JP4314288B2 - Photo mask - Google Patents

Description

  The present invention relates to a photomask for forming a fine pattern used for manufacturing a semiconductor integrated circuit device.

  In recent years, miniaturization of circuit patterns has become more and more necessary for high integration of large-scale integrated circuit devices (hereinafter referred to as LSIs) realized using semiconductors. As a result, it has become very important to make a wiring pattern constituting a circuit finer or to make a contact hole pattern (hereinafter referred to as a contact pattern) finely connecting wirings that are multilayered via an insulating layer.

  Hereinafter, the thinning of the wiring pattern and the miniaturization of the contact pattern by the conventional light exposure system will be described using a positive resist process. Here, the line pattern is a portion of the resist film that is not exposed to exposure light, that is, a resist portion (resist pattern) remaining after development. The space pattern is a portion exposed by exposure light in the resist film, that is, an opening portion (resist removal pattern) formed by removing the resist by development. Further, the contact pattern is a portion that is removed in a hole shape by development in the resist film, and may be considered as a particularly minute space pattern. In addition, when using a negative resist process instead of a positive resist process, the definitions of the above-described line pattern and space pattern may be interchanged.

<First Conventional Example>
As a conventional method for forming a fine line pattern, there has been proposed a method for forming a fine line pattern by emphasizing the contrast of the light intensity distribution caused by the mask pattern with a phase shifter (for example, HY Liu et al., Proc SPIE, Vol. 3334, P.2 (1998)).

  Hereinafter, a conventional line pattern forming method using a phase shifter will be described with reference to the drawings.

  FIG. 28A shows an example of the layout of a desired pattern (resist pattern) to be formed. As shown in FIG. 28A, the pattern 800 has a partial pattern 800a having a predetermined dimension or less.

  FIGS. 28B and 28C are plan views of two conventional photomasks used for forming the pattern shown in FIG. As shown in FIG. 28B, in the first photomask 810, a complete light-shielding film 812 (transmittance of exposure light is approximately 0%) is formed on a transparent substrate 811. In addition, the complete light-shielding film 812 is provided with a first opening 813 serving as a translucent part and a second opening 814 serving as a phase shifter with a light-shielding pattern 812a for forming the partial pattern 800a interposed therebetween. . The second opening 814 serving as the phase shifter transmits the exposure light so that a phase difference of 180 degrees is generated with reference to the first opening 813 serving as the light transmitting part. Further, as shown in FIG. 28C, in the second photomask 820, a desired pattern 800 (FIG. 28) is formed on the transparent substrate 821 by combining with the light shielding pattern 812a of the first photomask 810. A light shielding pattern 822 for forming (see (a)) is formed.

  A pattern forming method using the two photomasks shown in FIGS. 28B and 28C is as follows. First, using the first photomask 810, exposure is performed on a substrate coated with a resist film made of a positive resist. After that, the second photomask 820 is aligned so that the pattern 800 shown in FIG. 28A is formed, and then exposure is performed using the second photomask 820. Thereafter, by developing the resist film, a resist pattern as shown in FIG. 28A can be formed. At this time, an extra pattern (a pattern other than the pattern 800) that remains only by exposure using the first photomask 810 can be removed by exposure using the second photomask 820. . As a result, a partial pattern 800a having a very small width that cannot be formed by exposure using only the second photomask 820 can be formed.

  In this method, when the light-transmitting portion and the phase shifter are arranged with a pattern (that is, a light-shielding pattern) made of a complete light-shielding film having a predetermined dimension or less, the light-transmitting portion (opening portion) and the phase shifter are Since the light that is transmitted and diffracted to the back side of the light shielding pattern cancels each other, the light shielding property of the light shielding pattern can be improved, so that a line pattern having a predetermined dimension or less can be formed.

<Second Conventional Example>
As a conventional method for forming a minute contact pattern, a method using a halftone phase shift mask has been proposed. In this halftone phase shift mask, a light transmitting portion (an opening in the phase shifter) corresponding to the contact pattern is provided. In addition, a phase shifter that transmits light with an opposite phase of 180 degrees with respect to the light that has a low transmittance (about 3 to 6%) with respect to the exposure light and transmits through the opening is provided as the light shielding portion. Yes.

  Hereinafter, the principle of the pattern forming method using the halftone phase shift mask will be described with reference to FIGS.

  FIG. 29A is a plan view of a photomask in which an opening corresponding to a contact pattern is provided in a chromium film serving as a complete light-shielding portion provided on the mask surface, and FIG. 29B is a plan view of FIG. The amplitude intensity of the light transmitted through the photomask shown in (a) and transferred to the position corresponding to the line segment AA ′ on the exposed material is shown. FIG. 29C is a plan view of a photomask in which a phase shifter provided on the mask surface is provided with a chromium film corresponding to the contact pattern as a complete light shielding portion, and FIG. 29D is a plan view of FIG. The amplitude intensity of light transmitted through the photomask shown in c) and transferred to the position corresponding to the line segment AA ′ on the exposed material is shown. FIG. 29E is a plan view of a photomask (that is, a halftone phase shift mask) in which an opening corresponding to a contact pattern is provided in a phase shifter serving as a light shielding portion provided on the mask surface. FIG. 29F and FIG. 29G show the amplitude intensity and light intensity of light transmitted through the photomask shown in FIG. 29E and transferred to the position corresponding to the line segment AA ′ on the exposed material. Show.

  As shown in FIGS. 29 (b), 29 (d), and 29 (f), the amplitude intensity of the light transmitted through the halftone phase shift mask shown in FIG. 29 (e) is as shown in FIGS. This is the sum of the amplitude intensities of the light transmitted through the photomask shown in each of 29 (c). That is, in the halftone phase shift mask shown in FIG. 29 (e), the phase shifter serving as the light shielding portion transmits not only a part of the exposure light but also the light transmitted through the phase shifter through the opening. It is formed so as to give a phase difference of 180 degrees with respect to the light to be transmitted. Therefore, as shown in FIGS. 29 (b) and 29 (d), the light transmitted through the phase shifter has an amplitude intensity distribution having an opposite phase to the light transmitted through the opening. ) And the amplitude intensity distribution shown in FIG. 29D are combined to generate a phase boundary where the amplitude intensity becomes zero due to the phase change, as shown in FIG. 29F. As a result, as shown in FIG. 29 (g), at the end of the opening serving as the phase boundary (hereinafter referred to as the phase end), the light intensity expressed by the square of the amplitude intensity becomes 0 and a strong dark portion is present. It is formed. Therefore, in the image of the light transmitted through the halftone phase shift mask shown in FIG. 29 (e), a very strong contrast is realized around the opening, so that a minute contact pattern can be formed.

Here, an exposure light source used for exposure in this specification will be described. 30A to 30C are views showing the shape of an exposure light source that has been conventionally used. With respect to the normal exposure light source as shown in FIG. 30A, the oblique incidence exposure light source is obtained by removing a light component perpendicularly incident on a portion corresponding to the light source center in the photomask, as shown in FIG. This means a light source as shown in FIG. Typical oblique incidence exposure light sources include an annular exposure light source shown in FIG. 30 (b) and a quadrupole exposure light source shown in FIG. 30 (c). In general, the quadrupole exposure light source is more effective in enhancing contrast or increasing the depth of focus (DOF) than the annular exposure light source, although it depends slightly on the target pattern.
H. Y. Liu et al., Proc. SPIE, 1998, Vol. 3334, P.I. 2

However, the pattern forming method as in the first conventional example has the following problems.
(1) In order to improve the contrast of the light-shielded image corresponding to the light-shielding pattern by sandwiching the light-shielding pattern between the light-transmissive part and the phase shifter, the distance between the light-transmissive part and the phase shifter is a predetermined dimension or less. Must be next to each other. On the other hand, when the light transmitting part and the phase shifter are arranged on the photomask without interposing the light shielding pattern therebetween, a light shielding image corresponding to the boundary between the light transmitting part and the phase shifter is formed. Therefore, a pattern having an arbitrary shape cannot be formed only by the first photomask as shown in FIG. 28B, so that a pattern having a complicated shape such as a normal LSI pattern layout is created. For this purpose, exposure using a second photomask as shown in FIG. 28C in addition to the first photomask as shown in FIG. 28B is essential. As a result, mask costs increase and throughput decreases or manufacturing costs increase due to an increase in the number of steps in lithography.
(2) When a desired pattern (resist pattern) to be formed has a complicated pattern shape (for example, a T-shape having a predetermined dimension or less), the entire light-shielding pattern is formed with a translucent portion and a phase shifter having opposite phases For example, the light shielding property of a T-shaped light shielding pattern cannot be improved. Therefore, the pattern layout that can use the effect of the phase shifter is limited.

Further, the pattern forming method as in the second conventional example has the following problems.
(3) Depending on the halftone phase shift mask, the formation of isolated contact patterns arranged in isolation and the formation of dense contact patterns arranged in nectar can be performed simultaneously and satisfactorily by exposure using the same exposure source. Have difficulty. Similarly, it is difficult to form isolated line patterns that are arranged in isolation and dense line patterns that are arranged in nectar simultaneously and with a satisfactory finish by exposure using the same exposure source. That is, when an isolated contact pattern is formed, a vertical light source is used by using a small light source (see FIG. 30A) having an interference degree of 0.5 or less for illuminating only a normal incidence component incident perpendicularly to the mask. By performing incident exposure, it is possible to improve contrast and achieve a high depth of focus. However, when a dense contact pattern is formed by normal incidence exposure, contrast and depth of focus are significantly deteriorated. On the other hand, when a dense contact pattern is formed, a light source for performing illumination only with an oblique incidence component that is obliquely incident on the mask, for example, annular illumination with a vertical incidence component (illumination component from the center of the light source) removed. By performing oblique incidence exposure using a light source for the purpose (see FIG. 30B), it is possible to realize an improvement in contrast and a high depth of focus. However, when an isolated contact pattern is formed by oblique incidence exposure, the contrast and the depth of focus are significantly deteriorated.
(4) Depending on the halftone phase shift mask, it is difficult to form an isolated space pattern and an isolated line pattern simultaneously and with a satisfactory finish. That is, when forming an isolated space pattern, it is possible to realize an improvement in contrast and a high depth of focus by performing normal incidence exposure. However, when an isolated line pattern is formed by normal incidence exposure, contrast and depth of focus are significantly deteriorated. On the other hand, when an isolated line pattern is formed, an improvement in contrast and a high depth of focus can be realized by performing oblique incidence exposure. However, when an isolated space pattern is formed by oblique incidence exposure, the contrast and the depth of focus are significantly deteriorated. Thus, when the halftone phase shift mask is used, the optimum illumination condition for the isolated space pattern (including the isolated contact pattern) and the optimum illumination condition for the dense space pattern (including the dense contact pattern) or the isolated line pattern are as follows: There is a reciprocal relationship. For this reason, it is difficult to perform the formation of the isolated space pattern and the formation of the isolated line pattern or the dense space pattern at the same time and with an optimum finish under the same illumination conditions.

  In view of the above, an object of the present invention is to provide a photomask that can form a fine pattern under the same exposure conditions without depending on the shape or density of the pattern.

  In order to achieve the above object, a photomask according to the present invention includes a mask pattern having a light-blocking property for exposure light on a transparent substrate having a light-transmitting property to exposure light, and a transparent substrate. On the premise of a photomask provided with a translucent part in which no mask pattern is formed, the mask pattern is based on a translucent part that transmits exposure light in the same phase with the translucent part as a reference, and the translucent part as a reference. The semi-light-shielding part has a transmittance that partially transmits the exposure light, and the phase shifter is transmitted by the light transmitted through the phase shifter. It is provided at a position where a part of the light transmitted through the light part and the semi-light-shielding part can be canceled.

  According to the photomask of the present invention, the mask pattern is composed of the semi-light-shielding portion and the phase shifter, and the light transmitted through the phase shifter can cancel part of the light transmitted through the light-transmitting portion and the semi-light-shielding portion. A phase shifter is arranged in For this reason, since the contrast of the light intensity distribution in the light-shielded image corresponding to the mask pattern can be enhanced, a fine pattern can be formed under the same exposure condition without depending on the pattern shape or the degree of density.

  In the photomask of the present invention, the transmissivity of the semi-light-shielding portion with respect to exposure light is preferably 15% or less.

  In this way, it is possible to prevent resist film loss or optimize resist sensitivity during pattern formation. In particular, if the transmissivity of the semi-light-shielding portion with respect to exposure light is 6% or more and 15% or less, the DOF (depth of focus) or contrast is improved, the resist film is prevented from being reduced during pattern formation, or the resist sensitivity is optimized. It is possible to achieve both.

  In the photomask of the present invention, the semi-light-shielding portion transmits exposure light with a phase difference of (−30 + 360 × n) degrees or more and (30 + 360 × n) degrees or less (where n is an integer) with respect to the light-transmitting portion. In addition, the phase shifter may transmit the exposure light with a phase difference of not less than (150 + 360 × n) degrees and not more than (210 + 360 × n) degrees (where n is an integer) with reference to the light transmitting portion. That is, in this specification, a phase difference of (−30 + 360 × n) degrees or more and (30 + 360 × n) degrees or less (where n is an integer) is regarded as the same phase, and (150 + 360 × n) degrees or more and ( The phase difference of 210 + 360 × n) degrees or less (where n is an integer) is regarded as the opposite phase.

  In the photomask of the present invention, the phase shifter is disposed at a portion of (0.8 × λ / NA) × M or less from the boundary with the light transmitting portion in the mask pattern (where λ is the wavelength of the exposure light) And NA and M are respectively the numerical aperture and the reduction magnification of the reduction projection optical system of the exposure machine).

  This improves the exposure margin in pattern formation.

  In the photomask of the present invention, when the mask pattern is provided so as to surround the light transmitting portion and the phase shifter is provided in the vicinity of the light transmitting portion in the mask pattern, the width of the phase shifter is (0.3 × It is preferable that λ / NA) × M or less (where λ is the wavelength of exposure light, and NA and M are the numerical aperture and reduction magnification of the reduction projection optical system of the exposure machine, respectively).

  In this way, the focus margin in pattern formation is improved. However, it is preferable that the width of the phase shifter is not less than (0.1 × λ / NA) × M at which an optical action as a phase shifter is obtained.

  In the photomask of the present invention, the mask pattern is provided so as to surround the translucent part, and the phase shifter is provided in the vicinity of the translucent part in the mask pattern so as to be sandwiched between the semi-light-shielding part and the translucent part. It is preferable.

  In this way, it is possible to enhance the contrast of the light intensity distribution in the peripheral part of the image of the light transmitted through the light transmitting part.

  In the photomask of the present invention, it is preferable that the mask pattern is provided so as to surround the light-transmitting portion, and the phase shifter is provided in the vicinity of the light-transmitting portion in the mask pattern so as to be surrounded by the semi-light-shielding portion. .

  In this way, the contrast of the light intensity distribution in the peripheral part of the image of the light transmitted through the light transmitting part can be enhanced, and the light intensity distribution is hardly affected by the mask dimension error.

