JP5179028B2 - Display device manufacturing method and manufacturing apparatus thereof - Google Patents

Description

  The present invention relates to a panel type display device, and more particularly to a method and apparatus for manufacturing a semiconductor film of an active element formed on an insulating substrate constituting the display device.

  In the present invention, the amorphous or granular polycrystalline semiconductor film formed on one main surface of the insulating substrate constituting the device is irradiated with laser light (hereinafter also simply referred to as laser) so that the crystal grains are substantially band-shaped. The present invention is suitable for a manufacturing method and a manufacturing apparatus of a display device using an insulating substrate in which a band-shaped polycrystalline semiconductor film is formed by performing a modification that is expanded to an active element.

  Currently, panel type or flat type display devices such as liquid crystal display devices and organic EL display devices are composed of an amorphous or polycrystalline silicon film formed on an insulating film on a substrate such as glass or fused silica. An image is formed by switching active elements (thin film transistors) of a plurality of pixel circuits. The substrate on which the pixel circuit is formed is also called an active matrix substrate or simply an active panel. If it becomes possible to simultaneously form a peripheral circuit including a pixel driving circuit for driving a pixel circuit on such a substrate (hereinafter, also referred to as a pixel driving circuit or the like or simply referred to as a pixel driving circuit), dramatic manufacturing will be realized. Cost reduction and reliability improvement can be expected. However, when amorphous silicon is used as a silicon semiconductor film (hereinafter also referred to as a silicon thin film or a silicon film) that constitutes an active layer of a thin film transistor that constitutes a pixel driving circuit, the performance of the thin film transistor represented by mobility is It is difficult to manufacture a pixel driving circuit or the like that is low and requires high speed and high function.

  In order to manufacture such a high-speed and high-function pixel driving circuit, a high-mobility thin film transistor is required, and the crystallinity of the silicon thin film is required to be realized. Conventionally, excimer laser annealing has attracted attention as a method for improving crystallinity. This method uses an excimer laser to irradiate an amorphous silicon film formed on an insulating substrate such as glass via an insulating film to change the amorphous silicon film to a granular polycrystalline silicon film, thereby moving the amorphous silicon film. To improve the degree. However, the granular polycrystalline film obtained by excimer laser irradiation has a crystal grain size of about several tens to several hundreds of nanometers, and is still insufficient in performance to be applied to a pixel driving circuit for driving a pixel transistor of a display device. It is.

  As a means to solve this problem, a method of forming a so-called band crystal by laterally growing a crystal in the scanning direction by condensing time-modulated continuous wave laser light in a linear form and irradiating it while scanning at high speed Is disclosed in Patent Document 1. In this method, after the entire surface of the substrate is polycrystallized by excimer laser annealing, only the region where the drive circuit is formed is scanned with a laser beam in a direction matching the current path (drain-source direction) of the transistor to be formed. Thus, the crystal grains are laterally grown, and as a result, there is no crystal grain boundary crossing the current path, thereby greatly improving the mobility.

  However, a strip-like polycrystalline film is not formed regardless of the laser irradiation conditions. If the laser irradiation energy density is too low or too high, the crystal film becomes unsuitable for formation of a pixel driving circuit or the like. In particular, if the thickness of the amorphous silicon film or granular polycrystalline silicon film to be annealed varies, there is a risk that if annealing is performed under the same conditions, a crystal film that is not suitable for forming a pixel driving circuit or the like may be formed. large.

Further, Patent Document 2 discloses a laser irradiation method in which the beam intensity is varied depending on the scanning direction when scanning laser light with a laser irradiation apparatus provided with a beam intensity variable means. Further, Patent Document 3 divides a film to be irradiated into a plurality of regions, measures the film thickness for each of the divided regions, and adjusts the amount of light to be irradiated, thereby controlling the laser annealing apparatus and laser that are controlled to the optimum energy density. An annealing method is disclosed.
JP 2003-124136 A JP 2006-32928 A JP 2005-11840 A

  The method described in Patent Document 1 does not consider the case where the thickness of the amorphous silicon film formed on the insulating substrate or the thickness of the granular polycrystalline silicon film varies, and at least in one substrate. Irradiation is performed at a constant scanning speed and a constant energy density, so that a portion with a large variation in film thickness cannot be partially annealed properly, resulting in a decrease in panel yield.

  Further, the method described in Patent Document 2 does not take into account changing the beam intensity in accordance with the silicon film thickness. And although the apparatus and method described in patent document 3 adjust an irradiation energy density for every divided area, they cannot cope with fluctuations within the section. In addition, since measurement and annealing with an ellipsometer are performed with the same apparatus, it takes a long time for measurement, and annealing cannot be performed during measurement, so throughput is low.

  The object of the present invention is to solve the above-mentioned problems, and even when the silicon film thickness fluctuates without lowering the throughput, it is modified into a band-like silicon crystal by performing proper annealing over the entire surface of the substrate. An object of the present invention is to provide a method and a manufacturing apparatus capable of manufacturing a display device with a high yield by manufacturing a thin film transistor on a quality silicon film.

  A plurality of panel regions are arranged in the scanning direction of the laser beam on one main surface of the insulating substrate constituting the display device of the present invention. In order to achieve the above object, according to the present invention, the thickness of the amorphous silicon film or the granular polycrystalline silicon film formed on one main surface of the insulating substrate is changed along the laser beam scanning direction. These panels are measured in advance, and the energy density of the laser light applied to each panel region is adjusted based on the measurement result of the film thickness (film thickness data) when the laser light is applied. More specifically, the output of the laser oscillator is always constant, and the film thickness of the amorphous silicon film or granular polycrystalline silicon film varies by adjusting the transmittance with the optical system until it reaches the substrate surface. Even if it is, proper annealing is always possible. The adjustment of the energy density of the irradiated laser beam may be a continuous adjustment performed in each panel region, or an intermittent adjustment performed with a predetermined value calculated from film thickness data in each panel region.

  According to the present invention, it is possible to manufacture a high-quality flat display device without reducing the manufacturing yield.

  Hereinafter, the best mode of the present invention will be described in detail with reference to the drawings of the embodiments. First, a first example of the manufacturing apparatus of the present invention will be described as Example 1.

  FIG. 1 is a diagram for explaining Example 1 of a manufacturing apparatus suitable for carrying out the method for manufacturing a flat display device of the present invention. This manufacturing apparatus includes a laser oscillator 4 for generating a continuous wave laser beam (hereinafter also simply referred to as laser beam) 3 coupled with an excitation LD (laser diode) 1 and an optical fiber 2, and turning on / off the laser beam 3. The shutter 5 to be performed, the transmittance continuously variable ND filter 6 for adjusting the energy of the laser beam 3, and the laser beam 3 output from the laser oscillator 4 are amplitude-modulated to be pulsed or the temporal intensity (amplitude) modulation of energy. Are provided with a modulator 7 and a polarization beam splitter 8.

  A beam expander (or beam reducer) 9 for adjusting the beam diameter of the laser beam 3 and the laser beam 3 have an elongated shape, for example, a linear shape, a rectangular shape, an elliptical shape, an elliptical shape, and a flat top energy distribution. A beam shaper 11 for shaping into a beam shape, a mask 14 for adjusting the longitudinal direction of the shaped laser light 3 to a predetermined dimension, an imaging lens (tube lens) 15 for converting the image of the mask 14 into parallel light, An objective lens 19 for reducing and projecting the laser light transmitted through the imaging lens 15 onto the substrate 20 placed on the stage 21, an ND filter driver 22 for controlling the continuously variable transmittance ND filter 6, and the modulator 7. It comprises a modulator driver 23 for driving and controlling and a control device 29 for controlling each element of the manufacturing apparatus. The stage 21 scans the laser beam by moving two-dimensionally in the plane of the substrate 20 and relatively moving the laser beam and the substrate.

  An amorphous silicon film or a granular polycrystalline silicon film is formed on the main surface of the substrate 20. The control device 29 is provided with a memory 30 for storing film thickness distribution data of an amorphous silicon film or a granular polycrystalline silicon film formed on the substrate. The memory 30 receives the film thickness distribution data via the LAN 40.

Next, the operation and function of each unit will be described in detail. It is desirable that the continuous wave laser beam 3 has a wavelength that is absorbed by the amorphous or polycrystalline silicon thin film that is the object of the present manufacturing apparatus, that is, an ultraviolet wavelength and a visible wavelength. More specifically, Ar laser or Kr laser and its second harmonic, Nd: YAG laser, Nd: YVO ₄ laser, Nd: YLF laser second harmonic and third harmonic, visible wavelength semiconductor laser ( Including a laser diode). In addition, a so-called pseudo CW laser that performs pulse oscillation with an extremely short pulse width at a high repetition rate may be used. Among these, in consideration of the output magnitude and output stability, the second harmonic (wavelength 532 nm) of the LD (laser diode) pumped Nd: YAG laser or the second harmonic (wavelength of the Nd: YVO ₄ laser) 532 nm) is most desirable. In the following description, the case where the second harmonic of the LD-pumped Nd: YVO ₄ laser is used will be described.

  The continuous wave laser beam 3 oscillated from the laser oscillator 4 is turned on / off by the shutter 5. That is, the laser oscillator 4 is always in a state where the laser beam 3 is oscillated at a constant output. The shutter 5 is normally closed (OFF state), and the laser beam 3 is blocked by the shutter 5 to prevent the laser beam 3 from being irradiated when the substrate 20 is transported or positioned. Then, only when annealing is performed or only when an alignment mark is formed as necessary, the shutter 5 is opened (turned on) to output the laser beam 3. Although it is possible to turn on / off the laser beam 3 by turning on / off the excitation laser diode 1, it is not preferable for ensuring the stability of the laser output. In addition, even if it is desired to urgently stop the irradiation of the laser beam 3 from the viewpoint of safety, it is only necessary to close the shutter 5, thereby blocking the output of the laser beam 3 without adversely affecting the oscillator itself. .

  When the shutter 5 is open, the laser light 3 that has passed through the shutter 5 passes through the continuously variable transmittance ND filter 6 used for output adjustment and enters the modulator 7. As the transmittance continuously variable ND filter 6, it is desirable that the laser beam is transmitted and the polarization direction does not rotate. However, as will be described later, this is not the case when an AO modulator that is not affected by the polarization direction is used as the modulator 7.

  FIG. 2 is a diagram for explaining a configuration example of the continuously variable transmittance ND filter 6. The transmittance continuously variable ND filter 6 uses a combination of a half-wave plate 32 and a polarization beam splitter 33 that are rotatably installed by a rotary bearing 31 or the like so that the laser optical axis is the center of rotation. In FIG. 2, a driving mechanism for rotationally driving is not shown, but it can be driven by a pulse motor or a DC motor via a gear or a belt, or directly by an ultrasonic motor or the like.

  When the laser beam 3 is linearly polarized light, the laser beam that has passed through the half-wave plate 32 enters the polarization beam splitter 33 as P-polarized light and is adjusted so as to be totally transmitted. The direction of polarization of the laser light 3 transmitted through the half-wave plate 32 is twice that of the half-wave plate 32 by rotating the half-wave plate 32 around the optical axis by the output from the driver 22. It rotates at a speed, and only the P-polarized light component is transmitted by the polarization beam splitter 33. Further, the output of the transmitted laser light 3 is changed as shown in FIG. 3 by deflecting the S-polarized component by 90 degrees. That is, an arbitrary output can be set by rotating the rotation angle of the half-wave plate 32 to an arbitrary angle from 0 degree to 45 degrees. FIG. 3 shows the relationship between the rotation angle of the wave plate of the continuously variable transmittance filter shown in FIG. 2 and the transmittance.

  As the modulator 7, an EO modulator is most suitable. FIG. 4 is a diagram showing a configuration of an EO modulator suitable for carrying out the flat display device manufacturing method of the present invention. As shown in FIG. 4, the EO modulator applies a voltage to a Pockel's Cell (crystal) 35 via a driver 23, thereby rotating the polarization direction of the laser light 3 that passes through the crystal, and behind the crystal. Only the P-polarized light component is allowed to pass through the polarizing beam splitter 8 placed on the surface. Further, by turning the S-polarized component by 90 degrees, ON / OFF (or pulsing) of the laser beam 3 and output adjustment can be performed.

  FIG. 5 is a diagram showing the relationship between the applied voltage and the transmittance of the EO modulator shown in FIG. As shown in FIG. 5, the voltage V1 (usually 0V) for rotating the polarization direction of the laser beam 3 so as to be incident on the polarization beam splitter 8 as S-polarized light and the laser beam so as to be incident as P-polarized light. By applying an arbitrary voltage between the voltage V2 for rotating the polarization direction 3 to the Pockels cell 35, the output of the laser beam output as the P-polarized light from the polarization beam splitter 8 can be arbitrarily set. it can.

