JP2004235221A - Manufacturing method of mask, forming method of pattern, photomask for measuring distortion and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a mask and a forming method of a pattern, by which mask distortion in an exposure posture is measured without using a coordinate measuring unit, the position for plotting and transferring is corrected and positional precision is improved, and to provide a photomask used for the method and a manufacturing method of a semiconductor device using the method. <P>SOLUTION: A distortion measuring pattern is transferred and a distortion measuring mask is manufactured (ST 12). A distortion measuring pattern same as the above pattern is transferred and a distortion measuring wafer is manufactured (ST13). The distortion measuring mask is kept in a prescribed posture, and the distortion measuring wafer pattern is exposed so that a distortion measuring mask pattern is overlapped with it (ST14). Overlap precision is measured (ST15), and distortion data of the distortion measuring mask in the prescribed posture are created (ST16). The plotting position is corrected in accordance with obtained distortion data. A prescribed transfer pattern having a transmission part and an interruption part of a charged particle beam is formed in a thin film of the mask blanks, and the mask is manufactured (ST21). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１４】
ここで、ｒ_ＭＰはマスク製造プロセスで生じる誤差、ｒ_ＩＰＲＯは座標測定器の測定精度（±３ｎｍ程度）であり、一般には前者の方が大きい。
前者の主要因は電子線描画の位置精度であるが、散乱メンブレンマスクやステンシルマスクの場合は、メンブレン形成に伴う応力緩和なども原理的には寄与する。
ここでは、マスク上の座標を転写倍率（ＥＵＶＬやＥＰＬでは４、ＬＥＥＰＬやＰＸＬでは１）で割って、ウエハ上での相当量に変換している（以下同様とする）。
【００１５】
上記のマスクを露光機に固定すると、重力によりマスクが変形し、パターン変位（マスク歪）ｒ_ｇ が生じる。さらに、このマスクを露光すると、転写光学系の歪ｒ_{ｔｒａｎｓｆｅｒ}などが加わるので、転写パターンの位置Ｕ_２ は次式で表される。
【００１６】
【数２】

【００１７】
従って、座標測定の結果Ｕ_１ からマスク歪ｒ_ｇ を得ることはできない。
【００１８】
一方、ウエハ上の合わせ精度測定マークの位置Ｖ_１ もまた、先行プロセスによるチップ歪等の影響により、理想的な位置Ｒ_０ から変位している。
【００１９】
【数３】

【００２０】
従って、重ね合わせ精度測定の結果Ｗ_１ は次式で与えられる。
【００２１】
【数４】

【００２２】
ここで、ｒ_ＡＬとｒ_ＯＬはそれぞれアライメント精度と重ね合わせ精度測定器の精度（±３ｎｍ程度）である。
このデータにはマスク歪ｒ_ｇ が含まれているが、マスク製造プロセスによる誤差ｒ_ＭＰ（例えば、マスク描画機の精度）や先行プロセスによるチップ歪ｒ_ＷＰの成分も無視できず、マスク歪ｒ_ｇ を正確に計測したことにはならない。
【００２３】
さらに、図１１に示すフローチャートように、マスク歪の計測工程とマスクの製造工程が一体化している従来技術のプロセスでは、得られたマスク歪をもとに精度の高いマスクを再作製していない。従って、露光条件の最適化によりマスク歪を含む誤差全体を最小化するように補正するしか方法がない。
【００２４】
しかし、ＥＵＶＬやＰＸＬのように短波長放射を用いる方法では、マスクとチップの倍率や回転成分しか補正できない。ＥＰＬ、ＩＰＬ、ＬＥＥＰＬのように荷電粒子を用いる方法では、電子／イオン光学系により、より細かい補正が可能であるが、そのような位置補正には限界がある。
例えば、ステンシルマスクの重力によるパターン位置誤差は数十ｎｍになる場合があることが報告されており（非特許文献４参照）、これを荷電粒子の偏向だけで補正することは困難であり、マスク製造時にパターン位置の補正を行う必要がある。
【００２５】
【特許文献１】
米国特許５８３１２７２号明細書
【特許文献２】
特開平６−１８２２０号公報
【非特許文献１】
Ｔ．ウツミ（Ｔ．Ｕｔｓｕｍｉ），「ジャーナル・オブ・バキューム・サイエンス・アンド・テクノロジー（Ｊ．Ｖａｃ．Ｓｃｉ．Ｔｅｃｈｎｏｌ．）」Ｂ１７，ｐ．２８９７（１９９９）
【非特許文献２】
Ｌ．Ｒ．ハリオット（Ｌ．Ｒ．Ｈａｒｒｉｏｔｔ），「ジャーナル・オブ・バキューム・サイエンス・アンド・テクノロジー（Ｊ．Ｖａｃ．Ｓｃｉ．Ｔｅｃｈｎｏｌ．）」Ｂ１５，ｐ．２１３０（１９９７）
【非特許文献３】
Ｈ．Ｃ．ファイファー（Ｈ．Ｃ．Ｐｆｅｉｆｆｅｒ），「ジャパニーズ・ジャーナル・オブ・アプライド・フィジックス（Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．）」３４，ｐ．６６５８（１９９５）
【非特許文献４】
Ｃ．−ｆ．チェンら（Ｃ．−ｆ．Ｃｈｅｎ ｅｔ ａｌ．），「ジャーナル・オブ・バキューム・サイエンス・アンド・テクノロジー（Ｊ．Ｖａｃ．Ｓｃｉ．Ｔｅｃｈｎｏｌ．）」Ｂ１９，ｐ．２６４６（２００１）
【００２６】
【発明が解決しようとする課題】
上記の座標測定時と露光時でマスクの姿勢／保持方法が異なるので、実際に転写されるパターンには、座標測定では観測されない位置誤差が生じるという問題に対しては、（１）露光姿勢に近い状態で測定が可能なように座標測定器を改造する、あるいは（２）座標測定データをなんらかのルールで変換して、露光姿勢での位置精度誤差を算出することも考えられる。
【００２７】
しかしながら、座標測定器は非常に高価であり、測定速度が遅いので（一点６秒以上）、座標測定器の利用を前提としたマスク製造プロセスはスループットが低く、コストが高くなってしまうという問題がある。
また、（１）のような改造をして、普通のＰＭやウエハの測定と共用できなくなると不都合である。さらに、不用意な改造により、保証されている精度が達成できない可能性もある。
（２）に関しては、マスクの上下を反転させた時のパターン変位を正確に予想するアルゴリズムを考案する必要があり、簡単には行うことができない。
【００２８】
本発明は上記の問題点に鑑みてなされたものであり、従って本発明は、座標測定器を用いずに露光姿勢でのマスク歪を計測し、これを基に描画や転写の位置補正を行い、位置精度をより高めることができるマスクの製造方法あるいはパターンの形成方法と、それらに用いる歪計測用フォトマスク、さらにはマスクの製造方法およびパターンの形成方法を用いた半導体装置の製造方法を提供することを目的とする。
【００２９】
【課題を解決するための手段】
上記の目的を達成するため、本発明のマスクの製造方法は、歪計測用フォトマスクに形成された歪計測用パターンを転写して、少なくとも１層の薄膜を有するマスクブランクスの前記薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する工程と、前記歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する工程と、前記歪計測用ウエハの前記歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成する工程と、前記感光層に対して所定の距離を離間して前記歪計測用マスクを所定の姿勢で保持し、前記歪計測用ウエハパターンに対して前記歪計測用マスクパターンが重なるように、荷電粒子線により前記感光層を露光する工程と、前記歪計測用ウエハパターンと前記感光層に転写された前記歪計測用マスクパターンとの重ね精度を測定し、前記所定の姿勢における前記歪計測用マスクの歪データを生成する工程と、前記歪データに応じて描画位置を補正してパターンを描画して、少なくとも１層の薄膜を有するマスクブランクスの前記薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成し、マスクを作製する工程とを有する。
【００３０】
上記の本発明のマスクの製造方法は、歪計測用フォトマスクに形成された歪計測用パターンを転写して、マスクブランクスの薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する。
一方、上記と同一の歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する。
次に、歪計測用ウエハの歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成し、感光層に対して所定の距離を離間して歪計測用マスクを所定の姿勢で保持し、歪計測用ウエハパターンに対して歪計測用マスクパターンが重なるように、荷電粒子線により感光層を露光する。
次に、歪計測用ウエハパターンと感光層に転写された歪計測用マスクパターンとの重ね精度を測定し、所定の姿勢における歪計測用マスクの歪データを生成し、得られた歪データに応じて描画位置を補正してパターンを描画して、マスクブランクスの薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成し、マスクを作製する。
【００３１】
また、上記の目的を達成するため、本発明のパターンの形成方法は、歪計測用フォトマスクに形成された歪計測用パターンを転写して、少なくとも１層の薄膜を有するマスクブランクスの前記薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する工程と、前記歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する工程と、前記歪計測用ウエハの前記歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成する工程と、前記感光層に対して所定の距離を離間して前記歪計測用マスクを所定の姿勢で保持し、前記歪計測用ウエハパターンに対して前記歪計測用マスクパターンが重なるように、荷電粒子線により前記感光層を露光する工程と、前記歪計測用ウエハパターンと前記感光層に転写された前記歪計測用マスクパターンとの重ね精度を測定し、前記所定の姿勢における前記歪計測用マスクの歪データを生成する工程と、少なくとも１層の薄膜を有するマスクブランクスの前記薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成し、マスクを作製する工程と、前記歪データに応じて転写位置を補正して、前記マスクを用いて被露光ウエハにパターン露光する工程とを有する。
【００３２】
上記の本発明のパターンの形成方法は、歪計測用フォトマスクに形成された歪計測用パターンを転写して、マスクブランクスの薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する。
一方、上記と同一の歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する。
次に、歪計測用ウエハの歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成し、感光層に対して所定の距離を離間して歪計測用マスクを所定の姿勢で保持し、歪計測用ウエハパターンに対して歪計測用マスクパターンが重なるように、荷電粒子線により感光層を露光する。
次に、歪計測用ウエハパターンと感光層に転写された前記歪計測用マスクパターンとの重ね精度を測定し、所定の姿勢における歪計測用マスクの歪データを生成し、マスクブランクスの薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成する。
次に、マスクを作製し、歪データに応じて転写位置を補正して、マスクを用いて被露光ウエハにパターン露光する。
【００３３】
また、上記の目的を達成するため、本発明の歪計測用フォトマスクは、歪計測用パターンとして、マスクアライメント用パターン、ウエハアライメント用パターン、重ね精度測定用マスクパターンおよび重ね精度測定用ウエハパターンを有し、前記マスクアライメント用パターンおよび前記重ね精度測定用マスクパターンに対して、前記ウエハアライメント用パターンおよび前記重ね精度測定用ウエハパターンが、それぞれ同一の方向および距離にずれた位置に形成されている。
【００３４】
上記の本発明の歪計測用フォトマスクは、歪計測用パターンとして、マスクアライメント用パターン、ウエハアライメント用パターン、重ね精度測定用マスクパターンおよび重ね精度測定用ウエハパターンを有しており、マスクアライメント用パターンおよび重ね精度測定用マスクパターンに対して、ウエハアライメント用パターンおよび重ね精度測定用ウエハパターンが、それぞれ同一の方向および距離にずれた位置に形成されている構成である。
【００３５】
また、上記の目的を達成するため、本発明の半導体装置の製造方法は、被露光ウエハにパターン露光する工程を有する半導体装置の製造方法であって、歪計測用フォトマスクに形成された歪計測用パターンを転写して、少なくとも１層の薄膜を有するマスクブランクスの前記薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する工程と、前記歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する工程と、前記歪計測用ウエハの前記歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成する工程と、前記感光層に対して所定の距離を離間して前記歪計測用マスクを所定の姿勢で保持し、前記歪計測用ウエハパターンに対して前記歪計測用マスクパターンが重なるように、荷電粒子線により前記感光層を露光する工程と、前記歪計測用ウエハパターンと前記感光層に転写された前記歪計測用マスクパターンとの重ね精度を測定し、前記所定の姿勢における前記歪計測用マスクの歪データを生成する工程と、前記歪データに応じて描画位置を補正してパターンを描画して、少なくとも１層の薄膜を有するマスクブランクスの前記薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成し、マスクを作製する工程と、前記歪データに応じて転写位置を補正して、前記マスクを用いて被露光ウエハにパターン露光する工程とを有する。
【００３６】
上記の本発明の半導体装置の製造方法は、歪計測用フォトマスクに形成された歪計測用パターンを転写して、マスクブランクスの薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する。一方、上記と同一の歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する。
次に、歪計測用ウエハの歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成し、感光層に対して所定の距離を離間して歪計測用マスクを所定の姿勢で保持し、歪計測用ウエハパターンに対して歪計測用マスクパターンが重なるように、荷電粒子線により前記感光層を露光する。
次に、歪計測用ウエハパターンと感光層に転写された歪計測用マスクパターンとの重ね精度を測定し、上記の所定の姿勢における歪計測用マスクの歪データを生成し、この歪データに応じて描画位置を補正してパターンを描画して、少なくとも１層の薄膜を有するマスクブランクスの当該薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成し、マスクを作製する。
さらに、上記の歪データに応じて転写位置を補正して、マスクを用いて被露光ウエハにパターン露光する。
【００３７】
【発明の実施の形態】
本実施形態は、ＩＰＲＯに代表される座標測定器を用いずにマスク歪を計測する方法に関し、座標測定器よりも安価で測定時間の短い重ね合わせ精度測定器を用い、露光姿勢でのマスク歪を計測し、生産マスクのパターン描画時もしくは露光時にそのデータを用いた位置補正を行う。
以下に、本実施形態に係るマスクの製造方法、パターンの形成方法およびフォトマスクについて、図面を参照して説明する。
【００３８】
図１は、本実施形態に係る散乱メンブレンマスクやステンシルマスクなどのマスクを作製し、それを用いてパターン露光する方法のフローチャートである。
本実施形態に係る方法においては、マスク歪データの生成工程部分と生産マスク製造およびそれを用いた露光工程部分とが明確に分離しており、マスク外形と露光機内での保持方法が変わらない限り、前者は一回行うだけでよい。
【００３９】
まず、マスク歪データの生成工程部分において、後述する歪計測用パターンを含む歪計測用フォトマスク（ＰＭ）を作製する（ＳＴ１１）。
この歪計測用ＰＭに関しては、座標測定器により座標測定を行ってもよく、また、行わなくてもよい。例えば、ＰＭの作製をマスクメーカーに外注する場合、マスクメーカーにおいてはＰＭ製造における位置精度（長寸法精度）保証がマスクメーカーによりルーチン的に行われており、位置精度を指定すればマスクメーカーが座標測定をすることになり、本発明の実施者が座標測定器を保有する必要はない。
【００４０】
図２は、上記の歪計測用フォトマスクに形成される歪計測用パターンを示す平面図である。
歪計測用フォトマスク１０に形成されている歪計測用パターンは、アライメント用パターン１１として、マスクアライメント用パターン１１ｍおよびウエハアライメント用パターン１１ｗが形成されており、また、重ね精度測定用パターン１２として、重ね精度測定用マスクパターン１２ｍおよび重ね精度測定用ウエハパターン１２ｗが形成されている。
ここで、マスクアライメント用パターン１１ｍおよび重ね精度測定用マスクパターン１２ｍに対して、ウエハアライメント用パターン１１ｗおよび重ね精度測定用ウエハパターン１２ｗが、それぞれ同一の方向および距離にずれた位置に形成されている。この方向および距離を並進ベクトルｄで示すと、マスクアライメント用パターン１１ｍおよび重ね精度測定用マスクパターン１２ｍと、ウエハアライメント用パターン１１ｗおよび重ね精度測定用ウエハパターン１２ｗが同一の並進ベクトルｄで関連付けられている。
ここで、マスクアライメント用パターン１１ｍとウエハアライメント用パターン１１ｗは、それぞれのリソグラフィ法によって標準的なマークが存在し、それをそのまま用いることができる。
重ね精度測定用マスクパターン１２ｍと重ね精度測定用ウエハパターン１２ｗは一対のパターンであり、例えば後述の”ｂａｒ−ｉｎ−ｂａｒ”と呼ばれるパターンや”ｂｏｘ−ｉｎ−ｂａｒ”と呼ばれるパターンなどが用いられる。
【００４１】
次に、歪計測用フォトマスクに形成された歪計測用パターンを転写して、少なくとも１層の薄膜を有するマスクブランクスの当該薄膜に荷電粒子線の透過部と遮断部を有する歪計測用マスクパターンを形成し、歪計測用マスクを作製する（ＳＴ１２）。
例えば、歪計測用マスクの作製は、歪計測用フォトマスクから歪計測用パターンを転写露光し、現像して、得られたレジストパターンをマスクとしてエッチングなどを行い、マスクブランクスに歪計測用マスクパターンを形成して歪計測用マスクとする。
【００４２】
歪計測用マスクを作製する工程について、図３および図４に示す断面図を用いて説明する。
まず、図３（ａ）に示すように、歪計測用マスクの基板となるシリコンウエハ２０の一方の面上に酸化シリコン層２１を形成し、その上層にシリコン層２２を形成し、ＳＯＩ構造のウエハを形成する。
さらに、シリコンウエハ２０の他方の面上にも酸化シリコン層２３を形成する。
【００４３】
次に、図３（ｂ）に示すように、シリコンウエハ２０の他方の面上の酸化シリコン層２３を薄膜のマスクとなるシリコン層２２を支持する梁のパターンを残すようにエッチング加工し、さらにパターン加工された酸化シリコン層２３をマスクとして酸化シリコン層２３側から酸化シリコン層２１に達するまでシリコンウエハ２０をエッチング加工する。
シリコンと酸化シリコンのエッチング速度は数桁以上異なるため、酸化シリコン層２３および酸化シリコン層２１に対して選択的にシリコンウエハ２０がエッチングされる。エッチングは酸化シリコン層２１で停止する。
【００４４】
次に、図３（ｃ）に示すように、例えばフッ酸を用いたウェットエッチングにより、シリコンウエハ２０のエッチングにより露出した部分の酸化シリコン層２１を除去する。この結果、シリコン層からなるメンブレン２４が形成される。メンブレン２４を区分する部分のシリコンウエハ２０は梁２５となり、メンブレン２４を支持する。
また、このウェットエッチングにより、酸化シリコン層２３も同時に除去される。
このようにして、少なくとも１層の薄膜（メンブレン）を有するマスクブランクスが形成される。
【００４５】
次に、図４（ａ）に示すように、メンブレン２４上にレジスト膜２６を成膜し、前述の歪計測用フォトマスク１０を用いて、露光する。歪計測用フォトマスク１０に形成された、マスクアライメント用パターン１１ｍ、ウエハアライメント用パターン１１ｗ、重ね精度測定用マスクパターン１２ｍおよび重ね精度測定用ウエハパターン１２ｗなどの歪計測用パターンは、例えば数μｍ〜数十μｍ程度の大きさであり、パターンが大きいために光などで露光することができる。
このとき、例えば歪計測用フォトマスク１０の一方の表面Ｓが上面を向くようにする。
【００４６】
次に、図４（ｂ）に示すように、レジスト膜２６を現像する。
この結果、レジスト膜２６にはマスクアライメント用パターン２７ｍおよびウエハアライメント用パターン２７ｗからなるアライメント用パターン２７と、重ね精度測定用マスクパターン２８ｍおよび重ね精度測定用ウエハパターン２８ｗからなる重ね精度測定用パターン２８とを有する歪計測用パターンが転写される。
【００４７】
次に、図４（ｃ）に示すように、上記のパターン加工されたレジスト膜２６をマスクとして、メンブレン２４に対するエッチング処理を行い、メンブレン２４にマスクアライメント用パターン２９ｍおよびウエハアライメント用パターン２９ｗからなるアライメント用パターン２９と、重ね精度測定用マスクパターン３０ｍおよび重ね精度測定用ウエハパターン３０ｗからなる重ね精度測定用パターン３０とを有する歪計測用マスクパターンを形成する。
この後、レジスト膜２６を除去することで、歪計測用マスク３１となる。
歪計測用マスク３１において、メンブレン２４は歪計測用パターンに沿った荷電粒子線の透過部と遮断部を有する。
【００４８】
一方、歪計測用フォトマスクに形成された歪計測用パターンをウエハに転写して、歪計測用ウエハパターンを形成し、歪計測用ウエハを作製する（ＳＴ１３）。
例えば、歪計測用ウエハの作製は、歪計測用フォトマスクから歪計測用パターンを転写露光し、現像して、得られたレジストパターンをマスクとしてエッチングなどを行い、ウエハに歪計測用ウエハパターンを加工して歪計測用ウエハとする。
【００４９】
歪計測用ウエハを作製する工程について、図５に示す断面図を用いて説明する。
まず、図５（ａ）に示すように、シリコンウエハ４０上にレジスト膜４１を成膜し、前述の歪計測用フォトマスク１０を用いて、露光する。歪計測用フォトマスク１０に形成された、マスクアライメント用パターン１１ｍ、ウエハアライメント用パターン１１ｗ、重ね精度測定用マスクパターン１２ｍおよび重ね精度測定用ウエハパターン１２ｗなどの歪計測用パターンが露光される。
このとき、歪計測用ウエハに形成する歪計測用パターンと歪計測用マスク３１に形成する歪計測用パターンとが丁度反転した関係となるようにするため、例えば歪計測用フォトマスク１０の一方の表面Ｓが下面（シリコンウエハ４０側）を向くようにする。
【００５０】
次に、図５（ｂ）に示すように、レジスト膜４１を現像する。
この結果、レジスト膜４１にはマスクアライメント用パターン４２ｍおよびウエハアライメント用パターン４２ｗからなるアライメント用パターン４２と、重ね精度測定用マスクパターン４３ｍおよび重ね精度測定用ウエハパターン４３ｗからなる重ね精度測定用パターン４３とを有する歪計測用パターンが転写される。
【００５１】
