JP3294242B2 - Charged beam irradiation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for irradiating a charged beam used for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art Various electron beam irradiation apparatuses are used to form a desired pattern on a sample such as a semiconductor wafer or a mask substrate. In recent years, electrostatic deflectors have been used in such devices to scan or focus the beam. Electrostatic deflectors have the advantage that they have no hysteresis and quick response compared to coils, but on the other hand, the deflector itself is located very close to the beam path in the vacuum vessel, There is a disadvantage that contamination of the insulator easily adheres to the surface of the deflector, which causes a charge-up and significantly impairs the performance of the deflector. This contamination is mainly organic contaminants that are decomposed by the electron beam and polymerized and adhered to the surface of the electrostatic deflector, and the degree of vacuum in the deflector chamber was improved to prevent the deposition. In order to reduce the number of scattered electrons, the aperture on the electron gun side from the deflector is made thin knife-edge. However, the contamination did not completely disappear, and it was necessary to frequently remove the deflector from the apparatus and perform cleaning or replacement. Contamination is not limited to electrostatic deflectors, but can be found on all surfaces that are exposed to charged particle impact, such as apertures and lens barrel walls. Work is needed.

[0003] The contamination generated by the action of the electron beam cannot be removed by treatment with an organic solvent or the like, and a method of cleaning with a decomposition abrasive is generally employed. This not only drastically reduces the driving rate of the drawing apparatus, but also increases the labor cost required for removing and attaching the apparatus from the apparatus and disassembling, cleaning, and assembling parts. Further, there is a case where a cleaning method using an abrasive cannot be used because the underlying material is damaged. Therefore, a simple and effective method for removing contamination and a method for preventing deposition are desired. Another problem is that contaminants adhere to the sample.

[0004] In a method and apparatus for solving the above problems, a gas selected to react with a contaminant to form a volatile compound from the contaminant is introduced into a vacuum processing chamber and the volatile compound is removed. From the vacuum chamber (see JP-A-60-77340).

Further, an electrode is inserted into a column of an electron beam exposure apparatus along an axial direction thereof, and a high-frequency voltage is applied between the electrode and the inner wall of the column, so that gas plasma is generated in the column. There is a method of removing the organic contaminants on the inner wall surface of the column after the generation and subsequently performing an exposure process (see JP-A-61-20321).

However, the former method and apparatus only remove or reduce contaminants by utilizing only the reactivity of the gas itself, and thus have a problem that the efficiency of contaminant removal is greatly reduced.

In the latter method, when contaminants attached to the surface of a component such as an electrostatic deflector in a column chamber are removed, plasma in the chamber causes ion bombardment and a temperature rise accompanying the ion bombardment. This causes a problem that the base of the component is damaged.

The above problem is not limited to the electron beam irradiating apparatus, but can be similarly applied to a scanning electron microscope, an EB tester, an ion beam irradiating apparatus, and other various apparatuses which handle charged particles.

[0009]

As described above, in the conventional charged beam irradiation apparatus and method, since the disassembly and cleaning steps of the apparatus are required, the driving rate of the apparatus is greatly reduced, and the apparatus is cleaned. There are problems that the labor cost required for the operation is increased, and that the base material of the components inside the vacuum vessel is damaged during the decontamination process and the contamination prevention process.

The present invention has been made in view of the above circumstances, and contaminants adhering to or adhering to the surface of a vacuum vessel can be removed or prevented without damaging the base without removing or disassembling parts in the vacuum vessel. It is an object of the present invention to provide a charged beam irradiation apparatus.

Another object of the present invention is to provide a charged beam irradiation method capable of easily removing or preventing contaminants adhering to or adhering to a component surface of an apparatus without damaging a base. .

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electron beam generating section comprising a vacuum chamber, an electron beam control chamber comprising a vacuum chamber having an optical system for an electron beam, and a vacuum chamber. A sample chamber comprising: a sample chamber comprising: a discharge chamber for generating an electrically neutral active species for purifying the electron beam control chamber; and a device for connecting the electron beam control chamber to the discharge chamber. An electron beam irradiation method for processing a sample, wherein a gas containing oxygen and fluorine is supplied to the discharge chamber, and only the electrically neutral active species among the active species generated by the discharge are used. A charged beam irradiation method is provided, wherein the charged beam is selectively introduced into a discharge chamber to clean contaminants attached to the electron beam control chamber by electron beam irradiation.

[0013]

According to the present invention, a discharge chamber is connected to a vacuum chamber having a charged beam generating section, a charged beam control chamber having an optical system for the charged beam, and a sample chamber, and active species generated in the discharge chamber are connected. Since the vacuum chamber is cleaned by the method, removal or prevention of contaminants generated in members such as an optical system in the vacuum chamber during irradiation with a charged beam can be easily achieved without removing or disassembling the members. it can.

Further, since the active species does not react with the underlying material on the surface of the member, it is possible to remove or prevent the generation of contaminants without damaging the underlying material.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a charged beam irradiation apparatus and method according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing the configuration of a first embodiment of a charged beam irradiation apparatus according to the present invention. The device shown in this figure is an electron beam exposure device.

First, the vacuum chamber 1 of the apparatus is an electron gun chamber (charged beam generating unit) 2 and a beam optical system room (charged beam control room).
3, an ion pump 5
a, differential pumping is performed by the ion pump 5 b and the turbo molecular pump 6. Here, the electron gun room 2 and the beam optical system room 3
Is exhausted in advance by the turbo molecular pump 7 and then dry exhausted by the ion pumps 5a and 5b, respectively.
Gate valves 8 and 9 are provided between the electron gun chamber 2 and the beam optical chamber 3 and between the beam optical chamber 3 and the sample chamber 4, respectively. 2. The beam optical system room 3 and the sample room 4 are partitioned.

An electron gun 10 is provided inside the electron gun chamber 2, and the electron gun 10 emits an electron beam. This electron beam is supplied to a first focusing coil 11, a second focusing coil 12, an aperture 13,
After being controlled to a desired shape and orbit through the electrostatic deflector 14, the light enters the sample chamber 4.

An objective lens 15 is provided in the sample chamber 4, and the electron beam irradiates the sample 17 on a sample table 16 also installed in the sample chamber 4 via the objective lens 15.

In the beam optical system chamber 3, a quartz discharge tube 1 is provided.
8 is fixed so that its tip enters the beam optical system chamber 3 to form an active species introducing section 19. A gas introduction system 20 is connected to the other end, and a high-frequency cavity 21 is provided in the quartz discharge tube 18 between the active species introduction unit 19 and the gas introduction system 20 so as to surround the discharge tube 18. Is provided.

The gas introduction system 20 comprises gas introduction tubes 20a and 20b connected to the quartz discharge tube 18 at a connection portion 18a. The gas flow rates of the introduction pipes 20a and 20b are controlled by mass flow controllers 20c and 20d, respectively. 20e is a valve.

On the other hand, the coaxial cable 2 is
A high-frequency oscillator 23 is connected to the power supply 2 via an external power supply. High-frequency power is oscillated from the high-frequency oscillator 23, transmitted through the coaxial cable 22, and then supplied to the high-frequency cavity 21. The gas introduced from the gas introduction system 20 by the high-frequency power supplied to the high-frequency cavity 21 causes the quartz discharge tube 1
8 dissociates inside to generate active species. The active species generated by such a microwave discharge is transmitted to the active introduction section 1 described above.
From 9, it is introduced into the beam optical system room 3.

Next, a method using the apparatus configured as described above will be described.

In carrying out the method according to the present invention, in the present embodiment, the following treatment was performed on the sample in advance. That is, a sample 17 having a resist film or the like formed on its surface is placed in the vacuum chamber 1, and a desired process such as electron beam drawing is performed on the sample 17 in the container. Removed from

Hereinafter, contamination was removed according to the present invention.
First, the gate valves 8 and 9 were closed to isolate the beam optical system chamber 3 from the electron gun chamber 2 and the sample chamber 4, and the beam optical system chamber 3 was evacuated by the turbo molecular pump 7.

Next, 700 s of oxygen is supplied from the gas introduction pipe 20a.
ccm, CF from gas introduction pipe 20b _Four35 sccm for stone
It is introduced into the British discharge tube 18 and further in the beam optical system room 3.
The pressure was kept at 0.2 Torr. Next, from the high-frequency oscillator
High-frequency oscillation of the oscillated 2.45 GHz high-frequency power 100 w
Gas is applied to the quartz discharge tube 18 through the wave cavity 21 to release the gas.
I turned on. This discharge gas contains electrons, ions, and O-radika.
Neutral particles such as toluene, F radical, CF3 radical
Exists, of which the long-lived F radical and O radical
Only active neutral particles such as CuAl pass through the quartz discharge tube 18
It is transported to the beam optical system room 3. At this time, the neutral particles
Does not flow into the electron gun chamber 2 and the sample chamber 4.

On the other hand, on the surface of the deflector 14 in the beam optical system chamber 3, the electrons scattered by the aperture 13 and the hydrocarbon residual gas mixed from the oil system of the exhaust pump into the beam optical system chamber 3 are formed. A contaminant (polymer) composed of carbon, oxygen and hydrogen deposited by the above reaction is attached.
When the contaminated surface of the deflector 14 was exposed to F radicals and O radicals, the contaminants were completely removed.

At the time of removing the contaminants, the surface of the components such as the first converging coil 11, the second converging coil 12, the aperture 13, the electrostatic deflector 14 provided in the beam optical system chamber 3, Or fluorine may remain, or an oxide or a fluoride may be formed. Therefore, a heating means (not shown) is provided in the above-mentioned electron beam exposure apparatus, and heating is performed to about 120 ° C. simultaneously with or after the removal of contaminants by using this heating means, so that residual oxygen or fluorine on the surface of the component is removed. More preferably, oxides and fluorides formed on the surface of the component are vaporized and removed. In this example, contaminants were removed for the first time by adding F radicals to O radicals. This is considered to be due to the following reason.

That is, the F radical acts on the polymer of the contaminant to weaken the contaminant. Further, the contaminant is oxidized by the oxidation reaction of the O radical, and the decomposition of the contaminant proceeds. Such weakening and oxidation facilitate the removal of contaminants.

In the above embodiment, O ₂ 700 s
Although 35 sccm of CF ₄ was introduced with respect to ccm, O ₂
The effect of the CF ₄ flow rate on the flow rate was investigated. FIG. 2 is a characteristic diagram showing the result. Thus, 2% or more of the total gas flow rate (the sum of the oxygen gas flow rate and the CF ₄ gas flow rate) 20
% Of CF ₄ was able to maximize the effect of removing contaminants. More preferably, the flow rate is 5% or more and 15% or less. When CF ₄ was introduced at a flow rate of 10% of the total gas flow rate, the removal rate of contaminants was maximized, and contaminants could be efficiently removed.

It is considered that the above-mentioned ratio of the CF ₄ flow rate has an upper limit and a lower limit for the following reasons. That is, CF ₄
A certain amount of F radicals is required to weaken the contaminants by the F radicals generated from the water, and even if there are too many F radicals, a large amount of fluorine is incorporated into the surface of the contaminants and the action of oxygen radicals is hindered. Because.

As comparative examples, the O radical and F
Oxygen gas and CF instead of radicals _FourGas as it is
Into the optical system room 3. In this case,
It could not be removed at all.

In a vacuum chamber of an electron beam exposure apparatus, C
F ₄ and O ₂ were discharged to remove contaminants adhering to the parts by this discharge. Gold plating (gold deposited film) applied to the surface of the electrostatic deflector (base material is duralumin) of the beam optical system Part of it has come off. This is considered to be due to the ion bombardment due to the discharge and the accompanying temperature rise. Here, since the structure of the inside of the lens barrel becomes complicated by installing the discharge mechanism in the lens barrel, it has been almost impossible to control the discharge so that abnormal discharge does not occur.

As described above, according to the present embodiment, (1) strong contaminants that cannot be removed by a treatment with a normal organic solvent or the like can be removed, and (2) strong physical action such as an abrasive or ion bombardment. It is possible to remove contaminants on the surface of a base material that cannot be used with a process involving (3) decomposing a structure as long as active species such as radicals enter therein, for example, at the inner wall of a thin cylindrical structure. The effect that contaminants can be removed without the need is obtained.

That is, since the cleaning can be easily performed without removing the deflector and other parts from the apparatus and without exposing the apparatus to the atmosphere, it is possible to obtain an electron beam irradiation apparatus having a high driving rate and a high efficiency. Further, since the above components are not damaged at the time of cleaning, there is a great effect on maintenance of the apparatus.

Second Embodiment FIG. 3 is a schematic sectional view showing the configuration of a second embodiment of the charged beam irradiation apparatus according to the present invention. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The vacuum chamber 1 is divided into a lens barrel (charged beam control chamber) 32 and a sample chamber 4 by an aperture 31. The lens barrel 32 and the sample chamber 4 are turbo molecular pumps 33 and 6, respectively.
Differential exhaust. The sample chamber 4 is provided with a secondary electron detector 34.

The gas introduction system 20 is the same as that of the first embodiment. In this embodiment, the gas introduction system 20 comprises a gas introduction tube 20a, a mass flow controller 20c, and a valve 20e. A quartz discharge tube 18 is connected to the sample chamber 4. Have been.

Next, a method using the apparatus configured as described above will be described.

First, O ₂ 5 sccm was supplied from the gas introduction system 20.
Is introduced into the quartz discharge tube 18 and the degree of vacuum in the sample chamber is set to 1 × 10
-3 Torr. Next, high-frequency power 100 w of 2.45 GHz oscillated from the high-frequency oscillator 23 was applied to the quartz discharge tube 18 through the high-frequency cavity 21 to discharge the gas. At this time, O radicals do not flow into the lens barrel 32 due to differential exhaust. In this state, the sample 17 was irradiated with an electron beam for 30 minutes, and an area of 2 μm × 3 μm on the sample 17 was observed. As a result, almost no adhesion of contaminants was observed on the sample surface. This is probably because the residual gas decomposed by the electron beam reacted with oxygen radicals one after another and was exhausted without adhering to the sample. In this embodiment, the objective lens 15 and the sample 17 in the sample chamber 4 were not damaged.

As a modification of the above embodiment, O radicals may be introduced into the lens barrel 32 during beam irradiation.
In this case, adhesion of contaminants to structures such as components in the lens barrel could be prevented without damaging the base. By using this method, the driving rate of the device can be improved as compared with the first embodiment.

Also, in this embodiment, when removing contaminants, the electron gun 10, the first focusing coil 11, the second focusing coil 12, the aperture 13, the electrostatic deflector 14, and the Oxygen may remain on the surface of components such as the objective lens 15 and the aperture 31 and the surface of the sample 17 or oxides may be formed. Therefore, by heating to about 120 ° C. simultaneously with or after the removal of contaminants using a heating means (not shown) provided in the electron beam exposure apparatus as in the first embodiment, the surface of the component or sample is heated. It is more preferable to vaporize and remove residual oxygen, and further, oxides formed on the surface.

Next, in order to compare the above embodiment with a conventional apparatus and method, the following experiment was conducted.

That is, (1) when oxygen gas is not supplied,
(2) When oxygen gas is directly introduced into the vacuum chamber 1 without discharging, (3) when oxygen gas is dissociated by discharge into oxidized radicals and introduced into the vacuum chamber 1,
(4) Oxygen gas was dissociated by silent discharge into ozone, and electron beam irradiation was performed for 5 minutes in four types of atmospheres when the ozone was introduced into the vacuum chamber 1, and the state of adhesion of contamination was examined.

Table 1 shows the results.

[0046]

[Table 1]

As shown in Table 1, when oxygen gas is not supplied or when oxygen gas is directly introduced into the vacuum chamber without discharging, contaminants are conspicuously deposited. When it is introduced into the soil, the deposition of contaminants can be greatly suppressed.

In addition, even if O radicals and ozone were introduced into the vacuum chamber, no damage or the like was caused on the components in the vacuum chamber, for example, the surfaces of the electrostatic deflector and the objective lens.

Third Embodiment FIG. 4 is a schematic sectional view showing the structure of an embodiment of a contamination removing device based on charged beam irradiation. In the figure, parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

At the bottom of the vacuum vessel 41, a sample table 42 is provided, on which components to which contaminants are adhered by the above-mentioned charged beam are placed. Also, the vacuum container 41
A vacuum door 44 is provided on the side wall of the device, and the parts 43 to which contaminants adhere are put from the vacuum door 44 without being disassembled.
After evacuation, gases such as oxygen and fluorine are introduced from the gas introduction system 20 through the quartz discharge tube 18, and cleaning is performed in the same manner as in the above-described embodiment. By using the apparatus of this embodiment, the same effects as those of the above-described embodiment can be obtained. In addition, the cleaning of components from a plurality of charged beam devices can be performed by one cleaning dedicated device without attaching a pollution control mechanism to each device. Can be obtained.

Also in this embodiment, oxygen and fluorine remaining on the surface of the components such as the first focusing coil 11, the second focusing coil 12, the aperture 13, the electrostatic deflector 14 and the like during the removal of contaminants, It is more preferable to provide a heating means (not shown) in the above-mentioned removing apparatus and remove the oxides and fluorides formed in the above-mentioned step, and to heat to about 120 ° C. using this heating means.

The present invention is not limited to the above-described embodiment, but can be easily applied to any apparatus that emits a charged beam. Further, a gas used for removing or preventing contaminants may be appropriately selected. For example, first and third
For the cleaning method as in Example, NF ₃
It has been confirmed that a mixed gas of water and water, or a compound gas containing oxygen and halogen such as COF ₂ and OF, for example, fluorine, also has an effect of removing contaminants. In particular, contaminants with a low removal rate are exposed to hydrogen plasma in advance to obtain C-H
If a treatment of fluorine radicals and oxygen radicals is performed after the bond is formed, the effect of extracting hydrogen from contaminants by fluorine is exhibited, and the removal rate is greatly improved. Further, with respect to the contamination prevention method as in the second embodiment, ozone gas may be directly introduced from an ozone generator instead of applying a high frequency discharge by a quartz discharge tube. Further, the effect of preventing pollution could be obtained by a compound of oxygen and nitrogen, a compound of oxygen and halogen, such as a compound of oxygen and fluorine, or a compound of oxygen and chlorine.

Further, the introduction of the active species from the active species introduction section may be performed in any of the charged beam control room and the sample room. In short, the present invention can be variously modified and implemented without departing from the gist thereof.

[0054]

As described above, according to the present invention, it is possible to easily clean a surface of a component in a charged beam irradiation apparatus without damaging the substrate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the configuration of a first embodiment of a charged beam irradiation apparatus according to the present invention.

FIG. 2 is a characteristic diagram showing a result of examining an influence of a CF ₄ flow rate on an O ₂ flow rate.

FIG. 3 is a schematic sectional view showing the configuration of a second embodiment of the charged beam irradiation apparatus according to the present invention.

FIG. 4 is a schematic cross-sectional view showing a configuration of an embodiment of an apparatus for removing contamination based on charged beam irradiation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Electron gun room (charged beam generation part), 3 ... Beam optical system room (charged beam control room), 4 ... Sample room, 5a, 5b ... Ion pump, 6, 7, 33 ... Turbo molecule Pump, 8, 9 gate valve, 10 electron gun, 11 first focusing coil, 12 second focusing coil, 13 aperture, 14 electrostatic deflector, 15 objective lens, 16 sample stage, 17 ... Sample, 18 ... Quartz discharge tube, 18a ... Coupling part, 19 ... Activated species introduction part, 20 ... Gas introduction system, 20a, 20b ... Gas introduction pipe, 20c, 20d ... Mass flow controller, 20e ... Bulb, 21 ... High frequency cavity 22, coaxial cable, 23, high frequency oscillator, 31, aperture, 32, lens barrel (charged beam control room), 34, secondary electron detector, 41, vacuum vessel, 42, sample table, 43, contaminant Wearing the parts, 44 ... vacuum door, 45 ... turbo-molecular pump.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI G21K 5/00 G21K 5/04 M 5/04 H01J 37/16 H01J 37/16 H01L 21/30 541Z H01L 21/3065 541G 21 / 302 N (56) References JP-A-4-94524 (JP, A) JP-A-3-19314 (JP, A) JP-A-63-308856 (JP, A) (58) Fields investigated (Int. . ^7, DB name) H01J 37/16 H01L 21/027

Claims (3)

(57) [Claims] 1. An electron beam generator comprising a vacuum chamber, an electron beam control chamber comprising a vacuum chamber provided with an optical system for an electron beam, a sample chamber comprising a vacuum chamber, and the electron beam control chamber being purified. A discharge chamber for generating an electrically neutral active species, and an electron beam irradiation method for processing a sample using an apparatus including means for connecting the electron beam control chamber and the discharge chamber, A gas containing oxygen and fluorine is supplied to the discharge chamber, and among the active species generated by the discharge, only electrically neutral active species are selectively introduced into the discharge chamber and the electrons are irradiated by electron beam irradiation. A charged beam irradiation method characterized by purifying contaminants adhered in a beam control room. 2. The charged beam irradiation method according to claim 1, wherein the electron beam generator and the electron beam control chamber are separated by a valve. 3. The gas containing oxygen and fluorine is a mixed gas containing oxygen gas and carbon tetrafluoride gas, and the ratio of the flow rate of carbon tetrafluoride gas to the sum of the flow rates of the two is 2 to 20%. 3. The charged beam irradiation method according to claim 1, wherein: