JP4761734B2 - Method for manufacturing semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device in which an element such as a transistor is formed using a semiconductor film formed on a substrate, a laser beam irradiation method for annealing the semiconductor film, and a semiconductor device including laser beam irradiation in the process. It relates to a manufacturing method.

  In recent years, a technology for manufacturing a thin film transistor (hereinafter referred to as TFT) on a substrate has greatly advanced, and application development to an active matrix display device has been advanced. In particular, a TFT using a polycrystalline semiconductor film has higher field-effect mobility than a TFT using a conventional amorphous semiconductor film, and thus can operate at high speed. Therefore, a pixel driving circuit mounted with an external IC chip can be integrally formed using a TFT on the same substrate as the pixel.

  A polycrystalline semiconductor film suitable for manufacturing a TFT is obtained by crystallizing an amorphous semiconductor film, and a laser annealing method is usually used for this crystallization. This is because normal thermal annealing requires a high temperature of 600 ° C. or higher, whereas an inexpensive glass substrate has poor heat resistance and is easily deformed by heat. In other words, the laser annealing method can significantly reduce the processing time as compared with the annealing method using radiant heating or conduction heating, and the semiconductor substrate or semiconductor film is selectively and locally heated so that the substrate is almost thermally treated. Since it has an advantageous feature that it is not damaged, it is widely used for crystallization of an amorphous semiconductor film formed on a glass substrate.

  The laser annealing method here refers to a technique for recrystallizing a damaged layer or an amorphous layer formed on a semiconductor substrate or semiconductor film, or a technique for crystallizing an amorphous semiconductor film formed on a substrate. pointing. Moreover, the technique applied to planarization and surface modification of a semiconductor substrate or a semiconductor film is also included.

Laser oscillators used for laser annealing are roughly classified into two types, pulse oscillation and continuous oscillation, depending on the oscillation method. In recent years, it is more preferable to use a continuous oscillation (hereinafter also referred to as CW) laser oscillator such as an Ar laser or a YVO ₄ laser than a pulse oscillation laser oscillator such as an excimer laser in crystallization of a semiconductor film. It has been found that the grain size of the crystals formed therein increases. As the wavelength of the continuous wave laser beam used at this time, a wavelength in the visible region where the absorption rate of the amorphous semiconductor film is relatively high and the laser output is easily obtained is used. As the crystal grain size in the semiconductor film increases, the number of grain boundaries entering the TFT channel region formed using the semiconductor film decreases, so that the mobility increases, which can be used for the development of higher performance devices. Therefore, a semiconductor film crystallization technique using a continuous wave laser oscillator has attracted attention.

  However, when laser annealing is performed using a continuous wave laser oscillator, there is a problem that the annealing state in the semiconductor film becomes non-uniform. The cause is that the laser beam oscillated from the laser oscillator has a characteristic that energy is weakened from the center to the end in a Gaussian distribution. Therefore, it is difficult to anneal uniformly.

  In view of such problems, the present invention provides a laser beam irradiation method capable of uniformly performing laser processing such as annealing on an object to be processed such as a semiconductor film formed on a substrate, and a semiconductor device using the same. And a semiconductor device manufactured by the method.

  When manufacturing a semiconductor device, when a glass substrate is used as a substrate and laser annealing is performed by vertically irradiating a visible laser beam with a semiconductor film formed on the glass substrate as an irradiation surface, the glass substrate is Since the absorptance with respect to visible light is low, a laser beam incident on the substrate (hereinafter referred to as incident light) transmits through the first surface of the substrate and reaches the second surface of the substrate. Here, the first surface of the substrate indicates a surface of the substrate on which a semiconductor film is formed and irradiated with a laser beam, and the second surface of the substrate indicates a surface opposite to the first surface of the substrate. Yes. Then, the laser beam is reflected by the second surface of the substrate, and the reflected laser beam (hereinafter referred to as reflected light) reenters the semiconductor film. At this time, the reflected light reenters the semiconductor film heated and melted by the incident light. As a result, interference by incident light and reflected light occurs on the semiconductor film, so that a portion where the laser beams are strengthened and a portion where the laser beams are strengthened are formed, resulting in variations in the state of the semiconductor film annealed by the laser beams. It has been found.

  In the present invention, when performing laser processing such as laser annealing, the laser beam is reflected by the first surface of the substrate or absorbed in the substrate in accordance with the wavelength of the laser beam to be irradiated, or A substrate in which a part is reflected by the first surface of the substrate and a part can be absorbed in the substrate is used.

The present invention relates to a semiconductor device in which a semiconductor film having crystallinity is provided on a first surface of a substrate. The substrate is partly absorbed by the semiconductor film, and part of the substrate becomes transmitted light to form a first part of the substrate. A laser beam which reaches one surface and is irradiated with an energy density capable of crystallizing the semiconductor film is reflected on the first surface of the substrate or absorbed in the substrate, or a part of the laser beam The first surface is reflected and partly absorbed in the substrate. By using a substrate having such characteristics, when the intensity of reflected light from the second surface of the substrate becomes less than a threshold that affects the annealing state of the semiconductor film when a laser beam is incident on the substrate, The reflected light does not affect the annealing uniformity of the semiconductor film. Therefore, when a laser beam having a uniform intensity distribution is used, the semiconductor film can be annealed uniformly without being affected by reflected light. Furthermore, by performing laser annealing using a continuous wave laser oscillator having a wavelength in the visible region such as the second harmonic of the YVO ₄ laser, the substrate is relatively efficient compared to other higher harmonics. The entire surface can be a region made of polycrystalline having a large particle size (hereinafter referred to as a large particle region).

In the above invention, if the thickness of the substrate is d, the substrate absorption coefficient α for the laser beam preferably satisfies the condition of α ≧ ln10 / 2d. Actually, the reflectivity from the second surface of the substrate is about 4%, and this causes an uneven annealing. According to the experiment by the present inventor, the influence could be eliminated by setting the reflectance to 0.4%. Therefore, it is considered that the influence of interference can be eliminated if the light intensity becomes 1/10 while the light travels a distance (2d) twice the thickness of the substrate. Will be derived. Under the above-mentioned conditions, the intensity when the light having the incident light intensity I ₀ travels the distance 2d through the medium having the absorption coefficient α (that is, on the second surface of the substrate at the first surface of the substrate on which the beam is incident). the intensity of the reflected light) and I, and a minimum value of the absorption coefficient α when becomes I = I _0/10. If the absorption coefficient α of the substrate satisfies this condition, the intensity of the reflected light from the second surface of the substrate becomes less than the threshold that affects the annealing state of the semiconductor film, so annealing without considering the influence of the reflected light It can be performed.

  A substrate made of glass used for manufacturing a substrate with TFT is about 0.5 to 1.1 mm. In consideration of this, in the substrate having a thickness of 1.1 mm, the absorption coefficient α for preventing the intensity of the reflected light from the second surface of the substrate from affecting the annealing state of the semiconductor film is calculated by the above formula. To about 1 / mm. Therefore, even in a thin substrate, the absorption coefficient α needs to be 1 / mm or more so that the intensity of reflected light from the second surface of the substrate does not affect the annealing state of the semiconductor film. For this reason, in the above invention, the absorption coefficient α of the substrate with respect to the laser beam is 1 / mm or more.

In the above invention, the substrate described above is opaque to the laser beam to be irradiated. Being opaque to the laser beam to be irradiated means that the transmittance of the laser beam is small, that is, the reflected light is reflected on the second surface of the substrate (the surface on which the laser beam is not incident). It does not occur. Thereby, interference between incident light and reflected light does not occur, and it is possible to eliminate the influence on the uniformity of annealing. In particular, when laser annealing is performed using a continuous wave laser oscillator having a wavelength in the visible region such as the second harmonic (532 nm) of a YVO ₄ laser, the substrate must be opaque to visible light. For example, an insulating substrate such as a colored glass substrate or a ceramic substrate can be used.

  In the present invention, by using a substrate having such characteristics, the semiconductor film formed on the substrate has polycrystallinity, the crystal grains are long in one direction, and the length of the crystal grains is laser. What is 600 nm or more along one direction of scanning the beam can be obtained.

  The present invention relates to a laser irradiation method in which a laser beam emitted from a laser oscillator is converted into a laser beam having a uniform intensity distribution using an optical system, and is irradiated onto a substrate on which a light-absorbing thin film such as a semiconductor film is formed. The laser beam is reflected by the first surface of the substrate or absorbed in the substrate, or a substrate having a characteristic of partially reflecting the first surface of the substrate and absorbing a part thereof is used. Irradiates perpendicularly to the substrate on which the light-absorbing thin film is formed, and irradiates the substrate by reciprocally scanning the laser beam.

  In the above invention, when the thickness of the substrate is d, the substrate absorption coefficient α with respect to the laser beam preferably satisfies the condition of α ≧ ln10 / 2d. Further, considering that many substrates having a thickness of about 0.5 to 1.1 mm are in circulation, the absorption coefficient α of the substrate is preferably 1 / mm or more.

  In the present invention, a laser beam can be incident perpendicularly to the substrate. This is because a substrate that reflects or absorbs a laser beam on the first surface of the substrate or a substrate that partially reflects and absorbs part of the first surface of the substrate is used. This is because it is not necessary to consider the influence of the reflected light from the second surface.

In the above invention, the laser oscillator may be any one of YVO ₄ laser, YLF laser, Ar laser, excimer laser, YAG laser, and glass laser, or a combination thereof.

In the above invention, when laser annealing is performed using a continuous wave laser oscillator having a wavelength in the visible region such as the second harmonic (532 nm) of the YVO ₄ laser, the substrate is opaque to visible light. For example, an insulating substrate such as a colored glass substrate or a ceramic substrate can be used. By using an opaque substrate, reflected light from the back surface of the substrate is not generated, and therefore laser annealing can be performed without considering the influence of the reflected light. In this manner, when the influence of the reflected light from the back surface of the substrate is eliminated, the laser beam can be made to enter perpendicularly to the semiconductor film, so that laser annealing can be made the same regardless of the scanning direction of the substrate.

  The present invention includes a step of forming a semiconductor film on a substrate and a step of laser annealing using a laser beam emitted from a laser oscillator as a laser beam having a uniform intensity distribution using an optical system and using the substrate as an irradiation surface. In the laser annealing step, the laser beam irradiated when laser annealing the semiconductor film is reflected by the first surface of the substrate or absorbed by the substrate, or part of the laser beam is absorbed by the first surface of the substrate. A method for manufacturing a semiconductor device in which a substrate having a property of reflecting and absorbing part of a laser beam is used, and a laser beam is irradiated perpendicularly to the substrate, and the laser beam is relatively reciprocally scanned with respect to the substrate is there.

  In the above invention, it is preferable that a substrate satisfying the condition of α ≧ ln10 / 2d is used as the substrate absorption coefficient α with respect to the laser beam, where d is the thickness of the substrate. In particular, the absorption coefficient α of the substrate is preferably 1 / mm or more.

As the laser oscillator, any one or a combination of YVO ₄ laser, YLF laser, Ar laser, excimer laser, YAG laser, and glass laser can be used.

In the above invention, when laser annealing is performed using a continuous wave laser oscillator having a wavelength in the visible region such as the second harmonic (532 nm) of the YVO ₄ laser, the substrate is opaque to visible light. For example, an insulating substrate such as a colored glass substrate or a ceramic substrate can be used.

  By performing laser annealing using the present invention, the laser beam is reflected by the first surface of the substrate, absorbed by the substrate, or partially reflected by the first surface of the substrate. If the intensity of the reflected light from the second surface of the substrate becomes less than a threshold that affects the annealing state of the semiconductor film when the laser beam is incident on the substrate by absorbing the portion, the annealing of the semiconductor film Uniformity can be improved. If a substrate that is opaque to the laser beam used for annealing is used, the transmittance of the laser beam is reduced, and when the laser beam is incident on the substrate, incident light does not reach the second surface of the substrate. The reflected light is not generated on the second surface of the substrate, and the uniformity of annealing can be improved. Therefore, it is not necessary to consider the influence of reflected light when performing laser annealing.

For this reason, in order to suppress the influence of the reflected light, it is not necessary to make the laser beam obliquely incident on the semiconductor film, and it becomes possible to make the laser beam incident perpendicularly on the semiconductor film. When normal incidence is possible, a large degree of freedom can be given by optical design. For example, a beam homogenizer using diffractive optics can be used to easily form a laser beam with a uniform intensity distribution. Further, when the present invention is used, even if a laser beam having a uniform intensity distribution is incident on the substrate perpendicularly, there is little or no influence of the reflected light from the second surface of the substrate, so that the laser annealing is performed. The uniformity of crystallinity of the semiconductor film can be significantly improved. At this time, if a continuous wave laser oscillator having a visible wavelength such as the Ar laser oscillation wavelength or the second harmonic of the YVO ₄ laser is used, the energy efficiency is higher than that of other higher harmonics. Therefore, the entire surface of the semiconductor film can be made a large grain size region in a relatively short time. Further, when a TFT is manufactured using the semiconductor film, the mobility is significantly higher than that of a conventional crystalline semiconductor film, and the TFT can be applied to a semiconductor device that requires high-speed operation.

  Furthermore, when the present invention is used, it becomes possible to make the laser beam incident perpendicularly to the substrate, so there is no difference depending on the scanning direction of the laser annealing, and even if the annealing is performed by reciprocating the laser beam, Since the return path can have the same large particle size region, a large number of substrates can be processed in a short time. That is, there is an advantage that throughput is increased.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

(Embodiment 1)
A first embodiment of the present invention will be described in detail with reference to FIGS.

  First, as a substrate, a glass substrate that is colored by mixing impurities and is opaque to visible light is prepared. An amorphous semiconductor film or a non-single-crystal semiconductor film is formed over the glass substrate, and laser annealing is performed using this substrate as an irradiation surface. As the glass substrate, in addition to a colored glass substrate, any material can be used as the substrate as long as it has heat resistance that can withstand laser annealing treatment such as ceramics and is opaque to the laser beam to be used.

Next, a laser irradiation method will be described with reference to FIG. In FIG. 1, the laser beam propagates in the direction of the solid arrow. The laser oscillator 100 is a YVO ₄ laser and outputs a second harmonic. Note that the laser oscillator 100 is not limited to the YVO ₄ laser, and one or a combination of a YLF laser, an Ar laser, a YAG laser, an excimer laser, and a glass laser may be used. Excimer lasers, glass lasers, and the like are pulsed lasers, but the effects of the present invention can be obtained even when these lasers are used. Thereafter, a diffractive optics 101 is used as a beam homogenizer to form a rectangular laser beam having a uniform intensity distribution. Then, the length is adjusted in the long direction and the short direction using the convex cylindrical lenses 102 and 103. As a result, the laser beam is shaped into a rectangular laser beam having a desired aspect ratio, reflected by the mirror 104, and then the size of the rectangular laser beam is adjusted by the condenser lens 105, thereby forming an opaque semiconductor film 106. Incident on the glass substrate 107. Note that the laser beam condensed by the condenser lens 105 enters the glass substrate 107 perpendicularly. As the moving stage for moving the substrate, an X-axis stage 108 and a Y-axis stage 109 are used.

  On the first surface of the glass substrate 107, the laser beam is incident vertically, but the glass substrate 107 is colored glass that is opaque to visible light, and the laser beam does not pass through the glass substrate 107. Therefore, the reflected light from the second surface of the glass substrate 107 is not generated. For this reason, laser annealing can be performed without considering the influence of reflected light from the second surface of the glass substrate 107. Further, since the laser beam can enter perpendicularly to the substrate, the rectangular laser beam having a uniform intensity distribution formed by the diffractive optics 101 and the convex cylindrical lenses 102 and 103 is in the scanning directions A and B of the glass substrate 107. Are completely symmetrical. Therefore, since similar laser annealing can be performed regardless of the scanning directions A and B, uniform annealing can be efficiently performed on the entire surface of the glass substrate 107.

  Next, an irradiation method in which the entire surface of the amorphous semiconductor film 106 is a large grain size region will be described with reference to FIG. In order to facilitate identification, the same reference numerals in FIG. The substrate 107 on which the amorphous semiconductor film 106 is formed is fixed to an adsorption stage and irradiated with a laser beam. First, the amorphous semiconductor film 106 is linearly scanned by the X-axis stage 108. One line corresponds to the portion A1 in FIG. In FIG. 3, the X-axis stage 108 irradiates the portion of the forward path Am (m is a positive integer) with laser, and then the Y-axis stage 109 is perpendicular to the scanning direction by the length of the large particle size region 110. The direction of the return path Bm is irradiated with laser. By repeating such a series of operations, the entire surface of the amorphous semiconductor film 106 can be made a large grain size region.

  In order to solve such a problem, there is a method in which a laser beam is obliquely incident on the first surface of the substrate and annealed. This will be described with reference to FIG. 2A and 2B show a state where laser annealing is performed on a substrate 202 on which a semiconductor film 201 is formed using a visible laser beam while moving the moving stage 203 in the A direction or the B direction. Yes. At this time, when a glass substrate is used as the substrate as described above, since the substrate is transparent to visible light, incident light is transmitted through the first surface of the substrate and reflected by the second surface of the substrate. Re-incident on the semiconductor film 201. In order to prevent interference, it is necessary to make the laser beam incident at an incident angle such that the incident light and the reflected light do not overlap on the semiconductor film 201 as shown in FIG. However, when the incident angle is small as shown in FIG. 2A, the incident light and the reflected light overlap on the semiconductor film 201 even if the intensity distribution of the laser beam is uniform, causing interference and annealing. The state of can be non-uniform.

