JP3542106B2 - Pattern forming method and positive resist composition - Google Patents

Description

【００１２】
上述したパターン形成方法において、酸を触媒として前記レジスト間の架橋を促進させることを特徴とする。
【００１３】
また、前述した課題を解決するための、本発明によるポジ型レジスト組成物は、側鎖に芳香族水素を有するポジ型レジストと、下記の構造を有すると共に、前記ポジ型レジスト中に存在する高分子集合体の周囲のレジスト間を架橋する架橋剤とを含んでなることを特徴とする。
【化４】

【００１４】
上述したポジ型レジスト組成物において、酸を発生する酸発生剤を含んでいることを特徴とする。
【００１６】
［作用］
本発明の作用を説明するにあたり、まず始めに、集合体脱離現像について図２を用いて説明する。なお、図２は、従来のポジ型レジストを用いて作製したレジスト膜にパターンを形成する場合の状態説明図である。
【００１７】
高分子集合体の現像液に対する溶解速度は、高分子密度に依存する。高分子集合体１の内部のレジストの密度は、高分子集合体１の周囲のレジスト２の密度よりも大きい（図２（ａ）参照）。このため、放射線４の照射領域においては、高分子集合体１の内部のレジストと周囲のレジスト２とで溶解速度に局所的な差異を生じて、集合体脱離現像が発生してしまう。すなわち、現像液の分子は、高分子集合体１の内部のレジストよりも周囲のレジスト２に速く拡散してしまうため、高分子集合体１の内部のレジストよりも周囲のレジスト２を速く溶解してしまう。このため、その周囲のレジスト２を完全に溶解された高分子集合体１は、たとえその内部のレジストが溶解していない状態であっても脱離することができる（図２（ｂ）参照）。よって、放射線４の照射領域の境界に存在する高分子集合体１は、その周囲のレジスト２のうち、放射線４の照射領域部分のみが溶解されて、放射線４の照射領域外部分が溶解しないため、レジスト膜から脱離することなく残留してしまう（図２（ｃ）参照）。
【００１８】
このため、放射線４の照射領域の境界部分で残留した高分子集合体１がパターンの側壁で露出してしまい、ラインエッジラフネスの原因となるのである。つまり、現像液に対する高分子集合体１の内部のレジストと周囲のレジスト２との溶解速度の局所的な差異がラインエッジラフネスを生じさせているのである。したがって、高分子集合体１の内部のレジストと周囲のレジスト２との溶解速度の局所的な差異をなくせば、たとえレジスト膜中に高分子集合体１が存在していたとしても、ラインエッジラフネスを低減することができる。
【００１９】
そこで、本発明では、レジスト膜中の上述した溶解速度の局所的な差異をなくすため、高分子集合体１の周囲のレジスト２のみを架橋するようにしたのである。すなわち、高分子集合体１の周囲のレジスト２のみを架橋して高分子集合体１の周囲のレジストの分子量を増大させることにより、現像液に対する高分子集合体１の周囲のレジスト２の溶解速度を遅くして、高分子集合体１の内部のレジストと周囲のレジスト２との溶解速度を同程度にすることにより、レジスト膜中の溶解度の差異をなくすようにしたのである。
【００２０】
この作用を図１を用いてさらに詳しく説明する。なお、図１は、本発明によるポジ型レジスト組成物を用いて作製したレジスト膜にパターンを形成する場合の状態説明図である。
【００２１】
本発明によるポジ型レジスト組成物は、ポジ型レジストと架橋剤とを混合したものである。また、熱や光で酸を発生する酸発生剤をさらに混合するとより好ましい。このポジ型レジスト組成物を被加工基板に塗布してレジスト膜を形成する（図１（ａ）参照）。架橋剤は、高分子集合体１の周囲のレジスト２に主に分散している。この架橋剤が架橋反応を起こす条件でレジスト膜を処理することにより、高分子集合体１の周囲のレジスト２のみが架橋して架橋レジスト３となり、高分子集合体１の内部のレジストと周囲の架橋レジスト３との密度が略均一になる。酸発生剤を混合した場合には、レジスト膜全体を加熱や光照射して酸を発生させ、この酸を触媒として高分子集合体１の周囲のレジスト２を化学的に架橋させる。
【００２２】
