JPH0352209B2 - - Google Patents

Description

[Detailed Description of the Invention] (A) Technical Field of the Invention The present invention relates to an electron beam exposure method, and more specifically, to a method of correcting the proximity effect and forming a highly accurate electron beam exposure pattern. It is.

(a) Background of the technology Microfabrication of circuit patterns is necessary for the high integration of semiconductor devices such as LSI and VLSI, and research and development and improvement of electron beam lithography technology is required for this microfabrication. It's progressing.

In circuit pattern forming technology using electron beam exposure, in order to improve pattern accuracy, it is desirable to improve the electron beam lithography device, improve the characteristics of the resist, and correct the proximity effect. Proximity effect means that when a resist layer on a substrate is irradiated with an electron beam, the resist pattern after drawing is affected by scattering of the electron beam in the resist layer (forward scattering) and scattering of the reflected electron beam from the substrate (backward scattering). This is a phenomenon in which the electron beam spreads out more than the electron beam irradiation pattern. In short, this is a phenomenon that results in figure distortion, and in particular, when the gap between patterns is less than 2 μm (when the patterns are close to each other), pattern shape distortion occurs and the negative effect of reducing accuracy becomes noticeable. The electron beam exposure intensity distribution (accumulated charge distribution) in the resist layer due to these scattering is expressed as a function of the distance r from the center of the irradiation beam by the following formula: f(r)=e ^-(r/A)2 +Be ^{-(r/ C)2} ......(1) The first term is attributable to forward scattering and the second term is attributable to backward scattering. Note that A, B, and C in formula (1) are constants determined by conditions such as the thickness of the resist and the material of the substrate.

(C) Conventional techniques and problems A general method for correcting the proximity effect as described above involves calculating the electron beam exposure intensity distribution in Equation (1) for each rectangular pattern, its rectangular shape, and adjacent rectangles. There is a method of presetting an optimal dose for each rectangular pattern in consideration of the distance from the pattern, and/or a method of correcting (reducing) the rectangular pattern dimensions of the drawn pattern. In either method, the amount of correction is determined in advance at the time of creating pattern data.

For example, when rectangular patterns 1, 2, and 3 are close to each other but not in contact with each other as shown in Figure 1, correction using rectangular pattern 2 is performed using sample points (representative points) on each side of the rectangular pattern. ) Set a, b, c, and d (specifically, the midpoint of each side), and calculate the influence from other rectangular patterns 1 and 3 at each sample point using equation (1) above. Therefore, the energy intensity at each sample point is constant (i.e.,
This is done by determining the amount of dimensional correction and the amount of irradiation so that the phenomenon energy intensity E is equal to ₀ ). Energy intensity E at point a is expressed by the following equation.

Q ₁ F ₁ (r ₁ ) + Q ₂ F ₂ (r ₂ ) + Q ₃ F ₃ (r ₃ )=E (2) In equation (2), Q _i (i=1, 2, 3) is the irradiation amount of each rectangular pattern 1, 2, and 3, and F _i (i=
1, 2, and 3) are the influence strengths exerted on point a of each rectangular pattern, and for example, F ₂ (r ₂ ) is expressed by the following equation.

F ₂ (r ₂ )=∫(W-x1-x3)/2-(W-x1-x3)/
2∫(H−x2−x4)/2−(H−x2−x4)/2 f(r)d _y d _x ……(3) As shown in Figure 1, W and H are This is the width and length of the subsequent rectangular pattern 2, and the portion indicated by the broken line is the rectangular pattern 11, 12, irradiated with the electron beam.
It is 13. The distances r ₁ , r ₂ , and r ₃ are the respective distances between the center points of the irradiation rectangular patterns 11, 12, and 13 and point a, and the dimensional correction amounts x ₁ , x ₂ , x ₃ , and x ₄ are the distances of the irradiation rectangular patterns 11, 12, and 13, respectively. 12 and the rectangular pattern 2 after irradiation. The same relationship as the above equation (2) also holds true for the sample points (b, c, d) on other sides of the rectangular pattern 2.

However, when calculating the correction amount using the midpoint of each side of a rectangular pattern as a sample point, if the rectangular pattern is in contact with another rectangular pattern as shown in Figures 2 and 3, the calculated correction amount However, there is a problem in that the pattern accuracy of the pattern after irradiation decreases. For example, the rectangular pattern 31 in FIG.
When exposed and irradiated with the correction amount at the midpoint h, the tip part 31
In case a, the amount of irradiation becomes insufficient.

(D) Purpose of the Invention The purpose of the present invention is to provide a method for determining appropriate sample points in consideration of other surrounding rectangular patterns when a rectangular pattern constituting a figure pattern to be formed is in contact with another rectangular pattern. An object of the present invention is to provide an electron beam exposure method that obtains a highly accurate rectangular pattern (i.e., a graphic pattern) by setting an electron beam on the side of a rectangular pattern and determining the amount of correction at the sample point.

(E) Structure of the Invention An object of the present invention is to provide an electron beam exposure method for drawing a predetermined figure pattern by irradiating a large number of rectangular patterns with an electron beam, in which one first rectangular pattern is drawn on another second rectangular pattern adjacent to the first rectangular pattern. When the length of the side that contacts the pattern and includes the contacting portion of the first rectangular pattern is longer than the contact side of the second rectangular pattern, the second rectangular pattern on the contacting side of the first rectangular pattern An electron beam exposure method characterized in that a sample point is set at the midpoint of a portion not in contact with a rectangular pattern, and the dimensional correction amount and irradiation amount at this sample point are determined and electron beam irradiation is performed on a first rectangular pattern. It is achieved by doing so.

