JPS5983336A - Device for focusing and deflecting charged particle ray - Google Patents

Abstract

PURPOSE:To reduce deflectional aberration on the surface to be irradiated by placing a first and a second deflector within an electromagnetic lens system, and performing selection so that one of deflectional chromatic aberration, deflectional comatic aberration and vertical incidence error becomes zero. CONSTITUTION:An electron beam is focused on a drawing material 9 by means of an erosion electromagnetic lens 1 having a short focus and consisting of a yoke 2 and an excitation coil 3 as well as an electromagnetic projection lens 4 consisting of a yoke 5 and excitation coils 6a-6d. At the same time, the beam is deflected according to deflection voltages supplied to a first and a second deflector 7 and 8 changing an area of the material 9 irradiated by the beam. On the other hand, a large deflection signal and a small deflection signal are produced from an electronic computer 17. The large deflection signal is supplied to the first deflector 7 through a DA converter 12, and supplied to the second deflector 8 through a deflection-signal controlling circuit 13 and a DA converter 14. The small deflection signal is supplied to a third deflector through a DA converter 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charged particle beam focusing/deflecting device that can minimize the influence of aberrations accompanying the deflection even if the charged particle beam is deflected at a large angle.

Expanding the deflection range of the charged particle beam in an electron or ion beam drawing system reduces the number of movements of the drawing material, which takes significantly more time than deflection of the charged particle beam. Therefore, it is the most important factor in improving throughput to 1. However, as the deflection range is expanded, the problem of oblique incidence of the electron beam onto the material cannot be ignored, and various aberrations increase, making it difficult to draw fine figures with high precision.

In the invention disclosed in JP-A No. 5/1132962, at least three stages of electrostatic deflection electrodes are arranged in a rotationally symmetrical magnetic field having a similar axial distribution, and the position of each electrode is adjusted.

Parameters such as width, inner diameter, and applied voltage are selected to reduce oblique incidence of the charged particle beam and various aberrations. In theory, this invention can eliminate the effects of oblique incidence of charged particle beams and reduce chromatic aberrations, comatic aberrations, etc. to the extent that they can be ignored in practice. However, in practice, the configuration requires a large number of deflectors. However, it has been found that the present invention has the following drawbacks: In manufacturing the device, the work and assembly of the deflection electrodes cannot necessarily be performed with the accuracy required for this invention. Since this cannot be done, errors will occur in the size of the deflector, inner diameter 1 position, etc. after assembly.In order to correct this error, other parameters, such as the voltage applied to each deflector, may be It is necessary to readjust the voltage, magnetic field strength, etc., but it is difficult to find the optimal values of the voltage and magnetic field strength through readjustment. In addition, in this invention, correction of nonlinear aberrations, that is, deflection astigmatism and deflection curvature aberration, is extremely difficult due to the large number of deflection angles. Since this is done by so-called dynamic correction supplied to the device, the control circuit for creating the correction voltage is complex and expensive.Furthermore, as a matter of course, there are manufacturing errors in some of the parameters mentioned above. Therefore, the dynamic correction voltage must also be changed from a theoretical value determined in advance, but the correction voltage is determined by nl calculation for each deflector according to the deflection angle, and such minute It is almost impossible to add compensation for eliminating the error to all the correction voltages required for each deflector for each angle.

The present invention has been made in view of the above point, and is a charged particle beam focusing/deflecting device that has a simple structure that can extremely minimize aberrations even when a charged particle beam is deflected at a large angle, and does not require dynamic correction. I will provide a.

The inventor investigated in detail the relationship between the magnitude of aberration of a focusing/deflecting system and parameters such as the size and position of the deflector, applied voltage, etc., using a large electronic 81 calculator. The first and second deflectors are arranged at They discovered that by supplying a fixed deflection voltage, the total deflection aberration on the surface where the charged particle beam is irradiated can be reduced to a range that does not pose a practical problem, and has completed the present invention. reached.

A charged particle beam focusing/deflecting device according to the present invention includes a reduction electromagnetic lens for focusing a charged particle beam on a desired surface, a projection electromagnetic lens disposed after the reduction electromagnetic lens, and an image of the reduction electromagnetic lens. a first electrostatic deflector disposed near the object surface of the projection electromagnetic lens; a second electrostatic deflector disposed in the magnetic field formed by the projection electromagnetic lens; and a second deflector to deflect the charged particle beam, and supply a deflection voltage to the first and second deflectors in order to change the irradiation position of the charged particle beam on the desired surface. the ratio of the voltages supplied to the first deflector and the second deflector, the deflection direction of the charged particle beam by the first deflector and the second deflector; The angle formed with the deflection direction of the charged particle beam is selected such that any one of deflection chromatic aberration, deflection coma, or vertical incidence error of the charged particle beam on the desired surface becomes zero.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an electron beam focusing/deflecting device according to the present invention, and FIG. 2 shows the axial magnetic field distribution of the electromagnetic lens system used in the device of FIG. In the figure, 1 is the yoke 2, the excitation coil 3j, and a short focus reduction electromagnetic lens, and 4 is the yoke 5 and the four excitation coils 6a, 6b, 6.
This is a projection electromagnetic lens consisting of c and 6d. A strong excitation current is passed through the reduction electromagnetic lens 1, and a distribution r41 shown by Ml in FIG. 2 is formed. The yoke 5 of the projection electromagnetic lens 4 is shaped so that four gaps are formed between them. Excitation: Excitation currents are separately supplied to the coils 5a to 6d (box excitation) 41. By appropriately adjusting the currents (distribution M4 in Figure 2 Within the range, it is possible to obtain a desired magnetic field distribution 5, for example, a substantially uniform magnetic field distribution of 1q.If the number of gaps and excitation coils is increased and the respective excitation currents are adjusted, J. A desired magnetic field distribution can be obtained.The two electromagnetic lenses are arranged so that the image plane position of the reduction electromagnetic lens 1 and the object plane position of the projection electromagnetic lens 4 substantially match. A first electrostatic deflector 7 is arranged near the image plane (position O, link 1) of the electromagnetic lens 1 and the object plane position of the projection electromagnetic lens 4, and
A second electrostatic deflector 83 is disposed in the magnetic field formed by the projection lens 4 . Although both deflectors are shown as two deflection plates in FIG. 1, in reality, as shown in FIG. "To 8"; lf6 has been created. The number of electrodes constituting each deflector may be, for example, four, but in order to deflect the electron beam in an accurately determined direction,
It is preferable to have multiple poles such as 8 poles or 12 poles. The electron beam is focused onto a material 9 such as a material to be imaged by the electromagnetic lenses 1 and 4, and the electron beam is focused in accordance with the deflection voltages supplied to the first and second deflectors 7 and 8. The electron beam is deflected, and the irradiation position of the electron beam on the material 9 is changed. Note that a third deflector 10 is disposed between the first and second deflectors; Used to deflect an artificially deflected electron beam within a minute area.11
is an electronic calculation, and the electronic calculation fX111 generates a large deflection signal and a small deflection signal, and the large deflection signal is DA
The small deflection signal d3 is supplied to the first deflector 7 via the converter 12, and is also supplied to the second deflector 8 via the deflection signal adjustment circuit 13 and the DA converter 14. is supplied to the third deflector via the DA converter 15.

Now, in the above-mentioned configuration, the present inventor used the orbit Δl of the electron beam when each deflector was not operated and the orbit CI when the 1st and 20th) deflections were not operated;
'4'', '; Calculate each aberration using an electronic calculator. Then, the deflection voltage applied to the first deflector 7 and the deflection voltage applied to the second deflector 8 While fixing the applied deflection voltage to a certain value, the relative deflection angle (to which the deflection direction of the first deflector 7 and the deflection direction of the second deflector 8) is set to a certain value. Mr'Frl shows that even if the deflection voltage value is fixed, any one of the deflection color 11v, difference, deflection]711V, difference, or vertical incidence error of electronic uniformity to the material becomes zero. ICo Nao, 1st
The electron beam entering the electromagnetic lens system shown in the figure is focused by the electromagnetic lens, and is also subjected to deflection and rotation effects. As a result, in order to deflect the electron beam in the direction shown by the arrow J shown in FIG. J to 8,
It must be deflected in the direction of arrow 1 (arrow 1).

The 1° angle θ between the direction of the arrow D1 and the direction of the arrow D4 is the above-mentioned relative deflection angle. Furthermore, the present inventor determined the center positions of the first and second deflectors and configured the deflector at the deflection voltage ratio and the angle θ such that any one of deflection chromatic aberration, deflection coma aberration, or vertical incidence error becomes zero. When the length of the electrode is changed using an arbitrary parameter and a simulation is performed using an example of electronic calculation, it is found that when the arbitrary parameter has a certain value, other deflection aberrations or normal incidence error σ) l- It was discovered that one barrel becomes extremely small. Note that the value of this optimal arbitrary parameter changes depending on the strength of the magnetic field by the electromagnetic lens, the ratio of the voltages applied to the eight deflectors, and the relative deflection angle.

Here, an example of the above simulation is not shown in Table 1.

Regarding the robe, A, B, and C are simulation results when deflection comatic aberration, deflection chromatic aberration, and vertical incidence error are respectively set to zero. The unit of each aberration is pH, except for the case of J3 in the vestibule, where the unit of normal incidence error is radian. or,
The total aberration in the table does not include distortion, but this may be due to distortion, or the already common system in which the necessary correction voltage according to the deflection voltage is multiplied by Φ. This is because it can be removed independently using existing techniques.

Table 1 Note that the above stain corrosion occurs when the electron beam acceleration type j-1 is 20 kV, the electron beam energy spread is 20 V, and 4. f
The hearing angle of the electron beam J3 Cj on the l slope surface is 5 × 10-3
radian, the shape of the electron beam on the object plane of the electromagnetic lens system is a square with sides of 10 + rW, and the deflection area on the gain plane is 1.
This is performed under the square condition of 0 mn+, and the value of each aberration is the value at the corner of the deflection area.

As is clear from Table 1 above, the sum of all aberrations can be made extremely small in any case of A, B, and C.

In particular, if the first and second deflectors have voltage ratios and relative deflection angles that eliminate deflection chromatic aberration, the total aberration value can be significantly reduced to 0.175 pm, and the iQn+n+ angle can be significantly reduced. Even in the deflection area, 1 for 4 with movement of monthly interest
It becomes possible to draw with knob micron precision. An example of an electromagnetic lens system and an electrostatic deflection system that have zero deflection chromatic aberration is as follows.

Distance between object surface and shrine slope: 300mm
Reduction ratio of reduction electromagnetic lens 1/3 1st
Electrode length of the second deflector: 30mm Electrode length of the second deflector: 9Qn+
m Relative rotation angle between both deflectors...28° Ratio of voltage applied to both deflectors...1:2 Here, in the embodiment shown in FIG. The circuit 13
The voltage value applied to the second deflector 8 is always 248 by multiplying the voltage value applied to the second deflector 7 by 3×1, and the second deflector and the first deflector The relative rotation angle with
It is adjusted to J, which is °. If a large deflection signal and a small deflection signal corresponding to the drawn J-beg pattern are supplied to each deflector from this state C electron cutting board 11, an electron beam with extremely small aberration is projected onto the electron beam, and a fine patterns are drawn with high precision. Note that although no special correction is applied to the deflection voltage applied to the third deflector 9, the deflection by the third deflector 9 is in a minute area with an extremely limited deflection range. Ignoring the aberration caused by 1q.

As described in detail below, the present invention has a simple structure with a two-stage deflector. ,l
i ID 4t4, and furthermore, even if the electron beam is deflected by a large angle, the aberration caused by the deflection can be kept within a range that does not pose a practical problem, without the need for dynamic correction. In addition, even if there is a processing error or an assembly error during the manufacturing of the device, there are only two adjustment parameters: the ratio of the voltage applied to both deflectors and the relative rotation angle, and dynamic correction is also performed. Therefore, if the voltage ratio and rotation angle are slightly changed around the predetermined values, it is possible to find the best value with the least amount of aberration, so the error can be corrected. It can be easily performed. Therefore, if the focusing/deflecting device based on the present invention is incorporated into an electron beam lithography device, its practical value will be extremely large. Note that the above-mentioned embodiments have been explained using an electron beam as an example. However, the present invention can also be applied to ion beams.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing the axial magnetic field distribution of the electromagnetic lens system according to the embodiment shown in Fig. 1, and Fig. 3 is a diagram showing the static A diagram showing the IJJi surface shape of the electron deflector, Figure 4 shows the deflection direction of the electron beam on the material surface and the first and second
FIG. 1: Reduction electromagnetic lens 4: Projection electromagnetic lens 7.8.10: Electrostatic deflector 9: 1. 12.14.15: Electronics 51 12.14.15: DA converter 13: Deflection signal adjustment circuit Patent applicant: Raiko Hiki Co., Ltd. Representative: Ito-huu RIKEN Chairman: Tatsuoki Miyajima

Claims (1)

[Claims] 1.11 A reduction electromagnetic lens for focusing the electron beam on a desired surface, a projection electromagnetic lens disposed in contact with the reduction electromagnetic lens, and an image plane of the reduction Wi magnetic lens. is located near the object surface of the projection electromagnetic lens/: ff+1
a second electrostatic deflector disposed in the enclosure formed by the projection electromagnetic lens, and the first and second deflectors to deflect the charged particle beam and to avoid deflection of the charged particle beam. a circuit for supplying a deflection voltage to the first and second deflectors in order to avoid changing the irradiation position of the charged particle beam on the surface, the first deflector and the second deflector; and the angle between the direction of deflection of the charged particle beam by the first deflector and the direction of deflection of the charged particle beam by the second deflector on the desired surface. Deflection Chromatic Aberration and Deflection of Charged Particle Beam] 7. A charged particle beam focusing/deflecting device characterized in that either the convergence error or the normal incidence error is zero. 2. The projection electromagnetic lens has a plurality of gaps between magnetic poles, and excitation coils corresponding to the gaps are installed.
By adjusting the excitation current supplied to the excitation coil, a desired magnetic field is formed. 3. Claims 1 and 2, wherein the first and second deflectors perform deflection at a relatively large angle, and the third deflector performs deflection at a minute angle. The charged particle beam focusing and deflecting device described above.