JPS6231489B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure apparatus that enables ultra-high-speed, high-precision exposure.

In recent years, electron beam exposure systems have suddenly come into the limelight as a means of producing integrated circuits, especially large-scale integrated circuits (LSIs) and VLSIs.

There are two types of electron beam exposure equipment: a focused beam type that uses a narrowly focused electron beam, and an area exposure type that uses an electron beam with a rectangular cross section. Alternatively, a variable area type has been proposed in which the shape and size of an electron beam with a rectangular cross section are varied in accordance with the figure to be drawn in the circuit manufacturing process, thereby significantly increasing the scanning speed.

However, in any type of exposure equipment,
The irradiation position of the electron beam irradiated onto the sample is specified by a deflection system to which a position signal is supplied from a digital computer via a digital-to-analog converter (hereinafter referred to as D・A・C), and a desired shape is applied to the sample. Since it is drawn above, if you are trying to draw a figure in the entire area (range of 2 mm x 2 mm), it will be 1 μm x 1 μm.
If you try to scan with an electron beam with a cross-sectional shape of 0.05 μm vertically and horizontally (x direction, y direction),
A D/A/C with an accuracy of 0.05 μm/2 mm = 1/40000, that is, 16 bits or more in both the vertical and horizontal directions, is required, and as shown in Figure 1, the response speed of such a D/A/C is extremely slow. (settling time at full swing is about 25 μsec), and therefore the exposure time is also very slow.

In order to compensate for these drawbacks, an apparatus has been proposed in which the deflection range is divided into large and small sections and wide-area deflection is performed using separate deflection systems, thereby greatly speeding up the exposure time. That is, a certain area (e.g., 2 mm x 2 mm) on the sample surface is divided into reference sections (e.g., 100 μm x 100 μm), and the electron beam irradiation position within the reference sections is determined using a high-precision deflection system (e.g., 12-bit high-speed D/A).・Specify the reference sections sequentially using a high-precision deflection system (for example, using a 16-bit high-precision D・A・C) (so-called small section scanning) (as shown in Figure 2). P, Q, R, S,...
A desired figure is drawn on the sample by scanning the sample in a zigzag pattern every 100 μm (so-called broad section scanning). Here, we will compare the exposure speeds of an apparatus that specifies the electron beam irradiation position using one deflection system and an apparatus that specifies the electron beam irradiation position using large section scanning and small section scanning. In this case, 100μm
For example, if there are 20 figures in a standard section of ×100 μm, and if we draw the figure with an accuracy of 0.05 μm over the entire area of 2 mm × 2 mm, the scanning speed in the former case is approximately 25 μsec per step, so 25 μm
Requires exposure time of sec x 20 pieces x 400 times = 0.2 sec. On the other hand, the latter small section scanning D・A・C
(12bitD・A・C) has a response speed of less than 2μsec per step, so the exposure time is {(2μsec×20 pieces) +
25μsec} x 400 times = 0.026sec, which is about 8 times faster. However, the exposure speed of this device is still not satisfactory.

The present invention was made in view of these points,
The object of the present invention is to provide a new electron beam exposure apparatus that performs ultrahigh-speed exposure while maintaining high precision with a simple hardware configuration without using complicated software.

First, the principle of the present invention will be described below. As mentioned before, D・A・C has an inverse relationship between the number of bits and the response speed, so it is used in the deflection device for large section scanning used in conventional exposure equipment16 BIT's D/A/C has high precision, but its response (stabilization) speed is slow (it takes about 25 μsec for a full swing). However, if low-bit D/A/C is used instead, the speed will increase, but the precision of the graphics will decrease, which is not practical.
Furthermore, if the stability (response) of the 16-bit D/A/C is ignored and the data is moved at high speed, the precision of the figure will be extremely poor. Therefore, if there is no figure to be drawn in the reference section, the process moves to the next reference section without waiting for the response (stable) of the high-precision, low-speed D/A/C, and if there is a figure to be drawn in the reference section, As before, it waits for a response and performs high-precision exposure. By performing such an exposure, it is possible to eliminate wasted time such as spending a long response time even when moving to a reference section where there is no figure to be drawn, and the overall exposure time can be significantly shortened.

FIG. 3 shows an embodiment of the present invention based on this principle. In the figure, 1 indicates an electron gun, and the electron beam from the electron gun passes through a suitable focusing lens 2.
For example, the light is irradiated onto a mask plate 3m having a rectangular hole 3h. The electron beam, which has passed through the hole and has a rectangular cross section, is focused onto the sample 5 by the projection lens 4. 6 and 7 are subsection (reference section) deflection devices each consisting of a pair of x and y deflection coils, etc.;
Each of them is provided in two stages, upper and lower, and are configured to be mutually reversely excited. 8 is a large section deflection device consisting of x and y deflection coils, etc. Reference numeral 9 denotes a high speed data transmission control mechanism (hereinafter referred to as HSC) which issues various commands based on input data read out from a disk 10 storing data necessary for exposure via a memory 11 in a digital computer 12. The HSC supplies a position signal for scanning a subsection specifying a position within the reference section to the subsection (reference section) deflection devices 6 and 7 via, for example, a 12-bit high-speed D/A/C 13 and an amplifier 14. Further, a large section scanning position signal specifying the position of the reference section is supplied to the large section deflection device 8 at intervals of, for example, 1 .mu.sec via, for example, a 16-bit high-precision D/A/C 15 and an amplifier 16.

17 is an RS flip-flop, and when a beam shot start signal is supplied from HSC 9, it is in the set state and the beam shot time control circuit 2, which will be described later, is set.
When a shot end signal from 0 is supplied, a reset state is entered, and such a state signal is supplied to one input terminal of the AND circuit 18. Said HSC
The position signal for broad section scanning from 9 is supplied to a one-shot multivibrator 19, and the one-shot multivibrator 19 generates a pulse of a constant pulse width by supplying this signal. The pulse width is set to be equal to the time required for the D.A.C.15 to stabilize. The output terminal of the one-shot multivibrator 19 is connected to the other input terminal of the AND circuit 18. The output of the AND circuit 18 is supplied as an operation start signal to a beam shot time control circuit 20 which controls the beam shot time based on a beam shot time command signal from the HSC 9. The output signal of the control circuit is supplied to a blanking deflection system 21. The deflection system is controlled by the control circuit 20.
When a signal is received from the electron gun 1, the electron beam from the electron gun 1 is passed through the hole of the diaphragm 22 located below without being deflected.
When no signal is received, the electron beam is largely deflected to prevent it from passing through the aperture of the aperture 22. Note that the control circuit 20 supplies a shot end signal to the flip-flop and HSC 9 each time one beam shot is completed within a certain reference section, so the flip-flop is reset and the
When a new beam shot start signal is supplied from the HSC 9, the state is set again. or,
The HSC 9 sends new large section scanning position signals to the one-shot multivibrator 19 and the D.
It operates to supply a new position signal when all are drawn without supplying it to A/C15.

For convenience, the operation of such an apparatus will be described below for the case where there are minute figures to be drawn in reference sections A and E, but not in B, C and D, as shown in FIG.

