JP2553032B2 - Charged particle beam deflection circuit - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a charged particle beam deflection system used in an electron beam exposure apparatus or the like.

(Background of the Invention) The requirements for a charged particle beam deflection system used in an electron beam exposure apparatus and the like are (1) high resolution and high stability. (2) A large dynamic range.
(3) High speed. However, since it is difficult to satisfy these requirements with one deflection system at the same time, the drawing area (main field) is 100 to 10,000 by using two deflection systems, a main deflection system and a sub deflection system. A method of dividing into small areas (subfields) and drawing has been often used. This method is a main deflection system that satisfies the requirements (1) and (2) of the above conditions, deflects a charged particle beam (hereinafter simply referred to as a beam) to the center of a subfield to be drawn, and includes it in this subfield. It is an excellent feature that the three conditions (1) to (3) can be satisfied at the same time by performing beam writing at high speed on a sub-deflection system that satisfies the above condition (3) to draw the pattern. Is the way. That is,
Since the main deflection system has a large dynamic range and a high-resolution drive system takes time to settle (time to reach the target value), it is used only when moving the subfield, and the pattern drawing in the subfield is Since the dynamic range is small and the resolution is low, it is a method of increasing the drawing speed by using a sub-deflection system that can be driven at high speed, and the total drawing time is greatly reduced compared to the case of drawing with one deflection system. It is a method that can be done.

However, even with such a method, the loss of time required for the main deflection system to settle the beam from the subfield after the drawing is completed to the position of the center of the subfield to be drawn next cannot be ignored, In particular, it is a net to further shorten the drawing time when the number of subfields is large.

(Object of the Invention) The present invention solves these drawbacks and substantially shortens the time required for settling of the main drive amplifier.
The purpose is to dramatically reduce the total drawing time.

(Outline of the Invention) First, the inventor of the present invention firstly used a 16-18 bit DAC for positioning the main deflection system, but in the method of dividing into subfields and writing, If all corrections relating to positioning and positioning are performed by the sub-deflection system, the main-deflection-system drive circuit only needs to generate a signal corresponding to the central position of each sub-field, in which case accuracy and stability are even required. High-speed DA of about 4 to 7 bits if good
You can use C. Secondly, the amplifier that drives the main deflection system has a high dynamic range and a high voltage or a large current, which limits the speedup. However, it detects the error between the positioning information of the main deflection and the output signal of the main deflection amplifier. The present invention has been completed by paying attention to two points that the settling time of the main deflection drive amplifier can be substantially shortened by returning to the sub deflection system.

The present invention is configured such that the beam deflection and the correction relating to the positioning are performed by the sub-deflection system, and further the error between the positioning information (target data) of the main deflection and the output signal of the main-deflection amplifier is fed back to the sub-deflection system. The technical point is to operate the sub deflection system at the same time as the main deflection system in accordance with the error data.

(Embodiment) FIG. 1 is a schematic view showing an embodiment of an electron beam exposure apparatus using the present invention, 11 is an electron gun, 12 is a first condenser lens, 13 is a blanking deflector, and 14 is 2nd condenser lens, 3 main deflector, 7 sub-deflector, 15 objective lens, 16 XY
The stage, 10 is a main deflection drive circuit, and 20 is a sub deflection drive circuit. In addition to the blocks shown in FIG. 1, a number of correction electron optical systems are usually installed, but they are omitted because they are not directly related to the present invention.

FIG. 2 is a circuit showing an embodiment of the present invention, in which a block 10 surrounded by a dotted line is a main deflection system drive circuit 20 and a sub deflection system drive circuit 30 is a deflection electron optical system. In actual use, the electron beam must be deflected by the information in the X, Y Cartesian coordinate system, so another set of deflection systems shown in Fig. 1 is required. Since only the same deflection system is used, only the uniaxial deflection system will be described here for simplification.

Reference numeral 1 is a main deflection D / A converter (hereinafter, the D / A converter is referred to as a DAC) that converts the center position information (digital signal) of the subfield of the main deflection system into an analog signal, for example, 100 × 100 main fields. When dividing and drawing into subfields of, at least 7bit DAC is required, but it seems appropriate to use 10 to 12bit high-speed DAC in order to improve the position accuracy.

Reference numeral 2 is a main deflector drive amplifier for driving the main deflector 3. If the main deflector 3 is an electrostatic deflector, a high voltage of several hundred volts,
In the case of electromagnetic deflection, a large current output of several amperes is required, so it takes several μsec to several 100μ to settle to the required accuracy.
It takes sec. Therefore, even if a high-speed main deflection DAC 1 can be used, the total drawing time cannot be shortened unless the settling of the main deflector drive amplifier 2 can be shortened.

Reference numeral 4 denotes an error detector of the main deflector drive amplifier, which outputs an error between its input and output until the main deflector drive amplifier 2 settles.

Reference numeral 5 is a sub-deflection DAC that sequentially converts the position information digital signal of the pattern for driving the sub-deflection system to draw a pattern into an analog signal, which requires a high-speed conversion function.
A bit high speed DAC is used.

Reference numeral 6 is a sub-deflector driving amplifier for driving the sub-deflector 7. In the present invention, the dynamic range of this amplifier requires the deflection voltage output for two subfields.
Even so, the settling time is much shorter than that of the main deflector drive amplifier 2 and is about several hundreds, compared with that of the main deflector drive amplifier 2.
It is about nsec.

A sub-deflector 7 is required to have a high-speed response, and therefore an electrostatic deflector is used in most cases.

Reference numeral 8 is a correction DAC. Although omitted in the explanation so far, when actually drawing a pattern on the workpiece with an electron beam, the workpiece is fixed on the XY stage so that the center of the main field to be drawn is directly below the electron optical system. Work to move the stage is required. At this time, the stage does not certainly stop at the target position, so normally the output of a stop position error detector (not shown) is fed back to the electron beam deflection system to perform position correction equivalently. There is. The correction DAC 8 mainly converts this correction amount into an analog signal. The correction DAC 8 is also used to correct the influence of the external magnetic field, the distortion of the deflection system, and the like.

FIG. 3 shows how the output of the main deflection DAC 1 (a), the output of the main deflector drive amplifier 2 (b) and the output of the error detector 4 (c) are settled. As described above, the settling time T _A of the main deflector drive amplifier 2 is the longest and takes several μsec to several hundred μsec. In the conventional writing system, when moving the electron beam from one subfield to the next, a waiting time of T _A was always made and writing was paused at this time. In the present invention, the error detector 4 is assembled using a high-speed operation amplifier, and the error between the input and output of the main deflector drive amplifier 2 (shown in FIG. 6C) is fed back to the input of the sub deflector drive amplifier 6. The error within the settling time of the main deflection system drive circuit 10 is corrected by the sub deflection system. The sub-deflector drive amplifier 6 uses a high-speed amplifier because it draws a pattern at high speed.
It sufficiently follows the output C of the error detector 4 which varies in the order of several tens to several hundreds of microseconds, and can completely correct the error before settling of the main deflector drive amplifier 2 and also the error of the main deflector drive amplifier 2. Since the pattern information input from the sub-deflection DAC5 is also added at the input point of the amplifier while correcting the, it is possible to draw the pattern at the same time. The output signal of the sub-deflection DAC5 is shown in FIG. 3 (d), and the sub-deflection is shown in FIG. 3 (e).
The output states of the sub-deflector drive amplifier 6 in which the output signal d of the DAC 5 and the settling error signal c are superimposed are shown. As can be seen from the figure, since the sub-deflector drive amplifier 6 superimposes the settling error, the cost increases because it requires a dynamic range that is twice as large as the actual drawing area, that is, capable of deflecting two subfields. However, the merits that can reduce the pause (waiting time) of drawing are much larger, and the pause time when moving the subfield is shortened to about 1/10 to 1/100 of the conventional one, and the total throughput is greatly increased. Can be improved.

It should be noted that in the present invention, the DAC used for the main deflection system need only have an output corresponding to each sub-field as long as the accuracy and stability are good, so that a high speed and low resolution one can be used, and such a DAC is manufactured. Things are possible. However, when using a commercially available high-speed low-resolution (about 10 to 12 bits) DAC, the accuracy is almost ± 1/2 LSB, which does not satisfy the position accuracy required for the main deflection system. Therefore, when using a commercially available DAC, the amount of error between the target output corresponding to each subfield center position and the output of the main deflection DAC2 is measured in advance and stored in memory, and the electron beam is swung to each subfield. At this time, the error amount for the subfield is read from the memory, subtracted into the correction DAC8, and input.
By correcting, it can be used as a high precision DAC. With this usage, the same DAC can be used for all 1,5,8 DACs, which is very advantageous in terms of design and maintenance.

As described above, according to the present invention, the error amount between the input and output of the main drive amplifier is determined within the settling time of the main drive amplifier of the main deflection drive system, and the sub-deflection drive system is determined based on the error amount. Since they are operated at the same time, the settling time of the main drive amplifier can be substantially shortened, and the drawing time of all fields can be drastically shortened.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of a circuit system showing an embodiment of the present invention, and FIG. 3 is a signal waveform at various points in the circuit system of FIG. It is a figure. (Description of symbols of main parts) 1 ... Main deflection DAC 5 ... Sub deflection DAC 8 ... Correction DAC 2 ... Main deflector drive amplifier 4 ... Error detector 6 ... Sub deflector drive amplifier 3 ... … Main deflector 7 …… Sub deflector 10 …… Main deflection system drive circuit 20 …… Sub deflection system drive circuit 30 …… Deflection electron optical system

Claims (1)

(57) [Claims] 1. A main deflection system for driving a main deflection system having a main deflection system for deflecting a charged particle beam at a predetermined position in each subfield formed by dividing a main field and a main drive amplifier having a long settling time. A system, a sub-deflection system for deflecting the charged particle beam to form a pattern in the sub-field, and a sub-drive amplifier having a settling time shorter than the main-drive amplifier, the sub-deflection system for driving the sub-deflection system. In a charged particle beam deflector including a drive system, an error amount between an input value and an output value of the main drive amplifier is detected during settling of the main drive amplifier, and the error amount is detected by the sub-deflection drive system. An error amount detecting means for outputting is further provided, and during settling of the main drive amplifier, the output from the error amount detecting means is superposed on the positional information of the pattern and the sub-driving amplifier is output. The charged particle beam deflection apparatus, characterized in that input to the flop allowed the formation of the pattern by the sub-deflection system.