JPH0353736B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device for electrostatic deflection of charged particle beams. In general, electrostatic deflection devices are widely used in electron beam exposure devices, electron microscopes, cathode ray tubes, image pickup tubes, and the like to deflect beams at high speed and precision or to adjust the cross-sectional shape of beams. In an electrostatic deflection device used in such fields, in order to widen the deflection range, it is desirable that the deflection electric field has a cosine distribution to minimize deflection aberration over a wide range. Conventionally, such a deflection device is a multipole type electrostatic deflection device in which 12 electrode elements D ₁ to D ₁₂ are insulated and sequentially arranged at equal intervals on the circumference, as shown in Fig. 1. The device is known (Japanese Unexamined Patent Application Publication No. 1983-1999)
(Refer to Publication No. 134369). As shown in the figure, a deflection voltage +V _x in the X direction is applied to four electrode elements D ₂ and D ₁₂ , D ₆ and D ₈ facing each other at a central angle of 60°,
−V _{x is} printed _{, and} Y _- direction deflection voltage +V _y , −
Apply V _y and ground the remaining four electrode elements (zero)
By setting it as a potential, the deflection electric field has a cosine distribution. In this case, 3 for the angular coordinate θ of the potential distribution
The following Fourier component (electric field component involved in third-order aberration) can be removed. However, in this multipole electrostatic deflection device, since the four electrode elements are grounded electrodes, the deflection sensitivity tends to be poor. Furthermore, terms of fifth order or higher are supposed to remain in the high-order Fourier components. By eliminating the terms of fifth order or higher, aberrations can be reduced over a wider range. As a result of extensive research into electrostatic deflection devices, the present inventors have found that, without providing a ground electrode, not only the third-order electric field component with respect to the angular coordinate θ of the potential distribution, but also the
It has been found that an electrostatic deflection device can be obtained which can also remove higher-order electric field components such as fifth-order, seventh-order, and ninth-order electric field components. That is, the present inventors installed a hollow cylindrical electrode 4+8 m (m=1, 2, 3, 4) parallel to its central axis.
The strips obtained by dividing into pieces are alternately
The strip forming the deflection electrode in the It has been found that this can be achieved by arranging them in a positional relationship. Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.
FIG. 2A is a perspective view showing the hollow cylindrical electrode 1 in an xy section perpendicular to the central axis 2. FIG. Now, ± on the x-axis
The hollow cylindrical electrode is divided into four strips by two straight lines that intersect at α, and each strip is called D ₁ , D ₂ , D ₃ , and D ₄ . As shown in Figure 2B, +1 ^V to D ₁ and - to D ₃ .
When 1 ^V is applied and D ₂ and D ₄ are O ^V , the potential V ₁ θ along the strip on the circumference is expressed by the following formula from the Fourier expansion formula regarding the angular coordinate θ. V ₁ (θ)=4/π _∞ 〓 〓 ⁿ⁼⁰ 1/2n+1cos(2n+1)θ・sin(2n+1)α……(
1) Also, as shown in Figure 3, the potential V ₂ when the electrode configuration in Figure 2 is rotated counterclockwise by β
(θ) is V ₂ (θ)=4/π _∞ 〓 〓 ⁿ⁼⁰ 1/2n+1cos(2n+1)(θ−β)・sin(2n+1
)α...(2). Conversely, as shown in Figure 4, the potential when the electrode configuration in Figure 2 is rotated clockwise by β
V ₃ (θ) is V ₃ (θ)=4/π _∞ 〓 〓 ⁿ⁼⁰ 1/2n+1cos(2n+1)(θ+β)・sin(2n+1
) α...(3). Furthermore, as shown in Figure 5, the potential V ₄ (θ) in the case of an electrode configuration consisting of 12 strips can be calculated by adding equations (1), (2), and (3) from the principle of superposition. By combining, V ₄ (θ)=4/π _∞ 〓 ⁿ⁼⁰ 1/2n+1 {cos(2n+1)θ・sin(2n+1)α ₀ +cos(2n+1)(θ−β ₁ )・sin(2n+
1) α ₁ + cos (2n + 1) (θ + β ₁ )・sin (2n + 1) α
₁ }
...(4) It is expressed as. In equation (4), when θ = 0, it represents the voltage at the point where the electrode and the X-axis intersect, but if the radius of the cylinder is the unit of length, this value is -
It represents the strength of the electric field in the x direction [(5)
formula〕. V ₄ (O)=4/π _∞ 〓 ⁿ⁼⁰ 1/2n+1 {sin (2n+1) α ₀ +2cos (2n+1) β ₁・sin (2n+1) α ₁ } ...(5) In Fig. 5, α ₀ = 25°, α ₁ = 10°, and β ₁ = 55°, each component of θ is as shown in Table 4 for n = 0, 1, and 2 from equation (5), and the 3θ component is removed. .

[Table] Also, as shown in Figure 6, 20 strips D ₁ ,
In the electrode configuration consisting of D ₂ ...D ₂₀ , D ₁ , D ₃ ,
+X ^V , D 7 , D ₉ , D ₁₁ on the strips _{D 5} , D ₁₉ , D ₁₇ ,
When applying a deflection voltage of -X ^V to the strips D ₁₃ and D ₁₅ and setting the other strips to O ^V , α ₀ = 11.67°, α ₁ = 11.83°,
If α ₂ = 4.84°, β ₁ = 34.17°, and β ₂ = 73.49°, then
Table 2
As shown in , among the electric field components related to θ, 3θ and
The 5θ component is removed.

[Table] Also, as shown in Figure 7, 28 strips D ₁ ,
In the electrode configuration consisting of D ₂ ...D ₂₈ , D ₁ , D ₃ ,
+X ^V , D ₉ on the strips D ₅ , D ₇ , D ₂₃ , D ₂₅ , D ₂₇ ;
When a deflection voltage of -X ^V is applied to the strips D ₁₁ , D ₁₃ , D ₁₅ , D ₁₇ , D ₁₉ , and D ₂₁ and the other strips are set to O ^V , α ₀ = 2.38° α ₁ = 19.39゜ β ₁ = 11.63゜ α ₂ = 51.99゜ β ₂ = 6.99゜ α ₃ = 84.93゜ β ₃ = 2.69゜. components are removed.

[Table] Also, as shown in Figure 8, 36 strips D ₁ ,
In the electrode configuration consisting of D ₂ ...D ₃₆ , D ₁ , D ₃ ,
+ on strips D ₅ , D ₇ , D ₁₁ , D ₂₇ , D ₃₁ , D ₃₃ , D ₃₅
^XV , _D9 , _D13 , _D15 , _D17 , _D19 , _D21 , _D23 , _D27
Apply a deflection voltage of −X ^V to one strip, and apply a deflection voltage of −X V to the other strip.
When set to O ^V , α ₀ = 1.94° α ₁ = 12.54° β ₁ = 8.14° α 2 = 37.27° β ₂ = 7.74° α ₃ = 64.90° _{β 3 =} 4.43° α ₄ = 87.24° β ₄ = 1.42 As shown in Table 4, 3θ, 5θ, 7θ, and 9θ components are removed from among the electric field components related to θ.

[Table] Regarding the deflection electric field distribution in the Y direction, the phase is only changed by 90°, and the 3θ, 5θ, 7θ, and 9θ components are removed as in the case of the X direction described above. The deflection sensitivity is 0.792 for 12 poles in Figure 5, 0.755 for 20 poles in Figure 6, 0.738 for 28 poles in Figure 7, and 0.738 for 36 poles in Figure 8.
The result was 0.729, which was found to be superior to that of the conventional device shown in FIG. 1, which was approximately 0.571. As explained above, the electrostatic deflection device of the present invention, like the conventional electrostatic deflection device shown in FIG. Since a voltage is applied, the charged particle beam can be deflected with high precision and speed, which is not only effective, but also reduces not only third-order aberrations but also higher-order Fourier components that are involved in higher-order aberrations. Since it can be removed, it has the effect of allowing deflection with less aberration over a wider range. Furthermore, since no ground electrode is provided and all the strips are configured as deflection electrodes, there is an advantage of superior deflection sensitivity.

[Brief explanation of drawings]

Fig. 1 is a plan view of a conventional electrostatic deflection device, Figs. 2 to 4 are illustrations explaining the principle of the present invention, and Figs. 5 to 8 show embodiments of the electrostatic deflection device of the present invention. Plan view. Symbols in the figure: 1...Hollow cylindrical electrode, 2...Central axis, _D1 to _D36 ...Strip.

Claims (1)

[Claims] 1 4+8m (m=1, 2, 3, 4...) strips are arranged at intervals on the circumference, every other strip constitutes a deflection electrode in the X direction, and the remaining one The placing strip constitutes a deflection electrode in the Y direction, and the strip constituting the deflection electrode in the X direction and the strip constituting the deflection electrode in the Y direction are arranged at an angle of 45° from the X and Y axes. Electrostatic deflection devices characterized in that they are symmetrically related to each other about an axis of angular position.