JPS62115715A - Electron-beam exposure device - Google Patents

Abstract

PURPOSE:To vary the size and intensity of beams easily without resulting in the movement and revolution and the like of beams, to simplify the compensation of a proximity effect and to improve the precision of pattern exposure by mounting an electrostatic lens for blooming beams to an elctronic optical system. CONSTITUTION:An electrostatic lens 21 is fitted to the lower section, a working distance section, of an objective 14. When predetermined negative voltage V0 is applied to a central pole 23 for the electrostatic lens 21, beams are bloomed by the action of the lens 21, and the focal point of beams on a sample surface 15 is bloomed. When deflecting voltage V0 is applied to a blanking electrode 19 at the same time, one part of beams is cut by an aperture 13a for a condenser lens 13, thus reducing the quantity of beams. The diameter of beams (second beams) at that time is larger than that of first beams at a time when a pattern region is exposed and beam currents are small, and the second beams are used for exposing a non-pattern region. Accordingly, beams of two kinds can be extracted by the excitation-nonexcitation of the electrostatic lens 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to electron beam exposure technology, and particularly relates to an electron beam exposure 3A device that reduces the proximity effect.

[Technical background of the invention and its problems]

In recent years, various electron beam exposure apparatuses have been used to form fine patterns on samples such as semiconductor wafers and mask substrates. In this apparatus, as patterns become thinner, it is becoming necessary to correct the proximity effect caused by scattering of electron beams within the resist and sample plane.

There are three known methods for correcting the proximity effect: (1) Correcting the dose signal; (2) Correcting the pattern shape; and (2) Using a multilayer resist. The first method requires a huge number of sieves to obtain the correction amount, and furthermore, this method is difficult to apply to the rask scan method. The second method has the drawback of requiring extremely fine adjustment of pattern dimensions. Furthermore, the third method has the disadvantage that the current process of resist coating becomes complicated.

Recently, a fourth proximity effect correction method has been developed, in which the non-patterned area is exposed to a blurred beam with a small beam current, and a dose equivalent to the exposure of the resist by backscattered electrons from the sample is applied to the non-patterned background area. A method has been proposed to remove the influence of backscattered electrons from the sample on pattern dimensions by giving This method is described below.
I will explain to IJJI.

When a point beam is incident on a resist coated on a sample, the distribution of the amount of energy absorbed by the resist is divided into two components. The first component is due to the incident electrons themselves and electrons scattered only within the resist, and is called the forward scattered component. The second component is due to electrons scattered within the sample and is referred to as the backscattered component. Although it depends on the acceleration energy of the electron beam, the forward scattered component is 061
The backscattered component has a spread of about 1 to 10 [μTrL], whereas the backscattered component has a spread of about 1 to 10 [μTrL]. Due to the large spread of this backscattered component, when a pattern is drawn, the amount of energy absorbed by the resist at a certain point is
From that point on, the spread of the backscattered components depends on the pattern density within the range. For this reason, the pattern dimensions after development differ between areas with high pattern density and areas with low pattern density.

Therefore, if the background part without a pattern is additionally exposed with an electron beam that gives approximately the same energy absorption distribution as the backscattered component, the amount of energy absorbed by the backscattered component of the electron beam that exposed the patterned part and the background exposure The sum of the energy absorption amount and the amount of energy absorbed by is equalized within the plane, and the influence of the backscattered component on the pattern dimensions can be removed. Since the spread of the forward scattered component can be made sufficiently small (to 0.1 μm or less) by increasing the accelerating voltage, etc., it is possible to obtain a highly accurate pattern corrected for the proximity effect by this method.

However, there are the following problems when implementing the above method using a conventional electron beam exposure apparatus.

In other words, it is necessary to vary the size and intensity of the beam, but in order to vary these with conventional electron beam exposure equipment,
Various lens conditions must be reset, which is extremely troublesome. Furthermore, when the beam diameter, beam intensity, etc. are varied, the beam moves or rotates, which reduces pattern exposure accuracy.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to easily vary the size and intensity of the beam without causing movement or rotation of the beam, and to eliminate the proximity effect. An object of the present invention is to provide an electron beam exposure apparatus that can easily perform correction and improve pattern exposure accuracy.

[Summary of the invention]

The gist of the present invention is to provide an electrostatic lens in an electron optical system and blur a beam using only the electrostatic lens without changing the excitation conditions of the curved lens.

That is, the present invention provides an electron beam exposure apparatus that exposes a desired pattern on a sample by an electron optical system that focuses and deflects an electron beam emitted from an electron gun and scans the electron beam on the sample. An electrostatic lens is provided to blur the beam.

〔Effect of the invention〕

According to the present invention, since the beam can be deflected by the electrostatic lens, the beam does not move or rotate when the beam is blurred. Therefore, the fourth proximity effect correction method described above can be effectively performed, and exposure accuracy can be improved.

Further, there are advantages such as easy protrusion by simply adding an electrostatic lens to a conventional device.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing an electron beam exposure apparatus according to an embodiment of the present invention. In the figure, 11 is an electron gun, and the electron beam emitted from this electron gun 11 is transmitted through lenses 12 and 13.
．． 14 onto the sample surface 15. That is, the crossover created by the electron gun 11 is the condenser lens 12.1.
3, and is further reduced by an objective lens 14 and irradiated and imaged onto a test surface 15.

Here, the objective lens 14 includes the N1i coil 16. It is formed of a lens upper pole 17 and a lens upper pole 18. Also,
Between the lens 12 and the lens 13, the beam is 0N-O.
A blanking electrode 19 for FF is arranged. Furthermore, between the lenses 13 and 14, the beam is directed to the sample surface 1.
A beam scanning deflector 20 that scans in the X direction (the left-right direction of the Mi plane) and the Y direction (the front and back directions of the paper) is disposed on the image forming apparatus 5 .

The basic configuration up to this point is the same as that of the conventional device, and the difference of this device is that the electrostatic lens 21 is provided below the objective lens 14, that is, in the working distance section. The electrostatic lens 21 has three electrodes 22, 23, 24
This is a so-called Einzel lens, which functions as a lens by setting the upper electrode 22 and the lower electrode 24 at the same potential and setting the central pole 23 at a different potential. The upper pole 22 of the electrostatic lens 21 is connected to the objective lens 14.
The upper pole 2 of the electrostatic lens 21 is formed integrally with the lower pole 18 of the electrostatic lens 21.
2 and below If! 24 are both grounded.

Note that 31 and 32 in the figure are for applying a predetermined deflection voltage (not a voltage that completely blanks the beam but a voltage that cuts a part of the beam) to the blanking electrode 19. 33 indicates a power source for applying a negative voltage to the center Fi 23 of the electrostatic lens 21. Also, 34
, 35.36 are blanking electrodes 19. Electrostatic lens 21
Electric i1m to the central pole 23 of each! Switches for applying voltages 31, 32, and 33 are shown.

Next, the operation of this device configured as described above will be explained.

First, the voltage applied to the center pole 23 of the electrostatic lens 21 is O
I'll leave it as that. The excitation 2i current of the condenser lens 13 is adjusted to set the beam aperture angle, and the objective lens 14
The excitation current is adjusted to focus the electron beam on the sample surface 15. The beam at this time (first beam) is similar to the beam used in a conventional electron beam exposure device,
Used for exposing pattern areas.

On the other hand, when a predetermined negative voltage of 0 is applied to the center pole 23 of the electrostatic lens 21, the beam is blurred by the action of this lens 21, and the beam on the sample surface 15 is defocused. Along with this,
When the diagonal voltage VB is applied to the blanking electrode 19, a portion of the beam is cut off by the aperture 13a of the condenser lens 13, so that the amount of the beam can be reduced. The beam at this time (second beam) has a larger diameter and a smaller beam current than the first beam used to expose the pattern area, and the beam at the non-pattern head 1i! (background area).

In this way, two types of beams can be extracted by excitation/de-excitation of the electrostatic lens 21. Therefore, in the case of rusk scanning, while scanning the electron beam on the sample surface 15 at a constant speed using the beam scanning deflector 20, a pattern area is drawn with the first beam, and a background area without a pattern is drawn with the second beam. can be exposed to light. This results in
Proximity effects can be corrected and drawing accuracy can be improved.

Here, the dose distribution in this example is as shown in FIG. That is, when 81X of ■ is exposed with the focused first beam as shown in Fig. 2 (b), the dose distribution in the parts from ■ to ■ becomes as shown in Fig. 2 <a) solid line P. .

On the other hand, when parts other than ■ are exposed with a second beam that is out of focus as shown in Figure 2 (C), the dose distribution in the parts from ■ to ■ becomes as shown by the solid line Q in Figure 2 (a). . The dose distribution when the above-mentioned portion is exposed with these first and second beams is as shown by the broken line R in FIG. 2(a). In other words, the dose due to the proximity effect caused by backscattered electrons is canceled out, and as a result, the influence due to the proximity effect is significantly reduced.

Thus, according to this embodiment, due to the excitation/de-excitation of the electrostatic lens 21, the first beam (with a small beam diameter and high beam current and well-focused) and the first beam with a large beam diameter and low beam current (with a high focus) are separated. (It's blurry) You can easily change the VJ with the second beam. In this case, there is no need to change the lens conditions of the lenses 12, 13, 14, etc. outside the electrostatic lens Lx, so there is no problem such as beam movement or rotation. Furthermore, since the non-pattern area is exposed with the second beam during the conventional blanking of the rusk scan, the same drawing throughput as the normal rusk scan method without proximity effect correction can be obtained. In other words, the drawing throughput can be improved by about twice as much as compared to a method in which exposure is performed in two steps to perform proximity effect correction. It also has the advantage that it can be realized with a simple configuration simply by adding the electrostatic lens 21 to the conventional device.

Note that the present invention is not limited to the embodiments described above. In the embodiment described above, correction exposure is performed during blanking of the rask scan, but pattern drawing and non-pattern exposure may be separated and beam exposure performed twice. In general, it is possible to apply not only the rask scan method but also the vector scan method. In the case of the vector scan method, instead of correcting and exposing the entire backbone area where there is no pattern, the area around the pattern may be subjected to correction exposure. In addition, in the example, a part of the electrostatic lens is also used as the lower pole of the objective lens, but the electrostatic lens may also be installed completely independently, and its installation position is generally higher than that of the objective lens. What can be installed in the middle of the electron optical system on the gun side is:
Of course.

Furthermore, the voltage applied to the center pole of the electrostatic lens may be a positive voltage with respect to the upper and lower poles. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an electron beam exposure apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram for explaining the operation of the apparatus. 11...Electron gun, 12.13...Condenser lens, 13a...Aperture, 14...Objective lens, 1
5... Sample surface, 16... ill coil, 17...
Objective lens upper pole, 18... Objective lens lower pole, 19...
・Blanking electrode, 20... Beam scanning deflector,
21... Electrostatic lens, 22... Electrostatic lens upper pole, 2
3... Electrostatic lens center pole, 24... Electrostatic lens lower pole, 31, 32° 33... Power supply, 34, 35, 36...
·switch. Applicant's agent Patent attorney Takehiko Suzue■■■■■■■■■ Figure 2

Claims (3)

[Claims] (1) In an electron beam exposure apparatus that exposes a desired pattern on a sample using an electron optical system that focuses and deflects an electron beam emitted from an electron gun and scans the electron beam on the sample, the electron optical system An electron beam exposure apparatus comprising an electrostatic lens for blurring the beam. (2) The electron beam exposure apparatus according to claim 1, wherein the electrostatic lens is provided at a working distance portion of an objective lens. (3) The lower pole of the objective lens is also used as the upper pole of the electrostatic lens, thereby providing a central pole and a lower pole of the electrostatic lens on the working distance side. The electron beam exposure apparatus according to item 2.