次に、図５（ｃ）に示すように、上記のパターン加工されたレジスト膜４１をマスクとして、シリコンウエハ４０に対するエッチング処理を行い、マスクアライメント用パターン４４ｍおよびウエハアライメント用パターン４４ｗからなるアライメント用パターン４４と、重ね精度測定用マスクパターン４５ｍおよび重ね精度測定用ウエハパターン４５ｗからなる重ね精度測定用パターン４５とを有する歪計測用ウエハパターンを形成する。
この後、レジスト膜４１を除去することで、歪計測用ウエハ４６となる。
【００５２】
上記の歪計測用ウエハパターンを形成する工程は、１回エッチングをするだけの簡単なプロセスなので、チップ歪は小さく、ウエハ上の重ね精度測定用パターンの位置精度は主にフォトリソグラフィの精度で決まる。
一方、歪計測用マスクとなるマスクブランクスに露光された重ね精度測定用パターンの位置精度も、同様にフォトリソグラフィの精度で決まる。この精度は、最新のスキャナーで１０ｎｍ以下である。
【００５３】
ここで、上記の歪計測用マスクを形成するための歪計測用フォトマスクを用いての露光と、歪計測用ウエハを形成するための歪計測用フォトマスクを用いての露光は、上述のようにパターンとが丁度反転した関係とすることを除いて、可能な限り同じ条件で露光する。
また、歪計測用マスクと歪計測用ウエハは、ぞれぞれ複数枚作製して、複数の組み合わせを準備して以下の工程を進めることが好ましい。
【００５４】
次に、歪計測用ウエハの歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層を形成し、感光層に対して所定の距離を離間して歪計測用マスクを所定の姿勢で保持し、歪計測用ウエハパターンに対して歪計測用マスクパターンが重なるように、荷電粒子線により感光層を露光する（ＳＴ１４）。
【００５５】
上記の感光層を形成する工程および歪計測用ウエハパターンに対して歪計測用マスクパターンが重なるように露光する工程について、図６に示す断面図を用いて説明する。
図６（ａ）に示すように、歪計測用ウエハ４６の歪計測用ウエハパターン形成面上に荷電粒子線により感光する感光層４７を形成した後、歪計測用マスク３１のメンブレン２４側が感光層４７側となり、メンブレン２４と感光層４７の距離が所定の値となるように、歪計測用マスク３１を保持する。
【００５６】
上記の歪計測用マスク３１を位置合わせする位置は、図７の平面図に示すようにする。
即ち、歪計測用マスクパターンの内のマスクアライメント用パターン２９ｍと、歪計測用ウエハパターンの内のウエハアライメント用パターン４４ｗとが重なるようにする。これは、マスクアライメント用パターン１１ｍおよび重ね精度測定用マスクパターン１２ｍと、ウエハアライメント用パターン１１ｗおよび重ね精度測定用ウエハパターン１２ｗを関連付けている並進ベクトルｄの方向および距離で、歪計測用ウエハパターンに対して歪計測用マスクパターンをずらして配置することに相当する。
【００５７】
上記のように歪計測用マスク３１と歪計測用ウエハ４６を配置した状態で、歪計測用マスク３１側から荷電粒子線（不図示）を照射し、メンブレン２４の透過部である歪計測用マスクパターンを透過させ、感光層４７をパターン露光する。このとき、転写光学系の歪が最小の条件で露光を行う。例えば、ＬＥＥＰＬならば副偏向をかけずに、可能な限り平行な電子線でマスクを走査する。
【００５８】
上記のように露光した後、現像することで図６（ｂ）に示す状態となり、レジスト膜４７にマスクアライメント用パターン４８ｍおよびウエハアライメント用パターン４８ｗからなるアライメント用パターン４８と、重ね精度測定用マスクパターン４９ｍおよび重ね精度測定用ウエハパターン４９ｗからなる重ね精度測定用パターン４９とを有する歪計測用マスクパターンが転写される。
【００５９】
次に、歪計測用ウエハパターンと感光層に転写された歪計測用マスクパターンとの重ね精度を測定し（ＳＴ１５）、所定の姿勢における歪計測用マスクの歪データを生成する（ＳＴ１６）。
【００６０】
重ね精度の測定は、歪計測用ウエハパターンの内の重ね精度測定用ウエハパターン４５ｗと、歪計測用マスクパターンの内の重ね精度測定用マスクパターン４９ｍとの重なりを、例えば日立社のＬＡ３２００あるいはニコン社のＮＲＭ１０００などの重ね合わせ精度測定装置により測定する。
【００６１】
図８（ａ）は、歪計測用フォトマスク１０上の歪計測用パターンにおける重ね精度測定用マスクパターン１２ｍと重ね精度測定用ウエハパターン１２ｗの配置を示す平面図であり、重ね精度測定用マスクパターン１２ｍと重ね精度測定用ウエハパターン１２ｗとが並進ベクトルｄで関連付けられていることを示している。
ここでは、重ね精度測定用マスクパターン１２ｍと重ね精度測定用ウエハパターン１２ｗが、それぞれ”ｂａｒ”と呼ばれる４本の直線状のパターンが正方形を構成するように配置されたパターンであり、重ね精度測定用マスクパターン１２ｍよりも重ね精度測定用ウエハパターン１２ｗの方が大きな正方形となる。
【００６２】
また、図８（ｂ）は、歪計測用ウエハパターンの内の重ね精度測定用マスクパターン４５ｍおよび重ね精度測定用ウエハパターン４５ｗからなる重ね精度測定用パターン４５と、感光層に転写された歪計測用マスクパターンの内の重ね精度測定用マスクパターン４９ｍおよび重ね精度測定用ウエハパターン４９ｗからなる重ね精度測定用パターン４９との配置を示す平面図である。
重ね精度測定用マスクパターン４９ｍおよび重ね精度測定用ウエハパターン４９ｗが並進ベクトルｄの方向および距離でずれて配置されることにより、丁度重ね精度測定用ウエハパターン４５ｗの中央部に重ね精度測定用マスクパターン４９ｍが配置される。このときの重ね精度測定用ウエハパターン４５ｗの中心と重ね精度測定用マスクパターン４９ｍの中心とのずれから、重ね精度を測定することができる。
【００６３】
上記の重ね精度の測定で観測される量は、基本的に上述のＷ_１ であるが、（１）ウエハとマスクのマークが同一のＰＭで形成されている、（２）ウエハ上のマーク形成プロセスが単純でチップ歪ｒ_ＷＰが小さい、（３）転写光学系の歪ｒ_{ｔｒａｎ ｓｆｅｒ}が最小の条件で露光を行っている、という理由により、従来技術よりも｜δＷ_１ ｜が小さいので、重ね合わせ誤差の主要因はマスク歪になる。
【００６４】
上記のように、露光装置が備えるアライメント光学系により、歪計測用マスク上のマスクアライメント用パターン２９ｍと歪計測用ウエハ上のウエハアライメント用パターン４４ｗを重ねるように、歪計測用マスクと歪計測用ウエハの相対位置が保持され、即ち相対位置がｄだけシフトされ、露光が行われる。
このとき、図８（ｂ）に示すように、一対の重ね精度測定用マスクパターン４９ｍと重ね精度測定用ウエハパターン４５ｗが重なり合い、その重ね合わせ精度を測定することが可能である。並進ベクトルｄの大きさは、近接するマスクアライメント用パターン２９ｍとウエハアライメント用パターン４４ｗとが重なり合わない範囲で、できるだけ小さい方が望ましい。アライメント用パターンや重ね精度測定用パターンは数μｍ〜数十μｍの大きさなので、その程度以上離れていればよい。
【００６５】
以上で、図１に示すように、マスク歪データの生成工程部分が完了する。上記のように得られた歪データは、生産マスクの製造およびそれを用いた露光工程部分において、生産マスクのパターン描画の描画位置補正に利用できる。それにより、重力によるマスク変形の影響を受けないようにパターン位置を補正できる。また、露光装置にフィードバックすれば、転写位置の補正も可能である。
ここで生産マスクとは、上記の歪計測用マスクと異なり、所望の回路パターンや配線パターンなどのパターンが形成され、実際の半導体装置の製造において露光するのに用いるマスクである。
【００６６】
生産マスクの製造およびそれを用いた露光工程部分において、まず、上記のようにして得た歪データに応じて描画位置を補正してパターンを描画して、少なくとも１層の薄膜を有するマスクブランクスの当該薄膜に荷電粒子線の透過部と遮断部を有する所定の転写パターンを形成し、生産マスクを作製する（ＳＴ２１）。
例えば、図９（ａ）の断面図に示すように、生産マスク６５においてシリコンウエハ６０上に酸化シリコン層６１が形成されて、その上層にシリコン層のメンブレン６２が形成されている。メンブレン６２を区分する部分のシリコンウエハ６０は梁６３となり、メンブレン６２を支持する。
上記のメンブレン６２には、所定の荷電粒子線の透過部となる開口パターン６４が形成されている。
【００６７】
次に、上記で得られた歪データに応じて転写位置を補正して、生産マスクを用いて被露光ウエハにパターンをテスト露光する（ＳＴ２２）。
例えば、図９（ｂ）の断面図に示すように、被露光ウエハ７０上に形成されたレジスト膜７１に対して、生産マスク６５のメンブレン６２側がレジスト膜７１側となり、メンブレン６２とレジスト膜７１の距離が所定の値となるように、生産マスク６５を保持する。
上記の状態でテスト露光を行い、上記と同様に重ね精度を測定し（ＳＴ２３）、目標値以内であれば、上記の生産マスクを用い、上記の露光条件にて本番露光を行う（ＳＴ２４）。重ね精度が目標値からはずれている場合は、露光条件を変更して再度テスト露光を行うことを繰り返す。
【００６８】
上記においては、得られた歪データに応じて、生産マスクのパターン描画の描画位置補正およびその生産マスクを用いて露光するときの転写位置補正の両方に用いているが、いずれか一方のみにフィードバックする方法としてもよい。
【００６９】
（変形例）
図１０（ａ）は、歪計測用フォトマスク１０上の歪計測用パターンにおける重ね精度測定用マスクパターン１２ｍと重ね精度測定用ウエハパターン１２ｗの配置を示す平面図である。図８（ａ）と同様であるが、重ね精度測定用マスクパターン１２ｍが”ｂａｒ”と呼ばれる４本の直線状のパターンではなく、矩形の形状の重ね精度測定用マスクパターン１２ｍ’となっていることが図８と異なる。重ね精度測定用マスクパターン１２ｍ’と重ね精度測定用ウエハパターン１２ｗとは、上記と同様に並進ベクトルｄで関連付けられている。
また、図１０（ｂ）は、歪計測用ウエハパターンの内の重ね精度測定用マスクパターン４５ｍ’および重ね精度測定用ウエハパターン４５ｗからなる重ね精度測定用パターン４５と、感光層に転写された歪計測用マスクパターンの内の重ね精度測定用マスクパターン４９ｍ’および重ね精度測定用ウエハパターン４９ｗからなる重ね精度測定用パターン４９との配置を示す平面図である。
重ね精度測定用マスクパターン４９ｍ’および重ね精度測定用ウエハパターン４９ｗが並進ベクトルｄの方向および距離でずれて配置されることにより、直線状のパターンが正方形状に並べられた重ね精度測定用ウエハパターン４５ｗの中央部に、矩形形状の重ね精度測定用マスクパターン４９ｍ’が配置される。このときの重ね精度測定用ウエハパターン４５ｗの中心と重ね精度測定用マスクパターン４９ｍ’の中心とのずれから、重ね精度を測定することができる。
【００７０】
本実施形態において、重ね精度を測定するために用いる重ね合わせ測定器は座標測定器の数分の一以下の価格であり、スループットも２．５秒／マーク程度と迅速に処理を行うことができ、これによってマスクの位置精度評価が素早くできる。
本実施形態のマスクの製造方法とそれを用いたパターンの形成方法によれば、座標測定器を用いずに露光姿勢でのマスク歪を計測し、これを基に描画や転写の位置補正を行い、位置精度をより高めることができる。
【００７１】
また、ウエハＦＡＢには、広く普及している重ね合わせ精度測定器によって、簡便にマスクの歪計測が可能であり、マスクショップでなく、ユーザーサイドでもマスク精度を評価できる。
【００７２】
本発明は、上記の実施形態に限定されない。
例えば、本実施形態においては、ステンシルマスクについて説明したが、各種論文および特許により公知となっているマスク製造プロセスを適用することにより、各ＮＧＬ用のマスクとすることができる。
また、本実施形態においては、歪計測用フォトマスクや歪計測用マスクのパターンとして、アライメント用パターンと重ね精度測定用パターンのみを形成しているが、その他、より実用の系に近づけるために、適当な回路パターンを含むようなパターンとしてもよい。
また、本発明のマスクの製造方法やパターンの形成方法は、被露光ウエハにパターン露光する工程を有する半導体装置の製造方法において、パターン露光するためのマスクの製造方法やパターンの形成方法として適用できる。
その他、本発明の要旨を逸脱しない範囲で種々の変更が可能である。
【００７３】
【発明の効果】
本発明のマスクの製造方法によれば、座標測定器を用いずに露光姿勢でのマスク歪を計測し、これを基に描画や転写の位置補正を行い、位置精度をより高めることができる。
【００７４】
本発明のパターンの形成方法によれば、座標測定器を用いずに露光姿勢でのマスク歪を計測し、これを基に描画や転写の位置補正を行い、位置精度をより高めることができる。
【００７５】
本発明の歪計測用フォトマスクを用いることにより、マスクの製造方法とそれを用いたパターンの形成方法において、座標測定器を用いずに露光姿勢でのマスク歪を計測し、これを基に描画や転写の位置補正を行い、位置精度をより高めることができる。
【００７６】
本発明の半導体装置の製造方法によれば、半導体装置を製造するための露光工程で用いるマスクにおいて、座標測定器を用いずに露光姿勢でのマスク歪を計測し、これを基に描画や転写の位置補正を行い、位置精度をより高めることができる。
【図面の簡単な説明】
【図１】図１は、実施形態に係るマスクを作製し、それを用いてパターン露光する方法のフローチャートである。
【図２】図２は、実施形態に係る歪計測用フォトマスクに形成される歪計測用パターンを示す平面図である。
【図３】図３（ａ）〜（ｃ）は、実施形態に係るマスクを作製し、それを用いてパターン露光する方法の工程を示す断面図である。
【図４】図４（ａ）〜（ｃ）は、実施形態に係るマスクを作製し、それを用いてパターン露光する方法の工程を示す断面図である。
【図５】図５（ａ）〜（ｃ）は、実施形態に係るマスクを作製し、それを用いてパターン露光する方法の工程を示す断面図である。
【図６】図６（ａ）および（ｂ）は、実施形態に係るマスクを作製し、それを用いてパターン露光する方法の工程を示す断面図である。
【図７】図７は実施形態において歪計測用マスクを位置合わせする位置を示す平面図である。
【図８】図８（ａ）は、実施形態に係る重ね精度測定用マスクパターンと重ね精度測定用ウエハパターンの配置を示す平面図であり、図８（ｂ）は、重ね精度測定用ウエハパターンと重ね精度測定用マスクパターンの配置を示す平面図である。
【図９】図９（ａ）および（ｂ）は、実施形態に係るマスクを作製し、それを用いてパターン露光する方法の工程を示す断面図である。
【図１０】図１０（ａ）は、変形例に係る重ね精度測定用マスクパターンと重ね精度測定用ウエハパターンの配置を示す平面図であり、図１０（ｂ）は、重ね精度測定用ウエハパターンと重ね精度測定用マスクパターンの配置を示す平面図である。
【図１１】図１１は、従来例に係るマスクを作製し、それを用いてパターン露光する方法のフローチャートである。
【符号の説明】
１０…歪計測用フォトマスク、１１…アライメント用パターン、１１ｍ…マスクアライメント用パターン、１１ｗ…ウエハアライメント用パターン、１２…重ね精度測定用パターン、１２ｍ，１２ｍ’…重ね精度測定用マスクパターン、１２ｗ…重ね精度測定用ウエハパターン、２０…シリコンウエハ、２１…酸化シリコン層、２２…シリコン層、２３…酸化シリコン層、２４…メンブレン、２５…梁、２６…レジスト膜、２７，２９，４２，４４，４８…アライメント用パターン、２７ｍ，２９ｍ，４２ｍ，４４ｍ，４８ｍ…マスクアライメント用パターン、２７ｗ，２９ｗ，４２ｗ，４４ｗ，４８ｗ…ウエハアライメント用パターン、２８，３０，４３，４５，４９…重ね精度測定用パターン、２８ｍ，３０ｍ，４３ｍ，４５ｍ，４５ｍ’，４９ｍ，４９ｍ’…重ね精度測定用マスクパターン、２８ｗ，３０ｗ，４３ｗ，４５ｗ，４９ｗ…重ね精度測定用ウエハパターン、４０…シリコンウエハ、４１…レジスト膜、６０…シリコンウエハ、６１…酸化シリコン層、６２…メンブレン、６３…梁、６４…開口パターン、６５…生産マスク、７０…被露光ウエハ、７１…レジスト膜。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a mask and a method of forming a pattern used in a lithography process of manufacturing a semiconductor device, a photomask for measuring strain used in manufacturing the mask, and a method of manufacturing a semiconductor device using the method of manufacturing a mask. About.
[0002]
[Prior art]
As a next generation exposure technology (NGL; Next Generation Lithography) instead of photolithography, a transfer type exposure method using an electron beam, an ion beam, an X-ray, or extreme ultraviolet (EUV) light has been developed.
Since these NGLs are applied to device production in the 65 nm generation and beyond, the requirements for mask positional accuracy are very strict.
[0003]
For example, according to the ITRS roadmap (2001 version), the positional accuracy required for a 65-nm generation DRAM (dynamic random access memory) is 23 nm (on a wafer).
[0004]
In particular, in the case of X-ray lithography (PXL; Proximity X-ray Lithography) or low-energy electron-beam proximity transfer lithography (LEEPL; Low Energy Electron-beam Proximity Projection Lithography), the same-size mask is used as a basic mask on an equal-size mask. Position accuracy must be achieved.
However, in the LEEPL, the transfer pattern position can be corrected by changing the incident direction of the electron beam with the sub-deflection lens (see Non-patent Document 1 and Patent Document 1), so that the error budget may be reduced. .
[0005]
On the other hand, electron beam / ion beam transfer lithography (EPL; Electron-beam projection lithography / IPL; Ion-beam projection lithography) and EUV lithography (EUVL) generally have a reduction ratio of 4, and therefore, the precision is a reduction projection exposure method. Although it seems that the demand for the position accuracy is relatively relaxed, the demand for the positional accuracy is rather severe in consideration of the error caused by the transfer characteristic of the reduction optical system.
For example, according to the ITRS roadmap (2001 version), the positional accuracy required for the 65 nm generation EUVL mask is 14 nm.
[0006]
In a group of NGLs such as PXL, LEEPL, EPL, and IPL, a mask having low mechanical strength such as a scattering membrane mask (for example, see Non-Patent Document 2) or a stencil mask (for example, see Non-Patent Document 3) is used. Improvement is an important issue.
[0007]
Further, as a problem common to all the above-mentioned NGL masks, there is distortion of the mask in the exposure posture.
Generally, the positional accuracy of the manufactured mask is measured by a coordinate measuring instrument such as an IPRO manufactured by Leica or a light wave coordinate measuring apparatus manufactured by Nikon.
[0008]
FIG. 11 is a flowchart of a method of manufacturing a mask (hereinafter also referred to as a production mask) such as a scattering membrane mask or a stencil mask used in the above-described NGL and performing pattern exposure using the mask.
First, a mask such as a scattering membrane mask or a stencil mask on which a desired pattern is formed is created (ST101), and the positional accuracy (long dimension) of the manufactured mask is measured by a coordinate measuring instrument (ST102). Next, the measurement result of the obtained positional accuracy is determined (ST103). If the measurement result is outside the guaranteed value, the mask is re-manufactured. If the measurement result is within the guaranteed value, a preliminary test exposure is performed ( ST104). Next, the overlay accuracy of the test-exposed pattern and the underlying wafer is evaluated (ST105). Based on the results, if necessary, the actual exposure is performed after optimizing the exposure conditions (chip magnification, rotation error correction, etc.) (ST106).
Therefore, basically, it is necessary to measure the position accuracy for each production mask.
[0009]
The above-described methods of manufacturing a mask and performing pattern exposure require position accuracy measurement for each production mask, and thus require (1) an expensive coordinate measuring instrument, and (2) a long coordinate measurement time (about 6). Second / mark).
