Self-separation photoresist additive, modified photoresist and preparation method of structural wafer
By adding sulfonamide groups to modify the photoresist additive, the problem of photoresist corrosion caused by nitric acid removal of the surface metal layer was solved, achieving high-quality transfer of photolithographic patterns and stability of the development process.
Patent Information
- Application Number
- CN202511792870.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-02-06
AI Technical Summary
In the super-resolution lithography process, nitric acid removes the surface metal layer and corrodes the photoresist film, affecting the quality of the lithographic pattern.
A self-separating photoresist additive is used. This additive is based on sulfonamide groups and contains acrylate monomer polymer groups and fluorinated alkyl substituent groups. It can self-separate to the surface of the photoresist to form an upper barrier layer, which prevents nitric acid from corroding the photoresist layer and does not affect the development of the photoresist during the development process.
It effectively blocks nitric acid from corroding the photoresist layer, improves the quality of photolithography patterns, avoids additional removal processes and development defects, and enhances the pattern quality of the photomask.
Smart Images
Figure CN121477549A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of super-resolution imaging technology, and in particular to a method for preparing self-separating photoresist additives, modified photoresists, and structured wafers. Background Technology
[0002] Photolithography is a fundamental manufacturing process in the semiconductor industry and is widely used in chip development. Photoresist has always been a decisive factor in the advancement of photolithography technology because the essence of photolithography is to generate micro- and nano-patterns using photoresist. Typically, photoresist is spin-coated to form a film of a certain thickness with photolytic solubility transition and etch resistance, thus enabling rapid fabrication of nanostructures. The photolithographic micro- and nano-patterns can then be transferred to the target substrate through etching. Traditional photolithography processes include: wafer pretreatment, coating, photoresist application, post-split-bake (PAB), exposure, post-exposure-bake (PEB), development, and etching.
[0003] In the unique artificial superlens fabrication process of super-resolution lithography (SP lithography), a bottom metal layer, a photoresist layer, and a top metal layer are set on the bare wafer. After exposure, the top metal layer needs to be removed with nitric acid solution. The material of the top metal layer is usually a noble metal such as Ag. During the removal of the top metal layer with nitric acid, the photoresist layer will be corroded, affecting the subsequent exposure quality, thus limiting the application of magnifying or non-magnifying photoresist in the super-resolution lithography process. Summary of the Invention
[0004] (a) Technical problems to be solved To address the aforementioned issues, this disclosure provides a method for preparing self-separating photoresist additives, modified photoresists, and structured wafers. This method aims to solve the technical problem of the need for nitric acid to remove the surface metal layer after exposure in the GPG process unique to super-resolution lithography, where nitric acid corrodes the photoresist film layer, thus affecting the quality of the lithographic pattern.
[0005] (II) Technical Solution In a first aspect, the present invention provides a self-separating photoresist additive, wherein the bulk of the additive is a sulfonamide group, and the additive is formed by homopolymerization of a first monomer represented by the following formula I: Formula I; R1 is selected from hydrogen, halogen, cyano, alkyl or haloalkyl with no more than 3 carbon atoms; R2 represents a fluorinated alkyl substituent group; R3 represents a saturated alkane chain with 1-6 carbon atoms; The weight-average molecular weight range of the above additives is 3000-20000.
[0006] Preferably, R1 is selected from any one of the following groups: -H, -CH3, -CH2CH2CH3, -C(CH3)2OH.
[0007] Preferably, R2 is selected from any one of the following groups: -CF3, -C(CF3)2OH, -CF2CF2CF3, -CH(CF3)2, -CH2C3F7, -CF2(CF2)CF2H, .
[0008] Preferably, R3 is selected from any one of the following groups: -CH2-CH2-, -CH2-C(CH3)2- 、 -CH2-, -CH2-CH (CH3)-.
