Pattern forming method and mask pattern data

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-147957, filed Jul. 16, 2013, the entire contents of which are incorporated herein by reference.

Embodiments described herein relate generally to a pattern forming method and mask pattern data.

Known lithography technologies utilized in manufacturing semiconductor devices include double patterning technology using ArF immersion exposure, EUV lithography, nanoimprint, and others. The lithography technologies according to the related art suffer from a variety of problems such as an increase in cost, and a decrease in throughput as pattern features have become smaller.

Under such circumstances, the application of directed self-assembly (DSA) to lithography technologies has been considered. Self-assembly is achieved by energy stabilization in fluid materials to form patterns therefrom having a high degree of dimensional accuracy. Especially, a technology using microphase separation of a block copolymer can form periodic structures in a variety of shapes with dimensions of several nanometers (nm) to several hundred of nanometers (nm) by a simple coating and an annealing process. Microphase separation causes the block copolymer to change into spherical shapes (a sphere), columnar shapes (a cylinder), layer shapes (a lamella), and the like, according to the composition ratio of the components of the block copolymer, making it possible to form self-assembly patterns in a variety of shapes and dimensions.

FIGS. 1A and 1B are a top view and a cross-sectional view, respectively, illustrating a pattern forming method according to a first embodiment.

FIGS. 2A and 2B are a top view and a cross-sectional view, respectively, illustrating a process subsequent to the process shown in FIGS. 1A and 1B , respectively.

FIGS. 3A and 3B are a top view and a cross-sectional view, respectively, illustrating a process subsequent to the process shown in FIGS. 2A and 2B , respectively.

FIGS. 4A and 4B are a top view and a cross-sectional view, respectively, illustrating a process subsequent to the process shown in FIGS. 3A and 3B , respectively.

FIGS. 5A and 5B are a top view and a cross-sectional view, respectively, illustrating a process subsequent to the process shown in FIGS. 4A and 4B , respectively.

FIGS. 6A and 6B are a top view and a cross-sectional view, respectively, illustrating a process subsequent to the process shown in FIGS. 5A and 5B , respectively.

FIGS. 7A and 7B are a top view and a cross-sectional view, respectively, illustrating a process subsequent to the process shown in FIGS. 6A and 6B , respectively.

FIGS. 8A to 8C are top views illustrating chemical guides according to a second embodiment.

FIGS. 9A to 9C are top views illustrating other chemical guides according to the second embodiment.

FIGS. 10A to 10C are top views illustrating other chemical guides according to the second embodiment.

An object of the present disclosure is to provide a pattern forming method and mask pattern data capable of forming a self-assembly pattern in a desired area.

In general, according to one embodiment, a pattern forming method includes: forming a guide layer, including a base layer and a neutralization film with a plurality of line sections, on a processing target film, the plurality of line sections being parallel to each other forming a polymer material containing first segments and second segments, on the guide layer; performing microphase separation of the polymer material to form a self-assembly pattern in which first polymer portions containing the first segments and extending along the line sections, and second polymer portions containing the second segments and extending along the line sections are alternately disposed; and selectively removing the second polymer portions. The widths of line sections of both ends of the plurality of line sections of the neutralization film are about two times the width of each first polymer portion or each second polymer portion.

Hereinafter, embodiments of the present disclosure will be described on the basis of the accompanying drawings.

First Embodiment

A pattern forming method an etch mask according to a first embodiment will be described with reference to FIGS. 1A to 7B . FIGS. 1A , 2 A, 3 A, 4 A, 5 A, 6 A and 7 A show top surfaces, and FIGS. 1B , 2 B, 3 B, 4 B, 5 B, 6 B and 7 B show cross sections taken along lines A-A of FIGS. 1A , 2 A, 3 A, 4 A, 5 A, 6 A and 7 A, respectively.

