JP2680896B2 - Charged particle beam exposure apparatus and cleaning method thereof - Google Patents

Description

The present invention relates to a charged particle beam exposure apparatus for exposing a sample with a charged particle beam and a cleaning method therefor, which is capable of sufficiently removing deposits on a cylindrical body without the need for overhaul. A charged particle beam exposure apparatus that irradiates an exposed sample with a charged particle beam to form a pattern on the exposed sample for the purpose of not requiring adjustment of the axis is installed so as to surround the optical axis of the charged particle beam. The inner peripheral surface of the cylindrical body has a plurality of conductive parts divided along the optical axis, and a cleaning gas is flown into the cylindrical body to apply a high-frequency signal between the plurality of conductive parts to discharge the cleaning gas. The gas is activated to remove the deposits on the inner peripheral surface of the cylindrical body by etching.

[Industrial applications]

The present invention relates to a charged particle beam exposure apparatus and a cleaning method thereof, and more particularly to a charged particle beam exposure apparatus that exposes a sample with a charged particle beam and a cleaning method thereof.

In recent years, with the increase in the density of integrated circuits, an exposure apparatus using a charged particle beam such as an electron beam has been developed in place of photolithography, which has been the main method for forming a fine pattern. In the charged particle beam exposure apparatus, pattern formation is performed with an electron beam, for example. This exposure can form a fine pattern of about 1/2 micron or less, which could not be formed by photolithography, and expose the designed pattern data without making a reticle or mask just by computer processing. Since it uses data, it has a feature that turnaround is fast, and it is suitable for the production of a large amount of semiconductors in small quantities such as ASICs.

In order to expose a fine pattern to a precise position with such an apparatus, it is important that the electron beam is stable, and its lens barrel is a stable lens barrel that does not give a temporal change to the beam. Is desired.

[Conventional technology]

In the charged particle beam exposure apparatus, exposure data is given to a deflection system to deflect a charged particle beam (for example, an electron beam) to a position on a sample to be exposed. The optical axis of the exposure apparatus is surrounded by an inner peripheral surface of a cylindrical body having a circular cross section plated with a conductor such as gold. This is because if there is an insulator around the electron beam, the trajectory of the electron beam is affected by the charge of the insulator.

Also, since the exposure position shifts due to aberrations and deflection distortion that occur when the electron beam passes through the cylinder, a test exposure is performed before exposure to obtain a correction value, and this correction value is used during exposure. Is calculated to correct the positional deviation.

However, when the exposure is repeated, the carbon component of the residual gas in the vacuum, the organic components that volatilize from the grease of the vacuum seal, the resist scattered from the sample, and the like are evaporated onto the inner surface of the cylinder due to the electron beam irradiation. Since the deposits are accumulated and the deposits are charged, the exposure position is displaced. The amount of change in the positional deviation is gentle when the amount of deposits is small, but becomes steep as the amount of deposits increases. Therefore, an overhaul is performed to remove the deposits.

The overhaul consists of the steps of disassembly, cleaning, assembly and adjustment, and requires a great deal of time. Therefore, as a method of removing deposits on the cylinder without overhauling, a method of sending activated gas into the cylinder to remove the deposits, inserting a high-frequency electrode into the cylinder to cause discharge to decompose and remove the deposits The method of doing so is conventionally performed.

[Problems to be solved by the invention]

The method of feeding the activated gas has a problem that the gas gradually becomes inactive even in the pipe for feeding the activated gas into the cylindrical body and becomes almost inactive in the inner part of the cylindrical body, so that the deposit cannot be sufficiently removed.

Further, in the method of inserting the high-frequency electrode, if there is a portion with a small inner diameter of the cylinder or an aperture that crosses the inside of the cylinder,
I can not insert the high frequency electrode before that part,
In addition, there is a problem in that the optical axis must be changed, for example, the electron gun is removed in order to insert the high frequency electrode, and time is required for the adjustment thereafter.

The present invention has been made in view of the above points, and provides a charged particle beam exposure apparatus and a cleaning method thereof, which can sufficiently remove deposits on a cylindrical body without the need for overhaul and require adjustment of the optical axis after cleaning. The purpose is to do.

[Means for solving the problem]

 FIG. 1 shows the principle of the device of the present invention.

In the figure, the circumference of the optical axis M1 of the charged particle beam is surrounded by a cylinder M2, and a plurality of conductive portions M3, M4 divided along the optical axis M1 are provided on the inner peripheral surface of the cylinder M2. ing.

At the time of cleaning, the cleaning gas is introduced into the cylindrical body M2 by the cleaning gas introducing means, and the conductive portions M3 and M4 are introduced.
In the meantime, a high-frequency voltage is applied from the high-frequency voltage applying means M5 to cause discharge, and the cleaning gas is activated to remove the deposits on the inner peripheral surface of the cylindrical body M2 by etching.

[Action]

In the present invention, the cleaning gas is poured into the cylindrical body M2, the deposit can be sufficiently removed only by applying a high-frequency signal between the conductive portions M3, M4, and there is no need to disassemble the exposure device for cleaning. There is no need to adjust the optical axis after cleaning.

〔Example〕

 FIG. 2 shows a structural diagram of an embodiment of the device of the present invention.

In the figure, 3 is an electron gun for generating an electron beam, which is composed of a cathode 3a, a grid 3b, an anode 3c, and a grid bias 3d. Below the electron gun 3, there are a first slit 6 of approximately 200 μm ^□, a first lens 7, a slit deflector 9, a second lens 10, a second slit 11 of approximately 500 μm ^□ , a blanking 13,
A third lens 14 is provided. The first slit 6, the slit deflector 9 and the second slit form a rectangular molded portion.

Also, below these, an aperture 18 of approximately 100 μm ^φ ,
Refocus lens 19, fourth lens 20, main deflector coil 21 for beam alignment, focus deflector coil 22, sub deflector 23 for beam alignment, fifth lens for correcting defocus due to beam size 24 are sequentially provided, and a pattern 25 is formed by irradiating a sample 25 such as a wafer on which a stage 26 is placed under the sample 24 with an electron beam. The first, second, third, fourth, fifth lenses 7, 10, 14, 20, 24 and refocusing lens 19 respectively accelerate, deflect and converge the electron beam by a magnetic field.

For example, from the electron gun 3 to the first slit 6 on the optical axis of the exposure apparatus.
Between the first slit 6 and the second slit 11, the portion from the second slit 11 to the aperture 18, and the portion from the aperture 18 to the lower portion of the fifth lens 25, respectively, of the slit deflector 9. Except for some electrodes such as electrodes and electrodes of blanking 13 and electrodes of sub-deflector 23, conductors such as aluminum with different diameters, and inner surfaces of insulators such as ceramics are plated with conductors such as gold. It is surrounded by a plurality of cylindrical bodies having a circular cross section. Further, the outside of the electrode portion is also surrounded by the cylindrical body.

FIG. 3 shows the tubular body of the fifth lens 24 portion of the tubular body 30, the fifth lens 24 is provided on the outer periphery of the tubular body 30, and the sub deflector 23 is provided inside the tubular body 30.

FIG. 4 shows a sectional view of the tubular body 30. In the figure, the body of the cylinder
31 is made of insulating ceramic and has multiple T
A letter-shaped recess 32 is provided. The inner peripheral surface of the main body 31 of the cylindrical body is plated with a conductor such as gold, and then one end 32 of each recess 32 is formed.
The gold plating of a is removed by electric discharge machining, and the conductive parts 33a to 33h made of gold plating are insulated and separated from each other along the optical axis. The conductive portions 33a to 33h are separated by the one end portion 32a in this manner so that the insulating one end portion 32a does not look out from the electron beam in the central portion of the tubular body 30.

Of these, a high frequency signal is applied from the oscillator 35 between the opposing conductive portions 33a and 33e during cleaning.

During cleaning, oxygen (O ₂ , O ₃ ), argon (A
r), Freon (CF ₄ ), or a cleaning gas in which these are mixed is poured into the cylindrical body 30 at a vacuum degree of 1 mTorr to 1 Torr. Further frequency 10K～1MH _z output 50~60W about the high frequency signal oscillator 35 from the conductive portions 33a, is applied about 20 seconds between 33e, repeated several times.

As a result, a discharge in a mode depending on the frequency and the degree of vacuum is generated between the conductive parts 33a to 33h, the cleaning gas is activated, and the deposit on the entire inner peripheral surface of the cylindrical body 30 is etched and removed.

Further, since one discharge takes about 20 seconds, the temperature rise of the conductive portions 33a to 33h due to the discharge is small and there is no fear of blackening of the conductive portions 33a to 33h.

Thus, by simply applying the high frequency signal between the conductive portions 33a and 33e of the tubular body 30, the deposit on the entire inner circumferential surface of the tubular body 30 can be sufficiently removed. Further, there is no need to disassemble the exposure device or remove the electron mirror, and since the optical axis is not changed at all, there is no need to make adjustments after cleaning.

The conductive portion on the inner circumference of the cylindrical body 30 is not limited to 8 divisions, and may be divided into 2 divisions, 4 divisions, 16 divisions, or the like. To do.

〔The invention's effect〕

As described above, according to the charged particle beam exposure apparatus and the cleaning method thereof of the present invention, deposits on the entire inner surface of the cylindrical body can be removed only by flowing a cleaning gas into the cylindrical body and applying a high-frequency signal between a plurality of conductive parts. Since it can be sufficiently removed and there is no need to change the optical axis, there is no need to adjust the optical axis after cleaning, cleaning is simple and can be performed in a short time, and it is extremely useful in practice.

[Brief description of the drawings]

FIG. 1 is a principle view of the present invention, FIG. 2 is a structural view of an embodiment of the device of the present invention, FIG. 3 is a view showing a cylinder, and FIG. 4 is an embodiment of a cylinder of the device of the present invention. FIG. In the figure, M1 is an optical axis, M2, 30 are cylindrical bodies, M3, M4, 33a to 33h are conductive parts, M5,
35 indicates an oscillator.

Front page continuation (72) Inventor Akio Yamada 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited

Claims (2)

(57) [Claims] 1. A charged particle beam exposure apparatus for irradiating an exposed sample with a charged particle beam to form a pattern on the exposed sample, wherein an inner circumference of a cylindrical body surrounding the optical axis of the charged particle beam. A plurality of conductive parts divided along the optical axis on the surface, a high frequency voltage applying means for applying a high frequency voltage between the conductive parts, and a cleaning gas introducing means for introducing a cleaning gas into the cylinder. A charged particle beam exposure apparatus characterized in that a cleaning gas is introduced into the cylindrical body and a high-frequency voltage is applied to the conductive portion to cause discharge. 2. A method of cleaning a charged particle beam exposure apparatus, which irradiates an exposed sample with a charged particle beam to form a pattern on the exposed sample, the cleaning method being provided so as to surround an optical axis of the charged particle beam. A plurality of conductive parts divided along the optical axis are provided on the inner peripheral surface of the cylindrical body, a cleaning gas is introduced into the cylindrical body, and a high frequency voltage is applied to the conductive parts to discharge the cleaning gas. A method for cleaning a charged particle beam exposure apparatus, which comprises activating and removing a deposit on an inner peripheral surface of the cylindrical body by etching.