JPH04147548A - Charged particle beam device - Google Patents

Abstract

PURPOSE:To shield an external magnetic field in the direction transverse to the orbit direction of charged particle beams by providing a magnetic shield member made of the material having a high magnetic permeability in an exhaust port of a magnetic shield member along the direction transverse to the orbit direction of the charged particle beams. CONSTITUTION:Among external magnetic fields entering from an exhaust port, a magnetic field in the direction transverse to the orbit direction of electron beams is caught by each component 8a1-8a5 of a third magnetic shield member 8 provided in the direction transverse to the orbit direction of electron beams. Furthermore, magnetic fields near the exhaust port, which are not caught by the third magnetic shield member 8 and leaked, are caught by magnetic shield members 5a1-5a4 of a first magnetic shield member provided inside than the third magnetic shield member 8. Magnetic fields in the direction transverse to the orbit direction of the electron beams coming close to electron beam sources from the exhaust port are caught, and these caught magnetic fields are shielded without leakage to a space of the exhaust port.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charged particle beam device in which a magnetic shield member is formed around a charged particle beam source.

(Prior art) In a charged particle beam device using a field emission type charged particle beam source such as a field emission type ion gun or a field emission type electron gun, the charged particle beam source is small and the charged particle current is small. However, the charged particle beam emitted from the charged particle beam source cannot be significantly reduced by the charged particle optical system.

In a charged particle beam device using such a charged particle beam source,
The charged particle beam emitted from the charged particle beam source is irradiated onto the sample without being reduced much, so if the position of the charged particle beam changes due to an external floating magnetic field, the amount of change will not be reduced much. This causes a change in the position of the charged particle beam on the sample, which adversely affects the performance of the charged particle beam device.

Therefore, in order to prevent the charged particle beam source from being affected by external stray magnetic fields, a magnetic shielding member is provided inside or outside the vacuum envelope to surround the charged particle beam source, and the charged particle beam source is magnetically shielded. There are some charged particle beam devices.

The magnetic shielding member is a member that forms a magnetic circuit using a high magnetic permeability material to shield the inside of a space surrounded by the high magnetic permeability material from an external magnetic field.

Therefore, by surrounding the charged particle beam source with a magnetic shielding member, the influence of an external magnetic field on the charged particle beam source can be suppressed.

[Problem to be solved by the invention]

When a magnetic shielding member is provided to surround the charged particle beam source inside the vacuum envelope, the gas emitted from the surface of the magnetic shielding member must be evacuated in order to create a vacuum inside the vacuum envelope. and requires a large capacity exhaust pump.

However, when a magnetic shielding member is provided inside the vacuum envelope, the magnetic shielding member becomes an obstacle between the charged particle beam source and the exhaust port leading to the exhaust pump, resulting in a disadvantage that the exhaust conductance becomes small. Therefore, it is necessary to provide an exhaust port in the magnetic shielding member.

In addition, when a magnetic shielding member is installed outside the vacuum envelope of the charged particle beam source, the magnetic shielding member has a hole through which the exhaust pipe passes in order to connect the exhaust pipe leading to the exhaust pump to the exhaust port of the vacuum envelope. It is necessary to provide

Therefore, as described above, if the exhaust ports and holes necessary to create a vacuum inside the vacuum envelope are installed, the external magnetic field will enter the inside of the vacuum envelope through the exhaust ports and holes. The drawback is that the magnetic shielding rate decreases.

Therefore, in order to exhaust gas without installing an exhaust port on the magnetic shielding member, it is possible to install a magnetic shielding member to surround the vacuum envelope including the exhaust pump, but the magnetic shielding rate is , is inversely proportional to the diameter of the magnetic shielding member, so the diameter of the magnetic shielding member installed surrounding the vacuum envelope is smaller than that of the magnetic shielding member installed inside or adjacent to the outside of the vacuum envelope. increases, and the magnetic shielding rate decreases.

