JP2018189622A - Interference microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that it is difficult to observe fine structure of a crystal surface using an interference image obtained by a conventional interferometer, consequently, an individual differential interference microscope is used for the observation, and therefore the conventional interferometer is not adequate to observation of phenomenon during a crystal growth process having less reproducibility or high-speed phenomenon, and further, replacement of a magnification requires cumbersome works.SOLUTION: An interference microscope is provided in which a differential interference prism is arranged in an interferometer optical system and which therefore simultaneously allows for a differential interference observation of a fine crystal surface and measurement from an interference image. Further, an equivalent lens has been essential for objective lenses of a sample optical path and reference optical path even for varying a magnification, however quick varying of the magnification is achieved by matching an optical path difference being an optical error, a luminous flux and an aperture of the reference optical path with those of the sample optical path.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a reflection type interference microscope, such as measurement on a crystal surface, observation and measurement of a crystal growth process, measurement and inspection of each processing step such as a wafer in the semiconductor industry field, and further high-precision measurement and observation. An interference microscope that makes this easy.

Conventionally, as an interference optical system used for measurement of a reflection type sample, there is a Michelson type interference optical system of a separation type optical path interference optical system in which a sample optical path and a reference optical path are completely separated. Furthermore, a modified version of the Michelson-type interference optical system, there is a linic-type interference optical system for the purpose of achieving high resolution, and this both-separation type interference optical system is often used for the measurement of reflective samples. ing.

The differential interference microscope can visually observe the fine state of the reflective sample with high accuracy. FIG. 1 is a diagram showing the Michelson interference optical system. A light beam emitted from a light source 101 is converted into parallel light by a lens 102, and sample light to a sample optical path 104 and reference light to a reference optical path 105 by a beam splitter 103. It is divided into. Then, the sample light is reflected by the sample surface 106, the reference light is reflected by the reference surface 107, and is again matched by the beam splitter 103, and an interference image is generated by the objective lens 108 and the imaging lens 109, and an observation position 110 is obtained. Observed at

Next, FIG. 2 shows the linic type interference optical system. The speed of light emitted from the light source 201 is divided by the lens 202 by the beam splitter 203 and converged on the pupil, which is the rear focal position of each lens 208 arranged on the optical path of the sample optical path 204 and the reference optical path 205. It has become. Each of the light beams is converted into parallel light by the lens 208, irradiated and reflected on the sample surface 206 and the reference surface 207, and again matched by the beam splitter 203. Then, an interference image is generated and observed at the observation point 210 by the lens 209.

Further, FIG. 3 is a diagram showing the optical system of the differential interference microscope described above. Light emitted from the light source 301 has a polarization direction of 45 degrees by the polarizing plate 303 from the lens 302 and is guided toward the sample by the half mirror 304. , It converges on the pupil at the rear focal position of the objective lens 306. At that position, a differential interference prism 305 is disposed, which is divided into light having waves in the vertical and horizontal vibration directions and passes through the objective lens 306 to become light for visually recognizing the fine structure of the sample surface 307. The reflected light returns to the original optical path, and the differential interference prism 305 again matches the light having waves in the vertical and horizontal vibration directions, passes through the half mirror 304, and is polarized by the polarizing plate 308. Combine. Then, it is observed at the focal position 310 by the imaging lens 309.

Both the Michelson type interference optical system and the linic type interference optical system are configured to irradiate the sample with parallel light. Since this is an essential function as an interference microscope, the fine structure cannot be observed as it is. Therefore, the measurement operation of the interference optical system and the observation operation of the fine part in the differential interference microscope are performed separately. Therefore, there is a problem that it cannot be applied to the observation of a crystal growth process which is fast in time and difficult to reproduce.

Since the present invention has been made to solve the above-mentioned problems in the conventional interference optical system, it is possible to provide an interference microscope that can switch between measurement of a high-precision interference image and observation of a fine portion, or can perform simultaneous observation. It is intended.

