JP2005123262A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device for controlling cooling rate of a semiconductor device melted by laser irradiation and enlarging scale of a grown crystal, and to provide its manufacturing method. <P>SOLUTION: In the semiconductor device 1, a first base film 3, a second base film 4 and a semiconductor film 5 are stacked in this order on a substrate 2. It is characterized that thermal conductivity of the first base film 3 is higher than those of the substrate 2 and the second base film 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor device obtained by crystallizing a semiconductor material using a laser and a method for manufacturing the same.

In general, as a method for manufacturing a semiconductor device, there is a method using a single crystal silicon (Si) material. In addition to this manufacturing method, there is a manufacturing method using a silicon thin film in which a silicon thin film is formed on a glass substrate. A semiconductor device manufactured by using a silicon thin film formed on a glass substrate is used as a part of an image sensor or an active matrix liquid crystal display device.
In a liquid crystal display device, semiconductor devices are used for TFTs (Thin Film Transistors) arranged as a regular array on a transparent substrate. The TFT of the liquid crystal display device is formed of an amorphous silicon film, and each transistor of the TFT functions as a pixel controller in the liquid crystal display device.

However, in recent years, a TFT liquid crystal display that uses a polycrystalline silicon film with high electron mobility instead of an amorphous silicon film with low electron mobility to enhance the switching characteristics of the TFT and increase the display speed. Devices are being manufactured. For example, there is a method of manufacturing a polycrystalline silicon film by irradiating an excimer laser on an amorphous or microcrystalline silicon film deposited on a substrate to crystallize (ELC, excimer laser crystallization).
The ELC method is generally a method of continuously irradiating a semiconductor film with a linear laser beam having a length of about 200 to 400 mm and a width of about 0.2 to 1.0 mm while scanning a sample at a constant speed. It is. At this time, the portion of the semiconductor film irradiated with the laser does not melt over the entire thickness direction, but is melted while leaving a part of the semiconductor film region. For this reason, crystal nuclei are generated everywhere on the entire unmelted region / melted region interface, crystals grow toward the outermost layer of the semiconductor film, and crystal grains with random orientation are formed. It becomes very small as 100 to 200 nm.
A large number of unpaired electrons are present in the crystal grain boundary of the polycrystalline silicon film, so that a potential barrier is formed and acts as a strong carrier scatterer. Therefore, a TFT formed of a polycrystalline silicon film having a small crystal grain boundary, that is, a large crystal grain size generally has a higher field effect mobility and is preferable.

  However, in the conventional ELC method, as described above, since it is longitudinal crystal growth in which crystallization occurs at random positions at the unmelted region / melted region interface, it is difficult to obtain a polycrystalline silicon film having a large grain size. Therefore, it has been difficult to obtain a TFT having a high field effect mobility. In addition, since the crystallization is random, in such a case, non-uniformity of the structure occurs between the TFTs, and non-uniformity of the switching characteristics occurs in the TFT array. In addition, when such a problem occurs, in a liquid crystal display device using TFTs, there arises a problem that pixels with a high display speed and pixels with a low display speed coexist in one display screen.

Therefore, in order to obtain a higher performance TFT liquid crystal display device, it is necessary to increase the crystal grain size of the polycrystalline silicon film and to control the orientation of the silicon crystal. Therefore, many proposals have been made for the purpose of obtaining a polycrystalline silicon film having performance close to that of single crystal silicon.
Among them, laser crystallization techniques classified as “lateral growth methods” are particularly attracting attention because long crystals having a uniform orientation in the crystal growth direction can be obtained (for example, Patent Document 1 and Patent Document 2). Patent Document 3).

As in the method described in Patent Document 1, the lateral growth method irradiates a silicon thin film with a pulsed laser beam having a fine width, and melts the irradiated silicon thin film over the entire thickness direction of the laser light irradiation region. Reflection of laser light used for crystallization on a semiconductor thin film, such as a method of crystallization by repeating solidification (described as SLS (Sequential Lateral Solidification) method) and a method described in Patent Literature 2 and Patent Literature 3. It can be classified into a method of forming a prevention film (light absorption film) or a reflection film, and partially melting and solidifying the semiconductor thin film for crystallization (described as a capping method).
In the above-described lateral growth method, the basic crystallization principle is the same in any method, and here, the SLS method will be described among the conventional lateral growth methods.

FIG. 10 shows a laser processing apparatus for crystallizing the semiconductor film 5. This laser processing apparatus includes a laser oscillator 11, a variable attenuator 12, a field lens 13, a mask 14, an imaging lens 15, a sample stage 16 and several mirrors, and these elements are controlled by a controller 17. .
The SLS method uses a laser processing apparatus as shown in FIG. 10 to irradiate a semiconductor with a pulse laser having a small width, and melt and solidify the semiconductor film over the entire thickness direction of the laser irradiation region to perform crystallization. . According to this laser processing apparatus, the excimer laser emitted from the light source 11 is irradiated to the semiconductor device 1 on the stage 16.
FIG. 11 shows a conventional structure 1 of a semiconductor device 1 in a conventional lateral growth method. As shown in FIG. 11, a semiconductor film (semiconductor material) 103 is formed on a light-transmitting transparent substrate 102. The semiconductor film 103 includes a base film 104 and a silicon film 105 formed thereon. Consists of

  Hereinafter, the manufacturing procedure of the SLS method will be shown. First, as shown in FIG. 11, in order to form a crystal region along the extending direction (AB direction in the drawing) of the semiconductor film 103 on the transparent substrate 102, heat is induced to the region C in the semiconductor film 103. . The induction of heat is performed by masking a region other than the region C of the semiconductor film 103 and then laser-exposing the semiconductor film 103. Thereby, the energy of the laser light 8 irradiated to the region C is converted into thermal energy, and heat can be induced to the region C in the semiconductor film 103, and the silicon film 105, which is an upper layer portion of the semiconductor film 103, can be used. The silicon film 105 can be melted over the thickness.

Next, the silicon film 105 melted in the region C is solidified by cooling. Thereby, as shown in FIG. 12A, a needle-like crystal grows from the boundary between the region C and the other region toward the center of the region C. FIG. 12A is a top view of the semiconductor film 103 in FIG. In FIG. 12A, the central portion of the region C shows a microcrystalline region, and the left and right side portions of the region C show grown acicular crystal regions.
Further, as shown in FIG. 12B, a new region D adjacent to the region C is set so that a portion in which the needle-like crystal is not formed in the region C is included, and the region is similar to the above procedure. Melt D. Similarly to the above, when the silicon film 105 melted in the region D is solidified, a crystal grows in the region D as shown in FIG.

By repeating such a procedure and forming a desired crystal stepwise along the extending direction of the semiconductor film 103, the semiconductor crystal having a polycrystalline structure can be enlarged as shown in FIG. it can. Thereby, a polycrystalline silicon film having large crystal grains can be formed.
Japanese Patent No. 3204986 JP 58-184720 A JP 2000-260709 A

In the capping method of the conventional lateral growth method, when the substrate temperature is set to room temperature and an excimer laser with a wavelength of 308 nm is irradiated to an amorphous silicon thin film having a thickness of 50 nm with an energy amount of 300 mJ / cm ² , one time is used. The length of the silicon crystal grown by laser pulse irradiation, that is, the lateral growth distance is about 0.8 to 1.0 μm (Patent Document 3, paragraphs 34 and 37).
In addition, when forming a transistor using polycrystalline silicon as an active layer obtained by a lateral growth method combined with a capping method, in order to form a high-performance thin film transistor, in the movement direction of carriers in the polycrystalline silicon. It is necessary to use a portion having no grain boundary.

