JP2004128261A - Method of manufacturing semiconductor thin film and thin-film transistor, electro-optical apparatus, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a single-crystal-like silicon film at a low process temperature, high throughput rate, and low cost. <P>SOLUTION: A 1st insulating layer, a light absorbing layer shaped in an island shape, and a 2nd insulating layer are provided on a semiconductor layer. Beams emitted from a plurality of linear lamp light sources having their peak wavelength in the vicinity of 1 μm are converged for scanning, thereby growing crystal of a semiconductor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor thin film and a thin film transistor formed on a single crystal semiconductor substrate or an insulator, and a logic circuit, a memory circuit, a liquid crystal display device, and a display pixel or a display device of an organic electroluminescence (EL) display device formed thereby. The present invention relates to a method for manufacturing a thin film transistor used as a component of a drive circuit and a method for manufacturing a solar cell formed over an insulator.
[0002]
[Prior art]
Conventionally, semiconductor thin films such as polycrystalline silicon (poly-Si) have been widely used for thin film transistors (TFTs) and solar cells. In particular, a poly-Si TFT has a high carrier mobility and can be manufactured on a transparent insulating substrate such as a glass substrate, so that a switching element such as a liquid crystal display device, a liquid crystal projector or an organic EL display device, or a liquid crystal device is used. It is widely used as a circuit element of a driving driver.
[0003]
As a method for manufacturing a high-performance TFT on a glass substrate, a manufacturing method called a high-temperature process has already been put to practical use. Among the TFT manufacturing processes, a process using a high temperature with a maximum temperature of about 1000 ° C. is generally called a high-temperature process. The features of the high-temperature process are that relatively high-quality polycrystalline silicon can be formed by solid phase growth of silicon, that a high-quality gate insulating layer can be obtained by thermal oxidation of silicon, and that polycrystalline silicon is clean. The point is that an interface between silicon and the gate insulating layer can be formed. Due to these characteristics, a high-performance TFT with high mobility and high reliability can be stably manufactured in a high-temperature process. However, in a high-temperature process, a long-time heat treatment of about 48 hours is required at a temperature of about 600 ° C. in order to crystallize a Si film by solid phase growth. This is a very long process, and in order to increase the throughput of the process, a large number of heat treatment furnaces are inevitably required, which makes it difficult to reduce the cost. In addition, since quartz glass must be used as an insulating substrate having high heat resistance, the cost of the substrate is high, and it is said that it is not suitable for increasing the area.
[0004]
On the other hand, a technique for lowering the process temperature and manufacturing a poly-Si TFT on an inexpensive large-area glass substrate is a technique called a low-temperature process. Among TFT manufacturing processes, a process of manufacturing a poly-Si TFT on a relatively inexpensive heat-resistant glass substrate in a temperature environment having a maximum temperature of approximately 600 ° C. or less is generally called a low-temperature process. In a low-temperature process, a laser crystallization technique for crystallizing a silicon film using a pulse laser having an extremely short oscillation time is widely used. Laser crystallization is a technique that utilizes the property that a silicon thin film on a substrate is instantaneously melted by irradiating a high-power pulsed laser beam and then crystallized in the process of solidification. Recently, a technique for producing a large-area poly-Si film by scanning while repeatedly irradiating an amorphous silicon film on a glass substrate with an excimer laser beam has been widely used. As a gate insulating layer, silicon dioxide (SiO 2) is formed by a film forming method using plasma CVD.₂) A film can be formed on a large area substrate. With these techniques, a poly-Si TFT can now be manufactured on a large glass substrate having a side of about several tens of centimeters.
[0005]
However, a problem with this low-temperature process is that when a semiconductor layer (poly-Si film) serving as an active layer is formed by laser crystallization, the crystal grain size is as small as 0.5 μm at most. Is that the threshold voltage of the TFT manufactured using the method is high and the mobility is low. In addition, the excimer laser crystallization method has a problem that irregularities having a height equivalent to 30 to 40% of the film thickness are generated on the surface of the crystallized poly-Si film. This occurs at crystal grain boundaries where crystals grown from crystal growth nuclei collide with each other. Since the thickness of the gate insulating film is effectively reduced at the protruding portion, the withstand voltage is reduced. This is a major problem particularly in a TFT having a thin gate insulating film. In addition, since the excimer laser widely used in the laser crystallization process is a gas laser, there is a problem that energy stability between pulses is low, and it is difficult to reduce variation in TFT elements. Furthermore, excimer lasers have a problem that the unit cost of the excimer laser is high, the running cost by replacing the laser tube (oscillator) is high, and the throughput is low, so that the manufacturing cost of the product cannot be reduced.
[0006]
As means for solving the above problems, there are the following conventional technologies.
[0007]
Patent Document 1 includes a step of depositing a semiconductor film on one main surface of an insulating plate, a step of depositing an insulating film on the semiconductor film, and a step of depositing a light absorbing layer on the insulating film. A technique is disclosed in which a semiconductor layer is crystallized by irradiating a laser from above the absorption layer and heating.
[0008]
In Patent Literature 2, an energy absorption layer is provided on a non-single-crystal semiconductor layer via a heat resistance layer, and the semiconductor layer is heated and melted via the heat resistance layer by heating the energy absorption layer by irradiation with energy rays. A single crystallization technique has been disclosed.
[0009]
In Patent Document 3, a semiconductor region made of a non-single-crystal semiconductor is provided on an insulating layer, a film covering at least the semiconductor region and the vicinity thereof is formed, and the film is irradiated with energy rays to heat the film. Accordingly, a technique for melting a non-single-crystal semiconductor in the semiconductor region to form a single crystal has been disclosed.
[0010]
In Patent Document 4, a step of providing an amorphous or polycrystalline compound semiconductor layer to be recrystallized on an insulating substrate, a step of providing a heating layer having a higher melting point than the compound semiconductor on this compound semiconductor layer, There is disclosed a method of manufacturing a semiconductor device in which a step of irradiating and absorbing the heating layer and conducting heat of the heating layer to heat and recrystallize the compound semiconductor layer is performed.
[0011]
In Patent Document 5, a sample in which a non-single-crystal semiconductor layer partially in contact with a single-crystal seed is provided on an insulating film, and the non-single-crystal semiconductor layer is covered with an energy ray absorbing layer provided via an isolation layer. The energy ray absorbing layer is irradiated with energy rays and heated, and the non-single-crystal semiconductor layer is melted by a heat flow using the energy ray as a heat source, and the non-single-crystal semiconductor layer is laterally epitaxially grown from the single-crystal seed. A method for manufacturing a semiconductor device, which includes a step of single-crystallizing a layer, is disclosed.
[0012]
In Patent Document 6, a first layer serving as a heat conductive layer is provided on an insulator substrate, a semiconductor island region to be monocrystallized is formed on the first layer, and then a semiconductor island region is formed. Forming a second layer covering the upper surface and side surfaces and contributing as an energy ray absorber, and irradiating energy rays from above the second layer to monocrystallize the semiconductor island region. The manufacturing method of the semiconductor device described above is disclosed.
