JPH09213598A - Determining method of critical dosage in electron beam writing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely determine critical dosage, by setting a specific value of dosage wherein, in a collective pattern written and developed by changing dosage, the pattern widths of the resist surface and the bottom surface become identical in the central part of the collective pattern, as the critical dosage. SOLUTION: A collective pattern is constituted of the same rectangular repetition patterns which are arranged in a sufficiently wide region as compared with the spread of proximity effect in such a manner that the writing area ratio is 50% and translation symmetry is ensured. The collective pattern is written. Rectangles in one collective pattern are exposed with the identical dosage. After the collective pattern is written and developed by changing the dosage, a value equal to one-half of the dosage wherein, the widths of the patterns of the resist surface and the bottom surface become identical in the central part of the collective pattern is set as the critical dosage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a critical irradiation dose in electron beam writing for evaluating pattern forming conditions using an electron beam.

[0002]

2. Description of the Related Art The critical dose has been conventionally used as one of the process parameters for evaluating pattern forming conditions such as resist coating conditions, developing conditions and standard doses in electron beam lithography. The critical dose is defined as the minimum dose required to dissolve the resist after development in a positive resist and the minimum dose required to insolubilize the resist after development in a negative resist.

When evaluating the effect of various pattern forming conditions on the shape of the pattern to be formed or the pattern forming margin, the influence on each examination item such as developing condition and resist film thickness is separated from the influence of other items. It is important to evaluate them independently. Among the elements that affect the pattern shape or the pattern formation margin, the element that is particularly difficult to separate is the proximity effect. Until now, the critical dose was determined experimentally by excluding the effect of the proximity effect by measuring the residual film ratio of the resist at the center of the irradiation area that was sufficiently larger than the finite spread of the proximity effect. It was Here, the proximity effect means that incident electrons or reflected electrons spread beyond the irradiated position due to scattering of incident electron beams in the resist and reflection / scattering from the underlying substrate. It is a phenomenon that brings about. The degree of the proximity effect depends on the area of the exposed region, the accelerating voltage of the electron beam, the composition of the resist, the film thickness of the resist, the base substrate, the developing conditions and the like. The reason for using a sufficiently large pattern for the spread of the proximity effect is that the effect of the proximity effect is constant at the center of the pattern, and the critical dose can be determined without substantially considering the effect of the proximity effect. .

In the method of determining the critical dose which has been used conventionally, a region having a sufficiently large extent compared with the extent of the proximity effect is irradiated by varying the dose so that the resist at the center of the irradiated region is positive. In the case of a type resist, it is determined as the minimum dose of dissolution. Generally, the relationship between the dose and the residual film ratio is clarified by measuring the residual film ratio in the irradiation region of the pattern drawn by changing the dose, and the minimum irradiation amount at which the residual film ratio becomes 0 is determined. It is used as the critical dose.

[0005]

In the prior art, the accuracy of determining the critical irradiation dose largely depends on the accuracy of measuring the film thickness. Although the measurement technique has improved in recent years and the film thickness can be measured with high accuracy, it is difficult to accurately determine the irradiation dose at which the resist film thickness becomes 0 due to the non-uniformity of resist dissolution. It was

The object of the present invention is to achieve a high accuracy by using a pattern having a characteristic shape, which is different from the evaluation pattern used to determine the critical irradiation dose in order to solve the above problems. To obtain a method for determining the critical dose.

[0007]

The above-mentioned object is to provide a method for determining the critical dose in electron beam drawing for producing a mask for X-ray lithography or photolithography, in which the area is sufficiently wide compared to the extent of proximity effect. When the patterns are arranged so as to have a translational symmetry with a drawing area ratio of%, and a pattern composed of repeated patterns of the same rectangle is defined as one set pattern, the rectangles within one set are exposed with the same irradiation amount. In the central part of the aggregate pattern,
This can be achieved by setting the critical dose to a value 0.5 times the dose when the pattern widths of the resist surface and the bottom are the same.

