JPS60117623A - Inspecting method for exposure pattern - Google Patents

Abstract

PURPOSE:To enable to verify the proper correction of a proximity effect and the possibility of the resolution of an exposure pattern under the conditions of some exposure previously and simply by comparing a presence within a set range of energy strength and evaluating the exposure data of electron beams. CONSTITUTION:Design pattern data are read from a memory 2, data are corrected and arithmetically operated on the basis of a previously determined correction method in a correction arithmetic circuit 3, and the quantities of correction to size and dosage are calculated. Design patterns in solid lines are corrected by using the quantities of correction, and irradiation patterns in broken lines are obtained. Since data are not always corrected properly extending over the whole regions according to the conditions of patterns, a plurality of sample points a1- a15 are set on each side of the design patterns, and energy strength is calculated. Positions where correction patterns are not resolved are extracted by comparing energy strength at several sample points with development energy strength. Extracted pattern data are stored in a buffer memory 6.

Description

DETAILED DESCRIPTION OF THE INVENTION 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.

(bl Prior Art and Problems) In order to perform high-precision single-turn I-cutting using electron beam exposure, it is essential to correct the so-called proximity effect.As is well-known, the proximity effect The electron beam tik i'IL (
This is a phenomenon in which the resist pattern after writing spreads more than the electron beam irradiation amount due to electron beam scattering (back scattering) from the substrate, which is the exposed object. When the distance 1'M becomes approximately 2 μm or less, significant distortion of the resulting G) i-turn shape occurs, resulting in a decrease in pattern accuracy.Therefore, for each exposure pattern, the electron beam 11 is given a random intensity distribution. By considering the pattern shape and the influence of adjacent force, etc., we can determine the optimal irradiation amount and set it for each pattern.
Alternatively, the effects of adjacent edges are corrected by deforming the drawn turns.

On the other hand, as exposure patterns become finer and more complex, the need to check whether the -C1 proximity effect is reliably corrected is increasing.

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

Further, as integrated circuit devices become more highly integrated, exposure patterns become finer, and it becomes necessary to expose Ic patterns having submicron pattern widths and space widths.

Conventionally, when using a design pattern rule of 2 to 3 μm, a minimum pattern interval has been set and the design rule has been verified. However, when using a pattern rule of 1 μrn or less, even if the pattern spacing is the same, resolution may or may not be achieved depending on the exposure and pattern conditions such as the resolution of the resist. Verification is required.

(C1 Purpose of the Invention In view of the above circumstances, the present invention aims to determine in advance whether or not the proximity effect has been appropriately corrected, and whether or not an exposure pattern can be resolved under certain exposure conditions. An object of the present invention is to provide a method for inspecting an electron beam exposure pattern that can be verified relatively easily.

(di) Structure of the Invention The characteristics of the present invention are to apply dimension correction and dose correction to predetermined design pattern data based on exposure conditions, perform proximity effect correction, determine exposure data, Set a sample point on each side of 2, calculate the energy intensity if the electron beam irradiation on the exposure data does not reach each of the sample points, and compare whether the energy intensity is within the set range. By doing so, the above-mentioned electron beam exposure data is evaluated.

(e) Embodiment of the Invention Hereinafter, an embodiment of the present invention will be explained in detail 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 memory for storing design pattern data. Device Fffi (memory) 3; correction calculation circuit 4 for generating exposure data for correcting the proximity effect;
For example, the first buffer memory (buffer ■) is used to store the above-mentioned exposure data. 6, a second buffer memory for storing the output of the result of the test operation; and 7, a display device.

FIGS. 2 and 3 are diagrams showing one embodiment of the present invention, and this 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.

In order to obtain the above design pattern, the pattern indicated by the dashed line is obtained by correcting the proximity effect and actually using a non-area (
Hereinafter, this will be abbreviated as an irradiation pattern).

To inspect the exposure pattern of this example, first, the CP
In response to a command from the UI, the above setting rt+pattern data is read out from the memory 2, and in correction calculation time 1/33, a correction calculation is performed based on a predetermined correction method (dimension and irradiation amount correction), and the dimensions and irradiation amount are Calculate the correction amount for.

By correcting the design pattern shown by the solid line in FIG. 2 using the 7111 positive amount described above, the irradiation pattern shown by the broken line t is obtained.

Practical processing capable of high-speed processing is required to perform proximity effect correction on large-scale data in which the number of patterns is on the order of 101 to 1C6. Therefore, the correction amount is calculated using an approximation method.

Therefore, depending on the pattern conditions, it is not always the case that the entire area of each pattern is appropriately corrected.

Therefore, as shown in FIG. 3, a plurality of sample points (al to a19) are set on each side of the design pattern, and the energy intensity at each sample point is calculated.

For example, the energy intensity E at sample point a+7
a7 can be calculated using the following formula.

Ea7=Q+ F+(r+) +Q4 F2(rz
)-toQ3 F3(r3) +Q$F(r,+
) -(1) Here, Qi (i=1 to 4) is pattern K.

is the irradiation amount of L,,LL,M, and Fi(ri)(i=1
~4) is the influence strength that does not affect the sample point a7 of each irradiation pattern. Also, I? 1(ri) is obtained by integrating the scattering intensity distribution formula f (r) over the irradiation pattern.

Further, as is well known, the electron beam scattering intensity distribution f'(r) is expressed by the distance from the center of the beam irradiated from the outside. In equation (2), the first term indicates forward scattering, and the second term indicates backward scattering. In the above formula, A to C are constants determined by the sensitivity, thickness, substrate material, etc. of the resist, and are given in advance.

Thus, by comparing the energy intensity Ei at each sample point with the development energy intensity Eo, it is possible to extract unresolved locations in the correction pattern. Further, by correlating the energy intensity Ei with the pattern accuracy, it is possible to estimate the pattern accuracy after exposure.

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. This display device 7 displays design patterns as required.

Of course, it is also possible to display the irradiation pattern and the like.

The sample points shown in FIG. 3 are preferably set as follows.

That is, as shown in FIG. 4, sample points are set at the midpoints of each side of the design pattern, and the energy intensity at each sample point is calculated.

For example, the energy intensity Ea at sample point a (
I is determined by the following formula.

E a H= Q , F 1. (rρ〇zF2(r2
)+QI FJ(r3) +Ql, FL)(“l+)
-1---(11 Here, Qi (i=l~4) is pattern K.

L,,L2. is the irradiation dose of M, and F, i (ri) (
i=1 to 4) is the influence strength of each irradiation pattern on the sample point al. Further, Fi(ri) can be obtained by integrating the scattering intensity distribution formula f (') with respect to the irradiation pattern.

Further, as is well known, the electron beam scattering intensity distribution f (r) is expressed by the distance from the center of the beam irradiated from the outside. In equation (2), the first term indicates forward scattering, and the second term indicates backward scattering. In the two equations, ~C is a constant determined by the sensitivity and thickness of the resist I, or conditions such as the substrate material, and is given in advance.

When the energy intensity at the busy sample point is IE, as shown in FIG. 5, the following equation holds true at sample points 1), , and l)2.

Here, Q is the irradiation i, 2W is the pattern width of the irradiation pattern,
2a is the pattern width after exposure.

From (3), F (a) = (E/EO) F (W
) −(4) holds, and by using equation (4),
The pattern dimensions after exposure can be estimated.

Furthermore, by comparing the pattern dimensions after exposure with the designed pattern dimensions, it is possible to extract locations with irregularities in pattern accuracy. 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 design patterns, irradiation patterns, etc. on this display device 7 as necessary.

In the second embodiment described above, size correction and dose correction are performed on predetermined design pattern data based on exposure conditions. Proximity effect correction is performed to determine writing data, sample points are set at the midpoints on each side of the design pattern, and energy intensity E exerted on each of the sample points by electron beam irradiation on the writing data is determined. The pattern width of the drawing data is 2a, the development energy intensity is 1°W, and using the formula F (W) = (E/Eo) = F (a), the above-mentioned electron beam This is an exposure pattern inspection method characterized by evaluating i, 1iTi image data.

(fl) 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 and yield.

[Brief explanation of the drawing]

FIG. 1 is a pattern diagram for explaining the electronic beacon used in the embodiment of the present invention, and each design pattern and '4i
11 after 1i (indicates the i-ray pattern. In the figure, 1 is the central processing unit, 2 is the memory, 3 is the correction calculation circuit, 4 is the buffer, and 5 is the inspection calculation circuit. 6 is the buffer, and 7 is the display. The device is shown. (2/3 Plan 30

Claims (1)

[Claims] For a predetermined design pattern shape, perform dimension correction and dose correction based on exposure conditions, perform proximity effect correction, determine exposure data, and set sample points on each side of each of the design patterns. By setting the electron beam irradiation with respect to the exposure data and calculating the energy intensity when it does not reach each of the sample points, and comparing whether the energy intensity is within the set range, the exposure data of the electron beam is calculated. An exposure pattern inspection method characterized by evaluating.