JP3234513B2 - Beam homogenizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam homogenizer for uniformizing the intensity distribution of a light beam in a cross section.

[0002]

2. Description of the Related Art A cylinder array type beam homogenizer includes a front cylinder array, a rear cylinder array, and a focus lens. Each cylinder array is configured by arranging a plurality of equivalent cylindrical lenses in a direction perpendicular to the optical axis plane. The optical axis surfaces of the cylindrical lenses of the preceding cylinder array are arranged so as to coincide with the optical axis surfaces of the corresponding cylindrical lenses of the subsequent cylinder array. Here, the optical axis plane means a plane of symmetry of a plane-symmetric imaging system of the cylindrical lens.

[0003] When a light beam enters the preceding cylinder array, it is converged by each cylindrical lens. Each converged light beam is converged again by each cylindrical lens of the subsequent cylinder array. Thus, 2
One cylinder array divides the incident light beam into small light beams corresponding to the number of cylindrical lenses.

[0004] Depending on the relative positions of the two cylinder arrays, the obtained small light beam becomes divergent light, parallel light, or convergent light. By superimposing the small light beams on a certain surface using the focus lens group, it is possible to make the light intensity distribution in the irradiation area uniform in the direction perpendicular to the optical axis plane of the cylindrical lens.

[0005]

The uniformity of the light intensity in the irradiation area where the light beam is superimposed (homogenized) is evaluated by the top flat ratio. Here, the top flat ratio R _TF is defined as W _0.9 , where the width of a portion having an intensity of 90% or more of the maximum value of the light intensity distribution is W _0.9 , and the half width is W _0.5 .

[0006]

## EQU1 ## It is defined by R _TF = W _0.9 / W _0.5 . The width of the homogenized irradiation area is 1m
If it is at least m, a relatively high top flat ratio can be obtained, but if it is at most 1 mm, it will be difficult to obtain a high top flat ratio.

An object of the present invention is to provide a beam homogenizer capable of increasing a top flat ratio of a light intensity distribution.

[0008]

[0009]

[0010]

[0011]

According to one aspect of the present invention, a plurality of first cylindrical lenses make the generating lines and the optical axis planes of the respective cylindrical surfaces parallel to each other, and the first cylindrical lenses are parallel to the optical axis plane. The first cylinder array and the plurality of second cylindrical lenses arranged along a first virtual plane perpendicular to each other make the buses of the respective cylindrical surfaces and the optical axis surfaces parallel to each other, and A second cylinder array arranged along a second virtual plane parallel to the first virtual plane, wherein each second cylindrical lens has a common optical axis plane with the corresponding first cylindrical lens; The light beam transmitted through the first cylindrical lens is incident on the corresponding second cylindrical lens, the second cylinder array, and the light beam transmitted through the second cylinder array is converged. Along a line of intersection between the optical system and each of the first cylindrical lenses that are disposed between the first cylinder array and the second cylinder array and that constitute the first cylinder array. There is provided a beam homogenizer having a first light shielding plate having a slit formed therein.

[0012] Of the parallel light beam incident on the first cylinder array, a noise component propagating in a direction deviated from the optical axis plane by a certain angle or more is shielded by the light shielding plate. For this reason, an effect equivalent to increasing the parallelism of the incident light beam can be obtained, and a decrease in the top flat ratio of the light intensity distribution on the homogenized surface can be suppressed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An irradiation region homogenized by a cylinder array type beam homogenizer has a width of 1 mm.
Below, it becomes difficult to obtain a high top flat ratio. According to the evaluation experiment by the inventor of the present application, the noise component of the parallel light beam incident on the beam homogenizer, that is, the component propagating in a direction other than the direction parallel to the optical axis, is one of the causes of reducing the top flat ratio. I understand. Hereinafter, an embodiment for preventing a reduction in the top flat ratio due to a noise component of an incident light beam will be described.

