JP2005236253A - Crystallization device and crystallization method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology whereby how a semiconductor thin film is melted and a prescribed region of the thin film is crystallized can be monitored at a high spatial resolution on the order of several μm or below and at a high temporal resolution in real time. <P>SOLUTION: In a crystallization device comprising a crystallizing optical system which irradiates the semiconductor thin film formed on a substrate with pulse energy light having intensity distribution to melt the thin film and crystallizes the prescribed region of the thin film according to the intensity distribution by growing grains laterally immediately after the end of the irradiation of the pulse energy light, the device comprises: an illumination light source provided out of an optical path of the energy light and for emitting observation illumination light for illuminating the energy light irradiation region on the thin film; an illumination optical system including annular optical elements which provides the optical path of the energy light in a central portion and guides the illumination light to the thin film along the optical path; and an observing optical system which magnifies the illumination light transmitted through the substrate including the thin film and monitors a process of the grains growing laterally in the prescribed region after the end of irradiation of the pulse energy light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a crystallization apparatus and a crystallization method, and more particularly to a crystallization apparatus and a crystallization method capable of observing and monitoring a state in which a thin film melts and crystallizes in real time.

  A crystallization technique for melting and crystallizing a non-single-crystal semiconductor thin film using an energy beam, for example, a high-energy laser beam such as a short-pulse laser beam is, for example, a liquid crystal display device or an organic electroluminescence display device. It is used for crystallization of a semiconductor thin film that forms a thin film transistor (TFT) used in, for example. The present inventors have developed a liquid crystal display device for a large screen. For example, a switching element for a pixel portion of a liquid crystal display device is formed of a thin film transistor and is formed on a silicon thin film crystallized to have a large particle size because high speed operation is required. The crystallized silicon thin film is formed by a laser crystallization technique for crystallizing an amorphous silicon thin film formed on a support substrate such as a large glass substrate, for example.

  Among such crystallization techniques, a technique for crystallization by irradiating a semiconductor thin film with phase-modulated excimer laser light (Phase Modulated Excimer Laser Annealing: PMELA) has attracted attention. The PMELA technology irradiates a non-single crystal semiconductor thin film, for example, an amorphous silicon or polycrystalline silicon thin film, with an excimer laser beam having a predetermined light intensity distribution that is phase modulated by a phase modulation element, for example, a phase shifter, In this method, a predetermined region is crystallized by melting a silicon thin film. By appropriately controlling the crystallization, a crystallized silicon thin film having a large particle size can be obtained. In the currently developed PMELA technology, a predetermined area in a region of several mm square is melted and crystallized by a single irradiation, and a relatively uniform crystal having a size of several μm to 10 μm. A crystallized silicon thin film having grains and excellent quality is formed. The details are described in Non-Patent Document 1, for example.

  In a silicon thin film having a large particle diameter of several μm or more, one or more thin film transistors can be formed in one crystal grain. The liquid crystal display device constituted by the thin film transistor can reproduce a uniform color image by interfering with the front surface of a large screen and can perform high-speed switching. The manufacture of a semiconductor thin film having large-sized crystal grains having such characteristics requires high reliability and quality control.

  In the current PMELA technology, the power fluctuation of the excimer laser light that is put into practical use is about 5% to 10%. However, compared to the stability of this excimer laser beam, the process margin for forming a crystallized silicon thin film having a desired quality, for example, is very narrow. Therefore, in order to industrialize, it is necessary to expand the process margin in order to further improve the quality and stabilize the quality of the crystallized silicon thin film. In order to cope with this, the state of the silicon thin film changing from melting to crystallization in a minute region is real-time with high spatial resolution of several μm, or high time resolution on the order of nanoseconds immediately after laser irradiation. There is a request to monitor or monitor.

  As such in-situ observation, in Excimer Laser Crystallization (ELA) technology without phase modulation, an experimental example in which the thermal characteristics of a silicon thin film that has been melted and crystallized is measured in situ is described in Non-Patent Document 2. It has been reported. This report measures the thermal characteristics of a silicon thin film that is melted and crystallized with a high time resolution on the order of nanoseconds (hereinafter referred to as nsec). Specifically, helium-neon (He—Ne) laser light (wavelengths of 633 nm and 1520 nm), which is a probe light for observation, is irradiated obliquely from above to the melting part and the crystallization part. The reflected light and transmitted light from the melted part and the crystallized part are detected by an indium gallium arsenide photodetector and a silicon pn photodiode that respond at high speed, and the thermal characteristics of the silicon thin film are measured.

  In PMELA, a silicon thin film is melted by irradiation with laser light for crystallization of several tens of nsec to 100 nsec, and then crystallized. The time from the melting to the end of crystallization is several hundred ns, and the crystallization region to be observed and monitored is a region determined by the light intensity distribution, and the size is a minute region of about several tens of μm square. However, the method of Non-Patent Document 2 cannot specify at which position of the amorphous silicon thin film is melted by the irradiation of the crystallization laser beam, that is, the melting region of the amorphous silicon thin film. Of course, it is not possible to measure the temporal change of the melting region and the state of crystallization in the predetermined region. When a silicon thin film transistor having a crystallized silicon thin film that has been subjected to such an uncertain evaluation is used as a switching element of a liquid crystal display device, the electrical characteristics of the switching element are defective.

  Further, in the method of Non-Patent Document 2, position information important in lateral crystal growth (lateral growth) at a specific position as in PMELA, that is, a steep state change of 1 nsec or less in a region having an area of about 1 μm, a minute light It is not possible to measure the change. In order to realize higher performance displays by miniaturizing transistors and achieving higher integration, it is monitored at which position on the amorphous silicon thin film and on what process it is crystallized. This is important for process development, production control, and quality control.

  Therefore, although the method of Non-Patent Document 2 has high temporal resolution, it cannot be applied to an observation system that satisfies both high spatial resolution of several μm or less and high temporal resolution at the same time.

Further, the lateral growth speed at the time of laser crystallization of the amorphous silicon thin film is estimated to be 7 m / sec, and the currently announced crystal grain size is about several μm at the maximum. Therefore, in order to monitor the lateral growth of crystallization in real time, the time required for crystal growth is 10 ⁻⁶ m / (7 m / sec) ≈10 ⁻⁷ sec = 100 nsec.
It is preferable to measure at a time resolution of at least one digit (10 nsec or more) (in terms of spatial resolution).

Furthermore, the illumination light for observation is irradiated to the crystal growth portion, and according to the measurement data of the change in reflectance from the crystal growth portion, the phase change (solid → liquid → solid) time is about 10 nsec. In order to monitor the lateral growth of crystallization in real time, a resolution of about 1 nsec, which is 1/10 of 10 nsec, is required. Thus, in order to observe and monitor (monitor) the lateral growth by the laser crystallization method, it is possible to measure with a very short time resolution of 1 nsec or less, and the space to be observed and monitored is very narrow. There are problems such as being able to measure with high spatial resolution in an area of 1 μm or less, and being able to measure an image with a weak light amount. Compared with the measurement at time (seconds) or distance (m), the amount of light is a minute amount of about 10 ⁻⁹ × 10 ⁻⁶ , and there is a problem that the amount of light for observation is small.

Further, Patent Document 1 discloses an in-situ observation method in which crystallization laser light and observation light are simultaneously irradiated. In this method, a perforated objective lens is used to irradiate and detect crystallization laser light and observation light. The crystallization laser light is an excimer laser light that is not phase-modulated, and irradiates the film to be processed through the hole of the objective lens. In the annealing process, reflected light from the film to be processed is detected through a perforated objective lens, and for example, changes in the reflectance, Raman spectrum, etc. of the sample surface are measured in-situ. Patent Document 1 discloses a method for managing crystal growth by observing a state of crystallization in a specific region of a film to be processed required in PMELA or feeding back to crystal growth based on the observed crystallization information. Not described.
Japanese Patent Laid-Open No. 2002-176209 Hiroaki Inoue, Mitsuru Nakata, Masayoshi Matsumura; Transactions of the Institute of Electronics, Information and Communication Engineers Vol. J85-C, No.8, pp.624-629, 2002 2-D Position Control Large Grain Formation Method ” M. Hatano, S. Moon, M. Lee, K. Suzuki, and C. Grigoropoulos; J. Applied Physics, Vol.87, No.1, pp.36-43, 2000, “Excimer laser-induced temperature field in melting and resolidification of silicon thin films ”.

