JP2003289080A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which a semiconductor device can be manufactured by using a laser-beam crystallization method which can prevent the remarkable fall of the mobility of a TFT due to grain boundaries formed in the channel forming region of the TFT, the decrease of an on-current, and the increase of an off-current, and to provide a semiconductor device manufactured by the method. <P>SOLUTION: After a semiconductor film is formed so that the channel width of the film becomes almost equal to each width of crystal grains formed by using a continuously oscillated laser beam in the direction perpendicular to the scanning direction of the laser beam, single crystallinity is obtained in the channel forming region by irradiating the semiconductor film with the laser beam by aligning the moving direction of carriers with the scanning direction of the laser beam. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device formed by using a semiconductor film having a crystal structure, and more particularly to a field effect transistor, particularly a thin film transistor, having a crystalline semiconductor film grown on an insulating surface. The present invention relates to a used semiconductor device and a method for manufacturing the semiconductor device.

[0002]

2. Description of the Related Art In recent years, a technique for forming a TFT on a substrate has greatly advanced, and application development to an active matrix type semiconductor display device has been advanced. In particular, a TFT using a polycrystalline semiconductor film is a TFT using a conventional amorphous semiconductor film.
Since the field effect mobility (also referred to as mobility) is higher than that of FT, high speed operation is possible. Therefore, it is possible to control a pixel, which is conventionally performed by a drive circuit provided outside the substrate, by a drive circuit formed on the same substrate as the pixel.

As a substrate used for a semiconductor device, a glass substrate is considered more promising than a single crystal silicon substrate in terms of cost. The glass substrate has poor heat resistance and is easily deformed by heat. Therefore, the polysilicon TFT is mounted on the glass substrate.
In the case of forming a film, using laser annealing for crystallizing the semiconductor film is very effective in avoiding thermal deformation of the glass substrate.

Laser annealing is characterized by the fact that the processing time can be greatly shortened as compared with the annealing method using radiant heating or conduction heating, and that the semiconductor or semiconductor film is heated selectively and locally, so that almost no substrate is heated. It is mentioned that it does not cause thermal damage.

The laser annealing method here means a technique of recrystallizing a damaged layer formed on a semiconductor substrate or a semiconductor film, or a technique of crystallizing a semiconductor film formed on a substrate. . It also includes techniques applied to the flattening and surface modification of semiconductor substrates or semiconductor films.
The applicable laser oscillators are gas laser oscillators represented by excimer lasers and solid-state laser oscillators represented by YAG lasers, which irradiate a laser beam on a surface layer of a semiconductor for tens of nanoseconds to tens of microseconds. It is known to be heated and crystallized for a very short time.

Lasers are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. Since the pulsed laser has a relatively high output energy, it is possible to improve the mass productivity by setting the size of the laser beam to several cm ² or more. In particular, when the laser beam is processed into a linear shape having a length of 10 cm or more by using an optical system, the substrate can be efficiently irradiated with laser light, and mass productivity can be further improved. Therefore, it has been becoming mainstream to use a pulsed laser for crystallization of the semiconductor film.

However, in recent years, it has been found that the grain size of crystals formed in the semiconductor film becomes larger when a continuous wave laser is used in crystallization of the semiconductor film than when a pulsed laser is used. The larger the crystal grain size in the semiconductor film, the higher the mobility of the TFT formed using the semiconductor film. Therefore, continuous wave lasers are suddenly beginning to come into the limelight.

[0008]

A crystalline semiconductor film produced by a laser annealing method, which is roughly classified into pulse oscillation and continuous oscillation, is generally formed by assembling a plurality of crystal grains. The position and size of the crystal grains are random, and it is difficult to form the crystalline semiconductor film by specifying the position and size of the crystal grains. Therefore, an interface (grain boundary) of crystal grains may exist in the active layer formed by patterning the crystalline semiconductor film in an island shape.

For example, generally, when continuous wave laser light is used, it is possible to grow crystal grains having a width of 1 to 2 μm to a length of several tens μm along the scanning direction of the laser light. However, it is difficult to make the positions and sizes of the crystal grains uniform, and it is very difficult to control the positions of grain boundaries in the channel formation region of the TFT.

Unlike in the crystal grains, a large number of recombination centers and trap centers due to the amorphous structure and crystal defects are present in the grain boundaries. When the crystal orientations of adjacent crystal grains are different from each other, the number of recombination centers and trap centers tends to increase. It is known that when carriers are trapped in the trap center, the potential of the grain boundary rises and becomes a barrier against the carriers, so that the current transport characteristics of the carriers deteriorate. Therefore, when there is a grain boundary formed by adjacent crystal grains having different orientations in the active layer of the TFT, particularly in the channel formation region, the mobility of the TFT is significantly lowered, the on-current is reduced, In addition, the off current increases due to the flow of current at the grain boundaries, and TF
It has a significant effect on the properties of T. Further, in a plurality of TFTs manufactured on the assumption that the same characteristics are obtained, the characteristics may vary depending on the presence or absence of grain boundaries in the active layer.

When the semiconductor film is irradiated with laser light,
The position, size and orientation of the obtained crystal grains are random for the following reasons. It takes some time for solid phase nucleation to occur in the liquid semiconductor film which is completely melted by the irradiation of laser light. Then, with the passage of time, innumerable crystal nuclei are generated in the completely melted region, and crystals grow from the crystal nuclei. Since the positions where the crystal nuclei are generated are random, the crystal nuclei are unevenly distributed. Then, since the crystal growth ends when the crystal grains hit each other, the position, size, and orientation of the crystal grains are random.

Therefore, it is ideal to form the channel forming region, which has a great influence on the characteristics of the TFT, by removing the influence of the grain boundary and using crystal grains having a single crystallinity.
It was almost impossible to form an amorphous silicon film having no grain boundary by a laser annealing method. Therefore, a TFT using a crystalline silicon film crystallized by a laser annealing method as an active layer is a MOS manufactured on a single crystal silicon substrate.
No equivalent to the characteristics of transistors has been obtained to date.

In view of the above problems, the present invention prevents the mobility of the TFT from being significantly reduced, the on-current to be reduced, and the off-current to be increased due to the grain boundaries formed in the channel formation region of the TFT. An object is to provide a method for manufacturing a semiconductor device using a laser crystallization method that can be prevented, and a semiconductor device formed using the manufacturing method.

[0014]

The present inventors have defined the width of a channel formation region in the direction perpendicular to the direction in which carriers move, the so-called channel width, to the crystal grain formed by continuous wave laser light. To form a semiconductor film having a size approximately equal to the width of the laser light in the direction perpendicular to the scanning direction and irradiate the semiconductor film with the laser light in the same direction as the carrier moves and the scanning direction. so,
We considered that a single crystallinity could be obtained in the channel formation region.

This is because by making the channel width and the crystal grain width the same, it is possible to grow one crystal grain without colliding with another crystal grain and form one channel formation region. Is. Incidentally, the width of the crystal grain, the shape of the laser beam of the laser light and its energy distribution,
Although it varies depending on the feed width, the scanning speed, etc., it is generally about 1 to 2 μm.

By forming the channel forming region with one single crystal, it is possible to prevent the grain boundary from being formed in the channel forming region, so that the on current is reduced or the off current is increased by the grain boundary. Or, it is possible to prevent the characteristics from varying in a plurality of TFTs.

Further, in the present invention, it is possible to form a TFT in which the plurality of channel forming regions are sandwiched between one source region and one drain region. With the above structure, the area of the portion where the channel formation region is in contact with the gate insulating film can be increased instead of the channel width (in this case, the sum of the channel widths of all the channel formation regions), and a larger on-current can be obtained. Obtainable. Moreover, by forming a plurality of channel formation regions, heat generated in the channel formation regions during driving of the TFT can be radiated more efficiently. Note that in this specification, a gate insulating film means a portion of an insulating film provided between an active layer and a gate electrode, which overlaps with the active layer and the gate electrode.