  In the photomask of the present invention, it is preferable that the mask pattern is surrounded by the translucent part and the phase shifter is surrounded by the semi-light-shielding part.

  In this way, it is possible to enhance the contrast of the light intensity distribution at the center of the light-shielded image corresponding to the mask pattern. In this case, the width of the mask pattern is (0.8 × λ / NA) × M or less (where λ is the wavelength of the exposure light, and NA and M are the apertures of the reduction projection optical system of the exposure device, respectively). The above-described effects can be obtained with certainty. In this case, when the width of the phase shifter is (0.4 × λ / NA) × M or less, the exposure margin in pattern formation is further improved. Further, in this case, when the width of the phase shifter is not less than (0.1 × λ / NA) × M and not more than (0.4 × λ / NA) × M, the exposure margin and the DOF are simultaneously improved.

  In the photomask of the present invention, the mask pattern is a line pattern surrounded by a translucent part, and the phase shifter is provided at the center part in the line width direction of the mask pattern so as to be sandwiched by the semi-light-shielding part. Preferably it is.

  In this way, it is possible to enhance the contrast of the light intensity distribution at the center of the line-shaped light-shielded image corresponding to the mask pattern. In this case, the width of the mask pattern is (0.8 × λ / NA) × M or less (where λ is the wavelength of the exposure light, and NA and M are the apertures of the reduction projection optical system of the exposure device, respectively). The above-described effects can be obtained with certainty. In this case, when the width of the phase shifter is (0.4 × λ / NA) × M or less, the exposure margin in pattern formation is further improved. Further, in this case, when the width of the phase shifter is not less than (0.1 × λ / NA) × M and not more than (0.4 × λ / NA) × M, the exposure margin and the DOF are simultaneously improved.

  In the photomask of the present invention, the mask pattern is a line pattern surrounded by a light transmitting portion, and the phase shifter is provided so as to sandwich the semi-light-shielding portion at least at both ends in the line width direction of the mask pattern. It is preferable.

  In this way, it is possible to enhance the contrast of the light intensity distribution at the contour portion of the light shielding image corresponding to the mask pattern.

  In the photomask of the present invention, the mask pattern is a line pattern surrounded by a light transmitting portion, and the phase shifter sandwiches the semi-light-shielding portions at both ends and the center portion in the line width direction of the mask pattern. It is preferable to be provided.

  In this way, it is possible to enhance the contrast of the light intensity distribution at the contour portion of the light shielding image corresponding to the mask pattern. Further, it is possible to prevent a side lobe from occurring at the center of the light-shielded image due to the use of the semi-light-shielding part. In this case, the width of the mask pattern is (λ / NA) × M or less (where λ is the wavelength of exposure light, and NA and M are the numerical aperture and reduction magnification of the reduction projection optical system of the exposure machine, respectively) The above-mentioned effect can be obtained with certainty. Furthermore, in this case, when the width of the phase shifter is (0.3 × λ / NA) × M or less, the focus margin in pattern formation is further improved.

  In the photomask of the present invention, the mask pattern is a line pattern surrounded by a translucent portion, and the phase shifter is provided so as to be surrounded by the semi-light-shielding portions at both ends in the line width direction of the mask pattern. It is preferable.

  In this way, the contrast of the light intensity distribution in the contour portion of the light-shielded image corresponding to the mask pattern can be enhanced, and the light intensity distribution is hardly affected by the mask dimension error.

  In the photomask of the present invention, the mask pattern is a line pattern surrounded by a translucent portion, and the phase shifter is surrounded by the semi-light-shielding portions at both ends and the center in the line width direction of the mask pattern, respectively. Is preferably provided.

  In this way, the contrast of the light intensity distribution in the contour portion of the light-shielded image corresponding to the mask pattern can be enhanced, and the light intensity distribution is hardly affected by the mask dimension error. Further, it is possible to prevent a side lobe from occurring at the center of the light-shielded image due to the use of the semi-light-shielding part.

  In the photomask of the present invention, the translucent part has a first translucent part and a second translucent part, and the mask pattern surrounds the first translucent part and the second translucent part. The phase shifter is provided in the central portion between the first light transmitting portion and the second light transmitting portion, and the semi-light-shielding portions are provided on both sides of the phase shifter. Is preferred.

  In this way, it is possible to enhance the contrast of the light intensity distribution in the central portion of the shielded image corresponding to the portion sandwiched between the pair of light transmitting portions in the mask pattern. In this case, the distance between the first light transmitting portion and the second light transmitting portion is (0.8 × λ / NA) × M or less (where λ is the wavelength of the exposure light, and NA and M is the numerical aperture and the reduction magnification of the reduction projection optical system of the exposure machine), and the above-described effects can be obtained with certainty. In this case, if the width of the phase shifter is (0.4 × λ / NA) × M or less, the exposure margin in pattern formation is improved. Further, in this case, when the width of the phase shifter is not less than (0.1 × λ / NA) × M and not more than (0.4 × λ / NA) × M, the exposure margin and the DOF are simultaneously improved.

  The pattern forming method according to the present invention is based on the pattern forming method using the photomask of the present invention, and a step of forming a resist film on the substrate, and a step of irradiating the resist film with exposure light through the photomask, And developing a resist film irradiated with exposure light to form a resist pattern.

  According to the pattern forming method of the present invention, the same effect as the photomask of the present invention can be obtained. Moreover, in the pattern formation method of this invention, it is preferable to use an oblique incidence illumination method in the process of irradiating exposure light. In this way, in the light intensity distribution of the light transmitted through the photomask, the contrast between portions corresponding to the mask pattern and the light transmitting portion is improved. Also, the focus characteristic of the light intensity distribution is improved. Therefore, the exposure margin and focus margin in pattern formation are improved.

  The first mask data generation method according to the present invention is based on the photomask mask data generation method of the present invention, determines the shape of the mask pattern based on the pattern to be formed using the photomask, and is semi-shielded. A first step of setting the transmissivity of the part, a second step of extracting a region sandwiched between the translucent portions with a predetermined dimension or less in the mask pattern after the first step, and a second step And a third step of inserting a phase shifter in the vicinity of the translucent portion in the extracted region and mask pattern.

  According to the first mask data creation method, a photomask capable of enhancing the contrast of the light intensity distribution in the peripheral portion of the image of the light transmitted through the light transmitting portion and preventing the occurrence of side lobes in the central portion of the light shielding image is realized. it can.

  The first mask data creation method preferably includes a step of inserting a semi-light-shielding portion having a predetermined dimension or less between the phase shifter and the translucent portion after the third step.

  In this way, it is possible to realize a photomask in which the light intensity distribution is hardly affected by the mask dimension error.

  In the first mask data creation method, after the third step, the exposure light is transmitted in an opposite phase to a region sandwiched between the light transmitting portions having a predetermined dimension or less in the mask pattern with reference to the light transmitting portions. It is preferable that a step of inserting the phase shifter is provided.

  In this way, a photomask that can prevent the occurrence of side lobes can be realized. At this time, another phase shifter may transmit the exposure light with a phase difference of not less than (150 + 360 × n) degrees and not more than (210 + 360 × n) degrees (where n is an integer) with reference to the light transmitting portion. .

  In the first mask data creation method, after the third step, a line-shaped pattern end having a width equal to or smaller than a predetermined dimension is extracted from the mask pattern, and the extracted pattern end It is preferable to include a step of inserting another phase shifter in the peripheral portion parallel to the line direction.

  In this way, it is possible to realize a photomask that can prevent the line pattern end from retreating. Further, when the line pattern is close to another pattern, a photomask that can prevent a bridge between the patterns can be realized.

  In the first mask data creation method, after the third step, a corner is extracted from the mask pattern, and a phase shifter is arranged in a region within a predetermined dimension from the bending point of the extracted corner in the mask pattern. In such a case, it is preferable to provide a step of replacing the phase shifter with a semi-light-shielding portion or reducing the size of the phase shifter.

  In this way, a photomask capable of forming a pattern corner portion having a desired shape can be realized.

  In the first mask data creation method, after the third step, the dimension of the semi-light-shielding portion is fixed with the phase shifter dimension fixed so that the pattern to be formed using the photomask has a desired dimension. It is preferable that the method includes a step of correcting.

  In this way, it is possible to realize a photomask having a small pattern (resist pattern) dimension variation with respect to a change in mask dimension, that is, a photomask capable of forming a pattern having a desired dimension.

  The second mask data creation method according to the present invention is based on the photomask mask data creation method of the present invention, determines the shape of the mask pattern based on the pattern to be formed using the photomask, and is semi-shielded. A first step of setting the transmissivity of the part, a second step of extracting a region whose width in the mask pattern is a predetermined dimension or less after the first step, and after the second step, And a third step of inserting a phase shifter at the peripheral portion of the extracted region and the region where the width of the mask pattern exceeds a predetermined dimension.

  According to the second mask data creation method, the contrast of the light intensity distribution in each of the central portion of the light-shielded image corresponding to the narrow portion in the mask pattern and the contour portion of the light-shielded image corresponding to the wide portion in the mask pattern. A photomask capable of emphasizing can be realized.

  The second mask data creation method preferably includes a step of inserting a semi-light-shielding portion having a predetermined dimension or less between the phase shifter and the light transmitting portion after the third step.

  In this way, it is possible to realize a photomask in which the light intensity distribution is hardly affected by the mask dimension error.

  In the second mask data creation method, after the third step, another phase shifter that transmits the exposure light in the opposite phase with respect to the translucent portion is inserted in the region where the width of the mask pattern exceeds a predetermined dimension. It is preferable to provide the process to do.

  In this way, a photomask that can prevent the occurrence of side lobes can be realized. At this time, another phase shifter may transmit the exposure light with a phase difference of not less than (150 + 360 × n) degrees and not more than (210 + 360 × n) degrees (where n is an integer) with reference to the light transmitting portion. .

  In the second mask data creation method, after the third step, a line-shaped pattern end having a width equal to or smaller than a predetermined dimension is extracted from the mask pattern, and the extracted pattern end It is preferable to include a step of inserting another phase shifter in the peripheral portion parallel to the line direction.

  In this way, it is possible to realize a photomask that can prevent the line pattern end from retreating. Further, when the line pattern is close to another pattern, a photomask that can prevent a bridge between the patterns can be realized.

  In the second mask data creation method, after the third step, the corner is extracted from the mask pattern, and the phase shifter is arranged in a region within a predetermined dimension from the bending point of the extracted corner in the mask pattern. In such a case, it is preferable to provide a step of replacing the phase shifter with a semi-light-shielding portion or reducing the size of the phase shifter.

  In this way, a photomask capable of forming a pattern corner portion having a desired shape can be realized.

  In the second mask data generation method, after the third step, the dimension of the semi-light-shielding portion is fixed with the phase shifter dimension fixed so that the pattern to be formed using the photomask has a desired dimension. It is preferable that the method includes a step of correcting.

  In this way, it is possible to realize a photomask having a small pattern (resist pattern) dimension variation with respect to a change in mask dimension, that is, a photomask capable of forming a pattern having a desired dimension.

  According to the present invention, the mask pattern includes the semi-light-shielding portion and the phase shifter, and the phase shifter can cancel out a part of the light transmitted through the light-transmitting portion and the semi-light-shielding portion by the light transmitted through the phase shifter. Is arranged. For this reason, since the contrast of the light intensity distribution in the light-shielded image corresponding to the mask pattern can be enhanced, a fine pattern can be formed under the same exposure condition without depending on the pattern shape or the degree of density.

(First embodiment)
First, a resolution improvement method using a photomask devised by the present inventor for realizing the present invention, specifically, a photomask using a “contour enhancement method” for improving the resolution of an isolated space pattern will be described. To do.

  FIG. 1 shows a photomask using a contour emphasis method according to the first embodiment of the present invention (hereinafter referred to as a contour emphasis mask), specifically, a translucent portion corresponding to an isolated contact pattern. It is a top view of an outline emphasis mask.

  As shown in FIG. 1, the contour enhancement mask 1 has a transmissive substrate 2 that is transmissive to exposure light, and a transmittance that is formed on the main surface of the transmissive substrate 2 and that partially transmits the exposure light. A semi-light-shielding portion 3, a translucent portion (opening) 4 corresponding to the isolated contact pattern formed on the main surface of the transmissive substrate 2 so as to be surrounded by the semi-light-shielding portion 3, and the main surface of the transmissive substrate 2 A ring-shaped phase shifter 5 formed so as to surround the translucent part 4 is provided between the semi-light-shielding part 3 and the translucent part 4. In the contour emphasis mask 1, light shielding is performed by a semi-light-shielding portion 3 that transmits exposure light in the same phase with the light-transmitting portion 4 as a reference, and a phase shifter 5 that transmits exposure light in the opposite phase with the light-transmitting portion 4 as a reference. A mask pattern having a characteristic is configured.

  In this specification, a phase difference of (−30 + 360 × n) degrees or more and (30 + 360 × n) degrees or less (where n is an integer) is regarded as the same phase, and (150 + 360 × n) degrees or more and ( The phase difference of 210 + 360 × n) degrees or less (where n is an integer) is regarded as the opposite phase.

  Further, the transmittance of the semi-light-shielding portion 3 with respect to the exposure light is 15% or less, preferably 6% or more and 15% or less. Examples of the material of the semi-light-shielding portion 3 include a thin film (thickness of 50 nm or less) made of a metal such as Cr (chromium), Ta (tantalum), Zr (zirconium), or Mo (molybdenum), or an alloy of these metals. ) Can be used. Specific examples of the alloy include a Ta—Cr alloy, a Zr—Si alloy, and a Mo—Si alloy. Furthermore, when it is desired to increase the thickness of the semi-light-shielding portion 3, a material containing an oxide such as ZrSiO, Cr—Al—O, TaSiO, or MoSiO may be used.

  Further, the transmittance of the phase shifter 5 with respect to the exposure light is higher than the transmittance of the semi-light-shielding portion 3 and equal to or less than the transmittance of the light-transmitting portion 4.

<Principle of outline enhancement method>
Next, the “contour emphasis method” used in the present embodiment for improving the resolution of the isolated space pattern will be described by way of an example in which a contact pattern is formed by a positive resist process. Here, the “contour emphasis method” is a principle that holds true regardless of the shape of a minute space pattern in a positive resist process. In addition, the “contour emphasis method” can be applied in the same manner even when a negative resist process is used if a minute space pattern (resist removal pattern) in the positive resist process is replaced with a minute pattern (resist pattern).

  FIGS. 2A to 2G are views for explaining the principle for emphasizing the light transfer image in the contact pattern formation region.

  FIG. 2A is a plan view of a photomask in which an opening corresponding to a contact pattern is provided in a semi-light-shielding portion formed on the surface of a transmissive substrate and having a transmittance that transmits a part of exposure light. is there. FIG. 2B shows the amplitude intensity of light transmitted through the photomask shown in FIG. 2A and transferred to a position corresponding to the line segment AA 'on the material to be exposed.

  FIG. 2C shows a photomask in which a complete light-shielding portion formed on the main surface of the transparent substrate is provided with a ring-shaped phase shifter so as to correspond to the peripheral region of the opening shown in FIG. FIG. FIG. 2D shows the amplitude intensity of the light transmitted through the photomask shown in FIG. 2C and transferred to the position corresponding to the line segment AA ′ on the exposed material. Here, the amplitude intensity of the light shown in FIG. 2 (d) is in an opposite phase relationship to the amplitude intensity of the light shown in FIG. 2 (b) because the light is transmitted through the phase shifter.

  FIG. 2E is an example of the contour enhancement mask according to the present embodiment, and corresponds to the contact pattern similar to the photomask shown in FIG. 2A on the semi-light-shielding portion formed on the main surface of the transparent substrate. FIG. 3 is a plan view of a photomask in which a ring-shaped phase shifter similar to the photomask shown in FIG. 2C is provided in a peripheral region of the opening. 2 (f) and 2 (g) show the amplitude intensity of light transmitted through the photomask shown in FIG. 2 (e) and transferred to the position corresponding to the line segment AA 'on the exposed material. The light intensity (the square of the light intensity) is shown.

  Hereinafter, the principle of emphasizing the transferred image of the light transmitted through the contour emphasis mask shown in FIG. The structure of the photomask shown in FIG. 2 (e) is a structure in which the semi-light-shielding portion in FIG. 2 (a) and the phase shifter in FIG. 2 (c) are superimposed on a transparent substrate. Further, as shown in FIGS. 2B, 2D, and 2F, the amplitude intensity of the light transmitted through the photomask shown in FIG. 2E is shown in FIGS. The distribution is such that the amplitude intensity of the light transmitted through the photomask shown in each of (c) is superimposed. Here, as can be seen from FIG. 2 (f), in the photomask shown in FIG. 2 (e), the light transmitted through the phase shifter arranged around the opening is the light transmitted through the opening and the semi-shielding portion. A part of can be countered. Therefore, in the photomask shown in FIG. 2 (e), if the intensity of the light transmitted through the phase shifter is adjusted so that the light in the contour surrounding the opening is canceled, as shown in FIG. It is possible to form a light intensity distribution in which the light intensity corresponding to the periphery of the opening is reduced to a value close to approximately zero.

  In the photomask shown in FIG. 2E, the light transmitted through the phase shifter strongly cancels the light around the opening while weakly cancels the light near the center of the opening. As a result, as shown in FIG. 2 (g), the slope of the profile of the light intensity distribution that changes from the opening to the periphery of the light transmitted through the photomask shown in FIG. 2 (e) increases. An effect is also obtained. Accordingly, the intensity distribution of the light transmitted through the photomask shown in FIG. 2E has a sharp profile, so that an image with high contrast and light intensity is formed.

  The above is the principle of emphasizing the image of light intensity in the present invention. That is, the photomask shown in FIG. 2A is arranged by arranging the phase shifter along the contour of the opening of the mask formed using the semi-light-shielding portion having a transmittance that transmits a part of the exposure light. It is possible to form a very strong dark portion corresponding to the contour portion of the opening in the image of the light intensity formed by the above. As a result, a light intensity distribution with enhanced contrast can be formed between the light intensity at the opening and the light intensity at the contour. In this specification, a method of performing image enhancement based on such a principle is referred to as “contour enhancement method”, and a photomask that realizes this principle is referred to as “contour enhancement mask”.

  Here, the difference between the outline emphasis method which is the basic principle of the present invention and the principle of the conventional halftone phase shift mask will be described. The most important thing in the principle of the contour enhancement method is that a part of the light transmitted through the semi-light-shielding portion and the aperture is canceled by the light transmitted through the phase shifter, thereby forming a dark portion in the light intensity distribution. It is. That is, the phase shifter behaves like an opaque pattern. For this reason, as shown in FIG. 2F, a dark portion is formed by the intensity change on the same phase side in the amplitude intensity of the light transmitted through the contour emphasis mask. Only in this state, the contrast can be improved by the oblique incidence exposure.

  On the other hand, also in the light intensity distribution when a conventional halftone phase shift mask having an opening corresponding to the contact pattern is exposed, a strong dark portion is formed around the opening as shown in FIG. . However, FIG. 29 (f) showing the amplitude intensity of light when the conventional halftone phase shift mask is exposed is compared with FIG. 2 (f) showing the amplitude intensity of light when the contour emphasis mask is exposed. The following differences are clearly present. That is, as shown in FIG. 29 (f), there is a phase boundary in the amplitude intensity distribution when the halftone phase shift mask is exposed, and as shown in FIG. 29 (g), the phase boundary, Image enhancement is realized by producing a dark portion of the light intensity distribution by the phase edge. However, in order to form a dark part due to the phase edge and obtain a contrast enhancement effect, a component of light incident perpendicularly to the photomask is required. In other words, even if a phase boundary occurs due to oblique incidence exposure, a dark portion due to the phase edge is not formed, and as a result, a contrast enhancement effect cannot be obtained. This is the reason why the contrast enhancement effect does not occur even when oblique incidence exposure is performed on the halftone phase shift mask. Therefore, the halftone phase shift mask must be exposed using a small light source with low interference. On the other hand, as shown in FIG. 2 (f), there is no phase boundary in the amplitude intensity distribution when the contour emphasis mask is exposed, so that it is necessary to form a minute isolated space pattern even with the component of oblique incidence exposure. A high-contrast light transfer image can be formed.

<Optimization of phase shifter width in contour enhancement mask>
Next, in the contour emphasis method, before showing in detail that high contrast is obtained by the obliquely incident exposure component, even if the contour emphasis mask structure as shown in FIG. It will be explained that the effect of the contour emphasis method cannot be obtained if it becomes excessively large.

  FIG. 3A shows an opening corresponding to a contact pattern and a region surrounding the opening in a semi-light-shielding portion formed on the main surface of the transparent substrate and having a transmittance that transmits a part of the exposure light. It is a top view of the outline emphasis mask provided with the phase shifter of the small width | variety which performs. FIG. 3B shows the light intensity corresponding to the line segment AA ′ when the contour enhancement mask shown in FIG. 3A is exposed using a light source having a small interference degree σ = 0.4. FIG. 3C shows the distribution calculation result, and FIG. 3C shows the light intensity corresponding to the line segment AA ′ when the contour enhancement mask shown in FIG. 3A is exposed using the annular illumination. The distribution calculation results are shown.

  FIG. 3D shows an opening corresponding to the contact pattern and a region surrounding the opening in a semi-light-shielding portion formed on the main surface of the transparent substrate and having a transmittance that transmits a part of the exposure light. It is a top view of the outline emphasis mask provided with the large phase shifter located in FIG. FIG. 3E shows the light intensity corresponding to the line segment AA ′ when the contour enhancement mask shown in FIG. 3D is exposed using a light source having a small interference degree σ = 0.4. FIG. 3F shows the distribution calculation result, and FIG. 3F shows the light intensity corresponding to the line segment AA ′ when the contour enhancement mask shown in FIG. 3D is exposed using the annular illumination. The distribution calculation results are shown.

  Here, it is assumed that the width of the phase shifter in the contour enhancement mask shown in FIG. 3D is set excessively large so that the principle of the contour enhancement method does not hold. Specifically, the dimensions of the openings shown in FIGS. 3 (a) and 3 (d) are both 220 nm square, the width of the phase shifter shown in FIG. 3 (a) is 60 nm, and FIG. The width of the phase shifter shown in FIG. In addition, as the annular illumination, an annular exposure light source as shown in FIG. 30B, specifically, what is called a 2/3 annular zone with an outer diameter σ = 0.75 and an inner diameter σ = 0.5. Was used. As the exposure conditions, a light source wavelength λ = 193 nm (ArF light source) and a numerical aperture NA = 0.6 were used. Further, the transmittance of the phase shifter is 6%. In the following description, unless otherwise specified, the light intensity is expressed as a relative light intensity when the light intensity of exposure light is 1.

  As shown in FIGS. 3B and 3C, when the contour emphasis mask shown in FIG. 3A where the principle of the contour emphasis method is established is used, the dark part due to the opacifying action of the phase shifter depends on the type of the light source. As a result, the contrast in the light intensity distribution is higher due to the annular illumination.

  On the other hand, when the contour emphasis mask shown in FIG. 3D having an excessively large phase shifter is used, the light transmitted through the phase shifter becomes too strong, so that an intensity distribution having an opposite phase is formed in the amplitude intensity distribution. In such a situation, the same principle as the halftone phase shift mask works. As a result, as shown in FIGS. 3E and 3F, in the light intensity distribution when exposure is performed with a small light source, a dark portion due to the phase edge is formed and a contrast enhancement effect appears, while oblique incidence exposure is performed. In the light intensity distribution obtained, a dark portion due to the phase edge is not formed, so that an image with very poor contrast is formed.

  In other words, in order to realize the contour enhancement method, not only the phase shifter is arranged around the opening surrounded by the semi-light-shielding portion, but also the light transmitted through the phase shifter is limited. Need to be. In the latter case, according to the principle mechanism, the light transmitted through the phase shifter has an intensity higher than that of the light transmitted through the semi-light-shielding portion and the aperture, and has a constant magnitude in the amplitude intensity distribution. It means that the intensity distribution of the opposite phase is not formed.

  In order to limit the light that actually passes through the phase shifter, it is possible to use a method in which a condition (specifically, an upper limit) is set for the width according to the transmittance of the phase shifter. Hereinafter, this condition will be described with reference to results (see FIGS. 4A to 4D) of considering conditions for canceling light from the periphery of the phase shifter by light transmitted through the phase shifter.

  As shown in FIG. 4A, in exposure using a photomask (phase shifter mask) in which a phase shifter having transmittance T and line width L is provided on a transparent substrate, the mask pattern on the material to be exposed is changed. The light intensity generated at the position corresponding to the center is defined as Ih (L, T). Further, as shown in FIG. 4B, in the exposure using a photomask (light-shielding mask) provided with a complete light-shielding film instead of the phase shifter of the phase shifter mask, the center of the mask pattern on the material to be exposed The light intensity generated at the corresponding position is defined as Ic (L). Further, as shown in FIG. 4C, a normal light transmitting portion (opening) is provided in place of the phase shifter of the phase shifter mask, and a complete light shielding film is provided instead of the light transmitting portion of the phase shifter mask. In exposure using a photomask (transmission mask) provided with a light shielding portion, the light intensity generated at a position corresponding to the center of the mask pattern on the material to be exposed is defined as Io (L).

  FIG. 4D shows the light intensity Ih (L, T) when the transmittance T of the phase shifter and the line width L of the mask pattern are varied in the exposure using the phase shifter mask shown in FIG. The simulation results are shown with the transmittance T and the line width L taken on the vertical and horizontal axes, respectively, and represented by contour lines of light intensity. Here, a graph representing the relationship of T = Ic (L) / Io (L) is overwritten. The simulation conditions are as follows: exposure light wavelength λ = 0.193 μm (ArF light source), numerical aperture NA = 0.6 of the exposure optical system of the exposure machine, exposure light source interference degree σ = 0.8 (normal light source) is there.

  As shown in FIG. 4D, the condition that the light intensity Ih (L, T) is minimum can be expressed by the relationship of T = Ic (L) / Io (L). This physically represents a relationship in which T × Io (L) indicating the light intensity of light transmitted through the phase shifter and the light intensity Ic (L) of light transmitted outside the phase shifter are balanced. . Therefore, the width L of the phase shifter in which the amplitude intensity of the opposite phase appears in the amplitude intensity distribution due to excessive light passing through the phase shifter is called the width L that makes T × Io (L) larger than Ic (L). It will be.

  Although there is a slight difference depending on the type of light source, the width L when the light transmitted through the phase shifter having a transmittance of 1 is balanced with the light transmitted outside the phase shifter is 0.3 × λ (light source wavelength) / NA. It was empirically obtained from various simulation results that it was about (numerical aperture) (about 100 nm in the case of FIG. 4D). Further, as can be seen from FIG. 4D, in order to prevent light from being excessively transmitted through the phase shifter having a transmittance of 6% or more, the phase shifter having a transmittance of 1 (100%) is used. The width L needs to be twice or less. That is, in order to prevent light from being excessively transmitted through the phase shifter having a transmittance of 6% or more, the upper limit of the width L of the phase shifter must be 0.6 × λ / NA or less.

  When the above consideration is applied to the contour emphasis mask, in the contour emphasis mask, it is only necessary to consider only one side, not both sides of the phase shifter, as the light transmitted outside the phase shifter. The upper limit of the width L may be considered as half the upper limit based on the above consideration. Therefore, the upper limit of the phase shifter width L in the contour enhancement mask is 0.3 × λ / NA or less when the transmittance of the phase shifter is 6% or more. However, this is not a sufficient condition. When the transmittance of the phase shifter becomes higher than 6%, the upper limit of the width L of the phase shifter needs to be made smaller than 0.3 × λ / NA. However, the width L of the phase shifter is preferably not less than 0.1 × λ / NA at which an optical action as a phase shifter is obtained.

  In this specification, unless otherwise specified, various mask dimensions such as the phase shifter width are converted into dimensions on the material to be exposed, but the actual mask dimensions are the exposure dimensions. This can be easily obtained by multiplying the reduction magnification M of the reduction projection optical system of the machine.

<Contrast by combination of contour enhancement mask and oblique incidence exposure>
Next, the fact that image enhancement is realized by oblique incidence exposure in the contour enhancement mask will be described in detail based on changes in the contrast of the light intensity distribution when the contour enhancement mask is exposed from various light source positions. To do.

  FIG. 5A is a plan view of an example of the contour enhancement mask. Here, the transmittance of the semi-light-shielding portion is 7.5%, and the transmittance of the phase shifter and the opening is 100%. The dimension of the opening (converted on the exposed wafer) is 200 nm square, and the width of the phase shifter is 50 nm.

  FIG. 5C shows the line in FIG. 5A when the edge enhancement mask shown in FIG. 5A is exposed from point light sources at various light source positions normalized by the numerical aperture NA. The light intensity distribution corresponding to the minute AA ′ is calculated by optical simulation, and the light intensity Io at the position corresponding to the center of the opening in the calculation result (for example, the light intensity distribution as shown in FIG. 5B) is read. The result of plotting the light intensity Io with respect to each light source position is shown. Here, a result of performing a simulation by optical calculation with a light source wavelength λ of 193 nm (ArF light source) and a numerical aperture NA of 0.6 is shown. In the following description, unless otherwise specified, in the optical simulation, calculation is performed under the conditions of wavelength λ = 193 nm (ArF light source) and numerical aperture NA = 0.6.

  As shown in FIG. 5C, the light intensity Io at the center of the opening becomes larger as exposure is performed with a point light source at an outer light source position (a light source position far from the origin of FIG. 5C). That is, it can be seen that the contrast increases as exposure is performed with a light source having a strong oblique incidence component. This will be specifically described with reference to the drawings. FIGS. 5D, 5E, and 5F show the case of FIG. 5A when the point light source is located at each of the sample points P1, P2, and P3 shown in FIG. The light intensity distribution corresponding to the line segment AA ′ is plotted. As shown in FIG. 5D, FIG. 5E, and FIG. 5F, a high-contrast image is formed as the position of the point light source moves outward, in other words, as the position of the oblique incident light source increases. Has been.

