JPS63279103A - Minute displacement measuring microscope - Google Patents

Abstract

PURPOSE:To simply perform optical adjustment with high accuracy, by unifying an objective lens and a displacement measuring optical system as a single block structure and combining said structure with an observation optical system. CONSTITUTION:The laser beam emitted from a beam source 1 becomes parallel beam shaping apparatus 2 to be reflected by a beam splitter 6 while the reflected beam is further reflected by a semipermeable mirror 21 to pass through a 1/4 wavelength plate 7 and a fine spot for measuring displacement is projected on a specimen 9 by an objective lens 8. The reflected beam from the specimen 9 passes the objeive lens 8 and the 1/4 wavelength plate 7 and the laser beam reflected by the semipermeable mirror 21 is incident to the beam splitter 6 to be split into two beam and one of them is incident on critial angle prisms 15, 16 and projected on two-split photoreceptors 17, 18 by lenses 22, 23 to be photoelectrically converted. As mentioned above, by unifying the displacement measuring system containing the objective lens with a block 24, the shift of an optical axis is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a micro-displacement measuring microscope that measures the profile of a surface of a measurement object in a non-contact manner using an optical method.

[Conventional technology]

Regarding the means of measuring the profile of the surface of a 4111 constant object by an optical method in a non-contact manner, an invention that utilizes the focal shift of an objective lens has already been made, and was disclosed in Japanese Patent Laid-Open No. 5
It is disclosed in JP-A No. 9-90007, Japanese Patent Application Laid-Open No. 60-38606, and the like. A further development of the invention is to include an optical system that measures the profile of the surface of the object to be measured and a microscopic optical system that observes the same field of view, with the optical axes of the parts of both optical systems including the objective lens being coaxial. An invention for measuring the surface profile of an object while observing it is disclosed in Japanese Patent Laid-Open No. 62-36502.

Figure 4 is an example of an optical system showing the principle, where 1 is a laser light source that outputs linearly polarized light, 2 is a beam expander, and 3 is a laser light source that outputs linearly polarized light.
4, 6.14 is a beam splitter, 5 is an illumination system, 5a is a lamp, 5b.

5d is a lens, 5c is an aperture, 6a is a polarized beam splitting surface, 7 is a quarter wavelength plate, 8 is an objective lens, 9 is a sample,
10 is an imaging lens, 11 is a prism, 12 is an eyepiece, 13 is an observation illumination light cut filter, 15.16 is a critical angle prism, 17.18 is a two-split light receiving element, 19 is a stage, and 20 is a stage This is a knob for moving the table up and down.

A laser beam emitted from a laser light source 1 has its beam diameter expanded by a beam expander 2, becomes a parallel beam, and enters a beam splitter 4 through an aperture 3.

On the other hand, light from an observation illumination system 5 composed of a lamp 5a, a lens 5b, an aperture 5c, and a lens 5d enters a beam splitter 4, and enters a beam splitter 6 together with the laser light. The laser beam and illumination light incident on the observation optical axis by the beam splitter 6 form a polarized beam splitting surface 5a.

The light passes through the quarter-wave plate 7 and enters the objective lens 8 .

Note that when passing through the quarter-wave plate 7, the laser beam is converted from linearly polarized light to circularly polarized light. Further, the illumination light illuminates the entire field of view through the objective lens 8, and the laser light projects a minute spot for displacement measurement onto the sample 9.

The illumination light reflected from the sample 9 is passed through an objective lens 8° and a 1/4 wavelength plate 7. After passing through the beam splitter 6, the image forming lens 10. An image is formed by the prism 1.1 on the field stop plane of the eyepiece 12.

On the other hand, the sample reflected light of the laser beam is condensed by the objective lens 8, passes through the quarter-wave plate 7, becomes linearly polarized light whose vibration plane is rotated by 90 degrees from the time of incidence, and enters the polarized beam splitting surface 6a. . The laser beam is reflected by this surface 6a, passes through the observation illumination light cut filter 13, and is split into parts by the beam splitter 14, one of which is sent to the critical angle prism 15.
The other light enters the critical angle prism 16 and enters the two-split light receiving elements 17 and 18, respectively. The principle of displacement measurement from this point on is disclosed in Japanese Patent Application Laid-open Nos. 59-90007 and 60-3860.
Since it is described in detail in Publication No. 6, etc., it will be omitted here.

