JPH0636996A - Electron beam apparatus - Google Patents

Abstract

PURPOSE:To improve a throughput of an apparatus by bringing a settling latency time in the apparatus into coincidence with a settling time responsive to an original deflection amount, and reducing a longer CPU latency time than a settling time of a deflection controller. CONSTITUTION:A settling time controller 4 is set to outputs of various deflection controllers 5, 6 to be controlled according to lithograph data generated from a lithography controller 2. A settling time until the deflection controllers are settled to a target accuracy is detected. Thus, a settling latency time responsive to a deflection amount is regulated, and a blanking controller 3 is controlled. When a blanking plate 13 is controlled at this timing and a lithography is executed while controlling an exposure time by a CPU 1, more settling latency time than required can be eliminated. A settling time detection signal of the controller 4 is monitored in real time thereby to reduce a frequency of lithography malfunction due to an abnormal operation of an output of a deflector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measuring the response time (settling time) of a deflection circuit in an electron beam apparatus, and
The present invention relates to deflection control of an electron beam drawing apparatus and the like, and more particularly to a control circuit which apparently shortens the settling waiting time required for deflection and enables improvement of apparatus throughput.

[0002]

2. Description of the Related Art In an electron beam drawing apparatus, it is necessary to deflect an electron beam at high speed and with high precision in order to draw a fine circuit pattern. The deflection method employs electrostatic deflection using an electrostatic deflection plate, electromagnetic deflection using a coil, or the like, but a deflection control circuit that drives a load is indispensable for both deflection methods. This deflection control circuit has
High-speed and high-precision deflection of the electron beam to the target deflection position is required, but a settling time (settling time) until settling to the target deflection position is required to drive a heavy load. Since the drawing operation during the settling time in the electron beam drawing apparatus adversely affects the drawing result, the electron beam is normally turned off (drawing is stopped).
Every time the beam deflection operation is performed, control is performed so that writing is started after waiting for a settling time required for beam deflection measured in advance.

FIG. 3 shows an example of a conventional electron beam drawing apparatus. The electron beam emitted from the electron gun 7 has a first aperture 8, transfer lenses 9 and 11, a variable shaping deflector 10,
After passing through the second aperture 12, the blanking plate 13, the blank diaphragm 14, the reduction lens 15, the sub-deflection plate 16, the main deflection coil 17, the objective lens 18, etc., the wafer 19 is irradiated. The various deflectors are controlled by deflection signals from the blanking control circuit 3, the sub deflection control circuit 5, the main deflection control circuit 6, etc., which operate arbitrarily based on commands generated by the CPU 1 and the drawing control circuit 2.

FIG. 4 shows waveforms in an example of a deflection control method in a conventional electron beam drawing apparatus. The time width (settling waiting time) of the blanking control signal with respect to the deflection start signal is constant regardless of whether the sub-deflection output has a large amplitude or a small amplitude. Can be said to exist.

As a method of reducing the settling waiting time more than necessary, there is JP-A-60-236224. In this method, the settling waiting time for each deflection amount is measured and set in advance, and the settling waiting time corresponding to the corresponding deflection data is set.

[0006]

In the conventional electron beam drawing apparatus, the settling waiting time is fixed to a substantially constant waiting time (settling time at large amplitude) regardless of the amount of deflection. In addition, a waiting time longer than necessary is generated, and a drawing / deflection time given by “{exposure time + settling waiting time} × the number of drawing patterns” is required especially in a circuit for deflecting the drawing. In other words, the settling time of the deflection control circuit is an unnecessary waiting time for the electron beam drawing apparatus, which lowers the apparatus throughput.
Shortening the settling time associated with the deflection operation (shortening the settling waiting time) is one of the important issues.

According to the above-mentioned known example, since the settling waiting time corresponding to each deflection data is measured in advance, it is possible to set the settling waiting time corresponding to the data. However, considering the drawing position accuracy, from the standpoint of disturbance, deterioration of the deflection circuit characteristics, contact resistance of the cable connecting the deflection load and the deflection circuit, etc., it is easy to measure the settling time for any deflection amount in advance, Setting the settling waiting time may increase the frequency of drawing defects due to the deflection operation. In addition, considering that the settling characteristics vary depending on the deflection data even with the same deflection amount, measuring the settling time with respect to an arbitrary deflection amount is a time-consuming task, and there is a problem that the measurement time varies depending on the adjuster. There is.

An object of the present invention is to shorten the unnecessary settling waiting time in order to improve the throughput of the device,
Another object of the present invention is to provide a control method capable of improving reliability by reducing the frequency of drawing defects due to the deflection operation.

[0009]

In order to achieve the above object, according to the present invention, as shown in FIG. 1, settling time control is applied to the output of various deflection control circuits controlled by drawing data generated from the drawing control unit 2. By setting the circuit 4 and detecting the settling time until the deflection control circuit settles to the target accuracy, the settling waiting time (settling waiting time) according to the deflection amount is adjusted and the blanking control circuit 5 is controlled. . The blanking plate 13 is controlled at this timing, and C
If you draw while controlling the exposure time with PU1,
Unnecessary settling wait time can be eliminated. Originally, the settling time is closely related to the amount of deflection, and by setting the settling time according to the amount of deflection by actual measurement, it is possible to shorten the apparent settling waiting time and eventually improve the throughput of the apparatus.

Further, by monitoring the settling time detection signal of the settling time control circuit 4 in real time, it is possible to reduce the frequency of drawing defects due to abnormal operation of the deflection circuit output.

[0011]

According to the present invention, a settling time control circuit is installed at the output of the deflection control circuit, and the settling time until the deflection control circuit settles to the target deflection position is measured for any deflection amount, and the minimum required value is set. Since it is possible to set the settling wait time to a limit, the unnecessary settling wait time that was generated by fixing the settling wait time regardless of the deflection amount as in the conventional method becomes unnecessary, and the apparent The settling waiting time can be shortened. Further, it is not necessary to measure the settling time according to the deflection amount in advance, and by monitoring the detection signal during the drawing operation, when an abnormality occurs in the deflection circuit during drawing or due to disturbance to the deflection system. It is possible to easily detect drawing defects.

[0012]

1 is a block diagram showing an embodiment of a method for controlling a settling time for an electron beam drawing apparatus. The electron beam emitted from the electron gun 7 has a first aperture 8, transfer lenses 9, 11, a variable shaping deflector 10, a second aperture 12,
Blanking plate 13, blank diaphragm 14, reduction lens 1
5, sub-deflection plate 16, main deflection coil 17, objective lens 18
And the like, and is irradiated onto the wafer 19. The various deflectors include deflection signals of the sub deflection control circuit 5, the main deflection control circuit 6 and the like, which operate arbitrarily based on commands generated by the CPU 1 and the drawing control circuit 2, and the settling time control circuit 4,
It is controlled by the blanking control circuit 3. The settling time control circuit 4 uses the deflection signal of each deflection control circuit
The settling time to the final target accuracy is detected according to the deflection amount, and an optimal settling waiting time signal is generated for the blanking control circuit 3 and the drawing control circuit 2. The blanking control circuit 3 has a function of controlling the blanking plate 13 at the control signal timing of the drawing control circuit and the settling time control circuit 4 and performing arbitrary pattern drawing while the CPU 1 controls the exposure time.

FIG. 2 shows an embodiment of the settling time control circuit. When the drawing control circuit 2 supplies a deflection signal to the sub-deflection control circuit 5, a response waveform with settling time to the target position is output to the sub-deflector according to the deflection amount.
In the settling time control circuit, the response waveform is differentially shaped, and a signal having a difference from the comparison level is generated as a blanking control signal. In the settling time detection circuit, by using an integrating circuit, an analog switch, etc., only the differential signal of the amplifier response waveform and the waveform near the end of settling are cut out, and compared with the reference signal according to the target accuracy,
The settling end time corresponding to the deflection amount is detected.

FIG. 5 shows an embodiment of the settling time measuring circuit. In the settling time measurement circuit, the deflection response waveform given by the sub-deflection control circuit is generated as a differential waveform determined by the time constant of the coupling capacitor and the resistor, and the diode is clipped to the differential waveform near the end of settling,
After amplification, the settling time corresponding to the deflection amount is detected by comparing with a comparison level corresponding to the target accuracy (1/2 LSB) of the DAC used in the deflection control circuit. The detection signal starts drawing (unblanks) and sends an exposure start flag to the CPU. When an arbitrary exposure time has elapsed, the blank state is set again and waiting for settling to the next deflection position is performed. At this time, if a shot counter for exposure control is installed in the settling time measurement circuit, the blanking control from the end of settling (start of exposure) to the set exposure time (end of exposure) controls the exposure time. Will also be possible. At this time, it is also necessary to transmit the next data in advance so that the influence of the data transmission rate does not occur (the data is not in a waiting state).

By the way, the matching between the differential waveform generated by using the coupling capacitor and the resistor and the actual settling waveform is performed by determining the optimum value by measurement and adding the correction signal. When the deflection response waveform changes due to impedance, an impedance converter such as a buffer circuit is used. Further, by switching the constant of the differential waveform generation unit and the comparison level of the comparator by the switching element, it is possible to set an arbitrary target precision from the CPU, and to arbitrarily adjust the timing of the exposure start flag according to the drawing precision. You can also This settling time control circuit uses a settling time measurement circuit and a blanking time adjustment circuit to
It is characterized by having a function that enables control synchronized with. If a delay in the deflection response waveform occurs due to the use of an impedance converter such as a buffer circuit, measure the delay and reduce the circuit correction or target accuracy to ensure that it matches the actual settling waveform. Try. still,
In FIG. 5, the negative direction detection circuit is omitted for simplification of description.

FIG. 6 shows a waveform diagram in one embodiment of the sub-deflection (at large amplitude) control method, and FIG. 7 shows a waveform diagram in one embodiment of the sub-deflection (at small amplitude) control method. When the sub-deflection response signal shown in FIG. 6B is applied to the settling time control circuit,
The settling time measuring circuit generates a settling differential waveform (c) according to the input. By comparing the waveform with the comparison level of the final target accuracy (d), the comparator detects the settling time according to the deflection signal (e). A blanking control signal (f) is obtained from the detection time and the deflection start signal (a) obtained here. The settling time for FIG. 7 (b) is also detected in the same manner, but since the settling time according to the deflection amount is detected here, a blanking signal (f) having a shorter blanking time than that of FIG. 6 (f) is obtained. To be

Here, considering the device throughput,
The time required for drawing / deflecting is approximately given by “{exposure time + settling waiting time} × number of drawing shots”. That is, the reduction of the settling waiting time per shot according to the number of drawing shots (≈the number of deflections) can significantly improve the device throughput.

Conventionally, the settling waiting time was set almost independently of the deflection amount, but the value is set to 100 nS, the number of shots is 10 ⁹ pieces / wafer, and the exposure time per shot is 10 times.
Assuming 0 nS, the actual exposure time is 100 seconds, and the settling waiting time is 100 seconds. By drawing this in the drawing order such that the deflection distance of one shot becomes smaller, when the settling waiting time of the average 70 nS,
The dead time of about 30 seconds / wafer will be reduced.
As an example of a concrete deflection amount and settling wait time, 12-bit precision and large amplitude settling 100 nS (40 μm deflection)
When the response time of the deflection amplifier is considered as the first-order lag and the drawing is performed in the drawing order such that the deflection amount becomes about 1/10 (4 μm) of the maximum amplitude, the settling time until the deflection operation stabilizes is about 72 nS. become.

FIG. 8 shows a normal state when the output of the deflection circuit is monitored and an abnormality detection output waveform diagram when an abnormality occurs.

When the sub-deflection response signal shown in FIG. 8A is given to the settling time control circuit, the settling time measuring circuit generates a settling differential waveform according to the input and compares it with the comparison level of the final target accuracy (b). Thus, the comparator detects the settling time according to the deflection signal (c). At the time of drawing after measuring the settling time, the abnormal drawing is detected by monitoring the output of the comparator and detecting the state where the deflection output exceeds the comparison level. When the normal deflection operation is performed, the abnormal drawing detection signal (d) does not occur.

However, when a disturbance as shown in FIG. 8A is mixed in the sub-deflection response signal and an abnormal deflection operation is performed, the settling time measuring circuit detects a waveform as shown in FIG. 8B. In the comparator, the signal shown in (C) is obtained. When the output of the comparator during drawing is monitored, an abnormal drawing detection signal (D) is generated due to a change in the deflection operation during drawing.
By sending this detection signal to the control system, it is possible to detect the drawing position where the abnormal deflection operation has occurred, and it becomes a standard for inspecting the drawing defect position and its degree after drawing. Here, when the settling time measuring circuit having the built-in exposure control shot counter is used, the drawing operation is stopped (blocked) when the abnormal deflection operation is performed and the abnormal drawing detection signal (D) is generated. In addition, the control circuit is informed of the abnormal drawing detection signal and the shot counter data value (exposure time) at that time. Then, in the next and subsequent shots, redrawing is performed based on the abnormal drawing position data and the exposure shortage time (= set exposure time-exposed time), whereby the drawing failure due to the abnormal deflection operation is eliminated.
However, in reality, since there is a signal delay of about tens of nanoseconds until the comparison operation is detected and the drawing operation is stopped, when a disturbance with a high frequency component exceeding the signal delay is mixed, the abnormal exposure unit is It will remain a little. If the set exposure time is long, it does not cause a problem, but if the set exposure time is short, the degree of abnormal exposure increases, which may cause a problem. When the set exposure time is short and an abnormality occurs, a drawing defect confirmation inspection based on the abnormal drawing position data is required.

According to the present embodiment, the settling waiting time can be shortened more than necessary by hard-detecting the settling time corresponding to the deflection amount, and the throughput can be further improved when the drawing order is taken into consideration. Become. Further, by monitoring the detection signal during the drawing operation, it becomes possible to easily detect a defective drawing position due to an abnormality in the deflecting circuit during drawing or a disturbance to the deflection system.

