JP2002033330A - Semiconductor device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a TFT, capable of a high-speed operation by manufacturing a crystalline semiconductor film, for which the position and size of a crystal grain are controlled and using the crystalline semiconductor film in the channel- forming region of the TFT. SOLUTION: Among plural base insulation films of different refractive indexes, the base insulation film of at least one layer is provided with a step and the level difference of the film thickness is made. By emitting a laser beam from the back surface side of the substrate (or both of the front surface side and back surface side of the substrate), the effective intensity distribution of the laser beam to the semiconductor film is formed, and a temperature gradient corresponding to the step shape and film thickness distribution of the base insulation film is generated on the semiconductor film. By utilizing them, the generation place and direction of lateral growth are controlled, and the crystal grain of a large grain diameter is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having a circuit composed of thin film transistors (hereinafter, referred to as TFTs). For example, the present invention relates to a configuration of an electro-optical device typified by a liquid crystal display device, and an electric apparatus including the electro-optical device as a component. Further, the present invention relates to a method for manufacturing the device. Note that in this specification, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics, and the above-described electro-optical device and electric device are also included in the category.

[0002]

2. Description of the Related Art In recent years, techniques for performing laser annealing on an amorphous semiconductor film formed on an insulating substrate such as glass to crystallize or improve crystallinity have been widely studied. Silicon is often used for the amorphous semiconductor film.

A glass substrate is inexpensive, has good workability, and has an advantage that a large-area substrate can be easily manufactured, as compared with a synthetic quartz glass substrate which has been often used in the past.
This is the reason for the above research. A laser is preferably used for crystallization because the melting point of the glass substrate is low. The laser can apply high energy only to the amorphous semiconductor film without increasing the temperature of the substrate so much.

[0004] Since a crystalline semiconductor is made of many crystal grains, it is also called a polycrystalline semiconductor film. Since a crystalline semiconductor film formed by performing laser annealing has high mobility, a thin film transistor (TFT) is formed using the crystalline semiconductor film, and for example, a pixel portion is formed over a single glass substrate. And a TFT for a driving circuit, which is widely used in a monolithic liquid crystal electro-optical device and the like.

[0005] Further, a pulse laser beam such as an excimer laser having a large output is processed by an optical system so as to form a square spot of several cm square or a linear shape having a length of 10 cm or more on the irradiated surface. The method of performing laser annealing by scanning the beam (or moving the irradiation position of the laser beam relative to the irradiated surface) is preferred because of high productivity and excellent industrial properties. .

In particular, when a linear beam is used, unlike the case where a spot-shaped laser beam that needs to be scanned back and forth and right and left is used, the surface to be irradiated is scanned only in a direction perpendicular to the longitudinal direction of the linear beam. Since laser irradiation can be performed on the whole, the productivity is high. The scanning is performed in a direction perpendicular to the longitudinal direction because it is the most efficient scanning direction.
Due to this high productivity, the use of a linear beam obtained by processing a pulsed excimer laser beam with an appropriate optical system in the laser annealing method is becoming the mainstream of the manufacturing technology of a liquid crystal display device using a TFT. The technology uses a TFT (pixel TF) that forms a pixel portion on a single glass substrate.
T) and a monolithic liquid crystal display device in which a TFT of a driving circuit provided around the pixel portion is formed.

However, the crystalline semiconductor film produced by the laser annealing method is formed by assembling a plurality of crystal grains, and the positions and sizes of the crystal grains are random. A TFT manufactured on a glass substrate is formed by separating the crystalline semiconductor by island patterning for element isolation. In that case, it was not possible to form the crystal grains by specifying the position and size of the crystal grains. Compared with the inside of the crystal grain, the interface (crystal grain boundary) of the crystal grain has an infinite number of recombination centers and capture centers due to an amorphous structure, crystal defects, and the like. It is known that, when carriers are trapped in the trapping center, the potential of the crystal grain boundary increases and acts as a barrier for the carriers, so that the current transport characteristics of the carriers are reduced. Although the crystallinity of the semiconductor film in the channel formation region has a significant effect on the electrical characteristics of the TFT, it is almost impossible to form the channel formation region with a single crystal semiconductor film by eliminating the influence of the crystal grain boundaries. It was possible.

In order to solve such a problem, various attempts have been made in the laser annealing method to form a crystal grain having a controlled position and a large grain size. Here, first, a solidification process of the semiconductor film after the semiconductor film is irradiated with a laser beam will be described.

It takes some time until solid-phase nucleation occurs in the liquid semiconductor film completely melted by the laser beam irradiation, and countless uniform (or non-uniform) nucleation occurs in the completely melted region. By the crystal growth, the solidification process of the liquid semiconductor film ends. In this case, the positions and sizes of the crystal grains obtained are random.

In the case where the semiconductor film is not completely melted by the laser beam irradiation and the solid-state semiconductor region partially remains without being completely melted, the solid-state semiconductor region is immediately crystallized from the solid-state semiconductor region after the laser beam irradiation. Growth begins. As described above, it takes some time for nucleation to occur in the completely melted region. Therefore, before nucleation occurs in the completely melted region, the solid-liquid interface (the solid-state semiconductor region and the solid-state semiconductor region) which is the tip of crystal growth in a direction parallel to the film surface of the semiconductor film (hereinafter, referred to as a lateral direction). The crystal grain grows to a length of several tens of times the film thickness by moving the interface with the melting region, which corresponds to the tip of the growth of the crystal nucleus. Such growth can result in a myriad of uniform (or non-uniform) nucleations in the fully molten region,
The process ends when the crystal grows. Hereinafter, this phenomenon is referred to as super lateral growth.

[0011] Even in an amorphous semiconductor film or a crystalline semiconductor film, there is an energy region of a laser beam for realizing the super lateral growth. However, the energy region is very narrow, and the position where large crystal grains can be obtained cannot be controlled. Further, the region other than the large-grain crystal grains was a microcrystalline region in which countless nucleation occurred or an amorphous region.

As described above, if the temperature gradient in the lateral direction can be controlled (generates a heat flow in the lateral direction) in the energy region of the laser beam where the semiconductor film is completely melted, the growth position of the crystal grain And the growth direction can be controlled. Various attempts have been made to realize this method.

For example, "R. Ishihara and A. Burtsev: AM
-LCD '98., P153-p156, 1998 ', a refractory metal film is formed between the substrate and the underlying silicon oxide film, and an amorphous silicon film is formed above the refractory metal film, The laser beam of the excimer laser is defined as the front side of the substrate (defined as the surface on which the film is formed) and the back side (defined as the surface opposite to the surface on which the film is formed). There is a report on the laser annealing method of irradiating from both sides. The laser beam emitted from the front surface side of the substrate is absorbed by the silicon film and converted into heat. On the other hand, the laser beam emitted from the back side of the substrate is absorbed by the high melting point metal film and converted into heat, and heats the high melting point metal film at a high temperature. Since the heated silicon oxide film between the heated refractory metal film and the silicon film functions as a heat accumulation layer, the cooling rate of the molten silicon film can be reduced. Here, it is reported that by forming a high-melting-point metal film at an arbitrary location, a crystal grain having a maximum diameter of 6.4 μm can be obtained at an arbitrary location.

Also, James S. Im of Colombia University, et al., Has proposed a Sequential Lateral Solidification method that can realize super lateral growth at any place.
(Hereinafter referred to as the SLS method). The SLS method is 1
For each shot, the slit-shaped mask is shifted by a distance (about 0.75 μm) for performing super lateral growth,
It performs crystallization.

[0015]

SUMMARY OF THE INVENTION The present inventors have filed Japanese Patent Application No. Hei.
No. 1-351060 describes a method of providing a step on an underlayer to increase the grain size of crystal grains. Here, the method will be described.

FIG. 1A shows a first sample in which a step is provided in a base insulating film. In the first sample, a silicon nitride oxide film (A-type) is formed over a synthetic quartz glass substrate, and an amorphous silicon film having a thickness of 55 nm is formed over the silicon nitride oxide film (A-type). I have. The silicon nitride oxide film (A-type), which is a base insulating film, is provided with steps to have a thin portion and a thick portion. Here, in this specification, the silicon nitride oxide film (A-type) has a composition ratio of S
a silicon oxynitride film in which i = 32%, O = 59%, N = 7%, and H = 2%, and a silicon nitride oxide film (B-type)
Means that the composition ratio is Si = 32%, O = 27%, N = 24%, H
= 17% silicon oxynitride film. The first sample was irradiated with a laser beam from the front surface side of the substrate to perform a heat conduction analysis simulation for crystallizing the amorphous silicon film. Figure 1 shows the results.
It is shown in (B). However, the conditions used in the calculation are as follows: the laser beam wavelength is 308 nm, the irradiation energy is 400 mJ / cm ² , the pulse width (laser beam output time) is 30 ns, and the laser beam is irradiated in a vacuum. did. Table 1 shows other parameters used in the calculation.

[0017]

[Table 1]

The result as shown in FIG. 1B is obtained because
This is because a temperature gradient occurs when the base insulating film functions as a heat capacity. Region B in FIG. 1A cools faster than other locations because heat escapes from both the underlying insulating film immediately below and the underlying insulating film present in the lateral direction. Conversely, the temperature of the region C is difficult to decrease because there is heat that escapes from the region B to the underlying insulating film immediately below the region C. Therefore, a temperature gradient occurs between the B region and the C region or between the B region and the A region. Due to the temperature gradient, crystal growth starts from the low temperature B region,
Since the solid-liquid interface moves to the region C or region A where the temperature is high, large crystal grains can be obtained.

That is, it has the same structure as that of a conventional structure used for a TFT manufactured on a glass substrate, that is, a structure in which a base insulating film is formed on a glass substrate and a semiconductor film is formed on the base insulating film. Yes, but Japanese Patent Application No. 11-35106
In No. 0, a step is formed by etching a desired position with respect to the base insulating film. When such a sample is irradiated with a laser beam from the front surface side of the substrate, a temperature distribution is generated inside the semiconductor film corresponding to the shape of the step of the base insulating film, and the location and direction of lateral growth are controlled. be able to.

It is structurally possible to manufacture a top gate type TFT using a semiconductor film formed by the method of R. Ishihara et al. As an active layer. However, a parasitic capacitance is generated by the silicon oxide film provided between the semiconductor film and the refractory metal film, so that power consumption increases,
It is difficult to realize the high-speed operation of. On the other hand, by using a high melting point metal film as the gate electrode, it can be considered that it can be effectively applied to a bottom gate type or inverted stagger type TFT. However, in a structure in which a silicon oxide film is formed on a substrate, a refractory metal film is formed on the silicon oxide film, and an amorphous silicon film is formed on the refractory metal film,
Even if the thickness of the amorphous silicon film is excluded, the thicknesses of the refractory metal film and the silicon oxide film are both suitable for the crystallization step and suitable for the electrical characteristics of the TFT element. Since the thickness does not always match, both the optimum design in the crystallization step and the optimum design of the element structure cannot be satisfied at the same time.