このようにして架橋処理されたレジスト膜に放射線４を照射してパターンを形成した後（図１（ｂ）参照）、現像液に浸漬すると、放射線４を照射された領域部分が溶解する（図１（ｃ）参照）。前述した化学的な架橋により、高分子集合体１の内部のレジストと周囲の架橋済レジスト３との現像液に対する溶解速度が等しくなっているため、現像液の分子が放射線４の照射領域内を深さ方向に均一に拡散していき、放射線４の照射領域が表面を平らに保ちながら溶解していく。このため、パターンの側壁においても上述と同様に放射線４の照射強度分布をそのまま反映した平らな面となり、ラインエッジラフネスを生じることがない（図１（ｄ）参照）。
【００２３】
このような本発明によるポジ型レジスト組成物に対して、従来の架橋型のポジ型レジストを単体で用いた場合には、前述したように、高分子集合体の内部のレジストおよびその周囲のレジストで分子内やレジスト内の架橋が発生するため、高分子集合体の内部のレジストとその周囲のレジストとの溶解速度差がそのまま維持されてしまう。つまり、高分子集合体の周囲のレジストのみを架橋させることが重要なのである。そこで、本発明では、高分子集合体が既に形成されているポジ型レジストに対して、架橋剤や酸発生剤をあとから加えることにより、高分子集合体の内部への架橋剤や酸発生剤の侵入を極力抑えて、高分子集合体の周囲のレジストに対する架橋だけを行うようにしているのである。
【００２４】
酸発生剤を加えると、分子間やレジスト間での架橋を効率よく行うことができる。酸発生剤は、熱や光により分解して酸を発生し、当該酸が架橋反応の触媒として作用するため、架橋反応率を高めることができる。このような架橋反応は、非常に簡単に生じさせることができ、ポジ型レジストと架橋剤とを混合して加熱したり、酸発生剤を加えたりすることで実施することができる。
【００２５】
このような反応を生じさせる架橋剤としては、ヘキサメトキシメチルメラミン、ビス（ｐ−アセトキシメチルベンゼン）、テレフタルアルデヒド−ビスエチレンアセタール、１，３，５−トリメチル −２，４，６−トリアセトキシメチルベンゼンなどが挙げられる。酸発生剤としては、オニウム塩、トリスルフォニウム塩、トリアジン誘導体などが挙げられる。
【００２６】
なお、ポジ型レジストとして、α−クロロアクリル酸メチルとα−メチルスチレンとの共重合体（商品名：ＺＥＰ５２０（日本ゼオン株式会社））を用いる場合、架橋剤としては、現像に必要な分子量変化に影響を与えないように、ＺＥＰ５２０の側鎖のベンゼン環水素（芳香族水素）を架橋点として反応するものが望ましい。すなわち、ＺＥＰ５２０の側鎖の芳香族水素と求電子置換反応する置換基を少なくとも二つ以上有して自己架橋を生じない（ベンゼン環水素がない）ものである。具体的には、下記の化学式に示す構造を有するものが好ましく、特に、１，２，４，５−テトラメチル−３，６−（ジアセトキシメチル）ベンゼン、１，３，５−トリメチル−２，４，６−（トリアセトキシメチル）ベンゼンなどが好ましい。
【００２７】
【化５】

【００２８】
一方、酸発生剤としては、架橋剤と架橋することなく分解して酸を発生するものが望ましい。すなわち、ベンゼン環水素がなく２００℃以下で分解して酸を発生するものである。具体的には、シクロヘキシルメチル（２−オキソシクロヘキシル）スルフォニウムトリフルオロメタンスルフォネート、β−オキソシクロヘキシル（２−ノルボルニル）スルフォニウムトリフルオロメタンスルフォネートなどが挙げられる。
【００２９】
このような架橋剤や酸発生剤においては、ポジ型レジスト１００重量部に対して、１〜５０重量部程度でそれぞれ混合することが望ましい。
【００３０】
このような架橋剤や酸発生剤をＺＥＰ５２０に混合して加熱すると、高分子集合体の周囲のレジストの側鎖のベンゼン環が架橋剤を介して架橋するので、高分子集合体の内部と周囲との現像速度が均一になる。ここで、上述したような材料の組み合わせであれば、架橋反応を生じていても、露光によるレジストの主鎖の分解反応が良好に生じるため、レジスト膜にパターンを何ら問題なく形成することができる。
【００３１】
このように高分子集合体の周囲のレジスト間を化学的に架橋することにより、高分子集合体の内部の領域と周囲の領域とに存在するレジストの現像液に対する溶解速度の差異をなくして集合体脱離現像を抑制することができる。これにより、パターンの側壁への高分子集合体の露出を抑制することができ、ラインエッジラフネスを大幅に低減することができる。
【００３２】
【発明の実施の形態】
本発明によるポジ型レジスト組成物の実施の形態を以下に説明するが、本発明は、以下の実施の形態のみに限定されるものではない。
【００３３】
市販の電子線感光型のポジ型レジスト（ＺＥＰ５２０）の溶液を加熱した後、急冷して析出させて分取することにより精製する。精製したポジ型レジスト１００重量部に対して、架橋剤（１，３，５−トリメチル−２，４，６−（トリアセトキシメチル）ベンゼン）を３０重量部で混合すると共に、酸発生剤（シクロヘキシルメチル（２−オキソシクロヘキシル）スルフォニウムトリフルオロメタンスルフォネート）を１０重量部で混合したら、溶媒（２−メトキシエチルアセテート）に溶解した後、フィルタ（０．４５μｍ）で濾過して未溶解物を除去することにより、ポジ型レジスト組成物の溶液を得た。なお、溶媒１００重量部に対して、ポジ型レジストは２重量部とした。
【００３４】
次に、ポジ型レジスト組成物の溶液を基板（材料：Ｓｉ）上に回転塗布法（回転数：１５００ｒｐｍ）で塗布した後、ホットプレート上で加熱（２００℃×２分間）することにより、レジスト膜（厚さ：約５０ｎｍ）を形成した。
【００３５】
続いて、電子線描画装置（加速電圧：７０ｋＶ）により、レジスト膜に電子線を種々の照射量で照射して潜像を形成した後、現像液（酢酸ヘキシル）に浸漬（２３℃×９０秒）して現像し、リンス液（イソプロピルアルコール）に浸漬（３０秒）することにより、略垂直な側壁を有する矩型のラインのパターン（線幅：１００ｎｍ）を形成した。
【００３６】
このようにして作製されるレジスト膜において、ポジ型レジストを単体で用いた場合には、レジスト面感度が１００μＣ／ｃｍ^２ 程度であるのに対し、上記ポジ型レジスト組成物を用いた場合には、レジスト面感度が８００μＣ／ｃｍ^２ 程度となった。
【００３７】
また、レジスト膜のパターンを原子間力顕微鏡で観察して、ラインエッジラフネスの指標となる寸法揺らぎを求めた。具体的には、レジスト膜での電子線未照射部分の平均高さを基準とし、原子間力顕微鏡のチップの先端径の半分程度の大きさだけ上記基準高さから深い場所（例えば５ｎｍ）のパターンの幅を充分に長い範囲にわたって計測し、この計測した値の標準偏差を寸法揺らぎとして求めた。
【００３８】
その結果、ポジ型レジストを単体で用いたレジスト膜においては、寸法揺らぎが３ｎｍ以上であるのに対し、上記ポジ型レジスト組成物を用いたレジスト膜においては、寸法揺らぎが２．５ｎｍ以下に抑制されていた。
【００３９】
よって、ポジ型レジストに架橋剤および酸発生剤を混合したポジ型レジスト組成物を用いることにより、ラインエッジラフネスを低減したパターンを形成できることが確認できた。
【００４０】
なお、本実施の形態では、電子線で感光するポジ型レジストを用いたが、これに限らず、光やＸ線などの電磁線やイオンビームなどの粒子線など放射線で感光するポジ型レジストに適用することができる。
【００４１】
【発明の効果】
本発明のパターン形成方法およびポジ型レジスト組成物によれば、パターンの側壁への高分子集合体の露出を抑制することができ、ラインエッジラフネスを大幅に低減することができる。
【図面の簡単な説明】
【図１】本発明によるポジ型レジスト組成物を用いて作製したレジスト膜にパターンを形成する場合の状態説明図である。
【図２】従来のポジ型レジストを用いて作製したレジスト膜にパターンを形成する場合の状態説明図である。
【符号の説明】
１ 高分子集合体
２ 高分子集合体１の周囲のレジスト
３ 高分子集合体１の周囲の架橋済レジスト
４ 放射線[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a pattern and a positive resist composition used for manufacturing solid-state devices and functional devices including semiconductors, and is particularly effective when applied to a case where a fine pattern such as 100 nm or less is formed. is there.
[0002]
[Prior art]
In recent years, with further miniaturization of large-scale integrated circuits and active research and development of nanodevices typified by Si single-electron transistors, a technology for processing a structure with high accuracy of 100 nm or less has been required. . In such processing, the accuracy depends on the lithography technology. Lithography technology means that a photosensitive resin (resist) is applied on a substrate to be processed to form a resist film, and a predetermined area on the resist film is selectively exposed to light to cause a chemical change. Is a technique of forming a pattern on a resist film based on the difference in the dissolution rate of a developer between an irradiated area and a non-irradiated area by immersing the latent image in a developer and then immersing it in a developer. The type in which the inside of the irradiation area is dissolved and removed is called a positive type.
[0003]
When a fine pattern having a size of 100 nm or less is formed on a resist film, fine irregularities (line edge roughness) on the surface of the side wall of the pattern cannot be ignored, and pattern size fluctuation (pattern size fluctuation) cannot be ignored. Difference between the maximum value and the minimum value). This dimensional fluctuation is directly linked to the variation of the element characteristics, and therefore it is necessary to suppress the dimensional fluctuation to below the tolerance of the element. Assuming that the tolerance of the dimensional fluctuation is 10% or less of the pattern dimension, for example, when fabricating a quantum device having a width of 30 nm, the tolerance of the dimensional fluctuation is 3 nm or less.
[0004]
For example, it is reported that when the dimensional fluctuation is measured with an atomic force microscope and the width fluctuation of the pattern (the standard deviation σ of the line width of a pattern having a sufficiently long sampling length) is 2.8 nm. (See, for example, Microelectron. Eng., 30 , 419-422 (1996)). Here, assuming that the dimensional fluctuation corresponds to three times (3σ) the width fluctuation, the dimensional fluctuation is about 9 nm. Therefore, in the case of a pattern dimension of 90 nm or less, the dimensional fluctuation exceeds the tolerance. Therefore, when forming a fine pattern having a pattern size of 100 nm or less on a resist film, how to reduce the size fluctuation is extremely important when fabricating a semiconductor element having a size of 100 nm or less, a quantum device having a nanometer size, or the like. Requirements.
[0005]
The main cause of dimensional fluctuation has already been reported (see, for example, Appl. Phys. Lett., 71 , 2388-2390 (1997)). In the report, a resist film using a resist such as polymethyl methacrylate (PMMA) or a copolymer of α-methyl acrylate and α-methylstyrene (trade name: ZEP520 (Zeon Corporation)) was used. It is known that polymer aggregates having a diameter of 20 to 30 nm are present, and these polymer aggregates undergo assembly detachment development during development and are exposed on the side walls of the pattern, resulting in line edge roughness. Is said to be the main cause. Therefore, in order to reduce the dimensional fluctuation, it is necessary to suppress the line edge roughness by eliminating the polymer aggregate. However, it is very difficult to remove the polymer aggregate from the resist film.
[0006]
On the other hand, in order to form a fine pattern on the resist film, it is preferable to use a positive resist excellent in resolution. A typical example is PMMA. It is more preferable to use a crosslinked PMMA having improved heat resistance. This cross-linked PMMA is obtained by introducing a cross-linking reactive group into ordinary PMMA, and improves the heat resistance by reacting the cross-linking reactive groups in the molecule or in the resist. As the crosslinked PMMA, a positive resist (P (MMA-φMA)) obtained by copolymerizing methacrylic acid (MMA) with phenyl methacrylate (φMA) having a benzene ring, methacrylic chloride (MACl) having chlorine, or the like is used. Or φ-MAC), P (MMA-MCl) and the like. The crosslinking reaction is shown below.
[0007]
ＣＯCOOH + 〜COOC ₆ H ₅ → 〜COOCO + C ₆ H ₅ OH (1)
~ COOH + ~ COCl → ~ COOCO + HCl (2)
[0008]
Such a crosslinked positive resist is manufactured as a copolymer that can be easily crosslinked in the molecule or in the resist, and therefore hardly crosslinks between molecules or between the resists. Further, such a cross-linking type positive resist has almost the same basic molecular structure as PMMA, and thus forms a polymer aggregate similarly to the case of PMMA. For this reason, the cross-linking reaction does not affect the properties of the polymer assembly.
