JPS609121A - Evaluation of exposure pattern data - Google Patents

Abstract

PURPOSE:To evaluate adequacy of exposure data by obtaining an energy intensity at the specified position between patterns received from electron beam after determining exposure data of respective patterns through proximity effect compensation. CONSTITUTION:A design pattern data is read from a memory 2 in accordance with a command of CPU 1, calculation for compensation is carried out on the basis of compensating method predetermined in the compensating calculation circuit 3. Focusing on energy intensity at the center position between the patterns of irradiation pattern received from the electron beam projected, an energy intensity of center P of pattern interval is supposed as Ep and Ep when the pattern interval is resolved is supposed as Eop. In this case, the data of such an area not resolved can also be exracted from the relation, Ep>=Eop. The extracted pattern data is stored in a second buffer memory 6 and is displayed on a display unit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for evaluating exposure pattern data obtained by electron beam exposure, and more particularly to a method for evaluating correction results for proximity effects.

tbl Prior Art and Problems In order to form high-precision patterns by electron beam exposure, it is essential to correct the so-called proximity effect.As is well-known, the proximity effect is caused by This is a phenomenon in which the resist pattern after drawing spreads out more than the electron beam irradiation due to electron beam scattering (forward scattering) in the film and electron beam scattering (backward scattering) from the substrate, which is the object to be exposed. For this reason, when the distance between the patterns is approximately 2 μm or less, the pattern shape is significantly distorted as a result, and the pattern density becomes low.

Therefore, for each exposure pattern, we considered the electron beam scattering intensity distribution, pattern shape, and influence from adjacent patterns.
Proximity effects are corrected by setting the optimum dose for each pattern in advance, or by modifying the drawing pattern.

On the other hand, as exposure patterns become finer and more complex, there is an increasing need to verify whether correction of the proximity effect is being performed reliably.

However, the number of patterns is large-scale on the order of 105 to 10' and the pattern shape is complex (integrated circuit devices).
IC) patterns cannot be verified manually.

In addition, as integrated circuit devices become more highly integrated (integrated circuit devices become more highly integrated), exposure chimney turns become increasingly finer, and it becomes necessary to expose IC patterns having submicron turn widths and space widths.

Conventionally, for the design pattern rule of 2 to 3 μl, the minimum pattern spacing was set and the design/l/−/l was verified. However, when using a no-turn rule of 1 μm or less, even if the pattern spacing is the same, IW images may or may not be formed depending on the exposure and pattern conditions such as the resolution of the resist. Examination of the rules is necessary.

(Cl. Purpose of the Invention The purpose of the present invention is to monitor such circumstances and determine whether the proximity effect is properly corrected or not, and whether the exposure pattern can be resolved under certain exposure conditions. It is an object of the present invention to provide a method for evaluating electron beam exposure pattern data that can be relatively easily verified in advance.

(dl Structure of the Invention The feature of the present invention is that after applying proximity effect correction to the design data of a plurality of patterns to be exposed and determining the exposure data of each of the patterns, electrons at predetermined positions between the adjacent patterns are The object of the present invention is to evaluate the appropriateness of the exposure data by measuring the energy intensity received by the beam and determining whether the energy intensity is within a predetermined range.

(Ql Embodiment of the Invention Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of the control system of the electron beam exposure apparatus used in the above embodiment, and 1 is a central processing bag! (CP.U), 2 is a main storage device (memory) for storing design pattern data; h is a correction calculation circuit that generates exposure data for correcting the proximity effect; 4 is a storage unit for storing the exposure data. The first buffer memory for (
buffer l).

5, an inspection calculation circuit that calculates the energy intensity at the midpoint between the patterns of the exposure pattern, and compares and inspects whether the energy intensity is within a set range; 6, stores the output of the inspection calculation result; Second buffer memory for
(buffer ■), 7 is a display device, and 8 is a data bus.

Figures 2 to 4 are diagrams showing the principle of the present invention.
This embodiment will be described with reference to the drawings.

In the ffi2 diagram, solid lines indicate design patterns, and this design pattern data is stored in the memory 2 in advance. The dashed line pattern is to obtain the above design pattern.
The area where the proximity effect is corrected and the electron beam is actually irradiated (
Hereinafter, this will be abbreviated as the irradiation pattern).

In order to evaluate the exposure pattern data of this embodiment, first, the above design pattern data is read out from the memory 2 according to a command from the CPUI, and the fili positive calculation positive path calculating circuit 3 performs the fili positive calculation based on a predetermined correction method. Perform all calculations and calculate the correction amount. For example, one M for each pattern.
Set sample points on each side for each, and calculate the influence from other patterns. For example, a bisecting point on each side is selected as the sample point. At this time, a pattern with a complicated shape such as pattern L is divided into simple rectangular patterns for correction.

That is, in the case of pattern L, it is divided into pattern Ll and pattern L2, and sample points are set on each side of each of them as described above.

As is well known, the electron beam scattering intensity distribution f (r) is expressed as the distance r from the center of the beam irradiated from the outside. +1) In the equation, the first term indicates forward scattering and the second term indicates backward scattering. In the above formula, A-C are constants determined by the sensitivity and thickness of the resist, the substrate material, etc., and are given in advance.

Using this equation (1), for each irradiation pattern, the influence from other patterns is calculated by integrating, and the dimensions and Calculate the correction amount for the irradiation amount.

By correcting the design pattern shown by the solid line in FIG. 2 using the above correction amount, the irradiation pattern shown by the broken line is obtained.

The proximity effect correction in this embodiment described above is an average correction method in which one sample point is selected for each side and the amount of correction is determined using this sample point as the representative point of each side. Therefore, depending on the pattern conditions, it is not always the case that the entire area of each pattern is appropriately corrected.

Note that the proximity effect correction was performed for one sample point on each side, but this is because increasing the number of sample points would increase the time required, which is not practical.

Furthermore, due to the limits of resist resolution, it is not always possible to appropriately correct all pattern conditions.

Therefore, as shown in FIG. 3, attention is paid to the energy intensity received from the irradiation electron beam at the center position between the patterns of the irradiation pattern, and the energy intensity at the center P of the pattern interval is set as Ep.

If Eop is Eop when the pattern spacing is I/lv, Ep<Eop...pattern spacing resolution Ep≧Eop...no resolution...(2) The above relationship is established. Using this method, it becomes possible to extract unresolved locations in the correction pattern.

That is, as shown in FIG. 4, the midpoints P, Q, and R between the irradiation patterns are set as sample points, and the energy intensity at each sample point is calculated.

For example, the energy intensity B applied to the sample point P
p can be calculated using the following formula.

rzp, = Q, F+ (rl) 10z Fz (r
z ) →−Q3 F3 (r5 ) +QtIFu
(r4t) ・・・・・・(3) Gokode Qi (i=1~
4),B,in the pattern,Ll.

is the electron beam irradiation amount of I, λ, and Fi (ri) (i
−1 to 4) are influence strengths that are not as high as the sample point P of each pattern. Moreover, Fi(ri) can be obtained by integrating the scattering intensity distribution formula (1) for the irradiation pattern.

Thus, by comparing whether the energy intensity at each sample point is within the set range of condition (2), it is possible to extract unresolved locations in the correction pattern. The extracted pattern data is stored in the second buffer memory 6.

The pattern data obtained as described above is displayed on the display device 7. It is of course possible to display a design pattern irradiation pattern or the like on the display device 7 as required.

In this way, according to this embodiment, it is relatively easy to verify in advance whether or not the proximity effect has been appropriately corrected, and whether or not the exposure pattern can be resolved under certain exposure conditions. It is possible.

(fl) As described in detail, according to the present invention, it is possible to easily verify the correction result of the proximity effect, thereby improving pattern accuracy and yield.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing essential parts of a control system for an electron beam exposure apparatus according to the present invention, and FIGS. 2 to 4 are diagrams for explaining one embodiment of the present invention. In the figure, 1 is the CPU, 2 is the memory, and 3 is the ? ili positive arithmetic circuit; 5 is an inspection arithmetic circuit; 1. , , M indicates the pattern, and P, Q, R indicate the midpoint between the patterns. 3rd 4th ■

Claims (1)

[Claims] After applying proximity effect correction to the design data of a plurality of patterns to be exposed and determining the exposure data of each pattern, calculate the energy intensity received by the electron beam at a predetermined position between the adjacent patterns, and calculate the energy intensity. 1. A method for evaluating exposure pattern data, characterized in that the suitability of the exposure data is evaluated by determining whether or not the exposure data is within a predetermined range.