JP2001210591A - Laser irradiation apparatus and laser irradiation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser irradiation technique, which enables a polycrystalline semiconductor film having uniformly distributed and well- arranged particles of a large size to be formed accurately at a target place. SOLUTION: A laser beam comprises a first region, having energy density fewer than Eu which is microcrystallization energy of an amorphous semiconductor thin film, and the second region with an energy density of Eu or higher located at both sides of the first region, arranged along one direction in the irradiation region of a laser beam. The first region is set as a valley shape, for example, and the width is set at 3 μm or less, preferably less than 1.8 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser irradiation method for irradiating a non-single-crystal semiconductor thin film with a pulse laser beam for annealing, and more particularly to a channel layer of a polycrystalline silicon thin film transistor used for a liquid crystal display, a contact type image sensor and the like. And a laser irradiation method for forming the same.

[0002]

2. Description of the Related Art In recent years, it has become possible to form a liquid crystal display device having a drive circuit on an inexpensive glass substrate by using a polycrystalline silicon thin film transistor. As a method of forming a polycrystalline silicon thin film, an excimer laser crystal is used to crystallize an amorphous silicon thin film by irradiating excimer laser light to obtain a polycrystalline silicon thin film from the viewpoint of lowering a process temperature and increasing throughput. The chemical method is widely used.

However, the excimer laser crystallization method has a problem that the heat treatment of the thin film is limited because the laser light is a pulsed laser light, and the size of crystal grains obtained is limited. Therefore, using the obtained polycrystalline silicon thin film, a thin film transistor (TF
When a thin film transistor (T: Thin Film Transistor) is manufactured, the mobility is limited to about 100 cm ² / Vs, and it is difficult to form a high mobility element as desired at present.

Therefore, various studies have been made on a technique for increasing the grain size of a polycrystalline silicon thin film.

Japanese Patent Application Laid-Open No. 9-246183 discloses a method of irradiating a laser beam having a trapezoidal beam profile in the line width direction. In this method, a laser having a trapezoidal beam profile is irradiated to obtain a polycrystalline structure. Since the energy density at the center of the trapezoidal beam profile is equal to or higher than the microcrystallization threshold of the amorphous semiconductor (amorphous silicon), the energy of the energy slightly lower than the microcrystallization threshold at the slope of the trapezoidal profile is increased. There will be parts. It is stated that a polycrystalline semiconductor region having a large crystal grain diameter can be obtained in this region. However, in this method, although it is possible to obtain a polycrystalline semiconductor region having a large crystal grain diameter at a portion of energy slightly lower than the microcrystallization threshold, the arrangement of the large-diameter particles is disordered, and the particle size distribution is large. Are also generally wider. Therefore, when such a polycrystalline semiconductor region is used, for example, as a channel layer of a TFT, variations in TFT characteristics such as mobility are caused.

Also, Japanese Laid-Open Patent Publication No. 10-275781 and the 42nd Preliminary Lecture Meeting on Applied Physics, No. 2
A separate volume of page 694 discloses a technique for synthesizing a plurality of laser pulses and performing laser irradiation. However, even when these methods are used, although it is possible to increase the crystal grain size, it is difficult to make the arrangement and the grain size distribution uniform.

On the other hand, MRS BullEtin Vol. 21 (1996), March, p. 39 states that an extremely fine linear beam having a width of 5 μm is formed on an island-shaped amorphous silicon thin film at a pitch of 0.75 μm. There is disclosed a technique of forming a unidirectionally grown polycrystalline silicon thin film in which crystal grain boundaries are aligned substantially parallel by scanning irradiation. With this method, the uniformity of the polycrystalline particles is ensured, but the throughput is reduced and the transfer system becomes complicated due to the necessity of ensuring the submicron stage operation accuracy.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and forms a large-diameter polycrystalline semiconductor film having a uniform particle size distribution and a good particle arrangement state. An object of the present invention is to provide a laser irradiation technique. Also,
An object of the present invention is to provide a laser irradiation technique for forming a polycrystalline semiconductor film at a target location with high positional accuracy.

[0009]

According to the present invention for solving the above problems, the following laser irradiation apparatus and laser irradiation method are provided. [1] A laser light source for generating laser light, and means for adjusting the energy distribution of the generated laser light are provided, and the laser light after adjusting the energy distribution is applied to the non-single-crystal semiconductor thin film to form a polycrystalline semiconductor thin film. a laser irradiation apparatus for forming, the energy density distribution along one direction in the irradiation region of the laser beam to be irradiated to the non-single-crystal semiconductor thin film, fine crystallization energy of the amorphous semiconductor thin film as E _u, has a first region below the energy density E _u, the energy density E _u or more second region located on both sides of the first region, the width of the first region is 3μm or less A laser irradiation device characterized by the above-mentioned. [2] The laser irradiation device according to [1], wherein the width of the first region is 1.8 μm or less. [3] The laser irradiation device according to [1] or [2], wherein the first region has a steep valley shape. [4] The means for adjusting the energy distribution of the laser light is
A mask made of a base material and a dielectric film covering a part of the base material, wherein an irradiation region of the laser light transmitted through the base material only and an irradiation region of the laser light transmitted through the base material and the dielectric film The laser irradiation device according to any one of [1] to [3], wherein the first region is generated near a boundary surface. [5] The same spot is irradiated with a first laser beam having the energy density distribution and a second laser beam having the energy density distribution and having an average energy density lower than that of the first laser beam in this order. The laser irradiation apparatus according to any one of [1] to [4], wherein the laser irradiation apparatus is adjusted to perform the following. [6] A laser irradiation method for irradiating a non-single-crystal semiconductor thin film with laser light to form a polycrystalline semiconductor thin film, wherein an energy density distribution in one direction in a light irradiation region of the laser light is amorphous. fine crystallization energy of the semiconductor thin film when the E _u, the first region is less than the energy density E _u,
A second region having an energy density of _Eu or higher located on both sides of the first region, wherein the width of the first region is 3 μm or less. [7] The laser irradiation apparatus according to [6], wherein the width of the first region is 1.8 μm or less. [8] The laser irradiation method according to [6] or [7], wherein the first region has a steep valley shape. [9] Laser light is transmitted through a mask made of a base material and a dielectric film covering a part of the base material, and a region irradiated with laser light transmitted only through the base material, and a laser beam transmitted through the base material and the dielectric film The laser irradiation method according to any one of [6] to [8], wherein the first region is generated in the vicinity of a boundary with the irradiation region. [10] The same point is irradiated with a first laser beam having the energy density distribution and a second laser beam having the energy density distribution and having an average energy density lower than the first laser beam in this order. The laser irradiation method according to any one of [6] to [9].

As described above, in the present invention, 3 μm
The first area having the following narrow width is the energy density E
The energy density distribution is in the form of being sandwiched between the second regions of _u or more. Therefore, in the first area, FIG.
As shown in FIG. 6 and FIG. 6, the polycrystalline particles can be formed neatly in one or two rows, and the polycrystalline particles can be formed at desired positions with high precision. This is because the starting point of nucleus growth occurs only in a limited narrow region, that is, the first region. In a narrow width of 3 μm or less, only one or two rows of growth nuclei of polycrystalline particles are generated. Therefore, as described above, the polycrystalline grains are formed in a state of being arranged in one or two rows.

In the present invention, the polycrystalline particles have a uniform particle size. In the present invention, since the energy density of the second region existing on both sides of the first region is _{equal to} or higher than _Eu , nuclear growth that proceeds from the first region toward the high energy region side is the second region. It stops at the microcrystal generated in the second region. For this reason, even if the nucleus growth rate varies among the individual polycrystalline particles, the particle size of the polycrystalline particles finally formed is substantially uniform.

According to the invention of the above [2] or [7],
The particle diameter of the polycrystalline particles can be significantly increased, and the arrangement of the polycrystalline particles can be further improved. This is because only one row of growth nuclei is generated in the first region, so that the growth of crystal grains proceeds in both directions.

According to the invention of the above [3] or [8],
Growth nuclei can be generated with high accuracy at the bottom of the valley shape, the arrangement of particles can be further improved, and the particle size can be sufficiently increased.

According to the invention of the above [4] or [9],
The specific energy density distribution defined in the above [1] and the like can be realized with high accuracy by a simple method, and advantages such as excellent productivity can be obtained.

Further, according to the inventions of the above [5] and [10], the melting time of the film can be lengthened, so that polycrystalline particles having a larger particle size can be obtained.