  As can be seen from the above results, the contour enhancement mask enables contrast enhancement of light intensity distribution by oblique incidence exposure in the formation of minute isolated space patterns such as contact patterns, which could not be realized with conventional halftone phase masks. To do.

  Next, the dependence of the contrast of the light intensity distribution on the light source position in the case where exposure is performed from various light source positions on the contour emphasis mask provided with a plurality of openings corresponding to the dense contact pattern will be described.

  FIG. 6A is a plan view of an example of an edge enhancement mask provided with a plurality of openings. Here, the transmittance of the semi-light-shielding portion is 7.5%, and the transmittance of the phase shifter and the opening is 100%. As shown in FIG. 6A, in the contour emphasis mask in which the openings are densely arranged with the phase shifter interposed therebetween, the phase shifter provided around the one opening is adjacent to the one opening. It is combined with a phase shifter provided around the opening. The size of each opening (converted on the exposed wafer) is 200 nm square, and the repetition period (converted on the exposed wafer) of each opening is 270 nm. Accordingly, the width of the phase shifter (converted on the exposed wafer) is 70 nm.

  FIG. 6C shows the line in FIG. 6A when the contour enhancement mask shown in FIG. 6A is exposed from point light sources at various light source positions normalized by the numerical aperture NA. The light intensity distribution corresponding to the minute AA ′ is calculated by optical simulation, and the light intensity Io at the position corresponding to the center of one opening in the calculation result (for example, the light intensity distribution as shown in FIG. 6B). The light intensity Io is plotted against each light source position.

  As shown in FIG. 6C, the distribution of the light intensity Io at the center of the opening with respect to each light source position does not change concentrically, but the distribution shape of the light intensity Io changes depending on the repetition period of the opening. On the other hand, there is basically a region with the highest contrast at the outer light source position. In the case of the distribution of the light intensity Io shown in FIG. 6C, the light enters from an oblique position in the direction of 45 degrees with respect to the mask pattern arrangement direction, which is called a quadrupole exposure light source as shown in FIG. The highest contrast is obtained with light. 6 (d), 6 (e) and 6 (f) show the case of FIG. 6 (a) when the point light source is located at each of the sample points P1, P2 and P3 shown in FIG. 6 (c). The light intensity distribution corresponding to the line segment AA ′ is plotted. As shown in FIGS. 6 (d), 6 (e), and 6 (f), an image with high contrast is formed as the position of the point light source moves outward, in other words, as the position of the oblique incident light source increases. Has been.

  As can be seen from the above results, in the contour emphasis mask, the highest contrast can be achieved in the image of each light intensity distribution when forming the dense contact pattern as in the case of forming the isolated contact pattern. Of the light source. Therefore, it can be seen that by performing oblique incidence exposure on the contour enhancement mask, an isolated contact pattern and a dense contact pattern can be formed at the same time while enhancing the contrast in the light intensity distribution.

<Depth of focus in contour enhancement mask>
Next, it will be described that the depth of focus (DOF) increases in the light intensity distribution formed by the contour enhancement mask. In the contour emphasis mask, the DOF increase effect by using the semi-light-shielding portion and the DOF increase effect by the assistance of the phase shifter are combined, and the DOF increases dramatically.

  Hereinafter, conventional chrome masks and halftone masks will be described with respect to the results of simulating the defocus dependence of the pattern finish dimension (CD: Critical Dimension), that is, the DOF characteristics, when the contact pattern is formed using the contour emphasis mask of the present invention. And a case where each of the halftone phase shift masks is used will be described.

  FIG. 7A shows an opening (width W) corresponding to a contact pattern and a phase shifter (width d) located in a region surrounding the opening in a semi-light-shielding portion formed on the transmissive substrate main surface. It is a top view of the outline emphasis mask formed by. FIG. 7B is a plan view of a chromium mask in which an opening (width W) corresponding to a contact pattern is provided in a chromium film that is a complete light-shielding portion formed on the main surface of the transparent substrate. . FIG. 7C is a plan view of a halftone mask in which an opening (width W) corresponding to the contact pattern is provided in the semi-light-shielding portion formed on the transmissive substrate main surface. Further, FIG. 7D is a plan view of a halftone phase shift mask in which an opening (width W) corresponding to a contact pattern is provided in a phase shifter serving as a light shielding portion formed on the main surface of the transmissive substrate. It is. The mask dimensions such as the width W and the width d have the same exposure amount as the dimensions of the contact patterns formed by the best focus exposure using the masks shown in FIGS. Are adjusted to be the same (specifically, 0.12 μm).

  FIG. 7E shows DOF characteristics in exposure using the masks shown in FIGS. 7A to 7D. In the optical simulation, quadrupole exposure which is oblique incidence exposure is used. The focus position in the best focus state is set to 0 μm as a reference. As shown in FIG. 7E, the DOF characteristic of the halftone mask is improved as compared with the DOF characteristic of the chrome mask, and the DOF characteristic of the contour enhancement mask is further improved as compared with the DOF characteristic of the halftone mask. Yes. Also, the DOF characteristic of the halftone phase shift mask is worse than that of the chrome mask.

  As can be seen from the above results, the DOF characteristic of the contour enhancement mask is further improved than any of the DOF characteristics of the conventional chrome mask, halftone mask, and halftone phase shift mask.

<Transmittance dependence of semi-light-shielding part in contour enhancement mask>
So far, it has been explained that the contrast and DOF are improved by the contour enhancement mask. Next, the dependency of the contrast and DOF on the transmittance of the semi-light-shielding portion in the contour enhancement mask will be described. Specifically, description will be made based on the results of simulation of various margins (FIGS. 8B to 8F) in pattern formation using the contour enhancement mask shown in FIG. FIG. 8B shows a light intensity distribution formed when exposure is performed. In FIG. 8B, values relating to various margins defined when an attempt is made to form a hole pattern with a width of 100 nm are also shown in the figure. Specifically, the critical intensity Ith is the light intensity to which the resist film is exposed, and various margins are defined for this value. For example, when Ip is the peak value of the light intensity distribution, Ip / Ith is a value proportional to the sensitivity with which the resist film is exposed, and a higher value is more preferable. Further, if Ib is the background intensity of the light transmitted through the semi-light-shielding portion, the higher Ith / Ib means that the resist film does not decrease during pattern formation, and the higher this value, the better. Generally, it is desired that the value of Ith / Ib is 2 or more. Based on the above, each margin will be described.

  FIG. 8C shows the calculation result of the dependency of DOF on the transmittance of the semi-light-shielding portion at the time of pattern formation. Here, DOF is defined as the width of the focus position where the change in the finished dimension of the pattern falls within 10%. As shown in FIG. 8C, the higher the transmittance of the semi-light-shielding portion, the better for improving DOF. FIG. 8D shows the result of calculation for the peak value Ip with respect to the transmittance of the semi-light-shielding part at the time of pattern formation. As shown in FIG. 8D, it is preferable that the transmissivity of the semi-light-shielding portion is higher in order to improve the peak value Ip, that is, the contrast. From the above results, in the contour emphasis mask, it is preferable that the transmissivity of the semi-light-shielding portion is high. Specifically, as shown in FIGS. 8C and 8D, the transmissivity is about 0% to 6%. It can be understood that the improvement rate of the margin increases as the time increases, and it is preferable to use a semi-light-shielding portion having a transmittance of 6% or more.

  FIG. 8E shows the result of calculation for Ith / Ib with respect to the transmittance of the semi-light-shielding portion at the time of pattern formation. As shown in FIG. 8E, Ith / Ib decreases as the transmissivity of the semi-light-shielding portion increases, and it is not preferable that the transmissivity of the semi-light-shielding portion becomes too high for improving Ith / Ib. Specifically, when the transmissivity of the semi-light-shielding portion is about 15%, Ith / Ib is smaller than 2. FIG. 8F shows the calculation result of Ip / Ith with respect to the transmittance of the semi-light-shielding portion at the time of pattern formation. As shown in FIG. 8F, Ip / Ith has a peak when the transmissivity of the semi-light-shielding portion is about 15%.

  As described above, in the edge enhancement mask, the DOF or contrast increases as the transmittance of the semi-light-shielding portion increases, and the effect becomes more prominent when the transmittance of the semi-light-shielding portion exceeds 6%. On the other hand, from the standpoint of preventing the reduction of the resist film at the time of pattern formation or optimizing the resist sensitivity, the maximum value of the transmissivity of the semi-light-shielding portion is preferably about 15%. Therefore, it can be said that the optimum value of the transmittance of the semi-light-shielding portion in the contour enhancement mask is 6% or more and 15% or less.

<Variation of contour enhancement mask>
FIGS. 9A to 9F are plan views showing variations of the light-shielding mask pattern constituted by the semi-light-shielding portion and the phase shifter in the contour enhancement mask provided with the opening corresponding to the contact pattern. is there.

  The contour enhancement mask 1a shown in FIG. 9A has the same configuration as the contour enhancement mask shown in FIG. That is, a transmissive substrate 2a that is transmissive to exposure light, a semi-light-shielding portion 3a formed on the transmissive substrate 2a, and an opening provided by opening the semi-light-shielding portion 3a and corresponding to an isolated contact pattern And a ring-shaped phase shifter 5a formed so as to surround the opening 4a between the semi-light-shielding portion 3a and the opening 4a.

  An outline enhancement mask 1b shown in FIG. 9B opens a transparent substrate 2b that is transmissive to exposure light, a semi-light-shielding portion 3b formed on the transparent substrate 2b, and a semi-light-shielding portion 3b. Provided with an opening 4b corresponding to the isolated contact pattern and four rectangular phase shifters having the same length as each side of the opening 4b and in contact with each side of the opening 4b. And a phase shifter 5b. The contour enhancement mask 1b has almost the same characteristics as the contour enhancement mask 1a in forming an isolated pattern. By the way, when the mask pattern of the contour emphasis mask 1b (consisting of the semi-light-shielding portion 3b and the phase shifter 5b) is used as a basic structure, the opening corresponding to the contact pattern is arranged in the nectar, further effective effect. Is obtained. FIG. 10 is a plan view of the contour emphasis mask in which openings corresponding to the contact pattern are arranged in a niche using the mask pattern of the contour emphasis mask 1b shown in FIG. 9B as a basic structure. In the contour emphasis mask shown in FIG. 10, the phase shifters in contact with the respective openings are coupled only in two directions or less, so that the light of the opposite phase transmitted through the phase shifter is excessive at the coupling portion between the phase shifters. The situation can be prevented. Thereby, it is possible to prevent a light intensity peak (that is, a side lobe) from occurring in a location other than the location corresponding to the opening of the contour enhancement mask. That is, when the contour emphasis mask (the contour emphasis mask shown in FIG. 9B or FIG. 10) in which the periphery of the opening excluding the diagonal portion is surrounded by the phase shifter is used, even if the opening is in an isolated state. Even in a dense state, the principle of the contour enhancement method holds.

  The contour emphasizing mask 1c shown in FIG. 9 (c) opens the transmissive substrate 2c that is transmissive to exposure light, the semi-light-shielding portion 3c formed on the transmissive substrate 2c, and the semi-light-shielding portion 3c. And an opening 4c corresponding to the isolated contact pattern and four rectangular phase shifters having a length shorter than the length of each side of the opening 4c, and the center of each side of the opening 4c, And a phase shifter 5c formed so as to be in contact with each side of the opening 4c in a state where the center of each phase shifter is aligned. In the contour emphasis mask 1c, the width (size) of the opening 4c is fixed and the length of each phase shifter of the phase shifter 5c is changed to adjust the dimension of the resist pattern formed after exposure. be able to. For example, as the length of each phase shifter portion of the phase shifter 5c is shortened, the dimension of the resist pattern is increased. Here, the lower limit for changing the length of each phase shifter portion of the phase shifter 5c in order to maintain the effect of contour emphasis is limited to about half of the light source (exposure light) wavelength, while the change amount of the mask dimension is Since the pattern dimension changes only about half, adjusting the length of the phase shifter is a very excellent method for pattern dimension adjustment.

  The edge emphasis mask 1d shown in FIG. 9 (d) opens the transmissive substrate 2d that is transmissive to exposure light, the semi-light-shielding portion 3d formed on the transmissive substrate 2d, and the semi-light-shielding portion 3d. 4d and an opening 4d corresponding to the isolated contact pattern, and a ring-shaped phase shifter 5d formed at a position entering the semi-light-shielding portion 3d side by a predetermined dimension from the boundary between the semi-light-shielding portion 3d and the opening 4d. And. The phase shifter 5d is formed by opening the semi-light-shielding portion 3d in a ring shape, and the ring-shaped semi-light-shielding portion 3d is interposed between the phase shifter 5d and the opening portion 4d.

  The contour emphasizing mask 1e shown in FIG. 9 (e) is a transmissive substrate 2e that is transmissive to exposure light, and a half that is formed on the transmissive substrate 2e and has a transmittance that transmits part of the exposure light. The light shielding part 3e, the opening part 4e provided with the semi-light shielding part 3e open and corresponding to the isolated contact pattern, and the boundary between the semi-light shielding part 3e and the opening part 4e enter the semi-light shielding part 3e side by a predetermined dimension. And a phase shifter 5e formed at a different position. The phase shifter 5e includes four phase shifters each having a rectangular shape longer than the length of each side of the opening 4e and in contact with each other on the diagonal of the opening 4e. Here, a ring-shaped semi-light-shielding portion 3e is interposed between the phase shifter 5e and the opening 4e. In the contour emphasis mask 1e, the size and arrangement of the phase shifter 5e are fixed, and only the width (size) of the opening 4e is changed to adjust the size of the resist pattern formed after exposure. . For example, the dimension of the resist pattern increases as the width of the opening 4e is increased. According to the pattern dimension adjustment method that changes only the width of the opening, the MEEF (Mask Error Enhancement Factor: mask dimension change) is compared with the method of adjusting the pattern dimension by simultaneously scaling both the opening and the phase shifter. The ratio of the pattern dimension change amount to the amount) can be reduced to about half.

  The edge emphasis mask 1f shown in FIG. 9 (f) opens a transparent substrate 2f that is transmissive to exposure light, a semi-light-shielding portion 3f formed on the transparent substrate 2f, and a semi-light-shielding portion 3f. And an opening 4f corresponding to the isolated contact pattern, and a phase shifter 5f formed at a position entering the semi-light-shielding portion 3f side by a predetermined dimension from the boundary between the semi-light-shielding portion 3f and the opening 4f. ing. The phase shifter 5f includes four phase shifters each having a rectangular shape having the same length as each side of the opening 4f and facing each side of the opening 4f. Here, the length of each phase shifter portion of the phase shifter 5f may be longer or shorter than the length of each side of the opening 4f. According to the contour emphasis mask 1f, the dimension adjustment of the resist pattern can be performed in the same manner as the contour emphasis mask 1c shown in FIG.

  In the contour emphasis masks shown in FIGS. 9D to 9F, the width of the semi-light-shielding portion between the opening and the phase shifter is a dimension capable of exerting the light interference effect by the phase shifter, that is, λ. / NA (λ is the wavelength of exposure light and NA is the numerical aperture) is preferably 1/10 or less. In the contour emphasizing masks shown in FIGS. 9A to 9F, a square is used as the shape of the opening, but it may be a polygon such as an octagon or a circle. Further, the shape of the phase shifter is not limited to a continuous ring shape or a plurality of rectangles. For example, the phase shifter may be formed by arranging a plurality of square phase shifters.

  Next, the dependency of the DOF improvement characteristic on the positional relationship between the opening and the phase shifter in the contour enhancement mask will be described. FIG. 11A is a plan view showing the structure of the contour emphasis mask used in the simulation for obtaining the relationship between the dimension of the opening (opening width) and the DOF, and FIG. It is a figure which shows the simulation result of the dependence of DOF. Specifically, the contour emphasizing mask shown in FIG. 11A has an opening with a width W and a ring shape with a width d located on the outer periphery of the opening in a semi-light-shielding portion that covers the main surface of the transparent substrate. The phase shifter is generally defined as a structure provided with the phase shifter. FIG. 11B shows the result of simulating DOF characteristics when d is fixed to 50 nm and W is changed in the range of 170 to 280 nm in the contour enhancement mask shown in FIG. . Here, the exposure conditions in the simulation are λ is 193 nm, NA is 0.6, and the light source used is an annular exposure light source.

  As shown in FIG. 11 (b), when the width W of the opening is a value of 0.8 × λ / NA or less, an interference effect by the phase shifter is obtained, so that the DOF has a good value. In particular, when the width W of the opening is a value of 0.6 × λ / NA or less, the DOF improvement effect is remarkable. Therefore, the positional relationship in which the phase shifter is provided at the boundary between the opening and the semi-light-shielding portion is the most excellent positional relationship for improving DOF characteristics (more precisely, the positional relationship between the opening and the phase shifter in the contour enhancement mask) ) That is, in the contour emphasis mask, there is a special DOF characteristic improving effect due to the interference effect of the phase shifter reaching the center of the opening, and the width W of the opening that can reliably obtain the effect, ie, the interference effect of the phase shifter is strong. The resulting width W of the opening is 0.8 × λ / NA or less.

  As described above, in the mask pattern shapes shown in FIGS. 9A to 9F, the phase shifter is provided at the boundary between the semi-light-shielding portion and the opening portion from the viewpoint of optimizing the DOF characteristics. The mask pattern shapes shown in 9 (a) to (c) are preferable. On the other hand, in realizing the pattern dimension adjustment while suppressing the MEEF, the phase shifter is arranged at a position entering the semi-light-shielding part side by a predetermined dimension from the boundary with the opening, as shown in FIGS. The mask pattern shape shown in FIG.

  In the present embodiment, the case where a space pattern to be a contact pattern is formed has been described. However, the same effect can be obtained when a space pattern other than the contact pattern is formed instead. Can do.

  In the present embodiment, the case where the space pattern is formed using the contour emphasis mask in which the light-shielding mask pattern surrounds the opening (translucent portion) has been described. However, instead of this, when a line pattern is formed using a contour emphasis mask in which a light-shielding mask pattern is surrounded by an opening (translucent portion), for example, a peripheral region of a line-shaped semi-light-shielding portion That is, the same effect can be obtained by arranging the phase shifter in a region near the light transmitting portion in the mask pattern. Also in this case, from the viewpoint of optimizing the DOF characteristics, it is preferable to adopt a mask pattern shape in which a phase shifter is provided at the boundary between the semi-light-shielding portion and the light-transmitting portion. On the other hand, in order to realize pattern dimension adjustment while suppressing MEEF, it is preferable to adopt a mask pattern shape in which the phase shifter is arranged on the semi-light-shielding side by a predetermined dimension from the boundary with the opening.

(Second Embodiment)
Next, the inventor of the present application has realized a resolution improvement method using a photomask, specifically, a photomask using a “centerline enhancement method” for improving the resolution of an isolated line pattern. Will be described.

  FIG. 12 shows a photomask (hereinafter referred to as an image enhancement mask) using the centerline enhancement method according to the second embodiment of the present invention, specifically, an image enhancement mask for forming an isolated line pattern. It is a top view.

  As shown in FIG. 12, the image enhancement mask 6 is formed on the transmissive substrate 7 that is transmissive to the exposure light, and has a transmittance that transmits a part of the exposure light and is isolated. A semi-light-shielding portion 8 corresponding to the line pattern and a phase shifter 9 provided at an opening inside the semi-light-shielding portion 8 are provided. In the image enhancement mask 6, light is shielded by a semi-light-shielding portion 8 that transmits exposure light in the same phase with the light-transmitting portion 7 as a reference, and a phase shifter 9 that transmits exposure light in the opposite phase with respect to the light-transmitting portion 7. A mask pattern having a characteristic is configured.

  Further, the transmittance of the semi-light-shielding portion 8 with respect to the exposure light is 15% or less, preferably 6% or more and 15% or less. As a material of such a semi-light-shielding portion 8, for example, a thin film (thickness of 50 nm or less) made of a metal such as Cr, Ta, Zr or Mo or an alloy of these metals can be used. Specific examples of the alloy include a Ta—Cr alloy, a Zr—Si alloy, and a Mo—Si alloy. Furthermore, when it is desired to increase the thickness of the semi-light-shielding portion 8, a material containing an oxide such as ZrSiO, Cr—Al—O, TaSiO, or MoSiO may be used.

  Further, the transmittance of the phase shifter 9 with respect to the exposure light is higher than the transmittance of the semi-light-shielding portion 8 and equal to or less than the transmittance of the light-transmitting portion (portion where the mask pattern is not formed on the transmissive substrate 7). .

<Principle of centerline enhancement method>
Next, “center line emphasis method” for improving the resolution of an isolated line pattern will be described by taking as an example a case where a minute line pattern is formed by a positive resist process. In the “centerline enhancement method” as well as the “contour enhancement method”, the basic principle is to improve the contrast by forming a dark portion in the light intensity distribution by the opaque action of the phase shifter.

  First, the effect obtained by providing a phase shifter inside the semi-light-shielding portion constituting the line-shaped mask pattern will be described with reference to FIGS.

  FIG. 13A is a plan view of an image enhancement mask in which a phase shifter (transmittance Ts) having a width S is provided inside a semi-light-shielding portion (transmittance Tc) constituting a line-shaped mask pattern having a width L. The light intensity of the light that passes through the image enhancement mask and is transferred to the position corresponding to the line segment AA ′ is also shown. Here, the light intensity corresponding to the center of the mask pattern is represented as Ie (L, S). FIG. 13B is a plan view of a mask provided with a semi-light-shielding pattern composed of a semi-light-shielding portion (transmission Tc) having a width L, and is transferred to a position corresponding to the line segment AA ′ through the mask. In addition to the light intensity of the light. Here, Ic (L) is the light intensity corresponding to the center of the semi-light-shielding pattern. Note that the semi-light-shielding portions shown in FIGS. 13A and 13B transmit light having the same phase with respect to the light-transmitting portion. FIG. 13C is a plan view of a mask in which a phase shift pattern composed of a phase shifter having a width S (transmittance Ts) is provided on a complete light-shielding portion covering the mask surface, and a line segment AA ′ that passes through the mask. And the light intensity of the light transferred to the corresponding position. Here, the light intensity corresponding to the center of the phase shift pattern is Io (S).

  The image enhancement mask shown in FIG. 13A is obtained by superimposing the mask structures shown in FIGS. 13B and 13C. For this reason, Ie (L, S) can be minimized in the relationship between L and S such that Ic (L) and Io (S) are balanced, and thereby the contrast of the image enhancement mask shown in FIG. Emphasis can be realized. That is, by providing a phase shifter inside the semi-light-shielding portion constituting the line-shaped mask pattern, the contrast of the light intensity distribution, specifically, the contrast at the center of the mask pattern can be enhanced by the principle of the centerline enhancement method. it can.

  By the way, the shape of the phase shifter (opening area provided in the semi-light-shielding portion) of the image enhancement mask for generating the light intensity Io (S) does not need to correspond to the shape of the semi-light-shielding portion. 14A and 14B are plan views showing other shapes of the phase shifter in the image enhancement mask. Specifically, FIGS. 14A and 14B show phase shifters provided in the semi-light-shielding portions constituting the line-shaped mask pattern, and the phase shifters shown in FIG. The phase shifter shown in FIG. 14B is made up of five square patterns. The same effect as that of the image enhancement mask shown in FIG. 12 can be obtained also by the image enhancement mask provided with the phase shifter shown in FIGS. Therefore, the shape of the phase shifter of the image enhancement mask can be set to an arbitrary shape such as a rectangle, a square, a circle, or a polygon as long as it falls within the semi-shielding portion. The reason for this is that a fine aperture has the same optical behavior regardless of the shape of the aperture if the intensity of light transmitted therethrough is the same.

<DOF characteristics in image enhancement mask>
In order to clarify the effectiveness of the combination of the image enhancement mask and the oblique incidence exposure, the inventor of the present application uses a plurality of image enhancement masks having different sizes of openings serving as phase shifters, and various exposure light incidents. The DOF (focus depth) characteristics when exposure was performed from the direction were calculated by simulation. FIGS. 15A to 15C show the results, and FIG. 15A shows the exposure light incident direction in the light source coordinates (the x-axis and y-axis in the width direction and length direction of the line-shaped mask pattern, respectively). FIG. 15B shows a simulation result in the case where the incident light is perpendicularly incident from the center direction, and FIG. 15B shows the case where the incident light incident direction is obliquely incident from the X-axis direction or the Y-axis direction of the light source coordinates. FIG. 15C shows the simulation result, and FIG. 15C shows the simulation result when the incident direction of the exposure light is oblique incidence from the 45-degree direction of the light source coordinates (the direction that makes an angle of 45 degrees with the X-axis direction or the Y-axis direction). Indicates. Here, as an image enhancement mask, an image enhancement mask having an opening width (hereinafter, referred to as an optimum opening width) adjusted so as to maximize the light shielding property with respect to each exposure light incident direction, and an optimum opening portion An image enhancement mask having an opening width smaller than the width and an image enhancement mask having an opening width larger than the optimum opening width were used. For comparison, the DOF characteristics in the case of using a photomask (completely light-shielding mask) provided with a completely light-shielding pattern having the same outer shape in place of the mask pattern of the image enhancement mask are also calculated by simulation. saw. It should be noted that the DOF characteristics are determined by defocusing when the exposure energy is set so that the dimension of the pattern (resist pattern) formed corresponding to each mask pattern at the best focus is 0.12 μm. It is evaluated on the basis of how it changes. 15A to 15C, L indicates the mask pattern width, S indicates the opening width, and the focus position (horizontal axis) 0 corresponds to the best focus position.

  As shown in FIG. 15A, when the exposure light incident direction is the incident direction from the center direction of the light source coordinates, the DOF characteristic deteriorates as the opening width of the image enhancement mask is increased, and the complete light shielding mask. When DO is used (L = 0.12 μm, S = 0 μm) (hereinafter abbreviated as L / S = 0.12 / 0 μm), the DOF characteristics are the most excellent. On the other hand, as shown in FIG. 15B, when the exposure light incident direction is oblique incidence from the X-axis direction or the Y-axis direction of the light source coordinates, the DOF characteristic does not depend on the opening width of the image enhancement mask. In addition, the same DOF characteristics are obtained when the image enhancement mask is used and when the complete light-shielding mask is used (L / S = 0.13 / 0 μm). However, as shown in FIG. 15C, when the exposure light incident direction is oblique incidence from the direction of 45 degrees of the light source coordinates, the DOF characteristic is improved as the opening width of the image enhancement mask is increased. The DOF characteristic is the lowest when a complete light-shielding mask is used (L / S = 0.15 / 0 μm). In other words, in order to improve the defocus characteristics of the light intensity distribution caused by the interference between the mask pattern diffracted light and the mask pattern transmitted light in the oblique incidence exposure from the 45 degree direction, the minimum necessary effective light shielding performance is realized. It can be seen that the mask pattern transmitted light (that is, the region where the phase shifter is arranged) should be increased as much as possible.

  Next, the arrangement position of the phase shifter in the image enhancement mask will be described. FIG. 16A is a plan view of a photomask provided with a semi-light-shielding pattern having a width L made of a semi-light-shielding portion, and light transmitted through the mask to a position corresponding to a line segment AA ′. It shows together with the strength. When an image enhancement mask is created by providing a phase shifter inside such a semi-light-shielding pattern, the width of the phase shifter capable of realizing the maximum contrast decreases as the width L of the semi-light-shielding pattern increases. However, as shown in FIG. 16 (a), the light intensity corresponding to the center of the semi-light-shielding pattern does not become zero and the residual light intensity always exists, no matter how wide the semi-light-shielding pattern has. To do. Therefore, when a semi-light-shielding portion is used as the light-shielding portion constituting the mask pattern in the image enhancement mask, the width of the phase shifter decreases as the width L of the semi-light-shielding portion increases as shown in FIG. However, no matter how large the width L of the semi-light-shielding portion is, it is necessary to always provide a phase shifter that balances the above-mentioned residual light intensity. Therefore, by adjusting the minimum size of the phase shifter that can be formed on the mask to this residual light intensity, all the phase shifters necessary for realizing the image enhancement mask can be formed. However, it is necessary to determine the transmittance of the semi-light-shielding portion so that the residual light intensity is an amount that does not expose the resist film in actual exposure.

(Third embodiment)
Hereinafter, a photomask and a mask data creation method thereof according to a third embodiment of the present invention will be described with reference to the drawings.

  FIG. 17 shows a mask data generation method according to the third embodiment using a contour enhancement method and a centerline enhancement method, specifically, a mask pattern based on a desired pattern to be formed using a photomask. The flowchart of the mask data preparation method which performs preparation of is shown. FIGS. 18A to 18D and FIGS. 19A to 19D show the respective steps when a mask pattern for forming a space pattern is formed using the mask data generation method shown in FIG. FIG. FIGS. 20A to 20D and FIGS. 21A to 21C show the respective steps when a mask pattern for forming a line pattern is formed using the mask data creation method shown in FIG. FIG.

  First, in step S11, a desired pattern to be formed using a photomask is input. FIG. 18A and FIG. 20A each show an example of a desired pattern. The desired pattern shown in FIG. 18A is a resist removal pattern (opening in the resist pattern), and the desired pattern shown in FIG. 20A is a resist pattern.