In order to solve the above problems, the present invention provides an interference microscope for observing a reflection sample having a separation optical path interference optical system in which a sample optical path and a reference optical path are separated, wherein the separation optical path interference optical system is an objective of the sample optical path. A differential interference prism is disposed between the lens and the imaging lens. With this configuration, it is possible to obtain a composite image of an interference fringe interference image capable of quantitative observation and a differential interference image of a fine observation image. Also, each observation image can be acquired by attaching / detaching the differential interference prism.

According to the present invention, a clear observation image of a fine structure of a sample can be obtained simultaneously with a quantitative interference fringe interference image. Therefore, real-time measurement and observation were possible.

Conventional interferometer (Michelson type) Conventional interferometer (linic type) Conventional differential interference microscope Interferometer microscope according to the present invention (Michelson type) Interferometer microscope according to the invention (linic type) Interference loop lens configuration

Hereinafter, embodiments of the present invention will be described with reference to FIGS.

Next, Example 1 will be described. FIG. 4 is a conceptual diagram showing a basic configuration of an interference microscope according to the present invention. This conceptual diagram is a Michelson type interferometer.
The light beam emitted from the light source 401 is condensed by the lens 402 at the rear focal position of the objective lens 404 with a sufficient pupil size necessary for the brightness of the objective lens 404. The luminous flux is folded by the half mirror 403, enters the objective lens 404, and is emitted as parallel light. Further, the beam splitter 405 divides the sample light into the sample optical path 406 and the reference light into the reference optical path 407. Then, the sample light is reflected by the sample surface 408, the reference light is reflected by the reference surface 409, and is again matched by the beam splitter 405, passes through the objective lens 404 in the original optical path, and passes through the half mirror 403. The image is projected onto the observation position 411 by the imaging lens 410, and observation and measurement can be performed from the projected interference image.

Further, a differential interference prism 423 is disposed at the focal position on the rear side of the objective lens 404. Accordingly, polarizing plates 421 and 422 are also disposed at the same time. By doing so, a differential interference image for visually recognizing the fine structure of the crystal surface is also obtained. Further, when observing the differential interference image, it is possible to use either the beam slitter 404 or not. Further, when the interference image is observed, the arrangement of the differential interference prism 423 may be either.

When observing the interference pattern, if the differential interference prism 423 is disposed and slid horizontally with respect to the optical axis direction, the contrast of the interference fringes can be easily changed, and a further interference image can be obtained. At the same time, the hue of the differential observation image can be changed.

Next, a second embodiment will be described. FIG. 5 is a conceptual diagram of a linic interferometer, which is a modified version of the Michelson interferometer. The light beam emitted from the light source 501 is condensed by the lens 502 at a rear focal position of the objective lens 504 with a light beam having a sufficient pupil size for the required brightness of the objective lens 504. The light beam is folded by a half mirror 503 and further split by a beam splitter 505 into sample light to the sample optical path 506 and reference light to the reference optical path 507. The light is incident on the same objective lens 504 disposed in both optical paths, and is emitted as parallel light. Then, the sample light is reflected by the sample surface 508, and the reference light is reflected by the reference surface 509, returns to the respective objective lenses 504, and is again matched by the beam splitter 505, passes through the half mirror 503, and is connected. The image is projected onto the observation position 511 by the image lens 510, and observation and measurement can be performed from the projected interference image.

Further, a differential interference prism 523 is arranged at the back focal position of the objective lens 504. Accordingly, polarizing plates 521 and 522 are also disposed at the same time. By doing so, a differential interference image for visually recognizing the fine structure of the crystal surface is also obtained. Further, when observing a differential interference image, it is possible to use either the beam splitter 505 or not. Further, when the interference image is observed, the arrangement of the differential interference prism 523 may be either. If the differential interference prism 523 and the beam splitter 505 are exchanged, each image can be observed purely.

