JP2004233401A - Photomask, photomask fabrication method and exposing method - Google Patents

Photomask, photomask fabrication method and exposing method Download PDF

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JP2004233401A
JP2004233401A JP2003018422A JP2003018422A JP2004233401A JP 2004233401 A JP2004233401 A JP 2004233401A JP 2003018422 A JP2003018422 A JP 2003018422A JP 2003018422 A JP2003018422 A JP 2003018422A JP 2004233401 A JP2004233401 A JP 2004233401A
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film
pattern
resist film
plate portion
photomask
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Fumikatsu Uesawa
史且 上澤
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Sony Corp
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Sony Corp
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/60—Substrates

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  • General Physics & Mathematics (AREA)
  • Preparing Plates And Mask In Photomechanical Process (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask which can correctly transfer a pattern even when transferring the pattern on an uneven substrate, and has an easily fabricable configuration. <P>SOLUTION: This photomask 40 transfers an LSI circuit pattern on a resist film having a high film surface and a low film surface on the stepped substrate with a height difference z. The photomask is provided with a quartz mask substrate 42 having thick and thin parts, and first and second light shielding patterns 44a, 44b consisting of Cr light shielding films with the same thickness provided on the thick and thin parts, respectively. The first and second light shielding patterns compose patterns to be transferred to the low and high film surfaces of the resist film. Main surfaces of the thick and thin parts provided with the first and second light shielding patterns have a step Z therebetween. By shifting an imaging position of the first pattern by M<SP>2</SP>× Z = z, patterns by the first and second patterns are imaged correctly on the low and high film surfaces, respectively. Thus, a focal displacement caused by the step of the film surfaces of the resist film formed on the stepped substrate is compensated, to correctly transfer a desired pattern on the resist film on the stepped substrate. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、段差を有する被加工体上、例えば半導体装置の製造プロセスで段差基板上のレジスト膜にパターンを転写する際に好適に使用できるフォトマスク、そのようなフォトマスクの製造方法、及びそのようなフォトマスクを使って露光する方法に関するものである。
【０００２】
【従来の技術】
近年、ＬＳＩの集積度を高め、かつ性能を向上させるために、パターンの微細化が急ピッチで進行している。その結果、ＬＳＩの回路パターンに用いられる線幅の最小寸法がリソグラフィプロセスの解像限界に近づき、深刻な焦点深度不足を招いている。
【０００３】
ところで、ＬＳＩは、ＤＲＡＭに代表される「メモリー用ＬＳＩ」と、ＭＰＵに代表される「ロジック用ＬＳＩ」の２つに大別される。
メモリー用ＬＳＩとロジック用ＬＳＩの双方を必要とする半導体装置を製造する際には、従来は、それぞれ別々に製造し、実装するのが一般的であったが、ＬＳＩの小型化、高集積化に対する市場要求に応じるために、これら相互に異なる機能を有する２つのＬＳＩをワンチップ化した「ＤＲＡＭ混載ロジックＬＳＩ」の開発が、盛んに進められている。
ＤＲＡＭ混載ロジックＬＳＩは、配線等の回路パターンが高度に密集したＤＲＡＭ回路と、回路パターンの密度が比較的低いロジック回路とを１つのチップ内に集積させたＬＳＩである。
【０００４】
このようなＤＲＡＭ混載ロジックＬＳＩの製造では、回路パターンが密なメモリ用ＬＳＩ領域と、回路パターンが疎のロジック用ＬＳＩ領域との間で基板表面に高低差が生じる。
その結果、露光工程でマスクパターンをレジスト膜に転写する際、レジスト膜の下地層の高低差、つまり基板表面の高低差に応じてレジスト膜にも高低差が生じる。そのため、ＤＲＡＭ混載ロジックＬＳＩの製造では、リソグラフィプロセスを実施する際の焦点深度不足の問題が、より一層深刻になっている。
【０００５】
ここで、図５を参照して、ＤＲＡＭ混載ロジックＬＳＩの製造工程で、前工程で作り込まれた段差基板上にリソグラフィ処理を施す際に適用している従来の方法を説明する。図５は段差基板に適用するリソグラフィ処理の従来の方法を説明する模式図である。
本例では、図５に示すように、段差基板１２上のレジスト膜１４に投影レンズ１６を介してフォトマスク１８のパターンを転写する。
段差基板１２は、配線パターン等の回路パターンが密なために表面が高くなっている高部１２ａと、回路パターンが疎のために表面が高部１２ａより低い低部１２ｂとを基板上に有し、その結果、段差基板１２上に成膜されたレジスト膜１４は、段差基板１２の段差に応じて高膜面１４ａと低膜面１４ｂを有する。
【０００６】
フォトマスク１８は、遮光パターン１８ａを透明マスク基板１８ｂの主面に設けたマスクであって、光源（図示せず）から放射された光は遮光パターン１８ａで遮られていない領域、つまり転写パターン領域を透過してレジスト膜１４上に到達し、結像する。
これにより、レジスト膜１４が選択的に感光され、遮光パターン１８ａで構成されたマスクパターンがレジスト膜１４上に転写される。
【０００７】
ところで、例えば６５ｎｍ世代デバイスに要求されるパターン線幅では、開口数（ＮＡ）０．７５の最新のＡｒＦスキャナ（波長１９３ｎｍ）を露光装置として用いたとしても、０．２μｍ程度の焦点深度しか確保できない。
しかし、上述の高部と低部とが混在するＬＳＩ形成用段差基板では、およそ０．１μｍ程度の高低差が生じるため、ウエハが本来有する歪み、露光装置のオートフォーカス精度の誤差、露光装置の焦点面の歪み等が０．１μｍ程度の高低差に加わると、図５に示すように、０．２μｍ以上のフォーカスずれδがレジスト膜１４の低膜面１４ｂで生じる。
このため、結果として、ＬＳＩパターンを高精度にレジスト膜上に転写することができなくなるという問題が生じている。
【０００８】
ここで、段差基板上のフォーカスずれの一例として、図６に、０．５μｍの段差を有する段差基板上のレジスト膜に波長２４８ｎｍのＫｒＦステッパーを用いて、直径０．２４μｍのコンタクトホールパターンのパターン転写を行った際のＣＤ−ＳＥＭ写真を示す。図６（ａ）及び図６（ｂ）は、それぞれ、コンタクトホールを転写する段差基板の断面図、及び段差基板上のレジスト膜に転写したコンタクトホールの径を示すＣＤ−ＳＥＭ写真をである。図６（ｂ）のＡ及びＢは、それぞれ、段差基板１２の高部１２ａ上及び低部１２ｂのコンタクトホールを示す。
使用したフォトマスクは、透過率６％のハーフトーン位相シフトマスクで、ＫｒＦステッパーの照明条件はＮＡ＝０．５５とし、レジストには東京応化工業社製のＴＤＵＲ−ＰＯ１５を用いて、段差基板１２上に０．８８μｍの膜厚でレジスト膜を成膜した。
設計上では、全て同じ径のコンタクトホールのパターンがレジスト膜上に転写される筈であったが、段差基板１２のレジスト膜段差によって、フォーカスずれの影響を受けることにより、低部１２ｂ上に形成されたコンタクトホールは、高部１２ａ上に形成されたコンタクトホールに比べて、コンタクトホール径が著しく拡大している。
【０００９】
そこで、特開平４−２１２１５４号公報は、段差基板にパターンを転写する際に使用するフォトマスクを提案している。ここで、図７を参照して、前掲公報に開示されたフォトマスクの構成を説明する。図７は前掲公報に提案されているフォトマスクの構成を説明する模式図である。
前掲公報は、図７に示すように、段差基板２０上にパターンを転写する際に使用するフォトマスク２２として、透明基板２４の主面に設けた遮光パターン２６を光学距離調整膜２８で部分的に覆ったフォトマスクを提案している。フォトマスク２２に入射した光Ｌは、光学距離調整膜２８を透過した光Ｌ１ と、光学距離調整膜２８を透過しない光Ｌ２ とに別れ、レンズ３０を介して段差基板２０上のレジスト膜３２に到達する。
【００１０】
前掲公報によれば、光学的距離調整膜２８は、石英等により形成された、屈折率ｎが透明基板２４と同じ膜であって、光学的距離調整膜２８の位置及び膜厚は段差基板２０上のレジスト膜３２の段差によって決定される。
また、焦点距離Ｐ、Ｑ間の距離Ｄは、
Ｄ＝｛ｍ２ ・（ｎ−１）・ｄ｝／ｎ′
で表される。
ここで、ｎは光学的距離調整膜２８の屈折率、ｎ′はレジスト膜の屈折率、ｍはレンズ３０の倍率、及びｄは光学的距離調整膜２６の膜厚である。
そして、距離Ｄがレジスト膜３２の低い領域３２ａと高い領域３２ｂとの間の段差寸法Ｔに一致するように、光学的距離調整膜２８の膜厚ｄを設定する、つまり、
ｄ＝（ｎ′・Ｔ）／｛ｍ２ ・（ｎ−１）｝
に設定する。
これにより、光学距離調整膜２８を透過しない光Ｌ２ は焦点距離Ｐを低い領域３２ａに位置させ、光学距離調整膜２８を透過した光Ｌ１ は焦点距離Ｑを高い領域３２ｂに位置させることができ、レジスト膜３２の段差を補償することができるとしている。
【００１１】
【特許文献１】
特開平４−２１２１５４号公報（第３頁、図１）
【００１２】
【発明が解決しようとする課題】
しかし、前掲公報で提案されている所要の膜厚の光学的距離調整膜を遮光パターン上に設けることは、実際には、技術的にかなり困難を伴うことであって、実用化には更なる研究が必要であると思われる。
【００１３】
そこで、本発明の第１の目的は、段差基板上にマスクパターンを転写する際にも、マスクパターンを正確に転写でき、しかも作製容易な構成を備えたフォトマスクを提供することであり、第２の目的はそのようなフォトマスクの製造方法を提供することであり、第３の目的はそのようなフォトマスクを使って露光する方法を提供することである。
【００１４】
【課題を解決するための手段】
本発明者は、以下に説明するように、段差基板の高低差によって生じるフォーカスずれを補正するために、従来技術の光学的距離調整膜に代えて、高低差をマスク基板自体に設けることを着想した。そして、着想が有効であることを実験により確認して、本発明を発明するに到った。
【００１５】
投影光学系においては、必ず「物体面」と「像面」とが対で存在する。リソグラフィ工程で使用される露光装置では、「物体面」とはＬＳＩの回路パターンが描かれたマスク面であり、「像面」とはレジスト膜が成膜されたウエハの基板表面、つまりレジスト膜の膜面である。
物体面に凹凸がある場合には、それに対応して像面も凹凸を持つ。換言すれば、像面に凹凸を持たせたいときには、それと共役となるような凹凸を物体面に設けることにより解決できる。
【００１６】
像面の凹凸の段差を補償するために、低像面を高像面に一致させるための移動距離、つまり像面の高さ方向のシフト量をｚすると、それに共役な物体面での凹凸の段差、つまり物体面の高さ方向のシフト量Ｚとの間には、投影光学系の倍率Ｍを介して以下のような関係式（１）が成立する。
ｚ＝Ｍ２ ×Ｚ ・・・・・・・（１）
即ち、物体面の位置を縦方向にＺだけシフトさせると、像面での位置はＭ２ ×Ｚ＝ｚだけシフトして、凹凸のある面に所定のパターンを結像させることができる（投影光学系における縦倍率）。
一般的に、半導体製造装置に使われるステッパーでは、Ｍは、Ｍ＝１／５、スキャナでは、Ｍ＝１／４である。
【００１７】
露光工程の事前検討段階で、段差基板が有する段差（ｚ）を予め測定しておくことは可能なので、その段差を補正するためのフォトマスクの主面段差（Ｚ）を式（１）から求め、主面間に主面段差（Ｚ）を有するマスク基板を形成し、各主面にそれぞれ遮光パターンを設けたフォトマスクを使用することにより、フォーカスずれのない高精度なパターン転写が可能となる。ここで、主面とは、像面に対面する物体面、つまりレジスト膜に対面するフォトマスクの面を言う。
【００１８】
上記目的を達成するために、上述の知見に基づいて、本発明に係るフォトマスクは、段差を有する被加工体上に成膜され、被加工体の段差に応じて生じているレジスト膜段差を介して低膜面と高膜面とを有するレジスト膜に、投影光学系を介してマスクパターンを転写するフォトマスクであって、
板厚の厚い厚板部と、厚板部の板厚より薄い薄板部とを有し、厚板部の主面と薄板部の主面との主面段差がＺの透明マスク基板と、
厚板部の主面に設けられ、レジスト膜の低膜面に転写するパターンを構成する第１遮光膜パターンと、低膜面の主面に設けられ、レジスト膜の高膜面に転写するパターンを構成する第２遮光膜パターンとからなるマスクパターンと
を備え、
レジスト膜のレジスト膜段差をｚ、投影光学系の倍率をＭとするとき、
Ｚ＝ｚ／Ｍ２ ・・・・・・・式（１）
で規定されることを特徴としている。
【００１９】
本発明の透明マスク基板は、従来から既知の透明マスク基板であって、例えば石英製の基板等である。遮光膜も従来から既知のＣｒ膜等の遮光膜である。
本発明に係るフォトマスクでは、前述したように、フォトマスクの第１遮光パターンを有する厚板部の主面と第２遮光パターンを有する薄板部の主面との間にＺの主面段差を設けることにより、第１遮光パターンの結像位置をＭ２ ×Ｚ＝ｚだけシフトさせて、第１遮光パターンによるパターンをレジスト膜の低膜面に、第２遮光パターンによるパターンをレジスト膜の高膜面に正確に結像させることができる。
本発明に係るフォトマスクを適用してレジスト膜段差のあるレジスト膜上に転写することにより、従来のようなフォーカスずれが生じなくなり、結果として高精度なＬＳＩパターンの転写が可能となる。
【００２０】
本発明に係るフォトマスクは、２個以上の段差を有する被加工体上に成膜され、かつ被加工体の各段差に応じて生じているレジスト膜段差を介して高低の相互に異なる３面以上の膜面を有するレジスト膜にマスクパターンを転写することもできる。
その場合には、フォトマスクは、レジスト膜の各膜面に対応して３個の主面が透明マスク基板に設けられ、主面間の各主面段差が各レジスト膜段差に対応して式（１）の関係を有し、各主面がそれぞれ各膜面に転写する遮光膜パターンを備えている。
【００２１】
本発明に係るフォトマスクの作製方法は、段差を有する被加工体上に成膜され、被加工体の段差に応じて生じているレジスト膜段差を介して低膜面と高膜面とを有するレジスト膜に、投影光学系を介してマスクパターンを転写するフォトマスクの作製方法であって、
板状の透明マスク基板の厚板部形成領域を覆い、薄板部形成領域を露出するレジストマスクを透明マスク基板上に形成する工程と、
レジスト膜のレジスト膜段差をｚ、投影光学系の倍率をＭとするとき、
厚板部の主面と薄板部の主面との間の主面段差Ｚが、
Ｚ＝ｚ／Ｍ２ ・・・・・・・式（１）
で規定される主面段差Ｚを有するように、薄板部形成領域をエッチングして、板厚の厚い厚板部と、厚板部の板厚より薄い薄板部とを透明マスク基板上に形成する工程と、
レジスト膜の低膜面に転写するパターンを構成する第１遮光膜パターンを厚板部の主面に、レジスト膜の高膜面に転写するパターンを構成する第２遮光膜パターンを薄板部の主面に形成する工程と
を有することを特徴としている。
【００２２】
本発明に係るフォトマスクの作製方法は、透明マスク基板のエッチング工程と遮光膜パターンの形成工程とで構成され、光学的距離調整膜等の成膜工程を必要としないので、作製が容易である。
【００２３】
本発明に係る露光方法は、段差を有する被加工体上に成膜され、被加工体の段差に応じて生じるレジスト膜段差を介して低膜面と高膜面とを有するレジスト膜に、投影光学系を介してフォトマスクのマスクパターンを転写する露光方法であって、
被加工体上のレジスト膜の高膜面と低膜面とのレジスト膜段差ｚを測定する工程と、
投影光学系の倍率をＭとするとき、
Ｚ＝ｚ／Ｍ２ ・・・・・・・式（１）
式（１）で規定される主面段差Ｚを有する板厚の厚い厚板部と、厚板部の板厚より薄い薄板部とを有し、レジスト膜の低膜面に転写するパターンを構成する第１遮光膜パターンを厚板部の主面に、レジスト膜の高膜面に転写するパターンを構成する第２遮光膜パターンを薄板部の主面に備えるフォトマスクを使って、投影光学系を介して露光する工程と
を有することを特徴としている。
【００２４】
【発明の実施の形態】
以下に、添付図面を参照して、実施形態例に基づいて本発明をより詳細に説明する。
フォトマスクの実施形態例
本実施形態例は本発明に係るフォトマスクの実施形態の一例であって、図１は本実施形態例のフォトマスクの構成を示す断面図である。
本実施形態例のフォトマスク４０は、図４に示すような段差基板６２上に一様な膜厚で成膜されたレジスト膜６４上に投影倍率Ｍ＝１／４のＡｒＦスキャナを用いてＬＳＩの回路パターンを転写するフォトマスクである。
段差基板６２は回路パターンが密な高部６２ａと回路パターンが疎の低部６２ｂとを有し、レジスト膜６４は段差基板６２の高部６２ａに対応して高膜面６４ａを、低部６２ｂに対応して低膜面６４ｂを有する。
高部６２ａ上のレジスト膜６４の高膜面６４ａは、低部６２ｂ上のレジスト膜６４の低膜面６４ｂより高い位置にあり、高膜面６４ａと低膜面６４ｂとの段差ｚは０．１μｍである。
【００２５】
フォトマスク４０は、板厚が厚さｔａ の厚板部４２ａと板厚が厚板部４２より薄い厚さｔｂ の薄板部４２ｂとを有する石英製の透明マスク基板４２と、透明マスク基板４２の厚板部４２ａ及び薄板部４２ｂの主面それぞれに設けられ、同じ膜厚のＣｒ遮光膜からなる第１遮光パターン４４ａ、及び第２遮光パターン４４ｂとを備えている。厚板部４２ａ及び薄板部４２ｂの主面の反対側の面は、同じ平面上にある。
厚板部４２上の第１遮光パターン４４ａは段差基板６２上のレジスト膜６４の低膜面６４ｂに転写すべきパターンを構成する遮光パターンであり、薄板部４２ｂ上の第２遮光パターン４４ｂはレジスト膜６４の高膜面６４ａに転写すべきパターンを構成する遮光パターンである。
【００２６】
厚板部４２ａの厚さｔａ と薄板部４２ｂの厚さｔｂ との間には、式（１）に基づいて、

Figure 2004233401
の関係が成立するように、ｔａ 及びｔｂ が設定されている。
【００２７】
本実施形態例のフォトマスク４０は、第１遮光パターン４４ａを有する厚板部４２ａと第２遮光パターン４４ｂを有する薄板部４２ｂとの間にＺの主面段差を設けることにより、第１遮光パターン４４ａの結像位置をＭ２ ×Ｚ＝ｚだけシフトさせて、第１遮光パターン４４ａによるパターンをレジスト膜６４の低膜面６４ｂに、第２遮光パターン４４ｂによるパターンをレジスト膜６４の高膜面６４ａに正確に結像させることができる。
これにより、段差基板６２に成膜されたレジスト膜６４の表面の段差に起因する焦点ずれを補償して、フォトマスク４０より所望のマスクパターンを正確に段差基板６２上のレジスト膜６４に転写することができる。
【００２８】
フォトマスクの製造方法の実施形態例
本実施形態例は本発明に係るフォトマスクの製造方法を上述の実施形態例のフォトマスクの製造に適用した実施形態の一例である。図２（ａ）から（ｄ）及び図３（ｅ）から（ｇ）は、それぞれ、フォトマスクを製造する際の工程毎の断面図である。
先ず、図２（ａ）に示すように、マスク基板となる透明な基板４６にレジストを塗布して、レジスト膜４８を成膜する。
次いで、図２（ｂ）に示すように、レジスト膜４８にリソグラフィ処理を施して、基板４６の厚板部形成領域５０を覆い、薄板部形成領域５２を露出させるパターンを有するレジストマスク５４を形成する。
【００２９】
次に、図２（ｃ）に示すように、レジストマスク５４上から基板４６にエッチングを施して薄板部４２ｂを形成し、レジストマスク５４で覆うことによりエッチングしなかった厚板部形成領域５０を厚板部４２ａとする透明マスク基板４２を形成する。
次いで、レジストマスク５４を剥離した後、図２（ｄ）に示すように、ＣＶＤ法やスパッター等の金属膜の成膜プロセスを用いて透明マスク基板４２の厚板部４２ａ及び薄板部４２ｂ上に一様な膜厚のＣｒ膜からなる遮光膜５６を成膜する。
【００３０】
次いで、図３（ｅ）に示すように、遮光膜５６上にレジストを塗布してレジスト膜５８を成膜する。
続いて、図３（ｆ）に示すように、所望のＬＳＩ回路パターンをレジスト膜５８に転写して、エッチングマスク６０を形成する。
次に、エッチングマスク６０上から遮光膜５６をエッチングし、エッチング後、エッチングマスク６０を剥離して、図３（ｇ）に示すように、厚板部４２ａに遮光パターン４４ａを、薄板部４２ｂに遮光パターン４４ｂを形成する。
以上の工程を経ることにより、実施形態例のフォトマスク４０を簡単な工程で容易に作製することができる。
【００３１】
露光方法の実施形態例
本実施形態例は本発明に係る露光方法の実施形態の一例であって、図４は半導体装置の製造に際し本実施形態例の方法により段差基板上にパターンを転写する露光方法を説明する模式図である。
先ず、配線パターン等の回路パターンが密なために表面が高い高部６２ａと回路パターンが疎なために表面が高部６２ａより低い低部６２ｂとを有する段差基板６２上に一様な膜厚でレジスト膜６４を成膜する。
次いで、高部６２ａ上のレジスト膜６４の膜面と低部６２ｂ上のレジスト膜６４の膜面との段差ｚを測定して、ｚ＝０．１μｍを求める。
【００３２】
次いで、板厚が厚さｔａ の厚板部４２ａと板厚が厚板部４２より薄い厚さｔｂ の薄板部４２ｂとを有する透明マスク基板４２の透明マスク基板４２の厚板部４２ａ及び薄板部４２ｂのそれぞれに同じ膜厚の遮光膜からなる遮光パターン４４ａ、４４ｂを備えたフォトマスク４０を用意する。
厚板部４２上の遮光パターン４４ａは段差基板６２の低部６２ｂ上のレジスト膜６４に転写すべきパターンを構成する遮光パターンであり、薄板部４２ｂ上の遮光パターン４４ｂは段差基板６２の高部６２ａ上のレジスト膜６４に転写すべきパターンを構成する遮光パターンである。
厚板部４２ａの厚さｔａ と薄板部４２ｂの厚さｔｂ との間には、式（１）に基づいて、
Figure 2004233401
の関係がある。
【００３３】
次いで、投影倍率Ｍ＝１／４の投影レンズ６６を有するＡｒＦスキャナを用いて、遮光パターン４４ａ及び遮光パターン４４ｂで構成されるフォトマスク４０のＬＳＩ回路パターンを段差基板６２のレジスト膜６４上に転写する。
フォトマスク４０を使用することにより、図４に示すように、遮光パターン４４ａを有する厚板部４２ａを透過し、投影レンズ６６で集光された光は段差基板６２の低部６２ｂ上のレジスト膜６４の膜面６４ｂで結像し、遮光パターン４４ｂを有する薄板部４２ｂを透過し、投影レンズ６６で集光された光は段差基板６２の高部６２ａ上のレジスト膜６４ａの膜面で結像する。
よって、フォトマスク４０に設けられたＬＳＩ回路パターンを正確にレジスト膜６４上に転写することができる。
【００３４】
【発明の効果】
本発明に係るフォトマスクによれば、フォトマスクの第１遮光パターンを有する厚板部の主面と第２遮光パターンを有する薄板部の主面との間にＺの主面段差を設けることにより、第１遮光パターンの結像位置をＭ２ ×Ｚ＝ｚだけシフトさせて、第１遮光パターンによるパターンをレジスト膜の低膜面に、第２遮光パターンによるパターンをレジスト膜の高膜面に正確に結像させることができる。本発明に係るフォトマスクを適用してレジスト膜段差のあるレジスト膜上に転写することにより、従来のようなフォーカスずれが生じなくなり、結果として高精度なＬＳＩパターンの転写が可能となる。
【００３５】
本発明に係るフォトマスクの作製方法によれば、透明マスク基板のエッチング工程と遮光膜パターンの形成工程とで構成され、光学的距離調整膜等の成膜工程を必要としないので、作製が容易である。
本発明に係る露光方法は、本発明に係るフォトマスクを使った好適な露光方法を実現している。フォーカスずれがなくなることにより安定したパターン形成が可能となるので、従来より微細パターンの転写が可能になり、半導体製造プロセスのマージンが広がり、製造歩留まりが向上する。また、高低差に関わらず所望のパターン形状が得られるので、半導体デバイスの性能が向上する。
【図面の簡単な説明】
【図１】実施形態例のフォトマスクの構成を示す断面図である。
【図２】図２（ａ）から（ｄ）は、それぞれ、実施形態例のフォトマスクを製造する際の工程毎の断面図である。
【図３】図３（ｅ）から（ｇ）は、それぞれ、図２（ｄ）に続いて、実施形態例のフォトマスクを製造する際の工程毎の断面図である。
【図４】半導体装置の製造に際し本実施形態例の方法により段差基板上にパターンを転写する露光方法を説明する模式図である。
【図５】段差基板に適用したリソグラフィ処理の従来の方法を説明する模式図である。
【図６】図６（ａ）及び図６（ｂ）は、それぞれ、コンタクトホールを転写する段差基板の断面図、及び段差基板上のレジスト膜に転写したコンタクトホールの径を示すＣＤ−ＳＥＭ写真をである。
【図７】特開平４−２１２１５４号公報に提案されているフォトマスクの構成を説明する模式図である。
【符号の説明】
１２……段差基板、１２ａ……高部、１２ｂ……低部、１４……レジスト膜、１６……投影レンズ、１８……フォトマスク、１８ａ……遮光パターン、１８ｂ……透明マスク基板、 ２０……段差基板、２２……フォトマスク、２４……透明基板、２６……遮光パターン、２８……光学距離調整膜、３０……レンズ、３２……レジスト膜、４０……実施形態例のフォトマスク、４２……透明マスク基板、４２ａ……厚板部、４２ｂ……薄板部、４４ａ……第１遮光パターン、４４ｂ……第２遮光パターン、４６……透明な基板、４８……レジスト膜、５０……厚板部形成領域、５２……薄板部形成領域、５４……レジストマスク、５６……遮光膜、５８……レジスト膜、６０……エッチングマスク、６２……段差基板、６２ａ……高部、６２ｂ……低部、６４……レジスト膜、６４ａ……高膜面、６４ｂ……低膜面、６６……投影レンズ。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a photomask that can be suitably used when transferring a pattern to a resist film on a stepped substrate in a process for manufacturing a semiconductor device, for example, on a workpiece having a step, a method for manufacturing such a photomask, and a method for manufacturing the same. And an exposure method using such a photomask.
[0002]
[Prior art]
In recent years, pattern miniaturization has been progressing at a rapid pace in order to increase the integration degree of LSIs and improve performance. As a result, the minimum dimension of the line width used in the circuit pattern of the LSI approaches the resolution limit of the lithography process, causing a serious lack of depth of focus.
[0003]
Incidentally, LSIs are broadly classified into two types: "memory LSIs" represented by DRAMs; and "logic LSIs" represented by MPUs.
Conventionally, when manufacturing a semiconductor device that requires both a memory LSI and a logic LSI, it has conventionally been general to manufacture and mount each separately. However, miniaturization and high integration of the LSI have been conventionally performed. In order to meet the market demands for, a "DRAM embedded logic LSI" in which these two LSIs having different functions are integrated into one chip has been actively developed.
The DRAM-embedded logic LSI is an LSI in which a DRAM circuit in which circuit patterns such as wiring are highly dense and a logic circuit in which the circuit pattern density is relatively low are integrated in one chip.
[0004]
In the manufacture of such a DRAM-embedded logic LSI, a level difference occurs on the substrate surface between a memory LSI region having a dense circuit pattern and a logic LSI region having a sparse circuit pattern.
As a result, when the mask pattern is transferred to the resist film in the exposure step, a difference in elevation occurs in the resist film in accordance with the height difference of the underlying layer of the resist film, that is, the height difference of the substrate surface. For this reason, in the manufacture of a DRAM embedded logic LSI, the problem of insufficient depth of focus when performing a lithography process has become more serious.
[0005]
Here, with reference to FIG. 5, a description will be given of a conventional method applied in performing a lithography process on a stepped substrate formed in a previous process in a process of manufacturing a DRAM embedded logic LSI. FIG. 5 is a schematic diagram illustrating a conventional method of lithography processing applied to a step substrate.
In this example, as shown in FIG. 5, the pattern of the photomask 18 is transferred to the resist film 14 on the step substrate 12 via the projection lens 16.
The step board 12 has a high portion 12a having a high surface due to a dense circuit pattern such as a wiring pattern, and a low portion 12b having a lower surface than the high portion 12a due to a poor circuit pattern. As a result, the resist film 14 formed on the step substrate 12 has a high film surface 14a and a low film surface 14b according to the step of the step substrate 12.
[0006]
The photomask 18 is a mask in which a light-shielding pattern 18a is provided on the main surface of the transparent mask substrate 18b, and light emitted from a light source (not shown) is not blocked by the light-shielding pattern 18a, ie, a transfer pattern area. And reaches the resist film 14 to form an image.
As a result, the resist film 14 is selectively exposed to light, and the mask pattern composed of the light shielding patterns 18a is transferred onto the resist film 14.
[0007]
By the way, for example, in a pattern line width required for a 65 nm generation device, even if the latest ArF scanner (wavelength 193 nm) having a numerical aperture (NA) of 0.75 is used as an exposure apparatus, only a depth of focus of about 0.2 μm is secured. Can not.
However, in the stepped substrate for forming an LSI in which the above-described high portion and low portion are mixed, a height difference of about 0.1 μm occurs, so that the distortion inherent in the wafer, the error of the auto-focus accuracy of the exposure device, the error of the exposure device, When a distortion or the like of the focal plane is applied to a height difference of about 0.1 μm, a focus shift δ of 0.2 μm or more occurs on the low film surface 14b of the resist film 14 as shown in FIG.
As a result, there is a problem that the LSI pattern cannot be transferred onto the resist film with high accuracy.
[0008]
Here, as an example of a focus shift on a step substrate, FIG. 6 shows a pattern of a contact hole pattern having a diameter of 0.24 μm using a KrF stepper having a wavelength of 248 nm on a resist film on a step substrate having a step of 0.5 μm. 4 shows a CD-SEM photograph when transfer was performed. FIGS. 6A and 6B are a cross-sectional view of a step substrate for transferring a contact hole and a CD-SEM photograph showing the diameter of the contact hole transferred to a resist film on the step substrate, respectively. 6A and 6B show contact holes on the high portion 12a and the low portion 12b of the step substrate 12, respectively.
The photomask used was a halftone phase shift mask having a transmittance of 6%, the illumination condition of the KrF stepper was set to NA = 0.55, and the resist was TDUR-PO15 manufactured by Tokyo Ohka Kogyo Co., Ltd. A resist film having a thickness of 0.88 μm was formed thereon.
In design, all contact hole patterns having the same diameter should have been transferred onto the resist film. However, the resist film steps of the step substrate 12 were affected by the focus shift, and thus were formed on the lower portion 12b. The diameter of the contact hole thus formed is significantly larger than that of the contact hole formed on the high portion 12a.
[0009]
Therefore, Japanese Patent Application Laid-Open No. 4-212154 proposes a photomask used when transferring a pattern onto a stepped substrate. Here, the configuration of the photomask disclosed in the above-mentioned publication will be described with reference to FIG. FIG. 7 is a schematic diagram illustrating the configuration of a photomask proposed in the above-mentioned publication.
In the above-mentioned publication, as shown in FIG. 7, a light-shielding pattern 26 provided on a main surface of a transparent substrate 24 is partially covered with an optical distance adjusting film 28 as a photomask 22 used when transferring a pattern onto a stepped substrate 20. We have proposed a photomask that is covered. Light L incident on the photomask 22, the light L 1 having passed through the optical path length adjusting layer 28, separated into a light L 2 does not transmit the optical distance adjusting film 28, the resist film on the stepped substrate 20 through the lens 30 Reach 32.
[0010]
According to the above-mentioned publication, the optical distance adjusting film 28 is a film formed of quartz or the like and having the same refractive index n as that of the transparent substrate 24, and the position and the film thickness of the optical distance adjusting film 28 are different from those of the step substrate 20. It is determined by the step of the upper resist film 32.
The distance D between the focal lengths P and Q is
D = {m 2 · (n−1) · d} / n ′
Is represented by
Here, n is the refractive index of the optical distance adjusting film 28, n 'is the refractive index of the resist film, m is the magnification of the lens 30, and d is the film thickness of the optical distance adjusting film 26.
Then, the film thickness d of the optical distance adjusting film 28 is set so that the distance D matches the step size T between the low region 32a and the high region 32b of the resist film 32, that is,
d = (n ′ · T) / {m 2 · (n−1)}
Set to.
Thus, the light L 2 does not transmit the optical distance adjustment film 28 is positioned a focal length P in the lower region 32a, the light L 1 having passed through the optical path length adjusting layer 28 is possible to position the focal length Q to the high region 32b It is described that the step of the resist film 32 can be compensated.
[0011]
[Patent Document 1]
JP-A-4-212154 (page 3, FIG. 1)
[0012]
[Problems to be solved by the invention]
However, providing an optical distance adjusting film having a required film thickness on a light-shielding pattern as proposed in the above-mentioned publication is technically quite difficult in practice, and is further required for practical use. Research seems necessary.
[0013]
Therefore, a first object of the present invention is to provide a photomask having a configuration that can accurately transfer a mask pattern even when a mask pattern is transferred onto a stepped substrate, and that has an easily manufactured structure. A second object is to provide a method for manufacturing such a photomask, and a third object is to provide a method for exposing using such a photomask.
[0014]
[Means for Solving the Problems]
As described below, the present inventor has conceived of providing a height difference on the mask substrate itself instead of the optical distance adjustment film of the related art in order to correct a focus shift caused by a height difference of a stepped substrate. did. Then, it was confirmed by experiments that the idea was effective, and the present invention was reached.
[0015]
In a projection optical system, an “object plane” and an “image plane” always exist in pairs. In an exposure apparatus used in a lithography process, the “object surface” is a mask surface on which an LSI circuit pattern is drawn, and the “image surface” is a substrate surface of a wafer on which a resist film is formed, that is, a resist film. Film surface.
If the object surface has irregularities, the image surface also has irregularities correspondingly. In other words, when it is desired to have irregularities on the image plane, the problem can be solved by providing irregularities on the object plane that are conjugate to the irregularities.
[0016]
In order to compensate for the unevenness of the image plane, the moving distance for matching the low image plane to the high image plane, that is, the amount of shift in the height direction of the image plane is z. The following relational expression (1) is established between the step and the shift amount Z in the height direction of the object plane via the magnification M of the projection optical system.
z = M 2 × Z (1)
That is, when the position of the object plane is shifted by Z in the vertical direction, the position on the image plane is shifted by M 2 × Z = z, and a predetermined pattern can be formed on the uneven surface (projection). Longitudinal magnification in the optical system).
Generally, in a stepper used in a semiconductor manufacturing apparatus, M is M = 1/5, and in a scanner, M is 1/4.
[0017]
Since the step (z) of the step substrate can be measured in advance in the preliminary examination stage of the exposure process, the step (Z) of the main surface of the photomask for correcting the step is obtained from equation (1). By forming a mask substrate having a main surface step (Z) between main surfaces and using a photomask provided with a light-shielding pattern on each main surface, highly accurate pattern transfer without defocus can be achieved. . Here, the main surface refers to an object surface facing the image surface, that is, a surface of the photomask facing the resist film.
[0018]
In order to achieve the above object, based on the above findings, a photomask according to the present invention is formed on a processing object having a step, and removes a resist film step generated according to the step of the processing object. A photomask for transferring a mask pattern via a projection optical system to a resist film having a low film surface and a high film surface,
A transparent mask substrate having a thick plate portion having a large plate thickness and a thin plate portion having a thickness smaller than the plate thickness of the thick plate portion, and a main surface step between the main surface of the thick plate portion and the main surface of the thin plate portion is Z;
A first light-shielding film pattern provided on the main surface of the thick plate portion and forming a pattern to be transferred to the low film surface of the resist film, and a pattern provided on the main surface of the low film surface and transferring to the high film surface of the resist film And a mask pattern comprising a second light-shielding film pattern constituting
When the resist film step of the resist film is z and the magnification of the projection optical system is M,
Z = z / M 2 Equation (1)
It is characterized by the following.
[0019]
The transparent mask substrate of the present invention is a conventionally known transparent mask substrate, for example, a quartz substrate or the like. The light shielding film is also a conventionally known light shielding film such as a Cr film.
In the photomask according to the present invention, as described above, the Z main surface step is formed between the main surface of the thick plate portion having the first light shielding pattern and the main surface of the thin plate portion having the second light shielding pattern. With this arrangement, the imaging position of the first light-shielding pattern is shifted by M 2 × Z = z, so that the pattern of the first light-shielding pattern is on the low film surface of the resist film, and the pattern of the second light-shielding pattern is on the high surface of the resist film. An image can be accurately formed on the film surface.
By applying the photomask according to the present invention to transfer onto a resist film having a resist film step, the conventional focus shift does not occur, and as a result, an LSI pattern can be transferred with high accuracy.
[0020]
The photomask according to the present invention is formed on a workpiece having two or more steps, and has three mutually different high and low surfaces via a resist film step generated according to each step of the workpiece. The mask pattern can be transferred to a resist film having the above film surface.
In that case, the photomask has three main surfaces provided on the transparent mask substrate corresponding to the respective film surfaces of the resist film, and each main surface step between the main surfaces is expressed by a formula corresponding to each resist film step. It has the relationship of (1), and each main surface has a light-shielding film pattern that is transferred to each film surface.
[0021]
The method for manufacturing a photomask according to the present invention has a low film surface and a high film surface which are formed on a processing object having a step and through a resist film step generated according to the step of the processing object. A method for manufacturing a photomask for transferring a mask pattern to a resist film via a projection optical system,
Forming a resist mask on the transparent mask substrate, which covers the thick plate portion forming region of the plate-shaped transparent mask substrate and exposes the thin plate portion forming region,
When the resist film step of the resist film is z and the magnification of the projection optical system is M,
The main surface step Z between the main surface of the thick plate portion and the main surface of the thin plate portion is
Z = z / M 2 Equation (1)
The thin plate portion forming region is etched so as to have a main surface step Z defined by the formula, and a thick plate portion having a large plate thickness and a thin plate portion thinner than the thick plate portion are formed on the transparent mask substrate. Process and
The first light-shielding film pattern forming the pattern to be transferred to the low film surface of the resist film is formed on the main surface of the thick plate portion, and the second light-shielding film pattern forming the pattern to be transferred to the high film surface of the resist film is formed on the thin plate portion. And forming on a surface.
[0022]
The method for manufacturing a photomask according to the present invention includes a step of etching a transparent mask substrate and a step of forming a light-shielding film pattern, and does not require a film-forming step of an optical distance adjusting film or the like. .
[0023]
The exposure method according to the present invention is configured such that a film is formed on a workpiece having a step, and is projected onto a resist film having a low film surface and a high film surface through a resist film step generated according to the step of the workpiece. An exposure method for transferring a mask pattern of a photomask via an optical system,
Measuring a resist film step z between a high film surface and a low film surface of the resist film on the workpiece;
When the magnification of the projection optical system is M,
Z = z / M 2 Equation (1)
A pattern having a thick plate portion having a large plate thickness having a main surface step Z defined by the formula (1) and a thin plate portion thinner than the plate portion of the thick plate portion is formed to be transferred to a low film surface of a resist film. A projection optical system using a photomask having a first light-shielding film pattern to be transferred to the main surface of the thick plate portion and a second light-shielding film pattern forming a pattern to be transferred to the high film surface of the resist film on the main surface of the thin plate portion And a step of exposing through an interface.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail based on exemplary embodiments with reference to the accompanying drawings.
Embodiment of Photomask This embodiment is an example of an embodiment of a photomask according to the present invention, and FIG. 1 is a cross-sectional view showing a configuration of a photomask of the embodiment.
The photomask 40 of this embodiment is formed by using an ArF scanner with a projection magnification M = 1/4 on a resist film 64 formed on a stepped substrate 62 as shown in FIG. Is a photomask for transferring the circuit pattern of FIG.
The step substrate 62 has a high portion 62a having a dense circuit pattern and a low portion 62b having a sparse circuit pattern. The resist film 64 has a high film surface 64a corresponding to the high portion 62a of the step substrate 62 and a low portion 62b. Has a low film surface 64b.
The high film surface 64a of the resist film 64 on the high portion 62a is at a position higher than the low film surface 64b of the resist film 64 on the low portion 62b, and the step z between the high film surface 64a and the low film surface 64b is 0. 1 μm.
[0025]
The photomask 40 includes a transparent mask substrate 42 made of quartz having a thick plate portion 42 a having a thickness t a and a thin plate portion 42 b having a thickness t b smaller than the thick plate portion 42, and a transparent mask substrate. A first light-shielding pattern 44a and a second light-shielding pattern 44b are provided on the main surfaces of the thick plate portion 42a and the thin plate portion 42b, respectively, and are made of a Cr light-shielding film having the same thickness. The surfaces opposite to the main surfaces of the thick plate portion 42a and the thin plate portion 42b are on the same plane.
The first light-shielding pattern 44a on the thick plate portion 42 is a light-shielding pattern constituting a pattern to be transferred to the low film surface 64b of the resist film 64 on the step substrate 62, and the second light-shielding pattern 44b on the thin plate portion 42b is a resist. This is a light-shielding pattern constituting a pattern to be transferred to the high film surface 64a of the film 64.
[0026]
Between the thickness t b of the thickness t a and the thin portion 42b of the thick portion 42a on the basis of the equation (1),
Figure 2004233401
As relation is established, t a and t b are set.
[0027]
The photomask 40 of the present embodiment is provided with a first light-shielding pattern by providing a Z main surface step between the thick plate portion 42a having the first light-shielding pattern 44a and the thin plate portion 42b having the second light-shielding pattern 44b. By shifting the image formation position of 44a by M 2 × Z = z, the pattern of the first light-shielding pattern 44a is on the low film surface 64b of the resist film 64, and the pattern of the second light-shielding pattern 44b is on the high film surface of the resist film 64. 64a can be accurately imaged.
As a result, the defocus caused by the step on the surface of the resist film 64 formed on the step substrate 62 is compensated, and the desired mask pattern is accurately transferred from the photomask 40 to the resist film 64 on the step substrate 62. be able to.
[0028]
Embodiment of photomask manufacturing method This embodiment is an example of an embodiment in which the photomask manufacturing method according to the present invention is applied to the photomask manufacturing of the above-described embodiment. FIGS. 2A to 2D and 3E to 3G are cross-sectional views for respective steps in manufacturing a photomask.
First, as shown in FIG. 2A, a resist is applied to a transparent substrate 46 serving as a mask substrate, and a resist film 48 is formed.
Next, as shown in FIG. 2B, a lithography process is performed on the resist film 48 to form a resist mask 54 having a pattern which covers the thick plate portion forming region 50 of the substrate 46 and exposes the thin plate portion forming region 52. I do.
[0029]
Next, as shown in FIG. 2C, the thin plate portion 42b is formed by etching the substrate 46 from above the resist mask 54, and the thick plate portion forming region 50 that is not etched by being covered with the resist mask 54 is formed. A transparent mask substrate 42 to be a thick plate portion 42a is formed.
Next, after the resist mask 54 is peeled off, as shown in FIG. 2D, a thick film portion 42a and a thin plate portion 42b of the transparent mask substrate 42 are formed using a metal film formation process such as a CVD method or a sputtering method. A light-shielding film 56 made of a Cr film having a uniform thickness is formed.
[0030]
Next, as shown in FIG. 3E, a resist is applied on the light shielding film 56 to form a resist film 58.
Subsequently, as shown in FIG. 3F, a desired LSI circuit pattern is transferred to the resist film 58, and an etching mask 60 is formed.
Next, the light shielding film 56 is etched from above the etching mask 60, and after the etching, the etching mask 60 is peeled off. As shown in FIG. 3 (g), the light shielding pattern 44a is formed on the thick plate 42a and the light shielding pattern 44a is formed on the thin plate 42b. The light shielding pattern 44b is formed.
Through the above steps, the photomask 40 according to the embodiment can be easily manufactured by simple steps.
[0031]
Embodiment of exposure method This embodiment is an example of an embodiment of an exposure method according to the present invention, and FIG. 4 shows a pattern formed on a stepped substrate by the method of this embodiment when manufacturing a semiconductor device. FIG. 4 is a schematic view illustrating an exposure method for transferring a pattern.
First, a uniform film thickness is formed on a step substrate 62 having a high portion 62a having a high surface due to a dense circuit pattern such as a wiring pattern and a low portion 62b having a lower surface than the high portion 62a due to a sparse circuit pattern. To form a resist film 64.
Next, the level difference z between the film surface of the resist film 64 on the high part 62a and the film surface of the resist film 64 on the low part 62b is measured to obtain z = 0.1 μm.
[0032]
Then, the thick plate portion 42a of the transparent mask substrate 42 of the transparent mask substrate 42 having a thin plate portion 42b of reduced thickness t b from the thick plate portion 42a and the plate thickness is thick plate portion 42 of the thickness t a is the thickness and A photomask 40 having light-shielding patterns 44a and 44b made of a light-shielding film having the same thickness on each of the thin plate portions 42b is prepared.
The light-shielding pattern 44a on the thick plate portion 42 is a light-shielding pattern constituting a pattern to be transferred to the resist film 64 on the lower portion 62b of the step substrate 62, and the light-shielding pattern 44b on the thin plate portion 42b is a high portion of the step substrate 62. This is a light-shielding pattern constituting a pattern to be transferred to the resist film 64 on 62a.
Between the thickness t b of the thickness t a and the thin portion 42b of the thick portion 42a on the basis of the equation (1),
Figure 2004233401
There is a relationship.
[0033]
Next, the LSI circuit pattern of the photomask 40 composed of the light-shielding patterns 44a and 44b is transferred onto the resist film 64 of the step substrate 62 using an ArF scanner having a projection lens 66 with a projection magnification M = 1/4. I do.
By using the photomask 40, as shown in FIG. 4, the light transmitted through the thick plate portion 42a having the light shielding pattern 44a and collected by the projection lens 66 is converted into a resist film on the lower portion 62b of the step substrate 62. The light focused on the film surface 64b of the step 64, transmitted through the thin plate portion 42b having the light shielding pattern 44b, and condensed by the projection lens 66 forms an image on the film surface of the resist film 64a on the high portion 62a of the stepped substrate 62. I do.
Therefore, the LSI circuit pattern provided on the photomask 40 can be accurately transferred onto the resist film 64.
[0034]
【The invention's effect】
According to the photomask of the present invention, by providing a Z main surface step between the main surface of the thick plate portion having the first light shielding pattern and the main surface of the thin plate portion having the second light shielding pattern of the photomask. The image formation position of the first light-shielding pattern is shifted by M 2 × Z = z, and the pattern of the first light-shielding pattern is shifted to the lower film surface of the resist film, and the pattern of the second light-shielding pattern is shifted to the higher film surface of the resist film. An image can be formed accurately. By applying the photomask according to the present invention to transfer onto a resist film having a resist film step, the conventional focus shift does not occur, and as a result, an LSI pattern can be transferred with high accuracy.
[0035]
ADVANTAGE OF THE INVENTION According to the manufacturing method of the photomask concerning this invention, since it is comprised by the etching process of a transparent mask substrate and the formation process of a light-shielding film pattern, and does not require the film-forming process of an optical distance adjustment film etc., manufacture is easy. It is.
The exposure method according to the present invention realizes a preferable exposure method using the photomask according to the present invention. Eliminating the focus shift makes it possible to form a stable pattern, so that it is possible to transfer a finer pattern than before, thereby increasing the margin of the semiconductor manufacturing process and improving the manufacturing yield. In addition, since a desired pattern shape can be obtained regardless of the height difference, the performance of the semiconductor device is improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a photomask according to an embodiment.
FIGS. 2A to 2D are cross-sectional views for respective steps when manufacturing the photomask of the embodiment.
FIGS. 3 (e) to 3 (g) are cross-sectional views for respective steps in manufacturing the photomask of the embodiment, following FIGS. 2 (d).
FIG. 4 is a schematic diagram illustrating an exposure method for transferring a pattern onto a stepped substrate by the method of the present embodiment when manufacturing a semiconductor device.
FIG. 5 is a schematic view illustrating a conventional method of lithography applied to a step substrate.
FIGS. 6A and 6B are a cross-sectional view of a step substrate for transferring a contact hole and a CD-SEM photograph showing the diameter of the contact hole transferred to a resist film on the step substrate, respectively. Is.
FIG. 7 is a schematic diagram illustrating a configuration of a photomask proposed in Japanese Patent Application Laid-Open No. 4-212154.
[Explanation of symbols]
12 step substrate, 12a high part, 12b low part, 14 resist film, 16 projection lens, 18 photomask, 18a light-shielding pattern, 18b transparent mask substrate, 20 ... Step substrate, 22 photomask, 24 transparent substrate, 26 light-shielding pattern, 28 optical distance adjusting film, 30 lens, 32 resist film, 40 photo of the embodiment example Mask 42, transparent mask substrate 42a thick plate portion 42b thin plate portion 44a first light-shielding pattern 44b second light-shielding pattern 46 transparent substrate 48 resist film .., 50... Thick plate portion forming region, 52... Thin plate portion forming region, 54... Resist mask, 56... Light shielding film, 58. ... High section, 62b ..., Low portion, 64, resist film, 64a, high film surface, 64b, low film surface, 66, projection lens.

Claims (4)

段差を有する被加工体上に成膜され、被加工体の段差に応じて生じているレジスト膜段差を介して低膜面と高膜面とを有するレジスト膜に、投影光学系を介してマスクパターンを転写するフォトマスクであって、
板厚の厚い厚板部と、厚板部の板厚より薄い薄板部とを有し、厚板部の主面と薄板部の主面との主面段差がＺの透明マスク基板と、
厚板部の主面に設けられ、レジスト膜の低膜面に転写するパターンを構成する第１遮光膜パターンと、低膜面の主面に設けられ、レジスト膜の高膜面に転写するパターンを構成する第２遮光膜パターンとからなるマスクパターンと
を備え、
レジスト膜のレジスト膜段差をｚ、投影光学系の倍率をＭとするとき、
Ｚ＝ｚ／Ｍ２ ・・・・・・・式（１）
で規定されることを特徴とするフォトマスク。A resist film having a low film surface and a high film surface is formed through a resist film step formed on a processing object having a step and formed according to the step of the processing object via a projection optical system. A photomask for transferring a pattern,
A transparent mask substrate having a thick plate portion having a large plate thickness and a thin plate portion having a thickness smaller than the plate thickness of the thick plate portion, and a main surface step between the main surface of the thick plate portion and the main surface of the thin plate portion is Z;
A first light-shielding film pattern provided on the main surface of the thick plate portion and forming a pattern to be transferred to the low film surface of the resist film, and a pattern provided on the main surface of the low film surface and transferring to the high film surface of the resist film And a mask pattern comprising a second light-shielding film pattern constituting
When the resist film step of the resist film is z and the magnification of the projection optical system is M,
Z = z / M 2 Equation (1)
A photomask characterized by the following. フォトマスクが、２個以上の段差を有する被加工体上に成膜され、かつ被加工体の各段差に応じて生じているレジスト膜段差を介して高低の相互に異なる３面以上の膜面を有するレジスト膜にマスクパターンを転写するフォトマスクであって、
レジスト膜の各膜面に対応して３個の主面が透明マスク基板に設けられ、主面間の各主面段差が各レジスト膜段差に対応して式（１）の関係を有し、各主面がそれぞれ各膜面に転写する遮光膜パターンを備えていることを特徴とする請求項１に記載のフォトマスク。A photomask is formed on an object to be processed having two or more steps, and three or more film surfaces which are different from each other in height through a resist film step generated according to each step of the object. A photomask for transferring a mask pattern to a resist film having
Three main surfaces are provided on the transparent mask substrate corresponding to the respective film surfaces of the resist film, and each main surface step between the main surfaces has a relationship of Expression (1) corresponding to each resist film step, 2. The photomask according to claim 1, wherein each main surface is provided with a light-shielding film pattern transferred to each film surface. 段差を有する被加工体上に成膜され、被加工体の段差に応じて生じているレジスト膜段差を介して低膜面と高膜面とを有するレジスト膜に、投影光学系を介してマスクパターンを転写するフォトマスクの作製方法であって、
板状の透明マスク基板の厚板部形成領域を覆い、薄板部形成領域を露出するレジストマスクを透明マスク基板上に形成する工程と、
レジスト膜のレジスト膜段差をｚ、投影光学系の倍率をＭとするとき、
厚板部の主面と薄板部の主面との間の主面段差Ｚが、
Ｚ＝ｚ／Ｍ２ ・・・・・・・式（１）
で規定される主面段差Ｚを有するように、薄板部形成領域をエッチングして、板厚の厚い厚板部と、厚板部の板厚より薄い薄板部とを透明マスク基板上に形成する工程と、
レジスト膜の低膜面に転写するパターンを構成する第１遮光膜パターンを厚板部の主面に、レジスト膜の高膜面に転写するパターンを構成する第２遮光膜パターンを薄板部の主面に形成する工程と
を有することを特徴とするフォトマスクの作製方法。A resist film having a low film surface and a high film surface is formed through a resist film step formed on a processing object having a step and formed according to the step of the processing object via a projection optical system. A method for manufacturing a photomask for transferring a pattern,
Forming a resist mask on the transparent mask substrate, which covers the thick plate portion forming region of the plate-shaped transparent mask substrate and exposes the thin plate portion forming region,
When the resist film step of the resist film is z and the magnification of the projection optical system is M,
The main surface step Z between the main surface of the thick plate portion and the main surface of the thin plate portion is
Z = z / M 2 Equation (1)
The thin plate portion forming region is etched so as to have a main surface step Z defined by the formula, and a thick plate portion having a large plate thickness and a thin plate portion thinner than the thick plate portion are formed on the transparent mask substrate. Process and
The first light-shielding film pattern forming the pattern to be transferred to the low film surface of the resist film is formed on the main surface of the thick plate portion, and the second light-shielding film pattern forming the pattern to be transferred to the high film surface of the resist film is formed on the thin plate portion. Forming a photomask on a surface. 段差を有する被加工体上に成膜され、被加工体の段差に応じて生じるレジスト膜段差を介して低膜面と高膜面とを有するレジスト膜に、投影光学系を介してフォトマスクのマスクパターンを転写する露光方法であって、
被加工体上のレジスト膜の高膜面と低膜面とのレジスト膜段差ｚを測定する工程と、
投影光学系の倍率をＭとするとき、
Ｚ＝ｚ／Ｍ２ ・・・・・・・式（１）
式（１）で規定される主面段差Ｚを有する板厚の厚い厚板部と、厚板部の板厚より薄い薄板部とを有し、レジスト膜の低膜面に転写するパターンを構成する第１遮光膜パターンを厚板部の主面に、レジスト膜の高膜面に転写するパターンを構成する第２遮光膜パターンを薄板部の主面に備えるフォトマスクを使って、投影光学系を介して露光する工程と
を有することを特徴とする露光方法。A resist film having a low film surface and a high film surface is formed on a processing object having a step and a resist film having a low film surface and a high film surface through a resist film step generated according to the step of the processing object. An exposure method for transferring a mask pattern,
Measuring a resist film step z between a high film surface and a low film surface of the resist film on the workpiece;
When the magnification of the projection optical system is M,
Z = z / M 2 Equation (1)
A pattern having a thick plate portion having a large plate thickness having a main surface step Z defined by the formula (1) and a thin plate portion thinner than the plate portion of the thick plate portion is formed to be transferred to a low film surface of a resist film. A projection optical system using a photomask having a first light-shielding film pattern to be transferred to the main surface of the thick plate portion and a second light-shielding film pattern forming a pattern to be transferred to the high film surface of the resist film on the main surface of the thin plate portion And exposing through a method.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010062008A1 (en) * 2008-11-03 2010-06-03 한국과학기술원 Measurement pattern structure, processing pattern structure, substrate treatment apparatus, and substrate treatment method
CN108280317A (en) * 2018-04-27 2018-07-13 深圳市爱协生科技有限公司 Display driving integrated circuit structure and production method
US20210341830A1 (en) * 2020-03-23 2021-11-04 Kioxia Corporation Pattern forming method, photomask substrate creation method, photomask creation method, and photomask
CN113917799A (en) * 2021-09-28 2022-01-11 上海华力集成电路制造有限公司 Method for improving uniformity of exposure focal length

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010062008A1 (en) * 2008-11-03 2010-06-03 한국과학기술원 Measurement pattern structure, processing pattern structure, substrate treatment apparatus, and substrate treatment method
CN108280317A (en) * 2018-04-27 2018-07-13 深圳市爱协生科技有限公司 Display driving integrated circuit structure and production method
CN108280317B (en) * 2018-04-27 2024-02-13 深圳市爱协生科技股份有限公司 Display driving integrated circuit structure and manufacturing method thereof
US20210341830A1 (en) * 2020-03-23 2021-11-04 Kioxia Corporation Pattern forming method, photomask substrate creation method, photomask creation method, and photomask
CN113917799A (en) * 2021-09-28 2022-01-11 上海华力集成电路制造有限公司 Method for improving uniformity of exposure focal length
CN113917799B (en) * 2021-09-28 2023-11-10 上海华力集成电路制造有限公司 Method for improving exposure focal length uniformity

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