  In FIGS. 2 and 4, it has been described that the polarization beam splitters 33 and 8 are used to extract the P-polarized component. However, various polarization elements can be used instead of the polarization beam splitter. In FIG. 1, the modulator 7 and the polarization beam splitter 8 are shown as independent components. However, a component including various polarization elements may be commercially available as the modulator (EO modulator) 7. An entire combination of the polarizing beam splitters 8 (or various polarizing elements) may be referred to as an EO modulator.

  In addition to the EO modulator, an AO (acousto-optic) modulator can be used as the modulator 7. In general, the AO modulator has a lower driving frequency than the EO modulator and has a diffraction efficiency of 70 to 90%, which is less efficient than the EO modulator. However, it has a feature that it can be turned ON / OFF (or pulsed) even when the laser beam is not linearly polarized light. Even when a laser whose polarization direction of the transmitted laser beam is rotated is used as the continuously variable transmittance ND filter 6, or laser No problem arises even if the light itself is not linearly polarized. In this way, by using the modulator 7 such as the EO modulator 7 (and the polarization beam splitter 8) or the AO modulator, laser light having an arbitrary waveform (temporal energy change) from the continuous wave laser light at an arbitrary timing. Can be obtained. That is, desired amplitude modulation can be performed.

  The amplitude-modulated laser light 3 is adjusted in beam diameter by a beam expander (or beam reducer) 9 for adjusting the beam diameter, and enters the beam shaper 11. The beam shaper 11 is an optical element for shaping the laser light 3 into an elongated or rectangular beam. Usually, a gas laser or a solid-state laser outputs a circular beam having a Gaussian energy distribution. For this reason, it cannot be used as it is for the laser annealing of the present invention. If the oscillator output is sufficiently large, it is possible to obtain a substantially uniform energy distribution by sufficiently widening the beam diameter and cutting out only a relatively uniform part near the center of the beam. However, the peripheral part of the beam is discarded. And most of the energy is wasted. The beam shaper 11 is used to solve this drawback and convert the Gaussian distribution into a linear beam with a uniform distribution (top flat).

  A diffractive optical element can be used as the beam shaper 11. The diffractive optical element forms a fine step in a photoetching process on a substrate such as quartz, and synthesizes the diffraction pattern formed by the laser beam that passes through each step on the image plane, resulting in a match with the image plane. It is created so that a linear or rectangular energy distribution can be obtained on the mask 14 surface. That is, the diffractive optical element used here has a uniform distribution in one direction (longitudinal direction) and a Gaussian distribution in the perpendicular direction (short direction) when a Gaussian distribution laser beam is incident. Designed and manufactured as follows. When a diffractive optical element is used, a uniform distribution with a longitudinal intensity distribution of about ± 3% is obtained.

  Alternatively, a combination of a Powell lens and a cylindrical lens can be used as the beam shaper 11 instead of the diffractive optical element. A Powell lens is a kind of cylindrical lens, and when a Gaussian laser beam is incident, the part with high energy density in the central part in one direction becomes sparse, and the part with low energy density in the peripheral part is dense. An image is formed on the projection plane so that In the direction perpendicular to the direction, the energy distribution remains unchanged in the Powell lens alone, and thus the light is condensed by the cylindrical lens. As a result, an elongated beam having a uniform energy distribution in the longitudinal direction and a Gaussian distribution in the lateral direction is formed on the mask 14 surface. When a Powell lens is used, a uniform distribution with a longitudinal intensity distribution of about ± 5% is obtained.

  If necessary, a portion having a large energy density change in the periphery of the beam in the longitudinal direction or a skirt portion (high-order diffracted light in the case of a diffractive optical element) is shielded by the mask 14 or shaped to a required size. As a result, a linear light beam having a desired dimension with a sudden rise is obtained. Instead of the mask 14, it is also possible to use a slit whose dimension is set to be variable in the longitudinal direction of the beam.

  The linear light beam obtained here is converted into parallel light by an imaging lens (tube lens) 15, and is reduced and projected onto the substrate 20 by the objective lens 19 to the inverse of the objective lens magnification. That is, when a 10 × lens is used, projection is performed with a size that is 1/10 of the beam dimension shaped by the mask 14. By scanning the stage 21 at a high speed in the short direction of the linear beam while being irradiated with the laser light, the irradiated silicon film is melted and re-solidified and laterally grown in the scanning direction (strip-like polycrystal). Membrane).

  The control device 29 controls the laser oscillator 4, the shutter 5, and the stage 21, and processes the data of the film thickness measurement result measured in advance stored in the memory 30, so that the position of the substrate 20, the silicon film thickness, The appropriate energy density corresponding to the film thickness (or the transmittance for obtaining the appropriate energy density) is calculated and stored, and the transmittance of the continuously variable transmittance filter 6 is set so as to obtain an appropriate transmittance according to the scanning position of the laser beam during annealing. The driver 22 or the driver 23 of the EO modulator 7 is controlled.

Hereinafter, an embodiment of a method for manufacturing a flat display device using the manufacturing apparatus having the configuration shown in FIG. 1 will be described in detail as a second embodiment with reference to the drawings. The target substrate 20 is a transparent insulating substrate preferably made of glass, and is a multi-piece substrate for obtaining a plurality of thin film transistor substrates (panels) from a single substrate. An amorphous silicon film is formed on this substrate via an insulating film (underlying film) made of a SiO ₂ film and / or a SiN film. At this time, the film thickness of the amorphous silicon is set to 30 to 100 nm. This amorphous silicon film thickness is desirably uniform over the entire surface of the substrate, but in reality, film thickness unevenness occurs in the substrate. Further, the film thickness and the film thickness distribution are different among the film forming apparatuses, and the film thickness and the film thickness distribution vary with time even in the same apparatus. However, a substrate formed within a certain period of time by the same apparatus has film thickness unevenness in the substrate, but variation between the substrates is small.

  FIG. 6 is a diagram schematically illustrating an example of an in-plane film thickness distribution of an amorphous silicon film formed on a substrate. In FIG. 6, the film thickness is indicated by contour lines, and the numbers in the figure indicate the film thickness. An amorphous silicon film was formed on the substrate 20 with a target of a film thickness of 50 nm, but the central part of the substrate is thickest and becomes thinner toward the periphery. For the measurement of these film thickness distributions, an ellipsometer, a light interference film thickness meter, a fluorescent X-ray film thickness meter, a method of measuring the film thickness from the amount of light transmitted through irradiation with visible light or ultraviolet light, etc. may be used. it can. A portion where a peripheral circuit including a pixel driving circuit is formed is measured for each panel dimension in a direction perpendicular to the scanning direction of the laser light in the scanning direction of the laser light. Or you may measure every several panels. The film thickness distribution of the entire substrate can be known by complementing these measured values with, for example, a straight line.

  Although all film thickness distributions on the target substrate surface may be measured, in general, when an amorphous silicon film is continuously formed under the same apparatus and under the same conditions, the film thickness distribution The fluctuation is very small. Therefore, the film thickness distribution for one lot (for example, 20 sheets stored in one cassette) can be represented by measurement of one substrate.

  The measured film thickness data is sent to a host computer via, for example, a LAN, stored together with the lot number and the substrate number, and when converted into a strip-like polycrystalline film, these data are received via the LAN as necessary. By storing this in the memory 30, the film thickness distribution of each substrate (or representative substrate) can be read and given to the ND filter driver 22 to control the variable transmittance ND filter 6.

The substrate 20 on which the film thickness distribution of the amorphous silicon film has been measured in advance is in a state where measures are taken so that the laser is not irradiated to the peripheral portion of about 5 to 20 mm width by an excimer laser annealing apparatus. The entire surface is annealed. Usually, excimer laser light is shaped into a rectangular shape having a width of several hundred microns and a length of several hundred mm, and is irradiated while scanning under the condition that 5 to 30 pulses are irradiated to the same location. At that time, irradiation is performed according to irradiation conditions (energy density) corresponding to the film thickness distribution measured in advance. As a result, as shown in FIG. 7, the amorphous silicon film 51 remains in the peripheral portion of the substrate as it is, and the portion other than the peripheral portion becomes a granular polycrystalline silicon film 52 through a melt resolidification process by irradiation with an excimer laser. The polycrystalline silicon film 52 is a granular crystal having a crystal grain size of several tens to several hundreds of microns. The mobility of a TFT formed with this film is about 100 cm ² / Vs, and is used for a pixel switching TFT. It is enough performance.

  In the above description, the film thickness distribution is measured before the excimer laser irradiation. However, the film thickness distribution of the granular polycrystalline silicon film may be measured at the stage where the annealing by the excimer laser is finished. Also in this case, an ellipsometer, an optical interference film thickness meter, a fluorescent X-ray film thickness meter, a method of measuring the film thickness from the amount of light transmitted through irradiation with visible light or ultraviolet light, and the like can be used. The measurement result is sent to a host computer via LAN in the same manner as described above, stored together with the lot number and substrate number, and sent via LAN to a device for converting to a band-like other crystal film, which will be described later, if necessary. .

  Next, the granular polycrystallized substrate 20 excluding the peripheral portion is transferred to the apparatus shown in FIG. 1 and processed. The substrate 20 is placed on the stage 21 in FIG. 1, and the film thickness data of the substrate 20 is sent to the control device 29 via the LAN. The substrate 20 is pre-aligned by pressing against a plurality of pins (not shown) installed on the stage 21 in order to perform approximate alignment. Thereby, alignment of about ± 100 microns can be performed. Hereinafter, a description will be given with reference to FIG.

  FIG. 8 is a diagram illustrating alignment mark formation on a target substrate in the manufacturing method of the present invention. After roughly aligning the substrate on the stage 21, the portion of the substrate peripheral portion where the amorphous silicon film 51 remains is irradiated with laser light in the form of a mask pattern for alignment marks, An alignment mark is formed. At this time, although omitted in FIG. 1, the beam shaper 11 is replaced with a beam shaper that can obtain a rectangular or circular uniform distribution, and the mask 14 is replaced with a mask on which alignment marks are formed.

  In general, an alignment mark to be formed has a size of several tens of microns square to several hundreds of microns square, and a mask (not shown) on which an alignment mark pattern is formed is irradiated with a laser to Reduce and project the mask pattern. The laser used may be a continuous wave laser for annealing (formation of a band-like polycrystalline film), or a small pulse laser installed for mark formation. As a result, the amorphous silicon film is irradiated with the laser light transmitted through the mask, and only the irradiated portion is converted into a polycrystalline silicon film. This polycrystal film does not need to be a laterally grown crystal, and may be a granular polycrystal or a so-called fine crystal. In any polycrystalline state, the reflectance is different from that of the amorphous silicon film in the laser non-irradiated portion, so that it can be used as an alignment mark.

  After forming the first alignment mark, the stage 21 is moved, stopped at the second alignment mark position, and irradiated with laser light again to form the alignment mark. This procedure is repeated as many times as necessary, and marks are sequentially formed at locations where alignment marks are required. Thus, alignment marks 54, 55, 56, alignment marks 57, 58, 59, 60, etc. are formed in the amorphous silicon film portion 51 on the two sides of the substrate remaining in the peripheral portion of the substrate 20.

  In FIG. 8, the case where six alignment marks are formed in the substrate 20 is described as an example, but the number is not limited. In addition, various shapes can be selected as the alignment mark as required. This alignment mark is first performed after the substrate 20 is rotated by 90 degrees when annealing (formation of a band-like polycrystalline film) is performed in two directions (long axis direction and short axis direction) of the substrate and after the annealing step. It is used for alignment of a photomask (or reticle) in a photoresist process. When exposure is performed with a stepper, the alignment marks may be formed in a number corresponding to all the panels built in the substrate, or only at positions corresponding to the first panel, and the remaining panel is moved by the stepper. You may expose with precision. In the case of an aligner that exposes the entire surface at once, it is sufficient to form alignment marks at two or three locations.

  Next, the portion of each panel where the peripheral circuit including the pixel drive circuit is formed is irradiated with continuous-wave laser light shaped in a linear shape while scanning in the short (short axis) direction, and the polycrystal is formed by excimer laser annealing. A part of the portion 52 converted into the silicon film is converted into a band-like polycrystalline film grown laterally (laterally). First, consider the case where the arrow portion shown in FIG. 8 is converted into a band-like polycrystalline film.

