JPH0851077A - Manufacturing method and device of polycrystalline semiconductor, manufacture of image display device - Google Patents

Abstract

PURPOSE:To provide a method of easily manufacturing a polycrystalline semiconductor which is uniform in crystallinity, excellent in properties such as carrier mobility and the like, and high in evenness in a short time, wherein the polycrystalline semiconductor is formed by irradiating a semiconductor thin film with a laser beam, and the semiconductor thin film can be easily dehydrogenated. CONSTITUTION:A semiconductor thin film 2 is crystallized into a polycrystalline semiconductor as irradiated with a laser beam, wherein a region of the semiconductor thin film 2 located in an irradiation area of a laser beam is preheated with a preheating means 20 for dehydrogenation before a laser irradiation means 10 irradiates the semiconductor thin film 2 with a laser beam, and a region of the semiconductor thin film irradiated with a laser beam is post-heated with a post-heating means, if necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a polycrystalline semiconductor, a method of manufacturing an image display device, and a method for crystallizing various semiconductor thin films such as amorphous to obtain a polycrystalline semiconductor having good characteristics. It relates to a manufacturing apparatus used for carrying out the invention.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor material for an image display device such as a liquid crystal display, a plasma display or an EL, or a driving element of a contact image sensor,
In addition to a single crystal semiconductor, a semiconductor thin film formed on a substrate such as glass is used. Thus, a semiconductor thin film formed on a substrate can be manufactured at low cost and can have a large area. It has the characteristics of

In the past, as such a semiconductor thin film, one generally made of an amorphous semiconductor such as amorphous silicon has been mainly used. But,
In the case where the semiconductor thin film is made of an amorphous semiconductor, the mobility of carriers in the semiconductor is generally slow, so that the field of application of such a semiconductor thin film is limited.

Therefore, in recent years, active research has been conducted on a semiconductor thin film using a polycrystalline semiconductor such as polycrystalline silicon in place of the above amorphous semiconductor. That is, a semiconductor thin film made of a polycrystalline semiconductor has much higher carrier mobility than a thin film made of an amorphous semiconductor.

Therefore, when a semiconductor thin film made of a polycrystalline semiconductor is used, for example, conventionally, an integrated circuit formed on a silicon wafer is connected to a peripheral drive circuit by wire bonding or the like. , It can be integrated as a thin film drive circuit on the same substrate as the integrated circuit, there is an advantage that the manufacturing process such as wire bonding can be omitted to reduce the cost, and such a drive circuit can be made compact. It was

As a method of forming a semiconductor thin film made of the above-mentioned polycrystalline semiconductor on a substrate, a method of directly forming a polycrystalline semiconductor film on the substrate by a CVD method or the like has been conventionally used, After a semiconductor thin film such as an amorphous film is formed on a substrate, the semiconductor thin film is annealed in an electric furnace at a temperature of about 600 ° C. for several tens of hours to perform solid phase growth of crystals, or a method of forming a crystal on the substrate is used. A method such as a laser annealing method has been used in which a semiconductor thin film such as an amorphous film is irradiated with laser light to locally melt and crystallize the semiconductor thin film.

Here, when a polycrystalline semiconductor film is directly formed by the CVD method or the like, or when a polycrystalline semiconductor film is manufactured by annealing a semiconductor thin film such as an amorphous material in an electric furnace, both are generally 600. Since an inexpensive substrate such as a glass plate is used as the substrate because it is performed at a temperature of about ℃, an expensive substrate with excellent heat resistance such as quartz must be used for the substrate because the substrate may shrink due to heat. However, there is a problem that the manufacturing cost is high, and when a polycrystalline semiconductor is manufactured as described above, it is generally difficult to obtain a polycrystalline semiconductor with good characteristics, and it takes a lot of time to manufacture the polycrystalline semiconductor. However, there were problems such as poor productivity.

On the other hand, in the case of the laser annealing method for producing a polycrystalline semiconductor by irradiating a semiconductor thin film of amorphous or the like with a laser beam, the surface of the semiconductor of amorphous or the like is melted in an extremely short time to crystallize. In addition to the advantages that it is possible to reduce the thermal effect on the substrate, the polycrystalline semiconductor obtained has excellent crystallinity, and a polycrystalline semiconductor having a larger area can be easily formed. Has become the subject of much research into the production of polycrystalline semiconductors by such laser annealing method.

Here, in manufacturing a polycrystalline semiconductor by the laser annealing method, generally, as shown in FIG. 1, plasma CVD is performed on an insulating substrate 1 such as a glass plate.
After the amorphous semiconductor thin film 2 is formed by a sputtering method, a thermal CVD method, a sputtering method, or the like, the amorphous semiconductor thin film 2 is irradiated with a short-wavelength pulsed laser light such as an excimer laser from the laser device 3, The crystalline semiconductor thin film 2 is melted and crystallized to manufacture a polycrystalline semiconductor.

