JP2006049481A - Crystallization equipment, crystallization method, and phase modulation element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide crystallization equipment which produces a crystallized semiconductor film having a large grain diameter by growing a crystal from a crystal nucleus satisfactorily in a lateral direction. <P>SOLUTION: The crystallization equipment crystallizes a non-single crystal semiconductor film (5) by irradiating a flux of light having a prescribed light intensity distribution on the film, and comprises: a phase modulation element (1) consisting of a plurality of unit regions which are arranged in a prescribed cycle and have mutually the same patterns; and an imaging optical system (3) located between the phase modulation element and the non-single crystal semiconductor film. The unit regions of the phase modulation element each have a reference surface having a prescribed phase, a first phase region which is arranged near the center and has a first phase different with respect to the reference surface, and a second phase region which is arranged near the first phase region and has nearly the same phase difference with respect to the reference surface as the first phase region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crystallization apparatus, a crystallization method, and a phase modulation element, and particularly, generates a crystallized semiconductor film by irradiating a polycrystalline semiconductor film or an amorphous semiconductor film with laser light having a predetermined light intensity distribution. The present invention relates to a crystallization apparatus.

  Conventionally, for example, a thin-film-transistor (TFT) used as a switching element for controlling a voltage applied to a pixel of a liquid crystal display (LCD) is an amorphous silicon (Amorphous-Silicon). ) Layer or polycrystalline silicon (poly-Silicon) layer.

  The polycrystalline silicon layer has higher electron or hole mobility than the amorphous silicon layer. Therefore, when the transistor is formed on the polycrystalline silicon layer, the switching speed is faster than that when the transistor is formed on the amorphous silicon layer, and thus the response of the display is faster. In addition, it is possible to configure the peripheral LSI with thin film transistors. Furthermore, there is an advantage that the design margin of other parts can be reduced. Also, peripheral circuits such as driver circuits and DACs can be operated at higher speeds when incorporated in a display.

  Polycrystalline silicon consists of a collection of crystal grains, but has a lower mobility of electrons or holes than single crystal silicon. In addition, a large number of thin film transistors formed in polycrystalline silicon has a problem of variations in the number of crystal grain boundaries in the channel portion. Thus, recently, a crystallization method for generating crystallized silicon having a large grain size has been proposed in order to improve the mobility of electrons or holes and to reduce the variation in the number of crystal grain boundaries in the channel portion.

  Conventionally, as a crystallization method of this type, a phase shift ELA (Excimer Laser that generates a crystallized semiconductor film by irradiating a phase shifter close to a polycrystalline semiconductor film or an amorphous semiconductor film in parallel with an excimer laser beam. Annealing) method is known. Details of the phase modulation ELA method are disclosed in Non-Patent Document 1, for example.

  In the phase modulation ELA method, light having a reverse peak pattern with a light intensity of approximately 0 (a pattern in which the light intensity is substantially 0 at the center and the light intensity increases rapidly toward the periphery) at a point corresponding to the phase shift portion of the phase shifter. An intensity distribution is generated, and the polycrystalline semiconductor film or the amorphous semiconductor film is irradiated with light having the light intensity distribution of the reverse peak pattern. As a result, a temperature gradient is generated in the melting region in accordance with the light intensity distribution, and crystal nuclei are formed in the first solidified portion corresponding to the point where the light intensity is substantially zero. By growing in the lateral direction (hereinafter referred to as “lateral growth” or “lateral growth”), large-sized single crystal grains are generated.

  Conventionally, Patent Document 1 discloses a technique for performing crystallization by irradiating a semiconductor film with light having a light intensity distribution of a reverse peak pattern generated via a phase shift mask (phase shifter). Non-Patent Document 2 discloses a technique for crystallization by irradiating a semiconductor film with light having a light intensity distribution of a concave pattern + reverse peak pattern generated by combining a phase shifter and a light absorption distribution. (See related statement).

JP 2000-306859 A Surface Science Vol.21, No.5, pp.278-287, 2000 Inoue, Nakata, Matsumura, “Amplitude / Phase Controlled Excimer Laser Melting Recrystallization Method of Silicon Thin Films—New 2-D Position Controlled Large Grain Formation Method”, IEICE Transactions, The Institute of Electronics, Information and Communication Engineers, Vol.J85-C, No.8, pp.624-629, August 2002

  As disclosed in Japanese Patent Application Laid-Open No. 2004-228561, in the conventional technique in which a light intensity distribution having a reverse peak pattern is formed using a phase shifter, a light intensity distribution having a reverse peak pattern is formed in a portion corresponding to the phase shift portion. However, since the light intensity does not increase linearly, the crystal growth tends to end in the middle. In addition, since an extra uneven distribution is generated around the light intensity distribution of the reverse peak pattern, the light intensity distribution of the reverse peak pattern cannot be arrayed to generate crystal grains in an array.

  Note that it may be possible to bring the obtained light intensity distribution closer to the ideal distribution by adjusting the angular distribution of the illumination light with respect to the phase shifter or designing the arrangement position of the phase shifter. However, the design cannot be performed analytically with a prospect, and even if an analytical design can be realized, it is expected that the design conditions will be quite complicated.

  On the other hand, as disclosed in Non-Patent Document 2, the conventional technique combining a phase shifter and a light absorption distribution can obtain a light intensity distribution of a concave pattern + reverse peak pattern for crystallization. However, it is difficult to grow a crystal having a large grain size in the lateral direction. It is generally difficult to form a film having a light absorption distribution that changes continuously. In particular, light having a very high intensity for crystallization is not desirable because, when the film to be crystallized is irradiated, the film material of the film having the light absorption distribution is likely to be deteriorated due to heat or chemical change due to light absorption.

  The present invention has been made in view of the above-described problems, and a crystallization apparatus and a crystal capable of generating a crystallized semiconductor film having a large grain size by realizing sufficient lateral crystal growth from a crystal nucleus. The purpose is to provide a conversion method.

In order to solve the above problems, according to a first embodiment of the present invention, there is provided a crystallization apparatus for crystallization by irradiating a non-single crystal semiconductor film with a light beam having a predetermined light intensity distribution,
A phase modulation element composed of a plurality of unit regions arranged in a predetermined cycle and having substantially the same pattern, and an imaging optical system arranged between the phase modulation element and the non-single-crystal semiconductor film,
The unit region of the phase modulation element includes a reference surface having a constant phase, a first phase region disposed near the center of the unit region and having a first phase difference with respect to the reference surface, and the first region There is provided a crystallization apparatus comprising: a second phase region that is disposed in the vicinity of a phase region and has a phase difference substantially the same as the first phase difference with respect to the reference plane.

In the second embodiment of the present invention, a non-single crystal semiconductor film is melted by irradiation with a light beam having a predetermined light intensity distribution, and a single growth crystal nucleus is formed in the process of solidifying the melted portion of the non-single crystal semiconductor film. A crystallization method that periodically generates and grows crystals radially around the growth crystal nucleus to form a crystal grain array film,
The non-single-crystal semiconductor film emits a light beam having the predetermined light intensity distribution formed via a phase modulation element composed of a plurality of unit regions having substantially the same pattern and arranged in a predetermined cycle and an imaging optical system Irradiate
The unit region of the phase modulation element includes a reference surface having a constant phase, a first phase region disposed near the center of the unit region and having a first phase with respect to the reference surface, and the first phase There is provided a crystallization method comprising: a second phase region disposed in the vicinity of a region and having substantially the same phase as the first phase with respect to the reference plane.

According to a third aspect of the present invention, there is provided a semiconductor film on a substrate for producing a device, which is crystallized by the crystallization apparatus of the first form or the crystallization method of the second form,
There is provided a semiconductor film characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at a periodic interval of 4 μm to 20 μm and includes only twin grain boundaries inside the crystal grains.

In the fourth embodiment of the present invention, a semiconductor film which is crystallized by the crystallization apparatus of the first embodiment or the crystallization method of the second embodiment and formed on an insulating substrate, and a gate insulation layered on one surface of the semiconductor film. A top gate type thin film transistor having a stacked structure including a film and a gate electrode overlaid on the semiconductor film via the gate insulating film,
There is provided a thin film transistor characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at a periodic interval of 4 μm to 20 μm and includes only twin grain boundaries inside the crystal grains.

In the fifth embodiment of the present invention, a gate electrode formed on an insulating substrate, a gate insulating film overlaid on one surface of the gate electrode, and a crystal formed by the crystallization apparatus of the first form or the crystallization method of the second form. A bottom gate type thin film transistor having a stacked structure including a semiconductor film stacked to cover the gate electrode through the gate insulating film,
There is provided a thin film transistor characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at a periodic interval of 4 μm to 20 μm and includes only twin grain boundaries inside the crystal grains.

According to a sixth aspect of the present invention, there is provided a pair of substrates bonded to each other via a predetermined gap, and an electro-optical material held in the gap between the pair of substrates, and one of the pair of substrates A counter electrode is formed on the substrate, and a pixel electrode and a thin film transistor for driving the pixel electrode are formed on the other substrate of the pair of substrates. A display device formed by a semiconductor film crystallized by a crystallization method of a form and a gate electrode overlaid on one surface of the semiconductor film via a gate insulating film,
There is provided a display device characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at a periodic interval of 4 μm to 20 μm and includes only twin grain boundaries inside the crystal grains.

According to a seventh aspect of the present invention, there is provided a phase modulation element composed of a plurality of unit regions that are arranged at a predetermined cycle and have substantially the same pattern.
The unit region includes a reference surface having a constant phase, a first phase region disposed near the center of the unit region and having a first phase difference with respect to the reference surface, and in the vicinity of the first phase region. There is provided a phase modulation element having a second phase region that is disposed and has a phase difference substantially the same as the first phase difference with respect to the reference plane.

