JP2004072033A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when linear laser beams are overlapped and applied to a semiconductor film, fringes are generated on a semiconductor film and have an adverse effect on the characteristics of the semiconductor film. <P>SOLUTION: In an atmosphere containing oxygen, a laser beam of a first requirement is applied to an amorphous semiconductor film, whereby the film is crystallized. Thereafter an oxide film formed in a laser beam applying step of the first requirement is removed. In an inert gas or in a vacuum atmosphere, then, a planar laser beam is applied to the film using a laser beam applying device having an output energy of 15J or more under a second requirement that a laser beam applier have an energy distribution of ±3% or less and the laser beam have an application area of 30cm<SP>2</SP>or more, thus improving a flatness on the crystalline semiconductor film. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a favorable crystalline semiconductor film by irradiating a laser beam to crystallize an amorphous semiconductor film. Further, the present invention relates to a method for manufacturing a thin film transistor (TFT) having high operation performance and high reliability using such a favorable crystalline semiconductor film.
[0002]
[Prior art]
TFTs are frequently used as switching elements in a pixel portion of an active matrix substrate and in a driving circuit for driving the switching elements. In recent years, a high-speed operation capable of sufficiently writing data to a high-resolution display device in which the amount of information has been increased and the selection time has been shortened has been required. In particular, a crystalline semiconductor film having high field-effect mobility has been used. TFTs have been actively developed.
[0003]
As a method of forming a crystalline semiconductor film, a method of irradiating an amorphous silicon film formed on a glass substrate with a laser beam, particularly, a method of irradiating a laser beam of an excimer laser (hereinafter, referred to as an excimer laser beam). A generalization method is generally used. This is because the excimer laser beam has a large absorption coefficient of silicon, and further heats only the amorphous silicon film to crystallize the silicon film and does not thermally damage the glass substrate.
[0004]
Conventionally, when a semiconductor film is irradiated with laser light to crystallize or improve crystallinity, the semiconductor film is instantaneously melted from the surface, and then the semiconductor film melted due to heat conduction to the substrate is It cools and solidifies from the substrate side. During this solidification process, the semiconductor film is recrystallized to form a semiconductor film having a crystal structure with a large grain size, but once melted, volume expansion occurs and irregularities called ridges are formed on the semiconductor surface. Since the surface with a ridge becomes an interface with the gate insulating film, the device characteristics were greatly affected.
[0005]
In order to manufacture a semiconductor film having higher electric characteristics at a lower cost, a laser annealing technique is indispensable. However, in the conventional crystallization using a linear laser beam, uniform energy was not applied to the entire film, and a wavy trace of the laser beam irradiation remained in addition to the ridge.
[0006]
[Problems to be solved by the invention]
At present, a problem to be noticed is how to obtain a good crystalline semiconductor film by laser light and how to increase the crystal grain size. As a matter of course, as one crystal grain (also referred to as a grain) becomes larger, the number of crystal grain boundaries that traverse the TFT, particularly, the channel formation region decreases. Therefore, it is possible to improve variations in typical electric characteristics of the TFT such as the field-effect mobility and the threshold voltage.
[0007]
When linearly focused laser light is used for the crystallization process of a semiconductor film, it is difficult to keep the energy distribution of the linearly focused laser light uniform on the laser light irradiation surface. (The rate at which the laser beams are overlapped is referred to as an overlap ratio). More specifically, the semiconductor film is irradiated by overlapping while maintaining a high overlap ratio (90 to 98%). Although the problem of the uniformity of the energy distribution has been solved, fringes may be generated in the crystalline semiconductor film obtained by the over-irradiation. The stripes become irregularities (ridges) on the surface of the semiconductor film and have a great influence on the device characteristics.
[0008]
In addition, when a gas laser such as an excimer laser is used to condense laser light in a linear manner for processing, it is necessary to perform gas exchange due to deterioration of the gas in the laser oscillation unit. When the treatment was performed, there was a problem in the stability of the energy distribution. When the laser beam irradiation treatment is performed in a state where the energy is not stable, there is a problem that stripes are generated in the semiconductor film.
[0009]
The stripes generated in the semiconductor film adversely affect the crystal state. If the semiconductor film having such stripes is used as it is as the semiconductor layer of the TFT, the characteristics of the TFT are varied, and the reliability of the TFT becomes an issue. Was.
[0010]
In addition, when the overlap ratio is high during the laser light irradiation processing, the time required for the laser light irradiation processing on one substrate is prolonged, and the productivity (throughput) is deteriorated. .
[0011]
[Means for Solving the Problems]
According to the present invention, when crystallizing an amorphous semiconductor film, the semiconductor film is irradiated with a laser beam under a first condition (energy density of 400 to 600 mJ / cm) in an atmosphere containing oxygen. ² ) To remove the oxide film formed by the irradiation of the laser beam under the first condition, and thereafter, in an atmosphere containing no oxygen (typically, an inert gas atmosphere or a vacuum atmosphere). The area of the laser beam irradiation part is 30 cm ² As described above, the energy density is more than 30 to 300 mJ / cm than the laser light under the first condition. ² Irradiation with a laser beam under a high second condition can improve the flatness of the semiconductor film, can prevent the semiconductor film from being fringed, and can planarize the semiconductor film, and can further reduce the off-current value. it can. In particular, it is necessary to irradiate the laser beam under the second condition while using a laser beam irradiation device having an output energy of 15 J or more and maintaining a high overlap ratio because the energy distribution in the laser beam irradiation section is ± 3% or less. For example, the semiconductor film is flattened by irradiating a planar laser beam, thereby preventing generation of stripes and forming a favorable crystalline semiconductor film.
[0012]
Here, the laser light under the second condition has an energy density of 30 to 300 mJ / cm more than the laser light under the first condition. ² Although set to be high, this value is a preferable value and is not limited to this value.
[0013]
The laser light under the second condition has an area of the laser light irradiation part of 30 cm. ² As described above, this value is a preferable value and is not limited to this value. It is sufficient that the irradiation area is wider than the linear laser light and the energy distribution in the irradiation part is smaller. For example, a planar laser light may be used.
Here, the planar laser light refers to a laser light irradiated portion having an aspect ratio smaller than that of a linear laser light and having an area larger than that of the linear laser light.
[0014]
In addition, since the laser beam under the second condition has an energy distribution of ± 3% or less in the laser beam irradiating section, the laser beam under the laser beam is repeatedly shot to maintain a uniform energy distribution in the irradiating section (irradiation while maintaining a high overlap ratio). Therefore, the time required for the step of irradiating one substrate with laser light can be shortened (throughput can be improved).
[0015]
For example, the area is 30cm ² When the present invention is used in a manufacturing process of the following small display device (about 2 inches: a display device used for a display portion of a mobile phone or a portable information device, a display device used for a projector, and the like), irradiation with laser light under the first condition is performed. After removing the oxide film on the surface of the crystalline semiconductor film obtained by using the laser light irradiation apparatus having the output energy of 15 J or more, the energy distribution in the laser light irradiation part is ± 3%, Light irradiation area is 30cm ² By irradiating the laser light under the above second condition, a display device can be formed within one laser light irradiation area. A display device can be realized using a flattened favorable semiconductor film.
[0016]
In addition, according to the present invention, both the laser light under the first condition and the laser light under the second condition use a laser light irradiation device having an output energy of 15 J or more, and the energy distribution in the laser light irradiation portion is ± 3%, Laser irradiation area is 30cm ² The above laser may be used. Thus, it is not necessary to perform the irradiation process while maintaining a high overlap ratio, so that the throughput can be improved.
[0017]
Further, the present invention does not depend on the type of laser, and if a large output is obtained, generally known excimer laser (typically, KrF laser or XeCl laser), solid-state laser (typically, Nd: YAG laser) Alternatively, any of a laser, a gas laser (typically, an argon laser or a helium-neon laser), a metal vapor laser (typically, a copper vapor laser or a helium-cadmium laser), and a semiconductor laser can be used.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
Referring to FIG. 1, the amorphous semiconductor film is irradiated with a first laser beam to be crystallized, and then the oxide film formed on the surface of the semiconductor film is removed. ² A method for irradiating a planar laser beam having the above-described area to flatten a projection on the surface of a crystalline semiconductor film will be described.
[0019]
First, a base insulating film 11 and an amorphous semiconductor film 12 are formed on a glass substrate 10. As the semiconductor film, silicon or Si _x Ge _1-x (0 <x <1) can be used. In this embodiment, a silicon film is used. Next, as a pretreatment for laser annealing, the amorphous semiconductor film is washed with ozone water to form an oxide film (not shown) on the surface of the amorphous semiconductor film.
[0020]
Next, laser light irradiation under the first condition is performed. As the laser under the first condition, a gas laser such as an excimer laser or a solid-state laser such as an Nd: YAG laser or a YLF laser may be used. The energy density is 400 to 600 mJ / cm. ² , And the pulse width was 20 to 30 ns. The amorphous semiconductor film is crystallized by irradiating the laser beam under the first condition as described above to form the first crystalline semiconductor film 13. When laser light irradiation is performed in a state where an oxide film is present on the amorphous semiconductor film 12 or in a state where it is easily oxidized, a projection is formed on the surface when crystallized. In addition, it is known that the properties of the obtained crystalline semiconductor film are improved by performing a laser beam irradiation treatment such that a convex portion is formed on the surface of the crystalline semiconductor film. Therefore, the surface of the first crystalline semiconductor film 13 after the laser light irradiation treatment under the first condition has a convex portion. Note that the oxide film still remains on the first crystalline semiconductor film 13.
[0021]
After irradiating the laser light under the first condition, the oxide film 14 formed on the surface of the first crystalline semiconductor film 13 is removed.
[0022]
Next, using a laser beam irradiation apparatus in which a plurality of lasers of high output (15 J or more) are connected as the laser beam under the second condition, the energy distribution of the laser beam irradiation section is ± 3% or less, and the energy density is 430 to 700 mJ / cm ² , (Beam irradiation area is 30cm ² The above-mentioned planar laser light is applied. The energy density is the same as that of the laser beam under the first condition, or 30 to 300 mJ / cm. ² About higher. Since the in-plane energy distribution of the beam is ± 3% or less, the overlap ratio can be 50% or less.
[0023]
The second crystalline semiconductor film 15 is formed by irradiating a laser beam under the second condition to flatten the surface of the first crystalline semiconductor film 13. In the laser light irradiation under the second condition, the first crystalline semiconductor film 13 and the second crystalline semiconductor film 15 show no change in characteristics except for the surface shape.
[0024]
Alternatively, the irradiation treatment may be performed at a predetermined energy density by using a planar laser beam as the laser beam under the first condition, similarly to the laser beam under the second condition. By doing so, the time required for laser light irradiation under the first condition can be reduced.
[0025]
By irradiating the first crystalline semiconductor film 13 having the projections with laser light (plane laser light) under the second condition, the surface of the crystalline semiconductor film can be planarized. . By using planar laser light, crystallization unevenness (horizontal stripes) can be suppressed in the crystalline semiconductor film, and it is not necessary to overlap and irradiate like a linear laser light. Throughput is improved.
[0026]
(Embodiment 2)
First, a base insulating film 21 is formed on a glass substrate 20, and an amorphous silicon film 22 is formed on the base insulating film 21. Subsequently, an amorphous silicon film is formed as the amorphous semiconductor film 22 on the base insulating film 21. The amorphous silicon film 22 is formed with a thickness of 10 to 100 nm by a plasma CVD method, a low pressure CVD method, or a sputtering method.
[0027]
Subsequently, a catalytic element for promoting crystallization is added to the amorphous silicon film 22. As the catalytic element, one or more selected from Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au may be used. First, the surface of the amorphous silicon film 22 is coated with a nickel acetate solution containing 1 to 100 ppm by weight of a catalytic element (here, nickel) having a catalytic action to promote crystallization by a spinner to form a nickel-containing layer. 23 are formed (FIG. 2A). As a method other than the method of forming the nickel-containing layer 23 by coating, a method of forming an extremely thin film by a sputtering method, an evaporation method, or a plasma treatment may be used. Here, an example in which the coating is performed on the entire surface is described, but a nickel-containing layer may be selectively formed by forming a mask.
[0028]
Next, heat treatment is performed to crystallize the amorphous silicon film 22. In this case, in crystallization, silicide is formed in a portion of the semiconductor film in contact with a catalyst element that promotes crystallization of the semiconductor, and crystallization proceeds using the silicide as a nucleus. Thus, the first crystalline semiconductor film 24 shown in FIG. 2B is formed. Note that the concentration of oxygen contained in the first crystalline semiconductor film 24 is 5 × 10 ¹⁸ / Cm ³ It is desirable to make the following. Here, after the heat treatment for dehydrogenation (450 ° C., 1 hour), the heat treatment for crystallization (550 to 650 ° C. for 4 to 24 hours) is performed. Crystallization can also be performed by irradiation with strong light.
[0029]
Next, in order to increase the crystallization rate (the ratio of the crystal component in the total volume of the film) and repair defects remaining in the crystal grains, the first crystalline semiconductor film 24 is irradiated with laser light (under the first condition). (Laser light) in air or oxygen atmosphere. Irregularities are formed and a thin oxide film 26 is formed on the surface of the second crystalline semiconductor film 25 obtained by irradiating the laser light under the first condition (FIG. 2C). As the laser light under the first condition, an excimer laser light having a wavelength of 400 nm or less, or a second or third harmonic of a YAG laser is used. Further, light emitted from an ultraviolet lamp may be used instead of the excimer laser light.
[0030]
In the second crystalline semiconductor film 25 thus obtained, the catalytic element (here, nickel) remains. Although it is not uniformly distributed in the film, the average concentration is 1 × 10 ¹⁹ / Cm ³ At a concentration exceeding. Of course, various semiconductor elements including TFTs can be formed in such a state, but the elements are removed by a method described below.
[0031]
First, an oxide film (called a chemical oxide) is formed on the surface of the second crystalline semiconductor film 25 with an ozone-containing aqueous solution (typically, ozone water) to form a barrier layer 27 made of an oxide film having a total thickness of 1 to 10 nm. A semiconductor film (also referred to as a gettering region) 28 containing a rare gas element is formed over the barrier layer 27 (FIG. 2D). Note that here, the oxide film 25 formed when the first crystalline semiconductor film 24 is irradiated with laser light is also regarded as a part of the barrier layer. The barrier layer 27 functions as an etching stopper when selectively removing only the semiconductor film (gettering region) 28 in a later step. Alternatively, a chemical oxide can be similarly formed by treating with an aqueous solution obtained by mixing sulfuric acid, hydrochloric acid, nitric acid or the like with a hydrogen peroxide solution instead of the ozone-containing aqueous solution. As another method for forming the barrier layer 27, ozone may be generated by irradiation with ultraviolet light in an oxygen atmosphere to oxidize the surface of the semiconductor film having the crystal structure. As another method of forming the barrier layer 27, an oxide film of about 1 to 10 nm may be deposited as a barrier layer by a plasma CVD method, a sputtering method, an evaporation method, or the like. As another method of forming the barrier layer 27, a thin oxide film may be formed by heating to about 200 to 350 ° C. using a clean oven. Note that the barrier layer 27 is not particularly limited as long as the barrier layer 27 is formed by any one of the above methods or a combination of the above methods. It is necessary to have a film quality or film thickness that can move to the second semiconductor film.
[0032]
Next, a semiconductor film 28 containing a rare gas element is formed by a sputtering method to form a gettering site (FIG. 2D). Note that it is preferable to appropriately adjust sputtering conditions so that a rare gas element is not added to the second crystalline semiconductor film. As the rare gas element, one or more kinds selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) are used. Among them, argon (Ar), which is an inexpensive gas, is preferable. Here, the gettering region 28 is formed using a target made of silicon in an atmosphere containing a rare gas element. In the case where the gettering region is formed using a target containing phosphorus which is an impurity element of one conductivity type, gettering can be performed using Coulomb force of phosphorus in addition to gettering with a rare gas element.
[0033]
Further, at the time of gettering, since nickel tends to move to a region having a high oxygen concentration, the oxygen concentration contained in the gettering region 28 is higher than the oxygen concentration contained in the second crystalline semiconductor film 25. , For example, 5 × 10 ¹⁸ / Cm ³ It is desirable to make the above.
[0034]
Next, heat treatment is performed to move the catalyst element (nickel) remaining in the second crystalline semiconductor film 25 to the gettering region 28, and perform gettering for reducing or removing the concentration (FIG. 2D). ). As the heat treatment for gettering, heat treatment or irradiation with strong light may be performed. Here, all of the nickel is moved to the gettering region 28 so as not to segregate in the second crystalline semiconductor film 25, and nickel contained in the second crystalline semiconductor film 25 hardly exists. Is 1 × 10 ¹⁸ / Cm ³ Hereinafter, preferably 1 × 10 ¹⁷ / Cm ³ Getter enough so that:
[0035]
Note that in this specification, gettering means that a catalyst element in a region to be gettered (here, a first semiconductor film) is released by thermal energy and moves to a gettering site by diffusion. Therefore, gettering depends on the processing temperature, and the higher the temperature, the faster the gettering proceeds.
[0036]
In the case of performing heat treatment, heat treatment may be performed in a nitrogen atmosphere at 450 to 800 ° C. for 1 to 24 hours, for example, at 550 ° C. for 14 hours. Further, strong light irradiation may be performed in addition to the heat treatment.
[0037]
Next, after only the gettering region 28 is selectively removed by etching using the barrier layer 27 as an etching stopper, the barrier layer 27 made of an oxide film is removed.
[0038]
Subsequently, the second crystalline semiconductor film is irradiated with laser light under the second condition by using a laser light irradiation device having an output energy of 15 J or more, the energy distribution of the laser light irradiation portion is ± 3% or less, and the energy density is Is 430 to 700 mJ / cm ² , (Beam irradiation area is 30cm ² The above-mentioned planar laser light is applied. Since the in-plane energy distribution of the beam is ± 3% or less, the overlap ratio can be 50% or less. By the laser light irradiation under the second condition, the surface of the second crystalline semiconductor film 29 to which the catalyst element is gettered is planarized, and the third crystalline semiconductor film 30 is formed.
[0039]
The planar laser light used as the laser light of the second condition may be formed by connecting a plurality of high-output excimer lasers of 15 J or more, for example, or by irradiating the planar laser light. (For example, an excimer laser having a maximum energy of 15 J / shot and a 27 × 67 mm plane beam) may be used. FIG. 9 shows a schematic view of a laser beam irradiation apparatus in the case of connecting a plurality of excimer lasers having a high output of 15 J or more. It should be noted that the present invention does not depend on the type of laser, and if a large output is obtained, generally known excimer laser (typically, KrF laser or XeCl laser), solid-state laser (typically, Nd: YAG laser) Alternatively, any of a gas laser (typically, an argon laser or a helium-neon laser), a metal vapor laser (typically, a copper vapor laser or a helium-cadmium laser), or a semiconductor laser can be used.
[0040]
The laser light under the second condition is the same as the energy density of the laser light under the first condition, or 30 to 300 mJ / cm. ² To be high. Although the energy density differs between the laser light under the first condition and the laser light under the second condition, the crystallinity of the semiconductor (silicon) film hardly changes before and after the laser light irradiation step under the second condition. Further, no change was observed in the crystal state such as the particle size, and it is considered that only the planarization was performed.
[0041]
Note that gettering treatment of a catalyst element added to the amorphous semiconductor film may be performed after the second crystalline semiconductor film is flattened by irradiation with laser light under the second condition.
[0042]
Further, the laser beam under the first condition may be irradiated with a predetermined energy density using a planar laser beam similarly to the laser beam under the second condition.
[0043]
By irradiating the first crystalline semiconductor film formed by adding the catalytic element with the laser light under the first condition and the laser light under the second condition as described above, the surface is planarized. By the addition of the element, a favorable crystalline semiconductor film in which a large crystal grain size is collected can be formed. Further, since planar laser light is used as the laser light under the second condition, it is possible to suppress the occurrence of crystallization unevenness (horizontal stripes) in the crystalline semiconductor film, and furthermore, to overlap like linear laser light. Since there is no need to perform the irradiation, the throughput is improved.
[0044]
【Example】
(Example 1)
An embodiment of the present invention will be described with reference to FIGS. Here, a method for manufacturing a TFT serving as a switching element in a pixel portion and a TFT of a driver circuit (an n-channel TFT and a p-channel TFT) around the pixel portion over the same substrate will be described.
[0045]
First, a base insulating film 301 is formed over a glass substrate 300, and an amorphous silicon film 302 is formed over the base insulating film. As the base insulating film 301, an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film may be used. As a typical example, SiH ₄ , NH ₃ , And N ₂ The first silicon oxynitride film formed using O as a reaction gas is ₄ , And N ₂ A second silicon oxynitride film formed with O as a reaction gas is formed to a thickness of 100 to 150 nm.
A two-layer structure is used. Further, as one layer of the base insulating film 101, a silicon nitride film (SiN film) having a thickness of 10 nm or less or a second silicon oxynitride film (SiN film). _x O _y ) It is preferable to use a film (X≫Y). At the time of gettering, nickel tends to easily move to a region having a high oxygen concentration. Therefore, it is extremely effective to use a silicon nitride film as a base insulating film in contact with a semiconductor film. Alternatively, a three-layer structure in which a first silicon oxynitride film, a second silicon oxynitride film, and a silicon nitride film are sequentially stacked may be used.
[0046]
Subsequently, an amorphous silicon film 302 is formed over the base insulating film as an amorphous semiconductor film. The amorphous silicon film 302 is formed with a thickness of 10 to 100 nm by a plasma CVD method, a low pressure CVD method, or a sputtering method. In order to obtain a good crystalline semiconductor film in a later crystallization treatment, 5 × 10 5 impurity elements such as oxygen and nitrogen contained in the amorphous silicon film are removed. ¹⁸ / Cm ³ It is preferable to set the following (secondary ion mass spectrometry: atomic concentration measured by SIMS). These impurity elements can be factors that hinder subsequent crystallization. Further, even after the crystallization treatment, it causes an increase in the density of the trapping center recombination centers. Therefore, it is desirable to use not only a high-purity material gas but also an ultra-high vacuum-compatible CVD apparatus provided with a mirror surface treatment (electropolishing treatment) in the reaction chamber and an oil-free vacuum exhaust system.
[0047]
Subsequently, a catalytic element that promotes crystallization is added to the amorphous silicon film 302 to form a catalytic element containing layer 303. First, a nickel acetate solution containing 1 to 100 ppm by weight of a catalytic element (here, nickel) for promoting crystallization is applied to the surface of the amorphous silicon film 302 by a spinner to form a nickel-containing layer 303. (FIG. 3 (A)). As means other than the method of forming the nickel-containing layer 303 by coating, a method of forming an extremely thin film by a sputtering method, an evaporation method, or a plasma treatment may be used. Here, an example in which the coating is performed on the entire surface is described, but a nickel-containing layer may be selectively formed by forming a mask.
[0048]
Next, heat treatment is performed to perform crystallization. In this case, in crystallization, silicide is formed in a portion of the semiconductor film in contact with a catalyst element that promotes crystallization of the semiconductor, and crystallization proceeds using the silicide as a nucleus. Thus, a first crystalline silicon film is formed. Note that the concentration of oxygen contained in the first crystalline semiconductor film is 5 × 10 ¹⁸ / Cm ³ It is desirable to make the following. Here, after the heat treatment for dehydrogenation (450 ° C., 1 hour), the heat treatment for crystallization (550 to 650 ° C. for 4 to 24 hours) is performed. In the case where crystallization is performed by irradiation with strong light, any one of infrared light, visible light, or ultraviolet light or a combination thereof can be used. Typically, a halogen lamp, a metal halide, Light emitted from a lamp, a xenon arc lamp, a carbon arc lamp, a high-pressure sodium lamp, or a high-pressure mercury lamp is used. The lamp light source is turned on for 1 to 60 seconds, preferably 30 to 60 seconds, and is repeated once to ten times, and the semiconductor film may be heated to about 600 to 1000 ° C. instantaneously. Note that if necessary, heat treatment for releasing hydrogen contained in the first crystalline silicon film having an amorphous structure may be performed before irradiation with strong light. In addition, crystallization may be performed by simultaneously performing the heat treatment and the irradiation with strong light. In consideration of productivity, it is preferable that crystallization be performed by irradiation with strong light.
[0049]
Next, in order to increase the crystallization rate (the ratio of the crystal component in the total volume of the film) and repair defects remaining in the crystal grains, the first crystalline semiconductor film is irradiated with laser light (laser under the first condition). (Light) in air or oxygen atmosphere. The energy density of the laser beam under the first condition is 400 to 600 mJ / cm. ² And The second crystalline silicon film 304 formed by irradiating the laser beam under the first condition has an uneven surface and a thin oxide film 305 (FIG. 3B). As the laser light under the first condition, an excimer laser light having a wavelength of 400 nm or less, or a second or third harmonic of a YAG laser is used. Further, light emitted from an ultraviolet lamp may be used instead of the excimer laser light.
[0050]
Subsequently, the oxide film 305 formed on the surface of the second crystalline silicon film 304 is removed, and the second crystalline silicon film 304 is irradiated with laser light under the second condition. The second crystalline silicon film 304 is irradiated with a laser beam under the second condition. The laser beam irradiated portion has an energy distribution of ± 3% or less and an energy density of 430 to 700 mJ / cm. ² The beam irradiation area of the laser beam irradiation part is 30 cm ² The above-described planar laser light is applied to form a second crystalline silicon film 306 having a planarized surface. Since the in-plane energy distribution of the beam is ± 3% or less, the overlap ratio can be 50% or less. In this embodiment, the planar laser light is obtained by connecting a plurality of (100a to 100c) excimer lasers (VEL (Very Large Excimer Laser from SOPRA)) having a high output of 15 J or more to an optical system (101a to 101d). ) To realize a high output laser by using the output three times, and by using the fly-eye lens (102, 103), the energy distribution of the laser beam irradiation part is uniform and the irradiation part 108 It is possible to increase the area. FIG. 8 is a schematic diagram of such a laser beam irradiation device. It should be noted that the present invention does not depend on the type of laser, and if a large output is obtained, generally known excimer laser (typically, KrF laser or XeCl laser), solid-state laser (typically, Nd: YAG laser) Alternatively, any of a gas laser (typically, an argon laser or a helium-neon laser), a metal vapor laser (typically, a copper vapor laser or a helium-cadmium laser), or a semiconductor laser can be used.
[0051]
The laser light under the second condition is the same as the energy density of the laser light under the first condition, or 30 to 300 mJ / cm. ² To be high. Note that the laser light under the first condition and the laser light under the second condition have different energy densities, but before and after the laser light irradiation step under the second condition, the first crystalline semiconductor (silicon) film and the second crystalline The crystallinity with the silicon film hardly changes. Further, no change was observed in the crystal state such as the particle size, and it is considered that only the planarization was performed.
[0052]
Further, in the present embodiment, an example is shown in which laser light condensed linearly is used as the laser light under the first condition, but a planar laser light is used similarly to the laser light under the second condition. Alternatively, the irradiation treatment may be performed at a predetermined energy density.
[0053]
The energy density can be changed to a predetermined value by changing the laser irradiation area. By changing the distance d between the first fly-eye lens 102 and the second fly-eye lens 103, the laser irradiation area 108 is variable. The fly-eye lens is a lens in which small lenses are stuck vertically and horizontally. As the number of stuck small lenses increases, the variation in the energy distribution of the laser beam is averaged, and the energy distribution in the laser beam irradiating section becomes more uniform. Easily. Further, the shape of the small lens of the fly-eye lens and the shape of the irradiation beam have a similar relationship. In FIG. 9, the fly-eye lens is rectangular, but the shape of the fly-eye lens can be any figure that can be filled in a plane by parallel movement.
[0054]
In the second crystalline semiconductor film thus obtained, the catalytic element (here, nickel) remains. Although it is not uniformly distributed in the film, the average concentration is 1 × 10 ¹⁹ / Cm ³ At a concentration exceeding. Of course, various semiconductor elements including TFTs can be formed in such a state, but the elements are removed by a method described below.
[0055]
First, an oxide film (called a chemical oxide) is formed on the surface of the third crystalline silicon film 306 with an aqueous solution containing ozone (typically, ozone water) to form a barrier layer 307 made of an oxide film having a total thickness of 1 to 10 nm. Then, a semiconductor film (also referred to as a gettering region) 308 containing a rare gas element is formed over the barrier layer 307 (FIG. 3D). The barrier layer 307 functions as an etching stopper when only the gettering region 308 is selectively removed in a later step. Alternatively, a chemical oxide can be similarly formed by treating with an aqueous solution obtained by mixing sulfuric acid, hydrochloric acid, nitric acid or the like with a hydrogen peroxide solution instead of the ozone-containing aqueous solution. As another method for forming the barrier layer 307, ozone may be generated by irradiation with ultraviolet light in an oxygen atmosphere to oxidize the surface of the semiconductor film having the crystal structure. As another method for forming the barrier layer 307, an oxide film of about 1 to 10 nm may be deposited by a plasma CVD method, a sputtering method, an evaporation method, or the like to form a barrier layer. As another method for forming the barrier layer 307, a thin oxide film may be formed by heating to about 200 to 350 ° C. using a clean oven. Note that the barrier layer 307 is not particularly limited as long as the barrier layer 307 is formed by any one of the above methods or a combination of these methods. It is necessary that the film quality or thickness be such that nickel can move to the semiconductor film (gettering region) 308.
[0056]
Here, a semiconductor film 308 containing a rare gas element is formed by a sputtering method to form a gettering site (FIG. 3D). Note that it is preferable to appropriately adjust sputtering conditions so that a rare gas element is not added to the third crystalline silicon film 306. As the rare gas element, one or more kinds selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) are used. Among them, argon (Ar), which is an inexpensive gas, is preferable. Here, the gettering region 308 is formed using a target made of silicon in an atmosphere containing a rare gas element. There are two meanings to include a rare gas element ion, which is an inert gas, in the film. One is to form a dangling bond to give a strain to the semiconductor film, and the other is to give a strain between lattices of the semiconductor film. Distortion between the lattices of the semiconductor film is remarkably obtained when an element having a larger atomic radius than silicon, such as argon (Ar), krypton (Kr), or xenon (Xe), is used. In addition, by containing a rare gas element in the film, not only lattice distortion but also dangling bonds are formed, which contributes to gettering action.
[0057]
In the case where the gettering region 308 is formed using a target containing phosphorus which is an impurity element of one conductivity type, gettering can be performed using Coulomb force of phosphorus in addition to gettering with a rare gas element. .
[0058]
Further, at the time of gettering, since nickel tends to easily move to a region having a high oxygen concentration, the oxygen concentration contained in the gettering region 308 is higher than the oxygen concentration contained in the third crystalline silicon film 306. , For example, 5 × 10 ¹⁸ / Cm ³ It is desirable to make the above.
[0059]
Next, heat treatment is performed to perform gettering for reducing or removing the concentration of the catalyst element (nickel) in the third crystalline semiconductor film 306 (FIG. 3D). As the heat treatment for gettering, heat treatment or irradiation with strong light may be performed. By this gettering, the catalytic element moves in the direction of the arrow in FIG. 3D (that is, in the direction from the substrate side to the surface of the second semiconductor film), and the third crystalline material covered with the barrier layer 307 is formed. Removal of the catalyst element included in the semiconductor film 306 or reduction of the concentration of the catalyst element is performed. The distance that the catalyst element moves during gettering may be at least as long as the thickness of the third crystalline semiconductor film 306, and the gettering can be completed in a relatively short time. Here, all of the nickel is moved to the gettering region 308 so as not to segregate in the third crystalline semiconductor film 306, and nickel contained in the third crystalline semiconductor film 306 hardly exists, that is, the nickel concentration in the film is reduced. 1 × 10 ¹⁸ / Cm ³ Hereinafter, preferably 1 × 10 ¹⁷ / Cm ³ Getter enough so that:
[0060]
In addition, depending on the conditions of the heat treatment for the gettering, the crystallization rate of the third crystalline semiconductor film is increased at the same time as the gettering to repair defects remaining in crystal grains, that is, to improve the crystallinity. Can be.
[0061]
In this specification, the term “gettering” means that a catalytic element in a region to be gettered (here, the third crystalline semiconductor film) is released by thermal energy and moves to a gettering site by diffusion. Therefore, gettering depends on the processing temperature, and the higher the temperature, the faster the gettering proceeds.
[0062]
When a process of irradiating intense light is used as the heat treatment for the gettering, the lamp light source for heating is turned on for 1 to 60 seconds, preferably 30 to 60 seconds, and is turned on 1 to 10 times, preferably 2 to 60 times. Repeat ~ 6 times. Although the light emission intensity of the lamp light source is arbitrary, the semiconductor film is heated to about 600 to 1000 ° C., preferably about 700 to 750 ° C. instantaneously.
[0063]
In the case of performing heat treatment, heat treatment may be performed in a nitrogen atmosphere at 450 to 800 ° C. for 1 to 24 hours, for example, at 550 ° C. for 14 hours. Further, strong light irradiation may be performed in addition to the heat treatment.
[0064]
Next, after selectively removing only the gettering region 308 using the barrier layer 307 as an etching stopper, the barrier layer 307 made of an oxide film is removed. As a method for selectively etching only the second semiconductor film, ClF is used. ₃ Etching without using plasma by hydrazine or tetraethylammonium hydroxide (chemical formula (CH ₃ ) ₄ It can be performed by wet etching using an alkaline solution such as an aqueous solution containing NOH). After the gettering region 308 was removed, the surface of the barrier layer was measured for nickel concentration by TXRF. Since nickel was detected at a high concentration, the barrier layer was desirably removed, and an etchant containing hydrofluoric acid was used. You only have to remove it.
[0065]
Through the above steps, a favorable crystalline silicon film having a reduced catalytic element concentration and a flat surface is formed.