Since the channel forming region is formed from one single crystal, the crystal orientation is uniform in each channel forming region. Therefore, the film quality of the gate insulating film formed in contact with the channel formation region becomes uniform, so that the interface state density becomes low and thus the mobility of the TFT is improved,
In addition, the yield and variation of the device can be suppressed and the reliability can be remarkably improved. Note that if the length of the channel formation region in the direction in which carriers move, that is, the so-called channel length, becomes longer, the orientation may change due to rotation of the crystal axes of the crystal grains. However, even in this case, it can be said that the orientation is uniform as compared with the case where a plurality of crystal grains exist in the channel formation region.

After irradiation with laser light, microcrystals may be formed in the vicinity of the edge of the semiconductor film as seen from above the substrate, and protrusions (ridges) may appear along the crystal grain boundaries. . For example, in a pulse oscillation excimer laser, although depending on the thickness of the semiconductor film, many fine crystals with a grain size of less than 0.1 μm are found in the vicinity of the edge, and the grain size is smaller than that in the central portion. The diameter tends to be smaller. It is considered that this is because the heat given by the laser light diffuses into the substrate differently in the vicinity of the edge and in the central portion.

Therefore, in the present invention, after crystallizing by laser light, a portion having poor crystallinity near the edge may be removed by patterning to form a channel forming region having a single crystallinity. At this time,
When the side surface of the channel formation region has a tapered shape, it is possible to prevent the gate insulating film and the gate electrode formed thereon from being broken at the step portion.

Note that the designer can appropriately determine which part of the semiconductor film is to be removed by patterning to form a channel formation region having a single crystallinity. Therefore, in the channel formation region after patterning,
In addition to one crystal grain existing in the channel length direction, even if some crystallites exist near the edge of the channel formation region, the channel formation region has a single crystallinity. Can be said to be.

The energy density near the edge of the laser beam of the laser light is generally lower than that near the center, and the crystallinity of the semiconductor film is often inferior. Therefore, when scanning with laser light, it is desirable that the portion that will later become the channel formation region of the TFT and the edge of its locus do not overlap.

Therefore, in the present invention, first, the data (pattern information) of the shape of the semiconductor film viewed from the upper surface of the substrate, which is obtained in the design stage, is stored in the storage means. Then, based on the pattern information and the width of the laser beam in the direction perpendicular to the scanning direction of the laser beam, at least the portion to be the channel forming region of the TFT and the edge of the laser beam trajectory do not overlap with each other. Determine the scan path.
Then, the position of the substrate is aligned with the marker as a reference, and the semiconductor film on the substrate is irradiated with laser light according to the determined scanning path.

With the above structure, it is possible to scan the laser light only on at least an indispensable part, instead of irradiating the whole substrate with the laser light. Therefore, the time for irradiating the unnecessary portion with the laser light can be saved, and thus the time required for irradiating the laser light can be shortened and the processing speed of the substrate can be improved. Further, it is possible to prevent unnecessary damage to the substrate by irradiating unnecessary portions with laser light.

The marker may be formed by directly etching the substrate with a laser beam or the like, or at the same time as forming the semiconductor film, the marker may be formed on a part of the insulating film. . In addition, the shape of the actually formed semiconductor film is read using an image sensor such as a CCD,
The data stored in the first storage means as the data, the pattern information of the semiconductor film obtained in the design stage in the second storage means, and the data stored in the first storage means and the second storage The substrate may be aligned by collating it with the pattern information stored in the means.

By forming a marker on a part of the insulating film or using the shape of the insulating film as a marker, the number of masks for the marker can be reduced by one, and moreover, it is possible to reduce the number of masks on the substrate by laser light. The marker can be formed at an accurate position, and the alignment accuracy can be improved.

The energy density of the laser light is generally not completely uniform, and its height changes depending on the position within the laser beam. In the present invention, it is necessary to irradiate the laser beam having a constant energy density over the entire area that is the minimum channel formation region. Therefore, in the present invention, the energy density distribution is such that a region having a uniform energy density is completely overlapped with a portion which becomes a channel formation region, more preferably the entire semiconductor film which becomes an active layer, by scanning with laser light. It is necessary to use a laser beam having In order to satisfy the condition of the energy density, it is considered desirable to make the shape of the laser beam rectangular or linear.

Further, a portion of the laser beam having a low energy density may be shielded through a slit. By using the slit, laser light having a relatively uniform energy density can be applied to the entire channel formation region, and crystallization can be performed uniformly. Further, by providing the slits, the width of the laser beam can be partially changed depending on the pattern information of the insulating film or the semiconductor film, and restrictions on the layout of the channel formation region and the active layer of the TFT can be reduced.
The width of the laser beam means the length of the laser beam in the direction perpendicular to the scanning direction.

Further, one laser beam obtained by synthesizing laser beams emitted from a plurality of laser oscillators may be used for laser crystallization. With the above configuration, it is possible to compensate for the weak energy density of each laser beam.

After the semiconductor film is formed, laser light is irradiated so as not to be exposed to the air (for example, a specified gas atmosphere of a rare gas, nitrogen, oxygen, or a reduced pressure atmosphere) is irradiated to crystallize the semiconductor film. You may make it. With the above structure, it is possible to prevent contaminants at the molecular level in the clean room, such as boron contained in the filter for improving the cleanliness of air, from being mixed into the semiconductor film during crystallization by laser light. it can.

The present invention can also be applied to a semiconductor device in the submicron unit.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a method for manufacturing a semiconductor device used in the present invention will be described with reference to FIGS.

First, as shown in FIG.
An insulating film 101 is formed thereover. As the insulating film 101, a silicon oxide film, a silicon oxynitride film, a silicon nitride film, or the like can be used. Note that any other insulating film can be used as long as it can prevent impurities such as an alkali metal from being taken into a semiconductor film to be formed later and has an insulating property that can withstand a subsequent treatment temperature. Is also good. Further, it may have a laminated structure of two or more films.

The substrate 100 may be made of any material that can withstand the processing temperature of the subsequent steps, for example, the surface of a quartz substrate, a silicon substrate, a glass substrate such as barium borosilicate glass or aluminoborosilicate glass, a metal substrate or a stainless steel substrate. A substrate on which an insulating film is formed can be used. Alternatively, a plastic substrate having heat resistance high enough to withstand the treatment temperature may be used.

Next, 25 to 8 are formed so as to cover the insulating film 101.
A semiconductor film is formed with a thickness of 0 nm (preferably 30 to 60 nm). The semiconductor film is formed by known means (sputtering method, LP
The film can be formed by a CVD method, a plasma CVD method or the like). Note that the semiconductor film may be an amorphous semiconductor film, a microcrystalline semiconductor film, or a crystalline semiconductor film. Further, not only silicon but also silicon germanium may be used. Then, the semiconductor film is patterned, and a lattice-shaped semiconductor film (sub-island) 102 having a region having a width of about 1 to 2 μm to be a channel formation region later is formed.
To form.

Next, the sub-island 102 is irradiated with laser light so that the moving direction of carriers in the channel formation region (the direction indicated by the arrow) and the scanning direction are parallel to each other, and the semiconductor with enhanced crystallinity is irradiated. A film (after LC) 103 is formed. The energy density of the laser light is low in the vicinity of the edge of the laser beam 104, so that the crystal grains are small in the vicinity of the edge and a protruding portion (ridge) appears along the grain boundary of the crystal. Therefore, it is important that the sub-island 102 and the edge of the locus of the laser beam 103 do not overlap.

In the present invention, a known continuous wave type laser can be used. The continuous wave laser may be a gas laser or a solid laser. Gas lasers include excimer lasers, Ar lasers, Kr lasers, etc., and solid-state lasers include YAG lasers, YVO ₄ lasers, YLF lasers, YAlO ₃ lasers, glass lasers, ruby lasers, alexandrite lasers, Ti: sapphire lasers, Y. ₂ O ₃ laser and the like can be mentioned. As a solid-state laser, C
r, Nd, Er, Ho, Ce, Co, Ti, Yb or T
m-doped YAG, YVO ₄ , YLF, YA
A laser using a crystal such as 10 ₃ is applied. The fundamental wave of the laser differs depending on the material to be doped, and laser light having a fundamental wave of about 1 μm can be obtained. The harmonic wave with respect to the fundamental wave can be obtained by using a non-linear optical element.

