JP3363835B2 - Return light removal method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser annealing device of a type for projecting a mask image on a work and other laser processing devices.

[0002]

2. Description of the Related Art In a laser annealing apparatus, a linear beam of annealing light is irradiated onto a substrate on which an amorphous Si film is formed by using a beam shaping optical system called a homogenizer, and this long beam is irradiated onto the substrate. The amorphous Si film on the substrate is uniformly polycrystallized by uniaxial scan irradiation in the minor axis direction.

[0003]

However, since the above-described laser annealing apparatus uses a long beam with low accuracy, it is not suitable for the purpose of highly accurately laser annealing a target region.

Here, it is considered that high precision laser annealing can be performed by illuminating a mask having an elongated rectangular opening with annealing light and reducing and projecting the opening image of the mask onto the substrate, but returning from the mask. It is necessary to prevent light. That is, it is necessary to prevent unintended reflected light from the mask (light not used for processing) from condensing on the optical elements on the light source side and damaging them.

Therefore, an object of the present invention is to provide a laser annealing apparatus and other laser processing apparatus which can surely prevent the return light from the mask as described above.

[0006]

In order to solve the above problems, a laser processing apparatus of the present invention is a laser processing apparatus for processing a work by projecting an image of a mask illuminated by a laser beam onto the work. Therefore, the laser light is prevented from traveling backward from the mask by the reflecting member which is arranged on the incident surface side of the mask and which has the reflecting surface forming a predetermined angle with respect to the mask.

In this case, since the laser light is prevented from traveling backward from the mask by the reflecting member having the reflecting surface on the incident surface side of the mask that makes a predetermined angle with respect to the mask, the unintended reflected light from the mask is reflected. Can be prevented from damaging other optical elements on the light source side.

In a preferred aspect of the above apparatus, the reflecting member has a reflecting surface having a shape corresponding to the shape of the light transmitting portion of the mask, and the laser light incident on the periphery of the light transmitting portion excluding the light transmitting portion. Block off.

In this case, the shape of the reflecting surface is used to block the laser light incident on the periphery of the light transmitting portion excluding the light transmitting portion, so that the light transmitting portion of the mask can be completely illuminated and It is possible to effectively prevent return light due to reflected light around the light transmitting portion.

[0010]

1 is a diagram conceptually explaining the structure of a laser annealing apparatus which is an embodiment of a laser processing apparatus according to the present invention.

This laser annealing apparatus is for heat-treating a work W in which a semiconductor thin film such as amorphous Si is formed on a glass substrate. Excimer laser or other laser light AL for heating the semiconductor thin film is generated. A laser light source 10 for irradiating, an irradiation optical system 20 for making the laser light AL linear (fine rectangle) and incident on the work W with a predetermined illuminance, and the work W on which the work W is mounted.
And a process stage device 30 capable of smoothly moving in translation in the XY plane and rotating about the Z axis.

The irradiation optical system 20 receives the incident laser light AL.
And a homogenizer 2 which is a beam shaping means for making a desired cross-sectional shape.
From a mask assembly 22 incorporating a mask forming a slit for narrowing the laser beam AL passing through 1 into a narrow rectangular beam, and an imaging lens or projection lens 23 for reducing and projecting the slit image of the mask onto the work W. Become. Of these, the mask assembly 22 is supported by the mask stage device 40 in an exchangeable manner, and is driven by the mask stage device 40 to smoothly translate in the XY plane and rotate about the Z axis. It is movable.

The process stage device 30 is housed in the process chamber 50, and can support the work W in the process chamber 50 and move it appropriately with respect to the irradiation optical system 20. The laser light AL from the irradiation optical system 20 is irradiated onto a desired region on the work W supported at a proper position in the process chamber 50 through the window 50a.

Positions on both sides of the projection lens 23 are a light projecting device 61 for injecting the inspection light onto the surface of the work W through the window 50a, and a light receiving device 62 for detecting the light reflected from the surface of the work W. A detection device and the like are installed so that the work W on the process stage device 30 can be precisely aligned with the irradiation optical system 20.

Here, the mask stage device 40 and the projection lens 23 have a pedestal 65 extending from the process chamber 50.
It is suspended and fixed to. Although illustration is omitted, the laser light source 10 and the homogenizer 21 are also mounted on the pedestal 6
It is indirectly fixed to 5.

