JPH07146279A - Release detection method and ultrasonic microscope applying the method - Google Patents

Abstract

PURPOSE:To accurately observe the release of a sample including entire surface release using a reflection type ultrasonic microscope. CONSTITUTION:Release inside a sample S is detected by ultrasonic waves. The bottom surface of the sample S placed at a sample stand 24 is allowed to contact an air layer 26, ultrasonic waves converged by an acoustic lens 34 are applied from the upper surface of the sample S, at the same time reflection waves from the sample S are received by the acoustic lens 34, the received reflection waves are converted to reflection signals, signals equivalent to the bottom surface of the sample S for the reflection signals are extracted, and then a reflection image on the bottom surface of the sample is drawn from a plurality of signal components obtained by relatively scanning the sample S and the acoustic lens 34 within a horizontal plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peeling detection method for detecting peeling in a sample by using a reflection type ultrasonic microscope, and an ultrasonic microscope to which the method is applied.

[0002]

2. Description of the Related Art Conventionally, it is known that a reflection type ultrasonic microscope can be used to detect peeling occurring inside a sample such as a silicon wafer or a mold IC. FIG. 5 shows an example of the structure of a reflection type ultrasonic microscope.

This ultrasonic microscope applies a high frequency signal generated by a high frequency oscillator 1 to a transducer 3 via a circulator 2 to convert it into an ultrasonic wave. This ultrasonic wave is converged by the acoustic lens 4, and the sample 5 is placed at the convergence point. The sample 5 is held by a sample holder 6, and a coupler 7 such as water is provided between the sample 5 and the lens surface of the acoustic lens 4.
Is filled. The reflected wave from the sample 5 is received by the acoustic lens 4, converted into an electric reflected signal by the transducer 3, and then input to the display device 8 via the circulator 2. The sample holder 6 is driven XY in a horizontal plane by a scanning device 10 controlled by a scanning circuit 9.

In the ultrasonic microscope as described above, the converged ultrasonic waves incident on the sample 5 from the acoustic lens 4 are reflected at the interface having different acoustic properties such as the boundary between the sample surface and the coupler. When the bonded surface of the sample shown in FIG. 6 is scanned with convergent ultrasonic waves, the peeling portion reflects the ultrasonic waves by almost 100%, and the other contact portions reflect by a reflectance sufficiently lower than 100%. If such a reflected wave is converted into an electric reflected signal, and the signal intensity of the reflected signal is converted into a luminance value and displayed on the display device 8, the magnitude of the signal intensity is compared with the brightness of the displayed image. Therefore, the peeled portion can be determined.

However, when the entire bonding surface of the sample is peeled off, the reflected signal obtained when the interface is scanned has a uniform signal strength value, and the peeled portion is obtained by comparing the magnitude of the signal strength. Can no longer be judged. This is because, in the case of a reflection type ultrasonic microscope, a reflection signal having a uniform signal intensity can be obtained even when scanning a bonding surface that does not peel at all.

On the other hand, the peeling detection of the sample can also be carried out by using the transmission type ultrasonic microscope shown in FIG. In the transmission type ultrasonic microscope, two acoustic lenses 11 and 12 are arranged so as to be confocal to each other, a coupler 13 is filled between the lenses, and a sample S is placed on a holding film 15 fixed by a sample holder 14. And is placed at the confocal position.

In this ultrasonic microscope, a high frequency signal is applied from the high frequency oscillator 1 to the transducer 3a, and the focused ultrasonic wave is incident on the sample S by the acoustic lens 11. Then, the ultrasonic wave that has been subjected to the action of absorption or the like in the sample S is received by the acoustic lens 12 arranged oppositely, is converted into an electric reflection signal by the transducer 3b, and is displayed by the display device 8
Is output to.

According to such a transmission type ultrasonic microscope, since the ultrasonic wave incident on the peeling portion is reflected by almost 100%, the signal intensity of the reflected signal becomes almost zero. On the other hand, ultrasonic waves passing through the close contact portion are affected by absorption and the like, but are only slightly attenuated. Therefore, when the bonded surface of the sample is completely peeled off, the reflected signal becomes almost 0, and it can be judged that the whole surface is peeled off. Even if the reflected signal is uniform, if there is a predetermined signal intensity, it can be determined that there is no peeling.

[0009]

However, in the transmission type ultrasonic microscope, the two acoustic lenses 11 and 12 must be arranged in a confocal state, and the alignment adjustment is complicated, and the reflection type Since the structure is more complicated than the ultrasonic microscope and the number of parts is increased, the reflection type ultrasonic microscope is predominant except in a specific field. Therefore, it is strongly desired to detect the peeling of the sample by using the reflection type ultrasonic microscope.

The present invention has been made in view of the above circumstances, and a peeling detection method and a peeling detection method capable of accurately performing peeling observation including entire surface peeling by using a reflection type ultrasonic microscope are applied. The purpose of the present invention is to provide an ultrasonic microscope.

[0011]

In order to achieve the above object, the present invention has taken the following means. The peeling detection method according to claim 1 is a peeling detection method in which peeling inside a sample is detected using ultrasonic waves, and the bottom surface of the sample placed on the sample base is brought into contact with an air layer and converged by an acoustic lens. The reflected ultrasonic wave from the sample is received by the acoustic lens, the reflected ultrasonic wave received by the acoustic lens is converted into an electric reflected signal, and the reflected signal is received. A signal component is extracted by applying a gate to a time position corresponding to the bottom surface of the sample, and the sample is obtained from a plurality of the signal components obtained by relatively scanning the sample and the acoustic lens in a horizontal plane. The reflection image of the bottom was drawn.

An ultrasonic microscope according to a second aspect of the present invention is a high frequency generating means for generating a high frequency signal, a transducer for converting a high frequency signal generated by the high frequency generating means into an ultrasonic wave, and an ultrasonic wave generated by the transducer. To a predetermined position, a sample table that holds the sample in a state where the bottom surface of the sample on which the focused ultrasonic wave transmitted from the acoustic lens is incident is in contact with the air layer, and a sample table that reflects from the sample. Receiving means for inputting an electrical reflection signal obtained by converting the reflection wave received by the acoustic lens by the transducer and extracting a signal component corresponding to the bottom surface of the sample from the reflection signal, the sample and the acoustic lens And an image forming unit for forming a reflection image of the sample bottom surface from the signal component output from the receiving unit. It was configured to and a stage.

[0013]

According to the peeling detection method according to the first aspect, the reflected image is formed by extracting the signal component of the reflected wave corresponding to the bottom surface of the sample having the air layer formed on the bottom surface of the sample. If there is no peeling in the middle of the sample, almost 100% of the ultrasonic waves are reflected at the interface between the bottom surface of the sample and the air layer, and a reflected signal with a high signal intensity is obtained. On the other hand, if there is peeling in the middle of the sample,
Since almost 100% of the ultrasonic waves at the peeled portion are reflected by the peeled portion, the ultrasonic wave does not reach the bottom surface and no reflected wave returns from the bottom surface. Therefore, it is possible to determine that the portion where there is no reflected wave is the peeling portion, and when the entire surface of the predetermined interface is peeled, there is no reflected wave from the bottom surface, and therefore it can be determined that the entire surface is peeled. .

In the ultrasonic microscope according to the second aspect, when the high frequency signal generated by the high frequency generating means is applied to the transducer, the ultrasonic wave generated by the transducer is incident on the sample while being converged by the acoustic lens. If there is a peeled portion, the ultrasonic wave incident on the sample is almost totally reflected at that portion, and if there is a peeled portion, it is almost totally reflected at the bottom surface in contact with the air layer. Each reflected ultrasonic wave reflected on the bottom surface or the peeling portion of the sample is received by the acoustic lens, converted into a reflected signal by the transducer, and then input to the receiving means. The receiving means extracts the signal component of the reflected wave from the position corresponding to the bottom surface of the sample from the reflected signal. One operation at the bottom of the sample
Image information of points is obtained. The sample and the acoustic lens are relatively moved in the horizontal plane by the scanning means, image information of a plurality of points on the bottom surface of the sample is obtained, and a reflection image of the bottom surface of the sample is formed by the image forming means.

[0015]

EXAMPLES Examples of the present invention will be described below. FIG. 1 shows the overall structure of a reflection acoustic microscope according to an embodiment of the present invention. The reflection type ultrasonic microscope of the present embodiment includes a sample table that holds the sample S in a state where the bottom surface of the sample S is in contact with the air layer. The end of the hollow hose 22 is airtightly inserted into the water tank from the bottom of the water tank 21 containing the water 20, and the connecting tube 2 is inserted into the insertion end of the hollow hose 22.
The lower end of 3 is press-fitted. The other end of the hollow hose 22 is connected to a suction pump (not shown). The upper end of the connecting tube 23 has a larger inner diameter than the lower end, and the sample table 24 is fixed to the upper end opening. The sample table 24 has an opening in the center thereof that is slightly narrower than the plane area of the sample S, and with the center of the opening and the central axis of the connecting cylinder 23 aligned and kept horizontal, It is fixed to the upper end of the connecting tube 23. Around the opening on the upper surface of the sample table 24, a convex portion 25 having a predetermined elasticity and having a constant height is formed like a closed frame. By mounting the sample S on the convex portion 25 so as to cover the opening of the sample table 24, the bottom surface of the sample S, the convex portion 25, the opening of the sample table 24, the connecting tube 23, and the like are separated. , The air layer 26 in contact with the bottom surface of the sample S is formed.

The control circuit 30 manages the operation of the reflection type ultrasonic microscope. An output end of a transmitter 31 that generates a high frequency signal by receiving a transmission trigger signal from the control circuit 30 has a transducer 33 through a circulator 32.
It is connected to the. The transducer 33 is provided on one end surface of the acoustic lens 34 and functions as an electric / acoustic conversion element. The acoustic lens 34 has a lens surface on the other end surface, and converges the ultrasonic wave incident from the transducer 33 to a predetermined position. Further, the acoustic lens 34 propagates the reflected ultrasonic wave received by the lens surface to the one end surface on the transducer 33 side. The transducer 33 is also connected to the receiver 35 via the other terminal of the circulator 32. The reflected ultrasonic wave reflected from the sample S and received by the lens surface of the acoustic lens 34 is converted into an electric signal (reflected signal) by the transducer 33, and then input to the receiver 35 through the circulator.

The receiver 35 has a function of cutting out a signal component at an arbitrary position of the reflected signal based on the control signal input from the control circuit 30. In this embodiment, the cutout timing is set so that the signal component at the position corresponding to the bottom surface of the sample S is extracted. Further, the receiver 35 holds the peak value of the signal component cut out from the reflected signal for a certain period and inputs it to the image memory 36.

Further, an X moving device 37 for driving the acoustic lens 34 in the X direction in the horizontal plane and a Y moving device 38 for driving the stage 39 on which the water tank 21 is placed in the Y direction in the horizontal plane are provided. There is. The control circuit 30 gives instructions regarding the movement timing, the movement direction, and the movement amount of the X movement device 37 and the Y movement device 38, respectively.

The image data stored in the image memory 36 is displayed on the monitor 40 when the scanning of the bottom surface of the sample with the focused ultrasonic waves is completed. Next, in the present embodiment configured as described above, an operation in the case of performing peeling observation of the sample S in which the peeling portion 41 exists on a part of the bonding surface as shown in FIG. 2 will be described.

First, the sample S is placed on the convex portion 25 of the sample table 24, and the suction pump connected to the hollow hose 22 is driven. As a result, the air layer 26 is made to have a negative pressure, the sample S is sucked at a negative pressure and pressed downward, and the sample S and the convex portion 25 are in airtight contact with each other, so that water cannot enter the air layer 26.

Next, water is put in the water tank 21 to keep the water level higher than the upper surface of the sample S, and the lens surface of the acoustic lens 34 arranged to face the sample S is submerged in water as shown in FIG. To

When the relative position between the acoustic lens 34 and the sample S is initialized, a transmission trigger signal is given from the control circuit 30 to the transmitter 31. Upon receiving the transmission trigger signal, the transmitter 31 generates a high frequency signal. This high-frequency signal is converted into ultrasonic waves by the transducer 33, propagates through the acoustic lens 34, and then is refracted by the lens surface to be converged ultrasonic waves and incident on the sample S.

For example, the ultrasonic wave incident on the point A of the sample S passes through the interface 42 as it is with almost no reflection, and is reflected at the interface between the sample bottom surface and the air layer 26. Also,
The ultrasonic wave incident on the point B of the sample S is almost reflected by the peeling portion 41 formed on the interface 42. Such a sample S
The reflected ultrasonic wave from is received by the lens surface, converted into an electric reflected signal by the transducer 33, and input to the receiver 35.

FIG. 3 shows respective reflected signals obtained by acoustically / electrically converting the reflected ultrasonic waves from the points A and B of the sample S, and a gate signal for cutting out a signal component corresponding to the sample bottom surface from the reflected signals. ing. Surface reflection waves are received at the same time t1 for each of the reflection signals at points A and B. The reflected signal from the point A without peeling is received at time t3, and the reflected wave component at the interface between the sample bottom surface and the air layer 26 is received. On the other hand, the peeling part 4
Since the reflection signal from point B where 1 is present is reflected before the bottom surface of the sample, the reflection component appears at time t2 between time t1 and time t3, and the reflection component appears at time t3 corresponding to the bottom surface of the sample. Absent.

Therefore, when the signal component is extracted from the reflected signal by the gate signal whose cut-out timing is adjusted to the reflected wave on the bottom surface of the sample as in the present embodiment, the signal intensity of the reflected signal of the ultrasonic wave incident on the portion where there is no separation is shown. The reflected wave component from the large sample bottom surface is peak-detected and stored in the image memory 36. In addition, image data having a signal intensity of 0 is stored in the image memory 36 from the reflected signal of the ultrasonic wave that has entered the peeling unit 41.

By repeating the above operation, the entire bottom surface of the sample S is scanned with a focused ultrasonic wave, and the image data composed of the intensity of the reflected wave on the bottom surface of the sample is stored in the image memory 36. The reflected image of the bottom surface of the sample S is displayed by converting the signal intensity of the image data stored in the image memory 36 into a luminance value and displaying the luminance value on the monitor 40. A portion having a luminance value of 0 in the image displayed on the monitor 40 is a peeled portion.

As described above, according to the present embodiment, the ultrasonic reflection image of the bottom surface of the sample S is formed in a state where the bottom surface of the sample S is in contact with the air layer, so that the entire interface of the sample S is The peeling can be detected even when the peeling has occurred, and the peeling detection capability equivalent to that of the transmission type reflection microscope can be realized by the reflection type ultrasonic microscope.

The structure for bringing the bottom surface of the sample S into contact with the air layer is not limited to that of the above-described embodiment, and may be, for example, the suction cup structure shown in FIG.
The suction cup 43 with the suction concave surface facing upward is fixed in the water tank, and the bottom surface of the sample S is suction fixed by the suction concave surface of the suction disk 43.
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0029]

As described above in detail, according to the present invention, the peeling detection method and the peeling detection method capable of accurately observing the peeling of the sample including the entire surface peeling by using the reflection type ultrasonic microscope are applied. An ultrasonic microscope can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a reflective ultrasonic microscope according to an embodiment of the present invention.

FIG. 2 is a diagram showing a sample mounting state in the reflection ultrasonic microscope shown in FIG.

FIG. 3 is a diagram showing a waveform diagram of a reflected signal from each point shown in FIG.

FIG. 4 is a view showing a modified example of the sample mounting table.

FIG. 5 is a configuration diagram of a conventional reflection-type ultrasonic microscope.

FIG. 6 is a partial cross-sectional view of a sample in which a peeling portion is formed on a bonding surface.

FIG. 7 is a block diagram of a conventional transmission type ultrasonic microscope.

[Explanation of symbols]

21 ... Water tank, 22 ... Hollow hose, 23 ... Connection tube, 24 ...
Sample stage, 25 ... convex portion, 30 ... control circuit, 31 ... transmitter, 32 ... circulator, 33 ... transducer,
34 ... Acoustic lens, 35 ... Transmitter, 36 ... Image memory,
37 ... X moving device, 38 ... Y moving device, 39 ... Stage, 40 ... Monitor.

Claims (2)

[Claims] 1. A peeling detection method for detecting peeling inside a sample using ultrasonic waves, wherein the bottom surface of the sample placed on a sample stage is brought into contact with an air layer, and the ultrasonic wave focused by an acoustic lens is used. The reflected wave from the sample incident from the top surface of the sample is received by the acoustic lens, the reflected wave received by the acoustic lens is converted into an electrical reflected signal, and from the reflected signal to the bottom surface of the sample. A peeling detection method characterized by extracting a corresponding signal component and drawing a reflection image of the bottom surface of the sample from a plurality of the signal components obtained by relatively scanning the sample and the acoustic lens in a horizontal plane. . 2. A high-frequency generator for generating a high-frequency signal, a transducer for converting the high-frequency signal generated by the high-frequency generator into ultrasonic waves, and an acoustic lens for converging the ultrasonic waves generated by the transducer to a predetermined position. A sample stage that holds the sample in a state where the bottom surface of the sample on which the converged ultrasonic wave transmitted from the acoustic lens is incident is in contact with an air layer, and a reflection reflected from the sample and received by the acoustic lens Receiving means for inputting an electrical reflection signal obtained by converting a wave by the transducer and extracting a signal component corresponding to the bottom surface of the sample from the reflection signal, and the sample and the acoustic lens in a horizontal plane. And scanning means for relatively scanning in, and image forming means for forming a reflected image of the bottom surface of the sample from the signal component output from the receiving means. An ultrasonic microscope characterized by that.