JP2002261103A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make characteristics of a semiconductor device manufactured by using various anneals with laser beam uniform. SOLUTION: When a semiconductor material is annealed while scanning the laser beam formed in a line shape in the direction normal to the line, there is twice or more difference in the uniformity between the annealing effect for the beam transverse direction to be the line direction and the annealing effect for the scanning direction. Hence, by manufacturing a plurality of semiconductor elements in a state of adjusting them to the line direction that is irradiated with the linear laser beam, the semiconductor device having uniform characteristics can be obtained. In addition, by adjusting the line direction, in which a source/drain of a thin film transistor is connected, to the line direction of the linear laser beam, carriers move in a region of uniform annealing effect and thus the semiconductor device having high characteristics can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
The present invention relates to a technology for forming an integrated device such as a transistor using a thin film semiconductor. In particular, the present invention relates to a technique for manufacturing a plurality of thin film devices without a variation in characteristics using a linear laser beam. In addition, the present invention relates to a thin film device manufactured using this technique.

[0002]

2. Description of the Related Art In recent years, research has been actively conducted on lowering the temperature of a semiconductor device manufacturing process. The major reason is that a semiconductor element needs to be formed on an insulated substrate made of glass or the like, which is inexpensive and highly processable. Others
From the viewpoint of miniaturizing elements and increasing the number of layers of elements, there is a demand for lowering the manufacturing process of semiconductor elements.

[0003] In a semiconductor process, an amorphous component or an amorphous semiconductor material contained in a semiconductor material is crystallized, or a semiconductor material which was originally crystalline but has been reduced in crystallinity due to irradiation with ions. In some cases, it may be necessary to recover the crystallinity of the compound or to improve the crystallinity, although the crystallinity is high. Conventionally, thermal annealing has been used for such a purpose. 600 ° C. when silicon is used as the semiconductor material
Annealing at a temperature of from 1 to 100 ° C. for 0.1 to 48 hours or longer has resulted in crystallization of amorphous, recovery of crystallinity, improvement of crystallinity, and the like.

[0004] In general, the higher the temperature, the shorter the processing time may be. However, the thermal annealing has little effect at a temperature of 500 ° C or less. Therefore, from the viewpoint of lowering the temperature of the process, it has been necessary to replace the step conventionally performed by thermal annealing with another means. In particular, when a glass substrate is used as the substrate, since the heat resistance temperature of the glass substrate is about 600 ° C., a means comparable to conventional thermal annealing at a temperature lower than this temperature is required.

As a method for satisfying such demands, there is known a technique of performing various kinds of annealing by irradiating a semiconductor material with laser light. This laser beam irradiation technology is attracting attention as the ultimate low-temperature process. This means that the laser light can be applied only to the places where high energy equivalent to thermal annealing is required,
This is because it is not necessary to expose the entire substrate to a high temperature.

[0006] Regarding the irradiation of laser light, two methods have been proposed.

The first method uses a continuous wave laser such as an argon ion laser, and irradiates a semiconductor material with a spot beam. This is a method in which a semiconductor material is crystallized by utilizing a difference in energy distribution inside the beam and a movement of the beam, which causes the semiconductor material to melt and then slowly solidify.

The second method uses a pulsed laser such as an excimer laser to irradiate a semiconductor material with a high-energy laser pulse. At this time, the semiconductor material is instantaneously melted and solidified, whereby crystal growth proceeds. It is a method that utilizes that.

[0009]

The problem with the first method is that it takes a long time to process. This is because the maximum energy of the continuous wave laser is limited, and the size of the beam spot is at most a mm square unit. On the other hand, in the second method, the maximum energy of the laser is very large, and mass productivity can be further improved by using a large spot of several cm square or more.

However, with a commonly used square or rectangular beam, it is necessary to move the beam up, down, left, and right to process a single large-area substrate, and there is still room for improvement in terms of mass productivity. was there.

