JP4714311B2 - Multi-tone photomask manufacturing method and pattern transfer method for thin film transistor substrate - Google Patents

Multi-tone photomask manufacturing method and pattern transfer method for thin film transistor substrate Download PDF

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JP4714311B2
JP4714311B2 JP2008047670A JP2008047670A JP4714311B2 JP 4714311 B2 JP4714311 B2 JP 4714311B2 JP 2008047670 A JP2008047670 A JP 2008047670A JP 2008047670 A JP2008047670 A JP 2008047670A JP 4714311 B2 JP4714311 B2 JP 4714311B2
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transparent film
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JP2009204934A (en
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道明 佐野
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Hoya 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
    • G03F1/36—Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
    • 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
    • G03F1/54—Absorbers, e.g. of opaque materials
    • 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
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/76—Patterning of masks by imaging
    • 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
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/80—Etching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H01L21/033—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers
    • H01L21/0332—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their composition, e.g. multilayer masks, materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H01L21/033—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers
    • H01L21/0334—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane
    • H01L21/0337—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising inorganic layers characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane characterised by the process involved to create the mask, e.g. lift-off masks, sidewalls, or to modify the mask, e.g. pre-treatment, post-treatment

Description

本発明は、液晶表示装置（Liquid CrystalDisplay：以下、ＬＣＤと称する）製造等に好適に用いられる５階調フォトマスクの製造方法及び５階調フォトマスク、並びに当該フォトマスクを用いたパターン転写方法に関するものである。  The present invention relates to a five-tone photomask manufacturing method, a five-tone photomask, and a pattern transfer method using the photomask, which are suitably used for manufacturing a liquid crystal display (LCD). Is.

現在、ＬＣＤの分野において、薄膜トランジスタ液晶表示装置（Thin FilmTransistor Liquid Crystal Display：以下、ＴＦＴ−ＬＣＤと呼ぶ）は、ＣＲＴ（陰極線管）に比較して、薄型にしやすく消費電力が低いという利点から、現在商品化が急速に進んでいる。ＴＦＴ−ＬＣＤは、マトリックス状に配列された各画素にＴＦＴが配列された構造のＴＦＴ基板と、各画素に対応して、レッド、グリーン、及びブルーの画素パターンが配列されたカラーフィルターが液晶相の介在の下に重ね合わされた概略構造を有する。ＴＦＴ−ＬＣＤでは、製造工程数が多く、ＴＦＴ基板だけでも５〜６枚のフォトマスクを用いて製造されていた。このような状況の下、ＴＦＴ基板の製造を４枚のフォトマスクを用いて行う方法が提案されている。   Currently, in the field of LCDs, thin film transistor liquid crystal displays (hereinafter referred to as TFT-LCDs) are easier to make thinner and have lower power consumption than CRTs (cathode ray tubes). Commercialization is progressing rapidly. A TFT-LCD includes a TFT substrate having a structure in which TFTs are arranged in pixels arranged in a matrix, and a color filter in which red, green, and blue pixel patterns are arranged corresponding to each pixel. It has a schematic structure superimposed under the intervention of. In TFT-LCD, the number of manufacturing processes is large, and the TFT substrate alone is manufactured using 5 to 6 photomasks. Under such circumstances, a method of manufacturing a TFT substrate using four photomasks has been proposed.

この方法は、遮光部と透光部の他に半透光部（グレートーン部）を有するグレートーンマスクと称されるフォトマスクを用いることにより、使用するマスク枚数を低減するというものである。ここで、半透光部とは、マスクを使用してパターンを被転写体に転写する際、透過する露光光の透過量を所定量低減させ、被転写体上のフォトレジスト膜の現像後の残膜量を制御する部分をいう。   In this method, the number of masks to be used is reduced by using a photomask called a gray tone mask having a semi-transparent portion (gray tone portion) in addition to the light shielding portion and the translucent portion. Here, the semi-transparent portion means that when a pattern is transferred to a transfer object using a mask, the amount of exposure light transmitted therethrough is reduced by a predetermined amount, and the photoresist film on the transfer object after development is developed. The part that controls the amount of remaining film.

ここで用いられるグレートーンマスクとしては、半透光部が、グレートーンマスクを使用するＬＣＤ用露光機の解像限界以下の微細パターンで形成されている構造のものが知られている。また、半透光部を半透過性の半透光膜とする構造のものも従来知られている。何れの構造のものであっても、この半透光部での露光量を所定量少なくして露光することが出来、被転写体上に、レジスト残膜値の異なる２つの転写パターンを転写することができることから、１枚のグレートーンマスクを用いて従来のフォトマスク２枚分の工程が実施されることにより、マスク枚数が削減される。   As the gray tone mask used here, one having a structure in which the semi-transparent portion is formed with a fine pattern below the resolution limit of an LCD exposure machine using the gray tone mask is known. A structure having a semi-transparent portion as a semi-transparent semi-transparent film is also known. Regardless of the structure, it is possible to expose the semi-translucent portion with a predetermined amount of light exposure, and transfer two transfer patterns having different resist residual film values onto the transfer target. Therefore, the number of masks can be reduced by performing a process for two conventional photomasks using one gray tone mask.

上記グレートーンマスクは、遮光部と透光部と半透光部とを有し、露光光透過率を３段階に変化させる３階調のフォトマスクである。したがって、１枚のさらに多階調のフォトマスクを用いれば、さらにマスク枚数を削減することが可能になる。   The gray tone mask is a three-tone photomask having a light-shielding portion, a light-transmitting portion, and a semi-light-transmitting portion, and changing the exposure light transmittance in three stages. Therefore, if one more multi-tone photomask is used, the number of masks can be further reduced.

従来、レジストパターンの形成と金属化合物等の膜のエッチングとを所望回数繰り返すことにより得られる、光透過率が３段階以上の多段階に変化する多階調フォトマスクが下記特許文献１に開示されている。また、遮光部と透光部の他にそれぞれ異なる光透過率の第１半透光部と第２半透光部を有する４階調フォトマスクをリソグラフィ工程により少ない描画回数で製造できる４階調フォトマスクの製造方法が下記特許文献２に開示されている。   Conventionally, a multi-tone photomask whose light transmittance changes in three or more stages and obtained by repeating resist pattern formation and etching of a film such as a metal compound a desired number of times is disclosed in Patent Document 1 below. ing. In addition to the light-shielding portion and the light-transmitting portion, a 4-tone photomask having a first semi-transparent portion and a second semi-transparent portion having different light transmittances can be manufactured by a lithography process with a small number of times of drawing. A photomask manufacturing method is disclosed in Patent Document 2 below.

特開平９−１４６２５９号公報JP 9-146259 A 特開２００７−２４９１９８号公報JP 2007-249198 A

しかしながら、上記特許文献１に開示された多階調フォトマスクの製造方法の場合、金属化合物等の膜をエッチングする回数と、そのエッチングマスク用のレジストパターンを形成するための描画回数とが同一回数となるため、所望の多階調とするためには描画回数が増大してしまう。例えば、露光光透過率を５段階以上に変化させる多階調フォトマスクを製造するためには、少なくとも４回以上の描画を行わなければならず、描画回数が増えれば、その位置合わせを高精度に行うことが困難になり、形成されるマスクパターン精度に影響する。近年、ＴＦＴ基板の製造等においても、より微細なパターンを形成することが要求されてきており、フォトマスク上のパターン精度は非常に重要である。フォトリソグラフィ工程の回数が増えることは、欠陥などの不都合が生じる確率が増大することでもあり、単純に階調を増加させることには懸念がある。   However, in the method of manufacturing a multi-tone photomask disclosed in Patent Document 1, the number of times of etching a film of a metal compound or the like is equal to the number of times of drawing for forming a resist pattern for the etching mask. Therefore, the number of times of drawing increases in order to obtain a desired multi-gradation. For example, in order to manufacture a multi-tone photomask in which the exposure light transmittance is changed in five steps or more, drawing must be performed at least four times, and if the number of drawing increases, the alignment is highly accurate. However, it is difficult to carry out the process, which affects the accuracy of the mask pattern to be formed. In recent years, it has been required to form a finer pattern also in the manufacture of a TFT substrate, and the pattern accuracy on a photomask is very important. Increasing the number of photolithography processes also increases the probability of inconveniences such as defects, and there is concern about simply increasing the gradation.

また、上記特許文献２に開示された４階調フォトマスクの製造方法によれば、フォトリソグラフィ工程によって描画回数を２回に低減して、４階調のフォトマスクを製造することができるが、さらに多階調、例えば５階調のフォトマスクを製造する場合、上記の４階調フォトマスクに限定された製造方法をそのまま適用することは勿論できない。   In addition, according to the method for manufacturing a four-tone photomask disclosed in Patent Document 2, a four-tone photomask can be manufactured by reducing the number of times of drawing to two by a photolithography process. Further, when manufacturing a multi-tone photomask, for example, a 5-tone photomask, it is of course impossible to apply the manufacturing method limited to the 4-tone photomask as it is.

本発明は、上記従来の事情に鑑みてなされたものであり、５階調のフォトマスクを少ない半透光膜の膜数と少ない描画回数で製造できる５階調フォトマスクの製造方法を提供することを第１の目的とする。また、本発明は、微細パターンが高精度に形成された５階調フォトマスクを提供することを第２の目的とする。さらに、上記５階調フォトマスクを用いたパターン転写方法を提供することを第３の目的とする。   The present invention has been made in view of the above-described conventional circumstances, and provides a five-tone photomask manufacturing method capable of manufacturing a five-tone photomask with a small number of semi-transparent films and a small number of writings. This is the first purpose. A second object of the present invention is to provide a five-tone photomask in which a fine pattern is formed with high accuracy. It is a third object of the present invention to provide a pattern transfer method using the five-tone photomask.