  FIG. 9 is a diagram illustrating a part of the film thickness data stored in the memory included in the control device. FIG. 9 shows a state before the formation of the granular polycrystalline film corresponding to the substrate position when measured in the direction of the arrows in the first, second, and third rows indicated by arrows A, B, and C in FIG. The relationship of the film thickness before laser irradiation is shown as representative data. The horizontal axis (substrate position) in FIG. 9 corresponds to the position in the long axis (long side) direction in FIGS. The film thickness corresponds to that shown in the schematic diagram of FIG. 6 described above, and the film thickness at the center is large and decreases as it goes to the periphery.

  On the other hand, an appropriate energy density for converting a granular polycrystalline film into a band-shaped polycrystalline film differs depending on the silicon film thickness. FIG. 10 shows the relationship between the film thickness of the granular other crystalline silicon film and the energy density (relative value) necessary for conversion into the band-like polycrystalline film in the case of the laser wavelength (532 nm) in this example. In FIG. 10, the solid line indicates the minimum energy density for forming the band-like polycrystalline film. In the region below the solid line, no band-like polycrystal is formed, and the state is a granular polycrystalline film or a mixed film of a granular polycrystalline film and a band-like polycrystalline film. In the region above the solid line, a band-like polycrystalline film is obtained. However, if the energy density is too high, molten silicon aggregates due to surface tension, and in an extreme case, ablation occurs. In general, as an appropriate energy density, the minimum energy density + α (α is a margin for covering fluctuations in the output of the oscillator and the non-uniform portion of the linear beam), or the minimum for forming a band-shaped polycrystalline film. An intermediate value between the energy density and the maximum energy density (not shown in FIG. 10) is selected. Here, the appropriate energy density is 120% of the minimum energy density, and is indicated by a broken line in FIG.

  As can be seen from FIG. 10, when a visible wavelength is used as the laser, the appropriate energy density shows a minimum value when the film thickness is around 60 nm. When the film thickness is increased from 60 nm, an increase in the volume to be melted is a main factor, so that the required energy density gradually increases. Further, when the film thickness is decreased from 60 nm, a decrease in absorbed energy becomes a main factor, and thus a necessary energy density increases. FIG. 11 shows the relationship between the energy density appropriate for conversion into the band-shaped polycrystalline film and the substrate position with respect to the film thickness shown in FIG. The substrate position in FIG. 11 is the same as that in FIG. As shown in FIG. 11, the energy density is the lowest at the center of the substrate and increases at the periphery.

  That is, considering the case where the laser beam is scanned at the positions of arrows A, B, and C shown in FIG. 8, the transmittance continuously variable filter so that the energy density shown in FIG. 11 is obtained at each position of the substrate. While the transmittance of 6 is continuously adjusted, the EO modulator 7 performs an ON / OFF operation so that only the peripheral circuit portion including the drive circuit is irradiated with the laser. The relationship between the energy density actually applied to the substrate and the substrate position by the operation of the continuously variable transmittance filter 6 and the EO modulator 7 is as shown in FIG. Alternatively, the transmittance of the continuously variable transmittance filter 6 is constant, and the EO modulator 7 continuously turns on and off the laser beam simultaneously with the applied voltage when turning on according to the film thickness corresponding to the irradiation position. Let

  The position of the substrate can be easily known by using a position sensor installed on the stage 21, for example, a linear scale. As a result, the energy density applied to the substrate becomes as shown in FIG. 12 for each of the first row (A), the second row (B), and the third row (C). Irradiation can be performed with an appropriate power density according to the above.

  Thereafter, the laser beam is continuously adjusted in the position and direction indicated by arrows A, B, and C in FIG. As a result, as shown in FIG. 13, the pixel drive circuit portions 61, 62, 63,... Of each panel (shown in FIG. 13 as thick pixel lines as pixel drive circuit portions) are all formed into a strip-like polycrystalline film. Convert. FIG. 13 shows a case of taking a large number of sheets in which 72 panels (12 × 6) are formed on one substrate. When the regions (portions 61, 62, 63,... In FIG. 13) for forming the peripheral circuit including the pixel driving circuit are concentrated on only one side of the panel 20, the substrate 20 is formed as shown in FIGS. It only needs to scan and anneal in one direction as shown by the arrow, and irradiate the peripheral circuit parts including the pixel drive circuit of all panels manufactured in the substrate with laser, and convert those parts into a strip-like polycrystalline film To finish the process. Usually, the length of the peripheral circuit portion including the pixel driving circuit is about the size of one panel (width of about 500 to 3000 microns (0.5 to 3 mm)). When the length of the laser beam in the longitudinal direction is less than the size of the peripheral circuit portion, the laser beam is formed by a plurality of laser scans.

  When peripheral circuits including pixel drive circuits are formed on two adjacent sides of the panel, the substrate 20 is rotated 90 degrees in the plane, and laser scanning is performed in the same direction as before the rotation, or the laser is shaped linearly It is necessary to rotate the longitudinal direction and the short direction of light by 90 degrees and scan in a direction orthogonal to the direction before the rotation. In these cases, especially when the substrate is rotated, even if the substrate is pressed against the pressing pin, the positional accuracy of the rotation center of the substrate is only guaranteed to be about ± 100 microns. I need it. Therefore, a plurality of alignment marks formed first are detected as necessary, and the substrate is aligned based on the detected coordinates.

  Similar to the procedure shown in FIG. 8, after alignment, scanning is performed while irradiating a linearly shaped laser beam, so that a direction perpendicular to the previous scanning direction (short of the substrate 20) is obtained as shown in FIG. The strip-like polycrystalline film portions 71, 72, 73 and the like grown laterally in the side direction can be formed. In laser irradiation, as described above, for example, based on silicon film thickness data measured before or after excimer laser irradiation sent via LAN and stored in the memory of the control device, In order to obtain an optimum energy density, the transmittance of the continuously variable transmittance filter 6 or the voltage applied to the EO modulator 7 when irradiating laser light is continuously adjusted.

  Another embodiment of a method for manufacturing a flat display device using the manufacturing apparatus shown in FIG. 1 will be described as a third embodiment. When applied to the manufacture of a small display device typified by a cellular phone, it can be continuously adjusted regardless of the transmittance adjustment by the transmittance continuously variable filter 6 or the voltage applied to the EO modulator 7. Instead, the individual panels formed in the substrate may be irradiated with a constant transmittance, that is, a single panel with a constant power density.

  In this case, the transmittance is adjusted to obtain an appropriate energy density corresponding to the average film thickness in each panel calculated based on the silicon thickness distribution data measured in advance or the film thickness at the laser irradiation start point. Then, data obtained by converting the peripheral circuit region including the pixel driving circuit of each panel into a band-like polycrystalline film is stored in the memory 30 in sequence. The energy density applied to the substrate using this data is as shown in FIG. 15, and the irradiation is performed at an appropriate power density corresponding to the silicon film thickness from one end of the substrate 20 to the other end in the laser beam scanning direction. I can do it. FIG. 15 also shows a case where the energy density is adjusted according to the film thickness at the laser irradiation start position.

  Similar to the second embodiment, the laser beam is continuously scanned in the positions and directions indicated by arrows A, B, and C in FIG. As a result, as shown in FIG. 13, all the pixel driving circuit portions 61, 62, 63,... Of each panel are converted into a strip-like polycrystalline film. Also in the second embodiment, when the region (portions 61, 62, 63,... In FIG. 13) for forming the peripheral circuit including the pixel driving circuit is concentrated on only one side of the panel 20, the substrate 20 is formed as shown in FIG. It is only necessary to scan and anneal in one direction as indicated by the arrows in FIG. 11, and irradiate the peripheral circuit portions including the pixel driving circuits of all the panels manufactured in the substrate with a laser, and these portions are striped. The process ends after conversion to a crystal film. The laser multiple scans in the case where the length of the laser beam in the longitudinal direction is less than the size of the peripheral circuit portion are the same as in the first embodiment.

  Also in the third embodiment, when the peripheral circuit including the pixel driving circuit is formed on two adjacent sides of the panel, the substrate 20 is rotated 90 degrees in the plane, and laser scanning is performed in the same direction as before the rotation. The substrate alignment is also the same as in the first embodiment. The obtained substrate is the same as FIG. Thereby, the annealing process of Example 3 is completed.

  Thereafter, in both Example 2 and Example 3, when the processing of the first substrate 20 is completed, the substrate 20 is unloaded from the stage 21 and stored in a cassette (not shown) for transfer to the next process. At the same time, the second substrate is placed on the stage 21 and the second processing is started. As described above, since the film thickness variation between the substrates in the same lot is small, it is considered that the film thickness distribution is the same as that of the first film, so that the irradiation energy is adjusted so that an appropriate band-shaped polycrystalline film is obtained. Conversion to can be performed. Of course, when the film thickness distribution of all the substrates is measured, the measurement results of each substrate are received via a LAN or the like and stored in the memory, and based on the film thickness of the measurement results or the average film thickness calculated from the measurement results Adjust the irradiation energy. When processing of all the substrates stored in the cassette is completed, the cassette is transferred to the next process, and finally a flat display device is formed.

  The above description is based on the manufacturing method in the case where the amorphous silicon thin film formed on the substrate is converted into the granular polycrystalline silicon film by excimer laser irradiation, and then only the region for forming the drive circuit is converted into the band-shaped polycrystalline silicon film. However, it is also possible to convert only the region for forming the drive circuit directly from the amorphous silicon thin film into a band-shaped polycrystalline silicon film. In that case, the pixel circuit is composed of a thin film transistor formed of an amorphous silicon (a-Si) thin film.

  Next, another configuration of a manufacturing apparatus to which the manufacturing method of the present invention is applied will be described as a fourth embodiment. FIG. 16 is a diagram showing another configuration of the flat display device manufacturing apparatus according to the present invention. 16, the pumping LD 1, the optical fiber 2, the continuous wave laser oscillator 4, the shutter 5, the continuously variable transmittance ND filter 6, the continuously variable transmittance ND filter driver 22, the modulator 7, and the modulator illustrated in FIG. 1. In addition to the driver 23, the polarizing beam splitter 8, the beam expander 9, the beam shaper 11, the mask 14, the tube lens 15, the objective lens 19, the stage 21, and the like, the film thickness measuring unit 81 and each component are controlled. The controller 82 is configured.

  Of the configuration shown in FIG. 16, the details of the components indicated by the same numbers as in FIG. 1 are as described above. As the film thickness measuring unit 81, an ellipsometer, an optical interference type film thickness meter, a fluorescent X-ray film thickness meter, a method of measuring the film thickness from the amount of light transmitted through irradiation with visible light or ultraviolet light, or the like may be used. However, as a method that can be measured easily and in a short time, a method of measuring the film thickness from the amount of light that is transmitted through irradiation with visible light or ultraviolet light is optimal. Further, in addition to the function of the control device 29 described with reference to FIG. 1, the control device 82 processes the control of the film thickness measurement unit 81 and the data of the film thickness measurement result to obtain the substrate position, the silicon film thickness, and the film thickness. A function of calculating an appropriate energy density corresponding to (or a transmittance for obtaining an appropriate energy density) and storing it in the memory 83 and controlling the driver 22 of the continuously variable transmittance filter 6 or the driver 23 of the EO modulator 7 is also provided. Have.

Hereinafter, an embodiment of a method for manufacturing a flat display device using the manufacturing apparatus shown in FIG. The fifth embodiment will be described with reference to the drawings used to describe the above-described embodiments. A peripheral portion of a substrate having a thickness of 5 to 20 mm on which an amorphous silicon film having a thickness of 30 to 100 nm is formed on a transparent substrate such as glass via an insulating film (underlying film) made of a SiO ₂ film and / or a SiN film The entire surface other than the peripheral portion is annealed by an excimer laser in a state where measures are taken so that the laser is not irradiated to the extent.

Usually, excimer laser light is shaped into a rectangular shape having a width of several hundred microns and a length of several hundred mm, and is irradiated while scanning under the condition that 5 to 30 pulses are irradiated to the same location. As a result, as shown in FIG. 7, the amorphous silicon film 51 remains in the peripheral portion of the substrate as it is, and the portion other than the peripheral portion becomes a granular polycrystalline silicon film 52 through a melt resolidification process by irradiation with an excimer laser. The polycrystalline silicon film 52 is a granular crystal having a crystal grain size of several tens to several hundreds of microns. The mobility of a TFT formed with this film is about 100 cm ² / Vs, and is used for a pixel switching TFT. It is enough performance.

  Next, the granular polycrystallized substrate 20 excluding the peripheral portion is transferred to the apparatus shown in FIG. 16 while being stored in a cassette, and processed for each substrate. First, the substrate 20 is pre-aligned by pressing against a plurality of pins (not shown) installed on the stage 20 in order to perform approximate alignment. Thereby, alignment of about ± 100 microns can be performed.

  After the rough alignment, the alignment mark is formed by irradiating the portion where the amorphous silicon film 51 in the peripheral portion of the substrate remains with a laser beam projected onto the alignment mark mask pattern. . In general, an alignment mark to be formed has a size of several tens of microns square to several hundreds of microns square, and a mask (not shown) on which an alignment mark pattern is formed is irradiated with a laser to Reduce and project the mask pattern. The laser to be used may be a continuous wave laser for annealing (formation of a band-like polycrystalline film) or another small pulse laser installed for mark formation. As a result, the amorphous silicon film is irradiated with the laser light transmitted through the mask, and only the irradiated portion is converted into a polycrystalline silicon film. This polycrystal film does not need to be a laterally grown crystal, and may be a granular polycrystal or a so-called fine crystal. In any polycrystalline state, the reflectance is different from that of the amorphous silicon film in the laser non-irradiated portion, so that it can be used as an alignment mark.

  After forming the first alignment mark, the stage 21 is moved, stopped at the second alignment mark position, and irradiated with laser light again to form the alignment mark. This procedure is repeated as many times as necessary, and marks are sequentially formed at locations where alignment marks are required. Thus, as shown in FIG. 8, alignment marks 54, 55, 56, 57, 58, 59 are formed in the amorphous silicon film portion 51 remaining in the peripheral portion of the substrate 20.

  In FIG. 8, the case where six alignment marks are formed in the substrate 20 is described as an example, but the number is not limited. As the shape of the alignment mark, various shapes can be selected as necessary. These alignment marks are used to align the photomask (or reticle) in the photoresist process that is performed first after the substrate 20 is rotated by 90 degrees when annealing is performed in two directions and after the annealing process. To do. When exposure is performed with a stepper, the alignment marks may be formed in a number corresponding to all the panels built in the substrate, or only at positions corresponding to the first panel, and the remaining panel is moved by the stepper. You may expose with precision. In the case of an aligner that exposes the entire surface at once, it is sufficient to form alignment marks at two or three locations.

  In this state, the film thickness measurement unit 81 measures the silicon film thickness distribution in the region to be converted into the band-like polycrystalline film. In measurement, the film thickness measurement unit 81 may be moved for measurement, or the film thickness measurement unit 81 may be fixed and the substrate 20 may be moved. In this embodiment, the procedure for measuring the film thickness after fixing the substrate 20 on the stage 21 is described. However, before fixing on the stage 21, another station (not shown) is installed in the apparatus. It may be provided to measure the film thickness distribution, transmit the measurement result to the apparatus via the LAN, and place and fix the substrate 20 on the stage 21 after the measurement. In this case, since the film thickness of the next substrate can be measured while irradiating the laser, it is more desirable without reducing the throughput.

  Next, the peripheral circuit portion including the drive circuit is converted into a strip-like polycrystalline film. As a measurement result measured by the film thickness measuring unit 81, for example, the relationship between the substrate position and the film thickness shown in FIG. 9 (the film thickness at the center is large and small at the periphery) is obtained. On the other hand, an appropriate energy density for converting a granular polycrystalline film into a band-shaped polycrystalline film differs depending on the silicon film thickness. The relationship between the film thickness of the granular polycrystalline silicon film and the energy density (relative value) necessary for conversion to the band-shaped polycrystalline film in the case of the laser wavelength (532 nm) in this embodiment is as shown in FIG. The relationship between the energy density actually applied to the substrate and the substrate position by the operations of the continuous transmittance variable filter 6 and the EO modulator 7 is as shown in FIG. Since these explanations are duplicated, they are omitted.

  Similarly to the third embodiment, when applied to the manufacture of a small display device typified by a mobile phone, even when adjusting the transmittance with the continuously variable transmittance filter 6, the applied voltage to the EO modulator 7 is adjusted. However, the panel formed in the substrate may be irradiated with a constant transmittance without adjusting continuously, that is, the panel may be irradiated with a constant energy density. Since the detailed description is duplicated, it will be omitted. The same applies when a peripheral circuit including a drive circuit is formed on two sides of the panel.

  In the above description, the amorphous silicon thin film formed on the substrate is converted into a granular polycrystalline silicon film by excimer laser irradiation, and then only the region for forming the peripheral circuit including the drive circuit is converted into a band-shaped polycrystalline silicon film. In this manufacturing method, it is possible to convert only a region for forming a peripheral circuit including a driving circuit directly from an amorphous silicon thin film into a band-shaped polycrystalline silicon film in exactly the same procedure. In that case, the pixel switching uses a transistor formed of an amorphous silicon (a-Si) thin film.

  As described above, the method and apparatus for manufacturing a flat panel display device according to the present invention include a pixel driving circuit on an amorphous silicon film or a granular polycrystalline silicon film formed by irradiating an excimer laser. Only a region where the peripheral circuit is formed is irradiated with a continuous wave laser beam condensed linearly while scanning at high speed to form a band-shaped polycrystalline silicon film. At that time, irradiation with an appropriate energy density corresponding to the silicon film thickness measured in advance makes it possible to suppress the variation in the band-like polycrystalline film quality due to the unevenness of the silicon film thickness in the substrate and the variation between the substrates. That is, it is possible to improve the manufacturing yield and ensure the quality of the flat display device.

  The method and apparatus for producing a flat display device of the present invention can be applied to the production of a flat display device such as a liquid crystal display device or an organic EL display device.

It is a figure which shows the structure of the manufacturing apparatus suitable for implementing the manufacturing method of the flat display apparatus which is this invention. It is a figure which shows the structure of the transmittance | permeability continuous variable filter suitable for implementing the manufacturing method of the flat display apparatus which is this invention. It is a figure which shows the relationship between the rotation angle of the wavelength plate of the transmittance | permeability continuously variable filter shown in FIG. 2, and the transmittance | permeability. It is a figure which shows the structure of the EO modulator suitable for implementing the manufacturing method of the flat display apparatus which is this invention. FIG. 5 is a diagram illustrating a relationship between applied voltage and transmittance of the EO modulator illustrated in FIG. 4. It is a figure which shows an example of the silicon film thickness distribution of the board | substrate used as object with the manufacturing method of the flat display apparatus which is this invention. It is a figure which shows the state after implementing excimer laser annealing to the board | substrate used as object by the manufacturing method of the flat display apparatus which is this invention. It is a figure which shows the state after forming the alignment mark in the board | substrate used as object by the manufacturing method of the flat display apparatus which is this invention. It is a figure which shows the film thickness distribution (relationship between a substrate position and a film thickness) of the arrow part of FIG. It is a figure which shows the relationship between a silicon film thickness and the energy density required for converting into strip | belt-shaped polycrystal. It is a figure which shows an appropriate energy density (relationship between a substrate position and energy density) with respect to the film thickness distribution of FIG. It is a figure which shows the energy density (relationship between a substrate position and energy density) actually irradiated with respect to the film thickness distribution shown in FIG. 9 with the manufacturing method of the flat display apparatus of this invention. It is a figure which shows the energy density (relationship between a substrate position and energy density) actually irradiated with respect to the film thickness distribution shown in FIG. 9 with the manufacturing method of the flat display apparatus of this invention. It is a figure which shows the state of the board | substrate after converting into a strip | belt-shaped polycrystalline film the peripheral circuit part put together on one side of each panel with the manufacturing method of the flat display apparatus of this invention. It is a figure which shows the state of the board | substrate after converting into a strip | belt-shaped polycrystalline film the peripheral circuit part formed in 2 sides of each panel with the manufacturing method of the flat display apparatus of this invention. It is a figure which shows the structure of the other manufacturing apparatus suitable for implementing the manufacturing method of the flat display apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser diode, 2 ... Optical fiber, 3 ... Laser beam, 4 ... Laser oscillator, 6 ... Transmission continuously variable filter, 7 ... Modulator, 9 ... Beam Diameter adjuster, 11 ... Beam shaper, 14 ... Mask, 15 ... Imaging lens, 19 ... Objective lens, 20 ... Substrate, 21 ... Stage, 29, 82 ... Control device 30,83 ... Memory 32 ... 1/2 wavelength plate 33 ... Polarizing beam splitter 35 ... Pockels cell 40 ... LAN 51 ... Amorphous Quality silicon film 52... Granular polycrystalline silicon film 54, 55, 56, 57, 58, 59... Alignment mark 61, 62, 63, 71, 72, 73. ... Thickness measurement part.

Claims (9)

An insulating substrate having an amorphous semiconductor film or a granular polycrystalline semiconductor film formed on one main surface is placed on a stage, and a plurality of regions of the amorphous semiconductor film or the granular polycrystalline semiconductor film on the insulating substrate In addition, the amorphous semiconductor film or the granular polycrystalline semiconductor film is annealed by shaping the laser light oscillated from the oscillator into an elongated shape, and irradiating it while scanning through a variable transmittance filter. A method of manufacturing a flat panel display device, which is modified into a film to obtain an active matrix substrate for a display device,
Before scanning with the laser beam, measure the film thickness of the amorphous semiconductor film or granular polycrystalline semiconductor film formed on the insulating substrate along the scanning direction of the laser beam,
In the annealing, the output of the laser beam oscillated from the oscillator is made constant, and scanning is performed while adjusting the transmittance of the transmittance variable filter based on the film thickness data obtained by the measurement. A method of manufacturing a flat display device, wherein the laser beam is irradiated through a variable rate filter. In claim 1,
A method of manufacturing a flat display device, wherein the transmittance of the laser light is continuously adjusted while scanning the laser light at a constant speed. In claim 1,
On the insulating substrate, a plurality of panel regions are arranged in the scanning direction of the laser beam,
While scanning the laser beam at a constant speed, the transmittance of the laser beam in each of the panel regions is the transmittance set in the respective panel region calculated based on the film thickness data. A method of manufacturing a flat display device, wherein the adjustment is made intermittently along the scanning of the laser beam. A laser oscillator that generates laser light, a beam shaper that shapes the oscillated laser light into an elongated shape in a direction crossing the scanning direction, and a substrate on which a semiconductor film to be irradiated with laser light is formed are mounted. A display device manufacturing apparatus comprising a stage for two-dimensional movement in the plane of the substrate,
A plurality of panel regions are arranged on the substrate in the scanning direction of the laser beam,
A control device having a memory for storing film thickness data of a semiconductor film formed on the substrate measured in advance;
A transmittance adjusting mechanism for adjusting the transmittance of the laser beam based on the film thickness data stored in the memory;
Scanning the laser beam with the energy density of the laser beam at each laser beam irradiation position that irradiates the semiconductor film formed on the substrate while scanning the laser beam with a constant output, and the transmittance of the transmittance adjusting mechanism. An apparatus for manufacturing a display device, wherein adjustment is performed by changing the thickness based on the film thickness data. In claim 4,
An apparatus for manufacturing a display device, wherein the transmittance adjusting mechanism includes a half-wave plate and a polarization beam splitter that are rotatably installed with an optical axis as a rotation center. In claim 4,
An apparatus for manufacturing a display device, wherein the transmittance adjusting mechanism includes a Pockels cell and a polarization beam splitter. A laser oscillator that generates laser light, a beam shaper that shapes the oscillated laser light into an elongated shape in a direction crossing the scanning direction, and a substrate on which a semiconductor film to be irradiated with laser light is formed are mounted. A display device manufacturing apparatus comprising a stage for two-dimensional movement in the plane of the substrate,
A plurality of panel regions are arranged on the substrate in the scanning direction of the laser beam,
A film thickness measuring unit for measuring the film thickness of the semiconductor film formed on the substrate, and a control device having a memory for storing the measured film thickness data;
Transmittance that adjusts the transmittance of the laser light intermittently along the scanning of the laser light with the transmittance set in the respective panel area calculated based on the film thickness data stored in the memory With an adjustment mechanism,
While scanning a constant output laser beam oscillated by the laser oscillator at a constant speed on a semiconductor film formed on the substrate, the energy density of the laser beam at each laser beam irradiation position in the panel region An apparatus for manufacturing a display device, wherein the transmittance adjustment mechanism is intermittently adjusted based on data during scanning of the laser light. In claim 7,
An apparatus for manufacturing a display device, wherein the transmittance adjusting mechanism includes a half-wave plate and a polarization beam splitter that are rotatably installed with an optical axis as a rotation center. In claim 7,
An apparatus for manufacturing a display device, wherein the transmittance adjusting mechanism includes a Pockels cell and a polarization beam splitter.

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