JP4566504B2 - Laser irradiation apparatus, laser irradiation method, and manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for irradiating a laser beam (laser beam) and a laser irradiation apparatus for performing the method (an apparatus including a laser and an optical system for guiding a laser beam (laser beam) output from the laser to an object to be processed). About. Further, the present invention relates to a method for manufacturing a semiconductor device manufactured by including laser irradiation in a process. Note that the semiconductor device here includes an electro-optical device such as a liquid crystal display device and a light-emitting device and an electronic device including the electro-optical device as a component.
[0002]
[Prior art]
In recent years, techniques for obtaining a crystalline semiconductor film by performing laser annealing on a semiconductor film formed over an insulating substrate such as glass to crystallize or improve crystallinity have been widely studied. Note that in this specification, a crystalline semiconductor film refers to a semiconductor film in which a crystallized region exists, and includes a semiconductor film in which the entire surface is crystallized.
[0003]
A glass substrate is less expensive than a synthetic quartz glass substrate and has an advantage that a large-area substrate can be easily manufactured. In addition, the reason why lasers are used favorably for crystallization is that the melting point of the glass substrate is low. The laser can give high energy to the semiconductor film without significantly increasing the temperature of the substrate. In addition, the throughput is significantly higher than that of heating means using an electric furnace.
[0004]
Since a crystalline semiconductor film formed by laser light irradiation has high mobility, a thin film transistor (TFT) is formed using the crystalline semiconductor film, for example, on a single glass substrate. Alternatively, it is used in an active matrix type liquid crystal display device or the like for manufacturing TFTs for pixel portions and driving circuits.
[0005]
As the laser light, laser light oscillated from an excimer laser or the like is often used. The excimer laser has the advantage that it has a large output and can be repeatedly irradiated at a high frequency. Furthermore, the laser light oscillated from the excimer laser has a high absorption coefficient for a silicon film often used as a semiconductor film. Have advantages. For laser light irradiation, the laser light is shaped by an optical system so that the shape at or near the irradiation surface is rectangular, and the laser light is moved (or the irradiation position of the laser light on the irradiation surface). The method of irradiating with relatively moving is highly productive and industrially excellent. In this specification, a laser beam having a rectangular shape at or near the irradiation surface is referred to as a rectangular beam, and a laser beam having a dot shape is referred to as a dot beam.
[0006]
On the other hand, the area of the substrate to be used is increasing. This is because when a single large-area substrate is used to manufacture a plurality of semiconductor devices such as a panel for a liquid crystal display device, throughput is higher and cost reduction can be realized. As a large area substrate, for example, a substrate of 600 mm × 720 mm, a circular 12 inch substrate (diameter of about 300 mm), and the like are used. Furthermore, in the future, it is considered that a substrate having a side exceeding 1 m is also used.
[0007]
In general, an excimer laser used for laser annealing uses KrF (wavelength 248 nm) or XeCl (wavelength 308 nm) as an excitation gas for forming laser light. However, gases such as Kr (krypton) and Xe (xenon) are very expensive, and there is a problem that the manufacturing cost increases when the frequency of gas exchange increases.
[0008]
In addition, replacement of attached equipment such as a laser tube for performing laser oscillation and a gas purifier for removing unnecessary compounds generated during the oscillation process is required once every three to six months. Many of these accessory devices are expensive, and there is still a problem that the manufacturing cost increases.
[0009]
As described above, laser irradiation equipment using excimer lasers has high performance. However, it takes a lot of maintenance work, and as a production laser equipment, the running cost (here, the costs generated by operation) It also has the drawback of being expensive.
[0010]
Therefore, in recent years, it is conceivable to anneal the semiconductor film using a solid-state laser whose maximum output is remarkably improved. Since a solid-state laser can basically output laser light if there is a solid crystal, a resonant mirror, and a light source for exciting the solid crystal, it does not require maintenance work like an excimer laser. That is, since the running cost is very low compared to the excimer laser, the manufacturing cost of the semiconductor device can be greatly reduced. Further, if the number of maintenance operations is reduced, the operation rate of the mass production line is increased, so that the overall throughput of the manufacturing process is improved, which also greatly contributes to the reduction of the manufacturing cost of the semiconductor device. Furthermore, since the area occupied by the solid-state laser is smaller than that of the excimer laser, it is advantageous for designing the production line.
[0011]
Solid-state lasers are generally YAG lasers (usually Nd: YAG lasers), YVO _Four Laser, YLF laser, YAlO _Three Lasers, glass lasers, ruby lasers, alexandride lasers, Ti: sapphire lasers, and the like are known. Here, a YAG laser will be described as an example. A YAG laser is known as emitting a laser beam having a wavelength of 1065 nm as a fundamental wave. The absorption coefficient of the laser beam with respect to the silicon film is very low, and crystallization of an amorphous silicon film, which is one of the silicon films, has a large energy loss and is inefficient. However, this laser beam can be converted to a shorter wavelength by using a nonlinear optical element. The second harmonic (532 nm), the third harmonic (355 nm), the fourth harmonic (266 nm), and the fifth harmonic (213 nm) are named according to the wavelength to be converted. Since these harmonics have a higher absorption coefficient than the amorphous silicon film, they can be used for crystallization of the amorphous silicon film.
[0012]
[Problems to be solved by the invention]
However, the YAG laser is coherent light with very high coherence. The coherent length of the excimer laser is several μm to several tens μm, whereas the coherent length of the YAG laser is about 10 mm or more. Therefore, even if the laser beam is condensed on the irradiated surface or in the vicinity thereof, it is difficult to form a laser beam having a uniform energy distribution due to interference, and uniform laser annealing cannot be performed.
[0013]
Therefore, the present invention provides a method for irradiating laser light on the entire irradiation surface efficiently and a laser irradiation apparatus for performing the same even when a laser having a high coherence or a large area substrate is used. The issue is to provide. Another object is to provide a method for manufacturing a semiconductor device using a semiconductor film obtained by crystallization of a semiconductor film or activation of an impurity element by such a laser irradiation method.
[0014]
[Means for Solving the Problems]
The structure of the invention relating to the laser irradiation apparatus disclosed in this specification includes a laser, a dividing unit that converts a laser beam (laser beam) emitted from the laser into a plurality of laser beams (laser beams), and an irradiation surface or in the vicinity thereof. It comprises a laser beam (laser beam) forming unit having a periodic energy distribution by combining the plurality of laser beams (laser beam), and a substrate moving unit relative to the laser beam. .
[0015]
In addition, the configuration of the invention relating to the laser irradiation apparatus disclosed in this specification includes a laser, a first optical system that divides a laser beam (laser beam) emitted from the laser into a plurality, and the first optical system. A second optical system for synthesizing the divided laser beams (laser beams) to form a laser beam (laser beam) having a periodic energy distribution on the irradiated surface, the first optical system Is provided between the laser and the second optical system.
[0016]
In addition, the configuration of the invention relating to the laser irradiation apparatus disclosed in this specification includes a first optical system and a second optical system in a laser irradiation apparatus that irradiates an irradiated surface with laser light (laser beam) emitted from a laser. The second optical system is arranged so that the optical axis of the laser beam (laser beam) divided by the first optical system is superimposed on the irradiated surface, and is emitted from the laser. The laser light that has passed through the first optical system and the second optical system has a periodic energy distribution on the irradiated surface.
[0017]
In the configuration of the invention, the laser is a continuous wave or pulsed solid laser. As the solid-state laser, YAG laser, YVO _Four Laser, YLF laser, YAlO _Three A laser, a glass laser, a ruby laser, an alexandride laser, a Ti: sapphire laser, and the like can be given.
[0018]
In the configuration of the above invention, the first optical system and the second optical system are installed so as to irradiate laser light (laser beam) emitted from the laser obliquely to the irradiated surface of the sample. It is characterized by being.
[0019]
In the configuration of the invention described above, the periodic energy distribution is formed by combining and interfering the plurality of laser beams on or near the irradiated surface. However, when strong interference occurs, the difference in height of the energy density becomes too large, and there is a possibility that sufficient annealing cannot be performed in a region where the energy density is low. Therefore, the first interference formed by at least two of the plurality of laser beams and the second interference formed by at least two other laser beams are shifted and overlapped to form the first interference. The height difference of the energy density can be adjusted by changing the energy distribution of the second interference and the second interference. That is, by combining the energy distribution of the first interference and the energy distribution of the second interference, it is possible to form a laser beam (laser beam) having a small periodic change in the energy distribution. Further, when the first interference and the second interference have the same energy distribution, a laser beam having a uniform energy distribution can be formed on the irradiated surface if they are shifted and overlapped by a half period. Of course, the number of interferences to be superimposed is not limited to two.
[0020]
In the configuration of the above invention, the means for dividing the plurality of laser beams (laser beams) can be performed by using one kind selected from a cylindrical lens array, a prism and a mirror, or by using a plurality of kinds. Further, it is possible to divide the laser beam into many laser beams (laser beams).
