JPS61193130A - Light beam deflecting device - Google Patents

Abstract

PURPOSE:To compensate the color dispersion of an acousto-optic deflector and to prevent a deflected light beam from having color dispersion by arranging a dispersion optical system which causes color dispersion corresponding to the color dispersion of a light beam which is generated by the acousto-optic deflector and has plural wavelengths at at least either of the incidence side and projection side of the acousto-optic deflector. CONSTITUTION:A light beam deflecting device deflects the light beam which is emitted by a light source and has plural wavelengths by the acousto-optic deflector, and the dispersion optical system 5 which generates color dispersion corresponding to the color dispersion of the light beam generated by the acousto- optic deflector is arranged at at least either of the incidence side and projection side of the acousto-optic deflector. Consequently, the color dispersion of a light beam emitted after deflection is eliminated and the quality of a light beam after the deflection is held excellent.

Description

[Detailed Description of the Invention] [Technology of the Invention] The present invention relates to a light beam deflection device used in a laser beam scanning optical system of a laser pattern writing device, and more specifically, it relates to a light beam deflection device used in a laser beam scanning optical system of a laser pattern drawing device, and more specifically, to a light beam deflection device for controlling the quality of a laser light beam after deflection. The present invention relates to a light beam deflection device that can be maintained in good condition.

[Background of the invention]

FIG. 11 is a schematic diagram of a conventional light beam deflection device. In the figure, (1) is an acousto-optic deflector which is a light beam deflection device, (2) is a light beam on the incident side of the laser beam, and (3)
, (4) is the light beam on the emission side of the laser beam.

The acousto-optic deflector (1) uses ultrasonic waves to deflect the light beam (2) on the incident side of the laser beam.The light beams (3) and (4) on the exit side have excellent stability and can be used at relatively high speeds. Highly accurate angle control is possible.

However, since the conventional light beam deflection device is an element that utilizes the phenomenon of light diffraction, the light beam (2) on the incident side
When the light contains light of several wavelengths, so-called chromatic dispersion occurs in which the deflection angle differs depending on the wavelength. For example, when a plurality of adjacent wavelengths, such as a multi-wavelength argon ion laser beam, are on the same optical axis and are incident on the acousto-optic deflector (1), the deflection angle θ
is expressed by the following formula, where λ is the wavelength of light and A is the wavelength of ultrasound.

Image θ=λ/A Therefore, as shown in FIG. 11, the acousto-optic deflector (1)
The light beam that exits becomes a light beam (3) due to chromatic dispersion.

As shown in (4), the light beam is separated by f, resulting in a light beam that spreads in the direction of deflection, resulting in a problem that a deflected light beam of good quality cannot be obtained.

[Purpose of the invention]

The present invention was made in order to solve the above problems, and provides a light beam deflection device that compensates for the chromatic dispersion of an acousto-optic deflector so that no chromatic dispersion occurs in the deflected light beam. With the goal.

[Summary of the invention]

Therefore, in the present invention, a dispersion optical system that generates chromatic dispersion corresponding to the chromatic dispersion of a light beam containing a plurality of wavelengths occurring in the acousto-optic deflector is disposed on at least one of the input side or the exit side of the acousto-optic deflector. The technical point is to do so.

〔Example〕

Hereinafter, the first embodiment of the present invention will be described in detail with reference to the accompanying drawings.
This is customs.

FIG. 1 is a schematic diagram of the optical deflection device according to the present invention, FIG. ! Figure 1.

On the right side of Figure 1, (1) is the acousto-optic deflector of the light beam deflector, (5) is the dispersive optical system placed on the incident side of the acousto-optic deflector (1), and (6) is the dispersive optical system. A prism (7) is a dispersive element that forms part of the system (5), and a condensing optical system (7) for chromatic dispersion compensation forms part of the dispersive optical system (5). The condensing optical system (7) includes relay lenses (8) and (9).
) and is formed from. al is the incident light beam of the laser beam, (11) and (ls are the light beams colored by the prism (6), and kataku is the exit light beam deflected by the acousto-optic deflector (1).

In Figure 2, 80 is the dispersion/angle of the light beam separated by the chromatic dispersion f of the laser beam emitted from the acousto-optic deflector (1), and ε is the central angle of deflection of the chromatically dispersed light beam. be.

In Fig. 3, Δθ' is the condensed light beam αυ of the laser beam from the condensing optical system (7) to the acousto-optic deflector (1).
, a, the convergence angle %α is the exit light beam.

In the acousto-optic deflector (1), if the wavelength width Δλ of the laser beam is set to the wavelength A of the ultrasonic wave, the dispersion angle Δθ of the light beam by the acousto-optic deflector (1) is expressed by the following formula. Ru.

Δθki Δλ/A.

Here, %A is an amount that changes depending on the deflection angle of the acousto-optic deflection 1B (1), so for example, the chromatic dispersion corresponding to the wavelength A of the ultrasonic wave corresponding to the angle of the deflection center angle t, that is, the light at this time If chromatic dispersion is caused in advance by the prism (6) so as to compensate for the dispersion angles Δθ0 and Δλ of the beam, the greatest compensation effect can be obtained.

Here, if the apex angle of the prism (6) is α and the refractive index difference of the glass with respect to the wavelength of the light beam is bn, then the prism (6)
The dispersion angle Mζ, which is the refraction angle of ), is given by the following equation.

Mu δ Kimru − α Therefore, it is sufficient to determine α so that Mu ′δ and Mu θ0 match.

Also, the relay lens (8) of the condensing optical system (7) (!:
(9) The hub rhythm (6) and the acousto-optic deflector (1) are arranged in a conjugate relationship. This condensing optical system (7) produces a light beam an which is chromatically dispersed by a prism (6).

It fulfills the function of compensating for positional deviation (2).

For example, both the focal lengths of relay lenses (8) and (9) are f.
Then, the distance between the prism (@) and the relay lens (8) is f, the distance between the lenses (8) and (9) is 2f, and the distance between the relay lens (9) and the acousto-optic deflector (1) is f. , the value of the apex angle α of the prism (6) is the refraction angle of the prism (6), the dispersion angle Δδ, and the dispersion angle of the light beam of the acousto-optic deflector (1). When the dispersion angles Δθ0 are set to match, the incident beam of laser light containing multiple wavelengths is separated by the prism, and the relay lens (8) of the condensing optical system (7)
), (9), and the light is focused by an acousto-optic deflector (1
), the light beams are again concentrated at one point and deflected by the acousto-optic deflector (1), and are then emitted as a single emitted light beam (2).

Therefore, when the deflection angle of the acousto-optic deflector (1) is the angle ε, the chromatic dispersion of the emitted light beam (to) becomes zea, and the chromatic dispersion can be kept small even at deflection angles in the vicinity. In this case, as shown in FIG. 2, the dispersion angle Δθ of the light beam by the acousto-optic polarizer (1) and the light beam condensed by the relay lenses (8) and (9) as shown in FIG. The condition is that the convergence angles ゐθ' of And the dispersion angle Δ which is the refraction angle of the light beam of the prism (6)
When δ is equal to the condensing angle Δθ' of the light beam of the relay lens (8), the dispersion angles are kept equal on both the incident and exit sides of the light beam of the relay lenses (8) and (9).

The specific numerical values in this case are as follows. The wavelength is 488
When a light beam near +nm contains light of multiple wavelengths within a range of 10 nttl.

If the wavelength of the ultrasonic wave is 35 μ, the chromatic dispersion by the acousto-optic deflector (1) is 0.98 minutes, and the refractive index difference of the glass for the above wavelength difference is 45 x 1 (r'), the apex angle α of the prism (6) is It may be set to about 36.4°. In this numerical example, the wavelength range is set to around 488 nm, but the numerical value can be similarly determined in the ultraviolet region or the infrared region.

Next, if fIl, the component i1 θ of the light beam of the acousto-optic deflection 1B (1) and the dispersion angle δ of the light beam of the prism (6)
In this case, the relay lens ( 8) Adjust the magnification of (9) and use the acousto-optic deflector (
The dispersion angle ^θ of 1) and the condensing angle Δθ' of the relay lenses (8) and (9) are made to match. Therefore, in this case, not only the prism (6) but also the condensing optical system (7) is used.
) relay lenses (8) and (9) also compensate for the dispersion angle Δθ of the beam light.

Therefore, if the relay lenses (81, (9) are configured to have so-called magnification), the apex angle α of the prism (6) can be controlled to an appropriate size.

FIG. 4 is a diagram showing a second embodiment of the present invention.

In Figure 1, the same configuration as the first example is shown in the first example.
The V! configuration is duplicated using the same reference numerals as in the embodiments. Omit the description.

In this embodiment, the condensing optical system (7) of the first embodiment is configured as a zoom system consisting of relay lenses (8), (9) and a movable variable magnification lens system capable of adjusting magnification.

And the dispersion angle Δ0 of the beam light of the acousto-optic deflector (1)
If the dispersion angle ゐδ of the light beam of the prism (6) is different from E
This is a variable magnification lens system (relay lens (8) by moving L!19.

The magnification of (9) is set to M, and the dispersion angle θ of the acousto-optic deflector (1) and the convergence angle Δθ′ of the relay lens (a) * (9) are
can be adjusted to match.

Further, when the wavelength λ of the ultrasonic wave inputted into the acousto-optic deflector (1) is changed, the deflection center angle C changes, and the dispersion angle Δθ also changes. Since the dispersion angle δ of the prism (6) is constant, the relay lens (8),
By interlocking and varying the magnification of (9), even if the wavelength λ changes and the dispersion angle θ of the light beam of the acousto-optic deflector (1) changes, the relay lenses (8) and (9) always change. The condensing angle ^θ' can be made to match the dispersion angle θ of the acousto-optic deflector.

FIG. 5 is a diagram showing an M3 embodiment of the present invention.

In this embodiment, a diffraction grating (Lllil) is used as a dispersion element in place of the prism (6) used in the previous embodiments.

Other than the use of a diffraction grating (te), this embodiment has no difference in structure or function from the first embodiment, so the same or equivalent members as those in the first embodiment are denoted by the same reference numerals, and the structures are duplicated. The explanation of the effects and effects will be omitted.

If it is desired to vary the dispersion angle of the light beam, this can be done by rotating the diffraction grating like a spectroscope.

Figure jI6 is a diagram showing a fourth embodiment of the present invention.

In this embodiment, a dispersion optical system (5) similar to that in the first embodiment is disposed on the exit side of the acousto-optic deflector (1), and other than that, the rest is the same as in the first embodiment. The same reference numerals are given to the same or equivalent members as in the embodiment, and the explanation of the duplicated structure and operation will be omitted.

FIG. 7 is a diagram showing an embodiment of the IJ5 of the present invention.

In this embodiment, a prism C3 as a dispersive element is used.
1) and (to) are placed on the incident side and exit side of the acousto-optic deflector (1), respectively. The light beam α [containing multiple wavelengths] is spectrally (dispersed) by the prism 01 and divided into a plurality of light beams, 03, which are diffracted by the acousto-optic deflector (1) into light beams (b), ( It becomes (to) and enters the prism (to). The chromatic aberration is finally corrected by this prism (to), and the light beams (b) and (to) are emitted as a nearly coaxial light beam (4G).The stopper (to) is an acousto-optic deflector. This is to block the zero-order diffracted light (7), 07) from the light beam that has passed through (1).

In this embodiment, since the prism 01) produces -variable light beams, there is an advantage that the acousto-optic deflector (1) can be used at the most efficient incident diffraction angle for each wavelength of light beam. Of course, the light beam (b) emitted from the acousto-optic deflector (1), G! The exit angle of 9 is light beam C33,
The angle of incidence is equal to that of 0.03, and deflection can be performed under the most efficient conditions. Here, there are two prisms 0υ on the entrance side and the exit side.
, (to) compensate for chromatic dispersion.

FIG. 8 is a schematic diagram showing a state in which the light beam deflection device of the present invention is used in a laser beam scanning optical system of a laser pattern writing device.

In Fig. 8, (1) is a laser light source that emits argon ion laser light, etc., and the parallel laser beam LB of the laser light emitted from the laser light source is deflected by a mirror Q1) and subjected to acousto-optic modulation. The light is made incident on the element (2). The incident laser beam LB is turned on and off for drawing in the acousto-optic modulator (2), and when turned on, passes through the acousto-optic modulator (2) and is changed direction again by the mirror (c). and enters the optical beam deflection device of the present invention. The optical beam deflector (incorporated) corrects the laser beam LB by deflecting it in the direction indicated by the arrow in accordance with the amount of inclination of each mirror surface of the rotating polygon mirror (5).

The corrected laser beam LB is further changed direction by a mirror (to), passes through an enlarging optical system (1), is reflected by the mirror surface of a one-rotation polygon mirror, and passes through an f-〇 lens (to). to scan the required scanning plane.

Light beam deflection device of the present invention for laser beam scanning optical system
is used, the conventional 5 ra (to) or (
When the scanning unevenness of the laser beam was corrected by slightly correcting the reflection angle of the laser beam LB in synchronization with scanning according to the amount of inclination of each mirror surface of the rotating polygon mirror @, etc. There were also problems with stability and changes over time due to the presence of moving parts.

This problem is solved because there are no mechanical moving parts, and moreover, it is possible to perform surface tilt correction at high speed, and to perform light beam scanning with good quality. Furthermore, since the chromatic dispersion of multi-wavelength laser beams can be reduced, the power of scanning laser beams can be effectively extracted, and generally higher power can be expected than when using a single-wavelength light beam, resulting in improved energy efficiency. A laser beam scanning optical system is obtained.

For this reason, although not shown in the drawings, the laser pattern drawing device ilt stores in advance a correction amount corresponding to the amount of inclination of each mirror surface of the rotating polygon mirror (5), and each mirror of the rotating polygon mirror (5) Immediately before the surface is scanned, the corresponding correction amount is read out from the memory, and the ultrasonic frequency ( A control device is provided that changes the wavelength (wavelength) in synchronization with the scanning of each surface.

FIG. 9 is an explanatory diagram showing the ON/OFF operation of the light beam of the acousto-optic modulation element of the laser beam scanning optical system.

In the figure, 02 is an acousto-optic modulator, and (22a) is a stopper that cuts off the O-order light LBo of the laser beam LB. When the acousto-optic modulator (2) is turned ON, the laser beam LB is deflected and the diffracted light LB1 is turned on by the stopper (
22a), the beam is turned on, and when the acousto-optic modulator (manufactured by Co., Ltd.) is turned off, the zero-order light LBo is cut by the stopper (22a) and the beam is turned off. In this acousto-optic modulator Q, when the laser beam I/B is deflected into a beam-on state, chromatic dispersion occurs in the diffracted light LB1.

Therefore, there is a limit to the quality of the modulated light beam.

FIG. 10 is an explanatory diagram showing the ON/O1l'F operation of the acousto-optic modulator that corrects the drawbacks of the device shown in FIG. The items included were an acousto-optic deflector (1) and a prism (6).
It consists of a relay lens (8), (9) and a stopper (22a), and transmits the diffracted light LB when the beam is ON, and transmits the 0th order light LBo when the beam is OFF' to the stopper (22a).
) is similar to the case in Figure 9, but in this case Aoko uses a prism (6), relay lenses (8), and (9) to cut the acousto-optic deflector (1).
) deflects the laser beam LB, the diffracted light LB,
chromatic dispersion can be compensated for. Therefore, the quality of the modulated light beam can be kept good.

Incidentally, in the above description, the present invention was described for the case where it is used in a laser beam scanning system of a laser pattern writing apparatus, etc., but as another example of application, for example, when performing 7-line alignment between a mask and a wafer, markings on a mask or It can also be used to scan marks on a wafer with a laser spot, in which case a laser containing multiple wavelengths is used to help improve the S/N of optical information from the mask.

〔Effect of the invention〕

As explained above, according to the present invention, a dispersive optical system that generates chromatic dispersion corresponding to the chromatic dispersion of a light beam containing the decimal wavelength generated in an acousto-optic deflector is installed on the entrance side or exit side of an acousto-optic deflector. The light beam is placed on at least one of the sides to eliminate chromatic dispersion of the light beam emitted after deflection.
This has the effect of maintaining good quality of the light beam after deflection.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a light beam deflection device which is the first embodiment of the present invention, Fig. 2 is an explanatory diagram showing the chromatic dispersion of the light beam of the acousto-optic aS, and Fig. 3 is a diagram of the condensing optical system. 4 is a schematic diagram of a light beam deflection device according to a second embodiment of the present invention. FIG. 5 is a schematic diagram of a light beam deflection device according to a third embodiment of the present invention. 6 is a schematic diagram of a light beam deflection device according to a fourth embodiment of the present invention, FIG. 7' is a schematic diagram of a light beam deflection device according to a fifth embodiment of the present invention, and FIG. 8 is a schematic diagram of a light beam deflection device according to a fifth embodiment of the present invention. A schematic diagram showing a state in which the deflection device is used in a laser beam scanning optical system of a laser pattern drawing device, FIG. 9 is an explanatory diagram showing ON and OFF operations of an acousto-optic modulation element,
FIG. 10 is an explanatory diagram showing the ON/OFF operation of another acousto-optic modulation element, and FIG. 11 is a schematic diagram of a conventional light beam deflection device. (1)...Acousto-optic deflector, (2)...Incoming beam, (3), (4)...Outgoing beam, (5)...Dispersion optical system, (6)...Prism , (7)... Condensing optical system, (8), (9)... Relay lens, α9... Concave lens, αe... Diffraction grating. Agent Patent Attorney Sanro Kimura Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 τ Figure 6

Claims (1)

[Claims] In a light beam deflection device that uses an acousto-optic deflector to deflect a light beam including a plurality of wavelengths generated from a light source, dispersive optics generates chromatic dispersion corresponding to the chromatic dispersion of the light beam produced by the acousto-optic deflector. system,
A light beam deflection device, characterized in that the light beam deflection device is disposed on at least one of an entrance side and an exit side of the acousto-optic deflector.