JP2007208044A - Method for manufacturing semiconductor thin film, and manufacturing apparatus of semiconductor thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor thin film and a manufacturing apparatus of semiconductor thin film which can suppress damages by the irradiation of a laser beam and can manufacture efficiently the semiconductor thin film. <P>SOLUTION: In the method for manufacturing the semiconductor thin film, at least two kinds of laser beams are applied for melting a precursor semiconductor thin film in a solid state contained in a precursor semiconductor thin-film substrate before recrystallization. The method includes a process to detect the reflection coefficient of the irradiated portion of a reference laser beam applied to the precursor semiconductor thin film substrate, and a process to control the irradiation time of at least one kind of the laser beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor thin film manufacturing method and a semiconductor thin film manufacturing apparatus.

  A polycrystalline thin film transistor in which an amorphous semiconductor thin film is once melted and then recrystallized to form a polycrystalline semiconductor thin film, and a transistor is formed on the polycrystalline semiconductor thin film. Since the electron mobility is high, high-speed operation can be expected, and there is a possibility of realizing a large-scale integrated circuit on a glass substrate as well as a driving system of a liquid crystal device.

  For example, when a polycrystalline silicon thin film transistor is used, not only can a switching element be formed in the pixel portion of the display device, but also a drive circuit and a part of the peripheral circuit can be formed in the peripheral portion of the pixel. And a circuit can be formed on a single substrate. For this reason, it is not necessary to separately mount a driver IC or a drive circuit board on the display device, and it is possible to provide these display devices at a low price.

  In addition, when a polycrystalline silicon thin film transistor is used, the size of the transistor can be reduced, so that a switching element formed in a pixel portion of the display device can be reduced, and a high aperture ratio of the display device can be achieved. Therefore, it is possible to provide a display device with high brightness and high definition.

  A polycrystalline silicon thin film can be obtained, for example, by thermally annealing an amorphous semiconductor thin film obtained by vapor deposition on a glass substrate at a high temperature for a long time or by irradiating with a laser beam having a high energy density. It is done. Since the optical annealing can raise only the amorphous silicon thin film to a temperature higher than the melting point, it is very effective for forming a polycrystalline silicon thin film having a high electron mobility. In recent years, a technique for forming a polycrystalline silicon thin film from an amorphous silicon thin film using excimer laser light has been generalized, and a display device in which a polycrystalline silicon thin film transistor is formed on a low-cost glass substrate can be provided at a low price. It has become.

  The recrystallization technique using the excimer laser beam is generally referred to as an ELA (Excimer Laser Annealing) method and is industrially used as a laser crystallization technique with excellent productivity. Specifically, in the ELA method, a linear excimer laser beam having a length of about 200 to 400 mm and a width of about 0.2 to 1.0 mm is applied to an amorphous silicon thin film on a glass substrate while scanning the glass substrate at a constant speed. Irradiates in a pulsed manner. By this method, a polycrystalline silicon thin film is formed. At this time, the portion of the amorphous silicon thin film irradiated with the excimer laser beam is not melted over the entire thickness direction, but is melted while leaving a part of the amorphous region. Therefore, silicon crystal nuclei are generated everywhere over the entire surface of the laser light irradiation region, and silicon crystal grains grow in a direction perpendicular to the surface of the glass substrate.

  Here, in order to obtain a display device with higher performance, it is necessary to increase the crystal grain size of the polycrystalline silicon and to control the crystal grain orientation. Thus, many proposals have been made for the purpose of obtaining a polycrystalline silicon thin film having performance close to that of single crystal silicon. Among them, there is a technique for growing crystal grains in the horizontal direction (see, for example, Patent Document 1) (hereinafter referred to as “super lateral growth method”).

  This is because a silicon thin film formed on a glass substrate is first irradiated in pulses with a laser beam having a fine width of about several μm, and the silicon thin film is melted over the entire thickness direction of the laser light irradiation region and then solidified. To recrystallize. As a result, all crystal grains grow in the horizontal direction from the crystal nuclei generated at the boundary between the melted part and the non-melted part formed perpendicular to the surface of the glass substrate. As a result, one-time irradiation with laser light can provide needle-like crystal grains that are parallel to the surface of the glass substrate and have a uniform length. The length of crystal grains formed by one laser beam irradiation is about 1 μm, but sequentially overlaps with a part of the needle-like crystal grains formed by the previous laser beam irradiation. By irradiating the laser beam in a pulse shape, the crystal grains already grown by the laser beam irradiation are taken over, and longer needle-like crystal grains can be obtained.

  However, in the super lateral growth method, there is a problem that the length of the needle-like crystal grains formed by one laser light irradiation is about 1 μm and is very short. For example, when a region that is twice or more the length of the crystal grain is melted, fine crystal grains 32 are formed at the center of the melted region, as shown in the schematic enlarged plan view of FIG. The fine crystal grains 32 are not laterally grown crystal grains 31 but are grown in a direction perpendicular to the surface of the glass substrate, controlled by the outflow of heat to the glass substrate. Therefore, it is not possible to obtain needle-like crystal grains whose crystal grains are remarkably long by enlarging the melting region. Therefore, in the super lateral growth method, laser light irradiation is repeatedly performed at an extremely small laser light irradiation feed pitch of about 0.4 to 0.7 μm, and the lengths of already grown crystal grains are successively taken over, Long needle-like crystal grains are obtained. For this reason, it has been pointed out that a very long time is required to recrystallize the silicon thin film over the entire surface of a glass substrate used in a display device or the like, and the production efficiency is extremely poor.

  Therefore, for the purpose of improving the production efficiency, in order to promote the growth of crystal grains per one laser beam irradiation, a method of heating a substrate such as a glass substrate with a heater, or a substrate or a base film on the substrate Many methods have been proposed for heating the substrate with laser light. For example, Patent Document 2 discloses a laser processing method and a processing apparatus that irradiates laser light for melting during irradiation with laser light for preheating (hereinafter referred to as “double beam method”).

  However, when the substrate is heated with a heater, it is necessary to maintain the temperature for a long time over a wide area of the surface of the substrate, which may cause deterioration of the substrate, the base film, or the semiconductor thin film. For example, in the case of heating with a laser beam, the variation in irradiation energy for each laser beam irradiation becomes the variation in temperature as it is, and the temperature may rise more than necessary to damage the substrate. In particular, in the double beam method, when a part of the irradiation region of the laser beam for preheating overlaps, the substrate is easily damaged at a place where the number of overlaps is large.

Therefore, in order to keep the temperature of the substrate constant, a technique for detecting a temperature change on the surface of the substrate and controlling the laser light source has been proposed (for example, see Patent Document 3). Specifically, the technique described in Patent Document 3 is to detect the temperature of a laser light irradiation section with a radiation thermometer and modulate the laser light according to the result. When laser light having a pulse width on the order of several microseconds to 100 microseconds is used, the temperature of the substrate rises rapidly. However, the response speed of a radiation thermometer that can detect temperature changes is the fastest and is on the order of several milliseconds (1 millisecond or more and less than 10 milliseconds). There was a problem that it could not be measured.
Japanese Patent No. 3204986 Japanese Patent No. 3221149 Japanese Patent No. 3213338

  In view of the above circumstances, an object of the present invention is to provide a semiconductor thin film manufacturing method and a semiconductor thin film manufacturing apparatus capable of efficiently manufacturing a semiconductor thin film while suppressing damage caused by laser light irradiation. is there.

  The present invention relates to a method for producing a semiconductor thin film by irradiating at least two kinds of laser beams and recrystallizing the precursor semiconductor thin film in a solid state contained in the precursor semiconductor thin film substrate. A semiconductor thin film comprising: a step of detecting a reflectance of a reference laser light irradiated portion irradiated on the body semiconductor thin film substrate; and a step of controlling an irradiation time of at least one kind of laser light based on the reflectance. It is a manufacturing method.

  Here, in the method for producing a semiconductor thin film of the present invention, at least two types of laser light delay the first laser light for melting the solid precursor semiconductor thin film and the recrystallization of the molten precursor semiconductor thin film. A second laser beam to be generated.

  In the method for manufacturing a semiconductor thin film of the present invention, the second laser beam can be used as a reference laser beam.

  In the method for manufacturing a semiconductor thin film according to the present invention, the irradiation time of the second laser beam is controlled by stopping the irradiation of the second laser beam when the reflectance of the irradiated portion reaches a predetermined value. be able to.

  In the method for producing a semiconductor thin film of the present invention, the first laser beam may have an ultraviolet wavelength, and the second laser beam may have a visible wavelength or infrared wavelength.

  In the method for producing a semiconductor thin film of the present invention, the second laser beam may have a wavelength in the range of 9 μm to 11 μm.

  In the method for producing a semiconductor thin film of the present invention, the crystal grains grown during recrystallization can grow substantially parallel to the surface of the precursor semiconductor thin film.

  Furthermore, the present invention provides two or more laser light sources capable of irradiating at least two types of laser light, and a detecting means for detecting the reflectance of the irradiated portion of the reference laser light irradiated on the precursor semiconductor thin film substrate; And a control means for controlling the irradiation time of at least one kind of laser light according to the reflectance of the reference laser light.

  Here, in the semiconductor thin film manufacturing apparatus according to the present invention, two or more laser light sources irradiate a first laser beam for melting the solid state precursor semiconductor thin film included in the precursor semiconductor thin film substrate. One laser light source and a second laser light source for irradiating a second laser light for delaying recrystallization of the molten precursor semiconductor thin film, and the reference laser light is the second laser light. The detecting means detects the reflectance of the irradiated portion of the second laser light, and the control means can control the irradiation time of the second laser light based on the reflectance of the irradiated portion of the second laser light.

  In the semiconductor thin film manufacturing apparatus of the present invention, the control means stops the second laser light irradiation when the reflectance of the second laser light irradiation portion reaches a predetermined value. The irradiation time of the laser beam can be controlled.

  In the semiconductor thin film manufacturing apparatus of the present invention, the detection means includes an optical sensor and a signal processing circuit for processing a signal from the optical sensor, and the optical sensor reflects the second laser light before reflection and the reflection. The second laser beam after detection is detected, and a signal indicating the power of the second laser beam before reflection and a signal indicating the power of the second laser beam after reflection are respectively transmitted to the signal processing circuit, The processing circuit can generate a signal indicating the reflectivity by processing the signal transmitted from the optical sensor.

  In the semiconductor thin film manufacturing apparatus of the present invention, the first laser light source irradiates the first laser light having an ultraviolet wavelength, and the second laser light source has a second wavelength having a visible wavelength or infrared wavelength. The laser beam can be irradiated.