When observing the differential interference image and the interference image simultaneously, as an effect, when observing the interference image, if the differential interference prism 523 is arranged and slid, it is possible to easily change the contrast of the interference fringes. Interferograms can be obtained. At the same time, the hue of the differential observation image can be changed.
In the linic interferometer type interference microscope according to the second embodiment of the present invention, since the beam splitter 505 is not provided between the objective lens 504 and the sample surface 508, an original working distance of the objective lens 504 is ensured. An original image of the differential interference image can be obtained without any flare such as aberration. In addition, aberrations in the interference image can be eliminated, enabling even higher precision observation.

Furthermore, as the objective lens arranged in the reference optical path, when changing the magnification of the objective lens 504 in the sample optical path, it is essential to use a lens having the same properties as the objective lens 504 or the same objective lens 504. there were. However, in this embodiment, the objective lens portion of the reference optical path is configured as shown in FIG. Even if the objective lens in the sample optical path is exchanged, the properties can be easily matched.

The FIG. 6 will be described. FIG. 6 shows a so-called interference loop portion from the beam slitter 604 necessary for the linic interferometer of the separation type interferometer to the sample surface 607 of the sample optical path 605 and the reference surface 608 of the reference optical path 606. The other optical system configuration is the same. The lens 601 is disposed at a reference optical path position at a position equivalent to the rear focal position of the objective lens 603 in the sample optical path 605 of the optical system. Further, a compensator 602 for the optical path difference of each objective lens is arranged. The compensator 602 is prepared for each magnification.

In addition, when there is a problem such as aberration due to the compensator 602 at a high magnification, the lens 601 is disposed at the incident side position. Furthermore, the lens 601 and the compensator 602 can be moved parallel to the optical axis. Therefore, it is possible to easily change the magnification by configuring the sample optical path so that it can be aligned with the objective lens.

Measurements on crystal surfaces, observation and measurement of crystal growth processes, measurement and inspection of each processing step such as wafers in the semiconductor industry, and provision to the field of high-precision measurement and observation.

FIG.
101 Light source 102 Lens 103 Beam slitter 104 Sample light path 105 Reference light path 106 Sample surface 107 Reference surface 108 Objective lens 109 Imaging lens 110 Observation position

FIG.
201 light source 202 lens 203 beam slitter 204 sample light path 205 reference light path 206 sample surface 207 reference surface 208 objective lens 209 imaging lens 210 observation position

FIG.
301 Light source 302 Lens 303 Polarizing plate 304 Half mirror 305 Differential interference prism 306 Objective lens 307 Sample surface 308 Polarizing plate 309 Imaging lens 310 Observation position

FIG.
401 Light source 402 Lens 403 Half mirror 404 Objective lens 405 Beam slitter 406 Sample light path 407 Reference light path 408 Sample surface 409 Reference surface 410 Imaging lens 411 Observation position 421 Polarizer 422 Polarizer 423 Differential interference prism

FIG.
501 light source 502 lens 503 half mirror 504 objective lens 505 beam slitter 506 sample light path 507 reference light path 508 sample surface 509 reference surface 510 imaging lens 511 observation position 521 polarizing plate 522 polarizing plate 523 differential interference prism

FIG.
601 lens 602 compensator 603 objective lens 604 beam slitter 605 sample optical path 606 reference optical path 607 sample surface 608 reference plane

Claims (3)

  In an interference microscope used for observation of a reflection sample having a separation optical path interference optical system in which the sample optical path and the reference optical path are separated, a differential interference prism is provided between the objective lens and the imaging lens for observing the sample in the sample optical path. An interference microscope characterized by being arranged. An interference microscope comprising the same lens as the objective lens used for the sample optical path on the reference optical path side of the separated sample optical path and the reference optical path of the separation optical path interference optical system. The interference microscope according to claim 1. The lens arranged in the reference optical path includes a lens configured so that the optical path length, the light flux, the aperture, and the like of the objective lens at each magnification used in the sample optical path are the same. 2 interference microscope

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