  However, as described above, in the lateral growth method combined with the conventional capping method, the length of the silicon crystal grown by one laser pulse irradiation is about 0.8 to 1.0 μm, which is relatively small. Therefore, if a transistor whose channel length exceeds this length is formed, a crystal grain boundary is included in the carrier movement direction. Therefore, the longer the lateral growth distance obtained by one laser pulse irradiation, the more high-performance thin film transistors of various sizes can be formed. As a result, circuits having various functions are integrated on the glass substrate together with the thin film transistors. However, since a lateral growth distance is relatively small, a transistor manufactured by a lateral growth method using a capping method has a problem that performance may be extremely deteriorated.

On the other hand, in the case of the conventional SLS method, the laser growth method is different from the lateral growth method combined with the capping method, and the principle of crystal growth is the same. If so, crystals of the same length grow.
Therefore, in the conventional SLS method, in order to form a needle-like long silicon crystal as shown in FIG. 12 (d), the length of the crystal grown by one laser pulse irradiation (lateral growth distance) It is necessary to repeatedly perform laser pulse irradiation at a feed pitch of about 1/2 to 2/3, that is, an extremely fine feed pitch of about 0.4 to 0.7 μm.
For this reason, it takes a very long time to crystallize silicon over the entire surface of a substrate composite used in a display device or the like using the conventional SLS method, and there is a problem that the manufacturing efficiency is extremely poor.

  The present invention has been made in consideration of the above points, and in a semiconductor device having a semiconductor layer formed by utilizing a lateral growth method, the semiconductor layer is once melted and recrystallized by laser light irradiation. It is an object of the present invention to provide a semiconductor device in which a semiconductor layer is formed of a polycrystalline silicon film having a large grain size by increasing the lateral growth distance of the polycrystalline silicon crystal obtained by the fabrication, and a method for manufacturing the same. To do.

The present invention relates to a semiconductor device in which a first base film, a second base film, and a semiconductor film are stacked in this order on a substrate, and the first base film is formed from the substrate and the second base film. The present invention also provides a semiconductor device characterized by high thermal conductivity.
In the semiconductor device having such a configuration, the crystal grain size of the semiconductor film can be made larger than before. Therefore, the field effect mobility of a transistor formed using this semiconductor device can be increased.

Here, the semiconductor film is an amorphous, microcrystalline or polycrystalline silicon-based semiconductor film once formed by a conventional method, and when the semiconductor film is further subjected to heat treatment by laser light irradiation, The first base film may play a role of promoting crystal growth of the semiconductor film.
In addition, the first base film promotes crystal growth of the semiconductor film by diffusing heat of laser light irradiated from above the semiconductor film in an in-plane direction of the first base film. It will function.
In the present invention, the semiconductor film immediately after being stacked may have any structure of amorphous, microcrystalline, or polycrystalline. However, the semiconductor film after the heat treatment by the laser light has a polycrystalline structure.

Further, the first base film may contain as a main component any one of aluminum nitride, magnesium oxide, cerium oxide, silicon nitride, or a mixture of aluminum nitride and silicon nitride.
The first base film is a film mainly composed of any one of aluminum nitride, magnesium oxide, cerium oxide, silicon nitride, or a mixture of aluminum nitride and silicon nitride. The base film may be made of an insulating material.
Further, a glass or quartz substrate may be used as the substrate, and a substrate mainly composed of silicon oxide may be used as the second base film.
As the semiconductor film to be stacked, an amorphous film or a microcrystalline or polycrystalline crystalline semiconductor film is used. For example, in addition to amorphous silicon, a silicon-based semiconductor film containing silicon as a main component is used.

In the present invention, the semiconductor film is characterized by being crystallized and crystal-grown in an in-plane direction in a region melted by laser light irradiated from above the semiconductor film.
Further, the crystallized region of the semiconductor layer is enlarged by moving the region melted by the laser light irradiation stepwise in an in-plane direction.
Further, the laser beam has a first laser beam having an energy amount that can melt the semiconductor film in a solid state, and a second laser beam having an energy amount that does not melt the semiconductor film in a solid state. It consists of light.

The present invention also relates to a method of manufacturing a semiconductor device in which a first base film, a second base film, and a semiconductor film are stacked in this order on a substrate, the substrate and the second base film being formed on the substrate A step of laminating a first base film having a higher thermal conductivity, a step of laminating a second base film on the first base film, and a semiconductor on the second base film A semiconductor device comprising: a step of laminating a film; and a step of irradiating the semiconductor film with laser light to melt and crystallize the semiconductor film in the irradiated region, and further grow a crystal in an in-plane direction. The manufacturing method of this is provided.
According to this, the crystal grain size of the semiconductor film grown by laser irradiation can be increased. In addition, since the first base film has higher thermal conductivity than the substrate and the second base film, a semiconductor device having a semiconductor film having a large crystal grain size can be efficiently manufactured.
Here, the semiconductor film formed in the stacking process may have any structure of amorphous, microcrystalline, or polycrystalline. After the crystal growth, a polycrystalline semiconductor film is obtained.

  Furthermore, the present invention is a method for manufacturing a semiconductor device in which a first base film, a second base film, and a semiconductor film are laminated in this order on a substrate, wherein the substrate and the second base film are formed on the substrate. A step of laminating a first base film having a higher thermal conductivity, a step of laminating a second base film on the first base film, and a semiconductor on the second base film A step of laminating the film, and irradiating the semiconductor film with laser light to melt and crystallize the semiconductor film in the irradiated region, and further move the laser light irradiated region stepwise in the in-plane direction of the semiconductor film And a step of enlarging the crystallization region.

A method of manufacturing a semiconductor device in which a first base film, a second base film, and a semiconductor film are stacked in this order on a substrate, and is more thermally conductive than the substrate and the second base film on the substrate. Laminating a first base film having a high rate, laminating a second base film on the first base film, and laminating a semiconductor film on the second base film Irradiating the semiconductor film with a first laser beam having an energy amount capable of melting the semiconductor film in a solid state, and bringing the semiconductor film into a liquid state; and And crystallization of the liquid semiconductor film by irradiating the semiconductor film with a second laser beam having an energy amount that does not melt the semiconductor film. To do.
Here, after laminating the semiconductor film, a cap layer for preventing reflection of the first laser beam may be formed on the surface of the semiconductor film.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings. In addition, this invention is not limited by this.
FIG. 1 is a sectional view showing the structure of a semiconductor device according to the present invention.
In the semiconductor device 1 of the present invention, a first base film 3 is formed on a substrate 2, a second base film 4 is formed on the first base film 3, and a semiconductor is formed on the second base film 4. The film 5 is formed. The semiconductor film 5 is crystallized with the laser light 8 by a lateral growth method such as an SLS method or a capping method. Here, the first base film 3 has a higher thermal conductivity than the substrate and the second base film 4.
Such a semiconductor device 1 is manufactured mainly by the following two processes (a thin film stacking process and a semiconductor film crystallization process). In addition, by providing the first base film, a semiconductor film that is amorphous, microcrystalline, or polycrystalline at the time of stacking becomes a film having a larger crystal grain size than the conventional one after laser light irradiation.