上記課題を解決するため、本発明は以下の構成を有する。
（構成１）透明基板上に、遮光部、透光部、及びそれぞれ露光光透過率の異なる第1半透光部と第２半透光部と第３半透光部からなるマスクパターンを有する５階調フォトマスクの製造方法であって、透明基板上に、エッチャントに対するエッチング選択性のある第１半透光膜と遮光膜とをこの順に有するフォトマスクブランクを準備する工程と、前記フォトマスクブランクの前記遮光膜上に形成したレジスト膜を描画、現像して第１レジストパターンを形成する工程と、前記第１レジストパターンをマスクとして前記遮光膜をエッチングして第１のパターニングを行う工程と、前記第１レジストパターンを除去した後、パターニングされた前記遮光膜を含む面上に形成したレジスト膜を描画、現像して第２レジストパターンを形成する工程と、前記第２レジストパターンをマスクとして前記第１半透光膜をエッチングして第２のパターニングを行う工程と、前記第２レジストパターンを除去した後、パターニングされた前記遮光膜及び前記第１半透光膜を含む基板全面に、前記第１半透光膜とのエッチャントに対するエッチング選択性のある第２半透光膜を形成する工程と、前記第２半透光膜上に形成したレジスト膜を描画、現像して第３レジストパターンを形成する工程と、前記第３レジストパターンをマスクとして前記第２半透光膜をエッチングして第３のパターニングを行う工程とを有することを特徴とする５階調フォトマスクの製造方法。 In order to solve the above problems, the present invention has the following configuration.
(Configuration 1) On the transparent substrate, there is a light shielding portion, a light transmitting portion, and a mask pattern composed of a first semi-transmissive portion, a second semi-transmissive portion, and a third semi-transmissive portion having different exposure light transmittances. A method for manufacturing a five-tone photomask, comprising: preparing a photomask blank having a first semi-transparent film and a light-shielding film having etching selectivity with respect to an etchant in this order on a transparent substrate; A step of drawing and developing a resist film formed on the blank light shielding film to form a first resist pattern; a step of etching the light shielding film using the first resist pattern as a mask and performing a first patterning; , After removing the first resist pattern, drawing and developing a resist film formed on the patterned surface including the light shielding film to form a second resist pattern; Etching the first semi-transparent film using the second resist pattern as a mask and performing second patterning; and removing the second resist pattern and then patterning the light-shielding film and the first semi-transparent film Forming a second semi-transparent film having etching selectivity with respect to an etchant with the first semi-transparent film on the entire surface of the substrate including the translucent film; and a resist film formed on the second semi-transparent film Drawing and developing to form a third resist pattern, and etching the second semi-transparent film using the third resist pattern as a mask to perform a third patterning. A method for manufacturing a five-tone photomask.

（構成２）透明基板上に、遮光部、透光部、及びそれぞれ露光光透過率の異なる第1半透光部と第２半透光部と第３半透光部からなるマスクパターンを有する５階調フォトマスクの製造方法であって、透明基板上に遮光膜を有するフォトマスクブランクを準備する工程と、前記フォトマスクブランクの前記遮光膜上に形成したレジスト膜を描画、現像して第１レジストパターンを形成する工程と、前記第１レジストパターンをマスクとして前記遮光膜をエッチングして第１のパターニングを行う工程と、前記第１レジストパターンを除去した後、パターニングされた前記遮光膜を含む基板全面に第１半透光膜を形成する工程と、前記第１半透光膜上に形成したレジスト膜を描画、現像して第２レジストパターンを形成する工程と、前記第２レジストパターンをマスクとして前記第１半透光膜をエッチングして第２のパターニングを行う工程と、前記第２レジストパターンを除去した後、パターニングされた前記遮光膜及び前記第１半透光膜を含む基板全面に、前記第１半透光膜とのエッチャントに対するエッチング選択性のある第２半透光膜を形成する工程と、前記第２半透光膜上に形成したレジスト膜を描画、現像して第３レジストパターンを形成する工程と、前記第３レジストパターンをマスクとして前記第２半透光膜をエッチングして第３のパターニングを行う工程とを有することを特徴とする５階調フォトマスクの製造方法。 (Configuration 2) On a transparent substrate, a light shielding portion, a light transmitting portion, and a mask pattern made up of a first semi-transmissive portion, a second semi-transmissive portion, and a third semi-transmissive portion having different exposure light transmittances are provided. A method for manufacturing a five-tone photomask, comprising: preparing a photomask blank having a light shielding film on a transparent substrate; and drawing and developing a resist film formed on the light shielding film of the photomask blank. Forming a resist pattern, etching the light shielding film using the first resist pattern as a mask, performing a first patterning, removing the first resist pattern, and then patterning the light shielding film A step of forming a first semi-transparent film on the entire surface of the substrate, a step of drawing and developing a resist film formed on the first semi-transparent film to form a second resist pattern, and the second resist Etching the first semi-transparent film using a strike pattern as a mask to perform second patterning, and removing the second resist pattern, and then patterning the light-shielding film and the first semi-transparent film Forming a second semi-transparent film having etching selectivity with respect to an etchant with the first semi-transparent film, and drawing and developing a resist film formed on the second translucent film And forming a third resist pattern, and etching the second semi-transparent film using the third resist pattern as a mask to perform a third patterning. Mask manufacturing method.

（構成３）前記第1半透光部、前記第２半透光部、及び前記第３半透光部は、前記第１半透光膜、前記第２半透光膜、前記第１半透光膜と前記第２半透光膜の積層膜のそれぞれいずれかにより形成されていることを特徴とする構成１又は２に記載の５階調フォトマスクの製造方法。
（構成４）前記遮光膜及び前記第２半透光膜はいずれもクロムを主成分とした材料からなり、前記第１半透光膜はモリブデンシリサイドを主成分とした材料からなることを特徴とする構成１乃至３のいずれか一に記載の５階調フォトマスクの製造方法。 (Structure 3) The first semi-transparent part, the second semi-transparent part, and the third semi-transparent part are the first semi-transparent film, the second semi-transparent film, and the first semi-transparent film. 3. The method for manufacturing a five-tone photomask according to Configuration 1 or 2, wherein the method is formed by any one of a transparent film and a laminated film of the second semi-transparent film.
(Structure 4) The light shielding film and the second semi-transparent film are both made of a material containing chromium as a main component, and the first semi-transparent film is made of a material containing molybdenum silicide as a main component. A manufacturing method of a five-tone photomask according to any one of configurations 1 to 3.

（構成５）透明基板上に、遮光部、透光部、及びそれぞれ露光光透過率の異なる第1半透光部と第２半透光部と第３半透光部からなるマスクパターンを有し、前記遮光部は、少なくとも前記透明基板上に形成された遮光膜により形成され、前記透光部は、露出した前記透明基板により形成され、前記第1半透光部、前記第２半透光部、及び前記第３半透光部は、前記透明基板上に形成された、露光光透過率の異なる第１半透光膜と第２半透光膜、前記第１半透光膜と前記第２半透光膜の積層膜のうちのそれぞれいずれかにより形成されていることにより、露光光透過率を５段階に変化させることを特徴とする５階調フォトマスク。
（構成６）前記遮光膜及び前記第２半透光膜はいずれもクロムを主成分とした材料からなり、前記第１半透光膜はモリブデンシリサイドを主成分とした材料からなることを特徴とする構成５に記載の５階調フォトマスク。 (Configuration 5) On the transparent substrate, there is a light shielding portion, a light transmitting portion, and a mask pattern including a first semi-transmissive portion, a second semi-transmissive portion, and a third semi-transmissive portion having different exposure light transmittances. The light-shielding portion is formed of at least a light-shielding film formed on the transparent substrate, and the light-transmitting portion is formed of the exposed transparent substrate, and the first semi-transmissive portion and the second semi-transmissive portion are formed. The light part and the third semi-transparent part are formed on the transparent substrate, the first semi-transparent film and the second semi-transparent film having different exposure light transmittances, and the first semi-transparent film, A five-tone photomask, wherein the exposure light transmittance is changed in five stages by being formed by any one of the laminated films of the second semi-transparent films.
(Structure 6) The light shielding film and the second semi-transparent film are both made of a material containing chromium as a main component, and the first semi-transparent film is made of a material containing molybdenum silicide as a main component. 5. The five-tone photomask according to Configuration 5.

（構成７）構成１乃至４のいずれかに記載の製造方法によるフォトマスク、あるいは、構成５又は６に記載のフォトマスクを用いて、被転写体に露光光を照射する露光工程を有し、被転写体上に５階調の転写パターンを形成することを特徴とするパターン転写方法。 (Configuration 7) An exposure step of irradiating a transfer target with exposure light using the photomask according to any one of Configurations 1 to 4 or the photomask according to Configuration 5 or 6, A pattern transfer method, wherein a transfer pattern having 5 gradations is formed on a transfer object.

本発明の５階調フォトマスクの製造方法によれば、遮光膜の他に、互いに露光光透過率の異なる第１半透光膜と第２半透光膜との組み合わせを用い、フォトリソグラフィ法によって描画回数を３回に低減して、露光光透過率が５段階に異なる５階調のフォトマスクを製造することができる。
また、上述のように描画回数を３回に低減して製造できることにより、微細パターンが高精度に形成された５階調のフォトマスクが得られる。 According to the five-tone photomask manufacturing method of the present invention, in addition to the light-shielding film, a combination of a first semi-transmissive film and a second semi-transmissive film having different exposure light transmittances is used, and a photolithography method is used. Thus, the number of drawing can be reduced to 3 times, and a photomask having five gradations with different exposure light transmittances in five stages can be manufactured.
Further, as described above, since the number of times of drawing can be reduced to three, it is possible to obtain a five-tone photomask in which a fine pattern is formed with high accuracy.

また、本発明に係る５階調フォトマスクを用いたパターン転写方法によれば、精度の高い多階調のパターン転写を実施することができ、またその結果、例えばＴＦＴ基板の製造等においてマスク枚数の大幅な削減が可能になる。   Further, according to the pattern transfer method using the five-tone photomask according to the present invention, highly accurate multi-tone pattern transfer can be carried out. Can be significantly reduced.

以下、本発明を実施するための最良の形態を図面に基づき説明する。
［第１の実施の形態］
図１は、本発明に係る５階調フォトマスクの第１の実施の形態と、当該５階調フォトマスクを用いたパターン転写方法を説明するための断面図である。
図１に示す５階調フォトマスク１０は、例えば液晶表示装置（ＬＣＤ）の薄膜トランジスタ（ＴＦＴ）やカラーフィルタ、またはプラズマディスプレイパネル（ＰＤＰ）などを製造するための多階調グレートーンマスクとして用いられるものであり、図１に示す被転写体２０上に、膜厚が段階的または連続的に異なるレジストパターン２３を形成するものである。なお、図１中において符号２２Ａ、２２Ｂ、２２Ｃ、２２Ｄは、被転写体２０において基板２１上に積層された膜を示す。 The best mode for carrying out the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a cross-sectional view for explaining a first embodiment of a five-tone photomask according to the present invention and a pattern transfer method using the five-tone photomask.
A five-tone photomask 10 shown in FIG. 1 is used as, for example, a multi-tone graytone mask for manufacturing a thin film transistor (TFT), a color filter, a plasma display panel (PDP), or the like of a liquid crystal display device (LCD). Thus, resist patterns 23 having different thicknesses are formed stepwise or continuously on the transfer target 20 shown in FIG. In FIG. 1, reference numerals 22 </ b> A, 22 </ b> B, 22 </ b> C, and 22 </ b> D denote films stacked on the substrate 21 in the transfer target 20.

上記本実施の形態のフォトマスク１０は、具体的には、当該フォトマスク１０の使用時に露光光を遮光（透過率が略０％）させる遮光部１１と、ガラス基板等の透明基板１４の表面が露出して露光光を透過させる透光部１２と、透光部１２の露光光透過率を１００％としたとき透過率を１０〜８０％程度、好ましくは、２０〜７０％程度の範囲内に低減させ、この範囲内において露光光透過率が３段階に異なる第1半透光部１３Ａと第２半透光部１３Ｂと第３半透光部１３Ｃとを有して構成されている。上記半透光部は、透明基板１４上に光半透過性の半透光膜が形成されて構成され、本実施の形態では、そのうちの第1半透光部１３Ａは、露光光波長に対する透過率のそれぞれ異なる第１半透光膜１６と第２半透光膜１７の積層膜により形成され、第２半透光部１３Ｂは上記第１半透光膜１６により形成され、また第３半透光部１３Ｃは上記第２半透光膜１７により形成されている。また、上記遮光部１１は、透明基板１４上に、上記第１半透光膜１６、遮光層１５ａ及び反射防止層１５ｂの積層からなる遮光膜１５、及び上記第２半透光膜１７が順に設けられて形成されている。したがって、上記フォトマスク１０は、露光光透過率が５段階に異なる５階調のフォトマスクとなっている。なお、図１に示す遮光部１１、透光部１２、及び半透光部１３Ａ〜１３Ｃのパターン形状はあくまでも一例である。   Specifically, the photomask 10 of the present embodiment includes a light shielding portion 11 that shields exposure light (transmittance is approximately 0%) when the photomask 10 is used, and a surface of a transparent substrate 14 such as a glass substrate. Is exposed and transmits the exposure light, and the exposure light transmittance of the light transmitting portion 12 is 100%, the transmittance is about 10 to 80%, preferably about 20 to 70%. In this range, the first semi-transparent part 13A, the second semi-transparent part 13B, and the third semi-transparent part 13C having different exposure light transmittances in three stages are configured. The semi-translucent portion is configured by forming a semi-translucent film that is semi-transparent on the transparent substrate 14, and in the present embodiment, the first semi-transparent portion 13A of the semi-transparent portion is transmissive to the exposure light wavelength. The first semi-transparent film 16 and the second semi-transparent film 17 having different rates are formed, and the second semi-transparent portion 13B is formed by the first semi-transparent film 16 and the third semi-transparent film. The translucent part 13 </ b> C is formed by the second semi-transparent film 17. In addition, the light shielding unit 11 includes the first semi-transparent film 16, the light shielding film 15 formed by stacking the light shielding layer 15 a and the antireflection layer 15 b, and the second semi-transparent film 17 in this order on the transparent substrate 14. It is provided and formed. Therefore, the photomask 10 is a five-gradation photomask having different exposure light transmittances in five stages. In addition, the pattern shape of the light-shielding part 11, the translucent part 12, and the semi-transparent parts 13A-13C shown in FIG. 1 is an example to the last.

上述のような５階調フォトマスク１０を使用して、被転写体２０へのパターン転写を行ったときに、遮光部１１では露光光が実質的に透過せず、透光部１２では露光光が透過し、第１〜第３半透光部１３Ａ〜１３Ｃでは各々の光透過率に応じて露光光が低減される。そのため、被転写体２０上に塗布したレジスト膜（ここではポジ型フォトレジスト膜）は、パターン転写後、現像を経たとき、上記遮光部１１に対応する部分で膜厚が最も厚くなる。また、上記第１〜第３半透光部１３Ａ〜１３Ｃに対応する部分ではいずれも遮光部１１に対応する部分の膜厚よりも薄くなるが、例えば上記第１半透光膜１６の露光光透過率が上記第２半透光膜１７の露光光透過率よりも低く設定されている場合は、上記半透光部に対応する部分において段階的に膜厚が薄くなる。また、透光部１２に対応する部分では膜がない。その結果、膜厚が５段階に異なる（そのうちの１段階は膜がない）レジストパターン２３を形成する。例えば、第１〜第３半透光部の透過率は、透光部を１００％としたとき、それぞれ、２０％、４０％、６０％程度とすることができる。なお、ネガ型フォトレジストを用いた場合には、レジスト膜厚が上記と逆転することを考慮した設計を行う必要がある。   When the pattern transfer to the transfer target 20 is performed using the five-tone photomask 10 as described above, the exposure light is not substantially transmitted through the light shielding unit 11 and the exposure light is transmitted through the light transmitting unit 12. And the exposure light is reduced in the first to third semi-transparent portions 13A to 13C according to the respective light transmittances. Therefore, the resist film (here, positive photoresist film) applied on the transfer target 20 has the largest thickness in the portion corresponding to the light-shielding portion 11 when developed after pattern transfer. In addition, the portions corresponding to the first to third semi-transparent portions 13A to 13C are all thinner than the portion corresponding to the light-shielding portion 11, but for example, the exposure light of the first semi-transparent film 16 When the transmittance is set to be lower than the exposure light transmittance of the second semi-transparent film 17, the film thickness gradually decreases in the portion corresponding to the semi-transparent portion. Further, there is no film in the portion corresponding to the light transmitting portion 12. As a result, resist patterns 23 having different film thicknesses in five stages (one of which has no film) are formed. For example, the transmittance of the first to third semi-transparent parts can be about 20%, 40%, and 60%, respectively, when the translucent part is 100%. In the case of using a negative photoresist, it is necessary to design in consideration of the reverse of the resist film thickness.

そして、図１に示すレジストパターン２３の膜のない部分（上記透光部１２に対応する部分）で、被転写体２０における例えば膜２２Ａ〜２２Ｄに第１エッチングを実施する。続いて、レジストパターン２３の膜のうち膜厚が最も薄い部分（上記第３半透光部１３Ｃに対応する部分）をアッシング等によって除去しこの部分で、被転写体２０における例えば膜２２Ｂ〜２２Ｄに第２エッチングを実施する。続いて、レジストパターン２３のうち次に膜厚が薄い部分（上記第２半透光部１３Ｂに対応する部分）をアッシング等によって除去しこの部分で、被転写体２０における例えば膜２２Ｃ及び２２Ｄに第３エッチングを実施する。続いて更に、レジストパターン２３のうち次に膜厚が薄い部分（上記第１半透光部１３Ａに対応する部分）をアッシング等によって除去しこの部分で、被転写体２０における例えば膜２２Ｄに第４エッチングを実施する。このようにして、１枚の５階調フォトマスク１０を用いて、例えばＴＦＴ基板の製造における従来のフォトマスク４枚分の工程が実施されることになり、従来よりもマスク枚数を大幅に削減することが可能になる。   Then, first etching is performed on, for example, the films 22 </ b> A to 22 </ b> D in the transferred body 20 in a portion where the film of the resist pattern 23 shown in FIG. Subsequently, the thinnest part (the part corresponding to the third semi-transparent part 13C) of the film of the resist pattern 23 is removed by ashing or the like, and, for example, the films 22B to 22D in the transferred body 20 are removed. A second etching is performed. Subsequently, the next thinnest part of the resist pattern 23 (the part corresponding to the second semi-translucent portion 13B) is removed by ashing or the like, and this part is formed on, for example, the films 22C and 22D in the transferred body 20. A third etching is performed. Subsequently, the next thinnest portion of the resist pattern 23 (the portion corresponding to the first semi-translucent portion 13A) is removed by ashing or the like, and this portion is transferred to, for example, the film 22D in the transferred body 20. 4 Etching is performed. In this way, the process for four conventional photomasks in the manufacture of a TFT substrate, for example, is carried out using a single five-tone photomask 10, and the number of masks is greatly reduced compared to the prior art. It becomes possible to do.

次に、上記５階調フォトマスクの製造方法について説明する。図２は、上記第１の実施の形態の５階調フォトマスク１０の製造工程を工程順に示す断面図である。
使用するフォトマスクブランクは、図２（ａ）に示すように、ガラス基板等の透明基板１４上に、第１半透光膜１６と、遮光層１５ａ及び反射防止層１５ｂの積層からなる遮光膜１５が順に形成されている。ただし、上記第１半透光膜１６と上記遮光膜１５は、エッチング工程に用いるエッチャントに対するエッチング選択性のある材質の組み合わせが選択される。したがって、上記遮光層１５ａとしては、例えばクロム又はその化合物（例えばＣｒＮ，ＣｒＯ，ＣｒＣ等）が好ましく挙げられ、上記反射防止層１５ｂとしては、クロム系化合物（例えばＣｒＮ，ＣｒＯ，ＣｒＣ等）などが挙げられ、さらに上記第１半透光膜１６としては、例えば金属シリサイド、特にモリブデンシリサイド化合物（MoSixのほか、MoSiの窒化物、酸化物、酸化窒化物、炭化物など）等が好ましく挙げられる。上記第１半透光膜１６は、透明基板１４（透光部）の露光光の透過量に対し１０〜８０％程度、好ましくは２０〜７０％程度の透過量を有するものが好ましい。 Next, a method for manufacturing the above-described five-tone photomask will be described. FIG. 2 is a cross-sectional view showing the manufacturing steps of the five-tone photomask 10 of the first embodiment in the order of steps.
As shown in FIG. 2A, the photomask blank used is a light-shielding film comprising a first semi-transparent film 16, a light-shielding layer 15a and an antireflection layer 15b on a transparent substrate 14 such as a glass substrate. 15 are formed in order. However, the first semi-transparent film 16 and the light shielding film 15 are selected from a combination of materials having etching selectivity with respect to the etchant used in the etching process. Therefore, as the light shielding layer 15a, for example, chromium or a compound thereof (for example, CrN, CrO, CrC, etc.) is preferably mentioned, and as the antireflection layer 15b, a chromium compound (for example, CrN, CrO, CrC, etc.) or the like is preferable. Further, as the first semi-transparent film 16, for example, metal silicide, particularly molybdenum silicide compound (MoSix, MoSi nitride, oxide, oxynitride, carbide, etc.) and the like are preferably mentioned. The first semi-transparent film 16 preferably has a transmission amount of about 10 to 80%, preferably about 20 to 70% with respect to the transmission amount of the exposure light of the transparent substrate 14 (translucent portion).

なお、上記第１半透光膜１６と後述の第２半透光膜１７とは露光光透過率が異なるようにするため、第１半透光膜１６の膜材質と膜厚は、後述の第２半透光膜１７の膜材質と膜厚との兼ね合いも考慮して設定される。   The first semi-transparent film 16 and the second semi-transparent film 17 which will be described later have different exposure light transmittances. The second semi-transparent film 17 is set in consideration of the balance between the film material and the film thickness.

まず、上記フォトマスクブランク上にレジストを塗布してレジスト膜を形成し、１度目の描画を行う。本実施の形態では例えばレーザー光を用いる。また、上記レジストとしてはポジ型フォトレジストを使用する。そして、レジスト膜に対し、所定のデバイスパターンを描画し、描画後に現像を行うことにより、例えば製造されるフォトマスクの遮光部１１に対応する領域に第１レジストパターン３０を形成する（図２（ｂ）参照）。   First, a resist is applied on the photomask blank to form a resist film, and a first drawing is performed. In this embodiment, for example, laser light is used. A positive photoresist is used as the resist. Then, by drawing a predetermined device pattern on the resist film and performing development after the drawing, for example, a first resist pattern 30 is formed in a region corresponding to the light shielding portion 11 of the manufactured photomask (FIG. 2 ( b)).

次に、上記第１レジストパターン３０をエッチングマスクとして遮光層１５ａ及び反射防止層１５ｂの積層からなる遮光膜１５をエッチングして遮光膜パターンを形成する（図２（ｃ）参照）。クロムを主成分とする遮光膜１５を用いた場合、エッチング手段としては、ドライエッチングもしくはウェットエッチングのどちらでも可能であるが、たとえば大型液晶表示パネル製造に使用する大型サイズのフォトマスクでは、ウェットエッチングが好適である。ウェットエッチングでは、エッチング液として例えば硝酸セリウム第二アンモニウムを用いる。なお、上記遮光膜１５とその下の第１半透光膜１６は、エッチャントに対するエッチング選択性を有する材質で形成されているため、上記遮光膜１５のエッチング時には第１半透光膜１６はエッチングされにくい。   Next, by using the first resist pattern 30 as an etching mask, the light shielding film 15 formed by stacking the light shielding layer 15a and the antireflection layer 15b is etched to form a light shielding film pattern (see FIG. 2C). When the light shielding film 15 mainly composed of chromium is used, the etching means can be either dry etching or wet etching. For example, in the case of a large-sized photomask used for manufacturing a large liquid crystal display panel, wet etching is used. Is preferred. In the wet etching, for example, cerium diammonium nitrate is used as an etchant. Since the light shielding film 15 and the first semi-transparent film 16 therebelow are formed of a material having etching selectivity with respect to the etchant, the first semi-transparent film 16 is etched when the light shielding film 15 is etched. It is hard to be done.

残存する第１レジストパターン３０を除去した後（図２（ｄ）参照）、再び全面に上記と同じレジスト膜を形成し、２度目の描画を行う。すなわち、このレジスト膜に対し、所定のパターンを描画し、描画後に現像を行うことにより、例えば製造されるフォトマスクの遮光部１１と第１半透光部１３Ａ及び第２半透光部１３Ｂに対応する領域に第２レジストパターン３１を形成する（図２（ｅ）参照）。   After the remaining first resist pattern 30 is removed (see FIG. 2D), the same resist film as described above is formed again on the entire surface, and a second drawing is performed. That is, a predetermined pattern is drawn on the resist film, and development is performed after the drawing. For example, the light shielding part 11 and the first semi-transparent part 13A and the second semi-transparent part 13B of the manufactured photomask A second resist pattern 31 is formed in the corresponding region (see FIG. 2E).

次に、上記第２レジストパターン３１をエッチングマスクとして、露出した第３半透光部１３Ｃ及び透光部１２領域上の第１半透光膜１６をエッチングする（図２（ｆ）参照）。Ｍｏ化合物を主成分とする第１半透光膜１６を用いた場合、エッチング手段としては、ドライエッチングもしくはウェットエッチングのどちらでも可能であるが、ウェットエッチングではエッチング液として例えばフッ化水素アンモニウムを主成分とするものを用いる。   Next, using the second resist pattern 31 as an etching mask, the exposed third semi-transparent portion 13C and the first semi-transparent film 16 on the translucent portion 12 region are etched (see FIG. 2F). When the first semi-transparent film 16 containing Mo compound as a main component is used, either dry etching or wet etching can be used as an etching means. In wet etching, for example, ammonium hydrogen fluoride is mainly used as an etching solution. Use ingredients.

残存する第２レジストパターン３１を除去した後（図２（ｇ）参照）、パターニングされた遮光膜１５及び第１半透光膜１６を含む基板全面に、第２半透光膜１７を成膜する（図２（ｈ）参照）。ただし、第２半透光膜１７は、前記第１半透光膜１６とのエッチャントに対するエッチング選択性のある材質が選択される。従って、第１半透光膜１６に例えば前述のＭｏ化合物を用いる場合、上記第２半透光膜１７としては、例えばクロム化合物などが好ましく挙げられる。クロム化合物には、酸化クロム(ＣｒＯｘ)、窒化クロム(ＣｒＮｘ)、炭化クロム(ＣｒＣｘ)、酸窒化クロム(ＣｒＯｘＮ)、フッ化クロム(ＣｒＦｘ)や、これらに炭素や水素を含むものがある。また、上記第２半透光膜１７についても、透明基板２４（透光部）の露光光の透過量に対し１０〜８０％程度、好ましくは２０〜７０％程度の透過量を有することが望ましいが、同時に第１半透光膜１６とは露光光透過率が異なるように、第２半透光膜１７の膜材質と膜厚の選定によって設定される。   After the remaining second resist pattern 31 is removed (see FIG. 2G), the second semi-transmissive film 17 is formed on the entire surface of the substrate including the patterned light-shielding film 15 and the first semi-transmissive film 16. (See FIG. 2 (h)). However, the second semi-transparent film 17 is made of a material having etching selectivity with respect to the etchant with the first semi-transparent film 16. Therefore, when using, for example, the aforementioned Mo compound for the first semi-transparent film 16, the second semi-transparent film 17 is preferably a chromium compound, for example. The chromium compounds include chromium oxide (CrOx), chromium nitride (CrNx), chromium carbide (CrCx), chromium oxynitride (CrOxN), chromium fluoride (CrFx), and those containing carbon and hydrogen. The second semi-transparent film 17 also has a transmission amount of about 10 to 80%, preferably about 20 to 70% with respect to the transmission amount of the exposure light of the transparent substrate 24 (translucent portion). However, it is set by selecting the film material and film thickness of the second semi-transparent film 17 so that the exposure light transmittance is different from that of the first semi-transparent film 16 at the same time.

次に、上記第１半透光膜１７上の全面に再度前記と同じレジスト膜を形成し、３度目の描画を行う。すなわち、このレジスト膜に対し、所定のパターンを描画し、描画後、現像を行うことにより、例えば製造されるフォトマスクの遮光部１１と第１半透光部１３Ａ及び第３半透光部１３Ｃに対応する領域に第３レジストパターン３２を形成する（図２（ｉ）参照）。   Next, the same resist film as described above is formed again on the entire surface of the first semi-transparent film 17, and a third drawing is performed. That is, a predetermined pattern is drawn on the resist film, and development is performed after the drawing. For example, the light shielding portion 11 of the manufactured photomask, the first semi-transmissive portion 13A, and the third semi-transmissive portion 13C. A third resist pattern 32 is formed in a region corresponding to (see FIG. 2I).

次いで、上記第３レジストパターン３２をエッチングマスクとして、露出した第２半透光部１３Ｂ及び透光部１２領域上の第２半透光膜１７を同時にエッチングする（図２（ｊ）参照）。クロム化合物を主成分とする第２半透光膜１７を用いた場合、エッチング手段としては、ドライエッチングもしくはウェットエッチングのどちらでも可能であるが、ウェットエッチングではエッチング液として例えば硝酸セリウム第二アンモニウムを用いる。なお、第２半透光膜１７と第１半透光膜１６は、エッチャントに対するエッチング選択性を有する材質で形成されているため、例えば上記第２半透光部１３Ｂ領域上では、上記第２半透光膜１７のエッチング時にはその下の第１半透光膜１６はエッチングされにくい。エッチング選択性が十分でない場合には、エッチングストッパ膜を介在させることも可能であるが、フォトリソグラフィ工程をより効率化し、欠陥発生の確率を減少させるために、上記の手法はより有利である。   Next, using the third resist pattern 32 as an etching mask, the exposed second semi-transparent portion 13B and the second semi-transparent film 17 on the translucent portion 12 region are simultaneously etched (see FIG. 2J). When the second semi-transparent film 17 containing a chromium compound as a main component is used, the etching means can be either dry etching or wet etching. In wet etching, for example, cerium nitrate ammonium nitrate is used as an etching solution. Use. Note that the second semi-transparent film 17 and the first semi-transparent film 16 are formed of a material having etching selectivity with respect to the etchant, and thus, for example, in the region of the second semi-transparent portion 13B, At the time of etching the semi-transparent film 17, the first semi-transparent film 16 therebelow is hardly etched. If the etching selectivity is not sufficient, an etching stopper film can be interposed, but the above method is more advantageous in order to make the photolithography process more efficient and reduce the probability of defect occurrence.

そして、残存する第３レジストパターン３２を除去する。こうして、透明基板１４上に、第１半透光膜１６と、遮光層１５ａ及び反射防止層１５ｂからなる遮光膜１５と、第２半透光膜１７との積層によりなる遮光部１１、透明基板１４が露出する透光部１２、及び、第１半透光膜１６と第２半透光膜１７の積層によりなる第１半透光部１３Ａと、第１半透光膜１６によりなる第２半透光部１３Ｂと、第２半透光膜１７によりなる第３半透光部１３Ｃを有するマスクパターンが形成された、露光光透過率が５段階に異なる５階調のフォトマスク１０が出来上がる（図２（ｋ）参照）。   Then, the remaining third resist pattern 32 is removed. Thus, on the transparent substrate 14, the light-shielding portion 11 formed by stacking the first semi-transmissive film 16, the light-shielding film 15 including the light-shielding layer 15 a and the antireflection layer 15 b, and the second semi-transmissive film 17, the transparent substrate 14 is exposed, the first semi-transparent part 13A formed by stacking the first semi-transparent film 16 and the second semi-transparent film 17, and the second semi-transparent film 16 is formed. A photomask 10 having five gradations with different exposure light transmittances in five stages is formed, in which a mask pattern having a semi-transparent portion 13B and a third semi-transparent portion 13C made of the second semi-transparent film 17 is formed. (See FIG. 2 (k)).

以上のように本実施の形態によれば、遮光膜の他に、互いに露光光透過率の異なる第１半透光膜と第２半透光膜との組み合わせを用い、フォトリソグラフィ法によって描画回数を３回に低減して、少ない膜数と少ない描画回数で、露光光透過率が５段階に異なる５階調のフォトマスクを製造することができる。
また、上述のように描画回数を３回に低減して製造できることにより、微細パターンが高精度に形成された５階調のフォトマスクが得られる。 As described above, according to the present embodiment, in addition to the light-shielding film, a combination of the first semi-transmissive film and the second semi-transmissive film having different exposure light transmittances is used, and the number of times of drawing is performed by photolithography. Can be reduced to three times, and a five-gradation photomask with different exposure light transmittances in five stages can be manufactured with a small number of films and a small number of writings.
Further, as described above, since the number of times of drawing can be reduced to three, it is possible to obtain a five-tone photomask in which a fine pattern is formed with high accuracy.

また、前述の図１に示すような本発明に係る５階調フォトマスクを用いたパターン転写を実施すると、被転写体には精度の高い多階調の転写パターンを形成することができる。またその結果、例えばＴＦＴ基板の製造等においてマスク枚数の大幅な削減が可能になる。   In addition, when pattern transfer using the five-tone photomask according to the present invention as shown in FIG. 1 is performed, a highly accurate multi-tone transfer pattern can be formed on the transfer target. As a result, for example, the number of masks can be greatly reduced in the manufacture of TFT substrates.

［第２の実施の形態］
次に、図３及び図４に従って本発明の第２の実施の形態を説明する。図３は、本発明に係る５階調フォトマスクの第２の実施の形態と、当該５階調フォトマスクを用いたパターン転写方法を説明するための断面図であり、図４は、上記第２の実施の形態の５階調フォトマスク１０の製造工程を工程順に示す断面図である。なお、前述の第１の実施の形態を示す図１及び図２と同等の箇所には同一の符号を付している。 [Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view for explaining a second embodiment of a five-tone photomask according to the present invention and a pattern transfer method using the five-tone photomask, and FIG. It is sectional drawing which shows the manufacturing process of the 5-tone photomask 10 of 2nd Embodiment in process order. In addition, the same code | symbol is attached | subjected to the location equivalent to FIG.1 and FIG.2 which shows the above-mentioned 1st Embodiment.

図３に示す本実施の形態のフォトマスク１０は、前述の第１の実施の形態と同様、具体的には、当該フォトマスク１０の使用時に露光光を遮光（透過率が略０％）させる遮光部１１と、ガラス基板等の透明基板１４の表面が露出して露光光を透過させる透光部１２と、透光部１２の露光光透過率を１００％としたとき透過率を１０〜８０％程度、好ましくは、２０〜７０％程度の範囲内に低減させ、この範囲内において露光光透過率が３段階に異なる第1半透光部１３Ａと第２半透光部１３Ｂと第３半透光部１３Ｃとを有して構成されている。そして、上記第1半透光部１３Ａは、露光光波長に対する透過率のそれぞれ異なる第１半透光膜１６と第２半透光膜１７の積層膜により形成され、第２半透光部１３Ｂは上記第１半透光膜１６により形成され、また第３半透光部１３Ｃは上記第２半透光膜１７により形成されている。また、本実施の形態では、上記遮光部１１は、透明基板１４上に、遮光層１５ａ及び反射防止層１５ｂの積層からなる遮光膜１５、上記第１半透光膜１６、及び上記第２半透光膜１７が順に設けられて形成されている点が、第１の実施の形態とは異なっている。したがって、上記フォトマスク１０は、露光光透過率が５段階に異なる５階調のフォトマスクとなっている。   The photomask 10 of this embodiment shown in FIG. 3 specifically blocks exposure light (transmittance is approximately 0%) when the photomask 10 is used, as in the first embodiment. The light-shielding part 11, the light-transmitting part 12 through which the surface of the transparent substrate 14 such as a glass substrate is exposed to transmit the exposure light, and the light-transmitting part 12 exposure light transmittance of 100%, the transmittance is 10 to 80 %, Preferably within the range of about 20 to 70%, and within this range, the first semi-translucent portion 13A, the second semi-transparent portion 13B, and the third semi-transmission portion having different exposure light transmittances in three stages. The light transmitting portion 13C is included. The first semi-transparent portion 13A is formed of a laminated film of a first semi-transparent film 16 and a second semi-transparent film 17 having different transmittances with respect to the exposure light wavelength, and the second semi-transparent portion 13B. Is formed by the first semi-transparent film 16, and the third semi-transparent portion 13 C is formed by the second semi-transparent film 17. In the present embodiment, the light-shielding portion 11 is formed on the transparent substrate 14 with the light-shielding film 15 including the light-shielding layer 15 a and the antireflection layer 15 b, the first semi-transparent film 16, and the second half. The point from which the translucent film | membrane 17 is provided and formed in order differs from 1st Embodiment. Therefore, the photomask 10 is a five-gradation photomask having different exposure light transmittances in five stages.

本実施の形態に係る５階調フォトマスク１０を使用して、被転写体２０へのパターン転写を行ったときに、遮光部１１では露光光が実質的に透過せず、透光部１２では露光光が透過し、第１〜第３半透光部１３Ａ〜１３Ｃでは各々の光透過率に応じて露光光が低減される。そのため、被転写体２０上に塗布したレジスト膜（ここではポジ型フォトレジスト膜）は、パターン転写後、現像を経たとき、上記遮光部１１に対応する部分で膜厚が最も厚くなり、また上記第１〜第３半透光部１３Ａ〜１３Ｃに対応する部分ではいずれも遮光部１１に対応する部分の膜厚よりも薄くなるが、例えば上記第１半透光膜１６の露光光透過率が上記第２半透光膜１７の露光光透過率よりも低く設定されている場合は、上記半透光部に対応する部分において段階的に膜厚が薄くなり、また透光部１２に対応する部分では膜のない、膜厚が５段階に異なる（そのうちの１段階は膜がない）レジストパターン２３を形成する。   When pattern transfer to the transfer target 20 is performed using the five-tone photomask 10 according to the present embodiment, the light shielding portion 11 does not substantially transmit the exposure light, and the light transmitting portion 12 The exposure light is transmitted, and the exposure light is reduced according to the respective light transmittances in the first to third semi-transparent portions 13A to 13C. Therefore, the resist film (here, positive photoresist film) applied on the transfer target 20 has the largest thickness in the portion corresponding to the light shielding portion 11 when the development is performed after pattern transfer. Although the portions corresponding to the first to third semi-transparent portions 13A to 13C are all thinner than the portion corresponding to the light-shielding portion 11, the exposure light transmittance of the first semi-transparent film 16 is, for example, When the exposure light transmittance of the second semi-transparent film 17 is set lower than that of the second semi-transparent film 17, the film thickness gradually decreases in the portion corresponding to the semi-transparent portion and also corresponds to the translucent portion 12. A resist pattern 23 having no film and having different film thicknesses in five stages (one of which has no film) is formed.

そして、前述したように、図３に示す膜厚が５段階に異なるレジストパターン２３を用いて、被転写体２０における例えば膜２２Ａ〜２２Ｄのエッチングを実施することにより、例えばＴＦＴ基板の製造における従来のフォトマスク４枚分の工程が実施されることになり、従来よりもマスク枚数を大幅に削減することが可能になる。   Then, as described above, for example, in the manufacture of a TFT substrate, for example, by etching the films 22A to 22D in the transfer target 20 using the resist patterns 23 having different film thicknesses in five stages as shown in FIG. Thus, the process for four photomasks is carried out, and the number of masks can be greatly reduced as compared with the prior art.

次に、図４を用いて、上記本実施の形態に係る５階調フォトマスクの製造方法を説明する。
使用するフォトマスクブランクは、図４（ａ）に示すように、ガラス基板等の透明基板１４上に、遮光層１５ａ及び反射防止層１５ｂの積層からなる遮光膜１５が形成されている。上記遮光層１５ａとしては、例えばクロム又はその化合物（例えばＣｒＮ，ＣｒＯ，ＣｒＣ等）が好ましく挙げられ、上記反射防止層１５ｂとしては、クロム系化合物（例えばＣｒＮ，ＣｒＯ，ＣｒＣ等）などが挙げられる。
なお、製造されるフォトマスクにおける遮光部１１の透過率は、主に上記遮光層１５ａと上記反射防止層１５ｂの膜材質と膜厚との選定によって設定される。 Next, a manufacturing method of the five-tone photomask according to the present embodiment will be described with reference to FIG.
As shown in FIG. 4A, the photomask blank to be used has a light shielding film 15 formed of a laminate of a light shielding layer 15a and an antireflection layer 15b on a transparent substrate 14 such as a glass substrate. As the light shielding layer 15a, for example, chromium or a compound thereof (for example, CrN, CrO, CrC, etc.) is preferably mentioned, and as the antireflection layer 15b, a chromium compound (for example, CrN, CrO, CrC, etc.) can be mentioned. .
The transmittance of the light shielding part 11 in the photomask to be manufactured is set mainly by selecting the film material and film thickness of the light shielding layer 15a and the antireflection layer 15b.

まず、上記フォトマスクブランク上にレジストを塗布してレジスト膜を形成し、１度目の描画を行う。描画には、本実施の形態では例えばレーザー光を用いる。上記レジストとしてはポジ型フォトレジストを使用する。そして、レジスト膜に対し、所定のデバイスパターンを描画し、描画後に現像を行うことにより、例えば製造されるフォトマスクの遮光部１１に対応する領域に第１レジストパターン３０を形成する（図４（ｂ）参照）。   First, a resist is applied on the photomask blank to form a resist film, and a first drawing is performed. In the present embodiment, for example, laser light is used for drawing. A positive photoresist is used as the resist. Then, a predetermined device pattern is drawn on the resist film, and development is performed after the drawing, thereby forming a first resist pattern 30 in a region corresponding to the light shielding portion 11 of the manufactured photomask, for example (FIG. 4 ( b)).

次に、上記第１レジストパターン３０をエッチングマスクとして遮光層１５ａ及び反射防止層１５ｂの積層からなる遮光膜１５をエッチングして遮光膜パターンを形成する（図４（ｃ）参照）。クロムを主成分とする遮光膜１５を用いた場合、エッチング手段としては、ドライエッチングもしくはウェットエッチングのどちらでも可能であるが、たとえば大型サイズのフォトマスク製造に好適なウェットエッチングでは、エッチング液として例えば硝酸セリウム第二アンモニウムを用いる。   Next, by using the first resist pattern 30 as an etching mask, the light shielding film 15 formed by laminating the light shielding layer 15a and the antireflection layer 15b is etched to form a light shielding film pattern (see FIG. 4C). When the light shielding film 15 mainly composed of chromium is used, the etching means can be either dry etching or wet etching. For example, in wet etching suitable for manufacturing a large size photomask, Cerium diammonium nitrate is used.

残存する第１レジストパターン３０を除去した後、パターニングされた遮光膜１５を含む基板全面に、第１半透光膜１６を成膜する（図４（ｄ）参照）。
上記第１半透光膜１６としては、例えばＭｏ化合物（MoSixのほか、MoSiの窒化物、酸化物、酸化窒化物、炭化物など）が好ましく挙げられる。また、本実施の形態では、第１半透光膜１６は、遮光膜１５とのエッチング選択性はとくに要求されないため、例えば遮光膜と同様、クロム又はクロム系化合物を用いることもできる。クロム系化合物には、酸化クロム(ＣｒＯｘ)、窒化クロム(ＣｒＮｘ)、炭化クロム(ＣｒＣｘ)、酸窒化クロム(ＣｒＯｘＮ)、フッ化クロム(ＣｒＦｘ)や、これらに炭素や水素を含むものがある。上記第１半透光膜１６は、透明基板１４（透光部）の露光光の透過量に対し１０〜８０％程度、好ましくは２０〜７０％程度の透過量を有するものが好ましい。 After removing the remaining first resist pattern 30, the first semi-transparent film 16 is formed on the entire surface of the substrate including the patterned light shielding film 15 (see FIG. 4D).
Preferred examples of the first semi-transparent film 16 include Mo compounds (MoSix, MoSi nitride, oxide, oxynitride, carbide, etc.). In the present embodiment, the first semi-transparent film 16 is not particularly required to have etching selectivity with respect to the light shielding film 15, and therefore, for example, chromium or a chromium-based compound can be used as in the case of the light shielding film. The chromium-based compounds include chromium oxide (CrOx), chromium nitride (CrNx), chromium carbide (CrCx), chromium oxynitride (CrOxN), chromium fluoride (CrFx), and those containing carbon and hydrogen. The first semi-transparent film 16 preferably has a transmission amount of about 10 to 80%, preferably about 20 to 70% with respect to the transmission amount of the exposure light of the transparent substrate 14 (translucent portion).

また、上記第１半透光膜１６は、後述の第２半透光膜１７との関係では、エッチング選択性が要求されると同時に、両者の露光光透過率が異なるようにするため、第１半透光膜１６の膜材質と膜厚は、後述の第２半透光膜１７の膜材質と膜厚との兼ね合いも考慮して設定される。   In addition, the first semi-transparent film 16 is required to have etching selectivity at the same time as the second semi-transparent film 17 to be described later, and at the same time, the exposure light transmittance of the two is different. The film material and film thickness of the first semi-transparent film 16 are set in consideration of the balance between the film material and film thickness of the second semi-transparent film 17 described later.

次に、再び全面に上記と同じレジスト膜を形成し、２度目の描画を行う。すなわち、このレジスト膜に対し、所定のパターンを描画し、描画後に現像を行うことにより、例えば製造されるフォトマスクの遮光部１１と第１半透光部１３Ａ及び第２半透光部１３Ｂに対応する領域に第２レジストパターン３１を形成する（図４（ｅ）参照）。   Next, the same resist film as described above is formed again on the entire surface, and a second drawing is performed. That is, a predetermined pattern is drawn on the resist film, and development is performed after the drawing. For example, the light shielding part 11 and the first semi-transparent part 13A and the second semi-transparent part 13B of the manufactured photomask A second resist pattern 31 is formed in the corresponding region (see FIG. 4E).

次に、上記第２レジストパターン３１をエッチングマスクとして、露出した第３半透光部１３Ｃ及び透光部１２領域上の第１半透光膜１６をエッチングする（図４（ｆ）参照）。Ｍｏ化合物を主成分とする第１半透光膜１６を用いた場合、エッチング手段としては、ドライエッチングもしくはウェットエッチングのどちらでも可能であるが、ウェットエッチングではエッチング液として例えばフッ化水素アンモニウムを主成分とするものを用いる。また、クロム系化合物を主成分とする第１半透光膜１６を用いた場合、ドライエッチングもしくはウェットエッチングのどちらでも可能であるが、ウェットエッチングでは、エッチング液として例えば硝酸セリウム第二アンモニウムを用いる。   Next, using the second resist pattern 31 as an etching mask, the exposed third semi-transparent portion 13C and the first semi-transparent film 16 on the translucent portion 12 region are etched (see FIG. 4F). When the first semi-transparent film 16 containing Mo compound as a main component is used, either dry etching or wet etching can be used as an etching means. In wet etching, for example, ammonium hydrogen fluoride is mainly used as an etching solution. Use ingredients. In addition, when the first semi-transparent film 16 containing a chromium-based compound as a main component is used, either dry etching or wet etching is possible. In wet etching, for example, cerium nitrate ammonium nitrate is used as an etchant. .

残存する第２レジストパターン３１を除去した後（図４（ｇ）参照）、パターニングされた遮光膜１５及び第１半透光膜１６を含む基板全面に、第２半透光膜１７を成膜する（図４（ｈ）参照）。ただし、第２半透光膜１７は、前記第１半透光膜１６とのエッチャントに対するエッチング選択性のある材質が選択される。従って、第１半透光膜１６に例えば前述のＭｏ化合物を用いる場合、上記第２半透光膜１７としては、例えばクロム系化合物などが好ましく挙げられる。また反対に、第１半透光膜１６に例えばクロム系化合物を用いる場合、上記第２半透光膜１７としては、例えばＭｏ化合物などが好ましく挙げられる。また、上記第２半透光膜１７についても、透明基板２４（透光部）の露光光の透過量に対し１０〜８０％程度、好ましくは２０〜７０％程度の透過量を有することが望ましいが、同時に第１半透光膜１６とは露光光透過率が異なるように、第２半透光膜１７の膜材質と膜厚の選定によって設定される。   After removing the remaining second resist pattern 31 (see FIG. 4G), the second semi-transmissive film 17 is formed on the entire surface of the substrate including the patterned light-shielding film 15 and the first semi-transmissive film 16. (See FIG. 4 (h)). However, the second semi-transparent film 17 is made of a material having etching selectivity with respect to the etchant with the first semi-transparent film 16. Therefore, for example, when the Mo compound described above is used for the first semi-transparent film 16, the second semi-transparent film 17 is preferably a chromium compound, for example. On the other hand, when a chromium-based compound is used for the first semi-transparent film 16, for example, a Mo compound is preferably used as the second semi-transparent film 17, for example. The second semi-transparent film 17 also has a transmission amount of about 10 to 80%, preferably about 20 to 70% with respect to the transmission amount of the exposure light of the transparent substrate 24 (translucent portion). However, it is set by selecting the film material and film thickness of the second semi-transparent film 17 so that the exposure light transmittance is different from that of the first semi-transparent film 16 at the same time.

次に、上記第１半透光膜１７上の全面に再度前記と同じレジスト膜を形成し、３度目の描画を行う。すなわち、このレジスト膜に対し、所定のパターンを描画し、描画後、現像を行うことにより、例えば製造されるフォトマスクの遮光部１１と第１半透光部１３Ａ及び第３半透光部１３Ｃに対応する領域に第３レジストパターン３２を形成する（図４（ｉ）参照）。   Next, the same resist film as described above is formed again on the entire surface of the first semi-transparent film 17, and a third drawing is performed. That is, a predetermined pattern is drawn on the resist film, and development is performed after the drawing. For example, the light shielding portion 11 of the manufactured photomask, the first semi-transmissive portion 13A, and the third semi-transmissive portion 13C. A third resist pattern 32 is formed in a region corresponding to (see FIG. 4I).

次いで、上記第３レジストパターン３２をエッチングマスクとして、露出した第２半透光部１３Ｂ及び透光部１２領域上の第２半透光膜１７をエッチングする（図４（ｊ）参照）。第２半透光膜１７のエッチング手段としては、ドライエッチングもしくはウェットエッチングのどちらでも可能である。なお、第２半透光膜１７と第１半透光膜１６は、エッチャントに対するエッチング選択性を有する材質で形成されているため、例えば上記第２半透光部１３Ｂ領域上では、上記第２半透光膜１７のエッチング時にはその下の第１半透光膜１６はエッチングされにくい。   Next, using the third resist pattern 32 as an etching mask, the exposed second semi-transparent portion 13B and the second semi-transparent film 17 on the translucent portion 12 region are etched (see FIG. 4J). As an etching means for the second semi-transparent film 17, either dry etching or wet etching can be used. Note that the second semi-transparent film 17 and the first semi-transparent film 16 are formed of a material having etching selectivity with respect to the etchant, and thus, for example, in the region of the second semi-transparent portion 13B, At the time of etching the semi-transparent film 17, the first semi-transparent film 16 therebelow is hardly etched.

そして、残存する第３レジストパターン３２を除去する。こうして、透明基板１４上に、遮光層１５ａ及び反射防止層１５ｂからなる遮光膜１５と、第１半透光膜１６と第２半透光膜１７との積層によりなる遮光部１１、透明基板１４が露出する透光部１２、及び、第１半透光膜１６と第２半透光膜１７の積層によりなる第１半透光部１３Ａと、第１半透光膜１６によりなる第２半透光部１３Ｂと、第２半透光膜１７によりなる第３半透光部１３Ｃを有するマスクパターンが形成された、露光光透過率が５段階に異なる５階調のフォトマスク１０が出来上がる（図４（ｋ）参照）。   Then, the remaining third resist pattern 32 is removed. In this way, on the transparent substrate 14, the light-shielding part 11 formed by the lamination of the light-shielding film 15 including the light-shielding layer 15 a and the antireflection layer 15 b, the first semi-transparent film 16 and the second semi-transparent film 17, and the transparent substrate 14. Is exposed, the first semi-transparent portion 13A formed by stacking the first semi-transparent film 16 and the second semi-transparent film 17, and the second semi-transparent film 16. A photomask 10 having five gradations with different exposure light transmittances in five stages is formed, in which a mask pattern having a light transmissive part 13B and a third semi-light transmissive part 13C made of the second semi-light transmissive film 17 is formed ( (Refer FIG.4 (k)).

以上説明した本実施の形態においても、遮光膜の他に、互いに露光光透過率の異なる第１半透光膜と第２半透光膜との組み合わせを用い、フォトリソグラフィ法によって描画回数を３回に低減して、少ない膜数と少ない描画回数で、露光光透過率が５段階に異なる５階調のフォトマスクを製造することができる。
また、上述のように描画回数を３回に低減して製造できることにより、微細パターンが高精度に形成された５階調のフォトマスクが得られる。 Also in the present embodiment described above, in addition to the light-shielding film, a combination of the first semi-transmissive film and the second semi-transmissive film having different exposure light transmittances is used, and the number of times of drawing is 3 by photolithography. Thus, a five-tone photomask having different exposure light transmittances in five stages can be manufactured with a small number of films and a small number of writings.
Further, as described above, since the number of times of drawing can be reduced to three, it is possible to obtain a five-tone photomask in which a fine pattern is formed with high accuracy.

また、前述の図３に示すような本実施の形態に係る５階調フォトマスクを用いたパターン転写を実施すると、被転写体には精度の高い多階調の転写パターンを形成することができる。またその結果、例えばＴＦＴ基板の製造等においてマスク枚数の大幅な削減が可能になる。   In addition, when pattern transfer using the five-tone photomask according to the present embodiment as shown in FIG. 3 is performed, a highly accurate multi-tone transfer pattern can be formed on the transfer target. . As a result, for example, the number of masks can be greatly reduced in the manufacture of TFT substrates.

なお、本発明による５階調のフォトマスクには、上記のほか以下に述べる利点がある。
一般に、本発明の属する多階調フォトマスク（遮光部、透光部のほかに半透光部を有する３階調以上のフォトマスク）においては、被転写体上に所望の残膜値をもつレジストパターンを得るために、半透光部の露光光透過率を選択し、決定する。この透過率としては、透光部（すなわち透明基板が露出している部分）の透過率を１００％としたときの、半透過膜の透過率を用いて規定する。これは、一定以上の広い領域のパターンについて、その透過率を特定する場合には問題がないが、ある程度以下の寸法のパターンに対しては、厳密にいうと、実際のパターン転写に寄与する露光光量を正確に反映していないこととなる。これは露光光の回折が原因であるため、この傾向は微小なパターンになるほど、露光光波長が長いほど顕著になる。しかし、パターンの寸法や、分光特性の異なる光源に対する透過率の変化については正確に考慮されていないのが現状である。 In addition to the above, the five-tone photomask according to the present invention has the following advantages.
In general, a multi-tone photomask to which the present invention belongs (a photomask having three or more tones having a semi-transparent portion in addition to a light-shielding portion and a light-transmitting portion) has a desired remaining film value on a transfer target. In order to obtain a resist pattern, the exposure light transmittance of the semi-translucent portion is selected and determined. The transmittance is defined using the transmittance of the semi-transmissive film when the transmittance of the light transmitting portion (that is, the portion where the transparent substrate is exposed) is 100%. This is not a problem when specifying the transmittance of a pattern of a wide area above a certain level, but strictly speaking, for a pattern with a size of a certain degree or less, exposure that contributes to actual pattern transfer. The amount of light is not accurately reflected. Since this is due to diffraction of exposure light, this tendency becomes more prominent as the exposure light wavelength becomes longer as the pattern becomes smaller. However, the present situation is that the change in transmittance with respect to light sources having different pattern dimensions and spectral characteristics is not accurately taken into consideration.

具体的には、半透光部に、非常に狭い幅を含むパターン形状と、相対的に広い領域のパターン形状とが存在すると、半透光部には、被転写体上のレジスト膜に、常に一定の残膜値を与えるものであるべきところ、パターン形状に起因して異なる残膜値のレジストパターンが形成されてしまい、所望の許容範囲を越えた残膜値のばらつきを生じると、電子デバイス製造上の不安定要素となるという問題がある。   Specifically, when a pattern shape including a very narrow width and a pattern shape of a relatively wide region are present in the semi-transparent portion, the semi-transparent portion has a resist film on the transfer target, Where a constant residual film value should always be given, a resist pattern with a different residual film value is formed due to the pattern shape, and if the residual film value varies beyond the desired tolerance, There is a problem that it becomes an unstable factor in device manufacturing.

例えば、薄膜トランジスタ用の多階調フォトマスクとしては、チャネル部に相当する領域を半透光部とし、これを挟む形で隣接するソース及びドレインに相当する領域を遮光部で構成したものが多用される。このフォトマスクは、通常i線〜ｇ線の波長帯の露光光を用いて露光されるが、チャネル部の寸法（幅）が小さくなるにしたがい、隣接する遮光部との境界が、実際の露光条件下においてぼかされ、チャネル部の露光光透過率は半透過膜の透過率よりも低くなる。図５は、遮光部Ａに挟まれた半透光部Ｂのパターン（同図（１））と、該半透光部Ｂの透過光の光強度分布（同図（２））を示したもので、同図（ａ）は一例として半透光領域の幅が４μｍ、同図（ｂ）は２μｍの場合をそれぞれ示している。すなわち、図５（ａ），（ｂ）に示すように、遮光部Ａに挟まれた半透光部Ｂの透過光の光強度分布は、その半透光部Ｂの線幅が小さくなると、全体に下がり、ピークが低くなる。つまり、幅が狭い領域を有するパターンについては、実際に露光に寄与する透過率が相対的に低い一方、相対的に線幅が広い領域を有するパターンについては、実際の露光に寄与する透過率が相対的に高い。例えば、図６に示すように、チャネル幅が５μｍ以下では、該チャネル幅に対応した幅の半透光部における、実際の露光に寄与する光の透過率が顕著に低下する。   For example, a multi-tone photomask for a thin film transistor is often used in which a region corresponding to a channel portion is a semi-translucent portion and a region corresponding to a source and a drain adjacent to each other is formed by a light shielding portion. The This photomask is normally exposed using exposure light in the wavelength band of i-line to g-line, but as the size (width) of the channel portion becomes smaller, the boundary with the adjacent light-shielding portion is the actual exposure. The exposure light transmittance of the channel portion is lower than the transmittance of the semi-transmissive film. FIG. 5 shows a pattern of the semi-transparent portion B sandwiched between the light-shielding portions A (FIG. 1 (1)) and the light intensity distribution of the transmitted light of the semi-transparent portion B (FIG. 2). FIG. 6A shows the case where the width of the semi-translucent region is 4 μm as an example, and FIG. 6B shows the case where the width is 2 μm. That is, as shown in FIGS. 5A and 5B, the light intensity distribution of the transmitted light of the semi-transparent part B sandwiched between the light-shielding parts A is as follows. The whole is lowered and the peak is lowered. In other words, the transmittance that actually contributes to the exposure is relatively low for the pattern having the narrow width region, while the transmittance that contributes to the actual exposure is the pattern that has the relatively wide line width. Relatively high. For example, as shown in FIG. 6, when the channel width is 5 μm or less, the transmissivity of light contributing to actual exposure in the semi-transparent portion having a width corresponding to the channel width is significantly reduced.

そこで、一定の寸法をもつ半透光部の透過率を、その膜固有の透過率と区別し、実際の露光光の透過量を、透光部の透過量との比において、実効透過率として把握する必要が生じる。
一方で、膜固有の透過率とは、透明基板上の該膜を形成した、十分に広い領域において、該膜の組成や膜厚によって決定されるものである。十分に広い領域とは、該領域の広さの変化によって、実効透過率が実質的に変化しないような領域をいう。なお、図６においては、半透光部Ｂの透過光の光強度分布のピーク値によって、該領域の透過率を代表させている。この部分の透過率は、この多階調マスクを使用して露光したときの、被転写体上のレジスト残膜値と相関をもつ。 Therefore, the transmissivity of the semi-transparent part having a certain size is distinguished from the transmissivity inherent to the film, and the actual amount of exposure light transmission is determined as the effective transmissivity in the ratio of the transmissivity of the translucent part. It is necessary to grasp.
On the other hand, the transmittance specific to the film is determined by the composition and film thickness of the film in a sufficiently wide region where the film is formed on the transparent substrate. A sufficiently wide region refers to a region where the effective transmittance does not substantially change due to a change in the size of the region. In FIG. 6, the transmittance of the region is represented by the peak value of the light intensity distribution of the transmitted light of the semi-translucent portion B. The transmittance of this portion has a correlation with the resist residual film value on the transfer target when the multi-tone mask is used for exposure.

そこで、半透光部のパターン形状に応じて、その部分の膜透過膜を変えることにより、パターン形状に拘わらず、半透光部のレジスト膜の残膜値をほぼ同一にできることとなる。
例えば、本発明の方法によれば、５つの階調を有する多階調フォトマスクを得ることができる。すなわち、透光部、遮光部のほかに、３つの異なる膜透過率を有する半透光部を得ることができるのである。この３種類の半透光部によって、被転写体上に、それぞれ異なるレジスト残膜値をもつレジストパターンを形成してもよい。しかしながら、他方、この３種類の半透光部によって、被転写体上に、パターンの寸法が異なる（従って、同一の膜透過率を有する半透光部を使用すると、形成されるレジスト残膜値が異なってしまう）にもかかわらず、一定のレジスト残膜値を有するレジストパターンを形成してもよい。換言すれば、膜構成として３種類の膜透過率を有し、ほぼ同一の実効透過率を有する半透光部を形成しても良い。この場合、本発明のフォトマスクを３階調フォトマスクとして用いることになる。 Therefore, by changing the film-transmitting film in that portion according to the pattern shape of the semi-transparent portion, the remaining film value of the resist film in the semi-transparent portion can be made almost the same regardless of the pattern shape.
For example, according to the method of the present invention, a multi-gradation photomask having five gradations can be obtained. That is, in addition to the light transmitting portion and the light shielding portion, a semi-light transmitting portion having three different film transmittances can be obtained. With these three types of semi-transparent portions, resist patterns having different resist residual film values may be formed on the transfer target. However, on the other hand, the three types of semi-transparent portions have different pattern dimensions on the transfer target (thus, if semi-transparent portions having the same film transmittance are used, the resist residual film value formed However, a resist pattern having a certain resist residual film value may be formed. In other words, a semi-transparent portion having three types of film transmittances as the film configuration and having substantially the same effective transmittance may be formed. In this case, the photomask of the present invention is used as a three-tone photomask.

もちろん、３種類の半透光部のうち、２種類を、同一の実効透過率を有する異なる形状のパターンに用い、残りの１種類を、異なる実効透過率を有するパターンに供しても良い。この場合、本発明のフォトマスクを４階調のフォトマスクとして用いることになる。
本発明は、このような優れた効果をもたらす多階調フォトマスクを、効率的で、かつ欠陥発生の確率の低い工程によって、作製することができる点で、量産上のメリットが大きい。 Of course, two of the three types of semi-transparent portions may be used for differently shaped patterns having the same effective transmittance, and the remaining one type may be used for patterns having different effective transmittances. In this case, the photomask of the present invention is used as a four-tone photomask.
The present invention has a great advantage in mass production in that a multi-tone photomask that provides such an excellent effect can be manufactured by a process that is efficient and has a low probability of occurrence of defects.

なお、上述の第１の実施の形態及び第２の実施の形態においては、いずれも上記第１半透光膜１６の露光光透過率が上記第２半透光膜１７の露光光透過率よりも低く設定されている場合を説明したが、両者の露光光透過率が異なればよいので、これとは逆に、例えば上記第１半透光膜１６の露光光透過率が上記第２半透光膜１７の露光光透過率よりも高く設定されてもよい。   In both the first embodiment and the second embodiment described above, the exposure light transmittance of the first semi-transmissive film 16 is higher than the exposure light transmittance of the second semi-transmissive film 17. However, the exposure light transmittance of the first semi-transparent film 16 is opposite to that of the second semi-transparent film 16 because the exposure light transmittance of the two is different. The exposure light transmittance of the optical film 17 may be set higher.

本発明に係る５階調フォトマスクの第１の実施の形態と、当該５階調フォトマスクを用いたパターン転写方法を説明するための断面図である。It is sectional drawing for demonstrating 1st Embodiment of the 5 gradation photomask which concerns on this invention, and the pattern transfer method using the said 5 gradation photomask. 上記第１の実施の形態に係る５階調フォトマスクの製造工程を工程順に示す断面図である。It is sectional drawing which shows the manufacturing process of the 5-tone photomask which concerns on the said 1st Embodiment in order of a process. 本発明に係る５階調フォトマスクの第２の実施の形態と、当該５階調フォトマスクを用いたパターン転写方法を説明するための断面図である。It is sectional drawing for demonstrating 2nd Embodiment of the 5 gradation photomask which concerns on this invention, and the pattern transfer method using the said 5 gradation photomask. 上記第２の実施の形態に係る５階調フォトマスクの製造工程を工程順に示す断面図である。It is sectional drawing which shows the manufacturing process of the 5-tone photomask which concerns on the said 2nd Embodiment in order of a process. 遮光部Ａに挟まれた半透光部Ｂのパターン（同図（１））と、該半透光部Ｂの透過光の光強度分布（同図（２））を示し、同図（ａ）は半透光領域の幅が４μｍ、同図（ｂ）は２μｍの場合を示す。The pattern of the semi-translucent part B sandwiched between the light-shielding parts A (FIG. 1A) and the light intensity distribution of the transmitted light of the semi-transparent part B (FIG. 2B) are shown. ) Shows a case where the width of the semi-translucent region is 4 μm, and FIG. チャネル幅と該チャネル幅に対応した幅の半透光部における露光光の透過率との関係を示す図である。It is a figure which shows the relationship between the transmittance | permeability of exposure light in the semi-transmission part of the width | variety corresponding to the channel width and this channel width.

符号の説明Explanation of symbols

１０ ５階調フォトマスク
１１ 遮光部
１２ 透光部
１３Ａ 第１半透光部
１３Ｂ 第２半透光部
１３Ｃ 第３半透光部
１４ 透明基板
１５ 遮光膜
１６ 第１半透光膜
１７ 第２半透光膜
３０〜３２ 第１〜第３レジストパターン
２０ 被転写体
２３ レジストパターン
10 5 gradation photomask 11 light-shielding part 12 light-transmitting part 13A first semi-light-transmitting part 13B second semi-light-transmitting part 13C third semi-light-transmitting part 14 transparent substrate 15 light-shielding film 16 first semi-light-transmitting film 17 second Semi-transparent films 30 to 32 First to third resist patterns 20 Transfer object 23 Resist pattern

Claims (10)

透明基板上に、遮光部、透光部、及び第1半透光部と第２半透光部と第３半透光部からなるマスクパターンを有する多階調フォトマスクの製造方法であり、
透明基板上に、エッチャントに対するエッチング選択性のある第１半透光膜と遮光膜とをこの順に有するフォトマスクブランクを準備する工程と、
前記フォトマスクブランクの前記遮光膜上に形成したレジスト膜を描画、現像して第１レジストパターンを形成する工程と、
前記第１レジストパターンをマスクとして前記遮光膜をエッチングして第１のパターニングを行う工程と、
前記第１レジストパターンを除去した後、パターニングされた前記遮光膜を含む面上に形成したレジスト膜を描画、現像して第２レジストパターンを形成する工程と、
前記第２レジストパターンをマスクとして前記第１半透光膜をエッチングして第２のパターニングを行う工程と、
前記第２レジストパターンを除去した後、パターニングされた前記遮光膜及び前記第１半透光膜を含む基板全面に、前記第１半透光膜とのエッチャントに対するエッチング選択性のある第２半透光膜を形成する工程と、
前記第２半透光膜上に形成したレジスト膜を描画、現像して第３レジストパターンを形成する工程と、
前記第３レジストパターンをマスクとして前記第２半透光膜をエッチングして第３のパターニングを行う工程と、
により、前記第1半透光部、前記第２半透光部、及び前記第３半透光部を、前記第１半透光膜、前記第２半透光膜、前記第１半透光膜と前記第２半透光膜の積層膜のそれぞれいずれかにより形成した多階調フォトマスクの製造方法であって、
前記遮光膜及び前記第２半透光膜はいずれもクロムを主成分とした材料からなり、前記第１半透光膜はモリブデンシリサイドを主成分とした材料からなり、
前記第１半透光部、前記第２半透光部及び前記第３半透光部は、それぞれに形成された半透光膜の、露光光に対する膜固有の透過率が異なり、かつ、前記第１半透光部、前記第２半透光部及び前記第３半透光部のうち２つは、同一の実効透過率を有する、線幅が異なるパターンであることを特徴とする多階調フォトマスクの製造方法。 A method for producing a multi- tone photomask having a mask pattern comprising a light-shielding part, a light-transmitting part, and a first semi-light-transmitting part, a second semi-light-transmitting part, and a third semi-transparent part on a transparent substrate
Preparing a photomask blank having, in this order, a first semi-transparent film and a light-shielding film having etching selectivity with respect to an etchant on a transparent substrate;
Drawing and developing a resist film formed on the light-shielding film of the photomask blank to form a first resist pattern;
Etching the light shielding film using the first resist pattern as a mask to perform first patterning;
After removing the first resist pattern, drawing and developing a resist film formed on the surface including the patterned light-shielding film to form a second resist pattern;
Etching the first semi-transparent film using the second resist pattern as a mask to perform second patterning;
After removing the second resist pattern, a second semi-transparent film having etching selectivity with respect to the etchant with the first semi-transparent film is formed on the entire surface of the substrate including the patterned light-shielding film and the first semi-transparent film. Forming a photo film;
Drawing and developing a resist film formed on the second semi-transparent film to form a third resist pattern;
Etching the second semi-transparent film using the third resist pattern as a mask to perform third patterning;
Accordingly, the first semi-transparent part, the second semi-transparent part, and the third semi-transparent part are connected to the first semi-transparent film, the second semi-transparent film, and the first semi-transparent film. A method for manufacturing a multi- tone photomask formed by any one of a film and a laminated film of the second semi-transparent film,
The light-shielding film and the second semi-transparent film are both made of a material mainly containing chromium, and the first semi-transparent film is made of a material mainly containing molybdenum silicide,
The first semi-transmission part, the second semi-transmission part, and the third semi-transmission part have different transmissivities specific to the exposure light of the semi-transmission films formed respectively, and first semi-light-transmitting portion, the second two of semi-light-transmitting portion and the third semi-light-transmitting portion is a multi-floor, characterized in that have the same effective transmission rate, the line width is different patterns A method for producing a photomask. 線幅が５μｍ以下の半透光部を有することを特徴とする請求項１に記載の多階調フォトマスクの製造方法。 The method for producing a multi- tone photomask according to claim 1, further comprising a semi-transparent portion having a line width of 5 μm or less. 前記第１半透光部、前記第２半透光部及び前記第３半透光部は、同一の実効透過率を有することを特徴とする請求項１又は２に記載の多階調フォトマスクの製造方法。 3. The multi- tone photomask according to claim 1, wherein the first semi-transmissive portion, the second semi-transmissive portion, and the third semi-transmissive portion have the same effective transmittance. Manufacturing method. 前記第１半透光部、前記第２半透光部及び前記第３半透光部のうち２つは同一の実効透過率を有し、残りの１つが異なる実効透過率を有することを特徴とする請求項１又は２に記載の多階調フォトマスクの製造方法。 Two of the first semi-transmissive part, the second semi-transmissive part, and the third semi-transmissive part have the same effective transmittance, and the remaining one has a different effective transmittance. A method for producing a multi- tone photomask according to claim 1 or 2. 前記遮光膜、前記第１半透光膜及び前記第２半透光膜のエッチングは、ウェットエッチングにより行うことを特徴とする請求項１乃至４のいずれか一項に記載の多階調フォトマスクの製造方法。 5. The multi- tone photomask according to claim 1, wherein the light shielding film, the first semi-transparent film, and the second semi-transparent film are etched by wet etching. Manufacturing method. 前記遮光膜は、遮光層と反射防止層の積層からなることを特徴とする請求項１乃至５のいずれか一項に記載の多階調フォトマスクの製造方法。 The method for manufacturing a multi- tone photomask according to claim 1, wherein the light shielding film is formed by stacking a light shielding layer and an antireflection layer. 薄膜トランジスタ基板用であることを特徴とする請求項１乃至６のいずれか一項に記載の多階調フォトマスクの製造方法。 7. The method for producing a multi- tone photomask according to claim 1, wherein the method is for a thin film transistor substrate. チャネル幅が５μｍ以下のチャネル部に相当する半透光部パターンを有することを特徴とする請求項７に記載の多階調フォトマスクの製造方法。 8. The method for manufacturing a multi- tone photomask according to claim 7, further comprising a semi-transparent part pattern corresponding to a channel part having a channel width of 5 [mu] m or less. チャネル部に相当する半透光部パターンを、ソース及びドレインに相当する遮光部パターンが挟む形で隣接することを特徴とする請求項７又は８に記載の多階調フォトマスクの製造方法。 9. The method for manufacturing a multi- tone photomask according to claim 7, wherein the semi-transparent part pattern corresponding to the channel part is adjacent to the light-shielding part pattern corresponding to the source and drain. 請求項１乃至９のいずれかに記載の製造方法によるフォトマスクを用いて、被転写体に露光光を照射する露光工程を有し、被転写体上に転写パターンを形成することを特徴とする薄膜トランジスタ基板用パターン転写方法。   It has an exposure process of irradiating a to-be-transferred object with exposure light using the photomask by the manufacturing method according to claim 1, and forms a transfer pattern on the to-be-transferred object Pattern transfer method for thin film transistor substrate.
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