  According to the present invention, a high-quality crystalline semiconductor thin film having a large grain array structure whose position is controlled by one-shot laser annealing can be obtained. The thin film transistor using the semiconductor film obtained by the present invention has higher mobility and less variation in threshold voltage than the conventional polysilicon thin film transistor. When the thin film transistor of the present invention is applied to a display device such as a liquid crystal display or an organic EL, it becomes possible to form a high-performance arithmetic element or the like in a peripheral circuit. Is big. In addition, since the phase modulation element is simply inserted into the optical path, the optical system is not complicated and adjustment does not take time. In addition, since the depth of focus is deep, the process margin is wide and suitable for mass production.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram schematically showing a configuration of a crystallization apparatus according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing the internal configuration of the illumination system of FIG. Referring to FIG. 1 and FIG. 2, the crystallization apparatus of the present embodiment includes a phase modulation element 1 for phase-modulating an incident light beam to form a light beam having a predetermined light intensity distribution, and a phase through an aperture 2. And an illumination system 3 for illuminating the modulation element 1. The configuration and operation of the phase modulation element 1 will be described later.

  The illumination system 3 includes, for example, a KrF excimer laser light source 3a that supplies light having a wavelength of 248 nm in the optical system shown in FIG. As the light source 3a, another suitable light source having a capability of emitting an energy beam for melting the object to be crystallized, such as a XeCl excimer laser light source or a YAG laser light source, may be used. The laser light supplied from the light source 3a is expanded through the beam expander 3b and then enters the first fly's eye lens 3c. Thus, a plurality of light sources are formed on the rear focal plane of the first fly-eye lens 3c, and light beams from these plurality of light sources are incident on the incident surface of the second fly-eye lens 3e via the first condenser optical system 3d. Are illuminated in a superimposed manner.

  As a result, more light sources are formed on the rear focal plane of the second fly-eye lens 3e than on the rear focal plane of the first fly-eye lens 3c. Light beams from a plurality of light sources formed on the rear focal plane of the second fly's eye lens 3e illuminate the phase modulation element 1 in a superimposed manner via the second condenser optical system 3f and the diaphragm 2. Here, the first fly-eye lens 3c and the first condenser optical system 3d constitute a first homogenizer, and the laser beam supplied from the light source 3a by the first homogenizer is uniform with respect to the incident angle on the phase modulation element 1. Is achieved.

  Further, the second fly-eye lens 3e and the second condenser optical system 3f constitute a second homogenizer, and the laser light on the phase modulation element 1 with respect to the laser beam whose incident angle from the first homogenizer is made uniform by the second homogenizer. The light intensity at each position in the plane can be made uniform. A pair of cylindrical fly-eye lenses can be used instead of the first fly-eye lens 3c or the second fly-eye lens 3e. Here, the cylindrical fly-eye lens is composed of a plurality of cylindrical lens elements having refractive power in a certain plane and having no refractive power in a plane orthogonal to the plane.

  Thus, the illumination system 3 irradiates the phase modulation element 1 with the laser light having a substantially uniform light intensity distribution. The laser light phase-modulated by the phase modulation element 1 enters the substrate 5 to be processed via the imaging optical system 4. Here, the imaging optical system 4 optically conjugates the phase pattern surface of the phase modulation element 1 and the substrate 5 to be processed. In other words, the substrate 5 to be processed is set to a surface optically conjugate with the phase pattern surface of the phase modulation element 1 (image surface of the imaging optical system 4). The imaging optical system 4 includes an aperture stop 4c between the positive lens group 4a and the positive lens group 4b.

  The aperture stop 4c may include a plurality of aperture stops having different sizes of openings (light transmission portions), and the plurality of aperture stops 4c may be configured to be interchangeable with respect to the optical path. Alternatively, the aperture stop 4c may have an iris stop that can continuously change the size of the opening. In any case, the size of the aperture of the aperture stop 4c (and consequently the image-side numerical aperture NA of the imaging optical system 4) has a required light intensity distribution on the semiconductor film of the substrate 5 to be processed, as will be described later. It is set to generate. The imaging optical system 4 may be a refractive optical system, a reflective optical system, or a refractive / reflective optical system.

Further, the substrate 5 to be processed is formed by sequentially forming a lower insulating film, a semiconductor thin film, and an upper insulating film on the substrate. That is, the substrate to be processed 5 is obtained by sequentially forming a base insulating film, a non-single crystal film such as an amorphous silicon film, and a cap film on a glass plate for a liquid crystal display, for example, by chemical vapor deposition (CVD). . The base insulating film and the cap film are insulating films such as SiO ₂ . The base insulating film prevents the amorphous silicon film and the glass substrate from coming into direct contact to prevent foreign substances such as Na from entering the amorphous silicon film, and the melting temperature of the amorphous silicon film is directly transmitted to the glass substrate. Prevent it from being heated. An amorphous silicon film is a semiconductor film to be crystallized.

  The cap film is heated when the amorphous silicon film absorbs incident light and becomes part of the heat, and the heat is stored. This heat storage effect is that when the incidence of the light beam is interrupted, the high temperature part of the irradiated surface of the amorphous silicon film cools relatively rapidly, but this temperature gradient is relaxed and the large grain size is reduced in the lateral direction. Promotes crystal growth. The substrate 5 to be processed is positioned and held at a predetermined position on the substrate stage 6 by a vacuum chuck or an electrostatic chuck.

  FIG. 3 is a diagram schematically showing the configuration of the phase modulation element in Example 1 of the present embodiment. The phase modulation element 1 of Example 1 is a phase modulation element for producing a 5 μm square crystal grain array semiconductor thin film, and is a plurality of unit regions 1a that are two-dimensionally arranged at a predetermined cycle and have the same pattern. It is comprised by. In FIG. 3, for the sake of simplicity, two adjacent square unit regions 1a are shown. One side of each unit region 1 a is 5 μm in terms of a converted value on the image plane of the imaging optical system 4. Hereinafter, the dimensions of the phase modulation element 1 are indicated by converted values on the image plane of the imaging optical system 4.

  The unit region 1a includes a reference surface (blank portion in the drawing) 1aa having a constant phase, a first phase region 1ab and a second phase region 1ac arranged near the center of the unit region 1a, and a first phase region 1ab. And a plurality of dot regions 1ad arranged around the second phase region 1ac. Here, the first phase region 1ab and the second phase region 1ac are fan-shaped patterns obtained by equally dividing a circle having a radius of 0.5 μm into four, and the vertices thereof are in contact with the center of the unit region 1a. Is arranged.

  In the first embodiment, a square unit cell of 0.5 μm square (non-optically smaller than the radius of the point image distribution range of the imaging optical system 4 is formed around the first phase region 1ab and the second phase region 1ac. (Shown) is virtually set vertically and horizontally and densely. One dot region 1ad is selectively provided in each unit cell. The occupied area ratio of the dot region 1ad in the unit cell is configured to decrease as the distance from the contact point (center of the unit region 1a) between the first phase region 1ab and the second phase region 1ac increases. The first phase region 1ab, the second phase region 1ac, and all the dot regions 1ad have a phase of +90 degrees relative to the reference surface 1aa (when the phase (modulation amount) on the reference surface 1aa is normalized to 0 degree). Relative phase difference).

  Here, the light intensity formed along the transverse line corresponding to the line AA across the center of the unit region 1 a on the surface of the substrate 5 to be processed positioned at various positions with respect to the imaging optical system 4. Focus on distribution. First, the object to be processed is positioned by defocusing (+5 μm defocusing) in a direction (upper side in FIG. 1) closer to the imaging optical system 4 by 5 μm from the calculated focus position (focal position) of the imaging optical system 4. On the surface of the substrate 5, a light intensity distribution as shown in FIG. 4A is formed along a transverse line corresponding to the transverse line AA of the unit region 1a. Also, the surface of the substrate 5 to be processed positioned at the calculation focus position of the imaging optical system 4 is shown in FIG. 4B along a transverse line corresponding to the transverse line AA of the unit region 1a. Such a light intensity distribution is formed.

  Further, the substrate 5 to be processed is positioned by defocusing (-5 μm defocusing) in a direction away from the imaging optical system 4 by 5 μm from the calculated focus position of the imaging optical system 4 (lower side in FIG. 1). A light intensity distribution as shown in FIG. 4C is formed along the transverse line corresponding to the transverse line AA of the unit region 1a. Further, the surface of the substrate to be processed 5 positioned by defocusing (-7 μm defocusing) away from the imaging optical system 4 by 7 μm from the calculated focus position of the imaging optical system 4 has a unit region. A light intensity distribution as shown in FIG. 5A is formed along a transverse line corresponding to the transverse line AA of 1a.

  Further, a unit region is formed on the surface of the substrate 5 to be processed by defocusing (−10 μm defocusing) in a direction away from the imaging optical system 4 by 10 μm from the calculated focus position of the imaging optical system 4. A light intensity distribution as shown in FIG. 5B is formed along a transverse line corresponding to the transverse line AA of 1a. Finally, the surface of the substrate 5 to be processed is positioned by defocusing (-15 μm defocusing) away from the imaging optical system 4 by 15 μm from the calculated focus position of the imaging optical system 4. A light intensity distribution as shown in FIG. 5C is formed along a transverse line corresponding to the transverse line AA of the region 1a.

  In each example of the present embodiment, the magnification of the telecentric imaging optical system 4 on both sides is 1/5, the image-side numerical aperture NA is 0.13, and the illumination sigma value (the aperture of the illumination system) Number / object-side numerical aperture of the imaging optical system 4) is set to 0.43. 4 and 5, the vertical axis indicates the light intensity and the relative value when the maximum value is normalized to 1, and the horizontal axis indicates the distance from the point corresponding to the center of the unit region 1a ( μm). Note that the following light intensity distributions are the same as those shown in FIGS.

  Referring to the light intensity distribution obtained by changing the position of the substrate 5 to be processed with respect to the imaging optical system 4 as shown in FIGS. 4 and 5, the calculated focus position and the defocus position of −10 μm In the meantime, a change in which the light intensity rapidly increases from the bottom peak (position where the light intensity is the smallest) is maintained. Further, the shape of the light intensity distribution is maintained between the calculated focus position and the defocus position of −15 μm. That is, in Example 1, it can be seen that a focal depth of ± 5 μm to ± 7 μm is secured.

  As described above, in the phase modulation element 1 of the first embodiment, the phase step is 90 degrees, which is different from 180 degrees, and thus the actual focus position is deviated from the calculated focus position. Referring to FIGS. 4 and 5, in the light intensity distribution obtained at the position defocused by −7 μm from the calculated focus position, the light intensity gradient increasing from the bottom peak is the largest, and the calculated defocus of −7 μm. It can be seen that the position is the actual focus position. In Example 1, a light intensity distribution as shown in FIG. 6 is formed on the surface of the substrate 5 to be processed positioned at the actual focus position of the imaging optical system 4.

  That is, a light intensity distribution as shown in FIG. 6A is formed along the transverse line corresponding to the transverse line AA of the unit region 1a of the phase modulation element 1, and the unit region 1a on the left side of the drawing is in the drawing. A light intensity distribution as shown in FIG. 6B is formed along the diagonal line corresponding to the diagonal line B-B that rises to the right, and corresponds to the diagonal line C-C that rises to the left of the unit region 1a on the right side of the figure. A light intensity distribution as shown in FIG. 6C is formed along the oblique lines. Referring to FIG. 6, it can be seen that the light intensity distribution obtained via the phase modulation element 1 of Example 1 has almost no anisotropy.

  Further, referring to FIG. 6A, it can be seen that a bottom peak having the smallest light intensity is formed corresponding to the contact point (center of the unit region 1a) between the first phase region 1ab and the second phase region 1ac. . Further, an inverse peak distribution in which the light intensity rapidly increases radially from the bottom peak toward the periphery is formed by the action of the first phase region 1ab and the second phase region 1ac. In addition, an inclined distribution in which the light intensity gradually increases radially from the reverse peak distribution toward the periphery is formed by the action of the plurality of dot regions 1ad. The phase step pattern of the phase modulation element 1 can be manufactured, for example, by forming a thickness distribution corresponding to a required phase on a quartz glass substrate. The change in the thickness of the quartz glass substrate can be formed by selective etching or FIB (Focused Ion Beam) processing.

Next, by setting the occupying area ratio of the dot region 1ad to be smaller as it is away from the center of the unit region 1a, an inclined distribution is obtained in which the light intensity increases as the distance from the inverse peak distribution increases. The principle is described. FIG. 7 is a diagram for explaining the principle regarding the area occupied by the dot region and the light intensity distribution. In general, the light amplitude distribution U (x, y) of the image formed by the phase modulation element 1 is expressed by the following equation (1). In Equation (1), T (x, y) is the complex amplitude transmittance distribution of the phase modulation element 1, * is convolution (convolution integration), and ASF (x, y) is the imaging optical system 4. Each of the point spread functions is shown. Here, the point spread function is defined as the amplitude distribution of the point image by the imaging optical system.
U (x, y) = T (x, y) * ASF (x, y) (1)

The complex amplitude transmittance distribution T of the phase modulation element 1 is expressed by the following equation (2) because the amplitude is uniform. In Equation (2), T ₀ is a constant value, and φ (x, y) indicates a phase distribution.
T = T ₀ e ^{iφ (x, y)} (2)

When the imaging optical system 4 has a uniform circular pupil and has no aberration, the relationship shown in the following formula (3) is established with respect to the point spread function ASF (x, y). In equation (3), J ₁ represents a Bessel function, λ represents the wavelength of light, and NA represents the image-side numerical aperture of the imaging optical system 4 as described above.
ASF (x, y) ∝ 2J ₁ (2π / λ · NA · r) / (2π / λ · NA · r) (3)
However, r = (x ² + y ² ) ^1/2

  The point spread function of the imaging optical system 4 shown in FIG. 7A is shown in FIG. 7B, and is approximated by a cylindrical shape 4e having a diameter R (shown by a broken line in FIG. 7). The complex amplitude distribution in the circle of the diameter R ′ (the value optically corresponding to the diameter R) on the phase modulation element 1 shown in (c) determines the complex amplitude on the image plane 4f. As described above, the light amplitude, that is, the light intensity of the image formed on the image plane 4f is given by the convolution of the complex amplitude transmittance distribution of the phase modulation element 1 and the point spread function. When the point spread function is approximated by a cylindrical shape 4e, the result obtained by integrating the complex amplitude transmittance of the phase modulation element 1 with a uniform weight within the circular point spread range R shown in FIG. The complex amplitude at the surface 4f is obtained, and the square of the absolute value is the light intensity. The point image distribution range R in the imaging optical system 4 refers to a range within the intersection 4j with the 0 point 4i of the curve of FIG. 7B drawn by the point image distribution function.

  Therefore, the light intensity increases as the phase change in the point image distribution range R decreases, and conversely, the light intensity decreases as the phase change increases. This point can be easily understood by considering the sum of the phase vectors 4h in the unit circle 4g as shown in FIG. When the image plane 4f is an object such as a semiconductor film, the point spread function in FIG. 7B is a point spread function as shown in FIG. FIG. 8 is a diagram showing a typical relationship between the phase change in the point image distribution range R and the light intensity. FIG. 8A is a diagram showing a case where the phase values of the four regions are all 0 degrees. The sum of the four phase vectors 5g in the 0 degree direction corresponds to the amplitude 4E, and the square thereof is the light intensity 16I. Will respond.

  FIG. 8B is a diagram showing a case where the phase values of the two regions are 0 degrees and the phase values of the other two regions are 90 degrees. Two phase vectors in the 0 degree direction and the 90 degree direction The sum of the two phase vectors corresponds to the amplitude 2√2E, and the square thereof corresponds to the light intensity 8I. FIG. 8C is a diagram showing the case where the phase value is 0 degree, the phase value is 90 degrees, the phase value is 180 degrees, and the phase value is 270 degrees. The sum of the phase vector 5s, the phase vector 5t in the 90 degree direction, the phase vector 5u in the 180 degree direction, and the phase vector 5v in the 270 degree direction corresponds to the amplitude 0E, and the square thereof corresponds to the light intensity 0I.

  FIG. 9 is a diagram showing the relationship between the pupil function and the point spread function in the imaging optical system 4. In general, the point spread function is given by the Fourier transform of the pupil function. Specifically, when the imaging optical system 4 has a uniform circular pupil and has no aberration, the point spread function ASF (x, y) is expressed by the above-described equation (3). However, this is not the case when there is aberration in the imaging optical system 4 or when there is a pupil function other than the uniform circular pupil.

In the case of a uniform circular pupil and no aberration, it is known that the radius R / 2 of the central region (that is, Airy disk) until the point spread function first becomes 0 is expressed by the following equation (4). .
R / 2 = 0.61λ / NA (4)

  In this specification, the point image distribution range R is a circular central region until the point image distribution function F (x) first becomes 0, as shown in FIGS. 7B and 9B. I mean. As apparent from FIG. 8, when a plurality of (four in FIG. 8) phase modulation units are included in a circle optically corresponding to the point spread range R of the imaging optical system, It is possible to control the amplitude of light by the sum of a plurality of phase vectors 5g, and consequently the intensity of light, analytically and according to a simple calculation. As a result, a relatively complicated light intensity distribution can be obtained relatively easily.

  Therefore, in the present invention, in order to freely control the light intensity, the phase modulation unit of the phase modulation element 1 may be optically smaller than the radius R / 2 of the point image distribution range R of the imaging optical system 4. is necessary. In other words, the size of the phase modulation unit of the phase modulation element 1 on the image side of the imaging optical system 4 needs to be smaller than the radius R / 2 of the point image distribution range R of the imaging optical system 4. . Here, the phase modulation unit is, for example, the size of the shortest side of the cell in the case of the cell type described above, and represents the length of one side in the case of the pixel type.

  FIG. 10 is a diagram schematically showing a cell-type configuration corresponding to the dot region of the phase modulation element shown in FIG. Referring to FIG. 10A, this phase modulation element includes a first region 21a having a first phase value φ1 (shown by a hatched portion in the drawing) 21a and a second region having a second phase value φ2 (in the drawing). 21b) (shown by a blank part). Further, this phase modulation element has a plurality of cells 21 (shown by rectangular broken lines in the figure) 21 having a size optically smaller than the radius R / 2 of the point image distribution range R of the imaging optical system 4.

  As shown in FIG. 10 (a), the occupied area ratio of the first region 21a having the phase value φ1 (0 degree) and the second region 21b having the phase value φ2 (90 degrees) in each cell 21 varies from cell to cell. is doing. In other words, the occupation area ratio of the first region 21a having the phase value φ1 and the second region 21b having the phase value φ2 has a phase distribution that varies depending on the position. More specifically, the occupied area of the second region 21b of the phase value φ2 in the cell is the largest in the left cell in the figure, the smallest in the right cell in the figure, and monotonically changes between them. Incident light to the phase modulation element 1 is transmitted from the upper surface to the rear surface in FIG. 10 as indicated by an arrow 21c.

  As described above, the phase modulation element shown in FIG. 10 has a phase distribution based on the phase modulation unit (cell) 21 having a size optically smaller than the radius R / 2 of the point image distribution range R of the imaging optical system 4. Have. Therefore, the light intensity distribution formed on the substrate to be processed is analyzed by appropriately changing the occupied area ratio between the first region 21a and the second region 21b in each phase modulation unit 21, that is, the sum of the two phase vectors. And according to simple calculations. The manufacture of the phase modulation element 1 having the first and second phase values φ1 and φ2 is performed, for example, by selecting the thickness of quartz glass so that the first and second phase values φ1 and φ2 are formed. Element 1 can be manufactured. The change in the thickness of the quartz glass can be formed by selective etching or FIB.

  FIG. 11 is a diagram schematically showing a pixel type configuration different from the dot region of the phase modulation element shown in FIG. Referring to FIG. 11, the phase modulation element 1 includes a plurality of rectangular pixels 22 that are optically smaller than the radius R / 2 of the point image distribution range R of the imaging optical system 4. The plurality of pixels 22 are arranged vertically and horizontally and densely, and each pixel 22 has a constant phase value. Specifically, a first pixel (shown by a hatched portion in the figure) 22a having a first phase value φ1 (for example, 0 degrees) and a second pixel (for example, 90 degrees) having a second phase value φ2 (for example, 90 degrees). 22b). Incident light to the phase modulation element 1 is transmitted from the upper surface to the rear surface in FIG. 11 as indicated by an arrow 22c.

  As shown in FIG. 11, the number of pixels having the same phase value per unit range (indicated by a broken-line circle in the figure) optically corresponding to the point image distribution range R of the imaging optical system 4 changes for each unit range. ing. In other words, similarly to FIG. 10, the phase distribution in which the occupied area ratio of the first pixel 22a as the first region having the phase value φ1 and the second pixel 22b as the second region having the phase value φ2 varies depending on the position. Have.

  As described above, the phase modulation element shown in FIG. 11 has a phase distribution based on the phase modulation unit (pixel) 22 having a size optically smaller than the radius R / 2 of the point image distribution range R of the imaging optical system 4. Have. Therefore, the occupied area ratio of the first pixel 22a and the second pixel 22b in a unit range (not shown) optically corresponding to the point image distribution range R of the imaging optical system 4 is calculated, that is, the sum of a plurality of phase vectors. By appropriately changing, the light intensity distribution formed on the substrate to be processed can be controlled analytically and in accordance with a simple calculation.

  FIG. 12 schematically shows a crystallization process of a semiconductor thin film according to the present invention. In FIG. 12, a rectangular region indicated by a broken line is a unit substrate region (a 5 μm square region in Example 1) 10 corresponding to one unit region 1a of the phase modulation element 1 on the surface of the substrate 5 to be processed. It is. In the unit substrate region 10, first, at the initial stage of solidification, generation and disappearance of crystal nuclei are repeated in the vicinity of the center of the melted region 12, and then the crystal nuclei agglomerate to a critical diameter or more that allows growth. Crystal nuclei 11 are generated. The growing crystal nuclei 11 grow radially in all directions with the passage of time, and the solid-liquid interface 14 spreads.

  Since the semiconductor thin film of the present invention is crystallized by laser annealing in an ultra-quick solidification system, it does not grow in all directions while maintaining the plane orientation of the generated crystal nucleus. For example, in the crystal direction with a relatively high growth rate, such as the <110> direction, the crystal nucleus grows while maintaining the plane orientation of the generated crystal nucleus. However, for example in the <111> direction, the close-packed surfaces must be stacked, and in the crystal direction where the growth rate is relatively small, the growth is performed at a rate similar to the direction where the growth rate is large, following a temperature gradient spreading concentrically. For this reason, the crystal is grown by changing the direction to a plane orientation with a higher growth rate by twinning transformation during the growth. As a result, in the final structure, twin grain boundaries 13 enter the crystal grains. The twin grain boundaries 13 are different from the crystal grain boundaries 15 in the formation process.

  FIG. 13 schematically shows an example of a light intensity distribution suitable for realizing the crystallization process shown in FIG. The light intensity distribution shown in FIG. 13 (a) is a distribution along the diagonal line 10a of the unit substrate region 10 shown in FIG. 13 (b). In FIG. 13B, broken lines 16a and 16b indicate contour lines of light intensity (or temperature). In the light intensity distribution shown in FIG. 13 (a), the light intensity is the smallest in the vicinity of the center of the unit substrate region 10, and the reverse peak in which the light intensity rapidly increases radially from the bottom peak having the smallest light intensity toward the periphery. A slope-like distribution is formed in which the light intensity gradually increases radially from the reverse peak-like distribution toward the periphery.

  When the substrate 5 is irradiated with a laser beam having a funnel-shaped light intensity distribution as shown in FIG. 13A, the semiconductor thin film of the substrate 5 absorbs light and the light energy is converted into heat. The temperature distribution of the semiconductor thin film at the start of crystallization is also as shown in FIG. 13A, and a growth crystal nucleus 11 is generated only in the central region of the unit substrate region 10. The light intensity distribution has a threshold value α that is closely related to the start of crystal growth. The semiconductor film (Si) does not melt at the portion where the light intensity is less than the α value, or only a part of the surface melts even if it melts, so it remains in the state of polysilicon, and the crystal from where the light intensity exceeds the α value Growth begins.

  Therefore, it is desirable that the value of the light intensity at the bottom of the light intensity distribution is slightly lower than this α value. Specifically, the intensity of the bottom peak of the light intensity distribution is preferably 0.2 to 0.7 as a relative value. When the intensity of the bottom peak is less than 0.2, the intensity becomes too small, and the center portion remains amorphous without being crystallized. Further, when the intensity of the bottom peak exceeds 0.7, the intensity becomes too large, and a growth crystal nucleus cannot be generated only in the central portion. In order to realize the crystallization process more satisfactorily, the intensity of the bottom peak of the light intensity distribution is preferably 0.5 to 0.6.

  The reverse peak distribution in which the light intensity rapidly increases radially from the bottom peak near the center toward the periphery is the difference between the maximum value and the minimum value in the minimum value of light intensity (that is, the light intensity value at the bottom peak). It is preferable that the range is up to the light intensity obtained by adding about 2/5. In the case of the light intensity distribution shown in FIG. 13A, the light intensity obtained by adding 2/5 of the difference between the maximum value and the minimum value to the minimum value of the light intensity is 0.76 in relative value.

  The peak width W1 of the light intensity distribution at this light intensity of 0.76 is preferably 0.5 μm to 1.5 μm. When the peak width W1 is less than 0.5 μm, it becomes too small, the surrounding heat diffuses to the center, which is the minimum position of the light intensity, and the lowest temperature region spreads, making the growth crystal nucleus single. I can't. On the other hand, if the peak width W1 exceeds 1.5 μm and becomes too large, the lowest temperature region at the start of crystallization spreads, and a single growth crystal nucleus cannot be made.

  As shown in FIG. 13A, the light intensity gradually increases around the inverse peak distribution, that is, a funnel shape in which the light intensity increases linearly toward the outside as the distance from the center increases. An inclined distribution is preferred. This is because the growth crystal nuclei 11 generated at the center of the unit substrate region 10 are grown radially to form the inside of the unit substrate region 10 as one crystal grain. With such a funnel-shaped gradient distribution, the temperature gradient toward the outside becomes linear, so that a crystallized semiconductor film having a larger grain size can be generated without stopping crystal growth. . If there is an uneven distribution around the reverse peak distribution and there is a peak where the light intensity is steeply increased, the temperature of this region will rise too much when the semiconductor thin film absorbs the laser beam, causing film breakdown. It becomes easy to do.

  FIG. 14 schematically shows an example of the relationship between the arrangement pattern of the unit regions and the array pattern of the formed crystal structure in the phase modulation element. In the arrangement pattern of the unit regions 1a of the phase modulation element 1 shown in FIG. 14A, only the fan-shaped first phase region 1ab and second phase region 1ac arranged in the vicinity of the center of the unit region 1a are provided. Show. In the array pattern of the crystal structure shown in FIG. 14A, the crystal grain boundaries 15 are indicated by solid lines and the twin grain boundaries 13 are indicated by broken lines.

  One square crystal grain is formed corresponding to one unit region 1 a of the phase modulation element 1. That is, a plurality of square-shaped crystal grains are arrayed in a lattice shape corresponding to the plurality of unit regions 1a arranged in a lattice pattern at a predetermined cycle, and a high-quality crystallized semiconductor thin film is obtained. And only the twin grain boundary 13 is included inside the crystal grains. Thus, by controlling the generation position of the growth crystal nucleus 11, the position of the crystal grain can also be controlled two-dimensionally.

  FIG. 15 schematically shows another example of the relationship between the array pattern of unit regions and the array pattern of the crystal structure formed in the phase modulation element. In FIG. 15 (a), unlike FIG. 14 (a), a plurality of unit regions 1a, and thus the first phase region 1ab and the second phase region 1ac, are arranged in a regular triangular vertex shape with a predetermined period. As a result, in the corresponding crystal structure, as shown in FIG. 15B, a plurality of circular crystal grains are formed in an array of regular triangular vertices. Also in this case, only the twin grain boundary 13 is included inside the crystal grain, and the position of the crystal grain can be controlled two-dimensionally.

  The interval between the unit regions 1a of the phase modulation element 1 shown in FIGS. 14 and 15 is closely related to the crystal grain size of the crystal structure to be finally formed. The interval between the unit regions 1 a of the phase modulation element 1 is preferably 4 μm to 20 μm in terms of a converted value on the image plane of the imaging optical system 4. When the interval between the unit regions 1a is less than 4 μm, the distance becomes too small, the grain size of the crystal grain array becomes small, and the crystallized semiconductor thin film with high quality cannot be obtained. Further, if the interval between the unit regions 1a exceeds 20 μm, it becomes too large and crystal growth stops midway, so that a crystal grain array that covers almost the entire surface of the semiconductor film cannot be obtained.

  The shape of the phase regions 1ab and 1ac with inverted phase steps arranged at the center of the unit region 1a is not necessarily a fan shape, and may be a polygonal shape such as a quadrangle. Further, the areas of the phase regions 1ab and 1ac may be set so that the peak width W1 is sufficiently narrowed in the light intensity distribution shown in FIG. 13A in order to generate only single crystal nuclei. Specifically, the overall size of the phase region (1ab, 1ac) is set to 1.0 (= 0.5 × 2) μm, but is set to a size of 0.3 μm to 1.5 μm. It is preferable to set the size to 0.8 μm to 1.2 μm. The optimum values related to the areas of the phase regions 1ab and 1ac are closely related to the optical system of the crystallization apparatus to be used. The phase steps of the phase regions 1ab and 1ac are related to the relative value of the bottom peak light intensity in the light intensity distribution shown in FIG. 13A, but may be determined to be 0.2 to 0.7. .

  In Example 1, the substrate 5 to be processed positioned at the actual focus position (calculated −7 μm defocus position) using the phase modulation element 1 having the configuration shown in FIG. 3 in the crystallization apparatus shown in FIG. The upper semiconductor (Si) thin film was crystallized. For example, laser light having a light intensity distribution shown in FIG. 6A is formed on the substrate 5 to be processed, and after the crystallization process shown in FIG. 12, crystal grains of 5 μm square as shown in FIG. An array semiconductor thin film could be fabricated. As shown in FIGS. 4 and 5, even if the surface of the substrate 5 to be processed fluctuates to some extent with respect to the actual focus position of the imaging optical system 4 (for example, fluctuates in a defocus range of 0 μm to −15 μm). ) The light intensity distribution formed on the substrate to be processed 5 does not change so much and a depth of focus of about ± 7 μm is secured, so that a crystal grain array semiconductor thin film with good uniformity can be obtained.

  FIG. 16 is a diagram schematically showing the configuration of the phase modulation element in Example 2 of the present embodiment. Similarly to the first embodiment, the phase modulation element 1 of the second embodiment is a phase modulation element for producing a 5 μm-square crystal grain array semiconductor thin film, and has a configuration similar to that of the first embodiment. However, in the second embodiment, only the first phase region 1ab, the second phase region 1ac, and all the dot regions 1ad have a phase of −90 degrees (+90 degrees in the first embodiment) with respect to the reference plane 1aa. This is different from Example 1. Hereinafter, the second embodiment will be described by paying attention to differences from the first embodiment.

  In Example 2, the object to be positioned positioned by defocusing (−5 μm defocusing) in a direction away from the imaging optical system 4 by 5 μm from the calculated focus position of the imaging optical system 4 (lower side in FIG. 1). On the surface of the processing substrate 5, a light intensity distribution as shown in FIG. 17A is formed along a transverse line corresponding to the transverse line AA of the unit region 1a. Further, the surface of the substrate 5 to be processed positioned at the calculation focus position of the imaging optical system 4 is shown in FIG. 17B along a transverse line corresponding to the transverse line AA of the unit region 1a. Such a light intensity distribution is formed.

  Further, the surface of the substrate 5 to be processed positioned by defocusing (+5 μm defocusing) in a direction (upper side in FIG. 1) approaching the imaging optical system 4 by 5 μm from the calculated focus position of the imaging optical system 4. A light intensity distribution as shown in FIG. 17C is formed along a transverse line corresponding to the transverse line AA of the unit region 1a. Further, the unit region 1a is formed on the surface of the substrate 5 to be processed after being defocused (+7 μm defocus) in a direction approaching the image forming optical system 4 by 7 μm from the calculated focus position of the image forming optical system 4. A light intensity distribution as shown in FIG. 18A is formed along a transverse line corresponding to the transverse line AA.

  Further, the unit region 1a is formed on the surface of the substrate 5 to be processed after being defocused (+10 μm defocus) in a direction approaching the image forming optical system 4 by 10 μm from the calculated focus position of the image forming optical system 4. A light intensity distribution as shown in FIG. 18B is formed along the transverse line corresponding to the transverse line AA. Finally, the surface of the substrate to be processed 5 positioned by defocusing (defocusing of +15 μm) in the direction approaching the imaging optical system 4 by 15 μm from the calculated focus position of the imaging optical system 4 has a unit region. A light intensity distribution as shown in FIG. 18C is formed along a transverse line corresponding to the transverse line AA of 1a.

  Referring to the light intensity distribution obtained by changing the position of the substrate 5 to be processed with respect to the imaging optical system 4 as shown in FIGS. 17 and 18, between the calculated focus position and the defocus position of +10 μm. In FIG. 5, the change in which the light intensity rapidly increases from the bottom peak (position where the light intensity is the smallest) is maintained. Further, the shape of the light intensity distribution is maintained between the calculated focus position and the defocus position of +15 μm. That is, it can be seen that the focal depth of ± 5 μm to ± 7 μm is secured in the second embodiment as well as the first embodiment. Referring to FIGS. 17 and 18, in the light intensity distribution obtained at the position defocused by +7 μm from the calculated focus position, the light intensity gradient increasing from the bottom peak is the largest, and the calculated defocus of +7 μm. It can be seen that the position is the actual focus position.

  In Example 2, using the phase modulation element 1 having the configuration shown in FIG. 16 in the crystallization apparatus shown in FIG. 1, the substrate 5 is positioned at the actual focus position (calculated +7 μm defocus position). The semiconductor (Si) thin film was crystallized. For example, laser light having a light intensity distribution shown in FIG. 18A is formed on the substrate 5 to be processed, and after the crystallization process shown in FIG. 12, crystal grains of 5 μm square as shown in FIG. An array semiconductor thin film could be fabricated. As shown in FIGS. 17 and 18, even if the surface of the substrate 5 to be processed fluctuates to some extent with respect to the actual focus position of the imaging optical system 4 (for example, fluctuates in a defocus range of 0 μm to +15 μm). The light intensity distribution formed on the substrate 5 to be processed does not change so much and a deep depth of focus of about ± 7 μm is secured, so that a crystal grain array semiconductor thin film with good uniformity can be obtained.

  FIG. 19 is a diagram schematically showing the configuration of the phase modulation element in Example 3 of the present embodiment. The phase modulation element 1 of Example 3 is a phase modulation element for producing a 5 μm-square grain array semiconductor thin film, as in Examples 1 and 2, and has a configuration similar to that of Example 1. However, eight square dot areas 1ae each having a 0.2 μm square are arranged around the first phase area 1ab and the second phase area 1ac, and the first phase area 1ab and the second phase area 1ac and all the dot areas 1ae are different from the first embodiment in that the phase is +100 degrees (+90 degrees in the first embodiment) with respect to the reference plane 1aa. Hereinafter, the third embodiment will be described by focusing on the differences from the first embodiment.

  Although not shown, in the third embodiment, as in the first embodiment, defocusing is performed in a direction away from the imaging optical system 4 by 7 μm from the calculated focus position of the imaging optical system 4 (lower side in FIG. 1). The defocused position of −7 μm becomes the actual focus position, and a deep focal depth of about ± 7 μm can be secured. In Example 3, a light intensity distribution as shown in FIG. 20 is formed on the surface of the substrate 5 to be processed positioned at the actual focus position of the imaging optical system 4.

  That is, a light intensity distribution as shown in FIG. 20A is formed along the transverse line corresponding to the transverse line AA of the unit region 1a of the phase modulation element 1, and the unit region 1a on the left side of the drawing is in the drawing. A light intensity distribution as shown in FIG. 20B is formed along the diagonal line corresponding to the diagonal line B-B that rises to the left, and corresponds to the diagonal line C-C that rises to the left of the unit region 1a on the right side in the figure. A light intensity distribution as shown in FIG. 20C is formed along the oblique lines.

  In Example 3, the substrate 5 to be processed positioned at the actual focus position (calculated -7 μm defocus position) using the phase modulation element 1 having the configuration shown in FIG. 19 in the crystallization apparatus shown in FIG. The upper semiconductor (Si) thin film was crystallized. For example, laser light having a light intensity distribution shown in FIG. 20A is formed on the substrate 5 to be processed, and after the crystallization process shown in FIG. 12, crystal grains of 5 μm square as shown in FIG. An array semiconductor thin film could be fabricated. Further, even if the surface of the substrate to be processed 5 varies to some extent with respect to the actual focus position of the imaging optical system 4, the light intensity distribution formed on the substrate to be processed 5 does not change so much, and is about ± 7 μm. Since a deep depth of focus is ensured, a crystal grain array semiconductor thin film with good uniformity was obtained.

  FIG. 21 is a diagram schematically showing the configuration of the phase modulation element in Example 4 of the present embodiment. The phase modulation element 1 of Example 4 is a phase modulation element for producing a 5 μm-square crystal grain array semiconductor thin film, as in Examples 1 to 3, and has a configuration similar to that of Example 3. However, instead of the first phase region 1ab and the second phase region 1ac in the vicinity of the center of the unit region 1a, a 0.5 μm square phase region 1af is disposed, and a 0.2 μm square is formed around the periphery. A point where eight square dot regions 1ag are arranged in a lattice shape, and a point where the phase region 1af and all the dot regions 1ag have a phase of +120 degrees (+100 degrees in the third embodiment) with respect to the reference plane 1aa. Is different from the third embodiment. Hereinafter, the fourth embodiment will be described by paying attention to differences from the third embodiment.

  Although not shown, in Example 4, defocusing (-5 μm defocusing) is performed in a direction away from the imaging optical system 4 by 5 μm from the calculated focus position of the imaging optical system 4 (lower side in FIG. 1). This position becomes the actual focus position, and a deep depth of focus of about ± 7 μm can be secured. In Example 4, a light intensity distribution as shown in FIG. 22 is formed on the surface of the substrate 5 to be processed positioned at the calculation focus position of the imaging optical system 4. That is, a light intensity distribution as shown in FIG. 22A is formed along the transverse line corresponding to the transverse line AA of the unit region 1a of the phase modulation element 1, and the unit region 1a on the left side of the drawing is in the drawing. A light intensity distribution as shown in FIG. 22B is formed along the diagonal line corresponding to the diagonal line BB rising to the right. As described above, in Example 4, an inverse peak distribution in which the light intensity rapidly increases radially from the bottom peak toward the periphery is formed by the action of the phase region 1af arranged in the vicinity of the center of the unit region 1a. The

  In Example 4, the substrate 5 to be processed positioned at the actual focus position (calculated −5 μm defocus position) using the phase modulation element 1 having the configuration shown in FIG. 21 in the crystallization apparatus shown in FIG. The upper semiconductor (Si) thin film was crystallized. For example, laser light having a light intensity distribution shown in FIG. 22 (a) is formed on the substrate 5 to be processed, and after the crystallization process shown in FIG. 12, crystal grains of 5 μm square as shown in FIG. 14 (b). An array semiconductor thin film could be fabricated. Further, even if the surface of the substrate to be processed 5 varies to some extent with respect to the actual focus position of the imaging optical system 4, the light intensity distribution formed on the substrate to be processed 5 does not change so much, and is about ± 7 μm. Since a deep depth of focus is ensured, a crystal grain array semiconductor thin film with good uniformity was obtained.

  FIG. 23 is a diagram schematically showing the configuration of the phase modulation element in Example 5 of the present embodiment. The phase modulation element 1 of Example 5 is a phase modulation element for producing a 5 μm-square crystal grain array semiconductor thin film similarly to Examples 1 to 4, and has a configuration similar to that of Example 1. However, the first phase region 1ab and the second phase region 1ac have a phase of +100 degrees (+90 degrees in the first embodiment) with respect to the reference plane 1aa, and the periphery of the first phase region 1ab and the second phase region 1ac. This is different from the first embodiment in that no dot area is provided. Hereinafter, the fifth embodiment will be described by focusing on the difference from the first embodiment.

  In the fifth embodiment, the substrate to be processed positioned by defocusing (+5 μm defocusing) in a direction (upper side in FIG. 1) approaching the imaging optical system 4 by 5 μm from the calculated focus position of the imaging optical system 4. On the surface of 5, a light intensity distribution as shown in FIG. 24A is formed along a transverse line corresponding to the transverse line AA of the unit region 1 a. Further, the surface of the substrate 5 to be processed positioned at the calculation focus position of the imaging optical system 4 is shown in FIG. 24B along a transverse line corresponding to the transverse line AA of the unit region 1a. Such a light intensity distribution is formed.

  Further, the substrate 5 to be processed is positioned by defocusing (-5 μm defocusing) in a direction away from the imaging optical system 4 by 5 μm from the calculated focus position of the imaging optical system 4 (lower side in FIG. 1). A light intensity distribution as shown in FIG. 24C is formed along the transverse line corresponding to the transverse line AA of the unit region 1a. Further, the surface of the substrate to be processed 5 positioned by defocusing (−10 μm defocusing) away from the imaging optical system 4 by 10 μm from the calculated focus position of the imaging optical system 4 has a unit region. A light intensity distribution as shown in FIG. 25A is formed along a transverse line corresponding to the transverse line AA of 1a.

  Further, a unit region is formed on the surface of the substrate to be processed 5 which is positioned by defocusing (-15 μm defocusing) in a direction away from the imaging optical system 4 by 15 μm from the calculated focus position of the imaging optical system 4. A light intensity distribution as shown in FIG. 25B is formed along a transverse line corresponding to the transverse line AA of 1a. Finally, the surface of the substrate 5 to be processed is positioned by defocusing (−20 μm defocusing) away from the imaging optical system 4 by 20 μm from the calculated focus position of the imaging optical system 4. A light intensity distribution as shown in FIG. 25C is formed along a transverse line corresponding to the transverse line AA of the region 1a.

  Referring to FIG. 24 and FIG. 25, since no dot region is provided around the first phase region 1ab and the second phase region 1ac, the reverse peak in which the light intensity rapidly increases radially from the bottom peak to the periphery. However, unlike the first embodiment, an inclined distribution in which the light intensity gradually increases radially from the reverse peak distribution toward the periphery is not formed.

  In Example 5, the substrate 5 to be processed positioned at the actual focus position (calculated -7 μm defocus position) using the phase modulation element 1 having the configuration shown in FIG. 23 in the crystallization apparatus shown in FIG. The upper semiconductor (Si) thin film was crystallized. For example, laser light having a light intensity distribution shown in FIG. 24C or FIG. 25A is formed on the substrate 5 to be processed, and after the crystallization process shown in FIG. 12, as shown in FIG. 14B. A 5 μm square crystal grain array semiconductor thin film could be produced. Further, even if the surface of the substrate to be processed 5 varies to some extent with respect to the actual focus position of the imaging optical system 4, the light intensity distribution formed on the substrate to be processed 5 does not change so much, and is about ± 7 μm. Since a deep depth of focus is ensured, a crystal grain array semiconductor thin film with good uniformity was obtained. However, in Example 5, since the funnel-shaped gradient distribution is not formed as described above, only crystal grains smaller than those in Example 1 are generated.

  In each example of the above-described embodiment, the light intensity distribution can be calculated even at the design stage, but it is desirable to observe and confirm the light intensity distribution on the actual surface to be processed. For this purpose, the surface to be processed of the substrate to be processed may be enlarged by an optical system and input by an image pickup device such as a CCD. When the used light is ultraviolet light, the optical system is restricted, so that a fluorescent plate may be provided on the surface to be processed and converted into visible light. In each example of the above-described embodiment, a specific configuration example is illustrated for the phase modulation element 1, but various modifications may be made to the configuration of the phase modulation element 1 within the scope of the present invention.

  FIG. 26 is a process diagram showing a manufacturing process of the bottom-gate thin film transistor according to this embodiment. In this embodiment, a manufacturing method of an N-channel type thin film transistor is shown for the sake of convenience, but the same applies to the P-channel type only by changing the impurity species (dopant species). Here, a manufacturing method of a bottom-gate thin film transistor is described. First, as shown in FIG. 26A, Al, Ta, Mo, W, Cr, Cu or an alloy thereof is formed with a thickness of 100 to 300 nm on an insulating substrate 100 made of glass or the like and patterned. The gate electrode 101 is processed.

Next, as shown in FIG. 26B, a gate insulating film is formed on the gate electrode 101. In this embodiment, the gate insulating film has a two-layer structure of gate nitride film 102 (SiN _x ) / gate oxide film 103 (SiO ₂ ). The gate nitride film 102 was formed by a plasma CVD method (PE-CVD method) using a mixture of SiH ₄ gas and NH ₃ gas as a source gas. Note that atmospheric pressure CVD or reduced pressure CVD may be used instead of plasma CVD. In this embodiment, the gate nitride film 102 is deposited with a thickness of 50 nm. In succession to the formation of the gate nitride film 102, the gate oxide film 103 is formed with a thickness of about 200 nm.

Further, a semiconductor thin film 104 made of amorphous silicon was continuously formed on the gate oxide film 103 with a thickness of about 50 to 200 nm. Further, an insulating film 140 made of SiO ₂ was formed on the semiconductor thin film 104 with a thickness of 300 nm. The two-layer gate insulating film, the amorphous semiconductor thin film 104, and the insulating film 140 were continuously formed without breaking the vacuum system of the film forming chamber. In the case where the plasma CVD method is used for the above film formation, the hydrogen contained in the amorphous semiconductor thin film 104 is annealed by dehydrogenation annealing at a temperature of 400 to 450 ° C. for about 1 hour in a nitrogen atmosphere. Release.

  Next, the amorphous semiconductor thin film 104 is crystallized by irradiating the laser beam 150 in accordance with the method of the present invention of the system shown in Examples 1 to 5, for example. As the laser light 150, an excimer laser beam can be used. After adjusting the irradiation area of the laser beam 150, the laser beam 150 is focused and irradiated so that the periodic pattern of the phase modulation element can be transferred to the irradiation area, and the area is shifted so as not to overlap. Irradiation is repeated to crystallize a predetermined area. Subsequently, the insulating film 140 is peeled off by a method such as etching.

Next, as shown in FIG. 26C, Vth ion implantation is performed as necessary for the purpose of controlling the Vth of the thin film transistor. In this example, B + was ion-implanted so that the dose amount was about 5 × 10 ¹¹ to 4 × 10 ¹² / cm ² . In this Vth ion implantation, an ion beam accelerated at 10 KeV was used. Subsequently, SiO ₂ is formed to a thickness of about 100 nm to 300 nm on the polycrystalline semiconductor thin film 105 crystallized in the previous step by, for example, a plasma CVD method. In this example, silane gas SH ₄ and oxygen gas were plasma decomposed to deposit SiO ₂ .

The SiO ₂ thus formed is patterned into a predetermined shape and processed into a stopper film 106. In this case, the stopper film 106 is patterned so as to align with the gate electrode 101 by using a backside exposure technique. The portion of the polycrystalline semiconductor thin film 105 located immediately below the stopper film 106 is protected as a channel region Ch. As described above, B + ions are previously implanted into the channel region Ch at a relatively low dose by Vth ion implantation. Subsequently, impurities (for example, P + ions) are implanted into the semiconductor thin film 105 by ion doping using the stopper film 106 as a mask to form an LDD region. The dose at this time is, for example, 5 × 10 ¹² to 1 × 10 ¹³ / cm ² , and the acceleration voltage is, for example, 10 KeV.

Further, after patterning and forming a photoresist so as to cover the stopper film 106 and the LDD regions on both sides thereof, impurities (for example, P + ions) are implanted at a high concentration using this as a mask to form the source region S and the drain region D. To do. For example, ion doping (ion shower) can be used for the impurity implantation. In this example, impurities are implanted by electric field acceleration without mass separation. In this embodiment, impurities are implanted at a dose of about 1 × 10 ¹⁵ / cm ² to form a source region S and a drain region D. did. The acceleration voltage is, for example, 10 KeV. Although not shown, in the case of forming a P-channel thin film transistor, after covering the region of the N-channel thin film transistor with a photoresist, the impurity is switched from P + ions to B + ions, and the dose amount is about 1 × 10 ¹⁵ / cm ^2. Ion doping may be used.

  Here, impurities may be implanted using a mass separation type ion implantation apparatus. Thereafter, the impurities implanted into the polycrystalline semiconductor thin film 105 are activated by RTA (rapid thermal annealing) 160. In some cases, laser activation annealing (ELA) using an excimer laser may be performed. Thereafter, unnecessary portions of the semiconductor thin film 105 and the stopper film 106 are simultaneously patterned to separate the thin film transistor for each element region.

Finally, as shown in FIG. 26 (d), SiO ₂ is formed to a thickness of about 100 to 200 nm to form an interlayer insulating film 107. After the formation of the interlayer insulating film 107, SiN _x is formed to a thickness of about 200 to 400 nm by a plasma CVD method to form a passivation film (cap film) 108. At this stage, heat treatment is performed at about 350 to 400 ° C. in an atmosphere of nitrogen gas, forming gas, or vacuum for 1 hour to diffuse hydrogen atoms contained in the interlayer insulating film 107 into the semiconductor thin film 105. Thereafter, a contact hole is opened, and Mo, Al, etc. are sputtered to a thickness of 100 to 200 nm, and then patterned into a predetermined shape to be processed into the wiring electrode 109.

  Further, after applying a planarizing layer 110 made of acrylic resin or the like with a thickness of about 1 μm, a contact hole is opened. After a transparent conductive film made of ITO or the like is sputtered on the planarizing layer 110, it is patterned into a predetermined shape and processed into the pixel electrode 111. Since the channel is formed in accordance with the position of the crystal grain of the large grain crystal grain array as shown in FIG. 14, a thin film transistor with high mobility is formed.

FIG. 27 is a process diagram showing a manufacturing process of the top-gate thin film transistor according to the present embodiment. In this example, unlike the example 6, a thin film transistor having a top gate structure is manufactured. First, as shown in FIG. 27A, two layers of base films 106a and 106b serving as buffer layers are continuously formed on the insulating substrate 100 by a plasma CVD method. The first base film 106a is made of SiN _x and has a thickness of 500 nm.

Further, the second base film 106b is made of SiO ₂ and has a thickness of 500 nm. A semiconductor thin film 104 made of amorphous silicon is formed with a thickness of 50 to 200 nm on the base film 106b made of SiO ₂ by plasma CVD or LPCVD. Further, an insulating film 140 made of SiO _{2 is} formed with a thickness of 200 nm. When the plasma CVD method is used to form the semiconductor thin film 104 made of amorphous silicon, annealing is performed for about 1 hour in a nitrogen atmosphere at 400 to 450 ° C. in order to desorb hydrogen in the film. To do.

  Next, the amorphous semiconductor thin film 104 is crystallized, for example, according to the method of the present invention of the system shown in Examples 1-5. After adjusting the irradiation area of the laser beam 150, the laser beam 150 is focused and irradiated so that the periodic pattern arrangement of the phase modulation elements can be transferred to the irradiation area. A predetermined area is crystallized by repeatedly irradiating with shifting. Subsequently, the insulating film 140 is peeled off by a method such as etching.

If necessary, Vth ion implantation is performed as described above, and B + ions are implanted into the semiconductor thin film 104 at a dose of about 5 × 10 ¹¹ to 4 × 10 ¹² / cm ^2, for example. The acceleration voltage in this case is about 10 KeV. Subsequently, as shown in FIG. 27B, the crystallized silicon semiconductor thin film 105 is patterned into an island shape. On this, SiO ₂ is grown to 10 to 400 nm by the plasma CVD method, the atmospheric pressure CVD method, the low pressure CVD method, the ECR-CVD method, the sputtering method or the like to form the gate insulating film 103. In this embodiment, the thickness of the gate insulating film 103 is set to 100 nm.

Next, Al, Ti, Mo, W, Ta, doped polycrystalline silicon, or the like, or an alloy thereof is formed to a thickness of 200 to 800 nm on the gate insulating film 103, and patterned into a predetermined shape to form a gate electrode. 101. Next, P + ions are implanted into the semiconductor thin film 105 by ion implantation using mass separation to provide an LDD region. This ion implantation is performed on the entire surface of the insulating substrate 100 using the gate electrode 101 as a mask. The dose is 6 × 10 ^{12 to} 5 × 10 ¹³ / cm ² . The acceleration voltage is 90 KeV, for example.

The channel region Ch located immediately below the gate electrode 101 is protected, and B + ions previously implanted by Vth ion implantation are held as they are. After ion implantation into the LDD region, a resist pattern is formed so as to cover the gate electrode 101 and its periphery, and P + ions are implanted at a high concentration by a mass non-separation type ion shower doping method. Form. The dose amount in this case is, for example, about 1 × 10 ¹⁵ / cm ² . The acceleration voltage is 90 KeV, for example. As a doping gas, hydrogen diluted 20% PH ₃ gas was used.

In the case of forming a CMOS circuit, after forming a resist pattern for a P-channel thin film transistor, the doping gas is switched to a 5 to 20% B ₂ H ₆ / H ₂ gas system, and the dose is set to 1 × 10 ^{15 to} 3 ×. Ion implantation may be performed at about 10 ¹⁵ / cm ² and an acceleration voltage of 90 KeV, for example. The source region S and the drain region D may be formed using a mass separation type ion implantation apparatus. Thereafter, the activation process of the dopant implanted into the semiconductor thin film 105 is performed. In this activation process, the RTA 160 using an ultraviolet lamp can be used as in the sixth embodiment.

Finally, as shown in FIG. 27C, an interlayer insulating film 107 made of PSG or the like is formed so as to cover the gate electrode 101. After the formation of the interlayer insulating film 107, SiN _x is deposited by a plasma CVD method to a thickness of about 200 to 400 nm to form a passivation film (cap film) 108. At this stage, annealing is performed in a nitrogen gas at a temperature of 350 ° C. for about 1 hour to diffuse hydrogen contained in the interlayer insulating film 107 into the semiconductor thin film 105. Thereafter, a contact hole is opened.

  Further, Al—Si or the like is formed on the passivation film 108 by sputtering, and then patterned into a predetermined shape to be processed into the wiring electrode 109. Further, a flattening layer 110 made of acrylic resin or the like is applied with a thickness of about 1 μm, and then a contact hole is opened. A transparent conductive film made of ITO or the like is sputtered on the planarizing layer 110, patterned into a predetermined shape, and processed into the pixel electrode 111.

  In Example 7 shown in FIG. 27, the amorphous semiconductor thin film is crystallized in the same manner as described in Example 6 of FIG. However, in the case of this embodiment having a top gate structure, unlike in the case of Embodiment 6 having a bottom gate structure, crystallization is performed before the gate electrode pattern is formed. About shrinkage, tolerance is larger than Example 6. Therefore, the crystallization process can be performed using a laser irradiation apparatus with higher output. Since the channel is formed in accordance with the position of the crystal grain of the large grain crystal grain array as shown in FIG. 14, a thin film transistor with high mobility is formed.

  FIG. 28 shows an example of an active matrix display device using the thin film transistor according to Example 6 or Example 7. As shown in the drawing, the display device has a panel structure including a pair of insulating substrates 201 and 202 and an electro-optical material 203 held between the substrates. As the electro-optical material 203, a liquid crystal material is widely used. A pixel array unit 204 and a drive circuit unit are integrated on the lower insulating substrate 201. The drive circuit section is divided into a vertical drive circuit 205 and a horizontal drive circuit 206.

  In addition, a terminal portion 207 for external connection is formed at the upper end of the peripheral portion of the insulating substrate 201. The terminal portion 207 is connected to the vertical drive circuit 205 and the horizontal drive circuit 206 through the wiring 208. In the pixel array unit 204, row-like gate wirings 209 and column-like signal wirings 210 are formed. A pixel electrode 211 and a thin film transistor 212 for driving the pixel electrode 211 are formed at the intersection of both wirings. The thin film transistor 212 has a gate electrode connected to the corresponding gate wiring 209, a drain region connected to the corresponding pixel electrode 211, and a source region connected to the corresponding signal wiring 210.

  The gate wiring 209 is connected to the vertical drive circuit 205. On the other hand, the signal wiring 210 is connected to the horizontal drive circuit 206. The thin film transistor 212 for switching and driving the pixel electrode 211 and the thin film transistor included in the vertical drive circuit 205 and the horizontal drive circuit 206 are manufactured according to the present invention and have higher mobility than the conventional one. Therefore, not only the drive circuit but also a higher-performance processing circuit can be integrated.

  The crystallized semiconductor thin film manufactured by the above crystallization method of the present invention is applied to a thin film transistor and exhibits excellent TFT characteristics such as high mobility, so a liquid crystal display device (liquid crystal display), an EL (electroluminescence) display, etc. It can be applied to an integrated circuit such as a drive circuit, a memory (SRAM or DRAM), or a CPU.

It is a figure which shows roughly the structure of the crystallization apparatus concerning embodiment of this invention. It is a figure which shows schematically the internal structure of the illumination system of FIG. FIG. 3 is a diagram schematically illustrating a configuration of a phase modulation element according to the first embodiment. FIG. 6 is a diagram illustrating a light intensity distribution obtained at each defocus position of +5 μm to −5 μm in Example 1. FIG. 6 is a diagram showing a light intensity distribution obtained at each defocus position of −7 μm to −15 μm in Example 1. 6 is a diagram illustrating a light intensity distribution obtained at an actual focus position in Embodiment 1. FIG. It is a figure explaining the principle regarding the occupation area rate of a dot area | region, and light intensity distribution. FIG. 5 is a diagram showing a typical relationship between phase change and light intensity within a point image distribution range R. It is a figure which shows the relationship between the pupil function and point spread function in an imaging optical system. It is a figure which shows roughly the structure of a cell type corresponding to the dot area | region of the phase modulation element shown in FIG. It is a figure which shows schematically the structure of a pixel type different from the dot area | region of the phase modulation element shown in FIG. 1 schematically shows a crystallization process of a semiconductor thin film according to the present invention. It is a figure which shows roughly an example of light intensity distribution suitable for implement | achieving the crystallization process shown in FIG. It is a figure which shows typically an example of the relationship between the arrangement pattern of the unit area | region and the array pattern of the crystal structure formed in a phase modulation element. It is a figure which shows typically another example of the relationship between the array pattern of the unit area | region in the phase modulation element, and the array pattern of the crystal structure formed. It is a figure which shows schematically the structure of the phase modulation element in Example 2 of this embodiment. In Example 2, it is a figure which shows the light intensity distribution obtained in each defocus position of -5 micrometers-+5 micrometers. FIG. 6 is a diagram illustrating a light intensity distribution obtained at each defocus position of +7 μm to +15 μm in Example 1. It is a figure which shows schematically the structure of the phase modulation element in Example 3 of this embodiment. It is a figure which shows the light intensity distribution obtained in the actual focus position in Example 3. It is a figure which shows schematically the structure of the phase modulation element in Example 4 of this embodiment. It is a figure which shows the light intensity distribution obtained in the calculation focus position in Example 4. FIG. It is a figure which shows schematically the structure of the phase modulation element in Example 5 of this embodiment. In Example 5, it is a figure which shows the light intensity distribution obtained in each defocus position of +5 micrometer--5 micrometers. In Example 5, it is a figure which shows the light intensity distribution obtained in each defocus position of -10 micrometers--20 micrometers. It is process drawing which shows the manufacturing process of the bottom gate type thin-film transistor concerning this embodiment. It is process drawing which shows the manufacturing process of the top gate type thin-film transistor concerning this embodiment. It is a perspective view which shows roughly the structure of the display apparatus concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Phase modulation element 1a Phase modulation element unit area 3 Illumination system 3a KrF excimer laser light source 3b Beam expander 3c, 3e Fly eye lens 3d, 3f Condenser optical system 4 Imaging optical system 4c Aperture stop 5 Processed substrate 6 Substrate stage DESCRIPTION OF SYMBOLS 10 Unit board | substrate area | region 11 Growth crystal nucleus 12 Melting area | region 13 Twin grain boundary 14 Solid-liquid interface 15 Grain boundary

Claims (20)

A crystallization apparatus for crystallization by irradiating a non-single crystal semiconductor film with a light beam having a predetermined light intensity distribution,
A phase modulation element composed of a plurality of unit regions arranged in a predetermined cycle and having substantially the same pattern, and an imaging optical system arranged between the phase modulation element and the non-single-crystal semiconductor film,
The unit region of the phase modulation element includes a reference surface having a constant phase, a first phase region disposed near the center of the unit region and having a first phase difference with respect to the reference surface, and the first region A crystallization apparatus comprising: a second phase region disposed in the vicinity of a phase region and having substantially the same phase difference as the first phase difference with respect to the reference plane. The predetermined light intensity distribution has a plurality of unit distribution regions arranged in a predetermined cycle and having substantially the same two-dimensional distribution as each other,
The unit distribution region has an inverse peak distribution in which the light intensity increases rapidly from the region having the smallest light intensity toward the periphery in the vicinity of the center, and a radial shape from the inverse peak distribution toward the periphery. The crystallization apparatus according to claim 1, wherein the crystallization apparatus has an inclined distribution in which the light intensity gradually increases. The minimum value of light intensity in the unit distribution region has a relative value of 0.2 to 0.7 when the maximum value of light intensity in the unit distribution region is normalized to 1. 2. The crystallization apparatus according to 2. When the maximum value of the light intensity in the unit distribution region is normalized to 1, the light intensity is obtained by adding 2/5 of the difference between the maximum value and the minimum value to the minimum value of the light intensity in the unit distribution region. 4. The crystallization apparatus according to claim 2, wherein the width of the light intensity distribution is 0.5 μm to 1.5 μm. 5. The crystallization apparatus according to claim 2, wherein the unit distribution regions are arranged in a lattice shape or a triangular vertex shape at intervals of 4 μm to 20 μm. The non-single crystal semiconductor film is melted by irradiation with a light beam having a predetermined light intensity distribution, and a single growth crystal nucleus is periodically generated in the process of solidifying the melted portion of the non-single crystal semiconductor film, and the growth A crystallizing method in which a crystal grain array film is formed by radially growing a crystal around a crystalline crystal nucleus,
The non-single-crystal semiconductor film emits a light beam having the predetermined light intensity distribution formed via a phase modulation element composed of a plurality of unit regions having substantially the same pattern and arranged in a predetermined cycle and an imaging optical system Irradiate
The unit region of the phase modulation element includes a reference surface having a constant phase, a first phase region disposed near the center of the unit region and having a first phase with respect to the reference surface, and the first phase A crystallization method comprising: a second phase region disposed in the vicinity of a region and having substantially the same phase as the first phase with respect to the reference plane. The non-single crystal semiconductor film is positioned in the vicinity of an actual focal position different from a calculated focal position of the imaging optical system, and irradiated with a light beam having the predetermined light intensity distribution. 6. The crystallization method according to 6. The predetermined light intensity distribution has a plurality of unit distribution regions arranged in a predetermined cycle and having substantially the same two-dimensional distribution as each other, and the unit distribution region is a region having the smallest light intensity in the vicinity of the center. It has a reverse peak distribution in which the light intensity rapidly increases radially from the periphery to the periphery, and a sloped distribution in which the light intensity gradually increases radially from the reverse peak distribution toward the periphery. The crystallization method according to claim 6 or 7. A semiconductor film on a substrate for producing a device crystallized by the crystallization apparatus according to any one of claims 1 to 5 or the crystallization method according to any one of claims 6 to 8. Because
A semiconductor film characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at periodic intervals of 4 μm to 20 μm, and includes only twin grain boundaries inside the crystal grains. A semiconductor film formed on an insulating substrate by crystallization by the crystallization apparatus according to any one of claims 1 to 5 or the crystallization method according to any one of claims 6 to 8, and A top gate type thin film transistor having a stacked structure including a gate insulating film overlaid on one surface of a semiconductor film, and a gate electrode overlaid on the semiconductor film through the gate insulating film,
A thin film transistor characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at a periodic interval of 4 μm to 20 μm and includes only twin grain boundaries inside the crystal grains. A gate electrode formed on an insulating substrate, a gate insulating film overlaid on one surface of the gate electrode, the crystallization apparatus according to any one of claims 1 to 5, or any one of claims 6 to 8. A bottom-gate thin film transistor having a stacked structure including a semiconductor film that is crystallized by the crystallization method according to claim 1 and stacked so as to cover the gate electrode through the gate insulating film,
A thin film transistor characterized in that the crystal structure of the semiconductor film is composed of crystal grains arranged at a periodic interval of 4 μm to 20 μm and includes only twin grain boundaries inside the crystal grains. A pair of substrates bonded to each other through a predetermined gap; and an electro-optic material held in the gap between the pair of substrates. A counter electrode is formed on one of the pair of substrates. 6. A pixel electrode and a thin film transistor for driving the pixel electrode are formed on the other substrate of the pair of substrates, and the thin film transistor is the crystallization apparatus according to claim 1, or the claim. Item 9. A display device comprising a semiconductor film crystallized by the crystallization method according to any one of Items 6 to 8 and a gate electrode overlaid on one surface of the semiconductor film with a gate insulating film interposed therebetween. And
A display device, wherein the crystal structure of the semiconductor film is composed of crystal grains arranged at periodic intervals of 4 μm to 20 μm, and includes only twin grain boundaries inside the crystal grains. A phase modulation element comprising a plurality of unit regions arranged in a predetermined cycle and having substantially the same pattern,
The unit region includes a reference surface having a constant phase, a first phase region disposed near the center of the unit region and having a first phase difference with respect to the reference surface, and in the vicinity of the first phase region. A phase modulation element comprising: a second phase region that is disposed and has substantially the same phase difference as the first phase difference with respect to the reference plane. 14. The phase modulation element according to claim 13, wherein the first phase region and the second phase region have substantially the same pattern and are in contact with each other at substantially one point. The phase modulation element according to claim 13, wherein the first phase region and the second phase region each have a sector shape. 16. The first phase region and the second phase region as a whole have a size of 0.3 μm to 1.5 μm in terms of a diameter on the working surface. 2. The phase modulation element according to item 1. In the unit region, a dot region having a dot shape smaller than a predetermined dimension and having substantially the same phase as the first phase region is provided around the first phase region and the second phase region. The phase modulation element according to claim 13, wherein the phase modulation element is any one of the above. 18. The phase modulation element according to claim 17, wherein in the unit region, the occupied area ratio of the dot region with respect to the reference surface varies depending on the position. 18. The phase modulation according to claim 17, wherein the unit region has a plurality of cells smaller than the predetermined dimension, and the occupied area ratio of the dot region in each cell changes for each cell. element. The phase modulation element according to claim 18, wherein the occupation area ratio decreases as the distance from the center of the unit region increases.

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