In this regard, the beam is deformed linearly,
Significant improvement can be achieved by employing a method in which the width of the beam exceeds the substrate to be processed and the beam is scanned relative to the substrate. (The term “scanning” as used herein means that a linear laser beam is irradiated while being superposed with a slight shift.)

However, the above-described technique of irradiating the linear pulsed laser while overlapping it while shifting it little by little produces linear stripes on the surface of the semiconductor material irradiated with the laser. These stripes greatly affect the characteristics of a device formed on a semiconductor material or a device formed in the future. In particular, this effect becomes a serious problem when a plurality of devices are formed on a substrate and the characteristics of each of the devices must be made uniform. In such a case, one striped pattern 1
Although the characteristics are uniform in the book, the characteristics between the stripes vary.

As described above, even in the annealing method using the linear laser light, uniformity of the irradiation effect poses a problem. High uniformity here means that the same element characteristics are obtained regardless of where the element is formed on the substrate. To increase the uniformity means to make the crystallinity of the semiconductor material uniform. The following measures have been devised to improve the uniformity.

In order to reduce the non-uniformity of the laser irradiation effect, irradiation with a strong pulsed laser beam (hereinafter referred to as main irradiation)
Prior to this, it has been found that preliminary irradiation with a weaker pulse laser beam (hereinafter referred to as pre-irradiation) may improve the uniformity. This effect is very high, and the variation can be suppressed, and the characteristics of the semiconductor device circuit can be significantly improved.

The reason why the preliminary irradiation is effective in maintaining the uniformity of the film is that the film of the semiconductor material containing the amorphous portion as described above has a polycrystalline film or a monocrystalline film having an absorptivity of laser energy. This is because they have properties that are quite different from the above. That is, the effect of the two-step irradiation is to crystallize the amorphous portion remaining in the film by the first irradiation and further promote the overall crystallization in the second irradiation. As described above, by gradually promoting crystallization, it is possible to suppress to some extent the unevenness of stripes on the semiconductor material due to linear laser irradiation. With this contrivance, the uniformity of the irradiation effect of the laser beam is considerably improved, and the above-mentioned stripe pattern can be made relatively invisible.

However, when a large number (tens of thousands of units) of semiconductor debiases (for example, thin film transistors) must be formed on a glass substrate as in an active matrix type liquid crystal display, the above-mentioned method is used. Even the laser irradiation method by step irradiation was not satisfactory in terms of the uniformity of the effect.

The annealing method using the excimer laser beam processed in a linear beam as described above is excellent in that it can cope with a large area, but has a problem in terms of the uniformity of the effect. Was.

Therefore, in the invention disclosed in the present specification, when a large number of semiconductor devices are manufactured by using annealing by irradiation of a laser beam processed into a linear beam,
An object of the present invention is to provide a technique for minimizing a variation in characteristics of each semiconductor device.

[0019]

As long as a linear laser is used, it is inevitable that the above-mentioned striped non-uniformity will occur. Therefore, in the invention disclosed in this specification, from the idea of increasing the homogeneity of the semiconductor material, to the non-uniformity caused by laser irradiation, formed on the semiconductor material,
Alternatively, this problem can be solved by changing to an idea of combining formed elements.

FIG. 1 quantitatively shows the non-uniformity of the surface of the semiconductor material caused by the two-step irradiation of the laser beam as described above. FIG. 1 shows a width of 1 mm and a length of 125 mm.
A KrF excimer laser (wavelength: 248 nm, pulse width: 30 ns) beam-processed into a linear line having a thickness of 200 mm is scanned (scanned) in a direction perpendicular to the line to form a 500-mm-thick amorphous silicon film formed on a glass substrate. This is a result of measuring the refractive index of the silicon film after irradiation.

In FIG. 1, the scanning direction is
It shows the distribution of the refractive index in the scanning direction of the linear laser beam, that is, in the direction perpendicular to the line. The beam lateral direction indicates the distribution of the refractive index in the line direction (longitudinal direction) of the linear laser beam.
The amorphous silicon film is crystallized by irradiation with a laser beam, and the difference in crystallinity can be measured by the difference in the refractive index. The refractive index of the silicon film can be measured using an ellipsometer if the thickness of the thin film is known. The data shown in FIG. 1 is obtained when the above-described two-stage irradiation is performed.

It can be seen from this figure that the refractive index of the line parallel to the linear laser indicated by the square is much higher than that of the line substantially perpendicular to the line (the scanning direction of the laser light indicated by the circle). That is, the uniformity is good. The refractive index is closely related to the crystallinity of the film, and since there is no variation in the refractive index, it can be said that the crystallinity also has no variation. From this, it can be concluded that the homogeneity of the crystal is much better on the line parallel to the linear laser than on the line almost perpendicular to it.

From the measurement results shown in FIG. 1, the annealing effect by the linear laser light is good with no variation in the linear direction, but has a large variation in the scanning direction. You can see that it is.

This variation is about 0.6% in the linear direction of the linear laser, but is 1.3% which is twice or more as large as that in the scanning direction. When annealing is performed using a linear laser beam while scanning in a direction perpendicular to the line, the annealing effect in the line direction is smaller than the annealing effect in the scanning direction (direction perpendicular to the line). It can be seen that the number is twice or more.

This can be considered to be the same not only for the silicon semiconductor thin film but also for other thin film semiconductors. The effect of laser light irradiation as shown in FIG. 1 is not limited to the crystallization of an amorphous silicon film, but also broadly improves and improves the crystallization and crystallinity of a semiconductor thin film, and the activity of introduced impurities. This can be said also in the case of employment.

As shown in FIG. 1, in the invention disclosed in this specification, in various kinds of annealing using a linear laser beam, the annealing effect is two in a line direction and a scanning direction.
This is particularly effective when the difference is more than twice.

Therefore, when fabricating a plurality of elements formed on a semiconductor material, a circuit arrangement is adopted in which elements having particularly the same characteristics are arranged as linearly as possible. A region (or a region to be an element region) is irradiated with a linear laser beam to perform various kinds of annealing. Then, the annealing effect of the laser beam can be made uniform in each element region aligned on the straight line, and the characteristics of a plurality of elements aligned on the straight line can be made uniform.

When a crystalline silicon film is obtained by using a linear laser beam having a uniform annealing effect as shown in FIG. 1 and a thin film transistor is formed using this crystalline silicon film, the source of the thin film transistor is formed. By making the line (longitudinal direction) of the linear laser beam coincide with or substantially coincide with the line connecting the line and the drain, the crystallinity in the direction in which the carrier moves can be made uniform. In this case, since the movement of the carrier is performed in a region having uniform crystallinity, there is no obstacle (electrical obstacle) in the movement, and the characteristics can be improved.

Hereinafter, each invention disclosed in this specification will be described. One of the main inventions disclosed in this specification is a step of performing annealing by irradiating a thin-film semiconductor with a linear laser beam and aligning the thin-film semiconductor with a longitudinal direction of a region irradiated with the linear laser beam. And manufacturing a plurality of semiconductor devices.

The above process can be used, for example, when manufacturing a thin film transistor formed on a substrate having an insulating surface such as a glass substrate. The linear laser light can be obtained by using an excimer laser light which is formed into a linear shape by an optical system as described later in Examples. The longitudinal direction irradiated with the laser light refers to the linear direction of the region irradiated in a linear shape.

Another aspect of the invention has a step of irradiating a thin-film semiconductor with a linear laser beam, wherein a plurality of semiconductor devices are to be formed in at least one row in a line. The linear laser light is irradiated by matching the line direction of the laser light with the direction of the row.