However, when the amorphous semiconductor thin film 2 is formed on the insulating substrate 1 as described above, the formed amorphous semiconductor thin film 2 often contains hydrogen, In particular, a large amount of hydrogen is contained in the amorphous semiconductor thin film 2 formed at a low temperature by the plasma CVD method, and thus the amorphous semiconductor thin film 2 containing hydrogen is irradiated with laser light. When a polycrystalline semiconductor is manufactured by using the above method, there is a problem that the formed polycrystalline semiconductor film is roughened and the characteristics of the obtained polycrystalline semiconductor are deteriorated.

Therefore, conventionally, in order to prevent film roughness in the formed polycrystalline semiconductor, the insulating substrate 1 is used.
After forming the amorphous semiconductor thin film 2 thereon, it was heated in an electric furnace at a temperature of 450 to 550 ° C. for about 1 hour to perform dehydrogenation treatment. However, when the dehydrogenation treatment is performed separately from the crystallization of the semiconductor thin film 2 by the irradiation of the laser light as described above, there is a problem that the dehydrogenation treatment takes time and the productivity of the polycrystalline semiconductor is deteriorated. It was

Further, in irradiating the amorphous semiconductor thin film 2 formed on the insulating substrate 1 with laser light to crystallize it as described above, in the prior art, as shown in FIG. The amorphous semiconductor thin film 2 is subjected to raster scanning in the X direction and the Y direction while irradiating the amorphous semiconductor thin film 2 with a pulsed laser light of a short wavelength which is processed into a rectangular shape of several mm square through a system or the like. The amorphous semiconductor thin film 2 is crystallized to produce a polycrystalline semiconductor on the insulating substrate 1.

However, in this way, the rectangular laser lights are successively moved in the X direction and the Y direction while being overlapped, and the laser light is irradiated.
In order to crystallize a wide range of the amorphous semiconductor thin film 2, it is necessary to irradiate a large number of laser beams, and it takes a long time for the scanning to reduce the productivity, and the laser beams are repeatedly irradiated. There is also a problem that the number of parts to be irradiated is increased, the crystal state is different between the part where the laser light is overlapped and the other part, and the crystallinity becomes non-uniform to deteriorate the characteristics of the polycrystalline semiconductor.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to solve various problems as described above when a polycrystalline semiconductor is manufactured by irradiating a semiconductor thin film such as an amorphous film with laser light. It is what

That is, according to the present invention, when a polycrystalline semiconductor is manufactured by irradiating a semiconductor thin film such as an amorphous film with a laser beam, dehydrogenation of the amorphous semiconductor film can be easily performed. In addition to making it possible to easily obtain a polycrystalline semiconductor having no roughness, it is possible to easily manufacture a polycrystalline semiconductor having a uniform crystal state and excellent characteristics such as carrier mobility in a short time. It is an object to improve the characteristics of a display device.

[0016]

In the method for producing a polycrystalline semiconductor according to the present invention, in order to solve the above-mentioned problems, a semiconductor thin film is irradiated with laser light to crystallize the semiconductor thin film, and thus the polycrystalline semiconductor is crystallized. Prior to the irradiation of the laser light, a pre-heating means for heating the semiconductor thin film in the irradiation region of the laser light was provided in the manufacture of.

Here, as the semiconductor thin film to be crystallized as described above, for example, a semiconductor thin film such as amorphous, microcrystalline, or polycrystalline having poor characteristics can be used, and the laser for irradiating this semiconductor thin film can be used. As the light, a known laser light or the like which has been generally used for laser annealing can be used, for example, F ₂ , ArF, KrF, X.
Excimer laser such as eCl, XeF, copper vapor laser, A
The second and third harmonics of r laser and YAG laser can be used.

When the semiconductor thin film is irradiated with the laser light as described above, the laser light irradiation region is processed into a desired shape, for example, by linearly processing the laser light with a beam expander. The semiconductor thin film is irradiated, and the semiconductor thin film is crystallized by scanning while irradiating the semiconductor thin film with the laser beam having such a desired shape.

When the semiconductor thin film in the laser light irradiation region is heated by the preheating means prior to irradiating the semiconductor thin film with the laser light as described above, the semiconductor thin film is linearly formed as the preheating means. Use a heater that heats the semiconductor thin film in a shape corresponding to the irradiation area of the laser light, such as using a lamp heater to heat, and this preheating means, prior to the irradiation of the laser light, with the scanning direction of the laser light. Scan in the same direction.

Further, in the method for manufacturing a polycrystalline semiconductor according to the present invention, the semiconductor thin film in the laser light irradiation region is heated by the preheating means prior to the laser light irradiation as described above, and the preheating is performed in this manner. After irradiating the semiconductor thin film thus formed with the laser beam, the semiconductor thin film in the region irradiated with the laser beam is further post-heated by the post-heating unit, if necessary.