[0013]
Patent Document 7 discloses a process in which a polycrystalline or amorphous semiconductor film is formed on a substrate whose surface is at least covered with an amorphous insulating layer, and at least two types of amorphous insulating films having different light absorption coefficients are formed on the substrate. A single crystal semiconductor, comprising: forming and irradiating the substrate with light having a wavelength component that can be absorbed by the semiconductor, and irradiating the substrate with an electron beam to melt and recrystallize the semiconductor film. A method for manufacturing a thin film is disclosed.
[0014]
In Patent Literature 8, a semiconductor layer to be annealed is formed on a substrate, and when forming a refractory metal film on the semiconductor layer, an intermediate layer is formed between the semiconductor layer and the refractory metal film. Forming an intermediate layer and a refractory metal film on a semiconductor layer, and then irradiating an energy beam for annealing the semiconductor layer from the refractory metal film side. Is disclosed.
[0015]
Patent Document 9 discloses a heat treatment method for a thin film in which a thin film is heat-treated by light irradiation. After forming a structure in which the thin film is laminated on a heating layer, the structure is substantially transparent to the thin film and the heating is performed. Irradiating the structure with a first light having a first wavelength absorbed by the layer, and then irradiating the structure with a second light having a second wavelength absorbed by the thin film. A heat treatment method for a thin film characterized by the above is disclosed.
[0016]
Patent Document 10 discloses a process of forming a light reflection film on an insulating substrate, a process of forming a buffer layer on the reflection film, a process of forming an amorphous silicon film on the buffer layer, There is disclosed a technique for forming a polycrystalline silicon film by irradiating a plurality of times with lamp light in a very short time to melt-crystallize the silicon film.
[0017]
By using the above technique, it is possible to form a poly-Si film having a crystal grain size of 1 μm or more even on an insulating substrate, so that the crystal grain boundaries in the active layer region of the TFT are dramatically increased. And the performance of the TFT can be improved as a result.
[0018]
[Patent Document 1]
JP-A-57-113217
[Patent Document 2]
JP-A-59-158515
[Patent Document 3]
JP-A-59-205712
[Patent Document 4]
JP-A-60-18913
[Patent Document 5]
JP-A-60-126815
[Patent Document 6]
JP-A-60-231319
[Patent Document 7]
JP-A-61-30025
[Patent Document 8]
JP-A-4-332120
[Patent Document 9]
JP-A-6-291034
[Patent Document 10]
JP-A-8-51076
[0019]
[Problems to be solved by the invention]
In the above-mentioned prior art, since the absorption efficiency of the light energy of the irradiation light source by the absorption layer was low, it was difficult to sufficiently raise the absorption layer temperature with light emitted from a low-cost light source such as a general-purpose halogen lamp. In addition, there is a problem that the conventional technique cannot be applied to the heat treatment of a poly-Si film formed on a large-area substrate. Further, since the positions of the crystal grain boundaries generated in the crystal growth are random, there is a serious problem that the characteristics of the active layer of the TFT vary depending on whether or not the crystal boundaries are present. The main cause of these problems is that the material suitable for the light absorbing layer, the film structure and the shape of the absorbing layer are unclear, and the crystal grain boundaries cannot be controlled during crystal growth. As a result, it has been impossible to form a high-quality poly-Si film having a large grain size on an inexpensive glass substrate and to control variation in TFT.
[0020]
In view of the above-described problems, the present invention discloses a technique for forming a poly-Si film in which the generation of crystal grain boundaries is controlled in a large area while using an inexpensive irradiation light source to improve the characteristics of poly-Si TFTs and circuits. It is an object of the present invention to provide a method for manufacturing a semiconductor thin film and a thin film transistor which realizes a reduction in variation, and a technique for providing an electro-optical device and an electronic apparatus using the same at low cost.
[0021]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method of manufacturing a semiconductor thin film of the present invention includes a step of forming a first insulating layer on a semiconductor layer formed on a substrate, and forming at least W, Ti, Cr on the first insulating layer. Forming a light-absorbing layer containing any of the materials Ta, Mo, patterning the light-absorbing layer into a plurality of island regions, a light source having an output peak wavelength in an infrared region, and the substrate Irradiating the light absorbing layer with irradiation light from the light source while relatively moving the semiconductor layer to crystallize the semiconductor layer. By using the material as the light absorbing layer, the light in the infrared region, which is the peak output of the halogen lamp, which is inexpensive and has a large output, is most efficiently absorbed, and the light is absorbed in the crystal growth region and the crystal grain boundary position. Since control can be performed by the shape of the layer, a high-quality poly-Si film can be formed over a large area.
[0022]
Preferably, the light irradiation is performed in an inert gas. Thus, the oxidation of the light absorbing layer can be prevented without increasing the number of steps of providing an insulating layer for preventing oxidation, and thus the steps are simple.
[0023]
Preferably, the shape of the island region of the light absorbing layer is a shape sandwiched by a pair of V-shaped oblique sides forming an angle of 15 ° to 75 ° on one side with respect to a direction in which the irradiation light moves relative to the substrate. It is performed in. Here, the angle on one side corresponds to the angle 406 shown in FIG. The generation of crystal grain boundaries can be controlled by the appropriate light absorbing layer shape.
[0024]
Preferably, the shape of the island region of the light absorbing layer has a region 1 having a first width with respect to a direction in which irradiation light moves relative to the substrate, and a second width larger than the first width. The region 1 and the region 2 are formed by connecting regions which are connected to each other by a diagonal line having an angle of 15 ° to 60 ° on one side in a direction in which the irradiation light moves relative to the substrate. Here, the angle on one side corresponds to the angle 415 shown in FIG. Even with this method, the generation of crystal grain boundaries and the plane orientation of the Si crystal can be controlled, so that a high quality Si film can be provided.
[0025]
In the method of manufacturing a thin film transistor according to the present invention, a semiconductor layer formed below the island region of the light absorbing layer is used as an active layer. According to such a method, a high-quality Si film region in which crystal grain boundaries are controlled can be selectively used as an active layer, so that a thin film transistor having high mobility can be provided with less variation.
[0026]
The electro-optical device of the present invention includes the thin film transistor manufactured by the above method as a driving element of a display pixel and a component of a peripheral circuit. This makes it possible to provide the LCD or the organic EL display device with a memory, a fingerprint sensor, and a circuit group having an arithmetic function, thereby providing a more sophisticated display device.
[0027]
An electronic apparatus according to an aspect of the invention includes the above-described electro-optical device. As such an electronic device, for example, a mobile phone, a video camera, a personal computer, a head-mounted display, a projector, a facsimile device, a digital camera, a portable television, a portable information terminal, an electronic organizer, a multifunctional card, and the like are suitable.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a semiconductor thin film manufacturing process according to the present invention.
[0029]
(1. Formation of semiconductor layer)
In order to carry out the present invention, a base protective film (101) is generally formed on a substrate (100), and a semiconductor thin film (102) is formed thereon. Therefore, a series of forming methods will be described.