According to another aspect of the invention, in the step of irradiating a thin film semiconductor with a laser beam, a linear pattern is formed in a direction connecting a region where a source region of the thin film transistor is to be formed and a region where a drain region is to be formed. It is characterized by irradiating a laser beam having the following.

In the above configuration, the configuration of the thin film transistor may be staggered, inverted staggered, planar,
Any configuration of an inverted planar type may be used. This is particularly effective when a planar structure in which the source, channel, and drain regions are formed in one active layer is employed.

Crystallization is also performed for the purpose of irradiating laser light.
Includes those for promoting crystallization, improving crystallization, activating impurities, and other various annealings.

According to another aspect of the present invention, a thin film transistor having a step of irradiating a linear laser beam to a thin film semiconductor and a source region and a drain region along a linear direction of the linear laser beam is manufactured. And a step.

According to another aspect of the present invention, there is provided a step of irradiating a thin-film semiconductor with a linear laser beam, and a step of manufacturing a semiconductor device in which carriers move along the linear direction of the linear laser beam. It is characterized by having.

According to another aspect of the present invention, a step of implanting impurity ions imparting one conductivity type into a source region and a drain region of a thin film transistor, and a step of forming a linear laser along a line connecting the source region and the drain region Irradiating light.

Another aspect of the invention is a thin film transistor using a crystalline silicon film, wherein a variation in the refractive index of the crystalline silicon film in a direction connecting a source region and a drain region of the thin film transistor is different from the direction. It is characterized by being at least twice as large as the variation in the refractive index of the crystalline silicon film in a direction perpendicular to the direction.

According to another aspect of the invention, there is provided a semiconductor device using a crystalline silicon film, wherein a variation in a refractive index of the crystalline silicon film in a direction in which carriers move in the semiconductor device is perpendicular to the direction. The variation is more than twice as large as the variation of the crystalline silicon film in the direction.

[Operation] In the step of annealing a semiconductor using a laser beam having a linear beam pattern, for example, a plurality of laser patterns are formed in the line direction by utilizing the uniformity of the annealing effect in the line direction of the laser pattern. The characteristics of the thin film transistor can be made uniform.

Further, by matching the direction in which carriers move in the semiconductor device with the linear direction of the linear laser pattern, the electrical characteristics of the semiconductor device can be improved. This is because carriers move in a region having uniform crystallinity.

Further, by making the variation in the refractive index of the crystalline silicon film in the direction in which the carriers move, at least twice as large as the variation in the crystalline silicon film in a direction perpendicular to the direction, for example, A thin film transistor having high characteristics can be obtained.

[Embodiment 1] In this embodiment, an example in which an amorphous silicon film formed on a glass substrate is crystallized using the invention disclosed in this specification will be described. In the structure shown in this embodiment, a step of further irradiating a linear laser beam to the crystalline silicon film crystallized by heating to increase the crystallinity is shown. Further, an example in which a thin film transistor having uniform characteristics is manufactured using this crystalline silicon film will be described. In particular, an example of manufacturing a thin film transistor integrated over a glass substrate included in an active matrix liquid crystal display device will be described.

First, an apparatus for irradiating a laser beam will be described. FIG. 2 shows a conceptual diagram of a laser annealing apparatus used in this embodiment. The laser light is oscillated by the oscillator 2. The laser light oscillated by the oscillator 2 is KrF
Excimer laser (wavelength 248 nm, pulse width 30 n
s). Of course, other excimer lasers and other types of lasers can also be used.

The laser light oscillated by the oscillator 2 is amplified by the amplifier 3 via the total reflection mirrors 5 and 6 and further introduced into the optical system 4 via the total reflection mirrors 7 and 8.
Although not shown in FIG. 2, the mirror 8 and the optical system 4 are not shown.
Insert a machine to take out and put out the neutral density filter. This neutral density filter is for obtaining a required irradiation intensity by combining filters having different transmittances.

