JP2001044136A - Precision laser beam irradiation apparatus and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-precision and high efficiency laser beam machining device and a method. SOLUTION: Firstly, the laser beam AL from a laser light source 10 is made incident on a work W, while a process stage 30 is moved at a high speed in the X-axis direction with respect to a projecting optical system 20. At movement of the work W, the Y-direction displacement of the work W is compensated by synchronously moving a mask stage 70 with high accuracy by an amount corresponding the amount of the Y-direction positional error of the work W stored in a main controller 100. In addition, the X-direction speed variation of the work W is compensated, by synchronously moving the stage 70 through the amount corresponding to the amount of the X-direction positional error of the work W stored in the controller 100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus and method used for laser annealing and the like, and more particularly to a control mechanism for precisely and efficiently irradiating a laser beam.

[0002]

2. Description of the Related Art As a laser processing apparatus, for example, there is a laser annealing apparatus which irradiates a precisely shaped laser beam onto a substrate on which an amorphous Si film is formed, and polycrystallizes the amorphous Si film.

In such a laser annealing apparatus, first, a process stage on which a substrate is mounted is moved to a laser beam irradiation position using an alignment function. Next, using the focusing and tilt correction functions, the height of the substrate at the irradiation position is adjusted to correct the tilt of the substrate. Thereafter, the laser beam is scanned by, for example, precisely driving only the mask stage while keeping the process stage stationary, and then moving and stopping the process stage again. Thereafter, the entire surface of the substrate is irradiated with a laser beam by repeating scanning of the mask stage and movement of the process stage.

[0004]

The above-described apparatus can irradiate a laser beam onto a substrate with high accuracy. However, since the process stage and the mask stage are driven alternately, each time the process stage moves. Alignment work is required, so that it takes time to irradiate the entire surface of the substrate, resulting in poor process efficiency.

[0005] Therefore, an object of the present invention is to provide a laser processing apparatus and method which are highly accurate and have high process efficiency.

[0006]

In order to solve the above-mentioned problems, a laser processing apparatus according to the present invention comprises: an irradiation optical system for projecting an image of a mask illuminated by a laser beam onto a workpiece;
A process stage device for placing the workpiece and moving the workpiece with respect to the irradiation optical system, and an error amount corresponding to a deviation from a target position when the workpiece is moved by the process stage device. The storage device includes a storage device that stores in advance, and a mask driving device that displaces the mask based on the error amount stored in the storage device.

In this case, since the workpiece is moved by the process stage device, rapid laser processing becomes possible, and the process efficiency can be increased. Further, since the mask driving device displaces the mask based on the error amount stored in the storage device, the error amount when the workpiece is moved by the process stage is corrected, and the mask image is accurately projected on the target position. And the laser processing can be precise.

Further, according to a preferred embodiment of the above device,
The apparatus further includes a position sensor that detects a tilt and a focus position of the workpiece when irradiating the laser light, and the mask driving device corrects the tilt and the focus position of the workpiece in real time based on an output of the position sensor. Features.

In this case, since the mask driving device corrects the inclination and the focal position of the workpiece in real time based on the output of the position sensor, it is possible to perform laser processing with higher precision.

Further, according to the laser processing method of the present invention, before the image of the mask illuminated by the laser beam is projected on the workpiece by the irradiation optical system, the process stage apparatus for mounting the workpiece is irradiated with the irradiation optical system. Measuring the error amount corresponding to the deviation from the target position while moving with respect to, and storing the error amount, and irradiating the laser light, in synchronization with the movement of the workpiece by the process stage device And displacing the mask based on the stored error amount.

In this case, since the object to be processed is moved by the process stage device, rapid laser processing can be performed, the process efficiency can be increased, and the mask is displaced based on the error amount stored in the storage device. The mask image can be accurately projected on the target position, and the laser processing can be made precise.

Further, according to a preferred embodiment of the above device,
At the time of laser light irradiation, the tilt and the focal position of the workpiece are corrected in real time according to the irradiation position of the workpiece.