FIG. 1 is a sectional view of a beam homogenizer according to an embodiment of the present invention. Consider an xyz rectangular coordinate system having a z-axis parallel to the optical axis of a light beam incident on a beam homogenizer. FIG. 1A is a sectional view parallel to the yz plane, and FIG.
(B) shows a sectional view parallel to the xz plane. The beam homogenizer according to the embodiment includes a spatial filter unit SF and a homogenizing unit HN. The spatial filter unit SF
It is configured to include cylindrical lenses 5A and 5B and a light shielding plate 6 having slits. The homogenizing part HN
It is configured to include the cylinder arrays 1A, 1B, 2A, 2B and the converging lens 3.

As shown in FIG. 1A, each of the cylinder arrays 1A and 1B is constituted by seven equivalent cylindrical lenses. The optical axis plane of each cylindrical lens is parallel to the xz plane, and the generatrix of the cylindrical surface is parallel to the x axis. Here, the optical axis plane means a plane of symmetry of a plane-symmetric imaging system of a cylindrical lens. The cylindrical lenses arranged in this manner are arranged in parallel with the y-axis (along the xy plane) with their edge surfaces in close contact with each other. The cylinder array 1A is arranged on the light incident side (left side in the figure), and the cylinder array 1B is arranged on the light outgoing side (right side in the figure). Further, each cylindrical lens of the cylinder array 1A is disposed so as to share an optical axis plane with a corresponding cylindrical lens of the cylinder array 1B.

As shown in FIG. 1B, each of the cylinder arrays 2A and 2B is constituted by seven equivalent cylindrical lenses. The optical axis plane of each cylindrical lens is parallel to the yz plane, and the generatrix of the cylindrical surface is parallel to the y axis. The cylindrical lens arranged in this way,
The edge surfaces are closely attached to each other and are arranged parallel to the x-axis (along the xy plane). The cylinder array 2A is arranged on the incident side (left side in the figure) of the cylinder array 1A, and the cylinder array 2B is arranged between the cylinder arrays 1A and 1B. Further, each cylindrical lens of the cylinder array 2A is disposed so as to share an optical axis plane with a corresponding cylindrical lens of the cylinder array 2B.

A converging lens 3 is arranged on the emission side of the cylinder array 1B. The optical axis of the converging lens 3 is parallel to the z-axis.

A spatial filter section SF is arranged in front of the homogenizing section HN. The spatial filter section SF has a configuration in which a light shielding plate 6 is arranged between equivalent cylindrical lenses 5A and 5B. Cylindrical lens 5
The generatrix of the cylindrical surfaces of A and 5B is parallel to the y-axis, and the optical axis surface is parallel to the yz-plane. In addition, the cylindrical lens 5A
And 5B coincide with the optical axis plane of the central cylindrical lens of the cylinder arrays 2A and 2B.

The interval between the cylindrical lenses 5A and 5B is twice as long as the focal length, and the light shielding plate 6 is arranged at the focal position. The light shielding plate 6 is provided with a slit 6a along an intersecting line with the optical axis plane of the cylindrical lenses 5A and 5B.

Referring to FIG. 1A, the state of propagation of a light beam in the yz plane will be described. In the yz plane,
Since the cylindrical lenses 5A and 5B and the cylinder arrays 2A and 2B are equivalent to simple flat plates, they do not affect the convergence and divergence of the light beam. A parallel light beam 10 having an optical axis parallel to the z-axis enters the spatial filter SF. The incident light beam 10 has a light intensity distribution that is strong at the central portion and weak at the peripheral portion, as shown by a curve 21y, for example.

The parallel light beam 1 transmitted through the spatial filter SF
1 is transmitted through the cylinder array 2A,
Incident on. The incident light beam is divided into seven convergent light beams corresponding to each cylindrical lens by the cylinder array 1A. In FIG. 1A, only the light beams at the center and both ends are representatively shown. Each of the seven convergent light beams has a light intensity distribution indicated by curves 21ya to 21yg. The light beam converged by the cylinder array 1A is converged again by the cylinder array 1B.

The seven convergent light beams 12 converged by the cylinder array 1B converge in front of the converging lens 3, respectively. This condensing position is closer to the lens than the focal point on the incident side of the converging lens 3. Therefore, the light transmitted through the converging lens 3
The two light beams become divergent light beams and overlap on the homogenizing surface 4. Irradiate the homogenized surface 4 7
The light intensity distribution of the two light beams in the y-axis direction is equal to the distribution obtained by extending the light intensity distributions 21ya to 21yg in the y-axis direction. Since the light intensity distributions 21ya and 21yg, 21yb and 21yd, and 21yc and 21ye have respective inverted relations in the y-axis direction, the light intensity distribution obtained by superimposing these light fluxes is uniform as shown by the solid line 22y. Approach distribution.

Referring to FIG. 1B, the state of propagation of a light beam in the xz plane will be described. The incident light beam 10 enters the cylindrical lens 5A. The incident light beam 10 is
For example, as shown by a curve 21x, the light intensity distribution is strong in the central part and weak in the peripheral part in the x-axis direction. The light beam converged by the cylindrical lens 5A ideally passes through the focal point on the optical axis plane (actually, a straight line parallel to the generating line of the cylindrical surface of the cylindrical lens), and enters the cylindrical lens 5B.

The light is converged by the cylindrical lens 5B to form a parallel light beam 11. The parallel light beam 11 has a light intensity distribution obtained by inverting the curve 21x in the x-axis direction.

The incident light beam 10 usually includes noise components other than components parallel to the optical axis. The noise component is generated by a light source having a finite size, scattering by dust in the air, and the like. Even if the noise component of the incident light beam 10 is converged by the cylindrical lens 5A, it does not pass through the focal point. A noise component traveling at a certain angle or more from the optical axis is shielded by the light shielding plate 6 and does not reach the cylindrical lens 5B. Therefore, the parallel light beam 11 converged by the cylindrical lens 5B becomes a light beam with less noise component than the incident light beam 10.

The parallel light beam 11 enters the cylinder array 2A. The parallel light beam 11 is divided into seven convergent light beams corresponding to each cylindrical lens by the cylinder array 2A. In FIG. 1B, only the light beams at the center and both ends are representatively shown. Each of the seven convergent light beams has a light intensity distribution obtained by inverting the curves 21xa to 21xg in the x-axis direction. In the xz plane, since the cylinder arrays 1A and 1B are equivalent to a simple flat plate, they do not affect the convergence and divergence of the light beam.

Each light beam is condensed in front of the cylinder array 2B, and enters the cylinder array 2B as a divergent light beam. Each ray bundle incident on the cylinder array 2B exits at a certain exit angle, and enters the converging lens 3.

Each of the seven light beams transmitted through the converging lens 3 becomes a convergent light beam and overlaps on the homogenizing surface 4. X of seven ray bundles illuminating the homogenized surface 4
The light intensity distribution in the axial direction approaches a uniform distribution as shown by a solid line 22x as in the case of FIG. Since the noise component of the parallel light beam 11 incident on the homogenized portion HN is smaller than the noise component of the incident light beam 10, the top flat ratio of the light intensity distribution in the x-axis direction on the homogenized surface 4 can be improved.

The light irradiation area on the homogenizing surface 4 has a linear shape that is long in the y-axis direction and short in the x-axis direction. By using the beam homogenizer, it is possible to irradiate a long axial region in the y-axis direction almost uniformly.

Next, the effect when the spatial filter SF is provided will be described. FIG. 2 shows a light intensity distribution in the x-axis (short axis) direction on the homogenized surface. FIG. 2 (A)
In the case where the spatial filter SF is not provided, FIG.
This shows a case where a spatial filter SF is provided. Spatial filter S
When F was not provided, the top flat ratio was 0.66, whereas when the spatial filter SF was provided,
0.79.

The cylindrical lenses 5A and 5B used had a curvature of 138 mm and a focal length of 285.
mm, and the slit width of the light shielding plate 6 is 0.5 mm. Further, when the spatial filter SF was provided, the integrated value of the light intensity was reduced to 91% as compared with the case where the spatial filter SF was not provided. this is,
This is because the noise component of the incident light was shielded by the light shielding plate and did not reach the homogenized surface.

When the width of the slit 6a is reduced, the top flat ratio is improved, but the light intensity is reduced. Slit 6a
, The suitable top flat ratio and light intensity can be obtained.

In FIG. 1, a case has been described in which only the noise component related to the xz plane is reduced. However, another spatial filter may be arranged to reduce the noise component related to the yz plane. However, when the irradiation area on the homogenized surface has a shape that is long in one direction, the top flat ratio of the light intensity distribution in the long axis direction is hardly affected by the noise component of the incident light beam. Therefore, it is effective to provide a spatial filter that reduces noise components in a plane including the minor axis direction of the light irradiation area and the optical axis of the incident light beam.

Further, a spherical lens is used instead of the cylindrical lenses 5A and 5B shown in FIG.
A light-shielding plate having a pinhole may be used instead of the light-shielding plate 6 having a. In this case, one spatial filter x
It is possible to reduce noise components in both the z plane and the yz plane.

However, when the intensity of the incident light beam is high and the intensity at the condensing point of the spatial filter exceeds the ionization threshold value in the air, as described with reference to FIG. It is preferable to use a spatial filter combined with a light shielding plate.

In FIG. 1, the case where the two cylindrical lenses 5A and 5B of the spatial filter SF are equivalent, that is, the case where they have the same focal length has been described, but two cylindrical lenses having different focal lengths may be used. In this case, the distance between the cylindrical lenses is a total distance of the focal lengths of the two cylindrical lenses, and the light shielding plate 6 is disposed at a common focal position of the two cylindrical lenses.

Next, a beam homogenizer according to another embodiment of the present invention will be described with reference to FIG. FIG. 1 illustrates the case where the spatial filter SF is arranged on the incident side of the homogenizing portion. However, in FIG. 3, a light shielding plate 7 is arranged between the cylinder arrays 2A and 2B instead of the spatial filter SF. Other configurations are the same as those in FIG.

The distance between the light shielding plate 7 and the cylinder array 2A is equal to the focal length of each cylindrical lens constituting the cylinder array 2A. The light shielding plate 7 has seven slits 7 along the line of intersection with the optical axis plane of each cylindrical lens.
a is formed.

Light traveling parallel to the optical axis of the incident light beam 10 passes through the slit 7a, but noise components traveling in a direction deviated by a predetermined angle or more with respect to the optical axis of the incident light beam 10 are shielded. The light is shielded by the plate 7. That is, the light passing through the light shielding plate 7 becomes a light beam in which the noise component of the incident light beam 10 is reduced. Therefore, similarly to the case of FIG. 1, the top flat ratio in the x-axis direction can be improved.

Further, since there is no need to dispose a spatial filter outside the homogenizing portion, the size of the apparatus can be reduced. When there is a gap between the edge surfaces of the cylindrical lenses of the cylinder array 2A, a part of the incident light beam travels straight through this gap. The straight light prevents uniform light intensity distribution. Further, light scattered on the edge surface also becomes a noise component and hinders uniform light intensity. The light shielding plate 7 also has the function of shielding such light.

FIG. 4A is a front view of the light shielding plate 7 of FIG. 7 slits 7a in a rectangular plate made of stainless steel
Are formed at equal intervals.

FIG. 4B is a dashed line B4 of FIG.
The sectional view in -B4 is shown. The light shielding plate 7 includes two stainless plates 7A and 7B each having seven slits,
The slits are configured to be in close contact with each other so as to correspond to each other. The slit width provided in the stainless plates 7A and 7B is wider than the width of the slit 7a in FIG. By shifting the stainless plates 7A and 7B in a direction perpendicular to the longitudinal direction of the slit, the width of the slit 7a can be changed. The top flat ratio and the light intensity distribution can be adjusted by changing the width of the slit 7a.

FIG. 3 illustrates the case where only the light shielding plate 7 having a slit parallel to the y-axis is disposed between the cylinder arrays 2A and 2B. As shown in FIG. 1A, when the light beam does not converge between the cylinder arrays 1A and 1B in the yz plane, a light-shielding plate cannot be arranged between the cylinder arrays 1A and 1B. For example, another light shielding plate may be arranged at the light condensing position.

FIG. 5 shows a case where another light shielding plate 8 is arranged between the cylinder arrays 1A and 1B. The light-shielding plate 8 has the same configuration as the light-shielding plate 7, and is disposed at a light condensing position by the cylinder array 1 </ b> A so that each slit is parallel to the x-axis. In FIG. 3, the light shielding plate 7 is arranged outside the pair of the cylinder arrays 1A and 1B.
It is arranged between the cylinder arrays 1A and 1B. However, the position of the light shielding plate 7 is determined by the relative relationship with the cylinder array 2A, and the relative positional relationship with the cylinder array 1A is not essential.

By arranging the light shielding plates 7 and 8, noise components of the light beam in the yz plane and the xz plane are reduced, so that the light intensity distribution in the irradiation area can be made uniform.

Next, a laser annealing apparatus using the beam homogenizer shown in FIG. 1 or 3 will be described.

FIG. 6 is a schematic plan view of the laser annealing apparatus. The housing 50 includes a processing chamber 51, a transport chamber 52, a loading chamber 53, a loading chamber 54, a homogenizer 42, a CCD camera 58, and a video monitor 5.
9 is attached.

The processing chamber 51 and the transfer chamber 52 are connected via a gate valve 55, and the transfer chamber 52 and the carry-in chamber 53, and the transfer chamber 52 and the carry-out chamber 54 are connected via gate valves 56 and 57, respectively. I have. Processing chamber 51, loading chamber 53
The vacuum pump 61,
62 and 63 are attached, and the inside of each chamber can be evacuated.

A transfer robot 64 is housed in the transfer chamber 52. The transfer robot 64 transfers the processing substrate between the processing chamber 51, the loading chamber 53, and the unloading chamber 54.

On the upper surface of the processing chamber 51, a window 60 for transmitting laser light is provided. The pulsed laser beam output from the excimer laser device 41 passes through the attenuator 46 and enters the beam homogenizer 42 shown in FIG. 1 or FIG. The homogenizer 42 makes the cross section of the laser beam into an elongated shape. Homogenizer 42
Passes through the elongated window 60 corresponding to the cross-sectional shape of the laser light, and irradiates the processing substrate in the processing chamber 51. The relative position between the homogenizer 42 and the processing substrate is adjusted so that the surface of the processing substrate coincides with the homogenized surface.

The processing substrate moves in parallel in a direction orthogonal to the long axis direction of the window 60. By moving the processing substrate at such a speed that a part of the irradiation area for one shot overlaps a part of the irradiation area in the previous shot, a large area on the surface of the processing substrate can be irradiated. Processing substrate surface is CC
The substrate surface being photographed by the D camera 58 and being processed can be observed on the video monitor 59.

Excimer laser device 41, homogenizer 4
2. The operations of the transfer robot 64 and the gate valves 55 to 57 are controlled by the control device 65.

FIG. 7 is a schematic diagram showing an optical system of the laser annealing apparatus shown in FIG. The laser beam output from the excimer laser device 41 passes through the attenuator 46, is reflected by the turn mirrors 47 and 48, and enters the homogenizer 42. The laser beam that has passed through the homogenizer 42 is reflected by the turn mirror 49, passes through the glass window 60, and is introduced into the processing chamber 51.

The homogenizer 42 and the turn mirror 49
The parallel movement along the optical axis of the incident laser light can be performed while maintaining the mutual relative positional relationship. Turn mirror 4
When the laser beam reflected at 9 is at position c in the figure, the processing substrate 51 in the processing chamber 51 is irradiated with laser light.

In the processing chamber 51, a power meter 7 is provided.
2 are arranged. When the laser beam is moved to the position d, the laser beam is irradiated on the power meter 72, and the intensity of the laser beam can be measured. Further, a power meter 73 is also provided outside the processing chamber 51, and by moving the laser beam to the position b, the intensity of the laser beam before being introduced into the processing chamber 51 can be measured.

Outside the processing chamber 51, a beam profiler 74 in which optical sensors are linearly arranged is arranged. By moving the laser beam to the position a and irradiating the laser beam to the beam profiler 74, it is possible to measure the intensity distribution of the laser beam having a linear cross-sectional shape in the longitudinal direction in the cross section.

A power meter 70 is arranged between the attenuator 46 and the turn mirror 47, and a power meter 71 is arranged between the turn mirror 48 and the homogenizer 42. The power meters 70 and 71 can measure the intensity of the laser beam at that position.

By comparing the intensity of the laser beam detected by the power meters 70 to 73 with the normal value at each position, the deterioration state of each optical component can be known. Further, by analyzing the detection signal from the beam profiler 74, the normality of the intensity distribution in the major axis direction of the cross section of the laser beam can be confirmed.

As described in the embodiment of FIG. 1 or FIG. 3, by providing the homogenizer 42 with a spatial filter, the top flat ratio of the light intensity distribution can be compared even if the width of the linear light irradiation area is 1 mm or less. Can be kept high. By increasing the top flat ratio, the entire surface of the substrate can be more uniformly irradiated with laser light.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0061]

As described above, according to the present invention,
The light intensity distribution on the homogenized surface of the light beam transmitted through the beam homogenizer can be made more uniform.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a beam homogenizer according to an embodiment of the present invention.

FIG. 2A is a graph showing a light intensity distribution in a light irradiation area homogenized by a conventional beam homogenizer, and FIG. 2B is a graph showing light homogenized by the beam homogenizer shown in FIG. It is a graph which shows the light intensity distribution of an irradiation area.

FIG. 3 is a sectional view of a beam homogenizer according to another embodiment of the present invention.

4 is a front view and a sectional view of a light shielding plate of the beam homogenizer shown in FIG.

FIG. 5 is a sectional view of a beam homogenizer according to another embodiment of the present invention.

FIG. 6 is a plan view schematically showing a laser annealing apparatus using the beam homogenizer shown in FIG. 1 or FIG.

FIG. 7 is a diagram showing an optical system of the laser annealing apparatus shown in FIG.

[Explanation of symbols]

 Reference Signs List 1A, 1B, 2A, 2B Cylinder array 3 Converging lens 4 Homogenized surface 5A, 5B Cylindrical lens 6, 7, 8 Light shield plate having slit 10 Incident light beam 11 Parallel light beam 12 Divided light beam 21x, 21y, 22x, 22y Light intensity distribution 41 Excimer laser device 42 Homogenizer 46 Attenuator 47, 48, 49 Turn mirror 50 Housing 51 Processing chamber 52 Transport chamber 53, 54 Loading / unloading chamber 55-57 Gate valve 58 CCD camera 59 Video monitor 60 Window 61, 62 , 63 Vacuum pump 64 Transfer robot 65 Controller 70, 71, 72, 73 Power meter

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the plurality of first cylindrical lenses include:
A first cylinder array arranged along a first virtual plane perpendicular to the optical axis plane, with the generating lines of the cylindrical surfaces and the optical axis planes being parallel to each other, and a plurality of second cylindrical arrays A second cylinder array in which the lenses are arranged along a second virtual plane parallel to the first virtual plane, with the generatrix of the cylindrical surfaces and the optical axis planes being parallel to each other; Each second cylindrical lens has a common optical axis plane with the corresponding first cylindrical lens, and the light beam transmitted through the first cylindrical lens is incident on the corresponding second cylindrical lens. A converging optical system for converging a light beam transmitted through the second cylinder array; and a converging optical system disposed between the first cylinder array and the second cylinder array. Beam homogenizer having a first light-shielding plate that first each of the cylindrical lenses of the slit along the line of intersection of the optical axis surfaces constituting the Ndaarei is formed. 2. A plurality of third cylindrical lenses arranged on the incident side of the converging optical system, the generating lines of the respective cylindrical surfaces and the optical axis surfaces being parallel to each other, and A third cylinder array arranged along a third virtual plane parallel to the virtual plane, wherein each optical axis surface of the third cylindrical lens is an optical axis surface of the first and second cylinder arrays. A third cylinder array, which is orthogonal to the third cylinder array, and which is disposed on the exit side of the third cylinder array and on the entrance side of the converging optical system, and wherein a plurality of fourth cylindrical lenses are connected to each other with respect to the generating lines of the respective cylindrical surfaces. A fourth cylinder array having axial surfaces parallel to each other and arranged along a fourth virtual plane parallel to the first virtual plane,
Each fourth cylindrical lens is arranged between the third cylinder array and the fourth cylinder array, the fourth cylinder array having a common optical axis plane with the corresponding third cylindrical lens. 2. The beam homogenizer according to claim 1, further comprising: a second light blocking plate having a slit formed along a line intersecting with an optical axis surface of each of the third cylindrical lenses constituting the third cylinder array.