  In the semiconductor thin film manufacturing apparatus of the present invention, the second laser light emitted from the second laser light source can have a wavelength of 9 μm or more and 11 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a semiconductor thin film which can suppress the damage by irradiation of a laser beam, and can manufacture a semiconductor thin film efficiently and the manufacturing apparatus of a semiconductor thin film can be provided.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

(Precursor semiconductor thin film substrate)
FIG. 1 shows a schematic cross-sectional view of a preferred example of a precursor semiconductor thin film substrate irradiated with at least two types of laser beams in the present invention. Here, in the present invention, the “precursor semiconductor thin film substrate” includes a substrate and a precursor semiconductor thin film that is a semiconductor thin film in a state before being irradiated with laser light. A precursor semiconductor thin film substrate 5 shown in FIG. 1 has a structure in which a precursor semiconductor thin film 6 is formed on an insulating substrate 7 via a buffer layer 8.

As the precursor semiconductor thin film 6, any semiconductor material can be used. For example, hydrated amorphous silicon (a-Si) has been conventionally used in the manufacturing process of liquid crystal display devices and is easy to manufacture. It is preferable to use silicon containing amorphous silicon such as: H), but it may be silicon containing polycrystalline silicon or silicon containing microcrystalline silicon. Further, the precursor semiconductor thin film 6 is not limited to a material made only of silicon, and may be a material mainly composed of silicon containing other elements such as germanium. For example, the forbidden band width of the precursor semiconductor thin film 6 can be arbitrarily controlled by adding germanium. The thickness of the precursor semiconductor thin film 6 is preferably 30 nm or more and 200 nm or less. When the thickness of the precursor semiconductor thin film 6 is less than 30 nm, it tends to be difficult to form the precursor semiconductor thin film 6 with a uniform thickness. When the thickness exceeds 200 nm, the precursor semiconductor thin film 6 is formed. This is because it tends to take too much time. The precursor semiconductor thin film 6 is formed by, for example, CVD (Chemical
Vapor deposition (chemical vapor deposition) method or the like.

  As the insulating substrate 7, a known substrate formed of a material including glass or quartz can be suitably used. Among these materials, it is preferable to use a glass substrate in that it is inexpensive and a large-area insulating substrate can be easily manufactured.

  In the precursor semiconductor thin film substrate 5 shown in FIG. 1, the precursor semiconductor thin film 6 is preferably formed on the insulating substrate 7 via the buffer layer 8. By forming the buffer layer 8, there is a tendency that the influence of the heat of the molten precursor semiconductor thin film 6 does not reach the insulating substrate 7 at the time of melting and recrystallization by laser light irradiation. This is because impurity diffusion from the insulating substrate 7 to the precursor semiconductor thin film 6 tends to be prevented. The buffer layer 8 can be formed of a material such as silicon oxide or silicon nitride using a CVD method, and is not particularly limited. In particular, when the insulating substrate 7 is a glass substrate, the buffer layer 8 is preferably made of silicon oxide because it has the same components and various physical properties. Further, the thickness of the buffer layer 8 is not particularly limited, but is preferably 100 nm or more and 500 nm or less. When the thickness of the buffer layer 8 is less than 100 nm, the effect of preventing diffusion of impurities from the insulating substrate 7 to the precursor semiconductor thin film 6 tends to be insufficient, and when it exceeds 500 nm, it takes time to form the buffer layer 8. This is because the production efficiency tends to decrease due to excessive application.

(Semiconductor thin film manufacturing method)
The precursor semiconductor thin film 6 in the precursor semiconductor thin film substrate 5 shown in FIG. 1 includes, for example, a first laser beam capable of melting the precursor semiconductor thin film 6 in a solid state by one irradiation, and one time. The precursor semiconductor thin film 6 in a solid state cannot be melted by irradiation of the above, but is irradiated with a second laser beam capable of delaying recrystallization of the molten precursor semiconductor thin film 6.

  Here, the first laser beam and the second laser beam can be irradiated with the waveform shown in FIG. 2, for example. In addition, the vertical axis | shaft of FIG. 2 shows power and the horizontal axis has shown elapsed time. Further, reference numeral 1 in FIG. 2 indicates the waveform of the first laser beam (power change with respect to elapsed time), and reference numeral 2 indicates the waveform of the second laser beam.

  Referring to FIG. 2, first, the second laser beam is irradiated in a pulse shape. Next, the first laser beam is irradiated in a pulsed manner during the irradiation of the second laser beam. Subsequently, the irradiation of the second laser beam is completed after the irradiation of the first laser beam is completed. Accordingly, the solid state precursor semiconductor thin film heated by the second laser light irradiation is irradiated with the first laser light to melt the precursor semiconductor thin film, and the melted precursor semiconductor thin film is subjected to the second laser. By irradiating with light, the time required for recrystallization of the precursor semiconductor thin film can be delayed to make the crystal grains obtained by recrystallization longer. Then, after completing the irradiation of the second laser beam, the first laser beam and the second laser beam are positioned at a position that partially contacts or partially overlaps the irradiation region of the precursor semiconductor thin film. The first laser beam and the second laser beam are irradiated again in the same manner as described above by moving the irradiation region of the laser beam and the second laser beam. Then, by repeating the irradiation of the first laser beam and the second laser beam and the movement of the irradiation region, crystal grains grow substantially parallel to the surface of the precursor semiconductor thin film, and longer crystal grains Can be obtained.

