JP2010027933A - Method and device for correcting thermal expansion of imaging lens, and crystallization device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a shift in focus position due to thermal expansion of an imaging lens absorbing laser light. <P>SOLUTION: A position shift amount of the imaging lens determined by converting a height variation amount of a substrate and a position shift amount of the focus of the imaging lens determined on the basis of an irradiation integrated time of the laser light are summed up to calculate a correction movement amount for correcting a shift in beam condensing position due to thermal expansion of the imaging lens, and an imaging lens moving unit is driven using the correction movement amount to move the imaging lens, thereby correcting the position shift in focus position. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for melting and crystallizing an amorphous or polycrystalline semiconductor thin film using light rays, and particularly relates to suppression of thermal expansion due to laser irradiation.

  There is a technique for crystallizing an amorphous semiconductor layer formed on an insulator such as a glass substrate to obtain a crystalline semiconductor layer, and forming a thin film transistor (TFT) using the crystalline semiconductor layer as an active layer. Are known.

  For example, in an active matrix liquid crystal display device, a semiconductor film such as a silicon film is provided, a thin film transistor is formed on a glass substrate, and the thin film transistor is used as a switching element for switching display.

  The formation of a thin film transistor includes a crystallization step of a non-single-crystal semiconductor thin film such as an amorphous or polycrystalline film. As this crystallization technique, for example, a laser crystallization technique is known in which an irradiation region of a non-single-crystal semiconductor thin film is melted and crystallized using a short pulse laser beam with high energy.

  Currently, a laser crystallization apparatus used for production employs a technique of irradiating amorphous silicon with a laser beam having a long beam (for example, 500 μm × 300 mm) shape and a uniform intensity distribution. However, with this method, the crystal grain size of the obtained semiconductor film is as small as 0.5 μm or less, so that a crystal grain boundary exists in the channel region of the TFT, and the characteristics of the TFT are suppressed. There is a limit.

  In order to improve the performance of the TFT, a technique for manufacturing a high-quality semiconductor film having large crystal grains is required. As a crystallization method that satisfies this requirement, among various laser crystallization techniques, non-single-crystal semiconductor thin film is irradiated with an excimer laser beam with a reverse peak pattern-like light intensity distribution formed by phase modulation. As a result, crystallization technology (Phase Modulated Excimer Laser Annealing: PMELA) has attracted attention.

  The PMELA technique is a method of irradiating an excimer laser beam having a predetermined light intensity distribution onto a non-single crystal semiconductor thin film, melting the irradiated portion of the semiconductor film, and crystallizing. Excimer laser light having a predetermined light intensity distribution is obtained by phase-modulating incident laser light with a light modulation element such as a phase modulation element, for example, a phase modulation element such as a phase shifter. The non-single crystal semiconductor thin film is, for example, an amorphous silicon or polycrystalline silicon thin film formed on a glass substrate.

  In the currently developed PMELA technology, a region of several mm square is melted and crystallized by one excimer laser light irradiation. By this crystallized non-single crystal semiconductor thin film treatment, a crystallized silicon thin film having a relatively uniform crystal grain size of several μm to 10 μm is formed (for example, see Non-Patent Document 1). ). TFTs fabricated on crystallized silicon thin films formed by this technique have been shown to have excellent electrical properties.

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 Melt Recrystallization Method of Silicon Thin Films− New 2-D Position Control Large Grain Formation Method ” JP 2008-135456 A

  This PMELA crystallization technique has excellent characteristics that the use efficiency of laser light is high and crystals having a large particle diameter can be obtained. However, in order to obtain stable electrical characteristics, it is necessary to position the crystal grains with high accuracy. In order to crystallize a large-area semiconductor film, a so-called step-and-repeat irradiation method, called a so-called step-and-repeat irradiation method, after irradiating a non-single-crystal semiconductor film with laser light, the glass substrate was moved to the next irradiation position and stopped. An irradiation method is used in which the process of irradiating the laser beam again is repeated.

  In order to position crystal grains with high accuracy, it is necessary to precisely project the pattern of the light modulation element onto the substrate. However, if laser light is repeatedly irradiated at a high frequency, the ambient temperature of the optical system increases. The lens system is thermally expanded, causing a shift of the focal position, and a predetermined optical profile cannot be formed on the substrate.

