JP2014022559A - Charged particle beam exposure device - Google Patents

Abstract

The present invention provides a charged particle beam exposure apparatus capable of mitigating changes in the amount of heat flowing in by ON / OFF by a blanking electrode by a simple method.
A second aperture plate of a charged particle beam exposure apparatus shields at least a part of a non-drawing-selected charged particle beam and a first opening through which the drawing-selected charged particle beam passes. Two openings,
The first aperture plate includes an aperture that allows a charged particle beam from a charged particle source that has passed through the first aperture to pass to the exposure surface side, and an aperture plate that shields the charged particle beam that has passed through the second aperture. With
Adjusting the size or shape of the first and second openings and the opening of the first aperture plate, the difference in the amount of heat by the charged particle beam flowing into the first aperture plate between the drawing selection and the non-drawing selection is determined. Configured to be small,
The second aperture plate is disposed at a position that is not conjugated with the charged particle source or the exposure surface.
[Selection] Figure 1

Description

  The present invention relates to a charged particle beam exposure apparatus, and more specifically, a charged particle beam that scans a sample surface by deflecting a charged particle beam such as an electron beam and turns the charged particle beam ON / OFF according to a drawing pattern to draw a pattern. The present invention relates to an exposure apparatus.

An electron beam exposure apparatus is an apparatus that draws a target pattern by irradiating a sample surface with an electron beam emitted from an electron source, further deflecting them and scanning the sample surface.
In the electron beam exposure apparatus, drawing is performed using a plurality of electron beams formed by dividing the electron beam by a point beam type method that draws using a single electron beam or an aperture array having a plurality of openings. There are multi-beam type systems.
Each method is an apparatus that draws a pattern by turning the electron beam on and off by deflecting with a blanking electrode in accordance with the drawing pattern.

In the electron beam exposure apparatus, when the electron beam is turned on / off, an aperture plate having an opening for passing the electron beam selected for drawing and blocking the electron beam selected for non-drawing is used. .
In such an electron beam exposure apparatus, all electron beams selected for non-drawing are shielded by the aperture plate, and they flow into the aperture plate as heat.
On the other hand, only a part of the electron beam selected for drawing that has not passed through the opening of the aperture plate is shielded, and flows into the aperture plate as heat.
For this reason, since the amount of heat flowing into the aperture plate changes depending on the drawing pattern, the temperature of the aperture plate becomes unstable.
When this aperture plate is arranged at a position that is conjugate to the electron source, for example, or in the vicinity thereof, and functions as an aperture for the electron beam, the position of the opening becomes unstable due to a change in the amount of heat flowing in, There was a problem that drawing performance deteriorated.
In addition, when parts that require precision, such as a diaphragm or projection lens, are arranged near the aperture plate, changes in the amount of heat input to the aperture plate affect changes in the temperature of those parts, and drawing performance is reduced. There was a problem of getting worse.
In order to deal with these problems, Patent Document 1 proposes the following charged particle beam exposure apparatus.
In this apparatus, the amount of heat calculated so that the sum of the amounts of heat flowing into the aperture plate is always a constant value is supplied to the aperture plate by the heating means in synchronization with ON / OFF by the blanking electrode. Has been.

Japanese Patent Application Laid-Open No. 11-162811

When the above-mentioned conventional example of Patent Document 1 is applied to an aperture plate, the amount of heat flowing into the aperture plate can be kept constant to achieve temperature stability, but has the following problems.
That is, a mechanism for supplying heat to the aperture plate in synchronism with the ON / OFF of the blanking electrode needs to be installed on the aperture plate, and the configuration of the apparatus becomes complicated.
Further, when a plurality of electron beams such as a multi-beam type are handled, the same control is required for each electron beam, and the configuration as an apparatus is further complicated.

  In view of the above problems, the present invention provides a charged particle beam exposure apparatus that can reduce the change in the amount of heat flowing into the aperture plate by a simple method by ON / OFF using a blanking electrode, and can improve accuracy. The purpose is to provide.

The charged particle beam exposure apparatus of the present invention comprises a charged particle source that emits a charged particle beam,
A deflector that deflects a charged particle beam and selectively controls drawing and non-drawing;
A projection lens that projects a drawn image onto an exposure surface;
A charged particle beam exposure apparatus for forming a drawn image by forming a charged particle beam emitted from the charged particle source on the exposure surface via the projection lens,
An aperture unit between the deflector and the projection lens;
The aperture unit includes a first aperture plate and a second aperture plate,
The second aperture plate shields at least a part of the first opening through which the charged particle beam from the charged particle source selected for drawing passes and the non-drawn selected charged particle beam. And an opening of
The first aperture plate includes an opening for passing a charged particle beam from the charged particle source that has passed through the first opening to the exposure surface side, and a charged particle beam that has passed through the second opening. And an aperture plate portion that shields
By adjusting the size or shape of the openings of the first and second openings and the first aperture plate,
The difference between the amount of heat by the charged particle beam flowing into the first aperture plate when the drawing is selected and the amount of heat by the charged particle beam flowing into the first aperture plate when the non-drawing is selected Is configured to be small,
The second aperture plate is arranged at a position that is not conjugated with the charged particle source or the exposure surface.

  According to the present invention, it is possible to realize a charged particle beam exposure apparatus capable of mitigating changes in the amount of heat flowing into an aperture by a simple method by ON / OFF using a blanking electrode and improving accuracy. Can do.

It is a figure explaining an example of the charged particle beam exposure apparatus in Embodiment 1 of this invention. It is the figure which showed the example in which the electron beam in Embodiment 1 of this invention passes an aperture plate. It is the figure which showed the energy of the electron beam which passes or is blocked by the aperture plate in Embodiment 1 of this invention. It is a figure explaining an example of the aperture plate in Embodiment 2 of this invention.

Next, an embodiment of the present invention will be described.
(Embodiment 1)
As Embodiment 1, a configuration example of a multi-beam type charged particle beam exposure apparatus to which the present invention is applied will be described with reference to FIG.
The multi-beam type charged particle beam exposure apparatus of this embodiment includes a charged particle source that emits a charged particle beam, a deflector that deflects the charged particle beam and selectively controls drawing and non-drawing, and a drawing image on an exposure surface. A projection lens that projects onto the projector. Then, the charged particle beam emitted from the charged particle source is imaged on the exposure surface via the projection lens to draw a drawn image.
At that time, between the deflector and the projection lens, the charged particle beam selected for drawing is allowed to pass or the non-drawn selected charged particle beam is shielded by selection control of drawing and non-drawing by the deflector. The aperture unit is configured.

Specifically, the multi-beam type charged particle beam exposure apparatus of the present embodiment is configured as shown in the schematic diagram of FIG.
All the control circuits 21 to 24 in the multi-beam type charged particle beam exposure apparatus of this embodiment can be controlled through the main control system 20.
The electron beam emitted from the electron source 1 is converted into a collimated electron beam by adjusting the lens power of the electrostatic collimator lens 2 by the lens control circuit 21.
The electron beam is applied to the beam shaping plate 3 and is divided by the openings of the beam shaping plate 3 to form a plurality of electron beams. The electron beam that has passed through the beam shaping plate 3 is adjusted by the lens control circuit 21 with the lens power of the first focusing lens 4 so as to form an image on the first aperture plate 101, and the blanking deflector 5 is pass.
The blanking deflector 5 is a device having individual deflection electrodes, and individually turns on / off the electron beam based on the blanking signal generated by the blanking deflector control circuit 22.
Where the electron beam is ON (drawing selection), the electron beam is not deflected. When the electron beam is OFF (non-drawing selection), the electron beam is deflected by applying a voltage to the deflection electrode. The

FIG. 2 shows an example in which each electron beam selected or not selected by the blanking deflector 5 passes through the second aperture plate 102 and the first aperture plate 101.
The electron beam 1b not selected for drawing by the blanking deflector 5 is shielded at least in part by the second opening 102a of the second aperture plate 102 disposed in the subsequent stage.
After that, the electron beam 1b that has passed through the second opening 102a is completely shielded by the first aperture plate 101 and is in a non-drawing selection (OFF) state.
The electron beam 1a selected for drawing by the blanking deflector 5 passes through the second opening 102a of the second aperture plate 102 arranged at the subsequent stage. In FIG. 1 and FIG. 2, the electron beam 1a passes through all the second openings 102a of the second aperture plate 102. However, it is not necessary to pass all of them, and if the drawing performance is not affected, A part of the electron beam 1a may be shielded.
Thereafter, the electron beam 1a that has passed through the second opening 102a irradiates the first aperture plate 101, and the portion irradiated on the first opening 101a causes the first aperture plate 101 to be exposed on the exposure surface side. Otherwise, it is shielded by the first aperture plate portion.

The electron beam that has passed through the first aperture plate 101 is imaged by the second focusing lens 6 and further imaged on the exposure surface 9 a on the wafer 9 by the projection lens 8.
Scanning of the electron beam on the wafer 9 can be performed by the deflector 7. The deflector 7 is formed of a counter electrode, and is composed of four stages of counter electrodes to perform two stages of deflection in the X and Y directions (in the figure, the two-stage deflector is regarded as one unit for the sake of simplicity). Notation).
The deflector 7 is driven in accordance with a signal from the deflector control circuit 23.
During pattern drawing, the wafer 9 moves continuously by driving the stage 10 in the X direction in accordance with a signal from the stage drive control circuit 24.
At that time, the electron beam on the surface of the wafer 9 is deflected in the Y direction by the deflector 7 and the drawing pattern by the blanking deflector 5 on the basis of the measurement result in real time by a laser length measuring device (not shown). In response to this, the beams are individually turned on and off.
Thereby, a desired pattern can be drawn on the exposure surface 9a on the wafer 9 at high speed.

From the above, the reason why the amount of heat flowing into the first aperture plate 101 is stabilized by the shielding of the electron beam regardless of the drawing pattern, thereby providing a highly accurate charged particle exposure measure will be described with reference to FIG. explain.
FIG. 3 shows an electron beam that passes through or is shielded by the first aperture plate 101 and the second aperture plate 102 that constitute a part of a multi-beam type charged particle beam exposure apparatus that is an example of the present invention. It shows the amount of heat (energy).
Regarding the second opening 102a of the second aperture plate 102, the energy transmittance of the electron beam 1a selected for drawing is 1, and the energy transmittance of the electron beam 1b not selected for drawing is α (0 ≦ α <1). Suppose that
Further, with respect to the first opening 101a of the first aperture plate 101, the energy transmittance of the electron beam 1c selected by drawing by the blanking deflector 5 and passing through the second aperture plate 102 is expressed by β (0 <β ≦). 1).
Further, the electron beam 1d that has been selected for non-drawing by the blanking deflector 5 and has passed through the second aperture plate 102 is shielded by the first aperture plate 101 and flows into the first aperture plate 101 as a heat quantity.
Although the energy transmittance of the second opening 102a of the electron beam 1a selected for drawing is set to 1 for the sake of simplicity of explanation, even if it is not 1, there is no substantial difference.

In addition, it is assumed that there is no influence due to reflected electrons or thermal radiation for the same reason, but there is no substantial difference with respect to these even if the presence or absence of the influence is not taken into consideration. Further, the energy of the electron beam before being irradiated onto the second aperture plate 102 is P.
The electron beam 1 a selected for drawing passes through the second opening 102 a of the second aperture plate 102.
Since the energy transmittance of the second opening 102a of the electron beam 1a selected for drawing is set to 1, the first aperture plate 101 is irradiated with the electron beam 1c of energy P.

Next, in the first aperture plate 101, when the electron beam 1c passes through the first opening 101a, a part of the electron beam 1c is shielded, and the electron beam 1e with energy βP is applied to the first aperture plate 101a. 101 is passed.
At this time, the energy (1-β) · P of the electron beam shielded by the first aperture plate 101 flows into the first aperture plate 101 as a heat quantity.
The electron beam 1 b selected for non-drawing passes through the second aperture plate 102 with at least a part of the electron beam 1 b shielded at the second opening 102 a of the second aperture plate 102. Since the energy transmittance of the second opening 102a of the electron beam 1b selected for non-drawing is set to α, the first aperture plate 101 is irradiated with the electron beam 1d having energy α · P. In the first aperture plate 101, the electron beam 1d does not pass over the first opening 101a, and is thus completely shielded. At this time, the energy α · P of the electron beam shielded by the first aperture plate 101 flows into the first aperture plate 101 as a heat quantity.

  From the above, the first aperture 101a and the second opening 102a are adjusted in size and shape so that α = 1−β, for example, so that the first aperture can be used regardless of the drawing pattern. The amount of heat flowing into the plate 101 can be made equal. As a result, the temperature stability of the first aperture plate 101 is improved, so that a highly accurate charged particle beam exposure apparatus can be provided.

At this time, the second aperture plate 102 is arranged at a position that is not conjugate with the charged particle source 1 or the exposure surface 9a. The reason for this will be described below. When the energy transmittance of the first opening 101a and the second opening 102a is adjusted so that α = 1−β, the amount of heat flowing into the second aperture plate 102 is the first aperture plate 101. Unlike, it changes according to the drawing pattern. When the second aperture plate 102 is disposed at a position that is conjugate with the charged particle source 1 or the exposure surface 9a, an intermediate image is formed by the second aperture plate 102, and therefore the second aperture plate 102 Changes in drawing quality. From the above, when the second aperture plate 102 is disposed at a position that is conjugate with the charged particle source 1 or the exposure surface 9a, the temperature of the second aperture plate 102 changes due to the drawing pattern, and the intermediate Since the image changes, the drawing accuracy deteriorates.
In addition, regarding the shapes of the first opening 101a and the second opening 102a, there is no restriction as long as the required beam shape and the energy transmittance of the electron beam are set to achieve the purpose. A circle, an ellipse, a rectangle, a triangle, a keyhole shape, or the like may be used.
In FIG. 1, the first aperture plate 101 and the second aperture plate 102 need only have openings corresponding to the number of electron beams, for example, in the case of one electron beam. There may be only one opening.

Further, the material and thickness of the first aperture plate 101 and the second aperture plate 102 are not particularly specified, but these take into consideration the processing accuracy required for the charged particle beam exposure apparatus, the thermal load, and the like. Can be determined.
For example, regarding the material, metals such as copper, titanium, molybdenum, and tungsten or alloys thereof, ceramics such as alumina and silicon carbide, silicon wafers, and the like are conceivable.
Moreover, in order to improve thermal conductivity, the surface may be covered with a conductive film. Moreover, about thickness, it can be set as 50-1000 micrometers. Any of these may be selected so as to ensure required performance such as positional accuracy and heat resistance in an environment where the charged particle beam exposure apparatus is used.
In the first embodiment, the first aperture plate 101 is disposed so as to be disposed at the position where the electron beam is imaged. However, the present invention is not limited to this.
For example, in order to avoid concentration of energy density due to image formation, the position of the first aperture plate 101 may be arranged slightly back and forth from the image formation position. Further, the first aperture plate 101 may be arranged at a position that functions as an aperture for beam shaping.
According to the above configuration, it is possible to mitigate changes in the amount of heat flowing into the first aperture plate 101 regardless of ON / OFF by the blanking deflector, and the temperature stability of the first aperture plate 101 can be reduced. Can be improved.
Further, since a mechanism for synchronizing with ON / OFF of the blanking deflector is unnecessary, it is possible to prevent the configuration of the apparatus from becoming complicated.

(Embodiment 2)
As a second embodiment, a configuration example of a charged particle beam exposure apparatus having a different form from the first embodiment will be described with reference to FIG.
In this embodiment, in the charged particle beam exposure apparatus of Embodiment 1, a temperature adjustment unit (temperature adjustment means) 105 is mounted on the first aperture plate 101. Accordingly, for example, by mounting the temperature adjustment unit 105 as shown in FIG. 4 on the first aperture plate 101 described in the first embodiment, the temperature adjustment unit 105 can be used as a temperature adjustment unit for the first aperture plate 101. Can act as
Therefore, it is possible to control the temperature at which the first aperture plate 101 becomes stable and to control the deformation amount due to thermal expansion, so that the drawing accuracy can be further improved as a charged particle beam exposure apparatus.

FIG. 4 shows an example of the aperture plate in the present embodiment.
In FIG. 4, the material and thickness of the temperature adjustment unit 105 are not particularly specified, but the structure may be determined in consideration of the set temperature and the adjustment method.
For example, when functioning as a cooling mechanism by a water cooling system, the temperature adjustment unit 105 is configured by installing a circulation path (not shown) for circulating a coolant such as water or ammonia therein.
The first aperture plate 101 is cooled by circulating a refrigerant whose temperature, flow rate, and pressure are adjusted by a temperature adjusting device (not shown) installed outside through a temperature adjusting unit (not shown).
The material may be determined in consideration of workability and thermal conductivity. For example, metals such as copper, aluminum, titanium, molybdenum, tungsten, or alloys thereof, aluminum nitride ceramics with good thermal conductivity, etc. It is done.

Moreover, in order to improve thermal conductivity, the surface may be covered with a conductive film.
In addition, the contact portion with the first aperture plate 101 is fixed with an adhesive having a high thermal conductivity such as a silver paste or the heat transfer sheet for improving the flatness of the contact surface in order to ensure thermal conductivity. For example, the contact surfaces may be pressed and fixed with a fixing jig (not shown).
The thickness may be determined in consideration of the size of the circulation path inside the temperature adjusting unit 105, thermal conductivity, and the like, and may be set to 0.2 to 10 mm, for example.
Any of these may be selected so as to ensure required performance such as positional accuracy and heat resistance in an environment where the charged particle beam exposure apparatus is used.
Further, the temperature adjustment unit 105 may be configured by being integrally formed with the first aperture plate 101 in addition to being disposed in contact with the first aperture plate 101.

Examples of the present invention will be described below.
[Example 1]
As Example 1, a configuration example to which the charged particle beam exposure apparatus of Embodiment 1 is applied will be described.
In the charged particle beam exposure apparatus of the present embodiment, the first aperture plate 101 is a double-side polished single crystal silicon wafer having a thickness of 200 μm and a diameter of 100 mm, and charged particles pass through a square area having a central side of 4 mm. A plurality of first openings 101a.
The openings 101a are round holes, arranged in a square arrangement with a hole diameter of 21 μm and a pitch of 200 μm, and formed by photolithography and dry etching.
The second aperture plate 102 is the same except for the opening portion, and has a plurality of second opening portions 102a in a square area having a central side of 4 mm.
The second openings 102a are square holes with a side of 90 μm, and are arranged in a square array with a pitch of 200 μm.
The first aperture plate 101 and the second aperture plate 102 are positioned so that the center of the electron beam selected for drawing passes through the center of the first opening 101a and the center of the second opening 102a. They are arranged 5 mm apart from each other.
At this time, the non-drawing selected electron beam is set so as to pass through the second aperture plate 102 at a position 45 μm away from the center of the second opening 102a.

Consider a case where an electron beam is irradiated to the charged particle beam exposure apparatus of the present embodiment. One electron beam exists with respect to one opening of the opening 101a, and was set by a beam shaping plate or the like so that each has energy of 10 mW.
Each electron beam passes through the corresponding second opening 102a and first opening 101a.
Further, when this electron beam passes through each aperture plate without being shielded at all, the electron beam has a circular and uniform diameter of 35 μm at the position of the second aperture plate 102 and 30 μm at the position of the first aperture plate 101. It is assumed that the focused beam has a high intensity.

Under the above conditions, the energy transmittance of the second aperture 102a of the second aperture plate 102 is 1 for the electron beam 1a selected for drawing and 1 for the electron beam 1b selected for non-drawing. On the other hand, 0.5 is set.
The energy transmittance of the first aperture 101a of the first aperture plate 101 is about 0.49 for the drawing-selected electron beam 1a, and for the non-drawing-selected electron beam 1b. Since it does not pass through the first opening 101a, 0 is set.
When the electron beam is irradiated from the second aperture plate 102 side, the amount of heat flowing into the first aperture plate 101 is about 5.1 mW when drawing is selected for one electron beam. When non-drawing is selected, it is about 5 mW. For this reason, the difference in the amount of heat that flows due to ON / OFF of the electron beam is about 0.1 mW.

On the other hand, when the second aperture plate 102 does not exist, a heat amount of 10 mW flows into the first aperture plate 101 when non-drawing is selected, so the difference in the amount of heat that flows in due to ON / OFF of the electron beam is 4 About 9mW.
In addition, when the second aperture plate 102 exists but the second opening 102a is, for example, a square opening having a side of 40 μm, all of the electron beams 1b selected for non-drawing have the second aperture. It is shielded by the plate 102.
Therefore, since heat does not flow into the first aperture plate 101 when non-drawing is selected, the difference in the amount of heat that flows due to ON / OFF of the electron beam is about 5.1 mW.
As described above, in any case, since the difference in the amount of heat flowing in due to ON / OFF of the electron beam is larger than in the present invention, the present invention improves the temperature stability of the first aperture plate 101. It is possible.
In this example, the influence of reflected electrons and thermal radiation is not taken into account, but there is an influence of reflected electrons and thermal radiation by appropriately setting each opening in consideration of these. However, it is possible to obtain the same performance as the present embodiment.

[Example 2]
As Example 2, a configuration example to which the charged particle beam exposure apparatus of Embodiment 2 is applied will be described.
In the charged particle beam exposure apparatus similar to that of the first embodiment, a copper temperature adjustment unit 105 having a thickness of 4 mm and a 3 mmφ refrigerant circulation path is provided on the first aperture plate 101, and the electron beam trajectory is obstructed. It was placed in a position where it would not be.
Further, in consideration of thermal conductivity of the first aperture plate 101 and the temperature adjusting unit 105, the first aperture plate 101 was fixed to the first aperture plate 101 using a silver paste.
Cooling water whose temperature, flow rate, and pressure are adjusted by the temperature adjusting unit (not shown) installed outside is circulated through the temperature adjusting unit (not shown) to the temperature adjusting unit 105, and the first aperture. The plate 101 was cooled.
In the absence of the temperature adjustment unit 105, the first aperture plate 101 is thermally expanded due to the temperature rise until the first aperture plate 101 is thermally stabilized, and the first opening 101a changes. Therefore, it is necessary to set the first opening 101a.
On the other hand, since the temperature at which the first aperture plate 101 is in a thermally stable state can be controlled when the temperature adjustment unit 105 exists, the amount of change in the first opening 101a is predicted. The accuracy can be improved and the drawing accuracy can be improved.

1a: Electron beam selected for drawing 1b: Electron beam selected for non-drawing 101: First aperture plate 101a: First aperture 102: Second aperture plate 102a: Second aperture 105: Temperature adjusting unit

Claims (2)

A charged particle source that emits a charged particle beam;
A deflector that deflects a charged particle beam and selectively controls drawing and non-drawing;
A projection lens that projects a drawn image onto an exposure surface;
A charged particle beam exposure apparatus for forming a drawn image by forming a charged particle beam emitted from the charged particle source on the exposure surface via the projection lens,
An aperture unit between the deflector and the projection lens;
The aperture unit includes a first aperture plate and a second aperture plate,
The second aperture plate shields at least a part of the first opening through which the charged particle beam from the charged particle source selected for drawing passes and the non-drawn selected charged particle beam. And an opening of
The first aperture plate includes an opening for passing a charged particle beam from the charged particle source that has passed through the first opening to the exposure surface side, and a charged particle beam that has passed through the second opening. And an aperture plate portion that shields
By adjusting the size or shape of the openings of the first and second openings and the first aperture plate,
The difference between the amount of heat by the charged particle beam flowing into the first aperture plate when the drawing is selected and the amount of heat by the charged particle beam flowing into the first aperture plate when the non-drawing is selected Is configured to be small,
The charged particle beam exposure apparatus, wherein the second aperture plate is disposed at a position not in a conjugate relation with the charged particle source or the exposure surface.   The charged particle beam exposure apparatus according to claim 1, wherein the first aperture plate includes a temperature adjusting unit.

Images