[0066]
Next, after a thin oxide film is formed on the surface of the obtained crystalline silicon film (also called a polysilicon film) with ozone water, a mask made of a resist is formed, and is etched into a desired shape and separated into islands. The formed semiconductor layers 310 to 314 are formed. After the formation of the semiconductor layer, the resist mask is removed.
[0067]
After the semiconductor layer is formed, an impurity element imparting p-type or n-type may be added in order to control the threshold value (Vth) of the TFT. In addition, as the impurity element imparting p-type to the semiconductor, an element belonging to Group 13 of the periodic rule such as boron (B), aluminum (Al), and gallium (Ga) is known. As an impurity element that imparts n-type to a semiconductor, an element belonging to Group 15 of the periodic rule, typically, phosphorus (P) or arsenic (As) is known.
[0068]
Next, after removing the oxide film with an etchant containing hydrofluoric acid and cleaning the surface of the silicon film at the same time, an insulating film containing silicon as a main component and serving as the gate insulating film 307 is formed. In this embodiment, a silicon oxynitride film (composition ratio: Si = 32%, O = 59%, N = 7%, H = 2%) is formed with a thickness of 115 nm by a plasma CVD method.
[0069]
Next, as shown in FIG. 4A, a first conductive film 316 having a thickness of 20 to 100 nm, a second conductive film 317 having a thickness of 100 to 400 nm, A third conductive film 318 having a thickness of 100 nm is formed by stacking. In this embodiment, a 50-nm-thick tungsten film, a 500-nm-thick alloy (Al-Ti) film of aluminum and titanium, and a 30-nm-thick titanium film are sequentially stacked on the gate insulating film 315.
[0070]
The conductive material for forming the first to third conductive films is formed of an element selected from Ta, W, Ti, Mo, Al, and Cu, or an alloy material or a compound material containing the element as a main component. Further, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used as the first to third conductive films. For example, tungsten nitride may be used instead of tungsten for the first conductive film, or an alloy of aluminum and silicon (Al-Si) instead of the alloy film of aluminum and titanium (Al-Ti) for the second conductive film. ) A film may be used, or a titanium nitride film may be used instead of the titanium film of the third conductive film. The structure is not limited to a three-layer structure, and may be, for example, a two-layer structure of a tantalum nitride film and a tungsten film.
[0071]
Next, as shown in FIG. 4B, masks 319 to 324 made of resist are formed by a light exposure process, and a first etching process for forming a gate electrode and a wiring is performed. The first etching process is performed under the first and second etching conditions. It is preferable to use an ICP (Inductively Coupled Plasma) etching method for the etching. The film is formed into a desired tapered shape by appropriately adjusting the etching conditions (the amount of power applied to the coil-type electrode, the amount of power applied to the electrode on the substrate side, the temperature of the electrode on the substrate side, etc.) using the ICP etching method. Can be etched. The etching gas used is Cl. ₂ , BCl ₃ , SiCl ₄ , CCl ₄ Such as chlorine-based gas or CF ₄ , SF ₆ , NF ₃ Such as fluorine-based gas or O ₂ Can be used as appropriate.
[0072]
Although the etching gas used is not limited, here, BCl ₃ And Cl ₂ And O ₂ It is suitable to use Each gas flow ratio was set to 65/10/5 (sccm), 450 W RF (13.56 MHz) power was applied to the coil-type electrode at a pressure of 1.2 Pa to generate plasma, and etching was performed for 117 seconds. Do. A 300 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 Al film and the Ti film are etched under the first etching conditions to make the end of the first conductive layer tapered.
[0073]
Thereafter, the etching conditions are changed to the second etching condition, and the etching gas is CF. ₄ And Cl ₂ And O ₂ And a gas flow ratio of 25/25/10 (sccm), 500 W RF (13.56 MHz) power is applied to the coil type electrode at a pressure of 1 Pa to generate plasma for about 30 seconds. Etching to the extent of A 20 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. CF ₄ And Cl ₂ Is mixed, the Al film, the Ti film, and the W 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 may be increased by about 10 to 20%.
[0074]
In the first etching process, the first conductive layer, the second conductive layer, and the third conductive layer are formed by adjusting the shape of the resist mask to an appropriate shape, by the effect of the bias voltage applied to the substrate side. The ends of the layer are tapered. The angle of the tapered portion is 15 to 45 °. Thus, by the first etching process, the first shape conductive layers 325 to 330 (the first conductive layers 325 a to 330 a and the second conductive layer 325 a to 330 a) each including the first conductive layer, the second conductive layer, and the third conductive layer are formed. Of the conductive layers 325b to 330b and the third conductive layers 325c to 330c). Reference numeral 331 denotes a gate insulating film, and a region which is not covered with the first shape conductive layers 325 to 330 is etched by about 20 to 50 nm to form a thinned region.
[0075]
Next, a second etching process is performed without removing the resist masks 319 to 324 as shown in FIG. BCl for etching gas ₃ And Cl ₂ And a gas flow ratio of 20/60 (sccm), and a 600 W RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1.2 Pa to generate plasma to perform etching. 100 W of RF (13.56 MHz) power is applied to the substrate side (sample stage). The second conductive layer and the third conductive layer are etched under the third etching condition. In this manner, the aluminum film and the titanium film containing a small amount of titanium are anisotropically etched under the third etching condition to form the second shape conductive layers 332 to 337 (the first conductive layers 332a to 337a and the second conductive layer 332a to 337a). The layers 332b to 337b and the third conductive layers 332c to 337c) are formed. Reference numeral 338 denotes a gate insulating film, and a region which is not covered with the second shape conductive layers 332 to 337 is slightly etched to form a thinned region.
[0076]
Then, a first doping process is performed without removing the resist mask, and an impurity element imparting n-type is added to the semiconductor layer. The doping treatment may be performed by an ion doping method or an ion implantation method. The condition of the ion doping method is that the dose amount is 1.5 × 10 ¹⁴ atoms / cm ² And an acceleration voltage of 60 to 100 keV. Typically, phosphorus (P) or arsenic (As) is used as an impurity element imparting n-type. In this case, the second shape conductive layers 332 to 336 serve as a mask for the impurity element imparting n-type, and first impurity regions 339 to 343 are formed in a self-aligned manner. The first impurity regions 339 to 343 have 1 × 10 ¹⁶ ~ 1 × 10 ¹⁷ / Cm ³ Is added within the concentration range of n.
[0077]
Although the first doping process is performed in this embodiment without removing the resist mask, the first doping process may be performed after removing the resist mask.
[0078]
Next, after removing the mask made of resist, as shown in FIG. 5A, masks 344 and 345 made of resist are formed and a second doping process is performed. The mask 344 is a mask that protects a channel formation region of a semiconductor layer forming one of the n-channel TFTs of the driver circuit and a peripheral region thereof. And a mask for protecting the peripheral area.
[0079]
The conditions of the ion doping method in the second doping treatment are as follows: ^Fifteen atoms / cm ² And doping with phosphorus (P) at an acceleration voltage of 60 to 100 keV. Here, an impurity region is formed in each semiconductor layer by utilizing a difference in thickness between the second shape conductive layers 332 to 336 and the gate insulating film 338. Of course, phosphorus (P) is not added to the regions covered with the masks 344 and 345. Thus, second impurity regions 346 to 348 and third impurity regions 349 to 362 are formed. The third impurity regions 349 to 362 have 1 × 10 ²⁰ ~ 1 × 10 ²¹ / Cm ³ Is added in the concentration range of n. Further, the second impurity region is formed at a lower concentration than the third impurity region due to a difference in thickness of the gate insulating film, and 1 × 10 ¹⁸ ~ 1 × 10 ¹⁹ / Cm ³ Is added in the concentration range of n.
[0080]
Next, after removing the resist masks 344 and 345, masks 363 to 365 are newly formed, and a third doping process is performed as shown in FIG. By the third doping treatment, a fourth impurity region 368 and a fifth impurity region 366 and 367 in which an impurity element imparting p-type conductivity is added to a semiconductor layer forming a p-channel TFT are formed. . The fourth impurity region is formed in a region overlapping with the second shape conductive layer, and has a size of 1 × 10 ¹⁸ ~ 1 × 10 ²⁰ / Cm ³ The impurity element imparting p-type is added within the concentration range of. Further, 1 × 10 5 ²⁰ ~ 1 × 10 ²¹ / Cm ³ The impurity element imparting p-type is added within the concentration range of. Although the fifth impurity region 346 is a region to which phosphorus (P) is added in the previous step, the concentration of the impurity element imparting p-type is 1.5 to 3 times that of the fifth impurity region 346, and the conductivity type is increased. Is p-type.
