JPH0336294B2 - - Google Patents

Description

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

Prior Art and Problems Generally, when a pattern is formed using an electron beam exposure method, an electron beam exposure apparatus is controlled based on pattern data created in advance.

FIG. 7 shows a block diagram of the main parts of an electron beam exposure apparatus.

In the figure, 41 is the main body, 42 is an electron gun, and 43
is a convergent electron lens system, 44 is an X/Y deflector, 45
4 shows a workpiece, 46 a processor, 47 a DA converter, and 48 an amplifier, respectively.

In the illustrated device, pattern data is stored in the processor 46, and the pattern data is processed as needed.
Read data, DA converter 47, amplifier 48
The X and Y deflectors are driven through the wafer, thereby advancing the electron beam spot and irradiating the electron beam so as to fill in a predetermined pattern to perform drawing. Furthermore, irradiation and blanking control is applied to the electron beam by a blanking device in accordance with signals from the processor 46. In the case of the apparatus shown in FIG. 7, control of the electron beam irradiation density is achieved by controlling the stepping speed and blanking time of the electron beam spot.

When implementing such an electron beam exposure method, it is of course important to improve pattern accuracy, and for this purpose 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 layer coated on the exposed object and electron beam scattering (backward scattering) from the substrate, which is the exposed object. Therefore, it is a phenomenon in which the resist pattern after drawing expands more than the electron beam irradiation pattern, and especially when the interval between patterns becomes 3 [μm] or less, it results in significant distortion of the pattern shape and reduces accuracy. .

By the way, the electron beam scattering intensity distribution in the resist due to the above-mentioned scattering is expressed as a function of the distance r from the center of the externally irradiated beam: f(r)=e ^-(r/A)2 +B・e ^{-( r/C)2} (1) It is known that the first term is given by forward scattering and the second term is given by backward scattering. Note that A, B, and C used in equation (1) are constants determined depending on conditions such as the thickness of the resist and the material of the substrate.

Conventionally, the most common method for correcting the proximity effect is to calculate the optimal irradiation by considering the electron beam scattering intensity distribution expressed by equation (1) for each pattern and the distance between the pattern and the adjacent pattern. The amount of correction is set in advance for each pattern, or the pattern dimensions of the drawn pattern are corrected (reduced), but in both cases, the correction amount is determined in advance at the time of creating the pattern data. do.

Further, in the design figures of integrated circuit devices, patterns are usually described as polygons, whereas patterns in electron beam writing data are only allowed to be rectangular or at most trapezoidal.

Therefore, when forming an integrated circuit pattern using electron beam exposure, the pattern data obtained from the design in its original format does not become drawing data for electron beam exposure, for example, as shown in Figure 1. First, it is necessary to divide the pattern in the data into exposure pattern 1 and exposure pattern 2.
In that case, depending on the pattern, exposure pattern 2
It is often the case that the contact pattern is narrow in width and in contact with the large exposure pattern 1, as shown in FIG. In that case, as shown in Figure 1, an erect pattern with no surrounding pattern may be sufficient, but as shown in Figure 2, if there is a pattern 3 or 4 intervening close to the periphery, there is no problem. be.

That is, in the pattern shown in FIG. 2, in order to correct the proximity effect and obtain the desired pattern dimensions and spacing, it becomes necessary to correct the dimensions of the pattern itself. For example, if the influence of pattern 3 on exposure pattern 2 is large, it is necessary to eliminate exposure pattern 2 and correct the size of pattern 4 as well. The corrected pattern is, for example, as shown in FIG. 3, which is different from the pattern at the time of design.

Purpose of the Invention The present invention provides an electron beam exposure method in which, when performing electron beam exposure, size correction is performed so that the pattern shape after exposure does not change, and electron beam drawing is performed based on the corrected pattern size and irradiation amount. It is something to do.

Configuration of the Invention The present invention irradiates an electron beam onto a workpiece,
In an electron beam exposure method that draws a large number of patterns, a predetermined exposure pattern among the exposure patterns obtained by dividing the pattern to be formed into rectangles comes into contact with another exposure pattern, and electrons are applied to the predetermined exposure pattern. If the influence between patterns due to beam scattering is large, the predetermined exposure pattern is combined with another exposure pattern that was in contact with the exposure pattern, the pattern resulting from the combination is divided into new rectangles, and the divided pattern is On the other hand, the irradiation amount and dimensional correction amount for obtaining the target photosensitive pattern size are determined, and drawing is performed based on the irradiation amount and dimensional correction amount.

Embodiment of the Invention FIG. 4 is a plan view of a main part of a pattern for explaining an embodiment of the present invention, which is basically the same as the pattern in FIG. Parts are indicated with the same symbols.

In the figure, SP1 is the sample point (representative point), r
1 is sample point SP1 from the center of exposure pattern 1
r2 is the distance from the center of exposure pattern 2 to sample point SP1, r3 is the distance from the center of exposure pattern 3 to sample point SP1, W is the pattern width of exposure pattern 2, H is the pattern of exposure pattern 2 The length and l indicate the inter-pattern dimension correction amount on the side defining the sample point SP1, and 1A indicates the newly set exposure pattern, respectively.

Now, let us consider the case where the correction amount l of exposure pattern 2 is calculated.

FIG. 5 shows a flow chart for explaining the procedure for determining the correction amount l of the exposure pattern.
This flow will be explained below.

The steps shown in Figure 5 First, for each exposure pattern, new sample points S1, S2, S3, and S4 are set on the sides of the design pattern, and the energy intensity at the set new sample points is equal to the development energy intensity. Find the irradiation amount Qi of each exposure pattern so that

Qi=E/∫ ^bi/2 _-bi/2 ∫ ^ai/2 _-ai/2 f(r)dydx...(2) Here, r is the distance from the new sample point to the integration point, and E is the distance for each exposure. The developing energy intensity at the new sample point of the pattern, a _i and b _i are the pattern length and pattern width of each exposure pattern, and f(r) is the electron beam scattering intensity distribution in equation (1). , and Qi is obtained by dividing E by the amount obtained by integrating f(r) over the design pattern.

Steps shown in FIG. 5 Next, the correction amount l of the drawing pattern whose dimensions have been corrected so that the energy intensity at the sample point SP1 set on one side of the pattern 2 is equal to the development energy intensity is determined. Considering the influences from pattern 2 itself and all other patterns 1, 3, and 4, each exposure pattern is given the already determined dose Q ₁ ,
When it is decided to perform exposure at Q ₂ , Q ₃ , and Q ₄ , the following equation holds true at sample point SP1.

Q ₁ F (r1) + Q ₂ F (r2) + Q ₃ F (r3) + Q ₄ F (r4) ... (3) Here, Q ₁ to _{Q 4} that have already been calculated are for each exposure pattern 1, 2, 3, The radiation dose is 4. F(ri)(i=1
-4) are the exposure intensities of each of the exposure patterns 1 to 4, which are obtained by integrating equation (1) with respect to the drawing pattern.

The exposure intensity F(r2) of exposure pattern 2 is as follows. Note that F(r1), F(r3), and F(r4) can be calculated in the same way by taking W and H in each exposure pattern.

F(r2)=∫ ^(HL)/2 _-(HL)/2 ∫ ^W/2 _-W/2 f(r)dS...
(4) Stages and steps seen in Figure 5 The dimensional correction amount l of exposure pattern 2 is the pattern length H
If it does not exceed (l<H), it is sufficient to expose the drawing pattern with the dimensional correction obtained by the above formula (4) using the dose determined by the formula (2).

Steps seen in Fig. 5 If the exposure pattern 2 is a sub-micron pattern and the influence from the exposure pattern 3 is large, the dimensional correction amount l of the exposure pattern 2 exceeds the pattern length H (l /H), in which case you will proceed to the next step.

The stage seen in FIG. 5 In this case, exposure pattern 2 is
2, and then merge it with the exposure pattern 1 that is in contact with the exposed pattern 1 and erase it, and insert a new dividing line into the merged exposure pattern, as shown by the broken line, so that it overlaps the edge other than the edge that is in contact with the exposed exposure pattern 2 that has disappeared. , set exposure pattern 1A.

Steps seen in FIG. 5: The irradiation amount is determined again for the newly divided pattern as described above, and the above procedure is repeated.

The case where the stage shown in FIG. 5 is entered will be explained in more detail.

In FIG. 6, an exposure pattern 2 is placed in the area excluding exposure pattern 1A from exposure pattern 1 in FIG.
For exposure patterns 1 and 1A, new sample points S1, S1A, S3, and S4 are set on the sides of the design pattern.For example, exposure pattern 1A in FIG.
is the correction target pattern, the midpoints of the right side, the bottom side, and the top side are taken as sample points. Note that if all of the touching sides overlap with other patterns, no sample points are set. Now, after setting the sample point as described above, the inter-pattern dimension correction amount is calculated taking into account the influence from the pattern to be corrected and all other patterns so that the energy intensity at the sample point is equal to the development energy intensity. seek.

This process is performed for all patterns to be corrected.

Effects of the Invention According to the present invention, when performing electron beam exposure, a predetermined exposure pattern among the exposure patterns obtained by dividing a pattern to be formed into rectangular shapes is in contact with another exposure pattern and the predetermined exposure pattern is If the influence between the patterns due to electron beam scattering is large, the predetermined exposure pattern is eliminated, the exposure pattern that was in contact with the eliminated exposure pattern is divided into new rectangles, and the division is performed. For each exposure pattern generated in Dimensional correction can be performed without changing the shape, so correction of the proximity effect becomes easy, and a highly accurate pattern can be easily formed.

[Brief explanation of drawings]

1 to 3 are plan views of main parts showing patterns for explaining conventional problems, FIG. 4 is a plan view of main parts showing patterns for explaining one embodiment of the present invention, and FIG. 5 is a flow chart for explaining the procedure for determining the correction amount l of an exposure pattern, No. 6.
The figure is a plan view of a main part showing a pattern for explaining an embodiment of the present invention, and FIG. 7 is a block diagram showing an example of an apparatus for carrying out the present invention. In the figure, 1, 2, 3, 4 are exposure patterns,
1A is the newly divided exposure pattern, SP1 is the sample point, r1, r2, r3, r4 are the distances from each exposure pattern to the sample point, W and H are the pattern width and pattern length of exposure pattern 2, l is the pattern This is the distance dimension correction amount.

Claims (1)

[Claims] 1. In an electron beam exposure method in which a large number of patterns are drawn by irradiating an electron beam onto a workpiece, a predetermined exposure pattern is obtained by dividing the pattern to be formed into rectangular shapes. When the pattern is in contact with another exposure pattern and the influence between the patterns due to electron beam scattering on the predetermined exposure pattern is large, the predetermined exposure pattern is Combine the exposure patterns, divide the resulting pattern into new rectangles, calculate the irradiation amount and dimension correction amount to obtain the desired photosensitive pattern dimensions for each exposure pattern generated by the division, and calculate the irradiation amount and the dimension correction amount. An electron beam exposure method characterized by performing drawing based on a dimensional correction amount.