  Next, in step S12, the shape of the mask pattern is determined based on the desired pattern, and the transmissivity Tc of the semi-light-shielding portion used for the mask pattern is set. At this time, resizing is performed to enlarge or reduce the desired pattern depending on whether the exposure condition is overexposure or underexposure. FIG. 18B and FIG. 20B each show an example of a mask pattern created based on a desired pattern after resizing. The mask pattern shown in FIG. 18B includes a semi-light-shielding portion that surrounds an opening (translucent portion) corresponding to a desired pattern. The mask pattern shown in FIG. 20B is composed of a semi-light-shielding part surrounded by a light-transmitting part.

  Next, in step S13, a region sandwiched between the openings with a predetermined dimension D1 or less in the mask pattern, in other words, a region with a width in the mask pattern of the predetermined dimension D1 or less is extracted. Here, D1 is preferably about 0.8 × λ / NA (λ is the light source wavelength, and NA is the numerical aperture). FIG. 18C and FIG. 20C show regions sandwiched between the openings having a predetermined dimension D1 or less in the mask patterns shown in FIG. 18B and FIG. 20B, respectively.

  Next, in step S14, a phase shifter is inserted so that the centerline enhancement method is established in the region extracted in step S13. FIGS. 18D and 20D show phase shifters having appropriate widths so that the centerline enhancement method is established in the extracted regions shown in FIGS. 18C and 20C, respectively. Shows a state where is inserted.

  Next, in step S15, a phase shifter is inserted so that the contour enhancement method is established in the mask pattern. Specifically, FIG. 19A shows a state in which a phase shifter is inserted in the mask pattern shown in FIG. As shown in FIG. 19A, a phase shifter having a predetermined dimension is inserted into a region in contact with each side of the opening (square shape) in the mask pattern. In the mask pattern shown in FIG. 19A, the phase shifter arrangement of the type shown in FIG. 9B is performed, but the phase shifter arrangement is not limited to this. FIG. 21A shows a state where a phase shifter is inserted in the mask pattern shown in FIG. As shown in FIG. 21A, a phase shifter is inserted in the peripheral portion of the region where the width of the mask pattern exceeds a predetermined dimension D1. In FIG. 21A, the phase shifter arrangement of the type shown in FIG. 9A is performed, but the phase shifter arrangement is not limited to this.

  Through the processes from step S11 to step S15, a mask pattern that enables fine pattern formation can be created using the centerline enhancement method and the contour enhancement method. Therefore, normal mask data creation such as proximity effect correction for pattern dimension adjustment corresponding to the mask pattern formed by exposure, and conversion of mask dimension based on the reduction magnification value of the reduced exposure system, etc. If processing is performed, a mask pattern is completed. However, if the MEEF is large in the pattern dimension adjustment, a mask pattern having a large pattern dimension adjustment error is caused by the influence of the mask grid (minimum width capable of adjusting the mask dimension). Therefore, in the third embodiment, in order to further improve the mask pattern, it is possible to adjust the pattern dimension with a low MEEF upon performing the proximity effect correction, and reduce the pattern dimension adjustment error caused by the mask grid. Additional steps are performed.

  That is, in step S16, the MEEF reduction method is applied to the mask pattern to which the center line enhancement method and the contour enhancement method are applied. As described in the principle of the outline emphasis method, there are a method of changing the position or size of the phase shifter and a method of changing the size of the semi-light-shielding portion for adjusting the pattern size. In general, a phase shifter that is a region that transmits light of the opposite phase with respect to the translucent part has a very strong light-shielding property. The light intensity distribution is less affected. Therefore, the method of changing the size of the semi-light-shielding part is superior to the method of changing the position or size of the phase shifter in that the MEEF is lowered. Therefore, a semi-light-shielding part is inserted at the boundary between the opening and the phase shifter as a CD (pattern dimension) adjustment region for adjusting the pattern dimension. FIGS. 19B and 21B show a state where a semi-light-shielding portion for CD adjustment is set for the mask patterns shown in FIGS. 19A and 21A, respectively. As shown in FIG. 19B, the opening for forming the space pattern is always surrounded by the semi-light-shielding portion in step S16. Further, as shown in FIG. 21B, the phase shifter in the mask pattern for line pattern formation is always surrounded by the semi-light-shielding portion in step S16. Note that the semi-light-shielding portion provided as the CD adjustment area around the phase shifter is desirably of a size that does not affect the light-shielding property of the phase shifter. Therefore, in the third embodiment, the width of the CD adjustment area Was set to 0.1 × λ / NA or less. In other words, it is desirable that the width of the CD adjustment region is 1/10 or less of λ / NA, which is a dimension to which the light interference effect by the phase shifter reaches.

  The mask pattern created by the processes from step S11 to step S16 is a mask pattern capable of forming a fine pattern. In addition, when the proximity effect correction is applied in the creation of the mask pattern, if the pattern dimension is adjusted by changing the dimension of the semi-light-shielding portion surrounding the opening or the phase shifter, the pattern dimension can be adjusted with a low MEEF. . That is, it is possible to realize an excellent mask pattern creation method with low pattern dimension adjustment error due to the influence of the mask pattern grid.

  By the way, in general, the light intensity transferred when a mask pattern using a semi-light-shielding portion (that is, a light-shielding light-shielding pattern) is exposed does not simply decrease toward the inside of the mask pattern, but vibrates. Decrease. The vibration in the light intensity distribution has a peak, that is, a side lobe at λ / NA or less from the edge of the mask pattern. Therefore, in the third embodiment, a process for further expanding the exposure margin is added so that the portion corresponding to the semi-light-shielding portion in the resist film is not exposed by overexposure in the exposure at the time of actual pattern formation. To implement.

  That is, in step S17, a sidelobe reduction phase shifter is inserted into the mask pattern to which the centerline enhancement method, the contour enhancement method, and the MEEF reduction method are applied. Here, the side lobe generated independently around the isolated opening pattern or the side lobe generated inside the mask pattern is hardly a problem. However, when the openings are adjacent to each other at a distance of about λ / NA to 2 × λ / NA, a region where the peaks of the two side lobes overlap is generated. Therefore, when overexposure is performed, the resist film is formed by the light intensity of the region. May be exposed to light. Also, in the portion of the mask pattern whose width is 2 × λ / NA or less, the peaks of the two side lobes from both sides of the portion overlap each other. Therefore, when overexposure is performed, the resist film is exposed by the light intensity of that portion. There is a possibility that. However, as described above in the principle of the contour emphasis method, in the mask pattern using the semi-light-shielding portion, if the interval between the phase shifters is 0.8 × λ / NA or more, in other words, If the width of the mask pattern is 0.8 × λ / NA or more, a phase shifter for canceling light corresponding to the residual light intensity by the semi-light-shielding portion can be arranged at an arbitrary position. In the third embodiment, by utilizing this principle, by arranging a phase shifter that balances the residual light intensity by the semi-shielding portion in a region where the interval between the openings is 2 × λ / NA or less, It is possible to cancel all the light intensities in the region where the peaks overlap. Similarly, a phase shifter that balances the residual light intensity by the semi-light-shielding portion in a portion where the width of the mask pattern exceeds 0.8 × λ / NA (but after the phase shifter is arranged based on the contour emphasis method). By arranging, it is possible to cancel all the light intensities in the region where the side lobe peaks overlap. That is, in step S17, the overexposure margin when performing exposure using the mask pattern created in steps S11 to S16 can be expanded. FIG. 19C shows a state in which a sidelobe reduction phase shifter is inserted in a region sandwiched between openings in the mask pattern shown in FIG. 19B at intervals of 2 × λ / NA or less. . FIG. 21C shows a sidelobe reduction phase shifter in a portion where the width exceeds 0.8 × λ / NA in the mask pattern shown in FIG. The inserted state is shown.

  Finally, in step S18, the mask pattern created by the processes from step S11 to step S17 is output. Through the processes from step S11 to step S18, a fine pattern can be formed with high accuracy and a mask pattern with an excellent exposure margin during pattern formation can be created. Heretofore, it has been assumed that all of the light-shielding portions constituting the mask pattern are semi-light-shielding portions, but the phase shifter inserted for the centerline enhancement method and the opening to which the contour enhancement method is applied. It goes without saying that a region separated from each of the portions by a sufficient distance (that is, a distance larger than 2 × λ / NA which is a distance at which the influence of light interference can be ignored) may be a complete light shielding portion. FIG. 19D shows a state where an area sufficiently separated from the phase shifter and the opening in the mask pattern shown in FIG. 19C is set as a complete light shielding portion.

  As described above, according to the third embodiment, the light intensity at an arbitrary position of the mask pattern is formed by forming the mask pattern using the semi-shielding portion that transmits light that is weak enough not to expose the resist film. The phase shifter can be inserted to enhance the contrast. However, the phase shifters to be inserted need to be separated from each other by a predetermined dimension or more. This makes it possible to apply the centerline enhancement method and the contour enhancement method to the formation of a resist pattern having an arbitrary opening shape. In other words, the contrast of the light intensity distribution in the light-shielded image corresponding to the mask pattern can be strongly enhanced by oblique incidence exposure regardless of the pattern density, so that an isolated space pattern and an isolated line pattern or dense pattern can be formed simultaneously.

  In addition, according to the third embodiment, a mask pattern capable of forming a fine pattern can be realized, and a mask pattern capable of adjusting a pattern dimension with a low MEEF can be realized when applying proximity effect correction. Furthermore, since the phase shifter can be inserted at an arbitrary position of the mask pattern, the generation of side lobes can be suppressed, thereby enabling the formation of a mask pattern having a high exposure margin during pattern formation.

  Further, according to the third embodiment, in the mask pattern having the semi-light-shielding portion and the phase shifter, the phase shifter is arranged according to the center line emphasis method in a portion having a predetermined width or less, and in a portion exceeding the predetermined width. Arranges phase shifters according to the contour enhancement method. For this reason, it is possible to form an image with a very strong contrast at the time of exposure using a mask pattern having an arbitrary shape. Therefore, by using a photomask provided with such a mask pattern and exposing the substrate coated with the resist, a fine resist pattern can be formed. Further, by exposing the photomask using oblique incidence illumination, it is possible to form a minute pattern that hardly causes variation in pattern dimension with respect to focus variation.

  FIG. 22 collectively shows a phase shifter insertion method for realizing the centerline enhancement method or the contour enhancement method according to the line width of the mask pattern. As shown in FIG. 22, the contour emphasis method is applied to a mask pattern exceeding a predetermined line width, while the center line emphasis method is applied to a mask pattern having a predetermined line width or less. Become. Here, the predetermined line width is preferably selected based on 0.8 × λ / NA, but may be set to a value smaller than that. Further, as shown in FIG. 22, in the center line emphasis method, the phase shifter inserted into the mask pattern becomes thinner as the mask pattern line width is thicker, and the mask pattern line width is inserted into the mask pattern as the mask pattern line width becomes thinner. The phase shifter becomes thicker. The method for obtaining the optimum dimension of the line width of the phase shifter is as described above. When the center line emphasis method is applied, the mask pattern may be constituted only by the phase shifter.

  On the other hand, as shown in FIG. 22, in the edge enhancement method, a phase shifter is inserted in the peripheral portion of the mask pattern exceeding a predetermined line width. The line width of the phase shifter at this time may be a constant value in all mask patterns without depending on the line width of the mask pattern, as long as the light transmitted through the phase shifter does not become excessive. That is, whether to apply the centerline enhancement method or the contour enhancement method can be uniquely determined based on the line width of the mask pattern.

  By the way, due to the use of the semi-light-shielding portion, the sidelobe phenomenon occurs remarkably in the mask pattern having a predetermined dimension. However, for a mask pattern under such conditions, as described above, a phase shifter that can be arbitrarily inserted with a phase shifter that balances the residual light intensity by the semi-light-shielding portion becomes a mask pattern. A phase shifter for side lobe reduction may be inserted in the center of the mask pattern. In this case, when only the arrangement of the phase shifters in the mask pattern is viewed, the contour enhancement method and the centerline enhancement method are simultaneously applied to the same mask pattern. Further, in a mask pattern having a dimension sufficiently larger than the dimension at which the side lobe phenomenon is maximized, whether or not to insert the side lobe reducing phase shifter at the center of the mask pattern is arbitrarily determined. In the example shown in FIG. 22, when the dimension of the mask pattern is sufficiently large, the insertion of the sidelobe reduction phase shifter is treated as omitted.

(Fourth embodiment)
Hereinafter, a photomask and a manufacturing method thereof according to a fourth embodiment of the present invention will be described with reference to the drawings.

  FIG. 23 shows a photomask according to the fourth embodiment, specifically, a line pattern forming mask portion for realizing the center line emphasis method of the present invention and an edge emphasis method of the present invention. It is a top view of the photomask which has a mask part for contact pattern formation (The translucent part (opening part) is enclosed by the mask pattern). 24A to 24F are cross-sectional views taken along line AA ′ in FIG. That is, as a method for realizing a photomask having a planar configuration as shown in FIG. 23, there are basically six types as shown in FIGS. However, the cross-sectional configurations shown in FIGS. 24A to 24F are basic types, and a photomask having a cross-sectional configuration combining these can also be realized. Hereinafter, a method for producing the basic type photomask shown in FIGS. 24A to 24F will be described.

  In the type shown in FIG. 24A, a first phase shifter film 11 that transmits exposure light in an opposite phase with respect to a light transmitting portion is formed on a mask pattern forming region in the transmissive substrate 10. . In addition, a second phase shifter film 12 that transmits exposure light in the opposite phase with respect to the first phase shifter film 11 is formed on the semi-light-shielding portion forming region in the first phase shifter film 11. As a result, a semi-light-shielding portion having a laminated structure of the second phase shifter film 12 and the first phase shifter film 11 is formed, and a phase shifter having a single layer structure of the first phase shifter film 11 is formed. Is done. The semi-light-shielding portion having a laminated structure of the second phase shifter film 12 and the first phase shifter film 11 transmits the exposure light in the same phase with respect to the light transmitting portion. That is, in the type shown in FIG. 24A, the phase shifter and the semi-light-shielding are processed by processing the laminated film of the phase shifter film that reverses the phase of the transmitted light on the basis of the light transmitted through the light transmitting portion. A desired mask pattern composed of a portion is realized. In addition, a semi-light-shielding portion having a transmittance that transmits a part of the exposure light is realized by the laminated film of the phase shifter film.

  In the type shown in FIG. 24B, the exposure light is transmitted in the same phase on the translucent substrate 20 on the semi-light-shielding portion forming region and having a transmittance that allows a part of the exposure light to pass therethrough. A semi-light-shielding film 21 is formed. That is, a semi-light-shielding portion made of the semi-light-shielding film 21 is formed. Further, by digging a phase shifter formation region in the transmissive substrate 20 by a predetermined thickness, a phase shifter that transmits exposure light in an opposite phase with respect to the light transmitting portion is formed. That is, in the type shown in FIG. 24B, the semi-light-shielding portion and the phase are formed by combining the semi-light-shielding film 21 that hardly causes a phase difference as compared with the light-transmitting portion and the digging portion of the transmissive substrate 20. A desired mask pattern composed of a shifter is realized.

  In the type shown in FIG. 24C, a phase shifter film 31 that transmits exposure light in the opposite phase with respect to the phase shifter is formed on the semi-light-shielding portion forming region of the transmissive substrate 30. In addition, a translucent portion forming region in the transmissive substrate 30 is dug down by a predetermined thickness, thereby forming a translucent portion that transmits exposure light in an opposite phase with respect to the phase shifter. That is, in the type shown in FIG. 24C, the portion that has been defined so far as the translucent portion is replaced with a phase shifter having a high transmittance, and the portion that has been defined as the phase shifter is replaced with a translucent portion. A photomask is realized in which a portion that has been defined as a light shielding portion is replaced with a phase shifter having a transmittance that transmits a part of exposure light. At this time, the relationship of the relative phase difference between the constituent elements of the photomask shown in FIG. 24C is shown in FIG. 24A, FIG. 24B, and FIGS. Same as other types of photomasks.

  In the type shown in FIG. 24D, the exposure light is transmitted in the same phase on the translucent substrate 40 on the semi-light-shielding portion forming region, having a transmittance that allows a part of the exposure light to pass therethrough. A thinned light shielding film 41 is formed. That is, a semi-light-shielding portion made of the light-shielding film 41 is formed. Further, by digging a phase shifter formation region in the transmissive substrate 40 by a predetermined thickness, a phase shifter that transmits exposure light in an opposite phase with respect to the light transmitting portion is formed. Here, the light shielding film 41 having a transmittance that transmits a part of the exposure light can also be formed by thinning a normal metal film. The light passing through the light shielding film 41 has a slight phase change because the light shielding film 41 is thinned. Note that if the phase of the light transmitted through the semi-light-shielding part has a phase difference with respect to the light transmitted through the light-transmitting part, the focus position is slightly in the light image formed by the mask pattern using the semi-light-shielding part. Shift. However, if this phase difference is up to about 30 degrees, there is no influence on the shift of the focal position. Therefore, by using a thin metal film or the like as the light shielding film 41, it is possible to realize a semi-light shielding portion that weakly transmits light having substantially the same phase with respect to the light transmitting portion. That is, in the type shown in FIG. 24D, the same effect as the type shown in FIG. In addition, a thinned light-shielding film can be substituted as a semi-light-shielding film that hardly causes a phase difference compared to the light-transmitting part, so that the phase shifter and the semi-light-shielding part can be used without using a transparent thick film for phase control. A desired mask pattern composed of

  In the type shown in FIG. 24E, the exposure light is transmitted in the same phase on the mask pattern formation region of the transmissive substrate 50 with a transmittance that allows a part of the exposure light to pass therethrough and with the light transmitting portion as a reference. A semi-light shielding film 51 is formed. Further, by digging a phase shifter formation region in the semi-light-shielding film 51 by a predetermined thickness, a phase shifter that transmits exposure light in an opposite phase with respect to the light transmitting portion is formed. In other words, a semi-light-shielding portion made of a non-digged portion of the semi-light-shielding film 51 is formed and a phase shifter made of a dug-down portion of the semi-light-shielding film 51 is formed. That is, in the type shown in FIG. 24E, a phase shifter that inverts the phase of the light that is transmitted with reference to the light that is transmitted through the light transmitting portion is created using the dug-down portion of the semi-light-shielding film 51. A desired mask pattern composed of the phase shifter and the semi-light-shielding portion is realized.

  In the type shown in FIG. 24F, the exposure light is transmitted in the same phase on the mask pattern formation region of the transmissive substrate 60 with a transmittance that allows a part of the exposure light to pass therethrough and with the light transmitting part as a reference. A semi-light-shielding film 61 is formed. Further, a phase shifter film 62 that transmits the exposure light in the opposite phase with respect to the light transmitting portion is formed on the phase shifter forming region in the semi-light-shielding film 61. Thus, a semi-light-shielding portion having a single-layer structure of the semi-light-shielding film 61 is formed, and a phase shifter having a laminated structure of the semi-light-shielding film 61 and the phase shifter film 62 is formed. That is, in the type shown in FIG. 24F, by stacking the phase shifter film 62 on the semi-light-shielding film 61, a desired mask pattern composed of the phase shifter and the semi-light-shielding part is realized.

(Fifth embodiment)
Hereinafter, a pattern forming method according to the fifth embodiment of the present invention, specifically, a pattern forming method using the photomask according to any one of the first to fourth embodiments (hereinafter referred to as the photomask of the present invention). Will be described with reference to the drawings. As described above, a fine pattern can be formed by performing exposure using the photomask of the present invention, that is, a photomask created so that the contour enhancement method or the center line enhancement method is established. Further, for example, when exposure is performed on a photomask as shown in FIG. 23 and a pattern is reduced and transferred onto a wafer, as described in the principle of the edge enhancement method and the principle of the centerline enhancement method, the edge enhancement is performed. A high contrast image can be formed by performing oblique incidence exposure for both the mask portion (contour enhancement mask) that realizes the method and the mask portion (image enhancement mask) that realizes the centerline enhancement method. This also makes it possible to realize pattern formation in which the pattern dimension is less likely to vary with respect to focus variation.

  FIGS. 25A to 25D are cross-sectional views showing respective steps of the pattern forming method using the photomask of the present invention.

  First, as shown in FIG. 25A, a film to be processed 101 such as a metal film or an insulating film is formed on the substrate 100, and then, on the film to be processed 101 as shown in FIG. Then, a positive resist film 102 is formed.

  Next, as shown in FIG. 25 (c), the photomask of the present invention, for example, the photomask of the type shown in FIG. 24 (a) (however, only the contact pattern forming mask portion is shown in FIG. 25 (c)). The resist film 102 is exposed to the transmitted light 104 transmitted through the photomask. Incidentally, on the transparent substrate 10 of the photomask used in the step shown in FIG. 25C, a semi-light-shielding portion having a laminated structure of the first phase shifter film 11 and the second phase shifter film 12, and the first A mask pattern including a phase shifter having a single layer structure of one phase shifter film 11 is provided. This mask pattern surrounds an opening (translucent portion) corresponding to a desired pattern (resist removal pattern). That is, in the exposure step shown in FIG. 25C, the resist film 102 is exposed using a grazing incidence exposure light source through a photomask that realizes the contour enhancement method. At this time, since the semi-light-shielding portion having a low transmittance is used for the mask pattern, the entire resist film 102 is exposed with weak energy. However, as shown in FIG. 25C, only the latent image portion 102a corresponding to the opening portion of the photomask in the resist film 102 is irradiated with exposure energy sufficient to dissolve the resist in the development process.

  Next, as shown in FIG. 25D, the resist film 102 is developed to remove the latent image portion 102a, thereby forming a resist pattern 105. Next, as shown in FIG. At this time, in the exposure step shown in FIG. 25C, the contrast of the light intensity distribution between the opening and the region surrounding it is high, so the energy distribution between the latent image portion 102a and the region surrounding it is also Since it changes rapidly, a resist pattern 105 having a sharp shape is formed.

  As described above, according to the fifth embodiment, the photomask of the present invention having a mask pattern composed of a semi-light-shielding portion and a phase shifter is used for pattern formation. Here, a phase shifter is arranged in the vicinity of the translucent part of the photomask according to the contour emphasis method, and a phase between the translucent part below a predetermined dimension in the mask pattern is phased according to the centerline emphasis method. A shifter is placed. For this reason, the contrast of the light intensity distribution in the peripheral part of the translucent part or the minute width part of the mask pattern can be strongly enhanced by the oblique incidence exposure regardless of the density of the pattern. Therefore, a fine resist pattern can be formed by exposing the substrate coated with a resist using the photomask of the present invention. Further, by exposing the photomask using oblique incidence illumination, it is possible to form a minute pattern that hardly causes variation in pattern dimension with respect to focus variation.

  In the fifth embodiment, the case where the exposure using the photomask for which the contour emphasis method is established is performed in the positive resist process is described as an example, but the present invention is not limited to this. . That is, exposure using a photomask in which the centerline enhancement method is established or a photomask in which the contour enhancement method and the centerline enhancement method are established may be performed in a positive resist process. Alternatively, exposure using a photomask in which at least one of the edge enhancement method and the centerline enhancement method is performed may be performed in a negative resist process. Here, in the case of using a positive resist process, the positive resist film irradiated with the exposure light is developed, and the mask pattern is removed by removing portions other than the portion corresponding to the mask pattern in the positive resist film. A resist pattern having a shape can be formed. Also, when using a negative resist process, the negative resist film irradiated with exposure light is developed to remove the portion corresponding to the mask pattern in the negative resist film, thereby having an opening of a mask pattern shape. A resist pattern can be formed.

(Sixth embodiment)
Hereinafter, a photomask and a mask data creation method thereof according to a sixth embodiment of the present invention will be described with reference to the drawings. In any of the mask data creation methods described below, a pattern shape is easily deformed during pattern transfer from a mask pattern in which a phase shifter is inserted by the centerline emphasis method of the present invention or the edge emphasis method of the present invention. The shape portion is extracted, and the phase shifter is inserted, deformed, or deleted so that the shape portion has a desired shape. That is, the mask data creation method according to the present embodiment is combined with the mask data creation method according to the third embodiment, for example, so as to have a desired shape in addition to the reduction in pattern line width or pattern interval. A pattern can be formed.

  Specifically, as a shape portion whose pattern shape is easily deformed during pattern transfer, for example, there is an end portion of a line pattern thinner than a predetermined dimension as shown in FIG. Normally, the end of the mask pattern corresponding to such a line pattern has a poor light-shielding effect, so that the line length is reduced during pattern formation. This is a phenomenon called retreat of the line end. For such a phenomenon that the end of the line recedes, it is also possible to compensate for deformation by simply extending the length of the mask pattern. Another method for stabilizing the line length against exposure fluctuation and focus fluctuation during pattern formation is to increase the line end width of the mask pattern. This is also performed by a method using a mask pattern made of a normal complete light-shielding film, and the shape with thick line ends is called a hammerhead pattern. According to the center line emphasis method of the present invention, the light shielding effect can be improved by inserting a larger phase shifter in a portion where the light shielding effect is reduced in the mask pattern. That is, in the mask pattern, a high light shielding property can be realized by using a thicker phase shifter at the line end where the light shielding effect deteriorates than the line center. Therefore, as shown in FIG. 26A, the line end may be transformed into a hammerhead pattern made of a phase shifter.

  Instead of the deformation compensation method shown in FIG. 26 (a), as a more versatile deformation compensation method, as shown in FIG. 26 (b), a contour enhancement method can be applied to the line end. Specifically, a phase shifter is arranged in a peripheral portion parallel to the line direction in a region within a predetermined distance from both ends of the mask pattern for forming the line pattern. In this way, when the line pattern is present in isolation, the line end characteristic is substantially the same as the hammerhead pattern characteristic.

  By the way, according to the method shown in FIG. 26 (b), when the end of the line pattern exists close to another pattern, there is a special effect in reducing the MEEF particularly in the space formation between the two patterns. A very excellent effect can be obtained to prevent a fatal pattern deformation such as a pattern bridge. Hereinafter, a deformation compensation method when the end portion of the line pattern is close to another pattern will be described.

  First, as shown in FIG. 26C, when the ends of the line patterns are close to each other, the end of each line in the mask pattern for forming each line pattern is deformed. In such a case, it is necessary to form a pattern so that the line ends do not bridge each other and the space between the line ends is minimized. By using the deformation compensation method shown in FIG. 26 (c) of the present invention, the MEEF value at the same target pattern dimension is greatly reduced.

  Next, as shown in FIG. 26D, when the end of one line pattern and another line pattern that is thin enough to apply the center line emphasis method are close to each other, the line pattern is formed. The method for deforming the line end in one mask pattern is the same as in FIG. On the other hand, for other mask patterns for forming other line patterns, a phase shifter arranged within a predetermined dimension from the end on the one mask pattern side in the vicinity of one mask pattern is used as a semi-light-shielding portion. change. At this time, only the vicinity of one mask pattern in the phase shifter inserted on the center line of another mask pattern may be moved to the opposite end of the one mask pattern. FIG. 26D shows an example in which a predetermined portion of the phase shifter is changed to a semi-light-shielding portion. In this case, as a result, the width of the phase shifter is reduced. By using the deformation compensation method shown in FIG. 26 (d) of the present invention, the value of MEEF at the same target pattern dimension is greatly reduced.

  Next, as shown in FIG. 26 (e), when the end of one line pattern and another line pattern thick enough to apply the contour emphasis method are close to each other, one line pattern is formed. The method for deforming the line end in the mask pattern is the same as in FIG. On the other hand, for other mask patterns for forming other line patterns, the phase shifter disposed in the vicinity of one mask pattern is changed to a semi-light-shielding portion. At this time, in another mask pattern, the phase shifter arranged in the vicinity of one mask pattern may be moved more inward. The case shown in FIG. 26 (e) is an example in which the predetermined portion of the phase shifter is moved more inward in another mask pattern, but the effect in this case is that the predetermined portion of the phase shifter is changed to a semi-light-shielding portion. It is substantially the same as the case. By using the deformation compensation method shown in FIG. 26 (e) of the present invention, the MEEF value at the same target pattern dimension is greatly reduced.

  As described above, when pattern formation is performed using a mask pattern to which the deformation compensation method of the present embodiment shown in FIGS. 26A to 26E is applied, MEEF is greatly reduced. Since the margin for the dimensional error can be reduced, a finer pattern can be formed.

  In addition to the end portion of the line pattern as described above, for example, a center line enhancement method as shown in FIG. There is an L-shaped corner pattern composed of thin lines. As a deformation compensation method in this case, as shown in FIG. 27 (a), a center is formed in an area within a predetermined dimension from an inflection point of the L-shaped corner in the mask pattern (a portion where the contour line of the mask pattern is bent). A semi-light-shielding part is arranged in place of the line emphasis phase shifter. At this time, the size of the phase shifter for emphasizing the center line of the region may be reduced. Further, a phase shifter for corner emphasis may be arranged on the outer peripheral edge of the L-shaped corner in the mask pattern. The phase shifter for corner emphasis looks the same as the phase shifter for contour emphasis, but for corner emphasis, it is placed slightly outside the position where the phase shifter for contour emphasis is originally placed. is there. On the other hand, in the case of an L-shaped corner pattern composed of lines that are thick enough to apply the contour emphasis method as shown in FIG. 27B, a predetermined point from a bending point inside the L-shaped corner in the peripheral portion of the mask pattern. A semi-light-shielding portion is arranged in an area within the dimensions in place of the phase shifter for contour enhancement. At this time, the dimension of the phase shifter for enhancing the outline of the region may be reduced. Further, the above-described corner emphasizing phase shifter may be arranged instead of the contour emphasizing phase shifter in a region within a predetermined dimension from the bending point outside the L-shaped corner in the peripheral portion of the mask pattern.