First, the HSC 9 sends position signals P _A , x _A , y _A specifying the position of the reference section A as shown in FIG.
A position signal is supplied to the large section deflection device ₈ via the A.C.
3 and the subsection deflection devices 6, 7 via the amplifier 14.
Furthermore, a beam shot time command signal is supplied to the beam shot time control circuit 20. Accordingly, the one-shot multivibrator 19 has a time width t ₀ corresponding to the time required for the D・A・C 15 to stabilize based on the input position signal, as shown in FIG. _5b . A pulse as shown in ' is generated and the pulse is supplied to one input terminal of the AND circuit 18. Since the other input terminal of the AND circuit 18 is supplied with a beam shot start signal as shown in P _A1 in FIG. 5a from the HSC 9 via the flip-flop 17, the AND circuit 18
After t ₀ time after the HSC 9 supplies the position signal specifying the position of the reference section A to the large section deflection device 8, the circuit starts the beam shot time for a time corresponding to the time width of the beam shot start signal P _A1 . A beam shot start signal is supplied to the control circuit 20. During a period corresponding to the time, the control circuit:
Since the shot time command signal from the HSC 9 is supplied to the blanking deflection system 21, a minute figure _A1 is drawn within the reference section A on the sample 5. Microfigure A ₁
When is drawn, the control circuit 20 sends a shot end signal to the flip-flop 17 to put the flip-flop into a reset state. During this time,
The HSC 9 supplies a position signal specifying the position of the minute figure _A2 within the reference section A to the subsection deflectors 6 and 7 in the same way as described above, and also immediately after the flip-flop 1.
7 to the other input terminal of the AND circuit 18.
Since a beam shot start signal as shown at P _A2 in Figure b is supplied, the same process as described above is carried out.
A minute figure _A2 is drawn. When the minute figures A ₁ , A ₂ ′...A _o in the reference section A are drawn in this way,
From the HSC 9, position signals specifying the positions of the reference sections _B , _C , _D , and _E as shown in FIG. to the large section deflection device 8 at high speed (for example, each position signal is transmitted for 1 μsec
). During this time, each standard section B, C,
Since there is no minute figure to be drawn in D, HSC9
Since no beam shot start signal is supplied from the flip-flop 17 to the flip-flop 17, the AND circuit 18 does not supply a beam shot start signal to the beam shot time control circuit 20. Therefore, the position to be irradiated with the electron beam moves rapidly from B to C to D to E. However, since there is a minute figure to be drawn at E,
The one-shot multivibrator 19 into which the position signal P _E of the reference section E is introduced from the HSC 9 has a time width t ₀ from the time when the position signal is supplied, in the same way as when the position signal of the reference section A mentioned above was introduced. It generates an output that is kept at a low level until the time elapses, and supplies the output to one input terminal of the AND circuit 18. Applicable
Since the other input terminal of the AND circuit is supplied with a beam shot start signal as shown in P _E1 in FIG. 5c from the HSC 9 via the flip-flop 17, A similar process is repeated to draw minute figures E ₁ , E _{2 .} . . En in the reference section E.

The present invention can be applied to a plurality of masks each having a rectangular hole and a deflection system disposed between them, so that the cross-sectional shape of the electron beam passing through the hole in the mask provided at the final stage is varied by the deflection system. It is also effective for use in a variable area type exposure apparatus.

Furthermore, in the embodiment described above, the deflection device for small deflection that scans inside the reference section and the deflection device for large deflection that scans each reference section are separately provided.
It goes without saying that one deflection device can serve both purposes.

According to the present invention, without using complicated software and using an extremely simple hardware configuration, the response of a high-precision deflection system is automatically adjusted only when exposure is performed by changing the reference section to be drawn by performing a relatively large deflection. An electron beam exposure apparatus is provided that can perform exposure after waiting for the exposure time, and the exposure speed can be improved without impairing exposure accuracy.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the characteristics of the number of D/A/C bits and the response speed, Fig. 2 is a graph showing the deflection method of the conventional device in major categories, and Fig. 3 is a graph showing an embodiment of the present invention. The electron beam exposure apparatus shown in FIGS. 4 and 5 are diagrams used to explain the operation of the present invention. 1: Electron gun, 3m: Mask, 5: Sample, 6,
7: Small section deflection device, 8: Large section deflection device, 9:
High-speed data transmission control mechanism, 13, 15: D.A.
C, 17: RS flip-flop, 18: AND circuit, 19: one-shot multivibrator, 2
0: Beam shot time control circuit.

Claims (1)

[Claims] 1. A means for reading out data for controlling the electron beam irradiated onto the sample and issuing various commands, and a high-precision device that supplies a position signal for broad section scanning that specifies the reference section of the sample to be drawn from the means. a deflection system;
and a high-speed deflection system to which a position signal for sub-section scanning specifying a position of electron beam irradiation within the reference section to be drawn is supplied from the means, wherein a beam shot start signal supplied from the means is supplied. A flip-flop circuit is thus set, a gate circuit is supplied with a signal from the flip-flop circuit, and when the set signal is supplied through the gate circuit, blanking is performed in accordance with a beam shot time command signal from the means. a beam shot time control circuit for controlling the deflection system to start a beam shot, and requesting the next beam shot start signal from the means when the shot is completed and resetting the flip-flop circuit; a one-shot multivibrator that generates a pulse to close the gate circuit for a certain period of time required for the high-precision deflection system to stabilize, based on the supply of the position signal for broad section scanning supplied from the means each time the scanning is completed; An electron beam exposure apparatus comprising: