JPS6119042A - Sample chamber for charged particle ray device - Google Patents

Abstract

PURPOSE:To enable the sample to be measured in a hard vacuum by exhausting the gas emitted by the sample while it is separated from a vacuum atmosphere containing lead wires, terminal resistors, etc. emitting a great amount of gas. CONSTITUTION:A sample 11 is mounted on a separator plate 12. The periphery of the separator plate 12 is provided with separation bellows 13 to separate the sample 11 from the vacuum atmosphere of a sample chamber 15. The gas emitted by the sample 11 is exhausted from an exhaust hole 16 after passing through the hole of a magnetic field lens 10. The separator plate 12 is fixed over an X- axis stage 19a and a Y-axis stage 19b. It can be arbitrarily moved by a driving mechanism 20. Lead wires 17 are connected to an LSI power supply 23. The sample chamber 15 is exhausted through an exhaust hole 28. In an absorption cylinder 25, secondary electrons 24 produced from the sample 11 are introduced above the magnetic field lens 10 and detected by a secondary electron detector 27. Consequently, it is possible to measure the sample 11 in a hard vacuum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a sample chamber of a charged particle beam device such as a scanning electron microscope.

[Background of the invention]

FIG. 1 shows the structure of a conventional scanning electron microscope. In particular, a strobe-type scanning electron microscope for observing samples such as LSIs in an operating state is exemplified here. An electron beam is emitted from an electron gun 1 including an optical system and scans over a sample 2.

A lead wire 3 is connected to this sample (L8I).

The LSI is operated from a power source 4 of the LSI outside the vacuum through this lead wire 3. The sample 2 can be moved along the X-Y axes by a drive unit 5 that is mechanically or electrically connected to the outside of the vacuum.

The electron gun 1 is exhausted by an exhaust system 6, and the sample chamber 7 is exhausted by a sample chamber exhaust system 8. In order to operate the LSI, it is necessary to connect several dozen lead wires 3.

Furthermore, in high-speed LSIs, it is also necessary to install terminating resistors and the like in close proximity. For this reason, the degree of vacuum in the sample chamber 7 decreases. As a result, significant contamination occurs during measurement and observation, often causing serious problems in image observation and potential measurement.

[Purpose of the invention]

An object of the present invention is to provide a sample chamber for a charged particle beam device that reduces the aforementioned contamination.

[Summary of the invention]

In order to achieve the above object, the present invention is configured so that lead wires, terminal resistors, and the like, which emit a large amount of gas, are vacuum-separated and evacuated.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIG. The electron beam 9 is focused onto a sample (LSI) 11 by a magnetic field lens 10, and scanned in a rectangular shape by a scanning coil (not shown). Sample 11 is attached to separator 12 . An isolation bellows 13 is provided around the circumference of the isolation plate 12.

A slide ring 14 is attached to the tip of the isolation bellows 13, and separates the sample 11 from the vacuum atmosphere of the sample chamber 15 while sliding on the lower surface of the magnetic field lens 10 forming the upper wall of the sample chamber. The sample 11 is subjected to a magnetic field and is exhausted from the exhaust port 16 through the lens hole of the lens 10. This part is made up of parts that emit little gas, so it is under a high vacuum (10-'~
10-"l'orr). However,
Since the sample chamber 15 contains the lead wire 17 and the terminal resistor 18, it is difficult to create a high vacuum.
Torr is at most. This is why the sample 11 was moved to the high vacuum side using the isolation plate 12 and the isolation bellows 13. The separator 12 is fixed on an X-axis stage 19a and a Y-axis stage 19b. This X-axis stage 19a
The Y-axis stage 19b is a drive unit 20 placed outside the vacuum, and can be moved arbitrarily via drive shafts 21a and 21b. The lead wire 17 is taken out of the vacuum via a hermetic seal 22 and connected to an LSI power supply 23. The sample chamber 15 is evacuated through an exhaust port 28 .

Secondary electrons 24 generated by irradiation of the electron beam 9 from the sample 11
is the absorption cylinder 25 (for example, +50V applied) and the magnetic field lens 1
0, is energy-selected by a reflection grid 26 and detected by a 42nd order electron detector 27. This detection method makes it possible to know the potential distribution within the sample 11.

FIG. 3 shows another embodiment of the invention. This is an example of application to electron beam length measurement for measuring minute dimensions inside Ueno. Since length measuring machines are used in semiconductor processes, they are more sensitive to contamination than strobe-type scanning electron microscopes. Therefore, the present invention was applied to avoid the influence of gas release from the sample fine movement mechanism. In this example, the sample is a wafer 29, and the wafer 29 is an isolation bellows 13.
, set in an isolation cassette 30 with a sliding ring 14. These are placed together on a sample fine movement stage (X-axis stage 19a, Y-axis stage 19b).

When the isolation cassette 30 is placed on the sample fine movement stage, the sliding ring 14 comes into contact with the lower surface of the magnetic field lens 10, and the sample 29 is separated from the sample chamber 15 in a vacuum, and is discharged from the upper exhaust port 16 through the hole of the magnetic field lens 10. It is evacuated.

As a result of this structure, it becomes possible to subject the wafer sample 29 to dimensional measurements and the like under high vacuum. The isolation cassette with the sample 29 set therein can be moved into the sample exchange chamber 33 by opening the valve 31 and inserting the exchange rod 32. After this, the pulp 31 is closed and the sample exchange chamber 33 is brought into the atmosphere. The exchange window 34 can be opened and the isolation cassette 30 together with the wafer sample 29 can be taken out. Evacuation of the sample exchange chamber 33 and introduction of air to atmospheric pressure are performed through the exhaust port 35. The secondary electrons 24 emitted from the wafer 29 by the irradiation with the -order electrons 9 are guided into the magnetic field lens 10 by the suction cylinder 25, penetrate the magnetic field lens 10, and pass through the acceleration grid 36 (for example, 10 (1v)
The secondary electrons are further accelerated and guided to a secondary electron detector 27. Since the length measuring machine only needs to measure the total amount of secondary electrons, a reflection grid is not necessary. Moreover, although an example in which only one secondary electron detector is provided is shown here, it is also possible to more strongly detect the shape of the sample by symmetrically providing two or four secondary electron detectors.

〔Effect of the invention〕

As explained above, according to the present invention, a sample can be subjected to measurement in a high vacuum.

From a different point of view, by implementing the present invention, a degree of freedom in design can be given to the sample fine movement mechanism structure, which has hitherto been taken care of to minimize gas release.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional sample chamber structure, FIG. 2 is a diagram showing one embodiment of the present invention, and FIG. 3 is a diagram showing another embodiment of the present invention.

Claims (1)

[Claims] 1. In a charged particle beam device that scans finely focused charged particles onto a sample to observe the shape, size, and potential of the sample, the sample is placed in a container with an opening at the top. The container is fixed, and the container is placed on a sample fine movement table, and the top surface of the container is brought into contact with the lower surface of the upper wall of the sample chamber, and the inside of the container is evacuated through an opening made in the upper wall of the sample chamber. A sample chamber of a charged particle beam device featuring: 2. Only an electronic device such as an LSI is placed in the container having an opening, and lead wires, resistors, etc. for operating the electronic device are placed outside the container using the bottom plate of the container as a vacuum partition. A sample chamber of a charged particle beam device according to claim 1. 3. A sample chamber of a charged particle beam apparatus according to claim 1 or 2, wherein a side wall of the container having an opening is formed of a bellows.