JPH11121342A - Partial collective exposure mask and method for partial collective exposure using the mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transfer a pattern with high resolution, without degrading throughput, related to a partial collective exposure method. SOLUTION: A required pattern is separated into fine patterns 4a and 4b and a large area pattern 6, with each assumed as separate apertures 3 and 5. Double exposure is performed with each of the apertures 3 and 5 to form a desired pattern. Here, an aperture area of the aperture 3 is reduced for the fine patterns 4a and 4b, for reduced beam current and coulomb effect, resulting in improved resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial batch exposure mask and a partial batch exposure method using the mask.

[0002]

2. Description of the Related Art The electron beam exposure method has the advantages of higher resolution and a larger depth of focus than the light exposure method. Attention has been paid to the high resolution of the exposure method.

[0003] However, the electron beam exposure method has a problem that the throughput is lower than that of the light exposure method. That is, even if a high sensitivity resist of about several μC / cm ² is used for a variable-shaped electron beam exposure apparatus having a relatively high throughput, the throughput is about 1/10 as compared with the light exposure method using a stepper. is there.

That is, in the case of a variable-shaped electron beam exposure apparatus, a required pattern is divided into rectangles, an electron beam is formed into the divided rectangles, and the formed electron beam is sequentially exposed. .

In this case, in order to improve the throughput of electron beam exposure, the total number of figures after rectangular division, that is, the number of shots must be reduced. That is, if the number of shots is large, the time required for the entire exposure increases, and the throughput decreases.

Therefore, in recent years, attention has been paid to the partial batch transfer method as a method for improving the throughput by reducing the number of shots.

In this partial batch exposure method, a pattern having a high repetition frequency such as a memory cell is formed in advance as a stencil mask, and the pattern having a high repetition frequency is exposed in one shot, thereby reducing the total number of shots and increasing the throughput. It is a way to improve.

[0008]

In electron beam exposure, the steeper the electron beam profile, the higher the resolution.

However, in practice, various aberrations of the electron optical system cause blur at the beam edge.

For example, an electron optical system has a Coulomb effect in which electrons repel each other in a beam because electrons have electric charges. For this reason, even if an ideal electron optical system having no aberration is used, aberration due to the Coulomb effect remains.

The amount of blur at the beam edge due to the Coulomb effect is proportional to the beam current value, and is equal to 3 times the beam acceleration voltage.
There is a relationship that it is inversely proportional to / square.

In the partial batch exposure method, the above-mentioned beam current value is proportional to the opening area of the stencil mask. Therefore, when a stencil mask having a large opening area is used, the blur amount of the beam edge becomes large and the resolution is deteriorated.

For example, as shown in FIG. 3, it is assumed that a mask pattern 2 indicated by oblique lines is formed in a partial batch exposure area 1 (typically, about 5 μm square). The mask pattern 2 includes a fine pattern portion 2a having a fine line width of 0.2 μm or less and a large area pattern portion 2b having a length of several μm or more, and the left and right large area patterns 2b are adjacent to each other. And a minute space portion 10 exists between the two 2b.

When such a mask pattern 2 is formed, the beam current value increases due to the large opening of the large area pattern portion 2b, and the fine pattern 2a and the left and right large area pattern portions 2b are close to each other. It is difficult to ensure a sufficient resolution of the space portion 10.

In order to prevent such resolution degradation,
There are two methods of reducing the beam current value or increasing the acceleration voltage.

Here, in order to lower the beam current value,
It is sufficient to reduce the current density or reduce the area of the region where the partial batch transfer is performed. However, when the current density is reduced, the exposure time of one shot is increased and the throughput is reduced. In the case where the area of the region where the partial batch transfer is performed is reduced, the number of shots increases, and the throughput similarly decreases.

On the other hand, when the accelerating voltage is increased, the cross-sectional area of the collision of electrons is reduced and the sensitivity of the resist is reduced.
Since the deflection sensitivity of each deflector decreases, it becomes difficult to secure the deflection swing width, and moreover, the electron beam undesirably damages the sample and components in the exposure apparatus.

The present invention solves the above-mentioned conventional problems,
An object of the present invention is to enable a fine pattern to be transferred satisfactorily and collectively without lowering the throughput.

[0019]

According to the present invention, in a partial batch transfer mask, a pattern group exposed by partial batch exposure is divided into a plurality of pattern groups, and each separated pattern group is formed as a separate aperture. The apertures are arranged adjacent to each other in a region that can be selected only by beam scanning.

As a result, it is possible to transfer a fine pattern partially and collectively at a high throughput.

[0021]

According to the first aspect of the present invention, there is provided a partial batch exposure mask which divides a pattern group of the same region exposed by partial batch exposure into a plurality of pattern groups of the same region.
Each separated pattern group is formed as a separate aperture, and the apertures are arranged adjacently in a region that can be selected only by beam scanning.

As described above, by separating into a plurality of pattern groups, the beam current value at the time of transferring each aperture is reduced, the aberration due to the Coulomb effect is reduced, and the blur of the beam edge is reduced, and the resolution is reduced. While improving the
By arranging the apertures adjacent to each other, the beam deflection distance for aperture selection can be minimized, and the time required for stabilizing the selected beam deflector required for each shot can be minimized to improve the throughput.

According to a second aspect of the present invention, there is provided a mask for partial batch exposure, wherein a pattern group of the same region consisting of a large area portion and a fine portion exposed by partial batch exposure is replaced with a pattern group of the same region consisting of a large area pattern. Each pattern group is formed as a separate aperture.

As described above, by reducing the beam current value when transferring the fine pattern group, the aberration due to the Coulomb effect is reduced, the blur of the beam edge is reduced, and the resolution of the fine pattern portion is improved. Has an action.

According to a third aspect of the present invention, there is provided a mask for partial batch exposure, wherein a pattern group of the same region consisting of a large area portion and a fine portion exposed by partial batch exposure is replaced with a pattern group of the same region consisting of a large area pattern. Each pattern group is formed as a separate aperture, and each aperture is arranged adjacently in a region that can be selected only by beam scanning.

As described above, by reducing the beam current value when transferring the fine pattern group, the aberration due to the Coulomb effect is reduced, the blur of the beam edge is reduced, and the resolution of the fine pattern portion is improved. In addition, by arranging the apertures adjacent to each other, the selected beam deflection distance for aperture selection is minimized, and the time required for stabilizing the beam deflector required for each shot is minimized, thereby improving the throughput.

In the mask for partial collective exposure according to the present invention, a pattern group exposed by partial collective exposure is extracted as a pattern having a fine line width at a border portion of a narrow portion between adjacent patterns. The pattern group is separated into a pattern group including a pattern portion other than the border portion, and each pattern group is formed as a separate aperture.

As described above, the edge of a portion where the pattern interval is small is formed as a fine line, so that the beam current value when transferring the edge portion having a small interval is reduced. This has the effect of reducing aberration, reducing blur at the beam edge, and improving the resolution of portions where the pattern interval is narrow.

According to the fifth aspect of the present invention, the mask for partial collective exposure is obtained by extracting a pattern group exposed by partial collective exposure as a pattern having a fine line width at a border portion of a narrow portion between adjacent patterns. Separated into a pattern group and a pattern group consisting of pattern portions other than the border portion, each pattern group is formed as a separate aperture, and each aperture is arranged adjacently in an area that can be selected only by beam scanning Have been.

As described above, the edge of a portion where the interval between the patterns is narrow is made into a fine line, so that the beam current value at the time of transferring the edge portion having a narrow interval is reduced. Reduce aberration and reduce blur at the beam edge to improve the resolution of narrow pattern intervals, and minimize the beam deflection distance for aperture selection by placing apertures adjacent to each other. This has the effect of improving the throughput by minimizing the time required for stabilizing the beam deflector required for each shot.

According to a sixth aspect of the present invention, there is provided a partial batch exposure method for performing partial batch exposure using the partial batch exposure mask according to any one of claims 1 to 5, wherein all the apertures are the same. A plurality of apertures irradiated at the current density and separated from the same pattern group are sequentially irradiated with the beam.

Accordingly, since all the apertures are irradiated with the same current density, the time required for changing the current density is not required, and the beam position can be changed by transferring the apertures of the same pattern group in order. The beam deflection distance to be determined is reduced, the time required for stabilizing the beam positioning deflector required for each shot is reduced, and a high throughput can be obtained.

According to a seventh aspect of the present invention, there is provided a partial batch exposure method for performing partial batch exposure using the partial batch exposure mask according to any one of the first to fifth aspects. The pattern group having the area and the fine pattern group are exposed by separate beam irradiation.

Accordingly, since the beam current when transferring the fine pattern group is small, it has the effect of reducing the aberration due to the Coulomb effect, reducing the blur of the beam edge, and improving the resolution of the fine pattern portion.

According to a eighth aspect of the present invention, there is provided a partial batch exposure method, wherein the partial batch exposure is performed using the partial batch exposure mask according to any one of the first to fifth aspects. The exposure of the narrow portion and the portion other than the edge portion is performed by separate beam irradiation.

[0036] With this arrangement, the edge of the portion where the interval between the patterns is narrow is formed as a fine line, and the beam current value when transferring the edge of the narrow interval is reduced. To reduce the blur of the beam edge and improve the resolution of a portion where the pattern interval is narrow.

According to a ninth aspect of the present invention, in the partial batch exposure method according to the seventh or eighth aspect, all beam irradiations are performed at the same current density.

Accordingly, since all the apertures are irradiated with the same current density, the time required for changing the current density is not required, and a high throughput can be obtained.

According to a tenth aspect of the present invention, there is provided a partial batch exposure method according to the seventh or eighth aspect,
The exposure amount of the large area portion and other portions is changed.

Thus, by changing the exposure amount between the large area portion and the fine pattern portion, it is possible to correct the proximity effect due to the dependence of the stored energy on the pattern area.

An embodiment of the present invention will be described below with reference to FIGS.

When there is a stencil mask having the mask pattern 2 as shown in FIG. 3 in the partial batch exposure area, and when the partial batch transfer is performed using this, as described above, the large area pattern portion 2b Is large, the beam current value becomes large, and the fine pattern 2a and the left and right large-area pattern portions 2b are close to each other in the space 10
It is difficult to secure enough resolution.

Therefore, in this embodiment, FIGS. 1 (a) and 1 (b)
As shown in FIG. 3, the pattern 2 of FIG.
4b and a large area pattern 6.

That is, FIG. 1A shows an aperture region 3 of a fine pattern, and this region 3 is the same as the partial batch exposure region 1 in FIG. 3, and 4a is separated from the mask pattern 2. Line patterns 4b are border patterns separated from the mask pattern 2.

FIG. 1B shows an aperture region 5 of the remaining large-area pattern obtained by subtracting the pattern of FIG. 1A from the mask pattern 2 shown in FIG. 3, and this aperture region 5 The same area as the batch exposure area 1
Reference numeral 6 denotes a large area pattern portion.

Here, both the line pattern 4a and the border pattern 4b have a line width of 0.2 μm and a length of 1 μm, and the size of the opening of the large area pattern section 6 is 2 μm.
In the case of μm × 1 μm, the total opening area of the aperture region 3 of the fine patterns 4a and 4b is 0.2 μm ² × 12 = 2.4 μ
m ² , and the total opening area of the aperture region 5 of the large area pattern portion 6 is 2 μm ² × 4 = 8 μm ² .

On the other hand, the total aperture area of the aperture region 1 shown in FIG. 3 is (0.2 μm ² +2 μm ² ) × 4 = 8.8 μm ² , and the beam current value is proportional to the aperture area. 3
Compared with the aperture region 1 of FIG. 1, the beam current value required for collectively exposing the aperture region 3 of only the fine pattern in FIG. 1A is 2.4 / 8.8 = 3/11, Even when irradiation is performed at the same current density, the beam current value is significantly reduced.

As described above, since the mask pattern 2 shown in FIG. 3 is divided into the two patterns shown in FIGS. 1A and 1B, the beam current value when exposing a fine pattern is greatly reduced. Can be increased.

However, in order to obtain the pattern 2 shown in FIG. 3, a total of two patterns shown in FIGS.
Since the number of shots is required, the throughput is reduced accordingly. Therefore, in this embodiment, a decrease in throughput is suppressed by using a partial batch exposure aperture as shown in FIG.

FIG. 2 shows the arrangement of the partial batch exposure aperture having the pattern as shown in FIG. In FIG.
Reference numeral 7 denotes a beam scanable range, 8a, 8b, and 8c denote apertures for other partial batch exposure, and 9 denotes an aperture for forming a variable shaped beam used at the time of random pattern drawing.

The pattern of the original figure shown in FIG.
In the case of separation into two as shown in (a) and (b), FIG.
The apertures 3 and 5 of (b) are arranged adjacent to each other as shown in FIG.

