JPS5848041B2 - How to detect electron beam deviation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting a shift in an electron beam, and more specifically, the present invention relates to a method for detecting a deviation of an electron beam, and more specifically, the present invention involves scanning an electron beam having a rectangular or polygonal cross section on a material, for example, in the horizontal direction using a deflector. In particular, the present invention relates to a method of detecting an angle formed by a side direction of a cross section of an electron beam on the material and a scanning direction of the electron beam on the material by a deflector, that is, a rotational deviation.

Conventionally, for example, in an electron beam exposure system, a predetermined figure is drawn by scanning an extremely narrow electron beam (with a focused circular cross section) on the exposure material, but with this method, it takes a lot of time to fill in a large figure. It's time consuming.

Therefore, recently, an electron beam with a relatively large rectangular cross section is created using a deflection means placed between two slits having a polygonal aperture, and the electron beam is projected onto the exposure material through a projection lens. At the same time, an apparatus has been proposed in which a second deflection means is used to scan the material to draw a predetermined figure.

According to this device, a figure, which was conventionally drawn by filling it in, can be exposed at once, so it is possible to speed up the exposure.

However, in this device, the cross-sectional shape is rectangular, unlike the conventional circular cross-sectional shape, so the direction of the side is
It is necessary to match the scanning direction on the exposed material by the deflecting means.

If this does not match and the direction of the side of the electron beam is at a certain angle with respect to the scanning direction of the electron beam on the exposed material, causing rotational deviation, for example, the electron beam may be scanned intermittently in the horizontal direction. In this case, a band-shaped figure of a constant width should be drawn as shown in Figure 1a, but sawtooth-like unevenness should occur on both edges of the figure, as shown in Figure 1b. 1
No, I don't like it.

The present invention has been made in view of the above-mentioned points, and it sequentially extracts two types of electron beams passing through different positions of the polygonal opening of the latter slit among the two slits, and supplies each electron beam with a constant scanning signal. The material is scanned using a second deflection means, the information obtained from the material is detected by each electron beam scan, two types of image signals are obtained, and a shape is formed based on the two types of image signals. By determining the horizontal and vertical relative positional deviations of the same reference object that exists in common in two types of images, the direction of the side of the polygonal electron beam and the electron beam by the second deflection means can be determined. It is characterized by detecting the deviation from the scanning direction.

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

FIG. 2 is a schematic diagram of an electron beam exposure apparatus embodying the present invention, and in the figure, 1 is an electron gun.

The electron beam generated from the electron gun 1 is transmitted through a lens 2 with a side of 100 lI. It is projected onto a first slit 3 having a square aperture of m.

Electron beam B1 given a rectangular cross section by the slit
After being deflected by a first deflector 5 to which the deflection signal from the deflection signal generation circuit 4 is supplied, the light is projected onto a second slit 7 having the same shape as the first slit 3 via a lens 6 .

Of the electron beams B1 projected onto the second slit 7, the electron beam B2 that has passed through the second slit is reduced to, for example, 1/10 and projected onto the exposure material 9 by the projection lens 8.

At this time, the electron beam B2 is scanned on the material 9 by the second deflector 11 to which the scanning signal from the scanning signal generation circuit 10 is supplied.

A detector 12 for detecting secondary electrons, reflected electrons, etc. is installed near the material 9, and information on reflected electrons, secondary electrons, etc. generated from the material 9 by the projection of the electron beam B2 is detected by the detector 12. detected by the device 12.

The obtained detection signal is amplified by the amplifier 13 and then
-D converter 17 to the central control unit 16 and to the control grid G of the cathode ray tube 14.

A cathode ray tube scanning signal generated from the scanning signal generating circuit 10 is supplied to the X and Y deflection coils 15 of the cathode ray tube 14 .

Further, the deflection signal generation circuit 4 and the scanning signal generation circuit 10
is controlled by the central controller 16.

The electron beam B is projected onto the material 9 by pressing the button as described above.
For example, as shown in FIG. A device with a rectangular cross section can be realized.

When detecting rotational deviation of the electron beam according to the present invention, the central controller 16 first sends command signals to the deflection signal generation circuit 4 and the scanning signal generation circuit 10, respectively.

The deflection signal generating circuit 4 generates two types of constant deflection signals alternately every 1/60 seconds based on the command signal and sends them to the first deflector 5.

The two types of constant deflection signals have values that specify the projection position of the electron beam B1 on the second slit 7 to be at the positions L and R shown in FIG. 7
It is projected alternately to the L position and the R position above for 1760 seconds each.

The projection lens 8 reduces the rectangular aperture of the second slit 7 with a side of 100 μm to 1/10, and increases the intensity so that it forms a rectangular shape with a side of 10 μm on the material 9 as shown by the broken line in FIG. Because of the adjustment, when the electron beam B1 is projected to the position L, the electron beam B2L that passes through one corner of the rectangular opening of the second slit 7 and the next 1/60
When the electron beam B1 is projected to the position R during the period of
Projections are alternately switched and projected every 1/60 seconds to the respective hatched positions (separated by 10 μm) in the figure.

Then, the scanning signal generation circuit 10 and the electron beams B2L and B
In synchronization with the switching of 2R, a constant amplitude rask scanning signal for scanning one screen in 1/60 seconds is generated, and in order to send the rask scanning signal to the second deflector 11, the electron beams B2L and B2R are arranged as shown in FIG. Using the diagonally lined position as the scanning start point, rask scanning is performed once every 1/60 seconds in the areas indicated by buttons ZL and ZR in FIG.

Reflected electrons or secondary electrons generated from regions ZL and ZR by such electron beam scanning are detected by the detector 12, and the obtained video signal is amplified by the amplifier 13 and then sent to the grid G of the cathode ray tube 14. is sent as a brightness signal to

At this time, the electron beam in the cathode ray tube 14 is raster-scanned by the scanning signal from the scanning signal generation circuit 10 in synchronization with the raster scanning of the electron beams B21 and B2R on the material. Due to the principle of scanning electron microscope, the scanned image of area ZL and area ZR is 1/60
The images are displayed alternately every few seconds, and the superimposed images can be seen with the naked eye.

By the way, at this time, due to the rotational deviation caused by the lens 8, the image of the rectangular opening of the second slit 7 (the rectangle indicated by the broken line in FIG. 5) is shown by the arrow in FIG. 5 by the second deflector 11. The angle θ is tilted with respect to the scanning direction, so the direction of the side of the cross section of electron beams B2L and B2R (7) is the same as that of the second deflector 1.
Assuming that the scanning direction is tilted at the same angle θ as in the scanning direction of 1, the scanning area ZL by the electron beam B2L and the scanning area ZR by the electron beam B2R are shifted by 10 μm x cos θ in the horizontal direction and 10 μm x sin θ in the vertical direction. .

Therefore, the images of the body in the area ZL and ZR displayed on the screen of the cathode ray tube 14 also have their visual fields shifted in both the horizontal and vertical directions accordingly.

Here, for example, if we press the button in FIG. 5 and pay attention to a specific object P located in the overlapping area of regions ZL and ZR, the object P is located in the sixth region ZLO image displayed on the screen of the cathode ray tube 14. As shown in the figure, it is displayed as <PL, and the button on the image of area ZR is also displayed as <PR, and PL
and PR are shifted in both the horizontal and vertical directions by the amount that the visual field is shifted.

Therefore, by measuring either or both of the horizontal deviation f and the vertical deviation d between PL and PR displayed on the screen, the angle θ can be determined using the following equation.

(M is the magnification of the image) cos θ = f / (M × 10 μm) sin θ = d / (MX 1 0 ttm ) ta
nθ=d/f Therefore, the projection lens 8 should be rotated in the opposite direction by the calculated angle θ.
By adjusting the above, the rotational deviation can be made zero, and the direction of the side of the cross section of the electron beam can be made to coincide with the scanning direction of the electron beam on the material by the second deflector 11.

Similarly, instead of the operator observing the image displayed on the screen of the cathode ray tube and detecting rotational deviation as described above, the two types of video signals of the regions ZL and ZR are digitalized by the A-D converter 17. The signal is converted into a signal and sent to the central control device 16, and the device detects the relative horizontal and vertical positional deviation of the same specific object that exists in common in the two areas based on the two types of video signals. By detecting the angle θ and determining the angle θ, quick and accurate processing becomes possible.

In this case, if a cross-shaped reference mark or the like is used as the specific object, the central control device can easily detect the deviation.

As described in detail above, according to the present invention, it is possible to detect a deviation between the scanning direction of an electron beam on a material having a rectangular cross section and the side direction, and the effect thereof is extremely large.

Although slits with square openings were used in the above-described embodiments, the present invention is not limited to this, and it goes without saying that slits with polygonal openings may also be used.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining rotational deviation, FIG. 2 is a configuration diagram of a device implementing the present invention, and FIGS. 3 to 6 are diagrams for explaining the operation of the device shown in FIG. 2. It is a diagram. 1: Electron gun, 2, 6, 8: Lens, 3, 7: Slit, 4: Deflection signal generation circuit, 5, 11: Deflector, 9: Exposure material, 10: Scanning signal generation circuit, 12: Detector, 14:
Cathode ray tube, 15: Deflection coil, 16: Central controller, 1
7: A-D converter.

Claims (1)

[Claims] 1. Using an electron beam forming means with a polygonal cross section, which includes two slits each having a polygonal opening and a first deflection means disposed between the slits, the positions of both ends of one side of the polygonal opening of the subsequent slit are determined. by sequentially taking out two types of electron beams that pass through the material, by scanning each electron beam on the material using a second deflection means to which a constant scanning signal is supplied, and by scanning each electron beam, the electron beams obtained from the material are Detect information 2
Obtaining a seed image signal, and determining a relative positional shift in the horizontal and vertical directions of the same reference object that exists in common in two types of images formed based on the two types of image signals,
A method for detecting a deviation between a side direction of an electron beam having a polygonal cross section and a scanning direction of the electron beam by a second deflection means.