JP2006066462A - Crystallization apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallization apparatus and method in which melting and crystallizing state of a semiconductor film can be observed in real time, and a growing rate and a direction of the semiconductor film can be measured accurately. <P>SOLUTION: The crystallization apparatus 1 composed of an optical system 2 for irradiating an amorphous semiconductor film 27 provided on a substrate 26 with energy light and melting and crystallizing the amorphous semiconductor film 27 comprises an optical system 30 arranged on the outside of the optical path of energy light and irradiating illumination light for measurement; an optical element 41 for splitting a measuring light beam into a plurality of measuring light beams; lenses 45A and 45B for focusing each measuring light beam on the light receiving surface of a photodetector as the image of the amorphous semiconductor film 27; a plurality of measuring instruments 50A and 50B each including the photodetector and converting each image on the light receiving surface into crystallization information; and an image processor for processing the crystallization information. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus and a crystallization method for crystallization by irradiating a thin film with energy light.For example, it is possible to observe in real time a state in which a non-single crystal semiconductor film is melted and crystallized. The present invention relates to a crystallization apparatus and a crystallization method capable of measuring crystallization information when a non-single-crystal semiconductor film is crystallized.

Thin film transistor (TFT) circuits that can form integrated circuits on an arbitrary substrate, for example, a silicon substrate, have been put into practical use in many fields. This TFT is generally a device formed on an amorphous semiconductor film provided on a substrate at present, and the carrier mobility of this TFT is 0.5 to 1.0 cm ² / Vsec. In order to form a high-definition liquid crystal display (LCD), TFTs with higher carrier mobility are required, and TFTs formed on polycrystalline semiconductor films are now in practical use. I'm starting. A TFT formed on a polycrystalline semiconductor film has a carrier mobility that is about two orders of magnitude larger than that formed on an amorphous semiconductor film, and exhibits high performance characteristics.

  The present inventors have studied a technique for forming a TFT in a crystallized semiconductor film having a carrier mobility that is about an order of magnitude higher, and have developed an industrialization technique. That is, this is a technique for forming a crystallized region having large crystal grains in a predetermined region of an amorphous semiconductor film that forms a TFT circuit. A large crystal grain is a crystal grain having such a size that an active region of at least one or a plurality of TFTs can be formed in one single crystal grain. The fact that the active region of the TFT is formed in one single crystal region means that the TFT characteristic variation is controlled and a quality-controlled TFT circuit can be formed.

  A crystallization technique that melts and crystallizes a non-single crystal semiconductor film using energy light, for example, a high-energy short pulse laser beam, is a method for crystallizing a semiconductor film that forms a TFT, for example, an amorphous semiconductor film. It is used to Among such crystallization techniques, a crystallization technique (Phase Modulated Excimer Laser Annealing: PMELA) that emits phase-modulated excimer laser light has attracted attention. In the PMELA technique, a homogenized pulsed excimer laser beam is incident on a phase modulation element, for example, a phase shifter, to form an excimer laser beam having a predetermined phase intensity distribution. In this method, for example, an amorphous silicon film or a polycrystalline silicon film formed on a large-area glass substrate is irradiated with this laser light, and the silicon film is melted and crystallized. According to this PMELA technique, the non-single-crystal silicon film is formed into a crystallized silicon film having a quality of about several μm to 10 μm and relatively uniform crystal grains by one irradiation. This crystallization is completed in an instant, for example, 100-150 nanoseconds. The details are described in Non-Patent Document 1.

  In order to industrialize such a crystallization manufacturing technique, a technique capable of in-situ observation of the state of instant crystallization described above is required.

For example, Patent Document 1 discloses a method for evaluating crystallinity of a crystallized semiconductor thin film. In this method, the crystallized polycrystalline silicon thin film is irradiated with measurement light, and the reflected light is spectrally analyzed to measure the crystallinity of the polycrystalline silicon thin film. This Patent Document 1 does not disclose a technique for in-situ observation of a crystallization process of a semiconductor film required here.
JP 2001-257176 A Hiroaki Inoue, Mitsuru Nakada, Masayoshi Matsumura; Transactions of the Institute of Electronics, Information and Communication Engineers Vol.J85-C, No.8, pp.624-629, 2002, “Amplitude / Phase Controlled Excimer Laser Melting Recrystallization Method for Silicon Thin Films-New 2-D Position Control Large Grain Formation Method ”

  In the currently developed laser crystallization apparatus, the growth direction of crystal grains cannot be controlled in one direction. The laser crystallization technology currently performs one-dimensional crystal growth, but it is also conceivable to aim for two-dimensional crystal growth in order to obtain crystal grains with a larger area in the future.

  Therefore, it has been a challenge to develop a measurement system that can accurately measure both the growth rate and the growth direction even when crystal grains grow in an arbitrary direction.

  An object of the present invention is to allow a semiconductor film to be melted and crystallized in real time, and to measure the growth rate and growth direction of a semiconductor thin film accurately, for example. It is to provide a crystallization apparatus and a crystallization method.

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

  A crystallization apparatus according to one embodiment of the present invention includes a crystallization optical system that irradiates a non-single crystal semiconductor film provided on a substrate with energy light and melts and crystallizes the non-single crystal semiconductor film. A crystallization apparatus, disposed outside the optical path of the energy light, and measuring illumination optical system for irradiating the non-single crystal semiconductor film with measurement illumination light; and measuring light from the non-single crystal semiconductor film An optical element that divides the light into a plurality of measurement lights, and each of the measurement lights divided by the optical element are enlarged, and each of the measurement lights is connected as an image of the non-single crystal semiconductor film to a light receiving surface of a photodetector. A plurality of measuring instruments each including an image lens, the photodetector, and converting each of the images of the non-single-crystal semiconductor film formed on the light receiving surface into crystallization information; and An image processing apparatus for processing crystallization information It is characterized in.

  A crystallization method according to another aspect of the present invention includes a step of emitting energy light, irradiating the energy light to a non-single crystal semiconductor film provided on a substrate, and melting the non-single crystal semiconductor film to form a crystal. The step of illuminating the irradiation region of the energy light with the measurement illumination light, the step of dividing the measurement light from the non-single crystal semiconductor film, and the step of detecting each of the divided measurement lights And a step of converting the detected measurement light into each crystallization information, and a step of processing the crystallization information.

  According to the present invention, it is possible to observe in real time a state in which a semiconductor film is melted and crystallized, and crystallization capable of accurately measuring, for example, a growth rate and a growth direction of a semiconductor thin film. An apparatus and a crystallization method can be provided.

Problems for the industrialization of ELA devices include yield improvement in the crystallization process and stable quality control. In order to solve these problems, it is desired to measure a crystallized (or crystallized) region in situ (in real time). Embodiments of the present invention, energy light, for example, of a semiconductor film provided a pulsed excimer laser beam to the target substrate of crystallizing, for example, by irradiating a 4 mm ² in the area of 25 mm ² around the area, Melting and solidifying to crystallize, measuring the state change in the measurement area of the order of μm in a period of only a few tens of ns in real time to determine the crystallization information, for example, the growth rate and direction of crystallized crystal grains A crystallization apparatus and a crystallization method that can be measured.

  A configuration example of an embodiment according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, the crystallization apparatus 1 of this embodiment includes a crystallization optical system 2 and a microscopic measurement system 3. The crystallization optical system 2 uses a predetermined energy of the semiconductor thin film 27 to emit energy light, for example, excimer laser light, for melting and crystallizing a semiconductor film 27 provided on the substrate 26, for example, an amorphous silicon thin film. Irradiate the place. The microscopic measurement system 3 measures a melted and crystallized portion of the semiconductor thin film 27. The microscopic measurement system 3 includes a measurement illumination optical system 30 that irradiates measurement illumination light on a measurement location on the semiconductor thin film 27 and a measurement optical system 40 that measures a state in which the semiconductor thin film 27 is melted and crystallized. . The measurement optical system 40 includes a plurality of, for example, two sets of measuring instruments 50A and 50B, each of which measures the state in which the semiconductor thin film 27 is crystallized from substantially different directions, that is, crystallization information. Has been placed. The actual growth rate and growth direction of the crystal grains can be accurately obtained by synthesizing the results of real-time measurement of the crystallization state, for example, the state in which the crystal grains grow from two directions, and plotting it two-dimensionally. .

  First, the crystallization optical system 2 will be described. The crystallization optical system 2 used in this embodiment is a reduction projection type optical system that can reduce the phase modulation element 24, for example, a phase shift mask, and project it onto the semiconductor thin film 27.

  In the crystallization optical system 2, a laser light source 21, a beam expander 22, a homogenizer 23, a phase modulation element such as a phase shifter 24, an imaging optical system 25, and a substrate to be processed 26 are predetermined. And a substrate holding stage 28 for guiding the position. The pulsed excimer laser light from the laser light source 21 is expanded by the beam expander 22, the in-plane light intensity is made uniform by the homogenizer 23, and the phase shifter 24 is irradiated. The phase shifter 24 is an optical element that modulates incident excimer laser light into light having a desired light intensity distribution, for example, an inverse peak light intensity distribution. The excimer laser light transmitted through the phase shifter 24 irradiates a non-single crystal semiconductor thin film 27 formed on the substrate to be processed 26 via an imaging optical system 25, for example, an excimer imaging optical system.

The laser light source 21 is a pulsed laser beam having an energy sufficient to melt a non-single crystal semiconductor thin film 27 provided on the substrate 26 to be processed, such as an amorphous or polycrystalline semiconductor film, for example, 1 J / cm ^2. Is output. The laser light is preferably, for example, krypton fluoride (KrF) excimer laser light having a wavelength of 248 nm. In addition, energy light such as xenon chloride (XeCl) excimer laser light, argon fluoride (ArF) excimer laser light, argon (Ar) laser light, YAG laser light, ion beam, electron beam, xenon (Xe) flash lamp is used. it can. For example, the excimer laser light source 21 is a pulse oscillation type, the oscillation frequency is, for example, 100 Hz to 300 Hz, and the pulse width is a half value width, for example, 20 nsec to 100 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 semiconductor thin film 27 is about 1 J / cm ² . When the oscillation frequency is, for example, 100 Hz, the irradiation area of the excimer laser light is, for example, 2 mm × 2 mm, and the substrate 26 is moved by the substrate holding stage 28 in steps of, for example, 2 mm, excimer laser light is irradiated stepwise. The moving speed of the substrate 26 is 200 mm / sec.

  The beam expander 22 expands the incident laser light. The homogenizer 23 determines the size of the incident laser beam in the cross-sectional XY direction, uniformizes the incident angle of the laser beam within the determined shape, and equalizes the laser beam intensity regarding the in-plane position on the phase shifter 24. Has the function to Accordingly, the KrF excimer laser light is modulated by the homogenizer 23 into illumination light having a predetermined angular spread and a uniform light intensity in the cross section, and irradiates the phase shifter 24.

  The phase shifter 24 is an example of a phase modulation element. For example, a step is 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 24 with a phase difference of 180 ° on the left and right side modulates the incident light into laser light having a left-right symmetric 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 24 can be manufactured, for example, by forming a step corresponding to a predetermined phase difference on a quartz glass substrate. The change in the thickness 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. In the phase shifter 24, a step is formed so as to form a reverse peak light intensity distribution that allows phase growth of the large particle size by phase-modulating the incident light. As a result, the phase of the excimer laser light is shifted by a half wavelength with the phase shift portion as a boundary. As a result, the pulsed excimer laser light that irradiates the semiconductor film has a light intensity distribution 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 24 is distributed in a predetermined light intensity distribution on the semiconductor thin film 27 formed on the substrate 26 to be processed and placed in a conjugate relationship with the phase shifter 24 by the aberration-corrected excimer imaging optical system 25. To form an image. The imaging optical system 25, for example, a lens group including a plurality of calcium fluoride (CaF ₂₎ lenses and synthetic quartz lens. For example, the imaging optical system 25 has 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 imaging optical system 25 arranges the phase shifter 24 and the semiconductor thin film 27 at optically conjugate positions. In other words, the semiconductor thin film 27 is disposed on a surface optically conjugate with the phase shifter 24 (image surface of the imaging optical system). The imaging optical system 25 includes an aperture stop between the lenses.

  In general, the substrate 26 to be crystallized is formed by forming a film to be processed through an insulating film on the substrate and providing an insulating film as a cap film on the film. As the substrate 26, for example, a transparent glass substrate, a plastic substrate, or a semiconductor substrate (wafer) such as silicon is used. The film to be processed is a non-single-crystal semiconductor thin film 27, such as an amorphous silicon film, a polycrystalline silicon film, a sputtered silicon film, a silicon germanium film, or a dehydrogenated amorphous silicon film. The substrate to be processed used in this embodiment is formed by forming an amorphous silicon thin film 27 that has been dehydrogenated on a glass substrate 26 with a desired thickness, for example, 50 nm, through an insulating film. A silicon oxide film is formed on the porous silicon thin film 27 as a cap film. The substrate to be processed is detachably held on a substrate holding stage 28 that is movable in the X, Y, and Z directions for holding the substrate 26 at a predetermined position.

  As described above, the laser crystallization apparatus 1 forms a crystallization laser beam having a reverse peak light intensity distribution by phase-modulating the homogenized pulsed laser beam by the phase shifter 24, and this laser beam is converted into a semiconductor. This is a projection type crystallization apparatus for irradiating the thin film 27. The silicon thin film 27 melted by this light pattern forms a temperature gradient in the horizontal direction. In the temperature lowering process after laser light irradiation, solidification is performed according to this temperature gradient, and crystallization progresses in the horizontal direction. For example, a semiconductor film having a single crystal grain with a large grain size of about 5 to 10 μm can be formed.

  This crystallization process is a very high-speed change. If the irradiation time of the pulsed laser beam is set to, for example, 10 ns to 100 ns, the crystallization is completed in an extremely short time of several tens of ns. During irradiation with the pulsed laser beam, the amorphous silicon thin film 27 is heated to a high temperature of 1400 ° C. or higher and melted. Thereafter, through a rapid cooling and solidification process, the semiconductor thin film 27 having a single crystal grain having a large grain size of, for example, about 5 to 10 μm is obtained. In this embodiment, in order to observe and measure this ultrafast crystallization process, a microscopic measurement system 3 for microscopically measuring the crystallization process is provided on the lower surface side of the holding stage 28. The microscope measurement system 3 includes a measurement illumination optical system 30 and a measurement optical system 40. The measurement optical system 40 includes a plurality of measuring instruments, for example, two sets of measuring instruments 50A and 50B.

  First, the measurement illumination optical system 30 will be described. The measurement illumination optical system 30 is installed outside the optical path of the crystallization optical system 2. The measurement illumination optical system 30 includes, for example, a measurement illumination light source 31, a beam expander 33, a homogenizer 35, and a microscopic objective lens 37. The measurement illumination light emitted from the measurement illumination light source 31 is expanded by the beam expander 33 and adjusted by the homogenizer 35 so that the measurement illumination light intensity distribution in the irradiation region on the semiconductor thin film 27 becomes uniform. . The measurement illumination light emitted from the homogenizer 35 illuminates the crystallization process region on the semiconductor thin film 27 by the microscopic objective lens 37. Here, the crystallization process region is a region in which the semiconductor thin film 27 is irradiated with crystallization energy light and the semiconductor thin film 27 shifts from a melting process to a solidification process and completes crystallization.

  The measurement illumination light source 31 is capable of observing time resolution on the order of nanoseconds, so that it is a high intensity light source such as a xenon (Xe) flash lamp or an argon (Ar) laser beam, helium-neon (He-Ne). It is a light source that emits visible laser light such as laser light. The irradiation period of the measurement illumination light can include a part of the irradiation period of the crystallization energy light. The measurement illumination light source 31 is connected to a timing control mechanism (not shown) so that the measurement illumination light is generated at a predetermined timing in accordance with the irradiation timing of the crystallization laser light.

  The intensity distribution of the measurement illumination light emitted from the measurement illumination light source 31 usually has a light intensity distribution according to a Gaussian distribution instead of a uniform distribution. For the growth of crystal grains, as described later, the intensity distribution of reflected light or transmitted light from the non-single-crystal semiconductor thin film 27 is measured. For this reason, it is preferable to convert the measurement illumination light having a uniform light intensity distribution in the cross section by the homogenizer 35.

  Next, the measurement optical system 40 that images and displays the crystallization process state will be described. Here, a case where the measurement illumination light reflected from the semiconductor thin film 27 shown in FIG. 1 is measured by two sets of measuring instruments 50A and 50B will be described as an example. The measurement light reflected by the semiconductor thin film 27 is divided by the half mirror 41 through the microscopic objective lens 37 that forms an image by enlarging the reflected light from the crystallization process region. One measurement light reflected by the half mirror 41 and whose optical path is changed is imaged on the light receiving surface of the first measuring instrument 50A with a high resolution of sub μm by the imaging lens 45A. The other measurement light transmitted through the half mirror 41 is redirected by the reflecting mirror 43 in a direction different from that of the first measuring instrument, and is imaged on the light receiving surface of the second measuring instrument 50B by the imaging lens 45B. The configurations of the measuring instruments 50A and 50B are preferably the same, but measuring instruments having different configurations can be used as long as they have a desired function.

  As shown in FIG. 2, the two sets of measuring instruments 50A and 50B are arranged so as to measure from two substantially different directions within a plane perpendicular to the optical axis of the measuring light. FIG. 2 is a diagram viewed from the incident direction of the measurement light, and the measurement light travels from top to bottom in a direction perpendicular to the paper surface as indicated by a double circle. Part of the measurement light incident on the half mirror 41 is reflected in the first direction in which the first measuring instrument 50A is arranged, and part of it is transmitted. The measurement light transmitted through the half mirror 41 is directed to the second measuring instrument 50B arranged at a predetermined angle, for example, 45 ° and 90 ° with the first measuring instrument 50A by the reflecting mirror 43 arranged below the half mirror 41. And reflected in the second direction. The first and second directions in which the measurement light is reflected are preferably in a plane perpendicular to the optical axis of the measurement light.

  FIG. 3 shows an example of the configuration of one measuring instrument 50 (A and B are omitted in the description here). The two sets of measuring instruments 50A and 50B can have the same configuration. The measuring instrument 50 includes, for example, a photodetector 52 and a photodetector 52 as means for detecting and displaying a change in the crystallization process region enlarged and imaged by the microscopic objective lens 37 and the imaging lens 45. An image intensifier 54 that multiplies the obtained high-resolution image by brightness and an image sensor 56 that captures the image as image data are included. Image data from the image sensor 56 is subjected to image processing by an image processing unit 58. The image processing unit 58 includes, for example, a control circuit, a storage unit, and a display unit, and performs image processing such as image data analysis, image data storage, and image data display unit. The image processing unit 58 is used in common by the two measuring instruments 50A and 50B.

  The image of the non-single crystal semiconductor thin film 27 changing in the crystallization process region collected by the microscopic objective lens 37 is enlarged by the imaging lens 45 on the photocathode 52a which is the light receiving surface of the photodetector 52. To form an image. The photocathode 52a is provided with a slit S for measuring a predetermined portion of the crystallization process region in a predetermined direction. The size of the slit S is preferably limited to a region having a width of 1 μm or less and a length of several tens of μm on the substrate to be processed 26, for example. Along the long side direction of the slit S, the light intensity distribution at an arbitrary elapsed time of the image from the crystallization process region is measured. The slit S can be installed not only on the photocathode 52 a but at any position between the half mirror 41 or the reflecting mirror 43 and the photodetector 52.