Here, as the above-mentioned post-heating means, like the above-mentioned pre-heating means, a linear heater is used to heat the semiconductor thin film in a shape corresponding to the laser light irradiation region. The same can be used, and the post-heating means is scanned in the same direction as the scanning direction of the laser light as in the case of the pre-heating means, and the semiconductor in the region irradiated with the laser light as described above is used. The thin film can be post-heated. Then, the semiconductor thin film formed for the image display device was polycrystallized by the above method.

When the semiconductor thin film is scanned by the pre-heating means, the laser beam or the post-heating means as described above, the semiconductor thin film may be scanned by moving the pre-heating means, the laser beam or the post-heating means. It is also possible to move this side to scan the pre-heating means, the laser beam, and the post-heating means.

Further, in the image display device manufacturing apparatus according to the present invention, since the above-described manufacturing method is carried out, the semiconductor thin film is processed into a desired shape by processing the laser light irradiation region into a desired shape. A laser irradiation unit for irradiating the shaped laser beam and a pre-heating unit for heating the semiconductor thin film in a shape corresponding to the irradiation region of the laser beam prior to the irradiation of the laser beam are provided, and if necessary. Then, the post-heating means for post-heating the semiconductor thin film in the region irradiated with the laser beam is provided. The post-heating means is preferably located immediately below or immediately after the laser light irradiation position.

[0024]

According to the present invention, when the semiconductor thin film is irradiated with laser light to crystallize the semiconductor thin film to manufacture a polycrystalline semiconductor, the preheating means is provided as described above, and the laser light is emitted by the preheating means. Since the semiconductor thin film in the laser light irradiation region is heated prior to the irradiation with 1, the semiconductor thin film is dehydrogenated by the heating by the preheating means.

Since the semiconductor thin film thus dehydrogenated is irradiated with laser light from the laser irradiation means subsequently to crystallize the semiconductor thin film, dehydration of the semiconductor thin film as in the prior art is performed. It is not necessary to separately perform the crystallization process and the crystallization process by irradiation with laser light, and the polycrystalline semiconductor can be easily manufactured by a series of operations.

Further, in processing the laser light irradiation region into a desired shape, the laser light is linearly processed by a beam expander, and the semiconductor thin film is irradiated with the laser light thus linearized. While scanning,
When the semiconductor thin film is sequentially crystallized by the linear laser light, the semiconductor thin film is formed on the semiconductor thin film while raster-scanning in the X and Y directions so that the rectangular laser light of several mm square overlaps to some extent. Scanning of the laser light is less than that of the conventional method in which the semiconductor thin film is crystallized by irradiation, and the semiconductor thin film can be easily crystallized. In addition, the portion where the laser light is overlapped and irradiated is smaller than that of the conventional one, the nonuniformity of the crystalline state in the crystallized semiconductor thin film is reduced, and a polycrystalline semiconductor with good characteristics can be obtained. .

Further, as described above, prior to the irradiation of the laser beam, the semiconductor thin film in the irradiation region of the laser beam is heated by the preheating means, and after the semiconductor film preheated in this way is irradiated with the laser beam. When the semiconductor thin film in the region irradiated with the laser light is post-heated by the post-heating means, the solidification rate of the crystal in the region irradiated with the laser light becomes slow, and the grain size of the crystal formed becomes large, A polycrystalline semiconductor having even more excellent characteristics such as carrier mobility will be obtained, and the crystalline state in the portion where laser light is overlapped and irradiated is more uniform, resulting in a uniform polycrystalline semiconductor with good characteristics. You will get it.

When the semiconductor thin film formed for the image display device is polycrystallized as described above, the size of the thin film transistor for switching in the pixel portion can be reduced, and the aperture ratio of the pixel can be reduced. Can be significantly increased. In addition, since high field-effect mobility can be obtained in the driver portion, the driver portion can be formed integrally with the pixel portion, and the cost and size of the image display device can be reduced.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

Example 1 In this example, FIG.
As shown in FIG. 1, an amorphous silicon film 2 having a film thickness of 100 to 1000 Å is formed as a semiconductor thin film 2 on an insulating substrate 1 such as glass by a plasma CVD method under the conditions shown in Table 1 below.
Was formed. Here, the amorphous silicon film 2 thus formed contained hydrogen at about 10 atomic%. The method for forming the amorphous silicon film 2 is not limited to the plasma CVD method described above, but may be a thermal CVD method, a sputtering method, or the like.

[0031]

[Table 1]

On the other hand, as the laser light for irradiating the amorphous silicon film 2 formed as described above, an ArF excimer laser having a wavelength of about 193 nm is used in this embodiment.

