JPH03110403A - Observation device - Google Patents

Abstract

PURPOSE:To accurately align the tip of a probe on an observing point by arranging the tip of the probe of a scanning tunnel microscope so that it may be positioned in a luminous flux from the objective lens of an optical microscope to a sample. CONSTITUTION:The surface of the sample 6 is two-dimensionally scanned by the probe 4 and a probe scanning and finely adjusting mechanism part 22 which finely adjusts the probe 4 in an optical axis direction is arranged in the center part of an objective lens 21. The mechanism part 22 is constituted by using a piezo-electric element and supported by a frame(not illustrated) separately provided above the objective lens 21 in order to avoid vibration. The mechanism 22 and the frame are connected through about four thin couplers so as not to intercept the luminous flux wherever practicable. In order to observe the surface of the sample 6 by an observation device, the focal point 9 of the microscope is adjusted to the surface of the sample 6 and a stage 7 is moved to observe the sample 6 in a wide range. By moving the stage 7 so that the observation point 8 of the sample 6 may be in a visual field, adjusting the focal point 9 to the tip of the probe 4 and alternately focusing on the tip of the probe 4 and the surface of the sample 6 if necessary, the accurate alignment is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an observation device for observing, for example, the surface of a semiconductor chip or the open face of a crystal.

[Prior Art] Conventionally, an optical microscope has been used to observe the surface structure of an object over a wide range, but its resolution is limited to about 0.2 μm, making it impossible to observe the fine structure.

On the other hand, using the recently developed scanning tunneling microscope,
It is possible to observe fine structures at the atomic image level. In this scanning tunneling microscope, the tip of a conductive probe is brought close to the sample surface and scanned in two dimensions, and the fine uneven structure of the sample surface is observed by detecting the tunnel current flowing from the tip of the probe into the sample. be done.

However, since the observation area with a scanning tunneling microscope is very narrow (for example, about 10 μm×IQ μl), it is extremely difficult to specify and observe an arbitrary micro region in a sample. For this reason, it has been proposed to observe the probe and sample from an oblique direction using an optical microscope in order to align the probe with the intended observation point. Another method has also been attempted in which a scanning tunneling microscope and an optical microscope are placed facing each other on the front and back sides of a sample, and the scanning surface and probe are observed from the back side of the sample.

[Problems to be Solved by the Invention] However, in the conventional technology described above, the depth of focus is shallow when trying to obtain high resolution with an optical microscope. As a result, the in-focus area becomes narrow in the form of a line, which poses a problem in that it is not possible to align the probe at an arbitrary observation point while observing a wide range of the sample surface.

In addition, in the method of observing with an optical microscope from the back side of the sample,
In addition to the limitation that it can only be applied to samples whose scanning surface can be observed by transmitting light from the back surface, it is not possible to observe the sample surface from the same direction with a scanning tunneling microscope and an optical microscope, making it difficult to accurately align the probe. The problem was that it was difficult.

The present invention has been made in view of the above, and aims to provide an observation device that is capable of observing a sample over a wide range of areas and also capable of observing the structure of any minute region with high resolution. This is the purpose.

[Means for Solving the Problems] The present invention includes an optical microscope having an optical system including an objective lens, a conductive probe, and a scanning means for scanning a sample with the probe. In an observation device equipped with a scanning tunneling microscope, the above-mentioned problem is achieved by arranging the tip of the probe of the scanning tunneling microscope so as to be located within the beam of light from the objective lens of the optical microscope to the sample. are doing.

[Operation] FIG. 1 is an optical path diagram showing the basic configuration of the observation device according to the present invention.

The observation apparatus of the present invention includes an optical microscope (objective lens 1, eyepiece 5) for observing a wide range of the sample 6, and a scanning tunneling microscope ((objective lens 1, eyepiece 5) for observing the structure of a minute region of the sample 6 with high resolution. The tip of the probe 4 of the scanning tunneling microscope is located within the light beam from the objective lens l of the optical microscope to the sample 6 (preferably on the optical axis). located).