[0030]
The substrate (100) to which the present invention can be applied includes a conductive material such as a metal, silicon carbide (SiC), and alumina (Al).₂O₃), A ceramic material such as aluminum nitride (AlN), a transparent or non-transparent insulating material such as fused quartz or glass, a semiconductor material such as a silicon or germanium wafer, and an LSI substrate obtained by processing the same. The semiconductor film is deposited directly on the substrate or via a base protective film, a lower electrode, and the like.
[0031]
As a base protective film (101), a silicon oxide film (SiO_X: 0 <x ≦ 2) or a silicon nitride film (Si₃N_x: 0 <x ≦ 4). When it is important to control impurities in a semiconductor film such as when a thin-film semiconductor device such as a TFT is formed on a normal glass substrate, sodium (Na), potassium (K), etc. contained in the glass substrate are required. It is preferable to deposit the semiconductor film after forming the base protective film so that mobile ions do not enter the semiconductor film. In the case where a conductive material such as a metal material is used as the substrate and the semiconductor film must be electrically insulated from the metal substrate, a base protective film is indispensable to ensure insulation. Further, when a semiconductor film is formed on a semiconductor substrate or an LSI element, an interlayer insulating film between transistors and between wirings is also a base protective film.
[0032]
The undercoat protective film is first washed with an organic solvent such as pure water or alcohol, and then is deposited on the substrate by atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), or plasma chemical vapor deposition. It is formed by a CVD method such as a deposition method (PECVD method) or a sputtering method. (4) When a silicon oxide film is used as the underlayer protective film, the atmospheric pressure chemical vapor deposition method uses a monosilane (SiH₄) Or oxygen as a raw material. In the plasma chemical vapor deposition method and the sputtering method, the substrate temperature is from room temperature to about 400 ° C. The thickness of the base protective film must be sufficient to prevent diffusion and mixing of the impurity element from the substrate, and the value is at least about 100 nm or more. Considering the variation between lots and substrates, it is preferably about 200 nm or more, and if it is about 300 nm, it can sufficiently function as a protective film. When the underlying protective film also serves as an interlayer insulating film between IC elements and wiring connecting them, the thickness is usually about 400 nm to 600 nm. If the insulating film is too thick, cracks occur due to the stress of the insulating film. Therefore, the maximum thickness is preferably about 2 μm. When it is strongly necessary to consider productivity, the upper limit of the insulating film thickness is about 1 μm.
[0033]
Next, the semiconductor thin film (102) will be described. As a semiconductor film to which the present invention is applied, in addition to a semiconductor film of a group 4 element such as silicon (Si) and germanium (Ge), silicon germanium (Si)_xGe_1-x: 0 <x <1) or silicon carbide (Si_xC_1-x: 0 <x <1) or germanium carbide (Ge_xC_1-x: A semiconductor film of a group 4 element complex such as 0 <x <1), a compound semiconductor film of a group 3 element such as gallium arsenide (GaAs) or indium antimony (InSb) and a group 5 element, or cadmium. -There is a composite compound semiconductor film of a group II element such as selenium (CdSe) and a group VI element. Alternatively, silicon, germanium, gallium, arsenic (Si_xGe_yGa_zAs_z: X + y + z = 1), an N-type semiconductor film in which a donor element such as phosphorus (P), arsenic (As), antimony (Sb) is added to these compound semiconductor films, or boron (B). The present invention is also applicable to a P-type semiconductor film to which an acceptor element such as), aluminum (Al), gallium (Ga), and indium (In) is added. These semiconductor thin films are formed by a CVD method such as an APCVD method, an LPCVD method, or a PECVD method, or a PVD method such as a sputtering method or an evaporation method. In the case where a silicon film is used as a semiconductor film, in the LPCVD method, the substrate temperature is set to about 400 ° C. to about 700 ° C. and disilane (Si₂H₆) Can be deposited as a raw material. In the PECVD method, monosilane (SiH₄) Can be deposited at a substrate temperature of about 100 ° C. to about 500 ° C. When using the sputter method, the substrate temperature is from room temperature to about 400 ° C. The initial state (as-deposited state) of the semiconductor film thus deposited includes various states such as amorphous, mixed crystal, microcrystalline, and polycrystalline. In the present invention, the initial state is any one. It may be in the state. In the specification of the present application, not only amorphous crystallization but also polycrystalline or microcrystalline recrystallization is referred to as crystallization. When the semiconductor film is used for a TFT, the thickness is suitably about 20 nm to about 100 nm.
[0034]
(2. Formation of first insulating layer)
Next, a first insulating layer (103) is formed on the semiconductor layer. The role of this insulating layer is to separate the light absorbing layer (104) and the semiconductor layer (102) formed in the next step. In order to prevent diffusion of impurities from the light absorbing layer to the semiconductor layer in a later heat treatment step, a silicon oxide film (SiO_X: 0 <x ≦ 2) or a silicon nitride film (Si₃N_x: 0 <x ≦ 4). The first insulating layer is formed by etching a natural oxide film on the semiconductor layer with hydrofluoric acid, washing with pure water, and then performing a CVD method such as an APCVD method, an LPCVD method, a PECVD method, or a sputtering method. When a silicon oxide film is used as the insulating layer, the substrate temperature is set to about 250 ° C. to about 450 ° C. in the atmospheric pressure chemical vapor deposition method.₄And oxygen can be deposited as a raw material. In the PECVD method and the sputtering method, the substrate temperature is from room temperature to about 400 ° C. The thickness of the first insulating layer must be large enough to prevent the diffusion and mixing of the impurity element from the light absorbing layer, while the heat insulating layer from the light absorbing layer can efficiently conduct heat to the semiconductor layer. Is a condition. For this reason, there is naturally an optimum range for the thickness of the insulating layer, and its value is at least about 50 nm and at most about 1 μm, which is about the same as the thermal diffusion length.
[0035]
(3. Formation of light absorption layer)
Next, a light absorption layer (104) is formed on the first insulating layer (103). The light absorbing layer has a role of efficiently absorbing the light irradiated in the next step, and raising the temperature of the semiconductor layer to a high temperature by heat generation and heat conduction. Therefore, the relationship between the wavelength region of the irradiated light, the reflectance and the absorption coefficient in that wavelength region, and the heat resistance are important. A refractory metal material is suitable for such a purpose. Since a high concentration of free carriers (electrons) exists in the metal, the components other than the reflection component of the irradiation light are completely absorbed. For this reason, it is important to use a high melting point metal thin film having a low reflectance in order to efficiently absorb light by the metal thin film. FIG. 2 shows reflectance spectra of various refractory metal films. As will be described later, in the present invention, a halogen lamp which is relatively inexpensive and provides high output is used as a light source for light irradiation. Suitable as. As can be seen from FIG. 2, the reflectance at the same wavelength gradually decreases in the order of Ta, Mo, Cr, Ti, and W. In addition to such optical properties, the light absorbing layer is required to be a material that does not generate cracks due to heat treatment. Therefore, it is effective to use an alloy (for example, silicide) containing at least the above-mentioned Ta, Mo, Cr, Ti, and W, or to form a laminated structure of these metals and metal alloys.