In irradiating the amorphous silicon film 2 with the laser light, in this embodiment, the laser irradiation means 10 processes the laser light irradiation region into a desired shape. And then Fig. 4
(A), the laser beam emitted from the laser device 11 is guided to the beam homogenizer 12, and the intensity of the laser beam is homogenized by the beam homogenizer 12, and then the laser beam is beamed. The laser light is guided to the expander 13, and the laser light is expanded in one direction by the beam expander 13 to have a length of 30 to 360 mm in the longitudinal direction and a width of 0.
The top hat having a size of 1 to 3.0 mm was irradiated with a linear laser beam. The size of the emitted beam depends on the output of the emitted laser light. For example, the output of the emitted laser light is 400 mJ /
In case of cm ² , the size of the irradiation beam is 0.6
mm × 60 mm or 0.3 mm × 120 mm.

Further, as described above, before the laser irradiation means 10 irradiates the amorphous silicon film 2 with laser light, the pre-heating means 20 for heating the amorphous silicon film 2 in the laser light irradiation region. As a result, in this embodiment, the lamp heater 20 that linearly heats the amorphous silicon film 2 is used in correspondence with the laser light irradiation region.

Here, in this embodiment, as shown in FIGS. 5 and 6, the linear laser as described above is applied to the insulating substrate 1 on which the amorphous silicon film 2 is formed. Amorphous silicon film 2 is used as laser irradiation means 10 for irradiating light.
Is arranged on the surface side on which the amorphous silicon film 2 is formed, while the linear lamp heater 20 is arranged parallel to the linear laser beam on the side opposite to the surface on which the amorphous silicon film 2 is formed. Then, it is arranged at a position downstream of the laser irradiation means 10 in the scanning direction.

Further, in this embodiment, the laser irradiation means 10 and the lamp heater 20 arranged as described above are used.
In the same direction, first, the amorphous silicon film 2 provided on the insulating substrate 1 is linearly heated by the lamp heater 20 to perform dehydrogenation treatment in sequence, and The amorphous silicon film 2 in the dehydrogenated portion is sequentially irradiated with linear laser light from the laser irradiation means 10 while slightly overlapping in the scanning direction,
The amorphous silicon film 2 was linearly melted and crystallized in order.

In this way, the amorphous silicon film 2 is sequentially dehydrogenated by scanning the amorphous silicon film 2 once with the laser irradiation means 10 and the lamp heater 20 in one direction. The amorphous silicon film 2 does not need to be separately dehydrogenated as in the conventional case, and a rectangular shape is formed. Compared with the conventional one in which the amorphous silicon film 2 is irradiated with the laser light to be crystallized while being raster-scanned in the X and Y directions so that the laser light overlaps with each other to some extent, the scanning of the laser light is less,
The amorphous silicon film 2 can be easily crystallized, and the portion of the laser light which is overlapped and irradiated is reduced, so that the non-uniformity of the crystal state in the crystallized polycrystalline silicon film is reduced and the characteristics are excellent. A polycrystalline silicon film was obtained.

Here, in this embodiment, the amorphous silicon film 2 is linearly heated by the lamp heater 20 to be dehydrogenated as described above, and is also dehydrogenated as described above. When the amorphous silicon film 2 is crystallized by irradiating it with laser light, the lamp heater 20
The temperature of the amorphous silicon film 2 is 400 to 600 ° C.
The amorphous silicon film 2 thus heated and dehydrogenated is irradiated with laser light having an energy density of 100 to 400 mJ / cm ² .

Then, as described above, the amorphous silicon film 2
When heated to 400 to 600 ° C., the amorphous silicon film 2 is heated to about 10 atomic as described above.
% Of contained hydrogen is about 0.5 atomic% or less, and the amorphous silicon film 2 thus dehydrogenated.
When the film was irradiated with laser light and crystallized, a polycrystalline silicon film with less film roughness was obtained.

Here, as described above, the amorphous silicon film 2 is used.
It has been clarified that when the amorphous silicon film 2 in which hydrogen is dehydrogenated to about 0.5 atomic% is irradiated with laser light to be crystallized, the film roughness is reduced. Therefore, the energy density of the amorphous silicon film 2 that has been dehydrogenated as described above and the amorphous silicon film 2 that has not been dehydrogenated are 100 to 100
Crystallization is performed by irradiating with a laser beam of 400 mJ / cm ² , and the surface roughness (Ra) of each crystallized film is measured to check the film roughness state of each film, and the surface roughness of the dehydrogenated film is measured. The results of the surface roughness are shown by □, and the results of the surface roughness of those not subjected to the dehydrogenation treatment are shown by ◯, and they are shown in FIG. 7. As a result, the amorphous silicon film 2 that has undergone dehydrogenation treatment has less film roughness than the one that has not undergone dehydrogenation treatment, and in particular as the energy density of the laser light to be irradiated increases. The difference was noticeable.