  The photodetector 52 is preferably a photoelectric tube as shown in FIG. 4, for example, a streak camera. As the streak camera, for example, a streak tube that can convert an image of incident light into photoelectrons, then convert it back to light, and change the one-dimensional image with time with high time resolution of several nanoseconds can be used. The general streak tube 52 is a vacuum tube for special use, and has a configuration as shown in FIG. 4, for example. An image of incident light is imaged and received on a slit-shaped photocathode 52a. The slit-shaped image is a one-dimensional image of the crystallization process region. The photocathode 52a converts this one-dimensional image of incident light into photoelectrons. The photoelectron beam generated on the photocathode 52a passes through the sweep electrode 52b-2. The sweep electrode 52b-2 is provided with a pair of electrodes separated to sweep a photoelectron beam in the X or Y direction. A sweep voltage SV is applied to the sweep electrode 52b-2 from the sweep circuit 52b-1. The sweep circuit 52b-1 generates a sweep voltage SV (see FIG. 4) that changes with time at a timing controlled by a trigger signal P (see FIG. 4) from a timing control unit (not shown). 2 is supplied. The amount of bending of the photoelectron beam is changed according to the time change of the sweep voltage, and the projected image R of the photoelectron beam is displayed on the fluorescent plate 52c at a different position depending on the time. This projected image R becomes a two-dimensional image obtained by sweeping a slit-shaped one-dimensional image with time, and a time change in nanosecond order of the image received by the photocathode 52a is displayed as a change in position on the fluorescent plate 52c. It is a high resolution image. In order to improve the sensitivity of the streak tube 52, at least one of the acceleration electrode 52d and the electron multiplier 52e can be integrally incorporated.

  In the present embodiment using two measuring instruments 50A and 50B, the sweep voltage SV is applied at the same timing by synchronizing the two. This facilitates time analysis of measurement results.

  The high-resolution two-dimensional image formed on the fluorescent plate 52c of the streak tube 52 and swept in time is multiplied by the luminance by the image intensifier 54 to form a high-luminance two-dimensional light amplification image.

  A high-brightness two-dimensional light amplification image displayed on the phosphor screen of the image intensifier 54 is picked up by an image pickup device 56, for example, a two-dimensional CCD image pickup device, and converted into image data. This image data includes various crystallization information. Since the CCD image sensor 56 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 56 is processed and stored under the control of an image processing unit 58, for example, a control circuit of a personal computer. In the data processing, for example, based on image data from the two image pickup devices 56A and 56B, various crystallization information, for example, a growth rate and a growth direction of crystal grains after a predetermined time elapses are calculated. When the image data and the calculated data are stored in a storage unit of the image processing unit 58, for example, a memory, they are simultaneously displayed on the display unit as necessary. The data displayed on the display unit 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, a desired image can be extracted as a still image or a slow image and displayed on the display unit under the control of the control circuit.

  By configuring the microscopic measurement system 3 in this way, it becomes possible to perform real-time observation with a high temporal resolution on the order of several nanoseconds and with a high spatial resolution of sub-μm.

  The slits SA and SB for the two measuring instruments 50A and 50B can be arranged in an arbitrary direction within a plane perpendicular to the optical axis of the measuring light. For example, the long side of the slit SA is arranged in a direction (hereinafter referred to as the X direction) perpendicular to the direction of the valley of the crystallization laser light having the reverse peak light intensity distribution (hereinafter referred to as the Y direction). The long side of the slit SB can be shifted by 45 ° with respect to the X direction. The X direction is the direction in which the probability of crystal grain growth is the highest from the light intensity distribution of the laser light. Alternatively, the two slits SA and SB may be arranged at 45 ° or 30 ° opposite to each other in the X direction, or at an arbitrary angle different from each other.

  The arrangement of the two slits SA and SB, that is, the measurement directions of the two measuring instruments 50A and 50B are set to two substantially different directions, and the angle formed by the measuring light incident on each of the measuring instruments 50A and 50B is set to a predetermined value. The angle is set to 45 °, for example. The measurement is repeated at predetermined time intervals, for example, every 50 nanoseconds. By synthesizing and analyzing the measurement results obtained by the two measuring instruments thus obtained, the actual growth direction and growth rate of crystal grains in a predetermined period can be obtained. It is judged whether the growth rate is within a predetermined range, and the result is fed back to the crystallization conditions, for example, the intensity of the crystallization laser light. In this way, it becomes possible to stably manufacture a semiconductor film having a desired quality.

FIG. 5 is a diagram for explaining the measurement results obtained by the measuring instruments 50A and 50B according to the present embodiment. Here, the measuring direction of the measuring instrument 50A, that is, the slit SA is arranged in the X direction, and the measuring direction of the measuring instrument 50B and the slit SB are shifted by 45 ° with respect to this. The measurement results of the crystallization process by the two measuring instruments 50A and 50B are shown in FIGS. 5 (a) and 5 (b), respectively. The horizontal axis in the figure corresponds to the measurement direction of each slit SA, SB. The measuring instruments 50A and 50B simultaneously start applying the sweep voltage SV of the streak tubes 52A and 52B in response to the trigger signal P shown in FIG. 4 so as to synchronize with the irradiation timing of the crystallization laser light. Sweep field generator 52b of the streak tube 52, upon receiving the trigger signal P, it instructs the sweep circuit 52b-1 to generate between sweep voltage SV (see FIG. 4) the time t _s which varies with time, sweep A sweep voltage SV is applied to the electrode 52b-2. When the application of the sweep voltage is completed, the image sensor 56 captures a two-dimensional image on the phosphor screen of the image intensifier 54 as image data.

  FIG. 5 is a diagram for explaining the image data obtained as described above. When the semiconductor thin film 27 to be crystallized is irradiated with a crystallization laser light having a phase-modulated reverse peak light intensity distribution, the irradiated region of the semiconductor thin film 27 is melted. Here, the temperature of the melted region depends on the given light intensity distribution, and corresponds to the inverse peak light intensity distribution, and becomes a low temperature distribution at the center and a high temperature distribution on both sides thereof. When the laser beam for crystallization is interrupted, the temperature of the irradiated region is lowered. The temperature gradient at the time of temperature drop is ideally a temperature gradient corresponding to the reverse peak light intensity distribution. Accordingly, solidification, that is, crystallization starts from the valley (Y axis) of the laser light intensity distribution and proceeds in the lateral direction, ideally in the X or −X direction. However, as described above, the actual crystal grain growth direction is not limited to the ideal X direction or −X direction.

  The silicon film becomes metallic when melted and does not transmit visible light, and therefore reflects the measurement light. On the other hand, the solid portion (that is, the unmelted portion and the crystallized portion) transmits the measurement light. Therefore, the crystallized portion and the melted portion can be distinguished from the change in contrast. In the present embodiment, as shown in FIG. 1, since the reflected light from the silicon thin film 27 is measured, the melted portion becomes a bright image, and the crystallized portion becomes a dark image. In FIG. 5, the melting region of the silicon thin film 27 is indicated by a white region, and the solidified (crystallization) region is indicated by a hatched region. The center of FIGS. 5A and 5B is aligned with the valley portion (Y axis) of the laser light intensity distribution. The nucleation of crystals when the silicon thin film 27 is recrystallized has the highest probability of starting from this portion where the temperature is low. In FIG. 5A, the horizontal axis is the X direction, that is, the SA direction. The upper end of FIG. 5 is immediately after melting, and the whole is a bright image (white region). A dark portion crystallized with time elapses from the center, and it is observed that crystallization proceeds toward the bottom of FIG. The direction indicated by the thick white arrows in the figure is the apparent crystal growth direction in each of the measuring instruments 50A and 50B.

In FIG. 5, the width of the image is actually several hundred μm or more, but a part thereof is enlarged here, for example, 20 μm. The height of the image corresponds to the application time of the sweep voltage SV, for example, t _S = 400 nsec. The horizontal line in the figure indicates the time for extracting data at equal time intervals in order to calculate the crystallization rate. Here, as an example, the interval is set to 50 nsec. FIG. 5 (a), when comparing the (b), the same elapsed time, for example, the width of the crystallized region at time t ₄ is wider towards the (b). In other words, the measuring instrument 50B indicates that the crystal grains grown from the measuring instrument 50A are measured obliquely. In other words, the measurement direction of the measuring instrument 50B indicates that the deviation angle from the actual crystal grain growth direction is larger than the measurement direction of the measuring instrument 50A. Note that, for example, in FIG. 5 (a), the crystallized region from adjacent laser beam pattern appears as shaded portion from both sides of the picture from the vicinity of the time t _4. Since FIG. 5 shows continuous data, the time interval for extracting data can be arbitrarily set.

FIG. 6 shows the intensity distribution of the measurement light in the actual crystal grain growth direction G and the crystal grain growth direction at each time t _n by extracting data from time t ₁ to t ₆ in FIG. It is the result of synthesis. In FIG. 6, the light intensity distribution is displayed starting from the Y axis in FIG. The vertical axis indicates the intensity (I) of the measurement light, but the origin is shifted downward every time so that the graphs do not overlap. From the result of synthesizing the measurement results obtained by the two measuring instruments 50A and 50B shown in FIG. 6, the crystal growth rate and the crystal growth direction are obtained.

Next, a method for measuring the crystal growth rate and the crystal growth direction will be described with reference to FIGS. FIG. 7 is a view shown for explaining the movement of the solid-liquid interface in the XY plane in FIG. A line Sn extending from the upper left to the lower right in the figure represents the position of the solid-liquid interface in the XY plane at a certain time, for example, t _n . The upper right side of this line is the melting region, and the lower left side (the origin side is the crystallization region. Further, the white arrow indicated by G indicates the actual crystal growth direction.

  The irradiated portion of the amorphous silicon thin film 27 irradiated with the pulsed laser beam having the light intensity distribution is melted. A temperature gradient corresponding to the light intensity distribution is formed in the melting part. Next, when the laser light irradiation is interrupted, the temperature lowering process occurs, crystal nuclei are generated in the low temperature portion, and solidification, that is, crystallization proceeds. The solid-liquid interface generated by the solidification moves in the lateral direction (G direction in FIG. 7) according to the temperature gradient. Lines S-1, S-2,... Schematically show the movement of the solid-liquid interface, that is, the state in which crystallization proceeds, for each sampling time. FIG. 7 shows the directions of the slits SA and SB of the measuring instruments 50A and 50B in the measurement example of FIG.

  At this time, if the slit of the measuring instrument is arranged like SC and there is only one, if the crystal growth direction happens to be perpendicular or nearly perpendicular to the slit SC, the solid-liquid interface will be Passes through the slit SC in an instant. Therefore, the crystal growth rate cannot be obtained from the measurement. Therefore, two measuring instruments 50, that is, streak tubes 52, are prepared, and the directions of the slits SA and SB of each photocathode 52a are set in substantially different directions, for example, 90 ° different directions. With such an arrangement, it is possible to always obtain the growth rate and direction regardless of the crystal growth direction.

  Using this arrangement, the crystal growth rate and crystal growth direction can be measured as follows. The measurement procedure is shown in the flowchart of FIG. In the image processing unit 58 of the microscopic measurement system 3, information on the crystallization process of the semiconductor thin film 27 by the measuring instruments 50A and 50B is stored as continuous data.

First, in step 102, crystallization information, that is, FIGS. 5A and 5B are read from the storage unit of the image processing unit 58. FIG. In step 104, at a certain time t ₁ , the position La ₁ by the photocathode SA of the measuring instrument 50 A and the position Lb ₁ by the photocathode SB of the measuring instrument 50 B are measured, and the time t is stored in the storage unit of the image processing unit 58. ₁ is stored as each position information in ₁ . Similarly, in step 106, at time _{t 2,} the measured value Lb ₂ by the position La ₂ and the photocathode SB by the photoelectric surface SA is measured and stored as a respective position information at time _{t 2} in the storage unit. Although not shown, the position information at times t ₃ , t ₄ .

Based on the position information stored in the storage unit of the image processing unit 58, the crystal growth rates in the measurement directions SA and SB of the measuring devices 50A and 50B are obtained. In step 110, determine the crystal growth rate Ua measurement direction SA instrument 50A in the time from time _{t 2} to _{t 3} from equation (1).

Ua = (La ₃ −La ₂ ) / (t ₃ −t ₂ ) Formula (1)
Next, in step 112, similarly determine the crystal growth rate Ub measurement direction SB of the meter 50B in the time from time _{t 2} to _{t 3} from equation (2).

_{Ub = (Lb 3 -Lb 2)} / (t 3 -t 2) (2)
Therefore, the crystal growth rate U in the actual growth direction G is obtained as follows using the equation (3) (step 114).

U = (Ua ² + Ub ² ) ^1/2 equation (3)
Further, in step 116, the velocity vector Va is obtained through the crystallization information in the Ua and SA directions, and the velocity vector Vb is obtained through the crystallization information in the Ub and SB directions. In step 118, the crystal growth direction G can be obtained by obtaining the vector sum of the velocity vectors Va and Vb.

When the method described here is applied to the example shown in FIG. 5, for example, between the times t ₃ and t ₄ , the crystal grain growth rate is 30 m / sec, and the actual crystal growth direction G is It is determined that it is deviated by 15 ° from the X direction.

  The present invention is not limited to the above-described embodiment, and can be carried out by being modified. Also, some of them can be omitted.

  The microscopic measurement system 3 is not limited to be installed below the substrate to be processed 26 described here. If the optical path of the crystallization laser light is not blocked, the microscopic measurement system 3 is placed on the upper surface side of the substrate to be processed 26. Can be installed. As an installation example, for example, there is an arrangement in which illumination light for microscopic measurement is obliquely applied to a region in the crystallization process, and reflected light is measured therefrom. Alternatively, an illuminating light for microscopic measurement is irradiated to the crystallization region almost coaxially with the crystallization laser light by using an annular optical element provided with a window hole through which the crystallization laser light passes, and reflected or transmitted from there. An arrangement for measuring light can be used.

  Further, the microscopic measurement system 3 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, the streak tube 52 includes an acceleration electrode 52 d or an electron multiplier 52 e, and the intensity of the primary image that is the output of the streak tube 52 has sufficient intensity for the sensitivity of the CCD image sensor 56. In this case, or when the sensitivity of the CCD image sensor 56 is sufficiently high, the image intensifier 54 can be omitted.

  As described above, according to the embodiment of the present invention, the semiconductor film is melted and crystallized from two substantially different directions using two sets of measuring instruments in real time with high spatial resolution and high time resolution. By measuring the growth state of the crystal grains, the actual growth speed and direction of the crystal grains can be accurately determined even if the grains grow in any direction instead of the predetermined direction during crystallization. It becomes possible to ask. Furthermore, based on this measurement result, for example, by performing feedback that corrects the output energy value of excimer laser light that melts and crystallizes the semiconductor thin film 27, the crystallization process is stabilized, and high quality is achieved. A laser crystallization apparatus and a crystallization method capable of efficiently crystallizing a semiconductor film can be provided.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Furthermore, the above-described embodiment includes various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent requirements. 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.

It is a system configuration diagram for explaining an embodiment of the present invention. FIG. 2 is a layout diagram for explaining the measurement optical system of FIG. 1. It is a block diagram for demonstrating the structure of the measuring device of FIG. It is a block diagram for demonstrating the structure of the streak tube which is an example of the photodetector of FIG. FIGS. 5A and 5B are diagrams for explaining the measurement results observed according to the present embodiment. It is a figure for demonstrating the measurement result synthesize | combined based on Fig.5 (a), (b). FIG. 7 is a diagram for explaining a method of calculating the crystal growth rate based on the measurement result. FIG. 8 is a flowchart showing a procedure for obtaining the crystal growth rate and the growth direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Crystallization apparatus, 2 ... Crystallization optical system, 3 ... Microscopic measurement system, 30 ... Measurement illumination optical system, 40 ... Measurement optical system, 21 ... Laser light source, 22 ... Beam expander, 23 ... Homogenizer, 24 DESCRIPTION OF SYMBOLS ... Phase shifter, 25 ... Imaging optical system, 26 ... Substrate to be processed, 27 ... Semiconductor thin film, 28 ... Substrate holding stage, 31 ... Illumination light source for measurement, 33 ... Beam expander, 35 ... Homogenizer, 37 ... Microscopic objective Lens 41, Half mirror, 43 Reflector, 45 Imaging lens, 50 Measuring instrument, 52 Photo detector (streak tube) 52a Photocathode, 52b Sweep electric field generator, 52b-1 Sweep Circuit 52b-2 ... Sweep electrode 52c ... Fluorescent screen 54 ... Image intensifier 56 ... Image sensor 58 ... Image processing unit

Claims (12)

A crystallization apparatus comprising a crystallization optical system for irradiating energy light to a non-single crystal semiconductor film provided on a substrate to melt and crystallize the non-single crystal semiconductor film,
A measurement illumination optical system disposed outside the optical path of the energy light and irradiating the non-single crystal semiconductor film with measurement illumination light;
An optical element for dividing the measurement light from the non-single crystal semiconductor film into a plurality of measurement lights;
A lens for enlarging each measurement light divided by the optical element and forming each measurement light as an image of the non-single crystal semiconductor film on a light receiving surface of a photodetector;
A plurality of measuring instruments that include the photodetector and convert each of the images of the non-single-crystal semiconductor film imaged on the light-receiving surface into crystallization information;
An crystallization apparatus comprising: an image processing apparatus that processes crystallization information from the plurality of measuring instruments. The plurality of measuring instruments are:
A first measuring device that detects an image of the non-single-crystal semiconductor film and converts it into crystallization information;
2. A second measuring instrument configured to detect an image of the non-single-crystal semiconductor film from a direction substantially different from the first measuring instrument and convert the image into crystallization information. Crystallization equipment.   The first and second measuring instruments detect an image of the non-single-crystal semiconductor film from two substantially different directions within a plane perpendicular to the optical axis of the measurement light from the non-single-crystal semiconductor film. The crystallization apparatus according to claim 2, wherein the crystallization apparatus converts the information into crystallization information. Each of the plurality of measuring instruments is
The crystallization apparatus according to any one of claims 1 to 3, further comprising an imaging element that converts an image of the non-single-crystal semiconductor film into image data. Each of the plurality of measuring instruments is
The photodetector having a phosphor screen that forms a fluorescence image that has been multiplied by photoelectrons generated by an image of the non-single-crystal semiconductor film imaged on the photocathode that is the light-receiving surface;
The crystallization apparatus according to any one of claims 1 to 3, further comprising: an image sensor that converts an image on a fluorescent screen of the photodetector into image data. Each of the plurality of measuring instruments is
The photodetector having a phosphor screen that forms a fluorescence image that has been multiplied by photoelectrons generated by an image of the non-single-crystal semiconductor film imaged on the photocathode that is the light-receiving surface;
An image intensifier that multiplies the fluorescence image of the photodetector to form an image on the phosphor screen;
5. The crystallization apparatus according to claim 1, further comprising an image sensor that converts an image of a phosphor screen of the image intensifier into image data.   The image processing apparatus processes a plurality of the crystallization information obtained by the plurality of measuring devices and outputs either one or both of the crystal growth direction and the crystal growth speed in the crystal growth direction. The crystallization apparatus according to any one of claims 1 to 6. A process of emitting energy light;
Irradiating the non-single crystal semiconductor film provided on the substrate with the energy light, and melting and crystallizing the non-single crystal semiconductor film;
Illuminating the irradiation region of the energy light with measurement illumination light;
Dividing the measurement light from the non-single crystal semiconductor film;
Detecting each of the divided measurement lights;
Converting the detected measurement light into respective crystallization information;
And a step of processing the crystallization information.   9. The crystallization method according to claim 8, wherein the detecting step includes detecting from substantially different two directions within a plane perpendicular to an optical axis of measurement light from the non-single-crystal semiconductor film. The energy light is excimer laser light,
The excimer laser light is phase-modulated into light having a predetermined light intensity distribution,
The non-single crystal semiconductor film is irradiated with the phase-modulated excimer laser light to form a temperature distribution corresponding to the light intensity distribution,
10. The crystallization method according to claim 8, wherein the detecting step detects measurement light corresponding to the temperature distribution from the non-single-crystal semiconductor film.   11. The detection step according to claim 8, wherein the step of detecting simultaneously detects the divided measurement lights during and after irradiation of the non-single crystal semiconductor film with the energy light. 2. The crystallization method according to 1.   12. The process according to claim 8, wherein the processing step includes a step of obtaining one or both of a crystal growth direction and a crystal growth rate in the crystal growth direction from a plurality of the crystallization information. The crystallization method according to any one of the above.

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