JPS61191027A - Electron beam exposure method - Google Patents

Abstract

PURPOSE:To form high accurate pattern by a method wherein spread of the pattern caused by scattering and heat generation of electron beam is corrected using electron beam scattering strength distribution, and relation between the pattern edge's temp. at a bottom face of a resist and spread of the pattern. CONSTITUTION:Spot position of electron beam 20 irradiated on a sample 15 by an exposing device 11 is controlled based on pattern data of a computer 16. At the time of making the data, projection volume and the pattern size are corrected for both spread of the pattern by scattering and spread of the pattern by heat generation. These correction volume are computed using electron beam scattering strength distribution, and relation between the pattern edge's temp. at a bottom face of a resist and spread of the pattern.

Description

[Detailed Description of the Invention] [Summary of the Invention] During electron beam exposure, the expansion of the pattern due to electron beam scattering and the expansion of the pattern due to heat generation are determined by the electron beam scattering intensity distribution umbrella and the pattern on the bottom surface of the resist, respectively. - Correct using the relationship between edge temperature and pattern spread.

[Industrial application field]

The present invention relates to an electron beam exposure method, and in particular, when applied to a mask substrate, it corrects the pattern spreading caused by the 'proximity effect' and one heat generation 'K', thereby producing a highly accurate electron beam exposure pattern. It relates to a method of forming.

[Conventional technology]

In pattern forming technology using electron beam exposure, correction of the so-called "proximity effect" is essential in order to improve pattern accuracy.

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 (backscattering) from the substrate, which is the exposed object, causes the resist pattern after writing to spread out to a greater extent than the electron beam irradiation amount (turn). If the spacing is less than 2 μm, this will result in significant distortion of the pattern shape, resulting in a significant adverse effect of reducing pattern/accuracy.

The electron beam exposure intensity distribution in the resist due to this scattering is expressed by the following equation as a function of the distance T from the center of the beam irradiated from the outside.

(The first term in Equation 11 is the electron beam scattering in the coated resist; it is given by forward scattering; (The second term in Equation 11 is the electron beam scattering from the substrate, which is the object to be exposed; It is given by backscatter.

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.

In addition to the above-mentioned proximity effect based on the scattering of electron beams, there is a problem in that when a substrate with poor heat dissipation is used, heat accumulates in the resist and the pattern spreads. This is particularly noticeable for patterns whose pattern dimensions are larger than 2, for example, 5 squares or more.

Figure 6 shows the case where a resist is applied on a glass substrate (a chrome mask substrate on which chromium is vapor-deposited, and a pattern is formed by electron beam writing. The horizontal axis represents the pattern width;
The vertical axis represents the irradiation dose9, and the relationship between the expansion of the pattern width and the irradiation dose is investigated.The solid line is the calculated value considering only the scattering of the electron beam, while the circle is the actual value. be. As is clear from the figure, as the pattern becomes larger, the calculated values and actual values become less consistent. The results show that for patterns of 5 μm square or more, the spread of the pattern with respect to the irradiation amount cannot be approximated by the scattering exposure intensity distribution of the pattern obtained by integrating Equation 11 for the drawn pattern.

[Problem that the invention seeks to solve]

However, in the case of the conventional electron beam exposure method, it is not possible to correct the above-mentioned proximity effect and also to correct the influence of heat accumulation in the resist. Therefore,
Conventionally, when a resist is applied on a chrome mask substrate with chromium vapor-deposited on a glass substrate and a pattern is formed by electron beam writing, heat accumulates in the resist because the glass substrate has poor thermal conductivity. However, there is a problem that the pattern expands.

[Means for solving problems]

In the present invention, from the above, in order to form a high-precision pattern by electron beam writing on a mask substrate, it is necessary to expand the nodules due to electron beam scattering,
In view of the need to correct for both pattern spread due to heat generation, the present invention provides a method for forming a highly accurate electron beam exposure pattern by correcting the proximity effect and pattern spread due to heat generation.

Therefore, in the present invention, in an electron beam exposure method in which an electron beam is irradiated onto a sample to draw a large number of patterns, the electron beam scattering intensity distribution is used to calculate the exposure intensity of the pattern edge of each pattern based on the development energy of the resist. Determine the irradiation amount and dimension correction amount so that the intensity is the same, and then use the relationship between the temperature of the pattern edge at the bottom of the resist and the pattern expansion when drawing with the corrected pattern size and irradiation amount. Then, the irradiation dose and dimension correction amount that will result in the target pattern dimension are calculated, and electron beam lithography is performed based on the calculated irradiation dose and dimension correction amount.

[For production]

According to the method of the present invention, the ``proximity effect'' is corrected by adjusting the irradiation dose and dimension correction amount such that the exposure intensity of each pattern edge becomes the development energy intensity of the resist, and then the corrected pattern dimension By using the relationship between the temperature of the pattern edge at the bottom of the resist and the spread of the pattern when drawing with the irradiation amount, the irradiation amount and dimension correction amount that will result in the desired pattern size are calculated.1 Proximity effect It can also correct for "spreading due to joint heat generation."

〔Example〕

FIG. 2 shows a pattern for detailed explanation of the invention.

First, sample points are set at the midpoints of each side of each pattern (1) to (3) in FIG. 2 (black circles in the figure).

Looking at the 0 point of pattern (1), the exposure energy intensity E at the 0 point is as follows.

QrFC"+)+QtF(rt)+(hFcf"
s ) = E −... (2) Here, (h ~ Q
3 is the irradiation dose for each pattern (]) to (3)'),'
I-rM is the distance from the center of each pattern to sample point The same holds true for points.

In formula (2), F(r6) (i = 1 = 3)
can be obtained by integrating the scattering intensity distribution equation (1) with respect to the drawing pattern. This is schematically shown in FIG. 3 to illustrate '(r+)=J'', ff(r)ds, regarding the zero point when pattern (1) in FIG. 2 is drawn.

Then, the correction amount [irradiation amount Qi (i=
1 to 3) and the size correction amount Sj (j is a suffix for each side of each pattern; 1 to 12)] are determined.

Looking at the 0 point of pattern (1), the second of equation (2)
Since there is an influence from the irradiation of the term and the third term, that is, pattern (2) and pattern (3), if the irradiation is performed as set in pattern (1) as shown in Figure 2, (α)
The point becomes higher than the development energy intensity, and the line of development energy intensity spreads outside the point, and the resulting pattern becomes wider. Therefore, as described above, the irradiation fQ+ and the size correction amount S can be determined so that the energy intensity at the sample point ((Z) point is equal to the development energy intensity E0. In other words, E=E0. I will find Q and S.

Note that these things are made to hold true at all sample points. Based on the results, by irradiating a pattern with a reduced area as shown by the broken line in Figure 2, the energy intensity at each sample point can be made exactly equal to the developing energy intensity, and other patterns in the vicinity can be It is possible to eliminate the effects caused by scattering from the surrounding area, that is, the proximity effect.

Note that E in equation (2) for each sample point is E. Q+, Qt, Qs such that

Each pattern fll~(3) 12 patterns in total) can be obtained by solving simultaneous equations in which E is ED in equation (2) that holds true for each sample point.

Actually, since the radiation dose Ch (h + Qs T) is initially set for each of patterns (1), (21, and (3)), these are used in each of the above simultaneous equations to solve the simultaneous equations. All you have to do is ask for it.

Next, using the relationship between the temperature of the pattern edge at the bottom of the resist and the pattern expansion when drawing with the corrected pattern dimensions and irradiation dose, calculate the irradiation dose and dimension correction amount to achieve the desired pattern dimensions. Calculate.

In Fig. 4 G4), 0.1 μm thick chromium 2 was applied to the glass substrate 1.
Add 5 parts of resist (PMMI) to the evaporated chrome mask.
The case is shown in which a pattern with a width of 3 μm is drawn by applying the resist to a thickness of μm, and FIG. 3B shows the temperature distribution at the bottom of the resist in that case. In addition, the irradiation amount of the electron beam is 4X
10 C (coulombs)/ffi”,
Figure 4 (3) is obtained by simulation and is faked.

Using this temperature distribution, the dimension correction S0 is made so that the temperature of the edge of the pattern is below the temperature t0 that changes the quality of the resist.
Do the following. That is, in Fig. 2, at the edge of the 3 μm wide pattern (beam center collar 2 = 1.5 μm), the temperature is higher than °t0, the temperature that alters the resist, and at z = 1.5 + 50 (μrlL), The critical temperature t0 that just changes the quality of the resist
It has become. Therefore, the irradiation width of the electron beam is set to 3 μ
If we make SO narrower than m, the critical temperature t0 will be exactly at the planned pattern edge z = i, s μm,
It is possible to eliminate pattern expansion due to heat generation temperature. This is near the pattern edge (1,5-5° z≦1.5+
This is based on the fact that the temperature distribution can be linearly approximated with 50Cμm].

In actual correction, the dimension correction amount S is used to correct the expansion of the pattern due to this heat generation. 1 to 12; sample points on each side of each pattern) are calculated for various patterns using temperature distribution measurement results similar to those shown in Fig. 2.The temperature distribution measurement is performed in advance on the mask substrate. The field values obtained by irradiating electron beams with various widths and irradiation doses are determined by actual measurements or simulations, and are used.

Alternatively, instead of reducing the irradiation area as described above, it is also possible to reduce the irradiation amount so that the temperature at the edge of the pattern falls below t0, the temperature at which the resist deteriorates. .

Note that the temperature t0 at which the resist changes in quality varies depending on the type of resist, and is determined through experiments.

As described above, the temperature distribution of various patterns is simulated, and the size correction amount S is calculated to correct pattern expansion due to heat generation. Calculate j.

Fig. 1 shows an example in which the pattern shown in Fig. 2 previously shown is reduced in dimension by 50j by correcting the spread due to heat generation in addition to correcting the spread due to scattering of the electron beam (dose Qiv dimension correction S,). ing. In the example shown, pattern (1)
Patterns (2) and (3) represent cases where the area is small and correction of the spread due to heat generation is not required (Sos) because the area is large and the spread due to heat generation is corrected (Sos). There is.

FIG. 5 shows an example of the configuration of an apparatus used to implement the present invention. In the figure, the main body 11 of the electron beam exposure apparatus is
It has an electron gun 12, a converging electron lens system 3, and an xy deflector 14, and irradiates a sample (substrate) 15 coated with a resist with a narrowly focused electron beam 20, which is known per se. Spot position of electron beam 20 on sample 15, electronic calculation (1116 color pattern data,
XY deflector 14 via DA converter 17° amplifier 18
Controlled by driving. The electron beam 20 is irradiated onto the sample 5 by a blanking device in response to a signal from the electronic computer 16.

In the present invention, when actually using the apparatus as shown in FIG. Store it. and,
When exposing the sample 15, the electronic computer 16
The deflector 14 is driven to advance the beam spot, and irradiation is performed so as to cover a predetermined pattern.

〔Effect of the invention〕

As explained above, according to the present invention, both the proximity effect and pattern spreading due to heat generation can be corrected, so when performing electron beam writing on a mask substrate,
It becomes possible to form highly accurate electron beam exposure patterns.

[Brief explanation of the drawing]

Figure 1 is a pattern diagram of an embodiment of the present invention, Figures 2 and 3 are
The figure is an explanatory diagram of the pattern of the embodiment of the present invention. Figure 4 (2) and ω) is a cross-sectional view of the mask substrate showing the relationship between the temperature of the pattern edge and the spread of the pattern, and a diagram showing the temperature distribution. , FIG. 5 is a schematic diagram of an example of an apparatus for implementing the present invention, and FIG. 6 is a diagram showing pattern width and irradiation amount. 11...Main body of exposure apparatus 12...Electron gun 13...Converging electron lens system 14...XY deflector 15...Sample 16...Electronic computer 17...DA converter 18...・Amplifier 20...electron beam

Claims (1)

[Claims] Irradiating an electron beam onto a sample coated with a resist,
In an electron beam exposure method that draws multiple patterns, a sample point is set at the edge of each pattern, and the irradiation amount and dimension correction amount are determined by electron beam scattering so that the exposure intensity of each sample point becomes a predetermined development energy intensity. This is determined using the intensity distribution, and then the relationship between the temperature of the pattern edge at the bottom of the resist and the spread of the pattern when writing based on the irradiation amount and the amount of dimension correction is used to determine the irradiation to achieve the desired pattern size. 1. An electron beam exposure method characterized by calculating an amount of irradiation and a dimensional correction amount, and performing electron beam writing based on the calculated irradiation amount and dimensional correction amount.