<Thin film stacking process>
Hereinafter, in the semiconductor device of the present invention, a method for sequentially laminating the plurality of thin films on the substrate 2 will be described.
(Step 1: Formation of the first base film 3)
First, the first base film 3 is formed on the substrate 2.
The substrate 2 is preferably insulative, and a glass substrate, a quartz substrate, or the like can be used. However, it is preferable to use a glass substrate from the viewpoints of being inexpensive and capable of easily manufacturing a large-area substrate. Further, the thermal conductivity of the glass substrate is 0.8, and the thermal conductivity of the quartz substrate is 1.4 (W / mK), which is sufficiently lower than the thermal conductivity of the first underlayer described later. is there.

The first base film 3 is laminated by vapor deposition, ion plating, sputtering, or the like so that the film thickness is desirably 10 to 150 nm. When the film thickness is less than 10 nm, a sufficient heat conduction effect may not be obtained. On the other hand, when the film thickness exceeds 150 nm, the crystal growth of the semiconductor film 5 may be inhibited. It is. The first base film 3 is not particularly limited as long as it has a thermal conductivity higher than that of the substrate 2 and the second base film 4, but is preferably 10 (W / mK) or more. Preferably has a thermal conductivity of 20 (W / mK) or more. Here, the thermal conductivity means a value that is normally used (a ratio between the amount of heat that flows perpendicularly to a unit time through a unit area of an isothermal surface inside an object and a temperature gradient in this direction). .
The first underlayer 3 preferably has such a thermal conductivity and exhibits insulating properties. As such a first base film 3, for example, aluminum nitride, silicon nitride, a mixture of aluminum nitride and silicon nitride, magnesium oxide, cerium oxide or the like is preferably used. As an example, the thermal conductivity of the glass substrate 2 is 0.8, and the thermal conductivity of silicon oxide, which is the second base film 4, is 1.4, whereas the nitridation, which is the first base film 3, is performed. Aluminum has a thermal conductivity of 35 (see FIG. 8).

(Step 2: Formation of the second base film 4)
A second base film 4 is formed on the first base film 3.
The second base film 4 is laminated by vapor deposition, ion plating, sputtering or the like so that the film thickness is desirably 10 to 100 nm. When the film thickness is less than 10 nm, the flatness of the surface is poor and a uniform laser irradiation effect may not be obtained. On the other hand, when the film thickness exceeds 100 nm, a sufficient heat conduction effect cannot be obtained. Because there is. As the second base film 4, a film having a thermal conductivity lower than that of the first base film 3 is used. The second base film 4 preferably has such a thermal conductivity and exhibits insulating properties. As such a second base film 4, for example, a film mainly composed of silicon oxide, silicon nitride, silicon oxynitride, or the like is preferably used. The second base film 4 is also suitable as a barrier for preventing the material of the substrate 2 which is the lower layer from being melted into the melted semiconductor film by laser irradiation and adversely affecting the physical properties of the semiconductor as impurities. . Further, since it is insulative, it is convenient when a circuit is formed in a semiconductor film.

(Step 3: Formation of Semiconductor Film 5)
Next, a semiconductor film 5 is formed on the second base film 4.
The semiconductor film 5 is laminated so as to have a film thickness of 10 nm to 100 nm by using plasma enhanced chemical vapor deposition (PECVD), vapor deposition, sputtering, or the like. For the semiconductor film 5, a material exhibiting semiconductor characteristics may be used. However, it is preferable to use an amorphous silicon film in which various characteristics are remarkably improved by increasing the crystal growth length. However, the semiconductor film 5 before being crystallized by laser irradiation may be a crystalline semiconductor film such as a microcrystal or a polycrystal. The material of the semiconductor film 5 is not limited to a material made only of silicon, but is a material (referred to as a silicon-based semiconductor film or silicon-based material) containing silicon as a main component and containing other elements such as germanium. Also good.
Thus, the thin film layers constituting the semiconductor device of the present invention as shown in FIG. 1 are formed.

Examples of combinations of materials of “substrate 2 / first base film 3 / second base film 4 / semiconductor film 5” constituting the semiconductor device of the present invention include the following.
The numerical value in parentheses after the material name indicates the thermal conductivity (W / mK).
(A) glass (0.8) / aluminum nitride (35) / silicon oxide (1.4) / silicon (b) glass (0.8) / silicon nitride (10) / silicon oxide (1.4) / silicon (c) glass (0.8) / AlSiN (20) / silicon oxide (1.4) / silicon (d) glass (0.8) / magnesium oxide (60) / silicon oxide (1.4) / silicon (e) glass (0.8) / cerium oxide (10) / silicon oxide ( 1.4) / Silicon

<Semiconductor film crystallization process>
After the thin film layer is formed as described above, a predetermined region of the semiconductor film 5 is crystallized.
A method for crystallizing the semiconductor film 5 among the stacked films of the semiconductor devices will be described.
Crystallization is performed by irradiating the following laser beam.
FIG. 3 shows a laser processing apparatus for crystallizing the semiconductor film 5 of the semiconductor device of the present invention. This laser processing apparatus includes a first laser oscillator 93, a variable attenuator 12, a field lens 13, a mask 14, an imaging lens 15, a sample stage 16, several mirrors and a controller 17 similar to the one shown in FIG. And a second laser oscillator 94 that emits a second laser beam 81.
The first laser oscillator 93 emits the first laser beam 80. Further, the first laser beam 80 has a wavelength in a range in which the absorption rate of the semiconductor film in the solid state is higher than that of the second laser beam 81 and melts the semiconductor film 5 in the solid state. The second laser beam 81 has a wavelength in a range where the absorption rate to the semiconductor film 5 in a liquid state is higher than that of the first laser beam 80, and has a solid state. A material having an energy amount that does not melt a certain semiconductor film 5 is used.

Here, the first laser beam 80 needs to have a wavelength in a range where the absorption rate to the semiconductor film 5 in a solid state is higher than that of the second laser beam 81, but has a wavelength in the ultraviolet region. The XeCL excimer laser pulse having a wavelength of 308 nm is preferable.
Further, the first laser beam 80 needs to have an energy amount per irradiation area for melting the semiconductor film in a solid state per one pulse irradiation, and this energy amount depends on the material of the semiconductor film. Since it differs depending on the type, the thickness of the semiconductor film, the area of the crystallization region, etc., it cannot be uniquely determined. However, the energy amount of the first laser beam 80 is preferably an energy amount that can heat the semiconductor film 5 to a temperature equal to or higher than the melting point in the entire film thickness.