As shown in FIGS. 1A and 1B , a processing target film 101 is formed, on a semiconductor substrate (not shown), and on the processing target film 101 , a hard mask material 102 is formed. Further, on the hard mask material 102 , a base guide layer 103 and a neutralization film 104 are sequentially formed to form a mask substrate. The processing target film 101 may be an oxide film such as a TEOS film of a film thickness of about 300 nm.

The hard mask material 102 is provided for transferring a microphase separation pattern of a block copolymer, to be formed in a subsequent process, to the processing target film 101 . The hard mask material 102 can be formed by depositing a carbon film having a film thickness of about 100 nm, for example, by chemical vapor deposition (CVD).

The base guide layer 103 and the neutralization film 104 act as guides for forming the microphase separation pattern of the block copolymer in the subsequent process. The base guide layer 103 can be formed by depositing a silicon oxide film of a film thickness of about 15 nm, for example, by CVD.

The neutralization film 104 is neutral with respect to two polymer segments of the block copolymer to be used in the subsequent process. The neutralization film 104 can be formed, for example, by dissolving a random copolymer of polystyrene (PS) and polymethylmethacrylate (PMMA) in polyethylene glycol monomethyl ether acetate (PGMEA) at a concentration of 1.0 wt %, and applying the solution by spin coating at 2000 rpm, and performing baking on a hotplate at 110° C. for 90 seconds, and then performing baking at 240° C. for 3 minutes.

Next, a resist is applied over the neutralization film 104 by spin coating, and is exposed and developed, whereby a resist pattern 110 having a line-and-space pattern is formed, as shown in FIGS. 2A and 2B . The film thickness of the applied resist is, for example, 100 nm. Also, the exposure of the resist for forming a pattern therein may be performed with a dose of 20 mJ/cm 2 by an ArF excimer laser.

A pitch P1 of the resist pattern 110 is determined on the basis of the molecular weight and composition ratio of the block copolymer to be used in the subsequent process. The pitch P1 may be about three times the pitch (a pitch P2 of FIG. 5B ) of the self-assembly pattern to be formed by microphase separation of the block copolymer into a lamella shape. Also, each of widths L1 of line sections 110 b at opposed ends of the resist pattern 110 have the same as the pitch (the pitch P2 of FIG. 5B ) of the self-assembly pattern. In the central area of the resist pattern 110 (area between the opposed ends), each of widths L2 of line sections 110 a and widths L3 of space sections are about 1.5 times the pitch (the pitch P2 of FIG. 5B ) of the self-assembly pattern.

For example, in a case where the pitch (the pitch P2) of the self-assembly pattern is 30 nm, the widths L1 of the line sections 110 b at opposed ends is 30 nm, and the widths L2 of the line sections 110 a of the central area and the widths L3 of the space sections of the central area become 45 nm (30 nm×1.5), and the pitch P1 of the line-and-space pattern of the resist 110 are 90 nm (30 nm×3).

In order to form this resist pattern 110 , the pitch of the self-assembly pattern is used to generate mask pattern data in a computer as a first step. Next, on the basis of the mask pattern data, a mask for exposure is manufactured. Subsequently, the mask for exposure is used to perform exposure of the pattern in the resist layer, and the resist is then developed, whereby it is possible to form the resist pattern 110 .

Next, the resist pattern 110 is used as a mask to process the neutralization film 104 into a line-and-space shape as shown in FIGS. 3A and 3B . The processing of the neutralization film 104 may be performed by oxygen RIE (reactive ion etching). After the processing of the neutralization film 104 , the resist pattern 110 is stripped off by use of a solvent, or the like. The resulting patterned neutralization film 104 includes a plurality of line-shaped neutralization films 104 a and 104 b formed in parallel along a predetermined direction. The neutralization films 104 b positioned at the opposed ends correspond to the line sections 110 b , and the neutralization films 104 a therebetween are positioned at the central area to correspond to the line sections 110 a.

Next, as shown in FIGS. 4A and 4B , a block copolymer 105 is applied on the base guide layer 103 and the neutralization film 104 . The block copolymer bonds to the base guide layer 103 and the neutralization film 104 and includes first polymer block chains and second polymer block chains.

Next, the block copolymer 105 is heated and a lamellar microphase separation structure film (a self-assembly pattern 106 ) is formed by microphase separation as shown in FIGS. 5A and 5B . The self-assembly pattern 106 comprises alternating linear-shaped thin-films having first polymer portions 106 a containing the first polymer block chains (first segments) and linear-shaped thin-films having second polymer portions 106 b containing the second polymer block chains (second segments). The base guide layer 103 and the neutralization film 104 act as so-called chemical guides, such that the lamellar first polymer portions 106 a and the lamellar second polymer portions 106 b are aligned with the neutralization film 104 . More particularly, the first polymer portions 106 a containing the first segments and extending along the vertical direction of FIG. 5A , and the second polymer portions 106 b containing the second segments and extending along the vertical direction of FIG. 5A are alternately disposed along the left-right direction of the FIG. 5A , in the self-assembly pattern 106 .

The pitch P1 of the line-and-space pattern of the neutralization film 104 is about three times the pitch P2 of the self-assembly pattern 106 . The base guide layer 103 (exposed in the space sections between adjacent line portions of the neutralization films 104 of the line-and-space pattern) form pinning areas, and the first polymer portions 106 a are formed in the center of the surface of the base guide layer 103 . Also, due to the characteristics of lamellar microphase separation, the first polymer portions 106 a and the second polymer portions 106 b are alternately formed.

As shown in FIGS. 5A and 5B , over the line or strip shaped neutralization films 104 a of the central area between opposed ends, the first polymer portions 106 a are formed with the second polymer portions 106 b interposed therebetween. Also, on the neutralization films 104 b at the opposed ends, the first polymer portions 106 a are formed on the inner side (on the central area side) and the second polymer portions 106 b are formed on the outer side of the first polymer portions 106 a.

Also, in areas outside of the neutralization films 104 b at the opposed ends, regular phase separation of the block copolymer 105 does not occur. Thus, at the ends of the pattern, the block copolymer 105 is a mixed polymer 107 which is a mixture of the first polymer block chains and the second polymer block chains that are not phase separated.

As the block copolymer 105 , it is possible to use, for example, a block copolymer of polystyrene (PS) and polymethylmethacrylate (PMMA). The value of [AVERAGE MOLECULAR WEIGHT OF PS BLOCKS]/[AVERAGE MOLECULAR WEIGHT OF PMMA BLOCKS] is, for example, 21,000/21,000. This block copolymer is dissolved in PGMEA at the concentration of about 1.0 wt %, and this solution is applied at 2000 rpm by spin coating. Next, baking is performed at 110° C. for 90 seconds, and then an annealing process is performed in nitrogen atmosphere at 220° C. for 3 minutes to separate the block copolymer into a lamellar domain having linear portions with a half-pitch of 15 nm. In this case, the first polymer portions 106 a become the PS phase, and the second polymer portions 106 b become the PMMA phase.

Next, as shown in FIGS. 6A and 6B , a resist 112 is formed to cover the self-assembly pattern 106 (shown in FIG. 5B ) leaving the mixed polymer 107 of the areas outside of the neutralization films 104 b at both ends (shown in FIG. 5B ) exposed. Subsequently, the resist 112 is used as a mask to perform RIE, whereby the mixed polymer 107 is removed. After the removal of the mixed polymer 107 at opposed end, the resist 112 is stripped off.

Next, a wet developing process is performed to selectively remove the second polymer portions 106 b while leaving the first polymer portions 106 a remain as shown in FIGS. 7A and 7B . For example, ultraviolet light is irradiated onto the self-assembly pattern 106 , and then a developer is provided to the self-assembly pattern 106 . If ultraviolet light is utilized, PMMA is oxidized by oxygen and/or water in the atmosphere, so as to be soluble in the developer. As the developer, it is possible to use a variety of developers usable for developing exposed photoresist films in photolithography technologies. As an example, tetramethylammonium hydroxide (TMAH) can be used.

Although not shown in the drawings, the openings formed where the second polymer portions 106 b were removed, and the remaining first polymer portions 106 a , are used as a mask to process the base guide layer 103 after the wet developing process. In this way, the line-and-space shape is transferred to the base guide layer 103 . Next, the base guide layer 103 is used as a mask to process the hard mask material 102 by RIE or the like. In this way, the line-and-space shape is transferred to the hard mask material 102 . Next, the hard mask material 102 is used as a mask to process the processing target film 101 by RIE or the like. In this way, it is possible to transfer the line-and-space pattern to the processing target film 101 .

As shown in FIGS. 5A and 5B , on the neutralization films 104 b at the opposed ends, the second polymer portions 106 b to be removed by the wet developing process are formed on the outer side of the first polymer portions 106 a . Therefore, when the resist 112 is formed in the process shown in FIGS. 6A and 6B , it is possible to use an alignment margin corresponding to the widths of those second polymer portions 106 b at the opposed ends. Thus, it is possible to easily remove the mixed polymer 107 while leaving the first polymer portions 106 a at the opposed ends in the subsequent process.

As described above, according to the present embodiment, it is possible to form a self-assembly pattern in a desired area.

In the above described embodiment, an example in which the block copolymer of polystyrene (PS) and polymethylmethacrylate (PMMA) is used as the block copolymer has been described. However, any other materials such as a block copolymer of polystyrene (PS) and polydimethylsiloxane (PDMS) may be used.

Second Embodiment

In the above described first embodiment, the chemical guides are composed of the neutralization film 104 and pinning areas (the exposed portions of the base guide layer between the line shaped neutralization films 104 a in the first embodiment) 103 , and the width of each neutralization film 104 a in the central area (area between the opposed ends) are about 1.5 times the pitch P2 of the self-assembly pattern 106 , in other words, about three times the width of each first polymer portion 106 a or each second polymer portion 106 b . Also, the widths of the neutralization films 104 b at the opposed ends is the same as the pitch P2 of the self-assembly pattern 106 , in other words, about two times the width of each first polymer portion 106 a or each second polymer portion 106 b . Further, the widths of the pinning areas 103 is about 1.5 times the pitch P2 of the self-assembly pattern 106 (shown in dashed lines in FIGS. 8A-8C ), in other words, about three times the width of each first polymer portion 106 a or each second polymer portion 106 b (see FIG. 8A ).

Therefore, after the wet developing process is performed so as to selectively remove the second polymer portions 106 b , the number of remaining first polymer portions 106 a becomes 3n (n is an integer equal to or greater than 1).

The number of first polymer portions 106 a remaining after the wet developing process can be changed by adjusting the widths of the neutralization films 104 b at the opposed ends.

For example, if the width of one of the neutralization films 104 b at one of the opposed ends is set to about 1.5 times or about two times the pitch P2 of the self-assembly pattern 106 , (in other words, about three times or about four times the width of each first polymer portion 106 a or each second polymer portion 106 b ) the number of the first polymer portions 106 a that remain after the wet developing process becomes (3n+1). FIG. 8B shows a case where the width of one of the neutralization films 104 b at the opposed ends has been set to about two times the pitch P2 of the self-assembly pattern 106 , (in other words, about four times the width of each first polymer portion 106 a or each second polymer portion 106 b ).

Also, if the widths of the neutralization films 104 b at the opposed ends are set to about 1.5 times or about two times the pitch P2 of the self-assembly pattern 106 , (in other words, about three times or about four times the width of each first polymer portion 106 a or each second polymer portion 106 b ) the number of the first polymer portions 106 a that remain after the wet developing process becomes (3n+2). FIG. 8C shows a case where the widths of the neutralization films 104 b of both of the opposed ends have been set to about two times the pitch P2 of the self-assembly pattern 106 , (in other words, about four times the width of each first polymer portion 106 a or each second polymer portion 106 b ).

The above described examples relate to a case where the pinning areas 103 are hydrophilic. In a case where the pinning areas 103 are hydrophobic, the positions of the first polymer portions (PS phase) 106 a and the second polymer portions (PMMA phase) 106 b are reversed. In this case, if the widths of the neutralization films 104 b at the opposed ends are set to half of the pitch P2 of the self-assembly pattern 106 (shown in dashed lines in FIGS. 9A-9C ), in other words, the same width as the width of each first polymer portion 106 a or each second polymer portion 106 b (see FIG. 9A ), the number of the first polymer portions 106 a that remain after the wet developing process becomes (3n+2).

In the case where the pinning areas 103 are hydrophobic, if the width of one of the neutralization films 104 b of both ends is set to half of the pitch P2 of the self-assembly pattern 106 , (in other words, the same width as the width of each first polymer portion 106 a or each second polymer portion 106 b ), and the width of the other neutralization film 104 b is set to one time or about 1.5 times the pitch P2 of the self-assembly pattern 106 , (in other words, about two times or about three times the width of each first polymer portion 106 a or each second polymer portion 106 b ) the number of the first polymer portions 106 a that remain after the wet developing process becomes 3n. FIG. 9B shows a case where the width of one of the neutralization films 104 b at the opposed ends has been set to the same width as the width of each first polymer portion 106 a , and the width of the other neutralization film 104 b at the opposed ends has been set to about three times the width of each first polymer portion 106 a.

Also, in the case where the pinning areas 103 are hydrophobic, if the widths of the neutralization films 104 b at the opposed ends are set to one time or about 1.5 times the pitch P2 of the self-assembly pattern 106 , (in other words, about two times or about three times the width of each first polymer portion 106 a or each second polymer portion 106 b ) the number of the first polymer portions 106 a that remain after the wet developing process becomes (3n+1). FIG. 9C shows a case where the widths of the neutralization films 104 b at the opposed ends have been set to about three times the width of each first polymer portion 106 a.

Not only the widths of the neutralization films 104 b at the opposed ends, but also the widths of the neutralization films 104 a of the central area other than at the opposed ends, and the widths of the pinning areas 103 may be adjusted. Because of the characteristics of the lamellar microphase separation, the widths of the neutralization films 104 a and the pinning areas 103 are set to substantially odd multiples of the width of each first polymer portion 106 a (or each second polymer portion 106 b ).

For example, as shown in FIG. 10A , the widths of the neutralization films 104 b at the opposed ends may be set to about two times the width of each first polymer portion 106 a or each second polymer portion 106 b (shown in dashed lines in FIGS. 10A-10C ). The widths of the neutralization films 104 a of the central area may be set to about three times the width of each first polymer portion 106 a or each second polymer portion 106 b . The widths of the pinning areas 103 may be set to one time the width of each first polymer portion 106 a or each second polymer portion 106 b.

Also, as shown in FIG. 10B , the widths of the neutralization films 104 b at the opposed ends may be set to about two times the width of each first polymer portion 106 a or each second polymer portion 106 b . The widths of the neutralization films 104 a of the central area may be set to about five times the width of each first polymer portion 106 a or each second polymer portion 106 b . The widths of the pinning areas 103 may be set to one time the width of each first polymer portion 106 a or each second polymer portion 106 b.

Also, as shown in FIG. 10C , the widths of the neutralization films 104 b at the opposed ends may be set to about two times the width of each first polymer portion 106 a or each second polymer portion 106 b . The widths of the neutralization films 104 a of the central area may be set to about five times the width of each first polymer portion 106 a or each second polymer portion 106 b . The widths of the pinning areas 103 may be set to about three times the width of each first polymer portion 106 a or each second polymer portion 106 b.

As described above, if the widths of the neutralization films 104 a of the central area (areas between the opposed ends) and the widths of the pinning areas 103 are adjusted, it is possible to set the number of the first polymer portions 106 a that remain after the wet developing process, to a desired value. Therefore, it is possible to form a desired line-and-space patterns in a desired area.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, 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.