JP2007304196A - Optical element, focus adjustment device using the same, focus adjustment method, laser annealer, and laser annealing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element capable of finely adjusting an optical distance in a short time and easily without moving a lens and a lens group in the direction of an optical axis and to provide a focus adjustment mechanism. <P>SOLUTION: The optical element includes: a first optical member 2 having a pair of inclined faces 2a and 2b, which are inclined so as to be symmetrical, right and left, with a central axis between them; and a second optical member 3 and third optical member 4, which are disposed in relation to the first optical member so as to be symmetrical, right and left, with the central axis between them. The second and third optical members 3 and 4 have vertical faces 3a and 4a almost perpendicular to the optical axis, and inclined faces 3b and 4b almost parallel to the inclined faces 2a and 2b of the first optical member 2. The second and third optical members 3 and 4 are arranged so that the inclined faces 2a and 2b of the first optical member 2 and the inclined faces 3b and 4b of the second and third optical members 3 and 4 are almost parallel and opposite to each other. The first optical member 2 is movable in the direction of the central axis. Moving the first optical member 2 in the direction of the central axis adjusts an optical distance without changing the length of an optical path in the direction of the optical axis. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel optical element capable of changing an optical distance while keeping a physical distance constant. Further, the present invention relates to a focus adjustment device, a focus adjustment method, a laser annealing device, and a laser annealing method to which this is applied. About.

  In a liquid crystal display element, a thin film transistor for driving a liquid crystal of each pixel, a thin film transistor for a peripheral drive circuit, and the like are formed on a panel substrate. A technique for forming a polycrystalline thin film transistor using a polysilicon layer as a channel layer on a glass substrate has been developed. In recent years, progress in process technology has made it possible to form a high-performance polycrystalline thin film transistor on a glass substrate at a low process temperature.

  For example, a laser annealing method using an excimer laser is a method in which an amorphous silicon semiconductor film on a glass substrate is irradiated with an excimer laser to form a polycrystalline silicon semiconductor film, and the polycrystalline silicon semiconductor film is formed at a low process temperature. It is a typical example of the low temperature process to form.

  By the way, in a thin film transistor using a polycrystalline silicon semiconductor film, the grain size of the polycrystalline silicon constituting the polycrystalline silicon semiconductor film greatly affects the characteristics. The grain size of polycrystalline silicon greatly depends on the energy per unit area of the irradiated excimer laser in the laser annealing method using the excimer laser described above. Therefore, in order to mass-produce stable quality polycrystalline thin film transistors, it is important to control the energy per unit area of the excimer laser to be constant.

  From such a viewpoint, a beam profiler is installed at a position where a profile equivalent to the amorphous silicon semiconductor film irradiated with the laser beam is obtained, and the average height or maximum of the short axis profile of the beam profile obtained by the profiler is obtained. It has been proposed that a polycrystalline silicon semiconductor film having a constant grain size is obtained by controlling the transmittance of the attenuator so that the height is always constant (for example, (See Patent Document 1).

The invention described in Patent Document 1 provides a device and a manufacturing method for mass-producing a polycrystalline silicon thin film transistor device used for a pixel switch and a drive circuit of a liquid crystal display with a high yield, and is a glass on which an amorphous silicon semiconductor thin film is deposited. In a laser annealing system that generates a polycrystalline silicon semiconductor by irradiating a pulsed laser beam while moving the substrate, the fluence is determined from the short-axis profile height of the beam profiler placed at a position equivalent to the laser beam on the glass substrate. By adjusting the variable attenuator so that the height is constant, it is possible to always produce uniform polycrystalline silicon.
JP 2001-338893 A

  However, the invention described in Patent Document 1 does not consider the variation in the height of the glass substrate, and in this respect, it is difficult to keep the grain size of the polycrystalline silicon semiconductor film constant.

