JP2834873B2 - Electron beam exposure system - Google Patents

Description

The present invention relates to an electron beam exposure apparatus including an electrostatic deflector for deflecting an electron beam by an electric field, wherein an electron generated due to passing through the electrostatic deflector. The electron beam is deflected by an electrostatic deflector against an electrode constituting an electrostatic deflector, with the object of preventing blurring of the beam image and performing high-precision exposure. A voltage is applied so that the potential of the trajectory of the electron beam in the range along the optical axis is substantially the same as the potential of the inner surface of the lens barrel.

The present invention relates to an electron beam exposure apparatus used in an LSI manufacturing process or the like, and more particularly, to an electron beam exposure apparatus including an electrostatic deflector for deflecting an electron beam by an electric field.

[Prior Art] Conventionally, there has been proposed an electron beam exposure apparatus whose main part is shown in FIG.

In the drawing, reference numeral 1 denotes an electron gun, which is provided with a cathode electrode 2, a grid electrode 3, and an anode electrode 4.

Reference numeral 5 denotes an electron beam, 6 denotes a rectangular shaping aperture for shaping the electron beam 5 into a rectangle, 7 denotes an optical axis, 8 denotes an electromagnetic lens that converges the rectangularly shaped electron beam 5, 9 denotes a variable rectangular shaping deflector. , 10 are electromagnetic lenses for converting the electron beam 5 into a parallel beam.

Reference numeral 11 denotes a block mask (stencil mass). The block mask 11 is formed by forming various transmission patterns (block patterns) 13 on a substrate 12, as shown in FIG. FIG. 7 is a sectional view of the block mask 11.

In FIG. 5, reference numeral 14 denotes a mask deflecting unit for selecting a desired block pattern from among the block patterns 13 formed on the block mask 11, and the mask deflecting unit 14 comprises an electrostatic deflector. It is provided with four deflectors 15-18. Here, the electron beam 5 is
After being deflected in the direction of the selected block pattern 13 by 15 and then deflected in the vertical direction by the deflector 16,
It passes through the selected block pattern 13. The electron beam 5 that has passed through the block pattern 13 is deflected toward the optical axis 7 by the deflector 17 and then put on the optical axis 7 by the deflector 18.

Reference numeral 19 denotes an electromagnetic lens that converges the electron beam 5 converted into a parallel beam, 20 denotes a blanking electrode that controls blocking and passage of the electron beam 5, 21 denotes a reduction lens, 22 denotes an aperture aperture, and 23 and 24 denote projection lenses. , 25 a main deflector (main deflector) composed of an electromagnetic deflector, 26 a sub-deflector sub-deflector composed of an electrostatic deflector), 27 a wafer as a sample, 28
Denotes a wafer stage.

[Problems to be Solved by the Invention] By the way, each block pattern 13 to be formed on the block mask 11 has a size of several hundreds of μm square from the viewpoint of a manufacturing method, a reduction ratio of a lens to a sample surface, and the like. Therefore, depending on the number of the block patterns 13 formed on the block mask 11, the deflection amount of the electron beam required for selecting the block pattern 13 is several mm square. Here, the inventor used to perform the deflection of the electron beam 5 using an electromagnetic deflector having a high deflection efficiency. However, such an electromagnetic deflector has a problem that the response time of the coil is several hundreds of microseconds due to the influence of the inductance of the coil and the eddy current, so that the throughput cannot be improved. Then, the present inventor introduced an electrostatic deflector instead of the electromagnetic deflector in selecting the block pattern 13, and speeded up the time required for selecting the block pattern 13 to several μsec.

Here, the electrostatic deflector includes an electrostatic deflector for performing deflection in the X-axis direction and an electrostatic deflector for performing deflection in the Y-axis direction. FIG. 8 is a cross-sectional view of a so-called eight-pole type electrostatic deflector, which is an example of an electrostatic deflector that deflects in the X-axis direction. In the figure, 29 to 36 are electrodes, and these electrodes 29 to
The electrodes 36 are arranged at equal angular intervals at a distance R from the optical axis 7, and include electrodes 29 and 33, electrodes 30 and 32, electrodes 36 and 34.
Are the electrodes facing each other. FIG. 9 is a front view showing the electrode 29 and the electrode 33 as representatives.