  The inventor irradiates energy light, for example, in a laser crystallization apparatus, a state in which a predetermined region melts and crystallizes in real time with a high spatial resolution of several μm and a high temporal resolution of nanosecond order. Alternatively, an observation system that observes during melting or immediately after melting, that is, an optical system for observation has been developed. In order to incorporate an observation system into a laser crystallization apparatus, it is necessary to use an optical system in which excimer laser light for crystallization (ultraviolet light region) and illumination light for observation (visible light region) are simultaneously corrected for aberrations. preferable.

  In order to satisfy this problem and requirement, there are further problems as follows.

A lens actually used in an ELA apparatus is premised on the use in high light intensity, high duty, and large area from the viewpoint of production efficiency. Specifically, the laser light intensity is preferably about 1 J / cm ² on the substrate to be crystallized. Therefore, unlike an exposure apparatus for a large-scale integrated circuit that uses the same kind of excimer laser light, the laser light is used with a wide spectral width (0.5 nm). The excimer laser beam used is, for example, krypton fluoride (KrF) or xenon chloride (XeCl), and the wavelengths thereof are 248 nm and 308 nm, respectively. Considering the wavelength of these laser beams, the lens material that can be used has a material limitation that ultraviolet-grade synthetic quartz or calcium fluoride (CaF ₂ ) is preferable. In addition, a configuration including a bonded lens such as a microscope lens for visible light is not preferable in terms of heat resistance, and the degree of freedom in lens design is low.

  Furthermore, in a crystallization process using a phase modulation element, for example, a phase shifter, a laser beam having a predetermined light intensity distribution is irradiated to a predetermined region of a substrate where crystallization is performed. That is, for example, the mask pattern of the phase shifter is transferred to a specific region on the substrate with a high resolution of about several μm at a reduced or equal magnification. For this reason, the lens (group) used in the PMELA apparatus must be corrected for aberrations such as chromatic aberration and distortion aberration in the ultraviolet region. When excimer laser light and visible light for microscopic observation are used in this single optical system, aberration correction must be performed simultaneously in the two wavelength regions of the ultraviolet light region and the visible light region, which is extremely difficult. It is a difficult task. Even if chromatic aberration can be corrected, the number of lenses must be increased, and as a result of the increase in light absorption by the lenses, the intensity of the laser beam reaching the substrate decreases, which is a requirement to obtain a high light intensity. It goes against it.

  Furthermore, the crystallization optical system adapted to the excimer laser beam having the above-described performance has a problem that the resolution of visible light is reduced when visible light is transmitted. That is, since the resolution is proportional to the wavelength of light, in the case of visible light (wavelength: 480 nm-600 nm) having a wavelength about twice that of excimer laser light (wavelength: 248 nm, 308 nm), the excimer laser light is 2 μm. Is reduced to about 4 μm, which is twice that of visible light. As a result, the resolving power of 1 μm or less necessary for observing and monitoring a crystallized region of several μm cannot be obtained.

  Further, in order to observe and monitor the state in which the semiconductor thin film provided on the substrate melts and crystallizes in real time, it is necessary to observe with a very short time (nanosecond) time resolution. Therefore, an illumination light source for observation with high brightness corresponding to short-time observation is necessary. When such visible light as illumination light for observation is irradiated through a large number of optical lenses, not only the problem of losing the amount of light but also adversely affecting the imaging performance of the original crystallization excimer laser light. There's a problem.

That is, an optical system capable of meeting such a requirement has a high light intensity (for example, 1 J / cm ² or more on the substrate), an irradiation area (for example, 5 × 5 mm ² or more), and a high duty (for example, a laser operating frequency of 100 Hz or more). ) Excimer laser light (for example, wavelength 248 nm) and illumination light for observation, for example, visible light (for example, wavelengths 480 nm to 650 nm) at least two different wavelengths can be used stably.

  According to the present invention, an energy beam having an energy distribution, for example, a pulsed excimer laser beam that has been phase-modulated to give a light intensity distribution is irradiated to the semiconductor thin film to melt a predetermined region of the semiconductor thin film. Then, the state of lateral crystallization in a predetermined region controlled by the energy distribution is observed in real time or immediately after the end of pulsed laser light irradiation with a high spatial resolution of several μm or less and a high temporal resolution of nanosecond order, It is possible to monitor.

  Furthermore, based on the observation result, for example, by providing feedback, the crystallization process is stabilized, and a crystallization apparatus and a crystallization method capable of efficiently crystallizing a high-quality semiconductor thin film are provided. It is.

  The above problems and problems are solved by the following crystallization apparatus and crystallization method.

 The crystallization apparatus according to one aspect of the present invention irradiates a thin film provided on a substrate with pulsed energy light having a light intensity distribution to melt the thin film, and the light intensity immediately after the irradiation of the pulsed energy light is completed. A crystallization apparatus comprising a crystallization optical system for laterally growing crystal grains in a predetermined region of the thin film according to a distribution to crystallize the crystal grains, the crystallizing apparatus being disposed outside the optical path of the energy light, An illumination light source that emits observation illumination light that illuminates the energy light irradiation area of the optical fiber, and an optical ring that guides the illumination light from the illumination light source to the thin film along the optical path. The illumination light transmitted through the illumination optical system including the element and the substrate including the thin film is magnified, and after the irradiation with the pulsed energy light, crystal grains are laterally formed in the predetermined region. Comprising the observation optical system for observing the process of.

 The crystallization apparatus according to another aspect of the present invention irradiates a thin film provided on a substrate with pulsed energy light having a light intensity distribution to melt the thin film, and immediately after the irradiation of the pulsed energy light, A crystallization apparatus comprising a crystallization optical system that crystallizes a predetermined region of the thin film according to a light intensity distribution and moves a solid-liquid interface in a lateral direction, and is disposed outside the optical path of the energy light, An illumination light source that emits illumination light for observation that illuminates the energy light irradiation region on the thin film, and an optical path of the energy light is in a central portion, and the illumination light from the illumination light source is transmitted along the optical path to the thin film And an observation optical system for observing a process in which the solid-liquid interface moves laterally in the predetermined region by magnifying the illumination light transmitted through the substrate including the thin film, Comprising.

 A crystallization method according to still another aspect of the present invention includes a step of emitting pulsed energy light having a light intensity distribution, and irradiating the thin film provided on the substrate with the pulsed energy light to melt the thin film. A step in which crystal grains grow laterally and crystallize in a predetermined region of the thin film according to the light intensity distribution immediately after the end of the irradiation of the pulsed energy light, and are provided coaxially in the optical path of the energy light. The step of illuminating the irradiated portion of the energy light with the annular illumination light for observation along the optical path through the annular optical element that transmits the energy light, and the observation illumination light transmitted through the thin film is enlarged A step of detecting a process in which crystal grains grow laterally, a step of converting the detected process into electronic data, and a step of displaying the electronic data.

  A crystallization method according to still another aspect of the present invention includes a step of emitting pulsed energy light having a light intensity distribution, and irradiating the thin film provided on the substrate with the pulsed energy light to melt the thin film. A step in which a solid-liquid interface moves laterally in a predetermined region of the thin film according to the light intensity distribution immediately after the irradiation of the pulsed energy light and crystallizes, and is provided coaxially in the optical path of the energy light. And a step of illuminating the irradiated portion of the energy light with the annular illumination light for observation along the optical path through the annular optical element that transmits the energy light, and expanding the observation illumination light transmitted through the thin film. The method includes a step of detecting a process in which the solid-liquid interface moves in a lateral direction, a step of converting the detected process into electronic data, and a step of displaying the electronic data.

  According to the present invention, the state in which a semiconductor thin film in a predetermined region melts and crystallizes can be observed or monitored in real time or immediately after and with high spatial resolution and high time resolution of several μm or less. . Furthermore, based on this observation result, for example, by providing feedback, the crystallization process is stabilized, and a crystallization apparatus and a crystallization method capable of efficiently crystallizing a high-quality semiconductor thin film are provided. be able to.

  Configuration examples and application examples of embodiments of a crystallization apparatus and a crystallization method that solve the above problems will be described below with reference to the drawings.

  A crystallization apparatus according to an embodiment of the present invention melts a semiconductor thin film provided on a substrate by irradiation with pulsed laser light having a light intensity distribution, and crystal grains in a predetermined region of the semiconductor thin film immediately after the end of laser light irradiation. It is a device equipped with a mechanism to observe and monitor the process of growing in the horizontal direction in real time.

  In this embodiment, the position at which crystallization starts in the molten semiconductor thin film is determined by the light intensity distribution of the irradiated laser light. Therefore, crystallization can be started from a predetermined position of the semiconductor thin film by irradiating laser light having a predetermined light intensity distribution. As a result, the observation location can be specified in advance, so that high spatial resolution can be observed.

  As shown in FIG. 1, the laser crystallization apparatus 1 of this embodiment includes a crystallization optical system 20 and a microscopic observation system 40. The crystallization optical system 20 irradiates the substrate 32 with laser light for melting and crystallizing the semiconductor thin film 35 provided on the substrate 32. The microscopic observation system 40 observes a predetermined region where the semiconductor thin film is melted and crystallized. The microscopic observation system 40 further includes an observation illumination optical system 42 that irradiates observation illumination light, and a transmission type microscopic observation optical system 60 that observes and observes the state in which the semiconductor thin film 35 melts and crystallizes. . The optical system of the present embodiment is characterized by the fact that the imaging optical system 30 in the crystallization optical system 20 has a long focal length (50 mm to 70 mm), and the imaging optical system 30 and the substrate 32. An independent illumination optical system 42 for observation with high brightness and visible light, for example, is coaxially arranged in the space between the two. That is, the observation illumination optical system 42 is an optical system independent of the crystallization imaging optical system 30.

Another feature of this embodiment, the energy beam, for example, the semiconductor thin film 35 provided on the substrate 32 of crystallizing an excimer pulsed laser beam, for example, it is irradiated from 4 mm ² in the area of 25 mm ² approximately of the area The state in which the illumination light for observation in a period of only several hundred ns changes in a specific region within the irradiation region of the order of μm is observed in real time, for example, displayed on the monitor screen 74c. That is. Furthermore, based on this observation result, the crystallization process is controlled by feedback, for example. As a result, the crystallization process is stabilized and the crystallization is efficiently performed on a high-quality semiconductor thin film.

  A feature of the microscopic observation system 40 that observes an ultra-high-speed change in a predetermined ultrafine area as described above is that the crystallization optical system 20 is formed around the central axis, and the observation is performed around the optical path of the crystallization optical system 20. The annular optical systems 52 and 54 constituting the illumination optical system 42 are provided. The annular optical system 52 guides the observation illumination light coaxially with the crystallization laser light, and is, for example, an annular reflector. The annular optical system 54 forms an image of the annular illumination light on the substrate 32, and one annular optical lens is optimal. Although it is conceivable to use an objective lens using a plurality of annular lenses, it is not practical from the viewpoint of optical performance, price, and the like. The annular optical systems 52 and 54 enable observation and monitoring with high spatial resolution and high time resolution. The state change of the laser light irradiation region for crystallization is stored in the storage unit 74b of the image processing unit 74, for example, a memory, so that a desired condition of the observer, for example, a desired speed, immediately after crystallization, or real time Thus, the state change of the irradiation region can be displayed as a still image or a video on the monitor screen 74c, for example.

  The laser crystallization apparatus 1 shown in FIG. 1 is a laser crystallization apparatus 1 that includes a transmission microscope observation system 40 and projects an image of the phase modulation element 28 in a reduced scale. Further, it has a function of correcting the deviation in the height direction and the plane of the substrate 32 to be crystallized based on the observation result by the microscope observation system 40.

  That is, the laser crystallization apparatus 1 includes a crystallization optical system 20 that forms a crystallization optical pattern for crystallization with a large particle size, and an observation installed around the optical path of the crystallization laser light. The observation illumination optical system 42 for forming the annular light for observation, the microscopic observation optical system 60 for observing the processing region of the crystallization process, the timing control unit 10, and the stage driving unit 12 are provided.

  The crystallization optical system 20 includes a laser light source 22, a beam expander 24, a homogenizer 26, a phase modulation element 28, for example, a phase shifter, an imaging optical system 30, and a substrate 32 at predetermined positions. And a substrate holding stage 38 for guiding. The laser light from the laser light source 22 is expanded by the beam expander 24, the in-plane light intensity is made uniform by the homogenizer 26, and is irradiated to the phase modulation element 28, for example, the phase shifter. The excimer laser light transmitted through the phase shifter 28 is modulated into light having a predetermined light intensity distribution, for example, a light intensity distribution having an inverse peak pattern, and is reduced by an imaging optical system 30, for example, an excimer laser imaging optical system. Alternatively, the substrate 32 is irradiated at the same magnification.

The laser light source 22 outputs laser light having energy sufficient to melt a non-single crystal semiconductor thin film 35 provided on the substrate 32, for example, an amorphous semiconductor thin film or a polycrystalline semiconductor thin film, for example, 1 J / cm ^2. To do. The laser light is preferably, for example, krypton fluoride (KrF) excimer laser light or xenon chloride (XeCl) excimer laser light having a wavelength of 248 nm. In addition, an argon fluoride (ArF) excimer laser beam, an argon (Ar) excimer laser beam, a YAG laser beam, an ion beam, an electron beam, and a xenon (Xe) flash lamp can be used. For example, the excimer laser light source 22 is a pulse oscillation type, the oscillation frequency is, for example, 100 Hz to 300 Hz, and the pulse width is a half width, for example, 20 nsec to 200 nsec. In the present embodiment, pulsed KrF excimer laser light having a half width of 25 nsec is used. Further, the optical energy of the KrF excimer laser light irradiated on the substrate 32 is about 1 J / cm ² . When the oscillation frequency is set to 100 Hz, for example, the irradiation area of the excimer laser light is set to 2 mm × 2 mm, for example, and the substrate 32 is moved stepwise by the substrate holding stage 38, for example, in 2 mm steps, the substrate is The moving speed of 32 is 200 mm / sec.

  The beam expander 24 expands incident laser light, and includes a concave lens 24a that expands and a convex lens 24b that converts the light into parallel light, as shown in FIG. The homogenizer 26 has a function of determining the dimension of the incident laser light in the cross-sectional XY direction and uniforming the beam intensity distribution within the determined shape. For example, a plurality of X direction cylindrical lenses are arranged in the Y direction to form a plurality of light beams arranged in the Y direction, and each light beam is redistributed in the Y direction by the X direction condenser lens. Similarly, the Y direction cylindrical lens is arranged in the X direction. A plurality of light beams arranged in the X direction are formed, and each light beam is redistributed in the X direction by a Y-direction condenser lens. That is, as shown in FIG. 2, the first homogenizer includes a first fly-eye lens 26a and a first condenser lens 26b, and the second homogenizer includes a second fly-eye lens 26c and a second condenser lens 26d. The first homogenizer makes the laser light intensity in the Y direction uniform on the phase shifter 28, and the second homogenizer makes the laser light intensity in the X direction uniform on the phase shifter 28 and sets the incident angle. . Therefore, the KrF excimer laser light is modulated by the homogenizer 26 into laser light having a predetermined angular spread and a uniform beam intensity in the cross section, and irradiates the phase shifter 28.

  The phase shifter 28 is an example of a phase modulation element, for example, a step formed on a quartz glass substrate. The laser beam is diffracted and interfered at the boundary between the steps to give a periodic spatial distribution to the laser beam intensity. For example, a phase difference of 180 ° is added to the left and right. The phase shifter 28 with a 180 ° phase difference between the left and right phase modulates the incident light into a left-right symmetrical reverse peak light intensity distribution. The level difference (thickness distribution) d is obtained by d = λ / 2 (n−1) where λ is the wavelength of the laser beam and n is the refractive index of the transparent substrate of the phase shifter. From this equation, the phase shifter 28 can be manufactured, for example, by forming a step corresponding to a predetermined phase difference on a quartz glass substrate. The step of the quartz glass substrate can be formed by selective etching or FIB (Focused Ion Beam) processing. For example, assuming that the refractive index of the quartz substrate is 1.46, the wavelength of the XeC1 excimer laser light is 308 nm, so that the step for providing a 180 ° phase difference is 334.8 nm. The phase shifter 28 is stepped so as to form a reverse peak light intensity distribution by phase-modulating the incident light, and shifts the phase of the excimer laser light by a half wavelength. As a result, the laser light that irradiates the semiconductor thin film has a light intensity distribution with a pattern having a reverse peak where the portion corresponding to the phase shift portion has the minimum light intensity. According to this method, a predetermined beam light intensity distribution can be realized without shielding the excimer laser light by the metal pattern used in other methods.

The laser light transmitted through the phase shifter 28 is imaged with a predetermined light intensity distribution on a substrate 32 placed at a position conjugate with the phase shifter 28 by an aberration-corrected excimer imaging optical system 30. The imaging optical system 30 includes a lens group including, for example, a plurality of calcium fluoride (CaF ₂ ) lenses and a synthetic quartz lens. The imaging optical system 30 has, for example, a reduction ratio of 1/5, N.I. A. : 0.13, resolving power: 2 μm, depth of focus: ± 10 μm, focal length: a long focal lens having a performance of 50 mm to 70 mm.

  The substrate 32 is placed at a position optically conjugate with the phase shifter 28 of the imaging optical system 30, that is, an imaging position of the phase shifter 28 by the imaging optical system 30. The imaging optical system 30 can include an aperture stop between the lenses.

  As shown in FIG. 3, the substrate 32 to be crystallized is generally covered with an insulating film 34 on a support substrate 33 (for example, a transparent glass substrate, a plastic substrate, a semiconductor substrate (wafer) such as silicon). A treatment film 35, for example, a semiconductor thin film (for example, an amorphous silicon thin film, a polycrystalline silicon thin film, a sputtered silicon thin film, a silicon germanium film, a dehydrogenated amorphous silicon thin film) is formed on the film. An insulating film 36 is provided as a cap film. The substrate 32 used in this embodiment is obtained by forming a dehydrogenated amorphous silicon thin film 35 on a glass substrate 33 to a desired thickness, for example, 50 nm. The substrate 32 is detachably held by a substrate holding stage 38 that is movable in the X, Y, and Z directions for holding the substrate in a predetermined position.

  As described above, the laser crystallization apparatus 1 phase-modulates the homogenized pulsed laser beam by the phase shifter 28 to form a pulsed laser beam for crystallization having a reverse peak light intensity distribution on the substrate 32. 1 shows a projection type crystallization apparatus 1 that emits pulsed laser light. The semiconductor thin film 35 irradiated with the pulsed laser beam melts and starts to be crystallized immediately after the end of the laser beam irradiation. In the molten semiconductor thin film 35, crystallization starts from a position corresponding to the light intensity distribution of the irradiated laser light. The semiconductor thin film 35 immediately after laser light irradiation has a high melting temperature in the high light intensity portion and a low temperature in the low light intensity portion. Therefore, crystallization starts from the low light intensity portion of the laser light, and the solid-liquid interface moves in the lateral direction toward the high light intensity portion. That is, the crystal grains also grow at a high speed in the lateral direction. Thus, crystallization proceeds in the horizontal direction according to the light intensity distribution of the light pattern, and for example, the semiconductor thin film 35 having a single crystal grain with a large grain size of about 10 μm can be formed. Thus, since crystallization can be started from a predetermined position of the semiconductor thin film 35, the observation location can be specified in advance, and high spatial resolution observation becomes possible.

  This crystallization process is a very fast change and is completed in an extremely short time of several hundreds of nsec. A microscopic observation system 40 is provided to observe or monitor the movement of the solid-liquid interface and the ultra-high-speed change in the lateral growth of crystal grains in this specific region. As shown in FIG. 1, the microscope observation system 40 includes an observation illumination optical system 42 that emits observation illumination light, and a microscope observation optical system 60 that observes and displays the observation illumination light. The microscopic observation optical system 60 is provided on the lower surface side of the holding stage 38, and the process in which the semiconductor thin film 35 on the substrate 32 grows laterally immediately after the end of laser beam irradiation starts from a predetermined region melted and crystallized. The crystallization process is received in real time, and the crystallization process is observed, monitored or measured in real time. In order to observe, monitor, or measure with the microscopic observation optical system 60, a composite optical in which a part of the crystallization optical system 20 and a part of the observation illumination optical system 42 overlap each other on the upper surface side of the holding stage 38. A system is provided.

  In the observation illumination optical system 42, the observation illumination light is guided to the annular optical systems 52 and 54 installed between the imaging optical system 30 and the substrate 32, as shown in FIG. The optical system 20 is not passed. The observation illumination optical system 42 illuminates the substrate 32 with the observation illumination light in an annular shape, and an optical path of the crystallization laser light is formed on the central axes of the annular optical systems 52 and 54. The composite optical system is an optical system that allows a crystallization process and a crystallization state observation process to be performed simultaneously without interfering with each other. The annular illumination light for observation enables observation, monitoring, or measurement with high spatial resolution and high time resolution.

  As shown in FIG. 1, the observation illumination optical system 42 includes a high brightness observation illumination light source 44, a beam expander 50, an annular reflector 52, and an annular convergence lens 54. That is, the optical path of the observation illumination optical system 42 is configured by the annular optical systems 52 and 54 provided with window holes through which the laser light passes in the optical path so as not to block the optical path of the excimer laser light.

  The observation illumination light from the high-intensity observation illumination light source 44 is expanded by the beam expander 50 into parallel light, and becomes annular observation illumination light by the annular optical system including the annular reflector 52 and the annular converging lens 54. The annular observation illumination light converges on the substrate 32 from the same side along the optical path of the crystallization laser light, for example, from the outside of the excimer laser light incident on the substrate 32 at an angle of 7.5 ° from the perpendicular. Is incident on. That is, the illumination light for annular observation illuminates the crystallization process part during the crystallization process. The crystallization process section refers to a region of the semiconductor thin film 35 that is being irradiated with the crystallization laser light to shift from the melting process to the solidification process and completing the crystallization.

  The high-intensity observation illumination light source 44 enables observation with a time resolution on the order of nanoseconds, so that a high-intensity light source such as a xenon (Xe) flash lamp or Ar laser light, helium-neon (He-Ne) laser is used. It is a light source that emits visible laser light such as light. In this embodiment, a Xe flash lamp having a pulse width of 2 μsec and an output of 60 W is used. When laser light is used as the light source, it is preferable to use a homogenizer (not shown) in order to make the light intensity in the cross section of the laser light uniform. The beam expander 50 and the converging lens 54 are preferably configured with a small number of lenses in order to suppress loss due to absorption and reflection of illumination light. For example, an aspherical lens can be used. The annular reflector 52 and the annular converging lens 54 must be annular, but the beam expander 50 is not necessarily an annular lens. The size of the window hole of the annular reflector 52 is, for example, that the irradiation area of the crystallization laser light is about 5 mm × 5 mm at the maximum on the substrate 32, and the prospective angle of the crystallization laser light on the substrate 32 is Assuming that the angle is about 7.5 °, it is only necessary to pass a crystallization laser beam having a diameter of about 12 mm at a position about 25 mm away from the substrate 32. The shapes of the annular reflector 52 and the annular converging lens 54 can be annular or polygonal.