On the other hand, the second laser beam 81 needs to have a wavelength in a range where the absorption rate of the semiconductor film in a liquid state is higher than that of the first laser beam 80. For example, a YAG laser with a wavelength of 532 nm, a YAG laser with a wavelength of 1064 nm, or a carbon dioxide gas laser with a wavelength of 10.6 μm can be used.
The second laser beam 81 needs to have an energy amount per irradiation area that does not melt the semiconductor film 5 in a solid state per one pulse irradiation. Since it differs depending on the type of the material, the thickness of the semiconductor film, the area of the crystallization region, etc., it cannot be uniquely determined. However, when the second laser beam is irradiated alone, the energy amount of the second laser beam is preferably an energy amount that cannot heat the semiconductor film 5 to a temperature equal to or higher than the melting point.

In the present embodiment, for example, the first laser beam 80 may be incident from a direction perpendicular to the substrate surface, and the second laser beam 81 may be incident from an oblique direction.
The first laser beam 80 (for example, an excimer laser pulse having a wavelength of 308 nm) as described above is used for melting the semiconductor film 5. The second laser beam 81 (for example, a YAG laser with a wavelength of 532 nm) is used to control the solidification of the semiconductor film 5.
Here, for example, an image of a mask in which a predetermined pattern is formed may be formed on the semiconductor film 5, and the first laser beam 80 may be irradiated to the irradiation region 7 a as shown in FIG. Good. In this case, the irradiation region 7b (see FIG. 5) of the second laser beam 81 is preferably an irradiation region having a wider area so as to include the irradiation region 7a of the first laser beam 80.
Further, it is desirable to irradiate the second laser beam 81 at least while the semiconductor film 5 is melted in order to reduce the temperature decrease rate of the semiconductor film 5 and extend the time until solidification.

In FIG. 3, a first laser oscillator 93 is a laser oscillator that emits a laser beam capable of melting silicon. For example, an ultraviolet region such as various solid-state lasers represented by an excimer laser and a YAG laser is used. It is preferable to use a laser oscillator having a wavelength. In particular, an excimer laser oscillator having a wavelength of 308 nm that can emit pulses is preferable.
The second laser oscillator 94 is preferably an oscillator that can emit laser light 81 having a wavelength that is absorbed by a molten semiconductor film such as molten silicon.
In particular, the second laser beam 81 may be pulsed by an external modulator (not shown) using a second laser oscillator 94 that continuously emits a YAG laser having a wavelength of 532 nm.
The controller 17 also controls the first laser oscillator 93 and the sample stage 16 to adjust the laser irradiation timing and the position of the sample stage 16. Thereby, since the sample stage 16 can be moved in the direction of the arrow in the figure, the area irradiated with the laser light can be moved.

<Combination of capping method>
When irradiating with laser light, a capping method may be used in combination.
When the capping method is used in combination, the cap layer 90 for preventing the reflection of the first laser beam or the second laser beam is formed on the semiconductor film 5 after performing the above-described thin film stacking step. FIG. 4 shows a cross-sectional view in which a cap layer 90 is formed in the semiconductor device of the present invention. Here, the material and film thickness of the cap layer 90 are changed according to the material of the semiconductor film, the film thickness of the semiconductor film, the type of the laser beam, etc. so as to have an antireflection effect with respect to the wavelength of the laser beam. For example, when an excimer laser oscillator with a wavelength of 308 nm is used as the laser oscillator and an amorphous silicon film with a thickness of 50 nm is used as the semiconductor film, the cap layer 90 is laminated by vapor deposition, ion plating, sputtering, or the like. Silicon oxide with a thickness of 50 nm can be used.

FIG. 7 is a graph showing a change in the reflectivity of the excimer laser with respect to the film thickness of the cap layer (silicon dioxide film) formed on the silicon film having a thickness of 50 nm in the semiconductor device having the cap layer according to the present invention.
According to this graph, the reflectivity periodically changes as the film thickness increases, but the antireflection effect is achieved as compared with the case where the cap layer is not formed regardless of the film thickness of the cap layer.
However, in order to obtain an optimal antireflection effect, the thickness of the cap layer is preferably set to a thickness (50 nm, 150 nm, 250 nm, etc.) that minimizes the reflectance.
The cap layer 90 is selectively formed at a position where a TFT is formed.

<Laser light irradiation method>
FIG. 6 shows a graph for explaining an example of the relationship between the irradiation time t of the first laser beam 80 and the second laser beam 81 and the output (energy amount) of the present invention. However, the relationship as shown in FIG. 6 is not limited.
In FIG. 6, a pulse waveform 91 indicates an output waveform of the first laser beam, and indicates that irradiation of the first laser beam is started at time t = 0. The pulse waveform 92 shows the output waveform of the second laser beam, which is emitted at a relatively low output during the time except time t = t1 to t2, and is emitted at a relatively high output at time t = t1 to t2. Which indicates that. Note that the semiconductor film 5 is in a solid state at time t0, but the semiconductor film 5 is in a molten state at time t1.
By irradiating the semiconductor film 5 in the molten state with the second laser light in addition to the first laser light at the time t1, the temperature decrease rate of the semiconductor film 5 is decreased and solidified. Extend time. Accordingly, since the time until solidification is extended, the lateral growth distance of the semiconductor polycrystal produced by the solidification of the semiconductor film 5 in the molten state can be greatly extended.

[Embodiment 1]
The first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, FIG. 8, and FIG.
A semiconductor device 1 according to Embodiment 1 of the present invention has a layer configuration as shown in FIG. 1 and is configured by laminating an aluminum nitride film 3, a silicon dioxide film 4, and a silicon film 5 in this order on a transparent substrate 2. Is done. Here, the first embodiment is characterized in that aluminum nitride having a significantly different thermal conductivity than that of the silicon film 5 and the transparent substrate 2 is used as the first base film 3. As an example of the first embodiment, the aluminum nitride film 3 has a thickness of 100 nm, the silicon dioxide film 4 has a thickness of 20 nm, and the silicon film 5 has a thickness of 50 nm.

  As described above, the aluminum nitride film 3 is laminated on the transparent substrate 2 by vapor deposition, ion plating, sputtering, or the like. The silicon dioxide film 4 is laminated on the aluminum nitride film 3 by vapor deposition, ion plating, sputtering, or the like. The silicon film 5 as a semiconductor film is laminated on the aluminum nitride film 3 by plasma enhanced chemical vapor deposition (PECVD), vapor deposition, sputtering, or the like. In this case, in the stacked state, the silicon film 5 is in an amorphous state.

  Next, at room temperature, the surface of the silicon film 5 is irradiated with the short pulse laser 80 in the F direction in the drawing. The amorphous silicon film 5 is once melted by the energy of the short pulse laser 80. Thereafter, the melted silicon film 5 is crystallized by cooling. In the first embodiment, an excimer laser having a wavelength of 308 nm (XeCl) and a pulse width of 30 ns is used as the short pulse laser 80.

In order to compare the silicon film 5 crystallized by the process of the first embodiment and the silicon film crystallized by the conventional process, the crystal surface was observed by SEM (Scanning Electron Microscope). For the semiconductor device 1 of the first embodiment and the conventional semiconductor device, the silicon film is crystallized by one laser irradiation, SECCO etching is performed, and the silicon film after the processing is enlarged by SEM. The observation results are shown in FIG.
FIG. 2A is a film surface image obtained by photographing the film surface of the silicon film 5 crystallized by the process of the first embodiment by SEM, and FIG. 2B is a diagram of the silicon film crystallized by the conventional process. It is the film | membrane surface image which image | photographed the film | membrane surface by SEM. The difference between the first embodiment and the conventional process is that, in the first embodiment, aluminum nitride is used as the first base film 3 between the substrate 2 and the base film 4 in the conventional process. This is the point.

Comparing FIG. 2 (a) and FIG. 2 (b), the crystal growth length 18 of the grown crystal is larger in the process according to the first embodiment (FIG. 2 (a)) than in the conventional process. You can see that it ’s big. This difference is thought to be due to the following principle.
The conventional process has a structure in which a silicon dioxide film 104 is formed on a substrate 102 and a semiconductor film 5 is formed on the silicon dioxide film 104, and heat conduction of silicon dioxide as the base film 4 is performed. The rate is as low as about 1.4 (W / mK) as shown in FIG. Therefore, the thermal energy generated in the amorphous silicon film 5 by the laser irradiation is not easily diffused in the lateral direction, and therefore, due to the latent heat released when the melted portion solidifies in the cooling process after the laser irradiation, In the vicinity of the interface between the solidified region and the solidified region, there is a region in which the temperature locally increases. On the other hand, there is a problem that almost no thermal gradient is formed in the center of the molten region because thermal energy is difficult to diffuse laterally.

  For this reason, in the conventional process, the region below the solidification temperature gradually solidifies from the interface between the unmelted region and the molten region to the center of the molten region in the cooling process after laser irradiation. In addition, there was a region where solidification occurred below the solidification temperature at the center of the melting region. Therefore, in the center of the melting region, a wide range of the melting region falls below the solidification temperature almost simultaneously, so that the growth of the generated crystal nuclei is inhibited by the separately generated crystal nuclei, and the crystal grain size is very small. This was the cause of the generation of a large amount of microcrystals. As a result, in the conventional process, a crystal that grows laterally from the interface between the unmelted region and the molten region when a single pulse irradiation is performed grows by the microcrystal generated in the center of the molten region. It was obstructed and I could not grow so much.

  On the other hand, in the first embodiment of the present invention, the aluminum nitride film 3 is formed on the substrate 2, the silicon dioxide film 4 is formed on the aluminum nitride film 3, and the semiconductor film 5 is formed on the silicon dioxide film. It has a formed structure. Further, the thermal conductivity of aluminum nitride as the first base film 3 is about 35 (W / mK) as shown in FIG. 8, and the thermal conductivity of the transparent substrate (glass) 2 is as shown in FIG. It is about 0.8 (W / mK). Therefore, since the thermal conductivity of aluminum nitride as the first base film 3 is significantly higher than that of the transparent substrate 2 and the silicon dioxide film 4, the thermal energy generated by the laser irradiation passes through the silicon dioxide film 4. After reaching the aluminum nitride film 3, the inside of the aluminum nitride film 3 is quickly diffused in the lateral direction.

That is, in the semiconductor film 5 on the silicon dioxide film 4 in contact with the aluminum nitride film 3 in the cooling process after laser irradiation, the latent heat released when the melted portion solidifies is diffused in the lateral direction. There is no region in which the temperature locally increases near the interface with the solidified region, and the temperature gradient gradually decreases from the center of the molten region to the interface between the unmelted region and the molten region. For this reason, generation | occurrence | production of the microcrystal in the fusion | melting area | region center at the time of performing pulse irradiation once can be suppressed. Therefore, crystals that grow laterally from the interface between the unmelted region and the molten region during the solidification process of the molten region are suppressed by the microcrystals generated in the conventional process at the center of the molten region. There is nothing. As a result, the crystal that grows laterally from the interface between the unmelted region and the molten region becomes very large, and the crystal that grows when performing one pulse irradiation in this way becomes large. A polycrystalline silicon film can be obtained efficiently.
For example, when a laser having a slit width of 4 μm is irradiated, when the crystal is grown in the conventional structure 1, the crystal growth length is about 1 to 1.2 μm at most, but the structure of the present invention is adopted. As a result, the crystal growth length can be set to 2 μm or more.

  FIG. 9 shows the measurement result of the crystal growth length 18 when a sample having various thicknesses of the aluminum nitride film 3 is irradiated with a laser having a slit width of 4 μm. “◯” is written in the case where the crystal growth length 18 grows as large as 2 μm or more. According to FIG. 9, it can be seen that when the thickness of the aluminum nitride film 3 is 10 to 150 nm, the crystal grows greatly.

As described above, in the structure according to the first embodiment of the present invention, the lateral diffusion of the thermal energy generated by the irradiation with the laser beam 8 is promoted, so that the polycrystalline silicon film (semiconductor film 5) having a larger grain size Can be obtained.
With respect to the semiconductor device of Embodiment 1, a transistor can be formed by an existing method and can be used as a display element such as a liquid crystal panel. In addition, since the semiconductor device of the present invention has a crystal grain that is much larger than before, an element with high mobility of carriers flowing through the channel of the transistor can be obtained.

[Embodiment 2]
As another embodiment of the present invention, a description will be given of a case where “aluminum nitride” used as the first base film 3 in Embodiment 1 is changed to “silicon nitride”.
The semiconductor device 1 according to the second embodiment is configured by laminating a silicon nitride film 3, a silicon dioxide film 4, and a silicon film 5 in this order on a transparent substrate 2. Here, in the second embodiment, the thickness of the silicon nitride film 3 used as the first base film 3 is about 100 nm. The film thicknesses of the other films (4, 5) are the same as those in the first embodiment.

The silicon nitride film 3 is laminated on the transparent substrate 2 by vapor deposition, ion plating, sputtering, or the like. Other films may be formed by a method similar to that in Embodiment Mode 1.
Also in the second embodiment, the surface of the silicon film 5 is irradiated with a short pulse laser in the direction F in the drawing at room temperature. Also in the second embodiment, an excimer laser having a wavelength of 308 nm (XeCl) and a pulse width of 30 ns may be used as the short pulse laser.
The result of magnifying observation by SEM is the same as that of FIG. 2A shown in the first embodiment described above, and the process according to the second embodiment grows larger crystals than the conventional process. Understand.

In Embodiment 2 of the present invention, the thermal conductivity of silicon nitride as the first base film 3 is about 10 (W / mK) as shown in FIG. 8, and the thermal conductivity of the transparent substrate (glass) 2 is as follows. The rate is about 0.8 (W / mK) as shown in FIG. Therefore, since the thermal conductivity of silicon nitride as the first base film 3 is significantly higher than that of the transparent substrate 2, the thermal energy generated by the laser irradiation passes through the silicon dioxide film 4 and passes through the silicon nitride film 3. This is because the silicon nitride film 3 is quickly diffused in the lateral direction after reaching the above.
When a laser having a slit width of 4 μm is irradiated, the crystal growth length 18 of the semiconductor film 5 can be set to 2 μm or more by adopting the structure of the second embodiment.
Similarly to the aluminum nitride film, when the thickness of the silicon nitride film 3 is 10 to 150 nm, the crystal growth length 18 grows greatly.
As described above, also in the structure of the second embodiment of the present invention, the lateral diffusion of the thermal energy generated by the irradiation with the laser beam 8 is promoted, so that the polycrystalline silicon film (semiconductor film 5) having a larger grain size is further obtained. Can be obtained.