Furthermore, in addition to the above-mentioned method using a critical angle prism, JP-A No. 62-36502 also describes a method using an astigmatism method, which attempts to measure the surface profile of an object while observing it. In principle, this goal has been achieved.

Note that the minute displacement detection method described above will be referred to as a focus shift detection method in the following explanation.

[Problem that the invention seeks to solve]

In the above conventional example, since the displacement 4111 constant optical system and the observation optical system share an objective lens and configure their optical axes to be coaxial, the vibration of the mirror body directly affects the displacement measurement/optical system as noise. There are other problems, such as the fact that the optical adjustment is difficult and requires skill, and it is difficult to provide flexibility as a profile information collection function.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a micro-displacement measuring microscope that can easily and accurately perform optical adjustment and is resistant to vibrations.

[Means for solving problems]

In order to solve the above-mentioned problems and achieve the object, the present invention takes the following measures. That is, in a minute displacement measuring microscope that is equipped with a displacement measuring optical system and an observation optical system, and the optical axes of the parts including the objective lenses of both optical systems are coaxial, the objective lens and the displacement measuring optical system are constructed as a block structure. This was integrated and combined with the observation optical system.

[Effect]

By taking such measures, optical adjustment becomes simple, and the displacement measuring optical system can be made to have a low center of gravity, thereby increasing stability against external vibrations and the like.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, in which 1' is a light source that outputs linearly polarized light, 2' is a beam shape shaping device, and 21
．． 25 is a semi-transparent mirror, 22.23 is a lens, 24.35 is a block structure, 26 is a laser beam attenuation filter, 27.
28 is an XY moving stage, 29.30 is an XY moving stage drive source, 31 is a pinion, 32 is a rack, 33 is a fine movement drive device, and 34 is a fine movement device. Note that the same parts as in FIG. 4 are given the same reference numerals. Note that the light source 1', as in the present invention, has very high measurement sensitivity, dislikes vibration,
It is desirable to use semiconductor lasers in devices that require miniaturization.

Laser light emitted from a light source 1 that outputs linearly polarized light is turned into parallel light with a circular cross section by a beam shape shaping device 2 such as a silitrigal lens, reflected by a beam splitter 6, and further reflected by a semi-transparent mirror 21 to be 1/2 A minute spot for displacement measurement is projected onto a sample 9 by an objective lens 8 through a four-wavelength plate 7 . Note that the laser beam when passing through the quarter-wave plate 7 is converted from linearly polarized light to circularly polarized light.

The reflected light from the sample 9 passes through the objective lens 8 and the 1/4 wavelength plate 7. At this time, the laser beam becomes linearly polarized light whose vibration plane has been rotated by 90 degrees from that at the time of incidence. The laser beam reflected by the semi-transparent mirror 21 enters the beam splitter 6, is split into three directions, one enters the critical angle prism 15, the other enters the critical angle prism 16, and is split into two light receiving elements by lenses 22 and 23. 17. It is reduced and projected onto 18. Two-split light receiving element 1
The signal processing after photoelectric conversion in 7.18 was described in Japanese Patent Application Laid-Open No. 1983-
This is the same as JP-A No. 90007 and JP-A-60-38606.

In the present invention, the various elements of the optical system for determining the displacement 1llll described above are integrated into the block structure 24, and the second
The first thing is that it can be handled as a single unit as shown in the figure.
It is a feature of Note that FIG. T32 shows an example in which the position of the quarter-wave plate 7 in the displacement measuring optical system of FIG. 1 is changed to the position 7' shown by the solid line. By removing the quarter-wave plate 7 from the optical path of the observation optical system as in this example, flare mixed into the microscope image can be removed.
A sharp image can be obtained.

The observation optical system is as follows. Light from the illumination system 5 composed of a lamp 5a, lenses 5b, 5d, and an aperture 5c is reflected by a semi-transparent mirror 25, and then reflected by the semi-transparent mirror 21.
The beam passes through the 1/4 wavelength plate 7 and illuminates the entire field of view of the sample 9 through the objective lens 8.

The reflected light from the sample 9 is passed through the objective lens 8.1/4 wavelength plate 7.
Semi-transparent mirror 21, 25. The laser beam passes through the attenuation filter 26 and passes through the imaging lens 10. An image is formed by the prism 11 on the field stop surface of the eyepiece lens 12.