  The observation illumination optical system 42 may have other configurations and can also be used. For example, as shown in FIG. 4A, the converging lens 56 may be installed outside the optical path of the crystallization laser light (for example, excimer laser light) between the beam expander 50 and the annular reflector 52. Is possible. In this configuration, since the annular reflector 52 can be installed close to the substrate 32, the window hole for allowing the crystallization laser light to pass through can be made small. In this case, the annular converging lens 56 is not necessarily annular because it is disposed outside the optical path of the laser.

  As shown in FIG. 4B, an annular concave mirror (reflector) 58 having a function of combining the annular reflector 52 and the annular lens 54 of FIG. 1 may be adopted as the annular optical element. In this case, the number of optical elements is reduced by one compared to the configuration of FIG.

  Next, the microscopic observation optical system 60 for observing and displaying the crystallization process state will be described with reference to FIG. The microscopic observation optical system 60 is configured to change the optical path of the observation light from the microscopic objective lens 62 that magnifies and forms the transmitted light from the crystallization process unit, that is, the observation light by the observation illumination light. By detecting a change in the reflecting mirror 64 provided on the optical path, the imaging lens 66 for imaging the observation light, and the microscopic objective lens 62 and the crystallization process part enlarged and imaged by the imaging lens 66, It comprises a photodetector 68 as a means for displaying, an image intensifier 70, an image sensor 72, and an image processing unit 74.

  A semiconductor thin film 35 (for example, an amorphous silicon thin film or a polycrystalline silicon thin film) provided on the substrate 32 to be processed becomes metallic when melted and does not transmit visible light. On the other hand, the unmelted part and the crystallized and solidified silicon thin film 35 transmit red visible light fairly well. In this respect, the observation method using transmitted light has high contrast and is suitable for observation of a state in which the semiconductor thin film 35 is melted and crystallized. Further, when the observation illumination light is irradiated almost perpendicularly to the substrate 32 from the same side as the crystallization laser light, the microscopic objective lens 62 of the transmission type microscopic observation optical system 40 can use the center portion of the lens. There is an advantage that aberration correction is easy.

  In the microscopic observation optical system 60, the transmitted light image from the substrate 32 is collected by the microscopic objective lens 62, and passes through the reflecting mirror 64 to the photoelectric surface 68 a that is the light receiving surface of the photodetector 68 by the imaging lens 66. The image is formed with a high resolution of several μm or less. The photoelectric surface 68a of the photodetector 68 has a slit-shaped light receiving surface for observing a crystallization state that changes at high speed. The microscopic observation optical system 40 is set in advance so that an image from a predetermined crystallization region of the semiconductor thin film 35 enters the slit-shaped photocathode 68a. The size of the slit-shaped photocathode 68a is, for example, a square having a width of several millimeters and a length of several centimeters. The photodetector 68 photomultiplies the image incident on the photocathode 68a to form a high resolution image on the phosphor screen 68c. The high-resolution image obtained by the photodetector 68 is further multiplied in luminance by the image intensifier 70 and is captured by the image sensor 72 as image data. This image data is signal-processed by the image processing unit 74. This signal processing is, for example, analysis of image data, storage of image data, and display on a display unit of image data.

  The photodetector 68 is preferably a photoelectric tube as shown in FIG. 5, for example, a streak camera. As a streak camera, for example, a streak tube that can convert an incident light image into photoelectrons, then convert it back to light, and change the one-dimensional image with time with a high time resolution of several nanoseconds can be used. The general streak tube 68 is a special purpose vacuum tube, and has a configuration as shown in FIG. 5, for example. The image of the incident light is imaged and received on the slit-shaped photocathode 68a. The slit-shaped image is a one-dimensional image of a predetermined crystallization process part. The photocathode 68a converts this one-dimensional image of incident light into photoelectrons. The linear photoelectron beam generated on the photocathode 68a passes through the sweep electrode 68b-2. The sweep electrode 68b-2 is provided with a pair of electrodes separated to sweep a photoelectron beam in the X or Y direction. A sweep voltage SV (see FIGS. 5 and 6) is applied to the sweep electrode 68b-2 from the sweep circuit 68b-1. The sweep circuit 68b-1 is a timing controlled by a trigger signal P2 (see FIGS. 5 and 6) from the timing control unit 10 (see FIG. 1), and sweep voltage SV (see FIGS. 5 and 6) that changes with time. ) Is supplied to the sweep electrode 68b-2. When the linear photoelectron beam passes through the sweep electrode 68b-2, the amount of bending is changed according to the magnitude of the sweep voltage, and the projected image R of the photoelectron beam at a position on the phosphor screen 68c that varies with time. Form. The phosphor screen 68c has an afterimage effect and accumulates images formed at different positions. Therefore, this projected image R becomes a two-dimensional image obtained by sweeping a slit-shaped one-dimensional image with time, and the temporal change in the nanosecond order of the image received by the photocathode 68a is a change in position on the fluorescent screen 68c. It is a high-resolution image displayed. In order to improve the sensitivity of the streak tube 68, at least one of the acceleration electrode 68d and the electron multiplier 68e can be integrated.

  The high-resolution two-dimensional image formed on the phosphor screen 68c of the streak tube 68 is further subjected to luminance multiplication by the image intensifier 70 to form a high-luminance two-dimensional light amplification image. That is, the image intensifier 70 has the following functions although not shown. A high-resolution optical image obtained by the streak tube 68 is picked up by the image pickup lens and formed on the photocathode of the image intensifier 70. This photocathode is formed on the inner wall surface of the vacuum vessel. The photoelectrons emitted from the photocathode are accelerated and converged by the electron lens formed in the vacuum vessel and enter the phosphor screen. On the phosphor screen, an image whose luminance is multiplied by the acceleration and convergence is displayed.

  A two-dimensional photomultiplied image displayed on the fluorescent screen of the image intensifier 70 is captured by an image sensor 72, for example, a two-dimensional CCD image sensor, and converted into image data. Since the CCD image sensor 72 captures an image with an extremely small amount of light, it is preferable to suppress dark current and improve the S / N ratio. Therefore, a cooled CCD image sensor used at a low temperature (for example, minus several tens of degrees Celsius to about liquid nitrogen temperature) is preferable.

  Image data from the CCD image sensor 72 is processed and stored under the control of an image processing unit 74, for example, a control circuit 74a of a personal computer. Data processing is, for example, obtaining the width of the crystallized region after a predetermined time has elapsed. The image data and the calculated data are stored in the storage unit 74b, for example, a memory, and simultaneously displayed on the display unit 74c as necessary. The data displayed on the display unit 74c can be used for monitoring the progress of crystallization by a person in charge of the crystallization process. Further, since the image data is stored in the storage unit 74b, a desired image can be extracted as a still image or a slow image and displayed on the display unit 74c under the control of the control circuit 74a. By configuring the microscopic observation optical system 60 in this way, it becomes possible to perform necessary observation and monitoring with a high temporal resolution on the order of several nanoseconds and with a high spatial resolution of several μm.

The laser crystallization apparatus 1 is provided with a timing control unit 10. The timing control unit 10 performs various timing controls on the crystallization laser light source 22, the observation illumination light source 44, and the microscopic observation optical system 60, for example. An example is shown in FIG. The timing control unit 10 starts the irradiation of the observation illumination light OL and the application of the sweep voltage SV of the streak tube 68 in accordance with the timing when the irradiation pulse shape of the crystallization laser light EL (FIG. 6A) falls. As described above, the trigger signals P1 and P2 (FIG. 6B) are transmitted to the observation illumination light source 44 and the sweep voltage generator 68b, respectively. The observation illumination light source 44 emits observation illumination light OL (FIG. 6C) upon receiving the trigger signal P1. Sweep field generator 68b of the streak tube 68, upon receiving the trigger signal P2, instructs the sweep circuit 68b-1 to generate a period of sweep voltage SV (Fig. 6 (d)) of time _{t s} which varies with time The sweep voltage SV is applied to the sweep electrode 68b-2. When the application of the sweep voltage SV is completed, the timing control unit 10 transmits a trigger signal P3 to the image sensor 72, and the image sensor 72 captures a two-dimensional image on the phosphor screen of the image intensifier 70 as image data.

  For example, FIG. 7 is an example of image data obtained by the above observation, and is an observation of the crystallization process in a predetermined region of the semiconductor thin film 35. The crystallization substrate 32 is irradiated with a crystallization laser beam having a phase-modulated reverse peak light intensity distribution. As a result, although the region of the semiconductor thin film 35 on the irradiated substrate 32 is melted, the melting temperature is low in the central portion corresponding to the light intensity distribution of the laser beam, for example, the reverse peak light intensity distribution, on both sides thereof. High temperature distribution. When irradiation with the crystallization laser beam is interrupted, the temperature of the irradiated region is lowered. The temperature gradient at the time of cooling is a temperature gradient corresponding to the reverse peak light intensity distribution. Crystallization starts from this center, and the tip position of the crystallization, that is, the solid-liquid interface, moves laterally according to this temperature gradient. Thus, in PMELA, the crystallization of the semiconductor thin film 35 proceeds at a predetermined position according to a predetermined pattern, that is, the light intensity distribution of the laser beam. This crystallization process is simultaneously performed by irradiating a predetermined crystallization process unit with observation illumination light emitted from the observation illumination light source 44, so that the imaging device 72 of the microscopic observation optical system 60 captures an image. Observe and monitor. The observation here is observation of, for example, a state of crystallization in a predetermined region, and the measurement is, for example, measurement of the width of the crystallized region.

In FIG. 7, the width of the image is actually several hundred μm or more, but here, a predetermined region which is a part of the image is enlarged, for example, 10 μm. The height of the image corresponds to the application time of the sweep voltage SV, for example, t _S = 300 nsec. When melted, the amorphous silicon thin film 35 becomes metallic and does not transmit visible light. Therefore, the melted portion becomes a dark image, and the crystallized portion transmits visible light, so that it becomes a bright image. In FIG. 7, the hatched area indicates the melting area of the silicon thin film, and the white area indicates the crystallization (solidification) area. The upper end of FIG. 7 is immediately after melting, and the whole is a dark image (shaded area). A bright part crystallized with the passage of time spreads from the center, and it is observed that crystallization is progressing downward in FIG. The center of the horizontal axis in the figure is preliminarily aligned with a predetermined portion where the phase of the KrF excimer laser light changes by the phase shifter 28. In this portion, since the phase of the KrF excimer laser light is reversed on both sides thereof, the intensity of the excimer laser light becomes extremely weak (ideally zero) due to interference between the two. Therefore, the temperature after melting becomes the lowest, and the formation of crystal nuclei when the silicon thin film crystallizes starts from this portion. Thereafter, the crystal grains grow laterally according to the temperature gradient of the melted portion, and the width of the crystallized region (shaded region) becomes wider as the time passes in the downward direction of the figure. The size of crystal grains crystallized by the PMELA apparatus of this embodiment is, for example, about 6 μm.

  Thus, in this embodiment, since the semiconductor thin film 35 is crystallized using laser light having a predetermined light intensity distribution, it is possible to specify in advance the portion where crystallization starts after melting. Therefore, since the state of crystallization in this predetermined region can be observed, observation with high positional accuracy and high spatial resolution becomes possible.

(First application example)
As an application example to the crystallization process as a result of observing this crystallization process, there is imaging alignment between the substrate 32 and the imaging optical system 30. The imaging position shift is caused by several causes as described later. If the imaging position of the crystallizing laser beam (excimer laser beam) deviates from the surface of the substrate 32, the laser beam intensity at the phase inversion portion does not become sufficiently weak. Therefore, as compared with the case where the substrate 32 is at the imaging position, the temperature after melting of the phase inversion portion becomes higher and the formation of crystal nuclei is delayed. As a result, the timing at which crystallization starts is delayed. In addition, the place where the formation of crystal nuclei easily occurs randomly not only in the phase inversion part of the laser beam but also in other parts. For this reason, the chances of the crystal grains that have started growing collide with each other increase, and the size of the grown crystal grains decreases. That is, the quality of the crystallized polycrystalline silicon thin film is deteriorated.

  The cause of the change in the imaging position of the crystallization laser light, for example, excimer laser light, during the crystallization process is that, for example, the flatness of the substrate 32 is not perfect, or the large area substrate 32 is held. Deflection of the image forming position due to the generated deflection and the temperature change of the image forming optical system 30 is increased. Further, the imaging optical system 30 changes (increases) in temperature by irradiation with high-energy excimer laser light. When the temperature changes (rises) by 1 ° C., the imaging position in a certain imaging optical system changes, for example, by 10 μm. Considering that the focal depth of the imaging optical system 30 is, for example, ± 10 μm, this deviation is a size that cannot be ignored.

FIG. 8 is a flowchart for explaining an example of a process for correcting the deviation of the substrate 32 and adjusting it to the imaging position of the imaging optical system 30. In step 81, excimer laser light for crystallization is irradiated onto the substrate 32, and the silicon thin film 35 is melted. The observation illumination light illuminates a predetermined melted region of the silicon thin film 35 at a timing controlled by the timing control unit 10 in synchronization therewith. This initiates observation and monitoring of the crystallization process. In step 82, the width W of the crystallized region when a predetermined time t _M has elapsed from the irradiation of the excimer laser light to the substrate 32 is measured by the image processing unit 74. That is measured as shown in T-T in the middle of FIG. 7, when the elapsed time t _M, the width W of the region is crystallized (white area). The measured width W is compared with a predetermined width W1 in step 83. Here, the width W1 is the minimum width of the crystallization region where it is determined that good crystallization is performed. If the width W is greater than the width W1, it is determined that the crystallization has been successfully performed and the process proceeds to step 89. In step 89, it is determined whether or not the process has been completed for all the regions of the substrate 32 to be crystallized. If not completed, the substrate 32 is moved to the next irradiation position of the crystallization laser light in step 90 and the process returns to step 81. If the measured width W is smaller than the width W1, it is compared with a predetermined width W2 at step 84. Here, the width W2 is the width of the crystallization region corresponding to the acceptable lower limit of the crystallized quality. If the width W is greater than the width W2, it is determined that the crystallization process is acceptable. However, the next excimer laser light irradiation is performed after correcting the height of the substrate 32 in steps 87 and 88. In step 87, as will be described later from the observation result, the height of the substrate 32, that is, the deviation correction amount in the Z-axis direction is calculated. In step 88, the stage drive unit 12 corrects the height of the substrate 32 by the calculated deviation correction amount, and proceeds to step 89. If the measured width W is smaller than the width W2, it is determined that the crystal grains have not grown sufficiently large. Therefore, the height of the substrate 32 is similarly corrected in steps 85 and 86, and the process returns to step 81. Excimer laser light is re-irradiated on the area.

  In steps 85 and 87, the height correction amount of the substrate 32 is calculated as follows. The image processing unit 74 stores in advance an image corresponding to the shift amount (Z-axis shift amount) of the substrate 32 in the Z-axis direction. The image processing unit 74 calculates a Z-axis deviation correction amount (ΔZ) from the imaging position of the substrate 32 from the observed image pattern of the crystallized silicon thin film 35 and the stored deviation image pattern using a pattern recognition technique. calculate. The calculated Z-axis deviation correction amount (ΔZ) is input to the stage drive unit 12. In steps 86 and 88, the stage driving unit 12 drives the substrate holding stage 38 based on the Z-axis deviation correction amount (ΔZ), corrects the position of the substrate 32 in the height (Z-axis) direction, and excimer laser light. The silicon thin film 35 is made to coincide with the image forming position.

(Second application example)
As another example of application, the laser crystallization apparatus 1 of the present embodiment is used to observe a two-dimensional image of the excimer laser light irradiation region, and to correct the displacement of the in-plane position of the substrate 32, that is, the XY position. Is to do. A feature of the crystallization method in which the reverse peak light intensity distribution is formed by the phase shifter 28 is that a desired position can be crystallized. As shown in FIG. 9, the arrangement of the microscopic observation optical system 61 for this position observation is such that only the photodetector 68 shown in FIG. 1 is retracted from the optical path of the temporary imaging lens 66, and the image intensifier 70. Is moved to the imaging position of the imaging lens 66 and installed. Thereby, a two-dimensional image of the crystallization process region can be taken. When the measurement light from the substrate 32 has a sufficient intensity, this arrangement can be modified so that the image sensor 72 is installed at the imaging position of the imaging lens 66 without using the image intensifier 70. it can.

  Below, the XY alignment method of the board | substrate 32 using the observation optical system 61 shown in FIG. 9 is demonstrated. FIG. 9 is a flowchart for explaining an example of the alignment process of the substrate 32 in the XY direction. The alignment in the X-Y direction can be performed as follows. For example, the substrate 32 is positioned and placed in advance on the XYZ holding stage 38 with alignment marks. After precise alignment based on the alignment mark, the crystallization process can be performed. In step 91, excimer laser light for crystallization is irradiated onto the substrate 32 to melt the silicon thin film 35. In step 92, a two-dimensional image of the irradiation region of the excimer laser light is taken at an arbitrary timing of the crystallization process, and the X and Y positions of the irradiation pattern are measured. In step 93, the positions of the irradiation pattern and the alignment mark are compared to determine whether or not the positional deviation of the irradiation pattern is within an allowable range. If so, the process proceeds to step 96. If it is out of the permissible range, in step 94, the image processing unit 74 automatically calculates a positional deviation correction amount from the alignment mark. In step 95, the X-Y direction deviation of the substrate 32 is corrected via the stage drive unit 12. In step 96, it is determined whether the process has been completed for all of the regions of the substrate 32 to be crystallized. If not completed, in step 97, the laser beam moves to the next irradiation position of the crystallization laser beam and returns to step 91.

  This crystallization process can be displayed on the display unit 74c, and the alignment state can be displayed on the screen for confirmation. Further, this positional deviation correction may be automatically performed and finely adjusted every time the crystallization laser beam is emitted. In addition, the positional deviation correction result by the alignment mark can be used for a resist exposure process in a subsequent process.

(Modification of this embodiment)
A modification of the configuration of the crystallization optical system of the present embodiment is shown in FIG. In this modification, the phase shifter 28 and the imaging optical system 30 are removed from the configuration shown in FIG. 1, and the substrate 32 is disposed at the imaging position of the homogenizer 26. Since this modification can reduce the number of optical elements such as lenses as compared with the embodiment of FIG. 1, it can irradiate crystallization laser light with stronger intensity.

  The microscopic observation optical system 60 can have not only the above-described configuration but also a configuration in which a part thereof is omitted as follows, or another configuration.

  In one modification of the microscopic observation optical system 60, as shown in FIG. 12, the streak tube 68 is omitted, and a so-called gate having a structure in which the functions of the image intensifier 70 and the CCD image sensor 72 are integrated. An attached CCD image sensor 73 can be used. The gated CCD image sensor 73 is arranged to capture a two-dimensional image formed by the imaging lens 66. The gated CCD image sensor 73 has a function of capturing a two-dimensional image at a certain moment. That is, an image that changes with time is received by the two-dimensional photoelectric conversion unit of the image sensor 73, and a high voltage is applied to the photomultiplier for a predetermined moment to record the two-dimensional image at that moment on the phosphor screen. Thus, two-dimensional image data is obtained by the CCD image sensor. Therefore, continuous data in a specific area as in the case where the streak tube 68 is used cannot be obtained. However, since the high voltage applied to the photomultiplier of the gated CCD image sensor 73 can be controlled with a time resolution of several nanoseconds, a two-dimensional image of a wide observation region at a desired moment can be obtained.

An example of the result of imaging according to this modification is shown in FIG. FIG. 13A in the upper stage is a diagram immediately after excimer laser light irradiation (t = t ₀ ), and the silicon thin film 35 in the irradiation region is melted. The small melting regions are arranged in a matrix form vertically and horizontally. Since the illumination light does not transmit in the molten region, the image becomes dark. In the figure, this melting region is hatched with diagonal lines. Middle part of FIG. 13 (b), (c) is a diagram for the time has elapsed t ₁ after excimer laser irradiation, crystallization starts, the outer portion of the molten region is melted from the center of the melted region Indicates the state. The crystallized region is indicated by white spots in the figure. The shape of the region to be crystallized can be controlled by the pattern design of the phase shifter 28. FIG. 13B shows an example in which a phase shifter that forms a rectangular light intensity distribution is used, in which a region crystallized in a square from the center is formed. FIG. 13C shows an example in which a phase shifter that forms a line-symmetric light intensity distribution is used. A crystallized region extending in the vertical direction of the figure is observed, and crystallization proceeds in the horizontal direction of the figure. To do. Lower FIG. 13 (d) over time t ₂ from the excimer laser beam irradiation, a diagram crystallization is completed, are represented in white overall crystallizes. However, since the light reflection and transmission characteristics are different between the melted and crystallized region and the non-melted region, the boundary can be recognized even after crystallization.

  Still another modification is a case where the streak tube 68 shown in FIG. 5 includes at least one of the acceleration electrode 68d and the electron multiplier 68e. This arrangement can be used when the intensity of the primary image that is the output of the streak tube 68 is not sufficient for the sensitivity of the CCD image sensor 72.

  Conversely, when the intensity of the primary image output from the streak tube 68 has a sufficient intensity with respect to the sensitivity of the CCD image sensor 72, or when the sensitivity of the CCD image sensor 72 is sufficiently high, the image intensifier. 70 can be omitted.

  The present embodiment is not limited to the various embodiments described above, and can be further modified or used with a part thereof omitted. For example, the mechanism for correcting the positional deviation of the substrate 32 of the laser crystallization apparatus 1 is omitted, and the semiconductor thin film is simply melted and crystallized with time without feeding back the observation result to the laser crystallization apparatus. It is also possible to make a system that observes and monitors the changing state.

  As described above, according to the present invention, an energy beam having an energy distribution, for example, a pulsed excimer laser beam that has been phase-modulated to give a light intensity distribution is irradiated onto the semiconductor thin film, so Melt the area. Then, the state of lateral crystallization in a predetermined region controlled by the energy distribution is observed in real time or immediately after the end of pulsed laser light irradiation with a high spatial resolution of several μm or less and a high temporal resolution of nanosecond order, It is possible to monitor. Furthermore, based on the observation result, for example, by providing feedback, the crystallization process is stabilized, and a crystallization apparatus and a crystallization method capable of efficiently crystallizing a high-quality semiconductor thin film are provided. It is.

  The present invention is not limited to the embodiment described above. The above embodiments include various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, some configuration requirements may be deleted from all the configuration requirements shown in the embodiment.

  The present invention can be used for the production of thin film transistor materials used in liquid crystal display devices, organic electroluminescence display devices, etc., and is used by melting and recrystallizing amorphous and polycrystalline semiconductor thin films by laser light irradiation. For example, it can be used for laser crystallization of a material thin film for a solar cell.

FIG. 1 is a configuration diagram of a crystallization apparatus for explaining an example of an embodiment of the present invention. FIG. 2 is a configuration diagram for explaining an example of the configuration of the homogenizer in FIG. 1. FIG. 3 is a cross-sectional view showing an example of a substrate having a semiconductor thin film to be crystallized. FIGS. 4A and 4B are configuration diagrams for explaining a modification of the observation illumination optical system of the embodiment. FIG. 5 is a configuration diagram for explaining a configuration of a streak tube which is an example of the photodetector in FIG. 1. FIG. 6 is a diagram for explaining an example of operation timing when observing a state in which a semiconductor thin film is melted and crystallized by the apparatus shown in FIG. FIG. 7 is a diagram for explaining an example of an image displayed on the display unit of the microscopic observation optical system of FIG. FIG. 8 is a flowchart for explaining an example of a process for correcting the deviation from the imaging position of the substrate according to the embodiment of the present invention. FIG. 9 is a configuration diagram showing an example of a crystallization apparatus used for correcting a deviation of the in-plane position of the substrate. FIG. 10 is a flowchart for explaining an example of a process for correcting the positional deviation in the substrate plane by the crystallization apparatus shown in FIG. FIG. 11 is a configuration diagram for explaining a modification of the crystallization apparatus. FIG. 12 is a configuration diagram for explaining a modification of the microscopic observation optical system. FIG. 13 is a diagram for explaining a two-dimensional image observed by the modification shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser crystallization apparatus, 10 ... Timing control part, 12 ... Stage drive part, 20 ... Optical system for crystallization, 22 ... Laser light source, 24 ... Beam expander, 26 ... Homogenizer, 28 ... Phase shifter, 30 ... Connection Image optical system (excimer imaging optical system) 32... Substrate to be processed 38... Substrate holding stage 40... Microscopic observation system 42 .. illumination optical system for observation 44. 52 ... annular reflector, 54 ... annular converging lens, 60 ... microscopic observation optical system, 62 ... microscopic objective lens, 64 ... reflecting mirror, 66 ... imaging lens, 68 ... photodetector (streak tube), 68a ... photoelectric surface, 68b ... Sweep electric field generator, 68b-1 ... Sweep circuit, 68b-2 ... Sweep electrode, 68c ... Fluorescent screen, 70 ... Image intensifier, 72 ... Image sensor, 74 ... Image Management unit.

Claims (15)

A thin film provided on a substrate is irradiated with pulsed energy light having a light intensity distribution to melt the thin film, and a crystal is formed in a predetermined region of the thin film according to the light intensity distribution immediately after the irradiation of the pulsed energy light. A crystallization apparatus comprising a crystallization optical system for growing and crystallizing grains laterally,
An illumination light source that is arranged outside the optical path of the energy light and emits illumination light for observation that illuminates the energy light irradiation region on the thin film;
An illumination optical system including an annular optical element that guides illumination light from the illumination light source to the thin film along the optical path of the optical path of the energy light, and
An observation optical system for magnifying illumination light transmitted through the substrate including the thin film and observing a process in which crystal grains grow laterally in the predetermined region after the irradiation of the pulsed energy light is completed. A characteristic crystallization apparatus. A thin film provided on a substrate is irradiated with pulsed energy light having a light intensity distribution to melt the thin film, and a predetermined region of the thin film is crystallized according to the light intensity distribution immediately after the irradiation of the pulsed energy light. A crystallization apparatus comprising a crystallization optical system for moving the solid-liquid interface in a lateral direction by
An illumination light source that is disposed outside the optical path of the energy light and emits illumination light for observation that illuminates the energy light irradiation region on the thin film;
An illumination optical system including an annular optical element that guides illumination light from the illumination light source to the thin film along the optical path of the optical path of the energy light, and
A crystallization apparatus comprising: an observation optical system for observing a process in which the solid-liquid interface moves laterally in the predetermined region by magnifying illumination light transmitted through the substrate including the thin film.   The annular optical element is provided around an optical path of the energy light, and includes an annular reflector that reflects and guides illumination light from the illumination light source to the thin film, and one optical lens, The crystallization apparatus according to claim 1 or 2.   The said annular optical element is provided in the circumference | surroundings of the optical path of the said energy light, and consists of an annular concave mirror which reflects and guides the illumination light from the said illumination light source to the said thin film, It is characterized by the above-mentioned. Crystallization equipment.   The energy light is a pulsed excimer laser light, and the crystallization optical system phase-converts the homogenizer for homogenizing the laser light into light having a predetermined light intensity distribution. A phase modulation element to be modulated, and the laser light transmitted through the phase modulation element irradiates the thin film to melt the irradiated portion, and after the laser light irradiation ends, the solid-liquid interface in the predetermined region The crystallization apparatus according to claim 2, wherein the crystallization apparatus moves in a lateral direction. The observation optical system is
A lens for enlarging an image of the thin film including the predetermined region to form an image on a photocathode;
A photodetector that multiplies electrons generated on the photocathode and enters the phosphor screen to form a fluorescence image;
The crystallization apparatus according to claim 1, further comprising an image sensor that captures an image of the phosphor screen. An image processing unit for processing an image detected by the observation optical system;
The stage drive part which has a function which adjusts the position of the said board | substrate based on the position data of the said board | substrate obtained from the said image processed by the said image processing unit is further provided. The crystallization apparatus according to 1.   The crystallization apparatus according to claim 6, wherein the image sensor is a cooled CCD image sensor.   9. The crystallization apparatus according to claim 1, wherein the thin film is an amorphous silicon film or a polycrystalline silicon film.   10. The substrate according to claim 1, wherein the substrate is a transparent glass substrate, and the thin film is an amorphous silicon film or a polycrystalline silicon film formed on the glass substrate. The crystallization apparatus according to 1. Emitting pulsed energy light having a light intensity distribution;
The thin film provided on the substrate is irradiated with the pulsed energy light to melt the thin film, and crystal grains are laterally distributed in a predetermined region of the thin film according to the light intensity distribution immediately after the irradiation of the pulsed energy light. Growing and crystallizing,
Illuminating the irradiation portion of the energy light with the annular illumination light for observation along the optical path through an annular optical element that is coaxially provided in the optical path of the energy light and passes the energy light;
Expanding the observation illumination light transmitted through the thin film and detecting a process in which the crystal grains grow laterally;
Converting the detected process into electronic data;
And a step of displaying the electronic data. Emitting pulsed energy light having a light intensity distribution;
The thin film provided on the substrate is irradiated with the pulsed energy light to melt the thin film, and a solid-liquid interface is laterally spread in a predetermined region of the thin film according to the light intensity distribution immediately after the irradiation of the pulsed energy light. Moving in the direction and crystallizing;
Illuminating the irradiation portion of the energy light with the annular illumination light for observation along the optical path through an annular optical element that is coaxially provided in the optical path of the energy light and passes the energy light;
Expanding the observation illumination light transmitted through the thin film and detecting a process in which the solid-liquid interface moves laterally; and
Converting the detected process into electronic data;
And a step of displaying the electronic data.   The irradiation of the energy light to the thin film and the irradiation of the observation illumination light to the thin film are performed simultaneously or after irradiation of the energy light to the thin film. The crystallization method according to 11 or 12. The step of converting into the electronic data includes
Capturing an image of the thin film including the predetermined region;
Image processing the image data of the imaged thin film;
Calculating the position data of the substrate based on the result of the image processing;
The crystallization method according to claim 11, further comprising a step of adjusting the position of the substrate based on the position data.   15. The substrate according to claim 11, wherein the substrate is a transparent glass substrate, and the thin film is an amorphous silicon film or a polycrystalline silicon film formed on the glass substrate. The crystallization method according to 1.

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