Method for forming pattern and method for producing original lithography mask

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-213815, filed Sep. 27, 2012; the entire contents of which are incorporated herein by reference.

Embodiments described herein relate to the method for forming pattern and the method for producing original lithography mask.

Conventional lithography technology in the production of semiconductor devices includes double patterning technology with ArF immersion exposure, EUV lithography, and nano-imprint. In the conventional lithography technology, there are many problems associated with pattern miniaturization, such as increases in cost, a decrease in position accuracy of the pattern, and a decrease in throughput.

The application of directed self-assembly (DSA) methods to lithography technology is expected. DSA provides self-assembled phases of material generated by stable energy and therefore a pattern with high dimensional accuracy can be created. In particular, DSA provides a microphase separation of a macromolecule block copolymer that forms a periodic structure of various formations of several nanometers (nm) to several hundred nm wide by a simple coating and annealing process. The structure of the microphase material is changed into the various formations, such as spherical formations, pillar-shaped formations and a linear (layered) shape according to the composition ratio of the block copolymer. Hole, pillar, and the line patterns can be formed in various dimensions according to the molecular weight of the block copolymer, by selectively removing portions of the reacted copolymer in regions to create an etch mask from the reacted copolymer.

However, application of DSA to lithography techniques sometimes produces errors in the position of the patterns.

FIGS. 1A and 1B are a sectional view and a top view, respectively, for illustrating a method of forming a pattern according to one embodiment.

FIGS. 2A and 2B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 1A and 1B .

FIGS. 3A and 3B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 2A and 2B .

FIGS. 4A and 4B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 3A and 3B .

FIGS. 5A and 5B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 4A and 4B .

FIGS. 6A and 6B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 5A and 5B .

FIGS. 7A and 7B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 6A and 6B .

FIGS. 8A and 8B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 7A and 7B .

FIGS. 9A and 9B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 8A and 8B .

FIGS. 10A and 10B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 9A and 9B .

FIGS. 11A and 11B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 10A and 10 B.

FIGS. 12A and 12B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 11A and 11B .

FIGS. 13A and 13B are a sectional view and a top view, respectively, for illustrating the process following FIGS. 12A and 12B .

According to the embodiments, a method for forming a pattern and a method for producing an original mask with reduced errors in the relative positions of a self-assembled pattern and other patterns is provided.

In general, one embodiment of the invention is explained based on the drawings as follows.

According to one embodiment, a method of forming a pattern or mask is provided with a process of forming a self-assembly material on a substrate having a fiducial (reference) mark formed thereon. The method also includes a process of forming a self-assembled pattern, where the self-assembly material is micro phase separated. The method also includes a process of measuring a position error from a fixed position where the self-assembled pattern is formed based on the fiducial mark. The method also includes a process of forming a pattern for alignment and a pattern of a peripheral circuit, on the substrate. The formation position of at least one of the pattern for alignment and pattern of the peripheral circuit is corrected by using the position error.

FIG. 1A to FIG. 12B are drawings that explain the method for forming the pattern according to one embodiment.

As shown in FIG. 1A and FIG. 1B , a photo mask substrate is prepared having a shading film 102 (mask film) formed on a glass or quartz substrate 101 . FIG. 1B is a top view, and FIG. 1A is a sectional view along the I-I line in FIG. 1B . The shading film 102 is a film that contains chromium and tantalum. A fiducial mark FM (used subsequently at the time of measuring the position of the pattern) is formed on this photo mask substrate in the shading or mask film 102 . The fiducial mark FM can be formed on the shading film 102 as well as on the glass substrate 101 .

As shown in FIG. 2A and FIG. 2B , an underlayer 103 is formed on the photo mask substrate over the shading film 102 , including the fiducial marks. FIG. 2B is a top view, and FIG. 2A is a sectional view along the II-II line in FIG. 2B , of the substrate 101 , shading film 102 and underlayer 103 . The underlayer 103 becomes the base of the block copolymer formed in the following process. The surface state of the area where light of a fixed wave length is irradiated changes into the underlayer 103 . For instance, the underlayer 103 has hydrophobic properties before exposure to irradiating light, and the area where light is irradiated on the underfilm 103 changes to have hydrophilic properties.

A laminated film of a self-assembled monomolecular film layer and a polymer layer can be used as the underlayer 103 . A silane coupling agent which contains a benzophenone skeleton can be used for the self-assembled monomolecular film layer. Moreover, an acrylic resin derivative (meth) can be used for the polymer. In the light irradiation area of self-assembled monomolecular film layer and the polymer laminated structure, since the cross-linkage is caused in the portion of the polymer which comes in contact with the benzophenone structure, the surface is derived from the polymer. As a polymer, a hydrophilic resin such as (meth)acrylic resin is used and an optical irradiation part can be in the hydrophilic state.

As shown in FIG. 3A and FIG. 3B , a resist is applied on the underlayer 103 , and exposed and developed to form a frame pattern 104 which encloses area R 1 . FIG. 3B is a top view of the substrate 103 and the frame and FIG. 3A is a sectional view along the II-II line of FIG. 3B . The area R 1 within the frame is an area where a block copolymer is formed in subsequent processes to form pattern mask for a memory cell. Although area R 1 is an area corresponding to the a pattern of a memory cell, if it is a pattern area formed in a pitch of equal intervals, area R 1 is not an area limited to the memory cell.

The resist, which is a material of the frame pattern 104 , has the neutral characteristics for the two polymers (first polymer and the second polymer), which are included in the block copolymer formed in the following process. That is, the resist has a surface energy between the surface energy of the first polymer and the surface energy of the second polymer.

As shown in FIG. 4A and FIG. 4B , the fixed area of underlayer 103 is exposed to light through a mask (not shown in the figure). FIG. 4B is a top view of the exposed underlayer and FIG. 4A is a sectional view along the II-II line in FIG. 4B . The irradiating light is light of a wave length for exposing the underlayer 103 . For instance, a light from UV to DUV wavelength (365 nm, 248 nm, and 193 nm) may be used. An exposed part 103 a (first portion) of the underlayer 103 changes into hydrophilic properties and the unexposed part (second portion) covered by the mask retains hydrophobic properties. For instance, as shown in FIG. 4A and FIG. 4B , the underlayer 103 is exposed in lines having a fixed pitch in the area R 1 (shown in FIGS. 3A and 3B ) enclosed by the frame pattern 104 . As a result, when the block copolymer formed in the following process is micro phase separated, the underlayer 103 of area R 1 enclosed by the frame pattern 104 becomes a chemical guide layer which controls the position where the micro phase-separated pattern is formed.

As shown in FIG. 5A and FIG. 5B , a block copolymer layer 105 is formed on the underlayer 103 within the boundary of the frame pattern 104 . FIG. 5B is a top view and FIG. 5A is a sectional view along the II-II line in FIG. 5B of the substrate 103 having the block copolymer formed therein. A di-block copolymer, in which a first polymer block chain and a second polymer block chain are included, is used as the block copolymer. The block copolymer of polystyrene (PS) and polymethyl methacrylate (PMMA) can be used as the di-block copolymer. Due to the frame pattern 104 , the block copolymer can be contained by the frame pattern 104 and thereby prevent leakage outside of the frame pattern 104 .

Heat is then applied to the substrate 103 with a heat source such as a hot plate to the block copolymer to separate the block copolymer into regions 106 a , 106 b as shown in FIG. 6A and FIG. 6B . As a result, the block copolymer layer 105 is separated in micro phase, and a lamellar self-assembled pattern 106 is formed. FIG. 6B is a top view and FIG. 6A is a sectional view along the II-II line in FIG. 6B of the substrate 101 and separated block copolymer 106 . A laminated first polymer 106 a containing the first polymer block chain and a laminated second polymer 106 b containing the second polymer block chain are alternately arranged in the self-assembled micro phase pattern.

The first portion 103 a (where the surface state changes by exposure to light) and the underlayer 103 which has the second portion (where the surface state is not changed) form a chemical guide layer and thus, the lamellar self-assembled pattern 106 is formed with the underlayer as a guiding pattern. Moreover, as mentioned above, the frame pattern 104 can control the influence on the array of self-assembled pattern 106 because it has the neutral characteristics for the first polymer and the second polymer.

