JP2594452B2 - Surface profile measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) Surface defects and adsorbed substances in semiconductors, magnetic recording media, optical recording media and the like greatly affect their performance and yield. These defects can be problematic at submicron scales, and sometimes even at the atomic level as a cause of defect growth. These can be observed by measuring surface irregularities. However, it has been difficult to measure with a resolution of less than a micrometer. The present invention relates to a surface shape measuring device for measuring this.

(Prior Art and Problems to be Solved by the Invention) The most common measuring instrument for measuring surface irregularities is a conventional stylus-type surface roughness meter which presses a stylus against a surface and traces the surface. This imposes a pressing force on the surface of the stylus of the order of 10 milligrams or more, and in order for the stylus to withstand this load, its tip radius must be on the order of microns. Therefore, fine irregularities with a pitch of less than a micron meter cannot be detected. Furthermore, there is a danger that the surface may be damaged by this large load, or if there is a soft adsorbed substance, it may be scraped off, and an accurate surface cannot be measured.

Recently, an optical surface roughness meter that detects unevenness of a surface with light in a non-contact manner has been used. Although this does not pose a risk of damaging the surface, the diameter of the light spot is 1 micron or more, and the resolution is insufficient for the measurement of minute irregularities also having a pitch of less than 1 micron.

Further, although the scanning electron microscope has a high surface resolution, it is impossible to directly determine the height of the unevenness. In addition, since the measurement is performed in a vacuum, the adsorbed material may be dissipated and accurate measurement may not be performed.

In addition, a scanning tunneling microscope has been developed in which a sharp needle is brought close to the surface to the order of angstroms, and the tunnel current flowing during that time is detected. The resolution can be expected to the atomic level and can be measured even in air, but there is a major drawback that the surface is limited to conductors as long as tunnel current is used.

In addition, a conventional friction force microscope (FFM: Friction Force M)
icroscopy) is an atomic force microscope (AFM).
In combination with Microscopy, the height of the sample is changed so that the tip load applied to the sample surface during scanning is kept constant, and the feedback signal that changes the sample height at that time is used as shape information (AFM image). In addition, the change in frictional force under the condition of constant probe load is imaged (FFM image), or
There is a method in which a probe load on a sample surface is applied, scanning is performed in that state (the load changes according to the shape of the sample), and a change in frictional force at that time is imaged. Usually, the former is called a constant force mode, and the latter is called a constant height mode. In addition, as a method of measuring the change in the frictional force applied to the probe, the torsion of the cantilever is measured from above the cantilever with the probe attached thereto. There is a method of measuring the displacement of the cantilever due to the frictional force from the tangential direction of the sample surface (the tangential torsion corresponds to the FFM image).

However, in both of the above methods, there is a risk that a flexible sample such as a biomaterial is destroyed by probe scanning. In this case, when the probe scans from the sample substrate to the flexible material section, the tip of the probe enters the flexible material and the probe scratches the flexible material as it is for scanning under a constant probe load condition. Because it becomes. At this time, when the probe scans the flexible material portion, a larger frictional force acts than when the probe scans the sample substrate portion, and the torsion amount of the cantilever increases. Furthermore, when the amount of twist of the cantilever becomes extremely large, the height of the cantilever decreases, and this
Since the feedback control system of the M / FFM apparatus regards the load reduction as being lower, a higher load may be applied to the flexible material portion, and the sample destruction may be accelerated. In the case of (1), since the scanning is performed with the probe at a constant height, that is, the flexible material portion is directly scanned by the probe, it is inevitable that the sample is destroyed by the probe.

If there is a sharp protrusion or groove on the surface of the sample, the probe hits the protrusion or groove on the surface of the probe. At this time, the probe is inclined at the protrusion or groove. However, in both cases, the probe is scanned with a constant load and a constant height, and this tilt information is not returned to the feedback control system of the AFM / FFM device. .

As described above, the conventional friction force microscope has a problem that there is a danger of breaking the sample with respect to the flexible sample, and there is a risk of breaking the probe with a protrusion or groove on the surface of the sample.

An object of the present invention is to eliminate the disadvantages of these conventional measuring devices, and to easily form a surface shape at a specific position on a surface of any substance with high resolution regardless of whether the surface is a gas or a vacuum. An object of the present invention is to provide a surface shape measuring device capable of measuring.

(Means for Solving the Problems) In order to achieve the above object, the present invention relates to an apparatus for measuring a surface shape by sliding a stylus in contact with a measurement surface. A surface shape characterized by operating a feedback control system to reduce the load, and conversely, when the frictional force is reduced, operating the feedback control system to increase the load and using the feedback signal for shape information. The gist of the present invention is a measuring device.

(Function) The present invention obtains shape information by scanning the probe so that the frictional force becomes constant. That is, when the frictional force increases during scanning of the probe, the load is reduced so as to reduce the load. Activate the control system (because the friction force is proportional to the load,
When the frictional force is reduced, the feedback control system is operated so as to increase the load when the frictional force is reduced, so that the feedback signal is used for the shape information. As a result, in the case of a flexible material, or in the case where there are protrusions or grooves on the sample surface, the sample is operated to be lifted from the sample surface when the frictional force of the probe is increased. Can be avoided.

In other words, a sharp stylus that could not be realized by the conventional apparatus can be used without danger of destruction, so that it is possible to measure an accurate surface shape with high resolution and without scraping the soft adsorbent surface.

(Example) Next, an example of the present invention will be described.

It should be noted that the embodiments are merely examples, and it is needless to say that various changes or improvements can be made without departing from the spirit of the present invention.

FIG. 1 is a diagram showing aspects of an embodiment of the present invention and a control circuit.

In the figure, 1 is a stylus and 2 is a leaf spring. The stylus 1 is fixed to the tip of the leaf spring 2. 3 is a measuring surface, and a stylus 1
Slides on it. The tip radius of the stylus 1 is set to be submicrometer or less to obtain a resolution of submicrometer. The leaf spring 2 is easy to bend. For example, if the length is 10 mm, the width is 1 mm, and the thickness is several tens of micrometers, 100 microgram /
A rigidity of less than a micron meter can be obtained. Alternatively, a spring of less than a millimeter may be formed using an etching technique by photolithography and used.

Reference numeral 4 denotes a shape detection mechanism for detecting the displacement of the leaf spring 2, which is constituted by a capacitance sensor, an optical sensor, or the like. Reference numeral 5 denotes a load adjusting electromagnet for adjusting the load by sucking the plate ridge 2. Reference numeral 6 denotes a parallel spring, which is made of a flexible material similar to the plate 2. The parallel spring 6 bends due to the frictional force generated by the sliding contact of the stylus 1 with the measuring surface 3. Numeral 7 is for detecting the displacement of the parallel spring 6
This is a displacement detection mechanism having the same structure as that of FIG. Numeral 8 denotes a deflection adjusting electromagnet which attracts the parallel spring 6 and makes the deflection of the parallel spring 6 always zero. Reference numeral 9 denotes a friction displacement control circuit which controls the current of the deflection adjusting electromagnet 8 to which the displacement signal from the displacement detection mechanism 7 is input to make the deflection of the parallel spring zero. The attraction force of the deflection adjusting electromagnet 8 generated by the operation of the friction displacement control circuit 9 becomes equal to the friction force. Reference numeral 10 designates an output of the friction displacement control circuit 9, that is, an attraction force of the deflection adjusting electromagnet 8, as an input.
When the frictional force is excessive, the current of the load adjusting electromagnet 5 is reduced,
When the value is too small, the frictional force control circuit controls the current to be increased so that a constant frictional force is always generated. Reference numeral 11 denotes a display device for displaying a signal from the shape detection mechanism 4.

To operate this, first, the stylus 1 is brought into contact with the measurement surface 3. At this time, the force acting on the tip of the stylus and the measurement surface is almost an atomic attractive force and extremely small. When the measurement surface 3 is moved, a frictional force is generated, but the deflection of the parallel spring 6 is adjusted by the friction displacement control circuit 9 and the deflection adjusting electromagnet 8 so that the deflection is always zero. The friction force changes depending on the shape of the measurement surface. In particular, when the surface has a large convexity, the side surface, not the tip of the stylus, comes into contact with the measurement surface, so that the frictional force becomes extremely large. Such excessive frictional force creates a risk of destroying the stylus. The control of the load adjusting electromagnet 5 is intended to avoid this, and when the frictional force increases, the stylus 1 is separated from the measurement surface 3. However, since the frictional force is generated only in the contact state, the stylus 1 does not completely separate from the measurement surface 3. In this way, the stylus 1 slides on the measuring surface 3 in contact with a constant frictional force, and the vertical movement of the stylus 1 traces the unevenness of the measuring surface. This vertical movement can be detected by the shape detection mechanism 4 and shown as the surface shape of the display device 11.

The effect of the present invention is not lost even if a bar spring is used in place of the plate spring of the embodiment of the present invention, and a mechanism that generates another attractive force or repulsive force such as electrostatic force instead of the electromagnet is used. However, the effect of the present invention is not lost.

(Effects of the Invention) As described above, according to the present invention, in a device for measuring the surface shape by bringing a stylus into contact with a measurement surface, the frictional force at the time of the contact sliding is detected and the frictional force is measured. By moving the stylus up and down on the measurement surface so that is constant, it is possible to measure the surface shape with extremely small load and frictional force, and it is possible to use a sharp stylus that could not be realized with the conventional device without risk of destruction, There is an effect that a surface shape measuring device capable of accurately measuring a surface shape without shaving it even with a soft absorbing material surface with a high resolution can be implemented.

[Brief description of the drawings]

FIG. 1 shows aspects of the embodiment and a control circuit. 1 stylus, 2 leaf spring, 3 measurement surface, 4 shape detection mechanism, 5 load adjusting electromagnet, 6 parallel spring, 7
... Displacement detecting mechanism, 8... Deflection adjusting electromagnet, 9... Frictional displacement control circuit, 10... Frictional force control circuit, 11.

Claims (1)

(57) [Claims] In a device for measuring a surface shape by sliding a stylus in contact with a measurement surface, when a frictional force increases during scanning of the stylus, a feedback control system is operated so as to reduce the load, and conversely. When the frictional force is reduced, a feedback control system is operated so as to increase the load, and the feedback signal is used for shape information.