JPS6041222A - Electron beam exposure - Google Patents

Abstract

PURPOSE:To obtain a high precision pattern by drawing a pattern which requires correction with specific quantity of electron beam irradiation among exposure patterns obtained by diving a pattern which is to be formed into rectangles. CONSTITUTION:In order to correct the extent of each pattern, at first, quantity of dimension correction Si within a pattern and quantity of irradiation Qi to obtain the dimensions of a required pattern are sought. Among patterns A and B, if the pattern A requires correction, assume QA is quantity of irradiation of the pattern A, fB is strength of effect on a sample point (a) caused by the pattern B, FB is strength of effect on a sample point (b) caused by the pattern B and (q) is quantity of irradiation of the pattern A without considering effects of surrounding patterns, then quantity of irradiation QA of the minute pattern A becomes approximately, QA=q(1-fB/FB). Considering effects of surrounding patterns, quantity of correction of the dimensions between patterns is also sought for pattern data.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an electron beam exposure method, and more particularly to a method of forming a highly accurate electron beam exposure pattern by correcting the so-called proximity effect.

Background of the Technology In order to improve pattern accuracy in pattern forming technology using electron beam exposure, correction of the so-called proximity effect is essential.

As is well known, the proximity effect is caused by electron beam scattering (forward scattering) in the resist layer coated on the exposed object.
This is a phenomenon in which the resist pattern after drawing spreads out more than the electron beam irradiation pattern due to electron beam scattering (backscattering) from the substrate, which is the exposed object.Especially when the distance between patterns is 2 μm or less, the result is This results in significant distortion of the pattern shape, resulting in a noticeable negative effect of lowering accuracy.

It is known that the electron beam exposure intensity distribution in the resist due to this scattering is expressed as from the center of the beam irradiated from the outside, and the first item is given by forward scattering, and the second item is given by backward scattering. ing. In addition, in formula +1.1, A, 13. C is a constant determined by conditions such as the thickness of the resist and the substrate material *:1.

(C) Prior art and problems Conventionally, the most simple method for correcting adjacent J effects is to calculate the electron beam scattering intensity distribution (11
This is a method of setting the optimal dose for each pattern in advance, taking into consideration the pattern shape and distance from adjacent patterns, or correcting (reducing) the pattern dimensions of the drawn pattern. The amount of correction is determined at the time of data creation.

Therefore, as shown in FIG. 1, for example, pattern P1
Set the sample point SPI on the side - of all other patterns, for example, pattern P2. The influence from P3 is calculated using the formula (1
), this is done for each pattern, and corrections for dimensions and irradiance are determined based on simultaneous equations so that the exposure intensity at each sample point is constant.

However, as shown in equation (1), the electron beam scattering intensity distribution decreases exponentially as the distance increases, resulting in an equation with strong nonlinearity.

For this reason, an integrated circuit pattern having an arbitrary size, especially an exposure pattern after the pattern to be formed is divided into rectangles, as shown in FIG. , moreover, the pattern PI
If the width is small like 3, it is often impossible to solve the simultaneous equations, and since the integrated circuit pattern has several patterns ranging from 0'' to 10, there is the problem that calculation takes a very long time. Ta.

fd+ Purpose of the Invention The present invention is an approximate method when performing electron beam exposure, but it is relatively easy to reduce the amount of electron beam irradiation for a pattern that has a small pattern width and is in contact with other patterns. In addition, it is possible to obtain a highly accurate pattern.

(el) Structure of the Invention The present invention provides an electron beam exposure method in which a workpiece is irradiated with an electron beam to draw a large number of patterns. When another polygonal exposure pattern comes into contact with the exposure pattern and the predetermined exposure pattern becomes a correction target, the exposure intensity of the correction target pattern is set to f, and the exposure intensity of the exposure pattern that is in contact with the correction target pattern is set to F. Also, when the influence of patterns around the correction target pattern is not considered (fl
EXAMPLES Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 3 is a pattern for explaining the embodiment, and the procedure for calculating the correction amount will be explained with reference to this figure.

■ For each pattern, correct the spread of the pattern itself.

The pattern internal dimension correction cap Si and the irradiation 1iQl for obtaining the target pattern dimension are set.

At this time, if pattern A in FIG. 3 is the target of correction, the influence of pattern B that is in contact with it will be large.

It is not possible to determine the irradiation amount using pattern A alone.

Therefore, the dose of pattern A is calculated as follows.

The following equation holds between the sample point a to the pattern (dose calculation point) and the sample point B of pattern B.

QAfA+Q8fB =E −m−−−−−−+21Q
AFA+Q8F,=E −−−−−−−131 Here, QA and QB are the irradiation doses of patterns A and B, and fA
, f are the influence strengths that patterns A and B have on sample point a, and FA and F9 are the influence strengths that patterns A and B have on sample point a.

Also, E represents the development energy intensity at the sample point of each pattern, and the influence intensity f, , rB, F,.

FB is obtained by integrating the electron beam scattering intensity distribution represented by +11 with respect to the drawing pattern.

Since pattern A is minute, it does not affect the sample points and has almost no effect. So l? ,, It can be approximated as Q.

If the irradiation amount of the pattern A is q, then qfA=E, so the irradiation amount of the minute pattern A is determined by the following equation (5), including the distance correction 1ss.

At sample point a of pattern A in FIG. 3, the following equation holds true.

QAF (rA, SA, SS) + QBF (re, sB, 0) + Qc F (r c , S c , O) -E----
------- (6) Calculate the inter-pattern dimension correction amount SS so as to satisfy this equation (6).

Here, r, q, r B , r (are pattern A,
B.

This is the distance from the center of C to sample point a. Also F
(1, m, n) is the exposure intensity of the drawing pattern, fi
It is obtained by integrating Equation 1 over the drawing pattern. Also 1. m and n indicate unknown quantities.

As described above, the amount of correction for the dimensions and electron beam irradiation density is determined at the time of pattern data creation.

In the case of an apparatus like the one shown in FIG. 4, the data is stored in the electronic computer 6, which drives the XY deflector 4, advances the beam spot, and irradiates the predetermined pattern so as to fill it. Perform drawing. FIG. 4 is a conceptual diagram of the basic configuration of a typical electron beam exposure apparatus.

The electron beam exposure apparatus main body 1 includes an electron gun 2. Convergent electron lens system 3. It has an XY deflector 4 and irradiates a narrowly focused electron beam onto a substrate sample 5 coated with resist.
The position of the electron beam spot on the sample 5 is determined by the pattern data from the electronic computer 6 and the DA converter 7. amplifier 8
It is controlled by driving the XY deflector 4 via the XY deflector 4.

The electron beam is irradiated onto the sample 5 by a blanking device in response to a signal from the computer 6.

(gl) Effects of the Invention As described above, according to the present invention, when performing electron beam exposure, although it is an approximate method, it is relatively easy to apply electron beam exposure to patterns that have a small pattern width and are in contact with other patterns. On the other hand, it is possible to increase the amount of correction for the amount of electron beam irradiation, and moreover, it is possible to obtain a highly accurate pattern.

[Brief explanation of drawings]

Figures 1 and 2 are pattern diagrams for explaining the conventional method and problems, Figure 3 is a diagram for explaining the present invention in detail, and Figure 4 shows the basic configuration of an electron beam exposure system. FIG. 2 is a block diagram illustrating an example. In the figure, 1 is an electron beam exposure apparatus main body, 2 is an electron gun, 3 is a converging electron lens system, 4 is an XY deflector, 5 is a sample, 6 is an electronic computer, 7 is a DA converter, and 8 is an amplifier.

Claims (1)

[Claims] In an electron beam exposure method in which a resist on a workpiece is irradiated with an electron beam to draw a large number of patterns, the pattern to be formed is divided into rectangles, and among the exposure patterns obtained, a predetermined exposure pattern is For the predetermined exposure pattern that the rectangular exposure pattern is in contact with, the exposure intensity of the correction target pattern is f, the exposure intensity of the exposure pattern that is in contact with the correction target pattern is F, and the electron beam around the correction target pattern is Exposure method