JPS6157697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device or an integrated circuit device, and more particularly to a method of forming an exposure pattern on a photoresist using an exposure device using a charged beam such as an electron beam.

Generally, when manufacturing a semiconductor device or an integrated circuit device, first a mask for determining a diffusion position pattern and a mask for determining an electrode wiring position pattern are manufactured. Conventionally, in order to print such a pattern onto a photoresist coated on a mask substrate, and further to use the resulting mask to print on a photoresist coated on a semiconductor substrate, optical exposure is used. This method was commonly used. However, in this method of exposing photoresist with light, there is a limit to the dimensions of the photoresist exposure pattern that can be obtained due to the wavelength of the light, diffraction, etc., and the disadvantage is that it is unsuitable for obtaining fine photoresist exposure patterns. There is.

In order to eliminate this drawback, a method has recently been used that uses an electron beam exposure apparatus that uses an electron beam with a much shorter wavelength instead of light.
In this method, pattern data corresponding to the exposed positions of photoresist coated on a mask substrate or a semiconductor substrate is created using a CAD (automation system) device, converted into data for driving the electron beam, and then Using the data, an exposure pattern is formed on a photoresist on a mask substrate or a semiconductor substrate.

However, electron beam exposure apparatuses typically output a circular beam. It is well known that when a single point on a photoresist is irradiated with such a circular electron beam, the charge distribution accumulated in the resist is expressed by a Gaussian distribution function as shown in the following equation.

f(x)=C ₁ exp{−(x/βf) ² } +C ₂ exp{−(x/βb) ² } (1) x in the above equation represents the distance from the irradiation position,
C ₁ , C ₂ , βf, and βb are constants. Figure 1 shows the distribution of the amount of charge accumulated around one point when an electron beam is irradiated, that is, the equation (1) mentioned above, which is expressed as the sum of forward scattering and back scattering forming a Gaussian distribution. . This shows that when the 0 point is irradiated, it also affects positions approximately 3 μm away from the 0 point.

For example, when a rectangular pattern is scanned with such a circular beam, the four corners of the rectangular exposure pattern are rounded. This type of exposure pattern that appears as a rounded corner is not only useful when trying to obtain a rectangular exposure pattern, but also when trying to obtain an exposure pattern that has corners that form an angle smaller than 180 degrees. The same thing appears in the case. Therefore, with the conventional electron beam exposure method in which the electron beam simply scans only the position on the photoresist corresponding to the pattern to be formed, it is impossible to form an exposure pattern with highly accurate corners on the photoresist. be.

An object of the present invention is to apply a photoresist to a photoresist using an exposure apparatus using a charged beam such as an electron beam.
An object of the present invention is to provide a method for forming a high-precision exposure pattern capable of correcting droop that appears as a rounded shape at the corner of the exposure pattern, in a method of forming an exposure pattern having corners forming an angle of less than 180 degrees. .

The present invention provides a method for forming an exposure pattern on a photoresist using a charged beam exposure apparatus, which has corners forming an angle of less than 180 degrees. The charged beam is not only irradiated, but also placed close to the above-mentioned portion outside the above-mentioned pattern to be formed, so that the amount of charge accumulated at the position reaches an allowable charge amount that can exhibit a predetermined reaction to a predetermined developer. A correction charged beam is also irradiated to a position on the photoresist corresponding to the position, and the irradiation position and irradiation amount of the correction charged beam are adjusted until the amount of charge at the corner portion reaches the allowable amount of charge. Further, the present invention is characterized in that the amount of charge accumulated at the irradiation position of the correction electron beam is controlled to be less than the above-mentioned allowable amount of charge.

In the present invention, by utilizing the phenomenon that a charged beam irradiated to one point on a photoresist as described above accumulates charges in the surrounding area of the irradiation point, it is possible to eliminate corners where the sharpness of the exposure pattern to be formed is not satisfied. A charge is intentionally applied to the area from outside the exposure pattern to be formed. In the case of a positive resist, the allowable amount of charge that can be dissolved in the developer (allowable charge amount for resist peeling) also increases in the corners of the exposure pattern to be formed, while in the case of a negative resist, the amount of allowable charge that can be dissolved in the developer is Make sure that the allowable amount of charge is obtained so that the amount of charge becomes low. In addition, the amount of charge accumulated in the area where the beam is irradiated to the outside of the pattern for correction is the allowable amount of charge for resist peeling mentioned above in the case of a positive resist, and the allowable amount of charge that becomes insoluble in the developer in the case of a negative resist. The amount of charge is kept so that the position irradiated for correction is not peeled off during development in the case of a positive type resist, and so that it does not become insoluble in the developer in the case of a negative type resist.

Hereinafter, a case where an embodiment of the present invention is used to form a rectangular exposure pattern will be described in detail.

FIG. 2 is a diagram for explaining a high-precision rectangular exposure pattern forming method according to an embodiment of the present invention. Figure b shows the shape of an exposure pattern actually formed when an electron beam is irradiated to a position on the photoresist corresponding to the rectangular pattern a to be formed. The four corners of the rectangular pattern are under-illuminated. Therefore, when a correction electron beam is irradiated onto P ₁ to _{P 4} in c of the same figure, an exposure pattern as shown in d is finally obtained, and it is possible to draw a shape close to the desired pattern.

FIG. 3 is a diagram showing the irradiation positions P ₁ to _{P 4} of the correction electron beam and the pattern shape actually drawn.
Figure a is a diagram when the four corners of the pattern to be formed are irradiated with the correction electron beam, and the outer periphery of the pattern other than the irradiation points is adversely affected. In FIG. 3a, 10 indicates a pattern before correction, and 20 indicates a pattern after correction. Further, FIG. 3b shows an example in which the correction electron beam is irradiated n times to each of the four corners, and it is difficult to form the expected pattern. In FIG. 3b, 30 indicates a pattern to be formed, and 40 indicates a pattern after correction. In this way, if the irradiation position of the correction electron beam is too close to or too far away from the pattern to be formed, the clarity of other peripheral parts of the pattern will deteriorate. Therefore, in order to form a pattern with high precision, it is necessary to irradiate the correcting electron beam to an appropriate position outside the pattern to be formed.

Next, a method for determining the irradiation position and irradiation amount of the correction electron beam will be explained. First, the total amount of charge accumulated at the corner of the pattern to be formed is determined by the amount of charge accumulated due to the influence of the electron beam irradiated inside the pattern to be formed and the influence of the correction electron beam irradiated for correction. It is expressed as the following equation by the sum of .

T _dpes = nf(r) +∫∫ _A f(|x _p −y|) d ² y (2) T _dpes is the total amount of accumulated charge at the corner, and the first term is the point r away from the corner position The second term is the amount of charge accumulated in the corner due to the electron beam irradiation for correction when beam irradiation is applied n times to the inside of the pattern to be formed. In the second term, A is the area of the pattern to be formed, x _p is the corner position,
y indicates the position where the electron beam is irradiated.

On the other hand, the amount of charge accumulated in the part irradiated with the correction electron beam is nf (o) + ∫∫ _A f (|x _s − y |) d ² y
It is expressed as Here, x _s is the irradiation position of the correction electron beam. The conditions under which the charge accumulation amount at the corner portion reaches the above-mentioned allowable charge amount and the charge accumulation amount at the irradiation position of the correction electron beam is less than the above-mentioned allowable charge amount are as follows.

T _dpes ≧ε＞nf(o) +∫∫ _A f(｜x _s −y｜) d ² y (3) Here, ε is the allowable charge amount for resist stripping of a positive resist or the developer of a negative resist. This is the allowable amount of charge that becomes insoluble. By the way, for y included in the pattern to be formed, |x _s −y| takes a much larger value than |x _p −y|, so ∫∫ _f (|x _s −y|)d ² y is ∫∫ _{f
( ｜ x p} ^-y Determine the correction electron beam irradiation position and irradiation amount so as to satisfy the requirements.

Figure 4 is a diagram describing the method of determining the irradiation beam position, in which the correction electron beam is directed from the four corners at d ₁ ,
The amount of charge accumulated at corner 0 of the pattern to be formed when irradiating points d ₂ apart is ε ₁ +ε _b , respectively.
Expressed as ε ₂ + ε _b . Here, ε _b is the amount of charge accumulation in the state before correction. The amount of charge accumulated at the corner when the correction electron beam is irradiated onto the corner is ε ₀ + ε
When _b is the allowable charge amount for resist peeling in a positive resist or ε is the allowable charge amount for a negative resist to be insoluble by a developer, the position where ε〓ε ₂ +ε _b , i.e.
It is sufficient to irradiate the correction electron beam to the point _d2 .

As described above, according to the present invention, it is possible to form with high accuracy an exposure pattern having corners forming an angle smaller than 180 degrees of photoresist using a charged beam exposure apparatus. Furthermore, it has become possible to draw submicron patterns with fidelity, which not only helps dramatically improve the performance of integrated circuits, but also
This also greatly contributes to improving reliability.

In the above-described embodiment, a means for irradiating an electron beam is used, but it goes without saying that the same effect can be obtained by using a means for irradiating an ion beam.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the spread of the amount of charge accumulated around a point when an electron beam is irradiated to it.
FIG. 2 is a diagram for explaining irradiating the outside of a pattern to be formed with a correction electron beam in an embodiment of the present invention; in the figure, a is the exposure pattern to be formed, and b is the drawing exposure before correction. In the pattern, c indicates the correction electron beam irradiation position, and d indicates the exposure pattern shape after correction. Fig. 3a shows the pattern shape when the correction electron beam is irradiated at the corner of the exposure pattern to be formed, and Fig. 3b shows the pattern shape when the outside of the exposure pattern to be formed is irradiated n times. . FIG. 4 is a diagram for explaining a method of determining the irradiation position of the correction electron beam. P ₁ , P ₂ , P ₃ , P ₄ ... Correction electron beam irradiation position, 10 ... Exposure pattern before correction, 20 ... Exposure pattern after correction, 30 ... Exposure pattern to be formed.

Claims (1)

[Claims] 1. In a method of forming an exposure pattern having corners forming an angle of less than 180 degrees on a photoresist by using a means for irradiating a charged beam, a method for forming an exposure pattern on a photoresist at a position corresponding to the pattern to be formed. The charged beam is not only irradiated so that the amount of charge accumulated in the image reaches the allowable amount of charge that can cause a predetermined reaction to a predetermined developer, but also corresponds to a position close to the corner portion outside of the pattern to be formed. A correction charged beam is irradiated to the position on the photoresist for correction, and the irradiation position and irradiation amount of the correction charged beam are changed until the amount of charge at the corner reaches the allowable amount of charge and the amount of charge for correction is A pattern forming method comprising controlling the amount of charge accumulated at a beam irradiation position to be less than the above-mentioned allowable amount of charge.