Method for reducing exposure defect of immersion lithography machine
By using cation-controlled graphene oxide films in immersion lithography machines, the problem of low efficiency in immersion solution contamination control has been solved, achieving efficient contaminant separation and process stability, while reducing equipment and time costs.
Patent Information
- Application Number
- CN202511432239.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2025-11-18
AI Technical Summary
In existing immersion lithography technology, the contamination control efficiency of the immersion solution is low, and it is impossible to remove multiple contaminants simultaneously in one go. Furthermore, the immersion head is prone to re-contamination, leading to exposure defects and process instability.
Graphene oxide was prepared using the Hammer process, and a cation-controlled graphene oxide film was prepared by utilizing cation-π interaction. The film was then assembled in the liquid channel of an immersion lithography machine, and contaminants were separated and purified through the graphene oxide film.
It achieves efficient filtration of various pollutants, reduces exposure defects, ensures the stability of process parameters, reduces equipment and time costs, and is highly compatible with existing systems, requiring no large-scale modifications.
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Figure CN120972468A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for reducing exposure defects in immersion lithography machines. Background Technology
[0002] As a core piece of equipment in the semiconductor industry's advanced technology nodes, the stability of the immersion exposure process is paramount. The main difference between immersion lithography and dry lithography lies in the use of a high-refractive-index immersion liquid to increase the numerical aperture, thereby improving lithographic resolution. However, immersion lithography also introduces new challenges affecting system exposure performance. The unique immersion liquid in immersion lithography becomes a major source of contaminants in the exposure optical system, and the lithography process places extremely high demands on contaminant control. Contaminants in the immersion liquid include particles, metal ions, organic compounds, and small molecules. These contaminants not only cause exposure defects such as bridging, micropores, and particle adhesion, directly affecting chip manufacturing yield, but also cause the immersion system to fail due to contamination of the immersion head, indirectly impacting chip manufacturing productivity and cost.
[0003] Currently, immersion lithography systems primarily employ a multi-stage tandem purification scheme to control contamination of the immersion liquid, including ion exchange resin (to remove metal ions), UV irradiation (to degrade TOC and sterilize), and a precision filter (to remove particles). While this system can maintain the purity of the immersion liquid to a certain extent, it has several limitations:
[0004] Step-by-step treatment is inefficient: Existing technologies cannot achieve simultaneous removal of multiple pollutants in one step, resulting in long processing times, high time costs, and the potential introduction of secondary pollution during the process. For example, ion exchange resins themselves may release organic debris, and UV sterilization may produce bacterial residues, both of which require additional filtration steps to remove.
[0005] Unavoidable contamination of the immersion head: Even if the initial purity of the immersion liquid meets the standards, it may still be contaminated again during the circulation process due to contact with materials such as photoresist. Summary of the Invention
[0006] The purpose of this invention is to provide a method for reducing exposure defects in immersion lithography machines, so as to solve the problem of contamination control of immersion solution in existing immersion lithography technology.
[0007] To achieve the above objectives, the present invention provides a method for reducing exposure defects in immersion lithography machines, comprising:
[0008] Graphene oxide was prepared by the Hammer method, and cation-controlled graphene oxide films were prepared by utilizing cation-π interactions.
[0009] The graphene oxide film is assembled in the liquid channel of the immersion system of an immersion lithography machine so that the immersion liquid flows through the graphene oxide film for purification before flowing to the wafer surface.
[0010] Optionally, when preparing graphene oxide using the Hammer process, the degree of oxidation of the graphene oxide is not higher than 40%.
[0011] Optionally, the graphene oxide membrane is prepared by a dripping membrane method, a vacuum filtration membrane method, or a polymerization membrane method.
[0012] Optionally, the graphene oxide film is formed by immersion in an ionic liquid for a fixed period of time followed by rinsing and drying.
[0013] Optionally, the ionic liquid is a monovalent cation solution with a concentration of 0.05-0.5 mol / L.
[0014] Optionally, the graphene oxide film has a stable interlayer spacing.
[0015] Optionally, the graphene oxide film is assembled on the injection side of each level of liquid channel in the immersion system.
[0016] Optionally, the graphene oxide film is adapted to the diameter of the liquid channel.
[0017] Optionally, the graphene oxide film is assembled facing the direction of water circulation.
[0018] Optionally, the method further includes periodically replacing the graphene oxide film.
[0019] The method for reducing exposure defects in immersion lithography machines provided by this invention has at least one of the following beneficial effects:
[0020] 1) Utilizing the excellent separation performance of ion-controlled graphene oxide membranes, contaminants such as particles, metal ions, organic compounds, and small molecules can be filtered in one pass, reducing exposure defects caused by immersion liquid contamination in immersion lithography machines, ensuring the refractive index of the immersion liquid, providing stable process parameters, and also reducing the equipment and time costs of contamination separation.
[0021] 2) By adjusting the amount of graphene oxide added during the preparation process, separation membranes of various sizes can be easily formed, thus better adapting to different pipelines and equipment models; and without introducing other types of contaminants, the overall process stability can be improved by not contacting the wafer.
[0022] 3) It is highly compatible with existing immersion lithography systems, requiring no large-scale equipment modifications. It only requires the integration of functional thin films into existing liquid channel pipelines, resulting in good process compatibility. Attached Figure Description
[0023] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Wherein:
[0024] Figure 1 A flowchart of a method for reducing exposure defects in an immersion lithography machine according to an embodiment of the present invention;
[0025] Figure 2 This is a schematic diagram of the use of graphene oxide film in an immersion liquid according to an embodiment of the present invention.
[0026] in:
[0027] 100 - Graphene oxide film; 200 - Immersion solution; 300 - Wafer; 400 - Exposure lens. Detailed Implementation
[0028] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clearly illustrate the purpose of the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only used to complement the content disclosed in the specification, for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this invention. Any modifications to the structure, changes in proportions, or adjustments to the size, if they are the same as or similar to the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.
[0029] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the term “at least two” is generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature.
[0030] Reference Figures 1-2This embodiment provides a method for reducing exposure defects in an immersion lithography machine, including:
[0031] S1. Graphene oxide was prepared by the Hammer method, and a cation-controlled graphene oxide film 100 was prepared by utilizing cation-π interaction.
[0032] S2. The graphene oxide film 100 is assembled in the liquid channel of the immersion system of the immersion lithography machine so that the immersion liquid 200 flows through the graphene oxide film 100 for purification before flowing to the surface of the wafer 300.
[0033] Graphene oxide separation membranes have shown great application potential in liquid purification. However, plain graphene oxide membranes have low selectivity and cannot accurately screen target substances. But graphene oxide membranes controlled by cations (e.g., 100) can achieve stable interlayer spacing due to cation-π interactions that fix cations between graphene oxide layers. This achieves the performance of retaining only water molecules and eliminating other impurities. Based on this, the present invention develops the above-mentioned method for reducing exposure defects in immersion lithography machines. By utilizing the excellent separation performance of ion-controlled graphene oxide film 100, it can filter contaminants such as particles, metal ions, organic compounds, and small molecules in a single pass, reducing exposure defects in immersion lithography machines caused by contamination of the immersion solution 200, ensuring the refractive index of the immersion solution 200, providing stable process parameters, and at the same time reducing the equipment cost and time cost of contamination separation.
[0034] First, S1 is performed to prepare graphene oxide using the Hammer process, and then a cation-controlled graphene oxide film 100 is prepared using cation-π interactions. The Hammer process is one of the most commonly used and scalable chemical oxidation methods for preparing graphene oxide (GO). Its core principle is to intercalate and oxidize graphite using strong acids and strong oxidants, which can produce easily processed graphene oxide rich in oxygen-containing functional groups on a large scale. Then, by introducing cations as "molecular spacers," the interlayer spacing of the graphene oxide is precisely fixed, thereby transforming the random stacked graphene oxide into an ion-controlled graphene oxide film 100 (I-GOM) with ordered nanochannels. The advantages of controlling the graphene oxide film 100 through cation-π interactions are:
[0035] Precise and controllable: By selecting cations of different types and sizes, precise control of interlayer spacing at the angstrom level can be achieved;
[0036] Stable and durable: It can effectively inhibit the swelling of graphene oxide membrane 100 in the aqueous environment, so that the separation performance is stable for a long time.
