JPH05135725A - Removing method for organic gas molecule in charged particle beam device - Google Patents

Abstract

PURPOSE:To provide the removing method of organic gas molecules in a charged particles beam device preventing the formation of a film on the surface of a sample when an electron beam is radiated to the sample. CONSTITUTION:When no sample observation is made, a secondary electron detector 7 is turned off, a sample chamber 3 is leaked, a sample stage 5 is extracted, and a sample 6 is extracted from the sample stage 5. The sample stage 5 is set to the original position, and the sample chamber 3 is exhausted with a vacuum pump 4 to high vacuum. A power source 9 is controlled to feed a current to a tungsten filament 10. Thermoelectrons are radially emitted from the filament 10. The energy of the thermoelectrons is set from several eV to tens eV by the power source 9 and a resistor 11. When the thermoelectrons are radiated to organic gas molecules adsorbed on the wall face of the sample chamber 3, the organic gas molecules are polymerized and deposited on the wall face of the sample chamber 3 as a film. When an electron beam is radiated to the sample 6 for sample observation, no film is formed on the surface of the sample 6, and the sample 6 is not polluted.

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 organic gas molecules in a charged particle beam device such as a scanning electron microscope and an X-ray microanalyzer.

[0002]

2. Description of the Related Art In a scanning electron microscope, an X-ray microanalyzer, etc., a sample is two-dimensionally scanned with a focused electron beam, and this scanning causes secondary electrons, backscattered electrons, X-rays, etc. to be emitted from the sample. Is released. These are detected by the detector, and the image of the sample scanning area is displayed on the screen of the cathode ray tube based on the information signal specific to the sample.

In such an apparatus involving electron beam irradiation, vapor generated from oil of a vacuum pump or grease of a sample stage, that is, organic gas molecules mainly composed of hydrocarbon are adsorbed on a wall surface of a sample chamber or the like. Then, it becomes an oil film or moves in the sample chamber. The organic gas molecules in the sample chamber are repeatedly adsorbed and desorbed in this way, and do not easily decrease even after evacuation for a long time. When the sample is irradiated with an electron beam to observe the sample, the organic gas molecules are polymerized by the electron beam,
A film is formed on the sample surface. In order to reduce such sample contamination, set the sample chamber to 50-6
Baking is performed at 0 ° C. to remove organic gas molecules in the sample chamber.

[0004]

However, since a large amount of grease is used in the sample stage for setting the sample as described above, the baking process evaporates the grease, and the amount of organic gas molecules in the sample chamber increases. May be more than before baking. For this reason, when the sample is irradiated with an electron beam for observing the sample, the sample is further contaminated. When the sample is contaminated, the fine structure of the sample changes, and detailed image observation cannot be performed. Further, when the elemental analysis of the sample is carried out by the X-ray microanalyzer, the film formed on the surface of the sample cannot provide accurate elemental analysis.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the formation of a film on the surface of a sample when the sample is irradiated with an electron beam. It is to provide a method for removing gas molecules.

[0006]

A method for removing organic gas molecules in a charged particle beam apparatus according to the present invention is a method in which a sample is retracted from a sample chamber, and thermoelectrons emitted from a thermoelectron emission source arranged in the sample chamber are used. The organic gas molecules in the sample chamber were formed into a film and attached to the walls of the sample chamber. Also,
The surface of the sample was covered with a cover member, and the organic gas molecules in the sample chamber were made into a film by thermoelectrons emitted from a thermoelectron emission source arranged in the sample chamber to be attached to the wall of the sample chamber.

[0007]

EXAMPLE FIG. 1 is a schematic view of a scanning electron microscope shown for explaining the present invention. In the figure, 1 is an electron generation source, 2 is an electron optical system including a focusing lens, a deflector, an objective lens, etc., 3 is a sample chamber, 4 is a vacuum pump, 5 is a sample stage, 6 is a sample, 7 is a secondary electron. It is a detector. Reference numeral 8 is a thermionic emission mechanism, which includes a power source 9 and a tungsten filament 1.
It consists of 0 and resistance 11.

In such a structure, the sample chamber 3 is evacuated to a high vacuum by the vacuum pump 4. The electrons emitted from the electron beam generation source 1 are focused and deflected by the electron optical system 2 to scan the sample 6 two-dimensionally. Secondary electrons emitted from the sample 6 by this scanning are detected by the secondary electron detector 7 and supplied to a cathode ray tube (not shown).

As described above, the vapor generated from the oil of the vacuum pump 4 and the grease of the sample stage 5, that is, the organic gas molecules mainly composed of hydrocarbon are adsorbed on the wall surface of the sample chamber to form an oil film, Moves molecules indoors. When the sample 6 is irradiated with an electron beam to observe the sample,
The organic gas molecules are polymerized by the electron beam to form a film on the sample surface.

The cleaning of the sample chamber 3 will be described below.

The secondary electron detector 7 when the sample is not observed
Is turned off, the sample chamber 3 is leaked, the sample stage 5 is pulled out, and the sample 6 is removed from the sample stage 5. After removing the sample 6, the sample stage 5 is set to the original position, and the sample chamber 3 is evacuated to a high vacuum by the vacuum pump 4. Next, the power supply 9 is controlled to supply a current to the tungsten filament 10. As a result, thermoelectrons are radially ejected from the filament 10. The energy of this thermoelectron becomes several to several tens eV due to the product of the resistance 11 and the current flowing through the resistance 11. When the thermoelectrons are applied to the organic gas molecules adsorbed on the wall surface of the sample chamber 3, the organic gas molecules are polymerized and reach the sample chamber wall surface as a film. The energy of thermoelectrons emitted from the filament 10 is controlled to several to several tens of eV because the organic gas molecules mainly composed of hydrocarbon are most likely to form a film when hit with an electron beam of this energy. Then, the power source 9 is turned off, and the cleaning of the sample chamber 3 is completed.

When observing the sample, the sample chamber 3 is leaked and the sample stage 5 is pulled out. After the sample 6 is set on the sample stage 5, the sample stage 5 is set to the original position and the sample chamber 3 is evacuated to a high vacuum by the vacuum pump 4. Then, the secondary electron detector 7 is turned on, and the sample 6 is irradiated with an electron beam. As a result of the cleaning, the organic gas molecules in the sample chamber are formed into a film, so that the organic gas molecules in the sample chamber are reduced. Therefore, no film is formed on the sample surface, and sample contamination does not occur. The amount of organic gas molecules in the sample chamber increases with time, but if the cleaning is performed when the sample is not observed, the sample contamination can be greatly reduced as compared with the conventional case.

A cover member 12 is provided as shown in FIG.
If the cover member 12 is moved to cover the sample 6 at the time of cleaning the sample chamber 3, it is not necessary to remove the sample 6 from the sample stage 5.

Further, in the case of an apparatus having a sample exchange chamber, since the vacuum of the sample chamber is maintained even during sample exchange, the effect of adhering the organic gas as a film on the wall surface can be maintained for a long time.

The present invention can also be applied to an X-ray microanalyzer, an electron beam drawing apparatus, an ion beam drawing apparatus, and the like.

[0016]

According to the present invention, the sample is retracted from the sample chamber, or the sample surface is covered with a cover member,
The thermoelectrons emitted from the thermoelectron emission source placed inside the sample chamber made the organic gas molecules inside the sample chamber film-attached to the walls of the sample chamber, so that the sample was irradiated with electron beams during observation. However, no film is formed on the sample surface. Therefore, the sample can be sufficiently observed, and the sample can be analyzed accurately.

[Brief description of drawings]

FIG. 1 is a schematic view of a scanning electron microscope shown to explain the present invention.

FIG. 2 is a view shown for explaining covering a sample with a cover member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electron generation source 2 ... Electron optical system 3 ... Sample chamber 4 ... Vacuum pump 5 ... Sample stage 6 ... Sample 7 ... Secondary electron detector 8 ... Thermionic emission mechanism 9 ... Power supply 10 ... Tungsten filament 11 ... Resistor 12 ... Cover member

Claims (2)

[Claims] 1. A sample is evacuated from a sample chamber, and thermoelectrons emitted from a thermoelectron emission source arranged in the sample chamber are used to form a film of organic gas molecules in the sample chamber to adhere to the walls of the sample chamber. A method for removing organic gas molecules in a charged particle beam device. 2. The surface of the sample is covered with a cover member so that the organic gas molecules in the sample chamber are made into a film by thermoelectrons emitted from a thermoelectron emission source arranged in the sample chamber and adhered to the sample chamber wall or the like. Method for removing organic gas molecules in a charged particle beam device.