  In addition, when the glass substrate itself thermally expands on the order of millimeters, pseudo-single crystal grains of several microns formed in the plane of the substrate are not formed at predetermined position coordinates, and subsequent transistor formation straddles the crystal grain boundary. This is a factor causing deterioration of switching characteristics and the like.

  Even in a general crystallization technique known in the past, repeated continuous irradiation needs to be performed at a high frequency. At this time, if the depth of focus (DOF) is several tens of microns due to the properties of the optical system and the formed crystal grains are sufficiently smaller than the transistor, the thermal expansion of the lens or the substrate The significant performance degradation due to thermal expansion is not so great.

  On the other hand, the PMELA crystallization technique or the like requires formation of pseudo single crystal grains of several microns. In this way, when the pseudo single crystal grains of several microns are formed, the thermal expansion of the lens and the thermal expansion of the substrate are greatly affected.

  As a method for mitigating the influence of thermal expansion, for example, it is possible to irradiate the dummy substrate with laser light continuously until the thermal absorption of the imaging lens is saturated, and then irradiate the actual substrate. In this case, an absorber that passes through the lens and is irradiated with a dummy is necessary, and there is a problem that scattered matter generated from the absorber adheres to the lens side as a contaminant when the absorber is irradiated.

  Among the lenses provided in the optical system, in particular, the imaging lens has a great influence on the optical profile. Therefore, it is required to suppress thermal expansion of the imaging lens. The applicant has previously applied for a cooling mechanism that suppresses thermal expansion of the imaging lens (see Patent Document 1). In a configuration that suppresses thermal expansion by cooling the imaging lens, it is necessary to provide a cooling mechanism.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described conventional problems and to correct a focal position shift caused by thermal expansion of an imaging lens by absorbing laser light.

  It is another object of the present invention to perform focal position misalignment correction without requiring a cooling mechanism.

  The present invention can be implemented as various aspects of the imaging lens thermal expansion correction method, the imaging lens thermal expansion correction apparatus, and the crystallization apparatus. In either aspect, the amount of positional deviation of the imaging lens obtained by converting the amount of change in the height of the substrate is added to the amount of positional deviation of the focal point of the imaging lens obtained based on the integrated irradiation time of the laser beam. Then, the correction movement amount for correcting the fluctuation of the beam condensing position due to the thermal expansion of the imaging lens is calculated, and the imaging lens moving unit is driven by using the correction movement amount to move the imaging lens. Thus, a technical feature point of correcting the positional deviation of the focal position is provided in common.

  The imaging lens thermal expansion correction method according to the present invention includes an illumination optical system that continuously irradiates a laser beam to crystallize the substrate to be processed, a light modulation element that modulates the laser beam into a light beam having a predetermined light intensity distribution, and An imaging optical system that forms an image of the modulated light of this light modulation element on a substrate by an imaging lens and a substrate stage that supports the substrate, and the thin film provided on the substrate is melted and crystallized by the modulated light. In the crystallization apparatus, the crystallization apparatus includes an imaging lens thermal expansion correction unit that corrects fluctuations in the beam focusing position due to thermal expansion of the imaging lens included in the imaging optical system, and an imaging lens that moves the imaging lens. In the configuration including the moving unit, the thermal expansion of the imaging lens is corrected.

  In the imaging lens thermal expansion correction unit provided in the present invention, a measurement step for obtaining the height change amount of the substrate, a calculation step for converting the obtained height change amount of the substrate into a displacement amount of the imaging lens, and laser light The calculation step of calculating the focal position shift amount of the imaging lens based on the integrated irradiation time of the imaging lens, the positional deviation amount of the imaging lens and the focal position shift amount of the imaging lens obtained in the two calculation steps described above, And a calculation step for calculating a correction movement amount for correcting fluctuations in the beam focusing position due to thermal expansion of the imaging lens, and the imaging lens based on the correction movement amount calculated by the beam focusing position correction unit. By performing each step of moving the imaging lens by driving the moving unit, the imaging lens moving unit is driven by using the correction movement amount to move the imaging lens, thereby shifting the focal position. to correct.

  An aspect of a thermal expansion correction device for an imaging lens according to the present invention includes an illumination optical system that continuously irradiates a laser beam to crystallize a substrate to be processed, and a light modulation element that modulates the laser beam into a light beam having a predetermined light intensity distribution A thin film provided on the substrate is melted by the modulated light, and an imaging optical system for imaging the modulated light of the light modulation element on the substrate by an imaging lens and a substrate stage for supporting the substrate. An imaging lens thermal expansion correction device that corrects fluctuations in a beam condensing position due to thermal expansion of an imaging lens included in an imaging optical system, which is included in a crystallization apparatus that performs crystallization.

  This imaging lens thermal expansion correction device calculates the displacement amount of the focal point of the imaging lens based on the calculation that converts the amount of change in the substrate height into the displacement amount of the imaging lens and the integrated irradiation time of the laser beam. In order to correct the fluctuation of the beam condensing position due to the thermal expansion of the imaging lens from the positional deviation amount of the imaging lens and the positional deviation amount of the focal point of the imaging lens obtained by these two calculations. A beam condensing position correction unit that calculates the correction movement amount, and an imaging lens moving unit that moves the imaging lens based on the correction movement amount calculated by the beam condensing position correction unit.

  In addition, an aspect of the crystallization apparatus of the present invention includes an illumination optical system that continuously irradiates laser light to crystallize a substrate to be processed, a light modulation element that modulates laser light into light rays having a predetermined light intensity distribution, A thin film provided on the substrate, which includes an imaging optical system that forms an image of the modulated light of the light modulation element on the substrate by an imaging lens and a substrate stage that supports the substrate, is melted and crystallized by the modulated light. The crystallization apparatus includes an imaging lens thermal expansion correction unit that corrects fluctuations in the beam condensing position due to thermal expansion of the imaging lens included in the imaging optical system. The calculation for converting the amount of change in the amount of positional deviation of the imaging lens and the calculation for calculating the positional deviation amount of the focal point of the imaging lens based on the integrated irradiation time of the laser light were performed and obtained by these two calculations. Image lens misalignment and imaging lens Calculated by a beam condensing position correction unit and a beam condensing position correction unit that calculate a correction movement amount for correcting fluctuations in the beam condensing position due to thermal expansion of the imaging lens. An imaging lens moving unit that moves the imaging lens based on the correction movement amount.

  In each aspect, the calculation for calculating the focal position shift amount of the imaging lens is performed based on the arithmetic expression of a × log (t−b) + c, and the calculation for converting the focal position shift amount of the imaging lens is performed. , D × Zs + e. Here, t is the integrated irradiation time of the laser beam, Zs is the amount of change in the height of the substrate obtained by measurement, and a, b, c, d, and e are the energy of the laser beam and the repetition frequency at which the laser beam is irradiated. The parameter depends on the irradiation condition of the laser beam.

  This parameter can be stored in a memory corresponding to the irradiation condition of the laser beam. The calculation is performed by setting a calculation formula by reading parameters according to the irradiation condition of the laser beam, and performing the calculation process using the laser beam irradiation integration time t and the substrate height change amount Zs obtained by the measurement as variables. The amount of positional deviation of the focal point of the imaging lens and the amount of positional deviation of the focal point of the imaging lens are calculated.

  In the imaging lens thermal expansion correction apparatus aspect and the crystallization apparatus aspect of the present invention, the imaging lens moving unit is a piezo stage that is fixed to the substrate stage and moves the imaging lens in the Z-axis direction. Can be configured.

  According to the aspect of the present invention, with the same configuration, it is possible to correct the positional deviation of the focal position due to the thermal expansion of the imaging lens and also to correct the height fluctuation of the substrate surface.

  According to the present invention, it is possible to correct the positional deviation of the focal position due to thermal expansion of the imaging lens by absorbing laser light. Further, it is possible to correct the focal position displacement without using a cooling mechanism.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view for explaining the apparatus configuration of a crystallization apparatus 10 of the present invention. In FIG. 1, a crystallization apparatus 10 according to the present invention includes a laser light source 11 that emits excimer laser light, an illumination optical system 12 that irradiates laser light, and laser light that is emitted from the illumination optical system 12 with predetermined light. An optical modulation element 13 that modulates light of an intensity distribution, an imaging optical system 14 that forms an image of the modulated light of the optical modulation element 13 on a substrate 20 (substrate to be processed), and a substrate 20 that supports the substrate 20 and A substrate stage 15 for defining a dimensional position is provided. The modulated light applied to the substrate 20 via the imaging optical system 14 melts and crystallizes the thin film provided on the substrate.