Here, when the electron beam 5 is not deflected, the electrode
29 to 36 are all set to the ground potential, 0 [V]. On the other hand, when the electron beam 5 is deflected, the same positive or negative voltage corresponding to the amount of deflection and the position of each deflection electrode is applied to each counter electrode. For example, in the case of generating a deflection field in the X-axis direction is, for example, as shown in FIG. 10, is the electrode 29 + V _A [V] is applied, -V _A [V] to the electrode 33 Applied to the electrodes 30, 36 Is applied, and the electrodes 32 and 34 are Is applied. The potentials of the electrodes 31 and 35 are always 0.
[V]. The lower part of FIG. 10 shows the relationship between the position in the X-axis direction and the potential in this example.

However, it has been found that when an electrostatic deflector is used for selecting the block pattern 13 as described above, an electron beam image formed on the wafer 27 is not negligibly blurred. Here, in the mask deflecting unit 14, when the electron beam 5 passes through the first and fourth deflectors 15 and 18, it passes near the optical axis 7, but the second and third stages. When the light passes through the deflectors 16 and 17, the light passes through a portion distant from the optical axis 7, that is, a portion where the electric field is not uniform.

The inventor of the present invention considers that the deflectors 16 and 17 may cause blurring because the electron beam 5 passes through a portion away from the optical axis 7 where the electric field is not uniform.
The number of electrodes constituting 16 and 17 was increased, for example, a 16-pole configuration or a 32-pole configuration, and the distance between the facing electrodes was increased to ensure the uniformity of the electric field in the portion where the electron beam 5 passes. However, despite such measures, blurring of the electron beam image has not been resolved.

Meanwhile, such an electron beam exposure apparatus includes a main deflector 25 composed of an electrode deflector and a sub deflector 26 composed of an electrostatic deflector in order to deflect and scan the electron beam 5 on the wafer 27. It has been found that the aberration due to the deflection has a cubic function of the deflection amount, and that the larger the deflection amount, the larger the deflection aberration. Therefore, when the deflection amount is large, it is necessary to correct the aberration. Here, in the case of electrode deflection, since the response speed is slow, it is possible to perform correction according to the deflection amount,
In the case of electrostatic deflection having a response speed of nano (n) seconds, correction according to the deflection amount is practically impossible. Therefore, in general, a method is adopted for electrostatic deflection in which the deflection area is reduced, the aberration of the electron beam 5 is reduced, and no correction is performed.

By the way, a pattern that is largely deflected by electromagnetic deflection and then drawn by electrostatic deflection has an aberration correction by large deflection compared to a pattern drawn by only electrostatic deflection without large deflection by electromagnetic deflection. Regardless,
In addition, it was found that aberration occurred, and this caused blurring of the electron beam image.

Therefore, the inventor increased the number of electrodes constituting the sub-deflector 26 and increased the distance between the opposing electrodes in the same manner as in the case of the mask deflecting unit 14 so that the electric field in the portion through which the electron beam 5 passed was increased. Ensured uniformity. However, despite taking such measures, the aberration of the electron beam 5,
Therefore, blurring of the electron beam image has not been eliminated.

As a result of research and experiments according to the present invention, blurring of the electron beam image caused when the electron beam 5 passes through a portion of the electrostatic deflector distant from the optical axis 7 is caused by the acceleration electric field generated accompanying the deflection electric field. It was found that this was due to the beam 5 undergoing acceleration.

To explain this point in detail, the inner surface of the lens barrel is a conductor,
For example, it is formed of chromium or nickel and has a ground potential. This is to prevent charges from accumulating on the inner surface of the lens barrel, thereby generating an electric field (acceleration electric field) and preventing the electron beam 5 from being accelerated. However, the deflector 9, 15-1
In the electrostatic deflectors 8 and 26, the same positive and negative voltages are applied to the opposing electrodes as shown in FIG. 10 so that the optical axis 7 is set to the ground potential. The portion away from 7 has a potential proportional to the distance, and an accelerating electric field is generated between the portion and the inner surface of the lens barrel. Therefore, in the deflectors 16, 17, and 26, when the electron beam 5 passes through a portion distant from the optical axis 7, an acceleration electric field proportional to the potential of the portion is affected. For example, in the example of FIG. 10, when the electron beam 5 passes through the position of the coordinate L on the X axis, the electron beam 5
Was affected by the electric field due to the potential L / R · _VA , which was found to be the cause of the blur in the electron beam image.

In view of the foregoing, the present invention has been made to prevent an electron beam image from being blurred due to passing through an electrostatic deflector, thereby enabling high-precision exposure. An object of the present invention is to provide an exposure apparatus.

[Means for Solving the Problems] An electron beam exposure apparatus according to the present invention is an electron beam exposure apparatus including an electrostatic deflector for deflecting an electron beam by an electric field. Then, a voltage is applied so that the potential of the trajectory of the electron beam in the optical axis direction range in which the electron beam is deflected by the electrostatic deflector becomes substantially the same as the potential of the inner surface of the lens barrel. is there.

[Operation] In the present invention, when the electron beam passes through the electrostatic deflector, it passes through a portion having substantially the same potential as the potential of the inner surface of the lens barrel. That is, it passes through a part where the acceleration electric field is extremely weak or a part where the acceleration electric field does not exist. Therefore, blurring of the electron beam image caused by passing through the electrostatic deflector does not occur.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In this embodiment, an electrostatic deflector called a variable axis electrostatic deflector is used as a part of the deflector.

FIG. 1 shows the arrangement of the electrodes 37 to 44 of the variable-axis electrostatic deflector for performing deflection in the X-axis direction in the variable-axis electrostatic deflector (central cross-sectional view) and the variable-axis electrostatic deflector. FIG. 5 is a diagram showing the relationship between the position in the X-axis direction and the potential, and the physical configuration of the electrodes 37 to 44 of this variable axis electrostatic deflector is the same as the electrodes 29 to 36 ( (See Fig. 8)
The difference is that, among the electrodes 37 to 44, the opposing electrodes 37, 41, and 38
For 40, 44 and 42, the voltage corresponding to the deflection amount and the potential of the trajectory of the electron beam 5 are the potential of the lens barrel, that is, the ground potential,
The point is that the sum of the voltage and the voltage proportional to the amount of deviation of the electron beam 5 from the optical axis 7 is applied. That is, generally, an electric field of V _X / R is required as an electric field in the X-axis direction corresponding to the deflection amount, and the electron beam 5 is positioned on the X-axis at the coordinate x
(This can be calculated from the deflection position data), the following electrodes are applied to the electrodes 37-42.

For example, as in the case of the conventional example shown in FIG. 10, when an electric field of V _A / R is required as the electric field in the X-axis direction and the electron beam 5 is incident on the coordinate L on the X-axis, each electrode 37 ~ 42
As shown in FIG. 1, the following voltages are applied.
In FIG. 1, a two-dot chain line X is a line indicating the potential in the case of the conventional example shown in FIG.

It should be noted that 0 [V] is still applied to the non-opposing electrodes 39 and 43 as in the case of the conventional example in FIG. Further, a variable axis electrostatic deflector for deflecting in the Y-axis direction is similarly configured.

In the present embodiment, such a variable axis electrostatic deflector is provided, for example, as shown in FIG.
As shown in FIG. 3, the deflectors 16 and 17 in the first stage are applied to the sub deflector 26, and the other parts are configured in the same manner as the conventional example in FIG. In FIG. 3, 45,
46 and 47 are electromagnetic coils that constitute the main sub deflector 25. Here, regarding the deflector 9 for variable rectangular shaping and the first and fourth deflectors 15 and 18 of the mask deflecting unit 14, since the electron beam 5 passes near the optical axis 7, it is the same as the conventional one. It is sufficient to use a normal electrostatic deflector.

According to this embodiment, the electron beam 5 is deflected by the deflector 16,
In the case where the electron beam 5 passes through the portion 17 and the sub-deflector 26 and passes through a portion distant from the optical axis 7, the trajectory of the electron beam 5 is maintained at substantially the ground potential, 0 [V].
The electron beam 5 is not affected by the accelerating electric field, and the electron beam image formed on the wafer 27 is not blurred. Therefore, highly accurate exposure can be performed.

As shown in FIG. 4, even when the main deflector 25 and the sub deflector 26 are constituted by electrostatic deflectors and the sub deflector 26 is arranged below the main deflector 25, the present invention is applied to the sub deflector 26. Can be applied. That is, a variable axis electrostatic deflector can be applied to the sub deflector 26.

[Effects of the Invention] As described above, according to the present invention, the potential of the trajectory of the electron beam in the optical axis direction range in which the electron beam is deflected by the electrostatic deflector is applied to each electrode of the electrostatic deflector. By adopting a configuration in which a voltage that is substantially the same as the potential of the inner surface of the lens barrel is applied, when the electron beam passes through the electrostatic deflector, the portion of the electron beam has a potential that is substantially the same as the potential of the inner surface of the lens barrel. In other words, the electron beam passes through a part where the acceleration electric field is extremely weak or a part where the acceleration electric field is absent, so that blurring of the electron beam image caused by passing through the electrostatic deflector does not occur, and high precision Exposure can be performed.

[Brief description of the drawings]

FIG. 1 shows the arrangement of the electrodes of the variable axis electrostatic deflector for deflecting in the X-axis direction in the variable axis electrostatic deflector used in one embodiment of the present invention, and the X in the variable axis electrostatic deflector. FIG. 2 is a diagram showing a relationship between an axial position and an electric potential, FIG. 2 is a conceptual diagram showing a mask deflecting unit according to an embodiment of the present invention, and FIG. 3 is a main deflector and a sub deflector according to an embodiment of the present invention. FIG. 4 is a conceptual diagram showing a main deflector and a sub deflector according to another embodiment of the present invention. FIG. 5 is a conceptual diagram showing a main part of a conventional electron beam exposure apparatus. FIG. 5 is a plan view of a block mask used in the conventional electron beam exposure apparatus of FIG. 5, FIG. 7 is a sectional view of a block mask used in the conventional electron beam exposure apparatus of FIG. FIG. 5 shows an electrostatic deflector used in a conventional electron beam exposure apparatus. ,
9 is a cross-sectional view at the center of the electrostatic deflector in the X-axis direction. FIG. 9 is a front view showing a set of counter electrodes in the electrostatic deflector of FIG. 8 as an example. FIG. 10 is an example of FIG. FIG. 5 is a diagram showing a relationship between a position in the X-axis direction and a potential in the electrostatic deflector of FIG. 37-44 …… Electrode of variable axis electrostatic deflector

Continuation of the front page (56) References JP-A-62-273720 (JP, A) JP-A-59-121926 (JP, A) JP-A-58-71545 (JP, A) JP-A-53-134369 (JP) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027

Claims (3)

(57) [Claims] 1. An electron beam exposure apparatus comprising an electrostatic deflector for deflecting an electron beam by an electric field, wherein the electron beam is applied to an electrode constituting the electrostatic deflector by the electrostatic deflector. An electron beam exposure apparatus, wherein a voltage is applied so that the potential of the trajectory of the electron beam in the optical axis direction range that receives the deflection force is substantially the same as the potential of the inner surface of the lens barrel. 2. A voltage applied to each electrode of the electrostatic deflector generates an electric field having a strength necessary for deflecting an electron beam, and the potential on the optical axis becomes substantially the same as the potential on the inner surface of the lens barrel. The voltage applied to each of the electrodes is common to the electrodes in proportion to the amount of deviation of the electron beam from the optical axis such that the potential of the trajectory of the electron beam becomes substantially the same as the potential of the inner surface of the lens barrel. 2. The electron beam exposure apparatus according to claim 1, wherein the sum is the sum of the voltage and 3. The electron beam exposure apparatus according to claim 2, wherein a voltage common to said electrodes is calculated from deflection position data of said electron beam.