JPH03211458A - Inclination detecting device for ultrasonic microscope - Google Patents

Abstract

PURPOSE:To securely and easily detect the inclination between a lens and a sample by arranging plural subordinate piezoelectric elements on an acoustic lens and selecting some of them, and composing ultrasonic wave received signals and comparing the maximum value among them with a set value. CONSTITUTION:Two optionally selected subordinate piezoelectric elements 22a and 22b emit ultrasonic waves and then the waves pass through the flat part 21c of the acoustic lens 21 and are reflected by the sample 4 to return to the elements 22a and 22b. They are converted into electric signals, which are received by a receiver. If the sample 4 slants, there is a difference generated between the paths of the ultrasonic waves and the maximum amplitude becomes less than the maximum amplitude Vmax obtained when the sample 4 is parallel. Then the amplitude Vmax is stored as the set value and compared with the composite signals to securely and easily detect the inclination. Then a correcting device 8 is driven until the values become equal to correct the inclination.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic microscope that irradiates ultrasonic waves onto a subject to examine and analyze the subject. The present invention relates to a tilt detection device for an ultrasonic microscope that detects the presence or absence of a relative tilt.

[Conventional technology]

2. Description of the Related Art Ultrasonic microscopes that inspect and analyze objects (sample) using ultrasonic waves are commonly used and are well known.

In such inspection and analysis using an ultrasonic microscope, methods have been proposed in particular for investigating the surface condition of a sample, such as surface residual stress. The outline of this means will be explained with reference to the drawings.

FIG. 8 is a schematic diagram of a conventional ultrasonic microscope. In the figure, x, y, and z indicate coordinate axes. Reference numeral 1 denotes an acoustic lens, which has a flat upper surface 1a and a lower lens concave surface portion 1b.

The lens concave portion 1b is formed so as to focus the ultrasonic waves emitted from the acoustic lens 1. 2 is a piezoelectric element mounted on the upper surface 1a of the acoustic lens 1. An ultrasound probe 3 is configured by an acoustic lens 1 and a piezoelectric element 2. Reference numeral 4 indicates a sample to be inspected, and reference numeral 5 indicates water interposed between the acoustic lens 1 and the sample 4. 6 is an X-Y stage that drives the ultrasonic probe 3 in the X- and Y-axis directions, 7 is a Z-stage that moves the sample 4 in the Z-axis direction, and 8 is provided on the Z-stage 7 and drives the sample 4. This is an inclination angle correction device that corrects the inclination of the device.

10 is a transmitter that applies a voltage (a burst wave that becomes a sinusoidal voltage only for a specific time) to the piezoelectric element 2; 11 is a piezoelectric element 2;
a receiver for receiving reflected ultrasound signals converted by
2 is a circulator for switching between the transmitter 10 and the receiver 11; A stage controller 13 controls the driving of the XY stage 6 and Z stage 7. 14
indicates a processing device, which controls the output of the transmitter 10, controls the stage controller 13, and processes the signal received by the receiver 11.

Next, an overview of the operation of the ultrasound microscope described above will be explained. now,
When the positional relationship between the probe 3 and the sample 4 is fixed, the circulator 12 is switched to the transmitter 10 side, and a voltage (burst wave) is applied from the transmitter 10 to the piezoelectric element 2, an ultrasonic wave is output from the piezoelectric element 2. This ultrasonic wave passes through the acoustic lens 1,
The light is emitted from the lens concave portion Ib to the sample 4 via a medium (water 5 in this case). The emitted ultrasonic waves are reflected by the sample 4 and return to the piezoelectric element 2 through the water 5, the concave lens part 1b, and the acoustic lens 1, and the piezoelectric element 2 generates an electric signal corresponding to the intensity of the reflected ultrasonic waves. is converted and output. At this time, the circulator 12 is switched to the receiver 11 side, and the signal output from the piezoelectric element 2 is input to the receiver 11, amplified and detected, and sent to the processing device 14, where it undergoes processing necessary for inspection and analysis. will be done.