[0081]
Note that the fifth impurity regions 369 and 370 and the fourth impurity region 371 are formed in a semiconductor layer which forms a storage capacitor in the pixel portion.
[0082]
Through the above steps, impurity regions having n-type or p-type conductivity are formed in the respective semiconductor layers. The second shape conductive layers 332 to 335 serve as gate electrodes. Further, the second shape conductive layer 336 serves as one electrode forming a storage capacitor in the pixel portion. Further, the second shape conductive layer 337 forms a source wiring in the pixel portion.
[0083]
Next, an insulating film (not shown) covering almost the entire surface is formed. In this embodiment, a 50 nm-thick silicon oxide film is formed by a plasma CVD method. Of course, this insulating film is not limited to a silicon oxide film, and another insulating film containing silicon may be used as a single layer or a laminated structure.
[0084]
Next, a step of activating the impurity element added to each semiconductor layer is performed. This activation step is performed by a rapid thermal annealing method (RTA method) using a lamp light source, a method of irradiating a YAG laser or an excimer laser from the back surface, a heat treatment using a furnace, or a combination of any of these methods. Done by the method However, in this embodiment, since a material containing aluminum as a main component is used for the second conductive layer, it is important to set a heat treatment condition that the second conductive layer can withstand in the activation step.
[0085]
At the same time as the activation treatment, nickel used as a catalyst at the time of crystallization is gettered from the third impurity regions 349, 360, 361 and the fifth impurity regions 367, 370 containing high-concentration phosphorus. In addition, the concentration of nickel in the semiconductor layer serving as a channel formation region is reduced. As a result, a TFT having a channel formation region has a low off-current value and high crystallinity, so that high field-effect mobility can be obtained and favorable characteristics can be achieved. Note that in this example, the first gettering is performed by the method described in Embodiment 1 at the stage of forming the semiconductor layer, so that the gettering by phosphorus here is the second gettering. . In addition, when the gettering has been sufficiently performed by the first gettering, the second gettering need not be particularly performed.
[0086]
In this embodiment, the example in which the insulating film is formed before the activation is described. However, a step of forming the insulating film after the activation may be performed.
[0087]
Next, a first interlayer insulating film 372 made of a silicon nitride film is formed, heat treatment is performed (heat treatment at 300 to 550 ° C. for 1 to 12 hours), and a step of hydrogenating the semiconductor layer is performed (FIG. 5C )). In this step, dangling bonds in the semiconductor layer are terminated by hydrogen contained in the first interlayer insulating film 372. The semiconductor layer can be hydrogenated regardless of the presence of an insulating film (not shown) made of a silicon oxide film. However, in this embodiment, since a material containing aluminum as a main component is used for the second conductive layer, it is important to set heat treatment conditions under which the second conductive layer can withstand in the hydrogenation step. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.
[0088]
Next, a second interlayer insulating film 373 made of an organic insulating material is formed over the first interlayer insulating film 372. In this embodiment, an acrylic resin film having a thickness of 1.6 μm is formed. Next, a contact hole reaching the source wiring 337 and a contact hole reaching each impurity region are formed. In this embodiment, a plurality of etching processes are sequentially performed. In this embodiment, after the second interlayer insulating film is etched using the first interlayer insulating film as an etching stopper, the first interlayer insulating film is etched using the insulating film (not shown) as an etching stopper, and then the insulating film (illustrated). No) was etched.
[0089]
After that, a wiring and a pixel electrode are formed using Al, Ti, Mo, W, or the like. It is desirable to use a material having excellent reflectivity, such as a film containing Al or Ag as a main component or a laminated film thereof, for the material of these electrodes and pixel electrodes. Thus, source or drain wirings 374 to 379, a gate wiring 381, a connection wiring 380, and a pixel electrode 382 are formed.
[0090]
As described above, the driver circuit 406 including the n-channel TFT 401, the p-channel TFT 402, and the n-channel TFT 403, and the pixel portion 407 including the n-channel TFT 404 and the storage capacitor 405 can be formed over the same substrate. Yes (Figure 6). In this specification, such a substrate is referred to as an active matrix substrate for convenience.
[0091]
An n-channel TFT 401 (a second n-channel TFT) of the driver circuit 406 includes a channel formation region 383, a second impurity region 346 which partially overlaps the second shape conductive layer 332 which forms a gate electrode, and a source region. Alternatively, a third impurity region 349 functioning as a drain region is provided. The p-channel TFT 402 includes a channel formation region 384, a fourth impurity region 368 partially overlapping the second shape conductive layer 333 forming a gate electrode, and a fourth impurity region 366 functioning as a source or drain region. Have. In the n-channel TFT 403 (a second n-channel TFT), a channel formation region 385, a second impurity region 347 partly overlapping with a second shape conductive layer 334 forming a gate electrode, and a source or drain region And has a third impurity region 360 functioning as a third impurity region. With such an n-channel TFT and a p-channel TFT, a shift register circuit, a buffer circuit, a level shifter circuit, a latch circuit, and the like can be formed. In particular, the structure of the n-channel TFT 401 or 403 is suitable for a buffer circuit with a high driving voltage for the purpose of preventing deterioration due to the hot carrier effect.
[0092]
In the pixel TFT 404 (first n-channel TFT) of the pixel portion 407, a channel formation region 386, a first impurity region 342 formed outside a second shape conductive layer 335 forming a gate electrode, and a source region Alternatively, a third impurity region 361 functioning as a drain region is provided. Further, a fourth impurity region 371 and a fifth impurity region 369 are formed in a semiconductor layer functioning as one electrode of the storage capacitor 405. The storage capacitor 405 includes a second shape electrode 336 and a semiconductor layer 314 using an insulating film (the same film as the gate insulating film) as a dielectric.
[0093]
Note that, in the pixel TFT of the pixel portion 407, off-current and variation are significantly reduced by laser light irradiation under the second condition as compared with the related art.
[0094]
In addition, when the pixel electrode is formed using a transparent conductive film, a transmissive display device can be formed although the number of photomasks is increased by one.
[0095]
(Example 2)
In this embodiment, steps of manufacturing an active matrix liquid crystal display device from the active matrix substrate manufactured in Embodiment 1 will be described below. FIG. 7 is used for the description.
[0096]
First, according to the first embodiment, after obtaining the active matrix substrate in the state shown in FIG. 6, an alignment film is formed on the active matrix substrate shown in FIG. 6, and a rubbing process is performed. In this example, before forming the alignment film, a columnar spacer for maintaining the 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 scattered over the entire surface of the substrate.
[0097]
Next, a counter substrate is prepared. The opposite substrate is provided with a color filter in which a coloring layer and a light shielding layer are arranged corresponding to each pixel. Further, a light-shielding layer was provided also in a portion of the driving circuit. A flattening film covering the color filter and the light-shielding layer was provided. Next, a counter electrode made of a transparent conductive film was formed on the flattening film in the pixel portion, an alignment film was formed over the entire surface of the counter substrate, and rubbing treatment was performed.
[0098]
Then, the active matrix substrate on which the pixel portion and the driver circuit are formed and the counter substrate are attached with a sealant. A filler is mixed in the sealing material, and the two substrates are bonded together at a uniform interval by the filler and the columnar spacer. Thereafter, a liquid crystal material is injected between the two substrates, and completely sealed with a sealant (not shown). A known liquid crystal material may be used as the liquid crystal material. Thus, an active matrix type liquid crystal display device is completed. Then, if necessary, the active matrix substrate or the opposing substrate is cut into a desired shape. Further, a polarizing plate and the like were appropriately provided using a known technique. Then, an FPC was attached using a known technique.
[0099]
The configuration of the liquid crystal module thus obtained will be described with reference to the top view of FIG.
[0100]
At the center of the active matrix substrate 801, a pixel portion 804 is provided. Above the pixel portion 804, a source signal line driver circuit 802 for driving a source signal line is provided. On the left and right of the pixel portion 804, gate signal line driving circuits 803 for driving gate signal lines are arranged. In the example shown in this embodiment, the gate signal line driving circuit 803 is arranged symmetrically with respect to the pixel portion. However, it may be arranged on only one side, and the designer may consider the size of the substrate of the liquid crystal module. May be appropriately selected. However, considering the operation reliability and driving efficiency of the circuit, the symmetrical arrangement shown in FIG. 7 is desirable.
[0101]
Input of signals to each drive circuit is performed from a flexible printed circuit (FPC) 805. The FPC 805 forms a contact hole in the interlayer insulating film and the resin film so as to reach a wiring arranged to a predetermined position on the substrate 801, forms a connection electrode 809, and then press-bonds the same via an anisotropic conductive film or the like. Is done. In this embodiment, the connection electrode was formed using ITO.
[0102]
A sealant 807 is applied around the periphery of the driving circuit and the pixel portion along the outer periphery of the substrate, and a predetermined gap (a space between the substrate 801 and the counter substrate 806) is maintained by a spacer 810 formed in advance on the active matrix substrate. In this state, the counter substrate 806 is attached. After that, a liquid crystal element is injected from a portion where the sealant 807 is not applied, and is sealed with the sealant 808. Through the above steps, a liquid crystal module is completed.
[0103]
Although an example in which all the driving circuits are formed over a substrate is described here, several ICs may be used as a part of the driving circuit.
[0104]
(Example 3)
In this embodiment, another example of manufacturing a semiconductor device using the present invention will be described with reference to FIGS.
[0105]
According to the first embodiment, a base insulating film 41 and an amorphous silicon film 42 are formed on a glass substrate 40.
[0106]
Subsequently, a catalytic element is added to the amorphous silicon film 42 and heat treatment is performed to form a first crystalline semiconductor (silicon) film 44. Subsequently, the first crystalline silicon film 44 is irradiated with laser light under the first condition. As the catalytic element, one or more selected from Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu, and Au may be used. The energy density of the laser beam under the first condition is 450 to 700 mJ / cm. ² Irradiation treatment may be performed in the atmosphere using a laser having a repetition frequency of about 1 to 1000 Hz. In this embodiment, as the laser light under the first condition, the planar laser light is converted into an energy density of 650 mJ / cm by using the laser light irradiation apparatus as shown in the first embodiment. ² Irradiation in air. Thus, a second crystalline semiconductor (silicon) film 45 is formed. Laser light having an energy density slightly higher than the energy density applied for crystallization is applied, and the second crystalline silicon film 45 is formed by aggregation of fine crystal grains.
[0107]
Of course, linear laser light may be applied as the laser light under the first condition.
[0108]
Next, the second crystalline silicon film 45 is irradiated with laser light under the second condition. The laser light under the second condition is 400 to 650 mJ / cm smaller than the energy density of the laser light under the first condition. ² A laser having a repetition frequency of about 10 to 1000 Hz may be used. Here, a planar laser beam is used and the energy density is 600 mJ / cm. ² Then, laser light irradiation under the second condition is performed in the air to form a third crystalline silicon film 46. On the surface of the third crystalline silicon film 46, a projection and an oxide film 47 are formed.
[0109]
Of course, linear laser light may be applied as the laser light under the second condition.
[0110]
After that, the oxide film 47 formed on the surface of the third crystalline silicon film 46 is removed, and the second crystalline silicon film 46 is irradiated with a laser beam under the third condition to thereby flatten the fourth crystalline silicon film 46. Is formed. The laser light of the third condition has an energy distribution of ± 3% or less and a laser light irradiation area of 30 cm using a laser light irradiation device having an output of 15 J or more. ² As described above, the energy density is 430 to 700 mJ / cm ² A laser having a repetition frequency of about 1 to 1000 Hz may be used. Note that since the energy distribution is ± 3% or less, the irradiation may be performed with the overlap ratio being 50% or less. Thus, the fourth crystalline semiconductor film 48 in which the surface of the third crystalline semiconductor film 46 is flattened is formed. The third crystalline semiconductor film 46 and the fourth crystalline semiconductor film 48 differ only in the presence or absence of surface irregularities, and the other semiconductor (silicon) films hardly change in crystallinity. Further, no change was observed in the crystal state such as the particle size, and it is considered that only the planarization was performed.
[0111]
After that, the catalyst element added to the amorphous silicon film 42 for crystallization is moved from the fourth crystalline silicon film to the gettering region and included in the fourth crystalline silicon film 48. The concentration of the catalytic element to be reduced. This step may follow the second embodiment or the first embodiment.
[0112]
The good crystalline semiconductor film obtained as described above forms a semiconductor layer which is separated into islands, and then a TFT manufacturing process may be performed according to the process of the first embodiment.
[0113]
In this embodiment, the amorphous silicon film is irradiated with laser light under the first condition after a catalytic element is added thereto and heat-treated to form a crystalline silicon film. After irradiating the laser beam under the first condition and the laser beam under the second condition to remove the oxide film, the laser beam under the third condition may be irradiated.
[0114]
This embodiment can be implemented in combination with the first embodiment and the first and second embodiments.
[0115]
(Example 4)
In this embodiment, an example of manufacturing a light-emitting display device including an EL (Electro Luminescence) element is shown in FIGS.
[0116]
FIG. 10A is a top view illustrating the EL module, and FIG. 10B is a cross-sectional view of FIG. 10A taken along a line AA ′. A pixel portion 902, a source driver circuit 901, and a gate driver circuit 903 are formed over a substrate 900 having an insulating surface (eg, a glass substrate, a crystallized glass substrate, or a plastic substrate). These pixel units and drive circuits can be obtained according to the above embodiment. Further, reference numeral 918 denotes a sealing material, and 919 denotes a DLC film. The pixel portion and the driving circuit portion are covered with a sealing material 918, and the sealing material is covered with a protective film 919. Further, it is sealed with a cover material 920 using an adhesive. The cover material 920 is preferably made of the same material as the substrate 900, for example, a glass substrate in order to withstand deformation due to heat, external force, or the like. . It is desirable to further process to form a concave portion (50 to 200 μm in depth) in which the desiccant 921 can be placed. In the case where an EL module is manufactured by multi-cavity bonding, a substrate and a cover material may be bonded to each other, and then cut using a CO2 laser or the like so that the end faces are aligned.
[0117]
Note that reference numeral 908 denotes wiring for transmitting signals input to the source driver circuit 901 and the gate driver circuit 903, and receives a video signal and a clock signal from an FPC (flexible print circuit) 909 serving as an external input terminal. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this specification includes not only the light-emitting device body but also a state in which an FPC or a PWB is attached thereto.
[0118]
Next, a cross-sectional structure is described with reference to FIG. An insulating film 910 is provided over a substrate 900, and a pixel portion 902 and a gate driver circuit 903 are formed over the insulating film 910. The pixel portion 902 is electrically connected to a current control TFT 911 and a drain thereof. And a plurality of pixels including the pixel electrode 912. The gate driver circuit 903 is formed using a CMOS circuit in which an n-channel TFT 913 and a p-channel TFT 714 are combined.
[0119]
These TFTs (including 911, 913, and 914) may be manufactured according to the above embodiment.
[0120]
The pixel electrode 912 functions as an anode of a light emitting element (EL element). A bank 915 is formed at both ends of the pixel electrode 912, and an EL layer 916 and a cathode 917 of a light emitting element are formed over the pixel electrode 912.
[0121]
As the EL layer 916, an EL layer (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, a low molecular organic EL material or a high molecular organic EL material may be used. Further, as the EL layer, a thin film made of a light-emitting material (singlet compound) that emits light (fluorescence) by singlet excitation or a thin film made of a light-emitting material that emits light (phosphorescence) by triplet excitation can be used. Further, an inorganic material such as silicon carbide can be used for the charge transport layer and the charge injection layer. Known materials can be used for these organic EL materials and inorganic materials.
[0122]
The cathode 917 also functions as a common wiring for all pixels, and is electrically connected to the FPC 909 via the connection wiring 908. Further, elements included in the pixel portion 902 and the gate driver circuit 903 are all covered with a cathode 917, a sealant 918, and a protective film 919.
[0123]
Note that as the sealant 918, a material that is as transparent or translucent as possible to visible light is preferably used. It is preferable that the sealant 918 be a material that does not transmit moisture or oxygen as much as possible.
[0124]
After the light-emitting element is completely covered with the sealing material 918, a protective film 919 made of a DLC film or the like is preferably provided on at least the surface (exposed surface) of the sealing material 918 as shown in FIG. Further, a protective film may be provided on the entire surface including the back surface of the substrate. Here, care must be taken so that the protective film is not formed in a portion where the external input terminal (FPC) is provided. The protection film may not be formed using a mask, or the protection film may be prevented from being formed by covering the external input terminal portion with a tape used as a masking tape in a CVD apparatus.
[0125]
By enclosing the light-emitting element with the sealant 918 and the protective film with the above structure, the light-emitting element can be completely shut off from the outside and a substance which promotes deterioration of the EL layer due to oxidation of moisture or oxygen from the outside. Can be prevented from entering. Therefore, a highly reliable light-emitting device can be obtained.
[0126]
Further, the pixel electrode may be used as a cathode, and the EL layer and the anode may be stacked to emit light in a direction opposite to that in FIG. FIG. 10 shows an example. Note that the top views are the same, and thus are omitted.
[0127]
The cross-sectional structure shown in FIG. 11 will be described below. As the substrate 1000, a semiconductor substrate or a metal substrate can be used in addition to a glass substrate or a quartz substrate. An insulating film 1010 is provided over a substrate 1000, and a pixel portion 1002 and a gate driver circuit 1003 are formed above the insulating film 1010. The pixel portion 1002 is electrically connected to a current controlling TFT 1011 and a drain thereof. And a plurality of pixels including the pixel electrode 1012. The gate driver circuit 1003 is formed using a CMOS circuit in which an n-channel TFT 1013 and a p-channel TFT 1014 are combined.
[0128]
The pixel electrode 1012 functions as a cathode of the light emitting element. Banks 1015 are formed at both ends of the pixel electrode 1012, and an EL layer 1016 and an anode 1017 of a light emitting element are formed over the pixel electrode 1012.
[0129]
The anode 1017 also functions as a wiring common to all pixels, and is electrically connected to the FPC 1009 via the connection wiring 1008. Further, the elements included in the pixel portion 1002 and the gate side driver circuit 1003 are all covered with an anode 1017, a sealant 1018, and a protective film 1019 made of DLC or the like. Further, the cover material 1021 and the substrate 1000 were bonded with an adhesive. In addition, a concave portion is provided in the cover material, and a desiccant 1021 is provided.
[0130]
Note that as the sealant 1018, a material that is as transparent or translucent as possible to visible light is preferably used. It is preferable that the sealant 1018 be a material that does not transmit moisture or oxygen as much as possible.
[0131]
Further, in FIG. 11, since the pixel electrode is used as a cathode and the EL layer and the anode are stacked, the light emitting direction is the direction of the arrow shown in FIG.
[0132]
This embodiment can be implemented in combination with Embodiments 1 and 3.
[0133]
(Example 5)
A CMOS circuit or a pixel portion formed by implementing the present invention can be used for an active matrix liquid crystal display (liquid crystal display device). That is, the present invention can be applied to all electric appliances in which such a liquid crystal display device is incorporated in a display unit.
[0134]
Examples of such appliances include video cameras, digital cameras, projectors (rear or front type), head mounted displays (goggle type displays), personal computers, personal digital assistants (mobile computers, mobile phones, electronic books, etc.), etc. Is mentioned. Examples of these are shown in FIG. 12, FIG. 13 and FIG.
[0135]
FIG. 12A illustrates a personal computer, which includes a main body 2001, an image input portion 2002, a display portion 2003, a keyboard 2004, and the like.
[0136]
FIG. 12B illustrates a video camera, which includes a main body 2101, a display portion 2102, an audio input portion 2103, operation switches 2104, a battery 2105, an image receiving portion 2106, and the like.
[0137]
FIG. 12C illustrates a mobile computer (mobile computer), which includes a main body 2201, a camera unit 2202, an image receiving unit 2203, operation switches 2204, a display unit 2205, and the like.
[0138]
FIG. 12D illustrates a goggle-type display, which includes a main body 2301, a display portion 2302, an arm portion 2303, and the like. The present invention is particularly advantageous for a small display device, and is advantageous for a display device used for a display section of a goggle type display.
[0139]
FIG. 12E illustrates a player using a recording medium on which a program is recorded (hereinafter, referred to as a recording medium), and includes a main body 2401, a display portion 2402, a speaker portion 2403, a recording medium 2404, operation switches 2405, and the like. The player can use a DVD (Digital Versatile Disc), a CD, or the like as a recording medium, and can enjoy music, movies, games, and the Internet.
[0140]
FIG. 12F illustrates a digital camera, which includes a main body 2501, a display portion 2502, an eyepiece portion 2503, operation switches 2504, an image receiving portion (not shown), and the like.
[0141]
FIG. 13A illustrates a front type projector, which includes a projection device 2601, a screen 2602, and the like.
[0142]
FIG. 13B illustrates a rear projector, which includes a main body 2701, a projection device 2702, a mirror 2703, a screen 2704, and the like.
[0143]
Note that FIG. 13C is a diagram illustrating an example of the structure of the projection devices 2601 and 2702 in FIGS. 13A and 13B. The projection devices 2601 and 2702 include a light source optical system 2801, mirrors 2802 and 2804 to 2806, a dichroic mirror 2803, a prism 2807, a liquid crystal display device 2808, a phase difference plate 2809, and a projection optical system 2810. The projection optical system 2810 is configured by an optical system including a projection lens. In this 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.
[0144]
FIG. 13D illustrates an example of the structure of the light source optical system 2801 in FIG. In this embodiment, the light source optical system 2801 includes a reflector 2811, a light source 2812, lens arrays 2813 and 2814, a polarization conversion element 2815, and a condenser lens 2816. Note that the light source optical system shown in FIG. 13D 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.
[0145]
However, in the projector shown in FIG. 13, a case where a transmission type electro-optical device is used is shown, and an application example of a reflection type liquid crystal display device is not shown.
[0146]
FIG. 14A illustrates a mobile phone, 3001 a display panel, and 3002 an operation panel. The display panel 3001 and the operation panel 3002 are connected at a connection portion 3003. The angle θ between the surface of the connection panel 3003 on which the display portion 3004 of the display panel 3001 is provided and the surface of the operation panel 3002 on which the operation keys 3006 are provided can be arbitrarily changed.
Further, a voice output unit 3005, operation keys 3006, a power switch 3007, and a voice input unit 3008 are provided.
The present invention is particularly advantageous for a small display device and is advantageous for a display device used for a display portion of a mobile phone.
[0147]
FIG. 14B illustrates a portable book (e-book) including a main body 3101, display portions 3102 and 3103, a storage medium 3104, operation switches 3105, an antenna 3106, and the like.
[0148]
FIG. 14C illustrates a display, which includes a main body 3201, a support 3202, a display portion 3203, and the like.
[0149]
As described above, the applicable range of the present invention is extremely wide, and the present invention can be applied to electric appliances in all fields. Further, the electric appliance of this example can be realized by combining any one of the first and second embodiments and the first to third examples.
[0150]
(The invention's effect)
[0151]
According to the present invention, the flatness of a crystalline semiconductor film can be improved. In addition, since laser light irradiation uses planar laser light having a uniform energy distribution (± 3% or less), generation of crystallization unevenness (horizontal stripes) in the crystalline semiconductor film can be suppressed. In addition, since it is not necessary to irradiate while maintaining a high overlap ratio unlike a linear laser beam, the throughput is improved.
[0152]
Further, the semiconductor film crystallized by adding the catalytic element is irradiated with the laser light under the first condition and the laser light under the second condition, whereby the surface is flattened, and the addition of the catalytic element increases the crystal grain size. Can form a good crystalline semiconductor film. In addition, by manufacturing a TFT using such a crystalline semiconductor film, a semiconductor device having favorable characteristics can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
FIG. 2 illustrates an embodiment of the present invention.
FIG. 3 is a diagram showing an embodiment of the present invention.
FIG. 4 is a diagram showing an example of an embodiment of the present invention.
FIG. 5 is a diagram showing an example of an embodiment of the present invention.
FIG. 6 is a diagram showing an example of an embodiment of the present invention.
FIG. 7 is a diagram showing an example of an embodiment of the present invention.
FIG. 8 is a diagram showing an example of an embodiment of the present invention.
FIG. 9 is a simplified diagram of a laser beam irradiation device used in the present invention.
FIG. 10 is a diagram showing an upper surface and a cross section of an EL module.
FIG. 11 is a diagram showing a cross section of an EL module.
FIG. 12 illustrates an example of an electric appliance.
FIG. 13 illustrates an example of an electric appliance.
FIG. 14 illustrates an example of an electric appliance.

Claims (1)

A first step of forming an amorphous semiconductor film on an insulating substrate;
A second step of irradiating the amorphous semiconductor film with a linear laser beam under a first condition in an atmosphere containing oxygen to form a first crystalline semiconductor film;
In an atmosphere containing oxygen, the first crystalline semiconductor film is irradiated with a linear laser beam under a second condition having an energy density smaller than that of the laser beam under the first condition, thereby forming a second crystalline semiconductor film. A third step of forming;
The oxide film formed on the second crystalline semiconductor film is removed, and the output energy of the second crystalline semiconductor film is 15 J or more in an inert atmosphere or a vacuum atmosphere by using a laser light irradiation apparatus. A fourth step of irradiating a laser beam under a third condition in which the energy distribution of the laser beam irradiation unit is ± 3% or less and the laser beam irradiation area is 30 cm ² or more;
A method for manufacturing a semiconductor device, comprising:

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