If a refractory metal film having no translucency is formed on the entire surface of the glass substrate, it becomes impossible to manufacture a transmissive liquid crystal display device. Since a chromium (Cr) film or a titanium (Ti) film used as a high melting point metal material has high internal stress, there is a high possibility that a problem occurs in adhesion to a glass substrate. Further, the influence of the internal stress extends to the semiconductor film formed thereover, and it is highly likely that the internal stress acts as a force for giving a strain to the formed crystalline semiconductor film.

On the other hand, in order to control the threshold voltage (hereinafter, referred to as Vth), which is an important parameter in the TFT, within a predetermined range, in addition to controlling the valence electrons in the channel forming region, the threshold voltage is closely controlled to the active layer. It is necessary to reduce the charged defect density of the base film and the gate insulating film formed of the insulating film by using the method, and to consider the balance of the internal stress. In response to such demands, materials containing silicon as a constituent element, such as a silicon oxide film and a silicon oxynitride film, have been suitable. Therefore, there is a concern that providing a high melting point metal film between the substrate and the base film may break the balance.

In addition, the SLS method requires precise control on the micron level in the technique of relative positioning between the mask and the substrate, and is more complicated than an ordinary laser irradiation apparatus. Further, there is a problem in throughput when used for manufacturing a TFT applied to a liquid crystal display having a large area region.

The present invention is a technique for solving the above problems, in which a crystalline semiconductor film in which the positions and sizes of crystal grains are controlled is manufactured, and the crystalline semiconductor film is formed by using a TFT channel. By using the TFT in the formation region, a TFT which can operate at high speed is realized. Further such TF
It is an object of the present invention to provide a technique which can be applied to various semiconductor devices such as a liquid crystal display device of a transmission type T and a display device using an electroluminescent material.

[0025]

Means for Solving the Problems A silicon nitride film is formed on a synthetic quartz glass substrate, a silicon nitride oxide film (A-type) is formed on the silicon nitride film, and the silicon nitride oxide film (A) is formed.
Simulation is performed using a second sample in which a 55-nm-thick amorphous silicon film is formed on (type). The second sample is irradiated with a laser beam from the back side of the substrate, and the reflectance of the laser beam with respect to the amorphous silicon film is calculated. The results are shown in FIGS. 2A shows a calculation result depending on the thickness of the silicon nitride oxide film (A-type) when the thickness of the silicon nitride film is fixed to 50 nm, and FIG. ty
pe) Calculation results depending on the thickness of the silicon nitride film when the film thickness is fixed to 100 nm. At the time of calculation, the wavelength of the laser beam was 308 nm, and the other parameters shown in Table 1 were used.

FIG. 2A shows that even with the same irradiation energy of the laser beam, the silicon nitride oxide film (A-type)
It can be seen that the reflectance of the amorphous silicon film changes periodically by changing the thickness of the film. Also,
As shown in FIG. 2B, by changing the thickness of the silicon nitride film even with the same laser beam irradiation energy,
It can be seen that the reflectance for the amorphous silicon film changes periodically.

Next, the calculation result of the second sample with the wavelength of the laser beam set to 532 nm is shown in FIG.
Shown in FIG. 3A shows a calculation result depending on the thickness of the silicon nitride oxide film (A-type) when the thickness of the silicon nitride film is fixed to 50 nm, and FIG.
The graph shows a calculation result depending on the thickness of the silicon nitride film when the thickness of (type) is fixed to 100 nm. Table 2 shows the parameters used in the calculation.

[0028]

[Table 2]

FIG. 3A shows that the silicon nitride oxide film (A-type) is formed even with the same laser beam irradiation energy.
It can be seen that the reflectance of the amorphous silicon film changes periodically by changing the thickness of the film. Also,
FIG. 3B shows that the reflectance of the amorphous silicon film is periodically changed by changing the thickness of the silicon nitride film.

That is, when irradiating a laser beam from the back surface side of the substrate, the thickness of the amorphous silicon is changed by changing the thickness of at least one of the plurality of underlying insulating films having different refractive indexes. It can be seen that the effective irradiation intensity of the laser beam on the film can be changed. Further, it can be seen that the periodic change in the reflectance with respect to the amorphous silicon film appears even when the wavelength of the laser beam is changed. However, the period of the change in the reflectance varies depending on the wavelength of the laser beam, the thickness of the base insulating film, and the like.

Next, a lower silicon nitride oxide film is formed on the synthetic quartz glass substrate, and a film thickness of 1 is formed on the lower silicon nitride oxide film.
Forming a silicon nitride oxide film (A-type) of 00 nm;
55 nm thick on the silicon nitride oxide film (A-type)
A simulation is performed using a third sample forming the amorphous silicon film of FIG. Note that the lower silicon nitride oxide film is used for differentiating it from the silicon nitride oxide film (A-type) and the silicon nitride oxide film (B-type), and in this simulation, the composition ratio of the lower silicon nitride oxide film is used. Is changed, the refractive index of the lower silicon nitride oxide film is changed. FIG. 10A shows the reflectance of the third sample with respect to the amorphous silicon film when irradiated with a laser beam having a wavelength of 308 nm from the back side of the substrate.
FIG. 10A shows that the reflectance of the lower silicon nitride oxide film with respect to the amorphous silicon film changes as the refractive index of the lower silicon nitride oxide film changes.

On the other hand, a film thickness of 100
A fourth sample in which a silicon oxynitride film (A-type) having a thickness of 55 nm is formed and an amorphous silicon film having a thickness of 55 nm is formed on the silicon oxynitride film (A-type), has a wavelength of 308 nm.
The reflectance of the amorphous semiconductor film when irradiated with a laser beam of m is 0 nm when the thickness of the silicon nitride film in FIG.
In the case of reading the above case, it can be seen that it is 42.5%.
In other words, when the proportion of nitrogen in the composition ratio of the lower silicon oxynitride film is increased to make the film quality of the lower silicon oxynitride film closer to the silicon oxynitride film (A-type), the reflection of the laser beam on the amorphous silicon film is reduced. The rate is substantially the same as the case where the base insulating film is a stack of the lower silicon nitride oxide film and the silicon nitride oxide film (A-type) and the case where only the silicon nitride oxide film (A-type) is used. In other words, even if a base insulating film having a similar refractive index is stacked and a step is provided to one of the base insulating films to provide a step, the intensity distribution of the laser beam in the semiconductor film does not occur, and It turns out that there is not much meaning.

Subsequently, a wavelength of 532 nm was added to the third sample.
Is irradiated from the back side of the substrate to change the composition ratio of the lower silicon oxynitride film, thereby changing the refractive index of the lower silicon oxynitride film and changing the reflectance with respect to the amorphous silicon film. I have. The result is shown in FIG. On the other hand, when the fourth sample is irradiated with a laser beam having a wavelength of 532 nm, the reflectance with respect to the amorphous semiconductor film is:
Reading from the place where the thickness of the silicon nitride film in FIG. 3B is 0 nm, it can be seen that it is 10%. Even in the case of a laser beam having a wavelength of 532 nm, when the composition of the lower silicon nitride oxide film is changed so that the film quality of the lower silicon nitride oxide film approaches the silicon nitride oxide film (A-type), the amorphous silicon The reflectance is almost the same as the case where the base insulating film is a stack of the lower silicon nitride oxide film and the silicon nitride oxide film (A-type) and the case where only the silicon nitride oxide film (A-type) is used. In other words, even when a laser beam having a wavelength of 532 nm is used, even when a base insulating film having a similar refractive index is laminated and one of the base insulating films is provided with a step to give a step to the film thickness, It can be seen that no effective intensity distribution of the laser beam is generated in the porous silicon film, and that the lamination is not meaningful.

From Table 2, it can be seen that the silicon nitride oxide film (At
ype), a Corning 1737 substrate, and a synthetic quartz glass substrate have approximately the same refractive index for a wavelength of 532 nm. Thus, a silicon nitride oxide film (A-type) in which a 1737 glass substrate or a synthetic quartz glass substrate is used as a substrate and a step is provided on the substrate to give a graded film thickness.
Is formed, an amorphous silicon film is formed on the silicon nitride oxide film (A-type), and a laser beam is irradiated from the back side of the substrate. However, the silicon nitride oxide film (A
(Type), the unevenness on the surface of the substrate is coarser than the step provided in step (type). Therefore, even when the laser beam is irradiated from the back side of the substrate, an effective laser beam intensity distribution in the amorphous silicon film is obtained. Hardly occurs. That is, for the wavelength of the laser beam to be used, it is meaningless that the base insulating film formed on the substrate has the same refractive index as the substrate and has a different refractive index from the substrate. I understand.

As described above, the change in the reflectance with respect to the amorphous semiconductor film is caused by the interference effect of the thin films of the plurality of stacked base insulating films. By combining the rates, an arbitrary laser beam intensity distribution can be obtained. In view of the above, the present invention provides a large grain size by using a plurality of base insulating films, and providing at least one of the plurality of base insulating films with steps to provide a step to the film thickness. It is possible to form a crystalline semiconductor film having position-controlled crystal grains. However, it is assumed that at least two types of insulating films having different refractive indices are used for the plurality of base insulating films, and the laser beam irradiation is performed from the back side of the substrate or from both the front side and the back side of the substrate.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] FIG.
This will be described with reference to FIG. In FIG. 4A, an alkali-free glass substrate such as barium borosilicate glass or aluminoborosilicate glass or a synthetic quartz glass substrate is used as a substrate 1001. For example, Corning 7059 glass or 1
737 glass or the like can be preferably used.

A first base insulating film 1002 is formed on the substrate 1001 by a known means (LPCVD, plasma CVD, etc.).
Silicon nitride film, silicon oxynitride film (composition ratio Si
= 32%, O = 27%, N = 24%, H = 17%). In this embodiment, a silicon nitride film is formed to a thickness of 50 nm by a plasma CVD method.

A second base insulating film 1003 having a refractive index different from that of the first base insulating film 1002 is formed thereon by a known means (LPCVD, plasma CVD, etc.) using a silicon oxide film, a silicon oxynitride film, or the like. Form. In this embodiment,
Using a plasma CVD method, a silicon oxynitride film (composition ratio Si
= 32%, O = 59%, N = 7%, H = 2%)
To 150 nm.

After the formation of the second base insulating film 1003, a resist mask is formed by using a photolithography technique, and unnecessary portions are etched to have a thickness of 130 to 15 nm.
A third base insulating film 1004 having a portion of 0 nm and a portion of 78 to 98 nm is obtained (FIG. 4B). For the etching, a dry etching method using a fluorine-based gas may be used, or a wet etching method using a fluorine-based aqueous solution may be used. When the wet etching method is selected, for example, 7.13% of ammonium hydrogen fluoride (NH ₄ HF ₂ ) and ammonium fluoride (N
H ₄ F) may be etched with a mixed solution containing 15.4% (LAL500, manufactured by Stella Chemifa).