In this case, when irradiating the laser beam, the inclination and the focal position of the workpiece are corrected in real time in accordance with the irradiation position of the workpiece, so that more accurate laser processing can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a laser processing apparatus and method according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a view for explaining the overall structure of a laser annealing apparatus as a laser processing apparatus according to an embodiment. This laser annealing apparatus is for heat-treating a workpiece W, which is a workpiece having a semiconductor thin film such as amorphous Si formed on a glass plate, and emits a pulsed laser beam AL for heating the semiconductor thin film. An excimer laser or other laser light source 10 to be generated, an irradiation optical system 20 for making the laser light AL into a rectangular shape and incident on the work W with a predetermined illuminance, and a work W placed thereon for smooth translation in the XY plane A process stage 30 that is movable and tiltable around the X axis and the Y axis, and a stage driving device 40 that moves or tilts the process stage 30 on which the workpiece W is mounted with respect to the irradiation optical system 20 or the like by a required amount. And a main controller 100 that controls the operation of each part of the laser annealing apparatus in a comprehensive manner. Here, the process stage 30 and the stage driving device 40 constitute a process stage device, and are housed in a chamber 90 for reducing the pressure around the work W and adjusting the atmosphere. The process stage 30 can move the work W appropriately in the XY plane and can scan the entire surface of the work W at a high speed at a high speed. Further, the process stage 30 includes a tilt stage 31 at an upper portion, so that the height and the inclination of the work W can be adjusted.

Further, this laser annealing apparatus is
A position measuring device 50 for detecting the position and the amount of movement of the process stage 30 as optical information and electric information, and a non-contact displacement meter for detecting a signal corresponding to the height and the amount of inclination of the work W with respect to the irradiation optical system 20. 60.

The former position measuring device 50 can accurately measure the position in the XY plane when the process stage 30 moves.
Based on position detection information from the position measurement device 50 when the process stage 30 (that is, the work W) is moved before annealing beforehand, as a storage device that stores an error amount corresponding to a deviation from a target position as data based on position detection information. Function. Further, the position measuring device 50 can accurately detect the height and the inclination of the work W on the process stage 30, and can accurately position the height and the inclination of the work W.

The latter non-contact displacement gauge 60 is a laser displacement gauge, and emits a light projecting section 61 for making the inspection light DL incident on a flat area on the workpiece W as a measurement target and a specular reflection light RL from the measurement target. And a light receiving unit 62 for receiving and outputting information on the incident position of the regular reflection light RL. The light projecting unit 61 and the light receiving unit 62 are arranged to face each other with the irradiation optical system 20 interposed therebetween, and can detect the height and the amount of tilt of the work W near the irradiation position of the laser light AL on the work W. The irradiation position of the laser beam AL on the work W varies in height and inclination with respect to the irradiation optical system 20 due to the flatness of the work W and the guiding accuracy of the process stage 30. The non-contact displacement meter 60 allows the irradiation optical system 20
And the change in the distance and inclination in the Z direction from the object to the irradiation position on the surface of the workpiece W can be measured with high accuracy.

Here, the irradiation optical system 20 includes the laser light source 1.
A homogenizer 20a for making the laser beam AL incident from 0 through the mirror 15 a uniform distribution, and a homogenizer 20a
Mask 20b having a slit for forming an irradiation pattern for narrowing the laser beam AL having passed through the mask into a rectangular shape, and a projection lens 20 for reducing and projecting a slit image of the mask 20b on a work W
c. Note that the irradiation optical system 20 is
And a gantry 90b extending from the chamber 90 so as to face the work W via a transmission window 90a provided in
To the chamber 90 side.

A mask 20b constituting the irradiation optical system 20
Is mounted on the mask stage 70, is capable of smoothly translating in the XY plane, and is rotatable around the Z axis. In order to ensure parallelism between the mask 20b and the process stage 30, X The stage driving device 80 is a mask driving device that can be tilted around the axis and the Y axis.
Moves the mask stage 70 on which the mask 20b is mounted on the projection lens 2 based on a control signal from the main controller 100.
It is moved or rotated by a required amount with respect to 0c or the like.

FIG. 2 is a view for explaining the projection of a mask image by the irradiation optical system 20 and the scanning of the mask image by the process stage 30. FIG. 2A is a plan view illustrating the mask 20b, and FIG. 2B is a plan view illustrating the work W. The laser light that has passed through the slit 20f, which is an opening formed in the reflection layer formed on the surface of the mask 20b, is reduced and projected on one of predetermined irradiation areas IA1, IA2, IA3,. Each irradiation area IA1, IA2, I
A3,... Are similar to the slit 20f and are rectangles extending in the Y direction. If the workpiece W is moved at a constant speed, for example, in the −X direction while the mask 20b is fixed, the laser light oscillates in a pulsed manner at a constant cycle.
By synchronizing with the moving speed of 0, it is possible to project the irradiation areas IA1, IA2, IA3,. can do.

FIG. 3 is a graph conceptually illustrating a guide error in the XY plane of the process stage 30 and its correction.

When the process stage 30 is moved for scanning the irradiation area, the position in the XY plane fluctuates from an ideal scanning position with respect to the irradiation optical system 20 due to the guide accuracy of the process stage 30. I do. The amount of error due to this variation is indicated by a solid line as the scanning error of the process stage 30. Such a scanning error is mainly caused by a mechanical mechanism of the process stage 30, and has reproducibility. Therefore, if the mask 20b is moved in the XY plane so as to compensate and cancel the scanning error, the irradiation area can be accurately arranged at the target position. The amount of compensation at this time is indicated by a dotted line as a scanning input of the mask stage 70. The actual movement amount of the mask stage 70 is moved by an amount obtained by multiplying the reciprocal of the reduction magnification in consideration of the reduction magnification of the projection of the slit image by the projection lens 20c. Further, displacing the mask 20b in the X direction actually compensates for fluctuations in the moving speed of the process stage 30.

FIG. 4 is a diagram conceptually illustrating correction of the displacement and rotation of the work W in the Z direction during scanning. FIG. 4A shows a case where a positional shift has occurred, and FIG.
Indicates correction of positional deviation.

In the case shown in FIG.
S is a distance d below the focal position F of the projection lens 20c.
And is inclined by an angle θ with respect to a plane perpendicular to the optical axis of the projection lens 20c. The positional deviation and the inclination of the surface WS of the work W are determined by causing the inspection light DL from the light projecting unit 61 to be incident on the surface WS of the work W and detecting the incident position of the regular reflection light RL from the surface WS by the light receiving unit 62. Required by Although only the rotation about the Y axis is shown in the drawing, the rotation about the X axis can also be obtained by arranging the non-contact displacement meter 60 similar to the light emitting unit 61 and the light receiving unit 62 in the YZ plane. Can be.

FIG. 4B shows a state in which the tilt position of the work W is corrected by controlling the tilt stage 31 above the process stage 30 based on the result detected in FIG. That is, the work W moves upward by the distance d and rotates counterclockwise by the angle θ.

Hereinafter, the overall operation of the apparatus shown in FIG. 1 will be described. Before starting laser irradiation for annealing, the process stage 30 is scanned in advance by the same operation as that for annealing. At this time, the error amount of the movement of the process stage 30 in the XY plane is determined by the position measurement device 50.
And stored in a memory in main controller 100 as a function of time, for example.

Next, laser irradiation for annealing is performed while correcting the error amount. Specifically, first, the work W is transported and placed on the process stage 30. Next, the work W on the process stage 30 is aligned with the irradiation optical system 20 for guiding the annealing laser beam AL. Next, the laser light AL from the laser light source 10 is incident on the workpiece W while moving the process stage 30 in the X-axis direction with respect to the irradiation optical system 20 at a high speed. When the work W is moved, the main controller 100
The mask stage 70 is synchronously moved with high precision by an amount corresponding to the error amount of the position of the work W in the Y direction stored in the Y direction to compensate for the displacement in the Y direction. In addition, main controller 100
The mask stage 70 is synchronously moved with high precision by an amount corresponding to the error amount of the position of the workpiece W in the X direction stored in the X direction, thereby compensating the speed fluctuation in the X direction. The above operation is repeated by moving the work W stepwise in the Y direction by the length of the irradiation area, or repeated by moving the work W stepwise by a predetermined amount in the X direction or the Y direction. Work W
Is formed with a thin film of an amorphous semiconductor such as amorphous Si, and a desired region of the semiconductor is annealed and recrystallized by the above-described irradiation and scanning of the laser beam AL, thereby providing a semiconductor thin film having excellent electrical characteristics. Can be provided.

The height and inclination of the workpiece W that moves during scanning vary depending on the flatness of the glass substrate, the accuracy of the guide device incorporated in the process stage 30, and the like. That is, unless the height and inclination of the work W are adjusted by the tilt stage 31 of the process stage 30, the work W
The position of the surface in the Z direction deviates out of the focal position of the projection lens 20c, or the surface of the work W is not precisely perpendicular to the optical axis, and the irradiation pattern formed on the mask 20b is not accurately positioned on the surface of the work W. Will not be projected. Therefore, not only the X-direction scanning of the process stage 30 at the time of laser irradiation, but also the distance and inclination of the Z-direction between the surface of the workpiece W and the projection lens 20c at the laser beam irradiation position in the XY plane are online by the non-contact displacement meter 60. Since the measured value is fed back to the tilt stage 31, which is a tilt correction mechanism, and is controlled in real time, the position in the Z direction of the surface of the work W always coincides with the focal position of the projection lens 20c, and the surface of the work W is It is kept perpendicular to the optical axis. When the inclination of the surface of the work W does not significantly affect the imaging characteristics of the projection lens 20c, control for correcting the inclination of the surface of the work W is not necessarily required.

According to the laser annealing apparatus of the embodiment described above, a large area on the work W can be subjected to laser irradiation at a high speed and with high accuracy at a time for heat treatment.
The position error of the process stage 30 is not affected by the shape characteristics or the like of each work W, and
Since the characteristic depends only on the main control device 10, the error amount is measured at a frequency that takes into account the effects of aging.
It is sufficient to update the data stored in 0. Work W
Since there is no need to perform die-by-die alignment as in the case where laser irradiation is performed by dividing the upper part into a small area, the entire surface of the work W can be irradiated with laser in one scan, and the process can be performed without lowering the accuracy. Can be speeded up.

In this embodiment, the laser annealing apparatus is used to anneal the semiconductor layer on the work W using the laser beam AL. However, if the structures of the laser light source 10 and the irradiation optical system 20 are appropriately changed, the liquid crystal can be changed. A pulse laser processing apparatus or the like that enables not only annealing of a semiconductor material for a display device or a semiconductor device but also modification, cutting, welding, and the like of various materials can be used.

[0032]

As is apparent from the above description, according to the laser processing apparatus of the present invention, since the workpiece is moved by the process stage device, rapid laser processing becomes possible and the process efficiency can be improved. it can. Also,
Since the mask driving device displaces the mask based on the error amount stored in the storage device, the error amount when the workpiece is moved can be corrected, and the mask image can be accurately projected on the target position. Laser processing can be made precise.

According to the laser processing method of the present invention,
Since the workpiece is moved by the process stage device, rapid laser processing can be performed, the process efficiency can be improved, and the mask is displaced based on the error amount stored in the storage device, so that the mask can be accurately positioned at the target position. An image can be projected and the laser processing can be precise.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a structure of a laser annealing apparatus according to an embodiment.

FIG. 2 is a diagram illustrating laser irradiation in the apparatus of FIG.

FIG. 3 is a diagram illustrating correction of a scanning error in an XY plane in the apparatus of FIG. 1;

FIG. 4 is a view for explaining correction of a displacement error in an XY plane in the apparatus of FIG. 1;

[Explanation of symbols]

 Reference Signs List 10 laser light source 20 irradiation optical system 20a homogenizer 20b mask 20c projection lens 20f slit 30 process stage 40 stage driving device 50 position measuring device 60 non-contact displacement meter 70 mask stage 80 stage driving device 90 chamber 90a transmission window 100 main control device AL laser Light W Work WS Surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 101: 40

Claims (4)

[Claims] 1. An irradiation optical system for projecting an image of a mask illuminated by a laser beam onto a workpiece, and the workpiece is placed and the workpiece is moved with respect to the irradiation optical system. A process stage device, a storage device that previously stores an error amount corresponding to a deviation from a target position when the workpiece is moved by the process stage device, and a storage device that stores the error amount based on the error amount stored in the storage device. A laser processing apparatus comprising: a mask driving device that displaces a mask. 2. The apparatus according to claim 1, further comprising: a position sensor configured to detect a tilt and a focal position of the workpiece when irradiating the laser beam, wherein the mask driving device is configured to determine a tilt of the workpiece based on an output of the position sensor. 2. The laser processing apparatus according to claim 1, wherein the focal position is corrected in real time. 3. Before projecting an image of a mask illuminated by a laser beam onto a workpiece by an irradiation optical system, moving a process stage apparatus on which the workpiece is mounted with respect to the irradiation optical system while moving the target. Measuring the error amount corresponding to the deviation from the position and storing the error amount; and storing the error amount in synchronization with the movement of the workpiece by the process stage device during laser beam irradiation. Displacing the mask on the basis of the laser processing method. 4. The laser processing method according to claim 3, wherein, when irradiating the laser beam, the inclination and the focal position of the workpiece are corrected in real time according to the irradiation position of the workpiece.