JP3246609B2 - Cleaning method and cleaning device in charged particle exposure apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle exposure technique using a charged particle beam, and more particularly to a charged particle exposure apparatus using a mask for shaping the cross-sectional shape of the charged particle beam. The invention relates to a cleaning method and a cleaning device.

[0002] In this specification, the term "mask" broadly refers to a member capable of shaping the cross-sectional shape of a charged particle beam.
It may have any of a slit, a rectangular opening, a block pattern, and the like.

In recent years, charged particle exposure apparatuses are required to have high speed, high resolution, and short focus. In order to satisfy the high speed, a single stroke of the point beam is not enough, and a mask having slits and various opening pattern groups for variously shaping the cross-sectional shape of the beam is used, and a certain area is simultaneously exposed.

[0004] High resolution is required to be at least submicron, typically quarter micron (μ / 4), on an exposure object (resist). In order to realize such high resolution and high accuracy, the focal length is also shortened, and is approximately 10 cm or less.

By the way, when exposure is performed in a charged particle exposure apparatus, even if the apparatus is completely cleaned, the resist layer is irradiated with a charged particle beam and some constituent substances are desorbed from the resist layer. The mask gradually gets dirty. If the contamination of the mask is left unchecked, the accuracy of the exposed pattern cannot be maintained, so the contaminated mask needs to be cleaned.

[0006]

2. Description of the Related Art In a conventional charged particle exposure apparatus, when a mask having a slit or a pattern for shaping the cross-sectional shape of a charged particle beam is contaminated by the irradiation of the charged particle beam, it is usually about 1 × 10 ^-6 Torr. Then, the inside of the charged particle exposure apparatus operated in the step was returned to the atmospheric pressure, and the mask was taken out and washed.

Therefore, when the mask used is contaminated, the operation of the charged particle exposure apparatus is stopped, the inside of the apparatus is returned to atmospheric pressure, the mask used so far is taken out, and a new mask is used. The apparatus was set, the inside of the apparatus was evacuated again, and the optical axis was adjusted.

According to such a mask replacement / mask cleaning method, each time the mask is contaminated, a considerable amount of time and labor is required for mask replacement. As one method for speeding up the mask replacement operation, there is a method of providing a loading chamber which can be separated from an exposure space by a gate valve in a charged particle exposure apparatus.

When the mask is contaminated, the mask is moved into the loading chamber, the exposure space is cut off by a gate valve, and the mask is replaced while maintaining a vacuum. According to such a method, it is not necessary to return the inside of the exposure space to the atmospheric pressure.

The above method is based on the idea that when the mask is contaminated, the mask is taken out, cleaned, and then assembled again in the charged particle exposure apparatus. As a new concept, cleaning may be performed with the mask arranged in the vacuum space of the charged particle exposure apparatus.

[0011] Mask contamination is primarily carbon-based and can be removed, for example, by exposure to an oxygen plasma. A cleaning method according to this concept is shown in FIG. 3 as a reference technique.

In FIG. 3A, a cleaning space 34 is provided separately from the exposure space 33. This cleaning space 34 may be separated from the exposure space 33 by a gate valve or the like as necessary.

Exposure space 33, cleaning space 34
Are covered by a common airtight housing 35.
When the mask 37 mounted on the metal stage 36 in the exposure space 33 becomes contaminated, the metal stage 36 is moved to carry the mask 37 from the exposure space 33 to the cleaning space 34.

In the cleaning space 34, a 13.56 MHz high frequency power supply 39 is connected to the metal stage 36, and the metal electrode plate 4 disposed at a position facing the mask 37.
1 is installed, and a high-frequency voltage is applied during the installation.

At this time, a cleaning gas, for example, oxygen gas is introduced from a gas introduction system 42 to generate an RF plasma 43 between the metal electrode plate 41 and the metal stage 36.
Oxygen atoms in the RF plasma 43 are activated, and the mask 3
7 are removed, and the mask 37 is cleaned. The mask after cleaning may be moved from the cleaning space 34 to the exposure space 33 again.

In this method, the vacuum atmosphere during exposure is, for example, about 1 × 10 ^-6 Torr, and oxygen gas is supplied, for example, at 1 × 10 ^-1 Torr during cleaning.
The plasma 43 is generated by introducing about r to 1 Torr.

In the case of the structure shown in FIG. 3A, cleaning is performed in a cleaning space different from the exposure space. However, since the time required for cleaning is not long, after cleaning, the mask is returned to the exposure space. And the exposure is continued. In view of this, a method is conceivable in which the cleaning space is not provided, and the cleaning is directly performed in the exposure space.

FIG. 3B shows a configuration capable of in-situ cleaning. When the mask 37 disposed on the metal stage 36 is contaminated in the exposure space 33, a cleaning gas such as O ₂ is introduced into the exposure space 33 from the gas introduction system 42, and the metal stage 36 is switched to a high frequency power supply. 39
And a metal rod 45 is introduced directly above the mask 37 to generate a high-frequency electric field between the metal rod 45 and the mask 37.

Due to this high-frequency electric field, plasma 43 is generated between the tip of the metal rod 45 and the mask 37, and the plasma
7 is cleaned. The metal rod 45 has, for example, a spherical metal portion at the tip and a stem connected to the tip is covered with an insulator.

It is also possible to use the airtight housing 35 as one electrode and apply a high-frequency electric field between the airtight housing 35 and the mask 37. However, since the airtight housing 35 does not exist directly above the mask, the generated plasma is generated. Is low in the portion immediately above the mask. In order to effectively generate plasma directly above the mask 37, a metal rod 45 is required.
Is preferably introduced directly above the mask.

[0021]

As described above,
According to the conventional technique, when the mask is contaminated in the charged particle exposure apparatus, the mask is taken out and washed, so that the time required for mask replacement is long and much labor is required.

An object of the present invention is to provide a cleaning method capable of cleaning a mask without taking out the mask from the charged particle exposure apparatus.

[0023]

According to the present invention, there is provided a cleaning method comprising the steps of: introducing a cleaning gas into a charged particle exposure apparatus while exposing the exposure mask in a space where the exposure mask is to be disposed during exposure; A step of applying a high-frequency voltage between the metal part and the metal stage holding the mask, and a step of generating a magnetic field by an electromagnetic lens above the mask.

[0024]

In a charged particle exposure apparatus, an electromagnetic lens and an electrostatic deflection electrode are arranged in a narrow space on a mask. Therefore, there is a metal part that can be used as an electrode above the mask. If a high-frequency voltage is applied between the metal part above the mask and the metal table holding the mask, it becomes possible to generate plasma on the mask.

Further, there is an electromagnetic lens above the mask. If a magnetic field is generated above the mask by the electromagnetic lens, the magnetic field can increase the plasma density. Also, the magnetic field generated from the portion between the electromagnetic lenses to the space where the mask exists is a divergent magnetic field,
Ions generated in the plasma can be extracted toward the mask.

In this manner, the mask is efficiently cleaned in-situ in the charged particle exposure apparatus without requiring any additional members as described in the reference art other than the power supply for generating the high-frequency electric field. It becomes possible.

[0027]

FIG. 1 shows an electron beam exposure apparatus according to an embodiment of the present invention. The electrostatic deflecting electrodes 11 arranged above the exposure space 10 are a multiple number of opposing electrodes, and deflect the electron beam passing between them in a predetermined direction.

These electrostatic deflection electrodes 11 are held in a vacuum-sealed metal cylinder 15 by spacers 13 formed of an insulator. Above the electrostatic deflection electrode 11, a metal cap 12 connected to a vacuum seal metal cylinder is arranged.

Below the electrostatic deflection electrode 11, an electromagnetic lens 17 is arranged outside the vacuum seal metal cylinder 15.
The electromagnetic lens 17 generates a lens magnetic field 19 that is axially symmetric with respect to the optical axis 1 and causes a lens function to act on an electron beam passing therethrough.

The electron beam having passed through the electrostatic deflection electrode 11 and the electromagnetic lens 17 irradiates a predetermined portion of the mask 21 held on the metal stage 23. The electron beam is shaped into a predetermined shape by the mask 21 and is irradiated on the object. In order to irradiate an electron beam, the electron beam exposure apparatus further includes a reduction lens, a projection lens, a deflector, and the like.

When the mask 21 has a large number of block patterns and one of them is selected to form an electron beam, the block pattern is selected by the electrostatic deflection electrode 11. In the case of variable rectangular exposure, the rectangular shape is also changed by the electrostatic change electrode 1.
Perform by 1.

When the mask 21 is contaminated by a substance generated from the resist layer or the like irradiated by the electron beam, the electron beam exposure operation is interrupted and the mask 21 is cleaned.

An O ₂ gas, for example, of about 1 × 10 ⁻² Torr is introduced from the gas introduction system 25, the electrostatic deflection electrode 11 is grounded, and a DC bias power supply 28 and a high-frequency power supply 27 are connected to the metal stage 23. DC bias power supply 28
Generates a bias voltage of, for example, about 10 to 20 V, and the high-frequency power supply 27 outputs, for example, an RF of 13.56 MHz.
A high frequency of about 50 to 200 W is generated.

An electric current is applied to the electromagnetic lens 17 to generate a lens magnetic field 19 that is axially symmetric with respect to the optical axis 1. The lens magnetic field 19 forms a divergent magnetic field 20 that spreads downward in a portion on the mask 21. This magnetic field causes electrons moving up and down by a high-frequency electric field to spiral. Also, when an electron tries to move outward, it changes its direction and serves to confine it in a magnetic field.

As described above, when an RF electric field is applied in the space where the magnetic fields 19 and 20 are present, the O ₂ gas is turned into plasma by collision of electrons and gas molecules, and the plasma 3 is turned on.
1 is generated. The plasma 31 becomes a magnetic field plasma and is efficiently generated in a limited space.

With such a magnetic oxygen plasma,
If the mask 21 is cleaned, for example, for about 30 seconds to 1 minute, contaminants can be removed and the mask 21 can be restored to a clean state.

The mask 21 is formed by, for example, providing an opening in a Si substrate and forming a pattern. When such a mask is cleaned with a cleaning gas having a relatively high pressure, there is a problem of microloading in which the mask itself is damaged. In this embodiment, since cleaning can be performed at a low pressure by the magnetic field plasma, deterioration of the mask due to microloading can be prevented.

Since the gas pressure at the time of cleaning is low, the time required for re-evacuating the exposure space of the electron beam exposure apparatus after cleaning can be reduced. In addition to oxygen gas (including ozone gas),
A rare gas such as chlorine gas or Ar can also be used. However, it is preferable to use a gas having a high cleaning speed and a high exhaust speed.

In the electron beam exposure apparatus, in-situ cleaning can be performed without changing the position of the mask, so that it is not necessary to align the mask after cleaning. Although the mask is heated by the cleaning, the mask may be heated in some cases to prevent contamination, and the heating by the cleaning is not particularly problematic.

FIG. 2 shows an electron beam exposure apparatus according to another embodiment of the present invention. In this device, the electrostatic deflection electrode 11 is arranged inside the electromagnetic lens 17. A metal cap 12a is arranged above the vacuum seal metal cylinder 15 via a spacer 14 formed of an insulating material.
In this configuration, the metal cap 12a also serves as an electrode. The metal cap 12a is formed of, for example, stainless steel (SVS).

Other structures for exposure are the same as those shown in FIG. In the electron beam exposure apparatus shown in FIG. 2, exposure is performed in the same manner as in the electron beam exposure apparatus shown in FIG. That is, the electrostatic deflecting electrode 11 applies a deflecting electric field to the electron beam traveling downward from above, and the electromagnetic lens 17 forms a lens magnetic field having a lens action.
A predetermined portion of the mask 21 is selected in this manner, and the formed electron beam is directed downward, and is reduced and projected to form a desired pattern on the resist.

When the mask 21 is contaminated and cleaning is performed, a microwave high-frequency power supply 27a is connected to the metal stage 23 holding the mask 21. Further, the metal cap 12a is connected to the ground power supply 26, and the metal cap 12a
A DC bias power supply 28 is connected between the power supply and the metal stage 23.

The microwave power supply 27a is, for example, 2.45.
Generate a microwave microwave voltage of GHz. Further, the DC bias power supply 28 applies a bias voltage of about 5 to 15 V between the metal cap 12 a and the metal stage 23.

The electromagnetic lens 17 generates a magnetic field having a strength for realizing electron cyclotron resonance (ECR). That is, the electrons make a helical motion by the lens magnetic field 19, and the period of the helical motion and the period of the μ-wave coincide, and the oscillation period of the electron and the period of the rotational motion by the magnetic field coincide with each other. So that the number of collisions is maximized. When these conditions are met,
The plasma generation efficiency increases dramatically.

Therefore, the gas pressure to be introduced is about 10 ^-3 to 1
About 0 ^-4 Torr is enough. For example, the introduced O ₂ gas pressure is 5 × 10 ⁻⁴ Torr. In order to realize electron cyclotron resonance, the electromagnetic lens 17 generates a magnetic field of at least 5000 to 6000 gauss in the plasma generation space.

According to this embodiment, by using the ECR plasma, the pressure of the cleaning gas introduced at the time of cleaning can be further reduced, so that the time required for exhausting and restarting after cleaning can be further reduced.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0048]

As described above, according to the present invention,
In-situ cleaning of the mask in the charged particle exposure system eliminates the need to introduce special additional components into the vacuum chamber,
I can do it.

By using the magnetic field plasma, the pressure of the introduced gas can be reduced.
The time required for restarting can be reduced. Since there is no need to change the position of the mask during cleaning, there is no need to align the mask after cleaning.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electron beam exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of an electron beam exposure apparatus according to another embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating cleaning of a mask in an electron beam exposure apparatus according to a reference technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Electrostatic deflection electrode 12 Metal cap 13, 14 Spacer 15 Vacuum seal metal cylinder 17 Electromagnetic lens 19 Lens magnetic field 20 Divergent magnetic field 21 Mask 23 Metal stage 25 Gas introduction system 26 Ground power supply 27 High frequency power supply 28 DC bias power supply

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kiichi Sakamoto 1015 Ueodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (56) References JP-A-63-308856 (JP, A) JP-A-62- 202517 (JP, A) JP-A-3-46221 (JP, A) JP-A-3-19314 (JP, A) JP-A-61-59826 (JP, A) JP-A-3-3225 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 H01L 21/326 H01J 37/00

Claims (6)

(57) [Claims] In a charged particle exposure apparatus, a step of introducing a cleaning gas (25) while leaving an exposure mask in a space (10) in which the exposure mask is arranged during exposure, and a metal part (11) above the mask. , 12) and a metal stage (23) for holding a mask, a high-frequency voltage (27); and a magnetic field generated by an electromagnetic lens (17) above the mask. 2. The cleaning method according to claim 1, further comprising a step of applying a DC bias voltage between a metal portion above the mask and a metal table holding the mask. 3. The cleaning method according to claim 1, wherein the frequency of the high frequency and the intensity of the magnetic field are selected so as to generate electron cyclotron resonance. 4. The cleaning gas contains at least one of oxygen gas, ozone gas, rare gas, and chlorine gas,
The cleaning method according to claim 1, wherein the metal part above the mask is an electrostatic deflection electrode or a metal part for vacuum sealing, and the magnetic field is a diverging magnetic field diverging toward the mask. 5. A charged particle exposure apparatus including an electrostatic deflection electrode, an electromagnetic lens, a metal table for holding an exposure mask, an insulating metal member above the mask, and the like, wherein the charged particle exposure apparatus is connected to the electrostatic deflection electrode or the insulating metal member. A cleaning apparatus including: a plasma generation power supply including a ground power supply and a high-frequency power supply connected to the metal base; and a unit for supplying a cleaning gas into a space including the metal base. 6. The cleaning apparatus according to claim 5, further comprising means for applying a predetermined DC bias voltage between said electrostatic deflection electrode or insulating metal member and said metal base.