Furthermore, it is also possible to use an ultraviolet laser beam obtained by another nonlinear optical element after converting the infrared laser beam emitted from the solid-state laser into a green laser beam by the nonlinear optical element.

Of course, not only the laser crystallization method,
It may be carried out in combination with another known crystallization method (a thermal crystallization method using an RTA or a furnace annealing furnace, a thermal crystallization method using a metal element that promotes crystallization, etc.). When using a catalytic element, it is desirable to use the techniques disclosed in JP-A-7-130652 and JP-A-8-78329.

Note that FIG. 1B is a cross-sectional view taken along the line AA 'in the region which becomes the channel formation region in FIG. The width W _i1 in the region that becomes the channel formation region of the sub-island 102 in AA ′ is approximately the same as the width of the crystal grain formed using continuous wave laser light in the direction perpendicular to the scanning direction. To Generally, it is desirable to set the width W _i1 to about ₁ to 2 μm. By setting the width of the channel formation region to the above width, it becomes possible to form a channel formation region having a single crystallinity.

Next, as shown in FIG. 2A, the crystallized sub-island is patterned so as to remove the vicinity of the edge of the sub-island, which is considered to have many grain boundaries, and then the island 104 is formed. To form. Figure 2
FIG. 2B shows a cross-sectional view taken along the line AA ′ of the channel formation region in FIG. The width W _{i2 of the} island 104 is W _i1
It is the same size as or less than. Note that the removal of the vicinity of the edge may be performed by forming a mask for an island and isotropically etching the semiconductor film, or forming a mask for a sub-island again and etching the mask simultaneously with the semiconductor film. It may be performed by performing isotropic etching as described above. 2 (A), (B)
Then, the side surface of the channel formation region of the island 104 is
It is tapered.

In the portion which becomes the source region or the drain region, the channel formation region is closer to the TFT due to the crystallinity of the semiconductor film.
The effect on the characteristics of is not significant. Therefore, even if a portion where the crystallinity of the semiconductor film is poor is used as a source region or a drain region, it does not cause a problem so much.

Then, using the islands shown in FIGS. 2 (A) and 2 (B), a process of manufacturing a TFT is performed below. In this embodiment mode, as illustrated in FIG. 3A, the gate insulating film 105 is formed so as to cover at least a portion of the island 104 which is to be a channel formation region. Figure 3
In (A), the portion to be the source region or the drain region is exposed, but the island 1
The entire 40 may be covered.

Next, a gate electrode 106 is formed by forming a conductive film and patterning it. In addition,
A cross-sectional view taken along line AA ′ of FIG. 3A is shown in FIG. The gate electrode 106 overlaps with all the channel formation regions.

The TFT is completed through the above steps. In addition,
Since the manufacturing process of the TFT after forming the island differs depending on the TFT, the TFT included in the semiconductor device of the present invention is not limited to the structure shown in FIGS. 3A and 3B. However, in the TFT included in the semiconductor device of the present invention, the channel width of the channel formation region is equal to or less than the width in the direction perpendicular to the scanning direction of the laser light. The width of the crystal grain varies depending on the shape of the laser beam of the laser light, its energy distribution, the feed width, the scanning speed, etc., but it is generally about 1 to 2 μm. Further, it has a single crystallinity across the channel length direction of the channel formation region.

In the present embodiment, the island is formed by removing the vicinity of the edge of the sub-island, but the present invention is not limited to this. If it is determined that the microcrystals in the vicinity of the edge do not cause a problem so much, it is possible to use the sub-island as it is as an island for the active layer of the TFT.

By forming the channel forming region having a single crystallinity as described above, it is possible to prevent the grain boundary from being formed in the channel forming region. Increased off current, multiple TF
It is possible to prevent the characteristics from varying in T.

By forming a TFT in which a plurality of channel forming regions are sandwiched between one source region and one drain region, the channel width (in this case, the sum of the channel widths of all the channel forming regions is formed). In addition, the area of the portion where the channel formation region and the gate insulating film are in contact with each other can be increased, and a larger on-current can be obtained. Moreover, by forming a plurality of channel formation regions, heat generated in the channel formation regions during driving of the TFT can be radiated more efficiently.

Since the channel forming region is formed from one single crystal, the crystal orientation is uniform in each channel forming region. Therefore, the film quality of the gate insulating film formed in contact with the channel formation region becomes uniform, so that the interface state density becomes low and thus the mobility of the TFT is improved,
In addition, the yield and variation of the device can be suppressed and the reliability can be remarkably improved.

Next, the production system used in the present invention will be described. FIG. 4 shows a flowchart of the production system of this embodiment. First, design the island mask,
Next, a mask for the sub island is designed. Note that when the sub-island is used as the island, the island mask does not have to be formed. When the island is used as the active layer of the TFT, it is desirable to lay out the island so that the scanning direction of the laser light and the direction in which carriers in the channel formation regions of a plurality of TFTs, which do not want the characteristics to move, are aligned. However, the directions may not be intentionally aligned depending on the application.

Then, the information (pattern information) about the shape of the designed sub-island is input to the computer included in the laser irradiation device and stored in the storage means thereof. In the computer, the scanning path of the laser beam is determined based on the input sub-island pattern information and the width of the laser beam in the direction perpendicular to the scanning direction. At this time, the scanning path is determined so that the edge of the trajectory of the laser light and the sub-island do not overlap. In addition to the pattern information of the sub-islands, the pattern information of the islands is stored in the storage means of the computer so that the edge of the locus of the laser beam and the island or the channel formation region of the islands do not overlap with each other.
You may make it determine a scanning path.

When a slit is provided to control the width of the laser beam, the computer calculates the width of the sub-island in the direction perpendicular to the scanning direction based on the inputted sub-island pattern information. And the edge of the trajectory of the laser light, the sub-island,
More preferably, the width of the slit in the direction perpendicular to the scanning direction is set so as not to overlap the island or the channel formation region.

On the other hand, a sub-island is formed on the surface of the insulating film of the substrate according to the designed pattern information, the substrate is placed on the stage of the laser irradiation apparatus, and the substrate is aligned. In FIG. 3, the CCD camera is used to detect the marker and the substrate is aligned. The CCD camera means a camera using a CCD (charge coupled device) as an image pickup device.

The pattern information of the sub-island on the substrate set on the stage is detected by a CCD camera or the like, and the pattern information of the sub-island designed by CAD in the computer and the actual information on the substrate obtained by the CCD camera are detected. The position of the substrate may be aligned with the pattern information of the sub-island formed on the substrate.

Then, the sub-islands are crystallized by irradiating the laser light according to the determined scanning path.

Next, after irradiating with laser light, the sub-islands whose crystallinity has been enhanced by laser light irradiation are patterned to form islands. Hereinafter, a step of manufacturing a TFT from the island is performed. Although a specific manufacturing process of the TFT differs depending on the shape of the TFT, a gate insulating film is typically formed and an impurity region is formed in the island. Then, an interlayer insulating film is formed so as to cover the gate insulating film and the gate electrode, a contact hole is formed in the interlayer insulating film, and part of the impurity region is exposed. Then, a wiring is formed over the interlayer insulating film so as to be in contact with the impurity region through the contact hole.

Next, the structure of the laser irradiation apparatus used in the present invention will be described.

Next, the structure of the laser irradiation apparatus used in the present invention will be described with reference to FIG. 15
1 is a laser oscillator. Although four laser oscillation devices are used in FIG. 5, the number of laser oscillation devices included in the laser irradiation device is not limited to this.

The laser oscillation device 151 may use a chiller 152 to keep its temperature constant. Although it is not always necessary to provide the chiller 152, by keeping the temperature of the laser oscillator 151 constant, it is possible to prevent the energy of the output laser light from varying depending on the temperature.

Reference numeral 154 denotes an optical system, which can change the optical path output from the laser oscillator 151 or process the shape of the laser beam to focus the laser light. Further, in the laser irradiation apparatus of FIG. 5, a plurality of laser oscillators 1 are provided by the optical system 154.
The laser beams of the laser beams output from 51 can be combined by partially overlapping each other.

The AO modulator 153 for changing the traveling direction of the laser light in an extremely short time is provided with the substrate 1 which is the object to be processed.
It may be provided in the optical path between 56 and the laser oscillator 151. Further, instead of the AO modulator, an attenuator (light quantity adjustment filter) may be provided to adjust the energy density of the laser light.

Further, the laser oscillator 1 is provided in the optical path between the substrate 156 which is the object to be processed and the laser oscillator 151.
A means (energy density measuring means) 165 for measuring the energy density of the laser beam output from the laser 51 is provided, and the computer 16 measures the change with time of the measured energy density.
You may make it monitor at 0. In this case, the output from the laser oscillator 160 may be increased so as to compensate for the attenuation of the energy density of the laser light.

The combined laser beam is transmitted through the slit 1
The substrate 156 which is the object to be processed is irradiated via 55.
The slit 155 is preferably formed of a material that can block the laser light and that is not deformed or damaged by the laser light. The slit 155 has a variable width, and the width of the laser beam can be changed depending on the width of the slit.

When the slit 155 is not used,
The shape of the laser beam of the laser light emitted from the laser oscillator 151 on the substrate 156 varies depending on the type of laser, and can be shaped by an optical system.

The substrate 156 is placed on the stage 157. In FIG. 5, the position control means 158, 159 correspond to the means for controlling the position of the laser beam on the object to be processed, and the position of the stage 157 is controlled by the position control means 158, 159.

In FIG. 5, the position control means 158 controls the position of the stage 157 in the X direction, and the position control means 159 controls the position of the stage 157 in the Y direction.

The laser irradiation apparatus shown in FIG. 5 has a computer 160 having a storage means such as a memory and a central processing unit. Computer 160
The oscillation of the laser oscillating device 151 is controlled, the scanning path of the laser light is determined, and the laser beam of the laser light is scanned according to the determined scanning path.
The substrate can be moved to a predetermined position by controlling the position control means 158 and 159.

In FIG. 5, the position of the laser beam is
It is controlled by moving the substrate, but it may be moved by using an optical system such as a galvanometer mirror.
Both may be used.

Further, in FIG. 5, the width of the slit 155 can be controlled by the computer 160 to change the width of the laser beam according to the pattern information of the mask. Note that the slit does not necessarily have to be provided.

Further, the laser irradiation device may be provided with means for adjusting the temperature of the object to be treated. Also, since laser light is light with high directivity and energy density,
A damper may be provided to prevent reflected light from being applied to an inappropriate location. The damper preferably has a property of absorbing reflected light, and cooling water may be circulated in the damper to prevent the temperature of the partition wall from rising due to absorption of reflected light. Further, means for heating the substrate on the stage 157 (substrate heating means)
May be provided.

When the marker is formed by laser, a laser oscillating device for the marker may be provided. In this case, the computer 160 may control the oscillation of the marker laser oscillation device. Further, when providing the laser oscillating device for the marker, an optical system for condensing the laser light output from the laser oscillating device for the marker is separately provided. The laser used for forming the marker is typically a YAG laser, a CO ₂ laser, or the like, but it goes without saying that other lasers can be used.

In addition, one CCD camera 163 may be provided, or several CCD cameras 163 may be provided in some cases for alignment using the marker. A CCD camera is a CCD
It means a camera using (charge coupled device) as an image sensor.

It is also possible to align the substrate by recognizing the pattern of the insulating film or the semiconductor film by the CCD camera 163 without providing the marker. In this case, the pattern information of the insulating film or the semiconductor film by the mask input to the computer 160 and the CCD camera 1
The positional information of the substrate can be grasped by comparing with the pattern information of the actual insulating film or the semiconductor film collected in 63. In this case, it is not necessary to provide a marker separately.

The laser light incident on the substrate is reflected by the surface of the substrate and returns to the same optical path as when it is incident, that is, so-called return light. The return light is the output or frequency fluctuation of the laser or the rod. It has an adverse effect such as the destruction of. Therefore, an isolator may be installed in order to remove the return light and stabilize the oscillation of the laser.

Although FIG. 5 shows the configuration of the laser irradiation device provided with a plurality of laser oscillators, the number of laser oscillators may be one. FIG. 6 shows the configuration of a laser irradiation device having one laser oscillation device. In FIG. 6, 201 is a laser oscillator and 202 is a chiller. Further, 215 is an energy density measuring device, 20
3 is an AO modulator, 204 is an optical system, 205 is a slit,
213 is a CCD camera. Substrate 206 is stage 2
The position of the stage 207 is controlled by the X-direction position control means 208 and the Y-direction position control means 209. The operation of each means of the laser irradiation device is controlled by the computer 210 as in the case shown in FIG. 5, and the difference from FIG. 5 is that there is one laser oscillation device. Also, the optical system 204
Unlike in the case of FIG. 5, it is sufficient that it has a function of condensing one laser beam.

As described above, the semiconductor film is crystallized by scanning the laser beam so that the entire semiconductor film is not irradiated with the laser beam, but by scanning the laser beam so that at least an indispensable portion can be crystallized at least. The time for irradiating the portion to be removed by the post patterning with the laser light can be omitted, and the processing time required for one substrate can be significantly reduced.

[0077]

EXAMPLES Examples of the present invention will be described below.

Example 1 In this example, an example of manufacturing a TFT using an island in which one channel forming region is formed will be described.

FIG. 8A shows the structure of the TFT of this embodiment. In FIG. 8A, the insulating film 151 is formed over the substrate 150. Then, a plurality of islands 152 that are separated from each other are formed on the insulating film 151. The channel width of the plurality of islands 152 is set to be as large as or smaller than the width of the crystal grains formed by the laser light in the direction perpendicular to the laser light scanning direction. Specifically, about 1 to 2 μm is desirable. The island 152 is scanned with laser light in the same direction as the direction in which carriers in the channel formation region move.

A TFT using the island 152 as an active layer is shown in FIG. FIG. 8C is the same as FIG.
This corresponds to the cross-sectional view taken along the line AA ′ in (B). A gate insulating film 153 is formed on the island 152, and a gate electrode 154 is formed on the gate insulating film 153. Note that the gate insulating film 153 is formed so as to expose a portion of the island, which serves as an impurity region in FIG. 8A, but may be formed so as to cover the entire island 152. The gate electrodes 154 may be connected to each other depending on the circuit configuration.

The gate electrode 154 is the gate insulating film 153.
And the channel forming region of the island 152 are overlapped with each other. Although not shown, the channel formation region is sandwiched between two impurity regions also included in the island 152.

(Embodiment 2) In this embodiment, T formed by using an island having a plurality of channel formation regions is used.
The structure of the FT and the wiring electrically connected to the TFT will be described.

FIG. 9A shows a top view of the TFT of this embodiment. The TFT shown in FIG. 9A uses an island 161 having a plurality of channel formation regions. The island 161 is obtained by scanning the sub-island with laser light along the direction in which carriers in the channel formation region to be formed later move, and patterning the sub-island. The channel width of the island 161 is set to be as large as or smaller than the width of the crystal grains formed by the laser light in the direction perpendicular to the laser light scanning direction. Specifically, 1-2 μm
The degree is desirable.

When crystallization of the island, a solid-state laser capable of continuous oscillation can be used, and the second to fourth harmonics of the fundamental wave can be used. Typically, Nd: Y
Second harmonic of VO ₄ laser (fundamental wave 1064nm) (5
32 nm) or the third harmonic (355 nm) is preferably used. Specifically, the laser light emitted from the continuous wave YVO ₄ laser is converted into a harmonic by a non-linear optical element to obtain a laser light with an output of 10 W. There is also a method in which a YVO ₄ crystal and a non-linear optical element are put in a resonator to emit a higher harmonic wave. Then, it is preferably shaped into a rectangular or elliptical laser beam on the irradiation surface by an optical system, and the object to be processed is irradiated. The energy density at this time is about 0.01 to 100 MW / cm ² (preferably 0.1
10 MW / cm ² ) is required. And 10-2
The island is moved relative to the laser beam at a speed of about 000 cm / s for irradiation.