[0036]
The thickness of the absorbing layer is preferably thinner in order to reduce the tact time in the manufacturing process, but a minimum thickness that can sufficiently absorb the irradiation light is required. FIG. 3 shows the dependency of the reflectance on the film thickness at a wavelength of 1 μm when Cr and W are used for the absorption layer. In both materials, when the film thickness is 50 nm or less, the reflectance is extremely small. This is because the film is too thin to absorb the irradiation light and generate a transmission component. At a film thickness of 50 to 100 nm, the reflectance increases due to the interference effect between light reflected from the film lower surface and light reflected from the film surface. As can be seen from the above, it is important that the light absorbing layer has a thickness of 100 nm or more, more preferably 150 nm or more, in order to sufficiently absorb the irradiation light and realize a stable reflectance.
[0037]
As a method for forming these materials as a light absorbing layer on an insulating layer, there are a vacuum evaporation method and a sputtering method. Since these materials are high melting point metals, sputtering is most effective, and the sputtering method is also advantageous in that a film can be formed over a large area at high speed.
[0038]
Next, the light absorbing layer thus formed is shaped into an island region (104) having a desired shape. This is performed for the purpose of controlling a place that becomes a starting point of crystal growth during crystal growth accompanying light irradiation. As its shape, for example, it is effective to pattern it into the shape of a light absorbing layer as shown in FIG. If the light absorbing layer is not shaped into an island region, a crystal grain boundary runs at an arbitrary position when the semiconductor layer is crystallized. Therefore, if such a poly-Si film is used as an active layer of a TFT, there is a certain probability. A TFT without a crystal grain boundary and a certain TFT are formed, and this causes variation. By shaping the light absorbing layer of the present invention, the poly-Si film under the light absorbing layer becomes almost single crystal, and a region (109) having no crystal grain boundary can be formed. In addition, the plane orientation of the Si crystal can be controlled. Although the poly-Si film under the light absorption layer has no crystal grain boundaries, the peripheral region has a small crystal grain size and has many crystal grain boundaries. A portion of the formed monocrystalline poly-Si film is used. This makes it possible to manufacture a high-performance TFT with good controllability.
[0039]
(4. Formation of second insulating layer)
A second insulating layer (105) is formed on the light absorbing layer thus formed. This second insulating layer has two important roles.
[0040]
One is to prevent the light absorbing layer from being oxidized due to an increase in the temperature of the absorbing layer due to light irradiation. The light irradiation easily raises the temperature of the absorption layer to 1000 ° C. or higher. When this treatment is performed in the air, oxygen in the air reacts with the metal of the light absorption layer to form an oxide. Since the metal oxide becomes optically transparent, the light absorption efficiency of the light absorbing layer is significantly reduced during processing, and the temperature of the semiconductor layer cannot be increased or the reproducibility of the processing cannot be secured. Cause problems. By providing the second insulating layer, the atmosphere and the light absorbing layer can be shut off, so that the problem of oxidation of the light absorbing layer during such processing can be completely prevented. When the second insulating layer is not provided, it is effective to perform the light irradiation treatment in an inert gas atmosphere. This method has an advantage that oxidation of the light absorbing layer can be prevented without increasing the number of steps for forming the second insulating layer.
[0041]
Another role of the two insulating layers is to reduce the reflectance of the light absorbing layer by an anti-reflection film effect. In FIG. 4, Cr and W are used for the light absorbing layer, and SiO 2 is used as the second insulating layer.₂4 shows the dependency of the reflectance of light having a wavelength of 1 μm on the thickness of the second insulating layer when a film (n = 1.47) is used. Since the light absorption layer suitable for the present invention is a metal film, the refractive index difference from air is large. Therefore, in order to reduce the reflectance by the light absorbing layer, it is extremely effective to provide a layer having a refractive index (n) closer to air than a metal film. Since the antireflection film lowers the reflectance by the interference effect, the reflectance periodically changes depending on the thickness of the second insulating layer on the light absorbing layer as can be seen from FIG. Of course, there are several film thicknesses that can function as an anti-reflection film, but a minimum film thickness with a short film formation time is most preferable for shortening the process tact. Although it depends on what is used as the material of the second insulating film, a film thickness of approximately 50 to 250 nm is preferable as such a condition. Thus, for example, when W is used as the light absorbing material, 140 to 150 nm SiO 2 is used as the second insulating layer.₂If a film is formed, the reflectance can be drastically reduced from 48% to less than 20%, which is extremely effective in efficiently absorbing irradiation light to the light absorbing layer.
[0042]
(5. Light irradiation)
Light irradiation is performed on the laminated structure formed as described above. As described above, since the irradiation light is required to be efficiently absorbed by the light absorbing layer, its spectrum is important. In other words, what kind of light source is used largely determines the wavelength of the light source. The light source applicable to the present invention includes a halogen lamp, a metal halide lamp, a mercury lamp, a Xe lamp, an arc lamp, and the like. In order to enable processing in a large area, it is required that the lamp output be high and the running cost due to lamp replacement be low. For these reasons, a halogen lamp is most suitable as the light source of the present invention. Although there are various types of halogen lamps, they have a peak wavelength near 1 μm and can easily achieve an output of 8 kW or more. The cost of one linear lamp light source having an effective light source length of 400 mm is at most about 100,000 yen, which is extremely low as compared with an excimer laser tube of 15 million yen.
[0043]
In the present invention, for example, two linear halogen lamps (111) having a length of 400 mm are arranged in parallel, and light emitted from each light source is condensed on a substrate to be processed by a reflecting mirror (112) having a paraboloid. 106) is used. FIG. 1 schematically shows a cross-sectional structure of the lamp unit (110). The paraboloid (112) is coated with gold, and light from the two halogen lamp light sources (111) is efficiently focused on the same location on the substrate as shown in the figure. At this time, the arrangement is such that the center (111) of the linear light source is located at one focal position on the paraboloid (112), and the other focal position is the light-converging point (116) on the light absorbing layer. Therefore, the elliptical surfaces of the reflection optical systems of the two lamp light sources are arranged such that one focal point is shared by the light condensing points (116) on the light absorbing layer. Thus, light generated from a plurality of light sources can be most efficiently collected.
[0044]
It is necessary to adjust the relative position between the reflecting optical system of the present invention and the light source on the order of 10 μm. For this purpose, it is effective to provide a biaxially movable micrometer at the support portions at both ends of the linear light source for adjustment. If the central position of each linear light source and the elliptical surface of the reflection optical system have an ideal positional relationship, the short axis direction of the irradiation light condensed on the light absorption layer has a Gaussian distribution as shown by 510 in FIG. Show the distribution. If this shifts by several tens of μm, the distribution has two peaks, and light irradiation is performed on a region wider than the original light irradiation conditions. This results in an increase in the substrate temperature, which is a problem in applying the present invention to a low-temperature process. Therefore, as described above, it is important to perform fine adjustment using a micrometer and perform light irradiation using an ideal irradiation light distribution. Particularly, in the case of a halogen lamp or the like, when the lamp input power is increased, the effective lamp center point slightly shifts. Therefore, it is practically important to adjust the lamp position in this state.