Therefore, in order to compensate for these shortcomings and obtain a large magnetic shielding rate, there are methods that use thick high magnetic permeability materials, or use double or triple magnetic shielding materials, but these methods do not require sufficient magnetic field protection. There are disadvantages such as not being able to be shielded, increasing costs, and making it complicated to attach and detach the shield member during maintenance such as replacing the charged particle beam source.

Therefore, the present invention provides an exhaust port that can provide sufficient exhaust conductance to evacuate the inside of the vacuum envelope, and
The object of the present invention is to obtain a charged particle beam device equipped with a magnetic shielding member that shields a magnetic field in a direction perpendicular to the orbital direction of the charged particle beam that enters through the exhaust port and causes positional deviation of the charged particle beam. shall be.

[Means to solve the problem]

In order to solve the above problems, the present invention has the following configuration.

In the invention described in claim (1), a charged particle beam source (1°2.
3.4), a vacuum envelope (6) having an exhaust port (6a) installed surrounding the charged particle beam source, and an exhaust pipe (9) connected to the exhaust port of the vacuum envelope; , an exhaust pump (l0) connected to the exhaust pipe, and a position provided between the vacuum envelope and the charged particle beam source surrounding the charged particle beam source and facing the exhaust port of the vacuum envelope. In a charged particle beam device having a magnetic shielding member (5) that grows an exhaust port at the exhaust port of the magnetic shielding member (5),
Magnetic shielding member made of high magnetic permeability material (5bl~5b
4) ' is formed along a direction perpendicular to the trajectory direction of the charged particle beam emitted from the charged particle beam source (l, 2.3.4), thereby dividing the exhaust port into a plurality of parts. exhaust ports (5al to 5a5).

In the invention described in claim (2), a charged particle beam source (1°2.
3.4), a vacuum envelope (6) for growing an exhaust port (6a) installed surrounding the charged particle beam source, and one end connected to the exhaust port (6a) of the vacuum envelope. an exhaust pipe (9);
A charged particle comprising: an exhaust pump (IO) connected to the other end of the exhaust pipe; and a magnetic shield member (7) installed to surround the outside of the vacuum envelope except for the exhaust pipe (9). In the radiation device, a magnetic shield member (8bl to 8b4) made of a high magnetic permeability material is placed inside the exhaust pipe in the orbital direction of the charged particle beam emitted from the charged particle beam source (1, 2, 3, 4). It was formed along the direction perpendicular to.

In the invention described in claim (3), a charged particle beam source (1°2.
3.4) The surface of the magnetic shield member (5, 8) provided surrounding the magnetic shield member (5, 8) is coated with a metal that releases less gas.

[Effect]

In the invention described in claim (1), the magnetic shielding member (5)
By providing the magnetic shielding members (5b1 to 5b4) along the direction perpendicular to the trajectory direction of the charged particle beam at the exhaust port of the magnetic shielding member (5), the charged particle A magnetic circuit is formed in a direction perpendicular to the direction of the trajectory of the charged particle beam, and can sufficiently shield external magnetic fields in a direction perpendicular to the direction of the trajectory of the charged particle beam. (Hereinafter, the magnetic shielding member of claim (1) will be tentatively referred to as a first magnetic shielding member.) In the invention described in claim (2), the exhaust pipe (9) is provided with a hole through which the exhaust pipe (9) is passed. A magnetic shielding member (7) installed surrounding the enclosure (hereinafter tentatively referred to as the second magnetic shielding member)
In addition, a magnetic shielding member (8) (hereinafter tentatively referred to as a third magnetic shielding member) for capturing a magnetic field in a direction perpendicular to the orbital direction of the charged particle beam is provided inside the exhaust pipe. As a result, a magnetic circuit is formed inside the exhaust pipe in a direction perpendicular to the orbital direction of the charged particle beam, and a magnetic circuit is formed inside the exhaust pipe in a direction perpendicular to the orbital direction of the charged particle beam attempting to enter from the outside of the exhaust pipe to the inside. It can sufficiently shield external magnetic fields in different directions.

In addition, in the invention described in claim fil and claim (2),
The magnetic field in the direction parallel to the trajectory of the charged particle beam that attempts to enter from the exhaust port is not very well shielded, but compared to the magnetic field in the direction perpendicular to the trajectory of the charged particle beam, the magnetic field in the direction of the trajectory of the charged particle beam is Even if a magnetic field in a parallel direction enters the vacuum envelope 6, it hardly affects the charged particle beam and causes the charged particle beam to shift its position.

Furthermore, in the invention described in claim (1) and claim (2),
The aperture ratio of the exhaust port that not only shields the external magnetic field in the direction perpendicular to the orbital direction of the charged particle beam, but also connects to the exhaust pump that creates a vacuum around the charged particle beam source inside the vacuum envelope. [Total area of the exhaust port of the magnetic shielding member (=total area of the exhaust port divided into multiple parts by the magnetic shielding member)/area of the exhaust port 9a of the vacuum envelope (=when there is no magnetic shielding member at the exhaust port) (maximum area)] can be increased,
The exhaust conductance can also be set to a sufficiently large value.

In the invention described in claim (3), by coating the surface of the magnetic shielding member with a metal that releases little gas, it is possible to suppress the release of gas from the high magnetic permeability material.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below using an example in which the present invention is applied to an electron beam apparatus using a field emission electron gun (hereinafter referred to as an electron beam source).

FIG. 1 is a schematic sectional view showing the main parts of the embodiment as seen from the front.

FIG. 2 is a side view of FIG. 1 viewed from the exhaust port side.

As shown in FIG. 1, the electron beam source includes a thermal field emission cathode 1, a suppressor electrode 2, an extraction electrode 3, and an anode 4. 6 was installed at a position opposite to the exhaust port 6a formed in the exhaust port 6a.

The vacuum envelope 6 is made of stainless steel, is installed surrounding the charged particle beam source, and has a size large enough to prevent discharge from the installed charged particle beam source to the vacuum envelope 6.

A normal vacuum sealing material is used between the vacuum envelope 6 and the exhaust pipe 9 connected to the exhaust port 6a, the structure 1) to which the thermal field emission cathode 1 is attached, and the upper pole 12 of the electromagnetic lens. The metal O-rings 13, 14, and 15 are vacuum-sealed to constitute a vacuum wall for operating the electron beam source in a vacuum space.

The first magnetic shield member 5 made of permalloy, which is a high magnetic permeability material, has an exhaust port formed at a position opposite to the exhaust port 6a of the vacuum envelope, and has an electron beam source inside the vacuum envelope 6. 1. 2. 3. Place it around 4.

At that time, a permalloy magnetic shielding member 5 is provided at the exhaust port along a direction perpendicular to the trajectory direction of the electron beam.
al, 5 a2. 5 a3. 5a4, and exhaust ports 5bl, 5b2, which are divided into a plurality of parts. 5b
3. 5b4°5b5.

The exhaust ports 5bl to 5b5 are the exhaust ports 6a of the vacuum envelope.
The inside of the first shield member 5 is evacuated by an ion pump 10 connected to the other end of the exhaust pipe 9, which is connected to the other end of the exhaust pipe 9.

The second magnetic shield member 7 is also made of permalloy, and the exhaust pipe 9
The vacuum envelope 6 is surrounded except for the part shown in FIG.

Furthermore, inside the exhaust pipe 9, a magnetic shielding member 8 is provided along a direction perpendicular to the trajectory direction of the electron beam.
al, 8 a2. 8 a3. A third magnetic shield member 8 made of permalloy is provided, which is formed of a member 8 a4 and a member 8 a5 that supports the magnetic shield member along the inner wall of the exhaust pipe 9.

As a result, the inside of the exhaust pipe 9 is divided into a plurality of exhaust ports 8bl, 8b2. 8b3. 8b4. 8b
5 was formed.

Although permalloy is used for the above magnetic shielding members and magnetic shielding members, other than permalloy, high magnetic permeability materials such as super permalloy and soft iron may be used.

Further, in the first magnetic shield member 5 and the third magnetic shield member 8, magnetic shield members 5al to 5a4 provided along the direction perpendicular to the trajectory of the charged particle beam.
．． The respective intervals 8a1 to 8a5 are from the outside of the magnetic shielding members 5a1 to 5a4 of the first magnetic shielding member to the magnetic shielding members 8al to 8a of the third shielding member 8.
Install at the same or narrower distance than the distance to the inside of 4.

In this way, by defining the mutual relationship between the magnetic shielding members 5al to 5a4 of the first shielding member 5 and the third magnetic shielding member 8 and installing them, electronic Captures the external magnetic field in the direction perpendicular to the direction of the line's trajectory.

Furthermore, the first magnetic shielding member 5 and the third magnetic shielding member 8 are formed by electroplating gold on their surfaces to a thickness of 1 μm and then vacuum baking at 450'C for 1 hour. , is coated with a metal that releases less gas to suppress gas release from the magnetic shield member.

The material to be coated on the surface can be any metal that releases less gas, such as gold or platinum.

Next, the operation of the above embodiment will be explained.

First, when an ion pump (not shown) is operated, the gas in the vacuum envelope 6 surrounding the electron beam sources 1, 2, 3, 4,
The first magnetic shield member, the vacuum envelope, and the third magnetic shield member in the exhaust pipe.
Exhaust ports 5bl to 5b5 of magnetic shielding members. 6
a, is exhausted through 8bl to 8b5.

Once the vacuum has been evacuated to the specified degree of vacuum, the next step is to remove the electron beam source 1.
, 2, 3.4, an electron beam is emitted.

However, since gas is generated by ejecting the electron beam, the ion pump is kept in operation.

The emitted electron beam is deflected by an electromagnetic lens (not shown),
It is focused and irradiates the sample.

In the case of a drawing device, an electron beam is irradiated onto the sample to sensitize the photosensitive material applied on the sample, and in the case of a measuring device, an electron beam is irradiated onto the sample to detect the light generated from the sample. The sample is measured by detecting reflected electrons and secondary electrons.

Regarding the shielding of external magnetic fields, the external magnetic fields from the second magnetic shield member 7 installed surrounding the vacuum envelope 6 are
Most of the magnetic field is transmitted to the second magnetic shield member 7,
It is captured by the first magnetic shield member 5.

Among these, among the external magnetic fields that try to enter from the exhaust port, the magnetic field in the direction perpendicular to the orbit of the electron beam is
First, each component 8 al of the third magnetic shielding member 8 provided in a direction perpendicular to the trajectory direction of the electron beam,
8 a2. 8 a3. 8 a4. 8 Captured by a5.

Furthermore, the magnetic field near the exhaust port that cannot be captured by the third magnetic shielding member 8 is transferred to the magnetic shielding member 5a15 of the first magnetic shielding member provided inside the third magnetic shielding member 8. a2. 5 a3. 5
Captured by a4.

In this way, the magnetic shielding members 5bl to 5b5. 8
bl~8b4 becomes a path through which the magnetic field in the direction perpendicular to the orbital direction of the electron beam near the exhaust port easily passes, and the magnetic field in the direction perpendicular to the orbital direction of the electron beam trying to approach the electron beam source from the exhaust port. It captures magnetic fields and shields them from escaping into the space that is the exhaust port.

Further, the electron beam emitted from the electron beam sources 1, 2, 3.4 and exiting the vacuum envelope 6 passes through an electromagnetic lens (not shown) connected at the upper pole of the electromagnetic lens.

This electromagnetic lens is surrounded by a high permeability material such as permalloy, so compared to inside the electron beam source,
Not easily affected by external magnetic fields.

Therefore, the electron beam is irradiated onto a predetermined location on the sample without causing positional displacement due to the magnetic field.

According to the embodiments of the present invention described above, the following effects can be obtained.

Since the first magnetic shield member 5 is provided inside the vacuum envelope 6, the magnetic shield member has a small inner diameter.

In addition, in the vicinity of the exhaust port of the vacuum envelope 6, the magnetic shielding members 5bl to 5b5 are arranged in a direction perpendicular to the trajectory direction of the electron beam.
．． 8bl to 8b4, the structure has an exhaust port that is divided into a plurality of parts, and the magnetism in the direction perpendicular to the orbital direction of the electron beam, which is the main cause of positional fluctuation of the electron beam, can be suppressed. , electron beam source 1. 2. 3. Can be shielded outside of 4.

Furthermore, by providing a second magnetic shield member 7 outside the vacuum envelope 6, from the electron beam source l, 2° 3.4,
It is possible to shield magnetic fields at relatively far distances.

A first magnetic shielding member 5 having the above effects,
Second magnetic shield member 7. Third magnetic shield member 8
By providing double magnetic shielding, a magnetic shielding ratio of 300 or more against external magnetic fields in a direction perpendicular to the orbital direction of the electron beam was obtained.

Therefore, an apparatus using an electron beam source with a low acceleration voltage can be used even in a place where a stray magnetic field of about 10 Cm Gauss exists.

In addition, permalloy, which is a high magnetic permeability material, is expensive and difficult to process, so in the above embodiment, the vacuum envelope itself is made of permalloy, and the functions of the vacuum envelope and the magnetic shielding member are combined into one. Compared to the case where it is used as a vacuum envelope, it is necessary to process the vacuum wall with high accuracy, use permalloy even in areas that are not necessary for the magnetic shielding effect, or form a permalloy vacuum sealing material. Instead, it can be used as an inexpensive magnetic shielding member.

By plating the surface of the magnetic shielding member with gold and performing one baking process to coat the surface of the magnetic shielding member with gold, it is possible to suppress the release of gas from the magnetic shielding member.

Therefore, if it is installed in an electron beam device after coating, a 30 (1/s) ion pump is installed, and exhaust is performed, 1 x l O" (T.

rr) We were able to achieve a vacuum below.

At this time, the gas in the vacuum envelope 6, which is exhausted by the ion pump, moves linearly in the exhaust pipe 9 and is exhausted. When installed with the openings facing each other, the gas generated when emitting electron beams from the electron beam source can be sufficiently exhausted.

However, the vacuum envelope and magnetic shielding member that forms the exhaust port must be of the minimum necessary size to be able to surround the charged particle beam source and to maintain a distance that does not cause discharge into the vacuum envelope. Even if the location of the exhaust port, which connects a thick exhaust pipe with large conductance, is shifted to the top or bottom of the side wall of the vacuum envelope, at least a portion of the exhaust port faces the charged particle beam source, making it difficult to exhaust the gas. is sufficient.

Also, when using multiple exhaust pumps, the magnetic shielding member may be provided along a direction perpendicular to the trajectory direction of the electron beam at a position near the exhaust port connected to each exhaust pump. By providing the exhaust port, external magnetism in a direction perpendicular to the orbital direction of the charged particle beam can be shielded.

As described above, in the embodiment, the first magnetic shield member 5 is located inside the vacuum envelope 6, and the second magnetic shield member 7 is located outside the vacuum envelope 6. Although it was used in combination with the third magnetic shield member 8, if necessary,
It is also possible to use only one of the inner first magnetic shield member 5 or the outer second magnetic shield member 7 and third magnetic shield member 8.

In addition, when using one of the magnetic shielding members described above, simply installing two or three magnetic shielding members having magnetic shielding members at the exhaust port and its surroundings will prevent the magnetic shielding of either one of the magnetic shielding members. The magnetic field in the direction perpendicular to the orbital direction of the charged particle beam penetrating inward from the exhaust port can be more effectively blocked than when only the shield member is installed.

In addition, if the external stray magnetic field is large, it is better to be able to shield the magnetic field in the direction parallel to the orbital direction of the charged particle beam.
(As shown in BL, magnetic shielding members are provided not only in the direction perpendicular to the orbital direction of the charged particle beam but also in the direction parallel to the orbital direction of the charged particle beam. It is also possible to shield magnetism in a direction parallel to the orbital direction.

As described above, by being able to shield magnetism in the direction perpendicular to the orbital direction of the charged particle beam, a field emission type electron beam source (field emission type charged particle source)
When used in a charged particle beam device that uses Even in charged particle beam equipment,
Fluctuations in the intensity of charged particle beams due to magnetism can be reduced.

Furthermore, it is clear that even in a charged particle beam device provided with another charged particle beam source, external magnetism in a direction perpendicular to the orbital direction of the charged particle beam can be shielded.

In addition, in the example, the magnetic shielding members 5a1 to 5a5,
The present invention can be applied to a magnetic shield member having a rectangular cross-sectional shape as shown in FIG. 1, or other cross-sectional shapes such as an oval shape or a triangular shape.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

According to the invention of claim (1) or claim (2), by forming the magnetic shield member at the exhaust port of the magnetic shield member in a direction perpendicular to the trajectory direction of the charged particle beam, the conventional magnetic It is possible to sufficiently shield an external magnetic field in a direction perpendicular to the orbital direction of the charged particle beam that attempts to enter through the exhaust port seen in the shield member.

Moreover, the aperture ratio of the exhaust port required for exhausting gas can be made sufficiently large, and the exhaust conductance can be increased to a large value.

Therefore, even in a charged particle beam device using a field emission type charged particle beam source that is easily affected by external magnetic fields, the positional shift of the charged particle beam due to the external magnetic field is not likely to occur.

According to the invention of claim (3), gas emitted from the magnetic shielding member can be suppressed by coating the surface of the magnetic shielding member with a metal that releases less gas, such as gold.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a magnetic shielding member according to an embodiment of the present invention, FIG. 2 is a side view of FIG. 1 seen from the exhaust port side, and FIG. Diagrams showing other examples,
It is. [Explanation of main symbols] 1 to 4: Electron beam source, 5: First magnetic shielding member, 5
at, 5 a2. 5 a3. 5 a4: 1st
Magnetic shielding member of magnetic shielding member 5 of 51)1.
5b2. 5b3゜5b4. 5b5: Exhaust port divided into plurality of first magnetic shield member 5, 6: Vacuum envelope, 6 a: Exhaust port, 7 Second magnetic sole member, 8
Third magnetic shield member, 8 al, 8 a2.
8 a3. 8 a4. 8a5. Each component of the third magnetic shielding member 8, 8bl, 8b2. 8b3
．． 8b4. 8b5: Exhaust port divided into a plurality of third magnetic shielding member 8, 9. Exhaust pipe, 10: Ion pump, 1). Structure for attaching electron beam source, 12: Upper pole of electromagnetic lens, 13-15 : Vacuum sealing material

Claims (3)

[Claims] (1) A charged particle beam source that emits a charged particle beam, a vacuum envelope surrounding the charged particle beam source and having an exhaust port on a side wall, one end of which is connected to the exhaust port of the vacuum envelope. an exhaust pipe, an exhaust pump connected to the other end of the exhaust pipe, and made of a high magnetic permeability material, and provided between the vacuum envelope and the charged particle beam to surround the charged particle beam source, and the vacuum A charged particle beam device comprising: a magnetic shielding member having an exhaust port at a position opposite to an exhaust port of the envelope; A charged particle beam device characterized in that it is installed along a direction perpendicular to the trajectory direction of a particle beam. (2) a charged particle beam source that emits a charged particle beam; a vacuum envelope surrounding the charged particle beam source and having an exhaust port on a side wall; one end connected to the exhaust port of the vacuum envelope; an exhaust pipe; an exhaust pump connected to the other end of the exhaust pipe; and a magnetic shielding member made of a high magnetic permeability material, surrounding the vacuum envelope, and having a hole through which the exhaust pipe passes. In the particle beam apparatus, a magnetic shield member made of a high magnetic permeability material is installed inside the exhaust pipe along a direction perpendicular to the trajectory direction of the charged particle beam emitted from the charged particle beam source. Characteristic charged particle beam device. (3) The charged particle beam device according to claim (1) or claim (2), wherein the surface of the magnetic shield member is coated with a metal that releases less gas.