That is, in order to accurately determine the critical irradiation dose, a collective pattern composed of repetitive patterns of the same rectangle arranged with a drawing area ratio of 50% and translational symmetry is drawn. The rectangles in one set pattern are exposed with the same irradiation amount. This collective pattern is drawn by changing the irradiation dose, and after development, the critical value is 0.5 times the irradiation dose when the width of the pattern on the bottom surface of the resist is the same as the pattern width at the center of the collective pattern. The feature is that the dose is set.

[0009]

Embodiments of the positive resist of the present invention will be described. Usually, there is a proportional relationship between the dose given to the resist at any given point and the amount of energy stored at the bottom, which correspond one to one. Therefore, paying attention to a certain accumulated energy amount is equivalent to paying attention to the corresponding irradiation amount. Therefore, the following examples will be described using the irradiation amount given to the resist without using the accumulated energy amount.

First Embodiment The present invention uses the pattern shown in FIG. 1 which is arranged so as to have a writing area ratio of 50% and translational symmetry.
The set pattern shown in FIG. 1 has a proximity effect parameter of 5
It has a sufficiently large area compared to the spread of the proximity effect, which is estimated to be about double. Usually, the proximity effect component that spreads over the widest range is a component caused by backscattering on the underlying substrate. Therefore, the pattern is arranged in a sufficiently wide range with respect to the spread of this backscattering component.

2 and 3 show a part of the pattern near the center of the set pattern shown in FIG. 1 for the sake of explanation. The feature of the pattern shown in FIG. 1 is that a square rectangle whose side length is P is

[0012]

[Equation 1]

[0013]

[Equation 2]

[0014]

(Equation 3)

## EQU1 ## Here, h and k are integers, and when n is an integer, h + k = 2n ... (4) is satisfied. 2 and 3 have a relationship in which the patterns shown in FIG. 1 are displaced from each other by a half period P in the x-axis and y-axis directions.

Since the pattern shown in FIG. 1 has a finite spread, it is geometrically determined whether or not there is a symmetry axis having four-fold rotational symmetry at one point at the center of the aggregate pattern.
It depends on how many rectangles are placed and how they are placed. However, the influence of the proximity effect spreads over a certain finite region, and within that region only points 0, A, B, which have four-fold rotational symmetry,
There are many points that can be considered equivalent to C and D. Therefore, focusing on the four-fold rotational symmetry axis passing through the origin 0, the point A can be superimposed on the points B, C, and D by the rotation operation. This means that the four points A, B, C and D are equivalent points. Similarly, it is clear that points E, F, G, and H are also points equivalent to each other. Here, points A, B, C, D, E, F, G, and H are points on the boundary between the irradiation area and the non-irradiation area, and points A, B, C, and D are inside one side of one irradiation area. The points E, F, G, and H are points on the boundary between the two irradiation areas.

Since the points shown above are geometrically equivalent and the aggregate pattern has a sufficiently large area compared to the spread of the proximity effect, the doses Da and Db effectively received by the resist at the points. , Dc, Dd, De, Df, Dg,
Between Dh, Da = Db = Dc = Dd (5) De = Df = Dg = Dh (6) Similarly, A ′, B ′, C ′, shown in FIG.
At each of D ', E', F ', G', and H ', the dose Da', Db ', Dc', D effectively received by the resist is obtained.
Between d ', De', Df ', Dg', and Dh ', Da' = Db '= Dc' = Dd '(7) De' = Df '= Dg' = Dh '... (( 8) holds.

The patterns shown in FIGS. 2 and 3 have a sufficiently large area as compared with the spread of the proximity effect. In this case, the patterns shown in FIGS. 2 and 3 are arranged with a shift of a half period P in the x and y directions, respectively, but the pattern shown in FIG. 2 and the pattern shown in FIG. It can be considered as a pattern. Therefore, the points A, B, C, D shown in FIG. 2 correspond to B ', C', D ',
Each is equal to A '. Therefore, the doses at these points satisfy the following relational expressions.

