JPH03115903A - Method and device for measuring surface shape - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention is utilized to measure surface roughness.

It is particularly suitable for measuring surface irregularities of IIIA or lower.

〔overview〕

In the present invention, a conductive probe is brought very close to the surface of a test object without touching it, and the electric field of the probe is measured while minutely changing the relative position between the probe and the test object. In this method, the shape of the surface of the object to be measured is measured by interposing an insulating liquid between the probe and the surface, making it possible to perform this measurement in the atmosphere. be.

[Conventional technology]

In conventional devices, a probe is brought into contact with the surface of the object to be tested, and the probe is slid, and the amount of movement of the probe is detected.
There is a stylus type that measures the surface roughness. However, in this device, the probe slides on the surface, which may destroy the surface of the object to be examined.

For example, as shown in FIG. 5, in a recorded diagram obtained by measuring a mesh plate for an electron microscope having a mesh number of 2000 meshes/mm, the regularity due to the meshes is not included in the pattern. This is because the Menu and Nunyu plates were destroyed by the probe. FIG. 6 is a microscopic photograph thereof.

Furthermore, since the probe is likely to get caught in surface irregularities, disturbances occur in detecting the amount of movement of the probe, making it practically impossible to measure surface roughness on the order of 1 μs.

However, in electronic components, such as memory element substrates,
Fine measurements of this order or less are required.

For this reason, a scanning tunneling electron microscope (STM) structure for investigating the surface structure of crystals is used.

In this device, the distance between the probe and the object to be measured is set to an extent (about 1 nm) that allows tunneling current to flow, and measurement is performed in a non-contact manner. With this device, the probe does not destroy the surface of the object to be inspected. However, with this method, the tunnel current cannot be detected unless the distance between the surface of the object being tested and the tip of the probe is less than a certain value, but the actual measurement surface has a large valley, and the tunnel current is detected at that valley. It may not be possible to do so.

Therefore, the tobographing method was thought of.

In this method, a probe to which an electric field is applied is held in a non-contact manner to the surface of the object to be tested, and a current is emitted from the probe into the space between the probe and the object to be tested, and the value of this emitted current is measured. , which detects the distance between the probe and the portion of the surface of the object to be measured that faces it. This allows accurate measurement of surface roughness on the order of 1 μm.

[Problem to be solved by the invention]

However, in the above-described tobographing method, the magnitude of the measured electric field changes depending on the medium constant of the medium between the probe and the object to be measured. For this reason, measurements must be performed in an ultra-high vacuum atmosphere. Therefore, many limitations arise in practical devices.

The present invention solves these problems.Since the present invention is a non-contact type, there is no destruction of the surface of the object to be measured, it can be measured in the atmosphere, and it has a high-resolution surface shape that allows accurate measurement of minute irregularities. The purpose of the present invention is to provide a method and apparatus for measuring.

[Means to solve the problem]

In the present invention, a conductive probe is placed close to the surface of a test object but not in contact with it, and the electric field flowing through the probe is observed while changing the relative position between the surface and the probe. A method for measuring the surface shape of an object by detecting the distance between the probe and the surface from the electric field, which is characterized by interposing an insulating liquid between the surface of the object and the probe. do.

It comprises an electrically conductive probe and mechanical means for positioning the probe in close proximity to, but not in contact with, the surface of the object to be tested, the mechanical means determining the relative position of the probe and the object to be tested. A surface shape measuring device that includes a means for making minute changes, a power supply that applies a voltage between the probe and the object to be measured, and a means that detects the current flowing between the probe and the object to be measured. The method is characterized in that an insulating liquid is interposed between the probe and the surface of the object to be measured.

The insulating liquid can be an insulating oil.

The probe is preferably made of a metal material that does not chemically react with the insulating oil.

[Effect]

An insulating liquid is interposed between the surface of the object to be measured and the probe. Since the insulating liquid is a substance with a high electric medium constant, a uniform electric field is created between the surface and the probe.

Therefore, the radiation current is not affected by the temperature or humidity of the measurement atmosphere even if it is not vacuumed.

This simplifies the configuration of the device and facilitates measurement and reproduction of the device.

If insulating oil is used as the liquid, measurement can be performed at low cost.

It is desirable to use a metal material for the probe that does not chemically react with the insulating oil, so that stable measurements can be made over a long period of time.

Further, it is preferable that the insulating oil does not cause a chemical reaction with the object to be measured and the probe.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a structural diagram of main parts of an apparatus according to an embodiment of the present invention. In this figure, only parts related to the present invention are shown for ease of explanation.

In this figure, the method for measuring the surface shape is to place the conductive probe 2 at a position close to the surface of the object to be tested 1 but not in contact with it, and while changing the relative position between the surface and the probe 2. The radiation current flowing through the probe 2 is received by the collector plate 3 and read by the radiation current detector 21, thereby detecting the distance between the probe 2 and the surface of the object 1 to be measured.

Therefore, the device of this embodiment uses the base 2A of the probe 2 as a mechanical means for placing the probe 2 in a position where the probe 2 approaches the surface of the object 10 and does not come into contact with it (hereinafter simply referred to as the set position). The test object 1 is composed of a holder 5 that holds the test object 1 with an insulator 4 in between, and a leaf spring 6 that holds the lower part of the object 1 with the collector plate 3 in between. This collector plate 3 is a leaf spring 6
(earth) and is electrically insulated by an insulating plate 3A. The leaf spring 6 adjusts the probe 2 so that it is at the set position from the surface of the object 1 to be tested, so one end of the leaf spring 6 is connected to the pole) 6.
A is fixed to the frame 6B, and the other end is pressed down by the tip of a fine pitch screw 6C rotatably attached to the support frame 6D.

The support frame 6D is connected to the frame 6B via coarse pitch screws 6E.
is attached to. Therefore, the probe 2 is set at the set position relative to the object 1 by using the coarse pitch screw 6E.
Place the support frame 6D in the approximate position, then insert the fine pitch screw 6C.
Make precise adjustments.

Furthermore, this mechanical means has the above-mentioned holder 5 that holds the probe 2 in each direction of the Z axis, the Three fine movement shafts 7. are supported at one end along the line and the other ends are supported at fixed points x, ySz of the device, respectively.
8 and 9. This fine movement shaft body has a shaft of a piezoelectric element as its support structure, and a control unit 2 is attached to the pole of this piezoelectric element.
When a control voltage is inputted from 2, the axis of the piezoelectric element expands and contracts due to this control voltage. As a result, the holder 5 moves minutely in the directions of the x and ySz axes. A moving table 10 is provided which moves the frame 6B of the leaf spring 6 along the X-axis and the Y-axis according to a signal from the control unit 22, and scans by changing the relative position of the surface and the probe on the XY plane. This moving stage 10 has the structure of a common stage for a microscope.

It also includes a power supply section 23 for applying a voltage between the probe 2 and the object to be tested 1, and the collector electrode plate 3 and a radiation current detection section 21 as means for detecting the current flowing through the probe 2.

The feature of the present invention is that an insulating oil 11, which is an insulating liquid, is interposed between the surface of the object 1 to be examined and the probe 2. Further, the probe 2 is made of a metal material that does not chemically react with the insulating oil 11.

Examples of the insulating oil include liquid paraffin, high boiling point hydrocarbons such as n-decane, silicone oil, and fluid natural oils and fats. Among these, those with low viscosity are
The tip of the probe is exposed in the air, which is not desirable. The probe may be made of materials such as platinum, gold, tungsten, and nickel, with platinum and gold being the most preferred. The probes are formed by mechanical polishing for platinum and gold, and by soaking tungsten and nickel in aqueous solutions of sodium hydroxide and hydrochloric acid, respectively. The tip of the probe needs to be as sharp as possible. This sharp point, that is, a cusp, is not limited to one at the tip of one probe, and may be formed in plural numbers. This is because if there are multiple cusps, the current will normally be radiated from the one that can radiate the least amount of current, but if this one is worn out, the current will be radiated from the next one. Such wear of the tip is related to the field emission current value and the corrosion resistance of the probe to insulating oil. Therefore, as mentioned above, platinum or gold, which has good chemical stability, is preferable. In FIG. 1, reference numeral 24 is a display section that graphically displays the test results.

With this surface shape measurement method, the distance between the probe 2 and the surface can be determined from the change in the field emission current flowing through the probe 2 while changing the relative position between the surface of the test object 1 and the probe 2. There are two detection methods:

1. Scanning while keeping the distance constant while changing the relative position on the horizontal plane. At this time, the field emission current becomes constant. This is called constant current mode.

23 The potential difference between the probe and the surface is kept constant, the probe is scanned on a horizontal plane, and the distance is detected from the change in current value. This is called constant voltage mode.

In the constant voltage mode, the probe scans a fixed horizontal plane, so it is applied to surfaces with large differences in the amount of unevenness. However, if the protrusion protrudes above the horizontal plane, the probe collides with the protrusion. - In the force running current mode, this problem does not occur because the probe is scanned while moving in the vertical direction following the unevenness of the surface.

In the case of constant current mode, the distance between the probe and the surface is in the range of 0 to 10 μl, preferably in the range of 0.1 to 1 μm. Further, the current value is preferably in the range of 10-'μA to 1μ.

The lower limit of the voltage value in the constant voltage mode is preferably 0.1 V, and the upper limit is preferably 100 V in consideration of voltage breakdown of the insulating liquid.

FIG. 2 is a diagram showing the electric circuit of the device of this embodiment.

Next, using Fig. 2, explain about.

To explain an example using the constant current mode, first, the insulating oil 11 is interposed between the probe 2 and the object to be measured 1, and a constant voltage is applied from the power supply unit 23 to the probe 2 via the base 2A. Then the first
The coarse pitch screw 6E and fine pitch screw 6C shown in the figure are operated to set the distance between the probe 2 and the surface to be approximately 1 μl. Next, the processor 22A of the control unit 22 operates the X-axis drive unit 1°A or the Y-axis drive unit 10B of the movable table 1o in a predetermined direction (X-axis or Y-axis direction) to start scanning. If the tip of the probe 2 is now directed toward the concave portion of the surface, the distance between the two increases, and the field emission current decreases. The field emission current value is transmitted through the collector plate 3,
The radiation current detection section 21 detects and the comparison circuit 2 of the control section 22
2B detects the difference. In this case, the difference will be a negative value. The processor 22A uses this input to control the Z fine movement shaft 7.
A command is given to the Z-axis drive power supply section 7A, which supplies a constant control voltage to the Z-axis drive power supply section 7A, to increase the control voltage. The Z fine movement shaft body 7 thereby extends in its axial direction, and the comparison circuit 22
Expand until the difference detected in B becomes zero. In this way, probe 2
is projected downward, and the distance from the surface is constant (approximately 1 μm)
). When the tip of the probe 2 faces toward the convex portion, the operation is reversed to that described above. The holder 5 of the probe 2 is held by the piezo shaft in the three axes so that its position does not change unnecessarily, so in order to keep the distance between the probe and the surface constant, the processor 22A is not the Z-axis drive power supply section 7A, but each of the X-axis and Y-axis drive power supply sections 8A and 9.
The control voltage of A is controlled simultaneously to expand and contract the X-axis and Y-axis piezo shaft bodies 8 and 9. In this way, the vertical movement distance of the probe 2 is determined by changes in the control voltages sent out by the drive power supply units 7A, 8A, and 9A for each axis. The processor 22A fed back these values calculates the moving distance of the probe and displays this on the display unit 24.

As described above, the most important thing in the present measuring method and apparatus is how accurately the field emission current is measured. What has the greatest influence on the accuracy of this measurement is the variation in the electric medium constant between the radiation space, that is, the tip of the 4-probe and the surface of the object to be measured. However, in this embodiment, since an insulating liquid having a constant electric medium constant, particularly an insulating oil, is present in this space, stable measurements can be performed.

In the device of the present embodiment described above, the moving table 10 is installed on a vibration isolating table, and the entire device is covered with a heat insulating member.
This is aimed at stabilizing measurements. Further, the display section 24 can be changed to a recording section for recording graphic drawings, if necessary.

FIG. 3(a) is a recorded diagram when the mesh plate for an electron microscope is measured using the apparatus of this embodiment. The pattern is clearly defined by the mesh, and it can be seen that there are no scratches caused by the probe on the surface of the object to be inspected. Third
Figure (b) is a micrograph of the same.

〔Effect of the invention〕

As explained above, according to the present invention, field emission current can be detected stably even in a non-high vacuum atmosphere, and there is no risk of the probe coming into contact with the surface of the object to be measured even if the probe approaches the surface very closely. Therefore, it is possible to realize a high-resolution surface shape measuring method and apparatus that can easily measure minute irregularities on the surface.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of main parts of an apparatus according to an embodiment of the present invention. FIG. 2 is an electrical circuit diagram of the same embodiment device. FIG. 3 is a measurement record diagram of the same embodiment device. FIG. 4 is a micrograph showing the surface particle structure of the object to be tested after the measurement. FIG. 5 is a measurement record diagram according to a conventional example. FIG. 6 is a micrograph showing the surface particle structure of the object to be tested after the measurement. DESCRIPTION OF SYMBOLS 1... Test object, 2... Probe, 2A... Base of probe, 3... Collector electrode plate, 3A... Insulating plate, 4... Insulator, 5... Holder, 6... Leaf spring, 6A... Bolt, 6B... Frame, 6C... Fine pitch screw, 6D
...Support frame, 6E...Coarse pitch screw, 7.8.9.
...Fine movement shafts in the Z-axis, X-axis, and Y-axis directions, respectively, 7A1
8Δ, 9A...Z-axis, X-axis, Y-axis drive power supply unit respectively, 10...Movement table, ■OA, IOB...X respectively
Axis, Y-axis drive unit, 11... Insulating oil, which is an insulating liquid, 21... Emission current detection unit, 22... Control unit, 22A... Processor, 2
2B... Comparison circuit, 23... Power supply section, 24... Display section, x, y, z... Fixed point.

Claims (1)

[Claims] 1. A conductive probe is placed at a position close to but not in contact with the surface of the object to be tested, and a conductive probe is placed on the probe while changing the relative position between the surface and the probe. In the method of measuring the surface shape of the object by observing a flowing electric field and detecting the distance between the probe and the surface from the electric field, an insulating material is provided between the surface of the object to be measured and the probe. A method for measuring surface shape, characterized by intervening a liquid. 2. A conductive probe and a mechanical means for placing the probe in a position close to the surface of the object to be detected but not in contact with the surface of the object. A surface shape measuring device comprising: a power source for applying a voltage between the probe and the object; and a means for detecting a current flowing through the probe. A surface shape measuring device, characterized in that an insulating liquid is interposed between the probe and the surface of the object to be measured. 3. The surface shape measuring device according to claim 2, wherein the insulating liquid is an insulating oil. 4. The surface shape measuring device according to claim 3, wherein the probe is made of a metal material that does not chemically react with the insulating oil.