JPH09180274A - Optical device and probe therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to control magnitude of a recording bit and pattern width, etc., by controlling evanescent light quantity to be used in information recording and pattern forming. SOLUTION: The optical fiber probe for which an optical coupler 9 dividing laser beams into more than two optical fibers 8, 10 or an optical switch introducing beams to either one optical fiber among two are used and the top end of at least one optical fiber is made acute to be an evanescent optical probe 42 is used. Damage of the probe can be easily dealt with by integrating the fibers 8, 10 and the optical coupler 9 or the optical switch to form the probe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device using evanescent light, and more particularly to a structure of an evanescent light probe and an optical device using the same.

[0002]

2. Description of the Related Art Regarding an evanescent optical probe,
Applied Physics Letter Volume 61 (1992
Year) p. 142 (Appl. Phys. Lett. 61 (1992) 14
2).

FIG. 2 shows an outline of the prior art shown in this document. As shown in the figure, the laser light 1 is made incident on the evanescent optical probe 42 arranged so as to face the sample 13,
Evanescent light is output from the probe 42 to the sample 13 to perform necessary measurement or processing. At this time, the laser light 1 guided from the laser source 2 is supplied to the laser source 2 and the fiber 6
Is introduced into the fiber 6 by the first optical coupler 4 for coupling
The laser light introduced into the fiber 6 is passed through the fiber 6 and the fiber 62 formed at the tip of the probe 42.
The light is guided to the fiber 62 by the optical coupler 7.

[0004]

At this time, the coupling efficiency in the first optical coupler 4 and the second optical coupler 7 depends on the mechanical coupling. Further, the amount of light emitted from the laser source 2 itself also changes.
Therefore, by simply configuring the system shown in FIG.
It was unknown how much the laser light 1 used was guided to the probe 42. Therefore, for example, the amount of evanescent light is not determined for information recording or pattern formation,
This configuration alone is not sufficient when not only the presence / absence of the laser light but also the intensity of the laser light, such as the control of the bit size and the pattern width, is required. Of course, simply by configuring the system once and then measuring the light amount of the output laser light, this can be dealt with, but it is necessary to remeasure each time there is a change.

To solve the problem of the fluctuation of the light quantity in a general optical system, for example, as disclosed in Japanese Patent Laid-Open No. 2-206430, the light quantity of the input light is detected by using an optical coupler and is fed back to the light source. Compensation for fluctuations in light quantity and compensation for measurement output, or Applied Physics Letter, Volume 55 (1989) p. 2588 (Appl.Phy
s. Lett. 55 (19896 2588), an optical coupler is used to detect the light amount of the input light and the measurement output, and the measurement output is compensated.

[0006]

However, in these prior arts, damage to the probe unit 4 and the necessity of replacement accompanying it have been taken into consideration, as in the application to information recording of evanescent light, pattern formation, and the like. However, there was a limit to industrial application.

In order to solve the above problems, the present invention provides
In addition to using the probe as an optical fiber whose tip is processed, the above-mentioned JP-A-2-206430 or Applied Physics Letter 55 volumes is used.
(1989) p. 2588 also includes a configuration for measuring the amount of light from the light source or the reflected light.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the basic structure of a probe according to the present invention. 9 is an optical coupler or optical switch, which allows the optical fibers 8, 10, 11 and 12
Are combined. In the illustrated example, the optical fiber 8 is connected to the optical fiber 6 on the light source side shown in FIG. 2 by a coupler 7 to introduce laser light to the probe. The introduced laser light is distributed to the optical fibers 10 and 11 at a predetermined ratio.
The laser light introduced into the optical fiber 10 by reflection is distributed to the optical fibers 8 and 12 at a predetermined ratio. The tip of the optical fiber 10 is sharpened to form an evanescent optical probe 42. A photodetector 1 is provided at the other end of the optical fiber 11.
4 and a photodetector 15 at the other end of the optical fiber 11, respectively.

According to this structure, the amount of light introduced into the fiber 8 by the output of the photodetector 14 is introduced into the optical fiber probe at the tip of the fiber 12 by the output of the photodetector 15 and the reflection from the sample. You can monitor the amount of light. That is, here, an optical element in which a fiber and an optical coupler or an optical switch are integrated is used, and one of the fiber tips is used as a probe. If the elements are replaced as a unit, the coupling state of the optical coupler does not pose any problem. As a result, it is possible to accurately control the amount of evanescent light, and to improve the performance of the system, control the bit size in information recording, or control the formation pattern size in the semiconductor process. It will be easy.

The evanescent optical probe 42 at the tip of the fiber 10 in FIG. 1 is usually manufactured by a method of pulling and forming with a pipette puller while heating or a method of sharpening the tip by chemical etching. Further, in order to form a small pinhole in this, an oblique vapor deposition method of metal or the like, an ion etching method after vapor deposition, a lithography method using a resist, or the like is used. Although various combinations of light distribution ratios on the output side of the optical coupler or the optical switch 9 are possible, a large amount of laser light is emitted to the fiber 10 having the evanescent light probe 42 such as 90%: 10%. It is efficient to set to input. The light distribution ratio can be selected according to the purpose.

FIG. 3 shows a first embodiment of the present invention applied to an information storage device.
This is a specific example. Here, an example of phase change recording will be described. The probe shown in FIG. 1 was used for the bit writing and reading, and the R-θ system rotary motion (disk drive) was used for the bit address. The main configuration is composed of an evanescent optical probe head system, a disk rotation system, and a control system.

The head system of the evanescent optical probe has a structure in which the tip portion 42 of the probe is held by an xyz moving mechanism or a moving mechanism 20 having a gap control mechanism between the probe and the sample. As the gap control mechanism between the probe and the sample, a conventional detection method using shear force or atomic force is adopted, and further, z of the xyz moving mechanism 20 is used.
It can be controlled using a moving mechanism. In addition, the photodetection system used for reading the reflected light 21 from the sample 28 with respect to the incidence of the evanescent light 19 is a condensing lens 22 and a photomultiplier tube (or photodiode) 23.
Alternatively, the structure for detecting with the photodetector 15 described in FIG. 1 is used. These signals 40 or 38 are used as information (bit) signals or address signals. Here, the case of reflected light detection is shown, but transmitted light can also be detected and used as an information signal. The structure of the tip portion 42 of the evanescent optical probe is composed of a core 16 that guides light, an outer cladding 17, and a metal coat film 18. The metal coat film 18 is formed on the tip of the metal by oblique vapor deposition or the like.
An aperture of about nm is formed, and the evanescent optical probe diameter is determined by this aperture. The laser source 2 uses a semiconductor laser diode. For this drive, the drive circuit 34
Was used. This circuit 34 is provided with a write pulse generation circuit 33 and a read DC voltage supply circuit 32. The light intensity, pulse width, timing and the like of these are controlled by a control signal 36 from the control circuit 35. The end portion 42 of the optical probe may be formed by straightening the fiber or by bending it into an L-shape, but this allows greater elasticity of the probe.

The disk rotation system is composed of a disk table 29 on which the sample 28 is mounted, a rotation shaft 30 for transmitting rotation, and a motor 31.

In the control system, the control circuit 35 performs sequential control, positioning control of the evanescent optical probe 42,
Performs all information processing and communication with the outside. 37 is a monitor signal for setting the evanescent light amount, 39 is a signal for positioning control of the evanescent light probe 42, 41 is the motor 3
1 drive signal.

Sample 28 is a case of a phase change recording film. The structure is such that the first layer is a protective film 24 made of ZnS—SiO ₂ , the second layer is a GeSbTe phase change recording film 25, and the third layer is the same protective film 26 as the first layer. This is a polycarbonate substrate (or glass). It is laminated on 27. The recording film 25 can have two states of amorphous and crystal. At this time, the reflectance of the recording film 25 is small in the former case but high in the latter case. Utilizing this fact, information bits can be written and read. How to define the information bit for recording depends on the system design, but if the initial state is amorphous and the bit information is “0”, the temperature rise can be locally caused by the irradiation of the evanescent light 19. . When this temperature rises around 200 ° C., the crystalline state of the recording film 25 changes to crystal.
In this way, the recording bit 61 can be written. At this time, the reflectance of this local portion rises, the reflected light signal becomes strong at the time of reading, and bit information "1" can be read. In the experiment, writing was performed with a laser light amount of 8 mW in the fiber 10 and reading was possible with 0.2 mW. In addition, the size of the recording bit 61 is 60n.
We were able to write and read bits with a very small diameter and very small diameter.

This technology is organically combined with a disk rotation system and a control system, that is, sequential control of writing and reading by the control circuit 35, positioning control of the tip portion 42 of the evanescent optical probe, information processing, and communication with the outside. As described above, the system can be upgraded in the same manner as the conventional optical disk storage device to provide an ultra high density recording device of 100 Gb / in ² or more.

Although the erase function is not described in this embodiment,
A rewritable storage device having an erasing function can also be configured. Further, a magneto-optical recording device using polarized light, a storage device, or an optical recording device or optical storage device using irregularity information is also a system to which the present invention is applicable.

If the tip 42 of the probe is damaged for some reason during use, the fiber may be removed at the splicer 7 and the entire probe replaced according to the present invention. Even if the coupling state of the coupler 7 is different from before, this can be detected as an output change of the photodetector 14 or 15, and can be canceled by the control circuit 35. Therefore, a special operation accompanying replacement, No checks are required.

FIG. 4 shows an example in which the present invention is applied to a lithographic apparatus in a semiconductor process. The head part 42 of the head system of the evanescent optical probe uses the optical system and mechanical system described in FIG. 48 is a precision moving mechanism,
The sample 47 is mounted and positioned at a desired position.
For positioning, the position information 51 is input to the control circuit 35,
The drive signal 41 is input to a drive source (motor, piezoelectric element, etc.) in the precision moving mechanism 48 to position the sample 47 at a desired position. Here, the sample 4 in which the layer to be etched 45 is coated on the Si substrate 46 and the optical resist layer 44 is coated thereon
7 shows a case where a pattern is formed.

The evanescent optical probe head system differs from that shown in FIG. 3 in that a short wavelength laser source such as an Ar gas laser is used as the laser source, and an optical switch 52 is used in place of the optical coupler 9. Is. This is because the photoresist feels only at wavelengths below 456 nm.
The optical switch 52 functions as a switch function of the semiconductor laser 2. Thereby, the evanescent light 19 can be applied to the resist 44 at a position where light exposure is required. In the present invention, the latent image pattern 50 having a minute line width of about 50 nm can be formed. As a drawing method of the latent image pattern 50, an electron beam drawing method or a laser drawing method which is a conventional technique is used. There are mainly a vector system and a raster system, but the raster system is considered to be more suitable for the present invention. Further, when the optical switch 52 has a limited laser light amount, the optical coupler 9 is used to
The optical coupler 4 is provided with a switching function and a switching function between the drawing light amount and the mark detecting light amount by an acousto-optic element. The mark detection is used to measure the relative position between the tip portion 42 of the probe and the sample 47, and in the case of using the mark and the reflected light detector (22 and 23) preset on the sample or the optical coupler, It can be done with 15 detectors. It is also possible to reduce the drawing time by providing a plurality of heads. The use of a plurality of heads is also effective in the information recording and storage device shown in FIG.

When using the optical switch 52, in the strict sense, namely, fiber 8 to fiber 10
Since the light leaking into the fiber 11 is extremely small during transmission of light, it is impossible to monitor the amount of light input to the tip portion 42 of the probe at all times. It is better to monitor by time sharing. The program incorporates time interval control, before a series of operations, etc. Alternatively, the light is choppered for only a short time and the light is detected by the photodetector 14
It can also be monitored and monitored. This function can also be used for the photodetector 15 to detect the reflected light returning to the tip portion 42 of the probe. FIG. 4 shows an example applied to a lithographic apparatus. An etching gas and a chemical vapor deposition (CVD) gas are introduced between the sample 47 and the tip portion 42 of the probe to perform etching and chemical vapor deposition. It is also possible to directly form a fine pattern. In this case, it is necessary to provide a sample chamber so that the sample table 48 or the tip portion 42 of the probe can enter the chamber.

Also in this embodiment, damage to the probe can be easily dealt with by replacing the probe after the coupler 7.

FIG. 5 shows a specific example in which the present invention is applied to a microscope. An example of the same configuration as the above lithographic apparatus is shown. Here, the case where the optical characteristics of the sample are observed is shown, and the configuration is such that a reflected light image and a transmitted light image can be obtained. The sample stage 53 is equipped with a lens 55 for collecting and detecting the light of the evanescent light 19 transmitted through the sample 13 and a photodetector 56, and this signal 54 can be transferred to the control device 35. The transmitted light signal 54 and the reflected light signal 40
Alternatively, the signal amount for the sample position xy can be measured by the signal of 38. In this case, the tip portion 42 of the probe and the sample 1 are treated like a normal scanning near-field light microscope.
3, while maintaining a constant gap with the tip end portion 42 of the probe.
By raster-scanning, the reflected light signals 38 and 40 and the transmitted light signal 54 for the xy coordinates can be obtained.

By capturing these signals for one image, a reflected light image or a transmitted light image of the sample surface can be obtained. The distribution efficiency of the optical coupler 9 is 90%: 10% or 50%: 50%.
Etc. are used. An optical switch 52 may be used instead of the optical coupler 9. Photodetector 1 for detecting weak changes
The reflected light signal, 38, 40, and the transmitted light signal 54 may be divided by the monitor signal 37 from 4 and normalized (standardized). Further, to obtain a weak signal, a lock-in amplifier may be used for measurement. At this time, the driving of the laser source 1 is chopped, or the optical switch 52 is used instead of the optical coupler 9.
Can be used to chop the laser light.
Further, the tip portion 42 of the probe can be vibrated in the z or x direction for synchronous detection. Furthermore, in order to prevent contamination of the sample, it is desirable to put it in a vacuum for measurement.

In this embodiment as well, damage to the probe can be easily dealt with by replacing the probe after the coupler 7.

FIG. 6 shows an example in which the microscope of FIG. 5 is applied to a spectroscopic microscope. Sample 5 with fiber 12 using optical coupler 9
The reflected light from 2 is guided to the spectroscope 58, and the spectral spectrum of the reflected light is measured. Since this signal is weak, it is desirable to use the lock-in amplifier 59 by chopping the light source as in the embodiment of FIG. The output signal 60 of the amplifier 59 can be input to the control circuit 35 to measure the spectrum at an arbitrary position. Incidentally, the choppering of the primary laser light may be performed by pulsing the drive signal of the semiconductor laser, and the lock-in amplifier may be used with this frequency as a reference. In addition, while scanning the tip portion 42 of the probe, it is possible to take a spectrum and measure the intensity distribution of a specific spectrum. Although not shown here, the spectroscopic spectrum of the sample is also measured by guiding the reflected light obtained by the lens 22 and the photodetector 23 and the transmitted light obtained by the lens 55 and the photodetector 56 to the spectroscope 58. it can. At this time, these signals are changed to the monitor signal 37.
Highly accurate measurement is possible by normalizing with. On the other hand, in order to prevent the sample from being contaminated, it is desirable that the measurement be performed in a vacuum or at an extremely low temperature as in the above.

In this embodiment as well, damage to the probe can be easily dealt with by replacing the probe after the coupler 7.

Further, in the probe of the present invention, either of the fibers 11 or 12 may be omitted, and in such a case, if a control system corresponding thereto is constructed, the same as in the above-mentioned embodiment. An effective configuration can be achieved.

[0029]

According to the present invention, it is possible to accurately control the amount of evanescent light, improve the performance of an optical system, control the bit size in information recording, or control the formation pattern size in a semiconductor process.
Alternatively, the precision of the optical signal can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a probe of the present invention.

FIG. 2 is a diagram showing an example of a configuration of a conventional optical probe.

FIG. 3 is a diagram showing an example of application of the present invention to an optical recording (storage) device.

FIG. 4 is a diagram showing an example of application of the present invention to a semiconductor lithography apparatus.

FIG. 5 is a diagram showing an example of application of the present invention to a scanning near-field light microscope.

FIG. 6 is a diagram showing an example of application of the present invention to a spectroscopic microscope.

[Explanation of symbols]

1: laser light, 2: laser source (semiconductor laser, gas laser, excimer laser, etc.) 3, 5, 22, 55: lens, 4: first optical coupler, 6, 8, 10, 12, 62: fiber, 7: Second (1: 1) photocoupler, 9: 2: 2 photocoupler, 13: sample, 14, 15, 23, 56: photodetector (photomultiplier tube, photodiode, etc.), 16: Optical fiber core, 17: optical fiber clad, 18: light-shielding film, 19: evanescent light, 20: evanescent optical probe xyz moving mechanism and probe / sample gap detection,
Output, control mechanism, 21: reflected light, 24, 26: protective film, 2
5: Phase change recording film, 27: Transparent substrate (polycarbonate, glass, etc.), 28: Recording medium, 29: Disk table, 30: Rotating shaft, 31: Rotating mechanism, 32: DC circuit for constant laser light output, 33: Pulse generation circuit, 34: semiconductor laser drive circuit, 35: control circuit (including computer, display, printer, etc.), 36: laser drive signal, 3
7: Monitor light detection signal, 38: Tip portion 4 of the probe
2 reflected light detection signal, 39: tip portion 4 of the probe
2 xyz moving mechanism and the gap control signal, 40: reflected light detection signal, 41: rotation mechanism control signal, 42: tip of evanescent optical probe, 44: photoresist layer, 45:
Layer to be etched, 46: Si substrate, 47: Semiconductor process sample, 48, 53: Precision moving mechanism, 50: Latent image pattern, 51: Position information signal of precision moving mechanism, 52: Optical switch, 54: Transmitted light signal, 58: spectroscope, 59: lock-in amplifier, 60: spectroscopic signal, 61: recording (phase change) bit.

Claims (7)

[Claims] 1. A probe of an optical device using evanescent light, comprising an optical coupler for splitting light into two or more optical fibers, or an optical switch for passing the light to form the element. A probe characterized in that an evanescent optical probe is formed by sharpening the tip of at least one optical fiber. 2. An optical device utilizing evanescent light, which comprises an optical coupler for splitting the light into two or more optical fibers or an optical switch for passing the light, and at least one light constituting the element. The tip of the fiber is sharpened and equipped with a probe that is an evanescent optical probe.
An optical device which monitors the amount of light input to the evanescent optical probe from the amount of light output from the end face of an optical fiber which is not the evanescent optical probe of the optical coupler or the optical switch. 3. A laser beam is controlled from the light amount output from the end face of the optical fiber of the optical coupler or the optical switch which is not the evanescent optical probe, or the detected light amount of the light reflected from the sample or transmitted through the sample. The optical device according to claim 2, wherein the optical device is standardized. 4. The optical device according to claim 2, wherein the evanescent optical probe is used for photo resist pattern formation, photo etching, photo CVD, surface deformation or data recording or data reading. 5. The optical device according to claim 2, which is used for observing optical characteristics of a sample or observing spectral characteristics of a sample. 6. An optical device according to claim 2, 3 or 4, wherein light detection is performed by a lock-in amplifier using an input light source as a reference signal. 7. The optical device according to claim 2, wherein the evanescent optical probe and the sample are placed in a specific gas, a liquid, a vacuum, or at a low temperature.