  In a laser annealing apparatus used for crystallization, laser light having a predetermined wavelength emitted from a laser main body has a light intensity distribution that has a strong center and a weak periphery. As described above, when the amorphous silicon semiconductor film is irradiated with light having substantially the same intensity, a polycrystalline silicon semiconductor film having a substantially uniform grain size is formed. Therefore, the excimer laser irradiated to the amorphous silicon semiconductor film is The light intensity distribution needs to be substantially constant within the irradiation surface. Therefore, in the laser annealing apparatus, the light intensity in the irradiation surface is adjusted to be substantially constant by using a homogenizer. Also, considering mass production, it is common to perform laser irradiation while moving the substrate in one direction and shifting the irradiation position little by little. The size of the laser beam on the substrate (on the amorphous silicon semiconductor film) is For example, it has an elongated shape such as 30 cm × 0.5 mm.

  Here, the margin in the direction perpendicular to the substrate for making the light intensity constant is not so large, and there is a portion corresponding to the image plane in a normal optical system, and it is made uniform only in the vicinity thereof. On the other hand, the glass substrate used as a display substrate has irregularities on the surface. Therefore, in order to irradiate such a glass substrate with laser light whose light intensity is homogenized (uniformized), the position of the image plane is changed according to the surface irregularities of the glass substrate during the scanning of the laser light. There is a need.

  In this case, it is desirable to adjust the focal position to the substrate surface (amorphous silicon semiconductor film surface) by adjusting the optical system. If only the adjustment of the focal position is considered, it can be adequately handled by moving the lens or lens group in the optical path back and forth in the optical axis direction. However, since the size of the laser beam is very large as described above, the lens or the lens group for adjusting the focal position is also enlarged, and it is difficult to move back and forth (usually up and down) as described above. Business. Further, since the unevenness of the glass substrate is about several μm, the distance moved in the optical axis direction substantially corresponds to this, and its control is difficult.

  From such a situation, a normal laser annealing apparatus is often provided with a mechanism capable of finely changing the height of the substrate. However, as the size of the display increases, it has become difficult to change the height of the substrate. For example, when the substrate size becomes 1 m class, the mechanism for changing the height of the substrate needs to be large, and fine adjustment of the substrate height lowers the throughput. It is also not desirable.

  As described above, in order to irradiate the substrate with light such as a laser beam condensed by optical means, it is necessary to form an image plane of a desired image on the substrate surface. Therefore, in liquid crystal display substrates with irregularities on the surface, the height of the substrate was adjusted to hold the substrate at the focal position. However, as the substrate size increased, this work greatly reduced the throughput. In addition, the apparatus becomes a large scale, which is a factor of increasing the equipment. The present invention has been proposed in view of such a conventional situation, and is a novel capable of easily and finely adjusting the optical distance in a short time without moving the lens or the lens group in the optical axis direction. An object of the present invention is to provide an optical element, and thereby to provide a focus adjustment device and a focus adjustment method that can finely adjust the image plane position of laser light, for example. The present invention also provides a laser annealing apparatus and a laser annealing method capable of forming a desired image plane on a substrate surface without adjusting the height of the substrate and mass-producing a uniform polycrystalline silicon semiconductor film. The purpose is to provide.

  In order to achieve the above-described object, an optical element according to the present invention is formed of an optical material having a refractive index difference with air, has a central axis orthogonal to the optical axis, and has left and right sides sandwiching the central axis. A first optical member having a pair of symmetrically inclined surfaces and an optical material similar to the first optical member, and symmetrically sandwiching the central axis with respect to the first optical member Second and third optical members disposed, wherein the second and third optical members are substantially parallel to a vertical plane substantially orthogonal to the optical axis and an inclined surface of the first optical member, respectively. And the first optical member is arranged so as to face the first optical member substantially parallel to the inclined surface of the first optical member, and the first optical member is located at the center. It is characterized by being movable in the axial direction.

  The optical element of the present invention is based on the principle of changing the optical distance by inserting a material having a refractive index larger than that of air into the optical path. In the optical element of the present invention, the substantial optical path length changes by moving the first optical member in the central axis direction. For example, when each inclined surface of the first optical member is moved in a direction approaching the inclined surfaces of the second and third optical members, the distance transmitted through the first optical member is increased. Conversely, when each inclined surface of the first optical member is moved away from the inclined surfaces of the second and third optical members, the distance transmitted through the first optical member is reduced. The refractive index of the first optical member is larger than that of air. Therefore, changing the distance equivalent to the first optical member results in changing the optical distance of the entire optical path length, and functions as a focus adjustment mechanism, for example. To do. At this time, the optical path length in the real space in the optical axis direction is not changed.

  The focus adjustment device and focus adjustment method, and the laser annealing device and laser annealing method of the present invention utilize the focus adjustment mechanism of the optical element. In other words, the focus adjusting apparatus of the present invention includes the optical element, and the optical distance is adjusted without changing the optical path length in the optical axis direction by relatively moving the first optical member in the central axis direction. It is characterized by that. The focus adjustment method according to the present invention uses the optical element, makes light incident from the vertical surface of the second optical member, and relatively moves the first optical member in the central axis direction, so as to be in real space in the optical axis direction. The optical distance is adjusted without changing the optical path length.

  The laser annealing apparatus of the present invention is a laser annealing apparatus in which the amorphous silicon semiconductor film is made to be a polycrystalline silicon semiconductor film by irradiating a pulse laser beam while moving the substrate on which the amorphous silicon semiconductor film is deposited. The optical element is inserted in the optical path of the pulse laser beam. The laser annealing method of the present invention is a laser annealing method in which the amorphous silicon semiconductor film is made to be a polycrystalline silicon semiconductor film by irradiating a pulse laser beam while moving the substrate on which the amorphous silicon semiconductor film is deposited. The optical element is inserted into the optical path of the pulse laser beam, the pulse laser beam is incident from the vertical plane of the second optical member, and the first optical member is moved in the central axis direction. The optical distance is adjusted without changing the optical path length in the real space in the optical axis direction, and the focal position of the pulse laser beam is made to substantially coincide with the surface of the amorphous silicon semiconductor film.

  According to the present invention, it is possible to finely adjust the optical distance in a short time and easily without moving the lens or the lens group in the optical axis direction, thereby finely adjusting the image plane position of the laser light, for example. Focus adjustment is possible. At this time, it is not necessary to change the optical path length in the real space in the optical axis direction. Furthermore, by applying the laser annealing, a desired image plane can be formed on the substrate surface without adjusting the height of the substrate, and a uniform polycrystalline silicon semiconductor film can be mass-produced.

  Hereinafter, an optical element to which the present invention is applied, a focus adjustment device, a focus adjustment method using the same, a laser annealing device, and a laser annealing method will be described in detail with reference to the drawings.

(Configuration of optical element and focus adjustment mechanism)
The optical element of this embodiment is comprised by arrange | positioning the 2nd optical member 2 and the 3rd optical member 3 on both sides of the 1st optical member 1, as shown in FIG. Each of the optical members 1 to 3 must be formed of an optical material that has excellent light transmittance and a refractive index difference from air, and is formed of, for example, quartz or glass. The optical members 1 to 3 are all made of the same optical material.

  The first optical member 1 has a symmetrical shape about the central axis C, and has two inclined surfaces 1a and 1b that have the same inclination angle θ with respect to the central axis C and are inclined in opposite directions. Therefore, the cross-sectional shape of the first optical member 1 is a trapezoidal shape. The first optical member 1 is disposed so that the central axis C is substantially orthogonal to the optical axis direction of incident light.

  The second optical member 2 is disposed on the light incident side of the first optical member 1, and has a light incident surface 2 a that is substantially orthogonal to the optical axis of the incident light, and an inclined surface 1 a of the first optical member 1. It has the inclined surface 2b which opposes substantially parallel. Similarly, the third optical member 2 is disposed on the light emission side of the first optical member 1, and the light emission surface 3 a substantially orthogonal to the optical axis of the incident light, and the inclination of the first optical member 1. It has the inclined surface 3b which opposes the surface 1b substantially parallel.

  As shown in FIG. 2, the optical element 1 is designed according to the size of incident light. For example, the optical element 1 has a size that allows the incident light spot SP to be contained in the light incident surface 3a of the second optical member 3. Has been. Specifically, when the size of the incident light spot SP is D1 × D2, the sizes W1 and W2 of the optical element 1 are W1> D1 and W2> D2, for example, the incident light spot SP is elongated. In the case of a shape, the optical element 1 is also elongated in accordance with the incident light spot SP.

  In the optical element 1 having the above-described configuration, light enters from the light incident surface 2a of the second optical member 3, and the space between the second optical member 3 and the first optical member 2, the first optical member. 2. The light passes through the space between the first optical member 2 and the third optical member 4, and further through the third optical member 4, and is emitted from the light emitting surface 3a of the third optical member 4. Here, when the light transmitted through the second optical member 3 enters the first optical member 2 after passing through the space between the second optical member 3 and the first optical member 2, air and Although the optical axis is shifted due to the difference in refractive index with each of the optical members 1 to 3, it passes through the space between the first optical member 2 and the third optical member 4 and enters the third optical member 4. The offset of the optical axis is canceled (cancelled). Therefore, the state where the optical axis of the light incident on the second optical member 3 and the optical axis of the light emitted from the third optical member 4 coincide with each other is maintained.

  In the optical element 1, the first optical member 2 can move in the direction of the central axis C to change the optical distance. The focus can be adjusted by changing the optical distance. Hereinafter, focus adjustment using the optical element 1 will be described.

  As described above, in the optical element 1, the first optical member 2 can be moved in the central axis C direction (the arrow direction in FIG. 1). As a mechanism for moving the first optical member 2, for example, a driving mechanism using a piezoelectric element can be employed.

  Here, the change in the optical distance will be described with reference to the central state shown in FIG. The light transmission distance of the first optical element 2 in this reference state (a distance through which light passes) is L1. For example, when the first optical element 2 is moved from the reference state in the direction of arrow A (left direction in the figure), as shown in FIG. 3B, the light transmission distance L2 of the first optical element 2 is It becomes larger than the light transmission distance L1 in the reference state (L2> L1). On the contrary, when the first optical element 2 is moved in the direction of arrow B (right direction in the figure), as shown in FIG. 3C, the light transmission distance L3 of the first optical element 2 is It becomes smaller than the light transmission distance L1 in the reference state (L3 <L1).

  At this time, the distance (the length of the space) between the first optical member 2 and the second and third optical members 3 and 4 also slightly changes, but the refractive index of the first optical member 1 is air. Since the refractive index is larger than the refractive index, the light transmission distance in the first optical member 2 is dominant in the effective optical path length of the entire optical element 1. That is, if the first optical member 2 is moved in the direction of arrow A, the optical distance in the entire optical element 1 is increased, and if the first optical member 2 is moved in the direction of arrow B, the optical distance in the entire optical element 1 is increased. The target distance is reduced.

  As described above, the basic principle of the optical element 1 of the present invention is to change the optical distance by inserting a material (first optical member 2) having a large refractive index difference from air, such as quartz, into the optical path. It is. At this time, the thickness of a material having a large refractive index difference from air is continuously changed, and the changing direction is set as an insertion direction, so that the light beam travels an optical distance different from that of air according to the insertion amount. Therefore, it is possible to change only the optical distance without changing the optical path length in the entire real space. By using the optical element 1 of the present invention, it is possible to adjust the focus of the image plane of incident light by utilizing the change in the optical distance accompanying the movement of the first optical member 2 as described above.

  In the focus adjustment, for example, the inclination angle θ of each inclined surface 2a, 2b of the first optical member 2, and the corresponding inclination angle of the inclined surface 3b of the second optical member 3, the third optical member It is possible to change the adjustment range and adjustment accuracy in focus adjustment by changing the inclination angle of the four inclined surfaces 4b. For example, if the inclination angle θ of each of the inclined surfaces 2a and 2b is increased, the optical distance can be greatly changed with a small starting distance. This is effective in expanding the adjustable range in focus adjustment. Conversely, if the inclination angle θ of each of the inclined surfaces 2a and 2b is reduced, the change in the optical distance can be reduced as compared with the moving distance of the first optical member 2. This is effective for finely controlling the optical distance in focus adjustment.

  FIG. 4 shows the relationship between the movement distance of the first optical member 2 and the change in the optical distance of the optical element 1. FIG. 4 shows the movement distance of the first optical member 2 and the optical distance of the optical element 1 when the inclination angle θ of each of the inclined surfaces 2a and 2b is changed from 0.5 ° to 2.5 °. The relationship of changes is shown. FIG. 4 shows that by adjusting the tilt angle θ in the range of 0.5 ° to 2.5 °, it is possible to perform arbitrary focal position control (focus adjustment) as necessary.

(Application to laser annealing)
Next, application of the optical element 1 having the above-described configuration to a laser annealing apparatus and a laser annealing method will be described.

  As shown in FIG. 5, the laser annealing apparatus uses an amorphous silicon semiconductor film 12 on a glass substrate 11 as a polycrystalline silicon semiconductor film using pulsed laser light such as excimer laser. The glass substrate 11 on which the amorphous silicon semiconductor film 12 is formed is placed on a transfer table 13 and irradiated with the pulse laser light while moving the glass substrate 11 in one direction. Polycrystallized.

  The laser annealing apparatus includes a laser oscillator 21 that outputs a pulse laser beam having a predetermined wavelength and intensity, and an optical system that shapes and equalizes the pulse laser beam output from the laser oscillator 21. The amorphous silicon semiconductor film 12 on the glass substrate 11 is irradiated via the laser annealing.

  The optical system for shaping and homogenizing the pulsed laser beam includes a first homogenizer 22 for equalizing the intensity distribution in the major axis direction of the pulsed laser beam, and the intensity distribution in the minor axis direction of the pulsed laser beam. A second homogenizer 23, a field lens 24, a slit 25, a total reflection mirror 26 that reflects the pulse laser beam substantially at right angles, and a projection lens 27, and the pulse laser beam output from the laser oscillator 21. Are shaped and uniformed by these optical systems and irradiated to the amorphous silicon semiconductor film 12 on the glass substrate 11.

  The pulse laser beam output from the laser oscillator 21 has a light intensity distribution such that the center is strong and the periphery is weak. Since substantially uniform crystals are formed by irradiating the amorphous silicon semiconductor film 12 with light having substantially the same intensity, the pulse laser beam irradiated to the amorphous silicon semiconductor film 12 has a light intensity within the irradiation surface. The distribution needs to be almost constant. By installing the first homogenizer 22 and the second homogenizer 23, the light intensity in the irradiation surface is adjusted to be substantially constant.

  Further, the beam spot shape of the pulse laser beam is shaped by the field lens 24, the slit 25, and the projection lens 27. Here, in consideration of mass productivity in the laser annealing apparatus, it is preferable to move the glass substrate 11 in one direction by the transfer table 13 and perform laser irradiation while shifting little by little. Therefore, the pulse laser beam is shaped into a long and narrow shape by the optical system. The size of the pulse laser beam on the glass substrate 11 (on the amorphous silicon semiconductor film 12) is, for example, 30 cm × 0.5 mm.

  In the optical system, the vertical margin of the glass substrate 11 for making the light intensity constant is not so large. Some of the optical systems correspond to the image plane, and the light intensity is made uniform only in the vicinity thereof. Therefore, in order to make the surface of the glass substrate 11 and the image plane coincide with each other, for example, it may be possible to change the height of the glass substrate 11 by moving the transfer table 13 up and down. Along with the increase, finely adjusting the height of the glass substrate 11 lowers the throughput, which is not desirable from the viewpoint of mass productivity.

  Therefore, in the laser annealing apparatus of this embodiment, instead of adjusting the height of the glass substrate 11, the focus adjustment mechanism 28 using the optical element 1 is inserted into the optical path of the optical system to adjust the focus ( Image plane position adjustment). That is, the optical element 1 is inserted into the optical path of the pulse laser beam, the pulse laser beam is incident from the vertical surface 3a of the second optical member 3, and the first optical member 2 is moved in the direction of the central axis (arrow in the figure). The optical distance is adjusted without changing the optical path length in the real space in the optical axis direction, and the focal position of the pulse laser beam is made substantially coincident with the surface of the amorphous silicon semiconductor film 12. .

  In the focus adjustment, the height of the glass substrate 11 in the irradiation area can be measured, and the focus adjustment (change in optical distance) can be performed while feeding back the measurement result. In this case, the height of the glass substrate 11 may be measured prior to the pulse laser beam, and the first optical member 2 may be moved in the direction of the central axis based on the measurement result. The height distribution of the entire glass substrate 11 may be measured, and the first optical member 2 may be moved in the central axis direction based on the accumulated measurement data.

  For example, as described in the document “IDW′03 p415-418” and the like, it is generally known that the surface of the glass substrate has irregularities in one direction. Therefore, uniform crystallization of the entire amorphous silicon semiconductor film 12 can be achieved by aligning the direction of the uneven peaks and valleys with the width direction of the elongated pulse laser beam and adjusting the focus by the optical element 1. It is possible to realize. Further, the focus adjustment has an advantage that the controllability is much better than the height control of the glass substrate 11.

It is a figure which shows one structural example of the optical element to which this invention is applied. It is a schematic perspective view of the optical element shown in FIG. (A)-(c) is a figure which shows the mode of a change of the optical distance by the movement of a 1st optical member. FIG. 6 is a characteristic diagram showing the relationship between the moving distance of the movable part (first optical member) and the change in the optical distance at an inclination angle θ = 0.5 ° to 2.5 °. It is a figure which shows the structural example of the laser annealing apparatus using the optical element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical element 2 1st optical member 2a, 2b inclined surface 3 2nd optical member 3a light incident surface 3b inclined surface 4 3rd optical member 4a light output surface 4b inclined surface 11 Glass substrate, 12 Amorphous silicon semiconductor film, 13 Transport table, 21 Laser oscillator, 22 First homogenizer, 23 Second homogenizer, 24 Field lens, 25 Slit, 26 Total reflection mirror, 27 Projection lens, 28 Focus adjustment mechanism

Claims (9)

A first optical member formed of an optical material having a refractive index difference from air, having a central axis perpendicular to the optical axis, and having a pair of inclined surfaces that are symmetrically inclined with respect to the central axis;
A second and a third optical member that are formed of the same optical material as the first optical member and are arranged symmetrically with respect to the first optical member across the central axis;
The second and third optical members each have a vertical surface that is substantially orthogonal to the optical axis, and an inclined surface that is substantially parallel to the inclined surface of the first optical member, with respect to the first optical member. These inclined surfaces are arranged so as to face the inclined surface of the first optical member substantially in parallel,
The optical element, wherein the first optical member is movable in the central axis direction.   The optical element according to claim 1, wherein an inclination angle of each inclined surface of the first optical member is 0.5 ° to 2.5 ° with respect to the central axis.   The optical element according to claim 1 or 2, wherein the optical distance is adjusted without changing the optical path length in the optical axis direction by moving the first optical member in the central axis direction. Focus adjustment device.   3. The optical element according to claim 1 or 2, wherein light is incident from a vertical surface of the second optical member, and the first optical member is moved in the central axis direction so as to be in real space in the optical axis direction. A focus adjustment method, wherein the optical distance is adjusted without changing the optical path length of the lens. A laser annealing apparatus that uses the amorphous silicon semiconductor film as a polycrystalline silicon semiconductor film by irradiating a pulsed laser beam while moving the substrate on which the amorphous silicon semiconductor film is deposited,
3. A laser annealing apparatus, wherein the optical element according to claim 1 is inserted in an optical path of the pulse laser beam.   6. The laser annealing apparatus according to claim 5, wherein a dimension of each optical member of the optical element is larger than a width of the pulse laser beam in the central axis direction and a direction orthogonal to the optical axis direction. A laser annealing method in which the amorphous silicon semiconductor film is made to be a polycrystalline silicon semiconductor film by irradiating a pulsed laser beam while moving the substrate on which the amorphous silicon semiconductor film is deposited,
The optical element according to claim 1 or 2 is inserted in an optical path of the pulse laser beam,
The pulse laser beam is incident from the vertical plane of the second optical member, and the first optical member is moved in the direction of the central axis, so that the optical path length in the real space in the optical axis direction is not changed. A laser annealing method, wherein a focal distance is adjusted so that a focal position of the pulse laser beam substantially coincides with a surface of the amorphous silicon semiconductor film.   8. The laser annealing method according to claim 7, wherein a height of the substrate is measured prior to the pulsed laser beam, and the first optical member is moved in the central axis direction based on the measurement result. 8. The laser annealing method according to claim 7, wherein a height distribution of the entire substrate is measured in advance, and the first optical member is moved in the central axis direction based on the accumulated measurement result. .

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