JPH026504A - Low-temperature plasma apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform a pretreatment without coating for observing a biological sample with a scanning electron microscope and a plasma polymn. of an org. substance with only one plasma apparatus by attaching or detaching a magnet, by placing a magnet having its polarity in the axial direction of a cylinder on the periphery of a sample room receiving the plasma. CONSTITUTION:A low-temperature plasma apparatus is constituted of a plasma generating room 4 having an inert gas inlet 1 and an inert gas outlet 2, a plasma outlet 3, a sample room 8 contg. an electrode 9 for generating an electric field for drawing the plasma, drawing electrodes 10 and 11, and the following constitution is additionally attached. Namely, by placing a removable permanent magnet 13 on the periphery of the sample room 8 for increasing the plasma concn., it is possible to selectively use the apparatus for an application where the plasma concn. is relatively high such as plasma polymn. experiments or for an application where the plasma concn. is relatively low such as a pretreatment for observing a biological sample without coating with a scanning electron microscope.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a low-temperature plasma device capable of performing coating-free pretreatment and plasma polymerization of organic matter in one device for observing biological samples with a scanning electron microscope. .

[Background of the invention]

When observing a biological sample with a scanning electron microscope, a metal such as Au is coated with a thickness of about 3 to 5 nm by vapor deposition or sputtering to improve the secondary electron yield and obtain a secondary electron image. However, just like observing the surface of a snow-covered riverbank, the fine structure cannot be observed. As a means to solve this problem, we have developed an ion bombardment method that irradiates biological samples with ions in plasma to make them conductive.
It has been commercialized. However, the mechanism for imparting electrical conductivity to biological samples is ambiguous and the scope of application is narrow. There were some drawbacks that made it difficult to spread.

[Purpose of the invention]

According to the present invention, even if a biological sample is not coated, the secondary electron image is 1! with a scanning electron microscope! The purpose is to provide an apparatus that can perform low-temperature plasma treatment and also perform plasma polymerization so that the tissue is not destroyed.

[Summary of the invention]

In the present invention, by installing a cylindrical magnet with polarity in the axial direction on the outer periphery of the sample dish that receives the plasma, the trajectory of electrons in the plasma is lengthened, colliding with many inert gas molecules, and causing the gas Focusing on increasing plasma density by ionizing molecules, the plasma concentration in the sample chamber can be changed by attaching or removing a magnet without changing the high-frequency power that generates plasma or the voltage applied to the extraction electrode. It was made so that it could be done.

[Embodiments of the invention]

When examining a biological sample with a scanning electron microscope, the sample is
After applying conductive dyeing such as To (osmium tannic acid-osmium) treatment, coating with a metal with a large secondary electron yield (secondary electron emission rate) such as gold,
A secondary electron image with good contrast is formed. but,
When a metal coating is applied to a microstructure, the microstructure is filled with coating particles and cannot be amended. Therefore, a treatment that allows secondary electron emission without coating is required. Biological samples are proteins and polymers. The interior of a protein is a hydrophobic environment, and hydrophilic and dissociative residues exist on the molecular surface.

Almost all groups that can form hydrogen bonds form hydrogen bonds.

After conducting conductive staining (for example, osmium tannic acid-osmium treatment) on the biological sample to make it conductive, it is placed in the sample chamber 12 of the apparatus of the present invention, and an inert gas such as argon is introduced into the gas inlet. Pour from 30Pa to 100
The gas is evacuated from the gas exhaust port 2 using a vacuum pump so that the pressure becomes Pa. A high frequency power of about 10 W at maximum is applied to the induction coil 6 by the high frequency power source 5 to excite the inert gas and turn it into plasma. Due to the electric field formed by the electrode 9, the extraction electrode 10, and the extraction electrode 11, a part of the plasma is extracted into the sample chamber 8 and irradiates the sample 12.

Biological samples undergo the following changes during plasma irradiation in the sample chamber: hydrogen and water-unfriendly groups are extracted, and carbon atoms on the sample surface change into carbon radicals as shown below.

Electron or ion ■Ion radical Hydrogen radical
! Radical C: H-+ C+/H electron → C+ low energy such as secondary electron → C/covalent bond Hydroxyl radical C:O)I −+ C+-OH+ electron →
〃 → 〃When a sample that maintains a radical state is subjected to scanning electron microscopy, secondary electrons are generated from carbon radicals by the primary electrons from the electron gun, and the secondary electrons are imaged as shown below.

Primary electron Secondary electron imaging C
・→C+・Secondary electrons The primary electrons pass through the conductive dyed sample and escape to the ground potential and sample holder, so they are not charged, and the carbon radical state is maintained for 4 to 5 days. Eventually, the effect will change as follows, and the effect will disappear.

C・ + C・ → C=C Charcoal! 12 double bond carbonyl group in air C. +2) 1.0+30. → C・÷
(-008) → Coo) 1 In the apparatus of the present invention, when performing plasma polymerization of organic materials such as plasticac, the direction of the magnetic field lines can be adjusted in the axial direction of the cylinder as shown in Fig. 3 without increasing the output. The magnetic flux density is 0. By installing a cylindrical magnet on the order of IT (Tesler) around the outer periphery of the sample chamber, the plasma density can be increased by 5 to 10 times, and it can be used for polymerization experiments of organic substances.

Note that plasma polymerization refers to the aforementioned hydrogen abstraction occurring due to the action of electrons and ions in plasma, generating a large amount of carbon radicals, forming double bonds between carbons, and developing a crosslinked structure.

As shown in Figure 1, the high-frequency excitation electrodes used to generate plasma can be made using an inductive coupling method using an induction coil.
A similar effect can be obtained using a capacitive coupling method in which a pair of electrodes face each other.

〔Effect of the invention〕

According to the present invention, the plasma density can be increased by providing a cylindrical axial magnetic field around the outer circumference of the sample chamber, so when the magnet is removed, the plasma is weak and can be used as a pretreatment device for a scanning electron microscope. When installed, the plasma is strong and can be used as a plasma polymerization experimental device.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the low-temperature plasma device of the present invention used as a coating-free pretreatment device for a scanning microscope.6 Figure 2 is a vertical cross-sectional view of the low-temperature plasma device of the present invention used as a plasma polymerization experimental device. be. FIG. 3 is a side view showing the direction of the magnetic field lines of the cylindrical magnet in the present invention, 1 is a gas inlet, 2 is a gas outlet, 3 is a plasma extraction port, 4 is a plasma generation chamber, 5 is a high frequency power supply, 6 is a An induction coil, 7 a seal rubber, 8 a sample chamber, 9 an electrode, 10 an extraction electrode, 11 an extraction electrode, 12 a sample, and 13 a cylindrical magnet. Name of patent applicant Hitachi Koki Co., Ltd.-'111)7;8''2f13\

Claims (1)

[Claims] In a low-temperature plasma device, a plasma generation chamber 4 has a gas inlet 1 for introducing an inert gas excited by high frequency, a gas outlet 2, and a plasma outlet 3 for drawing out plasma at the lower part of the plasma generation chamber 4. The sample inside the sample chamber 8 is irradiated with plasma by an electrode 9, an extraction electrode 10, and an extraction electrode 11 that generate an electric field for extracting plasma into the sample chamber 8, which is kept airtight through the attached seal rubber 7. By installing a removable permanent magnet on the outer periphery of the sample chamber 8 to increase the plasma concentration, it is possible to perform applications with relatively high plasma concentrations such as plasma polymerization experiments, and to observe biological samples with a scanning electron microscope without coating. A low-temperature plasma device that can be used for applications with low plasma concentration as a pretreatment method for