JPH0344916A - Electron beam irradiating apparatus - Google Patents

Abstract

PURPOSE:To irradiate a target with an electron beam at a correct position accurately at a high speed by simulating an electron beam irradiating position error due to an eddy current by a correcting circuit, and correcting a current supplied to an electromagnetic deflection lens. CONSTITUTION:A correcting circuit 21 simulates an electron beam irradiating position error due to an eddy current generated in a structure, etc., near an electromagnetic deflection lens 3 by electromagnetic induction due to a current flowing to the lens 3 by an electric circuit and corrects it. A signal based on pattern data of a computer 9 is input to the circuit 21 through a digital controller 10, and a D/A converter 11, a corrected signal is supplied to the lens 3 through an electromagnetic deflection amplifier 4, and an electron beam 2 is deflected by the corrected magnetic field. Accordingly, a target 8 is irradiated with the beam 2 at a correct position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam irradiation device that irradiates a predetermined position on a target with an electron beam.

[Conventional technology]

FIG. 5 is a block diagram of a deflection system of a conventional electron beam irradiation device disclosed in, for example, Japanese Unexamined Patent Publication No. 59-124719. In the figure, (1> is an electron gun, and (2) is an electron gun (
Electron beam emitted from 1), (3) an electromagnetic deflection lens that generates a magnetic field and deflects the electron beam (2) with a large amplitude, and (4) supplies an output current I to the electromagnetic deflection lens (3). The electromagnetic deflection amplifier constitutes an electromagnetic deflection system together with an electromagnetic deflection lens (3). (6) electrostatically generates an electron beam (
2) broadband deflection lens, (7A).

(7B) is a broadband deflection amplifier that supplies voltage to the broadband deflection lens (6), and together with the broadband deflection lens (6) constitutes a broadband deflection system. (8) is a target to which the electron beam (2) is irradiated. (9) is an electron beam (2
) a computer storing pattern data for drawing a desired pattern on the target (8);
Q is a digital control circuit (hereinafter referred to as DCT) connected to the computer (9〉), αυ is a digital-to-analog converter (hereinafter referred to as DAC) that converts the pattern data from DCTα0 from digital values to analog values, O is DA
an amplifier that amplifies the analog pattern data from CQυ and outputs the electromagnetic deflection signal DI to the electromagnetic deflection amplifier (4);
0 is an inverting amplifier that is connected to the amplifier @ and outputs a reference signal that is an inversion of the electromagnetic deflection signal D1, and 04 is an electromagnetic deflection lens (3
The output current I is detected by an output monitor resistor inserted between the (to) is an addition amplifier that compares the reference signal from the inverting amplifier O and the signal of the output current I from the output monitor resistor α, and outputs the comparison result as an error signal e1. αG is the error signal e! from the summing amplifier (to). This is an inverting amplifier that outputs an error signal e2 which is an inversion of the error signal e1. e2 is connected to a wideband deflection amplifier (7A) through a resistor.

(7B) is input. Alpha power is a computer (9)
DCTl (18A) and (18B) connected to
DAC connected to T (b), (19A), (19B)
are amplifiers that are connected to the DACs (18A) and (18B) and output wideband deflection signals D2A and D2B, respectively, and the wideband deflection signals D2A and D2B are connected to the wideband deflection amplifiers (7A) and (7B) through resistors, respectively. has been entered.

Next, the operation will be explained. An electron beam (2) emitted from the electron gun (1) is focused onto a target (8) by a focusing lens (not shown). At the same time, an electromagnetic deflection signal D1 based on pattern data from the computer (9)
and broadband deflection signals D2A, D2B are generated,
Electromagnetic deflection amplifier (4) and broadband deflection amplifier (7), respectively.
A) and (7B). The electromagnetic deflection amplifier (4) drives the electromagnetic deflection lens (3) and directs the electron beam (2) to the entire deflection area (for example, size 5Il) on the target (8).
It is positioned in a desired subdivision area (for example, 100 μm×100 μm) (both not shown) within the 1In×5InI11). On the other hand, wideband deflection amplifier (7A), (7B)
drives the broadband deflection lens (6), and the electron beam (
2) is scanned within the small section area to draw a highly accurate pattern.

By the way, an electromagnetic deflection lens (3) with a large deflection area
The electromagnetic deflection amplifier (4) that drives the inductive load has a narrow frequency band and poor transient characteristics. Figure 6 shows the electromagnetic deflection amplifier (4) in Figure 5 hypothetically assuming that no correction is performed.
) is a waveform diagram for explaining the output current I when a stepwise input is made to . Therefore, in order to improve this, the following corrections have been made. First, the current I of the electromagnetic deflection lens (3) is detected by the output monitor resistor α♦, and this is compared with the reference signal obtained as the output of the inverting amplifier 0 using the summing amplifier (to) to extract the error signal el. The error signal e1 and the error signal e2 obtained by inverting the error signal e1 are each transmitted through a wideband deflection amplifier (7A),
(7B). Wideband deflection amplifier (7A),
(7B) shows error signals e1. A broadband deflection lens (6) is driven by the signal with e2 added thereto. In this way, the error in the irradiation position of the electron beam (2) on the target (8) due to poor transient characteristics of the electromagnetic deflection system is corrected, and the time tl required for position setting is shortened.

[Problem to be solved by the invention]

Since the conventional electron beam irradiation device is configured as described above, it is possible to correct the error appearing in the current of the electromagnetic deflection lens, but it is not possible to correct the error in the subsequent phenomenon, that is, the magnetic field generated by the current. Electrical conductors are used in structures such as the electromagnetic deflection lens itself, other lenses, and tubes for vacuum maintenance, and when current flows through the electromagnetic deflection lens, transient vortices are generated in nearby structures due to electromagnetic induction. Current flows. The magnetic field caused by this eddy current causes an error in the magnetic field that deflects the electron beam, resulting in an error in the electron beam irradiation position on the target.

FIG. 7 is a graph showing an example of a temporal change in the electron beam irradiation position, and shows a case where an error appears as an overshoot. The electron beam is deflected by the magnetic field caused by the eddy current, passes the set position, and then gradually returns to the set position as the eddy current attenuates. Conventional electron beam irradiation equipment does not allow for such errors. could not be corrected. Furthermore, the transient characteristics of the magnetic field caused by eddy currents often have a time constant that is larger than the electrical response delay of electromagnetic deflection systems, etc., so the amount of error does not decay for a long time, making it difficult to perform machining that requires high speed and high precision. There were serious problems with the electron beam irradiation equipment used for exposure.

This invention was made in order to solve the above-mentioned problems, and it is an electron beam that can correct errors caused by eddy currents and determine the electron beam irradiation position on a target at high speed and with high precision. The purpose is to obtain a source radiation device.

[Means to solve the problem]

The electron beam irradiation device according to the present invention includes a correction circuit that uses an electric circuit to simulate an error in the electron beam irradiation position caused by an eddy current transiently generated in a conductor near the electromagnetic deflection lens by electromagnetic induction due to the current of the electromagnetic deflection lens. The correction circuit corrects the current supplied to the electromagnetic deflection lens.

[For production]

The electron beam irradiation device according to the present invention adds a current to the current that should originally be passed through the electromagnetic deflection lens based on pattern data, etc. to cancel the effect of the magnetic field caused by the eddy current on the deflection of the electron beam, and then passes the added current to the electromagnetic deflection lens. Yo,
Corrected by a correction circuit. In other words, the beam is irradiated onto the correct position on the electron beam, which is deflected by the magnetic field generated by both the current flowing through the electromagnetic deflection lens and the eddy current.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram of a deflection system of an electron beam irradiation apparatus according to an embodiment of the present invention. In the figure, (1) to 04 are the same as in the case of FIG. 5, and their explanations will be omitted. (c)
is a correction circuit that uses an electric circuit to simulate and correct electron beam irradiation position errors caused by eddy currents generated in nearby structures (not shown) due to electromagnetic induction caused by current flowing through the electromagnetic polarizing lens (3). It is intended for computers (
DCT Ql of the signal Vi based on the pattern data of
, DACQl), and outputs the signal Vo to which the above correction has been added to the electromagnetic deflection amplifier (4).

The actual deflection response characteristics of the electron beam (2) are affected by eddy currents as described above, and therefore vary greatly depending on the material, shape, and zero position of the structures near the electromagnetic deflection lens (3). @2
The figure is a circuit diagram showing an example of a correction circuit used when an overshoot error like that shown in Fig. 7 occurs if no correction is made, and Fig. 3 is a waveform diagram of each signal in the circuit diagram of Fig. 2. be. When an input signal Vi of a step voltage with a peak value V as shown in FIG. 3 (4) is input to the correction circuit,
A simulated error signal Ve is generated at the + (plus) input terminal of the operational amplifier @ by the resistors R3, R4, R. and the capacitor C.

(Hereinafter, the resistors R1 to R5, the respective resistances 11d of the capacitor C, and the capacitance values are also expressed as R1 to R,,C.) Here,
Assuming that R3, R4>>R5 and the time from the input of the input signal Vi to t, Ve is as follows.

To illustrate this, as shown in FIG. 3 [F], the ratio P of the peak value of Ve to the peak value V of the input signal Vi is R5.
/ (R3+R6), and the time constant τ is C/(1/R
3+1/R4). Since the operational amplifier @ outputs an output based on 1Ve-Vi of Ve and Vi, the output signal has an undershoot waveform as shown in FIG. 3(C). (Note that the sign of the arithmetic converter is different because it is used as an inverting amplifier, but the figure shows the electron beam irradiation position error without correction, which varies depending on the sign, for example, the waveform shown in Figure 7. is determined in advance, P and τ of the error simulated signal are determined according to the peak value and time constant, and a correction circuit (goods) is created.
Configure. In FIG. 3, the electron beam (2) is deflected using a magnetic field that corrects the magnetic field caused by transiently generated eddy currents. Therefore, the electron beam (2) is irradiated to the correct position on the target (8). In the embodiment shown in FIG. 2, it is possible to cancel the overshoot of the peak value of 0.14% and the time constant of 1.1 ms.

In the above embodiment, the error in the electron beam irradiation position is an overshoot, but even if the error is an undershoot, for example, as shown in the circuit diagram of the correction circuit in FIG. By inputting the signal to the − (minus) input terminal of the operational amplifier and adding the simulated signal and the input signal, it is possible to correct the electron beam irradiation position error.

Further, in the above embodiment, the correction circuit Qυ is provided independently, but the same effect can be obtained even if it is provided at another position in the deflection system, such as by providing it in common with the electromagnetic deflection amplifier (4). Furthermore, if there are multiple locations where eddy currents are generated, and multiple eddy current characteristics result in errors that are synthesized at the electron beam irradiation position, multiple simulated signals corresponding to each eddy current may be calculated. It may be corrected.

Furthermore, although the above-mentioned embodiment has shown an example in which only an electromagnetic deflection system is provided as a deflection system, it is also possible to use a broadband deflection system similar to the conventional example in combination, thereby drawing images within a small section area.

〔Effect of the invention〕

As described above, according to the present invention, the correction circuit is provided to simulate the electron beam irradiation position error caused by eddy current and correct the current supplied to the electromagnetic deflection lens. This has the effect that the electron beam irradiation position error is corrected and the electron beam irradiation position on the target can be determined at high speed and with high precision.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a deflection system of an electron beam irradiation device according to an embodiment of the present invention, and FIG. 2 shows the electron beam of FIG.
Circuit diagram of the correction circuit used in the deflection system of the irradiation device, Part 3
2 is a waveform diagram of each signal in the circuit diagram of FIG. 2, FIG. 4 is a circuit diagram of a correction circuit used in an electron beam irradiation device according to another embodiment of the present invention, and FIG. 5 is a conventional electron beam irradiation device. 6 is a waveform diagram of the output current of the electromagnetic deflection amplifier when no correction is assumed in the electron beam irradiation device shown in FIG. 5, and FIG. 7 is a block diagram of the electron beam in the conventional electron beam irradiation device. It is a graph showing the time change of the irradiation position. In the figure, (2) is a boko beam, (3) is an electromagnetic deflection lens, (4) is an electromagnetic deflection amplifier, (8) is a target,
QD is a correction circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In devices in which an electron beam is deflected by a magnetic field generated by a current supplied to an electromagnetic deflection lens and irradiated to a predetermined position on a target, eddy currents are generated near the electromagnetic deflection lens due to electromagnetic induction caused by the current. An electron beam irradiation device characterized in that a correction circuit for simulating an electron beam irradiation position error using an electric circuit is provided, and the current supplied to the electromagnetic deflection lens is corrected by the correction circuit.