[0009] Secondly, the present invention provides a self-separating photoresist additive, wherein the additive is copolymerized from a first monomer and a second monomer, wherein the first monomer is the first monomer represented by Formula I in the self-separating photoresist additive, and the mass percentage of the first monomer is not less than 60%; the second monomer is selected from any one of the following groups: p-hydroxystyrene, , R4 is selected from any of the following groups: -H, -CH3, -CH2CH2CH3, -C(CH3)2OH.
[0010] Thirdly, the present invention provides a modified photoresist, comprising a photoresist solution and the aforementioned self-separating photoresist additive, wherein the self-separating photoresist additive accounts for 4%-10% of the mass percentage of the main resin in the aforementioned photoresist solution.
[0011] Preferably, the main resin of the photoresist solution is selected from any one of phenolic resin, polyacrylate resin, molecular glass resin, and organic-inorganic hybrid resin.
[0012] Preferably, the solvent of the photoresist solution is selected from at least one of alcohols, ethers, esters, ketones, alkanes, sulfones, amides, and aromatics.
[0013] Fourthly, the present invention provides a method for preparing a structured wafer, comprising the following steps: S1. A bottom metal film layer, a photoresist layer and a top metal film layer are sequentially prepared on the surface of a wafer to form a wafer to be exposed. The photoresist layer is prepared by the modified photoresist described above. S2. Perform super-resolution exposure on the wafer to be exposed, remove the surface metal film layer, and then develop to obtain a wafer with photolithographic patterns. S3. The photolithographic pattern is transferred to the wafer through etching, and the photoresist layer and the underlying metal film layer are removed to obtain the structured wafer.
[0014] Preferably, step S2 further includes a pre-baking step before super-resolution exposure, in which the photoresist layer forms a composite photosensitive film layer including a bottom photoresist layer and an upper barrier layer after pre-baking, and the upper barrier layer is formed by the above-mentioned self-separating photoresist additive.
[0015] (III) Beneficial Effects This invention designs a self-separating photoresist additive. The additive uses a sulfonamide group as the main component, linked to polymer groups containing acrylate monomers and fluorinated alkyl substituents. The acrylate monomer-containing polymer groups exhibit superior hydrophobicity compared to other polymers, and the fluorinated alkyl substituents have low surface energy, resulting in good hydrophobic and oleophobic properties, enabling the additive to self-separate to the photoresist surface. By blending this additive into the photoresist, it can self-separate to the photoresist surface during ultra-resolution lithography, increasing the surface contact angle and hydrophobicity, and preventing strong acids from corroding the photoresist layer. Simultaneously, it does not affect the development of the photoresist in the developer during subsequent development, avoiding additional removal processes and development defects, and significantly improving the pattern quality of the photomask. Attached Figure Description
[0016] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which: Figure 1 The diagram illustrates the mechanism by which a self-separating photoresist additive, according to an embodiment of the present disclosure, blocks nitric acid from corroding the photoresist. Figure 2 The schematic diagram illustrates the 1H NMR spectrum of the self-separating photoresist additive according to Example 1 of this disclosure; Figure 3 The schematic diagram illustrates the carbon NMR spectrum of the self-separating photoresist additive according to Example 1 of this disclosure; Figure 4 The schematic diagram illustrates the 1H NMR spectrum of the self-separating photoresist additive according to Example 2 of this disclosure; Figure 5 The schematic diagram illustrates the carbon NMR spectrum of the self-separating photoresist additive according to Example 2 of this disclosure; Figure 6 The schematic diagram illustrates the results of contact angle tests according to embodiments of the present disclosure and comparative examples; Figure 7 SEM images of wafers with structures according to embodiments of the present disclosure and comparative examples are schematically shown. Figure 8 The illustration shows a comparison of nitric acid immersion in a wafer according to an embodiment of the present disclosure and a comparative example. Detailed Implementation
[0017] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.