  Furthermore, the silicon nitride, silicon dioxide film 4, and silicon film 5 as the first base film 3 can all be formed by CVD. Further, when silicon nitride is used as the first base film 3, silicon nitride can be formed by reactive sputtering using the same silicon target, and amorphous silicon can be formed by normal sputtering. Therefore, when silicon nitride is used as the first base film 3 without using aluminum nitride, the thermal conductivity of the first base film 3 is reduced, but the manufacturing process can be simplified.

[Embodiment 3]
Instead of “aluminum nitride” used as the first base film 3 in the first embodiment, “a mixture of aluminum nitride and silicon nitride” may be used. Also in this case, a polycrystalline silicon film having a large grain size can be obtained as in the second and third embodiments.

A semiconductor device 1 according to Embodiment 3 of the present invention is configured by laminating a mixture 3 of aluminum nitride and silicon nitride, a silicon dioxide film 4 and a silicon film 5 in this order on a transparent substrate 2. Here, in Embodiment 3, the film thickness of the mixture 3 of aluminum nitride and silicon nitride used as the first base film 3 is about 100 nm.
The mixture 3 of aluminum nitride and silicon nitride is laminated on the transparent substrate 2 by vapor deposition, ion plating, sputtering, or the like. Other manufacturing processes may use the same method as in the first embodiment.

  Since the silicon film after the treatment is enlarged and observed by SEM, the surface image shown in FIG. 2A is obtained as in the first and second embodiments. It can also be seen that the process according to the third embodiment grows larger crystals.

  The third embodiment of the present invention is characterized in that a mixture 3 of aluminum nitride and silicon nitride is formed on the substrate 2, but a mixture of aluminum nitride and silicon nitride as the first underlayer 3 is used. The thermal conductivity of the transparent substrate 2 is about 20 (W / mK) as shown in FIG. 8, and the thermal conductivity of the transparent substrate 2 is about 0.8 (W / mK) as shown in FIG. Therefore, since the thermal conductivity of the mixture of aluminum nitride and silicon nitride as the first base film 3 is significantly higher than that of the transparent substrate 2, the thermal energy generated by the laser irradiation passes through the silicon dioxide film 4. This is because, after reaching the mixture 3 of aluminum nitride and silicon nitride, the inside of the mixture 3 of aluminum nitride and silicon nitride quickly diffuses in the lateral direction.

Therefore, for example, when a laser having a slit width of 4 μm is irradiated, the crystal growth length 18 of the semiconductor film 5 can be set to 2 μm or more by employing the structure of the present invention.
When the thickness of the mixture 3 of aluminum nitride and silicon nitride is 10 to 150 nm, the crystal growth length 18 grows greatly.
As described above, also in the structure of the third embodiment of the present invention, the lateral diffusion of the thermal energy generated by the irradiation of the laser 8 is promoted, so that a polycrystalline silicon film (semiconductor film 5) having a large grain size is obtained. be able to.
In the third embodiment, the thermal conductivity of the mixture of aluminum nitride and silicon nitride is set to about 20 (W / mK) as described above. However, the heat conductivity depends on the composition ratio of aluminum nitride and silicon nitride. It is possible to design the conductivity freely.

[Embodiment 4]
Instead of “aluminum nitride” used as the first base film 3 in the first embodiment, “magnesium oxide” may be used. Also in this case, a polycrystalline silicon film having a large grain size can be obtained as in the above-described embodiment.

A semiconductor device 1 according to Embodiment 4 of the present invention is configured by laminating a magnesium oxide film 3, a silicon dioxide film 4, and a silicon film 5 in this order on a transparent substrate 2. Here, in the fourth embodiment, the thickness of the magnesium oxide film 3 used as the first base film 3 is about 100 nm.
The magnesium oxide film 3 is laminated on the transparent substrate 2 by vapor deposition, ion plating, sputtering, or the like. Other manufacturing processes may use the same method as in the first embodiment.

As a result of magnifying and observing the silicon film processed in this way by SEM, the surface image shown in FIG. 2A is obtained as in the first to third embodiments. It can also be seen that the process according to the fourth embodiment grows larger crystals.
The fourth embodiment of the present invention is characterized in that the magnesium oxide film 3 is formed on the substrate 2, but the thermal conductivity of magnesium oxide as the first underlayer 3 is as shown in FIG. The thermal conductivity of the transparent substrate (glass) 2 is about 0.8 (W / mK) as shown in FIG. Therefore, since the thermal conductivity of magnesium oxide as the first base film 3 is significantly higher than that of the transparent substrate 2, the thermal energy generated by the laser irradiation passes through the silicon dioxide film and enters the magnesium oxide film 3. This is because, after reaching, the inside of the magnesium oxide film 3 is quickly diffused in the lateral direction.

Therefore, for example, when a laser having a slit width of 4 μm is irradiated, the crystal growth length 18 of the semiconductor film 5 can be set to 2 μm or more by employing the structure of the present invention.
Further, when the thickness of the magnesium oxide film 3 is 10 to 150 nm, the crystal growth length 18 is large and the crystal grows.
As described above, also in the structure of the fourth embodiment of the present invention, the lateral diffusion of the thermal energy generated by the irradiation with the laser beam 8 is promoted. Can be obtained.

[Embodiment 5]
“Cerium oxide” may be used instead of “aluminum nitride” used as the first base film 3 in the first embodiment. Also in this case, a polycrystalline silicon film having a large grain size can be obtained as in the above embodiment.

A semiconductor device 1 according to Embodiment 5 of the present invention is configured by laminating a cerium oxide film 3, a silicon dioxide film 4, and a silicon film 5 in this order on a transparent substrate 2. Here, in the fifth embodiment, the film thickness of the cerium oxide film 3 used as the first base film 3 is set to about 100 nm.
The cerium oxide film 3 is laminated on the transparent substrate 2 by vapor deposition, ion plating, sputtering, or the like. Other manufacturing processes may use the same method as in the first embodiment.

  The silicon film after the processing is enlarged and observed by SEM, and the surface image shown in FIG. 2A is obtained as in the first to fourth embodiments. It can also be seen that the process according to the fifth embodiment grows larger crystals.

  The fifth embodiment of the present invention is characterized in that the cerium oxide film 3 is formed on the substrate 2, and the thermal conductivity of cerium oxide as the first base film 3 is shown in FIG. In addition, the thermal conductivity of the transparent substrate (glass) 2 is about 0.8 (W / mK) as shown in FIG. Therefore, since the thermal conductivity of cerium oxide as the first base film 3 is significantly higher than that of the transparent substrate 2, the thermal energy generated by the laser irradiation passes through the silicon dioxide film 4 to the cerium oxide film 3. This is because, after reaching, the inside of the cerium oxide film 3 is quickly diffused in the lateral direction.

Therefore, for example, when a laser having a slit width of 4 μm is irradiated, the crystal growth length 18 of the semiconductor film 5 can be set to 2 μm or more by adopting the structure of the present invention.
Further, when the thickness of the cerium oxide film 3 is 10 to 150 nm, the crystal growth length 18 grows greatly.
As described above, also in the structure of the fifth embodiment of the present invention, the lateral diffusion of the thermal energy generated by the irradiation of the laser beam 8 is promoted. Can be obtained.

[Embodiment 6]
As described above, the laser processing apparatus shown in FIG. 3 is used for manufacturing the semiconductor device of the present invention, but the controller 17 using a microcomputer or the like is provided.
As described above, the controller 17 controls the first laser oscillator 93 and the sample stage 16 to adjust the laser irradiation timing and the position of the sample stage 16. Thereby, since the sample stage 16 can be moved in the direction of the arrow in the figure, the area irradiated with the laser light can be moved.
Therefore, by using the control by the controller, a crystal lateral growth method as shown in FIG. 12 which has been conventionally used can be used as a procedure for growing a crystal. According to this method, the crystal in the semiconductor film 5 can be grown in the extending direction by one laser irradiation. Further, each time laser irradiation is performed, the crystal region can be expanded stepwise by moving the irradiation area stepwise (step movement). Thereby, the growth direction of each crystal in the semiconductor device having a polycrystalline structure can be aligned with the extending direction.

  Further, in the configuration of the semiconductor device 1 according to the embodiment as described above, the lateral diffusion of the thermal energy generated by the irradiation of the laser beam 8 can be promoted, so that each crystal constituting the polycrystalline structure is Can be bigger. That is, if the crystal lateral growth method is applied to the semiconductor device 1 of the present invention, the crystal that can be grown per laser irradiation can be made larger than before, so the sample stage 16 is moved. By controlling the direction in which the crystal grows, it is possible to grow a larger crystal and align the growth direction.

[Embodiment 7]
Here, a semiconductor device having a configuration including the cap layer 90 described above will be described.
FIG. 4 shows a semiconductor device 1 having a cap layer 90. The semiconductor device 1 is laminated on a transparent substrate 2 in the order of an aluminum nitride film 3, a silicon dioxide film 4, a silicon film 5, and a cap film 90. Configured. In the seventh embodiment, similarly to the first embodiment, the aluminum nitride film 3 has a thickness of 100 nm, the silicon dioxide film 4 has a thickness of 20 nm, the silicon film 5 has a thickness of 50 nm, and the cap film 90 has a film thickness. The thickness is about 50 nm.

The aluminum nitride film 3, the silicon dioxide film 4, and the silicon film 5 are formed by the same method as in the above embodiment, and silicon oxide is formed on the silicon film 5 by vapor deposition, ion plating, sputtering, or the like. The cap layer 90 is stacked with a film thickness of 50 nm.
Next, at room temperature, the surface of the semiconductor device 1 is irradiated with laser light 8, which is a short pulse laser, in the F direction in the drawing. For example, an excimer laser having a wavelength of 308 nm (XeCl) and a pulse width of 30 ns may be used as the short pulse laser.

Here, when laser irradiation is performed on the silicon film 5 through the cap layer 90, the reflectance changes depending on the type of laser, the type of cap layer, the film thickness of the silicon film, and the like. As can be seen from the change in the reflectance of the excimer laser with respect to the thickness of the cap layer 90 shown in FIG. 7, when the thickness of the cap layer 90 is 50 nm, the reflectance with respect to the laser beam is minimized.
As a result, by irradiating the laser beam 8, the semiconductor film under the cap layer 90 is selectively heated and melted, and the amorphous silicon film 5 under the cap layer 90 is once melted. Thereafter, the melted silicon film 5 is crystallized by cooling.

  The semiconductor device according to the seventh embodiment of the present invention thus formed can also promote the lateral diffusion of the thermal energy generated by the irradiation with the laser light 8 as in the above-described embodiment. Therefore, a polycrystalline silicon film (semiconductor film 5) having a larger grain size can be obtained.

[Embodiment 8]
In the above embodiment, the laser beam is irradiated from the direction perpendicular to the surface of the semiconductor device (direction F in FIG. 1) as shown in FIG. That is, in FIG. 3, only the laser beam 80 emitted from the first laser oscillator 93 is used. Here, a method for crystallizing the semiconductor film 5 using the two laser beams (80, 81) as described above in order to form a silicon film having a larger particle diameter will be described.
As the semiconductor device 1, for example, the device having the structure shown in the first embodiment may be used, and the same process may be used for the stacking process.

In this embodiment, the apparatus shown in FIG. 3 irradiates the surface of the silicon film 5 with the first laser beam 80 and the second laser beam 81 in the direction F in the drawing at room temperature.
Here, the second laser beam may be incident from an oblique direction as shown in FIGS. 3 and 5 instead of the F direction perpendicular to the surface. For example, it may be incident on the device surface at an angle of about 45 degrees.
Moreover, what was mentioned above should just be used about the wavelength of the 1st laser beam and the 2nd laser beam, energy amount, irradiation timing, irradiation region, etc.
In this way, if the semiconductor film is crystallized using two laser beams (80, 81), a polycrystalline silicon film having a large grain size as shown in FIG. 2A can be formed.

In the eighth embodiment, the second laser beam 81 is irradiated while the silicon film 5 is melted.
In this way, by irradiating the silicon film in the liquid state with the second laser light in addition to the first laser light, the temperature decrease rate of the silicon film can be reduced until the silicon film is solidified. Therefore, it is possible to efficiently obtain a polycrystalline silicon film having a larger grain size.

For example, when a laser having a slit width of 4 μm is irradiated, when the crystal is grown on the conventional structure 1, the crystal growth length is about 1 to 1.2 μm at most, but the structure of the present invention is adopted. As a result, the crystal growth length can be set to 2 μm or more.
According to the eighth embodiment of the present invention, the lateral diffusion of the thermal energy generated by the irradiation of the two types of lasers 8 is promoted, so that a polycrystalline silicon film (semiconductor film 5) having a larger grain size can be formed. Can be obtained.

[Embodiment 9]
The semiconductor device 1 of the present invention shown in FIG. 4 may be irradiated with two types of laser beams (80, 81).
In this case, using the apparatus as shown in FIG. 3, the first laser beam 80 is irradiated in the direction F of FIG. 1 at room temperature, and the second laser beam 81 as shown in FIG. The surface of the semiconductor device 1 is irradiated from the direction.
What is necessary is just to use what was mentioned above about the wavelength of the 1st laser beam and the 2nd laser beam, the amount of energy, irradiation timing, irradiation region, etc.
Here, when laser irradiation is performed on the silicon film 5 through the cap layer 90, the reflectance changes depending on the type of laser, the type of cap layer, the film thickness of the silicon film, and the like. As can be seen from the graph of FIG. 7, when the film thickness of the cap layer 90 is 50 nm, the reflectance with respect to the laser beam is minimized. As a result, by irradiating the laser beam 8, the semiconductor film under the cap layer 90 is selectively heated and melted, and the amorphous silicon film 5 under the cap layer 90 is once melted. Thereafter, the melted silicon film 5 is crystallized by cooling.

Also in the ninth embodiment, the second laser beam 81 is irradiated while the silicon film 5 is melted.
In this way, by irradiating the silicon film in the liquid state with the second laser light in addition to the first laser light, the temperature decrease rate of the silicon film can be reduced until the silicon film is solidified. Therefore, it is possible to efficiently obtain a polycrystalline silicon film having a larger grain size.

