JP2663569B2 - Laser processing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for irradiating a laser beam with high precision alignment, and more particularly to a device for deflecting a wiring state in an integrated circuit.

[Prior Art] Conventionally, this type of device has a structure as shown in FIG. In FIG. 15, the laser beam emitted from the laser 1 was formed by the aperture 9 and then imaged on the wafer W using the lens 12. In order to measure the irradiation position, the aperture illumination light is guided by the fiber 7, the mirror 5 is inserted into the optical path, the aperture 9 is illuminated, and the reflected light of the image formed by the lens 12 is received by the light receiver 17. , The position was being measured.

[Problems to be solved by the invention]

However, the conventional technique has a problem that the light transmitting system and the light receiving system are complicated and expensive because the irradiation position measurement measures a minute spot (for example, a spot having an opening of 5 μm or less). That is, in the light transmission system, a light source having a high luminance, for example, a mercury lamp light source or the like is required to obtain the light amount, and therefore, cooling water is required, and the lamp needs to be replaced periodically. Further, since the light beam had to pass on the same optical axis as the processing optical system, a mechanism for moving the switching mirror 5 in and out was required, and its position reproducibility was required.

The light receiving system also requires an amplifier such as a photomultiplier tube to detect a very small amount of light, and its driving circuit is also complicated.

Further, since the wavelength of the light for measuring the irradiation position and the wavelength of the light at the time of laser processing were different, it was necessary to remove chromatic aberration when designing the lens 12.

It is also conceivable to measure the irradiation position using a pulsed laser beam used for processing. In that case, it is necessary to attenuate the energy as compared with the time of processing in order to protect the mark to be measured. In addition, since the detection light obtained by the light receiver is also pulsed, there is a problem that a high-speed processing circuit is required.

The present invention has been made in view of such conventional problems, and has as its object to perform irradiation position measurement by a simple method.

[Means to solve the problem]

In order to solve the above problem, the present invention has a configuration in which the fiber 7, the lens 8, and the mirror 5 are eliminated, and a control circuit that changes the oscillation state of the laser 1 according to the situation is adopted. When laser processing is performed by the control circuit, the laser is output in a pulsed manner, and when the irradiation position is measured, the laser is continuously output.

(Operation)

In the present invention, since the laser for laser processing is used as the light source for measuring the irradiation position, it is not necessary to newly provide a light source for measuring the irradiation position and an optical system for transmitting the beam, and the optical system can be simplified. .

〔Example〕

FIG. 1 is a perspective view of an embodiment of the present invention. In the figure, a processing laser light source 1, such as a YAG laser, a variable attenuator 2,
The condensing lens 3, the mirror 4, the aperture plate 9 having the aperture 9a, the beam splitter 10, and the objective lens 12 constitute a processing laser irradiation system. Further, there are a processing laser irradiation position measurement system for measuring the irradiation position of the processing laser and a processing laser irradiation position observation system for observing the laser irradiation position, which are attached to the processing laser irradiation system. The measurement system is the aperture plate 9 described above,
It consists of a beam splitter 10, an objective lens 12, a condenser lens 16, and a detector 17, and the observation system is an optical fiber for illumination.
18, a condenser lens 19, a beam splitter 20, the above-described dichroic mirror 11, an objective lens 12, an index reticle 21, a relay lens 22, and an image pickup tube 23. Further, there are WX, WY and Wθ sensors as global alignment sensors for aligning the wafer W.

These processing laser irradiation system, measurement system, observation system, and global alignment sensor are integrated into a laser processing apparatus main body (not shown). And sensor W
X, WY, Wθ and the objective lens 12 are fixed to a laser processing apparatus main body (not shown) so as to have a specific positional relationship. On the XY stage ST, a fiducial mark FM is fixed for use in measuring the relative position of the global alignment sensors WX, WY, Wθ and the processing laser irradiation position measurement system. The position of the XY stage ST is measured by the X-axis laser interferometer 24 and the Y-axis laser interferometer 25.

The XY stage ST is driven by an X motor 36 and a Y motor 35, and these motors are controlled by a stage control unit 34.
Is controlled by Further, a Z stage (not shown) is provided on the XY stage ST.
A rotation stage is provided, and the wafer W is mounted on the θ rotation stage. The θ rotation stage is also driven by a motor (not shown). The motor (not shown) is also controlled by the stage control unit 34. The Z stage is driven by a motor (not shown). This motor is also controlled by the stage control unit 34. Reference numeral 33 denotes a central control unit (hereinafter, referred to as a CPU), which issues a command to the stage control unit 34, a laser output command, an attenuation command, and also measures a laser irradiation position. Reference numeral 28 denotes a processing laser power supply, and reference numeral 29 denotes a control unit of the variable attenuator 2. Reference numeral 31 denotes a camera control unit, and reference numeral 32 denotes an ITV monitor, which can observe a magnified image by the objective lens 12 as well as magnified images through the global alignment sensors WX, WY, and Wθ in a switchable manner.

Although not shown, an autofocus system and the above-described Z stage are provided in order to focus the back surface of the wafer W so as to coincide with the image plane of the reduced projection image of the opening 9a. Thus, an optimal imaging state, that is, a state in which the image of the opening 9a is formed on the wafer W is maintained.

FIG. 2 is a plan view showing the relationship between the irradiation position of the processing laser and the global alignment sensor, and shows the same configuration as that described in detail in JP-A-56-102823 by the present applicant.

The processing laser irradiation position near the center of the objective lens 12 of the processing laser irradiation system is defined as the origin O, and X orthogonal to the origin O
Axis, Y axis. These X and Y axes are oriented in the same direction as the coordinate axes determined by the mirrors 26 and 27 of the laser interferometer of FIG. The X sensor WX is located on the X axis, and the Y sensor WY is located on the Y axis. θ
The sensor Wθ has the same Y coordinate as the Y sensor WY, and detects a rotation error of the wafer W together with the Y sensor WY. X sensor WX
Is used to detect the position of the wafer W in the X direction.
The Y sensor WY is used to detect the position of the wafer W in the Y direction. Also, the distance between the origin O and the Y sensor WY and the origin O
The distance between the X sensor WX and the X mark XL and the Y mark YL on the fiducial mark FM are detected by moving the XY stage ST by the X sensor WX, the Y sensor WY and the processing laser irradiation position measuring system. This is obtained by measuring the length with the laser interferometers 24 and 25. The details will be described later.

FIG. 3 shows a processing laser irradiation system, a processing laser irradiation position measuring system, and an observation system, and partially shows the apparatus shown in FIG. 1 in detail. The intensity of the laser light emitted from the processing laser light source 1 is changed by the variable attenuator 2, and is projected onto the opening 9 via the mirror 4 by the lens 3. Opening plate 9
The aperture 9a is square or rectangular, and the image of the aperture 9 is reduced and projected onto the wafer W by the objective lens 12. By changing the size of the opening 9a, the laser irradiation size on the wafer W can be changed. The above is the laser irradiation system.

By transmitting a signal for continuous oscillation from the CPU 33 in FIG. 1 to the processing laser power supply 28, the laser starts continuous oscillation and the processing laser position measurement system can be used. The continuously oscillated laser beam illuminates the aperture plate 9 by the condenser lens 8, and the image of the aperture 9 a is reduced and projected on the wafer W by the objective lens 12.

In order to perform continuous oscillation, the driving state of the Q switch element in the laser resonator may be changed. The Q-switching element is located in the laser cavity, and keeps the laser cavity Q value low to continue pumping. When the population inversion becomes sufficiently large, suddenly increase the cavity Q value. Thus, the energy stored in the upper level is extracted as laser output in a short time, and the peak value of the pulse output generated in this way is extremely high. Turn off the above Q switch element
In this state, continuous oscillation occurs. The method of turning off varies depending on the laser power supply.For example, use the method of keeping the level of the external signal input terminal for pulse output constant or the fact that the response of the driver of the Q switch can not catch up by applying high frequency There are various ways to do this.

The projection position is the same as the processing laser irradiation position. That is, the detection center of the processing laser irradiation position measurement system on the stage ST coincides with the center of the laser irradiation position on the stage ST of the processing laser irradiation system. The light reflected by the surface of the wafer W or another reflector (for example, a fiducial mark FM) at the position of the light image projected by the lens 12 is partially reflected by the beam splitter 10, And is detected by the detector 17. Therefore, a detection signal (a signal as shown in FIG. 7 to be described later) of the pattern at the processing laser irradiation position is obtained from the detector 17. The light guide 18 is an illumination light source for observation, and illuminates the wafer W via the on-densor lens 19, the beam splitter 20, the dichroic mirror 11, and the objective lens 12,
A pattern image on a wafer is formed on a reticle 21 placed on an image forming plane of the objective lens 12. This image is formed on the image pickup tube 23 by the relay lens 22.

FIG. 4 shows the principle of the global alignment sensors WX, WY, Wθ described in JP-A-57-19726,
The η axis is drawn in the direction in which the alignment error is detected. Therefore, in the X sensor WX, the η axis corresponds to the X axis, and in the Y sensor WY and the θ sensor Wθ, the η axis corresponds to the direction of the Y axis. The laser beam 40 is reflected by a reflecting mirror 45 that vibrates and rotates as indicated by an arrow 44, is focused by a lens 41, and is focused and scanned in the η-axis direction. The shape of the condensed beam is elongated in the ξ-axis direction due to the cost of a cylindrical lens system (not shown). That is, the condensed beam is configured to include a plurality of patterns arranged in the ξ-axis direction that form the alignment mark AM. When the converged beam scans on the grid-like alignment mark AM in the η-axis direction, diffracted light is generated. The diffracted light is received by the detectors 42 and 43 arranged in the ξ-axis direction, photoelectrically converted, and the When synchronous detection is performed in synchronization with the rotation, an alignment error signal is obtained. The sensor described above
WX, WY and Wθ are each configured as shown in FIG. As the laser beam 40, a CW laser is used. FIG. 6 shows an alignment pixel signal S1 when the alignment mark AM of the wafer moves under the X, Y, or θ sensor while the reflecting mirror 45 is vibrating and rotating,
At the zero point 60, the alignment mark AM coincides with the detection center of the X, Y and θ sensors.

Fig. 5 shows the shape of the fiducial mark FM formed on the XY stage. Short rectangles 50a, 50b ... are arranged at regular intervals on a line XL extending in the Y direction, and near the center of the arrangement. Is a rectangle with a length equal to one cycle of this rectangle
There are 51. That is, assuming that the length of one side of the short rectangles 50a, 50b... In the β direction is L ₁ and the interval between the short rectangles is L ₂ , the length of the long rectangle 51 in the β direction is (2L ₁ + L ₂ ). Similarly, a short rectangle 53 on the line YL extending in the X direction
a, 53b, 53c,... and a rectangle 52 having a long length are arranged with the same regularity as the mark in the Y direction. Below, XL
The rectangular row formed on the YL is called an X pattern, and the rectangular row formed on the YL is called an YL pattern. Where the rectangle 50
a, 50b, 50c, ..., 53a, 53b, 53c, ..., and rectangle 5
In detail, the parts 1 and 52 are constituted by partially removing the plated portion 55a of the disk 55 having the chrome plating. Therefore, these rectangles have a lower reflectance than the surrounding portions (chrome-plated portions). Fifth
The mark FM in the figure is the global alignment sensor WY, W
It can also be detected by θ and WX, and can also be detected by the processing laser irradiation position measuring system shown in FIG. As shown in FIG. 5, the lengths of both sides of the optical image LS projected on the XY stage ST by the irradiation position measuring system are (2L ₁ ) in the α direction (the same direction as X) and the β direction (the same direction as Y).
+ L ₂ ). The output when the fiducial mark FM is detected by each of the sensors WY, Wθ, and WX that perform global alignment is the same as in FIG. Next, a case where the mark FM is detected by the irradiation position measuring system will be described. When the mark FM is scanned so as to pass below the objective lens 12 by the movement of the XY stage ST in the Y direction, the movement amount Y in the Y direction and the detector 17 are moved.
Relationship of the output signal S ₂ is as signal 70 in FIG. 7. Y
The position in the direction is a value measured by the laser interferometer 25.