Therefore, as one of the methods taken to prevent the interference between the incident light and the reflected light, as shown in FIG. 2B, the incident light is incident obliquely with a large incident angle. There is a method for preventing the semiconductor films from overlapping, and in this case, non-uniform annealing due to interference does not occur. However, in this case, since the incident angle is large, there is a problem that it is difficult to design an optical system and it is difficult to use a beam homogenizer. The beam homogenizer is an optical system that makes the intensity distribution of a laser beam uniform, such as diffractive optics. As described above, the intensity distribution of the laser beam oscillated from the laser oscillator is a Gaussian distribution, and the intensity distribution is not uniform. Therefore, when forming a laser beam having a uniform intensity distribution on the irradiation surface, it is necessary to dispose a beam homogenizer as an optical system between the laser oscillator and the irradiation surface. However, a general beam homogenizer is designed to form a laser beam having a uniform intensity distribution on an irradiation surface located in parallel with the beam homogenizer. Therefore, when a general beam homogenizer is used and the laser beam is incident on the substrate at a large incident angle, a uniform laser beam with a uniform intensity distribution cannot be formed. I can't. However, by applying the present invention, a laser beam can be perpendicularly incident on the substrate, so that a uniform laser beam can be formed on the irradiation surface using a general beam homogenizer. If the substrate according to the present invention is used as the substrate on which the semiconductor film as the irradiation surface is formed and laser annealing is performed using a laser beam having a uniform intensity distribution, uniform annealing can be performed on the entire surface of the substrate.

  Further, as shown in FIG. 2B, the state of the semiconductor film (specifically, crystallinity and crystal orientation) after annealing by moving the substrate in the A direction is changed by moving the substrate in the B direction. There is a problem that it is different from the state of the semiconductor film after this. The reason is as follows. First, when moved in the A direction, the reflected light is incident on the semiconductor film before the incident light. On the other hand, when the substrate is moved in the B direction, the incident light enters before the reflected light. Since the incident light is partially reflected on the first surface of the substrate or transmitted through the second surface of the substrate, the reflected light from the second surface of the substrate has a lower energy than the incident light. When moved in the direction, the semiconductor film is first heated by weak reflected light and then heated by strong incident light. Moreover, since it becomes the reverse when it moves to B direction, the way of heating differs. For this reason, the annealing in the A direction and the annealing in the B direction result in different states of the semiconductor film after annealing. Therefore, when annealing is performed so that the entire surface of the semiconductor film is in the same state, scanning can be performed only in one direction. That is, since the moving stage cannot be reciprocally scanned in the A direction and the B direction for annealing, there is a problem that a long time is required for processing one substrate and the throughput is low.

  However, when the laser irradiation method disclosed in the present invention is used, during laser annealing, the laser beam is reflected by the first surface of the substrate, absorbed by the substrate, or both, As described above, the intensity of the reflected light from the second surface of the substrate is reduced, and the reflected light does not affect the uniformity of annealing of the semiconductor film, so the influence of the reflected light from the second surface of the substrate. There is no need to consider. Therefore, since the semiconductor film is heated only by incident light, the method of heating the semiconductor film is the same over the entire surface of the substrate, and the state of the semiconductor film after annealing becomes uniform. Therefore, in FIG. 2, the laser beam can be irradiated in both the A direction and the B direction. That is, since the annealing can be performed by reciprocating the laser beam, the throughput is improved as compared with the conventional method.

  As shown in FIG. 2, when the laser beam is incident obliquely on the substrate, the state of the annealed semiconductor film differs depending on the moving direction of the moving stage. Even if annealing is performed by irradiating a laser beam in both the A direction and the B direction shown in FIGS. Accordingly, since annealing by reciprocating scanning of a laser beam is possible, the time for processing one substrate is reduced, and a large number of substrates can be processed in a short time. That is, the throughput is increased.

(Embodiment 2)
A second embodiment of the present invention will be described in detail with reference to FIG. FIG. 7 shows an example in which laser annealing is performed on a large glass substrate.

  First, a large glass substrate 706 is prepared. The glass substrate 706 is a glass substrate that is opaque to visible light colored by mixing impurities, as in the best mode 1 for carrying out the invention. Then, an amorphous semiconductor film 705 is formed over the glass substrate 706 using a known means (such as sputtering, LPCVD, or plasma CVD), and laser annealing is performed using the glass substrate 706 as an irradiation surface. Alternatively, before laser annealing, the semiconductor film may be crystallized by introducing a metal element into the semiconductor film and then performing heat treatment.

As the laser oscillator 701, a second harmonic of a continuous wave YAG laser or YVO ₄ laser is used. As shown in FIG. 7, laser annealing is performed on a large glass substrate 706 using a total of ten laser oscillators. . Since the same laser oscillator and optical system are used in all laser irradiation apparatuses, reference numerals are not given to all laser irradiation apparatuses, and one laser irradiation apparatus will be described.

  Further, as shown in FIG. 7, the reason why the laser beam irradiation start position is shifted back and forth one by one is as follows. On the amorphous semiconductor film 705, the distance from the center of the rectangular laser beam to the center of the rectangular laser beam adjacent to the laser beam is as short as 60 mm, and the condenser lenses 704 are arranged at this interval. Is a little impossible. Even if the arrangement is possible, it is expected that the space required for the optical adjustment is not sufficient. Therefore, in order to maintain an appropriate distance between the optical systems, it is effective to shift the irradiation position of the laser beam one by one back and forth as shown in FIG. As a result, the adjacent optical systems are not touched, and the optical systems can be easily arranged and adjusted. However, since the irradiation start position of the laser beam is shifted back and forth, in order to crystallize the entire surface of the amorphous semiconductor film 705, it is necessary to make the scanning distance of the glass substrate 706 a little longer.

  The laser beam emitted from the laser oscillator 701 is shaped into a rectangular laser beam having a uniform intensity distribution by the diffractive optics 702, and the laser beam is reflected by the mirror 703 and then collected by the condenser lens 704. Then, the light is incident on the amorphous semiconductor film 705 perpendicularly. Similarly, in other laser irradiation apparatuses, a rectangular laser beam having a uniform intensity distribution is formed and incident perpendicularly on the amorphous semiconductor film 705.

  As a moving stage for moving the glass substrate 706, an X-axis stage 707 and a Y-axis stage 708 are used. Since the glass substrate 706 is large, two operating axes of the X-axis stage 707 are prepared in order to move the substrate more stably. The X-axis stage 707 and the Y-axis stage 708 are first formed by using the X-axis stage 707 to form the amorphous semiconductor film 705 in the P direction, as described with reference to FIG. 3 in the best mode 1 for carrying out the invention. Then, the Y-axis stage 708 is slid in the direction perpendicular to the P direction by the length in the width direction of the large particle size region, and the X-axis stage 707 is scanned in the Q direction again to perform laser irradiation. By repeating such a series of operations, the entire surface of the amorphous semiconductor film 705 can be made a large grain size region.

  In this embodiment, laser annealing is performed using 10 systems of laser irradiation apparatus, but laser annealing can be performed by applying the present invention even when, for example, half of 5 systems or double of 20 systems are used. it can. Thus, the entire surface of the amorphous semiconductor film formed over the large glass substrate can be a large grain size region. When a TFT is manufactured using the semiconductor film, the mobility is significantly higher than that of a conventional crystalline semiconductor film, and the TFT can be applied to a semiconductor device that requires high-speed operation.

  In this embodiment, the process of manufacturing a thin film chip using the substrate manufactured by the method described as the second embodiment of the present invention and mounting it on the substrate on which the pixel portion is formed is shown in FIGS. It explains using.

  First, a substrate on which a polycrystalline semiconductor thin film is formed by laser annealing is prepared according to the second embodiment. FIG. 4A shows a substrate 401 after laser annealing and a semiconductor film 402 formed over the substrate. Then, after the crystallized semiconductor film 402 on the substrate 401 is patterned or a gate electrode, a mask, or the like is formed, doping is performed. Note that the semiconductor film may be patterned before crystallization by a laser beam or may be crystallized before patterning. Thereafter, activation of the dopant, formation of various insulating films, wirings, and the like are performed, whereby a plurality of integrated circuits are formed on the substrate. In this process, the use of glass substrates and ceramics allows the use of large substrates in meters compared to the case of using silicon substrates or SOI substrates, and more integrated circuits can be obtained from each substrate. . Therefore, an improvement in throughput is expected and it is suitable for mass production. Then, after the integrated circuit is formed, as shown in FIG. 4B, a thin film chip 403 in which the integrated circuits are separated is formed by dividing the substrate 401.

  Next, a state in which the thin film chip formed using the above manufacturing method is mounted on the substrate over which the pixel portion is formed is illustrated in FIGS. In FIG. 5A, a pixel portion 502 and a scan line driver circuit 503 are formed over a substrate 501. A signal line driver circuit formed on the thin film chip 504 is mounted on the substrate 501. Specifically, a signal line driver circuit formed in the thin film chip 504 is attached to the substrate 501 and electrically connected to the pixel portion 502. Reference numeral 505 denotes an FPC, and the power supply potential, various signals, and the like are supplied to the pixel portion 502, the scanning line driver circuit 503, and the signal line driver circuit formed in the thin film chip 504 through the FPC 505, respectively. .

  In FIG. 5B, a pixel portion 512 and a scan line driver circuit 513 are formed over a substrate 511. The signal line driver circuit formed on the thin film chip 514 is further mounted on the FPC 515 mounted on the substrate 511. The potential of the power supply, various signals, and the like are supplied to the pixel portion 512, the scanning line driving circuit 513, and the signal line driving circuit formed in the thin film chip 514 through the FPC 515, respectively.

  The mounting method of the thin film chip is not particularly limited, and a known COG method, wire bonding method, TAB method, or the like can be used. Further, the position where the thin film chip is mounted is not limited to the position shown in FIG. 5 as long as electrical connection is possible. 5 shows an example in which only the signal line driver circuit is formed by a thin film chip, the scanning line driver circuit may be formed by a thin film chip, and a controller, a CPU, a memory, etc. are formed by a thin film chip. You may make it implement. Further, instead of forming the entire signal line driving circuit and the scanning line driving circuit with a thin film chip, only a part of the circuits constituting each driving circuit may be formed with a thin film chip.

  Note that in a semiconductor display device in which a driver circuit is mounted as a thin film chip, a transistor used for a pixel portion is not limited to a TFT formed using an amorphous semiconductor film such as amorphous silicon. A TFT using a microcrystalline semiconductor film or a polycrystalline semiconductor film may be used. A transistor formed using single crystal silicon or a transistor using SOI may be used. Further, a transistor using an organic semiconductor or a transistor using carbon nanotubes may be used. By forming an integrated circuit such as a driver circuit with a separate thin film chip and mounting it on a substrate, the yield can be increased compared to the case where all the circuits are formed on the same substrate as the pixel portion. The process can be easily optimized according to the characteristics.

  In this example, a configuration of a CPU (Central Processing Unit) manufactured using a polycrystalline semiconductor thin film substrate manufactured by the method described as the first embodiment of the present invention will be described.

  FIG. 6 shows the configuration of the CPU of this embodiment. 6 includes an arithmetic circuit (ALU) 601, an ALU controller 602, an instruction decoder 603, an interrupt controller 604, It mainly has a timing controller 605, a register 606, a register controller 607, a bus interface (Bus I / F) 608, and a read only memory (ROM) 609. ing. Needless to say, the CPU illustrated in FIG. 6 is just an example in which the configuration is simplified, and an actual CPU may have various configurations depending on the application.

  An instruction input to the CPU via the bus interface (Bus I / F) 608 is input to an instruction decoder 603 and decoded, and then an ALU controller 602, an interrupt controller ( Interrupt controller) 604, register controller 607, and timing controller 605.

  An ALU controller 602, an interrupt controller 604, a register controller 607, and a timing controller 605 perform various controls based on the decoded instructions. Specifically, the ALU controller 602 generates a signal for controlling the operation of the arithmetic circuit (ALU) 601. An interrupt controller 604 determines and processes an interrupt request from an external input / output device or a peripheral circuit from the priority or mask state during execution of a CPU program. A register controller 607 generates an address of the register 606, and reads and writes the register 606 according to the state of the CPU.

  A timing controller 605 includes an arithmetic circuit (ALU) 601, an ALU controller 602, an instruction decoder 603, an interrupt controller 604, and a register controller. A signal for controlling the timing of the operation 607 is generated. For example, the timing controller 605 includes an internal clock generation unit that generates an internal clock signal CLK2 based on the reference clock signal CLK1, and supplies the clock signal CLK2 to the various circuits. A read only memory (ROM) 609 stores various programs executed by the CPU.