[0037] Powerful Functions: Graphene oxide membranes possess excellent ion sieving, molecular sieving, and selective permeation capabilities, which are key to achieving high-performance separation.
[0038] Preferably, when preparing graphene oxide using the Hammer process, the degree of oxidation of the graphene oxide is no higher than 40%. The degree of oxidation is one of the most critical parameters of graphene oxide, directly affecting its chemical structure, hydrophilicity, interlayer spacing, mechanical strength, and subsequent functionalization capabilities. Controlling the degree of oxidation below 40% (usually achieved by controlling the amount of oxidant and reaction time) is primarily to achieve an optimal balance between introducing sufficient functional groups and maintaining the graphene framework structure.
[0039] In this embodiment, the graphene oxide membrane 100 is prepared by the dripping membrane method, the filtration membrane method, or the polymerization membrane method to obtain a graphene oxide membrane 100 with good uniformity.
[0040] In this embodiment, the graphene oxide membrane 100 is immersed in an ionic liquid for a fixed period of time, followed by rinsing and drying to form a stable ion control. The graphene oxide membrane 100 is prone to swelling in aqueous solutions, leading to increased and unstable interlayer spacing, which severely affects its ion sieving accuracy and long-term performance. This invention utilizes the strong hydrated ion-π interaction between hydrated cations in the solution and the aromatic ring structures on the graphene oxide sheets through immersion in an ionic liquid for a fixed period of time. This interaction causes the hydrated cations to strongly adsorb between the upper and lower graphene oxide sheets, acting like "bridge piers," thus precisely supporting and fixing the distance between the sheets. The graphene oxide membrane 100 treated in this way achieves a stable interlayer spacing, thereby retaining only water molecules and excluding other impurities.
[0041] Preferably, the ions include, but are not limited to, monovalent cations, with a concentration of 0.05 mol / L to 0.5 mol / L. By selecting appropriate ion types and concentrations, it is ensured that the final prepared cation-controlled graphene oxide membrane 100 (I-GOM) possesses stable nanochannels, excellent anti-swelling properties, and precise ion sieving capabilities.
[0042] In this embodiment, the specific steps for preparing the cation-controlled graphene oxide film 100 using cation-π interactions are as follows:
[0043] Preparation of basic graphene oxide film: First, graphene oxide solution is made into one or more stacked thin films by means such as vacuum filtration or drop coating.
[0044] Cationic solution immersion treatment: The prepared graphene oxide film is immersed in a solution containing specific cations. These cations are "pulled" towards the aromatic ring regions of the graphene oxide sheets through cation-π interactions and embedded into the gaps between the layers.
[0045] Stabilizing interlayer spacing: The embedded cations act like "pillars" or "shims," expanding and stabilizing the interlayer spacing of graphene oxide. The final stable interlayer spacing size depends on factors such as the hydration size of the cations used.
[0046] Post-processing: After soaking, rinsing and drying (such as vacuum drying) are usually performed to remove physically adsorbed ions, leaving those cations that are stably intercalated through strong interactions, thus obtaining the final cation-controlled graphene oxide film 100.
[0047] Then, S2 is executed to assemble the graphene oxide film 100 into the liquid channel of the immersion system of the immersion lithography machine, so that the immersion liquid 200 flows through the graphene oxide film 100 for purification before flowing to the surface of the wafer 300.
[0048] Preferably, the graphene oxide film 100 is assembled on the injection side of each level of liquid channel in the immersion system and does not contact the surface of the wafer 300.