In this embodiment, the laser irradiation means 10 is applied to the insulating substrate 1 on which the amorphous silicon film 2 is formed on the surface side on which the amorphous silicon film 2 is formed. The heater 20 is arranged on the opposite side of the surface on which the amorphous silicon film 2 is formed, and the laser irradiating means 10 and the lamp heater 20 are moved for scanning, but as shown in FIG. 20 is a laser irradiation means 1
0, the amorphous silicon film 2 is arranged on the side where the amorphous silicon film 2 is provided, and the insulating substrate 1 provided with the amorphous silicon film 2 is moved as shown in FIG. The irradiation means 10 and the lamp heater 20 may scan the amorphous silicon film 2.

(Embodiment 2) Also in this embodiment, as shown in FIG. 9, as in the case of the above-mentioned embodiment 1,
The laser irradiation means 10 and the lamp heater 20 are arranged on the insulating substrate 1 on which the amorphous silicon film 2 is formed,
The laser irradiation means 10 and the lamp heater 20 are moved to perform scanning.

In this embodiment, as the post-heating means 30 for post-heating the amorphous silicon film 2 in the region irradiated with the laser beam by the laser irradiation means 10, as shown in FIG. , The preheating means 2
Similar to 0, a lamp heater 30 that linearly heats the amorphous silicon film 2 is used, and the lamp heater 30 is linearly formed on the side opposite to the surface on which the amorphous silicon film 2 is formed. It was arranged at a position upstream of the laser irradiation means 10 in the scanning direction so as to be parallel to the laser light.

In the present embodiment, the laser irradiation means 10 and the lamp heaters 20 and 30 arranged as described above are caused to scan in the same direction, and first, the lamp heater used as the preheating means 20. The amorphous silicon film 2 provided on the insulating substrate 1 by 20 is linearly heated to sequentially perform dehydrogenation treatment, and the amorphous silicon film in the portion thus dehydrogenation treated. To 2,
The linear laser light is sequentially irradiated from the laser irradiation means 10 while slightly overlapping it in the scanning direction to melt the amorphous silicon film 2 linearly in order. The irradiated portion is linearly post-heated at a temperature of 200 to 600 ° C. by the lamp heater 30 used as the post-heating means 30 to slow the solidification rate of the crystal in the melted region as described above. And gradually crystallized.

When the portion irradiated with the laser beam is post-heated in this way to slow the solidification rate of the crystal and gradually crystallize it, in addition to the case of the first embodiment, The grain size becomes large, and a polycrystalline silicon film having more excellent characteristics such as carrier mobility is obtained, and the non-uniformity of the crystalline state in the portion where laser light is repeatedly irradiated is corrected, and as described above, A polycrystalline silicon film having excellent characteristics such as mobility and uniform characteristics was obtained.

Here, the obtained polycrystalline silicon film is irradiated with laser light in duplicate when the portion irradiated with laser light as described above is post-heated and when it is not post-heated. The half-width [cm ^-1 ] was determined by the well-known Raman spectroscopy in order to investigate the crystalline state in the exposed portion.
Was measured, and the result in the case of post-heating is shown by ◯, and the result in the case of not being post-heated is shown by □, and it is shown in FIG.
As a result, in the case of post-heating, the above-mentioned full width at half maximum is smaller than that in the case where no postheating is performed, and the fluctuation of this full width at half maximum is also small, resulting in a uniform crystalline state. A crystalline silicon film was obtained.

Further, each thin film transistor using a polycrystalline silicon film obtained by post-heating and crystallizing a portion irradiated with laser light as described above and a polycrystalline silicon film obtained by crystallizing without heating In, the field-effect mobility was measured in the portion irradiated with the laser light in duplicate, and the result in the case of using the post-heated polycrystalline silicon film was ○, and the non-post-heated polycrystalline silicon film was used. The results in the case are shown by □ and are shown in FIG. 11. As a result, the one using the post-heated polycrystalline silicon film has less variation in field-effect mobility than the one using the non-post-heated polycrystalline silicon film, and has uniform characteristics. A polycrystalline silicon film was obtained.

As described above, when the post-heating treatment is performed after the laser irradiation to increase the crystal grain size, the position of the heater for the post-heating is directly below the laser irradiation position on the back surface side of the substrate or immediately after that. Is desirable. Further, the heating temperature is set so as not to affect the glass substrate. Specifically, it is desirable that the temperature of the interface between the amorphous silicon film and the substrate be raised to about 100 ° C. to 450 ° C. by post-heating, and the temperature of the heater is adjusted so that it becomes so. With such a temperature, the speed at which the silicon melted by laser irradiation solidifies can be reduced, and the obtained crystal grain size can be increased. By using this polycrystalline film, a high speed TFT circuit can be formed as compared with the case without post-heating.

In each of the above embodiments, the semiconductor thin film 2 to be crystallized is made of amorphous silicon. However, the semiconductor thin film 2 made of other amorphous semiconductor, microcrystal, or the like. It is also possible to use a semiconductor made of a polycrystalline semiconductor having poor characteristics, and it is also possible to change the type of laser light to be irradiated, irradiation conditions, and the like.