The reason why the thickness of the third base insulating film 1004 is set to two levels is to form an effective intensity distribution of the laser beam with respect to the semiconductor film. In FIG. 2A, the film thickness corresponding to the maximum value of about 62.5% of the reflectance for the amorphous silicon film which periodically appears is 130 to 150 nm, and the minimum value for the amorphous silicon film is 22.7. % Is 78 to 98 nm. As already described, since the reflectance with respect to the amorphous silicon film has periodicity, if the film thickness corresponds to about the maximum value and the minimum value of the reflectance with respect to the amorphous silicon film, The thickness is not limited to the above. However, the third base insulating film 100
It is preferable that the difference between the two thicknesses of the four steps is smaller than the thickness of the amorphous semiconductor film formed thereafter. The angle of the side wall at the step of the second base insulating film 1004 is
001 to 5 ° or more and less than 85 ° (preferably 30 °
(.Degree. To 60.degree.) Is preferably tapered so as to secure the step coverage of the film to be laminated thereon.

The amorphous semiconductor film 1005 shown in FIG.
Is formed to a thickness of 25 to 200 nm (preferably 30 to 100 nm) along a third base insulating film 1004 having a step by a known method such as a plasma CVD method or a sputtering method. In this embodiment, the amorphous silicon film is formed with a thickness of 55 nm. However, as the amorphous semiconductor film, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.

FIG. 4 (c) is a view for explaining a crystallization step of irradiating a laser beam from the back side, and FIG. 4 (d) is a crystallization step of irradiating the laser beam from both the front side and the back side of the substrate. It is a figure explaining a process. In the present invention,
Either method will be used. In the crystallization by the laser annealing method, it is desirable that hydrogen contained in the amorphous semiconductor film is first released, and is exposed to a nitrogen atmosphere at 400 to 500 ° C. for about one hour to reduce the amount of hydrogen contained to 5 atom.
% Or less. This significantly improves the laser resistance of the film.

The laser oscillator used in the laser annealing method will be described. Excimer lasers are widely used because they have high output and can oscillate high repetition pulses of about 300 Hz at present. In addition to a pulse oscillation excimer laser, a continuous oscillation excimer laser,
An r laser, a YAG laser, a YVO ₄ laser, a YLF laser, or the like can also be used.

Using one of the laser oscillators described above,
The amorphous semiconductor film is crystallized by any one of the irradiation methods shown in FIGS. As described above, since the thickness of the third base insulating film 1004 has two stages, when the laser beam is irradiated from the back surface side, the reflectance of the amorphous semiconductor film 1005 with respect to the amorphous semiconductor film 1005 is reduced. Is about 22.7% in the area A and about 62.5% in the area B, and the effective intensities of the laser beams are different.

Further, the step edge (the boundary between the region A and the region B) in the third base insulating film 1004 in FIG. 4C or FIG. Since both the base insulating films exist in the lateral direction, they cool faster than in other places. Therefore, solidification starts from the semiconductor film on the step edge of the second base insulating film, which first drops in temperature, and crystal nuclei 1006 are generated. The crystal nucleus becomes the center of the crystal growth, and the crystal growth proceeds toward the region A or the region B where the temperature is high and in the molten state. However, since the region A has a higher laser beam absorptivity than the region B, the crystal nucleus grows in the direction indicated by 1007, so that a larger crystal grain is formed in the semiconductor film in the region A. In this manner, a crystalline semiconductor film having a large grain size and having position-controlled crystal grains can be formed.
(FIG. 4 (e))

After the irradiation with the laser beam, the crystalline semiconductor film is formed in an atmosphere containing 3 to 100% hydrogen.
The remaining defects can be neutralized by a heat treatment at 450 to 450 ° C. or a heat treatment at 200 to 450 ° C. in an atmosphere containing hydrogen generated by plasma.
By using the region A of the crystalline semiconductor film thus manufactured as a channel formation region to manufacture a TFT,
The electrical characteristics of the TFT can be improved.

[Embodiment 2] This embodiment will be described with reference to FIG. In FIG. 5A, an alkali-free glass substrate such as barium borosilicate glass or aluminoborosilicate glass or a synthetic quartz glass substrate is used as a substrate 1001.
For example, 7059 glass or 1737 glass manufactured by Corning Incorporated can be suitably used.

A first base insulating film 1009 is formed on the substrate 1001 by a known means (LPCVD, plasma CVD, etc.).
Silicon nitride film, silicon oxynitride film (composition ratio Si
= 32%, O = 27%, N = 24%, H = 17%). In this embodiment, a silicon nitride film is formed to a thickness of 55 to 85 nm by a plasma CVD method.

After the formation of the first base insulating film 1009, a resist mask is formed by using a photolithography technique, and unnecessary portions are etched to have a film thickness of 55-8.
A second base insulating film 1010 having a portion of 5 nm and a portion of 25 to 45 nm is obtained (FIG. 5B). For the etching, a dry etching method using a fluorine-based gas may be used, or a wet etching method using a fluorine-based aqueous solution may be used. When the wet etching method is selected, for example, 7.13% of ammonium hydrogen fluoride (NH ₄ HF ₂ ) and ammonium fluoride (N
H ₄ F) may be etched with a mixed solution containing 15.4% (LAL500, manufactured by Stella Chemifa).

A third base insulating film 1011 having a refractive index different from that of the second base insulating film 1010 is formed thereon by a known means (LPCVD, plasma CVD, or the like), such as a silicon oxide film or a silicon oxynitride film. Formed. In this embodiment, a 100-nm-thick silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N = 7%, H = 2%) is formed by a plasma CVD method.

The reason why the thickness of the second base insulating film 1010 is set to two levels is to form an effective intensity distribution of the laser beam with respect to the semiconductor film. In FIG. 2B, the film thickness corresponding to the maximum value of about 42.5% of the reflectance for the amorphous silicon film which periodically appears is 55 to 85 nm, and the minimum value of about 20% for the amorphous silicon film is shown. Is 25 to 45 nm. As already described, since the reflectance with respect to the amorphous silicon film has periodicity, if the film thickness corresponds to about the maximum value and the minimum value of the reflectance with respect to the amorphous silicon film, The thickness is not limited to the above. However, it is preferable that the difference between the thicknesses of the second base insulating film 1010 in the two stages be smaller than the thickness of the amorphous semiconductor film formed thereafter. The angle of the side wall at the step of the second base insulating film 1010 is
1 to 5 ° or more and less than 85 ° (preferably 30 ° to
(60 °) is desirably etched in a tapered shape to secure the step coverage of the film laminated thereon.

The amorphous semiconductor film 1012 shown in FIG.
Is formed along the third base insulating film 1011 to a thickness of 25 to 200 nm (preferably 30 to 100 nm) by a known method such as a plasma CVD method or a sputtering method. In this embodiment, an amorphous silicon film is formed to a thickness of 55 nm. However,
As the amorphous semiconductor film, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.

FIG. 5C is a view for explaining a crystallization step of irradiating a laser beam from the back side, and FIG. 5D is a crystallization step of irradiating the laser beam from both the front side and the back side of the substrate. It is a figure explaining a process. In the present invention,
Either method will be used. In the crystallization by the laser annealing method, it is desirable that hydrogen contained in the amorphous semiconductor film is first released, and is exposed to a nitrogen atmosphere at 400 to 500 ° C. for about one hour to reduce the amount of hydrogen contained to 5 atom.
% Or less. This significantly improves the laser resistance of the film.

The laser oscillator used in the laser annealing method will be described. Excimer lasers are widely used because they have high output and can oscillate high repetition pulses of about 300 Hz at present. In addition to a pulse oscillation excimer laser, a continuous oscillation excimer laser,
An r laser, a YAG laser, a YVO ₄ laser, a YLF laser, or the like can also be used.

Using any of the laser oscillators described above,
The amorphous semiconductor film is crystallized by the irradiation method shown in FIG. 5C or 5D. As described above, since the thickness of the second base insulating film 1010 has two levels,
When the laser beam is irradiated from the back side, the reflectivity of the laser beam with respect to the amorphous semiconductor film 1012 is about 20% in the area A and about 42.5% in the area B. Strength is different.

Further, the step edge (the boundary between the region A and the region B) in the second base insulating film 1010 in FIG. 5C or FIG. Since both the base insulating films exist in the lateral direction, they cool faster than in other places. Therefore, solidification starts from the semiconductor film on the step edge of the second base insulating film, which first drops in temperature, and crystal nuclei 1006 are generated. The crystal nucleus becomes the center of the crystal growth, and the crystal growth proceeds toward the region A or the region B where the temperature is high and in the molten state. However, since the region A has a higher laser beam absorptivity than the region B, the crystal nucleus grows in the direction indicated by 1007, so that a larger crystal grain is formed in the semiconductor film in the region A. In this manner, a crystalline semiconductor film having a large grain size and having position-controlled crystal grains can be formed.
(FIG. 5 (e))

After the irradiation with the laser beam, the crystalline semiconductor film is placed in an atmosphere containing 3 to 100% hydrogen.
The remaining defects can be neutralized by a heat treatment at 450 to 450 ° C. or a heat treatment at 200 to 450 ° C. in an atmosphere containing hydrogen generated by plasma.
By using the region A of the crystalline semiconductor film thus manufactured as a channel formation region to manufacture a TFT,
The electrical characteristics of the TFT can be improved.

[Embodiment 3] This embodiment will be described with reference to FIG. In FIG. 6A, an alkali-free glass substrate such as barium borosilicate glass or aluminoborosilicate glass or a synthetic quartz glass substrate is used as a substrate 1001.
For example, 7059 glass or 1737 glass manufactured by Corning Incorporated can be suitably used.

A first base insulating film 1016 is formed on the substrate 1001 by a known means (LPCVD, plasma CVD, etc.).
Silicon nitride film, silicon oxynitride film (composition ratio Si
= 32%, O = 27%, N = 24%, H = 17%). In this embodiment, a silicon nitride film is formed to a thickness of 50 nm by a plasma CVD method.

A second base insulating film 1017 having a refractive index different from that of the first base insulating film 1016 is formed thereon by a known means (LPCVD method, plasma CVD method, or the like), such as a silicon oxide film or a silicon oxynitride film. Formed. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N = 7%, H = 2%) is formed to a thickness of 78 to 98 nm by a plasma CVD method.

After forming the second base insulating film 1017, a resist mask is formed by photolithography, and unnecessary portions are etched to have a thickness of 25 to 45 n.
A third base insulating film 1018 having a portion of m and a portion of 78 to 98 nm is obtained (FIG. 6B). For the etching, a dry etching method using a fluorine-based gas may be used, or a wet etching method using a fluorine-based aqueous solution may be used. When the wet etching method is selected, for example, ammonium hydrogen fluoride (NH
₄ HF ₂ ) with ammonium fluoride (NH)
₄ F) a mixture containing 15.4% (Stella Chemifa Co.,
Etching may be performed using LAL500 (trade name).

The reason why the thickness of the third base insulating film 1018 is set to two levels is to form an effective intensity distribution of the laser beam with respect to the semiconductor film. In FIG. 2A, the film thickness corresponding to the maximum value of about 62.5% of the reflectance for the amorphous silicon film which periodically appears is 25 to 45 nm, and the minimum value for the amorphous silicon film is 22.7. % Is 78 to 98 nm. As already described, since the reflectance with respect to the amorphous silicon film has periodicity, if the film thickness corresponds to about the maximum value and the minimum value of the reflectance with respect to the amorphous silicon film, The thickness is not limited to the above. However, the third base insulating film 1018
It is desirable that the difference between the two thicknesses be smaller than the thickness of the amorphous semiconductor film formed thereafter. The angle of the side wall at the step of the third base insulating film 1018 is
01 to 5 ° or more and less than 85 ° (preferably 30 °
(.About.60 [deg.]), It is desirable to secure the step coverage of the film laminated thereon by etching in a taper shape.

The amorphous semiconductor film 1019 shown in FIG.
Is formed to a thickness of 25 to 200 nm (preferably 30 to 100 nm) along a third base insulating film 1018 having a step by a known method such as a plasma CVD method or a sputtering method. In this embodiment, an amorphous silicon film is formed to a thickness of 55 nm. However, as the amorphous semiconductor film, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.

FIG. 6 (c) is a view for explaining a crystallization step of irradiating a laser beam from the back side, and FIG. 6 (d) is a crystallization step of irradiating the laser beam from both the front side and the back side of the substrate. It is a figure explaining a process. In the present invention,
Either method will be used. In the crystallization by the laser annealing method, it is desirable that hydrogen contained in the amorphous semiconductor film is first released, and is exposed to a nitrogen atmosphere at 400 to 500 ° C. for about one hour to reduce the amount of hydrogen contained to 5 atom.
% Or less. This significantly improves the laser resistance of the film.

A laser oscillator used in the laser annealing method will be described. Excimer lasers are widely used because they have high output and can oscillate high repetition pulses of about 300 Hz at present. In addition to a pulse oscillation excimer laser, a continuous oscillation excimer laser,
An r laser, a YAG laser, a YVO ₄ laser, a YLF laser, or the like can also be used.

Using any of the laser oscillators described above,
The amorphous semiconductor film is crystallized by any one of the irradiation methods shown in FIGS. 6C and 6D. As described above, since the thickness of the third base insulating film 1018 has two levels, when a laser beam is irradiated from the back surface side, the reflectance of the amorphous semiconductor film 1019 with respect to the amorphous semiconductor film 1019 is reduced. Is about 22.7% in the area A and about 62.5% in the area B, and the effective intensities of the laser beams are different.

Further, the step edge (the boundary between the region A and the region B) in the third base insulating film 1018 in FIG. 6C or FIG. Since both the base insulating films exist in the lateral direction, they cool faster than in other places. Therefore, solidification starts from the semiconductor film on the step edge of the third base insulating film, which first drops in temperature, and crystal nuclei 1006 are generated. The crystal nucleus becomes the center of the crystal growth, and the crystal growth proceeds toward the region A or the region B where the temperature is high and in the molten state. However, since the region A has a higher laser beam absorptivity than the region B, the crystal nucleus grows in the direction indicated by 1007, so that a larger crystal grain is formed in the semiconductor film in the region A. In this manner, a crystalline semiconductor film having a large grain size and having position-controlled crystal grains can be formed.
(FIG. 6 (e))

After the irradiation with the laser beam, the crystalline semiconductor film is placed in an atmosphere containing 3 to 100% of hydrogen.
The remaining defects can be neutralized by a heat treatment at 450 to 450 ° C. or a heat treatment at 200 to 450 ° C. in an atmosphere containing hydrogen generated by plasma.
By using the region A of the crystalline semiconductor film thus manufactured as a channel formation region to manufacture a TFT,
The electrical characteristics of the TFT can be improved.

[0069]

[Embodiment 1] Here, a simulation result of the present invention will be described with reference to FIGS.

In FIG. 7A, a non-alkali glass substrate such as barium borosilicate glass or aluminoborosilicate glass or a synthetic quartz glass substrate is used as the substrate 1001. In this embodiment, a synthetic quartz glass substrate is used.

A first base insulating film 1023 is formed on the substrate 1001 by a known means (LPCVD, plasma CVD, etc.).
A silicon nitride film, a silicon oxynitride film, or the like. In this embodiment, a silicon nitride film is formed to a thickness of 50 nm by a plasma CVD method.

The second base insulating film 10 having a different refractive index from that of the first base insulating film 1023 is formed on the first base insulating film 1023.
24 by a known means (LPCVD method or plasma CV
D method or the like) to form a silicon oxynitride film or the like. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N = 7%, H = 2%) is used by a plasma CVD method.
Of 140 nm.

The second base insulating film 1024 was formed.
After that, a resist mask is formed using photolithography technology.
Formed and etched unnecessary parts to a thickness of 140n
Third underlying insulating film 1 having a portion of m and a portion of 88 nm
025 (FIG. 7 (b)). For the etching,
Dry etching method using elemental gas may be used
And a wet etching method using a fluorine-based aqueous solution
May be used. Where to choose the wet etching method
In this case, for example, ammonium hydrogen fluoride (NH _FourH
F_Two) And ammonium fluoride (NH)_FourF)
Liquid mixture containing 15.4% (trade name L, manufactured by Stella Chemifa)
(AL500).

The reason why the thickness of the third base insulating film 1025 is set to two levels is to form an effective intensity distribution of the laser beam with respect to the semiconductor film. In FIG. 2A, the film thickness that corresponds to the maximum value of 62.5% of the reflectance for the amorphous silicon film that periodically appears is 140 nm, and corresponds to the minimum value of 22.7% for the amorphous silicon film. The film thickness to be formed is 88 nm. As already described, since the reflectance with respect to the amorphous silicon film has periodicity, if the film thickness corresponds to about the maximum value and the minimum value of the reflectance with respect to the amorphous silicon film, The thickness is not limited to the above. However, it is desirable that the difference between the thicknesses of the third base insulating film 1025 in the two stages be smaller than the thickness of the semiconductor film formed thereafter. The angle of the side wall of the step of the third base insulating film 1025 with respect to the substrate 1001 is 5 ° or more and 8 ° or more.
Etching is performed in a tapered shape so as to be less than 5 ° (preferably 30 ° to 60 °) to secure the step coverage of the film to be laminated thereon.

The amorphous semiconductor film 1026 shown in FIG.
Is formed along a third base insulating film 1025 having a step with a thickness of 25 to 200 nm (preferably 30 to 100 nm) by a known method such as a plasma CVD method or a sputtering method. In this embodiment, an amorphous silicon film is formed to a thickness of 50 nm by a plasma CVD method. As the amorphous semiconductor film, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.

FIG. 7C is a view for explaining a crystallization step of irradiating a laser beam from the back side. In the present invention, either the irradiation from the back side of the substrate or the irradiation from both the front side and the back side of the substrate is used. In this embodiment, the irradiation is performed from the back side of the substrate. In the crystallization by the laser annealing method, it is preferable that hydrogen contained in the amorphous semiconductor film is first released, and 400 to 500 ° C.
Exposure to nitrogen atmosphere for about 1 hour at
It is good to keep it below atom%. This significantly improves the laser resistance of the film.

The laser oscillator used in the laser annealing method will be described. Excimer lasers are widely used because they have high output and can oscillate high repetition pulses of about 300 Hz at present. In addition to a pulse oscillation excimer laser, a continuous oscillation excimer laser,
An r laser, a YAG laser, a YVO ₄ laser, a YLF laser, or the like can also be used.

In this embodiment, an excimer laser (wavelength 308) is used.
nm and a pulse width of 30 ns), the amorphous silicon film was crystallized by the irradiation method shown in FIG. As described above, since the thickness of the third base insulating film 1025 has two stages, when the back surface side is irradiated with a laser beam,
The reflectance of the laser beam with respect to the amorphous silicon film is about 22.7% in the area A and about 62.5% in the area B, and the effective intensities of the laser beam are different.

Further, the third base insulating film 1 shown in FIG.
The step edge at 025 (the boundary between the region A and the region B) cools faster than other places because there is both a base insulating film immediately below and a base insulating film existing in the lateral direction as a place where heat escapes. . Therefore, solidification starts from the step edge of the third base insulating film 1025 where the temperature first decreases, and a crystal nucleus 1006 is generated. The crystal nucleus becomes the center of the crystal growth, and the crystal growth proceeds toward the region A or the region B where the temperature is high and in the molten state. However, since the region A has a higher laser beam absorptivity than the region B, the crystal nucleus grows in the direction indicated by 1007, so that a larger crystal grain is formed in the semiconductor film in the region A. In this manner, a crystalline semiconductor film having a large grain size and having position-controlled crystal grains can be formed.

For comparison, a sample in which a silicon nitride oxide film (A-type) was formed on a synthetic quartz glass substrate and an amorphous silicon film having a thickness of 55 nm was formed on the silicon nitride oxide film (A-type) was used. For the simulation,
FIG. 8 shows a comparison of the solidification start time. However, the thickness of the silicon nitride oxide film (A-type) has two levels of 88 nm and 140 nm as already described in this embodiment. FIG. 8 shows the lower edge of the base (the boundary between the area A and the area B in FIG. 7C).
2 shows the relationship between the distance from to the region A and the solid phase start time. As shown in FIG. 8, even when a base film having a step is used, in the crystallization in the structure of the present invention, solidification of the semiconductor film after laser beam irradiation progresses more slowly than when the base film is a single layer. Therefore, it can be seen that large crystal grains can be obtained.

After the irradiation with the laser beam, the crystalline semiconductor film is placed in an atmosphere containing 3 to 100% of hydrogen.
The remaining defects can be neutralized by a heat treatment at 450 to 450 ° C. or a heat treatment at 200 to 450 ° C. in an atmosphere containing hydrogen generated by plasma.
By using the region A of the crystalline semiconductor film thus manufactured as a channel formation region to manufacture a TFT,
The electrical characteristics of the TFT can be improved.

[Embodiment 2] Here, a method of performing laser annealing after partially crystallizing an amorphous silicon film by heat treatment using the structure of the present invention will be described. In FIG. 9A, an alkali-free glass substrate such as barium borosilicate glass or aluminoborosilicate glass or a synthetic quartz glass substrate is used as a substrate 1001. In this embodiment, a synthetic quartz glass substrate is used.

A first base insulating film 1028 is formed on the substrate 1001 by a known means (LPCVD, plasma CVD, or the like) using a silicon nitride film, a silicon oxynitride film, or the like. In this embodiment, a silicon nitride film is formed to a thickness of 50 nm by a plasma CVD method.

On this, a second base insulating film 1029 having a different refractive index from the first base insulating film 1028 is formed of a silicon oxynitride film or the like by a known means (LPCVD, plasma CVD, or the like). In this embodiment, the plasma CVD
Silicon oxynitride film (composition ratio Si = 32%, O =
(59%, N = 7%, H = 2%) was formed to a thickness of 140 nm.