  The illumination optical system 12, the light modulation element 13, and the imaging optical system 14 constitute a crystallization optical system. The illumination optical system 12 constitutes an excimer illumination optical system, and includes a beam expander that expands the beam of excimer laser light emitted from the laser light source 11, and a homogenizer that equalizes the in-plane light intensity, and performs light modulation. Crystallizing laser light for illuminating the element 13 is emitted and adjusted. In the figure, the beam expander and the homogenizer are not shown.

  A phase shifter can be used as the light modulation element 13, and the crystallization laser light is phase-modulated to be modulated into light having a desired light intensity distribution, for example, a light intensity distribution having an inverse peak pattern.

  The imaging optical system 14 irradiates the non-single-crystal semiconductor thin film for crystallizing the crystallization laser light phase-modulated by the light modulation element 13. FIG. 1 shows a projection system in which the light modulation element 13 is installed between the illumination optical system 12 and the imaging optical system 14.

The laser light source 11 generates energy sufficient to melt a non-single crystal semiconductor film provided on the substrate 20, for example, an amorphous or polycrystalline semiconductor film, for example, 1 J / cm ² on the non-single crystal semiconductor film. The light it has is output. The laser light source 11 is, for example, an excimer laser light source, and outputs a short pulse, for example, pulsed laser light having a half width of about 25 to 30 nsec. The laser beam is preferably, for example, a KrF excimer laser beam having a wavelength of 248 nm or a XeCl excimer laser beam having a wavelength of 308 nm.

  The excimer laser light source is, for example, a pulse oscillation type whose oscillation frequency is 100 Hz to 300 Hz.

  The beam expander expands incident laser light, and can be composed of, for example, a concave lens that expands and a convex lens that converts light into parallel light. The homogenizer has a function of determining the dimension of the incident laser beam in the XY cross-sectional direction and uniforming the light intensity distribution in 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 superposed in the Y direction and redistributed by the X direction condenser lens. Similarly, a plurality of Y-direction cylindrical lenses are arranged in the X direction to form a plurality of light beams arranged in the X direction, and each light beam is superposed in the X direction and redistributed by the Y-direction condenser lens. The excimer laser light is dimmed by the homogenizer into illumination light having a predetermined angular spread and uniform light intensity in the cross section.

  The phase shifter is an example of the light modulation element 13, and is, 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 ° between the left and right is added. A phase shifter having a phase difference of 180 ° on the left and right side modulates the incident light into a symmetric reverse peak light intensity distribution.

  In the phase shifter, for example, a step is formed so as to form a reverse peak light intensity distribution by phase-modulating incident light, and modulates the phase of the excimer laser light. As a result, the laser light that irradiates the semiconductor film has a light intensity distribution with a reverse peak pattern in which the portion corresponding to the phase shift portion (step) is intensity-modulated.

The laser light that has passed through the phase shifter of the light modulation element 13 has a predetermined light intensity on the substrate 20 placed at a position conjugate with the phase shifter (light modulation element 13) by the excimer imaging optical system 14 corrected for aberration. Imaging with a distribution. The excimer imaging optical system 14 includes, for example, an imaging lens (not shown) configured by a lens group including a plurality of calcium fluoride (CaF ₂ ) lenses and a synthetic quartz lens. For example, the excimer imaging optical system 14 has a reduction ratio of 1/5. A. : 0.13, resolving power: 2 μm, depth of focus: ± 10 μm, focal length: one-side telecentric lens having a working distance of 30 mm to 70 mm, but is not limited thereto. Moreover, not only a single-side telecentric lens but a double-sided telecentric lens may be used.

  The substrate 20 to be subjected to the crystallization process is generally a non-single-crystal semiconductor film (for example, an insulating substrate such as a glass substrate or a plastic substrate, or a holding substrate such as a semiconductor substrate (wafer) such as silicon via an insulating film). An amorphous silicon film, a polycrystalline silicon film, a sputtered silicon film, a silicon-germanium film, or a dehydrogenated amorphous silicon film) and insulated as a cap film on the non-single-crystal semiconductor film A film is provided.

  The film thickness of the non-single-crystal semiconductor film is, for example, 30 nm to 300 nm, for example, 50 nm in the case of an amorphous silicon film subjected to dehydrogenation treatment. The purpose of the insulating film is to prevent undesirable impurities from diffusing from the holding substrate into the non-single-crystal semiconductor film when crystallization of the non-single-crystal semiconductor film, or to accumulate Joule heat generated by laser irradiation. It is the film | membrane provided by.

  The cap insulating film has a function of storing heat when the non-single-crystal semiconductor film receives light and melts for crystallization by using transmission characteristics and light absorption characteristics of the cap insulating film with respect to laser light. The heat storage effect of the cap insulating film enables crystallization with a large grain size (5 μm or more) in the molten region of the non-single crystal semiconductor film. The cap insulating film is for increasing the efficiency of crystallization, but can be saved.

  The crystallization apparatus 10 of the present invention includes a substrate stage 15. The substrate stage 15 includes a position measuring unit (not shown) that measures a two-dimensional position on the XY stage, in addition to an XY stage on which the substrate 20 is placed and movable in two dimensions in the XY direction. it can. The XY stage includes an X-axis stage 15c that moves in the X-axis direction and a Y-axis stage 15b that moves in the Y-axis direction on the surface plate 15a. The surface plate 15a can be configured to include a vibration isolation mechanism. The substrate 20 is placed on the XY stage, and the substrate 20 is positioned by moving the XY stage in two dimensions.

  When the substrate 20 is crystallized by the crystallization apparatus 10 of the present invention, position calibration data stored in a storage unit (not shown) is read by a stage drive control device (not shown), and the position calibration data is used as the position calibration data. Based on this, it is driven while correcting the positional deviation of the XY stage, and the laser beam is scanned on the substrate 20 for crystallization.

  In the present invention, the imaging optical system 14 includes an imaging lens moving unit 5 that moves an imaging lens (not shown). The moving direction of the imaging lens moving unit 5 is a direction in which the focal position of the imaging lens is changed with respect to the substrate 20 placed on the substrate stage 15. When the substrate 20 placed on the XY stage is moved and positioned in the XY direction, the moving direction of the imaging lens moving unit 5 is the Z-axis direction, and the imaging lens moving unit 5 moves the imaging lens to the Z direction. The focal position of the imaging lens is aligned on the surface of the substrate 20 by moving in the axial direction.

  In the configuration in which the imaging lens is disposed above the substrate stage 15, the moving direction of the imaging lens moving unit 5 is the height direction when viewed from the surface of the substrate, and the imaging lens moving unit 5 causes the imaging lens to move. Is moved in the height direction so that the focal position of the imaging lens is aligned on the surface of the substrate 20.

  The imaging lens moving unit 5 can be constituted by, for example, a piezo stage formed by a piezo element, and can move the imaging lens by adjusting the magnitude of a voltage applied to the piezo element.

  The present invention includes an imaging lens thermal expansion correction unit 1 that corrects a positional shift at a focal point due to thermal expansion of the imaging lens. The imaging lens thermal expansion correction unit 1 aligns the focal point of the imaging lens on the surface of the substrate 20 by controlling the movement amount of the imaging lens moving unit 5 described above.

  The focal point alignment by the imaging lens thermal expansion correction unit 1 is performed by adding the positional deviation amount of the imaging lens based on the height change amount of the substrate and the focal positional deviation amount due to thermal expansion of the imaging lens. Based on the above, the correction movement amount for correcting the fluctuation of the beam condensing position due to the thermal expansion of the imaging lens is calculated, and the imaging lens moving unit is driven based on the calculated correction movement amount to move the imaging lens. To do.

  The imaging lens thermal expansion correction unit 1 includes a height detector 2 for detecting the height change amount of the substrate 20 and a beam condensing position correction unit for calculating a correction movement amount for correcting the beam condensing position. 3. The correction movement amount calculated by the beam condensing position correction unit 3 is sent to the drive circuit 4. The drive circuit 4 is a circuit for driving the imaging lens moving unit 5 such as a piezo stage, and generates a drive signal based on the correction movement amount input from the beam condensing position correcting unit 3 to select a piezo element of the piezo stage. By driving, the imaging lens is moved in the Z-axis direction or the height direction, and the focusing position of the beam is aligned with the surface of the substrate 20.

  The beam condensing position correction unit 3 includes a correction movement amount calculation unit 3a, a timer 3b, and a memory 3c (not shown in FIG. 1), and a positional deviation amount of the imaging lens based on a substrate height change amount; The amount of focal position deviation due to thermal expansion of the imaging lens is calculated, and the amount of correction movement for correcting the fluctuation of the beam condensing position due to thermal expansion of the imaging lens is calculated by adding the two positional deviation amounts. .

  Hereinafter, a configuration example of the beam condensing position correction unit 3 will be described with reference to FIG. The corrected movement amount calculation unit 3a includes a first change amount calculation circuit 3a1, a second change amount calculation circuit 3a2, and a change amount (correction movement amount) calculation circuit 3a3.

  The first change amount calculation circuit 3a1 is a calculation circuit that calculates the positional deviation amount of the focal point of the imaging lens based on the integrated irradiation time of the laser light, and after the laser light irradiation measured by the timer 3b is started. The elapsed time t is input, and the imaging lens position shift Δz1 is calculated based on the elapsed time t.

  When laser light is continuously irradiated under the same irradiation conditions, the focal position changes from the front of the substrate downward with the elapsed time t due to thermal expansion of the imaging lens. The amount of change (focal position shift amount of the imaging lens) ΔZ1 at this time can be expressed by the following equation.

  ΔZ1 = a × log (t−b) + c (1)

  Here, t represents an elapsed time from the start of laser light irradiation, and a, b, and c are parameters determined by irradiation conditions such as the energy of the laser light and the repetition frequency. This parameter can be stored in the memory 3c in association with the irradiation condition.

  The timer 3b starts measuring time based on a start signal indicating the start of laser beam irradiation. The first change amount calculation circuit 3a1 reads the parameters a, b, and c corresponding to the irradiation conditions from the memory 3c, and uses the time t input from the timer 3b as a variable to obtain the change amount (positional displacement amount of the imaging lens) ΔZ1. Calculate.

  The second change amount calculation circuit 3a2 is a calculation circuit that calculates the amount of displacement of the imaging lens based on the height change amount of the substrate. The second change amount calculation circuit 3a2 receives the height Zs detected by the height detector 2 and inputs this height. Zs is converted into a positional deviation ΔZ2 of the imaging lens.

  A change amount (position shift amount of the imaging lens) ΔZ2 accompanying a change in the height of the substrate surface that occurs when the substrate stage is driven can be expressed by the following equation (2).

  ΔZ2 = d × Zs + e (2)

  Here, Zs represents a change in the height of the substrate surface that occurs when the substrate stage is driven, and d and e are parameters. Normally, the parameter d can be 1.00.

  The parameters d and e can be stored in the memory 3c in the same manner as the parameters a, b and c. By associating these parameters d and e with the irradiation conditions, the influence of thermal expansion on the substrate side due to continuous irradiation of laser light can be taken into account.

  The change amount (correction movement amount) calculation circuit 3a3 includes the focus lens position shift amount calculated by the first change amount calculation circuit 3a1 and the image formation lens position shift amount calculated by the second change amount calculation circuit 3a2. Are added to calculate a correction movement amount ΔZ based on two positional deviation amounts.

  ΔZ = ΔZ1 + ΔZ2 (3)

  The drive circuit 4 receives the correction movement amount ΔZ calculated by the correction movement amount calculation unit 3a to generate a drive signal, drives the imaging lens movement unit 5 to move the imaging lens, and focuses the imaging lens. Align the position with the substrate surface.

  FIG. 3 is a flowchart for explaining the correction operation of the imaging lens by the imaging lens thermal expansion correction unit of the present invention.

  Steps S4 to S7 for calculating the focal position shift amount of the imaging lens based on the integrated irradiation time of the laser light by the first variation calculation circuit 3a1, and the surface of the substrate by the second variation calculation circuit 3a2. The correction movement amount is calculated by performing in parallel with the steps S1 to S3 for calculating the positional deviation amount of the imaging lens based on the height fluctuation.

  By the steps S1 to S3, the amount of displacement of the imaging lens based on the height fluctuation of the substrate surface is calculated. The height detector 2 acquires the height Zs of the substrate surface. For the height Zs, for example, the substrate surface 15 is used to measure the fluctuation of the substrate surface (S1). The parameters d and e are read out from the memory 3c (S2), the parameters d and e read out in the expression (2) in the second variation calculation circuit 3a2 are substituted, and the height Zs of the substrate surface is substituted as a variable to obtain ΔZ2 Is calculated (S3).

  Through the steps S4 to S7, the amount of misalignment of the focal point of the imaging lens is calculated based on the integrated irradiation time of the laser light. After the continuous irradiation of the laser beam is started (S4), the elapsed time is measured by the timer 3b (S5). The parameters a, b, c are read from the memory 3c (S6), the parameters a, b, c read in the equation (1) are substituted in the first change amount calculation circuit 3a1, and the elapsed time t is substituted as a variable. ΔZ1 is calculated (S7).

  In the change amount calculation circuit 3a3, the first change amount calculated in S7 and the second change amount calculated in S4 are added to calculate the correction movement amount ΔZ of the imaging lens, which is sent to the drive circuit 4 (S8). The drive circuit 4 generates a drive signal from the corrected movement amount ΔZ (S10). The imaging lens moving unit moves the imaging lens based on the drive signal generated by the drive circuit 4, and aligns the focal point with the substrate surface (S11).

  According to the aspect of the present invention, it is possible to correct a focus position change caused by thermal expansion of the lens due to high repetition irradiation and a focus position shift caused by a substrate surface change, thereby obtaining a stable crystal quality.

  According to an aspect of the present invention, if the quality of crystal grains formed by the PMELA crystallization technique is stabilized and a transistor is formed on the crystal grains in a later process, a high-performance circuit with little variation or a liquid crystal display device The formation can be expected.

It is the schematic for demonstrating the apparatus structure of the crystallization apparatus of this invention. It is a figure for demonstrating the structural example of the beam condensing position correction | amendment part of this invention. It is a flowchart for demonstrating the correction | amendment operation | movement of the imaging lens by the imaging lens thermal expansion correction | amendment part of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Imaging lens thermal expansion correction | amendment part, 2 ... Height detection part, 3 ... Beam condensing position correction | amendment part, 3a ... Correction movement amount calculation part, 3a1 ... 1st variation calculation circuit, 3a2 ... 2nd variation calculation Circuit, 3a3: change amount (correction movement amount) calculation circuit, 3b ... timer, 3c ... memory, 4 ... drive circuit, 5 ... imaging lens moving unit, 10 ... crystallization device, 11 ... excimer laser, 12 ... illumination Optical system 13... Light modulation element 14. Imaging optical system 15. Substrate stage 15a... Surface plate 15b... Y-axis stage 15 c.

Claims (8)

An illumination optical system that continuously irradiates a laser beam to crystallize a substrate to be processed, a light modulation element that modulates the laser light into a light beam having a predetermined light intensity distribution, and a modulation light of the light modulation element by an imaging lens In a crystallization apparatus that includes an imaging optical system that forms an image on a substrate and a substrate stage that supports the substrate, and melts and crystallizes a thin film provided on the substrate with modulated light.
The crystallization apparatus includes an imaging lens thermal expansion correction unit that corrects a variation in a beam condensing position due to thermal expansion of an imaging lens included in the imaging optical system, and an imaging lens moving unit that moves the imaging lens. The imaging lens thermal expansion correction unit includes
A measurement process for determining the height change of the substrate;
A calculation step of converting the obtained substrate height change amount into a displacement amount of the imaging lens;
A calculation step of calculating a positional deviation amount of the focal point of the imaging lens based on the integrated irradiation time of the laser beam;
Correction movement for correcting the fluctuation of the beam condensing position due to the thermal expansion of the imaging lens by adding the positional deviation amount of the imaging lens and the positional deviation of the focal point of the imaging lens obtained in the two calculation steps. A calculation step for calculating the quantity;
And a step of moving the imaging lens by driving the imaging lens moving unit based on the correction movement amount calculated by the beam condensing position correcting unit. The calculation for calculating the positional deviation amount of the focal point of the imaging lens is as follows.
a × log (t−b) + c
(T is a laser beam irradiation integration time, a, b, and c are parameters depending on laser beam irradiation conditions including laser beam energy and repetition frequency of laser beam irradiation),
The calculation for converting the focal position shift amount of the imaging lens is as follows.
d × Zs + e
(Zs is the height change amount of the substrate obtained by measurement, d and e are parameters depending on the laser light irradiation conditions including the laser beam energy and the repetition frequency of laser beam irradiation). The imaging lens thermal expansion correction method according to claim 1, wherein: An illumination optical system that continuously irradiates a laser beam to crystallize a substrate to be processed, a light modulation element that modulates the laser light into a light beam having a predetermined light intensity distribution, and a modulation light of the light modulation element by an imaging lens The imaging optical system comprising: an imaging optical system that forms an image on a substrate; and a substrate stage that supports the substrate, and a crystallization device that melts and crystallizes a thin film provided on the substrate with modulated light. An imaging lens thermal expansion correction device that corrects fluctuations in the beam focusing position due to thermal expansion of the imaging lens provided in the imaging lens,
The imaging lens thermal expansion correction device,
An operation for converting the amount of change in the height of the substrate into the amount of positional deviation of the imaging lens,
Performing calculation to calculate the amount of focal position shift of the imaging lens based on the integrated irradiation time of the laser beam,
The correction movement amount for correcting the fluctuation of the beam condensing position due to the thermal expansion of the imaging lens from the positional deviation amount of the imaging lens and the focal position deviation amount of the imaging lens obtained by the two calculations. A beam condensing position correction unit for calculating
An imaging lens thermal expansion correction device comprising: an imaging lens moving unit that moves the imaging lens based on the correction movement amount calculated by the beam condensing position correcting unit. The beam condensing position correction unit is
a × log (t−b) + c
(T is a laser beam irradiation integration time, a, b, and c are parameters depending on the laser beam irradiation conditions including the laser beam energy and the repetition frequency of laser beam irradiation). Calculate the amount of focus shift,
d × Zs + e
Image formation based on an arithmetic expression (Zs is a height change amount of the substrate obtained by measurement, d and e are parameters depending on laser beam irradiation conditions including laser beam energy and repetition frequency of laser beam irradiation). 4. The imaging lens thermal expansion correction device according to claim 3, wherein the amount of positional deviation of the focal point of the lens is converted.   5. The imaging lens thermal expansion correction according to claim 3, wherein the imaging lens moving unit is a piezo stage that is fixed to the substrate stage and moves the imaging lens in the Z-axis direction. apparatus. An illumination optical system that continuously irradiates laser light to crystallize the substrate to be processed;
A light modulation element that modulates the laser light into a light beam having a predetermined light intensity distribution;
An imaging optical system for imaging the modulated light of the light modulation element on a substrate by an imaging lens;
In a crystallization apparatus comprising a substrate stage for supporting a substrate and melting and crystallizing a thin film provided on the substrate with modulated light,
An imaging lens thermal expansion correction unit that corrects fluctuations in the beam focusing position due to thermal expansion of the imaging lens included in the imaging optical system;
The imaging lens thermal expansion correction unit,
An operation for converting the amount of change in the height of the substrate into the amount of positional deviation of the imaging lens,
Performing calculation to calculate the amount of focal position shift of the imaging lens based on the integrated irradiation time of the laser beam,
The correction movement amount for correcting the fluctuation of the beam condensing position due to the thermal expansion of the imaging lens from the positional deviation amount of the imaging lens and the focal position deviation amount of the imaging lens obtained by the two calculations. A beam condensing position correction unit for calculating
A crystallization apparatus comprising: an imaging lens moving unit that moves the imaging lens based on the correction movement amount calculated by the beam condensing position correcting unit. The beam condensing position correction unit is
a × log (t−b) + c
(T is a laser beam irradiation integration time, a, b, and c are parameters depending on the laser beam irradiation conditions including the laser beam energy and the repetition frequency of laser beam irradiation). Calculate the amount of focus shift,
d × Zs + e
Image formation based on an arithmetic expression (Zs is a height change amount of the substrate obtained by measurement, d and e are parameters depending on laser beam irradiation conditions including laser beam energy and repetition frequency of laser beam irradiation). The crystallization apparatus according to claim 6, wherein a displacement amount of a focal point of the lens is converted.   8. The crystallization apparatus according to claim 6, wherein the imaging lens moving unit is a piezo stage that is fixed with respect to the substrate stage and moves the imaging lens in the Z-axis direction.

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