JPH06265790A - Laser microscope - Google Patents

Abstract

PURPOSE:To provide a laser microscope capable of performing the secondary distribution analysis of the physical property and composition of a sample surface, etc. CONSTITUTION:The expanded image of a sample can be obtained by irradiating the sample with a laser beam, and amplifying by receiving reflected light 2b by a photomultiplier tube 50. A mirror device 51 is installed on the front stage of the photomultiplier tube 50, and the reflected light is introduced to a Raman spectroscope unit 53 by the mirror device at need. The Raman spectroscope unit performs the spectrum analysis of Raman scattered light in the reflected light, and performs the distribution analysis of the sample surface based on the spectrum analysis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser microscope having a structure for obtaining a magnified image by irradiating a sample with laser light and receiving the reflected light.

[0002]

2. Description of the Related Art This type of laser microscope is mainly used for measuring the line width of a fine pattern drawn on a wafer or a mask during the manufacture of a semiconductor integrated circuit and inspecting the overlay accuracy of them. A so-called confocal scanning laser microscope has been put into practical use.

The confocal scanning type laser microscope has a laser oscillator 1 as shown in FIGS. 8 (a) and 8 (b).
The laser beam 2a emitted from the mirror 3 is reflected by the mirror 3, narrowed by the lens 4, passed through the pinhole 5, passed through the beam splitter 6 and converged by the objective lens 7, and the sample (wafer, mask or reticle) 8 The reflected light 2b reflected on the surface of the sample 8 is reflected by the beam splitter 6, received by the photomultiplier tube 10 through the pinhole 9 and amplified.

In such a laser microscope, the laser beam 2
The focus F of a is fixed to the position below (or above) the pattern 11 formed as a convex portion on the surface of the sample 8 as shown in (a), and the scan controller 1
By slowly moving the sample 8 in the Y-axis direction while scanning the sample 8 in the X-axis direction by 2, the reflected light 2b is all pinned when the beam spot is passing under the pattern 11 as shown in FIG. The output of the photomultiplier tube 10 is high because it passes through the hole 9, but when the beam spot is passing over the pattern 11 as shown in FIG.
Since b is not focused at the position of the pinhole 9 and most of it is blocked by the pinhole 9, the photomultiplier tube 1
The output of 0 becomes small. Therefore, by sequentially drawing the brightness corresponding to the output of the photomultiplier tube 10 on the television monitor 13 in synchronization with the scan by the scan controller 12, the enlarged image 14 of the pattern 11 is displayed on the television monitor 13, and It is possible to perform automatic measurement of the line width of the pattern 11 with high accuracy based on the enlarged image 14.

A specific example of a confocal scanning type laser microscope using the above principle will be described with reference to FIG. FIG. 9 is a device configuration diagram of a confocal scanning type laser microscope (trade name SiScan-IIA), which is a product of SiScan Systems in the United States, which includes an optical module 22 and a workstation interconnected by a signal cable 21. Two
It is composed of three.

In the optical module 22, the XY stage 24 and the scanner 25, which are the main components of the optical module 22, are installed on a support base 26 having a vibration isolation function. That is, the support base 26 is provided above the support column 27 so as to be vertically displaceable via the air suspension 28 at four points, and the XY stage 24 is installed on the support base 26. A scanner 25 is installed on the scanner 25, and the sample is chucked and held on the scanner 25 by vacuum suction. The support base 26 is made of natural stone, granite.
It is generally adopted that the material is used as a material and processed into a solid rectangular plate shape. The support base 26 is supported by the air suspension 28 so as to be held horizontally at all times, whereby the XY stage 24 and the scanner 2 installed on the upper surface thereof are supported.
It is configured to hold 5 horizontally and prevent external vibrations from propagating to them.

A focusing device 30 for converging the laser light emitted from the laser head 29 by the objective lens 7 and irradiating the sample on the scanner 25 is arranged above the scanner 25. Figure 5
The optical system shown in FIG. Further, a TV camera 31 with a zoom lens for taking an image near the laser irradiation position of the sample is disposed adjacent to the laser head 29 so as to face downward. Further, below the support base 26, an electric circuit chassis 32, various indicators 33 such as vacuum equipment for chucking a sample, and a laser power source 34.
Alternatively, a robot controller for handling the sample, setting it on the scanner 25, and removing it from the scanner 25 is provided.

On the other hand, the workstation 23 has an operation panel (keyboard) 35, a television monitor 36, and a printer 3.
7. A control device 38 including a CPU is provided so that all of the above optical modules 22 can be operated from this workstation 23, and an image observed by a laser beam and an image captured by a television camera 31 are displayed on a television monitor 36. And menus required for operation are displayed.

[0009]

In the above laser microscope, scattered light of various wavelengths slightly different from the wavelength of the irradiation laser light 2a, so-called Raman scattered light, is mixed in the reflected light 2b from the sample 8. Is what you are doing.
The wavelength spectrum of the Raman scattered light differs depending on the physical properties and composition of the sample surface.Therefore, it is possible to perform two-dimensional distribution analysis of the physical properties and composition of the sample surface by performing spectral analysis of Raman scattered light. But
The above-mentioned conventional laser microscope can only measure the brightness of the entire reflected light 2b, but cannot analyze the spectrum of the Raman scattered light in the reflected light 2b. If such a thing is possible, the laser microscope can be widely used not only for the integrated circuit manufacturing process but also for various other purposes. Therefore, it is possible to provide a means for realizing such a thing. It was requested.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, in which a sample is irradiated with laser light and the reflected light is received by a photomultiplier tube and amplified. In a laser microscope configured to obtain a magnified image, a Raman spectroscope for detecting Raman scattered light of various wavelengths mixed in the reflected light from the sample is provided, and the reflected light from the sample is analyzed by the Raman spectroscope. Alternatively, it is characterized by comprising a mirror device for selectively guiding to one of the photomultiplier tubes.

[0011]

In the laser microscope of the present invention, the reflected light from the sample is made incident on the photomultiplier tube to be amplified, thereby functioning exactly like the conventional laser microscope. Further, if the reflected light is made incident on the Raman spectroscope through the mirror device, it is possible to perform spectrum analysis of Raman scattered light of various wavelengths mixed in the reflected light, and thereby the sample surface Two-dimensional distribution analysis of physical properties and composition can be performed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The laser microscope of this embodiment is based on the conventional confocal scanning laser microscope described above, and has a configuration in which a Raman spectroscope and a mirror device are added to the laser microscope. 1 and 2 are a partial plan view and a partial elevation view showing an optical system in the laser microscope of the present embodiment, in which reference numeral 41 is a laser oscillator, 42 and 43 are turning mirrors, 44 is a beam splitter, Reference numeral 45 is a spatial filter, 46 is a 1 / 4λ plate, 47 is a collimating lens, 48 is a vertical turning mirror, 49 is a turning mirror, and 50 is a photomultiplier tube. The above-mentioned respective devices are the same as those in the conventional laser microscope, but in this embodiment, in addition to the above-mentioned respective devices, a mirror device 51, a turning mirror 52, and a Raman spectroscope 53 are added as shown in FIG. Has been done. In addition,
54 is a lower stage, 55 is an upper stage, and 56 is an opening formed in the upper stage 55.

The structure and principle of this optical system are shown in FIGS. 8 and 9 except that a Raman spectroscope 53 and its associated mirror device 51 and turning mirror 52 are installed.
Basically, the laser beam 2a emitted from the laser oscillator 41 passes through each of the above-mentioned devices as shown by the arrow in the figure and is reflected by the vertical turning mirror 48 on the back side of the paper surface. The sample 8 (see FIG. 8; not shown in FIG. 1) disposed on the side of the sample 8 is irradiated.
Then, the reflected light 2b from the sample 8 follows the same path as shown by the arrow and returns to the beam splitter 44, and the beam splitter 44 selectively selects either the photomultiplier tube 50 or the Raman spectroscope 53 by the mirror device 51. It is designed to be incident on.

As shown in FIGS. 3 to 5, the mirror device 51 has a structure in which a mirror 63 is attached to a rotating disk 62 rotated by a stepping motor 61, and as shown in FIGS. 2 and 4. By reflecting the mirror 63 obliquely upward, the reflected light 2b is reflected upward and is made incident on the Raman spectroscope 53 through the opening 56 formed in the upper stage 55 and the turning mirror 52. . If the reflected light 2b is allowed to pass as it is by directing the mirror 63 downward as shown in FIG. 5, the reflected light 2b is incident on the photomultiplier tube 50 via the turning mirror 49 as shown in FIG. It is like this. Figure 3
In FIG. 5, reference numeral 64 is a base, 65 is a support portion, and 66.
Is a photo sensor for detecting the rotational position of the rotary disc 62.

The Raman spectroscope 53 comprises a beam splitter 71, slits 72, lenses 73 and 74, a diffraction grating 75, and a photodetector 76, as shown in the schematic structure of FIG. In the example, a so-called one-dimensional diode array detector in which a large number of photodiodes are arranged at high density is used as the light receiver 76. In the Raman spectroscope 53, the reflected light 2b guided through the mirror device 51 is incident on the diffraction grating 75 to be dispersed into each Raman scattered light, and the dispersed Raman scattered light is detected by any one of the detectors 76. The Raman scattered light is made incident on each of the photodiodes, the intensity of each Raman scattered light is detected by each photodiode, and the spectrum analysis of the Raman scattered light is performed.

The Raman spectroscope 53 in this embodiment is used.
Is divided into 3 rooms, and each of the above devices 71 to
Although 76 is installed, diffraction gratings 81 and 82, photodetectors 83 and 84, and slits 85 and 8 are also provided in the other two chambers, respectively.
6. Lenses 87 and 88 are installed. The reflected light 2b incident on the Raman spectroscope 53 is not only incident on the light receiver 76, but a part of the reflected light 2b is guided to another diffraction grating 81 in the adjacent room by the beam splitter 71, and a part thereof is further guided. Is guided to yet another diffraction grating 82 in the adjacent room, and the Raman scattered lights dispersed by the diffraction gratings 81 and 82 enter the other photodetectors 83 and 84, respectively.
Spectral analysis is also performed by these light receivers 83 and 84. In the Raman spectroscope 53 of the present embodiment, the noise components can be reliably removed by mutually complementing the data obtained by the three light receivers 76, 83, 84, and highly accurate spectrum analysis can be performed. Has become.

The laser microscope having the above-mentioned structure functions exactly like the conventional one by making the reflected light 2b from the sample 8 incident on the photomultiplier tube 50. By switching the optical path of the reflected light 2b and making it enter the Raman spectroscope 53, the Raman scattered light in the reflected light 2b can be spectrally analyzed, whereby two-dimensional analysis of the physical properties and composition of the sample surface is performed. Distribution analysis can be performed.

That is, as described above, when the sample 8 is irradiated with the laser light 2a having a constant wavelength, various wavelengths slightly different from the wavelength of the incident laser light 2a are emitted from the sample 8 in accordance with the physical properties and composition of the surface. The Raman scattered light of the wavelength is reflected, and the Raman scattered light is mixed in the reflected light of the same wavelength as the irradiation laser light 2a. However, in the conventional general laser microscope, the brightness of the entire reflected light 2b is multiplied by photoelectron multiplication. Since it is only possible to detect with the tube 50 and spectral analysis of the reflected light 2b is not possible, it is not possible to analyze the physical properties and composition of the sample surface from the obtained enlarged image 14 (see FIG. 8). . On the other hand, in the laser microscope of the present embodiment, the spectroscopic analysis can be performed only by making the reflected light 2b incident on the Raman spectroscope 53 by the mirror device 51. Therefore, by performing such an analysis, the physical properties of the sample surface can be improved. It is possible to easily and accurately perform a two-dimensional distribution analysis of the composition and composition.

Various types of Raman spectroscopes can be adopted, and another example is shown in FIG. The Raman spectroscope 90 shown in FIG. 7 is of the type called Triplemate manufactured by Spex. In this Raman spectroscope 90, the reflected light 2b from the sample enters through the slit 91 and the diffraction grating 92 Is dispersed in. Of the dispersed light, scattered light having the same wavelength as the incident laser light 2a is blocked by the slit 93, but all the other light is allowed to pass, and the passed light is allowed to enter the diffraction grating 94. Has become. This diffraction grating 94 is the same as the above diffraction grating 92, but its direction is reversed, so that the light dispersed by the diffraction grating 92 is refocused and becomes the same as when it enters the slit 91. Only reflected light equal to the wavelength of the incident laser light 2a is cut.
Then, this light is converted into three types of diffraction gratings 9 having different resolutions.
One of 5, 96, and 97 is selected and dispersed, and each dispersed Raman scattered light is received by a photodetector 98 which is a one-dimensional detector, and spectrum analysis is performed. is there. Reference numeral 99 is a mirror for extracting reflected light for testing.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and it is needless to say that various design changes can be made in the concrete constitution of each part. .

[0021]

As described above, the laser microscope of the present invention includes the Raman spectroscope and the mirror device for guiding the reflected light from the sample to either the Raman spectroscope or the photomultiplier tube. Therefore, in addition to functioning as a conventional laser microscope, it is possible to perform spectral analysis of Raman scattered light mixed in the reflected light from the sample. It is possible to perform a two-dimensional distribution analysis of the physical properties and composition of the sample surface, which is possible, and it can be widely applied to various uses.

[Brief description of drawings]

FIG. 1 is a partial plan view showing a schematic configuration of an optical system in a laser microscope that is an embodiment of the present invention.

FIG. 2 is a partial elevational view showing a schematic configuration of an optical system in the laser microscope.

FIG. 3 is a side view of a mirror device in the optical system.

FIG. 4 is a front view showing a state in which the mirror device guides reflected light to a Raman spectroscope.

FIG. 5 is a front view showing a state in which reflected light of the mirror device is guided to a photomultiplier tube.

FIG. 6 is a schematic configuration diagram showing an example of a Raman spectrometer.

FIG. 7 is a schematic configuration diagram showing another example of a Raman spectrometer.

FIG. 8 is a principle diagram of a confocal scanning laser microscope.

FIG. 9 is an overall schematic configuration diagram showing an example of a confocal scanning laser microscope.

[Explanation of symbols]

 2a laser light 2b reflected light 8 sample 14 enlarged image 41 laser oscillator 50 photomultiplier tube 51 mirror device 53,90 Raman spectroscope 75,81,82,96,97,98 diffraction grating 76,83,84,98 light receiver .

Claims (1)

[Claims] 1. A laser microscope having a structure for obtaining a magnified image of a sample by irradiating the sample with laser light and receiving and amplifying the reflected light by a photomultiplier tube.
A Raman spectroscope for detecting Raman scattered light of various wavelengths mixed in the reflected light from the sample is provided, and the reflected light from the sample is sent to either the Raman spectroscope or the photomultiplier tube. A laser microscope comprising a mirror device for selectively guiding.