After forming the second base insulating film 1029, a resist mask is formed by photolithography, and unnecessary portions are etched to a thickness of 140 nm.
Third underlying insulating film 1 having a portion of m and a portion of 88 nm
030 (FIG. 9B). For the etching, a dry etching method using a fluorine-based gas may be used, or a wet etching method using a fluorine-based aqueous solution may be used. When the wet etching method is selected, for example, ammonium hydrogen fluoride (NH ₄ H
F ₂ ) containing 7.13% of ammonium fluoride (NH ₄ F) and 15.4% of ammonium fluoride (NH ₄ F) (trade name L, manufactured by Stella Chemifa KK)
(AL500).

The reason why the thickness of the third base insulating film 1030 is set to two levels is to form an effective intensity distribution of the laser beam with respect to the semiconductor film. In FIG. 2A, the film thickness that corresponds to the maximum value of 62.5% of the reflectance for the amorphous silicon film that periodically appears is 140 nm, and corresponds to the minimum value of 22.7% for the amorphous silicon film. The film thickness to be formed is 88 nm. As already described, since the reflectance with respect to the amorphous silicon film has periodicity, if the film thickness corresponds to about the maximum value and the minimum value of the reflectance with respect to the amorphous silicon film, The thickness is not limited to the above. However, it is preferable that the difference between the thicknesses of the third base insulating film 1030 in the two stages be smaller than the thickness of the semiconductor film formed thereafter. The angle of the side wall at the step of the third base insulating film 1030 with respect to the substrate 1001 is 5 ° or more and 8 ° or more.
Etching is performed in a tapered shape so as to be less than 5 ° (preferably 30 ° to 60 °) to secure the step coverage of the film to be laminated thereon.

The amorphous semiconductor film 1031 shown in FIG.
Is formed along a third base insulating film 1030 having a step with a thickness of 25 to 200 nm (preferably 30 to 100 nm) by a known method such as a plasma CVD method or a sputtering method. In this embodiment, an amorphous silicon film is formed to a thickness of 50 nm by a plasma CVD method. As the amorphous semiconductor film, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.

Next, the amorphous silicon film is partially crystallized by a method described in JP-A-7-183540. Here, the method will be briefly described. First, a small amount of an element such as nickel, palladium, or lead is added to an amorphous semiconductor film. As a method of addition, a plasma treatment method, an evaporation method, an ion implantation method, a sputtering method, a solution coating method, or the like may be used. After the addition, for example, 55
When the amorphous semiconductor film is placed in a nitrogen atmosphere at 0 ° C. for 4 hours,
A crystalline semiconductor film with good electric characteristics can be obtained. The optimum heating temperature and heating time for crystallization depend on the amount of the element added and the state of the amorphous semiconductor film. For example, if the solution coating method is applied and a nickel acetate solution is used for the solution,
A metal-containing layer 1032 is formed by applying 5 ml of a solution having a concentration of 10 ppm in terms of weight on the entire surface of the film by spin coating. (FIG. 9B) Next, the substrate was heated to a temperature of 500 ° C.
550 ° C for 1 hour in nitrogen atmosphere at ℃
Is performed for 4 hours in a nitrogen atmosphere to obtain a first crystalline silicon film 1033 partially crystallized. (FIG. 9
(C))

FIG. 9D illustrates a crystallization step of irradiating a laser beam from the back side. In the present invention, either the irradiation from the back side of the substrate or the irradiation from both the front side and the back side of the substrate is used. In this embodiment, the irradiation is performed from the back side of the substrate. In the crystallization by the laser annealing method, it is preferable that hydrogen contained in the amorphous semiconductor film is first released, and 400 to 500 ° C.
Exposure to nitrogen atmosphere for about 1 hour at
It is good to keep it below atom%. This significantly improves the laser resistance of the film.

The laser oscillator used in the laser annealing method will be described. Excimer lasers are widely used because they have high output and can oscillate high repetition pulses of about 300 Hz at present. In addition to a pulse oscillation excimer laser, a continuous oscillation excimer laser,
An r laser, a YAG laser, a YVO ₄ laser, a YLF laser, or the like can also be used.

In this embodiment, an excimer laser (wavelength 308) is used.
nm, and a pulse width of 30 ns), the amorphous silicon film was crystallized by the irradiation method shown in FIG. 9D. As described above, since the thickness of the third base insulating film 1030 has two stages, when the back surface side is irradiated with a laser beam,
The reflectivity of the laser beam is about 22.7% in the area A and about 62.5% in the area B.
The effective intensity of the laser beam with respect to the crystalline silicon film 1033 is different.

Further, the third base insulating film 1 shown in FIG.
The step edge at 030 (the boundary between the region A and the region B) cools faster than other places because there is both a base insulating film immediately below and a base insulating film present in the lateral direction as a place where heat escapes. . Therefore, solidification of the semiconductor film starts from the step edge of the third base insulating film 1030 where the temperature first decreases, and a crystal nucleus 1006 is generated. The crystal nucleus becomes the center of the crystal growth, and the crystal growth proceeds toward the region A or the region B where the temperature is high and in the molten state. However,
Since the region A has a higher laser beam absorptivity than the region B, the crystal nucleus grows in the direction indicated by 1007, so that a larger crystal grain is formed in the semiconductor film in the region A. In this manner, a crystalline semiconductor film having a large grain size and having position-controlled crystal grains can be formed.

After the irradiation with the laser beam, the crystalline semiconductor film is placed in an atmosphere containing 3 to 100% of hydrogen.
The remaining defects can be neutralized by a heat treatment at 450 to 450 ° C. or a heat treatment at 200 to 450 ° C. in an atmosphere containing hydrogen generated by plasma.
By using the region A of the crystalline semiconductor film thus manufactured as a channel formation region to manufacture a TFT,
The electrical characteristics of the TFT can be improved.

[Embodiment 3] Here, a method for simultaneously manufacturing a pixel portion and TFTs (n-channel TFT and p-channel TFT) of a driving circuit provided around the pixel portion on the same substrate is described in detail with reference to FIG. This will be described with reference to FIG.

In FIG. 11A, a non-alkali glass substrate such as barium borosilicate glass or aluminoborosilicate glass or a synthetic quartz glass substrate is used as a substrate 1001. In this embodiment, a synthetic quartz glass substrate is used.

A first base insulating film 100a is formed on the substrate 1001 by a known means (LPCVD, plasma CVD, etc.).
A silicon nitride film, a silicon oxynitride film, or the like. In this embodiment, a silicon nitride film is formed to a thickness of 50 nm by a plasma CVD method.

On this, a second base insulating film 100b having a different refractive index from the first base insulating film is formed by a known means (LPC).
VD method, plasma CVD method, or the like) to form a silicon oxynitride film or the like. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59) is used by a plasma CVD method.
%, N = 7%, H = 2%).

After forming the second base insulating film, a resist mask is formed by using a photolithography technique.
Unnecessary portions are etched to obtain a third base insulating film 100c having a portion with a thickness of 140 nm and a portion with a thickness of 88 nm (FIG. 11B). For the etching, a dry etching method using a fluorine-based gas may be used, or a wet etching method using a fluorine-based aqueous solution may be used. When the wet etching method is selected, for example, 7.13% of ammonium hydrogen fluoride (NH ₄ HF ₂ ) and 15.3% of ammonium fluoride (NH ₄ F) are used.
Liquid mixture containing 4% (trade name LAL5 manufactured by Stella Chemifa)
00).

The reason why the thickness of the third base insulating film 100c is set to two levels is to form an effective intensity distribution of the laser beam with respect to the semiconductor film. In FIG. 2A, the film thickness that corresponds to the maximum value of 62.5% of the reflectance for the amorphous silicon film that periodically appears is 140 nm, and corresponds to the minimum value of 22.7% for the amorphous silicon film. The film thickness to be formed is 88 nm. As already described, since the reflectance with respect to the amorphous silicon film has periodicity, if the film thickness corresponds to about the maximum value and the minimum value of the reflectance with respect to the amorphous silicon film, The thickness is not limited to the above. However, it is preferable that the difference between the thicknesses of the third base insulating film 100b in the two stages is smaller than the thickness of the semiconductor film formed thereafter. Further, the angle of the side wall at the step of the third base insulating film 100b is not less than 5 ° and 8 ° with respect to the substrate 1001.
Etching is performed in a tapered shape so as to be less than 5 ° (preferably 30 ° to 60 °) to secure the step coverage of the film to be laminated thereon.

The amorphous semiconductor film 101 shown in FIG.
Is formed along the third base insulating film 100c having a step with a thickness of 25 to 200 nm (preferably 30 to 100 nm) by a known method such as a plasma CVD method or a sputtering method. In this embodiment, an amorphous silicon film is formed to a thickness of 50 nm by a plasma CVD method. As the amorphous semiconductor film, there are an amorphous semiconductor film and a microcrystalline semiconductor film, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be used.

FIG. 11C is a view for explaining a crystallization step of irradiating a laser beam from the back side. In the present invention, either of the irradiation from the back side of the substrate or the irradiation from both sides of the front side and the back side of the substrate is used,
In this embodiment, the irradiation is performed from the back side of the substrate. In the crystallization by the laser annealing method, first, it is desirable to release hydrogen contained in the amorphous semiconductor film, and 400 to 500
Exposure to a nitrogen atmosphere at a temperature of about 1 hour for about 1 hour to reduce the amount of hydrogen contained to 5 atom% or less. This significantly improves the laser resistance of the film.

A laser oscillator used in the laser annealing method will be described. Excimer lasers are widely used because they have high output and can oscillate high repetition pulses of about 300 Hz at present. In addition to a pulse oscillation excimer laser, a continuous oscillation excimer laser,
An r laser, a YAG laser, a YVO ₄ laser, a YLF laser, or the like can also be used.

In this embodiment, an excimer laser (wavelength 308) is used.
nm, and a pulse width of 30 ns), the amorphous silicon film was crystallized by the irradiation method shown in FIG. As described above, since the thickness of the third base insulating film 100c has two steps, when the laser beam is irradiated from the back surface side, the reflectance of the amorphous semiconductor film with respect to the amorphous A is about 62.5%, and area B is about 22.7%, and the effective intensities of the laser beams are different.

Further, since the step edge in the third base insulating film in FIG. 11C has both the base insulating film immediately below and the base insulating film existing in the lateral direction as a place for escaping heat, another step is taken. Cool faster than in place. Therefore, solidification starts from the semiconductor film on the step edge of the third base insulating film 100c where the temperature first decreases, and crystal nuclei are generated. This nucleus becomes the center of crystal growth, and crystal growth proceeds toward a region where the temperature is high and in a molten state. In this manner, a crystalline semiconductor film having a large grain size and having position-controlled crystal grains can be formed.

After the laser beam irradiation, semiconductor layers 102 to 106 were formed by patterning the crystalline semiconductor film using photolithography.

After the formation of the semiconductor layers 102 to 106, a slight amount of impurity element (boron or phosphorus) may be doped in order to control the threshold value of the TFT.

Next, a gate insulating film 107 covering the semiconductor layers 102 to 106 is formed. The gate insulating film 107 has a thickness of 40 to 40
The insulating film containing silicon is formed to have a thickness of 150 nm. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N =
7%, H = 2%). Needless to say, the gate insulating film is not limited to the silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure.

When a silicon oxide film is used, TEOS (Tetraethyl Orthosilicate) is formed by a plasma CVD method.
And O ₂ , a reaction pressure of 40 Pa and a substrate temperature of 300
It can be formed by discharging at a high-frequency (13.56 MHz) power density of 0.5 to 0.8 W / cm ² . The silicon oxide film thus manufactured can obtain good electrical characteristics as a gate insulating film by subsequent thermal annealing at 400 to 500 ° C.

Then, as shown in FIG. 11D, a first conductive film 108 having a thickness of 20 to 100 nm and a second conductive film 1 having a thickness of 100 to 400 nm are formed on the gate insulating film 107.
09 is laminated. In this embodiment, a first conductive film 408 made of a TaN film having a thickness of 30 nm and a
A second conductive film 109 made of a m-type W film was formed by lamination.
The TaN film was formed by a sputtering method, and was sputtered using a Ta target in an atmosphere containing nitrogen. The W film was formed by a sputtering method using a W target. In addition, thermal CV using tungsten hexafluoride (WF ₆ )
It can also be formed by Method D. In any case, it is necessary to lower the resistance in order to use it as a gate electrode,
It is desirable that the resistivity of the W film be 20 μΩcm or less. The resistivity of the W film can be reduced by enlarging the crystal grains. However, when the W film contains many impurity elements such as oxygen, the crystallization is inhibited and the resistance is increased. Therefore, in this embodiment, the W film is formed by a sputtering method using a high-purity W (purity of 99.9999%) target, and further taking care not to mix impurities from the gas phase during film formation. By forming, a resistivity of 9 to 20 μΩcm could be realized.

In this embodiment, the first conductive film 108
Is TaN and the second conductive film 109 is W, but there is no particular limitation, and any of Ta, W, Ti, Mo, Al, Cu,
It may be formed of an element selected from Cr and Nd, or an alloy material or a compound material containing the element as a main component.
Alternatively, a semiconductor film typified by a crystalline silicon film doped with an impurity element such as phosphorus may be used. AgP
A dCu alloy may be used. A first conductive film formed of a tantalum (Ta) film, a second conductive film formed of a W film, a first conductive film formed of a titanium nitride (TiN) film, and a second conductive film formed of a titanium nitride (TiN) film; Are combined with a W film, the first conductive film is formed of a tantalum nitride (TaN) film, and the second conductive film is formed of an Al film, and the first conductive film is formed of a tantalum nitride (TaN) film. Alternatively, a combination of the second conductive film and the Cu film may be used.

Next, masks 110 to 115 made of resist are formed by photolithography, and a first etching process for forming electrodes and wirings is performed. The first etching process is performed under the first and second etching conditions. In this embodiment, as the first etching condition, an ICP (Inductively Coupled Plasma) etching method is used, CF ₄ , Cl _2, and O ₂ are used as etching gases, and the respective gas flow ratios are 25. / 25/10 (sccm), RF power (13.56 MHz) of 500 W was applied to the coil-type electrode at a pressure of 1 Pa to generate plasma, and etching was performed. Here, a dry etching apparatus (Model E645- □ ICP) using ICP manufactured by Matsushita Electric Industrial Co., Ltd. was used.
150W RF (13.56MH) also on the substrate side (sample stage)
z) Turn on the power and apply a substantially negative self-bias voltage. The W film is etched under the first etching conditions to make the end of the first conductive layer tapered.

Then, a mask 110 made of resist is formed.
The second etching condition was changed without removing 115, CF ₄ and Cl ₂ were used as etching gases, the respective gas flow ratios were 30/30 (sccm), and the pressure was 1 Pa to form a coil-type electrode. RF (13.56 MHz) power of 500 W was supplied to generate plasma, and etching was performed for about 30 seconds. 20W RF (1) on the substrate side (sample stage)
3.56MHz) Power is applied and a substantially negative self-bias voltage is applied. Under the second etching condition in which CF ₄ and Cl ₂ are mixed, the W film and the TaN film are etched to the same extent. Note that in order to perform etching without leaving a residue on the gate insulating film, the etching time is preferably increased by about 10 to 20%.

In the first etching process, the shape of the mask made of resist is made appropriate so that
The ends of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side. The angle of the tapered portion is 15 to 45 °. Thus, by the first etching process, the first shape conductive layers 117 to 122 (the first conductive layers 117 a to 122 a and the second conductive layers 117 b to 117 b) each including the first conductive layer and the second conductive layer are formed.
2b) is formed. Reference numeral 116 denotes a gate insulating film,
The region not covered with the conductive layers 117 to 122 having the shape of
A region which is etched and thinned by about 50 nm is formed.

Then, the resist mask is removed.
First doping processing without adding an n-type semiconductor layer.
The added impurity element is added. (FIG. 12 (A)) Dopi
Is performed by ion doping or ion implantation.
Good. The condition of the ion doping method is that the dose amount is 1 × 1.
0¹³~ 5 × 10^Fifteenatoms / cm^TwoAnd the acceleration voltage
The operation is performed at 60 to 100 keV. In this embodiment, the dose
1.5 × 10^Fifteenatoms / cm^TwoAnd the accelerating voltage
Was performed at 80 keV. Impurity element imparting n-type
As an element belonging to the 15th group, typically phosphorus (P) or
Uses arsenic (As), but here uses phosphorus (P)
Was. In this case, the conductive layers 117 to 121 impart n-type.
A mask for impurity elements, self-aligned high concentration
Impurity regions 123 to 127 are formed. High concentration impurities
1 × 10 for areas 123 to 127 ²⁰~ 1 × 10^{twenty one}ato
ms / cm^ThreeImpurity element that imparts n-type in the concentration range of
Added.

Next, a second etching process is performed without removing the resist mask. Here, the W film is selectively etched using CF ₄ , Cl ₂ and O _{2 as} an etching gas. At this time, the first conductive layers 128b to 133b are formed by the second etching process. on the other hand,
The second conductive layers 117a to 122a are hardly etched to form second conductive layers 128a to 133a. Next, a second doping process is performed to
(B) state is obtained. Doping is performed on the second conductive layer 117
a to 122a are used as masks for impurity elements,
The semiconductor layer below the tapered portion of the first conductive layer is doped so that an impurity element is added. Thus, impurity regions 134 to 138 overlapping with the first conductive layer are formed.
The concentration of phosphorus (P) added to this impurity region is the first
Has a gentle concentration gradient according to the thickness of the tapered portion of the conductive layer. Note that in the semiconductor layer overlapping with the tapered portion of the first conductive layer, the impurity concentration is slightly reduced from the end of the tapered portion of the first conductive layer toward the inside, but is approximately the same. . Further, an impurity element is also added to the first impurity regions 123 to 127 to form impurity regions 139 to 143.

Next, a third etching process is performed without removing the resist mask. In the third etching treatment, the tapered portion of the first conductive layer is partially etched to reduce a region overlapping with the semiconductor layer. The third etching uses CHF as an etching gas.
₃ using a reactive ion etching method (RIE method). By the third etching, the first conductive layer 1
44 to 149 are formed. At this time, the insulating film 11
6 are also etched to form insulating films 150a to 150e, 1
51 are formed.

By the third etching, impurity regions (LDD regions) 134a to 138a which do not overlap with the first conductive layers 144 to 148 are formed. Note that the impurity regions (GOLD regions) 134b to 138b are still overlapped with the first conductive layers 144 to 148.

In this manner, the present embodiment provides the first
Region (GOLD) overlapping conductive layers 144 to 148 of
Regions) 134b to 138b and the first
Impurity regions that do not overlap with the conductive layers 144 to 148 (LD
The difference from the impurity concentration in the D regions 134a to 138a can be reduced, and the reliability can be improved.

Next, after removing the resist mask, new masks 152 to 154 are formed and a third doping process is performed. By the third doping process, impurity regions 155 to 160 are formed in a semiconductor layer serving as an active layer of a p-channel TFT, in which an impurity element imparting a conductivity type opposite to the one conductivity type is added. Using the second conductive layers 128a to 132a as a mask for the impurity element, an impurity element imparting p-type is added to form an impurity region in a self-aligned manner. In this embodiment, the impurity regions 155 to 160 are formed of diborane (B ₂ H ₆ ).
It is formed by an ion doping method using In the third doping process, the semiconductor layers forming the n-channel TFT are covered with resist masks 152 to 154. Phosphorus is added at different concentrations to the impurity regions 155 to 160 by the first doping process and the second doping process, but the concentration of the impurity element imparting p-type is set to 2 × in each of the regions. 10
^By performing the doping treatment so as to have a concentration of ^{20 to} 2 × 10 ²¹ atoms / cm ³ , no problem occurs because the p-channel TFT functions as a source region and a drain region. In this embodiment, since a part of the semiconductor layer serving as the active layer of the p-channel TFT is exposed, there is an advantage that an impurity element (boron) can be easily added.

Through the above steps, impurity regions are formed in the respective semiconductor layers.

Next, a mask 152 made of resist is used.
154 is removed to form a first interlayer insulating film 161.
The first interlayer insulating film 161 is formed by plasma CVD.
Thickness of 100 to 200 nm by using a sputtering method or a sputtering method
As an insulating film containing silicon. In this embodiment, a silicon oxynitride film with a thickness of 150 nm is formed by a plasma CVD method. Needless to say, the first interlayer insulating film 161 is not limited to the silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure.

Next, as shown in FIG. 13B, a step of activating the impurity element added to each semiconductor layer is performed. This activation step is performed by a thermal annealing method using a furnace annealing furnace. As the thermal annealing method, the oxygen concentration is 1 ppm or less, preferably 0.1 ppm
400 to 700 ° C, typically 5 in the following nitrogen atmosphere
The temperature may be set at 00 to 550 ° C.
The activation treatment was performed by a heat treatment at 4 ° C. for 4 hours. Note that, other than the thermal annealing method, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied.

In this embodiment, at the same time as the activation treatment, nickel used as a catalyst during crystallization is doped with impurity regions 139, 141, 142, and 1 containing high-concentration phosphorus.
The nickel concentration in the semiconductor layer which is gettered at 55 and 158 and mainly becomes a channel formation region is reduced. A TFT having a channel formation region manufactured in this manner has a low off-state current and high crystallinity; thus, high field-effect mobility can be obtained and favorable electric characteristics can be achieved.

The activation process may be performed before forming the first interlayer insulating film. However, when the wiring material used is weak to heat, an active layer is formed after an interlayer insulating film (an insulating film containing silicon as a main component, for example, a silicon nitride film) is formed to protect the wiring and the like as in this embodiment. It is preferable to carry out a chemical treatment.

Further, a heat treatment is performed at 300 to 550 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% of hydrogen to hydrogenate the semiconductor layer. In this embodiment, heat treatment was performed at 410 ° C. for one hour in a nitrogen atmosphere containing about 3% of hydrogen. In this step, dangling bonds in the semiconductor layer are terminated by hydrogen contained in the interlayer insulating film. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.

In the case where a laser annealing method is used as the activation treatment, it is desirable to irradiate a laser beam such as an excimer laser or a YAG laser after the hydrogenation.

Next, a second interlayer insulating film 162 made of an inorganic insulating material or an organic insulating material is formed on the first interlayer insulating film 161. In this embodiment, the film thickness is 1.6 μm
Was formed, but the viscosity was 10 to 1000
cp, preferably 40 to 200 cp, and those having irregularities on the surface were used. Alternatively, a film whose surface is planarized may be used as the second interlayer insulating film 162.

In the present embodiment, in order to prevent specular reflection, the second interlayer insulating film having the unevenness formed on the surface is formed to form the unevenness on the surface of the pixel electrode. In addition, a projection may be formed in a region below the pixel electrode in order to obtain light scattering by providing unevenness on the surface of the pixel electrode. In that case, the projection can be formed using the same photomask as that for forming the TFT, so that the projection can be formed without increasing the number of steps. Note that the protrusions may be appropriately provided on the substrate in the pixel portion region other than the wiring and the TFT portion. Thus, irregularities are formed on the surface of the pixel electrode along irregularities formed on the surface of the insulating film covering the convex portions.

Then, in the driving circuit, wirings 163 to 167 electrically connected to the respective impurity regions are formed. Note that these wirings are made of a 50 nm-thick Ti film and a 500 nm-thick alloy film (an alloy film of Al and Ti).
Is formed by patterning the laminated film.

In the pixel portion, the pixel electrode 17
0, a gate wiring 169, and a connection electrode 168 are formed.
(FIG. 13C) With this connection electrode 168, the source wiring (the lamination of 143b and 149) is electrically connected to the pixel TFT. The gate wiring 169 is connected to the pixel T
An electrical connection is formed with the gate electrode of the FT. Also,
The pixel electrode 170 is electrically connected to the drain region of the pixel TFT, and is also electrically connected to the semiconductor layer 158 that functions as one electrode forming a storage capacitor. Further, as the pixel electrode 170, Al or A
It is desirable to use a material having excellent reflectivity, such as a film containing g as a main component or a stacked film thereof.

As described above, the n-channel TFT 50
1 and a CMOS circuit comprising a p-channel TFT 502;
And driving circuit 506 having n-channel TFT 503
And a pixel portion 507 having a pixel TFT 504 and a storage capacitor 505 can be formed over the same substrate. Thus, an active matrix substrate is completed.

The n-channel TFT 50 of the driving circuit 506
Reference numeral 1 denotes a low concentration impurity region 13 which overlaps with the channel formation region 171 and the first conductive layer 144 forming a part of the gate electrode.
4b (GOLD region), a low concentration impurity region 134a (LDD region) formed outside the gate electrode, and a high concentration impurity region 1 functioning as a source region or a drain region.
39. The p-channel TFT 502 connected to the n-channel TFT 501 by the electrode 166 to form a CMOS circuit has a channel formation region 172, an impurity region 157 overlapping with the gate electrode, an impurity region 156 formed outside the gate electrode, and a source region. Alternatively, the semiconductor device includes a high-concentration impurity region 155 functioning as a drain region. The n-channel TFT 503 includes a channel formation region 173, a low-concentration impurity region 136b (GOLD region) overlapping with the first conductive layer 146 forming a part of the gate electrode, and a low-concentration impurity formed outside the gate electrode. It has a region 137a (LDD region) and a high-concentration impurity region 141 functioning as a source region or a drain region.

In the pixel TFT 504 in the pixel portion, a channel forming region 174 and a low-concentration impurity region 137b (GOLD) overlapping the first conductive layer 147 forming a part of the gate electrode are provided.
Region), a low-concentration impurity region 137a (LDD region) formed outside the gate electrode, and a high-concentration impurity region 142 functioning as a source region or a drain region. The semiconductor layers 158 to 160 functioning as one electrode of the storage capacitor 505 are each doped with an impurity element imparting p-type. The storage capacitor 505 is formed using electrodes (a laminate of 148 and 132b) and semiconductor layers 158 to 160 using the insulating film 151 as a dielectric.

In the pixel structure of this embodiment, the end of the pixel electrode is formed so as to overlap with the source wiring so that the gap between the pixel electrodes is shielded from light without using a black matrix.

FIG. 14 is a top view of a pixel portion of an active matrix substrate manufactured in this embodiment. In addition, FIG.
The same reference numerals are used for portions corresponding to FIG. Figure 1
The dashed line AA ′ in 3 corresponds to the cross-sectional view taken along the dashed line AA ′ in FIG. Further, a dashed line B- in FIG.
B ′ corresponds to a cross-sectional view taken along a chain line BB ′ in FIG.

In addition, according to the steps described in this embodiment, the number of photomasks required for manufacturing the active matrix substrate can be reduced to five. As a result, the process is shortened,
This can contribute to reduction in manufacturing cost and improvement in yield.

[Embodiment 4] In this embodiment, a process of manufacturing a reflective liquid crystal display device from the active matrix substrate manufactured in Embodiment 3 will be described below. Figure 15 for explanation
Is used.

First, according to the third embodiment, after obtaining the active matrix substrate in the state of FIG.
At least the pixel electrode 1 on the active matrix substrate
An alignment film 470 is formed on 70 and a rubbing process is performed.
In this embodiment, before forming the alignment film 470, a columnar spacer (not shown) for maintaining a substrate interval was formed at a desired position by patterning an organic resin film such as an acrylic resin film. Instead of the columnar spacers, spherical spacers may be spread over the entire surface of the substrate.

Next, a counter substrate 471 is prepared. Next, coloring layers 472 and 473 and a planarizing film 474 are formed over the counter substrate 471. The red coloring layer 472 and the blue coloring layer 473 are overlapped to form a light-shielding portion. Alternatively, the light-blocking portion may be formed by partially overlapping the red coloring layer and the green coloring layer.

In this embodiment, the substrate shown in Embodiment 3 is used. Therefore, FIG. 1 shows a top view of the pixel portion of the third embodiment.
4, at least the gate wiring 169 and the pixel electrode 170
, The gap between the gate wiring 169 and the connection electrode 168, and the gap between the connection electrode 168 and the pixel electrode 170 need to be shielded from light. In this embodiment, the colored layers are arranged such that the light-shielding portion formed of the colored layers is overlapped at the positions where the light is to be shielded, and the opposing substrates are bonded to each other.

As described above, the number of steps can be reduced by shielding the gap between each pixel with the light-shielding portion composed of the colored layers without forming a light-shielding layer such as a black mask.

Next, a counter electrode 475 made of a transparent conductive film was formed on at least the pixel portion on the flattening film 474, an alignment film 476 was formed on the entire surface of the counter substrate, and rubbing treatment was performed.

Then, the active matrix substrate on which the pixel portion and the driving circuit are formed and the opposing substrate are sealed with a sealing material 477.
Paste in. A filler is mixed in the sealing material 477, and the two substrates are bonded to each other at a uniform interval by the filler and the columnar spacer. afterwards,
A liquid crystal material 478 is injected between the two substrates, and completely sealed with a sealant (not shown). A known liquid crystal material may be used for the liquid crystal material 478. Thus, the reflection type liquid crystal display device shown in FIG. 15 is completed. Then, if necessary, the active matrix substrate or the opposing substrate is cut into a desired shape. Further, a polarizing plate (not shown) was attached only to the counter substrate. Then, using a known technique, F
PC was pasted.

The liquid crystal display panel manufactured as described above can be used as a display section of various electronic devices.

[Embodiment 5] A CMOS circuit and a pixel portion formed by implementing the present invention are used for various electro-optical devices (active matrix liquid crystal display, active matrix EC display, active matrix EL display). Can be done. That is, the present invention can be applied to all electronic devices in which the electro-optical device is incorporated in the display unit.

Such electronic devices include a video camera, digital camera, projector (rear or front type), head mounted display (goggle type display), car navigation, car stereo,
Examples include a personal computer and a portable information terminal (a mobile computer, a mobile phone, an electronic book, or the like). Examples of these are shown in FIGS. 16, 17 and 18.

FIG. 16A shows a personal computer, which includes a main body 3001, an image input section 3002, and a display section 30.
03, a keyboard 3004 and the like. The present invention can be applied to the image input unit 3002, the display unit 3003, and other signal control circuits.

FIG. 16B shows a video camera, which includes a main body 3101, a display portion 3102, an audio input portion 3103, operation switches 3104, a battery 3105, and an image receiving portion 310.
6 and so on. The present invention can be applied to the display portion 3102 and other signal control circuits.

FIG. 16C shows a mobile computer (mobile computer) which includes a main body 3201, a camera section 3202, an image receiving section 3203, operation switches 3204, a display section 3205, and the like. The present invention can be applied to the display portion 3205 and other signal control circuits.

FIG. 16D shows a goggle type display, which comprises a main body 3301, a display section 3302, and an arm section 330.
3 and so on. The present invention can be applied to the display portion 3302 and other signal control circuits.

FIG. 16E shows a player that uses a recording medium (hereinafter, referred to as a recording medium) on which a program is recorded, and includes a main body 3401, a display portion 3402, and a speaker portion 340.
3, a recording medium 3404, an operation switch 3405, and the like. This player uses a DVD (D
digital Versatile Disc), CD
And the like, it is possible to perform music appreciation, movie appreciation, games, and the Internet. The present invention can be applied to the display portion 3402 and other signal control circuits.

FIG. 16F shows a digital camera, which includes a main body 3501, a display section 3502, an eyepiece section 3503, operation switches 3504, an image receiving section (not shown), and the like. The present invention can be applied to the display portion 3502 and other signal control circuits.

FIG. 17A shows a front type projector, which includes a projection device 3601, a screen 3602, and the like. The present invention can be applied to the liquid crystal display device 3808 constituting a part of the projection device 3601 and other signal control circuits.

FIG. 17B shows a rear type projector, which includes a main body 3701, a projection device 3702, and a mirror 370.
3, including a screen 3704 and the like. The present invention provides a projection device 3
The present invention can be applied to the liquid crystal display device 3808 which constitutes a part of the signal control circuit 702 and other signal control circuits.

FIG. 17C is a diagram showing an example of the structure of the projection devices 3601 and 3702 in FIGS. 17A and 17B. Projection devices 3601, 37
02 denotes a light source optical system 3801, mirrors 3802, 380
4 to 3806, dichroic mirror 3803, prism 3807, liquid crystal display device 3808, retardation plate 380
9. It is composed of a projection optical system 3810. Projection optical system 38
Reference numeral 10 denotes an optical system including a projection lens. In the present embodiment, an example of a three-plate type is shown, but there is no particular limitation, and for example, a single-plate type may be used. Further, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarizing function, a film for adjusting a phase difference, and an IR film in the optical path indicated by the arrow in FIG. Good.

FIG. 17D is a diagram showing an example of the structure of the light source optical system 3801 in FIG. 17C. In this embodiment, the light source optical system 3801 includes a reflector 3811, a light source 3812, a lens array 3813,
814, a polarization conversion element 3815, and a condenser lens 3816. Note that the light source optical system shown in FIG. 17D is an example and is not particularly limited. For example, a practitioner may appropriately provide an optical system such as an optical lens, a film having a polarizing function, a film for adjusting a phase difference, and an IR film in the light source optical system.

However, in the projector shown in FIG. 17, a case in which a transmissive electro-optical device is used is shown, and an application example in a reflective electro-optical device is not shown.

FIG. 18A shows a mobile phone, and the main body 39 is provided.
01, audio output unit 3902, audio input unit 3903, display unit 3904, operation switch 3905, antenna 3906
And so on. The present invention can be applied to the audio output unit 3902, the audio input unit 3903, the display unit 3904, and other signal control circuits.

FIG. 18B shows a portable book (electronic book), which includes a main body 4001, display portions 4002 and 4003, a storage medium 4004, operation switches 4005, and an antenna 4006.
And so on. The present invention can be applied to the display portions 4002 and 4003 and other signal circuits.

FIG. 18C shows a display, which includes a main body 4101, a support 4102, a display portion 4103, and the like.
The present invention can be applied to the display portion 4103. The display of the present invention is particularly advantageous when the screen is enlarged, and is advantageous for a display having a diagonal of 10 inches or more (particularly 30 inches or more).

As described above, the applicable range of the present invention is extremely wide, and can be applied to electronic devices in all fields. Further, the electronic apparatus according to the present embodiment can be realized by using any combination of the configurations of the first to fourth embodiments.

[0162]

By adopting the configuration of the present invention, the following basic significance can be obtained. (A) fully compatible with conventional TFT fabrication processes,
It has a simple structure. (B) The thickness and refractive index of the base insulating film can be easily and precisely controlled. Therefore, it is easy to precisely control the position of the intensity distribution of the laser beam. (C) For the positioning of the slit and the like, the laser irradiation device does not require a special precise positioning technique on the order of microns, and a normal laser irradiation device can be used as it is. (D) This method is capable of producing a crystal grain having a large grain size whose position is controlled while satisfying the above advantages.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS (A) The inventors have filed Japanese Patent Application No. 11-35060.
Showing an example of the invention disclosed in Japanese Patent No. (B) The figure which shows the temperature history in each point of (A).

FIG. 2A shows a laser beam having a wavelength of 308 nm with respect to a second sample from the back surface side of a substrate, with the thickness of a silicon nitride film fixed and the thickness of a silicon nitride oxide film (A-type) changed. FIG. 4 is a graph showing a reflectance and an absorptance with respect to an amorphous silicon film when irradiation is performed. (B) When the thickness of the silicon nitride oxide film (A-type) is fixed and the thickness of the silicon nitride film is changed, and the second sample is irradiated with a laser beam having a wavelength of 308 nm from the back surface of the substrate. FIG. 4 is a diagram showing a reflectance and an absorptivity for an amorphous silicon film of FIG.

FIG. 3A shows a laser beam having a wavelength of 532 nm with respect to a second sample from the back surface side of a substrate by fixing the thickness of a silicon nitride film and changing the thickness of a silicon nitride oxide film (A-type). FIG. 4 is a graph showing a reflectance and an absorptance with respect to an amorphous silicon film when irradiation is performed. (B) When the thickness of the silicon nitride oxide film (A-type) is fixed and the thickness of the silicon nitride film is changed, and the second sample is irradiated with a laser beam having a wavelength of 532 nm from the back surface of the substrate. FIG. 4 is a diagram showing a reflectance and an absorptivity for an amorphous silicon film of FIG.

FIG. 4 is a diagram showing an example of formation of a base film and irradiation of a laser beam disclosed in the present invention.

FIG. 5 is a diagram showing an example of formation of a base film and irradiation of a laser beam disclosed in the present invention.

FIG. 6 is a diagram showing an example of formation of a base film and irradiation of a laser beam disclosed in the present invention.

FIG. 7 is a view showing an example of formation of a base film and irradiation of a laser beam disclosed in the present invention.

FIG. 8 shows a configuration disclosed in the present invention and Japanese Patent Application No. 11-351.
060 is a diagram showing a comparison of solid-phase crystallization start times in an example of the invention disclosed in Japanese Patent No. 060.

FIG. 9 illustrates an example of formation of a base film and irradiation of a laser beam disclosed in the present invention.

FIG. 10A shows how to change the refractive index of the lower silicon nitride oxide film to obtain a wavelength of 30 nm from the back side of the substrate with respect to the third sample.
FIG. 7 is a graph showing the reflectance and the absorptance of an amorphous silicon film when irradiated with an 8 nm laser beam. (B) changing the refractive index of the lower silicon oxynitride film, and irradiating the third sample with a laser beam having a wavelength of 532 nm from the back side of the substrate to obtain a reflectance and an absorptivity for the amorphous silicon film; FIG.

FIG. 11 is a cross-sectional view illustrating a manufacturing process of a pixel TFT and a TFT of a driver circuit.

FIG. 12 is a cross-sectional view illustrating a manufacturing process of a pixel TFT and a TFT of a driver circuit.

FIG. 13 is a cross-sectional view illustrating a manufacturing process of a pixel TFT and a TFT of a driver circuit.

FIG. 14 is a top view illustrating pixels in a pixel portion.

FIG. 15 is a cross-sectional view illustrating a manufacturing process of an active matrix liquid crystal display device.

FIG. 16 illustrates an example of a semiconductor device.

FIG. 17 illustrates an example of a semiconductor device.

FIG. 18 illustrates an example of a semiconductor device.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) FF28 FF30 FF36 GG01 GG02 GG13 GG25 GG32 GG43 GG45 HJ01 HJ04 HJ12 HJ13 HJ23 HL02 HL03 HL06 HL11 HM07 HM15 NN03 NN04 NN22 NN23 NN24 NN27 NN34 NN35 NN44 QNPP PPPPNPPNPPPP

Claims (12)

[Claims] A step of forming a first base insulating film having a refractive index different from that of the substrate on a substrate having a light transmitting property; and forming the first base insulating film on the first base insulating film. Forming a second base insulating film having a different refractive index;
Forming a plurality of recesses by partially etching the base insulating film of (a), forming an amorphous semiconductor film on the second base insulating film in which the plurality of recesses are formed, and Irradiating the crystalline semiconductor film with a laser beam from the back side of the substrate or from both the front side and the back side of the substrate to form a crystalline semiconductor film; and the crystalline semiconductor film formed on the concave portion. Forming a TFT using the semiconductor device as a channel formation region. A step of forming a first base insulating film having a refractive index different from that of the substrate on a light-transmitting substrate; and forming the first base insulating film on the first base insulating film. Forming a second base insulating film having a different refractive index;
Forming a plurality of protrusions by partially etching the base insulating film of (a), and forming an amorphous semiconductor film on the second base insulating film on which the plurality of protrusions are formed; Irradiating the amorphous semiconductor film with a laser beam from the back side of the substrate or from both the front side and the back side of the substrate to form a crystalline semiconductor film; and forming the crystalline semiconductor film on the convex portion. Forming a TFT using the high-quality semiconductor film as a channel formation region. 3. A step of forming a first base insulating film having a refractive index different from that of the substrate on a substrate having a light transmitting property, and forming a plurality of recesses by partially etching the first base insulating film. Forming a second base insulating film having a refractive index different from that of the first base insulating film on the first base insulating film in which the plurality of recesses are formed; Forming an amorphous semiconductor film on the base insulating film, and irradiating the amorphous semiconductor film with a laser beam from the back side of the substrate or from both the front side and the back side of the substrate. A method for manufacturing a semiconductor device, comprising: forming a semiconductor film; and forming a TFT using the crystalline semiconductor film formed over the concave portion as a channel formation region. 4. A step of forming a first base insulating film having a refractive index different from that of the substrate on a light-transmitting substrate, and forming a plurality of convex portions by partially etching the first base insulating film. Forming a portion, and forming a second base insulating film having a different refractive index from the first base insulating film on the first base insulating film on which the plurality of protrusions are formed; Forming an amorphous semiconductor film on the second base insulating film; and irradiating the amorphous semiconductor film with a laser beam from the back side of the substrate or from both the front side and the back side of the substrate. A method for manufacturing a semiconductor device, comprising: a step of forming a crystalline semiconductor film; and a step of forming a TFT using the crystalline semiconductor film formed over the projection as a channel formation region. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is a liquid crystal display device or an EL display device. 6. The semiconductor device according to claim 1, wherein the semiconductor device is a mobile phone, a video camera, a digital camera, a projector, a goggle display, a personal computer, a DVD player, an electronic book, or portable information. A method for manufacturing a semiconductor device, which is a terminal. 7. A first base insulating film having a refractive index different from that of the substrate is formed over a substrate having a light-transmitting property, and the first base insulating film is refracted on the first base insulating film. Forming a second base insulating film having a different ratio and a plurality of concave portions, forming an amorphous semiconductor film on the second base insulating film, and irradiating the amorphous semiconductor film with a laser beam. A semiconductor device, wherein a crystalline semiconductor film is formed by the above method, and the crystalline semiconductor film on the concave portion is used as a channel formation region of a TFT. 8. A first base insulating film having a refractive index different from that of the substrate is formed on a light-transmitting substrate, and the first base insulating film is refracted on the first base insulating film. Forming a second base insulating film having a different ratio and a plurality of convex portions, forming an amorphous semiconductor film on the second base insulating film, and irradiating the amorphous semiconductor film with a laser beam; Forming a crystalline semiconductor film, and forming the crystalline semiconductor film on the convex portion as a channel formation region of a TFT. 9. A first base insulating film having a different refractive index from the substrate and having a plurality of concave portions is formed on a substrate having a light transmitting property, and the first base insulating film is formed on the first base insulating film. Forming a second base insulating film having a different refractive index from that of the base insulating film, forming an amorphous semiconductor film on the second base insulating film, and irradiating the amorphous semiconductor film with a laser beam. A semiconductor device, wherein a crystalline semiconductor film is formed by the above method, and the crystalline semiconductor film on the concave portion is used as a channel formation region of a TFT. 10. A first base insulating film having a refractive index different from that of the substrate and having a plurality of projections is formed on a substrate having a light transmitting property, and the first base insulating film is formed on the first base insulating film. Forming a second base insulating film having a refractive index different from that of the first base insulating film, forming an amorphous semiconductor film on the second base insulating film, and irradiating the amorphous semiconductor film with a laser beam; Forming a crystalline semiconductor film, and forming the crystalline semiconductor film on the convex portion as a channel formation region of a TFT. 11. The semiconductor device according to claim 7, wherein the semiconductor device is a liquid crystal display device or an EL display device. 12. The semiconductor device according to claim 7, wherein the semiconductor device is a mobile phone, a video camera, a digital camera, a projector, a goggle type display, a personal computer, a DVD player, an electronic book, or a mobile phone. A semiconductor device characterized by being a type information terminal.