The signal 70 is compared with a constant level (reference level) 71 to determine the Y positions Y1 and Y2 where they match, and to determine the midpoint Y between Y1 and Y2.
_{If the FM} is obtained, the position in the Y direction at which the center of the light image LS and the center of the pattern 52 coincide can be found. Therefore, if the fiducial mark FM is moved in FIG. 2 and photoelectric detection is performed by the sensor WY and the laser irradiation position measurement system, the distance from the origin O of the optical image LS by the measurement system to the detection center of the Y sensor WY is obtained. L _WY can be measured.

Similarly, the distance _WX from the origin O to the X sensor WX is also measured using the X-direction pattern of the fiducial mark FM. The length of both sides of the light image LS is the length of the rectangles 51 and 52 (2L
₁ + L ₂ ) because the pattern 51 is moved in the α direction with respect to the light image LS and the pattern 52 is moved in the β direction with respect to the light image LS.
This is so as not to cover the end of 52 (the end in the longitudinal direction). If the light image LS hits the above-mentioned ends of the patterns 51 and 52, the output of the detector 17 is disturbed, and the detection of the patterns 51 and 52 becomes inaccurate. However, since the present embodiment is configured as described above, even if the patterns 51 and 52 are moved in the α direction or the β direction to cross the light image LS, the light image LS
The end of 52 is not hung and the output of the detector 17 is not disturbed. Therefore, accurate detection can be performed. L _WY and L _WX
Is stored in the CPU 33 obtained from the outputs of the laser interferometers 25 and 24, and is used as a constant when performing wafer alignment. Since the distance between the sensor WY and the sensor Wθ is a value unique to the device, it is predetermined and stored in the CPU 33.

When performing global alignment of the wafer W,
By moving the XY stage, the Y mark YM and the θ mark θM on the wafer W shown in FIG. 8 are detected by the Y sensor WY and the θ sensor Wθ, respectively, and the θ rotation stage is rotated to eliminate the rotation error of the wafer W. . Then, the stage position in the Y direction is obtained from the output of the interferometer 25 and stored in the CPU 33. Note that after this θ
The rotation stage may be fixed to the XY stage, and then the center position of the θ check mark YCM may be detected by the sensor WY to determine the remaining rotation error ε of the wafer W with respect to the XY coordinate system.

Next, the XY stage is moved, and the wafer W is moved by the X sensor WX.
The upper X mark XM is detected, the stage position in the X direction is obtained from the output of the interferometer 24, and is stored in the CPU 33. Through the above operation, the positional relationship of the pattern on the wafer W with respect to the coordinate system XY of the stage is known, and global alignment is performed. Details of these operations are disclosed in JP-A-56-102823. In this embodiment, the procedure in the same patent can be used in exactly the same manner. When the remaining rotation error ε is detected as described above, there is no problem even if a rotation error larger than the rotation alignment error at the time of chip pattern exposure remains. The reason for this is that the size irradiated by the processing laser is at most several microns, which is much smaller than the exposure size of an exposure apparatus (stepper) of 10 mm to 20 mm. However, in this case, it is necessary to position the irradiation point of the processing laser with submicron accuracy. Therefore, the remaining rotation error ε of the wafer is measured, and the rotation of the wafer coordinate system is calculated at the time of positioning to perform the processing. It is necessary to match the center of the laser irradiation position with the target position.

In the above embodiment, when the mark FM is detected by the Y sensor WY, the θ sensor Wθ, and the X sensor WX, it is not always necessary to stop the XY stage ST, and the stage coordinates at the mark FM detection center of each sensor are measured and stored. I just need.

FIG. 10 and FIG. 11 are flowcharts showing the operation of the CPU 33. Next, the operation of this embodiment will be described in detail with reference to this flowchart. First, an operation before the wafer W is loaded on the XY stage ST will be described. First, the CPU 33 sends a signal to a drive unit (not shown) to control the size of the opening 9a to an appropriate size. Next, the CPU 33 is the laser power supply unit 28
, A signal for continuous oscillation is sent to the laser to continuously oscillate the laser.
Next, the CPU 33 sends a signal to the stage control unit 34, and the control unit 34 drives a motor (not shown) to move the XY stage ST in the Z direction (vertical direction) to perform focusing. Therefore, the image of the aperture 9a illuminated by the laser 1 is
An image is formed on the XY stage ST, and the reflected light of the image is formed on the detector 17. Next, the CPU 33 sends a signal to the stage control unit 34, which drives the motors 35 and 36 to
Move the stage ST in the X and Y directions and position the YL pattern of the fiducial mark FM below the Y sensor MY.
The YL pattern, specifically the center YL of the YL pattern, is detected by WY. The detection is as described with reference to FIGS. The signals from the detectors 42 and 43 shown in FIG. Then, the CPU 33 determines from the signal as shown in FIG. 6 that the detection center of the Y sensor WY matches the center YL of the YL pattern (obtains 60 in FIG. 6) Y coordinate Y _{WY of the} stage ST.
Is stored. The position of the stage ST is obtained by referring to the interferometer 25. Next, the CPU 33 sends a signal to the stage control unit 34, which drives the X motor 36 to move the XY stage ST while maintaining the Y coordinate _YWY . At this time, even if the YL pattern comes under the θ sensor Wθ, the detection center of the θ sensor Wθ and the center YL of the YL pattern do not always match exactly. Accordingly, the CPU 33 shifts the detection center of the θ sensor Wθ by a known method, and accurately matches this with the center YL of the YL pattern. Next, the CPU 33 is the stage control unit 3
4 and the control unit 34 drives the motors 35 and 36, and the processing laser irradiation position measurement system uses the YL pattern and
Specifically, the XY stage ST is moved to a position where the pattern of the rectangle 52 can be detected. And the XY stage ST via the control unit 34
Is scanned in the Y direction, and the reflected light from the YL pattern illuminated by the fiber 7 is received by the detector 17. The CPU 33 processes the output of the detector 17 to obtain Y
The center YL of the L pattern is detected. The detection is as described with reference to FIGS. The CPU33 center of Y Zakata Y _FM, i.e. detection center O and YL pattern of the processing laser irradiation position measurement system of the XY stage ST centered YL of YL pattern is positioned by processing laser irradiation position measurement system
And the YL stores the Y coordinate Y _FM stage ST matching. The position of the stage ST is obtained by referring to the output of the interferometer 25. Next, the CPU 33 calculates the coordinate value ▲ Y ^WY _FM ▼ described above.
The value L _WY obtained by subtracting the above-mentioned coordinate value Y _FM from
(See the figure) and store this.

Next, the CPU 33 sends a signal to the stage control unit 34, which drives the motors 35 and 36 to control the XY stage ST to a position where the processing laser irradiation position measuring system can detect the XL pattern, specifically the rectangular 51 pattern. To move. The stage is driven by a continuous wave laser beam from the laser 1.
The pattern 51 on the ST is illuminated. Further, by scanning the stage ST in the X direction via the control unit 34, reflected light from the XL pattern is received by the detector 17. The CPU 33 processes the output of the detector 17 to obtain the center XL of the XL pattern.
Is detected. The detection is as described with reference to FIGS. Then, the CPU 33 determines that the X coordinate X _FM of the XY stage ST at which the center XL of the XL pattern is located by the processing laser irradiation position measurement system, that is, the detection center O of the processing laser irradiation position measurement system coincides with the center XL of the XL pattern. and stores the X coordinate X _FM of the XY stage ST to be. The position of the XY stage ST can be obtained by referring to the output of the interferometer 24. next
The CPU 33 sends a signal to the stage control unit 34, and this control unit 3
4 drive the motors 35 and 36 to move the XY stage ST to X and Y
In the direction, the XL pattern is positioned below the X sensor WX, and the XL pattern by the sensor WX, specifically, the center XL of the XL pattern is detected. The detection is as described with reference to FIG. 4 and FIG. The signals of the detectors 42 and 43 shown in FIG.
The processing is performed in the CPU 33. Then, the CPU 33 stores the X coordinate _XWX of the XY stage ST in which the detection center of the X sensor WX and the center XL of the XL pattern match (obtain 60 in FIG. 6) from the signal as shown in FIG. . XY stage ST position is interferometer 24
Is obtained by referring to the output of The CPU 33 obtains a value L _WX (see FIG. 2) obtained by subtracting the above-mentioned coordinate value X _WX from the above-mentioned coordinate value X _FM and stores it. Then, a signal is sent to the laser power supply unit 28 to stop continuous oscillation of the laser 1. Thus, the distance L between the detection center O of the processing laser irradiation position measurement system and the detection center of the Y sensor WY
_WY and the distance L _WX between the detection center O of the processing laser irradiation position measurement system and the X sensor WX are obtained. The detection center O of the processing laser irradiation position measuring system coincides with the center of the laser irradiation position on the XY stage ST in the processing laser irradiation system. Therefore, L _WY is the distance between the center of the laser irradiation position by the processing laser irradiation system and the detection center of the Y sensor WY, and L _WX is the center of the laser irradiation position by the processing laser irradiation system and the detection of the X sensor WX. It indicates the distance from the center.

