JPH085319A - Alignment device - Google Patents

Abstract

PURPOSE:To perform the measurement of alignment with high accuracy in a short time. CONSTITUTION:A chopper disk 30 is a rotary body, which is rotated with a motor 31 at a constant speed and has light blocking parts 29 and opening parts 28, which are alternately arranged along the circumferential direction of the disk. When the light blocking part 29 blocks one beam of the beams in the directions X and Y, the opening part 28 passes the other beam. In the measurement of alignment, at first, a wafer 12 and the beams in the directions of X and Y are relatively moved in correspondence to the result of the detection of a state-detecting sensor 34, and the marks in the direction X and Y in the wafer 12 are scanned by at least one reciprocation. The timing of the scan is synchronized with the rotating motion of the chopper disk 30. At this time, the detector signals in the directions X and Y are outputted from detectors 19 and 20 for measuring the direction X or Y. The position in the directions X and Y of the wafer 12 are recognized based on the moved position of the stage 22 at that time in the absolute coordinates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment apparatus, and more particularly to an alignment apparatus capable of performing alignment measurement of a semiconductor wafer in a short time.

[0002]

2. Description of the Related Art Alignment measurement is performed in order to accurately obtain the position coordinates of a wafer mounted on a wafer holder in a semiconductor manufacturing apparatus. A conventional alignment device used for the alignment measurement will be described with reference to FIG.

A laser light source (eg He-Ne laser) 1
The linearly polarized laser beam emitted from the λ / 2 plate 2
After passing through, the beam is split into a P-polarized component laser beam 4 and an H-polarized component laser beam 5 by a polarization beam splitter 3 (optical path splitting means). Among these branched laser beams 4 and 5, the laser beam 4 is a beam slit 6
a and the cylindrical lens 7a, and the laser beam 5 is shaped into an elongated rectangular beam by passing through the beam slit 6b and the cylindrical lens 7b. At this time, the directions of the cylindrical lenses 7a and 7b are set so that the laser beam 4 of the P-polarized component and the laser beam 5 of the H-polarized component are different in major axis directions by 90 °.

After the laser beams 4 and 5 are beam-shaped, they are merged into the same optical path by the beam splitter 8, pass through the half mirror 17, the relay lens 9 and the objective lens 10, and are processed by the wafer holder 11. The wafer 12 is irradiated. The laser beams 4 and 5 merged by the beam splitter 8 finally have a beam shape as shown in FIG. 6, that is, y in the major axis direction.
The wafer 12 is irradiated with an X-direction measurement alignment beam (hereinafter referred to as “X-direction beam”) Bx elongated in the direction and a Y-direction measurement alignment beam (hereinafter referred to as “Y-direction beam”) By elongated in the x direction.

The wafer 12 is pre-aligned by a known means (not shown) to be positioned within the allowable position error, and is held by suction on the wafer holder 11.
The precision of this pre-alignment is within ± 50 μm.

On the wafer 12, as shown in FIG. 7, a lattice-shaped X-direction measurement alignment mark (hereinafter referred to as "X-direction mark") 15 arranged in the design position in the X-direction, A lattice-shaped Y-direction measurement alignment mark (hereinafter referred to as "Y-direction mark") arranged in the Y direction 1
6 and 6 are provided in advance. And these marks 1
When the alignment beams 5 and 16 are irradiated with the same direction, that is, the X-direction beam 15
, And the Y-direction mark 16 is irradiated with the Y-direction beam By, diffracted light is generated. The diffraction angle of this diffracted light is determined by the grating pitch of these marks 15 and 16, the wavelength of the irradiated beam, and its incident angle.

The generated diffracted light passes through the objective lens 10 and the relay lens 9, and after being reflected by the half mirror 17,
The beam splitter 18 guides the X-direction measuring detector 19 and the Y-direction measuring detector 20. In front of these detectors 19 and 20, order cut filters 21a and 21b that pass only diffracted light of an appropriate order are arranged in order to improve the SN ratio of the detector output.

Wafer holder 11 for mounting wafer 12
Are installed on an XY stage (hereinafter referred to as “stage”) 22. When the X direction beam Bx or the Y direction beam By corresponding to the measurement direction is irradiated while moving the stage 22 in the measurement direction X or Y direction, the beam Bx or By corresponds to the X direction mark corresponding to the measurement direction. Diffracted light is generated when it hits the mark 15 or the Y direction mark 16, and the diffracted light is detected by the detectors 19 and 20, whereby the X direction detector signal Dx or the Y direction detector signal Dy appears. The stage 22 is provided with a position detecting device (moving position detecting means) which is not shown and is composed of a magnetic scale or an interferometer, and can detect the moving position of the stage 22. The moving position detecting means and the control means (not shown) can recognize the coordinates of the place where the detector signal Dx or Dy is output. This operation is called alignment measurement.

In this alignment measurement, by measuring only the beam in the measurement direction and blocking the beam in the non-measurement direction, disturbance of the detector output is prevented and the measurement accuracy is improved. Specifically, in the branch optical system of FIG.
The alignment shutter 23 is operating. The alignment shutter 23 has two functions of beam passing and beam blocking.
This is for performing a directional operation. As shown in FIG. 8, the shutter member 24 is driven by the actuator 25,
The stopper 2 in which the contact member 26 formed at one end of the shutter 24 is fixed at a predetermined position in the moving direction of the contact member 26
The desired operation is performed by contacting with 7a and 27b.

With this alignment shutter 23,
At the time of measurement, the beam in the non-measurement direction is blocked to improve the SN ratio of alignment measurement.

[0011]

However, in the alignment apparatus adopting the conventional shutter mechanism, mechanical vibration occurs when the contact member 26 is brought into contact with the limiting members 27a and 27b, and the vibration causes the alignment. In order to deteriorate the SN ratio of the measurement, it was necessary to wait for the alignment measurement until the vibration stopped. This vibration damping time is as high as several seconds.

When the operation speed of the shutter mechanism 23 is decreased to reduce the vibration, the increase in the operation time due to the decrease in the speed reaches the level of several seconds, and eventually the decrease in the vibration damping time is canceled out. The alignment operation time is not significantly shortened.

In particular, when the die-by-die alignment method for performing alignment for each chip is adopted, this waiting time becomes enormous as a whole, and there is a problem that alignment measurement requires a long time.

The present invention has been made in view of such circumstances, and an object thereof is to provide an alignment apparatus capable of performing accurate alignment measurement in a short time.

[0015]

In order to solve the above-mentioned problems, the alignment apparatus of the present invention is provided with an object to be machined having an X-direction measuring mark and a Y-direction measuring mark orthogonal to the mark. And moving means for moving the object in the X and Y directions, moving position detecting means for detecting the moving position of the moving means, optical path branching means for branching the optical path of the beam from the light source, and the optical path branching. The beam of one optical path branched by the means is used as the X-direction measurement beam,
By shaping the beam in the other optical path into a beam for measuring in the Y direction and irradiating each of the beams to the mark for measuring in the X and Y directions, and by receiving reflected light from the object to be processed. Mark position detecting means for detecting the position of the X and Y direction measurement marks, and a light shielding portion and an opening portion arranged alternately along the circumferential direction,
While the light blocking unit blocks one of the X and Y direction measurement beams, the opening allows the other of the X and Y direction measurement beams to pass therethrough, and the X
And a rotating body that alternately irradiates the Y-direction measurement beam,
A detection unit that detects which of the X and Y direction measurement beams is blocked by the rotating body, and the processing object and the X and Y direction measurement beams are made to correspond to each other based on the detection result of the detection unit. The timing for moving and scanning the X- and Y-direction measuring marks at least once back and forth is synchronized with the rotating operation of the rotating body, and is detected by the moving position detecting means when a detection signal from the mark position detecting means is output. Control means for measuring the X or Y direction position of the object to be processed based on the moved position of the moving means.

[0016]

As described above, the rotating body having the light-shielding portion and the opening portion is rotated to alternately irradiate the workpiece with the X- and Y-direction measuring beams. Generation of vibration due to switching of the beam for use disappears,
Highly accurate alignment measurement can be performed in a short time.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an alignment apparatus according to an embodiment of the present invention. The same parts as those of the alignment apparatus of FIG. 5 described above are designated by the same reference numerals and the description thereof is omitted.

In this embodiment, a chopper disk 30 is provided to pass and block the laser beams 4 and 5 in the branch optical system. As shown in FIG. 2, the chopper disk 30 is a rotating body that is constantly rotated by a motor 31 at a constant speed, and has a light shielding portion (non-opening portion) 29 and an opening portion 28 that are alternately arranged along the circumferential direction. While the light blocking portion 29 blocks one of the laser beams 4 and 5, the opening portion 28 allows the other beam to pass therethrough. Four light blocking portions 29 are formed at regular intervals in the circumferential direction of the chopper disk 30.

A state detection sensor (detection means) 34 is arranged near the chopper disk 30. The state detection sensor 34 detects which of the laser beams 4 and 5 is blocked by the chopper disk 30 and outputs a sensor signal S as a detection signal. State detection sensor 34
Is an optical sensor having a U-shaped cross section, and is a chopper disk 3
An ON signal is output when the opening 28 of 0 passes through the detection space 34a, and an OFF signal is output when the light shielding unit 29 passes through the detection space 34a.

The alignment measurement is performed as follows. First, according to the detection result of the state detection sensor 34, the wafer 12 and the X and Y direction beams Bx and By are relatively moved to scan the X and Y direction marks 15 and 16 at least once. The scanning timing is synchronized with the rotation operation of the chopper disk 30. At that time, the X-direction detector signal (mark position detecting means) 19, 20 outputs the X-direction detector signal Dx or Y.
The direction detector signal Dy is output. Based on the moving position of the stage 22 when the X-direction or Y-direction detector signals Dx, Dy are output, the X- and Y-direction positions of the wafer 12 on the stage (moving means) 22 are recognized in absolute coordinates.

When performing alignment measurement, the wafer 12
It is necessary to move the X- and Y-direction marks 15 and 16 therein to just below the objective lens 10. X and Y direction mark 1
The search areas for searching 5, 16 are as follows.
That is, the wafer 12 is positioned and adsorbed on the wafer holder 11 within a predetermined pre-alignment accuracy by a pre-alignment device (not shown). Since this pre-alignment accuracy is within ± 50 μm, after all the search area is centered around the design position of the alignment mark ±.
100 μm is sufficient.

Alignment measurement performed using this chopper disk 30 will be described with reference to FIGS. 3 and 4.
Here, the case where the alignment measurement of the X-direction mark 15 is performed is assumed and explained.

FIG. 3 is an explanatory diagram of the scanning operation of the X-direction beam Bx. When performing alignment measurement of the X-direction mark 15 using the X-direction beam Bx, the X-direction beam Bx
Scans the X-direction mark 15 in the direction indicated by the arrow in FIG. In this case, measurement is performed when scanning in the direction indicated by the solid arrow, and measurement is not performed when scanning in the direction indicated by the dotted arrow. This is because the measurement reproducibility is improved and the measurement accuracy is increased by measuring only in one direction.

FIG. 4 is a time chart during alignment measurement. In the figure, the sensor signal S of the state detecting sensor 34, the movement of the X-direction beam Bx irradiated onto the wafer 12, and the Y-direction beam B irradiated onto the wafer 12 are sequentially shown from the top.
The movement of y, the operation signal ST of the stage 2 and the X-direction detector signal Dx are shown.

The sensor signal S indicates either on (H) or off (L) according to the rotation of the chopper disk 30, and when it is on the H side, the X-direction beam Bx is irradiated on the wafer 12 and the L side. , The Y-direction beam By is irradiated onto the wafer 12. Here, when the sensor signal S is on the H side, the stage 22 moves (forward) in the measurement direction. During this movement, the X-direction beam Bx emits the X-direction mark 15
Scan the top and the X direction detector signal Dx appears.
The position of the X-direction mark 15 can be obtained from the position of the stage 22 at the time when the X-direction detector signal Dx is output. When the sensor signal S goes to the L side, the stage 22
Moves (returns) in the opposite direction. At this time, the Y-direction beam By is irradiated onto the wafer 12, but this does not contribute to the measurement.

This alignment measurement may be performed a plurality of times on the same mark in order to improve the measurement accuracy. In this case, the stage 22 is reciprocated around the X or Y direction marks 15 and 16 to carry out. As described above, the measurement reproducibility can be improved by performing the measurement only in the one-way movement of the reciprocating movement, for example, only in the forward movement, and not in the backward movement.

By the way, since the alignment beams (X-direction beam Bx and Y-direction beam By) are emitted alternately, it is necessary to complete the alignment measurement by reciprocating the stage 22 once while the beam in the measurement direction is being emitted. , This time is at most tens of milliseconds. This is because, as described above, it is sufficient that the alignment mark search area is ± 100 μm centering on the designed position of the mark, and if the distance is within this range, the stage 22 can be operated even if an ordinary driving device is used. It can move back and forth sufficiently in milliseconds. Also in the chopper disk 30, since the rotation speed may be such that the opening 28 is positioned in the optical path for a time obtained by adding a slight margin to this time, this can also be realized by using a normal motor.

If the alignment beam irradiation interval is 50 milliseconds and the chopper disk 30 has a shape in which an opening and a non-opening appear at 4 degrees per rotation as shown in FIG. 2, the rotation speed is: 1 / (4 × 0.05) = 5 rotations /
Seconds. The moving speed of the stage 22 is 200 μm / 50
Milliseconds = 4 milliseconds. In other words, alignment measurement is 5
It can be completed in 0 milliseconds, and even if a waiting time occurs, it can be completed in several hundred milliseconds because the beam irradiation in the measurement direction is taken.

In this embodiment, since the alignment beam is switched by the rotation of the chopper disk 30, vibration that deteriorates the SN ratio does not occur, and highly accurate alignment measurement can be performed in a short time.

As a modification of the above-described embodiment, the X-direction position of the workpiece is measured when the stage is moved forward by scanning the X-direction mark and the Y-direction mark at an angle, and the stage is returned. When moving, the Y-direction position of the object to be processed may be measured.

[0032]

As described above, according to the alignment apparatus of the present invention, since vibration is not generated due to beam switching, highly accurate alignment measurement can be performed in a short time.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an alignment apparatus according to an embodiment of the present invention.

FIG. 2 is a detailed view of a chopper disk of the alignment device of FIG.

FIG. 3 is an explanatory diagram of a scanning operation of an X-direction beam Bx.

FIG. 4 is a time chart during alignment measurement.

FIG. 5 is an overall configuration diagram of a conventional alignment apparatus.

FIG. 6 is an explanatory diagram of an alignment beam with which a wafer is irradiated.

FIG. 7 is a front view of alignment marks set on a wafer.

FIG. 8 is a front view of an alignment shutter.

[Description of Reference Signs] 1 laser light source 3,8 beam splitter 6a, 6b beam slit 7a, 7b cylindrical lens 10 objective lens 11 wafer holder 12 wafer 15 X direction mark (X direction measurement alignment mark) 16 Y direction mark (Y direction measurement) Alignment mark) 19 X-direction measurement detector 20 Y-direction measurement detector 22 Stage 28 Opening part 29 Light-shielding part 30 Chopper disk 31 Motor 34 State detection sensor Bx X-direction beam (X-direction measurement alignment beam) By Y-direction beam (Y (Alignment beam for direction measurement)

Claims (1)

[Claims] 1. A moving object on which an object to be processed having an X-direction measuring mark and a Y-direction measuring mark orthogonal to the mark is placed, and moving means for moving the object to be processed in the X and Y directions. A moving position detecting means for detecting a moving position of the moving means, an optical path branching means for branching an optical path of a beam from a light source, and a beam of one optical path branched by the optical path branching means
An optical member that shapes the beam for measuring the direction and the beam of the other optical path into the beam for measuring the Y direction, and irradiates each of the two beams to the mark for measuring the X and Y directions, and the reflection from the processing object. Mark position detecting means for detecting the positions of the X and Y direction measurement marks by receiving light, and light shielding portions and openings which are alternately arranged along the circumferential direction, the light shielding portion being the While blocking one of the X and Y direction measurement beams, the opening allows the other of the X and Y direction measurement beams to pass, and the X and Y direction measurement beams are applied to the workpiece. A rotating body that alternately emits light, a detection unit that detects which of the X and Y direction measurement beams is blocked by the rotating body, and a detection result of the detection unit, and the processing target and the X and Y When the detection signal from the mark position detection means is output by synchronizing the timing of scanning the X and Y direction measurement marks at least one reciprocating movement by moving the direction measurement beam relatively. An alignment apparatus comprising: a control unit that measures the X-direction or Y-direction position of the workpiece based on the movement position of the movement unit detected by the movement position detection unit.