The position where the self-assembled pattern 106 is formed is measured based on the fiducial mark FM (shown in FIG. 1 ). For instance, a SEM is used for the measurement. A position error of the measurement position and a target position is calculated. The barycentric coordinate position is measured and a position error of a target position is calculated for the first polymer 106 a ; and the second polymer 106 b of the lamellar self-assembled pattern 106 . Moreover, a position error for the entire self-assembled pattern 106 is calculated from the position error of each pattern (the first polymer 106 a and the second polymer 106 b ).

As shown in FIG. 7A and FIG. 7B , one of the first polymer 106 a and the second polymer 106 b is selectively removed in the self-assembled pattern 106 by a processing procedure, such as by application of a developer or a solvent that selectively removes one of the first polymer 106 a and the second polymer 106 b . The first polymer 106 a is removed here as shown. FIG. 7B is a top view and FIG. 7A is a sectional view along the II-II line in FIG. 7B of the substrate 103 having the first polymer layer 106 a selectively removed.

As shown in FIG. 8A and FIG. 8B , a resist 107 is applied on the underlayer 103 which is outside of the perimeter of the frame pattern 104 . FIG. 8B is a top view of the substrate 102 and resist layer 107 and FIG. 8A is a sectional view of the substrate along the II-II line in FIG. 8B .

As shown in FIG. 9A and FIG. 9B , the resist is exposed and developed and a pattern 110 (for alignment) and a peripheral circuit pattern 111 are formed in the resist 107 . For instance, an electron beam is used for exposure of the resist 107 . FIG. 9B is a top view and FIG. 9A is a sectional view along the III-III line in FIG. 9B of the substrate 102 and patterned resist 107 . For a precise alignment of the pattern 110 and the surrounding circuit pattern 111 , the formation position is corrected so that the relative positional relation with the self-assembled pattern 106 may get closer to the design value.

The position error calculated for the entire self-assembly pattern 106 is added to a first formation position (exposure position according to design information) for the pattern 110 for alignment, and the formation position is corrected.

Moreover, as shown in FIGS. 3A and 3B , the area R 1 corresponds to a memory cell area and the peripheral circuit pattern 111 corresponds to and aligns with the connection portions of the memory cell, i.e., the removed portions of the polymer 106 a . As shown in FIGS. 9A and 9B , the peripheral circuit pattern 111 includes a pattern 111 a in multiple numbers which are aligned with positions of the removed first polymer 106 a (shown in FIGS. 6A and 6B ) respectively. In this case, the position error of the corresponding first polymer 106 a is added to the first position (exposure position according to design information) where each pattern 111 a is formed and the formation position is corrected. That is, the formation position of each pattern 111 a is corrected for the peripheral circuit pattern 111 .

As shown in FIG. 10A and FIG. 10B , the frame pattern 104 is selectively removed. FIG. 10B is a top view and FIG. 10A is a sectional view along the II-II line in FIG. 10B of the substrate 102 showing the frame pattern removed therefrom.

As shown in FIG. 11A and FIG. 11B , a resist 120 is applied on the area where the frame pattern 104 is removed, and the resist is exposed and developed. FIG. 11B is a top view and FIG. 11A is a sectional view along the IV-IV line in FIG. 11B of the substrate 102 . A connection pattern 121 in which the first polymer 106 a of the self-assembly pattern 106 and the pattern 111 a of corresponding peripheral circuit pattern 111 are connected, is formed in the resist 120 .

As shown in FIG. 12A and FIG. 12B , the resist 107 , resist 120 and the second polymer 106 b are used as a mask, and the underlayer 103 and shading film 102 are etched. FIG. 12B is the top view and FIG. 12A is a sectional view along the IV-IV line in FIG. 12B .

The resist 107 , the resist 120 , the second polymer 106 b and the underlayer 103 are then removed as shown in FIG. 13A and FIG. 13B . FIG. 13B is the top view and FIG. 13A is a sectional view along the IV-IV line in FIG. 13B . As a result, the first polymer 106 a of the self-assembly pattern 106 , the pattern 110 for alignment, the peripheral circuit pattern 111 and a connection pattern 121 are transcribed to the shading (mask) film 102 on the glass or quartz substrate 101 and a photo mask substrate (for original lithograph) is obtained.

