JPH01141305A - Measuring instrument for depth of minute groove - Google Patents

Abstract

PURPOSE:To improve the portability, and also, to raise the measurement accuracy by connecting a spectral part and a sample part by using a multi-mode optical fiber so that the sample part can be detached physically from other part, in an optical type measuring instrument. CONSTITUTION:White color light which has been generated by a white color light generating part 16 is made incident on a spectral part 19, and a light beam whose spectral width is narrow is extracted, while sweeping its wavelength. This light beam from the spectral part 19 is made incident on a sample part 23 through a connecting part 20 whose main element is a multi-mode optical fiber 22. In this sample part 23, the light beam is radiated to a sample 12 in which a minute groove has been formed. Subsequently, its reflected light is detected by photodetectors 13, 27 and by inputting its detecting signal to a signal processing 28, the depth of the minute groove of the sample 12 is measured. In such a way, the spectral part 19 and the sample part 23 can be detached physically, although they are coupled, therefore, a transfer of vibration, etc., can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, VLSI (large-scale semiconductor integrated circuit)
, the depth of a microgroove or microhole (hereinafter referred to as a microgroove) for a capacitor formed on a semiconductor substrate can be easily determined.
The present invention also relates to a device that measures with high accuracy.

[Conventional technology]

FIG. 2 is a block diagram schematically showing a wavelength-sweeping microgroove depth measuring device using a conventional acousto-optic filter ([Microgroove depth measurement method] by Takada et al. in Japanese Patent Application No. 61-98087). and equipment).

1 is a white light source, 2 is an objective lens, 3 is a slit, 4 is an objective lens, 16 is a white light generation section constituted by 1 to 4, 5 is a polarizer, 6 is an acousto-optic filter, 9 is a slit,
10 is an analyzer, 7 is a high-frequency amplifier, 8 is a frequency sweep oscillator, 19 is a spectroscopic unit composed of 5.6, 9.10.7.8, 11 is a beam splitter, and 12 is a micrometer whose depth is to be measured. A sample to be measured has grooves formed therein, and 13 is a photodetector.

23 is 11.12.13. and a sample section consisting of a sample holder (not shown), 14 is an AD converter, 15
28 is a signal processing section composed of a computer and 14.15.

The light emitted from the white light source 1 becomes a parallel beam by objective lenses 2 and 4 and a slit 3, and is converted into a parallel beam by a polarizer 5, an acoustic filter 6, a slit 9, and an analyzer 10, which converts the light into a parallel beam with a wavelength of 4.
Light is generated that sweeps a wavelength range from 00 to 800 nm at a period of 300 m5ec. A frequency sweep oscillator 8 for driving the acousto-optic filter 6 sweeps a high frequency region from 90 to 40 MHz at a period of 300 m5ec, and after amplifying this high frequency output with a high frequency amplifier 7, it is sent to the acousto-optic filter 6. is being applied. This wavelength swept light passes through the beam splitter 11 and is irradiated onto the sample 12.

The reflected light from the sample 12 is reflected by the beam splitter 11 and is received by the photodetector 13. This photodetector 1
The output of No. 3 is digitally converted by the AD converter 14 and processed by the computer 15. If the power of the light incident on the sample 12 at the wavelength λ is P(λ), the reflected light intensity I(λ) is: ■(λ)=η(λ)P(λ) (1+Kcos(
4d/λ))...(1) It is expressed as follows. Here, d is the depth of the microgroove formed in the sample 12, η(λ) is the reflectance on the surface of the sample 12,
K is the attenuation rate of light in the microgroove. It becomes possible to eliminate the peak in equation (1) for sweeping the wavelength λ.

(Problems to be Solved by the Invention) In the conventional measuring device shown in FIG. 2, the spectroscopic section 19 and the sample section 23 are fixed and cannot be separated, so the portability of the sample section 23 is poor. In addition, in the manufacturing process including VLSI groove formation, in order to monitor the depth of the groove, the sample section 23 is installed in the process equipment, while the other parts 16.19.28 are installed in the process equipment. There is a problem in that it is difficult to satisfactorily meet the demand in semiconductor manufacturing lines to install the measurement equipment outside and away from the equipment.In other words, if each part 16, 19, 28 of the measurement equipment is installed inside the manufacturing process equipment, There is a problem in that the accuracy of measuring the microgroove depth decreases due to dust getting into the VLSI, or because various parts of the measuring device are affected by vibrations, noise, etc.

The object of the present invention is to provide a micro groove depth measuring device.

The object of the present invention is to provide an apparatus in which the sample part can be physically separated to be transportable to improve the portability of the sample part, and each part other than the sample part can be separated from the sample part.