Although omitted in the above description, since the reflected light from the wafer surface of the laser pulse during processing returns to each light receiving system,
It is necessary to take countermeasures. A shutter may be provided in front of the light receiver 17, and the shutter may be opened only when measuring the irradiation position. The image pickup tube 23 is provided with a filter having a wavelength characteristic for cutting laser light, and cuts laser light both at the time of irradiation position measurement and at the time of laser processing.

When the output of the continuous oscillation laser beam of the laser 1 fluctuates with time, the output from the light receiver 17 is read,
By driving the variable attenuator 2 to change the amount of transmitted light, the amount of light incident on the light receiver 17 can be made constant.

Next, using the flowchart of FIG.
Will be described. First, the CPU 33 performs wafer pre-alignment by a pre-alignment structure not shown in FIG. Then, the wafer is loaded onto the XY stage ST shown in FIG. 1 by a loading mechanism also not shown. This wafer is XY
It is attracted to a θ rotation stage (not shown) on the stage.
The wafer W shown in the first rain is the wafer thus loaded. Then, an auto focus detection system (not shown) and a Z stage are operated to open an opening 9a on the wafer W.
Is adjusted so that the image of (1) is formed. Since the wafer W loaded on the XY stage ST is loaded after being pre-aligned, it has a substantially predetermined positional relationship with respect to the XY stage ST. However, since it is not accurate, fine alignment is performed as follows. That is, the CPU 33 drives the motors 35 and 36 via the control unit 34, and the Y, θ sensors WY, Wθ provide alignment marks YM,
θM (see FIG. 3) is detected. Then, the XY stage ST and the θ rotation stage (not shown) are moved by driving the motors 35 and 36 and a motor (not shown). Thus, the Y alignment mark YM and the θ alignment mark θM of the wafer W are positioned on a line parallel to the X axis, that is, a line connecting the detection center of the sensor WY and the detection center of Wθ according to a known method.
Then, the Y coordinate of the XY stage for obtaining this state is stored.
The detection of θM of the mark YM is as described with reference to FIGS. 4 and 6. The signals of the detectors 42 and 43 shown in FIG. The position of the XY stage ST is interferometer 2.
Obtained by referring to the output of 5. Thereafter, the θ rotation stage is also attracted to the XY stage and fixed thereto.
Thereafter, the θ check mark YCM may be detected by the Y sensor WY to determine the remaining rotation error. Next, the CPU 33 drives the motors 35 and 36 via the stage control unit 34, moves the XY stage, and detects the X alignment mark XM at a specific position on the wafer W by the X sensor WX. Then, the X coordinate of the XY stage for detecting the X alignment mark XM is stored. The detection of the mark XM is as described with reference to FIGS. The signals of the detectors 42 and 43 shown in FIG.
Processed in U33. The position of the XY stage is obtained from the output of the interferometer 24. The CPU 33 performs the fine alignment of the wafer W as described above, and stores the position of the wafer W on the XY stage ST by detecting the alignment marks YM, θM, and XM at the specific positions of the wafer W. At this time, the CPU 33 stores information such as the size of the wafer, the size of the chips, the arrangement of the chips, which part of each chip is to be cut by the laser, the global alignment sensors WX and WY described above, and the processing laser. Information on the distance of the laser irradiation position from the irradiation system to the center O, and
Information on the position of the wafer fixed on the XY stage ST is stored. When the remaining rotation error ε is obtained, information relating to this avoidance is also accumulated. The CPU 33 then drives the motors 35 and 36 via the stage control unit 34, positions one chip on the wafer W under the lens 12 based on the accumulated information, and cuts the circuit for the chip. A specific part (cutting part) in the center is matched with the center O of the irradiation position by the processing laser irradiation system. And the control unit 29
To control the variable attenuator 2 via the power supply 28, and drive the processing laser light source 1 via the power supply 28 to cause laser oscillation. Therefore, the laser light emitted from the light source 1 is guided onto the chip via the variable attenuator 2, the condenser lens 3, the mirror 4, the aperture 9, the beam splitter 10, the dichroic mirror 11, and the objective lens 12, and the circuit in the chip Cut a specific part. Then CP
U33 determines whether or not all the chips in one wafer have been cut. If all of the chips in the wafer have not yet been cut, the cutting positions of other chips to be cut are read. Thereafter, the XY stage ST is moved based on the read information so that the cut position matches the center O of the irradiation position by the processing laser irradiation system, and this position is cut through the same steps as those described above. In this way, the cutting positions of the respective chips on the wafer W are sequentially cut, and the cutting of all the chips is completed. Then, the wafer is retracted from the XY stage by a loading mechanism (not shown) and returned to a predetermined storage position. As described above, processing of one wafer is completed.