As described above, according to the present invention, a polycrystalline structure having a large grain size and excellent grain size uniformity can be formed with a high degree of positional accuracy in an orderly arrangement. By utilizing this polycrystalline structure, a thin film transistor having high mobility can be uniformly formed over a large-area substrate.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to irradiating a non-single-crystal semiconductor thin film with laser light, particularly pulsed laser light. In the present invention, it is preferable that the entire region where the polycrystalline particles are to be formed be irradiated with laser light at a time. That is, it is preferable that the irradiation region of the laser beam be made to coincide with the entire region where the polycrystalline particles are to be formed. Thereby, high productivity can be realized. In addition, a method in which laser light having a linear or rectangular irradiation area is used and irradiation is performed while scanning the laser light may be employed. For example, when using laser light in a linear irradiation area, the irradiation area is moved in the short axis direction, and laser irradiation is performed on the entire desired area. In addition,
The laser irradiation according to the present invention can be performed while heating the substrate.

In the present invention, a non-single-crystal semiconductor thin film refers to a semiconductor thin film that is not a single crystal, and refers to an amorphous thin film such as amorphous silicon or a polycrystalline thin film such as polycrystalline silicon. The particle diameter of the crystal particles constituting the polycrystalline semiconductor thin film in the present invention is preferably 0.5 μm or more, more preferably 1 μm or more. By forming a polycrystalline semiconductor thin film with such large-diameter particles, a highly efficient device can be obtained.

[0019] The amorphous fine crystallization energy E _u of the present invention will be described below. In laser annealing of amorphous silicon, the crystal grain size of the formed polycrystalline silicon depends on the laser energy density. It is known that as the energy density increases, the particle size increases, but when the energy density exceeds a certain specific value, the particle size becomes extremely fine as 20 nm or less. The energy density of the called amorphous micro-crystallization threshold, expressed as E _u. Microcrystallization is thought to occur when the nucleation mechanism during recrystallization changes from heterogeneous nucleation with nucleation sites at the substrate thin film interface to uniform nucleation due to changes in the melting state of the thin film. Have been. This change in the nucleation mechanism depends on the temperature reached and the cooling rate of the thin film. Accordingly, the microcrystallization threshold _Eu changes depending on the thickness of the thin film, the structure of the thin film, the wavelength of the pulsed laser light, the pulse width, and the like.
For example, E of a polycrystalline silicon thin film once laser-crystallized
_u is a large value of about 14% with respect to E _u of the amorphous silicon thin film. This is because the reflectivity of the film surface to the laser and the thermal properties are different.

[0020] If the laser beam profile that includes regions of less than the energy density E _u or more areas and E _u was irradiated to the non-single-crystal semiconductor thin film, the energy density is slightly lower region than E _u, the large particle size Polycrystalline particles are formed. FIG.
Shows an example. Such polycrystalline particles tend to grow mainly from the low energy side to the high energy side. Nucleation occurs earlier on the lower energy side.

FIG. 1 shows an example of an energy density distribution of a laser beam used in the present invention. This laser light is a laser having a rectangular irradiation area, and the energy density distribution in the figure shows a profile along the long side direction. The energy density distribution shown in the figure has a shape having a substantially flat region and a steep valley inside the flat region. That is, fine crystallization energy of the amorphous semiconductor thin film as E _u, the first region is less than the energy density E _u, a second region of higher energy density E _u located on both sides of the first region The profile has The first region has a steep valley shape, and its width (W ₁ ) is 1.8 μm or less. In this figure, the second region has a flat shape, but is not limited to this and may have any shape as long as the energy density is equal to or higher than _Eu .

The above energy distribution can be realized by using a mask made of a dielectric film covering the base material and a part thereof. By using such a mask, a second region is generated in the vicinity of the boundary surface with the region irradiated with the laser light transmitted through the base material and the dielectric film. FIG.
Shows an example of such a mask, and the quartz plate 2
01 is coated with a SiO ₂ film 202. SiN or the like can be used instead of SiO ₂ . This mask is a one-time inversion type phase shift mask. When a laser beam having a normal top flat profile passes through a phase shift mask, the SiO ₂ film 2
With 02, the phase is inverted and the profile has a steep valley shape. The valley shape can be any shape depending on the design of the optical system including the phase shift mask. For details of the above method using a phase shift mask, see SPIE vol.1463 Optical Laser Microli.
thography IV (1991) p74-86, p87-100.

FIG. 9 is a schematic view of a laser irradiation apparatus according to the present invention. The laser beam emitted from the laser light source 1 is
After passing through the optical system 2, the light passes through the mask 6 and is irradiated onto the substrate 5 held on the stage 4 in the chamber 3. The mask 6 has the structure shown in FIG. By transmitting the light through the mask having such a special structure, the laser light having a top flat type energy density distribution before the transmission through the mask causes a sharp valley as shown in FIG. It becomes a laser beam having an energy density distribution.

According to the study of the present inventors, the number of large-sized polycrystalline particles generated in the first region is determined by the width (W) of the first region.
₁ ) It has been confirmed that it depends. If the W ₁ and at least twice the width of the particle size of the polycrystalline particles, polycrystalline particles along each of the energy gradient is two or more (2 or more columns) occurs. On the other hand, when W ₁ is less than twice the particle size of the polycrystalline particles, particularly less than 1.2 times, specifically, less than 1.8 μm,
In particular, when the thickness is less than 1 μm, one polycrystalline particle (one row)
Only, and at the same time the particle size shows a remarkable expansion. This may be due, for W ₁ is narrowed, nucleation is in one place, and is considered a growth direction of particles is to proceed along the energy gradient of the both.

In the case of FIG. 1, since W ₁ is 1.8 μm or less, only one polycrystalline particle (one row) is formed, and polycrystalline particles having a large particle size and good uniformity in particle size have good order. It is formed. On the other hand, FIG. 6 shows an example in which W _{1 is set} to about 2.5 μm, and two rows of polycrystalline grains are formed one by one along each energy gradient. FIG. 10 shows an example in which W _{1 is set} to about 5 μm, and a plurality of rows of polycrystalline particles are formed along each energy gradient. In this case, the arrangement of the polycrystalline particles becomes disordered and the particle size becomes non-uniform as it approaches the high energy side.

From the above, in the present invention, W _{1 is set} to 3
μm or less. As a result, only one or two rows of growth nuclei of polycrystalline particles are generated in the first region, and a large-diameter polycrystalline particle having a uniform particle size distribution and a good particle arrangement state is obtained. It is formed with high accuracy at the position.

In the present invention, W ₁ is 1.8 μm or less,
In particular, when the thickness is 1 μm or less, the particle size of the polycrystalline particles can be significantly increased, and the arrangement of the polycrystalline particles can be further improved. This is considered to be due to the fact that the growth of crystal grains proceeds in both directions as described above. The growth of the polycrystalline grains proceeds from a low energy region to a high energy region. When two rows of growth nuclei are generated in the first region as shown in FIG. 6, growth of each row of growth nuclei is suppressed on the side adjacent to the other growth nucleus, and grows mainly on the high energy side. To go. On the other hand, when a row of growth nuclei is generated in the first region as shown in FIG. 1, the growth nuclei grow on both high energy sides. Therefore, it is considered that when one row of growth nuclei is generated in the first region, the nucleus growth is about twice as large as when the growth nuclei are generated in two rows, and the grain size is significantly increased. In addition, when a single row of growth nuclei is generated in the first region, the arrangement of the particles is less likely to be disrupted even after the nucleus growth. It will be even better.

[0028] Note that to actually generate a row of growing nuclei in the first region is preferably set to less 1.8μm to W _1, particularly when the W ₁ and 1μm or less, more reliably a row Growth nuclei can be generated.

In the present invention, the shape of the energy distribution in the first region can be various, but is preferably a valley shape as shown in FIG. With such a shape, a growth nucleus can be generated with high accuracy at the bottom of the valley shape, the particle arrangement can be further improved, and the particle size can be sufficiently increased.

In the present invention, a plurality of first regions can be provided according to the purpose. If you do this,
A single irradiation makes it possible to form a plurality of polycrystalline structures. Although only one valley-shaped first region is shown in FIG. 1 for the sake of convenience of description, in practice, two first regions may be provided as shown in FIG. 11, or three or more regions may be provided. According to the present invention, since a polycrystalline structure can be formed with high positional accuracy, a target polycrystalline film can be suitably produced by providing a plurality of first regions as described above.

Although the present invention defines the energy density distribution in one direction in the irradiation area, the energy density distribution in a direction orthogonal to the one direction can have any shape. . FIG. 12 is an example in which the energy density distribution in the orthogonal direction is not provided. The profile is the same at any position in the orthogonal direction. FIG. 13 shows an example in which valleys are provided in the orthogonal direction. The width of the valley in the orthogonal direction is appropriately set according to the area where the polycrystalline particles are formed.

In the present invention, the same spot may be irradiated a plurality of times with laser light having a predetermined profile. That is, the same spot may be irradiated a plurality of times with laser light having a predetermined energy density profile without shifting the irradiation position. In this case, the size of the polycrystalline particles can be further increased. As described above, the nucleus growth that progresses from the first region toward the high energy region side stops at the microcrystal generated in the second region. Therefore, if the generation time of the microcrystalline particles in the second region is delayed, the nucleus growth time starting from the first region is longer, and as a result, the particle size of the polycrystalline particles is larger. When irradiation is performed a plurality of times, the melting time of the film in the second region becomes longer, and the generation of microcrystalline particles is suppressed, so that the polycrystalline particles have a larger particle size for the above-described reason.

When irradiating the first and second laser beams in this order, the average energy density of the second laser beam is preferably lower than the average energy density of the first laser beam. If the average energy density of the second laser light is too high, the portion that has been polycrystallized by the first laser light may be microcrystallized. In a case where the average energy density of the second laser light is reduced, it is preferable that the ratio between the highest value and the lowest value of the energy density is made substantially equal between the first laser light and the second laser light. This makes it possible to use the optical system used to generate the first laser light as it is, and to generate the second laser light simply by lowering the laser intensity. ,
The above irradiation can be realized.

It is preferable that the irradiation interval from the start of the first laser light irradiation to the start of the second laser light irradiation be six times or less the pulse width of the first laser light. Since the melting time of the film is generally within about six times the pulse width, the irradiation interval as described above can effectively delay the time at which microcrystalline particles are generated in the second region. This is because the polycrystalline particles can be further increased in particle size.
Here, the film melting time depends on the pulse shape and pulse width depending on the time of the laser beam. Generally, the pulse shape of the excimer laser light has a pulse shape composed of a plurality of peaks as shown in FIG. 4, and the pulse width indicates a half width. Here, the time from the rise of the pulse to the maximum value (t ₁ )
When the length of the film becomes long, the maximum temperature of the film decreases due to the transient cooling, and the energy efficiency decreases. Therefore, it is better that t ₁ is small, and it is desirable that t _{1 be} 20 ns or less.

There are no particular restrictions on the number of irradiations in the case of performing irradiation a plurality of times, but it is desirable that the number be as small as possible from the viewpoint of improving process efficiency. The number of irradiation is preferably 2 to 10
Times, more preferably twice. This is because the irradiation method of the present invention can sufficiently form a target polycrystalline silicon thin film by irradiation twice.

FIG. 3 shows an example of a laser irradiation apparatus for performing a so-called double pulse irradiation in which a second laser irradiation is carried out at the same point while the film is being melted by the first laser irradiation. A controller 303 synchronizes the two light sources 301 and 302 shown in the figure, and passes two pulsed laser beams shaped so as to have a sharp valley through an optical system 304 including a phase shift mask into a chamber 305. Double pulse irradiation is performed on the substrate 306 installed therein.

[0037]

Embodiments of the present invention will be described below.

Example 1 Before performing laser irradiation, a preliminary experiment was performed to determine the profile of a laser beam. As a result, a pulse width of 50 ns at a wavelength of 308 nm is formed on an amorphous silicon film having a thickness of 50 nm.
The E _u when the XeCl laser light irradiated at room temperature 47
It was 0 mJ / cm ² , and it was confirmed that the particle diameter of the polycrystalline particles formed immediately below the microcrystallization threshold was about 0.9 μm.

Subsequently, a substrate to be irradiated with the laser was manufactured. First, a 200-nm-thick silicon dioxide thin film was formed as a base insulating film on a glass substrate by a plasma CVD method. Next, an amorphous silicon thin film was formed to a thickness of 50 nm using a low pressure CVD method. As a method for forming the amorphous silicon thin film, PECVD, sputtering, or the like can be used. However, if a low-pressure CVD method is used, gas is prevented from being mixed into the amorphous silicon thin film. .

XeCl having a wavelength of 308 nm and a pulse width of 50 ns is applied to the amorphous silicon thin film obtained as described above.
Irradiated with laser light. The energy density distribution of the laser beam had the same shape as that of FIG. That is, 500 mJ /
cm ² and a minimum energy of 400
Irradiation was performed with laser light having a profile having mJ / cm ² and a steep valley where W ₁ was 1 μm. The substrate was not heated.

The obtained thin film was subjected to a scanning electron microscope (SE).
Observation in M) confirmed that a large-particle homogeneous structure in which large particles having a particle diameter of about 1.7 μm were regularly arranged in a line was generated. The center position of the formed crystal grain was equivalent to the lowest energy point in the profile. From the results of this example, it can be seen that according to the present invention, remarkably grown crystal grains can be produced with high positional accuracy.

Example 2 Laser irradiation was performed in the same manner as in Example 1 except that the substrate during laser irradiation was heated to 400 ° C. The average particle size of the obtained polycrystalline particles was 2.6 μm.

Example 3 Laser irradiation was performed in the same manner as in Example 1 except that W ₁ was set to 1.8 μm or more. A polycrystalline structure in which 0.9 μm large-diameter polycrystalline particles were arranged in two rows was obtained.

COMPARATIVE EXAMPLE 1 A control experiment was performed using a normal top flat beam shown in FIG. The maximum energy density is the same as in the first embodiment. Although the obtained polycrystalline structure contained large particles having a particle diameter of about 1 μm, they were randomly arranged as schematically shown in FIG. In addition, the particle size distribution in this region was approximately 0.02 to 1 μm, and the structure was heterogeneous.

Example 4 Before performing laser irradiation, a preliminary experiment was performed to determine the profile of laser light. As a result, a pulse width of 50 ns at a wavelength of 308 nm is formed on an amorphous silicon film having a thickness of 50 nm.
The E _u when the XeCl laser light irradiated at room temperature 47
It was 0 mJ / cm ² , and it was confirmed that the large-diameter polycrystalline particles formed immediately below the microcrystallization threshold value had a particle size of about 0.9 μm.

Subsequently, a substrate to be irradiated with the laser was manufactured. First, a 100-nm-thick silicon nitride thin film was formed as a base insulating film over a glass substrate by PECVD. Next, an amorphous silicon thin film was formed to a thickness of 50 nm using a low pressure CVD method.

The amorphous silicon obtained as described above
XeCl with a wavelength of 308 nm and a pulse width of 50 ns
Laser irradiation was performed using laser light. 2 shown in FIG.
The light sources 301 and 302 are synchronized by the control device 303,
Steep valley through optical system 304 including phase shift mask
Two pulsed laser beams shaped to have
Double pulse on substrate 306 installed in chamber 305
Irradiation was performed. As the double pulse irradiation conditions, the first
480 mJ / cm for a roughly flat area of laser light ^Two, Energy
Rugged minimum value is 380mJ / cm^Two, W₁Is 1 μm,
The second laser light has a profile substantially similar to that of the first laser light.
The energy density of the first laser
The light was set to 2/5 and the irradiation interval was set to 80 ns. First
The pulse width of each of the laser light and the second laser light is 5
0 and 35 ns.

The obtained thin film was subjected to a scanning electron microscope (SE).
M), the particle size was about 4.0 as shown in FIG.
It was confirmed that a large-sized homogeneous structure in which large particles of 4 μm were regularly arranged in a line was generated. The point in time when the growth of the crystal grains that have generated nuclei in the upper valley of the profile ends is the point in time when microcrystals generate nuclei in the high energy region. Therefore, in the present embodiment in which nucleation in a high energy region is suppressed by the second laser beam, more remarkable growth can be realized than in the first embodiment.

The center position of the formed crystal particle is
This corresponds to the lowest energy point in the profile, and it has been confirmed that according to the present invention, crystal grains that have grown remarkably can be produced with high positional accuracy.

[0050]

As described above, according to the present invention, the first region having a narrow width has an energy density distribution in a form sandwiched by the second regions having an energy density of _Eu or more. In addition, a large-diameter polycrystalline semiconductor film having a uniform particle size distribution and a good particle arrangement can be formed at a target location with high positional accuracy. By using this polycrystalline semiconductor film, a thin film transistor element having high mobility can be uniformly formed over a large-area substrate.

[Brief description of the drawings]

FIG. 1 is a diagram showing an energy density distribution of a laser beam used in the present invention and a state of polycrystalline semiconductor particles formed by the laser beam.

FIG. 2 is a diagram showing a structure of a mask used in the present invention.

FIG. 3 is a schematic view of a laser irradiation apparatus according to the present invention.

FIG. 4 is a diagram for explaining the time dependence of laser intensity.

FIG. 5 is a diagram showing an energy density distribution of a laser beam used in the present invention and a state of polycrystalline semiconductor particles formed by the laser beam.

FIG. 6 is a diagram illustrating an energy density distribution of a laser beam and a state of polycrystalline semiconductor particles formed by the laser beam.

FIG. 7 is a diagram showing an energy density distribution of laser light and a state of polycrystalline semiconductor particles formed by the laser light.

FIG. 8 is a diagram illustrating a conventional energy density distribution of laser light and a state of polycrystalline semiconductor particles formed by the laser light.

FIG. 9 is a schematic view of a laser irradiation apparatus according to the present invention.

FIG. 10 is a diagram showing an energy density distribution of a laser beam and a state of polycrystalline semiconductor particles formed by the laser beam.

FIG. 11 is a diagram showing an energy density distribution of a laser beam used in the present invention.

FIG. 12 is a diagram showing an energy density distribution of a laser beam used in the present invention.

FIG. 13 is a diagram showing an energy density distribution of a laser beam used in the present invention.

[Explanation of symbols]

Reference Signs List 1 pulse laser light source 2 optical system 3 chamber 4 stage 5 substrate 6 slit 201 quartz plate 202 SiO ₂ film 301, 302 light source 303 controller 304 optical system 305 chamber 306 substrate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Koji Sugioka 2-1 Hirosawa, Wako-shi, Saitama F-term (reference) in RIKEN 5F052 AA02 AA11 BA07 BA12 BA20 BB07 CA04 DA02 DB02 EA11 JA01

Claims (10)

[Claims] 1. A polycrystalline semiconductor comprising: a laser light source for generating laser light; and means for adjusting the energy distribution of the generated laser light, and irradiating the non-single-crystal semiconductor thin film with the laser light after adjusting the energy distribution. A laser irradiation apparatus for forming a thin film, wherein an energy density distribution along one direction in an irradiation region of a laser beam applied to the non-single-crystal semiconductor thin film is used to reduce the microcrystallization energy of the amorphous semiconductor thin film to _Eu.
As a first area less than the energy density E _u, and a energy density E _u or more second region located on both sides of said first region, the width of the first region is at 3μm or less A laser irradiation apparatus, comprising: 2. The laser irradiation apparatus according to claim 1, wherein the width of the first region is 1.8 μm or less. 3. The laser irradiation apparatus according to claim 1, wherein the first region has a steep valley shape. 4. A means for adjusting an energy distribution of a laser beam is a mask made of a base material and a dielectric film covering a part of the base material, and an irradiation area of the laser light transmitted only through the base material; The laser irradiation apparatus according to any one of claims 1 to 3, wherein the first area is generated near a boundary between the area irradiated with the laser light transmitted through the base material and the dielectric film. 5. A first laser beam having the energy density distribution and a second laser beam having the energy density distribution and having an average energy density lower than the first laser beam at the same point in this order. The laser irradiation apparatus according to any one of claims 1 to 4, wherein the laser irradiation apparatus is adjusted to irradiate the laser beam. 6. A laser irradiation method for irradiating a non-single-crystal semiconductor thin film with a laser beam to form a polycrystalline semiconductor thin film,
Energy density distribution along one direction in the light irradiation area of the laser light, fine crystallization energy of the amorphous semiconductor thin film when the E _u, the first region is less than the energy density Eu, said Energy density _Eu located on both sides of a region
Having a second region as described above, wherein the width of the first region is 3 μm.
m or less. 7. The laser irradiation apparatus according to claim 6, wherein the width of the first region is 1.8 μm or less. 8. The laser irradiation method according to claim 6, wherein the first region has a steep valley shape. 9. A laser beam is transmitted through a mask made of a base material and a dielectric film covering a part of the base material, and is irradiated with an area irradiated with laser light transmitted only through the base material and through the base material and the dielectric film. The said 1st area | region is produced | generated near the boundary surface with the irradiation area | region by a laser beam, The Claims 6 thru | or 8 characterized by the above-mentioned.
The laser irradiation method according to any one of the above. 10. A first laser beam having the energy density distribution and a second laser beam having the energy density distribution and having an average energy density lower than the first laser beam at the same point in this order. The laser irradiation method according to any one of claims 6 to 9, wherein the laser irradiation is performed.