JPH0743144A - Three-dimensional contour measurement device - Google Patents

Abstract

PURPOSE:To maintain the vertical sensitivity of a displacement detector at constant level by separating the output signal of the detector into displacement components on the basis of a sample irregularity and a reference signal, and adjusting the sensitivity of the detector on the basis of the reference signal. CONSTITUTION:An output signal from a displacement detector 15 is separated into a reference signal 19 and an irregularity signal 20 with HPF 17 and LPF 18. The amplitude of the signal 19 is taken out with an absolute value circuit 21, and the gain of an output gain controller 22 is adjusted on the basis of the value of the amplitude. With a probe 14 pressed to a sample 9, a reference signal generator 13 applies a signal to an actuator 10 for the constant amount of displacement in a vertical direction, and the deflection of a cantilever 6 due to the displacement is read out with a detector 15. A relationship between the motion of the sample 9 and the signal level of the detector 15, or the vertical sensitivity of the detector 15 is thereby calibrated. By using this calibration value, the output gain of the gain controller 22 is changed, and control is so made that the output sensitivity of the detector 15 becomes constant at all times. According to this construction, measurements on the order nm can be accurately undertaken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies the principle of an atomic force microscope. The displacement (deflection) of a cantilever can be detected by a displacement detecting means, and the sensitivity of the displacement detecting means can be calibrated based on this displacement amount. The present invention relates to a three-dimensional surface shape measuring device.

[0002]

2. Description of the Related Art Conventionally, in order to measure a fine shape such as roughness of a material surface, a non-contact type fine shape measuring apparatus using a laser spot has been used. In this fine shape measuring apparatus, the focus angle detection method such as the critical angle method, the astigmatism method, and the knife edge method is generally used as the method for measuring the distance between the surfaces to be measured.

[0003]

However, in the focus detection method, the laser spot diameter can be focused only up to about 2 μm, so that the lateral resolution is very poor as compared with the Z direction. In order to solve this, Japanese Patent Laid-Open No. 2-28
As described in Japanese Patent Laid-Open No. 1103, a cantilever for an atomic force microscope (AFM) is arranged between a laser and a sample, the sample surface is traced by this cantilever, and the deflection of the cantilever at that time is detected by a critical angle method. The method is being used.

In such a configuration, a problem in measuring the surface shape of the sample is calibration of vertical sensitivity. This will be described with reference to FIGS. 5 and 6. In the figure, 61 is a cantilever, 141 is a probe, 91 is a sample having a step 91a, and L and R are laser spots.

FIG. 5 (a) shows a state in which the cantilever 61 is not bent, and FIG. 5 (b) shows a state in which the cantilever 61 is bent in response to the step 91a of the sample 91. In this case, the sensitivity is higher when the laser spot is at the L point than when it is at the R point.

Further, when the cantilever 61 is perpendicular to the laser beam 1rf as shown in FIG. 6A, the reflected light returns uniformly, but as shown in FIG. When tilted with respect to the laser beam 1rf, only a part of the laser beam 1rf is returned and the sensitivity is lowered. In this way, the sensitivity greatly changes depending on the position of the laser spot and the inclination of the cantilever 61. further,
Since the inclination of the cantilever 61 increases as the amount of deflection of the cantilever 61 increases, it is practically difficult to perform accurate sensitivity calibration.

According to the present invention, the sensitivity of the displacement detecting means can be kept constant irrespective of the inclination of the cantilever and the spot position of the light source, and the sensitivity of the displacement detecting means can be maintained in the vertical direction even in the non-linear region. Sensitivity can be kept constant 3
An object is to provide a three-dimensional surface shape measuring device.

[0008]

In order to achieve the above object, the invention according to claim 1 provides a three-dimensional actuator capable of scanning a sample in the X-Y direction and movable in the Z direction. , X-for this actuator
Scanning signal generating means for giving a signal for scanning in the Y direction,
Reference signal generating means for generating a reference signal for moving the actuator by a certain amount in the Z direction, a probe for tracing the irregular shape of the sample surface, and a cantilever for supporting the probe and displacing in accordance with the movement of the probe. A displacement detection means for measuring the displacement of the cantilever or the probe, a separation means for separating the displacement measurement signal from the displacement detection means into the unevenness of the sample and the displacement of the reference signal, and the displacement of the reference signal. The three-dimensional surface shape measuring apparatus comprises: sensitivity adjusting means for adjusting the sensitivity of the displacement detecting means; and image display means for displaying a three-dimensional image by the scanning signal and the signal from the displacement detecting means.