The beam pattern of the laser light immediately before entering the optical system 4 has a rectangular shape of about 3 × 2 cm ² . By passing this laser light through the optical system 4, an elongated beam (linear beam) having a length of about 10 to 30 cm and a width of about 0.1 to 1 cm can be obtained. The energy of the laser beam passing through the optical system 4 has a maximum energy of about 1000 mJ / shot.

The reason why the laser beam is processed into such an elongated beam is to improve the irradiation efficiency. That is,
After leaving the optical system 4, the linear beam is irradiated on a substrate (sample) 11 through a total reflection mirror 9. By making the width of the beam longer than the width of the substrate, the substrate is moved in one direction. By moving, the entire substrate can be irradiated with laser light. Therefore, the stage on which the substrate is arranged and the driving device 10 have a simple structure and are easy to maintain. In addition, the positioning operation (alignment) when setting the substrate can be facilitated. Further, since the laser light can be irradiated to the entire target surface only by moving the substrate in one direction, the laser light irradiation process can be simplified and good controllability can be obtained.

The stage 10 on which the substrate 11 to be irradiated with the laser light is arranged is controlled by a computer and is designed to move at a required speed in a direction perpendicular to the linear laser light. Further, if the stage on which the substrate is placed has a function of rotating in the plane, it is convenient to change the scanning direction of the laser beam. Stage 10
A heater is built in under the substrate, and the substrate can be kept at a predetermined temperature during irradiation with laser light.

FIG. 3 shows an example of an optical path inside the optical system 4. The laser beam incident on the optical system 4 changes from a Gaussian distribution type to a rectangular distribution by passing through a cylindrical concave lens A, a cylindrical convex lens B, and lateral fly-eye lenses C and D. Further, the light passes through the cylindrical convex lenses E and F and passes through the mirror G,
The light is converged by the cylindrical lens H and becomes a linear laser light. In the configuration shown in FIG. 2, the mirror G corresponds to the mirror 9. In the configuration shown in FIG. 2, a cylindrical lens H (not shown in FIG. 2) is arranged between the mirror 9 and the substrate (sample) 11.

An example in which a crystalline silicon film is formed on a glass substrate by laser light irradiation will be described below. First, a 10 cm square glass substrate (for example, a Corning 7959 glass substrate or a Corning 1737 glass substrate) is prepared. And on this glass substrate, TE
A silicon oxide film is formed to a thickness of 2000 ° by a plasma CVD method using OS as a raw material. This silicon oxide film functions as a base film for preventing impurities from diffusing into the semiconductor film from the glass substrate side.

Next, plasma CVD or reduced pressure thermal CVD
Amorphous silicon film (amorphous silicon film)
Is formed. The thickness of the amorphous silicon film is 500Å
And Of course, this thickness may be a required thickness.

Next, the substrate was immersed in aqueous ammonia at 70 ° C.
For 5 minutes to form a silicon oxide film on the surface of the amorphous silicon film. Further, a liquid phase Ni acetate is applied to the surface of the amorphous silicon film by spin coating. Ni element is
When the amorphous silicon film is crystallized, it functions as an element that promotes crystallization. It is necessary that the concentration of the Ni element remaining in the silicon film is 1 × 10 ^{16 to} 5 × 10 ¹⁹ cm ⁻³ . Specifically, Ni in a Ni acetate solution
The concentration is adjusted to adjust the Ni element introduced into the silicon film.

Although the Ni element was used here, in addition to the Ni element, Fe, Co, Ru, Rh, Pd, Os, Ir,
One or a plurality of elements selected from Pt, Cu, and Au can be used.

Next, hydrogen in the amorphous silicon film is desorbed by holding at a temperature of 450 ° C. for 1 hour in a nitrogen atmosphere. This is because a dangling bond is intentionally formed in the amorphous silicon film to lower the threshold energy at the time of subsequent crystallization. Then, the amorphous silicon film is crystallized by performing heat treatment at 550 ° C. for 4 hours in a nitrogen atmosphere. The temperature at which the crystallization was performed could be set to 550 ° C. due to the effect of the Ni element. When the heating temperature in the heat treatment is 550 ° C., Corning 7 having a strain point of 593 ° C.
Thermal damage to the 059 glass substrate is not a significant problem. Generally, this heat treatment needs to be performed at a temperature lower than the strain point of the glass substrate used.

Thus, a crystalline silicon film can be obtained on the glass substrate. Next, using the apparatus shown in FIG. 2, a KrF excimer laser (wavelength: 248 nm, pulse width: 25 ns) is irradiated to the crystalline silicon film.
By this laser light irradiation, crystallinity can be further improved.

As shown in this embodiment, when a crystalline silicon film is obtained by heating using a metal element which promotes the crystallization of silicon, although the obtained film has crystallinity, it has an amorphous inside. Contains significant quality components. Therefore, it is very effective to increase the crystallinity by laser light irradiation.

The laser beam is formed into a linear beam pattern using an optical system as shown in FIG. here,
A linear laser beam having a beam pattern of 125 mm × 1 mm at the irradiated portion is used.

The substrate (sample) on which the silicon film is formed is placed on the stage 10, and the entire surface is irradiated with laser light by moving the stage at a speed of 2 mm / s. The moving speed of the stage 10 needs to be experimentally determined as appropriate depending on the film quality and film forming conditions of the silicon film.

The irradiation conditions of the laser beam are as follows: first, 150-300 mJ / cm ² for preliminary irradiation, and 2
Two-stage irradiation in which irradiation of 00 to 400 mJ / cm ² is performed. The pulse width is 30 ns and the pulse number is 30 pulses
/ s. Here, the two-stage irradiation is performed in order to suppress deterioration of the uniformity of the film surface due to laser light irradiation as much as possible and to form a film having better crystallinity.

For conversion of laser energy (for example, energy conversion from preliminary irradiation to main irradiation), a combination of a neutral density filter is used. This saves time and effort compared to changing the energy of the laser oscillation device main body.

When irradiating a laser beam, the substrate temperature is 2
It is kept at 00 ° C. This is performed in order to moderate the rate of rise and fall of the substrate surface temperature due to the irradiation of the laser beam. In this embodiment, the substrate temperature is set to 200 ° C., but in an actual implementation, the optimal temperature for laser annealing is set to between 100 ° C. and 600 ° C. (the upper limit is limited by the strain point of the glass substrate). Choose. The atmosphere is not particularly controlled, and irradiation is performed in the air.

Thus, a crystalline silicon film formed on a glass substrate is obtained. Hereinafter, an example in which a thin film transistor used for an active matrix type liquid crystal display device is manufactured by using the laser annealing method described above will be described.

The active type liquid crystal display device comprises:
As shown in FIG. 4, the pixel portion and the peripheral circuit portion are generally roughly divided. In the pixel portion, pixel electrodes arranged in a matrix are arranged in a number of several hundreds × several hundreds, and in each of the pixels, at least one or more thin film transistors are arranged as switching elements. . The peripheral circuit is a circuit for driving a thin film transistor arranged in the pixel region, and is constituted by a shift register circuit and a buffer circuit (an output circuit having a low impedance) for flowing a current. Peripheral circuits are also usually composed of thin film transistors.

In this embodiment, both the thin film transistor arranged in the pixel circuit and the thin film transistor arranged in the peripheral circuit are aligned in a straight line,
It is arranged so that the direction connecting the drains and the linear direction of the linear laser light are matched.

FIG. 5 shows a pattern in which thin film transistors are actually arranged. In FIG. 5, reference numeral 51 denotes a pattern of a thin film transistor which can handle a large current arranged in a peripheral circuit. Reference numeral 52 denotes a pattern of a thin film transistor arranged in the pixel circuit. At the stage where laser light is irradiated, these thin film transistors are not formed. Therefore, in this case, it can be said that the patterns indicated by 51 and 52 indicate a region where the thin film transistor is finally formed.