According to the ninth embodiment of the present invention, the lateral diffusion of the thermal energy generated by the two types of laser irradiation is promoted, so that a polycrystalline silicon film (semiconductor film 5) having a larger grain size is obtained. be able to.
As described above, the semiconductor device of the present invention in which a semiconductor film having a large particle diameter is formed on the surface can be used as a basic structure of a transistor, for example, and can also be used as a display element such as a liquid crystal panel.
In the transistor using the semiconductor device of the present invention, since the crystal grain of the semiconductor film is larger than that of a conventional transistor, an element with high mobility of carriers flowing through the channel of the transistor can be formed.

(The invention's effect)
According to the present invention, in the semiconductor film on the second base film in contact with the first base film in the cooling process after laser irradiation, the latent heat released when the melted portion solidifies is diffused in the lateral direction. Therefore, there is no region where the temperature locally increases in the vicinity of the interface between the melted region and the solidified region, and the temperature gradient gradually decreases from the center of the melted region to the interface between the unmelted region and the melted region. Become. For this reason, generation | occurrence | production of the microcrystal in the fusion | melting area | region center at the time of performing pulse irradiation once can be suppressed.
Therefore, crystals that grow laterally from the interface between the unmelted region and the molten region during the solidification process of the molten region are suppressed by the microcrystals generated in the conventional process at the center of the molten region. There is nothing. As a result, the crystals that grow laterally from the interface between the unmelted region and the molten region become very large, and the crystals that grow when a single pulse irradiation is performed become large. A semiconductor film can be obtained efficiently.

It is sectional drawing of the semiconductor device of this invention. (A) is the figure which showed the film | membrane surface image which image | photographed the crystallized semiconductor film in the semiconductor device of this invention by SEM, (b) is the SEM in the conventional semiconductor device. It is the figure which showed the film | membrane surface image image | photographed in FIG. It is a schematic block diagram of the laser processing apparatus used for formation of the semiconductor device of this invention. It is a side view of the semiconductor device of Embodiment 7 of this invention. It is explanatory drawing of one Example of the irradiation area | region of the 1st laser beam in this invention, and the irradiation area | region of a 2nd laser beam. It is a graph explaining the relationship between the irradiation time of a 1st laser beam and a 2nd laser beam, and an output in this Embodiment. It is a graph which shows the change of the reflectance of an excimer laser with respect to the film thickness of the cap layer which consists of a silicon dioxide film formed on 50-nm-thick silicon. It is explanatory drawing which showed the heat conductivity of various materials. It is a figure which shows the quality of the crystal growth length at the time of changing the film thickness of a 1st base film. It is a schematic block diagram of the laser processing apparatus used conventionally. It is a schematic sectional drawing of the conventional semiconductor device. It is a top view of the semiconductor device for demonstrating the procedure to grow a crystal | crystallization on the film | membrane surface by the conventional lateral direction crystal growth method.

Explanation of symbols

1 Semiconductor device 2 Transparent substrate (substrate)
3 First base film 4 Second base film 5 Silicon film (semiconductor film)
11 Laser oscillator 12 Variable attenuator 13 Field lens 14 Projection mask 15 Imaging lens 16 Sample stage 17 Controller 18 Crystal growth length 7a First laser light irradiation area 7b Second laser light irradiation area 80 First laser Light 81 Second laser light 90 Cap layer 91 Pulse waveform 92 of the first laser light Pulse waveform 93 of the second laser light 93 First laser oscillator 94 Second laser oscillator

Claims (13)

  A semiconductor device in which a first base film, a second base film, and a semiconductor film are stacked in this order on a substrate, wherein the first base film is more thermally conductive than the substrate and the second base film. A semiconductor device characterized by a high rate.   The semiconductor film is an amorphous, microcrystalline or polycrystalline silicon-based semiconductor film once formed by a conventional method, and when the semiconductor film is further subjected to heat treatment by laser light irradiation, the first film The semiconductor device according to claim 1, wherein the base film plays a role of promoting crystal growth of the semiconductor film.   The first base film promotes crystal growth of the semiconductor film by diffusing heat of laser light irradiated from above the semiconductor film in an in-plane direction of the first base film. The semiconductor device according to claim 1.   The first base film is mainly composed of any one of aluminum nitride, magnesium oxide, cerium oxide, silicon nitride, or a mixture of aluminum nitride and silicon nitride. Semiconductor devices.   The first base film is a film mainly containing any one of aluminum nitride, magnesium oxide, cerium oxide, silicon nitride, or a mixture of aluminum nitride and silicon nitride, and the substrate and the second base film The semiconductor device according to claim 1, wherein the semiconductor device is made of an insulating material.   6. The semiconductor device according to claim 1, wherein the second base film contains silicon oxide as a main component.   7. The semiconductor according to claim 1, wherein the semiconductor film is crystallized and crystal-grown in an in-plane direction in a region melted by a laser beam irradiated from above the semiconductor film. device.   8. The semiconductor device according to claim 7, wherein the crystallized region of the semiconductor film is enlarged by moving the region melted by the laser light irradiation stepwise in an in-plane direction. .   From the first laser beam having an energy amount capable of melting the semiconductor film in a solid state and the second laser beam having an energy amount not to melt the semiconductor film in a solid state. The semiconductor device according to claim 7 or 8, wherein: A method of manufacturing a semiconductor device in which a first base film, a second base film, and a semiconductor film are laminated in this order on a substrate,
On the substrate, a step of laminating a first base film having a higher thermal conductivity than the substrate and the second base film, a step of laminating a second base film on the first base film, A step of laminating an amorphous, microcrystalline, or polycrystalline semiconductor film on the second base film, and irradiating the semiconductor film with laser light to melt the semiconductor film in the irradiated region after crystallization. And further growing the crystal in the in-plane direction.   A method of manufacturing a semiconductor device in which a first base film, a second base film, and a semiconductor film are stacked in this order on a substrate, wherein the substrate has a thermal conductivity higher than that of the substrate and the second base film. A step of laminating a high first underlayer; a step of laminating a second underlayer on the first underlayer; and an amorphous, microcrystalline, or A step of laminating a polycrystalline semiconductor film and irradiating the semiconductor film with laser light to melt and crystallize the semiconductor film in the irradiated region, and further step the laser light irradiated region in the in-plane direction of the semiconductor film And a step of expanding the crystallization region by mechanically moving the semiconductor device.   A method of manufacturing a semiconductor device in which a first base film, a second base film, and a semiconductor film are stacked in this order on a substrate, wherein the substrate has a thermal conductivity higher than that of the substrate and the second base film. A step of laminating a high first underlayer; a step of laminating a second underlayer on the first underlayer; and an amorphous, microcrystalline, or A step of laminating a polycrystalline semiconductor film and irradiating the semiconductor film with a first laser beam having an energy amount capable of melting the semiconductor film in a solid state, thereby bringing the semiconductor film into a liquid state And crystallization of the liquid semiconductor film by irradiating the semiconductor film with a second laser light having an energy amount that does not melt the semiconductor film in the solid state. A method for manufacturing a semiconductor device.   A step of forming a cap layer for preventing reflection of the first laser light on the surface of the semiconductor film before irradiating the laser light after laminating the semiconductor films. Item 13. A method for producing a semiconductor device according to any one of Items 11 and 12.

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