JP2002162655A - Optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently obtain light formed to a beam shape of a ring band form. SOLUTION: The laser beam emitted from a UV solid-state laser 2 is made incident on a biaxial double refracting crystal 14. The laser beam is formed to the beam shape of the ring band form by this biaxial double refracting crystal 14 and is condensed to a semiconductor wafer 30 by an objective lens 17. Namely, the optical system utilizing apodization is embodied by a nonlinear optical crystal (biaxial double refracting crystal 14) having biaxial double refractions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for condensing light in the form of an annular beam.

[0002]

2. Description of the Related Art In recent years, the degree of integration of semiconductor integrated circuits has been steadily improving as a driving force of the electronic industry, which is being digitized. In order to improve the degree of integration of a semiconductor integrated circuit, it is necessary to form a fine circuit pattern with high precision by improving the optical resolution of an exposure apparatus (stepper) for exposing the circuit pattern.

In order to cope with higher resolution of an exposure apparatus,
High numerical aperture condenser lens, short wavelength excimer laser light source,
Development of a resist material having a non-linear developing process characteristic has been advanced. In the exposure optical system,
A super-resolution technique using a phase shift mask method, a modified illumination optical system, and the like are being developed.

As one of such super-resolution techniques, the present inventor has disclosed an exposure method using a diffraction type mask as disclosed in Japanese Unexamined Patent Publication No.
No. 50117, "Photomask and exposure method using the same".

[0005] In the field of optical microscopes as well, it is required to increase the optical resolution in order to observe a fine observation object with high accuracy. The present inventor has proposed a technique for improving the contrast of an observed image using an oblique incidence illumination method as one of techniques for achieving such a high resolution (Japanese Patent Application No. 11-29729).
No. 8). By incorporating the optical system to which this proposal is applied into various inspection apparatuses, it is possible to improve the contrast of an observation image in the inspection apparatus and achieve high resolution.

In the above-described exposure apparatus, optical microscope, and various inspection apparatuses, it is required to condense light to a smaller spot diameter in order to improve optical resolution. When condensing light in this way, as a method for obtaining a smaller spot diameter, a parallel light beam having a ring-shaped beam shape is made incident on a condensing lens, so that a method for condensing light as compared with a normal light beam is condensed. A method of obtaining a small spot diameter is also known. Such a method is called apodization, and is a method of optically filtering a spatial frequency to realize a minute spotlight using only high-frequency components of light.

It has been proposed to increase the recording density of an optical disk by using such a method ("Superresolution Elements for High-Density Optic").
al Storage "Tasso RMSales et al. International S
ymposium on Optical Memory and Optical Data Storag
e, OSA Technical Digest Series Volume 12, 1996).

[0008]

One of the techniques for obtaining the above-mentioned annular beam shape is to transform the beam shape into an annular shape by using a phase plate having a predetermined pattern. There is a method.
However, such a phase plate has a problem that high-precision technology is required for processing and manufacturing.

In recent years, as one of the technologies that have attracted attention,
A laser beam used for recording / reproducing of an optical disk is used as a solid immersion lens (hereinafter, referred to as SIL: Solid Immersion Lens).
The numerical aperture (NA) by condensing light using
There is a technique of performing recording / reproducing on an optical disc in an area where is equal to or more than one, that is, a so-called super-resolution technique. However, for example, in order to obtain an apodization effect by injecting an annular parallel light beam into such an SIL, it is necessary to make the phase plate correspond to the diameter of a minute SIL or a laser beam. It is extremely difficult to create a very small phase plate.

As a method for obtaining an annular beam shape, there is a method in which only a central portion of light having a predetermined beam diameter is shielded by an optical mask. However, in this case, naturally, there is a problem in that a loss occurs in the amount of light shielded by the mask, and it is not possible to efficiently obtain annular light.

Accordingly, the present invention provides an optical device capable of easily and efficiently obtaining light having an annular beam shape and condensing it into a high-precision, high-output spot light. Aim.

[0012]

An optical device according to the present invention has a light source that emits light in a predetermined wavelength range, a light source having biaxial birefringence, and light emitted from the light source. A nonlinear optical crystal for converting light into an annular beam shape, and a condenser lens for condensing light emitted from the nonlinear optical crystal are provided.

In the optical device according to the present invention configured as described above, light having an annular beam shape formed by the nonlinear optical crystal is incident on the peripheral portion of the condenser lens. For this reason, the light emitted from the light source does not lose the light amount when the beam shape is made into an annular shape, and the annular light can be efficiently obtained. Also, 2
Since a nonlinear optical crystal having axial birefringence is used, a ring-shaped beam shape can be obtained extremely simply and at low cost.

Further, the optical device according to the present invention may include a beam expander that converts a beam diameter of light emitted from the nonlinear optical crystal into a desired beam diameter and enters the light collecting lens. . This makes it easy to adjust the beam diameter to the diameter of the condenser lens used,
The degree of freedom in optical design can be improved.

Further, in the optical device according to the present invention, a laser oscillator for emitting laser light in an ultraviolet wavelength range may be used as the light source, and a lithium triborate crystal may be used as the nonlinear optical crystal. Since the lithium triborate crystal can transmit light having a wavelength of up to 160 nm, the lithium triborate crystal is used to form a laser beam in the ultraviolet wavelength region into a ring shape, and the laser beam in the ultraviolet wavelength region is used as a light source. By condensing with a condenser lens, it is possible to obtain a finer spot light.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. Hereinafter, first, as one configuration example of an optical device to which the present invention is applied, FIG.
An inspection device 1 as shown in FIG. The inspection apparatus 1 illuminates a semiconductor wafer 30 to be inspected by using an oblique incidence illumination method using a diffraction grating (grating), and generates a fine circuit pattern formed on the semiconductor wafer 30. This is a device for detecting a defect.

As shown in FIG. 1, the inspection apparatus 1 uses an ultraviolet solid-state laser 2 as a light source of illumination light. The ultraviolet solid laser 2 converts the wavelength of a solid laser such as a YAG laser using a nonlinear optical crystal.
A laser beam of about 6 nm is emitted.

In general, the inspection capability of an inspection apparatus depends on the wavelength of illumination light applied to an inspection object, and a shorter wavelength of the illumination light allows inspection of a finer structure. The inspection apparatus 1 uses the ultraviolet solid-state laser 2 as a light source of the illumination light, and illuminates the inspection target with the short-wavelength illumination light, so that a fine structure can be inspected. In addition, the ultraviolet solid-state laser 2 is excellent in handling such that the apparatus itself is small and does not require water cooling, and is optimal as a light source in the inspection apparatus 1.

[0019] As the ultraviolet solid laser 2 is, for example, Nd: YAG and Nd: third harmonic of light output with YVO ₄ or the like as a laser medium, fourth harmonic, or fifth harmonic A laser oscillator that outputs light can be used. Further, a laser oscillator that outputs ultraviolet laser light generated by a nonlinear optical effect such as sum frequency mixing may be used. Furthermore, KrF, ArF, F ₂
An excimer laser oscillator using such as a laser medium may be used.

In the inspection apparatus 1, illumination light emitted from the ultraviolet solid-state laser 2 is guided by the lens 3 and the optical fiber 4 for ultraviolet light, and is incident on the grating 5.

The grating 5 is a light diffraction element that diffracts incident illumination light. The inspection apparatus 1 irradiates the semiconductor wafer 30 to be inspected with the illumination light diffracted by the grating 5 so that the semiconductor wafer 30
Can be illuminated by so-called oblique incidence illumination. Note that a hologram may be used in addition to the grating 5 as a light diffraction element that diffracts illumination light. In the case of inspecting a two-dimensional shape such as a contact hole, a double grating having gratings in two directions orthogonal to each other may be used.

The grating 5 is supported by a moving mechanism 6 so as to be movable in the optical axis direction indicated by the arrow Z in FIG. For example, as shown in FIG. 2, the moving mechanism 6 includes a holder 7 that holds the grating 5, a drive shaft 8 and a guide shaft 9 that are arranged in parallel with each other, and that is connected to both left and right ends of the holder 7. 8 connected to the motor 10. The moving mechanism 6 converts the power of the motor 10 into a linear motion of the holder 7 and moves the grating 5 held by the holder 7 in the optical axis direction indicated by the arrow Z.

As described above, the inspection apparatus 1 changes the incident angle of the illumination light diffracted by the grating 5 to the semiconductor wafer 30 by the moving mechanism 6 moving the grating 5 in the optical axis direction. Has been made possible. The moving mechanism 6 is not limited to the example shown in FIG. 2, and may have any configuration as long as it can move the grating 5 in the optical axis direction. However, in order to accurately perform the operation of moving the grating 5 and efficiently inspect the semiconductor wafer 30, the moving mechanism 6 is desirably configured to be controllable by an external electric signal.

In the inspection apparatus 1, the illumination light passing through the grating 5 passes through the lens 11, the rotating diffuser 12, and the lens 13, and is incident on the biaxial birefringent crystal 14. The biaxial birefringent crystal 14
Is transmitted to the beam splitter 15.

Since the inspection apparatus 1 uses laser light having high coherence as illumination light, speckles occur in the illumination light. Therefore, unless the speckles are canceled, the semiconductor wafer 30 cannot be properly observed. Therefore, in the inspection apparatus 1, the rotating diffusion plate 12 is provided in the optical path of the illumination light to cancel the speckle.

The biaxial birefringent crystal 14 is a nonlinear optical crystal having biaxial birefringence and converting incident light into an annular beam shape. As such a biaxial birefringent crystal 14, for example, lithium triborate (LiB
₃ O ₅ , or LBO) crystals can be used. For example, when an LBO crystal manufactured by CASIX is used, it is possible to transmit ultraviolet light having a wavelength of up to 160 nm satisfactorily and efficiently transmit ultraviolet light emitted from the ultraviolet solid-state laser 2. it can.

Here, the principle in which a ring-shaped beam shape can be obtained by the biaxial birefringent crystal 14 will be described.

The biaxial birefringent crystal 14 has two refractive index surfaces overlapping near the optical axis. As shown in FIG. 3, light incident from the normal direction at this position is It is distributed in a conical shape including the intersection of the optical axis and the refractive index surface as the apex and the optical axis as the generatrix. Therefore, the incident surface 14a perpendicular to the optical axis of the biaxial birefringent crystal 14
Then, light is incident on the incident surface 14a in a direction perpendicular to the incident surface 14a, and the light is emitted from the emission surface 14b parallel to the incident surface 14a. And a ring-shaped beam shape is obtained.
In this case, since birefringence is generated in a conical shape inside the biaxial birefringent crystal 14, it can be said that a ring-shaped beam shape is generated using the internal conical birefringence. Become.

In the inspection apparatus 1, a non-linear optical crystal having biaxial birefringence such as an LBO crystal is cut perpendicularly to the optical axis on the optical axis of the light irradiated from the lens 13. A biaxial birefringent crystal 14 is provided. As a result, the light incident on the biaxial birefringent crystal 14 is formed into an orbicular beam shape by the biaxial birefringent crystal 14 and then applied to the beam splitter 15.

As shown in FIG. 4, when the light converged by the lens 40 or the like is incident on the biaxial birefringent crystal 14, a phenomenon opposite to the above-described internal conical birefringence occurs. It can be observed on the emission surface 14b. In this case as well, the emitted light has an annular beam shape in the same manner as in the case where internal conical birefringence occurs. In this case, since the light spreads conically outside the biaxial birefringent crystal 14, an annular beam shape is generated using the external conical birefringence.

Therefore, in the inspection apparatus 1, the lens 40 is disposed on the incident surface side of the biaxial birefringent crystal 14,
It may be configured to generate an annular beam shape using the above-mentioned external conical birefringence.

The beam splitter 15 separates an optical path of illumination light for irradiating the semiconductor wafer 30 to be inspected from an optical path of light reflected by the semiconductor wafer 30. In this inspection device 1, the illumination light reflected by the beam splitter 15
Irradiation is performed on the semiconductor wafer 30 to be inspected via the lens 6 and the objective lens 17.

In the inspection apparatus 1, the objective lens 17 has a function as a condensing lens for condensing light having a ring-shaped beam shape by the biaxial birefringent crystal 14. Further, in the inspection apparatus 1, the optical axis of the objective lens 17 is adjusted such that the light having the annular beam shape formed by the biaxial birefringent crystal 14 is incident on the peripheral edge of the objective lens 17. By optically filtering the spatial frequency using apodization, it is possible to irradiate the semiconductor wafer 30 with a minute spot light composed only of the high-frequency component of the light.

The semiconductor wafer 30 to be inspected is placed on the inspection stage 18. Inspection stage 1
Reference numeral 7 supports the semiconductor wafer 30 and moves the semiconductor wafer 30 in a horizontal direction or a vertical direction to position the semiconductor wafer 30 at a predetermined inspection position. Then, the semiconductor wafer 30 positioned at the predetermined inspection position is irradiated with the illumination light.

Here, the illumination light is light diffracted by the grating 5 (for example, +1 order light or −1 order light), and is obliquely incident on the semiconductor wafer 30 at a predetermined incident angle. The incident angle of the illumination light can be arbitrarily changed by moving the grating 5 in the optical axis direction by the moving mechanism 6. Therefore,
In the inspection apparatus 1, the incident angle of the illumination light is set to an optimum value according to the pattern of the semiconductor wafer 30 to be inspected, or the semiconductor wafer 30 is changed while changing the incident angle of the illumination light.
Can be repeatedly inspected, and a change in the shape of the pattern of the semiconductor wafer 30 can be appropriately and effectively detected.

The light reflected by the semiconductor wafer 30 is
The light passes through the objective lens 17 and the lens 16 and reenters the beam splitter 15. Then, in the inspection apparatus 1, the reflected light transmitted through the beam splitter 15 is
The light enters the polarization beam splitter 19.

The polarization beam splitter 19 transmits one polarized light component of the incident light and reflects the other polarized light component, so that the incident light is polarized and separated. And in this inspection device 1,
One of the reflected light components reflected by the semiconductor wafer 30 and transmitted through the polarization beam splitter 19 is detected by a first light receiving element 21 such as a CCD via a first eyepiece lens 20, and The polarized light component reflected by the polarization beam splitter 19 out of the reflected light from the wafer 30 is transmitted through the second eyepiece 22 to the C component.
The light is detected by a second light receiving element 23 composed of a CD or the like.

As described above, the inspection apparatus 1 converts each polarized component separated by the polarization beam splitter 19 into the first polarization component.
Are individually detected by the light receiving element 21 and the second light receiving element 23, and are image-processed by a processing device 24 such as a computer.
When the reflectance of the semiconductor wafer has polarization dependency, or when the semiconductor wafer 3
When the structure of the 0 pattern is very fine, information on the structure and material can be obtained.

In the inspection apparatus 1 configured as described above, the incident angle of the illumination light on the semiconductor wafer 30 to be inspected can be arbitrarily changed. It is possible to more effectively detect a change in the shape of the pattern on the semiconductor wafer 30 by setting the incident angle to be the most sensitive to the pattern variation.

In addition, since the inspection apparatus 1 can arbitrarily change the incident angle of the illumination light on the semiconductor wafer 30 to be inspected, the inspection apparatus 1 inspects the semiconductor wafer 30 while changing the incident angle of the illumination light. Can be repeated. In the inspection apparatus 1, by correcting the obtained inspection result by using the processing device 24 such as a computer, it is possible to more appropriately and accurately detect a change in the shape of the pattern of the semiconductor wafer 30 and the like. .

Further, the inspection apparatus 1 is configured so that the light having an annular beam shape formed by the biaxial birefringent crystal 14 is incident on the periphery of the objective lens 17.
It is configured as an inspection device using so-called apodization.

Since the inspection apparatus 1 generates an annular beam shape using the biaxial birefringent crystal 14, loss of the amount of light, such as when an annular beam shape is generated using a mask, is used. Does not occur, and all the light emitted from the ultraviolet solid-state laser 2 can be collected by the objective lens 17 and irradiated on the semiconductor wafer 30. Therefore, for example, by using the ultraviolet solid-state laser 2 having a small output, the cost of the entire apparatus can be reduced, and a sufficient amount of light can be secured to perform a highly accurate inspection.

In addition, the inspection apparatus 1 includes a biaxial birefringent crystal 1
Since a ring-shaped beam shape is generated by the method 4, it does not require advanced technology for processing and manufacturing as in the case of using a phase plate, for example. Can be generated.

In the inspection apparatus 1, for example, FIG.
As shown in (1), a beam expander 45 for converting a beam diameter may be provided between the biaxial birefringent crystal 14 and the objective lens 17 having a function as a condenser lens. The beam expander 45 constitutes both telecentric optical systems by the first lens 46 and the second lens 47, and has a function of converting a beam diameter of incident light into a desired beam diameter. are doing.

In the inspection apparatus 1, the provision of such a beam expander 45 makes it easy to match the outer diameter of the light beam having a ring-shaped beam shape to the diameter of the objective lens 17, and the optical design is improved. The degree of freedom can be improved. In addition, the beam expander 45 can be provided between the biaxial birefringent crystal 14 and the beam splitter 15 in the inspection apparatus 1, for example.

Next, a recording / reproducing apparatus 50 as shown in FIG. 6 will be described as another configuration example of the optical apparatus to which the present invention is applied. The recording / reproducing device 50 is a device that records and / or reproduces an information signal on the optical disc 100 by irradiating the optical disc 100 with light (hereinafter, referred to as recording / reproducing). In the following description, only the differences from the above-described inspection apparatus 1 will be described with respect to the features obtained by applying the present invention.

In the following description, the recording / reproducing apparatus 50 does not particularly limit the optical disc 100 to be recorded / reproduced, but the optical disc 100 is formed, for example, with a fine concavo-convex pattern corresponding to an information signal. A read-only optical disk, a phase-change type magneto-optical disk in which recording / reproduction is performed by forming / detecting a recording mark corresponding to an information signal, or a write-once optical disk in which a recording layer is formed of an organic dye material Can be used.

As shown in FIG. 6, the recording / reproducing device 50
A spindle motor 51 for rotating the optical disc 100 at a predetermined speed, an optical pickup 52 for irradiating the optical disc 100 with laser light, and a binarizing unit 53 for binarizing a signal read from the optical disc 100 A signal processing unit 54 for performing various processes on a signal for recording / reproducing to / from the optical disc 100; an interface unit 55 for inputting / outputting a signal to / from a host device 110 connected to the outside; And a power control unit 57 for controlling the irradiation power of the laser beam output from the optical pickup 3.

The spindle motor 51 includes a signal processing unit 54
Or the rotation is controlled by the control unit 56,
During recording and reproduction on the optical disk 100, the optical disk 100 is driven to rotate at a predetermined speed.

The optical pickup 52 will be described in detail later. For example, a light source such as a semiconductor laser diode (not shown in FIG. 6) and a laser beam emitted from this light source are reflected on the optical disk 100 and returned. A light detection unit (not shown in FIG. 6) for detecting return light. The light detection unit is configured by, for example, a photodiode or the like, and outputs a voltage signal corresponding to return light to the binarization unit 53 and the power control unit 57 by photoelectric conversion and current-voltage conversion. The optical pickup 52 also controls the optical disc 100 based on the return light detected by the light detection unit.
A focus servo signal and a tracking servo signal indicating a defocus amount and a detrack amount of the light spot of the laser spot irradiated on the recording track are output to the signal processing unit 54.

The optical pickup 52 is movable in the radial direction of the optical disk 100 by a drive mechanism (not shown), and can irradiate an arbitrary position on the optical disk 100 with laser light.

The binarizing section 53 performs a binarizing process on the voltage signal output from the optical pickup 52 in response to the return light from the optical disc 100 when reproducing the optical disc 100. Then, the processed signal is output to the signal processing unit 54 and the interface unit 55.

The signal processing unit 54 includes an optical pickup 52
Based on the focus servo signal and the tracking servo signal output from the optical disc 100, focus control and tracking control of the laser light emitted from the optical pickup 52 to the optical disc 100 are performed. The signal processing unit 54 controls the rotation speed of the optical disc 100 and controls the positioning of the optical pickup 52 by performing servo control of the spindle motor 51 and control of a driving mechanism that drives the optical pickup 52.

The interface unit 55 inputs / outputs various signals to / from a host device 110 connected to the outside.
Further, the interface unit 55 performs an encoding process and a decoding process of an information signal for recording and reproducing on the optical disc 100. Further, the interface unit 55 is used when the operation mode is switched in the binarization unit 53 and the power control unit 57 generates a pulse waveform in response to a recording / reproducing request for the optical disc 100 input from the host device 110. A recording clock as a light emission timing is generated.

The control section 56 is connected to each section of the recording / reproducing apparatus 50, and has a function of centrally controlling the operation of the entire recording / reproducing apparatus 50 by controlling the operation of each section. The control unit 56 includes, for example, a CPU (Central Pr
ocessing Unit), RAM (Random Access Memory),
It is composed of various semiconductor chips such as a ROM (Read Only Memory), and controls the operation of the entire recording / reproducing device 50 according to, for example, an operation program recorded in the ROM.

The power control unit 57 includes the optical pickup 5
2 has a function of controlling the irradiation power of the laser beam output from the optical disk 100, and controls the irradiation power to be optimal in accordance with the type and characteristics of the optical disk 100 on which recording and reproduction are performed. And a function of controlling the irradiation power to be optimal according to an operation state such as a reproduction operation or an initialization operation.

The optical pickup 52 of the recording / reproducing apparatus 50 includes, for example, as shown in FIG. 7, a laser diode 60 for emitting a laser beam of a predetermined wavelength,
A biaxial birefringent crystal 61 that forms a laser beam emitted from the laser diode 60 into an annular beam shape, and a laser beam that passes through the biaxial birefringent crystal 61 and has an annular beam shape are used. An incident beam splitter 62,
The laser beam transmitted through this beam splitter is incident,
An objective lens 63 for irradiating the laser light to the optical disc 100 is provided. Further, the beam splitter 62
The laser beam emitted by the objective lens 63 is configured to reflect the return light reflected from the signal recording surface of the optical disc 100 and returning without transmitting. The optical pickup 52 includes a condenser lens 64 and a light receiving element 65 on the optical path of the light reflected by the beam splitter 62.

In the optical pickup 52, the biaxial birefringent crystal 61 corresponds to the biaxial birefringent crystal 14 in the above-described inspection apparatus 1, and converts the laser light emitted by the laser diode 60 into an annular beam shape. After that, it has a function of causing the beam to enter the beam splitter 62.

The objective lens 63 includes a beam splitter 62
A laser beam having a ring-shaped beam shape is transmitted through the optical disk 1 and the laser beam is condensed to a small spot diameter by using apodization to form an optical disc 1.
Irradiate on the 00 signal recording surface. That is, in the recording / reproducing device 50, the objective lens 63 has a function as a condensing lens for condensing the laser light having the annular beam shape. Also, the objective lens 63 is
The return light from 00 is again incident on the beam splitter 62.

The return light reflected by the beam splitter 62 is condensed by a condenser lens 64 and is incident on a light receiving element 65. The light receiving element 65 is, for example, a CCD
It is constituted by elements and the like, detects the amount of incident return light, and outputs it as an electric signal.

As shown in FIG. 7, the objective lens 63 is composed of a first lens 70 and a second lens 71, and has a function as a solid immersion lens (SIL). .

SIL is a technology that has attracted attention in recent years. Instead of using an immersion lens using a liquid, the front lens of the lens is brought close enough to the object to be observed, so that the front lens of the lens and the object to be observed can be used. And evanescent light. In the SIL, the substantial numerical aperture can be improved to a value obtained by multiplying the numerical aperture (NA) of the lens by the refractive index of the lens. For example, when the NA of the lens is 0.6 and the refractive index of the front lens is 2, the actual NA in this SIL is 1.
2 can be set.

In the objective lens 63, the second lens 71 corresponds to the front lens of the optical disk 100.
Corresponds to the observation target. That is,
The recording / reproducing apparatus 50 includes an objective lens 63 configured as an SIL, and irradiates the optical disc 100 with evanescent light emitted from the second lens 71,
The optical disk 100 is configured to record and reproduce information signals on the signal recording surface. by this,
The optical resolution of the optical disc 100 is increased to achieve a higher recording density.

The recording / reproducing device 50 is configured as described above. Since the objective lens 63 functions as an SIL, an information signal is recorded on the optical disc 100 at a high density by a so-called super-resolution technique. It is possible to play.

In the recording / reproducing apparatus 50, an annular lens-shaped laser beam generated by the biaxial birefringent crystal 61 is focused by the objective lens 63,
By optically filtering the spatial frequency using apodization, it is possible to irradiate the optical disc 100 with a minute spot light only by the high frequency component of the laser light.

Therefore, in the recording / reproducing apparatus 50, the laser light is condensed into minute spot light with high precision by apodization, and the condensed laser light is converted into evanescent light by using the SIL technique. By these synergistic effects, recording and reproduction with respect to the optical disc 100 can be performed at an extremely high density.

In general, when recording / reproducing is performed on the optical disk 100 using apodization, a phenomenon occurs that coma is likely to occur due to the influence of the skew angle of the optical disk 100 and the like. However, in the recording / reproducing device 50, the objective lens 63 is configured as an SIL, and since the SIL is a lens that hardly generates coma aberration, there is an advantage that occurrence of such coma aberration can be suppressed. Further, since the recording / reproducing apparatus 50 is configured to perform recording / reproducing by evanescent light using the objective lens 63 having NA of 1 or more, the objective lens 63 and the optical disc 1 are used.
Even if the gap width with 00 fluctuates, there is an advantage that the processing of the detected signal is facilitated.

Further, in the recording / reproducing device 50, since the annular beam shape is generated by using the biaxial birefringent crystal 61, the loss of the light amount is suppressed as compared with the case where a mask is used. be able to. Also, for example, unlike the case of using a phase plate, does not require advanced technology for processing and manufacturing,
A highly accurate beam shape can be generated extremely simply and at low cost.

In the above, the inspection apparatus 1 and the recording / reproducing apparatus 50 have been described as an example of the configuration to which the present invention is applied. However, the present invention is not limited to the application to the above-described configuration example. It goes without saying that the present invention can be widely applied to various optical devices for condensing light having a ring-shaped beam shape without departing from the gist of the present invention. Specifically, the present invention can be widely applied to, for example, an optical microscope, a microfabrication device using laser light, or an illumination device that performs annular illumination. By applying the present invention, the light in the annular beam shape, with high accuracy,
It can be obtained easily at low cost.

[0070]

In the optical device according to the present invention, the light having an annular beam shape formed by the nonlinear optical crystal is incident on the periphery of the optical lens. For this reason, the light emitted from the light source does not lose the light amount when the beam shape is made into an annular shape, and the annular light can be efficiently obtained. In addition, since a nonlinear optical crystal having biaxial birefringence is used, a ring-shaped beam shape can be obtained extremely easily and at low cost. Therefore, according to the present invention, it is possible to easily and efficiently obtain light having a ring-shaped beam shape, and to condense it to a high-precision and high-output spot light using apodization technology. Becomes

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an inspection apparatus shown as one configuration example of an optical device to which the present invention is applied.

FIG. 2 is an enlarged schematic view of a main part showing a grating moving mechanism in the inspection apparatus.

FIG. 3 is a diagram illustrating a biaxial birefringent crystal in the inspection apparatus, and is a schematic diagram illustrating internal conical birefringence.

FIG. 4 is a diagram illustrating a biaxial birefringent crystal in the inspection apparatus, and is a schematic diagram illustrating an external conical birefringence.

FIG. 5 is a schematic diagram for explaining a beam expander provided in the inspection apparatus.

FIG. 6 is a schematic diagram of a recording / reproducing device shown as another configuration example of the optical device to which the present invention is applied.

FIG. 7 is an enlarged schematic view of a main part for describing an optical pickup in the recording / reproducing apparatus.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 inspection device, 2 ultraviolet solid laser, 5 grating (diffraction grating), 12 rotating diffuser, 14 biaxial birefringent crystal, 15 beam splitter, 17 objective lens, 21 first light receiving element, 23 second light receiving element , 3
0 semiconductor wafer, 45 beam expander, 50
Recording / reproducing device, 52 optical pickup, 61 biaxial birefringent crystal, 62 beam splitter, 63 objective lens, 65 light receiving element, 100 optical disk, 110 host device

Claims (3)

[Claims] 1. A non-linear optical crystal which emits light in a predetermined wavelength range, and which has biaxial birefringence, receives light emitted from the light source, and converts the light into an annular beam shape. An optical device, comprising: a condenser lens for condensing light emitted from the nonlinear optical crystal. 2. The optical system according to claim 1, further comprising a beam expander that converts a beam diameter of the light emitted from the nonlinear optical crystal into a desired beam diameter and enters the light collecting lens. apparatus. 3. The optical device according to claim 1, wherein the light source is a laser oscillator that emits laser light in an ultraviolet wavelength range, and the nonlinear optical crystal is a lithium triborate crystal.