JPS58218118A - Inspection of light exposure pattern - Google Patents

Abstract

PURPOSE:To be able to varify easily the results of compensation for proximity effect and thereby attempt increased accuracy of pattern by electron beam exposure by calculation all over the picture drawing area based on the light exposure data of the phenomenon energy intensity distribution in the case of light exposure to an electron beam and seeking an area that has a specified phenomenon energy intensity from the phenomenon energy intensity distribution. CONSTITUTION:Design pattern data is read out from a memory 2 by the instruction of a CPU1 to carry out compensation calculation based on compensation method that is beforehand determined in a compensation calculation circuit 3, and a value of compensation is calculated. For example, regarding each of patterns K-M a sample point is set up on each side to calculate the effects of individual patterns. The sample point is selected at the bisector point of each side, for example. Compensation is made by dividing a pattern into simple rectangular patterns for a pattern of complex shape as in a pattern L. By the instruction from CPU1, the logic calculation circuit 5 reads out exposure pattern data from a first buffer memory 4 and the design pattern data is read out from a main memory 2. Exclusive Or (EOR) of both readings is sought.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for inspecting an exposure pattern by electron beam exposure, and more particularly to a method for prior evaluation of correction results for proximity effects.

(b) Prior Art and Problems In order to form a highly accurate pattern by electron beam exposure, it is essential to correct the so-called proximity effect.

As is well known, the proximity effect is caused by electron beam scattering (forward scattering) in the resist film coated on the exposed object and electron beam scattering (backward scattering) from the substrate, which is the exposed object.
This is a phenomenon in which the resist pattern after drawing expands more than the electron beam irradiation pattern. For this reason, if the distance between the patterns is approximately 2 [μm] or less, significant distortion of the pattern shape will result, resulting in a decrease in pattern accuracy.

Therefore, for each exposure pattern, the optimal irradiation amount is set in advance for each pattern, taking into account the electron beam scattering intensity distribution, pattern shape, and influence from adjacent patterns, or the drawing pattern is modified. Corrects the proximity effect.

On the other hand, as exposure backgrounds become finer and more complex, the proximity effect can be reliably corrected, but there is an increasing need to verify whether the target pattern accuracy is being achieved.

However, large-scale integrated circuit devices (I
It is impossible to manually verify pattern C).

(c) Purpose of the Invention In view of the above circumstances, the purpose of the present invention is to develop an electron beam exposure pattern that allows relatively easy verification in advance whether the proximity effect is appropriately corrected and the target pattern accuracy is obtained. The objective is to provide an inspection method.

(d) Structure of the Invention A feature of the present invention is that exposure data corrected for the proximity effect is determined based on predetermined design pattern data, and the development energy intensity distribution when electron beam exposure is performed based on the exposure data is determined. calculating an exposure pattern obtained when electron beam exposure is performed based on the exposure data by calculating over the entire drawing area and determining a region having a predetermined development energy intensity from the development energy intensity distribution;
The purpose is to calculate the exclusive OR of exposure pattern data indicating the exposure pattern and the design pattern data, find out the difference between the exposure pattern from the design pattern from the calculation result, and evaluate the exposure data of the electron beam. .

(e) Embodiment of the Invention An embodiment of the present invention will be specifically described below 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, in which 1 is a central processing unit (CPU), and 2 is a main storage device (memory) for storing design pattern data. , 3 is a correction calculation circuit that generates exposure data for correcting the proximity effect, and 4 is a first buffer memory (4) for storing simulation pattern data obtained when exposure is performed based on the exposure data. Buffer I), 5 is a logic operation circuit for calculating the exclusive OR (EOR) of the simulation pattern data and the design pattern data, and 6 is a second logic operation circuit for storing the output of the logic operation circuit 5. Buffer memory (buffer ■), 7 is a display device.

FIGS. 2 to 6 are diagrams showing the principle of the present invention, and the present embodiment will be described below with reference to FIG. 1.

In FIG. 2, solid lines indicate design patterns, and this design pattern data is stored in the memory 2 in advance. The broken line pattern indicates the area where the proximity effect is corrected and the electron beam is actually irradiated (hereinafter referred to as the irradiation pattern) in order to obtain the above-mentioned designed pattern.

To perform the exposure pattern inspection of this embodiment, first the CPU 1
The design pattern data is read out from the memory 2 according to the command, and the correction calculation circuit 3 performs correction calculation based on a predetermined correction method to calculate the correction amount. For example, sample points are set on each side of each of the patterns K to M, and the influence from other patterns is calculated.

As the sample points, for example, bisecting points on each side are selected. At this time, a pattern with a complicated shape like pattern L is corrected by dividing it into simple rectangular patterns.

In other words, in the case of pattern L, pattern L1 and pattern L
2, and sample points are set on each side of each as described above.

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

The influence from other patterns is calculated using equation (1), and the amount of correction for the dimensions and irradiation amount is determined by solving simultaneous equations or the like so that the exposure intensity at each sample point is constant.

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 development energy intensity E of each pattern is determined by the product of Q and the equation (1) integrated over the entire area of the drawn pattern, where the electron beam irradiation amount is Q [C/cm2]. That is, here s is the area of the drawing pattern.

Therefore, the correction calculation circuit 3 calculates the pattern shape of a pattern obtained when exposure is performed according to the above-mentioned irradiation pattern (hereinafter referred to as exposure pattern) to have a certain equal energy intensity E0 according to equation (2). The exposure pattern thus obtained is shown in FIG. 3 by a chain line.

Up to this point, as described above, a complex pattern like pattern L has been treated by being divided into simple rectangular patterns L1 and L2. Therefore, the divided patterns are synthesized by calculating the logical sum (OR) of the exposure patterns. By doing so, it is possible to obtain an exposure pattern obtained when the electron beam is irradiated with the proximity effect corrected. FIG. 4 shows the exposure pattern simulated in this manner.

The pattern data of this exposure pattern is stored in the first buffer memory 4.

After completing the above operations, according to a command from CPU1,
The logic operation circuit 5 reads out the exposure pattern data from the first buffer memory 4 and calculates an exclusive OR (EOR) with the design pattern data read out from the main storage device 2.

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, it is not always the case that the entire area of each pattern is appropriately corrected. For example, in FIG. 4, on the left side of pattern L, pattern K exists close to it in the upper part, but there is no parallel pattern in the lower part. Therefore, since the influence of the proximity effect is large in the upper part, the pattern obtained in the upper part is generally different from the designed pattern, for example, the pattern becomes thicker in the upper part than in the lower part with average correction.

Therefore, by calculating the exclusive OR of the two as described above, the portions where the design pattern indicated by the solid line in FIG. 5 and the exposure pattern indicated by the dashed-dotted line do not match are extracted. Pattern N in FIG. 6 shows the error between the design pattern thus detected and the simulated exposure pattern.

The data of the pattern N is stored in the second buffer memory 6.

The pattern N obtained as described above is displayed on the display device 7. It is of course possible to display design patterns, irradiation patterns, exposure patterns, etc. on this display device 7 as necessary.

By inspecting the dimensions and position of the pattern N or the exposure pattern, it is possible to check whether the proximity effect correction is appropriate, that is, whether a pattern with the target accuracy can be obtained before performing electron beam exposure. It can be verified.

In this way, according to this embodiment, the proximity effect correction result can be verified relatively easily. Therefore, if the accuracy is insufficient, by repeating the above simulation, it is possible to find electron beam exposure conditions that can draw a pattern with high accuracy.

In the above embodiment, the proximity effect was corrected for one sample point on each side, but this is not practical because if the correction was performed over the entire area of each pattern, it would take an enormous amount of time. It is. However, the correction method is not limited to the above-mentioned method, and any commonly used correction method may be used.

(f) Effects of the Invention As described above, according to the present invention, it is possible to easily verify the correction result of the proximity effect, thereby improving pattern accuracy by electron beam exposure.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of a control system of an electron beam exposure apparatus used in an embodiment of the present invention, and FIGS. 2 to 6 are top views of the main parts of the above embodiment. In the figure, 1 is a central processing unit (CPU), 2 is a main storage device, 3 is a correction calculation circuit, 4 is a first buffer memory,
5 is a logic operation circuit that performs an exclusive OR (EOR) operation;
6 is a second buffer memory, 7 is a display device, K, L, L
1, L2, and M each indicate a pattern. Agent Patent Attorney Koshiro Matsuoka No. 1, No. 2, Figure 1, Question 3

Claims (1)

[Claims] Determine exposure data with the proximity effect corrected based on predetermined design pattern data, calculate the development energy intensity distribution over the entire drawing area when electron beam exposure is performed based on the exposure data, and calculate the development energy intensity distribution. An exposure pattern obtained when electron beam exposure is performed based on the exposure data is calculated by determining a region having a predetermined development energy intensity from A method for inspecting an exposure pattern, comprising calculating an exclusive OR, determining the difference between the exposure pattern and the design pattern from the result of the calculation, and evaluating the exposure data of the electron beam.