Method for reducing damage of registration mark during photoresist removal

Abstract

The invention provides a method for reducing the damage of a registration mark during photoresist removal, and the method comprises the steps: providing a semiconductor structure of which the photoresist is to be removed, the structure comprises a substrate, a registration mark mask layer located at one side of the substrate, and a photoresist layer located at one side, away from the substrate, of the registration mark mask layer, a groove is formed in the semiconductor structure; the photoresist layer of the semiconductor structure is removed through etching, sulfur dioxide protective gas is added in the etching process, and the side wall of the registration mark mask layer is protected; the semiconductor structure is cleaned; and coating a new photoresist on the surface of the cleaned semiconductor structure again. According to the method, the sulfur dioxide gas is added when the photoresist layer is etched, the alignment mask exposed on the side wall is protected, and the integrity and accuracy of the registration mark are ensured.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for reducing damage to registration marks during photoresist removal. Background Art

[0002] The structure order of semiconductor from bottom to top is substrate, coating, anti-reflective layer, photoresist, among which the structure order of coating from bottom to top is BARC (bottom anti-reflective coating) and PR (photoresist layer), and the photoresist layer is generally coated on the surface of the bottom anti-reflective coating. When the photoresist pattern on the wafer does not meet the requirements, rework (PR Rework) will be carried out, generally using etching and de-gumming treatment and then cleaning to achieve the purpose of removing the photoresist and reworking.

[0003] OVL (Overlay) is used to detect the overlay accuracy of the current and previous layers of the exposure machine. The morphology of the current and previous Mark Profiles is closely related to the overlay accuracy. After the semiconductor etching process enters 90nm, it is necessary to add a hard mask layer on the surface of the wafer to cooperate with the photoresist to form a mask pattern of the mark profile. For example, a patterned film layer APF (Advanced Patterning Film) is first added to the etching mask structure. As a special semiconductor material, it has high stability, excellent conductivity and low energy band gap. APF deposition belongs to the CVD (Chemical Vapor Deposition) process. Because gas acetylene (C2H2) is cracked into amorphous carbon under the action of plasma, it covers the wafer to form a carbon film. Its main component is amorphous carbon, which has a high etching selectivity. It can replace photoresist to form a pattern during etching and act as a mask layer. APF is usually used in high aspect ratio etching process, but in the process of etching high aspect ratio APF film layer, the side wall is easily not fully protected. Due to part of isotropic etching and base reflection phenomenon, the upper and middle parts of APF often first experience serious lateral etching phenomenon. Severe lateral etching phenomenon leads to poor load-bearing capacity of this part, and the head APF is tilted and adhered. In particular, in the ZERO layer, due to the deep trench depth, the subsequent alignment layer (such as ACTA) is easy to cause APF damage during lithography rework. Therefore, it is very important to prevent tilting and adhesion in the APF etching process, which is conducive to ensuring the accuracy and integrity of the registration mark.

[0004] Usually, the damage to the corresponding registration mark is prevented by optimizing the structure of the film layer. However, the additional increase / decrease of the film layer also complicates the etching process and greatly increases the application cost. Since the proportion of photoresist rework is low compared to normal over-the-counter products, adding film layers to the normal product process in order to optimize rework greatly increases the cost and difficulty. In the APF etching process, the proportion of protective gas is usually increased to form an additional insulating protective layer on the APF, thereby alleviating the severe lateral etching caused by substrate reflection. However, after increasing the proportion of protective gas, it is easy to form an insulating protective film on the surface of the APF, which hinders the lateral etching of the side wall. The protective gas will also form a protective layer with the lateral APF, which is easy to cause the etching speed in the lateral and vertical directions, and will also cause the transfer of key dimensions to shift, reducing the etching rate.

[0005] In another method, Solevent (propylene glycol methyl ether CH3OCH2CH(OH)CH3 & propylene glycol methyl ether acetate CH3OCH2CH(OAC)CH3, etc.) is used to remove the photoresist, etch and remove the anti-reflection layer, perform etching and cleaning processes, remove the APF based on H2O2+H2SO4, and then re-grow the APF and anti-reflection layer and other film layers. This method removes different film layers separately and then re-grows the required film layers to achieve the purpose of registration mark integrity, but this method greatly increases chip manufacturing time and cost in mass production processes, and there is a risk of unclean removal when using Solevent to remove photoresist. Therefore, it is necessary to propose a new method to solve the above problems. Summary of the invention

[0006] In response to the problems in the prior art, the purpose of the present application is to provide a method for reducing damage to registration marks during photoresist removal, improve the problem of mask dissolution in the process of removing photoresist during wafer lithography rework for high aspect ratios and weak points of the registration mark mask, reduce damage to the registration marks, improve product yield, and ensure the integrity and accuracy of the registration marks.

[0007] The embodiment of the present application provides a method for reducing damage to a registration mark during photoresist removal, comprising:

[0008] A semiconductor structure to be stripped of photoresist is provided, the structure comprising a substrate, an alignment mark mask layer located on one side of the substrate, and a photoresist layer located on a side of the alignment mark mask layer facing away from the substrate, wherein a groove is formed in the semiconductor structure;

[0009] Etching and removing the photoresist layer of the semiconductor structure, wherein sulfur dioxide protective gas is added during the etching process to protect the sidewalls of the registration mark mask layer;

[0010] Cleaning the semiconductor structure;

[0011] New photoresist is re-coated on the cleaned surface of the semiconductor structure.

[0012] In some embodiments, in the semiconductor structure from which the photoresist is to be removed, an oxide layer and a silicon nitride layer are sequentially formed between the substrate and the registration mark mask layer.

[0013] In some embodiments, in the semiconductor structure from which the photoresist is to be removed, a dielectric anti-reflective coating is further formed between the registration mark mask layer and the photoresist layer.

[0014] In some embodiments, the etching and removing the photoresist layer of the semiconductor structure includes: etching and removing the photoresist layer of the semiconductor structure by a thin film etching technology based on plasma reaction.

[0015] In some embodiments, the etching and removing the photoresist layer of the semiconductor structure includes: using oxygen to etch and remove the photoresist layer of the semiconductor structure through a plasma reaction-based thin film etching technology.

[0016] In some embodiments, cleaning the semiconductor structure includes wet cleaning the semiconductor structure.

[0017] In some embodiments, wet cleaning the semiconductor structure includes: wet cleaning the semiconductor structure using H2O2 and H2SO4 solutions.

[0018] In some embodiments, wet cleaning the semiconductor structure includes: wet cleaning the semiconductor structure using a solevent solution.

[0019] In some embodiments, the registration mark mask layer is an amorphous carbon-based patterned film layer.

[0020] In some embodiments, before re-coating a new photoresist on the surface of the cleaned semiconductor structure, the following steps are also included:

[0021] A dielectric anti-reflective coating is re-coated on the cleaned surface of the semiconductor structure.

[0022] The method provided in the present application for reducing the damage of the registration mark during photoresist removal has the following advantages:

[0023] By adopting the method of the present application, when etching and removing the photoresist, sulfur dioxide gas is added to protect the sidewalls of the registration mark mask layer, thereby reducing the corrosion of the sidewalls of the mask layer and alleviating the serious lateral etching phenomenon caused by wafer reflection. When reworking the photoresist, the photoresist and the corresponding film layer can be dissolved more evenly, and by controlling the etching time, a more ideal registration mark profile can be obtained, thereby ensuring the integrity and accuracy of the registration mark, which is beneficial to improving the accuracy of registration measurement and improving product yield.

[0024] Other advantages, objectives and features of the present application will be described in the following description to some extent, and will be apparent to those skilled in the art based on the following examination and study, or can be taught from the practice of the present application to some extent. The objectives and other advantages of the present application can be achieved and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings.

[0026] Figure 1 is a flow chart of a method for reducing damage to a registration mark during photoresist removal according to an embodiment of the present application;

[0027] Figure 2 is a schematic diagram of the effect of removing the existing photoresist on the registration mark;

[0028] Figure 3 is a schematic diagram of the effect on the registration mark after removing the photoresist using the method of the present application;

[0029] Figure 4 is a schematic diagram of a semiconductor structure from which photoresist is to be removed according to an embodiment of the present application;

[0030] Figure 5 is a schematic diagram of a semiconductor structure when etching to remove photoresist according to an embodiment of the present application;

[0031] Figure 6 is a schematic diagram of forming a protective layer by sulfur dioxide according to an embodiment of the present application;

[0032] Figure 7 It is a schematic diagram of cleaning a semiconductor structure after etching according to an embodiment of the present application.

[0033] Reference numerals:

[0034] 10. substrate; 20. oxide layer; 30. silicon nitride layer; 40. registration mark mask layer;

[0035] 50. dielectric anti-reflective coating; 60. photoresist layer; A. groove;

[0036] W, weak point of the registration mark mask layer; P, protective layer. DETAILED DESCRIPTION

[0037] The example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in a variety of forms and should not be construed as being limited to the embodiments set forth herein; on the contrary, these embodiments are provided so that the present application will be comprehensive and complete, and the concept of the example embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. "Or" and "or" in the specification may both represent "and" or "or". Spatial relationship terms such as "on..." and the like can be used here to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of devices in use and operation. For example, if the device in the drawings is flipped, the element or feature described as "on..." will be oriented to be "under..." other elements or features. Therefore, the exemplary term "on..." may include both upper and lower orientations. In addition, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptions used herein are interpreted accordingly.

[0038] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that when the terms "consisting of" and / or "comprising" are used in this specification, the presence of the features, integers, steps, operations, elements and / or parts can be determined, but the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups is not excluded. At the same time, when used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0039] In the process of removing photoresist, the integrity of the existing registration mark may be damaged because the hard mask is etched. If a protective gas (such as an inert gas) is added, an additional protective film will be formed on the hard mask and the etching speed will be affected. It will also cause the critical dimension transfer to shift and reduce the etching rate. In order to solve the technical problems in the prior art, the purpose of this application is to provide a method for reducing the damage of the registration mark during the photoresist removal, improve the problem of mask dissolution in the process of removing photoresist during wafer lithography rework for high aspect ratios and weak points of the registration mark mask, reduce damage to the registration mark, and improve product yield.

[0040] Figure 1 FIG. 1 is a flow chart of a method for reducing damage to a registration mark during photoresist removal according to an embodiment of the present application. Figure 1 As shown, the method comprises the following steps:

[0041] S100: providing a semiconductor structure from which photoresist is to be removed, the structure comprising a substrate, an alignment mark mask layer located on one side of the substrate, and a photoresist layer located on a side of the alignment mark mask layer facing away from the substrate, and a groove is formed in the semiconductor structure;

[0042] S200: etching and removing the photoresist layer of the semiconductor structure, wherein sulfur dioxide protective gas is added during the etching process to protect the sidewall of the registration mark mask layer;

[0043] S300: cleaning the semiconductor structure;

[0044] Thereby completing the photoresist removal process of the semiconductor structure;

[0045] S400: re-coating new photoresist on the cleaned surface of the semiconductor structure.

[0046] The photolithography process is an important step in the semiconductor device manufacturing process. It uses exposure and development to depict geometric structures on the photolithography material layer, and then transfers the pattern on the photomask to the substrate through an etching process. When the formed photolithography pattern does not meet the process requirements, the original photolithography material layer can be removed, and then the photolithography material layer can be re-coated and exposed and developed, that is, photolithography rework.

[0047] The registration accuracy of photolithography refers to the accuracy with which the photolithography machine aligns and overlays patterns at different levels during the chip manufacturing process. In the chip manufacturing process, it is usually necessary to overlay different patterns layer by layer onto the silicon wafer through multiple photolithography processes. The registration accuracy of photolithography is one of the key processes in chip manufacturing. The registration accuracy of photolithography directly affects the circuit connection and device structure of the chip. If the registration is inaccurate, it will cause the circuit connection to break or the device to fail, thereby affecting the performance and reliability of the chip and reducing the product yield. High-precision photolithography registration can reduce the scrap rate caused by pattern misalignment, improve the production efficiency of chip manufacturing, and reduce production costs. With the continuous development of chip manufacturing technology, the requirements for higher resolution and smaller size devices are becoming higher and higher, and high-precision photolithography registration is one of the key technologies to achieve these requirements.

[0048] By adopting the method of the present application, when etching and removing the photoresist, sulfur dioxide gas is added to protect the sidewalls of the registration mark mask layer, thereby reducing the sidewall corrosion of the mask layer and alleviating the serious lateral etching phenomenon caused by wafer reflection. When reworking the photoresist, the photoresist and the corresponding film layer can be dissolved more evenly, and by controlling the etching time, a more ideal registration mark profile can be obtained, thereby ensuring the integrity and accuracy of the registration mark.

[0049] Figure 2The figure shows the influence of the prior art on the registration mark when the photoresist coating rework is performed without using sulfur dioxide. Figure 2 It can be seen that after the wafer is stripped of photoresist once, the profile of the registration mark is greatly damaged, and after the wafer is stripped of photoresist twice, the profile of the registration mark is greatly damaged, which seriously affects the registration accuracy. After adopting the method of the present application, during the process of stripping photoresist, when etching and removing the photoresist layer, sulfur dioxide SO2 gas is introduced to protect the side wall of the registration mark mask, effectively ensuring the integrity and accuracy of the registration mark. Figure 3 As shown, after testing, after the wafer is stripped of photoresist and reworked, the complete registration mark outline can still be maintained, thereby ensuring the accuracy of the registration test and improving the product yield.

[0050] The following combination Figures 4 to 7 The following describes the implementation process of the method for reducing the damage of the registration mark during photoresist removal in a specific example. It can be understood that Figures 4 to 7 The semiconductor structure shown in the figure and the description of the implementation methods of the following steps are only examples, which are intended to more clearly illustrate the optional application methods of the scheme of the present application in specific examples, and are not intended to limit the scope of protection of the present application. Those skilled in the art can make changes to the structure shown in the figure and the technical details described below as needed without violating the protection purpose of the present application, which are all within the scope of protection of the present application.

[0051] Figure 4 Schematic diagram of a semiconductor structure of a photoresist to be removed according to an embodiment of the present application. In the semiconductor structure of the photoresist to be removed, an oxide layer 20 and a silicon nitride layer 30 are sequentially formed between the substrate 10 and the registration mark mask layer 40, and a dielectric anti-reflective coating (DARC) 50 is also formed between the registration mark mask layer 40 and the photoresist layer 60. Anti-reflection coating (ARC) is a substance that is spin-coated on the interface between the photoresist and the substrate to absorb the reflected light from the lithography. The material of the dielectric anti-reflection coating is, for example, silicon oxynitride or other nitrogen-containing compounds, and a nitrogen-free dielectric anti-reflection coating can also be used, but the present application is not limited to this, and other optional materials can also be used for the dielectric anti-reflection coating, all of which belong to the protection scope of the present application.

[0052] Therefore, in Figure 4From the perspective of FIG. 1 , from bottom to top, the semiconductor structure includes a substrate 10, an oxide layer 20, a silicon nitride layer 30, an alignment mark mask layer 40, a dielectric anti-reflective coating 50, and a photoresist layer (PhotoResist, PR) 60 arranged in sequence. A groove A is formed in the semiconductor structure. The semiconductor structure has been exposed and developed, and the photoresist layer 60 needs to be removed for photolithography rework. Figure 4 The point W in the middle is the weak point in the registration mark mask layer 40. If the photoresist layer is directly etched, the weak point of the registration mark mask layer 40 may be dissolved, thereby damaging the registration mark profile.

[0053] In this embodiment, the registration mark mask layer is a patterned film layer based on amorphous carbon. Amorphous carbon, also known as transition carbon, is a large class of carbon allotropes. Amorphous carbon refers to carbon materials with a very low degree of graphitization crystallization and an approximate amorphous form (or a structure without a fixed shape and periodicity). In one example, the depth of the groove is, for example, 3000A, the height of the oxide layer 20 is, for example, 800A, the height of the silicon nitride layer 30 is, for example, 900A, the height of the registration mark mask layer 40 is, for example, 3500A, and the height of the dielectric anti-reflective coating 50 is, for example, 350A. The height of each film layer and the depth of the groove are only examples here, and are not intended to limit the scope of protection of this application. Those skilled in the art can set the height of each film layer and the depth of the groove as needed to meet the needs of different products, all of which are within the scope of protection of this application.

[0054] Figure 5 Schematic diagram of a semiconductor structure when etching to remove photoresist in one embodiment of the present application. In this embodiment, in step S200, etching to remove the photoresist layer 60 of the semiconductor structure includes: using oxygen to etch and remove the photoresist layer 60 of the semiconductor structure by a plasma reaction-based thin film etching technology (Asher). Since the registration mark mask layer is a patterned film layer based on amorphous carbon, the main component is carbon, and oxygen can react with carbon to ensure that etching continues.

[0055] Figure 6 FIG. 1 is a schematic diagram of forming a protective layer by sulfur dioxide according to an embodiment of the present application. Figure 6As shown, during the etching process, the sidewalls of the dielectric anti-reflective coating 50 are removed due to etching, and the sidewalls of the registration mark mask layer 40 are exposed. During this process, sulfur dioxide gas is introduced to form a protective layer P on the sidewalls of the registration mark mask layer 40. The protective layer P protects the weak points of the registration mark mask layer 40, thereby protecting the integrity of the registration mark. Specifically, the oxygen in the sulfur dioxide can react with the carbon in the registration mark mask layer, and the sulfur in the sulfur dioxide can react with the carbon to form an SC polymer as the protective layer P, which protects the sidewalls of the registration mark mask layer 40. The protective layer P is divided into a sidewall protective layer and a bottom protective layer. The bottom protective layer will be eliminated by ion bombardment in the vertical direction during the etching process, so it will not affect the etching progress of the bottom surface. It will not have an adverse effect on the etching rate.

[0056] Figure 7 It is a schematic diagram of cleaning a semiconductor structure after etching according to an embodiment of the present application. In this embodiment, the step S300: cleaning the semiconductor structure includes: as the photoresist layer 60 is continuously consumed, the waste generated is removed by vacuuming, and the semiconductor structure is wet-cleaned (Wet). In one embodiment, the semiconductor structure is wet-cleaned, including: using H2O2 and H2SO4 solutions to wet-clean the semiconductor structure. In another embodiment, the semiconductor structure is wet-cleaned, including: using solevent (propylene glycol methyl ether CH3OCH2CH(OH)CH3 & propylene glycol methyl ether acetate CH3OCH2CH(OAC)CH3, etc.) solution to wet-clean the semiconductor structure. Here, only examples of the types of solutions for wet cleaning are given, and they are not used as limitations on the scope of protection of this application. The proportions of various components in the wet cleaning solution can be selected and set by the staff according to the needs of use, and are not limited here. Other types of solutions that can be used for wet etching can be used to implement step S300 of the present application and are within the scope of protection of the present application.

[0057] In this embodiment, the step S400: before re-coating a new photoresist on the surface of the cleaned semiconductor structure, further includes the following steps:

[0058] A dielectric anti-reflective coating is re-coated on the cleaned surface of the semiconductor structure.

[0059] Then, a new photoresist is re-coated on the side of the re-coated dielectric anti-reflective coating away from the registration mark mask layer to form a new semiconductor structure, and then the semiconductor structure is exposed and measured. If photolithography rework is required again, the semiconductor structure can be used as a semiconductor structure from which the photoresist is to be removed, and the photoresist is removed again using this method, and photolithography rework is performed again.

[0060] The description of the hierarchical structure of the semiconductor structure in this specification is only an example and is not intended to limit the scope of protection of this application. On this basis, those skilled in the art can reduce unnecessary film layers, add other film layers or change one or more of the film layers. The size of each film layer and the size of the grooves formed can also be set as needed, which will not affect the core protection scheme of this application. As long as the integrity of the registration mark is protected by introducing sulfur dioxide gas and forming a protective layer with the sidewall of the hard mask layer when removing the photoresist, various deformations are within the scope of protection of this application. The specific implementation methods used in the above etching steps and cleaning steps are also only examples and are not intended to limit the scope of protection of this application. Using other methods to achieve photoresist removal and semiconductor structure cleaning can also achieve the purpose of this application and are also within the scope of protection of this application.

[0061] In summary, compared with the prior art, the present application solves the problem that the integrity of the registration mark cannot be well maintained when removing the photoresist (removing the photoresist). Specifically, the method for reducing the damage of the registration mark when removing the photoresist provided by the present application has the following advantages:

[0062] By adopting the method of the present application, when etching and removing the photoresist, sulfur dioxide gas is added to protect the sidewalls of the registration mark mask layer, thereby reducing the corrosion of the sidewalls of the mask layer and alleviating the serious lateral etching phenomenon caused by wafer reflection. When reworking the photoresist, the photoresist and the corresponding film layer can be dissolved more evenly, and by controlling the etching time, a more ideal registration mark profile can be obtained, thereby ensuring the integrity and accuracy of the registration mark, which is beneficial to improving the accuracy of registration measurement and improving product yield.

[0063] The above content is a further detailed description of the present application in combination with specific preferred implementation methods, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the concept of the present application, which should be deemed to fall within the scope of protection of the present application.

Claims

1. A method for reducing damage to registration marks during photoresist removal, characterized in that: include: A semiconductor structure to be stripped of photoresist is provided, the structure comprising a substrate, an alignment mark mask layer located on one side of the substrate, and a photoresist layer located on a side of the alignment mark mask layer facing away from the substrate, wherein a groove is formed in the semiconductor structure; Etching and removing the photoresist layer of the semiconductor structure, wherein sulfur dioxide protective gas is added during the etching process to protect the sidewalls of the registration mark mask layer; Cleaning the semiconductor structure; New photoresist is re-coated on the cleaned surface of the semiconductor structure.

2. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: In the semiconductor structure from which the photoresist is to be removed, an oxide layer and a silicon nitride layer are sequentially formed between the substrate and the registration mark mask layer.

3. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: In the semiconductor structure from which the photoresist is to be removed, a dielectric anti-reflection coating is also formed between the registration mark mask layer and the photoresist layer.

4. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: The etching and removing the photoresist layer of the semiconductor structure includes: etching and removing the photoresist layer of the semiconductor structure by a thin film etching technology based on plasma reaction.

5. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: The etching and removing the photoresist layer of the semiconductor structure comprises: using oxygen to etch and remove the photoresist layer of the semiconductor structure through a thin film etching technology based on plasma reaction.

6. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: Cleaning the semiconductor structure includes wet cleaning the semiconductor structure.

7. The method for reducing damage to registration marks during photoresist removal according to claim 6, characterized in that: The semiconductor structure is wet cleaned, including: using H2O2 and H2SO4 solutions to wet clean the semiconductor structure.

8. The method for reducing damage to registration marks during photoresist removal according to claim 6, characterized in that: The semiconductor structure is wet cleaned, including: using a solevent solution to wet clean the semiconductor structure.

9. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: The registration mark mask layer is a patterned film layer based on amorphous carbon.

10. The method for reducing damage to registration marks during photoresist removal according to claim 1, characterized in that: Before re-coating a new photoresist on the surface of the cleaned semiconductor structure, the following steps are also included: A dielectric anti-reflective coating is re-coated on the cleaned surface of the semiconductor structure.

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