Further, in order to make the intensity of the laser beam applied to the semiconductor thin film 2 more uniform, as shown in FIG. 12, next to the beam expander 13, the length and width of the laser beam are larger than those of the laser beam. Small linear slit 1
4a is provided with the mask 14 and the slit 14
The peripheral portion of the laser light expanded as described above through a is removed, or the laser light that has passed through the slit 14a is imaged by the imaging lens 15 to form the semiconductor thin film 2
It is also possible to make it irradiate.

FIG. 13 shows a TFT (Thin Film).
FIG. 2A is a cross-sectional view showing the structure of a transistor (Transistor), in which FIG.
A drain (Drain) structure TFT and a self-aligned structure TFT are shown in FIG.

The LDD structure TFT shown in FIG. 9A will be briefly described. A base insulating film 102 is formed on the substrate 101, and an island-shaped polycrystalline semiconductor thin film 103 is formed on the base insulating film 102. This polycrystalline semiconductor thin film 103 can be obtained by polycrystallizing an amorphous semiconductor film as a starting film by the method of the present invention described above. A gate electrode 105 is formed on the polycrystalline semiconductor film 103 with a gate insulating film 104 interposed therebetween.
The polycrystalline semiconductor film 103 located below the gate electrode 105 becomes a channel region. Then, on both sides of this channel region, an n ⁺ type source region and a drain region are formed via n ⁻ type low-doped regions, respectively. Electrodes 106 and 106 are respectively connected to the source region and the drain region through contact holes.

The TFT having the self-aligned structure shown in FIG. 7B will be briefly described. A base insulating film 102 is formed on the substrate 101, and an island-shaped polycrystalline semiconductor thin film 103 is formed on the base insulating film 102. This polycrystalline semiconductor thin film 103 can be obtained by polycrystallizing an amorphous semiconductor film as a starting film by the method of the present invention described above. A gate electrode 105 is formed on the polycrystalline semiconductor film 103 with a gate insulating film 104 interposed therebetween. The polycrystalline semiconductor film 103 located below the gate electrode 105 becomes a channel region. This channel region is obtained by doping impurities using the gate electrode 105 as a mask. And, unlike the LDD structure, on both sides of the channel region, due to impurity doping using the gate electrode as a mask,
The n ⁺ type source region and the drain region are formed in self alignment without the n ⁻ type lightly doped region. Electrodes 106 and 106 are respectively connected to the source region and the drain region through contact holes.

By the way, the active matrix liquid crystal panel comprises a pixel portion 201 and a driver portion 202, as shown in FIG.
Although T can be used, the LDD structure shown in FIG. 13A is suitable for the switching TFTs 201 a ... Used in the pixel portion 201, while the LDD structure shown in FIG. As the TFT to be used, the self-aligned structure shown in FIG. 6B is preferable from the viewpoint of less restriction on the off current and rather prevention of voltage breakdown.

Both the semiconductor film that will form the pixel portion 201 and the semiconductor film that will form the driver portion 202 will be high quality and uniform polycrystalline semiconductor films using the method of the present invention. As a result, the following advantages can be obtained. That is, in the pixel portion 201, the TFT
The size can be reduced, and the aperture ratio of the pixel can be significantly increased. In addition, the driver unit 202
In the above, since the high field effect mobility can be obtained, the driver unit 202 can be formed integrally with the pixel unit 201, and the cost and size of the liquid crystal panel can be reduced. In other words, in the pixel portion 201, the crystallinity of the polycrystalline semiconductor of the channel is required to be uniform in order to make the write current uniform.
In order to realize a high-speed circuit, uniform crystallinity is required, but the method of the present invention makes it possible to meet all of these requirements.

On the other hand, the need for polycrystallization is greater in the driver section 202 than in the pixel section 201.
The semiconductor film to be the structure of (1) may be left as an amorphous semiconductor film, and only the driver section 202 may be made of a polycrystalline semiconductor film using the method of the present invention. In this case, in the driver unit 202, the above advantages can be obtained, and energy and time for irradiating the semiconductor film on which the pixel unit 201 is formed with a laser can be saved. In particular, when seed-shaped laser light is used, only the driver portion 202 can be selectively polycrystallized in an extremely short time.

Although the liquid crystal panel has been described in this embodiment, the polycrystalline semiconductor manufactured by the method of the present invention can be used as a driving element of another image display device such as a plasma display or an EL.

[0058]

As described above in detail, in the present invention, when a semiconductor thin film is irradiated with laser light to crystallize the semiconductor thin film to manufacture a polycrystalline semiconductor, prior to irradiation with this laser light, The semiconductor thin film in the laser light irradiation region is heated by the preheating means, whereby the semiconductor thin film in the laser light irradiation region is dehydrogenated, and the portion of the semiconductor thin film thus dehydrogenated is followed by the laser. Since the semiconductor thin film is crystallized by irradiating laser light from the irradiation means, it is not necessary to separately perform dehydrogenation treatment and crystallization treatment by laser light irradiation on the semiconductor thin film, unlike the conventional case. The dehydrogenation treatment and the crystallization treatment on the thin film can be performed by a series of operations, and the polycrystalline semiconductor can be efficiently and easily manufactured.

Further, in the present invention, when the irradiation region of the laser light for irradiating the semiconductor thin film is processed into a desired shape, the laser light is processed into a linear shape by a beam expander, and thus, into a linear shape. When the semiconductor thin film is scanned by irradiating the semiconductor thin film with the changed laser light and the semiconductor thin films are sequentially crystallized by the linear laser light, the rectangular laser light overlaps to some extent in the X direction. Also, compared with the conventional one in which a semiconductor thin film is irradiated while being raster-scanned in the Y direction to crystallize the semiconductor thin film, less laser light scanning is required, and a polycrystalline semiconductor can be manufactured more efficiently and easily. In addition, the portion where the laser light is overlapped and irradiated is smaller than that of the conventional one, and the crystal state of the crystallized semiconductor thin film is uneven. There decreased and so has characteristics good polycrystalline semiconductor with a certain uniformity obtained.

Further, as described above, before the laser light irradiation, the semiconductor thin film in the laser light irradiation region is heated by the preheating means, and after the semiconductor thin film thus preheated is irradiated with the laser light. When the semiconductor thin film in the region irradiated with the laser light is post-heated by the post-heating means, the solidification rate of the crystal in the region irradiated with the laser light becomes slow, and the grain size of the crystal formed becomes large, A polycrystalline semiconductor having more excellent characteristics such as carrier mobility can be obtained, and the crystalline state in a portion where laser light is overlapped and irradiated is more uniform, so that a uniform polycrystalline semiconductor with better characteristics can be obtained. It became so.

When the semiconductor thin film formed for the image display device is polycrystallized as described above, the size of the thin film transistor for switching in the pixel portion can be reduced, and the aperture ratio of the pixel can be reduced. Can be significantly increased. In addition, since high field-effect mobility can be obtained in the driver portion, the driver portion can be formed integrally with the pixel portion, and the cost and size of the image display device can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic side view of a conventional example in which an amorphous semiconductor thin film formed on a substrate is irradiated with laser light to manufacture a polycrystalline semiconductor.

[FIG. 2] X while overlapping rectangular laser beams to some extent
FIG. 7 is a schematic plan view of a conventional example in which an amorphous semiconductor thin film is irradiated with a raster scan in the Y direction and the Y direction to crystallize the amorphous semiconductor thin film to manufacture a polycrystalline semiconductor.

FIG. 3 is a schematic side view showing a state in which an amorphous silicon film is formed on an insulating substrate in the example of the present invention.

FIG. 4 is a diagram showing a laser irradiation means used for irradiating a linear laser beam and a plane shape of laser light emitted from the laser irradiation means in the example of the invention.

FIG. 5 is a schematic view of a first embodiment of the present invention in which a laser irradiation means is arranged on the surface side of an amorphous silicon film formed on an insulating substrate, while a lamp heater is arranged as a preheating means on the opposite surface side. It is a schematic side view which showed the state.

FIG. 6 is a schematic diagram showing a polycrystalline semiconductor according to the first embodiment of the present invention, in which the amorphous silicon film formed on the insulating substrate is dehydrogenated and crystallized by scanning the laser irradiation means and the lamp heater. It is a schematic diagram showing a state of manufacturing.

FIG. 7 is a polycrystalline silicon film formed by dehydrogenating an amorphous silicon film formed on an insulating substrate and not dehydrogenating it in Example 1 of the present invention. It is an explanatory view showing how the surface of the changes.

FIG. 8 is a schematic view showing a first embodiment of the present invention in which a lamp heater and a laser irradiation unit are provided on the same surface side of an amorphous silicon film, and an insulating substrate on which the amorphous silicon film is formed is moved to perform laser irradiation. It is the figure which showed the modification which scans a means and a lamp heater.

FIG. 9 is a schematic view of Embodiment 2 of the present invention in which a lamp heater is provided as a post-heating means in addition to a laser irradiation means and a lamp heater as a pre-heating means, and the laser irradiation means and each lamp heater are scanned to make a polycrystalline semiconductor. It is a schematic diagram showing a state of manufacturing.

FIG. 10 shows a polycrystalline silicon film which is post-heated by a lamp heater and a polycrystalline silicon film which is not post-heated by a lamp heater in Example 2 of the present invention in a portion where laser light is overlapped and irradiated. It is the figure which showed the difference of a crystalline state.

FIG. 11 shows that, in Example 2 of the present invention, a thin film transistor using a polycrystalline silicon film that was post-heated by a lamp heater and a thin film transistor using a polycrystalline silicon film that was not post-heated had overlapping laser beams. It is the figure which showed the difference of the field effect mobility in the irradiated part.

FIG. 12 is a view showing a modified example of a laser irradiation means used for irradiating a linear laser beam in the embodiment of the present invention.

FIG. 13A is a vertical side view showing a TFT having an LDD structure, and FIG. 13B is a self-aligned T structure.
It is a vertical side view showing FT.

FIG. 14 is a structural explanatory view of an active matrix liquid crystal panel.

[Explanation of symbols]

 1 substrate 2 semiconductor thin film (amorphous silicon film) 10 laser irradiation means 11 laser device 13 beam expander 20 pre-heating means (lamp heater) 30 post-heating means (lamp heater)

Claims (14)

[Claims] 1. A method for manufacturing a polycrystalline semiconductor, comprising irradiating a semiconductor thin film with laser light to crystallize the semiconductor thin film, prior to heating the semiconductor thin film in a laser light irradiation region prior to the laser light irradiation. A method of manufacturing a polycrystalline semiconductor, characterized by comprising heating means. 2. A method for producing a polycrystalline semiconductor, wherein a region irradiated with laser light is processed to have a desired shape, and the semiconductor thin film is irradiated with laser light having a desired shape to crystallize the semiconductor thin film. Prior to irradiation with the laser light,
A method for manufacturing a polycrystalline semiconductor, characterized in that a preheating means for heating a semiconductor thin film in a laser light irradiation region is provided. 3. A method for producing a polycrystalline semiconductor, which comprises crystallizing a semiconductor thin film by processing a laser light irradiation region into a desired shape and irradiating the semiconductor thin film with the laser light having the desired shape, Prior to irradiation with the laser light,
A method for producing a polycrystalline semiconductor, characterized in that preheating means for heating a semiconductor thin film in a shape corresponding to a laser light irradiation region is provided. 4. A method for producing a polycrystalline semiconductor, which comprises crystallizing a semiconductor thin film by processing a laser light irradiation region into a desired shape and scanning the semiconductor thin film while irradiating the semiconductor thin film with the laser light having the desired shape. In the method, prior to the laser light irradiation, a preheating means for heating the semiconductor thin film in a shape corresponding to the laser light irradiation region is provided. 5. A method for producing a polycrystalline semiconductor, in which a semiconductor thin film is crystallized by processing a laser light irradiation region into a desired shape and scanning the semiconductor thin film while irradiating the semiconductor thin film with the laser light having the desired shape. In the method, prior to the irradiation of the laser light, a preheating means for heating the semiconductor thin film in a shape corresponding to the irradiation area of the laser light is provided, and the preheating means is scanned in the same direction as the scanning direction of the laser light. A method for manufacturing a polycrystalline semiconductor, characterized in that 6. The method for producing a polycrystalline semiconductor according to claim 1, wherein the laser light irradiation region has a linear shape. 7. The method for producing a polycrystalline semiconductor according to claim 6, wherein the laser light is processed into a linear shape by a beam expander. 8. The method for producing a polycrystalline semiconductor according to claim 6 or 7, wherein preheating means for linearly heating the semiconductor thin film is used in correspondence with a laser light irradiation region. And a method for manufacturing a polycrystalline semiconductor. 9. The method for manufacturing a polycrystalline semiconductor according to claim 8, wherein a lamp heater is used as the preheating means. 10. The method for producing a polycrystalline semiconductor according to claim 1, further comprising a post-heating means for post-heating a semiconductor thin film in a region irradiated with laser light. Method of manufacturing polycrystalline semiconductor. 11. The method for producing a polycrystalline semiconductor according to claim 10, wherein the post-heating means is located immediately below or immediately after the laser light irradiation position. 12. The method for manufacturing a polycrystalline semiconductor according to claim 1, wherein at least a region which will be a driver portion in the semiconductor thin film formed for an image display device is polycrystallized. A method for manufacturing a characteristic image display device. 13. A laser irradiating means for irradiating a semiconductor thin film with a laser beam having a desired shape by processing the laser beam irradiating region into a desired shape, and a laser beam prior to the laser beam irradiation. And a pre-heating means for heating the semiconductor thin film in a shape corresponding to the irradiation region of the polycrystalline semiconductor. 14. A laser irradiating means for irradiating a semiconductor thin film with a laser beam having a desired shape by processing the laser beam irradiating region into a desired shape, and a laser beam prior to the laser beam irradiation. 2. An apparatus for producing a polycrystalline semiconductor, comprising: a pre-heating means for heating the semiconductor thin film in a shape corresponding to the irradiation area of 1. and a post-heating means for post-heating the semiconductor thin film in the area irradiated with the laser beam.