The ultrasonic microscope described above can perform various inspections and analyzes on the sample 4, but as described above, its major feature is that it can evaluate the physical properties of the sample 4, such as its surface condition. Therefore, an overview of the principles of such physical property evaluation is given in Part 9.
This will be explained with reference to the figures and FIG.

FIG. 9 is a side view showing the vicinity of sample 4. In the figure, the 8th
The same parts as those shown in the figures are given the same reference numerals. Among the ultrasonic waves emitted from the piezoelectric element 2, the ultrasonic beam B whose incident angle with respect to the sample 4 is greater than or equal to a critical angle of 0 passes through a distance l on the surface of the sample 4, returns to the lens concave surface portion 1b, and returns to the concave lens portion 1b with the critical angle of 0. The ultrasonic beam B2, which is less than 100 nm, is directly reflected from the surface of the sample 4. Note that the critical angle θ is determined by the sound speed of the water 5 and the sound speed of the ultrasonic wave (surface wave) passing through the surface of the sample 4.

Since each of these ultrasonic beams B+-Bz has different path lengths and path conditions, a difference occurs in the time it takes to return to the piezoelectric element 2, causing mutual interference between the image sound wave beams B, , B, in the piezoelectric element 2. The state of this interference varies depending on the distance between the acoustic lens 1 and the sample 4. FIG. 10 shows the state of the change. In this figure, the horizontal axis shows the acoustic lens 1
The distance in the Z-axis direction between and the sample 4 is plotted, and the output level from the piezoelectric element 2 is plotted on the vertical axis. The curve shown in this figure is called the V (Z) curve and changes with the same period ΔZ. Based on this value ΔZ, information (physical properties) regarding the propagation velocity of the surface wave, that is, the elasticity of the sample 4 can be obtained.

[Problems to be Solved by the Invention] Incidentally, the inspection and analysis using the ultrasonic microscope described above is based on the assumption that the relationship between the probe 3 and the sample 4 is in a parallel relationship, and it is necessary to maintain this parallel relationship. Without it, accurate inspection and analysis cannot be performed.

Particularly in fine analysis using the surface waves, a slight non-parallel state has a large adverse effect on the analysis results. This will be explained with reference to FIG. FIG. 11 is a side view of the same part as FIG. 9. This figure shows a state in which the sample 4 is tilted around the Y axis with respect to the acoustic lens. As is clear from the figure, when such an inclination exists, the surface wave propagation distance increases to a value of 1.0 compared to the case where the inclination is 0. On the other hand, the surface wave propagation distance in the Y-axis direction remains unchanged at the value l, and therefore, a situation arises in which the surface wave propagation distance differs depending on the direction. Furthermore, when the distance between the acoustic lens 1 and the sample 4 is changed to obtain the V (Z) curve shown in FIG. 10, the path of the ultrasonic wave passing through the center of the concave lens portion 1b changes with each change. This may result in a situation where the When the slope becomes even thicker, the ultrasonic beam B comes off the lens concave portion 1b, making it impossible to excite surface waves.

Conventionally, the following methods have been used to correct the above-mentioned inclination. First, the Z stage 7 is driven so that the focus of the ultrasonic waves is on the surface of the sample 4. Next, in this state, the X-Y stage 6 is driven, and the above-mentioned focusing is performed at at least three points. The angle of inclination is determined by the amount of movement of the Z stage 7 at each of these points. This tilt angle is corrected by a tilt angle correction device 8.

However, the above method has the following problems. That is, inspection and analysis, such as V<Z> curve measurement, are performed at a specific position on the X-Y plane, but since the X-Y stage 7 is driven and corrected as described above, the accuracy of the X-Y stage 7 is It has a big impact. Furthermore, since the correction uses focus, it is difficult to achieve accurate focusing due to the influence of the depth of focus. Furthermore, there is a problem that the entire operation is extremely troublesome and requires a great deal of effort and time.