[0049] like Figure 1 As shown, in this embodiment, the immersion system includes a water circulation section, which includes an injection side and a recovery side of primary and secondary liquid channels, and can perform single-stage or multi-stage membrane separation circulation.
[0050] A graphene oxide membrane 100 is assembled on the injection side of the primary liquid channel to prevent contaminants introduced from the purified water storage device, further purifying the immersion solution 200. After the immersion solution 200 contacts the surface of the wafer 300 for exposure, the liquid is recovered from the primary liquid recovery side. During this process, particles, metal ions, organic compounds, small molecules, etc., carried in by the wafer 300 itself or leached from surface photoresist and other chemicals are introduced, causing a certain degree of contamination to the circulating immersion solution 200.
[0051] The immersion system recirculates the immersion liquid 200 from the secondary injection side into the space between the wafer 300 and the exposure lens 400. Therefore, a graphene oxide film 100 is installed on the secondary liquid channel injection side to further purify the contaminants introduced by the primary liquid circulation, ensuring that the immersion liquid 200 maintains a stable refractive index and purity after circulation.
[0052] Preferably, the graphene oxide membrane 100 is replaced periodically after the immersion system is used repeatedly to avoid the accumulation of pollutants on the membrane surface, which would affect the filtration performance.
[0053] Preferably, the graphene oxide membrane 100 is adapted to the diameter of the liquid channel. By adjusting the amount of graphene oxide added during the preparation process, separation membranes of various sizes can be easily formed, thereby better adapting to different pipe diameters and equipment models. This prevents unfiltered immersion liquid 200 from flowing through the gap between the membrane and the pipe wall, and avoids the introduction of other types of contaminants. It also improves the overall process stability without requiring contact with the wafer 300.
[0054] Preferably, the graphene oxide membrane 100 is assembled facing the direction of water circulation. By aligning the membrane surface with the incoming flow direction, the immersion liquid 200 is allowed to pass through the membrane "face-on," ensuring that contaminants are primarily trapped on the outer surface of the membrane rather than being carried deep into the membrane's internal channels.
[0055] In summary, the embodiments of the present invention provide a method for reducing exposure defects in immersion lithography machines. By utilizing the excellent separation performance of the ion-controlled graphene oxide film 100, contaminants such as particles, metal ions, organic compounds, and small molecules can be filtered in one pass, reducing exposure defects caused by contamination of the immersion solution 200 in the immersion lithography machine. This ensures the stability of the exposure process parameters of the immersion lithography machine, achieves the ideal refractive index of the immersion solution 200, and eliminates exposure defects caused by contamination, thus guaranteeing the stability requirements of process parameters at advanced process nodes.
[0056] Furthermore, it should be understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.
Claims
1. A method for reducing exposure defects in an immersion lithography machine, characterized in that, include: Graphene oxide was prepared by the Hammer method, and cation-controlled graphene oxide films were prepared by utilizing cation-π interactions. The graphene oxide film is assembled in the liquid channel of the immersion system of an immersion lithography machine so that the immersion liquid flows through the graphene oxide film for purification before flowing to the wafer surface.
2. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, When preparing graphene oxide using the Hammer process, the degree of oxidation of the graphene oxide is no higher than 40%.
3. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The graphene oxide membrane is prepared by the dripping membrane method, the vacuum filtration membrane method, or the polymerization membrane method.
4. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The graphene oxide film is formed by immersing the film in an ionic liquid for a fixed period of time, followed by rinsing and drying.
5. The method for reducing exposure defects in an immersion lithography machine according to claim 4, characterized in that, The ionic liquid is a monovalent cation solution with a concentration of 0.05-0.5 mol / L.
6. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The graphene oxide film has a stable interlayer spacing.
7. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The graphene oxide membrane is assembled on the injection side of each level of liquid channel in the immersion system.
8. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The graphene oxide membrane is adapted to the diameter of the liquid channel.
9. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The graphene oxide film is assembled facing the direction of water circulation.
10. The method for reducing exposure defects in an immersion lithography machine according to claim 1, characterized in that, The method further includes periodically replacing the graphene oxide film.