Such means for dividing the laser beam (laser beam) has an effect of making the laser uniform in a laser having a beam distribution higher in the center than in the periphery, such as Gaussian.
[0021]
In the configuration of the above invention, the means for combining the plurality of laser beams (laser beams) can be performed using a mirror or a cylindrical lens, or can be performed using both a mirror and a cylindrical lens. Note that it is preferable to use a cylindrical lens because the length in one direction of the laser light is reduced and the energy density on the irradiated surface is increased.
[0022]
In addition, in the configuration of the invention relating to the laser irradiation method disclosed in this specification, a laser beam (laser beam) is divided into a plurality of laser beams (laser beams), and the plurality of laser beams (laser beams) at or near the irradiation surface. ) To form a laser beam (laser beam) having a periodic energy distribution, and irradiate the substrate while moving the substrate relative to the laser beam (laser beam).
[0023]
Further, in the configuration of the invention relating to the laser irradiation method disclosed in this specification, the optical path of laser light (laser beam) emitted from the same laser is divided into a plurality by the first optical system, and divided into the plurality. Laser light (laser beam) is irradiated obliquely to the irradiated surface by the second optical system, and the laser light (laser beam) is synthesized so as to have a periodic energy distribution on the irradiated surface. And irradiating the irradiated surface.
[0024]
Further, in the configuration of the invention relating to the laser irradiation method disclosed in this specification, the optical path of laser light (laser beam) emitted from the same laser is divided into a plurality by the first optical system, and the laser is divided into the plurality. Laser light (laser beam) is irradiated with light (laser beam) obliquely with respect to the irradiated surface by the second optical system and has a periodic energy distribution in the first direction of the irradiated surface. And irradiating in a first direction of the irradiated surface and a second direction perpendicular to the first direction.
[0025]
In the configuration of the invention described above, the laser beam (laser beam) is emitted from a continuous wave or pulsed solid laser. Moreover, as said solid state laser, YAG laser, YVO _Four Laser, YLF laser, YAlO _Three A laser, a glass laser, a ruby laser, an alexandride laser, a Ti: sapphire laser, and the like can be given.
[0026]
In the configuration of the invention described above, the periodic energy distribution is formed by combining and interfering the plurality of laser beams (laser beams) at or near the irradiated surface.
[0027]
In the configuration of the above invention, the means for dividing the plurality of laser beams (laser beams) can be performed by using one kind selected from a cylindrical array lens, a prism and a mirror, or by using a plurality of kinds. It is also possible to divide the laser beam into more laser beams.
[0028]
In the configuration of the above invention, the means for combining the plurality of laser beams (laser beams) can be performed using a mirror or a cylindrical lens, or can be performed using both a mirror and a cylindrical lens.
[0029]
Further, in the structure of the invention relating to the method for manufacturing a semiconductor device disclosed in this specification, a laser beam is divided into a plurality of laser beams (laser beams), and the plurality of laser beams (laser beams) are irradiated on or near an irradiation surface. A laser beam having a periodic energy distribution is formed by synthesis, and irradiation is performed while moving the semiconductor film with respect to the laser beam (laser beam).
[0030]
In the configuration of the above invention, the laser beam is emitted from a continuous wave or pulsed solid laser. Moreover, as said solid state laser, YAG laser, YVO _Four Laser, YLF laser, YAlO _Three A laser, a glass laser, a ruby laser, an alexandride laser, a Ti: sapphire laser, and the like can be given.
[0031]
In the configuration of the invention described above, the periodic energy distribution is formed by combining and interfering the plurality of laser beams (laser beams) at or near the irradiated surface.
[0032]
In the configuration of the above invention, the means for dividing the plurality of laser beams (laser beams) can be performed by using one kind selected from a cylindrical array lens, a prism and a mirror, or by using a plurality of kinds. Further, it is possible to divide the laser beam into many laser beams (laser beams).
[0033]
In the configuration of the above invention, the means for combining the plurality of laser beams (laser beams) can be performed using a mirror or a cylindrical lens, or can be performed using both a mirror and a cylindrical lens.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to FIGS.
[0035]
FIG. 1 shows an example of a laser irradiation apparatus of the present invention. The laser light oscillated from the laser 101 is converted into a harmonic by the nonlinear optical element 102 and is divided into a plurality of laser lights by the mirror 103 which is a dividing means. Each laser beam is reflected by mirrors 104 a and 104 b which are laser beam forming means having a periodic energy distribution, and reaches the substrate 110. In the substrate 110, a plurality of laser beams are combined to cause interference, and a laser beam having a periodic energy distribution is formed. The substrate 110 is installed on a movable stage 111 that is a means for moving the substrate relative to the laser light. By moving the stage 111, it is possible to irradiate laser light on a large-area substrate. Yes. The cylindrical lenses 105a and 105b are desirably installed to increase the energy density on the irradiation surface.
[0036]
The shape of the laser light emitted from the laser differs depending on the type of laser, and is circular if the rod shape is cylindrical, and rectangular if it is slab type.
[0037]
Here, the state of interference of laser light on the irradiated surface will be described with reference to FIG.
[0038]
As shown in FIG. 2A, interference occurs when a plurality of laser beams are superimposed on the irradiation surface. The energy density distribution at this time is a wave-like periodic distribution in which high energy density portions and low energy density portions appear alternately as shown in FIG. If attention is paid only to a portion having a high energy density, it can be considered that a plurality of dot-like laser beams form a line. When irradiation is performed using such a laser beam, the laser beam can be irradiated much more efficiently than when a single point laser beam is used. This is particularly effective when the semiconductor film is annealed using laser light having a high energy density oscillated from a high-power laser. Even if laser light with high coherence is used, periodic energy density distribution can be formed by causing interference on the irradiated surface, which is very effective.
[0039]
As shown in FIG. 2A, a plurality of laser beams are incident symmetrically on the irradiation surface. Therefore, the reflected light of the laser light 1 follows an optical path where the laser light 2 enters the irradiation surface, and the reflected light of the laser light 2 follows an optical path where the laser light 1 enters the irradiation surface. In other words, each reflected light behaves in the same manner as the return light, which may cause adverse effects such as laser output and frequency fluctuations and rod destruction. Therefore, it is preferable to install an isolator in order to remove the reflected light and stabilize the oscillation of the laser. For example, if it is installed between the nonlinear optical element 102 and the mirror 103, the reflected light can be removed.
[0040]
Next, a method for irradiating the entire surface of the substrate with such laser light will be described with reference to FIG.
[0041]
The substrate 110 (or the stage 111 in FIG. 1) is moved in the direction indicated by 112 with respect to the laser light, and subsequently moved in the direction indicated by 113. By repeating this operation, the entire surface of the substrate 110 can be irradiated. (FIG. 3A) Further, the substrate 110 (or the stage 111 in FIG. 1) is moved in the direction indicated by 112 with respect to the laser light, and further moved in the direction indicated by 114, and then moved in the direction indicated by 113. Alternatively, the substrate 110 (or stage 111 in FIG. 1) is moved in the direction indicated by 112 with respect to the laser light, and further moved in the direction indicated by 114 a plurality of times, and then the direction indicated by 113. You may move to. (FIG. 3B) Of course, the entire surface of the substrate may be irradiated by moving the laser beam.
[0042]
Next, a case where the semiconductor film is crystallized using such an irradiation method will be described. When the semiconductor film is irradiated with laser light, the irradiated region is in a molten state and is cooled and solidified as time passes. If irradiation is performed while moving the laser beam, regions that are in a molten state are formed one after another, while there are regions that cool and solidify over time. That is, a temperature gradient is formed in the semiconductor film, crystal grains grow along the moving direction of the laser light, and large crystal grains are formed in parallel.
[0043]
By obtaining a crystalline semiconductor film in which large crystal grains are formed in parallel, the performance of the semiconductor device can be greatly improved. For example, taking a TFT as an example, the number of crystal grain boundaries that can be included in the channel formation region can be reduced by forming crystal grains having a large grain size in parallel. In other words, the number of times that carriers cross the crystal grain boundary can be extremely reduced, so that high mobility (field effect mobility) equivalent to or higher than that of a transistor using a single crystal semiconductor can be obtained. Reduce variations in values (drain current values that flow when the TFT is on), off-current values (drain current values that flow when the TFT is off), threshold voltages, S values, and field-effect mobility Is also possible. As described above, the electrical characteristics of the TFT can be improved, and further, the operating characteristics and reliability of the semiconductor device can be improved. Note that since there are almost no crystal grain boundaries in the moving direction of the laser light, it is preferable to manufacture a TFT having a channel formation region parallel to this direction.
[0044]
Further, since crystal grains are formed by irradiating the entire surface of the semiconductor film with laser light, it is desirable to match the width of the crystal grains with the pitch p of interference formed by the laser light divided into a plurality of parts. Assuming that the wavelength of the laser beam is λ and the incident angle is θ, from FIG.
sin θ = λ / p
∴θ = arcsin (λ / p)
Holds. For example, YAG laser and YVO _Four When the second harmonic of the laser (wavelength 532 nm) is used and the width of the formed crystal grain is 1 to 10 μm,
θ = arcsin (532/1000)
= 32.14
θ = arcsin (532/10000)
= 3.05
Accordingly, the incident angle θ is 3 to 32 degrees.
[0045]
In addition, when the width of the formed crystal grain is 10 μm or more, there is a high possibility that a crack will occur in the crystal and a defect will occur. On the other hand, if it is less than 1 μm, the crystal grain boundaries in the film increase, which causes a leakage current. For this reason, the width of the crystal grains is preferably in the range of 1 to 10 μm.
By using such an irradiation method, laser annealing can be performed on the entire surface of a large-area substrate. In addition, when the semiconductor film is crystallized by such laser annealing, it is possible to form a semiconductor film in which large crystal grains exist in parallel. For this reason, the crystal grain boundary is reduced, the mobility (field effect mobility) is improved, the on-current value (drain current value that flows when the TFT is in an on state), and the off-current value (when the TFT is in an off state) It is also possible to reduce variations in drain current value), threshold voltage, S value, and field effect mobility. Therefore, the electrical characteristics of the TFT manufactured using the semiconductor film can be improved, and the operating characteristics and reliability of the semiconductor device can be improved.
In addition, when laser light is incident perpendicularly to the substrate surface, the laser light reflected from the back surface of the substrate and the irradiated laser light interfere with each other on the substrate surface, resulting in a non-uniform energy density distribution. However, this problem can be solved by irradiating the laser beam obliquely with respect to the substrate, and a uniform crystalline semiconductor film can be formed. .
[0046]
The present invention configured as described above will be described in more detail with reference to the following examples.
[0047]
【Example】
[Example 1]
In this embodiment, a method and an apparatus for irradiating a whole surface of a substrate with laser light will be described with reference to FIG.
[0048]
The laser light emitted from the laser 101 is preferably converted into a harmonic by the nonlinear optical element 102. In this embodiment, a continuous wave YAG laser is used as the laser 101 and is converted into the second harmonic by the nonlinear optical element 102.
[0049]
Then, by irradiating the mirror 103 with laser light, the optical path of the laser light is divided into two directions, and the respective laser lights are made incident on the mirrors 104a and 104b. Preferably, the length is reduced in one direction of the laser light by the cylindrical lenses 105a and 105b. By doing in this way, energy density can be raised.
[0050]
The laser light reflected by the mirrors 104a and 104b reaches the substrate 110 which is an irradiation surface. That is, the laser light reflected by the mirrors 104a and 104b is superimposed on the substrate 110 that is the irradiation surface. As shown in FIG. 2, on the substrate 110, laser beams that have arrived from two directions cause interference, and a periodic energy distribution is generated. This can be considered that a large number of dot-shaped laser beams are arranged, and laser beam irradiation can be performed more efficiently than when one dot-shaped laser beam is used.
[0051]
Although not shown, it is desirable to install an isolator because each reflected light may have an adverse effect on the laser by following the optical path leading to the incidence of each other.
[0052]
With respect to such laser light, the substrate 100 (or the stage 111 in FIG. 1) is moved in the direction indicated by 112 and subsequently moved in the direction indicated by 113. By repeating this operation, the entire surface of the substrate can be irradiated. (FIG. 3A) Further, the substrate 100 (or the stage 111 in FIG. 1) is moved in the direction indicated by 112 with respect to the laser light, and further moved in the direction indicated by 114, and then moved in the direction indicated by 113. Alternatively, the substrate 100 (or the stage 111 in FIG. 1) is moved in the direction indicated by 112 with respect to the laser light, and further moved in the direction indicated by 114, and then the direction indicated by 113 is repeated. You may move to. (FIG. 3B) Of course, the entire surface of the substrate may be irradiated by moving the laser beam.
[0053]
In this way, the laser beam can be efficiently irradiated onto the entire surface of the substrate. By using this irradiation method, annealing of the semiconductor film, activation of the impurity element, and the like can be performed.
[0054]
[Example 2]
In this embodiment, a method and apparatus for irradiating the entire surface of a substrate with laser light by a laser light splitting method different from that in Embodiment 1 will be described with reference to FIG.
[0055]
The laser light emitted from the laser 101 is preferably converted into a harmonic by the nonlinear optical element 102. In this embodiment, the laser 101 is a continuous wave YVO. _Four Using a laser, the nonlinear optical element 102 converts it to a third harmonic.
[0056]
Then, by irradiating the prism 121 with the laser beam, the optical path of the laser beam is divided into two directions, and the respective laser beams are made incident on the mirrors 122a and 122b. The length of the laser light in one direction is preferably reduced by the cylindrical lenses 105a and 105b. By doing in this way, energy density can be raised.
[0057]
Subsequently, the laser light reaches the substrate 110 that is the irradiation surface. That is, the laser light reflected by the mirrors 122a and 122b is superimposed on the substrate 110 that is the irradiation surface. As a result, as shown in FIG. 2, laser light that has reached from two directions causes interference on the substrate 110, and a periodic energy distribution is generated. This state can be considered that a large number of dot-shaped laser beams are arranged, and laser beam irradiation can be performed more efficiently than when one dot-shaped laser beam is used.
[0058]
The substrate moving method is the same as in the first embodiment.
[0059]
In this way, the laser beam can be efficiently irradiated onto the entire surface of the substrate.
By using this irradiation method, annealing of the semiconductor film, activation of the impurity element, and the like can be performed.
[0060]
[Example 3]
In this embodiment, a method and an apparatus for dividing a laser beam by a method different from that in Embodiments 1 and 2 and irradiating the entire surface of the substrate with the laser beam will be described with reference to FIG.
[0061]
The laser light emitted from the laser 101 is preferably converted into a harmonic by the nonlinear optical element 102. In this embodiment, a YLF laser is used as the laser 101 and converted into the third harmonic by the nonlinear optical element 102.
[0062]
Then, the laser beam is split by being incident on the cylindrical lens array 131. In this embodiment, the number of divisions is four. Subsequently, the cylindrical lens 132 collects and diverges the laser light. As a result, the traveling directions of the laser beams divided into four (that is, the optical paths of the laser beams) can be made different from each other, so that the respective laser beams can be easily incident on different optical elements. Then, the divided laser light is made incident on the lenses 133a to 133c. The lenses 133a and 133c are installed asymmetrically with respect to the lens 133b (specifically, the distance (X) between the side surface of the lens 133b and the lens 133a, and the distance (Y) between the side surface of the lens 133b and the lens 133c). In the irradiation surface, the energy distribution between the interference caused by the laser beams transmitted through 133a and 133c and the interference caused by the two laser beams transmitted through 133b can be shifted. Further, if installed symmetrically, the difference in height of the energy distribution of the laser beam on the irradiated surface can be increased. Note that it is preferable that the lenses 133a and 133c be movable using a micrometer or the like because fine adjustment is possible.
[0063]
Since the two laser beams transmitted through the lenses 133a and 133c are portions at both ends of the laser beam emitted from the laser 101, the energy density is lower than that of the laser beam transmitted through the lens 133b. Therefore, the energy density of the interference due to the laser light transmitted through the lenses 133a and 133c and the interference due to the interference between the two laser lights transmitted through the lens 133b are overlapped with a shift of, for example, a half cycle, so that the energy density is extremely low on the irradiation surface. It is possible to prevent the occurrence of the part. (FIG. 6) Of course, the energy density of each laser beam is made the same, and the energy distribution of the interference by the laser beam transmitted through the lenses 133a and 133c and the interference by the two laser beams transmitted through 133b are shifted by a half cycle and overlapped. If so, it is also possible to produce a laser beam having a uniform energy distribution. (Fig. 7)
[0064]
In addition, a cylindrical lens may be installed between the lenses 133 a to 133 c and the substrate 110.
[0065]
The substrate moving method is the same as that in the first embodiment.
[0066]
In this way, the laser beam can be efficiently irradiated onto the entire surface of the substrate. By using this irradiation method, annealing of the semiconductor film, activation of the impurity element, and the like can be performed.
[0067]
In the present embodiment, the laser beam is condensed and diverged by the cylindrical lens 132 and then further condensed by the lens 133. However, the plurality of laser beams can be interfered by 132.
[0068]
[Example 4]
In this embodiment, a method and an apparatus for dividing laser light by a method different from that in Embodiments 1 to 3 and irradiating the entire surface of the substrate with laser light will be described with reference to FIG.
[0069]
The laser light emitted from the laser 101 is preferably converted into a harmonic by the nonlinear optical element 102. As the laser 101, a continuous wave or pulsed YAG laser, YVO, _Four Laser, YLF laser, YAlO _Three A laser, a glass laser, a ruby laser, an alexandride laser, a Ti: sapphire laser, or the like can be used. In this embodiment, a YLF laser is used and converted to the second harmonic.
[0070]
Then, the light beam is divided by irradiating the prism 141 with laser light. In this embodiment, the number of divisions is four. The prism 141 has the same role as the combination of the cylindrical lens array 131 and the cylindrical lens 132 shown in the third embodiment. By using the prism 141, the number of optical elements can be reduced from 2 to 1, so that the optical transmittance can be improved. Further, there is an effect that the optical path length may be shorter than the system shown in the third embodiment. The short optical path is particularly effective when installed in a clean room where the cost per unit area is very high.
Then, the divided laser light is made incident on the lenses 133a to 133c. The lenses 133a and 133c are disposed asymmetrically with respect to the lens 133b, that is, the lenses 133a and 133b are disposed at positions where the distance between the lenses 133a and 133b and the distance between the lenses 133c and 133b are different from each other. , The interference caused by the laser beams transmitted through 133a and 133c can be shifted from the interference caused by the two laser beams transmitted through 133b. Further, if installed symmetrically, the difference in height of the energy distribution of the laser beam on the irradiated surface can be increased. Note that it is preferable that the lenses 133a and 133c be movable using a micrometer or the like because fine adjustment is possible.
[0071]
Since the two laser beams transmitted through the lenses 133a and 133c are portions at both ends of the laser beam emitted from the laser 101, the energy density is lower than that of the laser beam transmitted through the lens 133b. Therefore, by superimposing the interference caused by the laser light transmitted through the lenses 133a and 133c and the interference caused by the two laser lights transmitted through the lens 133b, for example, by shifting by a half cycle, a portion having an extremely low energy density is generated on the irradiated surface. Can be prevented. (FIG. 6) Of course, if the energy density of each laser beam is made the same, the interference by the laser beam transmitted through the lenses 133a and 133c and the interference by the two laser beams transmitted through the lens 133b are shifted by a half cycle and overlapped. It is also possible to produce a laser beam having a uniform energy density. (Fig. 7)
[0072]
In addition, a cylindrical lens may be installed between the lenses 133 a to 133 c and the substrate 110.
[0073]
The substrate moving method is the same as that in the first embodiment.
[0074]
In this way, the entire surface of the substrate can be efficiently irradiated. By using this irradiation method, annealing of the semiconductor film, activation of the impurity element, and the like can be performed.
[0075]
[Example 5]
In this embodiment, a method for manufacturing an active matrix substrate will be described with reference to FIGS. In this specification, a substrate in which a pixel portion having a CMOS circuit, a driver circuit, a pixel TFT, and a storage capacitor is formed over the same substrate is referred to as an active matrix substrate for convenience.
[0076]
First, in this embodiment, a substrate 400 made of glass such as barium borosilicate glass or alumino borosilicate glass is used. Note that the substrate 400 may be a quartz substrate, a silicon substrate, a metal substrate, or a stainless substrate on which an insulating film is formed. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this embodiment may be used.
[0077]
Next, a base film 401 made of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed over the substrate 400 by a known means (a sputtering method, an LPCVD method, a plasma CVD method, or the like). Although a two-layer structure is used as the base film 401 in this embodiment, a single-layer film of the insulating film or a structure in which two or more layers are stacked may be used.
[0078]
Next, a semiconductor layer is formed over the base film. The semiconductor layer is formed by forming a semiconductor film with a thickness of 25 to 80 nm (preferably 30 to 60 nm) by a known means (sputtering method, LPCVD method, plasma CVD method, etc.), and is crystallized by a laser crystallization method.
In the laser crystallization method, any one of the first to fourth embodiments is applied, and laser light emitted from the laser is divided into a plurality of laser lights by an optical system and then combined into one to form interference, Irradiate the semiconductor film. Of course, not only the laser crystallization method but also other known crystallization methods (thermal crystallization method using an RTA or furnace annealing furnace, thermal crystallization method using a metal element that promotes crystallization, etc.) You may go. Then, the obtained crystalline semiconductor film is patterned into a desired shape to form semiconductor layers 402 to 406. Examples of the semiconductor film include an amorphous semiconductor film, a microcrystalline semiconductor film, a crystalline semiconductor film, and the like, and a compound semiconductor film having an amorphous structure such as an amorphous silicon germanium film may be applied.
[0079]
In this embodiment, first, a 55 nm amorphous silicon film is formed by plasma CVD. And YVO of continuous oscillation of output 10W _Four After the laser light emitted from the laser is converted into a second harmonic by a non-linear optical element, it is divided into a plurality of laser lights by the optical system shown in any one of Examples 1 to 4, and synthesized on a substrate. Form interference. The energy density distribution at this time is wavy, but the peak value is 150 mJ / cm for crystallization. ² Or more (preferably 200 mJ / cm ² A laser beam having an energy density of (above) is required. Then, irradiation is performed by moving the stage at a speed of about 10 to 200 cm / s to form a crystalline silicon film. Subsequently, semiconductor layers 402 to 406 are formed by a patterning process using a photolithography method.
[0080]
Further, after forming the semiconductor layers 402 to 406, a small amount of impurity element (boron or phosphorus) may be doped in order to control the threshold value of the TFT.
[0081]
Next, a gate insulating film 407 covering the semiconductor layers 402 to 406 is formed. The gate insulating film 407 is formed of an insulating film containing silicon with a thickness of 40 to 150 nm by plasma CVD or sputtering. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N = 7%, H = 2%) with a thickness of 110 nm is formed by plasma CVD. 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.
[0082]
When a silicon oxide film is used, TEOS (Tetraethyl Orthosilicate) and O ₂ The reaction pressure is 40 Pa, the substrate temperature is 300 to 400 ° C., and the high frequency (13.56 MHz) power density is 0.5 to 0.8 W / cm. ² And can be formed by discharging. The silicon oxide film thus produced can obtain good characteristics as a gate insulating film by thermal annealing at 400 to 500 ° C. thereafter.
[0083]
Next, a first conductive film 408 with a thickness of 20 to 100 nm and a second conductive film 409 with a thickness of 100 to 400 nm are stacked over the gate insulating film 407. In this embodiment, a first conductive film 408 made of a TaN film with a thickness of 30 nm and a second conductive film 409 made of a W film with a thickness of 370 nm are stacked. The TaN film is formed by sputtering, and is sputtered in a nitrogen-containing atmosphere using a Ta target. The W film was formed by sputtering using a W target. In addition, tungsten hexafluoride (WF ₆ It can also be formed by a thermal CVD method using In any case, in order to use as a gate electrode, it is necessary to reduce the resistance, and the resistivity of the W film is desirably 20 μΩcm or less. The resistivity of the W film can be reduced by increasing the crystal grains. However, when there are many impurity elements such as oxygen in the W film, the crystallization is hindered and the resistance is increased. Therefore, in this embodiment, a sputtering method using a target of high purity W (purity 99.9999%) is used, and the W film is formed with sufficient consideration so that impurities are not mixed in from the gas phase during film formation. By forming, a resistivity of 9 to 20 μΩcm can be realized.
[0084]
In this embodiment, the first conductive film 408 is TaN and the second conductive film 409 is W. However, there is no particular limitation, and all of them are Ta, W, Ti, Mo, Al, Cu, Cr, Nd. You may form with the element selected from these, or the alloy material or compound material which has the said element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Further, an AgPdCu alloy may be used. In addition, the first conductive film is formed using a tantalum (Ta) film, the second conductive film is formed using a W film, the first conductive film is formed using a titanium nitride (TiN) film, and the second conductive film is formed. The first conductive film is formed of a tantalum nitride (TaN) film, the second conductive film is formed of an Al film, and the first conductive film is formed of a tantalum nitride (TaN) film. The second conductive film may be a combination of Cu films.
[0085]
Next, resist masks 410 to 415 are formed by photolithography, and a first etching process is performed to form electrodes and wirings. The first etching process is performed under the first and second etching conditions. (FIG. 9 (B)) In this embodiment, ICP (Inductively Coupled Plasma) etching is used as the first etching condition, and CF is used as an etching gas. _Four And Cl ₂ And O ₂ The gas flow ratio is 25:25:10 (sccm), and 500 W of RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma and perform etching. 150 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. The W film is etched under the first etching condition so that the end portion of the first conductive layer is tapered.
[0086]
Thereafter, the resist masks 410 to 415 are not removed and the second etching condition is changed, and the etching gas is changed to CF. _Four And Cl ₂ The gas flow ratio is 30:30 (sccm), and 500 W of RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma and etching for about 30 seconds. Went. 20 W of RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. CF _Four And Cl ₂ Under the second etching condition in which is 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, it is preferable to increase the etching time at a rate of about 10 to 20%.
[0087]
In the first etching process, the shape of the mask made of resist is made suitable, and the end portions 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. It becomes. The angle of this taper portion is 15 to 45 °. Thus, the first shape conductive layers 417 to 422 (first conductive layers 417 a to 422 a and second conductive layers 417 b to 422 b) composed of the first conductive layer and the second conductive layer by the first etching treatment. Form. Reference numeral 416 denotes a gate insulating film, and a region not covered with the first shape conductive layers 417 to 422 is etched and thinned by about 20 to 50 nm.
[0088]
Next, a second etching process is performed without removing the resist mask.