The purpose of the present invention is to solve the problems in the above-mentioned prior art,
An object of the present invention is to provide a tilt detection device for an ultrasonic microscope that can reliably and easily detect the presence of a relative tilt between an acoustic lens and a sample.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a probe comprising an acoustic lens having a concave surface formed on the surface facing the sample, and a piezoelectric element disposed on the surface opposite to the surface of the acoustic lens. , in an ultrasonic microscope that receives reflected wave signals from the sample of ultrasonic waves generated by excitation of the piezoelectric element and performs predetermined processing, a flat surface is formed around the concave surface of the acoustic lens; A selection means for arranging a plurality of sub-voltage type elements around the piezoelectric element, arbitrarily selecting a plurality of these sub-voltage type elements, and a signal for synthesizing signals from the sub-voltage type elements selected by the selection means. The present invention is characterized in that it includes a combining means and a comparing means for comparing the maximum value of the signal combined by the signal combining means with a predetermined set value.

[Effect]

Before examination and analysis using an ultrasonic microscope, reflected wave signals from the selected secondary pressure 1T sample are received and synthesized. The maximum value of this composite signal is compared with the maximum value (set value) of the composite signal when the parallel relationship between the acoustic lens and the sample is maintained, and if there is a difference between the two values (the It is determined that this is the case, and measures are taken to scrape the slope.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a configuration diagram of a tilt detection device for an ultrasound microscope according to an embodiment of the present invention, and FIG. 2 is a side view of the probe shown in FIG. 1. In each figure, 21 is the acoustic lens of this example, and 2
1a is the upper surface thereof, and 211) is the concave surface portion of the lens. 21
c is a flat portion formed around the concave portion of the lens. 2
A piezoelectric element 2 is provided on the upper surface 21a of the acoustic lens 21 at a position facing the lens concave portion 21b, and emits ultrasonic waves for inspecting and analyzing the sample 4.

This pressure 'T4 element 22 corresponds to the piezoelectric element 2 of the conventional device. 22a to 22d are sub-pressure elements 1i provided around the piezoelectric element 22 on the upper surface 21a of the acoustic lens 21, and are arranged at intervals of approximately 90 degrees at positions facing the flat part 21c of the acoustic lens 21. There is. These sub-pressure type elements 22a to 22d are used during tilt detection. 23 is an acoustic lens 21, a piezoelectric element 22, and a sub-pressure type element 22a.
22d shows the probe of this embodiment.

24a to 24d are circulators connected to the sub-pressure type elements 22a to 22d, respectively, and 25 is each sub-pressure type element 22a.
A transmitter 26 provides an excitation voltage to the sub-pressure elements 22a to 22d, and a receiver 26 receives a signal corresponding to an ultrasonic reflected wave output from each of the sub-pressure elements 22a to 22d. 27 is a selector for selecting any one of the sub-pressure type elements 22a to 22d.

This selector 27 has two terminals connected to each sub-pressure element via a circulator (eight terminals in total), and two switches 27a to 27 connected to the receiver 26.
Consists of b. As a result, each of the sub-pressure type elements 22a to 2
Any two of 2d can be connected. In addition, 4 shown in FIG. 2 is a sample, 7 is a Z stage, and 8 is a tilt angle correction device, which are the same as those shown in FIG. or,
Illustrations of processing devices and the like are omitted.

Next, the operation of this embodiment is shown in Figs. 3(a) to (C), Figs. 4(a) to (C), Figs. 5(a) to (C), and Fig. 6(a).
This will be explained with reference to the waveform diagrams shown in (c). Prior to performing inspection and analysis using an ultrasonic microscope, the relative positions of the sample 4 and the probe 23 are set at predetermined positions. next,
The selector 27 is operated to selectively connect any two sub-pressure type elements, for example, sub-pressure type elements 22a and 22b. When the transmitter 25 is excited in this state, each sub-pressure type element 22a to 22d
Ultrasonic waves are emitted from the acoustic lens 21.
The light passes through the flat portion 21c of the sample 4, is reflected by the sample 4, returns to each sub-pressure type element 22a to 22d via the same path, and is converted into an electrical signal. Of these electrical signals, only the signals of the sub-pressure type elements 22a, 22b selected by the selector 27 are received by the receiver 26.

Note that the circulators 24a to 24d have the same function as the circulator 12 described above.