[0045]
In this example, a case where two linear light sources are used is shown, but the optical arrangement as described above can be applied to a case where three or more linear light sources are condensed. However, when the number of light sources increases, the oblique direction component of the light incident on the light absorption layer increases and the reflectivity increases, and the use efficiency of the light emitted from each light source decreases because the restriction on the arrangement of the reflection optical system increases, In practice, two light sources have the highest light use efficiency.
[0046]
Further, it is effective to provide a light shielding slit (115) in order to block the light irradiated on the substrate other than the light condensing portion. In order to apply the present invention to a low-temperature process, it is important how light is condensed in a narrow area on the light absorption layer to form a high-power light irradiation area, as described later. Irradiation of the leaked light to the other regions may cause the substrate temperature to be inadvertently increased, so that not only the light absorbing layer / semiconductor layer but also the substrate temperature is increased during the light irradiation. To prevent this, it is effective to provide a slit between the reflecting optical system and the light absorbing layer to completely block the leaked light.
[0047]
As described above, the substrate and the lamp unit are moved relative to each other as indicated by 114, and the processing is performed while continuously irradiating the lamp light on the substrate in a very thin linear shape. As a result, the temperature rises abruptly at the lamp light converging portion (107) of the light absorbing layer, and the heat diffused through the first insulating layer locally raises the temperature of the semiconductor layer (108). By appropriately selecting the irradiation conditions, the temperature of the portion to be processed 108 of the semiconductor layer reaches the melting point or higher and is melted. Since the melted portion 108 moves in the direction of 114 along with the movement of the lamp unit, large grain size poly-Si (109) crystallized by continuous lateral crystal growth in the cooling process after melting is formed behind the melted portion 108. Is done. Thus, a high quality poly-Si film can be easily provided at low cost.
[0048]
The lamp unit of the present invention has a radiation thermometer (113) at an intermediate position between the two halogen lamps, and has a cylindrical collimator or lens on the front surface so that the measurement range is not widened. Measuring the substrate temperature at this position has the advantage that the problem that infrared light emitted from the lamp light source directly enters the radiation thermometer and exhibits an abnormally high temperature can be avoided, and the substrate temperature can be accurately measured. . Thus, by measuring the temperature of the substrate to be processed and applying feedback to the lamp output, a stable lamp irradiation process can be performed, and there is an advantage that the quality of the resulting poly-Si film can be stabilized.
[0049]
The above-mentioned reflection optical system is formed in a cylindrical shape in the major axis direction of the halogen lamp, and as a result, a large area processing can be performed by irradiating light having a line shape as shown in FIG. . FIG. 5 shows a state in which scanning (505) is performed while irradiating the substrate (100) with the linear irradiation light (500). As described above, a 400-mm line light source can be easily formed with a halogen lamp. For example, a large-sized substrate having a size of 400 mm × 500 mm may be formed once with a 400 mm side parallel to the long axis direction of the halogen lamp. By performing scanning, a high-quality poly-Si film having a large grain size can be formed on the large-area substrate. For example, when processing is performed while moving the lamp unit at a speed of 10 mm / s, the processing of the entire surface of the substrate is completed in only 50 seconds. Therefore, the method for manufacturing a semiconductor thin film of the present invention not only reduces the manufacturing apparatus cost, but also reduces the process cost. Since the throughput is high, an inexpensive and high-performance thin film transistor can be provided.
[0050]
Next, specific lamp irradiation conditions will be described. When the lamp light is condensed and irradiated on the substrate as shown in FIG. 5, the intensity distribution of the lamp light on the substrate (light absorbing layer) (503) typically has a Gaussian distribution shape as shown by 501. It becomes. The irradiation light shape suitable for the present invention has a half width of this spatial distribution of about 1 to 10 mm. When the irradiation light is scanned over the substrate at a constant speed, the temporal change of the light power applied to an arbitrary point (e.g., 504) on the substrate becomes an irradiation profile like 511 at a high scanning speed, and conversely. If it is slow, an irradiation profile like 512 is obtained. In the light irradiation of the present invention, the peak power of the irradiation profile and the irradiation time (the full width at half maximum of the irradiation profile is defined as the irradiation time in this specification) are important. For example, FIG. 6 shows the irradiation peak power of 500 W / cm.²And temperature changes at the light absorbing layer / semiconductor layer and each substrate depth position when light irradiation is performed under the irradiation time of 600 ms. Here, a case is shown in which the irradiation light profile is substituted by using a trapezoidal shape having a shape close to a Gaussian distribution, the light absorption layer is W, and the effective reflectance is 25% by providing a second insulating layer. In the time order as considered here, the thicknesses of the light absorption layer and the semiconductor layer are sufficiently smaller than the thermal diffusion length, so that the temperatures of these two layers are exactly the same. As can be seen from FIG. 6, the temperature of the light absorbing layer / semiconductor layer sharply rises locally by the light irradiation of the present invention and reaches a maximum of about 1780 K, so that the Si film is melted. When the irradiation light passes and the temperature decreases, the Si film crystallizes simultaneously with solidification. Under these light irradiation conditions, since the irradiation time is relatively long, the substrate temperature also increases, and eventually reaches about 1200K. Therefore, the irradiation conditions shown in FIG. 6 are appropriate when a heat-resistant substrate such as quartz is used as the substrate. In order to locally increase the temperature of only the light absorption layer and the semiconductor layer without increasing the substrate temperature, it is necessary to irradiate a high power in a shorter time. As is apparent from the above description, this can be realized by reducing the half width of the irradiation light in the spatial distribution (focusing) or increasing the scan speed and simultaneously increasing the lamp output. For example, as shown in FIG.²Assuming that the irradiation time is 300 ms, the substrate temperature eventually rises only to about 900 K even though the temperature of the light absorption layer / semiconductor layer reaches 1750 K. This is because the light-absorbing layer / semiconductor layer near the surface of the substrate is heat-treated in a non-thermal equilibrium because the light irradiation condition has a higher power for a shorter time. As described above, the method for manufacturing a semiconductor thin film of the present invention can be easily applied to a low-temperature process by controlling a light irradiation profile.
[0051]
In addition, in the method of manufacturing a semiconductor thin film according to the present invention, the crystal growth direction is the horizontal direction, and the semiconductor layer is sandwiched between the insulating layers on the upper and lower sides. Therefore, the surface of the semiconductor layer after crystallization is extremely flat. Since this does not lower the withstand voltage even when a thin-film transistor having a thin gate insulating film is formed, it can be applied to a finer TFT and a TFT having a thinner gate insulating film. There is an advantage that a higher-speed circuit can be formed than when a poly-Si film is used. The TFT manufactured using the poly-Si film manufactured in this manner has a feature that the mobility is extremely small because the plane orientation is uniform, and the threshold voltage is low because the defect density is low.