  The deformation compensation method shown in FIGS. 27A and 27B erases the emphasis pattern (phase shifter) inside the corner where the light shielding effect is strong in the mask pattern, and the enhancement pattern outside the corner where the light shielding effect is weak in the mask pattern. It will be deformed. By the deformation compensation method of the present embodiment shown in FIGS. 27A and 27B, a shape close to the target pattern shape can be obtained. This is because the light shielding balance is improved because the phase shifter is removed from the corner portion where the light shielding property in the mask pattern is excessive.

  In addition, as another example of a shape portion in which the pattern shape is easily deformed at the time of pattern transfer, for example, a T-shaped corner pattern composed of thin lines to which the center line emphasis method is applied as shown in FIG. is there. As a deformation compensation method in this case, as shown in FIG. 27C, a semi-light-shielding portion is provided in a region within a predetermined dimension from the bending point of the T-shaped corner in the mask pattern instead of the phase shifter for centerline enhancement. Place. At this time, the size of the phase shifter for emphasizing the center line of the region may be reduced. Further, a phase shifter for contour emphasis may be arranged on the opposite side of the T-shaped corner branch at the peripheral edge of the mask pattern. On the other hand, in the case of a T-shaped corner pattern composed of lines that are thick enough to apply the contour emphasis method as shown in FIG. 27D, within a predetermined dimension from the bending point of the T-shaped corner at the peripheral edge of the mask pattern. In this area, a semi-light-shielding part is arranged instead of the phase shifter for contour emphasis. At this time, the dimension of the phase shifter for enhancing the outline of the region may be reduced. Further, a corner emphasizing phase shifter may be arranged on the opposite side of the T-shaped corner branch at the peripheral edge of the mask pattern instead of the contour emphasizing phase shifter.

  The deformation compensation methods shown in FIGS. 27C and 27D are for erasing the highlight pattern inside the corner having a strong light shielding effect in the mask pattern and modifying the highlight pattern outside the corner having a weak light shielding effect in the mask pattern. is there. A shape close to the target pattern shape can be obtained by the deformation compensation method of this embodiment shown in FIGS. This is because the light shielding balance is improved because the phase shifter is removed from the corner portion where the light shielding property in the mask pattern is excessive.

  Furthermore, as another example of a shape portion in which the pattern shape is easily deformed at the time of pattern transfer, for example, a cross-type corner pattern composed of lines that are thin enough to apply the center line emphasis method as shown in FIG. is there. As a deformation compensation method in this case, as shown in FIG. 27E, a semi-light-shielding portion is provided in a region within a predetermined dimension from the bending point of the cross-type corner in the mask pattern, instead of the phase shifter for centerline enhancement. Place. At this time, the size of the phase shifter for emphasizing the center line of the region may be reduced. On the other hand, in the case of a cross-type corner pattern composed of lines that are thick enough to apply the contour emphasis method, as shown in FIG. 27 (f), within a predetermined dimension from the bending point of the cross-type corner at the periphery of the mask pattern. In this area, a semi-light-shielding part is arranged instead of the phase shifter for contour emphasis. At this time, the dimension of the phase shifter for enhancing the outline of the region may be reduced.

  The deformation compensation method shown in FIGS. 27E and 27F is to erase the emphasis pattern inside the corner having a strong light shielding effect in the mask pattern. By the deformation compensation method of this embodiment shown in FIGS. 27E and 27F, a shape close to the target pattern shape can be obtained. This is because the light shielding balance is improved because the phase shifter is removed from the corner portion where the light shielding property in the mask pattern is excessive.

  As described above, according to the sixth embodiment, in a mask pattern having a semi-light-shielding portion and a phase shifter, a phase shifter is disposed in a portion having a predetermined width or less according to the centerline enhancement method, A phase shifter is arranged in the part exceeding the width according to the contour emphasis method. For this reason, it is possible to form an image with a very strong contrast at the time of exposure using a mask pattern having an arbitrary shape. Therefore, by using a photomask provided with such a mask pattern and exposing the substrate coated with the resist, a fine resist pattern can be formed. Further, by exposing the photomask using oblique incidence illumination, it is possible to form a minute pattern that hardly causes variation in pattern dimension with respect to focus variation.

  Further, according to the sixth embodiment, the light shielding effect can be reduced by using the semi-light shielding portion even in a portion where the light shielding effect is too strong in the normal complete light shielding pattern, such as the inside of the corner portion in the mask pattern. . In other words, if the phase shifter for enhancing the light shielding effect is not simply inserted in accordance with the center line emphasis method or the contour emphasizing method in the portion where the light shielding effect in the mask pattern is excessive, an unnecessary light shielding effect is generated. Can be prevented. Therefore, by using this effect to limit the insertion of the phase shifter, it becomes easy to create a pattern having an arbitrary shape according to the target shape.

  In the sixth embodiment, the case where exposure using a photomask for which the contour enhancement method or the centerline enhancement method is performed is described as an example in the positive resist process, but it goes without saying that the present invention is applied to this. It is not limited. In other words, exposure using a photomask in which at least one of the contour enhancement method and the centerline enhancement method is performed may be performed in a positive resist process. Alternatively, exposure using a photomask in which at least one of the edge enhancement method and the centerline enhancement method is performed may be performed in a negative resist process. Here, in the case of using a positive resist process, the positive resist film irradiated with the exposure light is developed, and the mask pattern is removed by removing portions other than the portion corresponding to the mask pattern in the positive resist film. A resist pattern having a shape can be formed. Also, when using a negative resist process, the negative resist film irradiated with exposure light is developed to remove the portion corresponding to the mask pattern in the negative resist film, thereby having an opening of a mask pattern shape. A resist pattern can be formed.

  As described above, the present invention is useful for forming a fine pattern used for manufacturing a semiconductor integrated circuit device.

FIG. 1 is a plan view of a photomask using a contour enhancement method according to the first embodiment of the present invention. FIGS. 2A to 2G are diagrams for explaining the principle of the contour enhancement method of the present invention. FIGS. 3A to 3F are diagrams for explaining the dimensional limit of the phase shifter in the contour enhancement method of the present invention. FIGS. 4A to 4D are diagrams for explaining the size limit of the phase shifter in the contour emphasizing method of the present invention. FIGS. 5A to 5F are diagrams for explaining the change in contrast of the light intensity distribution when an isolated pattern is formed by exposing the contour enhancement mask of the present invention from various light source positions. . FIGS. 6A to 6F are diagrams for explaining the change in contrast of the light intensity distribution in the case where a dense pattern is formed by exposing the contour emphasis mask of the present invention from various light source positions. . FIGS. 7A to 7E are diagrams for explaining the DOF improvement effect by the contour enhancement mask of the present invention. FIGS. 8A to 8F are views for explaining the dependency of contrast and DOF on the transmittance of the semi-light-shielding portion in the contour enhancement mask of the present invention. FIGS. 9A to 9F show variations of the light-shielding mask pattern composed of the semi-light-shielding portion and the phase shifter in the contour emphasis mask of the present invention provided with the opening corresponding to the contact pattern. FIG. FIG. 10 is a plan view of the contour emphasizing mask of the present invention in which the opening corresponding to the contact pattern is arranged in a niche using the mask pattern of the contour emphasizing mask of the present invention shown in FIG. . FIGS. 11A and 11B are diagrams for explaining the dependency of DOF on the size of the opening in the contour emphasis mask of the present invention. FIG. 12 is a plan view of a photomask using the centerline enhancement method according to the second embodiment of the present invention. FIGS. 13A to 13C are diagrams for explaining the principle of the centerline enhancement method of the present invention. FIGS. 14A and 14B are diagrams showing variations in the shape of the phase shifter in the image enhancement mask of the present invention. FIGS. 15A to 15C show DOFs when exposure is performed from various incident light incident directions using a plurality of image enhancement masks of the present invention having different sizes of openings serving as phase shifters. It is a figure which shows the result of having calculated the characteristic by simulation. FIGS. 16A and 16B are views for explaining advantages of using a semi-light-shielding portion as a light-shielding portion constituting a mask pattern in the image enhancement mask of the present invention. FIG. 17 is a flowchart of a mask data creation method according to the third embodiment of the present invention. FIGS. 18A to 18D are diagrams showing respective steps when a mask pattern for forming a space pattern is formed using the mask data creating method according to the third embodiment of the present invention. FIGS. 19A to 19D are diagrams showing respective steps when a mask pattern for forming a space pattern is formed by using the mask data creating method according to the third embodiment of the present invention. FIGS. 20A to 20D are diagrams showing respective steps when a mask pattern for forming a line pattern is formed using the mask data creating method according to the third embodiment of the present invention. FIGS. 21A to 21C are diagrams showing respective steps when a mask pattern for forming a line pattern is formed using the mask data creation method according to the third embodiment of the present invention. FIG. 22 is a diagram showing a phase shifter insertion method corresponding to the line width of the mask pattern in the mask data creation method according to the third embodiment of the present invention. FIG. 23 is a plan view of a photomask according to the fourth embodiment of the present invention. 24A to 24F are cross-sectional views taken along the line AA 'in FIG. 25 (a) to 25 (d) are cross-sectional views showing respective steps of the pattern forming method according to the fifth embodiment of the present invention. FIGS. 26A to 26E are views for explaining a deformation compensation method for line ends in the mask data creation method according to the sixth embodiment of the present invention. FIGS. 27A to 27F are views for explaining a deformation compensation method for a corner portion in the mask data creation method according to the sixth embodiment of the present invention. FIG. 28A is a diagram showing an example of a layout of a desired pattern to be formed in the conventional pattern forming method, and FIG. 28B and FIG. 28C are the patterns shown in FIG. FIG. 2 is a plan view of two conventional photomasks used for forming the film. FIGS. 29A to 29G are views for explaining the principle of a pattern forming method using a conventional halftone phase shift mask. 30A is a diagram showing the shape of a normal exposure light source, FIG. 30B is a diagram showing the shape of an annular exposure light source, and FIG. 30C is the shape of a quadrupole exposure light source. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outline emphasis mask 2 Transparent substrate 3 Semi-light-shielding part 4 Translucent part 5 Phase shifter 6 Image emphasis mask 7 Transmissible substrate 8 Semi-shielding part 9 Phase shifter 10 Transparent substrate 11 1st phase shifter film 12 2nd phase Shifter film 20 Transparent substrate 21 Semi-light-shielding film 30 Transparent substrate 31 Phase shifter film 40 Transparent substrate 41 Light-shielding film 50 Transparent substrate 51 Semi-light-shielding film 60 Transparent substrate 61 Semi-light-shielding film 62 Phase shifter film 100 Substrate 101 Processing Film 102 Resist film 102a Latent image portion 103 Exposure light 104 Transmitted light 105 Resist pattern

Claims (13)

On the main surface of a transmissive substrate that is transmissive to exposure light, a mask pattern that includes a semi-light-shielding portion and a phase shifter and that is light-shielding to the exposure light, and the mask pattern are formed. A photomask provided with no translucent part,
The semi-light-shielding portion has a transmittance that partially transmits the exposure light and transmits the exposure light in the same phase with respect to the light-transmitting portion,
The phase shifter transmits the exposure light in an opposite phase with respect to the translucent part,
The mask pattern is provided so as to surround the translucent part,
The phase shifter is formed in a ring shape around the translucent part,
The phase shifter is formed by digging the transmissive substrate by a predetermined thickness so as to transmit the exposure light in an opposite phase with respect to the light transmitting portion .
The phase shifter is provided apart from the translucent part,
A part of the semi-light-shielding part is arranged in a ring shape between the light transmitting part and the phase shifter . On the main surface of a transmissive substrate that is transmissive to exposure light, a mask pattern that includes a semi-light-shielding portion and a phase shifter and that is light-shielding to the exposure light, and the mask pattern are formed. A photomask provided with no translucent part,
The semi-light-shielding portion has a transmittance that partially transmits the exposure light and transmits the exposure light in the same phase with respect to the light-transmitting portion,
The phase shifter is composed of a plurality of phase shifters that transmit the exposure light in an opposite phase with respect to the translucent part and that are formed around the translucent part.
The mask pattern is provided so as to surround the translucent part formed in a square shape ,
The phase shifter is formed by digging the transmissive substrate by a predetermined thickness so as to transmit the exposure light in an opposite phase with respect to the translucent part, and is formed in the vicinity of each side of the translucent part. A photomask comprising four rectangular phase shifters . The photomask according to claim 2 , wherein
Each of the phase shifter portions is formed so as to be in contact with the light transmitting portion. The photomask according to claim 2 , wherein
Wherein each phase shifter portion, the photomask, characterized in that it is formed in contact with respective sides of 且 one said translucent portions having respective sides of the same length of the translucent portion. The photomask according to claim 2, wherein
Wherein each phase shifter portion, the photomask, characterized in that it is formed in contact with respective sides of 且 one said light transmission portion shorter than the length of each side of the translucent portion. The photomask according to claim 2 , wherein
Each of the phase shifter portions is formed away from the light transmitting portion,
A part of the semi-light-shielding part is disposed between the phase shifter and the light transmitting part. The photomask according to claim 2 , wherein
Wherein each phase shifter portion, the photomask, characterized in that it is spaced apart from said 且 one longer than the length of each side of the transparent portion the light transmitting portion. The photomask according to claim 2 , wherein
Wherein each phase shifter portion is formed spaced apart from 且 one shorter than the length of each side of the light transmitting portion and the light transmitting portion,
A part of the semi-light-shielding part is disposed between the phase shifter and the light transmitting part. In the photomask of any one of Claims 1-8 ,
The photomask according to claim 1, wherein a transmittance of the semi-light-shielding portion with respect to the exposure light is 6% or more and 15% or less. The photomask according to any one of claims 1 to 9
The semi-light-shielding portion transmits the exposure light with a phase difference of (−30 + 360 × n) degrees or more and (30 + 360 × n) degrees or less (where n is an integer) based on the light-transmitting portion, and The phase shifter transmits the exposure light with a phase difference of not less than (150 + 360 × n) degrees and not more than (210 + 360 × n) degrees (where n is an integer) with reference to the light transmitting portion. mask. The photomask according to any one of claims 1-10,
A photomask using a thin film made of a metal of Cr, Ta, Zr or Mo or an alloy of these metals as a material of the semi-light-shielding portion. On the main surface of a transmissive substrate that is transmissive to exposure light, a mask pattern that includes a semi-light-shielding portion and a phase shifter and that is light-shielding to the exposure light, and the mask pattern are formed. A photomask provided with no translucent part,
The semi-light-shielding portion has a transmittance that partially transmits the exposure light and transmits the exposure light in the same phase with respect to the light-transmitting portion,
The phase shifter transmits the exposure light in an opposite phase with respect to the translucent part,
The mask pattern is provided so as to surround the translucent part,
The phase shifter is formed in a ring shape around the translucent part,
The phase shifter is formed by digging the transmissive substrate by a predetermined thickness so as to transmit the exposure light in an opposite phase with respect to the light transmitting portion.
The transmittance of the phase shifter with respect to the exposure light is substantially equal to the transmittance of the light transmitting part with respect to the exposure light. The photomask according to claim 12, wherein
The photomask, wherein the phase shifter is provided in contact with the light transmitting portion.

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