Da = Db '(9) Db = Dc' (10) Dc = Dd '(11) Dd = Da' (12) Further, FIGS. The patterns shown are in a mutually inverted pattern relationship. That is, the unirradiated area of the collective pattern shown in FIG. 2 is the irradiated area of the collective pattern shown in FIG. 3, and the irradiated area of the pattern shown in FIG. 2 is the unirradiated area of the pattern shown in FIG. Drawing these patterns overlappingly is the same as drawing a pattern having a sufficiently large area as compared with the spread of the proximity effect. Compared with the spread of the proximity effect, the dose of the resist effectively received by the resist near the center of the pattern having a wide area is expressed by the following equation.

D = E · ∬f · dx · dy = E (13) Here, the function f is an irradiation intensity distribution function, and is standardized so that the integral value in all xy planes is 1. . The irradiation dose satisfies the expression (13) at the central portion of the aggregate pattern having a sufficiently large area as compared with the spread of the proximity effect, because the irradiation intensity distribution function f satisfies the following expression.

∬f · dx · dy = 1 (14) Therefore, when the collective patterns shown in FIGS. 2 and 3 are drawn in an overlapping manner, the point A overlaps with the point A ′ having an inversion relation, The effective dose of the overlapping resists at this point is E. Therefore, the following equation holds.

Da + Da ′ = E (15) Further, the same relationship holds at the points B, C and D.

Db + Db ′ = E (16) Dc + Dc ′ = E (17) Dd + Dd ′ = E (18) Here, from equation (9) and equation (7), Da = Db ′. = Da '... (19) holds, and from this and the equation (15), Da = 0.5E ... (20) holds.

The other points B, C, D, E, F, and
The same relationship holds for G and H, and the effective dose of the resist at each point is 0.5 times the dose set by the electron beam writing apparatus when writing each rectangle.

Next, let us consider the irradiation dose effectively received by the resist at an arbitrary point on the side of the rectangle ABCD, that is, at an arbitrary point on the boundary between the exposed area and the unexposed area. 2 and 3
When a pattern shifted by a half period P in the X-axis direction is overlapped and irradiated as shown in FIG. 3, the effective dose of the resist at an arbitrary point Q is the point Q ′ in FIG. Calculated as the sum of. From the above consideration, this is equal to the irradiation amount E when drawing each pattern, and the following equation holds.

Dp + Dp ′ = E (21) Here, assuming that the length of one side is P in the pattern shown in FIG. 3, x = n · P (n is an integer) ... (22) Due to the mirror inversion symmetry, the dose at point Q ′ in FIG. 3 is equal to the dose at point Q ″ in FIG. 3, and point Q ″ in FIG. 3 is equal to point Q in FIG. So Figure 3
The irradiation amount at the point Q'inside is equal to the irradiation amount at the point Q in FIG. Therefore, Dq '= Dq "= Dq (23) is established, where Dq = 0.5E (24) is obtained from the equations (21) and (23). When the pattern shown is irradiated with the same set irradiation amount E, the effective irradiation amount of the resist at any point on the boundary between the irradiation region and the non-irradiation region is 0.5 times the irradiation amount E. However, in the above description, the irradiation region width P is sufficiently large with respect to the size of the beam edge resolution, and the beam edge resolution can be substantially ignored.

At the central portion of the pattern having a writing area ratio of 50% and translational symmetry as shown in FIG.
The effective dose of the resist at an arbitrary point on the boundary between the non-irradiated region and the irradiated region is always 0.5 times the dose given to each rectangle. This indicates that the dose at any point on the boundary between the irradiated and unirradiated regions does not depend on the range affected by the proximity effect. That is, at the point of interest on the boundary between the irradiation area and the non-irradiation area of the pattern shown in the present invention, even if there is the influence of the proximity effect from the adjacent pattern, the degree of the acceleration voltage of the electron beam, the resist It does not depend on the composition, the resist film thickness, the base substrate, the developing conditions, etc.