[Means for solving problems]

In order to achieve the above object, the present invention uses a multimode optical fiber to connect a sample section and a spectroscopic section, and also installs an optical system for entering and exiting the multimode optical fiber.

That is, the present invention provides a white light generating section, a spectroscopic section that extracts light with a narrow spectrum width from the white light emitted by the white light generating section while sweeping the wavelength thereof, and a spectroscopic section that extracts light with a narrow spectrum width from the white light emitted by the white light generating section; white light.

Or from a sample section for extracting reflected light when a sample in which microgrooves are formed is irradiated with light obtained by dividing the white light by the spectroscopic section, and a photodetector for receiving the reflected light from the sample. A microgroove depth measuring device comprising a signal processing section for signal processing the output of the microgroove depth measuring device, comprising a connecting section mainly composed of a multimode optical fiber for optically connecting the spectroscopic section and the sample section. It is characterized by:

[Effect]

As described above, in the apparatus of the present invention, the sample section and the spectroscopic section are connected using a multimode optical fiber, so that the sample section and the spectroscopic section are optically coupled, and the sample section and the spectroscopic section are optically coupled. This greatly improves the portability of the
Since it can be placed outside the SI manufacturing process equipment and separated from the equipment, it is possible to reduce the contamination of dust into the VLSI being manufactured, and to measure the depth of microgrooves because each part of the measuring equipment is affected by vibrations, noise, etc. It is possible to prevent the accuracy from decreasing.

〔Example〕

Embodiment 1 FIG. 1 is a schematic configuration diagram showing an apparatus according to a first embodiment of the present invention.

16 is a white light generator, 1 is a white light source, 2 is an objective lens,
17 is a multimode optical fiber, 18 is an objective lens, 19 is a spectroscopic unit, 5 is a polarizer, 6 is an acousto-optic filter, 9 is a slit, 10 is an analyzer, 7 is a high frequency amplifier, 8 is a frequency sweep oscillator, and 20 is a 21 is an objective lens, 22 is a multimode optical fiber, 24 is an objective lens, 23 is a sample part, 1
1 is a beam splitter, 12 is a sample in which microgrooves are formed, 25 is a reference sample with a smooth surface without microgrooves, 26 is a total reflection mirror, 13.27 is a photodetector, 2
8 is a signal processing section, 14 is an AD converter, and 15 is a computer. Although the multimode optical fiber 17 is used in the white light generating section 16, it may be replaced with the white light generating section 16 in the conventional device shown in FIG.

Emitted light from the white light source 1 enters into the multimode optical fiber 17 via the objective lens 2. The emitted light is turned into a parallel beam by the objective lens 18.

This parallel beam passes through a polarizer 5, enters an acousto-optic filter 6 as a specific linearly polarized light, is split into light of a specific wavelength, passes through an analyzer 10, and then passes through an objective lens 21 to a coupling section. 20 into a multimode optical fiber 22 . The light emitted from the multimode optical fiber 22 is focused by the objective lens 24 to become a focused beam that is focused on the sample 12. The reflected light from the sample 12 is reflected by the beam splitter 11 and is totally reflected l! 126 and enters the photodetector 13. On the other hand, multimode optical fiber 2
Of the light emitted from the beam splitter 2, the light reflected by the beam splitter 11 is reflected on the surface of the reference sample 25 in which microgrooves are not formed, passes through the beam splitter 11, and is totally reflected by the total reflection mirror 26. , enters the photodetector 27.

In the measuring device having such a configuration, the spectroscopic section 19 and the sample section 23 use a multimode optical fiber 22.

Since they are connected by the connecting part 22 which is the main element, the two can be separated and the sample part 23 can be transported to any location.On the other hand, the white light generating part 16 and the spectroscopic part 19 are
It can be fixed at a predetermined location outside the manufacturing process equipment and away from the equipment.

Note that the reason why the reference sample 25 is installed and the light reflected from the reference sample 25 is independently received by the photodetector 27 is to avoid measurement errors due to the fluctuations in the output of the white light source. be. That is, as explained in the section of the prior art, the output from the photodetector 13 is expressed as η(λ)P(λ)(1+Kcos (4gd/λ) from equation (1).
), while the output from the photodetector 27 is proportional to η(λ
) P(λ). Therefore, the output from the photodetector 27 is constant as the wavelength λ is swept.

Amplitude modulation is applied to the frequency sweep oscillator 8 to temporally change the spectral characteristics of the acousto-optic filter 6 so that η(λ)P(λ)=P0 is constant.

At this time, the output from the photodetector 13 is Po(1+Kc
os (4πd/λ)), the DC component is Po, and the AC component is P, Kcos (4πd/λ), so by extracting only the AC component with a bypass filter, P, Kc
os(4πd/λ) can be extracted. Therefore, even when K is sufficiently small, by amplifying the alternating current component and performing time averaging, the microgroove depth can be measured with high accuracy even when the amount of reflected light from the microgrooves is sufficiently small. Note that the photodetector 2
Amplitude modulation may be applied to the frequency sweep oscillator 8 so that the output from the acousto-optic filter 7 changes in a specific manner instead of being constant, thereby changing the spectral characteristics of the acousto-optic filter 6 over time.

Embodiment 2 FIG. 3 is a schematic configuration diagram showing a second embodiment of the present invention. Each component is the same as that of the first embodiment shown in FIG. 1, so a description thereof will be omitted.

The difference from the first embodiment is that the apparatus of the first embodiment has a white light generating section 16, a spectroscopic section 19. Connecting part 20, sample part 23
In contrast, in the apparatus of this embodiment, as shown in FIG. 3, a white light source section 16, a sample section 23,
The point is that the connecting section 20 and the spectroscopic section 19 are configured in this order. In the first embodiment, the light separated by the 1-split section 19 is made to enter the multimode optical fiber 22 of the coupling section 20 via the objective lens 21, and an acousto-optic filter 6 is provided for each wavelength.
Since the angle of the diffracted light changes slightly, the coupling efficiency of the diffracted light to the multimode optical fiber 22 changes for each wavelength. On the other hand, in this embodiment, as shown in FIG. 3, since the diffracted light from the acousto-optic filter 6 is incident on the photodetector 13, if the receiving diameter of the photodetector 13 is large to some extent, the wavelength of the diffraction angle will depend on the wavelength of the diffraction angle. The advantage is that the effects of change no longer matter. Note that in this embodiment, only the sample portion 23 is set to VL.
A multimode optical fiber 17 having a certain length is effective for installation in the SI manufacturing process equipment.

Embodiment 3 FIG. 4 is a schematic diagram showing a white light generating section and a sample section of an apparatus according to a third embodiment of the present invention.

In the figure, 29 is a multimode optical fiber coupler that performs multiplexing and demultiplexing of light. The other constituent elements are the same as those in the second embodiment shown in FIG. 3, so their explanation will be omitted.

The emitted light from the white light source 1 is focused by the objective lens 2, enters the multimode optical fiber coupler 29 from the first end C1, and is divided into two parts, the second end C2 and the third end. It emits from C1. The light emitted from the second end C2 is
The light irradiated onto the sample 12 to be measured and reflected from the sample 12 enters from the second end C2, passes through the multimode optical fiber coupler 29, and is connected to the 1-split section 19. With such a configuration, in this embodiment, (1) the multimode optical fiber 17 and the input optical system (objective lens 18) in the second embodiment are unnecessary, and (2) the bulk type beam splitter 11 is replaced by Since the fiber-type coupler 29 is used, there is an advantage that the optical multiplexing and demultiplexing can be performed stably and there is no problem of optical axis misalignment.

Embodiment 4 FIG. 5 is a schematic configuration diagram showing a white light generating section and a sample section in an apparatus according to a fourth embodiment of the present invention.

In the figure, 30 and 31 are objective lenses, and the other components are the same as in FIGS. 3 and 4.

The explanation will be omitted.

The emitted light from the white light source 1 is focused by the objective lens 2, and is directed to the first end D1 of the multimode optical fiber coupler 29.
The light enters the field, is divided into two parts, and exits from the second end D2 and the third end D3. The light emitted from the second end D2 is
A parallel beam is formed by the objective lens 30 and irradiates the surface of the sample 12 to be measured. Of the reflected light from the sample 12, high-order diffracted light generated by the microgrooves formed on the surface of the sample 12 is transmitted to two ends D2.

A multimode optical fiber coupler 2 is connected to the optical fiber via an objective lens 31.
9 and guided to the spectroscopic section 19 .

The reason for using higher-order diffracted light is that higher-order diffracted light is significantly less affected by light reflected from the surface of sample 12 than O-order diffracted light (that is, light reflected perpendicularly from the surface of sample 12). ,For this reason.

This is because the effect of interference between the light reflected from the microgrooves formed on the surface of sample 12 and the light reflected from the surface of sample 12 is significant (Proceedings of the 46th Japan Society of Applied Physics Academic Conference 198
(see Fall 2015 2P-H-13), that is, in equation (1) in the description of the conventional technology, the DC component η(λ)P(λ)
This is because it becomes significantly smaller.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and that various modifications and improvements can be made within the scope of the claims of the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, the sample section can be moved while the sample section and the spectroscopic section are optically coupled,
Only the sample part is installed in the VLSI manufacturing process equipment,
Since other parts can be installed separately outside the manufacturing process equipment, it is possible to reduce the amount of dust entering the VLSI during manufacturing, and also prevent micro-grooves from entering the VLSI because each part of the measuring equipment is affected by vibrations, noise, etc. Deterioration of depth measurement accuracy can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a microgroove measuring device according to a first embodiment of the present invention, FIG. 2 is a schematic diagram of a conventional device, and FIG. 3 is a diagram of a microgroove measuring device according to a second embodiment of the present invention. FIG. 4 is a schematic diagram of the apparatus according to the third embodiment of the present invention, and FIG. 5 is a schematic diagram of the apparatus according to the fourth embodiment of the present invention. 1... White light source 2.4.18.21.24.30.31... Objective lens 3.9... Slit 5... Polarizer 6... Acousto-optic filter 7... High frequency amplifier 8... Frequency sweep oscillator 10... Analyzer 11... Beam splitter 12... Sample to be measured with micro grooves formed 13.27
... Photodetector 14 ... AD converter 15 ... Computer 16 ... White light generation section 17 ... Multimode optical fiber 19 ... Spectrometer 20 ... Connection section 22 ... Multi Mode optical fiber 23...sample part 25...reference sample 26 in which microgrooves are not formed
... Total reflection mirror 28 ... Signal processing unit 29 ... Multimode optical fiber coupler Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Scope of Claims] 1. A white light generating section, a spectroscopic section that extracts light with a narrow spectrum width from the white light emitted by the white light generating section while sweeping the wavelength thereof, and a spectroscopic section that extracts light with a narrow spectrum width from the white light emitted by the white light generating section; a sample section for extracting reflected light when a sample in which microgrooves are formed is irradiated with emitted white light or light separated by the white light by the spectrometer; and a sample section for extracting reflected light from the sample. A microgroove depth measuring device comprising a signal processing section that processes the output from a photodetector that receives light, the main element of which is a multimode optical fiber for optically connecting the spectroscopic section and the sample section. A microgroove depth measuring device characterized by comprising a connecting portion. 2. The microgroove depth measuring device according to claim 1, wherein the spectroscopic section includes an acousto-optic filter and a frequency sweep oscillator for driving the acousto-optic filter. 3. The spectroscopic unit includes an acousto-optic filter and a frequency sweep oscillator for driving the acousto-optic filter, and the sample unit includes a first photodetector that receives reflected light from the sample, and A sample including a sample of the same type as the sample in which microgrooves are not formed and a second photodetector that receives reflected light from the sample, and the output of the second photodetector is constant as the wavelength is swept. The signal processing section is characterized by comprising a feedback system for applying amplitude modulation to the frequency sweep oscillator of the acousto-optic filter so that the frequency sweep oscillator of the acousto-optic filter has a specific change in the frequency sweep oscillator so that the output changes in a specific manner as the wavelength sweeps. A micro groove depth measuring device according to claim 1. 4. The microscopic device according to claim 1, wherein each of the parts is connected in the order of the white light generating part, the spectroscopic part, the connecting part, the sample part, and the signal processing part. Groove depth measuring device. 5. The microscopic device according to claim 1, wherein each of the parts is connected in the order of the white light source generating part, the sample part, the connecting part, the spectroscopic part, and the signal processing part. Groove depth measuring device. 6. The respective parts are connected in the order of the white light source generation part, the sample part, the connection part, the spectroscopy part, and the signal processing part, and the main element of the connection part is composed of a multimode optical fiber coupler, And, the multimode optical fiber coupler is
The method of claim 1 is characterized in that the sample is irradiated with white light from the white light generating section, the reflected light from the sample is incident, and the reflected light is guided to the spectroscopic section. The micro groove depth measuring device according to scope 1. 7. Inject the white light from the first end of the multimode optical fiber coupler, irradiate the sample from the second end of the multimode optical fiber, and emit the white light from the sample from the second end. The reflected light of the multimode optical fiber coupler is made to enter the multimode optical fiber coupler, and the reflected light is guided from the third end to the spectroscopic section. Groove depth measuring device. 8. The white light is incident from the first end of the multimode optical fiber coupler, the sample is irradiated from the second end of the multimode optical fiber, and the white light is emitted from the sample from the third end. A patent claim characterized in that at least the diffracted light of the diffracted light and the reflected light is made to enter the multimode optical fiber coupler, and the entered light is guided from the fourth end to the spectroscopic section. The micro groove depth measuring device according to item 6.