In such an observation device, since the tip of the probe 4 of the scanning tunneling microscope is placed within the light beam of the optical microscope, the surface of the sample 6 and the tip of the probe 4 are simultaneously observed within the field of view of the optical microscope.

That is, align the focal point 9 of the optical microscope with the surface of the sample 6 to observe the microstructure (I!) After moving the observation point 8 within the field of view, align the focal point 9 with the tip of the probe 4 and adjust the position of the sample 6. By finely adjusting (moving the stage 7), the tip of the probe 4 can be accurately and easily aligned on the observation point 8.If the probe 4 is accurately aligned, the desired position can be achieved. The structure of microscopic regions can be observed using a scanning tunneling microscope.

Note that the tip of the probe 4 does not necessarily have to be placed on the optical axis as shown in Figure 1 as long as it can be focused within the light beam, but it is important to ensure that the tip of the probe 4 is in focus. In order to perform accurate positioning, it is preferable to arrange the probe 4 on the optical axis6 [Embodiment] FIG. 2 is an optical path diagram showing the configuration of an observation device according to a first embodiment of the present invention. It is.

Such a device includes an objective lens 21. It is equipped with an optical microscope having an optical system including an eyepiece 5, and a scanning tunneling microscope having a probe 4 made of platinum, tungsten, etc., and a probe scanning/fine movement mechanism section 22 (scanning means, described later). The probe 4 of the scanning tunneling microscope is placed on the optical axis of the optical microscope. Further, the conductive sample 6 is placed on a stage 7 perpendicular to the optical axis of the optical microscope, and the stage 7 is movable in two dimensions by a drive means (not shown).

In this embodiment, a probe scanning/fine movement mechanism section 22 that scans the surface of the sample 6 two-dimensionally with the probe 4 and slightly moves the probe 4 in the optical axis direction is arranged in the center of the objective lens 21. There is. This probe scanning/fine movement mechanism section 22 is constructed using a piezoelectric element, and is not fixed to the housing (not shown) of the optical microscope itself, but is placed above the objective lens 21 for the purpose of avoiding vibration. It is supported by a separate frame (not shown). The frame and the probe scanning/fine movement mechanism section 22 are arranged 4
It is connected with a thin joint of this degree.

In the tunneling microscope that constitutes the observation device of this embodiment, the probe 4 is brought close to the surface of the sample 6 to a distance of about 5i1 nm, and an area (observation point 8) of about several tens of μm x several tens of μm is two-dimensionally scanned. At the same time, a tunnel current flowing from the tip of the probe 4 to the sample 6 is detected.

The magnitude of this tunneling current varies depending on the distance between the sample 6 and the probe 4, that is, the unevenness of the sample surface, so the probe 4 is slightly moved in the optical axis direction so that the tunneling current remains constant.
By extracting a value corresponding to the amount of movement in the optical axis direction as an electrical signal, an enlarged image of the observation point 8 can be obtained on the oscilloscope.

To observe the surface of the sample 6 using the above-described observation device, first, the focus 9 of the optical microscope is set on the surface of the sample 6, and the stage 7 is appropriately moved to observe the sample 6 over a wide range. Then, the stage 7 is moved so that the part (observation point 8) where the microstructure of the sample 6 is to be observed is within the field of view.

Thereafter, the focal point 9 of the optical microscope is aligned with the tip of the probe 4 and the position of the stage 7 is finely adjusted so that the tip of the probe 4 faces the observation point 8 . At this time, accurate alignment can be achieved by alternately focusing on the tip of the probe 4 and the surface of the sample 6, if necessary.

After that, by scanning the surface of the sample 6 with the probe 4, the fine structure at the target observation point 8 can be observed with a resolution of atomic image level (for example, 0.1 in the optical axis direction and 1 in the 9-plane direction). .

That is, by using the observation device of the present invention as described above, it is possible to observe the sample 6 over a wide range to understand the whole, and then observe the extremely fine structure at a specific observation point 8 within the sample 6. becomes. Furthermore, in the observation apparatus of this embodiment shown in FIG. 2, the probe scanning/fine movement mechanism section 22 of the scanning tunneling microscope is incorporated into the objective lens 21 of the optical microscope, so the entire apparatus can be made compact. It also has excellent operability because there are no protruding parts that would obstruct observation.

Next, FIG. 3 is an optical path diagram showing the configuration of an observation device according to a second embodiment of the present invention.

In the observation device of this embodiment, the probe 4 of the scanning tunneling microscope is arranged on the optical axis 3 of the optical microscope as in the first embodiment, but the arrangement position of the probe scanning/fine movement mechanism section 32 is This is different from the first embodiment.

That is, in this embodiment, the objective lens 31 of the optical microscope is a normal one, and the probe scanning/fine movement mechanism section 32 is arranged outside the field of view of the optical microscope. A stay 10 is extended from the probe scanning/fine movement mechanism section 32 to the optical axis position of the optical microscope, and the probe 4 is attached to the tip of the stay 10.

The operation of the scanning tunneling microscope itself is similar to that of the first embodiment, and it is possible to observe a wide range of the sample and observe the microstructure at a specific observation point 8 according to the procedure described above.

The observation device of this embodiment has a simple configuration because the scanning/fine movement mechanism section 32 of the tunneling microscope is arranged separately from the optical microscope, and can be easily manufactured using a conventional scanning tunneling microscope and an optical microscope. It has the advantage of being able to

In addition, in the first and second embodiments described above, the probe 4
Although the entire probe 4 is placed on the optical axis 3, the probe 4 does not necessarily have to be parallel to the optical axis (orthogonal to the sample 6), but the probe 4 can be tilted so that only the tip is located on the optical axis. You can also do it.

In addition, although the above description describes the case of observing a conductive sample, when observing the molecular structure of an organic substance (for example, the structure of DNA), the sample is made into a thin film and pasted on a conductive substrate. This can be countered by attaching a tunnel current from the probe to the substrate through the thin film of the sample.

[Effects of the Invention] As described above, in the observation device of the present invention, the tip of the probe of the scanning tunneling microscope is placed within the light beam from the objective lens of the optical microscope to the sample, and it can be used to detect arbitrary points on the surface of the sample. The probe tip can be accurately and easily positioned at the observation point.

That is, by using the observation apparatus of the present invention, it is possible to observe the surface of a sample over a wide range and then observe the fine structure at any observation point with very high resolution.

Such an observation device is extremely useful in various research and development activities, including failure analysis of semiconductor chips, elucidation of the atomic structure of crystal side open planes, and the molecular structure of organic substances.

4. Simple description of the drawings Fig. 1 is an optical path diagram showing the basic configuration of the present invention, Fig. 2 is an optical path diagram showing the configuration of the observation device according to the first embodiment of the invention, and Fig. 3 is an optical path diagram showing the configuration of the observation device according to the first embodiment of the invention. FIG. 7 is an optical path diagram showing the configuration of an observation device according to a second embodiment.

[Explanation of symbols of main parts] 1.21. : ] 1... Objective lens 22) 2... Probe scanning/fine movement mechanism section (scanning means) 4... Probe 5... ...Eyepiece 6...
...Sample 7...Stage 8...Observation point

Claims (2)

[Claims] (1) In an observation device equipped with an optical microscope having an optical system including an objective lens, and a scanning tunneling microscope having a conductive probe and a scanning means for scanning a sample with the probe, An observation device characterized in that the tip of the probe of the scanning tunneling microscope is located within a beam of light extending from the objective lens of the optical microscope to the sample. (2) The observation device according to claim 1, wherein the probe of the scanning tunneling microscope is arranged on the optical axis of the optical microscope.