[0052]
According to the method for forming a semiconductor thin film of the present invention, since the power of the irradiation light source is a high power of the order of kW and the heat treatment time is of the order of milliseconds, crystallization is possible even if the thickness of the semiconductor layer to be processed exceeds 100 nm. . In the conventional laser crystallization method, the irradiation time of one pulse is as short as nanoseconds, and the input energy density is 1 cm.²Since 1J is a practical upper limit, it was theoretically impossible to crystallize a semiconductor layer having a thickness of 100 nm or more. On the other hand, the method for forming a semiconductor thin film of the present invention can sufficiently crystallize even a semiconductor layer having a thickness of about 1 micron, and thus can be applied to the formation of a polycrystalline silicon film used for solar cells. Have.
[0053]
In order to apply the method for producing a semiconductor thin film of the present invention to a low-temperature process, it is effective to set the initial substrate temperature to room temperature or to cool the substrate during processing. If the substrate is cooled, a rise in the substrate temperature can be prevented even if a light irradiation profile as shown in FIG. As a method of cooling the substrate, a method of cooling by spraying a gas to the substrate, or a structure in which the substrate is completely adhered to the substrate holder with an electrostatic chuck and cooling water is circulated through the substrate holder to take heat of the substrate. The method is effective.
[0054]
Although the conditions for melting and crystallizing the semiconductor layer have been described above, the method for manufacturing a semiconductor thin film of the present invention can crystallize the semiconductor layer without necessarily melting it. In the conventional solid phase growth method, heat treatment was performed at 600 ° C. for about 48 hours. However, in the method for manufacturing a semiconductor thin film of the present invention, the temperature of the semiconductor layer easily reached 1000 ° C. or more. However, solid phase growth occurs. For example, irradiation peak power 400 W / cm²An irradiation time of 1 second is an example of an irradiation profile that causes such solid phase growth. Although a crystal having a large grain size as in the case of melting and crystallization cannot be obtained, a poly-Si film having a crystal grain size of 1 μm or more and a flat surface can be easily obtained. However, in this case, since the substrate temperature is also high, application to a high-temperature process is appropriate.
[0055]
Embodiment 1
An embodiment of the method for producing a semiconductor thin film according to the present invention will be described with reference to FIGS. 1 and 12 (a). The substrate and the underlying protective film used in the present invention are in accordance with the above description, but here, a 300 mm × 300 mm square general-purpose alkali-free glass (100) is used as an example of the substrate. First, a base protective film (101), which is an insulating material, is formed on a substrate 100. Here, a silicon oxide film having a thickness of about 200 nm is deposited by an ECR-PECVD method at a substrate temperature of 150 ° C. Next, a semiconductor film (102), such as an intrinsic silicon film, to be an active layer of the thin film transistor later is deposited. The thickness of the semiconductor layer is about 50 nm. In this example, a high-vacuum type LPCVD apparatus is used, and disilane (Si₂H₆) Is flowed at 200 SCCM, and an amorphous silicon film 102 is deposited at a deposition temperature of 425 ° C. First, a plurality of (eg, 17) substrates are placed inside a reaction chamber of a high vacuum LPCVD apparatus with the reaction chamber at 250 ° C., with the front side facing downward. After this, the operation of the turbo-molecular pump is started. After the turbo-molecular pump has reached steady rotation, the temperature in the reaction chamber is raised from 250 ° C. to a deposition temperature of 425 ° C. over about one hour. During the first 10 minutes after the start of the temperature rise, the temperature is raised in a vacuum without introducing any gas into the reaction chamber. Thereafter, nitrogen gas having a purity of 99.9999% or more is continuously supplied at 300 SCCM. The equilibrium pressure in the reaction chamber at this time was 3.0 × 10^-3Torr. After reaching the deposition temperature, disilane (Si₂H₆) At 200 SCCM and helium (He) for dilution having a purity of 99.9999% or more at 1000 SCCM. The pressure in the reaction chamber immediately after the start of the deposition is about 0.85 Torr. As the deposition proceeds, the pressure in the reaction chamber gradually increases, and the pressure immediately before the end of the deposition becomes approximately 1.25 Torr. The silicon film (102) thus deposited has a thickness variation within ± 5% within a 286 mm square area excluding the peripheral portion of about 7 mm of the substrate. Next, a first insulating layer (103) is formed. Here, SiO having a thickness of about 100 nm by ECR-PECVD is used.₂The film was deposited. SiH as source gas₄And O₂Were flowed at 30 sccm and 40 sccm, respectively, and plasma discharge was started while the substrate was heated to 100 ° C. to form a film. Next, a Ta film was formed to a thickness of 800 nm as a light absorbing layer (104) by sputtering. Irradiation light could be stably absorbed by forming Ta with this thickness, and the temperature of the light absorbing layer during processing was extremely stable because cracks did not occur. Next, island patterning of the light absorbing layer was performed. In this example, the light absorbing layer was patterned into a shape sandwiched between the V-shaped sides shown in FIG. The island region (400) was formed such that the angle (406) between the apex portion and the light scanning direction (409) was 45 degrees.
[0056]
Next, on the light absorbing layer, SiO 2 is used as a second insulating layer (105).₂A film was formed at 145 nm. This was formed under exactly the same conditions as the first insulating layer. Ta is used as a light absorbing material, and 145 nm SiO 2 is used as a second insulating layer.₂Since the film was formed, the effective reflectance could be reduced to about 50%. Thereafter, two halogen lamps each having a diameter of 6 mm and a length of 400 mm having an intensity peak near 1 μm are arranged in parallel, and the light is converted to a long axis of 300 mm by using a lamp unit capable of disposing a reflection optical system having an elliptical surface on the back. (Effective length for obtaining uniformity), shaped into a line with a short axis of 5.5 mm, and a power density of 950 W / cm²Irradiated from the light absorbing layer side. The lamp unit was made of aluminum, and the reflecting surface was plated with gold. Adjust the relative position of the light source and the optical system with a micrometer while applying power equivalent to the processing conditions to the lamp linear light source before processing, so that the distribution at the focusing position is close to a Gaussian distribution having a single peak. did. In order to suppress a rise in the substrate temperature, the substrate was scanned in the short-axis direction of the irradiation light at a speed of 36 mm per second. The light irradiation time at an arbitrary point is 150 ms. The temperature of the light absorbing layer or the second insulating layer during the processing was monitored by a radiation thermometer (113), and the power supplied to the lamp light source was fed back so that the temperature was stabilized. A molten silicon layer (108) is formed behind the irradiation light, and continuous lateral crystal growth occurs at the solid-liquid interface (boundary between 108 and 109) with the movement of the substrate. A layer (109) was formed. As described above, the light-absorbing layer is formed in the shape of FIG. 12A, and the linear lamp light has the positional relationship of 410 in FIG. Scanning was performed in the direction. As a result, the Si film immediately below the light absorbing layer is melted, but the crystal growth after the passage of the lamp light always occurs from the apex (405) as a starting point. As a result, the Si under the island-shaped light absorbing layer becomes V-shaped. This results in a single crystal thin film. Since the boundary region (407, 408) of the light absorbing layer region is polycrystalline, the TFT is formed only on the Si film portion under the light absorbing layer. Therefore, the island region (400) is formed to have at least the necessary circuit block. By such a method, a poly-Si film in which many portions are formed of a single-crystal Si film can be formed. FIG. 8 shows a temperature change at each depth of the light absorption layer / semiconductor layer and the substrate in the irradiation profile. In the method of manufacturing a semiconductor thin film according to the present invention, the substrate temperature rises only up to about 400 ° C., and conventional alkali-free glass can be cut off sufficiently. In this embodiment, the irradiation profile (irradiation peak power 700 W / cm) shown in FIG.², Irradiation time of 300 ms) is sufficiently applicable. Since the thermal effect is small in the irradiation profile of FIG. 8, the method for manufacturing a semiconductor thin film of the present invention was applicable to a thin glass substrate having a thickness of 0.5 mm. By the above light irradiation method, a Si film close to a single crystal could be easily formed by a low-temperature process.
[0057]
Embodiment 2
A second embodiment of the present invention will be described with reference to FIG. The method of forming the underlying protective film, the semiconductor layer, the first insulating layer, and the second insulating layer is exactly the same as in the first embodiment. As the light absorbing layer, one formed in an island region having the shape shown in FIG. 12B was used. In FIG. 12A, since the island region is interrupted in the scanning direction (409) of the irradiation light, it is difficult to control the uniformity of the plane orientation of the Si crystal formed thereby. On the other hand, in the pattern of this example, since the island regions are connected in the scanning direction of the irradiation light, it is possible to make the plane orientations of the crystals uniform. When the crystal growth distance increases with the scanning of the irradiation light, the plane orientation of the crystal may be gradually inclined, or crystal growth with another plane orientation may start suddenly. In order to prevent this, the island pattern of the present example is composed of a thin area 1 (411), a thick area 2 (412), and a connection area (413) connecting them. As described above, if the region 2 is long, the uniformity of the crystal is impaired, so that a preferential crystal growth surface is selectively grown in the narrow region 1, and this is formed through the connection region 413 to have a larger area. The area is expanded to the area 2 (412). As a result, as the region 2, a single crystal having a well-oriented crystal plane could be obtained. The light irradiation conditions are exactly the same as in the example. As a result, a higher quality Si film than in Example 1 could be obtained. When the semiconductor thin film of the present invention is applied to a TFT, a first insulating layer, a light absorbing layer, and a second insulating layer are formed on the semiconductor layer, and after irradiating light, these three layers are removed by etching to form the semiconductor layer as an active layer. Use as In this case, of course, a TFT is manufactured in a region below the light absorption layer where a high-quality Si crystal is formed.
[0058]
Embodiment 3
In the third embodiment of the present invention, a semiconductor thin film was manufactured under different light irradiation conditions. The method of forming the substrate to be processed is exactly the same as that of Example 2 except that a plastic substrate having relatively high heat resistance was used as the substrate. Thereafter, the halogen lamp light having an intensity peak near 1 μm is shaped into a long line having a length of 300 mm and a short axis of 1 mm, and a power density of 1800 W / cm.²Irradiated from the light absorbing layer side. In order to suppress a rise in the substrate temperature, the substrate was scanned in the short-axis direction of the irradiation light at a speed of 23 mm per second. The light irradiation time at an arbitrary point is 44 ms. FIG. 9 shows a temperature change at each depth of the light absorption layer / semiconductor layer and the substrate due to the irradiation profile. As a result, the temperature rise of the substrate can be further reduced, and only rises up to 220 ° C. In addition, a single-crystal Si region formed under the light absorption layer can be of the same quality as that of the second embodiment. In this example, it was confirmed that the method for manufacturing a semiconductor thin film of the present invention can be applied even when a plastic substrate is used.
[0059]
Embodiment 4
An embodiment of the method for manufacturing a thin film transistor according to the present invention will be described with reference to FIG. The structure of the sample used in the present embodiment may be either the structure of the embodiment 1 or 2, but the structure of the embodiment 2 is used here. Light irradiation is performed by shaping a halogen lamp having an intensity peak near 1 μm into a long line having a length of 300 mm and a short axis of 5.5 mm, and a power density of 700 W / cm.²Irradiated from the light absorbing layer side at a moving speed of 18 mm per second. Thus, a single-crystal Si film was formed immediately below the island-shaped light absorbing layer region. In this embodiment, the second insulating layer, the light absorbing layer and the first insulating layer were removed by etching in order to use the thus formed single crystal Si film as an active layer. SiO₂The film was etched with a 5% HF solution, and the light absorbing layer W was removed by dry etching using radicals generated by plasma discharge of a chlorine-based gas. The substrate on which the Si film 901 is exposed is set in the plasma processing chamber. In the plasma processing chamber, the substrate temperature was set to 250 ° C., hydrogen gas was flowed at 80 sccm, and plasma discharge was performed at a pressure of 1 Torr and a power of 1 kW using a parallel plate RF electrode. As a result, the trap level (defect) passivation treatment of the Si film and the hydrogen termination treatment of the surface were performed for 160 seconds. As described above, the Si film obtained in this example is a single crystal, but some defects such as dislocations and point defects have occurred. Therefore, it is necessary to inactivate these by plasma treatment in this step. It is aim. Thereafter, a photoresist pattern is formed by photolithography on the Si film region formed under the light absorbing layer, and CF is formed.₄And O₂Dry etching by remote plasma discharge using a mixed gas was performed. The substrate is set in an insulating film forming chamber to form a gate insulating film (902) on the Si film patterned in an island shape. 10 in the chamber^-6(Torr), the chamber was evacuated to a vacuum degree, silane gas and oxygen gas were introduced at a flow ratio of 1: 6, and the chamber pressure was set to 2 × 10^{− 3}(Torr). When the gas pressure in the chamber is stabilized, the ECR discharge is started, and the formation of the insulating film is started. The inputted microwave power was 1 kW, and the microwave was introduced from the introduction window in parallel with the magnetic force lines. There is an ECR point at a position 14 cm from the introduction window. The film was formed at a film formation rate of 10 nm / min. As a result, a gate insulating film (902) was formed to a thickness of 100 nm. Subsequently, a thin film to be a gate electrode (905) is deposited by a PVD method or a CVD method. Normally, since the gate electrode and the gate wiring are made of the same material in the same process, it is desired that this material has low electric resistance and is stable to a heat process at about 350 ° C. In this example, a tantalum thin film having a thickness of 600 nm is formed by a sputtering method. The substrate temperature when forming the tantalum thin film is 180 ° C., and an argon gas containing 6.7% of a nitrogen gas is used as a sputtering gas. The tantalum thin film thus formed has an α-structure crystal structure, and its specific resistance is about 40 μΩcm. After depositing a thin film to be a gate electrode, patterning is performed, and then impurity ions are implanted into the semiconductor film to form source / drain regions (903, 904) and a channel region. At this time, since the gate electrode serves as a mask for ion implantation, the channel has a self-aligned structure formed only under the gate electrode. As a source gas for the ion doping method, phosphine (PH) having a concentration of about 0.1% to about 10% diluted in hydrogen is used.₃) And diborane (B₂H₆) And the like are used. In this example, a 5% concentration phosphine (PH) diluted in hydrogen is used by using an ion doping apparatus with the aim of forming an NMOS.₃) Is injected at an acceleration voltage of 100 keV. Total ion implantation amount including PH3 + and H2 + ions is 1 × 10¹⁶cm^-2It is.
[0060]
Next, an interlayer insulating film was formed by using the PECVD method. The source gas is TEOS (tetraethoxysilane), N₂Electric discharge was performed using O and Ar gases at a pressure of 1.5 Torr and a power of 1 kW to form an 800 nm interlayer insulating film. Next, a contact hole is formed on the source / drain, and a source / drain extraction electrode (907, 908) and a wiring are formed of aluminum by a PVD method, a CVD method, or the like, thereby completing a thin film transistor. As a result, a high-performance TFT having almost the same performance as that of a single-crystal Si MOSFET could be manufactured with extremely uniformity.
[0061]
The thin film transistor obtained by the manufacturing method of the present invention is applicable to various electronic devices including an electro-optical device. FIG. 11 illustrates an example of an electronic device to which the electro-optical device can be applied. FIG. 9A shows an example of application to a mobile phone. A mobile phone 230 includes an antenna unit 231, an audio output unit 232, an audio input unit 233, an operation unit 234, and the electro-optical device 10 of the present invention. . Thus, the electro-optical device 10 of the present invention can be used as a display unit of the mobile phone 230. FIG. 8B shows an example of application to a video camera. The video camera 240 includes an image receiving unit 241, an operation unit 242, and the electro-optical device 10 of the present invention. As described above, the electro-optical device according to the invention can be used as a finder or a display unit. In addition, the present invention can be applied to portable personal computers, head mounted displays, rear projectors, and front projectors. As described above, the electro-optical device of the present invention can be used as an image display source.
[0062]
The electro-optical device 10 of the present invention is not limited to the above example, and can be applied to any electronic device to which an active matrix type electro-optical device can be applied. For example, in addition to the above, the present invention can be applied to a fax device with a display function, a finder of a digital camera, a portable TV, a DSP device, a PDA, an electronic organizer, an electronic bulletin board, and a display for advertising.
[0063]
As described above, according to the conventional technology, an effective process for forming a Si film having a large crystal grain size and substantially the same quality as a single crystal and having a flat surface with a low temperature process, a high throughput, and a low cost is clearly defined. Was not. However, as described above, an extremely high-quality Si film can be formed by using the method for manufacturing a semiconductor thin film and a thin film transistor according to the present invention. As a result, it is possible to manufacture a thin film transistor having a high mobility, a low threshold voltage and an extremely small variation, realize an ultra-low power consumption circuit, and provide a multifunctional electro-optical device and an electronic device at a low price. it can.
[Brief description of the drawings]
FIG. 1 is a process sectional view showing a method for manufacturing a semiconductor thin film of the present invention.
FIG. 2 is a diagram showing reflectance spectra of various refractory metal films.
FIG. 3 is a diagram showing the film thickness dependence of the reflectance at a wavelength of 1 μm of the Cr and W films.
FIG. 4 is a diagram showing the relationship between the thickness of a second insulating layer provided on Cr and W and the reflectance at a wavelength of 1 μm.
FIG. 5 is a diagram illustrating a method of applying the light irradiation method of the present invention to a large-area substrate and an irradiation profile.
FIG. 6 is a diagram showing a light irradiation profile of the present invention and a temperature rise at each depth of a light absorbing layer / semiconductor layer and a glass substrate.
FIG. 7 is a diagram showing a light irradiation profile of the present invention and a temperature rise at each depth of a light absorbing layer / semiconductor layer and a glass substrate.
FIG. 8 is a diagram showing a light irradiation profile of the present invention and a temperature rise at each depth of a light absorbing layer / semiconductor layer and a glass substrate.
FIG. 9 is a diagram showing a light irradiation profile of the present invention and a temperature rise at each depth of a light absorbing layer / semiconductor layer and a glass substrate.
FIG. 10 is a process sectional view showing the method for manufacturing the thin film transistor of the present invention.
FIG. 11 illustrates an example of an electronic apparatus including the electro-optical device according to the invention.
FIG. 12 is a diagram showing an example of an island-shaped light absorbing layer pattern of the present invention.
[Explanation of symbols]
100. . . substrate
101. . . Underlayer protective film
102. . . Semiconductor film
103. . . First insulating layer
104. . . Light absorbing layer
105. . . Second insulating layer
106. . . Focus point of irradiation light on substrate
107. . . Temperature rise part of light absorption layer
108. . . Liquid silicon
109. . . poly-Si
110. . . Lamp unit
111. . . Lamp light source
112. . . Reflective optical system / reflective surface
113. . . Radiation thermometer
114. . . Scan direction
115. . . slit
400, 414. . . Island-shaped light absorption layer
410. . . Linear lamp light
500. . . Irradiation light
501. . . Irradiation end area
502. . . Unirradiated area
503. . . Irradiation light irradiation position
504. . . Arbitrary point on substrate
510. . . Irradiation light intensity distribution on substrate
511, 512. . . Irradiation profile example
901. . . poly-Si film
902. . . Gate insulating film
903, 904. . . Source and drain regions
905. . . Gate electrode
906. . . Interlayer insulating film
907, 908. . . Source and drain electrodes
10. . . Electro-optical device using TFT manufactured using semiconductor thin film of the present invention

Claims (7)

Forming a first insulating layer on the semiconductor layer formed on the substrate, and forming a light absorbing layer containing at least one of W, Ti, Cr, Ta, and Mo on the first insulating layer Performing the step of patterning the light-absorbing layer into a plurality of island regions, and irradiating the light from the light source while relatively moving a light source having an output peak wavelength in an infrared region and the substrate. Crystallizing the semiconductor layer by irradiating the absorption layer with a semiconductor thin film. The method according to claim 1, wherein the light irradiation is performed in an inert gas atmosphere. The shape of the island region of the light absorbing layer is a shape sandwiched by a pair of V-shaped oblique sides forming an angle of 15 ° to 75 ° on one side with respect to the direction in which the irradiation light moves relative to the substrate. The method for manufacturing a semiconductor thin film according to claim 1. The shape of the island-shaped region of the light absorbing layer includes a region 1 having a first width in a direction in which irradiation light moves relative to the substrate, and a region 2 having a second width larger than the first width. The region 1 and the region 2 are formed by connecting regions which are connected to each other by an oblique line which forms an angle of 15 ° to 60 ° on one side in a direction in which the irradiation light moves relative to the substrate. The method for producing a semiconductor thin film according to claim 1. A method for manufacturing a thin film transistor, wherein a semiconductor layer formed below an island region of the light absorption layer is used as an active layer. An electro-optical device comprising a thin film transistor manufactured by the method according to claim 5 as a driving element of a display pixel. An electronic apparatus comprising the electro-optical device according to claim 6.

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