FIG. 6 shows details of the thin film transistors 51 and 52 shown in FIG. As shown in FIG. 5, each thin film transistor is configured to be aligned on a straight line. Then, the line connecting the source / drain is made to match or substantially match the line direction of the linear laser light.

When annealing is performed by irradiating a linear laser beam as shown in FIG. 1, the effect of annealing in the linear direction of the beam pattern is excellent in uniformity. Therefore, by arranging the thin film transistors in a straight line in the longitudinal direction of the laser beam, the characteristics of the thin film transistors aligned in a straight line can be uniformed. Also, by aligning the line connecting the source / drain regions of each thin film transistor with the longitudinal direction of the linear beam,
Since carriers move in a region having uniform crystallinity between the drains, a structure with high mobility can be obtained. The fact that the crystallinity in the direction connecting the source and the drain is uniform means that the influence of the trap level due to the discontinuity of the crystal state is small in the source / drain direction. The effect of the trap level causes problems such as instability of operation and an increase in OFF current. Therefore, as described above, the effect of the trap level in the direction connecting the source and the drain can be reduced. This is useful for producing an element.

The laser irradiation method is as described above.
Two-stage irradiation.

[Embodiment 2] In this embodiment, a crystalline silicon film is obtained by irradiating an amorphous silicon film formed on a glass substrate with a laser beam. An example in which a thin film transistor which forms a pixel circuit portion and a peripheral circuit portion of a matrix liquid crystal display device is manufactured will be described.

First, a silicon oxide film is formed as a base film to a thickness of 3000 ° on a glass substrate by a sputtering method.
Next, the amorphous silicon film is subjected to plasma CVD or reduced pressure CV.
A film is formed to a thickness of 500 ° by Method D. In this state, heat treatment is performed in a nitrogen atmosphere at a temperature of 400 ° C. for one hour.
This heat treatment is performed to release hydrogen from the amorphous silicon film.

Next, as shown in FIG. 5, a linear excimer laser beam is applied to the amorphous silicon film to obtain a crystalline silicon film.
At this time, a linear laser beam is applied to a linear region where a thin film transistor is to be formed (of course, the thin film transistor must be arranged on a straight line).

After obtaining the crystalline silicon film, a thin film transistor is manufactured according to a thin film transistor manufacturing process. At this time, the thin film transistors are formed such that the thin film transistors are arranged in a state as shown in FIG. That is, the thin film transistor is placed in the line direction of the irradiated linear laser.
The thin film transistors are aligned in a straight line, and the line connecting the source and the drain of the thin film transistor is aligned with the line direction of the linear laser. Irradiation with laser light is performed on the entire surface while scanning (scanning) using the apparatus shown in FIG.

[Embodiment 3] In this embodiment, an example in which the invention disclosed in this specification is used in a step of activating source / drain regions required in a manufacturing process of a thin film transistor will be described.

In the case where a thin film transistor is formed using a crystalline silicon film, impurity ions for imparting one conductivity type to phosphorus or boron are ion-doped or plasma-doped in source / drain regions using a gate electrode as a mask and a self-alignment technique. When doping is performed by doping, the region becomes amorphous or remarkably deteriorates in crystallinity due to accelerated ion bombardment. Therefore, an annealing step for restoring the crystallinity of the source / drain regions is required. On the other hand, the doped impurity ions alone do not act as impurities for controlling the conductivity type. Therefore, an annealing step is required for the activation.

This embodiment shows an example in which the annealing step performed for the above purpose is performed by irradiating a laser beam. First, a thin film transistor using a crystalline silicon film in an arrangement shown in FIG. 5 is manufactured according to the method described in the first or second embodiment. After the impurity ions are implanted into the source / drain regions of these thin film transistors, linear laser light irradiation as shown in FIG. 5 is performed.