Further, by switching the circuit constant of the settling time measuring circuit by the switching element, it is possible to speed up (shorten the settling waiting time) according to the required drawing accuracy. It goes without saying that other means may be used to detect the settling time, and even after the adjustment of the settling time measuring circuit, even when the circuit of the deflection control circuit which conventionally requires a special jig is adjusted. Can easily measure the settling time of the deflection control circuit by measuring the pulse width of the digitized detection signal.

[0024]

According to the present invention, the settling waiting time in the device is matched with the settling time corresponding to the original deflection amount, and the CPU waiting time longer than the settling time of the deflection control circuit is reduced, so that the device throughput can be improved. Becomes
Further, it is possible to detect a drawing defect due to disturbance to the deflection system, facilitate adjustment, and perform high-speed drawing in the order of pattern drawing.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a settling time control method for an electron beam drawing apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a settling time control circuit according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a deflection control method in a conventional electron beam drawing apparatus.

FIG. 4 is a waveform diagram showing an embodiment of a deflection control method in a conventional electron beam drawing apparatus.

FIG. 5 is an explanatory diagram showing an embodiment of a settling time measurement circuit according to the present invention.

FIG. 6 is a waveform diagram showing an embodiment of a sub-deflection (at large amplitude) control method according to the present invention.

FIG. 7 is a waveform diagram showing an embodiment of a sub-deflection (at small amplitude) control method according to the present invention.

FIG. 8 is a waveform diagram showing an embodiment of an abnormality detection operation of the settling time measurement circuit according to the present invention.

[Explanation of symbols]

1 ... CPU, 2 ... Drawing control section, 3 ... Blanking control circuit, 4 ... Settling time measuring circuit, 5 ... Sub deflection control circuit, 6 ... Main deflection control circuit, 7 ... Electron gun, 8 ... First aperture, 9 ... first transfer lens, 10 ... variable shaping deflector, 1
DESCRIPTION OF SYMBOLS 1 ... 2nd transfer lens, 12 ... 2nd aperture, 13 ... Blanking plate, 14 ... Blank diaphragm, 15 ... Reduction lens, 16 ... Sub deflection plate, 17 ... Main deflection coil, 18 ... Objective lens, 19 ... Wafer.

Claims (9)

[Claims] 1. An electron beam generation source, an electron optical system for shaping the electron beam, a blanking part for controlling the on / off of the electron beam, and a position control for deflecting the electron beam on a material to be exposed. A D / A converter and a deflection circuit for controlling the deflection control unit, the deflection control unit, and
In an electron beam apparatus equipped with a drawing control section for controlling the blanking section, a signal waveform obtained by directly or impedance-converting or shaping the response output of a deflection circuit for controlling a deflector such as an electrostatic deflection plate or an electromagnetic coil. And a target final output level are compared using a comparator to measure a settling waiting time until the response output of the deflection circuit settles to a target voltage value (current value). Beam device. 2. The settling time of a deflection control circuit output for controlling a load can be detected with arbitrary target accuracy by switching a target final output level for a beam deflection output or a waveform shaping time constant. Electron beam apparatus having a settling time measuring circuit capable of performing 3. The electron beam apparatus according to claim 1, wherein the settling time of the deflection control circuit is detected by a settling time measuring circuit, and the blanking operation of the electron beam is controlled by the signal. 4. The electron beam apparatus according to claim 1, which has a function of monitoring the operation state of the deflection control circuit by a settling time measurement circuit and controlling the blanking operation of the electron beam. 5. The electron beam apparatus according to claim 1, wherein the settling time of the deflection control circuit is monitored by a settling time measuring circuit, and the blanking operation is controlled to control the exposure time. 6. The settling time measuring circuit having a built-in exposure time control shot counter monitors the settling time of the deflection control circuit, and controls from the start of exposure to the set exposure time after completion of settling. An electron beam device that controls the blanking operation. 7. The settling time measuring circuit according to claim 1, wherein the operating state of the deflection control circuit is monitored to prevent unexpected occurrence due to disturbances in the deflection circuit or troubles in the control circuit. An electron beam device having a function capable of notifying the control system that controls the state of the deflection operation in which an abnormal operation has occurred, when the deflection operation is performed. 8. The electron beam according to claim 1, further comprising a settling time control circuit having a function of detecting only a response output end point of a deflection circuit for controlling a load and detecting a response time by comparing with a target final output level. apparatus. 9. An electron beam capable of adjusting the deflection control circuit by measuring the settling time until the deflection control circuit settles to a target accuracy by the settling time control circuit according to any one of claims 1 to 8. apparatus.