(F) Embodiments of the invention The present invention will be described in detail below by way of embodiments of the invention with reference to the accompanying drawings.

The figure pattern shown in Figure 2 is rectangular pattern 2.
1, 22 and 23, and the case where pattern 21 is irradiated with an electron beam will be explained.

The setting locations of the sample points of the rectangular pattern 21 are determined as follows. Since the right side of this rectangular pattern 21 is in full contact with the adjacent rectangular pattern 22, no sample points are set on this right side. If a sample point is set at the midpoint of this right side to determine the correction amount and then electron beam irradiation is performed, the entire rectangular pattern 21 will be exposed to an insufficient amount of irradiation. Part of the left side of the rectangular pattern 21 is in contact with the rectangular pattern 23, so the lengths m and n of the sides of the non-contacting part of the rectangular pattern 21 are compared, and the midpoint of the longer side m is sampled. Let it be point e. The midpoints of the upper and lower sides of the rectangular pattern 21 are defined as sample points f and g.

Energy intensity E at sample point e can be expressed as follows.

Q ₂₁ F (r ₂₁ ) + Q ₂₂ F (r ₂₂ ) + Q ₂₃ F (r ₂₃ ) = E (4) In equation (4), Q ₂₁ , Q ₂₂ , and Q ₂₃ represent each rectangular pattern. 21, 22 and 23 doses, F
(r ₂₁ ), F (r ₂₂ ), and F (r ₂₃ ) are each rectangular pattern 21
，
This is the influence intensity exerted on point e from 22 and 23.
Distances r ₂₁ , r ₂₂ , and r ₂₃ in FIG. 2 are the respective distances between the center points of the irradiation rectangular patterns 21, 22, and 23 and point e. Similarly, the energy intensity at other sample points (point f and point g) is expressed, and the amount of correction (dimensional correction amount and irradiation amount) is adjusted so that the energy intensity at these sample points is equal to the development energy intensity _E ). Then, by performing electron beam irradiation with the calculated correction amount,
The rectangular pattern 21 can be formed with high precision.

Furthermore, when performing electron beam irradiation on the rectangular pattern 23 shown in FIG. , u
It is desirable to set it as .

The figure pattern shown in Figure 3 is rectangles 31 and 32.
and 33, and in the case of electron beam irradiation of pattern 31, adjacent rectangular pattern 3
The lengths o and p of the sides that do not touch 2 and 33 are compared, and the midpoint (point i) of the longer side o is set as the sample point. Furthermore, this rectangular pattern 3
The midpoints of the upper and right sides of 1 (point j and point k) are also taken as sample points, and the correction amount is determined from these sample points as described above. Then, by performing electron beam irradiation with the obtained correction amount, a highly accurate pattern can be obtained without underexposure of the tip portion 31a of the rectangular pattern 31. In addition, the third
In the figure pattern shown in the figure, the adjacent portion 31b of the other rectangular patterns 32 and 33 in the rectangular pattern 31
There is a possibility of overexposure, and the influence strength at the sample point i and the intersection l of the sides is compared, and if it is above the predetermined setting range, a rectangular pattern is created using the broken line at the intersection l. Perform 31 divisions.

Practically, the required irradiation amount and dimensional correction amount are calculated and determined when graphic pattern data is created, and the data is stored in the control electronic computer of the electron beam lithography apparatus. In the case of the typical electron beam exposure apparatus shown in FIG.
has an electron gun 42, a blanking device 43, a converging electron lens system 44, an XY deflector 45, and a substrate sample 47 on which a resist is applied on a stage 46.
is located. When the electron beam 48 from the electron gun 42 is focused narrowly and irradiated onto the substrate sample 47, the blanking device 43 is controlled by a signal from the electronic computer 50 according to the pattern data, and the position of the electron beam spot is adjusted. DA converter 51
and is controlled by an XY deflector 53 via an amplifier 52. In this way, the computer 50 advances the beam irradiation spot using the pattern data with the correction amount determined in accordance with the present invention, and performs drawing so as to fill in a predetermined figure pattern.

(G) Effect of the invention If the sample points are set according to the present invention,
An elongated rectangular pattern that is in contact with another rectangular pattern can be formed with high precision by correcting the proximity effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of rectangular patterns that are separated from each other, FIGS. 2 and 3 are explanatory diagrams of graphic patterns consisting of rectangular patterns that are in contact, and FIG. 4 is a schematic diagram of an electron beam lithography apparatus. It is a diagram. 1, 2, 3...Rectangular pattern, 21, 22, 2
3...Touching rectangular patterns, 31, 32,
33... Contacting rectangular pattern, 42... Electron gun, 43... Blanking device, 45... XY
Deflection machine, 47...Substrate sample, 48...Electron beam, 50...Electronic computer.

Claims (1)

[Scope of Claims] 1. In an electron beam exposure method in which a predetermined figure pattern is drawn by irradiating a large number of rectangular patterns with an electron beam, one first rectangular pattern is in contact with another adjacent second rectangular pattern, and When the length of the side of the first rectangular pattern including the contacting part is longer than the contacting side of the second rectangular pattern, the second rectangular pattern on the contacting side of the first rectangular pattern
An electron beam exposure method characterized in that a sample point is set at the midpoint of a portion not in contact with the rectangular pattern, and the electron beam irradiation of the first rectangular pattern is performed by determining the dimension correction amount and irradiation amount at this sample point. . 2. When there are two parts of the contacting side of the first rectangular pattern that do not contact the second rectangular pattern, the sample point is set at the midpoint of the longer part in comparison. The electron beam exposure method according to claim 1.