Therefore, at an arbitrary point on the boundary between the non-irradiated part and the irradiated part, the same irradiation amount is accumulated in the depth direction of the resist. Normally, with respect to the depth direction of the resist,
There is a distribution in the intensity of the dose that the resist substantially receives. This is because the degree of proximity effect is distributed in the depth direction of the resist. Since the resist at the point of interest on the boundary between the irradiation region and the non-irradiation region of the pattern shown in the present invention does not substantially depend on the range in which the irradiation dose receives the influence of the proximity effect, the degree of influence of the proximity effect is It is constant in the depth direction of the resist. Therefore, the resist pattern formed after the development has the line width as designed, and the pattern side wall becomes perpendicular to the base substrate. At this time, the amount of irradiation given to the pattern is twice the amount of irradiation effectively received by the resist at the end of each rectangular pattern.

The pattern shape obtained after development has a close relationship with the critical irradiation dose. A resist portion whose effective irradiation dose is less than the critical irradiation amount remains without being dissolved after development, and a resist portion having a critical irradiation amount or more is dissolved after developing. Therefore, the effective dose of the resist on the surface of the pattern formed after development is equal to the critical dose. This idea does not depend on the method of determining the critical dose. That is, the same applies to the method of determining the critical dose that has been conventionally used and the present invention.

In the conventional method, the critical dose is defined as the dose at which the residual film ratio at the center of the pattern is sufficiently larger than the spread of the influence of the proximity effect. This is because the effective dose of the target point of the pattern to be used is equal to the dose of the pattern as expressed by the equation (1),
It can be said that the conventional method directly determines the critical dose. The critical irradiation dose determined in the present invention is a critical irradiation dose that is 1/2 times the irradiation dose in which the pattern side wall becomes perpendicular to the underlying substrate after development. Even when the pattern side wall becomes vertical to the underlying substrate after development, the resist surface, that is, the resist side wall, effectively receives the critical dose. At this time, the irradiation dose of each rectangle is twice the irradiation dose received by the resist on the resist surface portion from the formula (24), that is, twice the critical irradiation dose. Therefore, a value that is 1/2 times the irradiation dose at which the pattern side wall becomes perpendicular to the underlying substrate after development becomes equal to the critical irradiation dose. The critical dose determined in this way is the same as the critical dose determined in the conventional method.

Generally, there are many conditions in which the pattern side wall is perpendicular to the underlying substrate near the edge of the resist pattern. However, the relationship between the dose given to each rectangle and the dose effectively received by the edge resist is not constant, but depends on the size and density of the pattern. This is because it is affected by the proximity effect. When such a pattern is used, the critical dose cannot be determined even if the pattern side wall becomes vertical to the underlying substrate after development. In addition, in the vicinity of the midpoint of one side of the pattern, which is sufficiently larger than the spread of the influence of the proximity effect, no matter what kind of condition is evaluated, the pattern side wall becomes 1 /% of the irradiation amount perpendicular to the base substrate after development. There are cases where the doubled value corresponds to the critical dose. However, it is difficult to judge whether the side wall of such a large pattern is vertical to the base substrate. Since the present invention uses a periodically arranged pattern having translational symmetry, it is relatively easy to determine whether the pattern side wall is vertical to the underlying substrate after development. Therefore, the accuracy of determining the critical dose is improved as compared with the case where the critical dose is determined at a point on one side of the pattern having a sufficiently large area compared to the spread of the proximity efficiency.

As is apparent from the above description, the pattern shown in FIG. 1 is drawn by changing the irradiation amount, and the irradiation amount at which the pattern side wall becomes vertical to the base substrate after development is halved. The critical dose can be calculated accurately.

Second Embodiment In the present invention, the pattern shown in FIG. 4 is used which has a drawing area ratio of 50% and is arranged so as to have translational symmetry. The exposed region width and the unexposed region width are both P and are equal. The pattern shown in FIG. 4 has a sufficiently large region as compared with the spread of the proximity effect estimated to be about 5 times the proximity effect parameter. Usually, the proximity effect component that spreads over the widest range is a component caused by backscattering on the underlying substrate.
Therefore, the pattern is arranged in a sufficiently wide range with respect to the spread of this backscattering component.

FIGS. 5 and 6 show some patterns near the center of the set pattern shown in FIG. 4 for the sake of explanation. In FIGS. 5 and 6, the pattern shown in FIG. 4 is arranged so as to be shifted by a half period P in the x-axis direction. The pattern arranged as shown in FIG. 4 has mirror reversal symmetry with respect to the straight line L1 or the straight line L2 shown in the figure in a finite region where the proximity effect influences. Focusing on the straight line L1, the point A can be superimposed on the point B by the mirror inversion operation. This means that the two points A and B are equivalent points. Here, points A and B are points on the boundary between the irradiation area and the non-irradiation area, and points A and B are midpoints of one side of one irradiation area.

Since the points shown above are equivalent, Da = Db (25) holds between the doses Da and Db at the points. Similarly, Da '= Db' (26) holds between the doses Da 'and Db' at the points A'and B'shown in FIG.

Although the patterns shown in FIGS. 5 and 6 are arranged with a shift of a half cycle in the x direction, they have a sufficiently large area compared to the spread of the proximity effect, so that the patterns shown in FIGS. The patterns shown are the same pattern. Therefore, the points A and B shown in FIG. 5 correspond to B ′ and A ′ in FIG.
Respectively. Therefore, the irradiation doses at these points satisfy the following relational expression.

Da = Db '... (27) Db = Da' ... (28) Further, the patterns shown in FIGS. 5 and 6 have a relationship of mutually inverted patterns. That is, the unirradiated area of the pattern shown in FIG. 5 is the irradiated area of the pattern shown in FIG. 6, and the irradiated area of the pattern shown in FIG. 5 is the unirradiated area of the pattern shown in FIG. Drawing these patterns overlappingly is the same as drawing a pattern having a sufficiently large area as compared with the spread of the proximity effect, that is, uniformly exposing a pattern having a sufficiently large area as compared with the spread of the proximity effect. Is. The irradiation amount near the center of the pattern having a wider area than the spread of the proximity effect is not affected by the proximity effect and becomes E · ∬f · dx · dy = E (29). Here, the function f is an irradiation intensity distribution function, and all x
It is standardized so that the integral value on the y-plane becomes 1. The rectangles shown in FIGS. 4, 5, and 6 are all exposed with the same dose E. In the central portion of the pattern having a sufficiently large area as compared with the spread of the proximity effect, the irradiation amount satisfies the expression (29) because the irradiation intensity distribution function f satisfies the following expression.

∬f · dx · dy = 1 (30) Therefore, at point A in FIG. 5, it overlaps with point A ′ in FIG. 6 having an inversion relation, and the total irradiation amount becomes E. Da + Da ′ = E ... (31) holds, and the same relationship holds at point B as well.

Db + Db ′ = E (32) Here, Da = Db ′ = Da ′ (33) is established from the equations (27) and (26), and from this and the equation (31), Da is obtained. = 0.5E ............ (34) is established.

The same relationship is established at the other points B described above, and the irradiation amount at each point is equal to 0.5E. Since the irradiation dose at each point is a constant 0.5 times the irradiation dose, the irradiation dose at each of the above points in a pattern having a writing area ratio of 50% and translational symmetry as shown in FIG. Does not depend on the range of influence of the proximity effect.

Next, consider the irradiation amount at an arbitrary point on the boundary between the irradiation area and the non-irradiation area near the center of the pattern shown in FIG. As shown in FIGS. 5 and 6, when a pattern shifted by a half cycle in the x-axis direction is overlapped and irradiated, the irradiation amount at an arbitrary point Q is the sum of points Q ′ in FIG. It is calculated. From the above consideration, this is equal to the irradiation amount E, and the following equation holds.