In order to achieve the above object, the invention according to claim 2 provides an actuator capable of scanning a sample in the XY direction, and an X-axis for this actuator.
The scanning signal generating means for giving a signal for scanning in the −Y direction, the probe for tracing the uneven shape of the sample surface, the cantilever supporting the probe and displaced according to the movement of the probe, and the cantilever Reference signal generating means for giving a reference signal for moving a certain amount in the Z direction to an actuator for moving an optical system for focusing light on the cantilever in a state of being pressed against the sample, and displacement detection for measuring displacement of the cantilever. Means, a separation means for separating the displacement measurement signal from the displacement detection means into the unevenness of the sample and the displacement by the reference signal, and adjusting the sensitivity of the displacement detection means to be constant based on the displacement by the reference signal. Sensitivity adjusting means and image display means for displaying a three-dimensional image by the scanning signal and the signal from the displacement detecting means. A three-dimensional surface shape measurement apparatus Bei.

[0010]

According to the invention corresponding to claim 1 or claim 2, a certain amount of displacement is applied to the actuator in the Z direction in a state in which the probe of the cantilever is pressed against the sample, and the displacement detecting means is perpendicular to the vertical direction. Since the output sensitivity in the direction is made constant, the three-dimensional shape measurement on the order of nm, which has been difficult in the past, can be accurately performed, and the configuration is simple and inexpensive even in comparison with the conventional atomic force microscope.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of a three-dimensional surface shape measuring apparatus according to the present invention, which is configured as follows. That is, a laser diode 1 for emitting a laser beam, a collimator lens 2 for making the laser beam a parallel beam, a polarization beam splitter 3 for splitting the laser beam, and a laser beam reflected by the beam splitter 3 for a quarter wavelength plate. Objective lens 5 that collects light through 4
And a cantilever 6 which irradiates the light condensed by the objective lens 5 onto its upper surface to reflect the light, and the light reflected by the cantilever 6 through the objective lens 5, the quarter-wave plate 4 and the beam splitter 3. The critical angle prism 7 that reflects the guided light and the reflected light that is reflected by the critical angle prism 7 are input, and the difference (light that enters from the critical angle prism 7 at an angle smaller than the critical angle and angle that is greater than or equal to the critical angle A two-divided photodetector 8 for detecting a signal corresponding to the difference between the incident light and a displacement detector 15 for detecting the displacement of the cantilever 6 from the signal from the two-divided photodetector 8.

On the other hand, a three-dimensional cylindrical actuator 10 capable of scanning the sample 9 in the XY directions and movable in the Z direction, and scanning for generating a signal for causing the actuator 10 to scan in the XY directions. A signal generator 11,
A reference signal generator 13 that generates a reference signal that moves the actuator 10 by a certain amount in the Z direction, a probe 14 that traces the uneven shape of the surface of the sample 9, and a probe 14 that supports the probe 14 and changes the movement of the probe 14. A cantilever 6 that is displaced together, a displacement detector 15 that measures the displacement of the cantilever 6 or the probe 14, and a displacement measurement signal 16 from this displacement detector 15 is the uneven signal 20 of the sample 9 and the reference signal 1.
A high-pass filter 17 and a low-pass filter 18 for separating the displacement due to 9; a gain control 22 and an absolute value circuit 21 for adjusting the sensitivity of the displacement detector 15 from the displacement due to the reference signal 20; and a scanning signal from the scanning signal generator 11. An image display device 28 that displays a three-dimensional image according to a signal from the displacement detector 15 is provided.

The scanning signal generator 11 constitutes a scanning signal generating means, the reference signal generator 13 constitutes a reference signal generating means, and the two-division photo detector 8 and the displacement detector 1 are arranged.
5 constitutes displacement detection means, the high-pass filter 17 and the low-pass filter 18 constitute separation means, the absolute value circuit 21 and the output gain adjuster 22 constitute sensitivity adjustment means, and the image display device 28 constitutes image display means. I am configuring.

Next, the operation of the thus constructed three-dimensional surface shape measuring apparatus will be described. Here, a displacement detection method using the critical angle method will be described. The laser light emitted from the laser diode 1 is reflected by the collimator lens 2
Is collimated by. The parallel light is reflected by the polarization beam splitter 3 and then enters the objective lens 5 through the quarter-wave plate 4 and is condensed. The condensed light is reflected by the upper surface of the cantilever 6, and the reflected light passes through the objective lens 5, the quarter-wave plate 4 and the beam splitter 3 and is incident on the critical angle prism 7. The reflected light reflected by the critical angle prism 7 is the light that is incident at an angle smaller than the critical angle and the light that is incident at an angle equal to or greater than the critical angle, and this is guided to the two-divided photodetector 8 and the difference between the two is detected. A corresponding signal is guided to the displacement detector 15, where the displacement of the cantilever 6 is detected.

On the other hand, the sample 9 is XY scanned as follows. That is, an X signal and a Y signal are generated from the scanning signal generator 11, these signals are amplified by the high voltage circuit 12 and applied to the three-dimensional cylindrical actuator 10, thereby scanning in XY. In this case, the reference signal generator 13
Therefore, a high-frequency displacement reference signal is given to the actuator 10 so that the actuator 10 moves in the Z direction by a constant amount, for example, 0.1 μm.

The output of the displacement detector 15 when the sample 9 is scanned in the X and Y directions while the probe 14 near the tip of the cantilever 6 is pressed against the sample 9 is the uneven signal 16. The uneven signal and the reference displacement signal are added together. Therefore, the displacement detector 1
The output of No. 5 is separated into a reference displacement signal 19 and an unevenness signal 20 by a high pass filter 17 and a low pass filter 18. The absolute value circuit 21 takes out the amplitude of the reference displacement signal 19, and the gain of the output gain adjuster 22 is adjusted by the value. In this case, the reference signal 19 of the cantilever 6
The gain is adjusted to be low when the deflection due to A is large, that is, when the sensitivity is high, and to be increased when the deflection due to the reference signal 19 of the cantilever 6 is small, that is, when the sensitivity is low.

The Z displacement signal output from the output gain adjuster 22 and the X displacement signal output from the scanning signal generator 11 are output.
The −Y coordinate position is input to the image display device 28, and the three-dimensional uneven shape of the surface of the sample 9 is accurately displayed here.

According to the embodiment described above, with the probe 14 pressed against the sample 9, the actuator 10 is vertically displaced by a fixed amount from the reference signal generator 13.
The deflection of the cantilever 6 due to this displacement is detected by the displacement detector 1
5, the movement of the sample 9 and the change in the signal level of the displacement detector 15, that is, the vertical sensitivity of the displacement detector 15 are calibrated. This is controlled so that the output gain of the output gain adjuster 22 is changed by the calibration value and the output sensitivity of the displacement detector 15 is always constant.

As a result, it becomes possible to accurately perform the three-dimensional shape measurement on the nm order, which has been difficult in the past. In this case, even when compared with the conventional atomic force microscope, the device configuration, the circuit, etc. are relatively simple and can be obtained at low cost. In the conventional atomic force microscope, the sample is moved in the Z direction (servo) so that the deflection of the cantilever is adjusted to be constant according to the unevenness of the sample, and the measurement is performed in comparison with the present embodiment. Is a mode in which the sample 9 is scanned in the XY directions without applying servo and the unevenness of the sample 9 is measured by the deflection (ZP signal) of the cantilever 6 at that time, so the configuration is simple. Further, even in the non-linear region of the sensitivity of the displacement detector 15, the vertical sensitivity can be kept constant.

Further, since no servo is applied, high speed scanning is possible without oscillation, and the actuator 2
No voltage is applied to drive 4 in the Z direction, so X
There is no interference between the −Y direction drive signal and the Z direction drive signal, so that the XY drive signal can be accurately calibrated. Also,
There is no influence of creep and hysteresis in the Z direction.

Next, the second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. FIG. 2 shows a configuration for calibrating the sensitivity of the displacement detector 15, and the reference signal generator 1
The reference signal output from 3 is applied to the objective lens moving actuator 23 disposed above the objective lens 5,
The objective lens 5 is configured to be moved up and down.
The other configuration is the same as that of FIG.

With such a structure, the movement of the sample 9 can be moved in the XY direction by the actuator 24.
It can be done only by itself, the structure is simple, and even when the sample 9 becomes large, it can be dealt with.

Further, a third embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows a schematic structure thereof. The sample 9 is placed on a cylindrical actuator 25 having four electrodes X, -X, Y, -Y on the outside, and a probe 14 is further provided thereon. The displacement of the cantilever 6 is read by the displacement meter 26 via the cantilever 6,
This is input to the computer 27.
To the four electrodes of the cylindrical actuator 25, a voltage is applied from the computer 27 to the electrodes X, -X, Y, -Y. This configuration is equivalent to the displacement detector 15 of FIG.
Is replaced by a displacement meter 26, and the high-pass filter 1 of FIG.
7, the low pass filter 18, the absolute value circuit 21, and the output gain adjuster 22 are replaced with the computer 27.

In such a configuration, the computer 27 sends the electrodes X, -X, Y,-, as shown in FIG.
The uneven shape of the sample 9 can be measured by applying a voltage to Y, reading the displacement signal of the sample 9 by the displacement meter 26 at that time, and inputting this to the computer 27. In this case, the sensitivity of the displacement meter 26 is calibrated by the displacement when the reference signals are input to the electrodes X, -X, Y, -Y in the same phase before scanning. With this configuration, the configuration of the device is simplified and the cost is reduced. Even if the computer 27 of FIG. 3 includes the image display device 28 of FIG.
The same effect as that of the embodiment can be obtained.

[0025]

According to the present invention, the sensitivity of the displacement detecting means can be kept constant regardless of the inclination of the cantilever and the spot position of the light source, and the sensitivity of the displacement detecting means is in a non-linear region. It is possible to provide a three-dimensional surface shape measuring apparatus capable of maintaining a constant sensitivity in the vertical direction.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a three-dimensional surface shape measuring apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing a second embodiment of a three-dimensional surface shape measuring apparatus according to the present invention.

FIG. 3 is a schematic configuration diagram showing a third embodiment of a three-dimensional surface shape measuring apparatus according to the present invention.

FIG. 4 is a diagram for explaining the operation of the three-dimensional surface shape measuring apparatus of FIG.

FIG. 5 is a diagram for explaining a problem of a conventional atomic force microscope.

FIG. 6 is a diagram for explaining a problem of a conventional atomic force microscope.

[Explanation of symbols]

1 ... Laser diode, 2 ... Collimator lens, 3 ... Polarization beam splitter, 4 ... Quarter wave plate, 5 ... Objective lens, 6 ... Cantilever, 7 ... Critical angle prism, 8 ... Detector, 9 ... Sample, 10 ... 3 -Dimensional cylindrical actuator, 11 ... Scan signal generator, 12 ... High-voltage circuit, 13 ...
Reference signal generator, 14 ... Probe, 15 ... Displacement detector, 16
... unevenness signal, 17 ... high-pass filter, 18 ... low-pass filter, 19 ... reference displacement signal, 20 ... unevenness signal,
21 ... Absolute value circuit, 22 ... Output gain adjuster, 23 ... Objective lens moving actuator, 24 ... Actuator, 25 ... Cylindrical actuator, 26 ... Displacement meter, 27
... computer, 28 ... image display device.

Claims (2)

[Claims] 1. A three-dimensional actuator capable of scanning a sample in the XY directions and movable in the Z direction, and scanning signal generating means for giving a signal for scanning the actuator in the XY directions. A reference signal generating means for generating a reference signal for moving the actuator in the Z direction by a certain amount; a probe for tracing the uneven shape of the sample surface; and a probe for supporting the probe and displacing in accordance with the movement of the probe. A cantilever, a displacement detecting means for measuring the displacement of the cantilever or the probe, a separating means for separating the displacement measuring signal from the displacement detecting means into the unevenness of the sample and the displacement due to the reference signal, and the reference signal. Sensitivity adjustment means for adjusting the sensitivity of the displacement detection means from the displacement caused by the displacement, and three-dimensional by the scanning signal and the signal from the displacement detection means. Three-dimensional surface shape measurement apparatus comprising image display means for displaying an image, a. 2. An actuator capable of scanning a sample in the XY directions, a scanning signal generating means for giving a signal for scanning the actuator in the XY directions, and tracing the uneven shape of the sample surface. And a cantilever that supports the probe and is displaced in accordance with the movement of the probe, and an actuator for moving an optical system for focusing light on the cantilever while the cantilever is pressed against the sample. On the other hand, a reference signal generating means for giving a reference signal for moving a fixed amount in the Z direction, a displacement detecting means for measuring the displacement of the cantilever, and a displacement measuring signal from the displacement detecting means for the unevenness of the sample and the displacement by the reference signal. And a separation means for separating the displacement detection means and an adjustment means for adjusting the sensitivity of the displacement detection means based on the displacement based on the reference signal Sensitivity adjustment means, the scanning signal and the displacement image display means for displaying the 3-dimensional image by a signal from the detecting means, three-dimensional surface shape measurement apparatus provided with the to.