In this case, since the source / drain is located in the line direction of the linear laser, the annealing effect can be made uniform in one thin film transistor.

Further, since the direction in which the thin film transistors are arranged is the same as the line direction of the linear laser, the annealing effect on each thin film transistor can be made uniform.

In the above embodiment, an example in which a thin film transistor constituting an active matrix type liquid crystal display device is manufactured has been described. However, the invention disclosed in this specification can be used for steps in manufacturing various integrated circuits. The present invention is not limited to thin film transistors, and can be used for manufacturing various semiconductor devices, for example, thin film diodes and bipolar transistors.

[0078]

The effect of the invention disclosed in the present specification is to minimize the inconvenience caused by the non-uniformity of the characteristics of the semiconductor material caused in the step of irradiating the semiconductor material with the linear laser while scanning it in one direction. To keep it down. That is, for example, when forming a plurality of thin film devices using a semiconductor thin film such as a liquid crystal display device,
By arranging a plurality of thin film transistors on one straight line and irradiating linear laser light in accordance with the arrangement direction, the characteristics of each thin film transistor can be made uniform.

Further, by irradiating the linear laser with the direction to become the source / drain of the thin film transistor and the linear direction of the linear laser, the crystal state in the moving direction of the carrier is made uniform. Thus, a thin film transistor having high carrier mobility, low OFF current due to non-uniform crystal state, and stable characteristics can be obtained.

The invention disclosed in the present specification can be used for all laser processing processes used for processing semiconductor devices. In particular, when used for manufacturing a TFT liquid crystal panel using a thin film transistor as a semiconductor device, the characteristics of each thin film transistor can be made uniform, so that a liquid crystal display device with high image quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a refractive index of a silicon film irradiated with a linear laser beam.

FIG. 2 is a diagram showing an outline of a laser beam irradiation device.

FIG. 3 shows an optical system for forming a laser beam into a linear pattern.

FIG. 4 shows an outline of an active matrix type liquid crystal display device.

FIG. 5 is a diagram showing a pattern of a thin film transistor to be manufactured on a glass substrate and a state of irradiation of a linear laser beam to be irradiated.

FIG. 6 is a diagram showing a schematic pattern of a thin film transistor (TFT).

[Description of Signs] 2 Oscillator of laser light 5, 6, 7, 8, 9 Total reflection mirror 4 Optical system 11 Substrate (sample) 10 Stage and driving device 51 Thin film transistor for peripheral circuit 52 Thin film transistor for pixel circuit

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[Procedure amendment]

[Submission date] January 16, 2002 (2002.1.1
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 29/786 B23K 26/00 G // B23K 26/00 101: 40 H01L 29/78 618Z B23K 101: 40 627G F-term (reference) 2H092 JA28 MA30 4E068 AH01 DA00 5F052 AA01 AA02 AA11 AA17 AA18 BA07 BB07 DA02 DB02 DB03 EA15 FA06 FA19 JA01 5F110 AA01 AA06 AA30 BB02 CC02 DD02 DD07 DD13 GG02 GG12J01 GG02 GG12J01 PP05 PP06 PP10 PP13 PP23 PP24 PP29 PP34 PP35 QQ11

Claims (1)

[Claims] 1. A plurality of first thin film transistors formed on a substrate having an insulating surface and arranged in a first direction, and a plurality of first thin film transistors arranged in a second direction perpendicular to the first direction. A semiconductor device having at least two thin film transistors; the first and second thin film transistors each being formed on an insulating surface and having a channel forming region, a source region, and a drain region; a gate insulating film; , A gate electrode, and the channel forming region is arranged so that carriers flow in a direction parallel to the first direction, and a variation in a refractive index of the crystalline semiconductor film in the plurality of second thin film transistors. Wherein the dispersion of the crystalline semiconductor film in the plurality of first thin film transistors is at least twice as large as the variation in the refractive index thereof. Body device.