Here, CF is used as an etching gas. _Four And Cl ₂ And O ₂ Then, the W film is selectively etched. At this time, second conductive layers 428b to 433b are formed by a second etching process. On the other hand, the first conductive layers 417a to 422a are hardly etched, and the second shape conductive layers 428 to 433 are formed.
[0089]
Then, a first doping process is performed without removing the resist mask, and an impurity element imparting n-type conductivity is added to the semiconductor layer at a low concentration. The doping process may be performed by ion doping or ion implantation. The condition of the ion doping method is a dose of 1 × 10 ¹³ ~ 5x10 ¹⁴ /cm ² The acceleration voltage is set to 40 to 80 keV. In this embodiment, the dose is 1.5 × 10 ¹³ /cm ² The acceleration voltage is set to 60 keV. As an impurity element imparting n-type, an element belonging to Group 15, typically phosphorus (P) or arsenic (As), is used here, but phosphorus (P) is used. In this case, the conductive layers 428 to 433 serve as a mask for the impurity element imparting n-type, and the impurity regions 423 to 427 are formed in a self-aligning manner. Impurity regions 423 to 427 have a size of 1 × 10 ¹⁸ ~ 1x10 ²⁰ /cm ^Three An impurity element imparting n-type is added in a concentration range of.
[0090]
After removing the resist mask, new resist masks 434a to 434c are formed, and the second doping process is performed at an acceleration voltage higher than that of the first doping process. The condition of the ion doping method is a dose of 1 × 10 ¹³ ~ 1x10 ¹⁵ /cm ² The acceleration voltage is set to 60 to 120 keV. In the doping treatment, the second conductive layers 428b to 432b are used as masks against the impurity element, and doping is performed so that the impurity element is added to the semiconductor layer below the tapered portion of the first conductive layer. Subsequently, the third doping process is performed by lowering the acceleration voltage than the second doping process to obtain the state of FIG. The condition of the ion doping method is a dose of 1 × 10 ¹⁵ ~ 1x10 ¹⁷ /cm ² The acceleration voltage is set to 50 to 100 keV. The low-concentration impurity regions 436, 442, and 448 overlapping with the first conductive layer by the second doping process and the third doping process have 1 × 10 ¹⁸ ~ 5x10 ¹⁹ /cm ^Three An impurity element imparting n-type is added in a concentration range of 1 × 10 to the high-concentration impurity regions 435, 441, 444, and 447. ¹⁹ ~ 5x10 ^{twenty one} /cm ^Three An impurity element imparting n-type is added in a concentration range of.
[0091]
Needless to say, by setting the acceleration voltage to be appropriate, the second and third doping processes can be performed in a single doping process to form the low-concentration impurity region and the high-concentration impurity region.
[0092]
Next, after removing the resist mask, new resist masks 450a to 450c are formed, and a fourth doping process is performed. By this fourth doping treatment, impurity regions 453, 454, 459, and 460 in which an impurity element imparting a conductivity type opposite to the one conductivity type is added to the semiconductor layer that becomes the active layer of the p-channel TFT are formed. To do. The second conductive layers 428a to 432a are used as masks against the impurity element, and an impurity element imparting p-type is added to form an impurity region in a self-aligning manner. In this embodiment, the impurity regions 453, 454, 459, 460 are diborane (B ₂ H ₆ ) Using an ion doping method. (FIG. 10B) In the fourth doping process, the semiconductor layer forming the n-channel TFT is covered with masks 450a to 450c made of resist. By the first to third doping treatments, phosphorus is added to the impurity regions 453 and 459 at different concentrations, and the concentration of the impurity element imparting p-type is 1 × 10 5 in any of the regions. ¹⁹ ~ 5x10 ^{twenty one} atoms / cm ^Three By performing the doping treatment so as to become, no problem arises because it functions as the source region and drain region of the p-channel TFT.
[0093]
Through the above steps, impurity regions are formed in the respective semiconductor layers.
[0094]
Next, the resist masks 450 a to 450 c are removed, and a first interlayer insulating film 461 is formed. The first interlayer insulating film 461 is formed of an insulating film containing silicon with a thickness of 100 to 200 nm by using a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film having a thickness of 150 nm is formed by a plasma CVD method. Needless to say, the first interlayer insulating film 461 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.
[0095]
Next, as shown in FIG. 10C, a laser irradiation method is used as the activation process. In the laser irradiation method, any one of the first to fourth embodiments is applied, the laser light emitted from the laser is divided into a plurality of laser light by an optical system, and then combined into one to form interference, and the semiconductor film Irradiate.
[0096]
In this embodiment, continuous oscillation YVO with an output of 10 W _Four After the laser beam emitted from the laser is converted into the third harmonic by a non-linear optical element, it is divided into a plurality of laser beams using the optical system shown in any one of Examples 1 to 4 and synthesized on the substrate. To form interference. The energy density distribution at this time is wavy, but the peak value is 80 mJ / cm for crystallization. ² Or more (preferably 100 mJ / cm ² A laser beam having an energy density of the above is necessary. Then, irradiation is performed by moving the stage at a speed of about 10 to 200 cm / s.
[0097]
In addition, an activation process may be performed before forming the first interlayer insulating film.
[0098]
Then, hydrogenation can be performed by heat treatment (heat treatment at 300 to 550 ° C. for 1 to 12 hours). This step is a step of terminating dangling bonds in the semiconductor layer with hydrogen contained in the first interlayer insulating film 461. The semiconductor layer can be hydrogenated regardless of the presence of the first interlayer insulating film. As other means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) or heat treatment at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen may be performed. good.
[0099]
Next, a second interlayer insulating film 462 made of an inorganic insulating film material or an organic insulating material is formed over the first interlayer insulating film 461. In this embodiment, an acrylic resin film having a thickness of 1.6 μm is formed, but a film having a viscosity of 10 to 1000 cp, preferably 40 to 200 cp, and having a surface with unevenness is used.
[0100]
In this embodiment, in order to prevent specular reflection, the surface of the pixel electrode is formed with the unevenness by forming the second interlayer insulating film having the unevenness on the surface. In addition, a convex portion may be formed in a region below the pixel electrode in order to make the surface of the pixel electrode uneven to achieve light scattering. In that case, since the convex portion can be formed using the same photomask as that of the TFT, it can be formed without increasing the number of steps. In addition, this convex part should just be suitably provided on the board | substrate of pixel part area | regions other than wiring and a TFT part. Thus, irregularities are formed on the surface of the pixel electrode along the irregularities formed on the surface of the insulating film covering the convex portions.
[0101]
Alternatively, a film whose surface is planarized may be used as the second interlayer insulating film 462. In that case, after forming the pixel electrode, adding a step such as a known sandblasting method or etching method to make the surface uneven, prevent specular reflection, and increase the whiteness by scattering the reflected light Is preferred.
[0102]
In the driver circuit 506, wirings 463 to 467 that are electrically connected to the impurity regions are formed. Note that these wirings are formed by patterning a laminated film of a Ti film having a thickness of 50 nm and an alloy film (alloy film of Al and Ti) having a thickness of 500 nm. Of course, not only a two-layer structure but also a single-layer structure or a laminated structure of three or more layers may be used. Further, the wiring material is not limited to Al and Ti.
For example, a wiring may be formed by patterning a laminated film in which Al or Cu is formed on a TaN film and a Ti film is further formed. (Fig. 11)
[0103]
In the pixel portion 507, a pixel electrode 470, a gate wiring 469, and a connection electrode 468 are formed. With this connection electrode 468, the source wiring (stacked layer of 443a and 443b) is electrically connected to the pixel TFT. In addition, the gate wiring 469 is electrically connected to the gate electrode of the pixel TFT. In addition, the pixel electrode 470 is electrically connected to the drain region of the pixel TFT, and further electrically connected to the semiconductor layer 459 functioning as one electrode forming a storage capacitor. Further, as the pixel electrode 470, it is desirable to use a highly reflective material such as a film containing Al or Ag as a main component or a laminated film thereof.
[0104]
As described above, a CMOS circuit including an n-channel TFT 501 and a p-channel TFT 502, a driver circuit 506 having an n-channel TFT 503, and a pixel portion 507 having a pixel TFT 504 and a storage capacitor 505 are formed over the same substrate. can do. Thus, the active matrix substrate is completed.
[0105]
The n-channel TFT 501 of the driver circuit 506 includes a channel formation region 437, a low concentration impurity region 436 (GOLD region) overlapping with the first conductive layer 428a which forms part of the gate electrode, and a high concentration functioning as a source region or a drain region. An impurity region 452 and an impurity region 451 into which an impurity element imparting n-type conductivity and an impurity element imparting p-type conductivity are introduced are provided. The p-channel TFT 502, which is connected to the n-channel TFT 501 and the electrode 466 to form a CMOS circuit, includes a channel formation region 440, a high-concentration impurity region 454 that functions as a source region or a drain region, and an impurity element that imparts n-type conductivity And an impurity region 453 into which an impurity element imparting p-type conductivity is introduced. The n-channel TFT 503 includes a channel formation region 443, a low concentration impurity region 442 (GOLD region) overlapping with the first conductive layer 430a which forms part of the gate electrode, and a high concentration impurity which functions as a source region or a drain region. The region 456 includes an impurity region 455 into which an impurity element imparting n-type conductivity and an impurity element imparting p-type conductivity are introduced.
