semiconductor film formed on one side, a photocatalytic layer is formed directly on the semiconductor film, and the photocatalytic layer is made of a material that transmits the laser beam.
A substrate stage for supporting the substrate from the other side of the substrate;
A laser irradiation apparatus for irradiating the semiconductor film with laser light from one side of the substrate;
An excitation light irradiation device for irradiating the photocatalyst layer with the excitation light from one side of the substrate,
The laser annealing apparatus irradiates the semiconductor film adjacent to the photocatalyst layer irradiated with the excitation light with a laser beam.

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