Dq + Dq ′ = E (35) Here, the pattern shown in FIG. 6 has mirror inversion symmetry with respect to x = (n + 0.25) P (n is an integer) (36). In order to have, the dose at point Q ′ in FIG. 6 is equal to the dose at point Q ″ in FIG. 6, and point Q ″ in FIG. 6 is equal to point Q in FIG.
The dose at point Q'inside is equal to the dose at point Q in FIG. Therefore, Dq '= Dq "= Dq (37) is established. Here, Dq = 0.5E ... (38) is obtained from the equations (35) and (37), which is shown in FIG. When the pattern is irradiated with the same reference irradiation amount, the irradiation amount at an arbitrary point on the boundary between the irradiation region and the non-irradiation region is 0.5 times the reference irradiation amount.

In the central portion of the pattern having a writing area ratio of 50% and translational symmetry as shown in FIG.
The effective dose of the resist at an arbitrary point on the boundary between the non-irradiated region and the irradiated region is always 0.5 times the dose given to each rectangle. This indicates that the dose at any point on the boundary between the irradiated and unirradiated regions does not depend on the range affected by the proximity effect. That is,
At the point of interest on the boundary between the irradiated region and the non-irradiated region of the pattern shown in the present invention, even if there is an influence of the proximity effect from the adjacent pattern, the extent of the influence is the acceleration voltage of the electron beam, the composition of the resist. , Resist film thickness, base substrate,
It does not depend on development conditions.

Therefore, at an arbitrary point on the boundary between the unirradiated part and the irradiated part, the same irradiation amount is accumulated in the depth direction of the resist. Normally, with respect to the depth direction of the resist,
There is a distribution in the intensity of the dose that the resist substantially receives. This is because the degree of proximity effect is distributed in the depth direction of the resist. Since the resist at the point of interest on the boundary between the irradiation region and the non-irradiation region of the pattern shown in the present invention does not substantially depend on the range in which the irradiation dose receives the influence of the proximity effect, the degree of influence of the proximity effect is It is constant in the depth direction of the resist. An example thereof is shown in FIG. FIG. 7 shows the dose distribution on the resist surface and the bottom surface (interface between the base substrate) calculated by a computer. The horizontal axis shows the x-coordinate shown in FIG. 5, and the vertical axis shows the normalized irradiation dose. In the calculation, it was assumed that the incident electron beam from the electron beam drawing device had an ideal shape. It can be seen that the normalized irradiation dose is 0.5 at the boundary between the irradiated area and the unirradiated area on both the resist surface and the bottom surface. Therefore, the resist pattern formed after the development has the line width as designed, and the side wall of the pattern is perpendicular to the base substrate. At this time, the amount of irradiation given to each pattern is twice the amount of irradiation effectively received by the resist at the end of each rectangular pattern.

The pattern shape obtained after development has a close relationship with the critical irradiation dose. A resist portion whose effective irradiation dose is less than the critical irradiation amount remains without being dissolved after development, and a resist portion having a critical irradiation amount or more is dissolved after developing. Therefore, the effective dose of the resist on the surface of the pattern formed after development is equal to the critical dose. This idea does not depend on the method of determining the critical dose. That is, the same applies to the method of determining the critical irradiation amount that has been used conventionally and the present invention.

In the conventional method, the critical dose is defined as the dose at which the residual film ratio at the center of the pattern is sufficiently larger than the spread of the influence of the proximity effect. This is because the effective dose of the target point of the pattern to be used is equal to the dose of the pattern as expressed by the equation (1), and the critical dose is directly determined in the conventional method. Can be said.
The critical irradiation dose determined in the present invention is a critical irradiation dose that is 1/2 times the irradiation dose in which the pattern side wall becomes perpendicular to the underlying substrate after development. Even when the pattern side wall becomes vertical to the underlying substrate after development, the resist surface, that is, the resist side wall, effectively receives the critical dose. At this time, the irradiation dose of each rectangle is twice the irradiation dose received by the resist on the resist surface portion from the formula (38), that is, twice the critical irradiation dose. Therefore, a value that is 1/2 times the irradiation dose at which the pattern side wall becomes perpendicular to the underlying substrate after development becomes equal to the critical irradiation dose. The critical dose determined in this way is the same as the critical dose determined in the conventional method.

Generally, there are many conditions in which the pattern side wall is perpendicular to the base substrate near the edge of the resist pattern. However, the relationship between the dose given to each rectangle and the dose effectively received by the edge resist is not constant, but depends on the size and density of the pattern. This is because it is affected by the proximity effect. When such a pattern is used, the critical dose cannot be determined even if the side wall of the pattern becomes vertical to the underlying substrate after development. In addition, in the vicinity of the midpoint of one side of the pattern, which is sufficiently larger than the spread of the effect of the proximity effect, even if the evaluation is performed under any conditions, the pattern side wall becomes perpendicular to the base substrate after development by half the irradiation dose. There is a case where the value of is equal to the critical dose. However, it is difficult to judge whether the side wall of such a large pattern is vertical to the base substrate. Since the present invention uses a periodically arranged pattern having translational symmetry, it is relatively easy to determine whether the pattern side wall is vertical to the underlying substrate after development. Therefore,
The accuracy of determining the critical dose is improved at a point on one side of the pattern having a sufficiently large area compared to the spread of the proximity effect, as compared with the case of determining the critical dose.

As is apparent from the above description, the pattern shown in FIG. 4 is drawn by changing the irradiation amount, and the irradiation amount at which the pattern side wall becomes vertical to the base substrate after development is halved. The critical irradiation dose can be calculated accurately.

[0049]

As described above, the method for determining the critical dose in electron beam writing according to the present invention is the proximity effect in the method for determining the critical dose in electron beam writing prepared by a mask for X-ray lithography or optical lithography. In a region that is sufficiently wider than the spread of the pattern, the pattern is arranged so as to have translational symmetry at a drawing area ratio of 50%, and a pattern composed of repeating patterns of the same rectangle is defined as one set pattern, and a rectangle within one set is defined. Is the same amount of exposure, the collective pattern drawn and developed by changing the amount of irradiation is the same as the amount of irradiation when the pattern width on the resist surface and the bottom surface is the same in the central part of the collective pattern. By setting the value 0.5 times as the critical dose, the process parameter of the process for evaluating the pattern formation condition of the electron beam exposure method The critical irradiation dose, which is one, can be accurately evaluated. Further, it becomes possible to evaluate the magnitude of the beam edge resolution which substantially affects the pattern formation.

[Brief description of drawings]

FIG. 1 is an evaluation pattern diagram including a rectangle having a square as a first embodiment of a method of determining a critical dose in electron beam writing according to the present invention.

FIG. 2 is an enlarged view of a coordinate system near the center of the evaluation pattern shown in FIG.

FIG. 3 is an enlarged view of a different coordinate system near the central portion of the evaluation pattern shown in FIG.

FIG. 4 is an evaluation pattern diagram when one side is long as a second embodiment of the present invention.

5 is an enlarged view of a coordinate system near the center of the evaluation pattern shown in FIG.

6 is an enlarged view of a different coordinate system near the center of the evaluation pattern shown in FIG.

FIG. 7 is a diagram showing irradiation intensity on the resist surface and the resist bottom surface of the pattern shown in FIG.

Claims (1)

[Claims] 1. A method of determining a critical irradiation dose in electron beam writing for producing a mask for X-ray lithography or optical lithography, in which a translational symmetry with a writing area ratio of 50% is provided in a region sufficiently wider than the spread of the proximity effect. When a pattern composed of repeated patterns of the same rectangle arranged so as to have the property is set as one set pattern and the rectangles in one set are exposed with the same dose, the drawing dose is changed and the pattern is drawn. Critical irradiation in electron beam writing, wherein the critical irradiation dose is 0.5 times the irradiation dose when the pattern widths of the resist surface and the bottom face in the center of the developed aggregate pattern are the same. How to determine the amount.