JP2000182956A - Crystallization method for semiconductor thin film and laser crystallization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser crystallization device for a semiconductor thin film which controls crystal orientation. SOLUTION: Related to a laser crystallization device, a semiconductor thin film 4 formed on a substrate 0 is irradiated with laser beam 50 while applied with a magnetic field 25, so that the semiconductor thin film 4 is melted once and crystallized in a cooling process. The laser crystallization device comprises a stage 31 on which the substrate 0 to be processed is placed, a vessel 30 where the stage 31 is housed, a laser light source 51 for generating the laser beam 50, an optical system for guiding the laser beam 50 to the substrate 0 placed on the stage 31, and a magnetic field generating device which applied the unidirectional magnetic field 25 to the entire vessel 30 where the stage 31 and at least a part of the optical system are housed. Here, the semiconductor thin film 4 is irradiated with the laser light 50 for melting once, and the crystal orientation of crystal particles contained in the semiconductor thin film 4 is aligned under the action of unidirectional magnetic field in a cooling process. A unidirectional electric field may be acted instead of magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for crystallizing a semiconductor thin film and a laser crystallization apparatus. In particular, the present invention relates to a technique for manufacturing a polycrystalline silicon thin film transistor formed as a switching element of a display device using a liquid crystal or the like as an electro-optical material.

[0002]

2. Description of the Related Art Among thin film transistors widely used as switching elements of a liquid crystal display device, a thin film transistor using polycrystalline silicon as an active layer can incorporate a driving circuit in addition to the switching elements on the same substrate. or,
Because polycrystalline silicon thin film transistors can be miniaturized,
The pixel structure can have a high aperture ratio. For these reasons, polycrystalline silicon thin film transistors have attracted attention as elements for high definition display devices. In recent years, techniques for forming a polycrystalline silicon thin film transistor by a low-temperature process of, for example, 600 ° C. or less have been actively studied. The so-called low-temperature process eliminates the need to use an expensive heat-resistant substrate, which can contribute to cost reduction and size increase of the display. In particular, in recent years, in addition to switching elements for pixels and peripheral driving circuits, demands for integrating advanced functional elements represented by a central processing element (CPU) on a substrate have been increasing. In order to realize this, a technique for forming a high-quality polycrystalline silicon thin film close to single-crystal silicon has been desired.

In a conventional low-temperature process, an amorphous silicon film is formed on a substrate, and the surface of the substrate is irradiated by scanning with a long or linear excimer laser beam or an electron beam. Convert silicon to polycrystalline silicon. By irradiating a high energy beam such as a laser beam or an electron beam, the amorphous silicon is rapidly heated without damaging the substrate and is brought into a molten state. Thereafter, crystallization of silicon occurs in the cooling process, and a polycrystalline aggregate having a certain grain size is obtained.

[0004]

Conventionally, when an amorphous silicon thin film is polycrystallized by irradiating it with a laser beam, the amorphous silicon thin film is naturally melted and solidified. In order to perform irregular crystal growth,
Its crystal orientation was random. For this reason, a large number of trap levels due to the discontinuity of the crystal orientation exist at the boundaries (grain boundaries) of individual crystal grains, resulting in a decrease in mobility.

[0005] In general, when forming an amorphous silicon thin film and then performing laser annealing to achieve polycrystallization, the recrystallization speed of silicon depends on the plane orientation. For example,
The recrystallization speed is significantly different between the 100 plane orientation and the 111 plane orientation. As a result, the surface state of the recrystallized silicon is extremely rough. Originally, the silicon film before recrystallization had a plurality of microcrystals with different plane orientations, and the crystal growth rate of each plane orientation when crystallized or recrystallized by laser annealing was different, so large irregularities Appear on the surface. The mobility of charges (carriers) is limited by the presence of the unevenness.

From the above, it is important to make the crystal orientation uniform in order to improve the mobility of the polycrystalline thin film transistor. In this regard, there has been proposed a technique of controlling the crystal orientation of crystal grains by performing solid phase growth using a catalyst such as a metal. However, this method leaves metal in the crystal. Also, unlike laser annealing, it is difficult to crystallize at low temperature in solid phase growth.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a method of crystallizing a semiconductor thin film and a laser crystallization apparatus capable of controlling the crystal orientation. That is, a method of crystallizing a semiconductor thin film in which a semiconductor thin film formed on a substrate is irradiated with laser light while applying a magnetic field, and the semiconductor thin film is once melted and crystallized in a cooling process. Irradiating a pulse of the laser beam exceeding the predetermined time width in the cooling process, and applying a magnetic field in a certain direction during the cooling process to align crystal orientations of crystal grains contained in the semiconductor thin film. Preferably, when irradiating laser light emitted from the laser light source, the semiconductor thin film is irradiated with lamp light emitted from a lamp light source provided separately from the laser light source, thereby extending the cooling process time.
A laser crystallization apparatus that irradiates a semiconductor thin film formed on a substrate with a laser beam while applying a magnetic field to melt the semiconductor thin film and crystallize the semiconductor thin film during a cooling process. A stage for mounting, a container for storing the stage, a laser light source for generating laser light, an optical system for guiding the laser light to a substrate mounted on the stage, and at least a part of the stage and the optical system. A magnetic field generator for applying a magnetic field in a certain direction to the whole of the container, and irradiating a laser beam to once melt the semiconductor thin film and apply a magnetic field in a certain direction in a cooling process to be included in the semiconductor thin film It is characterized in that the crystal orientation of the crystal grains is aligned. Furthermore,
A semiconductor thin film formed on an insulating substrate, a gate insulating film formed on one surface thereof, and a thin film transistor including a gate electrode overlaid on the semiconductor thin film via the gate insulating film, wherein the semiconductor thin film is It is characterized in that the crystal orientation of crystal grains is uniformed by the action of a magnetic field in a certain direction when the material is once melted by irradiation with an energy beam and then polycrystallized in a cooling process under the action of a magnetic field in a certain direction.

The present invention also relates to a method for crystallizing a semiconductor thin film in which a semiconductor thin film formed on a substrate is irradiated with a laser beam to be once melted and crystallized in a cooling process.
A pulse of a laser beam exceeding 00 ns is irradiated to give a predetermined time width to the cooling process, and an electric field in a certain direction is applied during that time to make the crystal orientations of the crystal grains contained in the semiconductor thin film uniform. Preferably, when irradiating laser light emitted from the laser light source, the semiconductor thin film is irradiated with lamp light emitted from a lamp light source provided separately from the laser light source, thereby extending the cooling process time. In addition, a laser crystallization apparatus for irradiating a semiconductor thin film formed on a substrate with a laser beam to once melt and crystallize during a cooling process, and a stage on which a substrate to be processed is mounted, A container, a laser light source that generates laser light, an optical system that guides the laser light to a substrate mounted on the stage, and a stage and at least a part of the container that houses at least a part of the optical system. And an electric field generator for applying an electric field in a direction, irradiating a laser beam to once melt the semiconductor thin film, and applying an electric field in a certain direction during a cooling process to align crystal orientations of crystal grains contained in the semiconductor thin film. Features. Furthermore, a thin film transistor comprising: a semiconductor thin film formed on an insulating substrate; a gate insulating film formed on one surface thereof; and a gate electrode overlaid on the semiconductor thin film via the gate insulating film. Is characterized in that the crystal orientation of crystal grains is uniformed by the action of an electric field in a certain direction when the material is once melted by irradiation with an energy beam and then polycrystallized in a cooling process by the action of an electric field in a certain direction.

According to the present invention, when a semiconductor thin film is once melted by irradiating a laser beam and crystallized in a cooling process, a sufficient time is secured and a constant magnetic field or electric field is applied during this time, whereby the crystal is formed. The crystal orientation of crystal grains contained in the converted semiconductor thin film is made uniform. The electrons contained in the individual silicon atoms in the molten state interact with a magnetic field or an electric field, and the electron spins are directed in a direction corresponding to the magnetic field or the electric field. When crystallizing or solidifying through a cooling process in this state, the crystal orientations are aligned. Since the orientations of the individual crystal grains are aligned, the barrier of the electron potential due to the discontinuity of the crystal orientation at the grain boundary is reduced, and as a result, the carrier mobility is increased. Further, since the crystal grains are aligned, there is no unevenness on the surface of the semiconductor thin film. By flattening the surface of the semiconductor thin film, the state of the interface between the semiconductor thin film and the gate insulating film formed in contact with the semiconductor thin film is improved, which can contribute to improvement in mobility.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view showing the structure of a laser crystallization apparatus according to the present invention. The present laser crystallization apparatus irradiates a semiconductor thin film 4 formed on an insulating substrate 0 with a laser beam 50 while applying a magnetic field 25 to melt the semiconductor thin film 4 once and crystallize it in a cooling process. For this reason, the present laser crystallization apparatus uses the insulating substrate 0 to be processed.
, A container 30 for storing the stage 31, and a laser light source 51 for generating a laser beam 50
And an optical system such as a mirror 52 that guides the laser beam 50 to the substrate 0 mounted on the stage 31. As a characteristic feature, the present laser crystallization apparatus includes a container 30 for storing at least a part (mirror 52) of the stage 31 and the optical system.
Are provided with a magnetic field generator for applying a magnetic field in a fixed direction. In the present embodiment, the magnetic field generator includes a pair of magnetic poles 20N and 20S that hold the container 30 from above and below. A vertical magnetic field 25 is generated between the pair of parallel plate-type magnetic poles 20N and 20S as shown by arrows, and is applied to the semiconductor thin film 4 formed on the insulating substrate 0 in advance. The container 30
The nozzle 32 for introducing gas from the outside if necessary
And a vacuum pump 33 for exhausting the inside. The laser light 50 emitted from the laser light source 51 is introduced into the container 30 via the optical control unit 53 and the optical window 54.

Subsequently, a method of using the present laser crystallization apparatus will be specifically described with reference to FIG. Container (chamber)
Stage 3 for holding optical mirror 52 and substrate 0 within 30
1 is stored. The stage 31 is movable, and the insulating substrate 0 on which the semiconductor thin film 4 to be processed is formed is mounted thereon. The atmosphere inside the container 30 is evacuated. Alternatively, for example, nitrogen gas or hydrogen gas may be introduced.
The laser light 50 emitted from the laser light source 51 is
The light is shaped and uniformed at 3, and enters the mirror 52 via the optical window 54. The light is irradiated onto the insulating substrate 0 by changing the optical path by the mirror 52. At this time, the entire container 30 is placed in the vertical magnetic field 25. That is, magnets or electromagnets having a pair of magnetic poles 20N and 20S are arranged above and below the container 30 so that a magnetic field is always applied to the semiconductor thin film 4. When melting and recrystallization is performed by the laser beam 50 in such a laser crystallization apparatus, the semiconductor thin film 4 once melted
Electron spins contained in silicon atoms interact with a magnetic field and are directed in a certain direction. When solidifying from this state in the cooling process, the crystal orientations are aligned. Since the crystallized film thus obtained has almost the same crystal orientation, the electron potential barrier at the grain boundary is lowered and the mobility is increased. At this time, it is important to align the crystal orientations in a certain direction, and the crystals may be aligned in the vertical direction of the semiconductor thin film 4 depending on the outer orbital structure of the atoms, or may be aligned in the horizontal direction.

In particular, in order to align the crystal orientation, it is important to apply a laser beam pulse having a light emission time exceeding 100 ns to give a predetermined time width to the cooling process, and to apply a magnetic field in a certain direction during the cooling process. is there. If the light emission time is shorter than 100 ns, the time width of the cooling process is shortened accordingly, and it becomes difficult to sufficiently apply a magnetic field. In order to obtain a laser light pulse having a light emission time of 100 ns or more, for example, a high-output excimer laser light source can be used. Furthermore, when irradiating the laser light emitted from the laser light source, the semiconductor thin film may be irradiated with lamp light emitted from a lamp light source provided separately from the laser light source to extend the cooling process time. By combining excimer laser annealing (ELA) and lamp annealing (RTA), a cooling time of, for example, about 1 to 10 seconds can be secured.

FIG. 2 is a schematic view showing another example of the laser crystallization apparatus according to the present invention. The present laser crystallization apparatus irradiates the semiconductor thin film 4 formed on the insulating substrate 0 with a laser beam 50 while applying an electric field 25x to melt the semiconductor thin film 4 once and crystallize it in a cooling process. For this reason, the present laser crystallization apparatus includes a stage 31 on which the insulating substrate 0 to be processed is placed and a container 3 on which the stage 31 is stored.
0, a laser light source 51 for generating a laser beam 50, and an optical system such as a mirror 52 for guiding the laser beam 50 to the substrate 0 mounted on the stage 31. As a feature,
The laser crystallization apparatus includes an electric field generator that applies an electric field 25x in a certain direction to the entire stage 30 and the entire container 30 that accommodates at least a part (mirror 52) of the optical system. In the present embodiment, the electric field generator includes a pair of electrodes 20p and 20n that hold the container 30 from above and below. A vertical electric field 25x is generated between the pair of parallel plate type electrodes 20p and 20n as shown by arrows, and is applied to the semiconductor thin film 4 formed on the insulating substrate 0 in advance. In addition, container 3
Nozzle 3 for introducing gas from outside if necessary
2 and a vacuum pump 33 for evacuating the inside are connected. The laser light 50 emitted from the laser light source 51 is introduced into the container 30 via the optical control unit 53 and the optical window 54.

