JPH04343040A - Ion milling device with ion gun for finishing - Google Patents

Abstract

PURPOSE:To enable a flatness of a sample surface to be enhanced and an observation accuracy to be improved by performing ion milling according to an inactive gas ion such as argon for allowing the sample surface to be exposed in observation using an electron microscope. CONSTITUTION:An ion gun 5 for etching using an inactive gas as well as an ion gun 4 for finishing using a light gas such as oxygen for eliminating a recessed and projecting surface of a sample surface are provided. Also, ion milling is switched rapidly by allowing the inactive gas and oxygen gas to be supplied to each ion gun through each independent piping system and at the same time contamination of each system by another gas is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion milling apparatus for etching the surface of a sample for use in an electron microscope or the like by irradiating the surface with an ion beam, and more particularly to an ion milling apparatus capable of processing the surface of a sample with less irregularities.

0002

2. Description of the Related Art In transmission type or scanning type electron microscopes, there are cases where the surface of a sample is etched in advance and then observed. For this reason, ion milling is performed in which a sample is irradiated with an ion beam and etched by a sputtering effect. The conditions for the ion milling described above vary depending on the sample material, milling purpose, etc., but are usually set as the following four points. 1. Gas introduced into the ion gun; argon gas 2. Ion acceleration voltage; 3 to 6 kV 3. Discharge current inside the ion gun: 0.5-1.5mA4
．． Ion incidence angle on the sample surface: For transmission electron microscopes: 7 to 20 degrees For scanning electron microscopes: 30 to 90 degrees In addition, the introduced gas has a high etching rate and there is no risk of reaction with the sample. Inert gases are generally preferred, and among these, argon gas is widely used because it is economical and readily available.

0003

[Problems to be Solved by the Invention] Although the argon gas introduced into the ion gun has the advantage of a high etching rate and no reaction with the sample, it is heavy and the surface of the sample is damaged by the ion irradiation. There was a problem in that unevenness occurred on the surface, which obstructed high-resolution observation. In addition, in order to alleviate the above-mentioned problems, steps have been taken to reduce the accelerating voltage to about 2 kV, reduce the discharge current, and make the ion incidence angle shallower in the finishing stage of ion milling. It was not possible to sufficiently reduce the damage.

0004

[Means for Solving the Problems] In order to solve the above problems, at least two systems of ion guns are provided, the first ion gun is supplied with an inert gas such as argon, and the second ion gun is supplied with an inert gas such as oxygen. A gas having a light mass number is supplied, and the first ion gas mills the sample surface to a predetermined depth, and the second gas removes unevenness on the sample surface. Further, the first and second gases are supplied to each of the ion guns through independent piping systems.

[0005]

[Operation] The sample surface is milled to a predetermined depth by the first ion gas irradiation, and the unevenness of the sample surface is removed and smoothed by the second gas irradiation. In addition, by supplying the first and second gases to each of the ion guns through independent piping systems, switching between the first and second gases can be speeded up, and at the same time each system can be connected to other gases. Prevent contamination.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of an ion milling apparatus with a finishing ion gun according to the present invention. In FIG. 1, a sample chamber 1 is evacuated by a vacuum pump 2, and a sample 7 is placed on a sample stage 6 inside, and is exposed to ion irradiation from an etching ion gun 5 and a finishing ion gun 4. There is. Further, the etching state of the sample 7 can be observed through the observation window 3. Argon gas is supplied from an argon gas cylinder 10 to a pipe 91 and a pressure reducing valve 121.
, and the flow rate control valve 81 into the etching ion gun 5, where it is ionized and irradiated onto the sample 7.

Since ions of an inert gas such as argon gas have a heavy mass, they can etch the surface of a sample to a required depth in a short time. However, on the other hand, there was a problem in that the sample surface was easily damaged and unevenness was formed on the surface due to the heavy ion mass. This is because these irregularities impede high-resolution observation of the sample using a transmission or scanning electron microscope. In the present invention, the above problem is solved by providing a finishing ion gun 4. Oxygen gas is introduced into the finishing ion gun 4 from the oxygen gas cylinder 10 via the pipe 92, the pressure reducing valve 122, the flow control valve 82, etc., and is ionized and irradiated onto the sample 7.

[0008] Since the mass of oxygen ions is lighter than that of argon gas ions, the etching rate thereof is 3 to 4 times slower than that of argon gas ions. Therefore, it is inefficient to etch the sample surface to a predetermined depth by oxygen ion irradiation. But on the other hand,
Similar to final polishing, the effect of scraping away surface irregularities and smoothing them becomes remarkable. Therefore, in the present invention, after the etching ion gun 5 performs conventional etching on the sample surface, the finishing ion gun finishes the sample surface smoothly. Note that it is also possible to increase the number of finishing ion guns 4 than the one system shown in FIG. 1 and use different finishing ion gases depending on the degree of finishing of the sample surface, the number of types of samples to be handled, etc. .

Furthermore, in the present invention, as shown in FIG. 1, since the etching gas and the finishing gas are supplied to each gun through separate flow rate control valves and piping systems, the etching gas and the finishing gas are The gas can be quickly switched, and etching using the argon gas and oxygen gas can be performed continuously and efficiently. Furthermore, since the etching ion gun 5 and the finishing ion gun 4 are used exclusively for each of the above-mentioned etching operations, there is no possibility of contamination with foreign gases. This provides advantages such as ease of maintenance and inspection, such as easy setting of maintenance intervals. Note that depending on the purpose of finishing the sample surface, the gas introduced into the finishing ion gun 4 may be changed to a gas other than oxygen gas.

0010

Effects of the invention: The sample surface is milled to a predetermined depth by irradiation with inert gas ions such as argon to expose the surface for electron microscope observation, and the unevenness of the sample surface is smoothed by irradiation with light ions such as oxygen ions. Since it is removed, the flatness of the observation surface of the sample can be increased and observation accuracy can be improved. Furthermore, since the argon and oxygen gases are supplied to each ion gun through independent piping systems, it is possible to speed up gas switching and at the same time prevent each system from being contaminated by other gases.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

[Explanation of symbols]

1 Sample room 2 Vacuum pump 3 Observation window 4 Ion gun for finishing 5 Ion gun for etching 6 Sample stage 7 Sample 10 Argon gas cylinder 11 Oxygen cylinder 81 Flow rate adjustment valve 91 pipe 121 Pressure reducing valve

Claims (3)

[Claims] Claim 1: An ion milling device for ion milling by irradiating a sample placed on a sample stage in a sample chamber with ions, comprising at least two systems of ion guns for ionizing gas and irradiating the sample. A finishing ion gun, characterized in that a first gas is supplied to the first ion gun, and a second gas having a lighter mass number than the first gas is supplied to the second ion gun. Ion milling equipment with. 2. The ion milling apparatus with a finishing ion gun according to claim 1, wherein the first gas is an inert gas such as argon, and the second gas is oxygen gas. Claim 3: In claim 1 or 2, the first
An ion milling apparatus with a finishing ion gun, characterized in that the gas and the second gas are supplied to each of the two systems of ion guns through independent piping systems.