FIG. 2 is a diagram for explaining the configuration of the irradiation optical system 20. The homogenizer 21 on which the laser light AL from the laser light source 10 is incident is composed of first to fourth cylindrical lens arrays CA1 to CA4 for independently controlling vertical and horizontal beam sizes, and a condenser lens 21a for condensing. . Here, the first and third cylindrical lens arrays CA1 and CA3 have a curvature in a cross section parallel to the plane of the drawing, and the second and fourth cylindrical lens arrays C
A2 and CA4 have a curvature in a cross section perpendicular to the paper surface.

The laser light AL from the homogenizer 21 is
The light enters the mask assembly 22 through the turn mirror 25. The mask assembly 22 is illuminated by the laser light AL and has a pattern on the lower surface 80 for irradiating the work W, and the laser light AL around the light transmitting portion (that is, the opening) of the pattern of the mask 22a. Reflecting member 2 that prevents incident light from entering and causing return light
2b and a field lens 22c for adjusting the pupil position. Here, the reflection member 22b is arranged so as to be inclined with respect to the mask 22a, and the upper surface 81 of the reflection member 22b is arranged.
The reflected light RL from is emitted in a direction deviated from the optical axis OA, and is incident on the beam damper 26 via the field lens 22c. The field lens 22c can be considered as a part of the homogenizer 21.

The laser light AL that has passed through the mask 22a is
It enters the projection lens 23. The projection lens 23 reduces and projects, that is, forms an image of, a slit image, which is a light transmission pattern formed on the mask 22a illuminated by the laser light AL, on the processed surface of the work W.

FIG. 3 is a side sectional view for explaining the structure of the mask stage device 40 and the support of the mask assembly 22. The mask stage device 40 moves the mask assembly 22 to the X position.
An X-axis stage portion 41 that translates in the axial direction, a Y-axis stage portion 42 that translates the mask assembly 22 together with the X-axis stage 41 in the Y-axis direction, and the Z-axis stage 41 and the Y-axis stage portion 42. Rotate around θ
The shaft stage 43. The X-axis stage 41 and the Y-axis stage unit 42 are slidably connected via a slide guide 45. On the other hand, the Y-axis stage unit 42 and the θ-axis stage 43 are rotatably connected via a bearing 46.

The mask assembly 22 has a tapered outer surface TP1 which is tapered downward on the outer periphery of a cylindrical mask holder body 22d which holds the mask 22a, the reflecting member 22b and the field lens 22c. On the other hand, the X-axis stage 4
1 also has a taper outer surface TP in the circular opening provided in the bottom portion 41a.
It has a tapered inner surface TP2 that fits into 1. As a result, the taper outer surface TP1 and the taper inner surface TP2 are fitted to each other by simply inserting the mask assembly 22 from the insertion opening 40a of the X-axis stage 41 into the circular opening provided in the bottom portion 41a, and the taper outer surface TP1 is fitted to the X-axis stage 41. Thus, the mask assembly 22 can be precisely aligned. Further, the mask assembly 22 is urged downward with a constant force by an annular fixing nut 25 screwed into the bottom portion 41a of the X-axis stage 41.

The mask assembly 22 and the fixing nut 25 are attached to the bottom portion 41 of the X-axis stage 41 by using the attachment jig 70.
It is attached to a. The mask assembly 22 has a recess 22g that can be engaged with a hook-shaped hooking member 71 provided on the lower surface of the attachment jig 70, and moves up and down with the operation of the attachment jig 70. As a result, the bottom portion 41 of the X-axis stage 41 is
The mask assembly 22 can be easily and surely inserted into the circular opening provided in a. Further, the fixing nut 25 also has a recess 25g that can be engaged with the hook member 71 of the attachment jig 70.
And moves up and down with the operation of the attachment jig 70.
Accordingly, the fixing nut 25 can be screwed from above the mask assembly 22 inserted into the bottom portion 41a of the X-axis stage 41 to easily and reliably fix the mask assembly 22.

FIG. 4 is a diagram for explaining the shapes of the mask 22a and the reflecting member 22b. Here, FIG. 4A is a plan view of the mask 22 a, and FIG. 4B is a reflection member 22.
It is a top view of b. A pair of facing notches 91 for positioning are formed in the mask 22a, and the reflecting member 22 is formed.
Also in b, a pair of facing notches 92 for positioning are formed, and roughly positioning is possible between them. The mask 22a and the reflecting member 22b respectively have irradiation areas IA1 and IA2 for irradiating the laser beam at their centers. As will be described later, a plurality of rectangular slits are formed in both of the irradiation areas IA1 and IA2 as light transmitting portions. The mask 22a and the reflection member 22b can be relatively aligned with each other by an adjusting screw (not shown) provided on the mask holder body 22d.
1, IA2 can be matched exactly.

FIG. 5 is a diagram schematically illustrating the shapes of the rectangular slits formed in the irradiation areas IA1 and IA2 set in the mask 22a and the reflecting member 22b. here,
FIG. 5A shows the case of the mask 22a, and FIG.
Shows the case of the reflection member 22b. In the irradiation area IA1 on the mask 22a, a plurality of rectangular slits SS to be reduced and projected onto the work W are formed. As a result, a pattern having a contrast of light and dark is formed on the work W, but a portion corresponding to the rectangular slit SS is a bright portion. On the other hand, the irradiation area I on the reflecting member 22b
In A2, these rectangular slits SS are formed so as not to block the laser light entering the rectangular slits SS on the mask 22a side.
A plurality of rectangular slits LS that are slightly larger in size and have the same pitch are formed.

FIG. 6 shows the mask 22a shown in FIGS.
FIG. 6 is a side cross-sectional view showing a state in which the irradiation area IA1 and the irradiation area IA2 of the reflecting member 22b are aligned. The mask 22a is made of a substantially parallel plate quartz glass substrate 83, and a light shielding pattern 84 made of a dielectric layer or a metal layer is formed on the lower surface 80 side thereof. The light-shielding pattern 84 is a rectangular slit SS of FIG.
The laser light incident on these rectangular slits SS is transmitted, but the laser light incident on the periphery of the rectangular slit SS is reflected.

The reflecting member 22b is also made of a substantially parallel plate quartz glass substrate 85, and a reflecting pattern 86 made of a dielectric layer or a metal layer is formed on the upper surface 81 side thereof. The reflection pattern 86 has the rectangular slits LS shown in FIG. 5B as openings, and the light incident on these rectangular slits LS is transmitted, but the light incident on the periphery of the rectangular slit SS is reflected. That is, only the light PL that has passed through the rectangular slit SS of the reflection pattern 86 is incident on the mask 22a. Here, the reflected light from the reflection pattern 86 deviates from the optical axis as described above, enters the beam damper 26 shown in FIG. 2, and is absorbed there.

The light-shielding pattern 84 provided on the mask 22a may be of a type that absorbs incident light, but the light-shielding pattern 84 is distorted due to heat generated by absorption, or the light-shielding pattern 84 and the mask 22a itself are damaged. It is of a type that reflects incident light in order to prevent it from being given. When the light-shielding pattern 84 is of the reflection type as described above, if the above-described reflection member 22b is not provided, the light reflected by the light-shielding pattern 84 flows back as return light, and an optical element on the laser light source 10 side, for example, The condenser lens 21a of the homogenizer 21 may be damaged. In particular, when the aperture ratio of the light shielding pattern 84 is small, the ratio of the reflected light to the transmitted light is large, so that the adverse effect of the return light as described above is likely to occur. For this reason, in this apparatus, by disposing the reflecting member 22b that is disposed above the mask 22a and tilted with respect to the mask 22a, the laser light is optically transmitted before the laser light is incident on the unnecessary portion of the mask 22a. It is deflected outside the system and absorbed by the beam damper 26.

At this time, it is conceivable to tilt the mask 22a itself, but the projected image of the mask 22a may be blurred or changed depending on the tilted position. Especially, when the object depth of the projection lens 23 is shallow, the work W This will reduce the accuracy of the slit image formed above. Therefore, in this apparatus, the reflecting member 22b is provided separately from the mask 22a.

FIG. 7 shows the mask 22a shown in FIGS.
It is a top view explaining the arrangement relation of the rectangular slit LS on the side and the rectangular slit SS on the side of the reflecting member 22b. In this way, when the rectangular slit SS is arranged inside the rectangular slit LS, the reflecting member 22b does not block the laser light incident on the rectangular slit SS of the mask 22a, but the laser incident on the periphery of the rectangular slit SS. Since the light is almost blocked, it is possible to suppress the generation of return light from the mask 22a to the laser light source 10 side.