Then, a gate insulating film 162 is formed so as to contact the island 161. Note that a cross-sectional view taken along the line AA ′ in FIG. 9A is shown in FIG. 9B, a cross-sectional view taken along the line BB ′ is shown in FIG. 9C, and a cross-sectional view taken along the line CC ′ is shown in FIG. ).

A gate electrode 163 is formed by forming a conductive film on the gate insulating film 162 and patterning the conductive film. The gate electrode 16
3 is the island 1 with the gate insulating film 162 sandwiched therebetween.
The channel forming region 164 overlaps with the channel forming region 164 of 61, and the channel forming region 164 is sandwiched by two impurity regions 165 included in the island 161.

Then, the gate electrode 163 and the island 16
A first interlayer insulating film 166 is formed so as to cover 1 and the gate insulating film 162. First interlayer insulating film 166
Is made of an inorganic insulating film, and has an effect of preventing the island 161 from being mixed with a substance such as an alkali metal that adversely affects the characteristics of the TFT.

Then, a second interlayer insulating film 167 made of an organic resin is formed on the first interlayer insulating film 166. An opening is formed in the second interlayer insulating film 167, the first interlayer insulating film 166, and the gate insulating film 162 by etching, and two impurity regions 165 and a gate electrode 163 are formed through the opening. Wirings 168, 169 and 170 connected to the second interlayer insulating film 16 respectively.
It is formed on 7.

This embodiment can be implemented in combination with the first embodiment.

(Embodiment 3) In this embodiment, the shape of a laser beam synthesized by superposing a plurality of laser beams will be described.

FIG. 10A shows an example of the shape of a laser beam emitted from a plurality of laser oscillators on the object to be processed when it does not pass through a slit. The laser beam shown in FIG. 10A has an elliptical shape. In the present invention, the shape of the laser beam of the laser light emitted from the laser oscillator is not limited to an ellipse. The shape of the laser beam differs depending on the type of laser, and it can be shaped by an optical system. For example, XeCl excimer laser (wavelength 308 nm, pulse width 30 ns) L33 manufactured by Lambda Corporation
The shape of the laser beam emitted from 08 is 10 mm x 3
It has a rectangular shape of 0 mm (both are half-widths in the beam profile). The shape of the laser beam emitted from the YAG laser is circular if the rod shape is cylindrical, and rectangular if it is a slab type. It is also possible to form a laser beam of a desired size by further shaping such a laser beam with an optical system.

FIG. 10B shows the energy density distribution of the laser beam in the direction of the major axis L of the laser beam shown in FIG. The laser beam shown in FIG. 10A corresponds to a region in which the energy density of 1 / e ² of the peak value of the energy density in FIG. 10B is satisfied. The energy density distribution of the laser light in which the laser beam has an elliptical shape is higher toward the center O of the ellipse. As described above, in the laser beam shown in FIG. 10A, the energy density in the central axis direction has a Gaussian distribution, and the region where the energy density can be determined to be uniform becomes narrow.

Next, FIG. 10C shows the shape of the laser beam when the laser light having the laser beam shown in FIG. 10A is synthesized. Note that FIG. 10C illustrates the case where one linear laser beam is formed by overlapping laser beams of four laser lights, but the number of laser beams to be overlapped is not limited to this.

As shown in FIG. 10C, the laser beams of the respective laser beams are synthesized by matching the major axes of the ellipses and overlapping the laser beams with each other.
One laser beam 360 is formed. In the following, a straight line obtained by connecting the centers O of the respective ellipses will be the central axis of the laser beam 360.

FIG. 10D shows the energy density distribution of the laser beam in the central axis y direction of the combined laser beam shown in FIG. 10D. Note that FIG.
The laser beam shown in (C) corresponds to a region satisfying the energy density of 1 / e ² of the peak value of the energy density in FIG. 10 (B). The energy densities are added at the overlapping portions of the respective laser beams before the combination. For example, when the energy densities E1 and E2 of the overlapping beams are added as shown in the figure, the energy density peaks E3 of the beams are almost equalized, and the energy density is flattened between the centers O of the ellipses.

Although it is ideal that E1 and E2 are equal to E3, the values are not necessarily equal to each other in reality. The allowable range of deviation between the value obtained by adding E1 and E2 and the value at E3 can be appropriately set by the designer.

When the laser beam is used alone, the energy density distribution follows a Gaussian distribution, so that it is difficult to irradiate a laser beam having a uniform energy density on the entire island or channel formation region. However,
As can be seen from 0 (D), by superimposing a plurality of laser beams so as to complement each other in a portion having a low energy density, the energy density is more uniform than when a plurality of laser beams are not superposed and used alone. This region is enlarged, and the crystallinity of the semiconductor film can be efficiently improved.

The distribution of energy densities at BB ′ and CC ′ in FIG.
It shows in FIG. Note that FIG. 11 is based on the region where the energy density of the laser beam before synthesis satisfies 1 / e ² of the peak value. The laser beam length before synthesis is 37 μm in the short axis direction and 410 μm in the long axis direction.
And when the distance between the centers is 192 μm, B-
The energy densities in B ′ and CC ′ have distributions as shown in FIGS. 11 (A) and 11 (B), respectively. BB 'has a weaker crown than CC', but it can be regarded as almost the same size, and is a region satisfying the energy density of 1 / e ² of the peak value of the laser beam before synthesis. The shape of the combined laser beam in can be expressed as a linear shape.

FIG. 12A shows the energy distribution of the combined laser beam. The region indicated by 361 is a region having a uniform energy density, and the region indicated by 362 is a region having a low energy density. In FIG. 12, the length of the laser beam in the central axis direction is W _TBW, and the length of the laser beam in the central axis direction in the region 361 having a uniform energy density is W _max . As W _TBW becomes larger than W _max , the ratio of the region 362 that cannot be used for crystallization of the semiconductor film and that has a non-uniform energy density to the region 361 that has uniform energy density that can be used for crystallization is obtained. growing. In the semiconductor film irradiated only with the region 362 where the energy density is not uniform, microcrystals are generated and the crystallinity is poor. Therefore, it becomes necessary to determine the layout of the scanning path and the island so that only the region 362 which does not overlap with the region which becomes the island of the semiconductor film is formed, and the restriction becomes larger as the ratio of the region 362 to the region 361 becomes higher. Therefore, using the slits to prevent the islands from being irradiated with only the region 362 where the energy density is not uniform is effective in reducing the restrictions that occur during the layout of the scanning paths and the islands.

This embodiment can be implemented in combination with Embodiment 1 or 2.

(Embodiment 4) In this embodiment, an optical system of a laser irradiation apparatus used in the present invention and a positional relationship between each optical system and a slit will be described.

FIG. 13 shows an optical system in which four laser beams are combined into one laser beam. The optical system shown in FIG. 13 has six cylindrical lenses 417 to 422. The four laser beams incident from the direction of the arrow are four cylindrical lenses 4
It is incident on each of 19 to 422. Then, the two laser beams formed by the cylindrical lenses 419 and 421 are shaped again by the cylindrical lens 417 in the shape of the laser beam, and the slit 42
The object to be processed 423 is irradiated through the beam path 4. On the other hand, the two laser beams formed by the cylindrical lenses 420 and 422 have their laser beam shapes formed again by the cylindrical lens 418, and the slits 4
The object to be processed 423 is irradiated through 24.

The laser beams of the laser beams on the object to be processed 423 are synthesized by partially overlapping each other, and
Forming two laser beams.

The designer can set the focal length and the incident angle of each lens as appropriate, but the focal lengths of the cylindrical lenses 417 and 418 closest to the object 423 are the focal lengths of the cylindrical lenses 419 to 422. Smaller than. For example, if the focal length of the cylindrical lenses 417 and 418 closest to the object to be processed 423 is 20 m
m, and the focal length of the cylindrical lenses 419 to 422 is 150 mm. And the cylindrical lens 4
The angle of incidence of the laser light from 17, 418 on the object to be processed 400 is 25 ° in the present embodiment, and the cylindrical lenses 419 to 422 to the cylindrical lenses 417, 41.
Each lens is installed so that the incident angle of the laser beam on 8 is 10 °. In addition, in order to prevent returning light and perform uniform irradiation, it is desirable to keep the incident angle of the laser light on the substrate larger than 0 °, preferably 5 to 30 °.

FIG. 13 shows an example in which four laser beams are combined. In this case, four cylindrical lenses corresponding to the four laser oscillators, and two cylindrical lenses corresponding to the four cylindrical lenses are shown. have. The number of laser beams to be combined is not limited to this, and the number of laser beams to be combined may be 2 or more and 8 or less. n (n = 2, 4,
In the case of synthesizing the laser beams of 6 and 8), it has n cylindrical lenses respectively corresponding to the n laser oscillators and n / 2 cylindrical lenses corresponding to the n cylindrical lenses. n (n = 3,
When synthesizing the laser beams of 5 and 7), n cylindrical lenses respectively corresponding to the n laser oscillation devices and (n +)
1) / 2 cylindrical lens.

When five or more laser beams are superposed, it is desirable to irradiate the fifth and subsequent laser beams from the opposite side of the substrate in consideration of the place where the optical system is arranged and interference. Must also be provided on the opposite side of the substrate. In addition, the substrate needs to be transparent.

Further, in order to realize uniform irradiation of laser light, a plane which is a plane perpendicular to the irradiation surface and which includes short sides when the shape of each beam before combination is regarded as a rectangle, or When one of the surfaces including the long side is defined as the incident surface, the incident angle θ of the laser light is set on the irradiation surface such that the length of the short side or the long side included in the incident surface is W, In addition, when the thickness of the substrate that is transparent to the laser light is d, θ ≧ arctan (W / 2d)
It is desirable to meet. This argument needs to hold for each laser beam before synthesis. When the locus of the laser beam is not on the incident surface, the incident angle of the locus projected on the incident surface is θ. When the laser light is incident at this incident angle θ, the reflected light on the front surface of the substrate does not interfere with the reflected light from the back surface of the substrate, and uniform laser light irradiation can be performed. The above discussion is
The substrate has a refractive index of 1. In practice, the refractive index of the substrate is often around 1.5, and if this value is taken into consideration, a calculated value larger than the angle calculated in the above discussion can be obtained. However, since the energy at both ends of the beam spot in the longitudinal direction is attenuated, the influence of interference at this portion is small, and the above calculated value is sufficient to obtain the effect of interference attenuation. The above inequality for θ is applied only to the case where the substrate is transparent to the laser beam.

If the laser light has a large output of 20 W or more, it is possible to obtain a linear laser beam having a sufficient energy density by superimposing only two laser beams. However, the larger the number of laser beams to be superposed, the larger the ratio of the region where a constant energy density can be obtained in the central axis direction.

Note that the optical system included in the laser irradiation apparatus used in the present invention is not limited to the structure shown in this embodiment.

This embodiment can be implemented in combination with Embodiments 1 to 3.

(Embodiment 5) The laser light having the elliptical laser beam has a Gaussian distribution in the energy density in the direction perpendicular to the scanning direction, so that the ratio of the low energy density region to the entire area is rectangular. Alternatively, it is higher than laser light having a linear laser beam. Therefore, in the present invention, it is desirable that the laser beam of the laser beam be rectangular or linear with a relatively uniform energy density distribution.

A typical gas laser that can obtain a rectangular or linear laser beam is an excimer laser, and a typical solid-state laser is a slab laser. In this embodiment, a slab laser will be described.

FIG. 14A shows the structure of a slab type laser oscillator as an example. The slab-type laser oscillator shown in FIG. 14A includes a rod 7500, a reflection mirror 7501, an output mirror 7502, and a cylindrical lens 7503.

When the rod 7500 is irradiated with the excitation light, the laser light is emitted to the reflecting mirror 7501 or the emitting mirror 7502 side along the zigzag optical path inside the rod 7500. The laser light emitted to the reflecting mirror 7501 side is reflected, enters the rod 7500 again, and is emitted to the emitting mirror 7502 side. The rod 7500 is a slab type using a plate-like slab medium, and can form a relatively long rectangular or linear laser beam at the emitting stage. Then, the emitted laser light is processed by the cylindrical lens 7503 so that the shape of the laser beam becomes smaller, and is emitted from the laser oscillation device.

Next, the structure of the slab type laser oscillator different from that shown in FIG.
It shows in (B). In FIG. 14B, a cylindrical lens 7504 is added to the laser oscillator shown in FIG.
Cylindrical lens 7504
Allows the length of the laser beam to be controlled.

If the coherent length is 10 cm or more, preferably 1 m or more, the laser beam can be made thinner.

In order to prevent the temperature of the rod 7500 from rising excessively, cooling water is circulated, for example.
A means for controlling the temperature may be provided.

FIG. 14C shows an example of the shape of the cylindrical lens. Reference numeral 7509 denotes the cylindrical lens of this embodiment, which is fixed by a holder 7510. The cylindrical lens 7509 has a shape in which a cylindrical surface and a rectangular flat surface face each other, and two generatrixes of the cylindrical surface and two opposite sides of the rectangle are all parallel to each other. The two planes formed by the two generatrixes of the cylindrical surface and the two parallel sides intersect with the rectangular plane at an angle larger than 0 and smaller than 90 °. The two surfaces formed by the two sides that are parallel to each other in this manner are
By intersecting at an angle of less than 90 °, the focal length can be shortened as compared with the case of 90 ° or more, the shape of the laser beam can be made narrower, and the laser beam can be made closer to linear.

This embodiment can be implemented in combination with Embodiments 1 to 4.

(Embodiment 6) In this embodiment, the relationship between the distance between the centers of the beam spots and the energy density when the beam spots are superposed will be described.

FIG. 15 shows the energy density distribution in the direction of the central axis of each beam spot with a solid line, and the energy density distribution of the combined beam spots with a broken line. The value of the energy density in the direction of the central axis of the beam spot generally follows a Gaussian distribution.

When the distance in the central axis direction that satisfies the energy density of 1 / e ² or more of the peak value in the beam spot before synthesis is 1, the distance between the peaks is X.
And Further, in the combined beam spot, the peak value after the combination and the increment of the peak value with respect to the average value of the valley values are Y. X and Y obtained by simulation
FIG. 16 shows the relationship of In FIG. 16, Y is expressed as a percentage.

In FIG. 16, the energy difference Y is expressed by the following approximate expression of Expression 1.

[0124]

[Formula 1] Y = 60-293X + 340X ² (X is the larger of the two solutions)

According to the equation 1, for example, the energy difference is 5%.
It can be seen that if it is desired to set the degree, it is sufficient to set X≈0.584. Ideally, Y = 0, but since the length of the beam spot is shortened, X should be determined in balance with the throughput.

Next, the allowable range of Y will be described. FIG. 17 shows the distribution of the output (W) of the YVO ₄ laser with respect to the beam width in the central axis direction when the beam spot has an elliptical shape. The shaded region is the range of output energy required to obtain good crystallinity, and it is understood that the output energy of the synthesized laser light should be within the range of 3.5 to 6 W.

When the maximum value and the minimum value of the output energy of the beam spot after synthesis are within the output energy range necessary for obtaining good crystallinity, the energy difference Y that gives good crystallinity is the maximum. become. Therefore, FIG.
In the case of 7, the energy difference Y is ± 26.3%, and it can be seen that good crystallinity can be obtained if the energy difference Y is within the above range.

The range of output energy required to obtain good crystallinity varies depending on how far the crystallinity is judged to be good, and the distribution of output energy also varies depending on the shape of the beam spot. The allowable range of the energy difference Y is not necessarily limited to the above value. It is necessary for the designer to appropriately set the range of output energy required to obtain good crystallinity and set the allowable range of the energy difference Y from the distribution of output energy of the laser used.

This embodiment can be implemented in combination with the first to fifth embodiments.

(Embodiment 7) The present invention can be applied to various semiconductor devices, and the form of the display panel manufactured based on Embodiments 1 to 6 will be described with reference to FIGS. 18 and 19.

In FIG. 18, the pixel portion 9 is formed on the substrate 901.
02, gate signal side drive circuits 901a and 901b, a data signal side drive circuit 901c, an input / output terminal portion 908, and a wiring or wiring group 904. The shield pattern 905 may partially overlap a wiring or a wiring group 904 that connects the gate signal side driving circuits 901a and 901b and the data signal side driving circuit 901c to the input terminal. By doing so, the area of the frame region (the peripheral region of the pixel portion) of the display panel can be reduced. The FPC 903 is fixed to the external input terminal portion.

