JPS58118958A - Ultrasonic microscope - Google Patents

Abstract

PURPOSE:To simultaneously obtain an optical microscope image having the same field of view as an ultrasonic microscope image, by simultaneously picturizing the same part of a sample on the surface side and the reverse side of the sample by use of an optical microscope and an ultrasonic microscope, respectively. CONSTITUTION:From the surface side of a sample 260, a focusing light beam 320 is irradiated, its reflected ray is detected by a photodiode 305, is converted to an electric signal, the signal is processed by a receiver 370 for light, and after that, it is Z-inputted (luminance input) to a cathode-ray tube 390. Also, to the reverse side of the sample 260, a focusing ultrasonic beam 325 is irradiated through water 330, a reflected acoustic wave from the sample 260 is detected by a piezoelectric sensor 341, is converted to an electric signal, the signal is processed by a receiver 360 for acoustic wave, and after that, it is Z-inputted to a cathode ray tube 400. A stage 385 for supporting the sample 260 is two-dimensionally scanned on the (x)-(y) surface by a mechanical scanning part 380, and an (x)-(y) synchronizing signal which has synchronized with this scanning is supplied in common to the cathode-ray tube 390 for light and the cathode-ray tube 400 for acoustic wave.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mechanical scanning microscope, particularly to a microscope that uses light and sound simultaneously.

Efforts to observe the fine structure of objects have been made in the past using light, electron beams, etc.1! ! Ta.

Ultrasound, which has recently been applied in the medical world as an effective wave for observing the internal structure of the human body, has the property of being able to penetrate optically opaque objects, something that light and electron beams cannot. The higher the frequency, the more minute objects can be drawn. Furthermore, since the information extracted by ultrasound reflects the mechanical properties of the object, such as elasticity, density, and viscosity, it is possible to see internal structures that cannot be obtained with light or electron beams.

In recent years, the sound wave frequency IGH! Therefore, a telephonic ultrasound microscope is being considered that takes advantage of the above-mentioned properties of ultrasonic waves by making use of ultra-high frequencies of up to 1 micron meter in sound waves in water. In principle, this ultrasonic microscopic value is obtained by mechanically scanning the sample surface two-dimensionally with an ultrasonic beam narrowed to approximately 1 μm, and collecting disturbing sound waves such as scattering, reflection, and transmission attenuation caused by the sample. Converts the sound into an electrical signal and transmits the signal to a CRT
By displaying the image in two dimensions in synchronization with the above-mentioned mechanical scanning, microscopic advantages can be obtained. Since the present invention utilizes a reflection type ultrasonic microscope that utilizes reflected ultrasonic waves from a sample, its basic configuration will be explained using FIG. 1.

The transducer that generates and detects ultrasonic waves is a piezoelectric thin film 2.
0. It mainly consists of an acoustic lens 40. Acoustic lens 40 (eg, sapphire.

One end surface 41 of the cylindrical crystal of fused silica is an optically polished flat surface, and a hemispherical hole 42 with a radius of approximately 0.1 to 1 mm is formed in the other end surface. When the output of the RF pulse oscillator 100 is applied between the upper and lower electrodes of the layered structure consisting of the upper electrode 10 , the piezoelectric thin film 2 o and the lower electrode 30 deposited on the end surface 41 , the piezoelectric thin film generates a plane wave RF inside the lens crystal 40 . Pulsed ultrasound waves 80 are emitted. This plane ultrasonic wave is focused onto a sample 60 at a predetermined focus by a positive acoustic spherical lens formed at the interface between the hemispherical hole 42 and a medium 50 (generally water is used).

The ultrasonic waves reflected by the sample 60 are collected by the same transducer and sent to the receiver 110 as an RF pulse electric signal.
After diode detection, the video signal is used as the Z input of the cathode ray tube 130.

The sample 60 is pasted on the sample stage 70 and x-
Two-dimensional mechanical vibration is performed by a secondary mechanical scanning system 120 in the y-plane, and if the electron beam of the cathode ray tube is scanned in synchronization with this scanning, the microscopic mr* can be obtained.

Now, while such a sonic microscope utilizes the fact that the reflection of sound waves reflects the elastic properties, an optical microscope reflects the optical refractive index. Therefore, when observing the same part of a sample, it is absolutely necessary in fields such as medicine, biology, and engineering to compare the images with the ultrasonic microscope #J and the optical microscope images.

For this reason, conventionally, a specimen observed with an ultrasonic microscope was removed from the scanning device and placed on the sample stage of an optical microscope for observation.

At this time, it takes considerable effort to find the same field of view as the ultrasonic microscopic image from a wide area. On the other hand, even when determining in advance the field of view on the specimen surface to be observed using an optical microscope, it takes considerable effort to search for ultrasound microscopic images of the same field of view.

This situation is unavoidable as long as the optical microscopic image and the sonic microscopic image fl are attempted to be filmed independently.

The object of the present invention has been achieved in view of the above points, and is to provide a means that can simultaneously obtain an ultrasonic microscopic image and an optical microscopic image of the same field of view.

The present invention will be explained using FIG. 2. That is, sample 20
For example, the same part of 0 can be observed using an optical microscope 210 from the front and a sonic microscope @11220 from the back. It is obvious that the same part of the sample can be observed at the same time if the axis of the optical microscope and the axis of the sonic microscope are made to coincide. I would like to emphasize here that this configuration only becomes meaningful when sound waves are used. In other words, if you optically observe the optically opaque sample 200 from the front and back, each
However, according to the present invention, an image of the 41st surface observed by light from the front can be obtained, and an image obtained by observing the 41st surface from the back with sound can be obtained. You can get it. This is due to the most distinctive characteristic of sound waves, which is that they can propagate even inside an optically opaque sample.

In an ultrasonic microscope, by setting the focal point on an arbitrary slice plane within the sample (this is done by moving the acoustic beam closer to or farther away from the sample), a slice image with a thickness equal to the focal depth can be obtained. -You can get it.

According to the present invention, 41 planes of sound wave images are obtained for the optical system shown in 41 figures.

It is possible to obtain a large number of images of 41 planes at the same site and at the same time as the optical image.

In particular, in the case of 18 surfaces, optical bonds and acoustic images of the same layer at the same site can be taken at the same time.

The reason why light and sound are placed on opposite sides of the sample surface as shown in FIG. 2 is that the propagation medium 230 that is good for sound waves is generally water, but it is an unfavorable propagation medium for light.
At the same time, it should be added here that the air 240, which is originally a good propagation medium, is an inconvenient propagation medium for sound with extremely large attenuation.

Next, as described above, a specific means for simultaneously imaging the same part of a sample using an optical microscope and an ultrasonic microscope on the front side and the back side of the sample will be explained based on an example.

ε FIG. 3 is an embodiment of a mechanical scanning type microscope embodying the present invention ρ. In this figure, 300 is a light source, 3111 is a sensor part of an optical microscope that irradiates the front side of the sample 260 with a focused light beam 320, detects the reflected light from the sample 260 with a photodiode 305, converts it into an electrical signal, and converts it into an electrical signal. After amplification and signal processing by the receiver 370, the signal is used as the Z input (luminance input) of the cathode ray tube 390 that displays the acoustic intensity. Also, 3
50 is an RF pulse transmitter, 340 is a sensor section of a sonic microscope, which irradiates the back side of the sample 260 with a focused ultrasonic beam 325 through water 330t, and detects the reflected sound waves from the sample 260 with a piezoelectric sensor 341. The signal is converted into an electrical signal, amplified by a sound wave receiver 360, and after signal processing is used as the Z input of a cathode ray tube 400 that displays the sound. With this configuration, the sample door 385 supporting the sample 260 is mechanically scanned two-dimensionally within the x-y plane by the mechanical scanning unit 380, and X and Y synchronization signals synchronized with this scanning are sent to the optical plow. /pipe 390 and sound plow/pipe 400 in common. It is clear that if the optical beam axis and the acoustic beam axis are aligned, it is possible to obtain the same field of view of the sample at the same time and in synchronization with the optical microscope and the acoustic microscope.

In this embodiment, an optical system using a laser beam, a focusing optical lens, and a photodiode detector is employed, but a so-called ordinary optical microscope may be used instead. In this case, if mechanical scanning is performed, the acoustic truth can be obtained, and if the mechanical scanning is stopped, the optical truth can be obtained. In order to observe the sound sg1 in the same field of view as the field of view of the optical microscope, it is only necessary to adjust the scanning period of the mechanical scan.

Note that as the sound wave transmission medium 330, a liquid metal such as mercury may be used instead of water, which is conventionally used.

In other words, the silicon substrate is generally the thickest part of the wafer. Therefore, in order to observe the multilayer structure on the surface from the back side of the wafer, the acoustic spherical lens 220 requires a certain working distance, and the distance between the lens and the sample is Since the ultrasonic attenuation of the medium 210 filling the gap cannot be ignored, a liquid metal such as mercury is used, which has less attenuation than water and has good acoustic matching.

Additionally, the silicon surface 190 on the back side of the wafer is generally not polished, and the scattering of ultrasonic waves on this surface causes deterioration of the image quality of acoustic compensation, but liquid metal and silicon have very similar acoustic impedances. This is because since it is a single surface, the unevenness of the silicon surface 190 is filled in, so that the scattering of sound waves on this surface can be ignored and reduced to a negligible extent. In addition, if the silicon substrate on the back side of the wafer can be made sufficiently thin and flat by polishing or chemical etching, the working distance can be adjusted as usual, and an acoustic spherical lens with a small offset diameter can be used ~ with water as the medium. May be used.

As described above, according to the present invention, 1) If the multilayer structure of Ueno is optically transparent and each layer can be observed as a focused image using an optical microscope, each layer can be individually focused from the back side using a sonic microscope. 2) When the surface of the multilayer structure of the wafer is optically opaque and only the surface structure can be observed optically, This is because the layers below the wafer surface can only be observed using a sonic microscope.
In this case as well, the optical microscope can be used as a reference image to show which field of the sample the sonic microscope is currently displaying, and the contribution to the field of ultrasonic microscopes, such as producing sound effects such as these, is extremely large.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the schematic configuration of conventional ultrasonic microscopic values, Figure 2
The figures are for explaining the present invention.

Claims (1)

[Claims] 1. Mechanical scanning microcasting characterized by simultaneously observing the front and back surfaces of a sample both optically and acoustically. 2. Simultaneously observe the front surface optically and the back surface acoustically 11!
The mechanical scanning type microcasting according to item 1, characterized by: 3. The first device characterized by using mercury as an acoustic medium
Mechanical scanning microscope as described in section. 4. Mechanical scanning microcasting according to item 1, characterized in that a mechanical scanning reflected light microscope is used as the optical inspection means. 5. The mechanical scanning microscope according to item 1, characterized in that metal optics WI is used as the optical observation means.