  In this embodiment, the CPU is described as an example. However, the semiconductor device of the present invention is not limited to the CPU. As in the first embodiment, by using a glass substrate or a ceramic substrate, a large number of CPUs can be manufactured on one large-area substrate, which is advantageous for mass production.

3A and 3B illustrate a laser irradiation method of the present invention. The figure explaining the method of annealing by injecting a laser beam diagonally. 10A and 10B illustrate an irradiation method in which the entire surface of a semiconductor film 106 is a large grain size region. 4A and 4B illustrate a thin film chip of Example 1. FIG. 3A and 3B illustrate a mode in which the thin film chip of Example 1 is mounted on a substrate on which pixels are formed. FIG. 6 is a diagram illustrating a CPU according to a second embodiment. FIG. 6 illustrates Embodiment 2 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Laser oscillator 101 Diffractive optics 102 Convex cylindrical lens 103 Convex cylindrical lens 104 Mirror 105 Condensing lens 106 Amorphous semiconductor film 107 Glass substrate 108 X-axis stage 109 Y-axis stage 110 Large grain area 201 Semiconductor film 202 Substrate 203 Movement Stage 401 Substrate 402 Semiconductor film 403 Thin film chip 501 Substrate 502 Pixel unit 503 Scan line driver circuit 504 Thin film chip 505 FPC (flexible printed circuit)
511 Substrate 512 Pixel portion 513 Scan line driver circuit 514 Thin film chip 515 FPC
600 Substrate 601 Arithmetic logic unit (ALU)
602 ALU Controller
603 Instruction Decoder
604 Interrupt Controller
605 Timing Controller
606 Register
607 Register Controller
608 Bus interface (Bus I / F)
609 Read-only memory (ROM)
701 Laser 702 Deflective optics 703 Mirror 704 Condensing lens 705 Amorphous semiconductor film 706 Glass substrate 707 X-axis stage 708 Y-axis stage

Claims (6)

Forming a semiconductor film on the substrate;
Irradiating the semiconductor film with a laser beam having a wavelength in the visible region and having a uniform intensity distribution perpendicularly to the semiconductor film,
The substrate has a property of absorbing the laser beam transmitted through the semiconductor film;
When the thickness of the substrate is d [mm], the absorption coefficient α [mm ⁻¹ ] of the substrate with respect to the laser beam satisfies the condition of α ≧ ln10 / 2d,
Irradiating the laser beam with reciprocating scanning relative to the substrate,
The method for manufacturing a semiconductor device, wherein the substrate is a colored glass substrate that is opaque to visible light. Forming a semiconductor film over the first surface in a substrate having a first surface and a second surface;
Irradiating the semiconductor film with a laser beam having a wavelength in the visible region and having a uniform intensity distribution perpendicularly to the semiconductor film,
The substrate has a characteristic of absorbing a part of the laser beam transmitted through the semiconductor film and reflecting a part of the laser beam on the first surface;
When the thickness of the substrate is d [mm], the absorption coefficient α [mm ⁻¹ ] of the substrate with respect to the laser beam satisfies the condition of α ≧ ln10 / 2d,
Irradiating the laser beam with reciprocating scanning relative to the substrate,
The method for manufacturing a semiconductor device, wherein the substrate is a colored glass substrate that is opaque to visible light. The method for manufacturing a semiconductor device, characterized in that in claim 1 or claim 2, wherein the absorption coefficient of the substrate relative to the laser beam α is 1 [mm ^-1] or more. Forming a semiconductor film over the first surface in a substrate having a first surface and a second surface;
Irradiating the semiconductor film with a laser beam having a wavelength in the visible region and having a uniform intensity distribution perpendicularly to the semiconductor film,
The substrate has a property of reflecting the laser beam transmitted through the semiconductor film and reaching the first surface to the first surface;
The reflectance of the laser beam reflected by the second surface is 0.4% or less,
Irradiating the laser beam with reciprocating scanning relative to the substrate,
The method for manufacturing a semiconductor device, wherein the substrate is a colored glass substrate that is opaque to visible light. In any one of claims 1 to 4, wherein the substrate is a method for manufacturing a semiconductor device, characterized in that opaque to the laser beam. In any one of claims 1 to 5, by coloring by mixing impurities in a substrate, the method for manufacturing a semiconductor device characterized by forming the colored glass substrate.

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