CN114924462A - Photomask and design method thereof - Google Patents

Photomask and design method thereof Download PDF

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Publication number
CN114924462A
CN114924462A CN202210185191.8A CN202210185191A CN114924462A CN 114924462 A CN114924462 A CN 114924462A CN 202210185191 A CN202210185191 A CN 202210185191A CN 114924462 A CN114924462 A CN 114924462A
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CN
China
Prior art keywords
photomask
transparent substrate
photoresist layer
structure area
height difference
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202210185191.8A
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Chinese (zh)
Inventor
高松
胡丹丹
张聪
郭晓波
张瑜
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shanghai Huali Integrated Circuit Manufacturing Co Ltd
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Shanghai Huali Integrated Circuit Manufacturing Co Ltd
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Publication date
Application filed by Shanghai Huali Integrated Circuit Manufacturing Co Ltd filed Critical Shanghai Huali Integrated Circuit Manufacturing Co Ltd
Priority to CN202210185191.8A priority Critical patent/CN114924462A/en
Publication of CN114924462A publication Critical patent/CN114924462A/en
Pending legal-status Critical Current

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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
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/70—Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for 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

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

Abstract

The invention provides a design method of a photomask, which comprises providing a first photomask with a first transparent substrate, wherein an opaque graphic structure is formed on the surface of the first transparent substrate; providing a first substrate, forming a first structure area and a second structure area on the substrate, wherein the pattern density of the second structure area is smaller than that of the first structure area, then forming a photoresist layer covering the first structure area and the second structure area, and detecting to obtain the height difference of the photoresist layer; and providing a second photomask, wherein the first photomask is provided with a second transparent substrate, etching the second transparent substrate, and then forming an opaque graphic structure on the surface of the second photomask, so that when the exposure machine exposes the photoresist layer by using the second photomask, the difference of the focal heights of the first and second structure areas is the height difference. The invention realizes that different positions are in the optimal exposure position, ensures the optimal exposure focal length of the graph, solves the problem of out-of-focus of the graph caused by poor flatness of the photoetching filling material on the current layer due to the density of the graph on the front layer, and improves the yield of the product.

Description

Photomask and design method thereof
Technical Field
The present invention relates to the field of semiconductor technology, and more particularly, to a photomask and a design method thereof.
Background
In the manufacturing of integrated circuits, especially in the rear-stage dual damascene trench structure manufacturing process, the phenomenon of uneven coating of filling materials is easy to occur due to uneven density of patterns on the front layer. For the surface of the wafer, due to uneven distribution of the density of the front layer of patterns or difference of the deposition thickness of the thin film, when the coating flatness of the layer of photoetching filling material is poor, the uneven photoetching material cannot be completely considered because the exposure focal length is fixed during photoetching exposure, so that the partial patterns exposed on the wafer are out of focus, and the yield of products is influenced.
As shown in FIG. 1, the front layer is a cross-sectional view of the photoresist coating layer of the dense pattern region and the isolated pattern region and a scanning electron micrograph formed by a photolithography exposure light path. The difference of the thickness of the photoresist material is caused by the inconsistent volatilization degree of the solvent when the photoresist of the pattern dense area and the isolated pattern area is baked. Theoretically, the photoresist thickness is uneven, the optimal exposure focal length can deviate when the photoresist with different thickness is exposed, and the exposure focal length can not be dynamically changed in real time when the exposure machine is exposed, so that the phenomenon that the image defocuses due to the fact that the exposure focal length is different from the optimal exposure focal length of the image easily occurs on part of the image.
Therefore, it is necessary to provide a method for improving the exposure defocus caused by the photoresist load by the mask structure design.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a photomask and a design method thereof, for solving the problems in the prior art that the photoresist has uneven thickness, the optimal exposure focal length of the photoresist with different thicknesses will deviate during exposure, the exposure focal length of the exposure machine cannot be dynamically changed in real time during exposure, and the pattern defocusing is easily caused due to the inconsistency between the exposure focal length and the optimal exposure focal length of the pattern in a part of the pattern.
To achieve the above and other related objects, the present invention provides a method for designing a mask, comprising:
providing a first photomask, wherein the first photomask is provided with a first transparent substrate, and an opaque graphic structure is formed on the first transparent substrate;
providing a first substrate, wherein a first structure area and a second structure area are formed on the first substrate, the pattern density of the second structure area is smaller than that of the first structure area, then forming a photoresist layer covering the first structure area and the second structure area, and detecting to obtain the height difference of the photoresist layer on the first structure area and the second structure area;
and step three, providing a second photomask, wherein the second photomask is provided with a second transparent substrate, etching the second transparent substrate, and then forming an opaque graphic structure on the surface of the second photomask, so that when an exposure machine station exposes the photoresist layer by adopting the second photomask, the difference of the focal heights of the first and second structure areas is the height difference.
Preferably, the material of the first transparent substrate in the first step and the material of the second transparent substrate in the third step are both silicon dioxide.
Preferably, the material of the pattern structure in the first step is metal chromium.
Preferably, the height difference in the second step is read by the exposure machine.
Preferably, in the third step, when the exposure machine is used to expose the photoresist layer with the set focal length, the difference between the distances corresponding to the upper focal point of the first structure region and the upper surface of the photoresist layer is the height difference, and the set focal length is defined as the optimal focal length.
Preferably, the method further includes a fourth step of developing and baking the exposed photoresist layer, and then detecting the set focal length by using a metrology machine.
A mask structure formed by the method of any of the above steps, comprising:
and the second photomask is provided with a transparent substrate, a groove is formed on the transparent substrate, and then lighttight graph structures are formed on the surface of the second photomask and the bottom surface of the groove, so that when an exposure machine platform exposes the photoresist layer on the substrate by adopting the second photomask, the height difference of the focus in the graph structures without the groove and the groove is the same as the height difference of the upper surface of the photoresist layer.
Preferably, the material of the transparent substrate is silicon dioxide.
Preferably, the material of the pattern structure is metallic chromium.
As described above, the photomask and the design method thereof of the present invention have the following advantages:
the invention forms the light shield through the quartz glass etching technology, so that the height of the pattern on the light shield is matched with the density of the pattern on the front layer, the specific value setting of the height of the pattern on the light shield is realized by designing the corresponding relation between the height of the pattern on different light shields and the optimal focal length of the pattern on a plane wafer and combining the height difference of the pattern on the surface of the specific wafer, the inconsistent exposure focal lengths at different positions are realized when the light shield is used for exposure, thus the uneven light resistance of the current layer is considered, the optimal exposure positions of different positions are realized, the optimal exposure focal length of the pattern is ensured, the problem of defocusing of the pattern caused by the poor flatness of the photoetching filling material on the current layer due to the density of the pattern on the front layer can be effectively solved, and the yield of the product is improved.
Drawings
FIG. 1 is a schematic illustration showing an exposure of a mask according to the prior art;
FIG. 2 is a schematic diagram showing the relationship between the optimal focal length and the height of the mask pattern according to the present invention;
FIG. 3 is a schematic diagram of a mask exposure according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of the method of the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Referring to FIG. 4, the present invention provides a method for designing a mask, comprising:
referring to fig. 1, a first photomask is provided, wherein the first photomask has a first transparent substrate, an opaque pattern structure is formed on the first transparent substrate, and the pattern structure is used for exposing a photoresist layer by light;
in an alternative embodiment, the material of the first transparent substrate in the first step and the material of the second transparent substrate in the third step are both silicon dioxide.
In an alternative embodiment, the material of the opaque pattern structure in the first step is metal chromium.
Step two, please refer to fig. 1, providing a first substrate, wherein a first structure area and a second structure area are formed on the first substrate, the pattern density of the second structure area is smaller than that of the first structure area, the first structure area is an area covered by a density pattern photoresist, the second structure area is an area covered by an isolated pattern photoresist, and then a photoresist layer covering the first structure area and the second structure area is formed, because the structure densities of the first structure area and the second structure area are different, the covered photoresist has a height difference, and the height difference between the first structure area and the photoresist layer on the second structure area is detected;
in an alternative embodiment, the height difference in the second step is read by the exposure tool.
Referring to fig. 3, a second photomask is provided, the first photomask has a second transparent substrate, the second transparent substrate is etched, and then a light-tight pattern structure is formed on the surface of the second photomask, so that when the exposure machine exposes the photoresist layer by using the second photomask, the difference between the focal heights of the first and second structure areas is the height difference.
Specifically, the height difference between the dense pattern photoresist and the isolated pattern photoresist is H2, and the distance from the etching area to the etching area is H1, wherein the etching area corresponds to the area covered by the isolated pattern photoresist, and the distance from the focus to the etching area is H2, so as to compensate the focal length, and thus, the distances between the focuses of the dense pattern photoresist and the isolated pattern photoresist and the upper surface of the photoresist are the same during exposure.
In an alternative embodiment, referring to fig. 2, in the third step, when the exposure tool is used to expose the photoresist layer with the set focal length, the difference between the distances corresponding to the upper focal point of the first structure region and the upper surface of the photoresist layer is defined as a height difference, and the set focal length is defined as an optimal focal length.
In an optional embodiment, the method further includes a fourth step of developing and baking the exposed photoresist layer, and then detecting the set focal length by using a measuring machine.
A mask structure formed by the method of any of the above steps, comprising:
and the second photomask is provided with a transparent substrate, a groove is formed on the transparent substrate, and then the lighttight graph structures are formed on the surface of the second photomask and the bottom surface of the groove, so that when an exposure machine platform exposes the photoresist layer on the substrate by adopting the second photomask, the graph structures without the groove and the groove respectively correspond to the graph structures without the groove, and the height difference of the focus is the same as the height difference of the upper surface of the photoresist layer.
In an alternative embodiment, the material of the transparent substrate is silicon dioxide.
In an alternative embodiment, the material of the pattern structure is metallic chromium.
It should be noted that the drawings provided in this embodiment are only for schematically illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings and not drawn according to the number, shape and size of the components in actual implementation, and the form, quantity and proportion of each component in actual implementation may be arbitrarily changed, and the component layout may be more complicated.
In summary, the invention forms the photomask by the quartz glass etching technology, so that the height of the pattern on the photomask is matched with the density of the pattern on the front layer, the specific value setting of the height of the pattern on the photomask is realized by designing the corresponding relation between the height of the pattern on different photomasks and the optimal focal length of the pattern on a plane wafer and combining the height difference of the pattern on the surface of the specific wafer, and the inconsistent exposure focal lengths at different positions are realized when the photomask is used for exposure, thereby taking account of the uneven photoresist on the current layer, realizing that different positions are at the optimal exposure position, ensuring the optimal exposure focal length of the pattern, effectively solving the problem of pattern defocusing caused by the poor flatness of the photoetching filling material on the layer due to the density of the pattern on the front layer, and improving the yield of products. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims (9)

1. A method for designing a mask, comprising:
providing a first photomask, wherein the first photomask is provided with a first transparent substrate, and an opaque graphic structure is formed on the first transparent substrate;
providing a first substrate, wherein a first structure area and a second structure area are formed on the first substrate, the pattern density of the second structure area is smaller than that of the first structure area, then forming a photoresist layer covering the first structure area and the second structure area, and detecting to obtain the height difference of the photoresist layer on the first structure area and the second structure area;
and step three, providing a second photomask, wherein the second photomask is provided with a second transparent substrate, etching the second transparent substrate, and then forming an opaque graphic structure on the surface of the second photomask, so that when an exposure machine station exposes the photoresist layer by adopting the second photomask, the difference of the focal heights of the first and second structure areas is the height difference.
2. The method of claim 1, wherein: the first transparent substrate in the first step and the second transparent substrate in the third step are both made of silicon dioxide.
3. The method of claim 1, wherein: the material of the graph structure in the first step is metal chromium.
4. The method of claim 1, wherein: and in the second step, the height difference is read by the exposure machine.
5. The method of claim 1, wherein: in the third step, when the exposure machine station is used for exposing the photoresist layer with the set focal length, the difference value corresponding to the distance between the upper focal point of the first structure area and the upper surface of the photoresist layer is the height difference, and the set focal length is defined as the optimal focal length.
6. The method of claim 5, wherein: the method further comprises a fourth step of developing and baking the exposed photoresist layer, and then detecting the set focal length by using a measuring machine.
7. A photomask, comprising:
and the second photomask is provided with a transparent substrate, a groove is formed on the transparent substrate, and then the lighttight graph structures are formed on the surface of the second photomask and the bottom surface of the groove, so that when an exposure machine platform exposes the photoresist layer on the substrate by adopting the second photomask, the graph structures without the groove and the groove respectively correspond to the graph structures without the groove, and the height difference of the focus is the same as the height difference of the upper surface of the photoresist layer.
8. The mask structure of claim 7, wherein: the material of the transparent substrate is silicon dioxide.
9. The mask structure of claim 7, wherein: the material of the pattern structure is metal chromium.
CN202210185191.8A 2022-02-28 2022-02-28 Photomask and design method thereof Pending CN114924462A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210185191.8A CN114924462A (en) 2022-02-28 2022-02-28 Photomask and design method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210185191.8A CN114924462A (en) 2022-02-28 2022-02-28 Photomask and design method thereof

Publications (1)

Publication Number Publication Date
CN114924462A true CN114924462A (en) 2022-08-19

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Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210185191.8A Pending CN114924462A (en) 2022-02-28 2022-02-28 Photomask and design method thereof

Country Status (1)

Country Link
CN (1) CN114924462A (en)

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