Now, the apertures 3 and 3 shown in FIGS.
Exposure is performed by dividing the shot into two shots by using the mask pattern 5, and the mask pattern 2 shown in FIG. That is, first, one of the apertures 3 is irradiated with an electron beam to form the fine portions 4a,
4b is transferred, and subsequently, the other aperture 5 is irradiated with an electron beam to transfer the large area portion 6. At this time, since the apertures 3 and 5 are adjacent to each other, it is possible to minimize the time required for selective beam deflection for aperture selection.

Regarding the beam position deflection, the beam position deflection is basically unchanged during step-and-repeat. Further, during continuous movement of the stage, only the amount by which the stage has moved changes the beam position deflection amount minutely.

Further, even if it is necessary to finely adjust the beam position deflection with respect to the aperture position, the adjustment amount can be minimized because the apertures are adjacent to each other.

In any case, the time required for beam position deflection can be minimized. Thereby, a decrease in throughput can be suppressed.

In the above example, the original pattern shown in FIG. 3 is divided into two types of apertures 3 and 5 as shown in FIG. 1, but it is also possible to separate it into three or more types of apertures. In addition, the proximity effect can be corrected by changing the exposure amount for each aperture as needed.

[0057]

According to the present invention, it is possible to realize a partial batch exposure method having high resolution performance without lowering the throughput.

[Brief description of the drawings]

FIG. 1 is a plan view of a mask pattern for partial batch exposure according to an embodiment of the present invention.

FIG. 2 is a plan view showing the entire partial batch exposure aperture according to the embodiment of the present invention;

FIG. 3 is a plan view of a mask pattern for partial batch exposure according to a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Partial batch exposure area, 2 ... Original pattern for partial batch exposure, 2a ... Fine part, 2b ... Large area part, 3 ... Fine pattern aperture, 4a ... Fine pattern opening, 4b ... Edge pattern opening, 5 ... Large area pattern aperture, 6 large area pattern opening, 7 beam scanning range, 8a, 8b, 8
c ... aperture, 9 ... aperture for variable shaping.

Claims (10)

[Claims] 1. A pattern group of the same area exposed by partial batch exposure is divided into a plurality of pattern groups of the same area, and the separated pattern groups are formed as separate apertures, respectively. A partial batch exposure mask, which is arranged adjacently in an area that can be selected only by beam scanning. 2. A pattern group of the same region composed of a large area portion and a fine portion exposed by partial batch exposure is separated into a pattern group of the same region composed of a large area pattern and a pattern group of the same region composed of a fine pattern. A partial batch exposure mask, wherein each pattern group is formed as a separate aperture. 3. A pattern group of the same region composed of a large area portion and a fine portion exposed by partial batch exposure is separated into a pattern group of the same region composed of a large area pattern and a pattern group of the same region composed of a fine pattern. A partial collective exposure mask, wherein each pattern group is formed as a separate aperture, and each aperture is arranged adjacently in a region that can be selected only by beam scanning. 4. A pattern group obtained by extracting a pattern group exposed by partial batch exposure from a border portion of a narrow portion between adjacent pattern portions as a fine line width pattern.
A partial batch exposure mask, wherein the mask is separated into a pattern group including a pattern portion other than a border portion, and each pattern group is formed as a separate aperture. 5. A pattern group obtained by extracting a pattern group exposed by partial batch exposure from a border portion of a narrow portion between adjacent patterns as a pattern having a fine line width;
Separating into a pattern group consisting of pattern parts other than the border part, forming each pattern group as a separate aperture, and that each aperture is arranged adjacently in a region that can be selected only by beam scanning. A featured mask for partial batch exposure. 6. A method for performing partial batch exposure using the mask for partial batch exposure according to claim 1, wherein all apertures are irradiated at the same current density and the same pattern group is used. A plurality of apertures separated from the substrate are sequentially irradiated with a beam. 7. A method for performing partial batch exposure using the mask for partial batch exposure according to claim 1, wherein a group of large-area patterns and a group of fine patterns existing in the same region are separated by different beams. A partial batch exposure method, wherein exposure is performed by irradiation. 8. A method for performing partial batch exposure using the mask for partial batch exposure according to claim 1, wherein a border between adjacent patterns having a small pattern interval is bordered.
A partial batch exposure method comprising exposing portions other than a border portion by separate beam irradiation. 9. The partial batch exposure method according to claim 7, wherein all beam irradiations are performed at the same current density. 10. The partial batch exposure method according to claim 7, wherein the exposure amount of the large area portion and the other portion is changed.