Here, in the present invention, the first laser light is well absorbed by a precursor semiconductor thin film made of a silicon thin film such as amorphous silicon in a solid state, and is 1 in an extremely short time on the order of several microseconds to 100 microseconds. From the viewpoint of making it possible to melt a silicon thin film in a solid state by a single irradiation, it is preferable to use laser light having a wavelength in the ultraviolet region. Here, the wavelength in the ultraviolet region means a wavelength of 1 nm or more and less than 400 nm. As such a first laser beam, for example, various solid-state laser beams typified by excimer laser beam and triple wave of YAG laser beam can be suitably used. Among them, excimer laser beam having a wavelength of 308 nm is particularly suitable. It is particularly preferred to use it. Further, as the second laser beam, it is preferable to use a laser beam having a wavelength in the visible region or the infrared region, from the viewpoint of delaying the recrystallization of the silicon thin film melted by the irradiation of the first laser beam. . In this case, the second laser beam is absorbed by the molten silicon thin film, and the molten silicon thin film can be heated. Here, the visible wavelength means a wavelength of 400 nm or more and less than 750 nm. Further, the wavelength in the infrared region means a wavelength of 750 nm or more and 1 mm or less. As such second laser light, for example, a double wave of a YAG laser light having a wavelength of 532 nm, a YAG laser light having a wavelength of 1064 nm, or a CO ₂ laser light having a wavelength of 10.6 μm is preferably used. be able to.

Further, in the waveform shown in FIG. 2, the first energy fluence of the laser beam is preferably not more than 1500 J / m ² or more 3500J / m ^2, and more preferably 2500 J / m ² or more 3000 J / m ² or less . When the energy fluence of the first laser beam is less than 1500 J / m ² , long crystal grains tend not to be formed. When the energy fluence of the first laser beam is greater than 3500 J / m ² When the silicon thin film is irradiated with the first laser beam, the silicon thin film tends to ablate. In particular, when the energy fluence of the first laser beam is 2500 J / m ² or more and 3000 J / m ² or less, it is preferable in that longer crystal grains can be formed without ablating the silicon thin film.

When the irradiation time of the second laser beam in the waveform shown in FIG. 2 is 120 microseconds or more and 140 microseconds or less, the energy fluence of the second laser light is 7500 J / m ² or more and 10000 J / m ² or less. It is preferable that it is 8000 J / m ² or more and 9000 J / m ² or less. When the energy fluence of the second laser beam is less than 7500 J / m ² , long crystal grains tend not to be formed. When the energy fluence of the second laser beam is greater than 10,000 J / m ² When the second laser beam is irradiated onto a silicon thin film such as amorphous silicon, the silicon thin film tends to ablate. In particular, when the energy fluence of the second laser beam is 8000 J / m ² or more and 9000 J / m ² or less, it is preferable in that longer crystal grains can be formed without ablating the silicon thin film.

In FIG. 3, the second laser beam (CO ₂ laser beam having a wavelength of 10.6 μm) is irradiated onto a precursor semiconductor thin film made of a hydrated amorphous silicon thin film formed on a glass substrate through a buffer layer made of silicon oxide. The relationship between the energy fluence (total energy injection amount per unit area of the irradiated region; J / m ² ) and the length of the crystal grains obtained by recrystallization after melting (represented by the positions of the squares in FIG. 3) Is shown). In FIG. 3, the horizontal axis indicates the energy fluence per one irradiation of the second laser light, and the vertical axis indicates the length (μm) of the crystal grains. In the horizontal axis of FIG. 3, the energy fluence of the second laser beam increases as it proceeds from left to right. The energy fluence of the second laser beam in FIG. 3 is obtained by measuring the thermal change as the energy fluence by irradiating the energy meter after the second laser beam is branched by the beam splitter. The maximum length of crystal grains is measured by observation using an optical microscope.

  Referring to FIG. 3, as the energy fluence of the second laser beam increases, the length of the crystal grains obtained by recrystallization after melting increases, which is higher than that obtained by using the conventional super lateral growth method. The grain length is 10 times or more. Therefore, since the movement distance (feeding pitch) of the irradiation region after the irradiation with the first laser beam and the second laser beam can be increased to 10 times or more, the manufacturing time is greatly shortened and the manufacturing efficiency is dramatically increased. Can be improved.

  However, in this case, there is a problem that the precursor semiconductor thin film substrate is damaged due to the energy fluctuation for each irradiation of the second laser beam.

FIG. 4 shows the result of measuring the energy fluctuation for each irradiation of the second laser beam (CO ₂ laser beam having a wavelength of 10.6 μm). In FIG. 4, the horizontal axis indicates elapsed time (seconds), and the vertical axis indicates energy (J) for each irradiation of the second laser beam. Here, when the second laser beam is irradiated at a frequency of 300 Hz, when the time of the first irradiation is the elapsed time of 0 seconds, the time of the 301st irradiation is 0 (seconds) + (301 −1) × 1/300 = 1 (seconds). Referring to FIG. 4, it can be seen that the energy of the second laser beam varies with each irradiation. And it turns out that the 2nd laser beam of very high energy is rarely irradiated. In particular, this rarely emitted second laser beam with very high energy causes damage to the precursor semiconductor thin film substrate. This causes a decrease in yield in the manufacturing process of the semiconductor thin film.

  For this reason, in the present invention, the step of irradiating the precursor semiconductor thin film substrate with the reference laser light and detecting the reflectance of the irradiated portion of the reference laser light, and the irradiation time of the second laser light are controlled by the reflectance. And at least a process is performed. Here, as the reference laser beam, a third laser beam other than the first laser beam and the second laser beam may be used. However, in order to simplify the apparatus, the second laser beam is used as the reference laser beam. It is also preferable to serve as light.

FIG. 5 shows a waveform before reflection and a waveform after reflection when a precursor semiconductor thin film made of a hydrated amorphous silicon thin film is irradiated with the second laser light (CO ₂ laser light with a wavelength of 10.6 μm) in the present invention. Indicates. Here, the vertical axis of FIG. 5 indicates power, and the horizontal axis indicates the irradiation time of the second laser beam. Referring to FIG. 5, waveform 3 after reflection is not similar to waveform 4 before reflection, and reflectivity (power of second laser light after reflection / power of second laser light before reflection). ) Is suggested to increase as the irradiation time of the second laser beam increases. In the data shown in FIG. 5, the power of the second laser light before reflection is obtained by irradiating the waveform measuring device with CO ₂ laser light having a wavelength of 10.6 μm through the attenuation optical system. The power of the second laser beam later was obtained by irradiating the waveform measuring device through the attenuation optical system with the reflected light by irradiating the amorphous silicon thin film with a CO ₂ laser beam having a wavelength of 10.6 μm. Here, the attenuation rate of the attenuation optical system is individually adjusted.

  FIG. 6 shows the relationship between the reflectance obtained from FIG. 5 and the irradiation time of the second laser beam. In FIG. 6, the vertical axis represents the reflectance, and the horizontal axis represents the irradiation time of the second laser light. Referring to FIG. 6, it can be seen that the reflectance increases as the irradiation time of the second laser light increases. That is, it is considered that the reflectivity of the second laser light changes as the temperature rises due to the irradiation of the second laser light. Therefore, it can be seen from this result that the temperature change of the irradiated substance can be detected by detecting the change in the reflectance of the second laser beam.

  In the present invention, the precursor semiconductor thin film and the precursor semiconductor thin film substrate are heated by irradiation with the second laser beam. As shown in FIG. 4, the energy of the second laser beam fluctuates with each irradiation, and even if the irradiation time of the second laser beam is the same, the highest reach of the precursor semiconductor thin film and the precursor semiconductor thin film substrate is achieved. Since the temperature differs for each irradiation of the second laser beam, the precursor semiconductor thin film substrate may be damaged.

  Therefore, in the present invention, the precursor semiconductor thin film substrate is irradiated with the reference laser light, and the temperature change of the irradiated part is detected by detecting the reflectance of the irradiated part, and the temperature of the irradiated part is a predetermined temperature. The irradiation of the second laser beam is stopped when (predetermined reflectance) is reached. Thereby, the irradiation time of the second laser light is controlled according to the temperature of the precursor semiconductor thin film substrate, so that damage to the precursor semiconductor thin film substrate due to the irradiation of the second laser light can be suppressed. Become.

  In general, a semiconductor material or a metal material has a predetermined reflectance with respect to light of each wavelength. This is because the reflectance depends on the refractive index of each material at each wavelength. Furthermore, the refractive index is dependent on the temperature of the material. Therefore, since the reflectance has temperature dependence, it becomes possible to detect the temperature of each material by detecting the reflectance of light of a predetermined wavelength.

  The inventors reflect the reflectance of the precursor semiconductor thin film substrate with respect to the second laser beam having a wavelength of 10.6 μm at about 16% and about 19% at room temperature (25 ° C.), about 300 ° C., and about 600 ° C., respectively. And experimental results of about 20% were obtained. The reflectance is determined by irradiating a second laser beam with a wavelength of 10.6 μm that does not increase the temperature of the precursor semiconductor substrate from an oblique direction, and the energy of the second laser beam before and after reflection of the irradiated portion. Each measurement was performed using an energy meter, and the ratio of the measured value after reflection to the measured value before reflection was calculated. Here, in the precursor semiconductor thin film substrate, a buffer layer made of silicon oxide having a thickness of 100 nm is formed on a glass substrate, and a precursor semiconductor thin film made of hydrated amorphous silicon having a thickness of 45 nm is formed on the buffer layer. Used. Moreover, the reflectance other than room temperature was measured while heating the precursor semiconductor thin film substrate with a heater.

The power density of the second laser beam after reflection of the precursor semiconductor thin film substrate at each temperature can be obtained by (power density of the second laser beam before reflection) × (reflectance at each temperature). When the energy fluence of the second laser light is 8100 J / m ² and the pulse width (irradiation time) is 130 microseconds, the power density after reflection of the detected second laser light is room temperature, about 300 ° C., about 600 each 10.0 mW / m ^2, a 11.9 mW / m ² and 12.5 mW / m ² at ° C.. From this result, for example, in the waveform shown in FIG. 2, it was detected when the first laser beam was irradiated when the temperature of the irradiation portion of the precursor semiconductor thin film substrate of the second laser beam was 300 ° C. What is necessary is just to irradiate a 1st laser beam, after detecting that the power density after reflection of a 2nd laser beam became 11.9MW / m < ² >. When the temperature of the irradiated portion of the precursor semiconductor thin film substrate is about 300 ° C., the power density of the second laser light after reflection is 0.03 MW every time the temperature of the irradiated portion is displaced by about 10 ° C. / m ² by the displacement. Desirably, the displacement amount of 0.03 MW / m ² is recognized and the irradiation time of the second laser light can be controlled, so that the control can be performed with high accuracy.