Here, looking at the ultrasonic waves emitted from the subpressure type elements 22a and 22b, the ultrasonic waves E3 from the subpressure type elements 22a
The ultrasonic wave Bttb from zza and the subpressure type element 22b passes through the path shown in FIG. Now, if the sample 4 is tilted as shown in Figure 2, the path of the ultrasonic wave B2□b will be changed to the ultrasonic wave BH.
Since it is longer than the path a, the sub-pressure type elements 22a and 22b
A shift occurs in the phase of the electrical signal converted in accordance with the difference between the two paths. This is shown in Figures 3(a) and (b).

FIG. 3(a) shows the signal waveform of the sub-pressure type element 22a, and FIG.
b) shows the signal waveform of the sub-pressure type element 22b, and the latter signal waveform has a phase delayed from the former by a time t corresponding to the difference between the two paths. These signals are added (combined) and input to the receiver 26.

This combined signal waveform is shown in FIG. 3(c).

By the way, if the sample 4 is rotated around the Y axis from the tilted state shown in FIG.
), the phase becomes a waveform delayed by t/2, and the signal waveform of the sub-pressure type element 22b becomes a waveform whose phase is advanced by t/2, as shown in FIG. 4(b). . That is, both signal waveforms have the same phase. The combined signal waveform becomes the waveform shown in FIG. 4(C).

Maximum amplitude of this composite signal ■1. is clearly larger than the maximum amplitude of the composite signal when the sample 4 is tilted.

Therefore, in this embodiment, the maximum amplitude V, o is stored in the processing device as a set value, and this value VsmX is compared with the maximum amplitude of the composite signal received by the receiver 26.
When the received maximum amplitude is less than the value 7.18, it is determined that a relative tilt exists between the sample 4 and the acoustic lens 21.

Then, the tilt angle correction device 8 is driven to correct the tilt until the two become equal. Furthermore, by selecting the sub-pressure type elements 22c and 22d, the inclination in those directions can be detected.
This is corrected by the tilt angle correction device 8. The correction by the 1IJi tilt angle correction device 8 may be performed by feedback controlling the tilt angle correction device 8 so that the difference between the maximum value of the composite signal and the set values ■ and □ becomes zero.

Although the relative tilt between the acoustic lens 21 and the sample 4 is corrected by the above means, a problem may occur if the tilt of the sample 4 is greater than the tilt shown in FIG. This will be explained with reference to FIGS. 5(a) to 5(c). Sample 4
When the slope becomes a certain larger slope, the sub-pressure type element 2
The signal waveforms of 2a and 22b are shown in FIG. 5(a) and 22b, respectively.
As shown in (b), the phase of the former is further advanced, and the phase of the latter is further delayed, resulting in a waveform that is shifted by exactly -period.

The composite signal waveform at this time becomes the waveform shown in FIG. 5(C), and its maximum amplitude is the value ■. Becomes equal to X.

That is, it is determined that there is no relative tilt between the acoustic lens 21 and the sample 4.

Such misjudgments can be prevented by adopting the following measures. That is, the sub-pressure type elements 22a, 22b
is selected, switch the selector 27 to select the auxiliary piezoelectric element 22C (or 22d) instead of the auxiliary voltage type element 22b.
). The waveform of the sub-pressure type element 22a at this time is shown in FIG. 6(a), and the waveform of the sub-pressure type element 22c is shown in FIG. 6(b).
) is shown. The signal waveform of the sub-pressure type element 22C is determined by the signal waveform of the sub-pressure type element 2 from the positional relationship with the sub-pressure type elements 22a and 22b.
The waveform is exactly half a cycle behind the signal waveform of signal 2a.

Therefore, the waveform of the combined signal of both is the waveform shown in FIG. 6(c), and the maximum amplitude of this waveform is the value v, which does not vary. As a result, as shown above, both signal waveforms are exactly -
Even if there is a shift in the period, the inclination can be detected.

In this way, in this example, four sub-pressure type elements are arranged at equal intervals around the acoustic lens, two of them are selected by a selector, and the maximum value of the composite signal of their output signals is Since it is compared with the set value, the relative inclination between the acoustic lens and the sample can be detected reliably and easily.

FIGS. 7(a) and 7(b) are a plan view and a side view of a probe of a tilt detection device for an ultrasonic microscope according to another embodiment of the present invention. In each figure, parts that are the same as those shown in FIGS. 1 and 2 are given the same reference numerals, and explanations thereof will be omitted. The only difference between this embodiment and the previous embodiment is that while the previous embodiment had a configuration in which four sub-pressure type elements were arranged, this embodiment had three sub-pressure type elements arranged. , the other configurations are the same. That is, in this embodiment, the sub-pressure type elements 22e, 22f, and 22g are arranged around the piezoelectric element 22.

In this embodiment, first, the sub-pressure type elements 22e and 22f are selected, their combined signals are collected, and the maximum value thereof is compared with a set value, and the slope α is detected and corrected. Then,
Sub-pressure type element 22e (or 22f) and sub-pressure type element 22g
, and correct the tilt using the same method. Thereby, the inclination between the acoustic lens 21 and the sample 4 can be corrected. This embodiment also has the same effect as the previous embodiment.

In addition, in the description of the above embodiment, three or four sub-pressure type elements are used.
Although an example has been described in which five or more are arranged, the arrangement is not limited to this, and five or more may be provided. Further, the number of sub-pressure type elements to be selected can be arbitrarily selected depending on the total number of arranged elements. Furthermore, the transmitter and receiver are not only for tilt detection, but also for inspection,
Of course, it can be used in common with analysis. Furthermore, it is clear that the tilt angle correction devices for the X-axis and the Y-axis may be provided separately. Also, contrary to the above embodiment,
Even if a selector is connected to a transmitter and a sub-pressure type element to be transmitted is selected, the inclination can be detected in exactly the same way.

〔Effect of the invention〕

As described above, in the present invention, a plurality of sub-pressure type elements are arranged in an acoustic lens, a plurality of these sub-pressure type elements are selected, their ultrasonic reception signals are combined, and the maximum value of the combined signal is Since the angle is compared with the set value, the inclination between the acoustic lens and the sample can be detected reliably and easily.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a tilt detection device for an ultrasound microscope according to an embodiment of the present invention, FIG. 2 is a side view of the acoustic lens shown in FIG. 1, and FIGS. Figures (a) to (C), Figures 5 (a) to (C), and Figures 6 (a) to (c) are
A signal waveform diagram explaining the operation shown in the figure, FIG. 7(a),
(b) is a top view and a side view of a probe of a tilt detection device for an ultrasonic microscope according to another embodiment of the present invention, FIG. 8 is a configuration diagram of a conventional ultrasonic U-microscope, and FIG. 9 is a FIG. 8 is a side view of the vicinity of the sample, FIG. 10 is a waveform diagram showing the V (Z) curve, and FIG. 11 is a side view of the vicinity of the inclined sample. 4・・・・・・・・・・・・Sample, 8・・・・・・・・・
...Inclination angle correction device, 21...
・Acoustic lens, 21c...Flat part, 22a to 22g...Sub-pressure type element, 23... ...Probe, 25...
・・・・・・・・・Transmitter, 26・・・・・・・・・・・・
・Receiver, 27...Selector. Figure 1 Figure 7 (a) (b) Figure 0 Cause Figure 0

Claims (1)

[Claims] The probe includes an acoustic lens having a concave surface formed on a surface facing the sample, and a piezoelectric element disposed on a surface opposite to the surface of the acoustic lens. In an ultrasonic microscope that receives reflected wave signals from a sample and performs predetermined processing, a flat surface is formed around the concave surface of the acoustic lens, and a plurality of sub-piezoelectric elements are arranged around the piezoelectric element. At the same time, a selection means for arbitrarily selecting a plurality of these sub-piezoelectric elements, a signal synthesis means for synthesizing the signals from the sub-piezoelectric elements selected by the selection means, and a signal synthesized by the signal synthesis means. 1. A tilt detection means for an ultrasound microscope, comprising a comparison means for comparing a maximum value of a signal with a predetermined set value.