Subsequently, a method of using the present laser crystallization apparatus will be specifically described with reference to FIG. Container (chamber)
Stage 3 for holding optical mirror 52 and substrate 0 within 30
1 is stored. The stage 31 is movable, and the insulating substrate 0 on which the semiconductor thin film 4 to be processed is formed is mounted thereon. The atmosphere inside the container 30 is evacuated. Alternatively, for example, nitrogen gas or hydrogen gas may be introduced.
The laser light 50 emitted from the laser light source 51 is
The light is shaped and uniformed at 3, and enters the mirror 52 via the optical window 54. The light is irradiated onto the insulating substrate 0 by changing the optical path by the mirror 52. At this time, the entire container 30 is placed in the vertical electric field 25x. That is, a pair of electrodes 20p and 20n are arranged above and below the container 30, so that an electric field is always applied to the semiconductor thin film 4. In this example, the electrode 20
n is grounded, and an AC power supply is connected to the electrode 20p to generate an AC electric field. Instead, a DC electric field may be applied. In such a laser crystallization apparatus, a laser beam 50
When the melt recrystallization is performed, the electron spins contained in the silicon atoms of the semiconductor thin film 4 once melted interact with the electric field and turn in a certain direction. When solidifying from this state in the cooling process, the crystal orientations are aligned. Since the crystallized film thus obtained has almost the same crystal orientation, the electron potential barrier at the grain boundary is lowered and the mobility is increased. At this time, it is important to align the crystal orientation in a certain direction,
Depending on the shell orbital structure of the atoms, the crystals may be aligned in the vertical direction of the semiconductor thin film 4 or the crystal orientation may be aligned in the horizontal direction.

In particular, in order to make the crystal orientation uniform, it is important to apply a laser beam pulse having a light emission time exceeding 100 ns to give a predetermined time width to the cooling process, and to apply an electric field in a certain direction during the cooling process. is there. If the light emission time is shorter than 100 ns, the time width of the cooling process becomes shorter correspondingly, and it becomes difficult to make the electric field act sufficiently. In order to obtain a laser light pulse having a light emission time of 100 ns or more, for example, a high-output excimer laser light source can be used. Furthermore, when irradiating the laser light emitted from the laser light source, the semiconductor thin film may be irradiated with lamp light emitted from a lamp light source provided separately from the laser light source to extend the cooling process time. By combining excimer laser annealing (ELA) and lamp annealing (RTA), a cooling time of, for example, about 1 to 10 seconds can be secured.

FIG. 3 is a process chart showing a method of manufacturing a thin film transistor according to the present invention, and a semiconductor thin film is crystallized using the laser crystallization apparatus shown in FIG. 1 or FIG. The mobility of the polycrystalline silicon thin film transistor manufactured in this embodiment is 130 to 30 in the N-channel type.
0 cm ² / Vs, 60 to 150 cm for P-channel type
² / Vs, and a much higher mobility than in the past has been achieved. In this embodiment, a method for manufacturing an N-channel thin film transistor is shown for convenience, but the same applies to a P-channel type thin film transistor only by changing an impurity type (dopant type). Here, a method for manufacturing a thin film transistor having a bottom gate structure is described. First, as shown in (a), for example, Al, Ta, Mo, W,
Cr, Cu or an alloy thereof is, for example, 100 to 200
The gate electrode 1 is formed by patterning with a thickness of nm.

Next, a gate insulating film is formed on the gate electrode 1 as shown in FIG. In this embodiment, the gate insulating film has a two-layer structure of, for example, a gate nitride film 2 (SiN _x ) / gate oxide film 3 (SiO ₂ ). Gate nitride film 2
Was formed by a plasma CVD method (PCVD method) using a mixture of SiH ₄ gas and NH ₃ gas as a source gas. It should be noted that normal pressure CVD or reduced pressure C is used instead of plasma CVD.
VD may be used. In this embodiment, the gate nitride film 2 is deposited with a thickness of 50 nm. Subsequent to the formation of the gate nitride film 2, a gate oxide film 3 is formed with a thickness of about 200 nm. Further, a semiconductor thin film 4 made of amorphous silicon was continuously formed on the gate oxide film 3 to a thickness of about 30 to 80 nm. Gate insulating film of two-layer structure and amorphous semiconductor thin film 4
Formed a continuous film without breaking the vacuum system of the film forming chamber. When the plasma CVD method is used in the above film formation, for example, 40
Heat treatment is performed in a nitrogen atmosphere at a temperature of 0 to 450 ° C. for about 1 hour to release hydrogen contained in the amorphous semiconductor thin film 4. A so-called dehydrogenation anneal is performed.

Here, in order to control Vth of the thin film transistor, Vth ion implantation is performed as necessary. In this example, the dose of B + is 1 × 10
Ions are implanted at ¹² to 6 × 10 ¹² / cm ² approximately. In this Vth ion implantation, a line beam of ions shaped to a width of 620 nm was used. Then, according to the present invention, the laser beam 5 is applied while applying a magnetic field or an electric field.
Irradiation is carried out to crystallize the amorphous semiconductor thin film 4. An excimer laser beam can be used as the laser beam 50. Thereby, the crystal orientation can be made uniform.

[0019] As shown (c), the front about 100nm to 30 of SiO _2, for example, a plasma CVD method on the polycrystalline semiconductor thin film 5 which has been crystallized in a state of uniform crystal orientation in step
It is formed with a thickness of 0 nm. In this example, the silane gas SH ₄
And oxygen gas were plasma-decomposed to deposit SiO ₂ . The SiO ₂ thus formed is patterned into a predetermined shape and processed into an etching stopper film 6. In this case, the etching stopper film 6 is patterned so as to be aligned with the gate electrode 1 using a backside exposure technique. The portion of the polycrystalline semiconductor thin film 5 located immediately below the etching stopper film 6 is protected as a channel region Ch. As described above, B + ions are previously implanted into the channel region Ch at a relatively low dose by Vth ion implantation. Subsequently, the etching stopper film 6
Is used as a mask to implant impurities (for example, P + ions) into the semiconductor thin film 5 by ion doping, thereby forming an LDD region. The dose at this time is, for example, 6 × 10 ^{12 to} 5 × 10 ¹³ / cm ² . Further, after a photoresist is formed by patterning so as to cover the stopper film 6 and the LDD regions on both sides thereof, impurities (for example, P + ions) are implanted at a high concentration using the photoresist as a mask to form a source region S and a drain region D. . For impurity implantation, for example, ion doping (ion shower) can be used. This is to implant impurities by electric field acceleration without applying mass separation. In this embodiment, 1 × 10 ¹⁵ / cm
Impurities were implanted at a dose of about ² to form a source region S and a drain region D. Although not shown, in the case of forming a P-channel thin film transistor, the impurity is switched from P + ions to B + ions after covering the region of the N-channel thin film transistor with a photoresist, and the dose is about 1 × 10 ¹⁵ / cm ^2. Ion doping. Here, the impurities may be implanted using a mass separation type ion implantation apparatus. Thereafter, the impurities implanted in polycrystalline semiconductor thin film 5 are activated. For example, laser activation annealing (ELA) using an excimer laser is performed. Thereafter, unnecessary portions of the semiconductor thin film 5 and the etching stopper film 6 are simultaneously patterned to separate thin film transistors for each element region.

[0020] As shown in the last (d), the the SiO ₂ about 2
The interlayer insulating film 7 is formed with a thickness of 00 nm. After the formation of the interlayer insulating film 7, for example, SiN _x is formed to a thickness of about 200 to 400 nm by a plasma CVD method to form a passivation film (cap film) 8. At this stage, for example, a heat treatment at about 350 ° C. is performed for one hour in a nitrogen gas, a forming gas, or an atmosphere in a vacuum to diffuse hydrogen atoms contained in the interlayer insulating film 7 into the semiconductor thin film 5. After that, a contact hole is opened and, for example, Mo, Al, or the like is sputtered with a thickness of 200 to 400 nm, and then patterned into a predetermined shape to process the wiring electrode 9. Further, a contact hole is opened after a flattening layer 10 made of, for example, an acrylic resin is applied with a thickness of about 1 μm. Flattening layer 10
Then, a transparent conductive film made of, for example, ITO or IXO is sputtered thereon, patterned into a predetermined shape, and processed into the pixel electrode 11.

FIG. 4 shows an example of an active matrix type display device using the thin film transistors manufactured by the manufacturing method shown in FIG. As illustrated, the display device has a panel structure including a pair of insulating substrates 101 and 102 and an electro-optical material 103 held between the pair of insulating substrates 101 and 102.
As the electro-optic material 103, a liquid crystal material is widely used. On the lower insulating substrate 101, a pixel array section 104 and a drive circuit section are integrally formed. The drive circuit section is divided into a vertical drive circuit 105 and a horizontal drive circuit 106. Further, a terminal portion 107 for external connection is formed at an upper end of a peripheral portion of the insulating substrate 101. The terminal unit 107 is connected to the vertical drive circuit 105 and the horizontal drive circuit 1
06. A row-shaped gate wiring 109 and a column-shaped signal wiring 110 are formed in the pixel array unit 104. A pixel electrode 111 and a thin film transistor 112 for driving the pixel electrode 111 are formed at the intersection of the two wires. The gate electrode of the thin film transistor 112 is
9 and the drain region is connected to the corresponding pixel electrode 111
, And the source region is connected to the corresponding signal wiring 110. The gate wiring 109 is connected to the vertical driving circuit 105, while the signal wiring 110 is connected to the horizontal driving circuit 106. The thin film transistor 112 for switchingly driving the pixel electrode 111 and the thin film transistors included in the vertical drive circuit 105 and the horizontal drive circuit 106 are formed according to the present invention, and have higher mobility than the conventional one. Therefore, not only a driving circuit but also a higher-performance processing circuit can be integrated. That is, these thin film transistors include a semiconductor thin film formed on the insulating substrate 101, a gate insulating film formed on one surface thereof, and a gate electrode overlaid on the semiconductor thin film via the gate insulating film. When the semiconductor thin film is irradiated with an energy beam such as a laser beam and once melted and then polycrystallized in a cooling process, the crystal orientation of crystal grains is aligned by the action of a magnetic field or an electric field in a certain direction. .

FIG. 5 is a block diagram showing a modification of the laser crystallization apparatus according to the present invention shown in FIG. Parts corresponding to those of the embodiment shown in FIG. 1 are denoted by corresponding reference numerals to facilitate understanding. The difference from the embodiment shown in FIG. 1 is that the container 30 is housed in a coil constituting the electromagnet 20 as a whole. As a result, the magnetic field 25 in the horizontal direction is applied to the semiconductor thin film 4 formed on the insulating substrate 0 as shown by the arrow. This magnetic field 2
5, the crystal orientation of the crystal grains contained in the semiconductor thin film 4 is aligned in a certain direction.

FIG. 6 is a schematic view showing a development of the laser crystallization apparatus according to the present invention, and shows only an optical part excluding a magnetic field generator, an electric field generator, and a container. In this development, more efficient crystallization is performed by combining laser light and lamp light. That is, when irradiating the laser light emitted from the laser light source, the semiconductor thin film is irradiated with the lamp light emitted from a lamp light source provided separately from the laser light source to extend the cooling process time. This device is basically an ELA (Excimer LaserAnn).
eal) and RTA (Rapid Thrmal Ann)
eal). RTA instantaneously emits ultraviolet light having a wavelength of 240 to 400 nm (for example, about 1
This is a technology that enables high-temperature heat treatment without damaging the substrate itself by irradiating the insulating substrate 0 made of glass or the like at (sec). As shown in the figure, the insulating substrate 0 is provided with infrared heaters 71 to 73 such as infrared lamps.
Are preliminarily heated (gradually heated) in Zones 1 to 3 in which is disposed. The insulating substrate 0 is transferred at a predetermined speed and sent to the RTA unit. In this example, the laser beam 50
, A first RTA unit located immediately before the irradiation area and a second RTA unit located immediately after the irradiation area. The first RTA unit is a pair of upper and lower arc lamps 61, 62.
The second RTA unit also comprises a pair of upper and lower arc lamps 67, 68. Each arc lamp 61, 62,
67 and 68 are covered with a reflector 82,
In the vicinity, a radiation thermometer 83 for control is arranged.
After passing through the RTA unit, the insulating substrate 0 is transported to a zone 4 for cooling in which the infrared heater 74 is also arranged, where it is gradually cooled. On the other hand, the ELA uses an excimer laser light source, and intermittently generates, for example, a linearly shaped laser beam 50 as a pulse. The laser beam 50 is mirror 52
And irradiates the insulating substrate 0.

The laser crystallization apparatus having such a configuration is used for heat treatment of a semiconductor thin film formed in advance on the surface of an insulating substrate 0 extending in a longitudinal direction and a width direction orthogonal to each other. In the drawing, the longitudinal direction of the insulating substrate 0 coincides with the substrate traveling direction indicated by the arrow. As described above, the present apparatus basically includes a laser light source, a plurality of lamp light sources, and a transfer unit. The laser light source irradiates the semiconductor thin film with a relatively high energy laser beam 50 linearly shaped along the width direction of the insulating substrate 0 at an intermittent timing. The pair of upper and lower arc lamps 61 and 62 synchronize two lamp lights having relatively low energy formed linearly (long) along the width direction of the insulating substrate 0 with the irradiation timing of the laser light 50. Then, the semiconductor thin film is irradiated intermittently. The same applies to a pair of upper and lower arc lamps 67 and 68. The transportation means
The insulating substrate 0 is transferred in the longitudinal direction (substrate traveling direction) in accordance with the irradiation timing of the laser light 50 and the lamp light.
Further, since the insulating substrate 0 is gradually heated and cooled before and after the irradiation of the laser beam 50 and the lamp beam, the infrared heaters 71 to 74 are used.
Are arranged along the transfer means.

[0025]

As described above, according to the present invention,
When polycrystalline non-single-crystal semiconductor thin film such as amorphous silicon formed on an insulating substrate by laser irradiation,
By applying a magnetic field or an electric field, the crystal orientation of the crystal grains is aligned in a certain direction. Thereby, the carrier mobility of the thin film transistor having the polycrystalline semiconductor thin film as the active layer can be improved. In addition, the laser crystallization apparatus used for this purpose only needs to arrange the entire chamber in a magnetic field or an electric field in a certain direction, and requires a relatively simple apparatus configuration.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a laser crystallization apparatus according to the present invention.

FIG. 2 is a schematic block diagram showing another example of the laser crystallization apparatus according to the present invention.

FIG. 3 is a process chart showing a method for manufacturing a thin film transistor according to the present invention.

FIG. 4 is a perspective view showing an example of a display device using a thin film transistor manufactured according to the present invention.

FIG. 5 is a schematic view showing a modification of the laser crystallization apparatus according to the present invention.

FIG. 6 is a schematic perspective view showing a development of a laser crystallization apparatus according to the present invention.

[Explanation of symbols]

0 ... insulating substrate, 4 ... semiconductor thin film, 20N ...
Magnetic pole, 20S: magnetic pole, 20p: electrode, 20n
..Electrode, 25 ... magnetic field, 25x ... electric field, 30.
..Container, 31 ... Stage, 50 ... Laser light,
51: laser light source, 52: mirror

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hisao Hayashi F-term (reference) 5F052 AA02 AA24 BB07 DA02 DB03 EA12 JA01 5F110 AA01 BB02 CC08 DD02 EE03 EE04 EE23 FF02 FF03 FF30 GG02 GG13 GG17 GG25 GG32 GG34 GG45 HJ01 HJ04 HJ13 HJ23 HL03 HL23 HM15 NN03 NN04 NN16 NN23 NN24 NN35 PP03 PP23 PP35 QQ09 QQ11

Claims (10)

[Claims] 1. A method of crystallizing a semiconductor thin film, wherein the semiconductor thin film formed on a substrate is irradiated with laser light while applying a magnetic field, and the semiconductor thin film is once melted and crystallized in a cooling process. Is characterized by irradiating a pulse of laser light exceeding 100 ns to give a predetermined time width to the cooling process, and applying a magnetic field in a certain direction during that time to align crystal orientations of crystal grains contained in the semiconductor thin film. A method for crystallizing a semiconductor thin film. 2. The method according to claim 1, wherein when irradiating laser light emitted from the laser light source, the semiconductor thin film is irradiated with lamp light emitted from a lamp light source provided separately from the laser light source to extend the cooling process time. The method for crystallizing a semiconductor thin film according to claim 1. 3. A laser crystallization apparatus for irradiating a semiconductor thin film formed on a substrate with a laser beam while applying a magnetic field to melt the semiconductor thin film and crystallize the semiconductor thin film in a cooling process. A stage for mounting a substrate, a container for storing the stage, and a laser light source that generates laser light,
An optical system that guides the laser light to a substrate mounted on the stage, and a magnetic field generator that applies a magnetic field in a fixed direction to the whole of the stage and at least a part of the container that houses the optical system, A laser crystallization apparatus characterized by irradiating a laser beam to once melt the semiconductor thin film and applying a magnetic field in a certain direction during a cooling process to align crystal orientations of crystal grains contained in the semiconductor thin film. 4. It has a pair of substrates joined to each other via a predetermined gap, and an electro-optical material held in the gap,
A counter electrode was formed on one of the transparent substrates, a pixel electrode and a thin film transistor for driving the pixel electrode were formed on the other insulating substrate, and the thin film transistor was overlaid on one side of the semiconductor thin film via a gate insulating film. A method for manufacturing a display device formed with a gate electrode, comprising: a film forming step of forming a semiconductor thin film on a surface of the insulating substrate;
An annealing step of irradiating the semiconductor thin film formed on the insulating substrate with a laser beam while applying a magnetic field to once melt the semiconductor thin film and crystallizing the semiconductor thin film in a cooling process; and a thin film transistor using the crystallized semiconductor thin film as an active layer. The annealing step includes irradiating a pulse of laser light having a light emission time exceeding 100 ns to give a predetermined time width to the cooling process, and applying a magnetic field in a certain direction during the cooling process. A method for manufacturing a display device, comprising: aligning crystal orientations of crystal grains included in a thin film. 5. A thin film transistor comprising: a semiconductor thin film formed on an insulating substrate; a gate insulating film formed on one surface thereof; and a gate electrode overlaid on the semiconductor thin film via the gate insulating film. The thin film transistor, wherein the semiconductor thin film is once melted by irradiation of an energy beam and then polycrystallized in a cooling process, and is subjected to the action of a magnetic field in a certain direction to have a uniform crystal orientation of crystal grains. . 6. A method for crystallizing a semiconductor thin film, which comprises irradiating a semiconductor thin film formed on a substrate with a laser beam to melt and crystallize the semiconductor thin film in a cooling process, wherein the semiconductor thin film is irradiated with a pulse of a laser beam having an emission time exceeding 100 ns. A method of crystallizing a semiconductor thin film, characterized in that a predetermined time width is given to a cooling process and an electric field in a certain direction is applied during the cooling process so as to align crystal orientations of crystal grains contained in the semiconductor thin film. 7. When irradiating laser light emitted from a laser light source, the semiconductor thin film is irradiated with lamp light emitted from a lamp light source provided separately from the laser light source to extend the cooling process time. The method for crystallizing a semiconductor thin film according to claim 6. 8. A laser crystallization apparatus for irradiating a semiconductor thin film formed on a substrate with a laser beam to once melt and crystallize in a cooling process, comprising: a stage on which a substrate to be processed is placed; And a laser light source that generates laser light,
An optical system that guides the laser light to a substrate mounted on the stage, and an electric field generator that applies an electric field in a fixed direction to the entirety of the stage and at least part of the container that houses the optical system, A laser crystallization apparatus characterized in that the semiconductor thin film is once melted by irradiating a laser beam and an electric field is applied in a certain direction during a cooling process to align crystal orientations of crystal grains contained in the semiconductor thin film. 9. A semiconductor device comprising: a pair of substrates joined to each other via a predetermined gap; and an electro-optical material held in the gap;
A counter electrode was formed on one of the transparent substrates, a pixel electrode and a thin film transistor for driving the pixel electrode were formed on the other insulating substrate, and the thin film transistor was overlaid on one side of the semiconductor thin film via a gate insulating film. A method for manufacturing a display device formed with a gate electrode, comprising: a film forming step of forming a semiconductor thin film on a surface of the insulating substrate;
An annealing step of irradiating the semiconductor thin film formed on the insulating substrate with laser light to once melt and crystallize in a cooling process, and a processing step of forming a thin film transistor using the crystallized semiconductor thin film as an active layer, The annealing step includes irradiating a pulse of laser light having a light emission time exceeding 100 ns to give a predetermined time width to the cooling process, and by applying an electric field in a certain direction during the irradiation, the crystal orientation of the crystal grains contained in the semiconductor thin film. A method for manufacturing a display device, comprising: 10. A semiconductor thin film formed on an insulating substrate,
A thin film transistor including a gate insulating film formed on one surface thereof and a gate electrode overlaid on the semiconductor thin film with the gate insulating film interposed therebetween, wherein the semiconductor thin film is once melted by being irradiated with an energy beam. A thin film transistor characterized in that the crystal orientation of crystal grains is aligned by the action of an electric field in a certain direction when polycrystallized in a post-cooling process.