The XY movement stage 27.28 is a table on which the sample 9 is placed, and can be moved in the X direction or the Y direction by an XY movement stage drive source 29.30. In this way, the laser beam focused on the sample 9 and its surface can be scanned relative to each other.

According to this embodiment, the following effects are achieved.

The defocus detection method is an extremely sensitive surface measurement method, and its sensitivity far exceeds the depth of focus of the objective lens.
Since it reaches the order of nanometers, even the slightest deviation of the optical axis has a negative effect on accuracy. Second, setting the focal position of the displacement measurement optical system and eliminating vibrations are important points. For this reason, it is difficult to realize the required functions using generally well-known microscope construction methods. However, in this device, the displacement measurement optical system including the objective lens 8 is mounted on the block structure 24.
By integrating the displacement measurement optical system with the optical system, it is possible to prevent optical axis deviation, and after the observation image is focused, the focal position of the displacement measurement optical system can be adjusted more finely.

Furthermore, since it is configured separately from the block structure 35, the center of gravity of the displacement measuring optical system can be set low.

Therefore, it has the advantage of being less susceptible to external vibrations and the like.

In other words, the second feature of the present invention is that, of the observation optical system, the illumination optical system, the eyepiece optical system, and the sample stage are integrated into the block structure 35, and the displacement Δ including the objective lens is
1) It is separated from the advanced science system.

Note that it is desirable that the axially movable fine movement device 34 have a structure that utilizes elastic deformation to provide a buffering effect.

FIG. 3 is a perspective view showing a specific example thereof. As shown,
The fine movement device 34 is a device for connecting the block structure 24 (not shown in this figure) and the rack 32, and has positional axis movability in the Z-axis direction.

That is, 41.42 is a block support fixed to one side of the rack 32, and this block support 41.42
Spring members 43 and 44 are fixed to both upper and lower ends of the body with a plurality of screws 45. And between both spring members 43 and 44, a block 4 is installed to attach the block structure 24.
6 is being held. A displacement end of the fine movement drive device 33 is in contact with the upper surface of the spring member 43 . In this way, the energy of the fine movement drive device 33 moves the block structure 24 to Z.
It is capable of coarse movement in the axial direction.

In the above explanation, the case where a critical angle prism is used has been explained, but the present invention can also be applied to an optical system using the astigmatism method as described in Japanese Patent Application Laid-Open No. 62-36502. It is obvious that this method can be used, and it can also be applied to other defocus detection methods such as the Knifezi method. In addition, it goes without saying that various modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, the objective lens and the displacement constant optical system are integrated as a block structure, and this is combined with the observation optical system, so that optical adjustment can be performed easily and with high precision. It is possible to provide a micro-displacement measuring microscope that is resistant to vibrations.

[Brief explanation of drawings]

1 to 3 are views showing one embodiment of the present invention, FIG. 1 is a side view showing the overall configuration, and FIG. 2 is a block structure 2.
FIG. 3 is a perspective view of the fine movement device 34. FIG. FIG. 4 is a diagram showing a conventional example. 1.1'... Laser light source that outputs linearly polarized light, 2.
... Beam expander, 2'... Beam shape shaping device, 6... Beam splitter, 5... Illumination system, 5a
...Lamp, 5b, 5d...Lens, 5c...Aperture, 7...1/4 wavelength plate, 8...Objective lens, 9...
... Sample, 10... Imaging lens, 11... Prism, 12... Eyepiece, 15.16... Critical angle prism, 17° 18... Two-split light receiving element, 21.25.
・・Semi-transparent mirror, 22.23・・Lens, 24.35・・
・Block structure, 26... Laser light attenuation filter, 27.28... XY movement stage, 29.30...
・XY moving stage drive source, 31...binion, 32
...Rack, 33...Fine movement drive device, 34...Fine movement device. Applicant's agent Patent attorney Jun Tsuboi Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) In a minute displacement measuring microscope comprising a displacement measuring optical system and an observation optical system, with the optical axes of the parts of both optical systems including the objective lens being coaxial, the objective lens and the displacement measuring optical system are integrated into a single unit. A minute displacement measuring microscope characterized by being integrated into a single block structure. (2) Micro displacement measurement according to claim 1, wherein the block structure that integrates the objective lens and the displacement measurement optical system is provided so as to be able to make coarse and fine movements in a direction perpendicular to the sample surface. microscope.