For the precise alignment pattern 110 and the surrounding circuit pattern 111 , the difference in the position during formation of the self-assembly pattern 106 is considered and the formation position is corrected. Therefore, the position errors of the self-assembly pattern 106 , the alignment or fiducial mark pattern 110 for alignment and the peripheral circuit pattern 111 can be reduced.

Thus, according to this embodiment, even when there is a difference in position on the formation of the self-assembly pattern, the error in a relative positional relation between the self-assembly pattern and other patterns can be reduced.

In the embodiment, the position where the self-assembly pattern 106 is formed, is measured, and the position error of relative to a target position is calculated. However, the position where the second polymer 106 b is formed can be measured and the position error relative to the target position can be calculated after removing the first polymer 106 a of the self-assembly pattern 106 . Moreover, the position where the first removed polymer 106 a is formed can be measured and the position error relative to the target position can be calculated.

Moreover, after forming of the peripheral circuit pattern 111 , the position where the peripheral circuit pattern 111 is formed, can be measured, the position error of the target position can be calculated and the position (exposure position) where the connection pattern 121 is formed, can be corrected.

The lithographic exposure is not limited to the electron beam. EUV light, UV light, ion beam, X rays, visible radiation, and infrared light can also be used. Moreover, the frame pattern 104 , the pattern 110 for alignment, the peripheral circuit pattern 111 , and the connection pattern 121 can be created by an imprint process.

In the embodiment, the shading film 102 with the first polymer 106 a of self-assembly pattern 106 , the pattern 110 for alignment, the peripheral circuit pattern 111 and the transcribed connection pattern 121 are used as a mask and the glass substrate 101 is processed. The template for imprint can be made.

In the embodiment, although the position where the pattern 110 for alignment and the peripheral circuit pattern 111 are formed is corrected, the position where only either pattern is formed can be corrected as well. Moreover, when there is position error in the formation position and target position of the self-assembly pattern 106 is within a fixed range, the position where the pattern 110 for the alignment and/or the peripheral circuit pattern 111 is formed cannot be corrected.

In the embodiment, the connection pattern 121 can be formed by using the micro phase separation of the self-assembly material. For instance, the self-assembly material which contains the second polymer 106 b of the self-assembled pattern 106 , and the polymer having large affinity with the surface of the resist 107 , is used, and the self-assembly pattern corresponding to the connection pattern 121 is formed. Moreover, the self-assembly material which contains the second polymer 106 b of the self-assembled pattern 106 , and the polymer having the large affinity with the surface after re-forming the surface state of the resist 107 , can also be used. Moreover, the chemical guide layer which corresponds to the connection pattern 121 is formed in the area where the frame pattern 104 is removed; the self-assembly material can be applied on the chemical guide layer. The self-assembly material is separated in micro phase according to the second polymer 106 b and the resist 107 . Therefore, even if the position of the first polymer 106 a or the peripheral circuit pattern 111 is moved, the connection pattern 121 in which the first polymer 106 a and the peripheral circuit pattern 111 are connected can still be formed.

In the embodiment, although the chemical guide layer is formed in the frame pattern 104 , when the block copolymer layer 105 is separated in micro phase by using the frame pattern 104 as a physical guide and the self-assembly pattern 106 is obtained, the chemical guide layer can be omitted. In that case, the frame pattern 104 contains any one of the polymer among two polymers included in the block copolymer layer 105 and the material having the large affinity.

In the embodiment, the example of forming the lamellar self-assembled pattern 106 is explained, however, other shapes such as cylindrical is also acceptable.

The glass substrate is used as the processed substrate in the embodiment. The glass substrate may be a fused silica substrate and a sapphire glass substrate. Moreover, the substrate which constitutes the original mask for EUV lithography, character aperture for EB, optical imprint and original thermal imprint, can also be used for the processed substrate.

While certain embodiments have been described, these embodiments have been presented as examples only, and are not intended to limit the scope of the inventions. In fact, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.