JPS5813889B2 - Hikari Sousaniokeru Doushingou Toridashihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for extracting signals synchronized with optical scanning when scanning is performed with a light beam.

For example, when attempting to reproduce an image of a test sample optically scanned by a scanning microscope on a monitor scope, a signal synchronized with the optical scan is required to drive the monitor scope.

For example, when a flat reflecting mirror is used to generate scanning light and is vibrated, a synchronization signal can be easily extracted from the electrical signal that drives the flat reflecting mirror.

However, when a rotating polygon mirror is used as a deflector, a synchronization signal cannot be extracted from the electrical signal that rotates the rotating polygon mirror.

An object of the present invention is to provide a method that can effectively and easily extract a signal accurately synchronized with optical scanning even in cases where a synchronizing signal cannot be extracted from an electrical signal that drives a polarizer that produces scanning light. This is what I am trying to do.

The method of the present invention provides a method for scanning a surface to be rask-scanned by a light beam deflected in horizontal and vertical directions perpendicular to each other by first and second vibrating mirrors or rotating polygonal mirrors or a surface optically conjugate to this rask-scanning surface. An optical system extending over the entire vertical direction is provided at the end when viewed in the horizontal direction, and the light beam incident on this optical system is made incident on the Kyuden element, and the light beam is horizontally deflected from the photoelectric element. It is characterized by generating synchronized signals.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a scanning microscope to which the synchronous signal extraction method according to the present invention is applied.

A He-Ne laser light source 1 is provided to emit a thousand line light beam with a wavelength of 6328A.

In this example, a rotating polygon mirror is used as the first deflector 2, and this is rotated around an axis 3 at a constant speed.

The light beam reflected and deflected by the first rotating polygon mirror 2 is passed through a second deflector 6 through a 1-magnification aural lens system 4 and 5.
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This second deflector 6 is also a rotating polygonal mirror, and is rotated about an axis 7 at a constant speed.

By inserting the equal-magnification afocal lens systems 4 and 5 in this way, the first and second deflectors can be separated, and the second deflector 6 can be made smaller.
The further deflected light beam becomes a thousand-row light beam, which is accurately two-dimensionally deflected.

In this example, the rotating polygon mirrors 2 and 6 are both 40-sided mirrors and have the same structure.

Further, the first rotating polygon mirror 2 is rotated at a high speed, for example, at 6000 rpm, and the second rotating polygon mirror 6 is rotated at a low speed at 6.5 rpm.

Therefore, when considering a normal scanning raster, horizontal deflection is performed by the first rotating polygon mirror 2, and vertical deflection is performed by the second rotating polygon mirror 6. In the above numerical example, the line scanning frequency is One frame frequency of 3900 Hz is 10 Hz.

The laser beam deflected by the rotating polygon mirrors 2 and 6 as described above is focused as a spot on the image plane 9 via the relay lens 8.

For example, if the diameter of this spot is 80 μm, it is possible to scan a field of view of 19 mm in length and width on the image plane 9 with this spot.

The scanning raster thus formed on the image plane 9 scans the test sample through the epi-reflection microscope.

For this purpose, a laser beam spot formed on an image plane 9 is projected onto a test sample 13 via a prism 10, a semi-transparent mirror 11 and an objective lens 12.

In this example, the test sample 13 is a semiconductor chip such as an IC or LSI, and semiconductor regions, junctions, connection conductors, etc. formed on this chip are tested.

This utilizes the well-known phenomenon that a photocurrent or photovoltaic force is generated by irradiating a semiconductor with light.

Since such inspection using a light beam is a non-contact method, it has the advantage that it does not damage the sample and allows reliable inspection.

The size of the spot on the test sample 13 is determined by the objective lens 12.
The scanning area on the sample 13 is also determined by the magnification of the objective lens 12.

In this case, the smaller the diameter of the spot on the sample surface, the more accurate the inspection can be, but if the magnification of the objective lens 12 is increased, the working distance will generally become shorter, and there is a risk of damaging the sample 13.

For example, if a 100x dry objective lens with a working distance of 0.49 mm is used, the diameter of the scanning spot on the sample surface will be 0.8 μm, and the scanning range will be 0.19 mm.

An illumination light source 14 is provided to observe the sample 13, and the emitted light is directed to the sample 1 through a semi-transparent mirror 11 and an objective lens 12.
3. Epi-illumination is applied above.

Light reflected from the sample surface is guided to an eyepiece 15 via an objective lens 12, a semi-transparent mirror 11, and a prism 10.

Further, an electrical signal generated by irradiating the sample 13 with the scanning spot light is supplied to the monitor scope 17 via the signal processing circuit 16, a visible image is reproduced on the monitor scope, and this image is observed. The sample 13 can be inspected.

When the above-mentioned optical deflection device is used in combination with an epi-illuminated microscope, it is very advantageous because the deflection device is small and lightweight.

In such a scanning microscope, rotating polygon mirrors 2 and 6
Since the scanning light is generated by using the mirror, it is difficult to extract a signal synchronized with the optical scanning from the electrical signal that drives the rotating polygon mirror, unless the monitor scope 17 is driven as described above.

In this example, in order to extract a synchronization signal, a triangular prism 18 extending over the entire vertical deflection area is arranged at the end of the image plane 9 when viewed in the horizontal direction.

As clearly shown in FIG. 2, a portion of the scanning light 19 also scans this triangular prism 18 during each scan.

A portion of this scanning light is reflected by the triangular prism 18, focused by the lens 20, and then incident on the photoelectric element 21.

Therefore, a signal is generated from the photoelectric element 21 every time the scanning light 19 passes through the triangular prism 18.

This signal is in the form of a pulse and is completely synchronized with the horizontal deflection of the optical scan, so it can be used as a synchronization signal in the monitor scope 17.

In the present invention, the scanning light is detected at the image plane 9, but since the optical scanning light is most focused at this image plane, even if a small and low-sensitivity photoelectric element 21 is used. It is also possible to accurately obtain the horizontal deflection synchronization signal.

The present invention is not limited to the above-mentioned examples, but can be modified in many ways.

For example, in the above-mentioned example, the triangular prism 18 for generating the synchronization pulse is placed on the image plane 9, but it can also be placed on the plane of the sample 13.

Also, other reflective surfaces can be used instead of the triangular prism 18.

Furthermore, it is also possible to arrange the photoelectric element directly at the edge of the image plane 9.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a scanning microscope to which the synchronization signal extraction method according to the present invention is applied, and FIG. 2 is a diagram showing a portion of the microscope in an enlarged manner. DESCRIPTION OF SYMBOLS 1... Light source, 2... First rotating polygon mirror, 4, 5... Equal magnification afocal lens system, 6... Second rotating polygon mirror, 9... Image surface, 12...
Objective lens, 13... Sample, 17... Monitor scope, 1
8... Triangular prism, 19... Scanning light, 20... Condensing lens,
21...Photoelectric element.

Claims (1)

[Claims] 1 The horizontal direction of a surface that is rask-scanned by the light beams deflected in horizontal and vertical directions orthogonal to each other by the first and second vibrating mirrors or rotating polygon mirrors, or of a surface that is optically conjugate to this rask-scanning surface. An optical system extending over the entire vertical direction is provided at the end of the optical system, and a light beam incident on this optical system is made incident on a photoelectric element, and a signal synchronized with the horizontal deflection of the light beam is transmitted from the photoelectric element. A method for extracting a synchronization signal in optical scanning, characterized in that the method generates a synchronization signal.