JP2002257702A - Method of eliminating static charge of charged sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate charge to be adapted to AFM measurement, even in a sample of an insulator having strong chargeability. SOLUTION: The charged sample 3 is irradiated with an X-ray from a Geissler tube 1 or the like to eliminate the charge. The Geissler tube is vacuum- evacuated up to vacuum pressure of an area where fluorescence is emitted, or about 1 Pa. The Geissler tube is set in an atomic force microscope to make the X-ray from the Geissler tube irradiate the sample having the chargeability observed by the microscope.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing charge from a sample in order to accurately observe a fine structure on the surface of the sample by an atomic force microscope (AFM).

[0002]

2. Description of the Related Art Conventionally, when performing various measurements and analyzes on a sample, if the surface of the sample or the entire sample is charged, the measurement or analysis cannot be performed, or very erroneous information is given due to the influence of the charging. There is. To prevent these inconveniences,
This is to remove the charge on the surface or the entire surface. Generally, the short-wavelength light (UV) irradiation method and the corona discharge irradiation method are known as the charge removal method. Suitable for.

[0003]

AFM observation for the purpose of observing the fine structure of the sample surface is often performed in the air, and the target sample is a tunnel microscope (STM) which is limited to a conductive sample. Unlike this, there is a feature that measurement can be performed even on an insulating material such as a non-conductive organic material or a non-conductive ceramic.
However, when charge accumulates inside the sample due to some effect, a charge phenomenon appears. In many cases, this charge acts as a repulsive force on the short hand of the AFM during measurement, so that a signal reflecting the surface structure is obtained. Brings inconvenience. This phenomenon appears more strongly as the sample becomes larger. In such a case, by performing the charge elimination by applying corona discharge, the AFM measurement can be performed if the conditions are appropriate. However, in this method, appropriate conditions are different depending on the state of the sample, and if the conditions are not satisfied, the charging is strengthened. In addition, since the charge for static elimination hardly penetrates into the inside of the substance due to its nature, a considerable time may be required for neutralization. Furthermore, depending on the sample, the chargeability is very strong, and it is difficult to remove the charge (for example, a ferroelectric substance), so that the AFM measurement cannot be performed.

As a means for observing the surface structure of an insulator,
As a generally well-known method, there is a method using a scanning electron microscope (SEM). However, even with the SEM, observation cannot be performed due to the charging effect of the electron gun of the excitation source in the observation method. A method for avoiding this is to coat the sample surface with a very thin noble metal film (10 nm or less), treat the surface to be conductive, and observe the sample. This coating conductive treatment method can be applied to AFM if the structure to be observed is relatively large. However, most of the AMF observation is aimed at microstructure observation. This has a significant effect on the measurement and makes it impossible to clearly observe the surface structure. Therefore, in order to observe the fine structure of the insulator with the AFM, in most cases, static elimination is required, and a static elimination method in which setting conditions are easy in a short time is desired.

According to the present invention, even a highly charged insulator sample
It is an object of the present invention to provide a method for removing static electricity so as to be suitable for FM measurement.

[0006]

In the present invention, in order to achieve the above object, a charged sample is irradiated with X-rays to eliminate the charge. It is easy and convenient to irradiate the X-rays from a Geisler tube.
It is preferable to use one evacuated to about a. The object of the present invention can be more appropriately achieved by installing a Geisler tube in an atomic force microscope and irradiating a charged sample to be observed with the microscope with X-rays from the Geisler tube.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an AFM will be described with reference to the drawings.
Reference numeral 1 denotes a Geisler tube which is evacuated and sealed to a region where fluorescence is emitted at a pressure of about 1 Pa inside an existing glass tube, and 2 denotes an atomic force microscope (AFM) for observing a microstructure of a sample 3 of an insulator. 2) shows a probe portion as a main body, and the Geisler tube 1 was installed at a position where the surface of the sample 3 was irradiated. When the probe 2 is moved along the surface of the sample 3, the atomic force is measured as a two-dimensional distribution of voltage, and the fine structure of the surface can be detected. 4 is 8000-15000V
High-voltage power supply for the Geisler tube 1;
It is a wire protection cover. The high-voltage power supply 4 may be a neon transformer or an induction coil. However, the latter uses a neon transformer because the voltage is adjusted by the discharge gap, so that the high-voltage line is apt to carry noise and may be charged conversely. Is preferred. The Geisler tube 1
The distance between the sample and the sample 3 was set to about 20 cm. However, there is no limitation on this distance, and a distance suitable for the configuration of the apparatus may be selected. 1 can shorten the operation time. The Geisler tube 1 used was a sealed one,
The Geisler tube may be operated while exhausting the inside of the Geisler tube to a predetermined pressure (1 Pa or less) with a vacuum pump.

Prior to AFM observation of the fine structure of the insulator sample 3, a high voltage is applied between the electrodes 1a and 1a of the Geisler tube 1 from the high voltage power supply 4 for, for example, 10 seconds or less in accordance with the degree of charging of the sample 3. For several seconds. This Geisler tube 1
Is a vacuum pressure that emits X-rays, the sample 3 is irradiated with X-rays, and since the X-rays have penetrating power to the inside of the sample 3, the charge can be quickly removed to the inside of the sample 3 and at the same time, the vicinity of the sample 3 The gas molecules in the atmosphere are ionized, the ionized gas molecules deprive the sample 3 of the charge, and the charge can be efficiently removed. Thereafter, when the AFM observation is performed, an accurate surface morphology without the influence of charging can be observed. The reason why the Geisler tube 1 is used is that X-rays can be generated relatively easily and inexpensively.

To explain a specific example, the surface of polycarbonate was subjected to plasma etching processing, and the surface was subjected to AFM in order to evaluate the fine structure of the sample 3 in which the fine structure was known to some extent. FIG. 2 shows the result of AFM observation performed as it is after the plasma etching processing. As a result, a very strong charging effect was observed, and the fine structure in the processed state could not be observed. The microstructure of the processed polycarbonate sample 3 was observed by removing the static electricity by operating the Geisler tube for 5 seconds by the AFM equipped with the Geisler tube 1, and the result is shown in FIG. Could be observed.

[0010]

As described above, according to the present invention, a charged sample is irradiated with X-rays from a Geisler tube to eliminate the charge, so that the inside of the sample can be quickly removed, and especially the surface shape of the insulator sample can be reduced. There is an effect that it can be conveniently used for observation, and there is an effect that by equipping an atomic force microscope with a Geisler tube, sufficient and simple static elimination can be performed quickly and a fine structure can be observed.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an apparatus used for carrying out the present invention.

FIG. 2 is an observation image of an insulator sample by a conventional AFM.

FIG. 3 is an AFM image of an insulator sample according to the method of the present invention.

[Explanation of symbols]

 1 Geisler tube, 2 AFM probe, 3 samples,

Claims (5)

[The claims] 1. A method for removing electricity from a charged sample, comprising irradiating the charged sample with X-rays to remove the charge. 2. A method for neutralizing a charged sample, comprising irradiating a charged sample with X-rays from a Geisler tube to eliminate the charge. 3. The method according to claim 2, wherein a soft glass tube or a hard glass tube is evacuated to a region where fluorescence is emitted from the Geisler tube. 4. The method according to claim 2, wherein the Geisler tube is evacuated to about 1 Pa. 5. A method for removing static electricity from a charged sample, wherein the Geisler tube is installed in an atomic force microscope and a charged sample to be observed with the microscope is irradiated with X-rays from the Geisler tube.