[0010]
Further, (3) since the attitude / holding method of the mask is different between the coordinate measurement and the exposure, there is also a problem that a pattern to be actually transferred has a position error that cannot be observed in the coordinate measurement.
This is because the position of the mask is different between coordinate measurement (generally, the mask pattern surface is upward and stationary) and mask exposure, and the mask pattern surface is often downward during exposure. Since the (chucking) method is different from that of the coordinate measuring device, the distortion is newly induced which is not measured by the coordinate measuring device such as IPRO.
[0011]
It has been pointed out that even if a mask is formed on a glass substrate similar to a photomask (PM) like an EUVL mask and has relatively high mechanical strength, mask distortion due to gravity cannot be ignored. (See Patent Document 2).
[0012]
Data U obtained by mask coordinate measurement₁  Sets the pattern coordinates of the design data to R₀Then, the following equation is obtained.
[0013]
(Equation 1)

[0014]
Where r_MPIs the error in the mask manufacturing process, r_IPROIs the measurement accuracy of the coordinate measuring instrument (about ± 3 nm), and the former is generally larger.
The former main factor is the positional accuracy of electron beam writing, but in the case of a scattering membrane mask or a stencil mask, stress relaxation accompanying the membrane formation also contributes in principle.
Here, the coordinates on the mask are divided by the transfer magnification (4 for EUVL or EPL, 1 for LEEPL or PXL) and converted to a substantial amount on the wafer (the same applies hereinafter).
[0015]
When the above-mentioned mask is fixed to the exposure device, the mask is deformed by gravity, and the pattern displacement (mask distortion) r_g  Occurs. Further, when this mask is exposed, the distortion r of the transfer optical system_transferIs added, the position U of the transfer pattern₂  Is represented by the following equation.
[0016]
(Equation 2)

[0017]
Therefore, the result of coordinate measurement U₁  From mask distortion r_g  Can not get.
[0018]
On the other hand, the position V of the alignment accuracy measurement mark on the wafer₁  Also, due to the influence of chip distortion due to the preceding process, the ideal position R₀  Is displaced from
[0019]
(Equation 3)

[0020]
Therefore, the result W of the overlay accuracy measurement₁  Is given by the following equation.
[0021]
(Equation 4)

[0022]
Where r_ALAnd r_OLAre the alignment accuracy and the accuracy of the overlay accuracy measuring device (about ± 3 nm), respectively.
This data contains the mask distortion r_g  , But the error r due to the mask manufacturing process_MP(Eg, the accuracy of a mask drawing machine) and chip distortion r due to a preceding process._WPCannot be ignored, and the mask distortion r_g  Is not exactly measured.
[0023]
Further, as shown in the flowchart of FIG. 11, in the conventional process in which the mask distortion measuring step and the mask manufacturing step are integrated, a highly accurate mask is not re-created based on the obtained mask distortion. . Therefore, there is no other way than to correct the exposure error by optimizing the exposure condition so as to minimize the entire error including the mask distortion.
[0024]
However, in a method using short-wavelength radiation such as EUVL or PXL, only the magnification and rotation components of the mask and the chip can be corrected. In a method using charged particles such as EPL, IPL, and LEEPL, finer correction can be performed by an electron / ion optical system, but such position correction has a limit.
For example, it has been reported that a pattern position error due to gravity of a stencil mask may be several tens of nm (see Non-Patent Document 4), and it is difficult to correct this only by deflection of charged particles. It is necessary to correct the pattern position during manufacturing.
[0025]
[Patent Document 1]
U.S. Pat. No. 5,831,272
[Patent Document 2]
JP-A-6-18220
[Non-patent document 1]
T. T. Utsumi, "Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.)" B17, p. 2897 (1999)
[Non-patent document 2]
L. R. Harriott, "Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.)" B15, p. 2130 (1997)
[Non-Patent Document 3]
H. C. HC Pfeiffer, "Japanese Journal of Applied Physics (Jpn. J. Appl. Phys.)" 34, p. 6658 (1995)
[Non-patent document 4]
C. -F. Chen et al. (C.-f. Chen et al.), "Journal of Vacuum Science and Technology (J. Vac. Sci. Technol.)", B19, p. 2646 (2001)
[0026]
[Problems to be solved by the invention]
Since the attitude / holding method of the mask is different between the above coordinate measurement and the exposure, there is a problem that a pattern to be actually transferred has a position error not observed in the coordinate measurement. It is also conceivable to modify the coordinate measuring device so that the measurement can be performed in a close state, or to (2) convert the coordinate measurement data according to some rule to calculate the position accuracy error in the exposure posture.
[0027]
However, since the coordinate measuring device is very expensive and the measurement speed is slow (6 seconds or more per point), there is a problem that the mask manufacturing process based on the use of the coordinate measuring device has low throughput and high cost. is there.
In addition, it is inconvenient if the remodeling as in (1) cannot be shared with ordinary PM and wafer measurement. In addition, inadvertent modifications may not achieve the guaranteed accuracy.
Regarding (2), it is necessary to devise an algorithm for accurately predicting the pattern displacement when the mask is turned upside down, and this cannot be easily performed.
[0028]
The present invention has been made in view of the above problems, and therefore, the present invention measures a mask distortion in an exposure posture without using a coordinate measuring instrument, and performs position correction of drawing and transfer based on the measured distortion. Provided are a method of manufacturing a mask or a method of forming a pattern capable of further improving positional accuracy, a photomask for strain measurement used for the method, and a method of manufacturing a mask and a method of manufacturing a semiconductor device using the method of forming a pattern. The purpose is to do.
[0029]
[Means for Solving the Problems]
In order to achieve the above object, a method of manufacturing a mask according to the present invention includes the steps of: transferring a strain measurement pattern formed on a strain measurement photomask to charge the thin film of the mask blank having at least one layer of charged particles; Forming a strain measurement mask pattern having a transmission portion and a cutoff portion of the line, and manufacturing a strain measurement mask; and transferring the strain measurement pattern formed on the strain measurement photomask to a wafer, forming a strain on the wafer. Forming a wafer pattern for measurement, forming a wafer for strain measurement, forming a photosensitive layer that is exposed to charged particle beams on the surface of the strain measurement wafer on which the strain measurement wafer pattern is formed, The strain measurement mask is held in a predetermined posture at a predetermined distance from the layer, and the charge is applied so that the strain measurement mask pattern overlaps the strain measurement wafer pattern. Exposing the photosensitive layer with a sagittal wire, measuring overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer, and measuring the strain measurement mask in the predetermined posture. Generating a strain data, and drawing a pattern by correcting a drawing position according to the strain data, and forming a transmission portion and a blocking portion of a charged particle beam on the thin film of the mask blank having at least one thin film. Forming a predetermined transfer pattern and forming a mask.
[0030]
The method of manufacturing a mask according to the present invention described above includes transferring the strain measurement pattern formed on the strain measurement photomask to a mask pattern for strain measurement having a transmission part and a cutoff part of a charged particle beam on a thin film of a mask blank. Is formed to form a strain measurement mask.
On the other hand, the strain measurement pattern formed on the same strain measurement photomask as described above is transferred to a wafer to form a strain measurement wafer pattern, and a strain measurement wafer is manufactured.
Next, a photosensitive layer exposed by a charged particle beam is formed on the strain measurement wafer pattern forming surface of the strain measurement wafer, and the strain measurement mask is placed in a predetermined posture at a predetermined distance from the photosensitive layer. Then, the photosensitive layer is exposed to the charged particle beam so that the strain measurement mask pattern overlaps the strain measurement wafer pattern.
Next, the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer is measured, and strain data of the strain measurement mask in a predetermined posture is generated, and according to the obtained strain data. Then, the pattern is drawn by correcting the drawing position, and a predetermined transfer pattern having a transmitting portion and a blocking portion of the charged particle beam is formed on the thin film of the mask blank, and a mask is manufactured.
[0031]
Further, in order to achieve the above object, the pattern forming method of the present invention transfers a strain measurement pattern formed on a strain measurement photomask to the thin film of a mask blank having at least one thin film. Forming a mask pattern for strain measurement having a transmission part and a cutoff part of the charged particle beam, a step of manufacturing a mask for strain measurement, and transferring the strain measurement pattern formed on the photomask for strain measurement to a wafer Forming a strain measurement wafer pattern, manufacturing a strain measurement wafer, and forming a photosensitive layer exposed by a charged particle beam on the strain measurement wafer pattern forming surface of the strain measurement wafer, The strain measurement mask is held in a predetermined posture at a predetermined distance from the photosensitive layer, and the strain measurement mask pattern overlaps the strain measurement wafer pattern. Exposing the photosensitive layer with a charged particle beam, measuring overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer, and measuring the strain in the predetermined posture. A step of generating strain data of a mask for use, a step of forming a predetermined transfer pattern having a transmitting portion and a blocking portion of a charged particle beam on the thin film of the mask blank having at least one layer of thin film, and forming a mask; Correcting the transfer position according to the distortion data and pattern-exposing the exposed wafer using the mask.
[0032]
The above-described pattern forming method of the present invention includes the steps of transferring a strain measurement pattern formed on a strain measurement photomask, and forming a strain measurement mask pattern having a transmitting portion and a blocking portion of a charged particle beam on a thin film of a mask blank. Is formed to form a strain measurement mask.
On the other hand, the strain measurement pattern formed on the same strain measurement photomask as described above is transferred to a wafer to form a strain measurement wafer pattern, and a strain measurement wafer is manufactured.
Next, a photosensitive layer exposed by a charged particle beam is formed on the strain measurement wafer pattern forming surface of the strain measurement wafer, and the strain measurement mask is placed in a predetermined posture at a predetermined distance from the photosensitive layer. Then, the photosensitive layer is exposed to the charged particle beam so that the strain measurement mask pattern overlaps the strain measurement wafer pattern.
Next, the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer is measured, strain data of the strain measurement mask in a predetermined posture is generated, and the thin film of the mask blank is charged. A predetermined transfer pattern having a transmitting portion and a blocking portion of the particle beam is formed.
Next, a mask is prepared, the transfer position is corrected according to the distortion data, and the wafer to be exposed is subjected to pattern exposure using the mask.
[0033]
In order to achieve the above object, the photomask for strain measurement of the present invention includes, as a strain measurement pattern, a mask alignment pattern, a wafer alignment pattern, an overlay accuracy measurement mask pattern, and an overlay accuracy measurement wafer pattern. The wafer alignment pattern and the overlay accuracy measurement wafer pattern are formed at positions displaced in the same direction and distance from the mask alignment pattern and the overlay accuracy measurement mask pattern, respectively. .
[0034]
The strain measurement photomask of the present invention has a mask alignment pattern, a wafer alignment pattern, an overlay accuracy measurement mask pattern, and an overlay accuracy measurement wafer pattern as the strain measurement patterns. The configuration is such that a wafer alignment pattern and an overlay accuracy measurement wafer pattern are formed at positions deviated by the same direction and distance from the pattern and the overlay accuracy measurement mask pattern, respectively.
[0035]
In order to achieve the above object, a method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device having a step of pattern-exposing a wafer to be exposed, wherein a strain measurement formed on a strain measurement photomask is performed. Transferring a pattern for use, forming a mask pattern for strain measurement having a transmission part and a cut-off part of a charged particle beam on the thin film of the mask blank having at least one thin film, and forming a mask for strain measurement, Transferring the strain measurement pattern formed on the strain measurement photomask to a wafer, forming a strain measurement wafer pattern, and manufacturing a strain measurement wafer; and Forming a photosensitive layer exposed by a charged particle beam on the wafer pattern forming surface, and holding the strain measurement mask in a predetermined posture at a predetermined distance from the photosensitive layer. Exposing the photosensitive layer with a charged particle beam so that the strain measurement mask pattern overlaps the strain measurement wafer pattern; and the strain measurement transferred to the strain measurement wafer pattern and the photosensitive layer. Measuring the overlay accuracy with the mask pattern for generation, and generating distortion data of the distortion measurement mask in the predetermined posture, and drawing a pattern by correcting a drawing position according to the distortion data, Forming a predetermined transfer pattern having a transmission portion and a blocking portion of the charged particle beam in the thin film of the mask blank having a layer of thin film, a step of manufacturing a mask, and correcting the transfer position according to the distortion data, Pattern-exposing a wafer to be exposed using the mask.
[0036]
The method for manufacturing a semiconductor device according to the present invention described above includes transferring a strain measurement pattern formed on a strain measurement photomask to a mask for strain measurement having a transmission portion and a cutoff portion of a charged particle beam on a thin film of a mask blank. A pattern is formed, and a strain measurement mask is manufactured. On the other hand, the strain measurement pattern formed on the same strain measurement photomask as described above is transferred to a wafer to form a strain measurement wafer pattern, and a strain measurement wafer is manufactured.
Next, a photosensitive layer exposed by a charged particle beam is formed on the strain measurement wafer pattern forming surface of the strain measurement wafer, and the strain measurement mask is placed in a predetermined posture at a predetermined distance from the photosensitive layer. Then, the photosensitive layer is exposed to the charged particle beam so that the mask pattern for strain measurement overlaps the wafer pattern for strain measurement.
Next, the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer is measured, and the strain data of the strain measurement mask in the above-described predetermined posture is generated. Then, a pattern is drawn by correcting the drawing position, and a predetermined transfer pattern having a transmitting portion and a blocking portion of the charged particle beam is formed on the thin film of the mask blank having at least one layer of thin film, thereby producing a mask.
Further, the transfer position is corrected in accordance with the distortion data, and pattern exposure is performed on the wafer to be exposed using a mask.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
The present embodiment relates to a method for measuring mask distortion without using a coordinate measuring device represented by IPRO. Is measured, and position correction using the data is performed at the time of pattern drawing or exposure of the production mask.
Hereinafter, a method for manufacturing a mask, a method for forming a pattern, and a photomask according to the present embodiment will be described with reference to the drawings.
[0038]
FIG. 1 is a flowchart of a method for fabricating a mask such as a scattering membrane mask or a stencil mask according to the present embodiment and performing pattern exposure using the mask.
In the method according to the present embodiment, the mask distortion data generation step and the production mask manufacturing and exposure step using the same are clearly separated, as long as the mask outer shape and the holding method in the exposure machine do not change. The former need only be performed once.
[0039]
First, in a mask distortion data generation step, a distortion measurement photomask (PM) including a distortion measurement pattern described later is manufactured (ST11).
Regarding the strain measurement PM, the coordinate measurement may be performed by the coordinate measuring device, or may not be performed. For example, when outsourcing the production of PM to a mask manufacturer, the mask manufacturer routinely guarantees the positional accuracy (long dimension accuracy) in PM manufacturing. The measurement is performed, and the practitioner of the present invention does not need to have a coordinate measuring instrument.
[0040]
FIG. 2 is a plan view showing a strain measurement pattern formed on the strain measurement photomask.
The distortion measurement pattern formed on the distortion measurement photomask 10 includes a mask alignment pattern 11m and a wafer alignment pattern 11w as an alignment pattern 11, and an overlay accuracy measurement pattern 12 as An overlay accuracy measurement mask pattern 12m and an overlay accuracy measurement wafer pattern 12w are formed.
Here, the wafer alignment pattern 11w and the overlay accuracy measurement wafer pattern 12w are formed at positions displaced in the same direction and distance from the mask alignment pattern 11m and the overlay accuracy measurement mask pattern 12m, respectively. . When this direction and distance are indicated by a translation vector d, the mask alignment pattern 11m and the overlay accuracy measurement mask pattern 12m are associated with the wafer alignment pattern 11w and the overlay accuracy measurement wafer pattern 12w by the same translation vector d. I have.
Here, the mask alignment pattern 11m and the wafer alignment pattern 11w have standard marks by respective lithography methods, and can be used as they are.
The overlay accuracy measurement mask pattern 12m and the overlay accuracy measurement wafer pattern 12w are a pair of patterns, for example, a pattern called "bar-in-bar" or a pattern called "box-in-bar", which will be described later. .
[0041]
Next, the strain measurement pattern formed on the strain measurement photomask is transferred to the mask blank having at least one layer of thin film, and the strain measurement mask pattern having a charged particle beam transmission portion and a cutoff portion is formed on the thin film. Is formed to produce a strain measurement mask (ST12).
For example, a mask for strain measurement is manufactured by transferring and exposing a pattern for strain measurement from a photomask for strain measurement, developing, and performing etching using the obtained resist pattern as a mask, and forming a mask pattern for strain measurement on a mask blank. To form a mask for strain measurement.
[0042]
A process for manufacturing a strain measurement mask will be described with reference to cross-sectional views shown in FIGS.
First, as shown in FIG. 3A, a silicon oxide layer 21 is formed on one surface of a silicon wafer 20 serving as a substrate of a strain measurement mask, and a silicon layer 22 is formed thereon to form an SOI structure. Form a wafer.
Further, a silicon oxide layer 23 is also formed on the other surface of the silicon wafer 20.
[0043]
Next, as shown in FIG. 3B, the silicon oxide layer 23 on the other surface of the silicon wafer 20 is etched so as to leave a beam pattern for supporting the silicon layer 22 serving as a thin film mask. Using the patterned silicon oxide layer 23 as a mask, the silicon wafer 20 is etched from the silicon oxide layer 23 side to the silicon oxide layer 21.
Since the etching rates of silicon and silicon oxide differ by several orders of magnitude or more, the silicon wafer 20 is etched selectively with respect to the silicon oxide layer 23 and the silicon oxide layer 21. The etching stops at the silicon oxide layer 21.
[0044]
Next, as shown in FIG. 3C, a portion of the silicon oxide layer 21 exposed by the etching of the silicon wafer 20 is removed by, for example, wet etching using hydrofluoric acid. As a result, a membrane 24 made of a silicon layer is formed. The portion of the silicon wafer 20 that divides the membrane 24 becomes a beam 25 and supports the membrane 24.
In addition, the silicon oxide layer 23 is simultaneously removed by this wet etching.
In this way, a mask blank having at least one thin film (membrane) is formed.
[0045]
Next, as shown in FIG. 4A, a resist film 26 is formed on the membrane 24, and is exposed using the above-described photomask 10 for strain measurement. The distortion measurement patterns formed on the distortion measurement photomask 10, such as the mask alignment pattern 11m, the wafer alignment pattern 11w, the overlay accuracy measurement mask pattern 12m, and the overlay accuracy measurement wafer pattern 12w, are, for example, several μm to Since the size is about several tens of μm and the pattern is large, it can be exposed to light or the like.
At this time, for example, one surface S of the distortion measurement photomask 10 faces the upper surface.
[0046]
Next, as shown in FIG. 4B, the resist film 26 is developed.
As a result, the resist film 26 has an alignment pattern 27 including a mask alignment pattern 27m and a wafer alignment pattern 27w, and an overlay accuracy measurement pattern 28 including an overlay accuracy measurement mask pattern 28m and an overlay accuracy measurement wafer pattern 28w. Is transferred.
[0047]
Next, as shown in FIG. 4C, an etching process is performed on the membrane 24 using the patterned resist film 26 as a mask, and the membrane 24 is composed of a mask alignment pattern 29m and a wafer alignment pattern 29w. A strain measurement mask pattern having an alignment pattern 29 and an overlay accuracy measurement pattern 30 including an overlay accuracy measurement mask pattern 30m and an overlay accuracy measurement wafer pattern 30w is formed.
Thereafter, the resist film 26 is removed to form the strain measurement mask 31.
In the strain measurement mask 31, the membrane 24 has a charged particle beam transmitting portion and a blocking portion along the strain measuring pattern.
[0048]
On the other hand, the strain measurement pattern formed on the strain measurement photomask is transferred to a wafer to form a strain measurement wafer pattern, and a strain measurement wafer is manufactured (ST13).
For example, to fabricate a strain measurement wafer, a strain measurement pattern is transferred and exposed from a strain measurement photomask, developed, and etched using the obtained resist pattern as a mask. It is processed into a strain measurement wafer.
[0049]
A process for manufacturing a strain measurement wafer will be described with reference to a cross-sectional view shown in FIG.
First, as shown in FIG. 5A, a resist film 41 is formed on a silicon wafer 40, and is exposed using the strain measurement photomask 10 described above. The strain measurement patterns such as the mask alignment pattern 11m, the wafer alignment pattern 11w, the overlay accuracy measurement mask pattern 12m, and the overlay accuracy measurement wafer pattern 12w formed on the strain measurement photomask 10 are exposed.
At this time, in order that the strain measurement pattern formed on the strain measurement wafer and the strain measurement pattern formed on the strain measurement mask 31 have a relationship just inverted, for example, one of the strain measurement photomasks 10 may be used. The front surface S faces the lower surface (the silicon wafer 40 side).
[0050]
Next, as shown in FIG. 5B, the resist film 41 is developed.
As a result, the resist film 41 has an alignment pattern 42 including a mask alignment pattern 42m and a wafer alignment pattern 42w, and an overlay accuracy measurement pattern 43 including an overlay accuracy measurement mask pattern 43m and an overlay accuracy measurement wafer pattern 43w. Is transferred.
[0051]
Next, as shown in FIG. 5C, an etching process is performed on the silicon wafer 40 using the patterned resist film 41 as a mask, and an alignment process including a mask alignment pattern 44m and a wafer alignment pattern 44w is performed. A strain measurement wafer pattern having a pattern 44 and an overlay accuracy measurement pattern 45 including an overlay accuracy measurement mask pattern 45m and an overlay accuracy measurement wafer pattern 45w is formed.
After that, the resist film 41 is removed to form the strain measurement wafer 46.
[0052]
Since the above-described process of forming the strain measurement wafer pattern is a simple process of performing only one etching, the chip distortion is small, and the position accuracy of the overlay measurement pattern on the wafer is mainly determined by the accuracy of photolithography. .
On the other hand, the position accuracy of the overlay accuracy measurement pattern exposed on the mask blanks serving as the distortion measurement mask is also determined by the photolithography accuracy. This accuracy is less than 10 nm with modern scanners.
[0053]
Here, the exposure using the strain measurement photomask for forming the strain measurement mask and the exposure using the strain measurement photomask for forming the strain measurement wafer are as described above. Exposure is performed under the same conditions as much as possible, except that the pattern and the pattern are just inverted.
It is preferable that a plurality of strain measurement masks and a plurality of strain measurement wafers are manufactured, and a plurality of combinations are prepared, and the following steps are performed.
[0054]
Next, a photosensitive layer exposed by a charged particle beam is formed on the strain measurement wafer pattern forming surface of the strain measurement wafer, and the strain measurement mask is placed in a predetermined posture at a predetermined distance from the photosensitive layer. Then, the photosensitive layer is exposed to the charged particle beam so that the mask pattern for strain measurement overlaps the wafer pattern for strain measurement (ST14).
[0055]
The above-described step of forming the photosensitive layer and the step of exposing the wafer pattern for strain measurement so that the mask pattern for strain measurement overlaps with the wafer pattern will be described with reference to the cross-sectional view of FIG.
As shown in FIG. 6A, after a photosensitive layer 47 that is exposed to charged particle beams is formed on the surface of the strain measurement wafer 46 on which the strain measurement wafer pattern is formed, the strain measurement mask 31 is exposed to the photosensitive layer. The strain measurement mask 31 is held so as to be on the 47 side so that the distance between the membrane 24 and the photosensitive layer 47 becomes a predetermined value.
[0056]
The position at which the distortion measuring mask 31 is aligned is set as shown in the plan view of FIG.
That is, the mask alignment pattern 29m in the distortion measurement mask pattern and the wafer alignment pattern 44w in the distortion measurement wafer pattern are overlapped. This is the direction and distance of the translation vector d that associates the mask alignment pattern 11m and overlay accuracy measurement mask pattern 12m with the wafer alignment pattern 11w and overlay accuracy measurement wafer pattern 12w. This corresponds to displacing the mask pattern for distortion measurement.
[0057]
In the state where the strain measurement mask 31 and the strain measurement wafer 46 are arranged as described above, a charged particle beam (not shown) is irradiated from the strain measurement mask 31 side, and the strain measurement mask which is a transmission part of the membrane 24 is provided. The pattern is transmitted and the photosensitive layer 47 is subjected to pattern exposure. At this time, the exposure is performed under the condition that the distortion of the transfer optical system is minimum. For example, in the case of LEEPL, the mask is scanned with parallel electron beams as much as possible without applying sub-deflection.
[0058]
After exposure as described above, development is performed to obtain the state shown in FIG. 6B. The resist film 47 has an alignment pattern 48 including a mask alignment pattern 48m and a wafer alignment pattern 48w, and an overlay accuracy measurement mask. A mask pattern for distortion measurement having the pattern 49m and the pattern 49 for overlay measurement comprising the wafer pattern 49w for overlay accuracy measurement is transferred.
[0059]
Next, the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer is measured (ST15), and strain data of the strain measurement mask in a predetermined posture is generated (ST16).
[0060]
The measurement of the overlay accuracy is performed by measuring the overlap between the overlay accuracy measurement wafer pattern 45w of the strain measurement wafer pattern and the overlay accuracy measurement mask pattern 49m of the strain measurement mask pattern, for example, LA3200 by Hitachi, or Nikon. It is measured by an overlay accuracy measuring device such as NRM1000 of the company.
[0061]
FIG. 8A is a plan view showing the arrangement of the overlay accuracy measurement mask pattern 12m and the overlay accuracy measurement wafer pattern 12w in the strain measurement pattern on the strain measurement photomask 10. 12m shows that the overlay pattern measurement wafer pattern 12w is associated with the translation accuracy vector d.
Here, the overlay accuracy measurement mask pattern 12m and the overlay accuracy measurement wafer pattern 12w are patterns in which four linear patterns each called “bar” are arranged so as to form a square. The overlay accuracy measurement wafer pattern 12w has a larger square shape than the use mask pattern 12m.
[0062]
FIG. 8B shows an overlay accuracy measurement pattern 45 composed of an overlay accuracy measurement mask pattern 45m and an overlay accuracy measurement wafer pattern 45w of the distortion measurement wafer pattern, and the strain measurement transferred to the photosensitive layer. FIG. 9 is a plan view showing an arrangement of an overlay accuracy measurement pattern 49 including an overlay accuracy measurement mask pattern 49m and an overlay accuracy measurement wafer pattern 49w among mask patterns for use in the present invention.
The overlay accuracy measurement mask pattern 49m and the overlay accuracy measurement wafer pattern 49w are displaced in the direction and the distance of the translation vector d, so that the overlay accuracy measurement mask pattern is located at the center of the overlay accuracy measurement wafer pattern 45w. 49m are arranged. At this time, the overlay accuracy can be measured from the deviation between the center of the overlay accuracy measurement wafer pattern 45w and the center of the overlay accuracy measurement mask pattern 49m.
[0063]
The quantity observed in the above measurement of the overlay accuracy is basically the W₁  However, (1) the mark of the wafer and the mark of the mask are formed by the same PM, (2) the mark forming process on the wafer is simple and the chip distortion r_WP(3) distortion r of the transfer optical system_{tran sfer}Is smaller than the prior art because the exposure is performed under the minimum condition.₁  Is small, the main cause of the overlay error is mask distortion.
[0064]
As described above, the mask for distortion measurement and the mask for distortion measurement are overlapped by the alignment optical system provided in the exposure apparatus so that the mask alignment pattern 29m on the distortion measurement mask and the wafer alignment pattern 44w on the distortion measurement wafer are overlapped. The relative position of the wafer is held, that is, the relative position is shifted by d, and exposure is performed.
At this time, as shown in FIG. 8B, the pair of overlay accuracy measurement mask patterns 49m and the overlay accuracy measurement wafer pattern 45w overlap, and the overlay accuracy can be measured. It is desirable that the magnitude of the translation vector d be as small as possible within a range where the adjacent mask alignment pattern 29m and the wafer alignment pattern 44w do not overlap. Since the size of the alignment pattern and the pattern for measuring the overlay accuracy are several μm to several tens μm, it is sufficient that they are separated by at least that much.
[0065]
As described above, as shown in FIG. 1, the mask distortion data generation step is completed. The distortion data obtained as described above can be used to correct the drawing position of the pattern drawing of the production mask in the production of the production mask and in the exposure step using the production mask. Thus, the pattern position can be corrected so as not to be affected by the mask deformation due to gravity. Further, by feeding back to the exposure device, the transfer position can be corrected.
Here, the production mask is a mask that is different from the above-described distortion measurement mask and is used for forming a pattern such as a desired circuit pattern or wiring pattern and performing exposure in actual manufacturing of a semiconductor device.
[0066]
In the manufacture of a production mask and an exposure step using the same, first, a pattern is drawn by correcting a drawing position according to the strain data obtained as described above, and a mask blank having at least one layer of thin film is formed. A predetermined transfer pattern having a transmitting portion and a blocking portion of the charged particle beam is formed on the thin film, and a production mask is manufactured (ST21).
For example, as shown in the cross-sectional view of FIG. 9A, a silicon oxide layer 61 is formed on a silicon wafer 60 in a production mask 65, and a silicon layer membrane 62 is formed thereon. The portion of the silicon wafer 60 that separates the membrane 62 becomes a beam 63 and supports the membrane 62.
The membrane 62 has an opening pattern 64 that serves as a transmission part of a predetermined charged particle beam.
[0067]
Next, the transfer position is corrected according to the distortion data obtained as described above, and the pattern is test-exposed on the wafer to be exposed using the production mask (ST22).
For example, as shown in the cross-sectional view of FIG. 9B, the resist film 71 formed on the wafer 70 to be exposed has the membrane 62 side of the production mask 65 on the resist film 71 side, and the membrane 62 and the resist film 71 The production mask 65 is held so that the distance of the predetermined value becomes a predetermined value.
Test exposure is performed in the above state, the overlay accuracy is measured in the same manner as above (ST23), and if it is within the target value, actual exposure is performed using the above production mask under the above exposure conditions (ST24). If the overlay accuracy deviates from the target value, the exposure condition is changed and the test exposure is repeated.
[0068]
In the above, according to the obtained distortion data, it is used for both the drawing position correction of the pattern drawing of the production mask and the transfer position correction at the time of exposure using the production mask, but the feedback is performed to only one of them. It is good also as a method.
[0069]
(Modification)
FIG. 10A is a plan view showing the arrangement of the overlay accuracy measurement mask pattern 12m and the overlay accuracy measurement wafer pattern 12w in the strain measurement pattern on the strain measurement photomask 10. FIG. 8 (a), except that the overlay accuracy measurement mask pattern 12m is a rectangular overlay accuracy measurement mask pattern 12m 'instead of four linear patterns called "bar". This is different from FIG. The overlay accuracy measurement mask pattern 12m 'and the overlay accuracy measurement wafer pattern 12w are associated with the translation vector d in the same manner as described above.
FIG. 10B shows an overlay accuracy measurement pattern 45 composed of an overlay accuracy measurement mask pattern 45m ′ and an overlay accuracy measurement wafer pattern 45w among the distortion measurement wafer patterns, and the distortion transferred to the photosensitive layer. It is a top view which shows the arrangement | positioning of the overlay accuracy measurement pattern 49 which consists of the overlay accuracy measurement mask pattern 49m 'and the overlay accuracy measurement wafer pattern 49w among the measurement mask patterns.
The overlay accuracy measurement mask pattern 49m 'and the overlay accuracy measurement wafer pattern 49w are displaced in the direction and distance of the translation vector d so that the linear pattern is arranged in a square shape. At the center of 45w, a rectangular overlay accuracy measuring mask pattern 49m 'is arranged. At this time, the overlay accuracy can be measured from the deviation between the center of the overlay accuracy measurement wafer pattern 45w and the center of the overlay accuracy measurement mask pattern 49m '.
[0070]
In the present embodiment, the overlay measuring device used for measuring overlay accuracy is less than a fraction of the cost of a coordinate measuring device, and the throughput can be as fast as about 2.5 seconds / mark. Thus, the position accuracy of the mask can be quickly evaluated.
According to the mask manufacturing method of the present embodiment and the pattern forming method using the same, the mask distortion in the exposure posture is measured without using the coordinate measuring device, and the position of drawing and transfer is corrected based on the measured distortion. The position accuracy can be further improved.
[0071]
In addition, mask distortion can be easily measured on the wafer FAB by using a widely used overlay accuracy measuring device, and the mask accuracy can be evaluated not only at the mask shop but also at the user side.
[0072]
The present invention is not limited to the above embodiment.
For example, in the present embodiment, a stencil mask has been described, but a mask for each NGL can be obtained by applying a mask manufacturing process known from various papers and patents.
Further, in the present embodiment, as the pattern of the strain measurement photomask and the strain measurement mask, only the alignment pattern and the overlay accuracy measurement pattern are formed, but in order to make it closer to a practical system, The pattern may include an appropriate circuit pattern.
Further, the method for manufacturing a mask and the method for forming a pattern according to the present invention can be applied as a method for manufacturing a mask for pattern exposure and a method for forming a pattern in a method for manufacturing a semiconductor device having a step of pattern exposure on a wafer to be exposed. .
In addition, various changes can be made without departing from the spirit of the present invention.
[0073]
【The invention's effect】
According to the mask manufacturing method of the present invention, it is possible to measure the mask distortion in the exposure posture without using a coordinate measuring instrument, and perform the position correction of the drawing and the transfer based on the measured distortion, thereby further improving the position accuracy.
[0074]
According to the pattern forming method of the present invention, it is possible to measure the mask distortion in the exposure posture without using a coordinate measuring instrument, and perform the position correction of the drawing and the transfer based on the measured mask distortion, thereby improving the position accuracy.
[0075]
By using the photomask for distortion measurement of the present invention, in a method of manufacturing a mask and a method of forming a pattern using the same, a mask distortion in an exposure posture is measured without using a coordinate measuring instrument, and drawing is performed based on the measured distortion. And transfer position correction, thereby improving the position accuracy.
[0076]
According to the method of manufacturing a semiconductor device of the present invention, in a mask used in an exposure process for manufacturing a semiconductor device, mask distortion in an exposure posture is measured without using a coordinate measuring device, and drawing and transfer are performed based on the measured distortion. And the position accuracy can be further improved.
[Brief description of the drawings]
FIG. 1 is a flowchart of a method for fabricating a mask according to an embodiment and performing pattern exposure using the mask.
FIG. 2 is a plan view showing a strain measurement pattern formed on a strain measurement photomask according to the embodiment.
FIGS. 3A to 3C are cross-sectional views illustrating steps of a method for fabricating a mask according to the embodiment and performing pattern exposure using the mask.
FIGS. 4A to 4C are cross-sectional views illustrating steps of a method of manufacturing a mask according to the embodiment and performing pattern exposure using the mask.
FIGS. 5A to 5C are cross-sectional views illustrating steps of a method for fabricating a mask according to the embodiment and performing pattern exposure using the mask.
FIGS. 6A and 6B are cross-sectional views illustrating steps of a method of manufacturing a mask according to the embodiment and performing pattern exposure using the mask.
FIG. 7 is a plan view showing a position for aligning a distortion measurement mask in the embodiment.
FIG. 8A is a plan view showing an arrangement of an overlay accuracy measurement mask pattern and an overlay accuracy measurement wafer pattern according to the embodiment; FIG. 8B is an overlay accuracy measurement wafer pattern; FIG. 4 is a plan view showing an arrangement of mask patterns for measuring overlay accuracy.
FIGS. 9A and 9B are cross-sectional views illustrating steps of a method for manufacturing a mask according to the embodiment and performing pattern exposure using the mask.
FIG. 10A is a plan view showing an arrangement of a mask pattern for overlay accuracy measurement and a wafer pattern for overlay accuracy measurement according to a modification, and FIG. 10B is a plan view of the wafer pattern for overlay accuracy measurement. FIG. 4 is a plan view showing an arrangement of mask patterns for measuring overlay accuracy.
FIG. 11 is a flowchart of a method of manufacturing a mask according to a conventional example and performing pattern exposure using the mask.
[Explanation of symbols]
Reference numeral 10: Photomask for strain measurement, 11: Pattern for alignment, 11m: Pattern for mask alignment, 11w: Pattern for wafer alignment, 12: Pattern for overlay accuracy measurement, 12m, 12m ': Mask pattern for overlay accuracy measurement, 12w ... Lamination accuracy measurement wafer pattern, 20: silicon wafer, 21: silicon oxide layer, 22: silicon layer, 23: silicon oxide layer, 24: membrane, 25: beam, 26: resist film, 27, 29, 42, 44, 48: alignment pattern, 27m, 29m, 42m, 44m, 48m: mask alignment pattern, 27w, 29w, 42w, 44w, 48w: wafer alignment pattern, 28, 30, 43, 45, 49: overlay accuracy measurement Pattern, 28m, 30m, 43m, 45m, 45m , 49m, 49m ': mask pattern for measuring overlay accuracy, 28w, 30w, 43w, 45w, 49w: wafer pattern for measuring overlay accuracy, 40: silicon wafer, 41: resist film, 60: silicon wafer, 61: silicon oxide layer Reference numeral 62, a membrane, 63, a beam, 64, an opening pattern, 65, a production mask, 70, a wafer to be exposed, 71, a resist film.

Claims (8)

The strain measurement pattern formed on the strain measurement photomask is transferred to form a strain measurement mask pattern having a charged particle beam transmitting portion and a blocking portion on the thin film of the mask blank having at least one thin film. Producing a strain measurement mask,
Transferring the strain measurement pattern formed on the strain measurement photomask to a wafer, forming a strain measurement wafer pattern, and manufacturing a strain measurement wafer;
Forming a photosensitive layer exposed by a charged particle beam on the strain measurement wafer pattern forming surface of the strain measurement wafer;
The strain measurement mask is held in a predetermined posture at a predetermined distance from the photosensitive layer, and the strain measurement mask pattern is overlapped with the strain measurement wafer pattern by a charged particle beam. Exposing the photosensitive layer,
Measuring the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer, and generating strain data of the strain measurement mask in the predetermined posture;
Correcting the drawing position according to the distortion data and drawing a pattern, forming a predetermined transfer pattern having a transmission part and a cutoff part of a charged particle beam on the thin film of the mask blank having at least one thin film, Producing a mask. The strain measurement pattern of the strain measurement photomask has a mask alignment pattern, a wafer alignment pattern, an overlay accuracy measurement mask pattern and an overlay accuracy measurement wafer pattern,
2. The wafer alignment pattern and the overlay accuracy measurement wafer pattern are formed at positions deviated in the same direction and distance from the mask alignment pattern and the overlay accuracy measurement mask pattern, respectively. 3. The method for manufacturing a mask according to item 1. Exposing the photosensitive layer with a charged particle beam so that the strain measurement mask pattern overlaps the strain measurement wafer pattern, wherein the wafer alignment pattern in the strain measurement wafer pattern; Exposure so that the mask alignment pattern in the mask pattern for the overlap,
In the step of measuring the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer, the overlay measurement wafer pattern in the strain measurement wafer pattern, The mask manufacturing method according to claim 2, wherein the overlay accuracy is measured from an overlap of the mask pattern with the overlay accuracy measurement mask pattern. The strain measurement pattern formed on the strain measurement photomask is transferred to form a strain measurement mask pattern having a charged particle beam transmitting portion and a blocking portion on the thin film of the mask blank having at least one thin film. Producing a strain measurement mask,
Transferring the strain measurement pattern formed on the strain measurement photomask to a wafer, forming a strain measurement wafer pattern, and manufacturing a strain measurement wafer;
Forming a photosensitive layer exposed by a charged particle beam on the strain measurement wafer pattern forming surface of the strain measurement wafer;
The strain measurement mask is held in a predetermined posture at a predetermined distance from the photosensitive layer, and the strain measurement mask pattern is overlapped with the strain measurement wafer pattern by a charged particle beam. Exposing the photosensitive layer,
Measuring the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer, and generating strain data of the strain measurement mask in the predetermined posture;
Forming a predetermined transfer pattern having a transmission portion and a blocking portion of a charged particle beam on the thin film of the mask blank having at least one thin film, and forming a mask;
Correcting the transfer position according to the distortion data, and performing pattern exposure on the wafer to be exposed using the mask. In the step of forming the mask, a pattern is drawn by correcting a drawing position in accordance with the strain data, and the thin film of the mask blank having at least one thin film has a transmitting portion and a blocking portion of a charged particle beam. The pattern forming method according to claim 4, wherein a predetermined transfer pattern is formed. 5. The method according to claim 4, wherein in the step of pattern-exposing the exposed wafer using the mask, the exposure is performed while maintaining the mask in the same attitude as the predetermined attitude while keeping a predetermined distance from the exposed wafer. 3. The method for forming a pattern according to item 1. As the distortion measurement pattern, having a mask alignment pattern, a wafer alignment pattern, an overlay accuracy measurement mask pattern and an overlay accuracy measurement wafer pattern,
With respect to the mask alignment pattern and the overlay accuracy measurement mask pattern, the wafer alignment pattern and the overlay accuracy measurement wafer pattern are formed at positions displaced in the same direction and distance, respectively. Photo mask. A method of manufacturing a semiconductor device having a step of pattern exposure on a wafer to be exposed,
The strain measurement pattern formed on the strain measurement photomask is transferred to form a strain measurement mask pattern having a charged particle beam transmitting portion and a blocking portion on the thin film of the mask blank having at least one thin film. Producing a strain measurement mask,
Transferring the strain measurement pattern formed on the strain measurement photomask to a wafer, forming a strain measurement wafer pattern, and manufacturing a strain measurement wafer;
Forming a photosensitive layer exposed by a charged particle beam on the strain measurement wafer pattern forming surface of the strain measurement wafer;
The strain measurement mask is held in a predetermined posture at a predetermined distance from the photosensitive layer, and the strain measurement mask pattern is overlapped with the strain measurement wafer pattern by a charged particle beam. Exposing the photosensitive layer,
Measuring the overlay accuracy of the strain measurement wafer pattern and the strain measurement mask pattern transferred to the photosensitive layer, and generating strain data of the strain measurement mask in the predetermined posture;
Correcting the drawing position according to the distortion data and drawing a pattern, forming a predetermined transfer pattern having a transmission part and a cutoff part of a charged particle beam on the thin film of the mask blank having at least one thin film, A step of producing a mask;
Correcting the transfer position in accordance with the distortion data, and pattern-exposing the exposed wafer using the mask.

Images