  Therefore, the present invention is obtained not only when the laser light irradiation time is controlled by the reflectance itself, but also by utilizing the reflectance such as the power density of the second laser light after the reflection described above. The case where the irradiation time of the laser beam is controlled depending on the object is also included.

(Semiconductor thin film manufacturing equipment)
The semiconductor thin film manufacturing apparatus of the present invention detects at least two laser light sources capable of irradiating at least two types of laser light and the reflectance of the irradiated portion of the reference laser light irradiated on the precursor semiconductor thin film substrate. Detection means, and control means for controlling the irradiation time of at least one kind of laser light according to the reflectance of the reference laser light.

  FIG. 7 schematically shows a configuration of a preferred example of the semiconductor thin film manufacturing apparatus of the present invention. The semiconductor thin film manufacturing apparatus 10 of the present invention includes, as two or more laser light sources, a first laser light source 11 that irradiates a first laser beam, and a second laser light source 12 that irradiates a second laser beam. have. In the semiconductor thin film manufacturing apparatus of the present invention shown in FIG. 7, the second laser beam also serves as the reference laser beam.

In the semiconductor thin film manufacturing apparatus 10 of the present invention, the second laser light emitted from the second laser light source 12 is branched into two by the beam splitter 25. One of the branched second laser beams enters the detector 26 and its power is detected. The other branched second laser light passes through the attenuator 14, and then the power density distribution is made uniform by the uniform irradiation optical system 16 and shaped to an appropriate size, and is uniformly irradiated onto the pattern forming surface of the mask 18. The Next, the second laser light that has passed through the mask 18 is reflected by the mirror 21, and the precursor semiconductor thin film substrate in a state where the image of the mask 18 is formed at a predetermined magnification (for example, 1/4) by the imaging lens 24. 5 is irradiated to the precursor semiconductor thin film, and the power of the second laser beam after reflection at the irradiated portion is detected by the detector 22. Here, as the second laser light source 12, for example, a YAG laser beam having a wavelength of 532 nm, a YAG laser beam having a wavelength of 1064 nm, or a CO ₂ laser beam having a wavelength of 10.6 μm is irradiated. Those are preferably used.

  On the other hand, the first laser light emitted from the first laser light source 11 passes through the attenuator 13, and then the power density distribution is made uniform by the uniform irradiation optical system 15 and shaped to an appropriate size. The pattern forming surface is uniformly irradiated. Next, the first laser light that has passed through the mask 17 is reflected by the mirror 21, and the precursor semiconductor thin film substrate in a state where the image of the mask 17 is formed at a predetermined magnification (for example, 1/4) by the imaging lens 20. 5 is irradiated perpendicularly to the surface of the precursor semiconductor thin film 5. Here, as the first laser light source 11, for example, a light source capable of irradiating various solid-state laser light typified by excimer laser light and YAG laser light can be suitably used. Among these, the first laser light source 11 is particularly preferably a light source that emits excimer laser light having a wavelength of 308 nm. The first laser light source 11 is preferably a light source that can irradiate the first laser light in a pulsed manner.

  Moreover, in the semiconductor thin film manufacturing apparatus 10 of the present invention, the precursor semiconductor thin film substrate 5 is placed on a stage 19 that can move at a predetermined speed in the horizontal direction. Moreover, in the above, there is no restriction | limiting in the quantity of the mirror 21, Moreover, it can set suitably also about an installation location.

  Furthermore, the semiconductor thin film manufacturing apparatus 10 of the present invention includes a detector 26 that can detect the power before reflection of the second laser beam, and a detector 22 that can detect the power after reflection of the second laser beam. And a signal processing circuit 27. Here, the detector 26 can generate a signal indicating the power before reflection of the detected second laser light and transmit the signal to the signal processing circuit 27. The detector 22 can generate a signal indicating the power after reflection of the detected second laser light and transmit the signal to the signal processing circuit 27. The signal processing circuit 27 receives signals transmitted from the detectors 22 and 26, and processes these signals to generate a signal indicating the reflectance of the second laser beam.

Here, as the detectors 22 and 26, for example, optical sensors or pyroelectric sensors can be used. In particular, it is preferable to use optical sensors excellent in high-speed response as the detectors 22 and 26. As the optical sensor, for example, a photoconductive portion made of silicon may be used. Further, when YAG laser light having a wavelength of 1064 nm is used as the second laser light, it is preferable to use an optical sensor in which the photosensitive portion is made of AgOCs or InGaAs. Further, when a CO ₂ laser beam having a wavelength of 10.6 μm is used as the _second laser beam, it is preferable to use an optical sensor in which the photosensitive portion is composed of HdCdZnTe. As the detectors 22 and 26 shown in FIG. 7, specifically, PD-10.6 Series Photovoltaic CO ₂ Laser Detectors (photosensitive part: HdCdZnTe, rise time: about 1 nanosecond or less) manufactured by Vigo System Co. are used. It was. Further, since the sensor has a predetermined laser resistance, it is preferable to have an attenuation optical system (not shown).

  Furthermore, the semiconductor thin film manufacturing apparatus 10 of the present invention includes control means 23 connected to the signal processing circuit 27. Here, the control unit 23 can receive the signal generated by the signal processing circuit 27 from the signal processing circuit 27. The control means 23 is connected to the first laser light source 11 and the second laser light source 12, and controls the irradiation time of the second laser light based on the signal received from the signal processing circuit 27. Can do. Further, the control means 23 can appropriately control not only the irradiation time of the second laser light but also conditions such as the power or irradiation timing of the first laser light and / or the second laser light.