[0009]
[Problems to be solved by the invention]
As described above, the polymer aggregates undergo desorption development during development and are exposed on the side walls of the pattern, thereby causing line edge roughness, which causes pattern dimensional fluctuations. Therefore, exposing these polymer aggregates to the side walls of the pattern, that is, suppressing as much as possible the assembly desorption development is extremely important in forming a fine pattern of 100 nm or less.
[0010]
An object of the present invention is to provide a pattern forming method capable of reducing dimensional fluctuation in consideration of a polymer aggregate present in a resist film, and to expose a polymer aggregate on a side wall of a pattern even when a pattern is formed. An object of the present invention is to provide a positive resist composition which does not cause a positive resist composition.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the pattern forming method according to the present invention comprises a cross-linking agent having the following structure between the resists around the polymer aggregate present in the positive resist having aromatic hydrogen in the side chain. It is characterized in that a pattern is formed by photosensitizing after crosslinking.
Embedded image

[0012]
The above-described pattern forming method is characterized in that an acid is used as a catalyst to promote crosslinking between the resists.
[0013]
In order to solve the above-mentioned problems, a positive resist composition according to the present invention has a positive resist having aromatic hydrogen in a side chain, the following structure, and a high resist present in the positive resist. And a cross-linking agent for cross-linking between the resists around the molecular assembly.
Embedded image

[0014]
The positive resist composition described above is characterized by containing an acid generator that generates an acid.
[0016]
[Action]
In describing the operation of the present invention, first, aggregate detachment development will be described with reference to FIG. FIG. 2 is an explanatory diagram of a state in which a pattern is formed on a resist film manufactured using a conventional positive resist.
[0017]
The dissolution rate of the polymer aggregate in the developer depends on the polymer density. The density of the resist inside the polymer assembly 1 is higher than the density of the resist 2 around the polymer assembly 1 (see FIG. 2A). For this reason, in the irradiation area of the radiation 4, a local difference occurs in the dissolution rate between the resist inside the polymer assembly 1 and the surrounding resist 2, and the assembly detachment development occurs. That is, since the molecules of the developer are diffused into the surrounding resist 2 faster than the resist inside the polymer assembly 1, the surrounding resist 2 is dissolved faster than the resist inside the polymer assembly 1. Would. For this reason, the polymer aggregate 1 in which the resist 2 around it is completely dissolved can be desorbed even if the resist in the inside is not dissolved (see FIG. 2B). . Therefore, in the polymer aggregate 1 existing at the boundary of the irradiation area of the radiation 4, only the irradiation area portion of the radiation 4 in the surrounding resist 2 is dissolved, and the portion outside the irradiation area of the radiation 4 is not dissolved. However, they remain without being separated from the resist film (see FIG. 2C).
[0018]
For this reason, the polymer aggregate 1 remaining at the boundary of the irradiation region of the radiation 4 is exposed on the side wall of the pattern, which causes line edge roughness. That is, a local difference in the dissolution rate between the resist inside the polymer assembly 1 and the surrounding resist 2 with respect to the developer causes line edge roughness. Therefore, if the local difference in the dissolution rate between the resist inside the polymer assembly 1 and the surrounding resist 2 is eliminated, even if the polymer assembly 1 is present in the resist film, the line edge roughness is reduced. Can be reduced.
[0019]
Therefore, in the present invention, only the resist 2 around the polymer aggregate 1 is crosslinked in order to eliminate the above-mentioned local difference in the dissolution rate in the resist film. That is, by increasing the molecular weight of the resist around the polymer aggregate 1 by crosslinking only the resist 2 around the polymer aggregate 1, the dissolution rate of the resist 2 around the polymer aggregate 1 in the developing solution is increased. And the dissolution rates of the resist in the resist film are eliminated by making the dissolution rates of the resist inside the polymer assembly 1 and the surrounding resist 2 about the same.
[0020]
This operation will be described in more detail with reference to FIG. FIG. 1 is an explanatory view of a state in which a pattern is formed on a resist film produced using the positive resist composition according to the present invention.
[0021]
The positive resist composition according to the present invention is a mixture of a positive resist and a crosslinking agent. It is more preferable to further mix an acid generator that generates an acid by heat or light. This positive resist composition is applied to a substrate to be processed to form a resist film (see FIG. 1A). The cross-linking agent is mainly dispersed in the resist 2 around the polymer assembly 1. By processing the resist film under the condition that this cross-linking agent causes a cross-linking reaction, only the resist 2 around the polymer aggregate 1 is cross-linked to form a cross-linked resist 3, and the resist inside the polymer aggregate 1 and the surrounding The density with the crosslinked resist 3 becomes substantially uniform. When an acid generator is mixed, the entire resist film is heated or irradiated with light to generate an acid, and the acid 2 is used as a catalyst to chemically crosslink the resist 2 around the polymer assembly 1.
[0022]
After irradiating radiation 4 onto the crosslinked resist film in this manner to form a pattern (see FIG. 1B), when the resist film is immersed in a developer, the region irradiated with radiation 4 dissolves (see FIG. 1B). 1 (c)). Due to the chemical cross-linking described above, the dissolution rates of the resist inside the polymer assembly 1 and the surrounding cross-linked resist 3 in the developing solution are equal, so that the molecules of the developing solution pass through the irradiation area of the radiation 4. The radiation 4 is uniformly diffused in the depth direction, and the irradiation area of the radiation 4 dissolves while keeping the surface flat. For this reason, the pattern side wall also becomes a flat surface directly reflecting the irradiation intensity distribution of the radiation 4 as described above, and does not cause line edge roughness (see FIG. 1D).
[0023]
For such a positive resist composition according to the present invention, when a conventional cross-linked positive resist is used alone, as described above, the resist inside the polymer assembly and the resist around it are used. As a result, cross-linking occurs in the molecule and in the resist, so that the dissolution rate difference between the resist inside the polymer assembly and the surrounding resist is maintained as it is. That is, it is important to crosslink only the resist around the polymer assembly. Therefore, in the present invention, a crosslinking agent or an acid generator is added to the inside of the polymer assembly by adding a crosslinking agent or an acid generator to the positive resist in which the polymer assembly has already been formed. Thus, only the cross-linking of the resist around the polymer assembly is performed while minimizing the penetration of the polymer aggregate.
[0024]
When an acid generator is added, crosslinking between molecules or between resists can be efficiently performed. The acid generator is decomposed by heat or light to generate an acid, and the acid acts as a catalyst for the cross-linking reaction, so that the cross-linking reaction rate can be increased. Such a cross-linking reaction can be very easily generated, and can be carried out by mixing a positive resist and a cross-linking agent, heating the mixture, or adding an acid generator.
[0025]
Examples of the crosslinking agent that causes such a reaction include hexamethoxymethylmelamine, bis (p-acetoxymethylbenzene), terephthalaldehyde-bisethyleneacetal, 1,3,5-trimethyl-2,4,6-triacetoxymethyl. Benzene is exemplified. Examples of the acid generator include onium salts, trisulfonium salts, and triazine derivatives.
[0026]
When a copolymer of methyl α-chloroacrylate and α-methylstyrene (trade name: ZEP520 (Zeon Corporation)) is used as the positive resist, the cross-linking agent may be a molecular weight change required for development. It is desirable that the reaction be performed using benzene ring hydrogen (aromatic hydrogen) in the side chain of ZEP520 as a cross-linking point so as not to affect the reaction. That is, it has at least two or more substituents that undergo an electrophilic substitution reaction with the aromatic hydrogen in the side chain of ZEP520 and does not cause self-crosslinking (no benzene ring hydrogen). Specifically, those having a structure represented by the following chemical formula are preferable, and in particular, 1,2,4,5-tetramethyl-3,6- (diacetoxymethyl) benzene, 1,3,5-trimethyl-2 , 4,6- (triacetoxymethyl) benzene and the like are preferred.
[0027]
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[0028]
On the other hand, as the acid generator, those which decompose without cross-linking with a cross-linking agent to generate an acid are desirable. That is, there is no benzene ring hydrogen, and it decomposes at 200 ° C. or less to generate an acid. Specific examples include cyclohexylmethyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate, β-oxocyclohexyl (2-norbornyl) sulfonium trifluoromethanesulfonate, and the like.
[0029]
It is desirable that such a cross-linking agent or acid generator be mixed in an amount of about 1 to 50 parts by weight with respect to 100 parts by weight of the positive resist.
[0030]
When such a cross-linking agent or acid generator is mixed with ZEP520 and heated, the benzene ring of the side chain of the resist around the polymer aggregate is cross-linked via the cross-linking agent, so that the inside and the periphery of the polymer aggregate are cross-linked. And the developing speed becomes uniform. Here, if a combination of the above-described materials is used, even if a cross-linking reaction occurs, a decomposition reaction of the main chain of the resist by exposure occurs favorably, so that a pattern can be formed on the resist film without any problem. .
[0031]
In this way, by chemically cross-linking the resist around the polymer assembly, the difference in the dissolution rate of the resist present in the developer in the inner region and the peripheral region of the polymer assembly in the developing solution is eliminated. Body detachment development can be suppressed. Thus, exposure of the polymer aggregate to the side wall of the pattern can be suppressed, and line edge roughness can be significantly reduced.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the positive resist composition according to the present invention will be described below, but the present invention is not limited to the following embodiments.
[0033]
After heating a solution of a commercially available electron beam-sensitive positive resist (ZEP520), the solution is quenched, precipitated and fractionated for purification. 30 parts by weight of a crosslinking agent (1,3,5-trimethyl-2,4,6- (triacetoxymethyl) benzene) is mixed with 100 parts by weight of the purified positive resist, and an acid generator (cyclohexyl) is mixed. After mixing 10 parts by weight of methyl (2-oxocyclohexyl) sulfonium trifluoromethanesulfonate, the mixture was dissolved in a solvent (2-methoxyethyl acetate), and then filtered through a filter (0.45 μm) to remove undissolved substances. Was removed to obtain a solution of a positive resist composition. The positive resist was 2 parts by weight with respect to 100 parts by weight of the solvent.
[0034]
Next, the solution of the positive resist composition is applied onto a substrate (material: Si) by a spin coating method (rotation speed: 1500 rpm), and then heated (200 ° C. × 2 minutes) on a hot plate to thereby form a resist. A film (thickness: about 50 nm) was formed.
[0035]
Subsequently, the resist film was irradiated with an electron beam at various doses by an electron beam lithography system (acceleration voltage: 70 kV) to form a latent image, and then immersed in a developing solution (hexyl acetate) (23 ° C. × 90 seconds). ), Developed, and immersed (30 seconds) in a rinse solution (isopropyl alcohol) to form a rectangular line pattern (line width: 100 nm) having substantially vertical side walls.
[0036]
In the resist film thus produced, when a positive resist is used alone, the resist surface sensitivity is about 100 μC / cm ² , whereas when the positive resist composition is used, And the resist surface sensitivity was about 800 μC / cm ² .
[0037]
Further, the pattern of the resist film was observed with an atomic force microscope, and a dimensional fluctuation as an index of line edge roughness was obtained. Specifically, based on the average height of the unirradiated portion of the electron beam in the resist film, a portion (for example, 5 nm) deep from the reference height by about half the tip diameter of the tip of the atomic force microscope. The width of the pattern was measured over a sufficiently long range, and the standard deviation of the measured values was determined as dimensional fluctuation.
[0038]
As a result, the dimensional fluctuation was suppressed to 3 nm or more in the resist film using the positive resist alone, while the dimensional fluctuation was suppressed to 2.5 nm or less in the resist film using the positive resist composition. It had been.
[0039]
Therefore, it was confirmed that a pattern with reduced line edge roughness could be formed by using a positive resist composition in which a crosslinking agent and an acid generator were mixed with a positive resist.
[0040]
In this embodiment, a positive resist sensitive to an electron beam is used. However, the present invention is not limited to this. Can be applied.
[0041]
【The invention's effect】
According to the pattern forming method and the positive resist composition of the present invention, exposure of the polymer aggregate to the side wall of the pattern can be suppressed, and line edge roughness can be significantly reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a state in which a pattern is formed on a resist film produced using a positive resist composition according to the present invention.
FIG. 2 is an explanatory diagram of a state in which a pattern is formed on a resist film manufactured using a conventional positive resist.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 polymer assembly 2 resist around polymer assembly 1 3 cross-linked resist around polymer assembly 1 radiation

Claims (4)

A pattern characterized in that a pattern is formed by photosensitizing after cross- linking between resists around a polymer aggregate present in a positive resist having an aromatic hydrogen in a side chain with a cross-linking agent having the following structure. Forming method.

The pattern forming method according to claim 1,
A method for forming a pattern, comprising: promoting crosslinking between the resists using an acid as a catalyst. A positive resist having aromatic hydrogen in a side chain ,
Which has the following structure, the positive resist composition characterized by comprising a crosslinking agent for crosslinking between resist around the macromolecular assemblies present in the positive resist.

The positive resist composition according to claim 3,
A positive resist composition comprising an acid generator that generates an acid.

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