In the present embodiment, the optical image LS can be projected by the processing laser irradiation position measuring system, and at the same time, the position of the wafer pattern and the optical image LS can be observed by illuminating the observation optical system. In this case, the filter in front of the above-described imaging tube may be inserted only during laser processing, and may be removed during LS position observation. FIG. 9 is a view showing an optical image LS of a laser beam and an observation image of a cutting circuit when cutting a circuit in a chip formed on the wafer W, and FIG. FIG. 9 (b) shows a case where the cut portion 94 extends in the Y direction. The use of the observation system described above not only allows confirmation of the position of the cutting point, but also enables observation of the observation system even when a small amount of alignment error remains due to position drift of the optical system, expansion and contraction of the wafer, and the like. While the XY stage ST is slightly moved, the circuit can be cut accurately regardless of the alignment error.

Next, another embodiment will be described with reference to FIG. 12 and FIG. In this embodiment, a detector corresponding to the detector 17 in FIG.
This embodiment is different from the above-described embodiment in that it is provided below the fiducial mark FM fixed to the XY stage ST, that is, in the XY stage ST. FIG. 12 is a sectional view showing the vicinity of the fiducial mark FM. In FIG. 12, the detector 17 'is the first
This corresponds to the detector 17 in the figure. And detector 17 '
Detects light that has passed through the YL pattern or XL pattern of the fiducial mark FM. More specifically, as in the above-described embodiment, the illumination light of the illumination fiber 7 causes the YL
Detector 17 'when pattern or XL pattern is illuminated
Receives the transmitted light of the pattern and obtains a detection output. The output of the detector 17 'is as shown in FIG. In the figure, the output signal S ₂ 'of the detector 17' is like the signal 70 '. Then, from this signal 70 ', YL is determined in the same manner as in the previous embodiment.
A pattern and an XL pattern are detected. The principle is as detailed in the above-described embodiment.

In this embodiment, the fiducial mark FM and the detector
A filter 101 which can be put in and taken out is provided between 17 'so as to remove pulsed laser light. The configuration other than the detector 17 'and the filter 101 and the manner of control by the CPU 33 are the same as in the above-described embodiment. In this embodiment, the components 9, 12, 17 ', and 101 constitute a processing laser irradiation position measuring system.

In the two embodiments described above, the laser light from the laser light source 1 is applied to the fiducial mark FM, and YL, XL
Instead of illuminating each pattern of
Guides a CW laser (continuous light) to irradiate each pattern of YL and XL, and detects each pattern of YL and XL with the slow response detectors 17 and 17 'to perform good measurement (detection) of S / N. It goes without saying that you can do it.

Although the above two embodiments have been described as a device for cutting a circuit, this device changes the conduction state of a circuit by partially annealing a circuit in a chip with a processing laser. It can also be used for applications that change the operation of the circuit.

Also, if the pre-alignment accuracy is poor in a device that attenuates the cutting laser beam so that the appearance of the pattern is not damaged, and the position of the pattern is detected,
Although there is a defect that the MOS diode is destroyed, such a problem does not occur if a small output CW laser is used as in the processing laser irradiation position measuring system of the above embodiment.

FIG. 14 shows a third embodiment. This embodiment is described in JP-A-62-31.
It is a modification of the example shown in 6829. In FIG. 14, the laser beam from the alignment laser 201 passes through the lens 204, is reflected by the mirror 202, and is imaged by the objective lens 12. The reflected light obtained by scanning the laser spot with respect to the mark on the fiducial mark FM is guided to the light receiver 206 via the mirror 203 and the lens 205, and the position of the alignment beam is determined from the change in intensity. You can ask. Although omitted in FIG. 14, the alignment beam is formed by a band-shaped spot orthogonal to the X and Y directions.

In the example of FIG. 14, the optical system is simplified by aligning the optical axis of the alignment beam with the optical axis of the processing beam.However, in this example, the relative position between the beams may be slightly shifted for some reason. Therefore, measurement of the irradiation position is necessary. The measuring method is the same as in the first embodiment.

〔The invention's effect〕

As described above, according to the present invention, by using the processing laser for the irradiation position measurement, the light source for the irradiation position measurement and its optical system are not required, and the optical system can be simplified.

In addition, since the irradiation position is measured using a laser beam having good directivity, the intensity of the reflected light increases, and it is not necessary to prepare a high-sensitivity light receiver.

In addition, since the wavelength at the time of processing and the measurement of the irradiation position are the same,
The design of the objective lens becomes easy.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a plan view showing a relationship between a processing laser irradiation position and a global alignment system, FIG. 3 is a schematic diagram of a main optical system, and FIG. FIG. 5 is a plan view of a fiducial mark pattern, FIG. 6 is a diagram showing signals at the time of mark position measurement of a global alignment sensor, and FIG. 7 is a diagram of a laser irradiation position measurement system for processing. FIG. 8 is a diagram showing signals at the time of dual mark measurement, FIG. 8 is a diagram showing the arrangement of alignment marks on the wafer W, FIG. 9 is a diagram showing the relationship between the circuit to be cut and the irradiation position of the processing laser; 10 and 11 are flowcharts showing the operation of the CPU 33, FIG. 12 is a partial sectional view showing another embodiment, and FIG. 13 is a detector.
FIG. 17 is a diagram showing an output signal of 17 ', FIG. 14 is a schematic diagram of an optical system of a third embodiment, and FIG. 15 is a schematic diagram of an optical system of a conventional embodiment. [Description of Signs of Main Parts] 1-4, 9, 10, 12 ... Processing laser irradiation system 5, 5a, 7-10, 12, 16, 17; 5, 5a, 7-10, 12, 1
7 ', 101: Processing laser irradiation position measurement system 11, 12, 18 to 23: Processing laser irradiation position observation system WX, WY, Wθ Global alignment sensor W Wafer FM Fiducial mark ST ... XY stage 33 ... CPU 201 ... Laser for alignment

Claims (1)

(57) [Claims] 1. A laser processing apparatus for performing thermal processing by pulsating a laser beam to irradiate a laser beam to an object to be processed, comprising: a mark detection optical system for detecting a mark provided on the object to be processed; A beam focusing optical system for focusing a beam, and a unit for measuring an optical axis positional relationship between the mark detection optical system and the beam focusing optical system, wherein the laser is continuously oscillated at the time of operation of the measuring unit. Laser processing equipment.