According to the present invention, the pixel portion 902, the gate signal side drive circuits 901a and 901b, and the data signal side drive circuit 90 are provided.
It can be used as an active element constituting 1c.

FIG. 19 is an example showing the configuration of one pixel of the pixel portion 902 shown in FIG. In this embodiment, a pixel of a light emitting device which is one of the semiconductor devices of the present invention will be described. The light emitting device is a general term for a display panel in which a light emitting element formed on a substrate is enclosed between the substrate and a cover material, and a display module in which a TFT or the like is mounted on the display panel. Note that the light-emitting element is a luminescence (Electro Luminescen) generated by applying an electric field.
ce) having a layer containing an organic compound (light emitting layer), an anode, and a cathode.

In the light emitting device used in this example, the hole injection layer, the electron injection layer, the hole transport layer, the electron transport layer, etc. are made of an inorganic compound alone or an organic compound mixed with an inorganic compound. It may also be in the form of a material. Further, these layers may be partially mixed with each other.

Reference numeral 801 denotes a TFT (switching TFT) as a switching element for controlling the input of a video signal input to the pixel, and 802 a TFT for supplying a current to the pixel electrode based on the information contained in the video signal.
(Driving TFT).

The switching TFT 801 has a size of 1 to 2 μm.
It has an active layer 803 having a channel width of about m and having a plurality of channel formation regions, a gate insulating film (not shown), and a gate electrode 805 which is a part of the gate line 804. The switching of the switching TFT 801 is controlled by a selection signal input from the gate signal side drive circuits 901a and 901b to the gate line 804.

Active layer 80 of switching TFT 801
One of the source region and the drain region included in 3 is a signal line 806 to which a video signal is input by the data signal side driver circuit 901c, and the other is a wiring 80 for connecting elements.
Connected to 7.

On the other hand, the driving TFT 802 includes an active layer 808 having a channel width of about 1 to 2 μm and having a plurality of channel forming regions, a gate insulating film (not shown), and a gate which is a part of the capacitor wiring 809. And an electrode 810.

One of a source region and a drain region of the active layer 808 of the driving TFT 802 has a power supply line 811.
The other is connected to the pixel electrode 812.

Reference numeral 813 denotes a capacitor semiconductor film, which overlaps with the capacitor wiring 809 with the gate insulating film interposed therebetween.
The capacitor semiconductor film 813 is connected to the power supply line. The overlapping portion of the capacitor semiconductor film 813, the gate insulating film, and the capacitor wiring 809 functions as a capacitor for holding the gate voltage of the driving TFT 802. Also,
The capacitor wiring 809 and the power supply line 811 overlap with each other with an interlayer insulating film (not shown) interposed therebetween. A portion where the capacitor wiring 809, the interlayer insulating film, and the power supply line 811 overlap with each other can also function as a capacitor for holding the gate voltage of the driving TFT 802.

In the present specification, the term "connection" means electrical connection unless otherwise specified.

Active layer 80 of switching TFT 801
3 and the active layer 808 of the driving TFT 802 has a channel forming region in which the carriers move,
All are aligned with the scanning direction of the laser beam shown by the arrow.

The number of channel formation regions included in the active layer 808 of the driving TFT 802 is the same as that of the switching TFT 80.
It is desirable that the number is larger than the number of channel formation regions included in one active layer 803. Because the driving TFT 80
This is because 2 requires a larger current capacity than the switching TFT 801, and the on-current can be increased as the number of channel formation regions increases.

In this example, the T used in the light emitting device was used.
Although the structure of the FT substrate has been described, a liquid crystal display device can be manufactured by using the manufacturing process of this embodiment.

This embodiment can be implemented by freely combining with Embodiments 1 to 6.

(Embodiment 8) The semiconductor device of the present invention can be applied to various electronic devices. Examples thereof include personal digital assistants (electronic notebooks, mobile computers, mobile phones, etc.), video cameras, digital cameras, personal computers, television receivers, mobile phones, projection display devices, and the like. Specific examples of those electronic devices are shown in FIGS.

FIG. 20A shows a display device, which is a housing 20.
01, support base 2002, display unit 2003, speaker unit 2004, video input terminal 2005 and the like. The display device of the present invention is completed by using the semiconductor device of the present invention for the display portion 2003. The display device is for PC
It includes all display devices for displaying information such as TV broadcast reception and advertisement display.

FIG. 20B shows a digital still camera including a main body 2101, a display portion 2102, an image receiving portion 2103,
An operation key 2104, an external connection port 2105, a shutter 2106 and the like are included. The semiconductor device of the present invention has a display unit 21.
02, the digital still camera of the present invention is completed.

FIG. 20C shows a laptop personal computer, which has a main body 2201, a housing 2202, and a display section 2.
203, keyboard 2204, external connection port 220
5, including a pointing mouse 2206 and the like. The notebook personal computer of the present invention is completed by using the semiconductor device of the present invention for the display portion 2203.

FIG. 20D shows a mobile computer, which has a main body 2301, a display portion 2302, and a switch 230.
3, an operation key 2304, an infrared port 2305 and the like. The mobile computer of the present invention is completed by using the semiconductor device of the present invention for the display portion 2302.

FIG. 20E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, a recording medium ( DVD, etc.) reading unit 240
5, an operation key 2406, a speaker portion 2407, and the like. The display unit A2403 mainly displays image information, and the display unit B2404 mainly displays character information. In addition,
The image reproducing device provided with the recording medium includes a home game machine and the like. The semiconductor device of the present invention is provided with display units A and B24.
03, 2404, the image reproducing apparatus of the present invention is completed.

FIG. 20F shows a goggle type display (head mounted display), which is a main body 250.
1, a display portion 2502 and an arm portion 2503 are included. The goggle type display of the present invention is completed by using the semiconductor device of the present invention for the display portion 2502.

FIG. 20G shows a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, and an image receiving portion 260.
6, a battery 2607, a voice input unit 2608, operation keys 2609, an eyepiece unit 2610, and the like. The video camera of the present invention is completed by using the semiconductor device of the present invention for the display portion 2602.

[0154] Here, FIG. 20H shows a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, a voice input portion 2704, a voice output portion 2705, operation keys 2706,
An external connection port 2707, an antenna 2708, and the like are included.
Note that the display portion 2703 can suppress current consumption of the mobile phone by displaying white characters on a black background.
By using the semiconductor device of the present invention for the display portion 2703,
The mobile phone of the present invention is completed.

As described above, the applicable range of the present invention is extremely wide, and the present invention can be applied to electronic devices in all fields. Further, this embodiment can be implemented in combination with any of the configurations shown in the first to seventh embodiments.

(Embodiment 9) Since the channel formation region of the TFT of the semiconductor device of the present invention is almost single crystal,
Circuits that are usually made of elements that use single crystal silicon,
For example, a CPU using an LSI, a storage element of various logic circuits (for example, SRAM), a counter circuit, a frequency dividing circuit logic, and the like can be formed.

The minimum size of the VLSI is approaching the submicron region, and it is necessary to partially make the elements three-dimensional in order to achieve higher integration. In this embodiment, a structure of a semiconductor device of the present invention having a stack structure will be described.

FIG. 7 shows a sectional view of the semiconductor device of this embodiment. A first insulating film 701 is formed on the substrate 700. Then, the first TFT 70 is formed on the first insulating film 701.
2 is formed. The channel width of the channel formation region of the first TFT 702 is about 1 to 2 μm.

A first interlayer insulating film 703 is formed so as to cover the first TFT 702, and the first interlayer insulating film 7 is formed.
03, the first connection wiring 705 and the first TFT 70.
2 and a wiring 704 electrically connected to the wiring 2.

Then, the wiring 704 and the first connection wiring 70
A second interlayer insulating film 706 is formed so as to cover 5. The second interlayer insulating film 706 is formed of an inorganic insulating film, and contains silicon oxide, silicon oxynitride, or the like with a substance that absorbs laser light emitted in a later step, such as a colored pigment or carbon. Use the mixture of the mixture.

Then, when the upper surface of the second interlayer insulating film 706 is polished by the chemical mechanical polishing method (CMP method), the second insulating film formed later is further flattened,
When the semiconductor film formed over the second insulating film is crystallized by laser light, its crystallinity can be further increased.

A second insulating film 707 is formed on the second interlayer insulating film 706. Then, a second TFT 708 is formed over the second insulating film 707. Note that the channel width of the channel formation region of the second insulating film 707 is approximately 1 to 2 μm.

A third interlayer insulating film 709 is formed so as to cover the second TFT 708, and the third interlayer insulating film 7 is formed.
09, a second connection wiring 711 and a second TFT 70.
The wiring 710 electrically connected to 8 is formed. Note that the first connection wiring 705 and the second connection wiring 7
An embedded wiring (plug) 712 is formed between the wiring 11 and the wiring 11 by a damascene process or the like.

Then, the wiring 10 and the second connection wiring 711.
A fourth interlayer insulating film 713 is formed so as to cover the.

In this embodiment, the first TFT 702 and the second TFT 702
The TFT 708 has a so-called stack structure in which it can be overlapped with the inter-layer insulating film. Figure 7
Although the semiconductor device having a stack structure of two layers is shown in (A), it may have a stack structure of three or more layers. In that case, in order to prevent the element formed in the lower layer from being irradiated with laser light, an inorganic insulating film which absorbs laser light, such as the second interlayer insulating film 706, is provided between the layers. .

The three-dimensionalized semiconductor device can be highly integrated and the wiring for electrically connecting the elements can be shortened, so that signal delay due to wiring capacitance can be prevented. , Faster operation is possible.

The TFT using the present invention is described in the 4th New Functional Device Technology Symposium Proceedings, July 1985, p20.
5. It can also be used for the CAM and RAM coexisting chips described in Section 1. FIG. 7B shows a memory (RAM)
Content-Addressable Memory (CAM)
And a model in which a RAM coexisting chip is achieved. First
The second layer is a layer in which a word processing circuit is formed.
The third layer is a layer in which a processor corresponding to the third layer RAM is formed by various logic circuits, and the third layer is a layer in which RAM cells are formed. An associative memory (CAM) is formed by the second layer processor and the third layer RAM cell. Further, the fourth layer is a data RAM (data RAM), and coexists with the associative memory formed by the second and third layers.

As described above, the present invention can be applied to various three-dimensional semiconductor devices.

This embodiment can be implemented by freely combining with Embodiments 1 to 11.

(Embodiment 10) In this embodiment, an example in which an optical fiber is used for an optical system to form a laser beam of laser light output from one laser oscillation device into a linear or rectangular shape will be described.

FIG. 21A is a block diagram showing the structure of the optical system of this embodiment. In FIG. 21A, 7000
Is a lens group including a plurality of lenses, and 7001 is an optical fiber group including a plurality of optical fibers. Each lens of the lens group 7000 is an optical fiber group 70
00 corresponds to each optical fiber and has a role of condensing the laser light so that the laser light output from the laser oscillation device enters each optical fiber. At this time, it is important to control the incident angle of the laser light in each lens so that the laser light is totally reflected and proceeds in each optical fiber.

FIG. 21B shows the structure of the optical fiber group 7001. FIG. 21B shows an example of an optical fiber group. The arrangement of the bundled optical fibers 7004 is different between the incident side and the emitting side of the optical fiber group 7001, and the incident laser light is emitted from random positions to form a laser beam 7003 having a uniform energy density. The shape of the laser beam can be rectangular or linear.

With the above structure, a linear or rectangular laser beam having a uniform energy density can be formed.

This embodiment can be implemented by freely combining with Embodiments 1 to 9.

[0175]

According to the present invention, it is possible to prevent the formation of grain boundaries in the channel formation region, so that the grain boundaries reduce the on-current, increase the off-current, and increase the number of TFs.
It is possible to prevent the characteristics from varying in T.

By forming a TFT in which a plurality of channel forming regions are sandwiched between one source region and one drain region, the channel width (in this case, the sum of the channel widths of all the channel forming regions is formed). In addition, the area of the portion where the channel formation region and the gate insulating film are in contact with each other can be increased, and a larger on-current can be obtained. Moreover, by forming a plurality of channel formation regions, heat generated in the channel formation regions during driving of the TFT can be radiated more efficiently.

Since the channel forming region is formed from one single crystal, the crystal orientation is uniform in each channel forming region. Therefore, the film quality of the gate insulating film formed in contact with the channel formation region becomes uniform, so that the interface state density becomes low and thus the mobility of the TFT is improved,
In addition, the yield and variation of the device can be suppressed and the reliability can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a diagram showing how a sub-island is irradiated with laser light.

FIG. 2 is a diagram of an island formed by patterning a crystallized sub-island.

3 is a diagram showing a structure of a TFT formed using the island shown in FIG.

FIG. 4 is a diagram showing a flowchart of a production system.

FIG. 5 is a diagram of a laser irradiation device.

FIG. 6 is a diagram of a laser irradiation device.

7A and 7B are cross-sectional views of a TFT having a stack structure and an example of a structure of a semiconductor device using the TFT.

FIG. 8 is a diagram of a TFT formed using islands that are isolated from each other.

FIG. 9 is a diagram showing a state of wirings connected to a TFT having a plurality of channel formation regions.

FIG. 10 is a diagram showing a distribution of energy density of a laser beam.

FIG. 11 is a diagram showing a distribution of energy density of a laser beam.

FIG. 12 is a diagram showing a distribution of energy density of a laser beam.

FIG. 13 is a diagram of an optical system.

FIG. 14 is a diagram of an optical system.

FIG. 15 is a diagram showing a distribution of energy density in the direction of the central axis of the superposed laser beams.

FIG. 16 is a diagram showing the relationship between the distance between the centers of laser beams and the energy difference.

FIG. 17 is a diagram showing a distribution of output energy in the direction of the central axis of a laser beam.

FIG. 18 illustrates a structure of a light emitting device which is an example of a semiconductor device of the present invention.

FIG. 19 is a diagram showing a structure of a pixel of a light emitting device which is an example of a semiconductor device of the invention.

20A to 20C are diagrams of electronic devices each including a semiconductor device of the present invention.

FIG. 21 is a diagram of an optical system using an optical fiber.

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Claims (6)

[Claims] 1. A semiconductor film is formed on an insulating surface, the semiconductor film is patterned to form a sub-island having a plurality of regions to be a channel formation region, and the plurality of regions to be a channel formation region are formed. The sub-islands are separated from each other, and the continuous-wave laser light is scanned in the channel length direction of the channel formation region to irradiate the laser light to the sub-island, and the edge of the sub-island irradiated with the laser light A method for manufacturing a semiconductor device, characterized in that an island having a plurality of the channel formation regions is formed by etching the vicinity, and a TFT is manufactured using the island. 2. A semiconductor film is formed on an insulating surface, the semiconductor film is patterned to form a sub-island having a plurality of regions to be a channel formation region, and the plurality of regions to be a channel formation region are formed. The plurality of regions that are separated from each other and serve as the channel formation region have a width of 3 μm or less in a direction perpendicular to the channel length direction, and scan continuous wave laser light in the channel length direction. Then, the sub-island is irradiated with the laser light, and the vicinity of the edge of the sub-island irradiated with the laser light is etched to form an island having a plurality of the channel formation regions. A method for manufacturing a semiconductor device, which comprises: 3. The method for manufacturing a semiconductor device according to claim 1, wherein the scanning with laser light is performed under a reduced pressure atmosphere or an inert gas atmosphere. 4. The laser beam according to claim 1, wherein the laser light is YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, glass laser, ruby laser, alexandride laser, Ti: A method for manufacturing a semiconductor device, wherein the semiconductor device is produced by using one or more selected from sapphire laser, Y ₂ O ₃ laser, and Nd: YVO ₄ laser. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the laser light is output using a slab laser. 6. The method for manufacturing a semiconductor device according to claim 1, wherein the laser light is a second harmonic.