The operation of the laser annealing apparatus shown in FIGS. 1 and 2 will be described below. First, the work W is transported and placed on the process stage device 30 of the laser annealing device. Next, the work W on the process stage device 30 is aligned with the projection lens 23 of the irradiation optical system 20. Next, the mask stage device 40 is driven to align the mask assembly 22 with the projection lens 23. Next, while moving the mask 22 assembly, the laser light AL from the laser light source 10 is incident on a predetermined area on the work W as a reduced rectangular beam.
A thin film such as amorphous Si, which is an amorphous semiconductor thin film, is formed on the work W, and a predetermined region of the semiconductor is annealed and recrystallized by irradiation and scanning with a rectangular beam, which has excellent electrical characteristics. A semiconductor thin film can be provided. The laser annealing as described above is repeated in a plurality of predetermined regions provided on the work W, and the semiconductor thin film is annealed in the plurality of predetermined regions.

At this time, in the mask assembly 22, a mask 22a is formed on the incident surface side of the mask 22a having slits, and a reflecting member 2 inclined by a predetermined angle with respect to the mask 22a.
2b is incorporated, the laser beam A is reflected by the reflection pattern 86 which is a reflection surface formed on the reflection member 22b.
It is possible to prevent L from moving backward from the mask 22a and prevent unintended reflected light from the mask 22a from damaging the homogenizer 21 and the like on the light source side.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments.
For example, in the above laser annealing apparatus, the structure of the homogenizer 21 is not limited to that shown in FIG. 2, and the homogenizer 21 itself may be unnecessary depending on the application.

Further, the projection lens 23 is not limited to the one for reduction projection, but may be one for enlargement projection, and the projection lens 23 itself becomes unnecessary depending on the application.

Further, although the reflecting member 22b is formed by the parallel plate quartz glass substrate 85, the quartz glass substrate 85 is formed into a wedge shape, and the upper surface of the quartz glass substrate 85 and the mask 22 are formed.
The upper surface or the lower surface of a may have a certain inclination.
Further, the reflection member 22b may be formed of a metal plate, quartz glass, or the like to form an actual opening in itself.

The tilt angle of the reflection member 22b with respect to the mask 22a is generally set to several degrees to several tens of degrees although it depends on the arrangement of the optical system constituting the laser annealing device. Is preferable from the viewpoints of reliable removal and optical design.

Further, although the above-mentioned apparatus anneals the semiconductor layer on the work W by using the laser beam AL, if the structures of the laser light source 10 and the irradiation optical system 20 are appropriately changed, the semiconductor material can be changed. It is possible to provide a pulse laser processing device or the like that enables not only annealing but also modification, cutting and welding of various materials.

[0036]

As is clear from the above description, according to the laser processing apparatus of the present invention, the reflecting member which is arranged on the incident surface side of the mask and has the reflecting surface forming a predetermined angle with respect to the mask is used. Since the laser light is prevented from traveling backward from the mask, it is possible to prevent unintended reflected light from the mask from damaging other optical elements on the light source side.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a laser annealing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an optical configuration of the apparatus of FIG.

FIG. 3 is a diagram for explaining the structure of a mask stage device that constitutes the device of FIG.

FIG. 4A is a diagram illustrating a structure of a mask,
(B) is a figure explaining the structure of a reflection member.

5A is a diagram illustrating a slit formed in a mask, and FIG. 5B is a diagram illustrating a slit formed in a reflecting member.

FIG. 6 is a side view illustrating alignment between a mask and a reflecting member.

FIG. 7 is a plan view illustrating alignment between a mask and a reflecting member.

[Explanation of symbols]

10 Laser light source 20 Irradiation optical system 21 Homogenizer 22 Mask assembly 22a mask 22b reflective member 22c field lens 22d mask holder body 23 Projection lens 25 fixing nut 26 beam damper 30 process stage equipment 40 Mask stage device 50 process chambers 50a window 65 stand 83 Quartz glass substrate 84 light-shielding pattern 85 Quartz glass substrate 86 reflection pattern LS rectangular slit OA optical axis SS rectangular slit W work

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Claims (2)

(57) [Claims] 1. A laser processing apparatus for processing a work by projecting an image of a mask illuminated by a laser beam onto the work, the laser processing device being arranged on an incident surface side of the mask and with respect to the mask. A laser processing apparatus for preventing the laser light from traveling backward from the mask by a reflecting member having a reflecting surface forming a predetermined angle. 2. The reflection member has a reflection surface having a shape corresponding to the shape of the light transmitting portion of the mask, and blocks the laser light incident on the periphery of the light transmitting portion excluding the light transmitting portion. The laser processing apparatus according to claim 1, wherein: