JP2001345062A - Electron gun, exposing device and exposing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron gun in which energy dispersions of electron beam are small and in which the homogeneity of lighting is superior, and provide an exposing device and exposing method to use it wherein the resolution is enhanced and the exposure unevenness is smaller. SOLUTION: Numerous minute protrusions 5a, 5b to 5n are formed at a tip surface of a negative electrode 1, and a single or numerous drawing out electrodes 3, 4 are installed at the same time, and the electron gun (lighting beam source) having many points of electron emission source is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electron gun for forming an electron beam, an observation apparatus (SEM or TEM) using the electron beam from the electron gun, an exposure apparatus for forming a fine pattern on a semiconductor, and an exposure apparatus. About the method.

[0002]

2. Description of the Related Art An electron gun used in an EB exposure apparatus or the like generally uses a hot cathode (a LaB ₆ having a Wehnelt (lattice electrode) attached thereto) as a cathode. In general, in a variable-shaped EB exposure apparatus or a partial batch EB exposure apparatus, an electron beam is irradiated from an electron beam source not in a spot but in a planar manner, so that in-plane uniformity of beam intensity in an irradiation area is important.

At this time, the degree of in-plane uniformity of the electron beam intensity in the irradiation area is required to be several percent or less. Therefore, the actual hot cathode (LaB ₆ to that with a Wehnelt) is or processed the tip of the filament in flat, are performed such as using only a portion of the widened electron beam.

In general, the energy spread (ES; energy dispersion) of a hot cathode is relatively large, about 5 eV due to its characteristics.

An important problem in the EB exposure apparatus is to reduce chromatic aberration. If the chromatic aberration is large, the exposure resolution (for example, when exposing a line width of 100 nm, 30 to 90 n
The image must be blurred on the order of m, but this blur corresponds to the resolution). Since chromatic aberration is proportional to the energy spread ES / beam acceleration voltage,
In a general EB exposure apparatus, the energy spread ES /
Beam acceleration voltage = 5 eV / 50 kv (30 kv-100
kv) = 10 ⁻⁴ , which is an allowable value in the high-acceleration EB exposure apparatus on the order of 30 kv to 100 kV.

On the other hand, a thermal field emission type cathode is known as a technique capable of reducing the energy spread. The thermal field emission cathode has, for example, a ZrO / W with an extraction electrode attached thereto, and usually has an energy spread of about 1 eV. Therefore, the energy spread of the thermal field emission type cathode is 1/5 of that of the hot cathode, and therefore, the energy spread has a preferable performance as the cathode of the low acceleration type EB exposure apparatus with respect to the energy spread.

[0007]

However, a general hot cathode (LaB ₆ with Wehnelt) is replaced with a low-acceleration EB.
When used in an exposure apparatus (apparatus having an acceleration voltage of the order of 5 kv), this value is calculated as energy spread ES / electron beam acceleration voltage = 5 eV / 5 kv (3 kv to 10 kv) = 10
⁻³ , which is 10 times as large as 10 ⁻⁴ , which is an unacceptable value. Therefore, when the energy spread is on the order of 5 eV, the chromatic aberration increases, which is not preferable, and the energy spread is desirably about 0.5 eV.

On the other hand, when a thermal field emission cathode is used,
Electrons are extracted by the electric field strength, so that the smaller the radius of curvature at the tip of the electron emission portion is, the higher the electric field strength is (the electric field strength is inversely proportional to the tip radius). You are. That is, since the radius of curvature at the tip is small, when a thermal field emission cathode is used, the electron beam is divergently emitted from the power supply. As a result, the electron beam intensity is strong only at the center and weak at the periphery, for example, in a Gaussian distribution. When this is used as an illumination beam, there is a problem that the in-plane uniformity is reduced.

The present invention has been made on the basis of these circumstances, and has an electron gun having a small energy dispersion of an electron beam and excellent uniformity of illumination. An object of the present invention is to provide an exposure apparatus and an exposure method that are not uneven.

[0010]

According to the first aspect of the present invention, there is provided a cathode disposed in a vacuum vessel for generating an electron beam, an extraction electrode for extracting the electron beam generated by the cathode, and An electron gun comprising: an anode that accelerates an electron beam generated by a cathode in the beam axis direction to form a path for the electron beam; wherein a plurality of protrusions are formed on a tip end surface of the cathode. It is a characteristic electron gun.

According to the second aspect of the present invention,
The plurality of protrusions may have the same shape or a random shape.

According to the third aspect of the present invention,
The extraction gun is characterized in that holes are formed at positions corresponding to the protrusions formed on the tip end surface of the cathode, respectively.

According to the fourth aspect of the present invention,
An electron gun, wherein a second extraction electrode is provided in front of the extraction electrode along the beam axis.

[0014] According to the means of claim 5,
The cathode is an electron gun formed of lanthanum hexaboride.

According to the means of the invention of claim 6,
An exposure apparatus using the electron gun as the exposure means.

Further, according to the means of the invention of claim 7,
An exposure method characterized by exposing a workpiece using the above-mentioned electron gun.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electron gun, an exposure measure and an exposure method according to the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing the basic structure of the periphery of the cathode portion of the electron gun of the present invention. The configuration of the electron gun includes a cathode 1, a suppressor 2, and a Z-axis along the electron beam axis.
An extraction electrode 3 (extractor electrode) and a second extraction electrode 4 are arranged, and further in front of them, an electron lens, an anode, and a blanking aperture (both not shown) are arranged.

The cathode 1 is an electron emission source is formed by a LaB _6. The suppressor 2 applies a voltage of about -200 to -500 V with respect to the cathode potential.

The voltage applied to the extraction electrode 3 (extractor electrode) is dependent on the gap _{G 1,} for example, G
₁ = Voltage of about +20 to 500 V for ₁₀ μm to 50 μm. Further, the applied voltage of the second lead-out electrode 4 is dependent on the gap _{G 2,} for _example, G 2 = 1 m
The voltage is about +200 V to +5 Kv for m to 5 mm.

FIG. 2 is an enlarged perspective view of the portion A in FIG. The tip of the cathode 1 is frusto-conical, and
6 mm in the range of several hundred μm (240 μm here)
.Times.6 = 36 protrusions 5a, 5b... 5n are formed. On the other hand, the extraction electrode 3 has a structure in which many fine holes 6a, 6b... 6n are formed in the center of a dish-shaped circular plate. The holes 6a, 6b... 6n have a hole diameter of, for example, several tens μm to several hundreds μm, and the center pitch P of the holes 6a, 6b. (Here, the thickness of the extraction electrode 3 is 10 μm, and the hole diameter is φ20.
μm and the pitch P is 40 μm). The pitch P of the holes 6a, 6b... 6n of the extraction electrode 3 and the pitch P of the projections 5a, 5b.

Therefore, by mechanically adjusting, the centers of the holes 6a, 6b... 6n of the extraction electrode 3 and all the projections 5a, 5b.
Are configured so as to be coaxial with each other, as shown in FIG.

[0023] Production of cathode 1, first crystals of LaB ₆ is formed in a cylindrical shape, machining a tip in a conical shape. Next, a flat surface is formed at the tip portion, and the surface is further processed so that a number of sharp projections 5a, 5b,..., 5n are formed as shown in FIG. At this time, the tip radius of the tops of the protrusions 5a, 5b,..., 5n is, for example, from sub μm to several μm (here, 2 μm). The projections 5a, 5b... 5n form 36 × 6 = 36 projections in the range of several hundred μm (here, 240 μm).

Referring to FIGS. 4A and 4B, FIG.
And projections 5a, 5b,.
The processing method of n will be described. As shown in FIG.
The tip of the diamond cutting tool 7 is formed in a conical shape. this
The tip of the diamond tool 7 is formed in advance on the tip of the cathode 1.
To cut a flat surface that has been formed linearly in the Y direction
Therefore, V groove V₁, V₂, ... V_nAt the same pitch P
Work. At this time, as shown in FIG.
H is set to be smaller than the opening width W of the first groove.
It is. Therefore, protrusions formed at the boundaries of adjacent grooves
(Linear) means that the cutting surfaces
Since it is formed by intersection, a sharp V-groove V ₁, V₂…
V_nIs formed as Next, the same processing is performed in the X direction.
By doing so, the projections 5a, 5b,.
n can be formed.

Next, the holes 6a, 6b,.
The processing method of n will be described with reference to FIG. The holes 6a, 6b... 6n of the extraction electrode 3 are processed by electric discharge machining. The electrode 8 of the electric discharge machine (not shown) is a cylindrical metal at the tip, and the diameter φ ₁ of the cylinder at the tip is slightly smaller than the hole diameter φ _{2 of} the holes 6a, 6b. It is thin. By using this electrode 8 and performing electrical discharge machining at predetermined positions of the extraction electrode 3 sequentially at a constant pitch, predetermined minute holes 6a, 6b... 6n can be formed.

Next, the operation of the electron gun having the above configuration will be described with reference to FIG.

In this case, for the sake of explanation, it is assumed that four projections 5a, 5b, 5c and 5d are formed at a pitch p at the tip of the cathode 1.

First, the cathode 1 is moved by a mechanism not shown.
Heat to 1500K-1800K. As a result, thermoelectrons are emitted from the projections 5a, 5b, 5c, and 5d at the tip of the cathode 1, and an electron cloud is formed at the tip of the cathode 1. In this case, since the projections 5a, 5b, 5c, and 5d are close to points, the optical conditions are stable, and there is little effect even if the fluctuation is increased.

In this state, +20 to 5 is applied to the extraction electrode 3.
A voltage of about 00V is applied. As a result, each protrusion 5a,
The electron beams emitted from 5b, 5c and 5d are extracted by the extraction electrode 3 and pass through holes 6a, 6b... 6n formed in the extraction electrode 3. These holes 6a, 6b
... by the electron beam and the second lead-out electrode 4 passing through the 6n, it was submitted further argument, respectively, spread as the electron beam _{B 1, B 2, B 3} , B 4.

Here, as shown in the graph of FIG. 7, when the voltage of the extraction electrode 3 is adjusted and the cathode emission current density Jc at the tip of the cathode 1 is set to be equal to or higher than the saturation current density Js, Schottky Due to the effect (the logarithm of the saturation current as a function of the square root of the anode voltage is linear), the energy spread ES of the electron beam is 5
It becomes smaller than eV.

Further, as shown in FIG. 6, the electron beam emitted from each of the projections 5a, 5b, 5c and 5d becomes an electron beam having _a diameter φa at the position La from the tip of the cathode 1, and the position of the position Lb in becomes the electron beam diameter phi _b. For this reason, the electron beams emitted from the large number of protrusions 5a, 5b, 5c, and 5d do not overlap each other in the section of La.
The sections b overlap each other. In this case, each 2
The overlap between the two electron beams is about 70%.

Under such an overlapping condition, Lb
Of the electron beams B ₁ , B ₂ , B
₃ , and B ₄ are equalized by the overlap, and as a whole, an electron beam having excellent in-plane uniformity is obtained.

Next, modifications of the above-described electron gun with respect to the electrode configuration and electrode structure / material will be described. In each example, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted.

First, a modification of the electrode configuration will be described.

(Modification 1) As shown in FIG. 8, in this case, the structure is such that the second extraction electrode 3 is removed. Thus, the electron beam from the cathode 1 is configured to overlap immediately in the vicinity of the extraction electrode 3.

(Modification 2) As shown in FIG. 9, in this case, the extraction electrode 3 is removed. Thus, the electron cloud at the tip of the cathode 1 is extracted only by the voltage applied to the extraction electrode 3.

Hereinafter, modifications of the electrode structure will be described. The electrode configuration in this case can be applied to the above-described embodiment and each of the modifications.

(Modification 3) In the arrangement of the projections 5a, 5b... 5n formed on the cathode 1 shown in FIG.
a, 5b... 5n are arranged at an equal pitch p in the XY directions.
And the same number of protrusions 5a, 5b... 5 in the X direction and the Y direction.
Although n is arranged, the arrangement direction may be different between the X direction and the Y direction, and the arrangement number may be different between the X direction and the Y direction.

(Modification 4) In the arrangement of the projections 5a, 5b... 5n formed on the cathode 1 shown in FIG.
5n are arranged in a grid in the X and Y directions.
The arrangement of the projections 5a, 5b... 5n may be a staggered arrangement as shown in FIG. 10, or any other arrangement may be used.

(Modification 5) The shapes of the holes 6a, 6b... 6n formed in the extraction electrode 3 shown in FIG. 2 are circular, but the shapes of the holes are not circular, as shown in FIG. The holes may be rectangular holes 6a ', 6b'... 6n ', and it is possible to use not only rectangles but also triangles and N-gons.
Further, the N polygon may be any N polygon other than the regular N polygon.

(Modification 6) In the extraction electrode 3 shown in FIG. 2 described above, holes 6a, 6b... 6n having the same diameter in the extraction electrode 3 are spatially formed in accordance with the spatial arrangement of the projections of the cathode 1. Although they are arranged, it is also possible to arrange them so that the diameters of the holes of the extraction electrodes 3 are different, or to arrange arbitrary figures.

Thus, the hole of the extraction electrode 3 is connected to the cathode 1
It is also possible to improve the in-plane uniformity by using a shape that depends on the spatial position of the projections. (For example, a method of changing the hole diameter at the periphery to the hole diameter at the center to increase the amount of electron beams at the periphery, etc.) (Modification 7) In the cathode 1 shown in FIG.
.. 5n were formed by mechanical grinding to form geometrically identical projections 5a, 5b. However, without being limited to this method, the surface can be formed by roughening the surface with diamond coating particles or the like as shown in FIG.

As a result, it is possible to produce a surface having many fine irregularities as shown in FIG. 12B and use the same as random projections to perform the same function.

(Modification 8) In the above embodiment, lanthanum hexaboride (Lab ₆ ) is used as the material of the cathode 1.
However, the material of the cathode 1 is not limited to this.
W (used at 2500-3000K), Ta (2300-3000K)
2500K), BaO (used at 1100-1300K) and the like can also be used.

According to each configuration described above, by using an electron beam simultaneously emitted from the multiple electron emission sources of the cathode as the illumination beam, the ES (energy dispersion) is small (5 eV or less) and the illumination is reduced. An electron source having excellent in-plane uniformity (uniformity of several percent or less) can be obtained.

The above-described exposure technique using an electron beam emitted from an electron gun can be used for direct drawing, reduced projection, step-and-repeat, and one-time batch projection.

An example used in an electron beam writing apparatus will be described below.

FIG. 13 is a structural view showing the structure of an electron optical system on which the electron gun 20 is mounted. Inside the housing, from above, the electron gun 20, the first forming aperture 21, the forming deflector 2
2, a second shaping aperture 23, a return deflector 24, a blanking electrode 25, a magnification correcting lens 26, a deflector and a focusing lens 27, and a processing chamber 28 are provided in this order.

A moving stage (not shown) for moving a sample is provided inside the processing chamber 28. This stage also has a laser interferometer (not shown) that accurately measures XY coordinates, and is driven by a motor to have a size of several tens to several nm. Positioning is performed with accuracy. The positioning is performed by detecting a mark provided on the moving table or the sample.

[0050] Here, in order to take out the current long stable in the electron gun 20, it is necessary to reduce the influence of the gas generated from the wafer as a sample, the differential pumping, the electron gun chamber 5 × 10 ^- It is configured to maintain a high vacuum of ⁹ Torr or more.

The control system transfers data from a computer (not shown) to the drawing control system via an interface. The drawing control system selects an aperture figure corresponding to the pattern to be drawn on the wafer from the second forming aperture 23,
The required voltage from which this can be selected is input to the shaping deflector 22, and the beam is returned on-axis by the swing-back deflector 24. The selected drawing pattern is imaged on the sample (wafer) surface using the magnification correction lens 26 and the focusing lens 27.

At this time, an image is formed after the focus of the focusing lens 27 is accurately adjusted based on the accurate distance measured in advance from the focusing lens 27 to the sample. The deflector formed in the focusing lens 27 also forms an image of the drawing pattern on a portion other than the axis. The minimum size of a pattern that can be drawn is limited by aberrations and blurs of the electron optical system, and is approximately 0.1%.
Dimensions below μm are possible.

At this time, a single drawing pattern on the sample is exposed with, for example, L μm × L μm (3 μm × 3 μm), and N · N ′ solid components (eg, 10 × 12) are deflected by the deflector in the focusing lens. It deflects and performs exposure. As a result, N ·
The exposure of the area of L μm × N ′ · L μm (30 μm × 36 μm) is completed. Next, the sample is moved on the moving stage,
On-axis exposure and deflection exposure are repeated, and the entire sample (for example, 1
It operates to complete the exposure of the entire surface of the 2-inch wafer).

As described above, by mounting the electron gun of the present invention on the electron beam lithography system, a variable acceleration type EB exposure system or a partial batch EB exposure system with a low acceleration method can obtain a high resolution (resolution). Better, less blur),
An exposure apparatus with less in-plane exposure unevenness (in-plane uniformity of exposure) can be realized.

[0055]

According to the present invention, it is possible to obtain an electron gun in which an electron beam emitted from a cathode forms an illumination beam having excellent uniformity on an exposure surface.

Further, by using the electron gun, an exposure apparatus and an exposure method having high resolution and less exposure unevenness can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a basic configuration around a cathode portion of an electron gun of the present invention.

FIG. 2 is an enlarged perspective view of the surface of a cathode and an extraction electrode of the electron gun of the present invention.

FIG. 3 is an explanatory diagram of a positional relationship between a projection of a cathode and a hole of an extraction electrode.

FIGS. 4A and 4B are explanatory views of a method for forming a projection of a cathode according to the present invention.

FIG. 5 is an explanatory view of a method for forming a hole in an extraction electrode according to the present invention.

FIG. 6 is an explanatory diagram showing the overlap of electron beams by the electrodes of the present invention.

FIG. 7 is an explanatory graph of the Schottky effect.

FIG. 8 is an explanatory view showing a modification of the electron gun of the present invention.

FIG. 9 is an explanatory view showing a modification of the electron gun of the present invention.

FIG. 10 is an explanatory view showing a modification of the electron gun of the present invention.

FIG. 11 is an explanatory view showing a modification of the electron gun of the present invention.

FIG. 12 is an explanatory view showing a modification of the electron gun of the present invention.

FIG. 13 is a configuration diagram showing a structure of an electron optical system of an electron beam writing apparatus equipped with the electron gun of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Suppressor, 3 ... Extraction electrode, 4 ... Second extraction electrode, 5a, 5b-5n ... Protrusion, 6a, 6b
~ 6n ... hole, 7 ... diamond tool

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/027 H01L 21/30 541B

Claims (7)

[Claims] 1. A cathode disposed in a vacuum vessel for generating an electron beam, an extraction electrode for extracting an electron beam generated by the cathode, and an electron beam generated by the cathode being accelerated in the beam axis direction. An electron gun comprising: an anode forming an electron beam passage; and a plurality of projections formed on a tip surface of the cathode. 2. The electron gun according to claim 1, wherein the plurality of protrusions have the same shape or a random shape. 3. The electron gun according to claim 1, wherein the extraction electrode has holes formed at positions corresponding to the protrusions formed on the tip end surface of the cathode. 4. The electron gun according to claim 1, wherein a second extraction electrode is provided in front of the extraction electrode along the beam axis. 5. The electron gun according to claim 1, wherein the cathode is formed of lanthanum hexaboride. 6. An exposure apparatus using the electron gun according to claim 1 as exposure means. 7. An exposure method, wherein a workpiece is exposed using the electron gun according to any one of claims 1 to 5.