[0018] Embodiments of this disclosure provide a self-separating photoresist additive, the bulk of which is a sulfonamide group, and the additive is formed by homopolymerization of a first monomer represented by the following formula I: Formula I; R1 is selected from hydrogen, halogen, cyano, alkyl or haloalkyl with no more than 3 carbon atoms; R2 represents a fluorinated alkyl substituent group; R3 represents a saturated alkane chain with 1-6 carbon atoms; The weight-average molecular weight range of the above additives is 3000-20000.
[0019] In this embodiment, the additive involves an acrylate polymer, which has better hydrophobic properties than other polymers; R2 is a fluorinated material with low surface energy, which can self-separate to the surface in the photoresist solution; the fluorinated material has hydrophobic and oleophobic properties.
[0020] Additives are blended into the photoresist, and during the ultra-resolution lithography process, they separate to the photoresist surface, increasing the contact angle and hydrophobicity to protect the photoresist layer from strong acid corrosion. The mechanism is as follows: Figure 1 As shown in the diagram, the modified photoresist undergoes additive state changes before and after the pre-baking (PAB) process. By separating itself to form an upper barrier layer on the photoresist surface, the structure of this upper barrier layer provides comprehensive protection for the photoresist layer. After exposure, it effectively blocks the nitric acid solution from corroding the photoresist during the removal of the surface silver layer.
[0021] R1 includes any one of the following groups: -H, -CH3, -CH2CH2CH3, -C(CH3)2OH.
[0022] Wherein, R2 is selected from any one of the following groups: -CF3, -C(CF3)2OH, -CF2CF2CF3, -CH(CF3)2, -CH2C3F7, -CF2(CF2)CF2H, .
[0023] The R3 mentioned above is selected from any one of the following groups: -CH2-CH2-, -CH2-C(CH3)2- 、 -CH2-, -CH2-CH(CH3)-.
[0024] On the other hand, this disclosure provides a self-separating photoresist additive, wherein the additive is copolymerized from a first monomer and a second monomer, wherein the first monomer is the first monomer represented by Formula I in the self-separating photoresist additive, and the mass percentage of the first monomer is not less than 60%; the second monomer is selected from any one of the following groups: p-hydroxystyrene, R4 is selected from any of the following groups: -H, -CH3, -CH2CH2CH3, -C(CH3)2OH.
[0025] More specifically, embodiments of this disclosure provide a modified photoresist, comprising a photoresist solution and the aforementioned self-separating photoresist additive, wherein the self-separating photoresist additive accounts for 4%-10% of the mass percentage of the main resin in the photoresist solution.
[0026] Specifically, the additive is a solid powder, and the proportion of the self-separating photoresist additive in the main resin of the photoresist solution is 4wt%-10wt%. Preferably, the proportion of the additive in the main resin of the photoresist solution is 5wt%-6wt%.
[0027] The aforementioned photoresists include all amplification photoresists and non-amplification photoresists. In particular, chemical amplification photoresists, due to the introduction of photoacids, cannot come into contact with nitric acid. After employing a self-separating functional barrier layer, they can be applied to super-resolution lithography.
[0028] Specifically, the main resin of the photoresist solution is selected from any one of phenolic resin, polyacrylate resin, molecular glass resin, and organic-inorganic hybrid resin, and the solvent of the photoresist solution is selected from at least one of alcohol, ether, ester, ketone, alkanes, sulfone organic solvents, amide organic solvents, and aromatic solvents.
[0029] Specifically, in the unique process of super-resolution lithography, after exposure, the surface metal layer needs to be removed with acid. The surface metal layer is made of precious metals such as Ag, and its thickness is 10nm-20nm. During the removal of the silver layer with nitric acid, the traditional photoresist layer is corroded, affecting the quality of subsequent exposures. This disclosure addresses this issue by adding a self-separating photoresist additive to the photoresist. This additive includes polymer groups containing acrylate monomers and R2 groups. The polymer groups containing acrylate monomers have better hydrophobic properties than other polymers; the R2 groups are fluorine-containing materials with low surface energy, allowing them to self-separate to the surface; fluorine-containing materials have hydrophobic and oleophobic properties; and the self-separating photoresist additive is formed by modifying the sulfonamide groups. After pre-baking the wafer to be exposed, the additive self-separates from the photoresist solution to form an upper barrier layer. This upper barrier layer provides comprehensive protection for the photoresist layer, effectively preventing the nitric acid solution from corroding the photoresist during the removal of the surface silver layer after exposure. Meanwhile, based on the material characteristics of the upper barrier layer, the additive material is hydrophilic and can be fully dissolved in the developer during the subsequent photoresist development process, without affecting the subsequent photolithography pattern.
[0030] The embodiments of this disclosure also provide an application of the above-described modified photoresist in a super-resolution photolithography process. Specifically, a method for fabricating a structured wafer is provided, comprising the following steps: S1. A bottom metal film layer, a photoresist layer and a top metal film layer are sequentially prepared on the surface of a wafer to form a wafer to be exposed. The photoresist layer is prepared by the modified photoresist described above. S2. Perform super-resolution exposure on the wafer to be exposed, remove the surface metal film layer, and then develop to obtain a wafer with photolithographic patterns. S3. The photolithographic pattern is transferred to the wafer through etching, and the photoresist layer and the underlying metal film layer are removed to obtain the structured wafer.
[0031] In step S2, a pre-baking step is included before super-resolution exposure. After pre-baking, the photoresist layer forms a composite photosensitive film layer comprising a bottom photoresist layer and an upper barrier layer. The upper barrier layer is formed by the aforementioned self-separating photoresist additive. This upper barrier layer increases the surface contact angle and hydrophobicity, preventing strong acids from corroding the bottom photoresist layer. Furthermore, this upper barrier layer does not affect the development of the photoresist in the developer solution during subsequent development, avoiding additional removal processes and development defects.
[0032] The present disclosure will be further described below through specific embodiments. The following examples specifically illustrate the above-described photoresist composition, its preparation method, and its application. However, the following examples are merely illustrative of the present disclosure, and the scope of the disclosure is not limited thereto.
[0033] Example 1 This embodiment 1 discloses a self-separating photoresist additive #1, the structural formula of which is shown below: ; The additive described above has a sulfonamide group as its main component, which is used in the first monomer structure of the homopolymer. R1 is -CH3; R2 is -CF3; R3 is a saturated alkane chain with 1-6 carbon atoms; in this embodiment, the number of C atoms is 4, and R3 is specifically -CH2-C(CH3)2-; Additive #1 has a number-average molecular weight (Mn) of 7255 and a weight-average molecular weight (Mw) of 18918; its PDI is 2.608. Its 1H and 1C NMR spectra are as follows: Figures 2-3 As shown.
[0034] The above additives are prepared by the following method:
[0035] Azobisisobutyronitrile (AIBN) is used as the initiator, and tetrahydrofuran (THF) is used as the solvent for the reaction.
[0036] Example 2 This embodiment 2 discloses a self-separating photoresist additive #2, the structural formula of which is shown below: ; The additive described above has a sulfonamide group as its main component, and the first monomer used for copolymerization has the same structure as in Example 1. The second monomer is: In the second monomer, R4 is -CH3. The additive is prepared in the same way as in Example 1, wherein the mass percentage of the first monomer is 70%.
[0037] Additive #2 has a number-average molecular weight (Mn) of 4381 and a weight-average molecular weight (Mw) of 10277; its PDI is 2.346. Its 1H NMR spectrum is as follows: Figures 4-5 As shown.
[0038] Example 3 This embodiment 3 discloses a self-separating photoresist additive #3, the structural formula of which is shown below: ; In the above additives, in the first monomer structure used for homopolymerization, R1 is -CH3; R2 is -CF3; R3 is a saturated alkane chain with 1-6 carbon atoms; in this embodiment, the number of C atoms is 2, and R3 is specifically -CH2-CH2-; the preparation method of the additives is the same as in Example 1.
[0039] Additive #3 has a number-average molecular weight (Mn) of 6661, a weight-average molecular weight (Mw) of 10708, and a PDI of 1.608.
[0040] The structural information of the additives in Examples 1-3 is summarized in Table 1: Table 1 is a summary table of additive information for Examples 1-3.
[0041] Example 4 This embodiment provides a modified photoresist, comprising a photoresist solution and the additives in Example 1, wherein the photoresist is a molecular glass photoresist, and this type of photoresist is a chemically amplified photoresist, and the additives account for 5% of the mass percentage of the main resin in the photoresist solution.
[0042] Example 5 This embodiment provides a method for fabricating a structured wafer, including the following steps: S1. A bottom metal film layer, a photoresist layer and a top metal film layer are sequentially prepared on the surface of a wafer to form a wafer to be exposed. The photoresist layer is prepared by the modified photoresist described above. The surface metal film and the bottom metal film are both Ag metal, and the photoresist layer is the modified photoresist of Example 4. S2. Perform super-resolution exposure on the wafer to be exposed, remove the surface metal film layer, and develop to obtain a wafer with photolithographic patterns; before super-resolution exposure, a pre-baking step is also included, in which the photoresist layer forms a composite photosensitive film layer including a bottom photoresist layer and an upper barrier layer after pre-baking, and the upper barrier layer is formed by the above-mentioned self-separating photoresist additive; the surface metal film layer is removed using a nitric acid solution.
[0043] S3. The photolithographic pattern is transferred to the wafer by etching, and the photoresist layer and the bottom metal film layer are removed to obtain the structure wafer #1.
[0044] Comparative Example 1 This comparative example provides a photoresist, wherein the photoresist is a molecular glass photoresist and does not contain any additives.
[0045] The photoresists of Example 4 and Comparative Example 1 were subjected to contact angle tests. The test results are as follows: Figure 6 As shown. (Through) Figure 6 It can be seen that the contact angle of the photoresist mixed with additives increased from the original 73.73° to 94.73°.
[0046] Comparative Example 2 This comparative example provides a method for preparing a structured wafer, comprising the following steps: S1. A bottom metal film layer, a photoresist layer, and a top metal film layer are sequentially prepared on the surface of a wafer to form a wafer to be exposed. The top metal film layer and the bottom metal film layer are both Ag metals, and the photoresist layer is the molecular glass photoresist of Comparative Example 1; it does not contain any additives.
[0047] S2. Perform super-resolution exposure on the wafer to be exposed, remove the surface metal film, and then develop to obtain a wafer with photolithographic patterns; the surface metal film is removed using a nitric acid solution.
[0048] S3. The photolithographic pattern is transferred to the wafer by etching, and the photoresist layer and the bottom metal film layer are removed to obtain the structure wafer #2.
[0049] SEM tests were performed on structured wafers #1 and #2 respectively to obtain... Figure 7 A comparison chart of test results. From Figure 7 As can be seen, the left side shows the structure wafer #2 obtained in Comparative Example 2, where the photolithographic pattern lines are relatively rough; while the right side shows the structure wafer #1 obtained in Example 5, where the photolithographic pattern lines are clearly distinguishable and without breaks. It is evident that the additive of this invention plays a certain role in blocking nitric acid, thus significantly improving the quality of the photolithographic pattern.
[0050] Figure 8 The images show the results of removing the surface Ag layer from the wafers after exposure in Examples 5 and 2, respectively. Figure 8 (a) is an image of the wafer to be exposed after exposure and immersion in nitric acid in Example 5. Figure 8 (b) is an image of the wafer in Comparative Example 2 after exposure and subsequent nitric acid immersion. From Figure 8 It can be seen that molecular glass photoresist without additives does not block nitric acid. When applied to SP lithography, during the removal of the surface Ag layer by nitric acid, it penetrates beneath the photoresist and damages the underlying Ag layer, leading to exposure failure. Molecular glass photoresist with additives, however, blocks the penetration of nitric acid, thus completing the exposure process without affecting the exposure quality.
[0051] As can be seen from the comparison of the above embodiments and comparative examples, the additive in the above embodiments uses sulfonamide groups as the main body, and is linked with polymer groups containing acrylate monomers and fluorinated alkyl substituent groups. Based on the fact that the hydrophobic properties of the polymer groups containing acrylate monomers are superior to other polymers, and that the fluorinated alkyl substituent groups have low surface energy, exhibiting good hydrophobic and oleophobic characteristics, the additive can self-separate to the photoresist surface. By blending the additive into the photoresist, it can self-separate to the photoresist surface in the super-resolution lithography process, increasing the surface contact angle and hydrophobicity, and preventing strong acids from corroding the photoresist layer; simultaneously, in the subsequent development process, it does not affect the development of the photoresist in the developer, avoiding additional removal processes and development defects, and greatly improving the pattern quality of the photomask.
[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A self-separating photoresist additive, characterized in that, The additive is composed of sulfonamide groups and is formed by homopolymerization of a first monomer represented by Formula I: Formula I; R1 is selected from hydrogen, halogen, cyano, alkyl or haloalkyl with no more than 3 carbon atoms; R2 represents a fluorinated alkyl substituent group; R3 represents a saturated alkane chain with 1-6 carbon atoms; The weight-average molecular weight of the additive is in the range of 3000-20000.
2. The self-separating photoresist additive according to claim 1, characterized in that, R1 is selected from any of the following groups: -H, -CH3, -CH2CH2CH3, -C(CH3)2OH.
3. The self-separating photoresist additive according to claim 1, characterized in that, The R2 is selected from any one of the following groups: -CF3, -C(CF3)2OH, -CF2CF2CF3, -CH(CF3)2, -CH2C3F7, -CF2(CF2)CF2H, .
4. The self-separating photoresist additive according to claim 1, characterized in that, The R3 is selected from any one of the following groups: -CH2-CH2-, -CH2-C(CH3)2- 、 -CH2-, -CH2-CH (CH3)-.
5. A self-separating photoresist additive, characterized in that, The additive is formed by copolymerization of a first monomer and a second monomer, wherein the first monomer is the first monomer represented by formula I in the self-separating photoresist additive of any one of claims 1-4, and the mass percentage of the first monomer is not less than 60%; The second monomer is selected from any one of the following groups: p-hydroxystyrene, R4 is selected from any of the following groups: -H, -CH3, -CH2CH2CH3, -C(CH3)2OH.
6. A modified photoresist, characterized in that, It includes a photoresist solution and the self-separating photoresist additive according to any one of claims 1-5, wherein the self-separating photoresist additive accounts for 4%-10% of the mass percentage of the main resin in the photoresist solution.
7. The modified photoresist according to claim 6, characterized in that, The main resin of the photoresist solution is selected from any one of phenolic resin, polyacrylate resin, molecular glass resin, and organic-inorganic hybrid resin.
8. The modified photoresist according to claim 6, characterized in that, The solvent of the photoresist solution is selected from at least one of alcohols, ethers, esters, ketones, alkanes, sulfones, amides, and aromatics.
9. A method for preparing a structured wafer, characterized in that, Includes the following steps: S1. A bottom metal film layer, a photoresist layer, and a top metal film layer are sequentially prepared on the surface of a wafer to form a wafer to be exposed. The photoresist layer is prepared by the modified photoresist according to any one of claims 6-8. S2. Perform super-resolution exposure on the wafer to be exposed, remove the surface metal film layer, and then develop to obtain a wafer with photolithographic pattern. S3. The photolithographic pattern is transferred to the wafer by etching, and the photoresist layer and the underlying metal film layer are removed to obtain the structured wafer.
10. The method for preparing the structured wafer according to claim 9, characterized in that, In step S2, a pre-baking step is also included before super-resolution exposure. After pre-baking, the photoresist layer forms a composite photosensitive film layer including a bottom photoresist layer and an upper barrier layer. The upper barrier layer is formed by the self-separating photoresist additive according to any one of claims 1-5.