[0106]
The pixel TFT 504 in the pixel portion includes a channel formation region 446, a low concentration impurity region 445 (LDD region) formed outside the gate electrode, and a high concentration impurity region 458 functioning as a source region or a drain region. In addition, an impurity element imparting n-type conductivity and an impurity element imparting p-type conductivity are added to the semiconductor layer functioning as one electrode of the storage capacitor 505. The storage capacitor 505 is formed of an electrode (stack of 432a and 432b) and a semiconductor layer using the insulating film 416 as a dielectric.
[0107]
In the pixel structure of this embodiment, without using a black matrix, the end portions of the pixel electrodes are formed so as to overlap the source wiring so that the gaps between the pixel electrodes are shielded from light.
[0108]
FIG. 12 shows a top view of a pixel portion of an active matrix substrate manufactured in this embodiment. In addition, the same code | symbol is used for the part corresponding to FIGS. 9-12. A chain line AA ′ in FIG. 11 corresponds to a cross-sectional view taken along the chain line AA ′ in FIG. Further, a chain line BB ′ in FIG. 11 corresponds to a cross-sectional view taken along the chain line BB ′ in FIG.
[0109]
[Example 6]
In this embodiment, a process for manufacturing a reflective liquid crystal display device from the active matrix substrate manufactured in Embodiment 5 will be described below. FIG. 13 is used for the description.
[0110]
First, after obtaining the active matrix substrate in the state of FIG. 11 according to Example 5, an alignment film 567 is formed on at least the pixel electrode 470 on the active matrix substrate of FIG. In this embodiment, before forming the alignment film 567, an organic resin film such as an acrylic resin film is patterned to form columnar spacers 572 for maintaining a substrate interval at a desired position. Further, instead of the columnar spacers, spherical spacers may be scattered over the entire surface of the substrate.
[0111]
Next, a counter substrate 569 is prepared. Next, colored layers 570 and 571 and a planarization film 573 are formed over the counter substrate 569. The red colored layer 570 and the blue colored layer 571 are overlapped to form a light shielding portion. Further, the light shielding portion may be formed by partially overlapping the red colored layer and the green colored layer.
[0112]
In this example, the substrate shown in Example 5 is used. Therefore, in FIG. 12, which shows a top view of the pixel portion of Example 5, at least the gap between the gate wiring 469 and the pixel electrode 470, the gap between the gate wiring 469 and the connection electrode 468, and the gap between the connection electrode 468 and the pixel electrode 470 are provided. It is necessary to shield the light. In this example, the respective colored layers were arranged so that the light-shielding portions formed by the lamination of the colored layers overlapped at the positions where light shielding should be performed, and the counter substrate was bonded.
[0113]
As described above, the number of steps can be reduced by shielding the gap between the pixels with the light shielding portion formed by the lamination of the colored layers without forming a light shielding layer such as a black mask.
[0114]
Next, a counter electrode 576 made of a transparent conductive film was formed over the planarization film 573 in at least the pixel portion, an alignment film 574 was formed over the entire surface of the counter substrate, and a rubbing process was performed.
[0115]
Then, the active matrix substrate on which the pixel portion and the driver circuit are formed and the counter substrate are attached to each other with a sealant 568. A filler is mixed in the sealing material 568, and two substrates are bonded to each other with a uniform interval by the filler and the columnar spacer. Thereafter, a liquid crystal material 575 is injected between both substrates and completely sealed with a sealant (not shown). A known liquid crystal material may be used for the liquid crystal material 575. In this way, the reflection type liquid crystal display device shown in FIG. 13 is completed. If necessary, the active matrix substrate or the counter substrate is divided into a desired shape. Further, a polarizing plate (not shown) was attached only to the counter substrate. And FPC was affixed using the well-known technique.
[0116]
The liquid crystal display device manufactured as described above has a TFT manufactured using a semiconductor film in which large-grain crystal grains are formed by irradiation with laser light having a periodic or uniform energy distribution. Therefore, the operation characteristics and reliability of the liquid crystal display device can be sufficient. And such a liquid crystal display device can be used as a display part of various electronic devices.
[0117]
Note that this embodiment can be freely combined with Embodiments 1 to 5.
[0118]
[Example 7]
In this example, an example of manufacturing a light-emitting device using the manufacturing method of a TFT when manufacturing an active matrix substrate shown in Example 5 will be described below. In this specification, the light emitting device is a general term for a display panel in which a light emitting element formed on a substrate is sealed between the substrate and a cover material, and a display module in which a TFT or the like is mounted on the display panel. It is. Note that the light-emitting element includes a layer (light-emitting body) containing a compound capable of obtaining luminescence (Electro Luminescence) generated by applying an electric field, an anode layer, and a cathode layer. In addition, the luminescence in the compound includes light emission (fluorescence) when returning from the singlet excited state to the ground state and light emission (phosphorescence) when returning from the triplet excited state to the ground state, either of these, Includes both emissions.
[0119]
Note that in this specification, all layers formed between an anode and a cathode in a light-emitting element are defined as light emitters. Specifically, the light emitter includes a light emitting layer, a hole injection layer, an electron injection layer, a hole transport layer, an electron transport layer, and the like. Basically, a light-emitting element has a structure in which an anode layer, a light emitter, and a cathode layer are sequentially laminated. In addition to this structure, an anode layer, a hole injection layer, a light-emitting layer, a cathode layer, and an anode layer , A hole injection layer, a light emitting layer, an electron transport layer, a cathode layer and the like may be laminated in this order.
[0120]
FIG. 14 is a cross-sectional view of the light emitting device of this example. In FIG. 14, a switching TFT 603 provided over a substrate 700 is formed using the n-channel TFT 503 in FIG. Therefore, the description of the n-channel TFT 503 may be referred to for the description of the structure.
[0121]
Note that although a double gate structure in which two channel formation regions are formed is used in this embodiment, a single gate structure in which one channel formation region is formed or a triple gate structure in which three channel formation regions are formed may be used.
[0122]
A driver circuit provided over the substrate 700 is formed using the CMOS circuit of FIG. Therefore, for the description of the structure, the description of the n-channel TFT 501 and the p-channel TFT 502 may be referred to. In this embodiment, a single gate structure is used, but a double gate structure or a triple gate structure may be used.
[0123]
Further, the wirings 701 and 703 function as source wirings of the CMOS circuit, and the wiring 702 functions as a drain wiring. The wiring 704 functions as a wiring that electrically connects the source wiring and the source region of the switching TFT, and the wiring 705 functions as a wiring that electrically connects the drain wiring and the drain region of the switching TFT.
[0124]
Note that the current control TFT 604 is formed using the p-channel TFT 502 of FIG. Accordingly, the description of the p-channel TFT 502 may be referred to for the description of the structure. In this embodiment, a single gate structure is used, but a double gate structure or a triple gate structure may be used.
[0125]
A wiring 706 is a source wiring (corresponding to a current supply line) of the current control TFT, and 707 is an electrode that is electrically connected to the pixel electrode 711 by being overlaid on the pixel electrode 711 of the current control TFT.
[0126]
Reference numeral 711 denotes a pixel electrode (anode of the light emitting element) made of a transparent conductive film. As the transparent conductive film, a compound of indium oxide and tin oxide, a compound of indium oxide and zinc oxide, zinc oxide, tin oxide, or indium oxide can be used. Moreover, you may use what added the gallium to the said transparent conductive film. The pixel electrode 711 is formed on the flat interlayer insulating film 710 before forming the wiring. In this embodiment, it is very important to flatten the step due to the TFT using the flattening film 710 made of resin. Since a light emitter to be formed later is very thin, a light emission failure may occur due to the presence of a step. Therefore, it is desirable to planarize the pixel electrode before forming it so that the light emitter can be formed as flat as possible.
[0127]
After the wirings 701 to 707 are formed, a bank 712 is formed as shown in FIG.
The bank 712 may be formed by patterning an insulating film or organic resin film containing silicon of 100 to 400 nm.
[0128]
Note that since the bank 712 is an insulating film, attention must be paid to electrostatic breakdown of elements during film formation. In this embodiment, carbon particles or metal particles are added to the insulating film that is the material of the bank 712 to reduce the resistivity and suppress the generation of static electricity. At this time, the resistivity is 1 × 10 ⁶ ~ 1x10 ¹² Ωm (preferably 1 × 10 ⁸ ~ 1x10 ^Ten The added amount of carbon particles and metal particles may be adjusted so that the resistance becomes Ωm).
[0129]
A light emitter 713 is formed on the pixel electrode 711. Although only one pixel is shown in FIG. 14, in this embodiment, light emitting layers corresponding to each color of R (red), G (green), and B (blue) are separately formed. In this embodiment, a low molecular weight organic light emitting material is formed by a vapor deposition method. Specifically, a copper phthalocyanine (CuPc) film having a thickness of 20 nm is provided as a hole injection layer, and a tris-8-quinolinolato aluminum complex (Alq) having a thickness of 70 nm is formed thereon as a light emitter. _Three ) A laminated structure provided with a film. Alq _Three The emission color can be controlled by adding a fluorescent dye such as quinacridone, perylene, or DCM1.
[0130]
However, the above example is an example of an organic light emitting material that can be used as a light emitter, and is not necessarily limited to this. A light-emitting body (a layer for performing light emission and carrier movement therefor) may be formed by freely combining a light-emitting layer, a charge transport layer, or a charge injection layer. For example, in this embodiment, an example in which a low molecular weight organic light emitting material is used as the light emitting layer is shown, but a medium molecular weight organic light emitting material or a high molecular weight organic light emitting material may be used. Note that in this specification, an organic light-emitting material that does not have sublimation and has 20 or less molecules or a chain molecule length of 10 μm or less is referred to as a medium molecular organic light-emitting material. As an example of using a polymer organic light emitting material, a 20 nm polythiophene (PEDOT) film is provided by a spin coating method as a hole injection layer, and a paraphenylene vinylene (PPV) film of about 100 nm is provided thereon as a light emitting layer. Alternatively, a laminated structure may be used. If a PPV π-conjugated polymer is used, the emission wavelength can be selected from red to blue. It is also possible to use an inorganic material such as silicon carbide for the charge transport layer or the charge injection layer. Known materials can be used for these organic light emitting materials and inorganic materials.
[0131]
Next, a cathode 714 made of a conductive film is provided on the light emitting layer 713. In this embodiment, an alloy film of aluminum and lithium is used as the conductive film. Of course, a known MgAg film (magnesium and silver alloy film) may be used. As the cathode material, a conductive film made of an element belonging to Group 1 or Group 2 of the periodic table or a conductive film added with these elements may be used.
[0132]
When the cathode 714 is formed, the light emitting element 715 is completed. Note that the light-emitting element 715 here refers to a diode formed of a pixel electrode (anode) 711, a light-emitting layer 713, and a cathode 714.
[0133]
It is effective to provide a passivation film 716 so as to completely cover the light emitting element 715. As the passivation film 716, an insulating film including a carbon film, a silicon nitride film, or a silicon nitride oxide film is used, and the insulating film is used as a single layer or a combination thereof.
[0134]
At this time, it is preferable to use a film with good coverage as the passivation film, and it is effective to use a carbon film, particularly a DLC (diamond-like carbon) film. Since the DLC film can be formed in a temperature range from room temperature to 100 ° C., it can be easily formed over the light-emitting body 713 having low heat resistance. In addition, the DLC film has a high blocking effect against oxygen and can suppress oxidation of the light-emitting layer 713. Therefore, the problem that the light emitter 713 is oxidized during the subsequent sealing process can be prevented.
[0135]
Further, a sealing material 717 is provided over the passivation film 716 and a cover material 718 is attached thereto. As the sealing material 717, an ultraviolet curable resin may be used, and it is effective to provide a substance having a hygroscopic effect or a substance having an antioxidant effect inside. In this embodiment, the cover material 718 is formed by forming a carbon film (preferably a diamond-like carbon film) on both surfaces of a glass substrate, a quartz substrate, or a plastic substrate (including a plastic film).
[0136]
Thus, a light emitting device having a structure as shown in FIG. 14 is completed. Note that it is effective to continuously process the steps from the formation of the bank 712 to the formation of the passivation film 716 using a multi-chamber type (or in-line type) film formation apparatus without releasing to the atmosphere. . Further, it is possible to continuously process the process up to the step of bonding the cover material 718 without releasing to the atmosphere.
[0137]
Thus, n-channel TFTs 601 and 602, a switching TFT (n-channel TFT) 603 and a current control TFT (n-channel TFT) 604 are formed on the substrate 700.
[0138]
Furthermore, as described with reference to FIGS. 14A and 14B, an n-channel TFT which is resistant to deterioration due to the hot carrier effect can be formed by providing an impurity region overlapping with the gate electrode through an insulating film. Therefore, a highly reliable light emitting device can be realized.
[0139]
Further, in this embodiment, only the configuration of the pixel portion and the drive circuit is shown. However, according to the manufacturing process of this embodiment, other logic circuits such as a signal dividing circuit, a D / A converter, an operational amplifier, and a γ correction circuit are provided. Can be formed on the same insulator, and a memory and a microprocessor can also be formed.
[0140]
The light-emitting device manufactured as described above has a TFT manufactured using a semiconductor film on which large-sized crystal grains are formed by irradiation with laser light having a periodic or uniform energy distribution. The operational characteristics and reliability of the light emitting device can be sufficient. And such a light-emitting device can be used as a display part of various electronic devices.
[0141]
Note that this embodiment can be freely combined with any one of Embodiments 1 to 5.
[0142]
[Example 8]
By applying the present invention, various semiconductor devices (active matrix liquid crystal display device, active matrix light emitting device, active matrix EC display device) can be manufactured. That is, the present invention can be applied to various electronic devices in which these electro-optical devices are incorporated in a display unit.
[0143]
Such electronic devices include video cameras, digital cameras, projectors, head-mounted displays (goggles type displays), car navigation systems, car stereos, personal computers, personal digital assistants (mobile computers, mobile phones, electronic books, etc.), etc. Can be mentioned. Examples thereof are shown in FIGS. 15, 16 and 17.
[0144]
FIG. 15A shows a personal computer, which includes a main body 3001, an image input portion 3002, a display portion 3003, a keyboard 3004, and the like. The present invention can be applied to the display portion 3003.
[0145]
FIG. 15B illustrates a video camera, which includes a main body 3101, a display portion 3102, an audio input portion 3103, operation switches 3104, a battery 3105, an image receiving portion 3106, and the like. The present invention can be applied to the display portion 3102.
[0146]
FIG. 15C illustrates a mobile computer, which includes a main body 3201, a camera portion 3202, an image receiving portion 3203, operation switches 3204, a display portion 3205, and the like. The present invention can be applied to the display portion 3205.
[0147]
FIG. 15D illustrates a goggle-type display, which includes a main body 3301, a display portion 3302, an arm portion 3303, and the like. The present invention can be applied to the display portion 3302.
[0148]
FIG. 15E shows a player using 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, a speaker portion 3403, a recording medium 3404, an operation switch 3405, and the like. This player uses a DVD (Digital Versatile Disc), CD, or the like as a recording medium, and can perform music appreciation, movie appreciation, games, and the Internet.
The present invention can be applied to the display portion 3402.
[0149]
FIG. 15F illustrates a digital camera, which includes a main body 3501, a display portion 3502, an eyepiece portion 3503, an operation switch 3504, an image receiving portion (not shown), and the like. The present invention can be applied to the display portion 3502.
[0150]
FIG. 16A illustrates a front type projector, which includes a projection device 3601, a screen 3602, and the like. The present invention can be applied to a liquid crystal display device 3808 constituting a part of the projection device 3601 and other driving circuits.
[0151]
FIG. 16B shows a rear projector, which includes a main body 3701, a projection device 3702, a mirror 3703, a screen 3704, and the like. The present invention can be applied to the liquid crystal display device 3808 constituting a part of the projection device 3702 and other driving circuits.
[0152]
Note that FIG. 16C is a diagram illustrating an example of the structure of the projection devices 3601 and 3702 in FIGS. 16A and 16B. The projection devices 3601 and 3702 include a light source optical system 3801, mirrors 3802 and 3804 to 3806, a dichroic mirror 3803, a prism 3807, a liquid crystal display device 3808, a phase difference plate 3809, and a projection optical system 3810. The projection optical system 3810 is composed of an optical system including a projection lens. Although the present embodiment shows a three-plate type example, it is not particularly limited, 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 polarization function, a film for adjusting a phase difference, an IR film, or the like in the optical path indicated by an arrow in FIG. Good.
[0153]
FIG. 16D illustrates an example of the structure of the light source optical system 3801 in FIG. In this embodiment, the light source optical system 3801 includes a reflector 3811, a light source 3812, lens arrays 3813 and 3814, a polarization conversion element 3815, and a condenser lens 3816. Note that the light source optical system illustrated in FIG. 16D is an example and is not particularly limited. For example, the practitioner may appropriately provide an optical system such as an optical lens, a film having a polarization function, a film for adjusting a phase difference, or an IR film in the light source optical system.
[0154]
However, the projector shown in FIG. 16 shows a case where a transmissive electro-optical device is used, and an application example in a reflective electro-optical device and a light-emitting device is not shown.
[0155]
FIG. 17A illustrates a mobile phone, which includes a main body 3901, an audio output portion 3902, an audio input portion 3903, a display portion 3904, operation switches 3905, an antenna 3906, and the like. The present invention can be applied to the display portion 3904.
[0156]
FIG. 17B illustrates a portable book (electronic book), which includes a main body 4001, display portions 4002 and 4003, a storage medium 4004, operation switches 4005, an antenna 4006, and the like. The present invention can be applied to the display portions 4002 and 4003.
[0157]
FIG. 17C illustrates a display, which includes a main body 4101, a support base 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 displays having a diagonal of 10 inches or more (particularly 30 inches or more).
[0158]
As described above, the applicable range of the present invention is so wide that the present invention can be applied to electronic devices in various fields. Moreover, the electronic device of a present Example is realizable even if it uses the structure which consists of a combination of Example 1-6 or 7th.
[0159]
【The invention's effect】
By adopting the configuration of the present invention, the following basic significance can be obtained.
(A) Laser light having high coherence energy can be formed into laser light having an energy density suitable for a semiconductor film.
(B) It can sufficiently cope with laser light having high coherence.
(C) By moving the substrate, it is possible to irradiate a large area substrate with laser light.
(D) After satisfying the above advantages, the laser irradiation method and the laser irradiation apparatus for performing the laser irradiation can efficiently perform the laser beam irradiation. Further, in a semiconductor device typified by an active matrix liquid crystal display device, improvement in operating characteristics and reliability of the semiconductor device can be realized. Furthermore, the manufacturing cost of the semiconductor device can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of the configuration of a laser irradiation apparatus of the present invention.
FIG. 2 is a diagram showing an example of interference of laser light on an irradiation surface of the present invention.
FIG. 3 is a diagram showing an example of a method for moving a substrate on an irradiation surface according to the present invention.
FIG. 4 is a diagram showing an example of the configuration of a laser irradiation apparatus of the present invention.
FIG. 5 is a diagram showing an example of the configuration of a laser irradiation apparatus of the present invention.
FIG. 6 is a diagram showing an example of laser beam interference on the irradiation surface of the present invention.
FIG. 7 is a diagram showing an example of interference of laser light on the irradiation surface of the present invention.
FIG. 8 is a diagram showing an example of interference of laser light on the irradiation surface of the present invention.
FIG. 9 is a cross-sectional view illustrating a manufacturing process of a pixel TFT and a driver circuit TFT;
FIG. 10 is a cross-sectional view illustrating a manufacturing process of a pixel TFT and a TFT of a driver circuit.
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 top view illustrating a structure of a pixel TFT.
FIG. 13 is a cross-sectional view of an active matrix liquid crystal display device.
FIG 14 is a cross-sectional structure diagram of a driver circuit and a pixel portion of a light-emitting device.
FIG 15 illustrates an example of a semiconductor device.
FIG 16 illustrates an example of a semiconductor device.
FIG 17 illustrates an example of a semiconductor device.

Claims (19)

Laser,
A first optical system for dividing a laser beam emitted from the laser into a plurality of parts;
A second optical system that combines the laser beams divided by the first optical system to form a laser beam having a periodic energy density distribution on the irradiated surface;
The first optical system is a cylindrical lens array and a cylindrical lens, or a prism,
The second optical system includes a second lens in the center, and a first lens and a third lens on both sides of the second lens,
The first optical system is provided between the laser and the second optical system,
The second optical system is provided such that a distance between the first lens and the second lens is different from a distance between the second lens and the third lens, and the first optical system is different from the first lens and the second lens . Each of the laser beams divided by the optical system is provided so as to irradiate any one of the first lens, the different part of the second lens, and the third lens . The laser irradiation apparatus characterized by the above-mentioned. In a laser irradiation apparatus that irradiates an irradiated surface with a laser beam emitted from a laser,
A first optical system and a second optical system;
The first optical system is a cylindrical lens array and a cylindrical lens, or a prism,
The second optical system includes a second lens in the center, and a first lens and a third lens on both sides of the second lens,
The second optical system is provided such that a distance between the first lens and the second lens is different from a distance between the second lens and the third lens . Each of the laser beams divided by the optical system is irradiated to any one of the first lens, the different part of the second lens, and the third lens , and the first optical system. Is provided so that the laser beam divided by is superimposed on the irradiated surface,
The laser irradiation apparatus, wherein the laser beam emitted from the laser and having passed through the first optical system and the second optical system has a periodic energy density distribution on the irradiated surface. 3. The laser irradiation apparatus according to claim 1 , wherein the laser beam applied to the irradiated surface is formed by interfering with the plurality of divided laser beams. In any one of claims 1 to 3, wherein the first optical system and the second optical system to irradiate a laser beam emitted from the laser at an angle relative to the surface to be illuminated The laser irradiation apparatus characterized by being installed in. In any one of claims 1 to 4, wherein the first optical system and the second optical system, the 3 to 32 ° a laser beam emitted from the laser to the surface to be illuminated A laser irradiation apparatus which is installed so as to irradiate at an incident angle. In any one of claims 1 to 5, wherein the laser is a laser irradiation apparatus which is a solid-state laser of continuous oscillation or pulse oscillation. In the claims 1 to any one of claims 6, wherein the laser, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, a glass laser, ruby laser, alexandrite laser or Ti: that the sapphire laser A featured laser irradiation device. The optical path of a laser beam emitted from the same laser is divided into a plurality by a cylindrical lens array and a cylindrical lens, or a prism,
Each of the plurality of divided laser beams is arranged on the second lens arranged in the center or on both sides of the second lens, and the first lens or the first lens having different distances to the second lens, respectively. After irradiating the third lens , the irradiated laser beam is irradiated obliquely to the irradiated surface by the first lens, the second lens, and the third lens. A laser irradiation method comprising combining a laser beam so as to have a periodic energy density distribution on a surface. The optical path of a laser beam emitted from the same laser is divided into a plurality by a cylindrical lens array and a cylindrical lens, or a prism,
Each of the plurality of divided laser beams is arranged on the second lens arranged in the center or on both sides of the second lens, and the first lens or the first lens having different distances to the second lens, respectively. After irradiating the third lens , the irradiated laser beam is irradiated obliquely to the irradiated surface by the first lens, the second lens, and the third lens. A laser beam is synthesized so as to have a periodic energy density distribution in a first direction of the surface, and the laser beam is irradiated in a first direction of the irradiated surface and a second direction perpendicular to the first direction. A laser irradiation method characterized by relatively moving. The optical path of laser beams emitted from the same laser is divided into a plurality of parts by a cylindrical lens array and a cylindrical lens or a prism to form a plurality of laser beams having equal energy density,
Each of the plurality of laser beams having the same energy density is disposed on the second lens disposed in the center or on both sides of the second lens, and the first lens having a different distance to the second lens or After irradiating the third lens , the energy of the laser beam that passes through the first lens and the third lens and the laser beam that passes through the second lens in the plurality of laser beams having the same energy density A laser irradiation method characterized by synthesizing a laser beam so as to have a uniform energy density distribution on the irradiated surface by irradiating the irradiated surface obliquely with respect to the irradiated surface while shifting the density distribution by a half cycle. The optical path of laser beams emitted from the same laser is divided into a plurality of parts by a cylindrical lens array and a cylindrical lens or a prism to form a plurality of laser beams having equal energy density,
Each of the plurality of laser beams having the same energy density is disposed on the second lens disposed in the center or on both sides of the second lens, and the first lens having a different distance to the second lens or after irradiating the third lens, and the laser beam passing through said first lens and said third lens in a plurality of laser beams is equal of the double energy density, the laser beam passing through the second lens The energy density distribution is shifted by a half period and obliquely irradiated to the irradiated surface, and a laser beam is synthesized so as to have a uniform energy density distribution in the first direction of the irradiated surface, and the irradiated surface A laser irradiation method characterized by relatively moving the laser beam in a first direction and a second direction perpendicular to the first direction. In any one of claims 8 to 11, wherein the laser beam to be irradiated to the irradiated surface, the laser irradiation method, which comprises forming by interference split laser beams to said plurality. In any one of claims 8 to 12, the angle of the laser beam to be irradiated to the irradiated surface, the laser irradiation method which is a 3 to 32 degrees. In any one of claims 8 to 13, wherein the laser is a laser irradiation method which is a solid-state laser of continuous oscillation or pulse oscillation. In any one of claims 8 to 14, wherein the laser, YAG laser, YVO ₄ laser, YLF laser, YAlO ₃ laser, a glass laser, ruby laser, alexandrite laser or Ti: that the sapphire laser The laser irradiation method characterized. Using a laser irradiation apparatus according to any one of claims 1 to 7, a method for manufacturing a semiconductor device, characterized in that to improve the crystallinity of the semiconductor film is crystallized, or a semiconductor film. Using a laser irradiation apparatus according to any one of claims 1 to 7, a method for manufacturing a semiconductor device, characterized in that to activate the impurity element. Using the laser irradiation method according to any one of claims 8 to 15, a method for manufacturing a semiconductor device, characterized in that to improve the crystallinity of the semiconductor film is crystallized, or a semiconductor film. Using the laser irradiation method according to any one of claims 8 to 15, a method for manufacturing a semiconductor device, characterized in that to activate the impurity element.

Images