  FIG. 8 shows a schematic configuration diagram of the control means 23 shown in FIG. In FIG. 8, the control means 23 includes a comparator 28, a first pulse generation circuit 29, and a second pulse generation circuit 30.

  FIG. 9 shows an example of a signal timing chart in the control means 23. Here, the signal 41 is a signal for starting irradiation of the second laser beam transmitted from the first pulse generation circuit 29 to the second pulse generation circuit 30 shown in FIG. The signal 42 is a signal for controlling the irradiation of the second laser light transmitted from the second pulse generation circuit 30 shown in FIG. 8 to the second laser light source 12. The signal 43 is a signal indicating the power of the second laser beam before reflection transmitted from the detector 26 shown in FIG. 7 to the signal processing circuit 27. The signal 44 is a signal indicating the power of the reflected second laser light transmitted from the detector 22 shown in FIG. 7 to the signal processing circuit 27. The signal 45 is a signal indicating the reflectance of the second laser light transmitted from the signal processing circuit 27 shown in FIG. 8 to the comparator 28. The signal 46 is a signal for stopping irradiation of the second laser light transmitted from the comparator 28 to the second pulse generation circuit 30.

  As shown in FIG. 9, first, a signal 41 for starting irradiation of the second laser light is transmitted from the first pulse generation circuit 29 shown in FIG. 8 to the second pulse generation circuit 30. Next, a signal 42 for starting the irradiation of the second laser light is transmitted from the second pulse generation circuit 30 to the second laser light source 12, and the second laser light is irradiated from the second laser light source 12. The Next, the irradiated second laser light is branched by the beam splitter 25 shown in FIG. 7, and the branched second laser light is incident on the detector 26, and the second laser light before being reflected by the detector 26. A signal 43 indicating the power of the signal is generated and transmitted to the signal processing circuit 27. Subsequently, the reflected second laser light enters the detector 22, and a signal 44 indicating the power of the reflected second laser light is generated in the detector 22 and transmitted to the signal processing circuit 27. Next, in the signal processing circuit 27, a signal indicating the reflectance of the second laser light from the signal 43 indicating the power of the second laser light before reflection and the signal 44 indicating the power of the second laser light after reflection. 45 is generated and transmitted to the comparator 28. In the comparator 28, the received signal 45 indicates a predetermined voltage value 47 set in the comparator 28 (reflectance capable of suppressing damage to the precursor semiconductor thin film substrate due to irradiation with the second laser light). When the voltage value) is exceeded, a signal 46 for stopping the irradiation of the second laser light is transmitted from the comparator 28 to the second pulse generation circuit 30. Thereafter, a signal 42 for stopping the irradiation of the second laser light is transmitted from the second pulse generation circuit 30 to the second laser light source 12, and the irradiation of the second laser light is stopped.

  Although not shown, the control means 23 controls the position of the stage 19, stores the irradiation target positions of the first laser beam and the second laser beam, controls the temperature inside the manufacturing apparatus 10, and controls the atmosphere. It is preferable that it is comprised so that it can perform.

In the above description, the case where the second laser light is used as the reference laser light has been described. However, the third laser light source that emits the third laser light other than the first laser light and the second laser light. Needless to say, a sensor capable of detecting the power corresponding to the wavelength of the third laser beam may be used as the detecting means. In this case, the third laser beam preferably has a wavelength at which the reflectivity changes more greatly with respect to the temperature change of the precursor semiconductor thin film substrate. For example, when comparing a YAG laser beam having a wavelength of 532 nm as a reference laser beam and a CO ₂ laser beam having a wavelength of 10.6 μm, the temperature of the precursor semiconductor thin film substrate is about In the case of 300 ° C., the reflectance changes when the temperature of the precursor semiconductor thin film substrate was displaced by about 10 ° C. were 0.07% and 0.09%, respectively. It is considered that it is preferable to use CO ₂ laser light rather than YAG laser light, since the temperature change is more easily detected when the amount of change in reflectance per unit temperature rise is larger. In this case, it is preferable to use an optical sensor in which a photosensitive part capable of detecting the power of CO ₂ laser light is formed of HdCdZnTe.

  Thus, in the present invention, the precursor semiconductor thin film is applied to the surface of the precursor semiconductor thin film by irradiating the first laser beam perpendicularly to the surface of the precursor semiconductor thin film in the precursor semiconductor thin film substrate. To melt vertically. The molten precursor semiconductor thin film is solidified and recrystallized so that crystals grow from the surface of the non-melted portion of the precursor semiconductor thin film substantially parallel to the surface of the precursor semiconductor thin film. At this time, by irradiating the second laser beam and delaying the recrystallization, longer needle-like crystal grains can be obtained and the irradiation time of the second laser beam is controlled as in the present invention. By doing so, damage due to irradiation of the precursor semiconductor thin film substrate can be suppressed.

  In the above description, the case where the crystal grains are grown substantially parallel to the surface of the precursor semiconductor thin film has been described. However, the present invention is a case where the crystal grains are grown in a direction perpendicular to the surface of the precursor semiconductor thin film. It can also be applied to.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be suitably used for forming a gate insulating film made of, for example, a polycrystalline silicon semiconductor thin film.

In this invention, it is typical sectional drawing of a preferable example of the precursor semiconductor thin film substrate with which at least 2 types of laser beams are irradiated. In this invention, it is the figure which showed an example of the waveform (power change with respect to elapsed time) of the 1st laser beam and 2nd laser beam irradiated to a precursor semiconductor thin film. It was obtained by recrystallization after melting and energy fluence when a precursor semiconductor thin film made of a hydrated amorphous silicon thin film formed on a glass substrate through a buffer layer made of silicon oxide was irradiated with a second laser beam. It is a figure which shows the relationship with the length of a crystal grain. It is a figure which shows the result of having measured the energy fluctuation | variation for every irradiation of a 2nd laser beam. In this invention, when a 2nd laser beam is irradiated to the precursor semiconductor thin film which consists of a hydrated amorphous silicon thin film, it is a figure which shows the waveform before reflection, and the waveform after reflection. It is a figure which shows the relationship between the reflectance calculated | required from FIG. 5, and the irradiation time of a 2nd laser beam. It is a figure which shows schematically the structure of a preferable example of the manufacturing apparatus of the semiconductor thin film of this invention. It is a typical block diagram of the control means shown in FIG. It is an example of the timing chart of the signal in the control means used in this invention. It is a typical enlarged plan view of an example of the crystal grain formed in the conventional super lateral growth method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Waveform of 1st laser beam 2 Waveform of 2nd laser beam 3 Waveform after reflection 4 Waveform before reflection 5 Precursor semiconductor thin film substrate 6 Precursor semiconductor thin film 7 Insulating substrate 8 Buffer Layers, 10 manufacturing apparatus, 11 first laser light source, 12 second laser light source, 13, 14 attenuator, 15, 16 uniform irradiation optical system, 17, 18 mask, 19 stage, 20, 24 imaging lens, 21 mirror , 22, 26 detector, 23 control means, 25 beam splitter, 27 signal processing circuit, 28 comparator, 29 first pulse generation circuit, 30 second pulse generation circuit, 31 crystal grains, 32 fine crystal grains, 41, 42 , 43, 44, 45, 46 signal, 47 predetermined voltage value.

Claims (13)

  A method of manufacturing a semiconductor thin film by irradiating at least two types of laser light and melting a solid state precursor semiconductor thin film contained in a precursor semiconductor thin film substrate and then recrystallizing the precursor semiconductor thin film, A step of detecting a reflectance of an irradiation portion of a reference laser beam irradiated on a substrate, and a step of controlling an irradiation time of at least one kind of laser beam by the reflectance. Production method.   The at least two types of laser beams include a first laser beam that melts the precursor semiconductor thin film in a solid state and a second laser beam that delays recrystallization of the melted precursor semiconductor thin film. The method for producing a semiconductor thin film according to claim 1, wherein:   3. The method of manufacturing a semiconductor thin film according to claim 2, wherein the second laser beam is the reference laser beam.   3. The irradiation time of the second laser light is controlled by stopping the irradiation of the second laser light when the reflectance of the irradiation part reaches a predetermined value. 3. A method for producing a semiconductor thin film according to 3.   5. The semiconductor thin film according to claim 2, wherein the first laser beam has a wavelength in an ultraviolet region, and the second laser beam has a wavelength in a visible region or an infrared region. Manufacturing method.   6. The method of manufacturing a semiconductor thin film according to claim 2, wherein the second laser beam has a wavelength in a range of 9 [mu] m to 11 [mu] m.   7. The semiconductor thin film production according to claim 1, wherein the crystal grains grown during the recrystallization grow substantially parallel to the surface of the precursor semiconductor thin film. Method.   Two or more laser light sources capable of irradiating at least two types of laser light, detection means for detecting the reflectance of the irradiated portion of the reference laser light irradiated to the precursor semiconductor thin film substrate, and the reference laser light And a control means for controlling the irradiation time of at least one type of laser light according to the reflectance.   The two or more laser light sources are a first laser light source that irradiates a first laser light for melting a solid state precursor semiconductor thin film included in the precursor semiconductor thin film substrate, and the molten precursor. A second laser light source for irradiating a second laser beam for delaying recrystallization of the semiconductor thin film, wherein the reference laser beam is the second laser beam, and the detection means is the first laser beam. The second laser light irradiation site is detected, and the control means controls the irradiation time of the second laser light according to the reflectance of the second laser light irradiation site. Item 9. The semiconductor thin film manufacturing apparatus according to Item 8.   The control means controls the irradiation time of the second laser light by stopping the irradiation of the second laser light when the reflectance of the irradiated portion of the second laser light reaches a predetermined value. The apparatus for producing a semiconductor thin film according to claim 9, wherein:   The detection means includes an optical sensor and a signal processing circuit for processing a signal from the optical sensor, and the optical sensor includes a second laser beam before reflection and a second laser beam after reflection. And a signal indicating the power of the second laser light before the reflection and a signal indicating the power of the second laser light after the reflection are transmitted to the signal processing circuit, respectively. 11. The semiconductor thin film manufacturing apparatus according to claim 9, wherein a signal indicating the reflectance is generated by processing the signal transmitted from an optical sensor.   The first laser light source emits a first laser light having a wavelength in the ultraviolet region, and the second laser light source emits a second laser light having a wavelength in the visible region or infrared region. The apparatus for manufacturing a semiconductor thin film according to any one of claims 9 to 11.   The apparatus for producing a semiconductor thin film according to any one of claims 9 to 12, wherein the second laser light irradiated by the second laser light source has a wavelength of 9 µm or more and 11 µm or less.

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