Positive photoresist composition and application thereof

Abstract

The invention provides a positive photoresist composition and application thereof, and the positive photoresist composition comprises the following components in percentage by mass: 20-35% of cresol phenolic resin A, 3-15% of cresol phenolic resin B, 5-10% of a photosensitizer, 0.01-2% of an additive and 50-70% of a solvent. The weight-average molecular weight of the cresol phenolic resin A is 15000 to 30000, and the weight-average molecular weight of the cresol phenolic resin B is 5000 to 10000; the main absorption wavelength of the photosensitizer is within the range of 365-436 nm, and the absorption intensity of the photosensitizer is not less than 14 L / g.cm. The photoresist composition can adapt to different processing technologies of a G line, an H line and an I line, and when the film thickness reaches 10-20 microns, the photoresist composition has high chemical resistance and steepness, the side morphology inclination angle is not less than 83 degrees, and the pattern resolution reaches 5-10 microns; and the electroplating tolerance is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of photoresist in advanced packaging, and more specifically, to a positive photoresist composition and its application. Background Art

[0002] In semiconductor advanced packaging, the Re-Distribution Layer (RDL) is a core technology in wafer-level packaging, playing the role of electrical extension and interconnection in the XY plane. The essence of the RDL process technology is to add one or more layers on the original wafer: first, deposit a copper seed layer on the substrate, then coat a layer of photoresist on this structure, then pattern it using lithography equipment, and finally, the electroplating system deposits a copper metallization layer therein to form the final RDL. In the field of semiconductor manufacturing, photoresist is one of the materials with relatively high costs. The thickness of photoresist usually remains within 1 μm in conventional front-end processes, but in the back-end packaging process such as the RDL process, the height of copper wires is generally 5 - 10 μm, and the corresponding thickness of the coated photoresist should be 10 - 15 μm. Therefore, the photoresist applied to RDL needs to have excellent performance indicators such as high thickness, high chemical resistance, and high steepness while obtaining a high thickness, and the corresponding photoresist application film thickness is high and the usage amount is large. There are certain requirements for the use cost of such photoresists at the application end.

[0003] According to the different exposure principles of photoresists, they are mainly divided into two categories: positive photoresists and negative photoresists. A positive photoresist means that the exposed part is more easily dissolved in the developer, leaving the unexposed part of the photoresist as a barrier layer or mask. Its working principle is that ultraviolet light irradiates the exposed area, and the photoresist undergoes a chemical reaction, resulting in a decrease in the resin molecular weight or a change in polarity, accelerating the dissolution of the resin, and the unexposed area is a high-molecular resin that is difficult to dissolve. A negative photoresist is the opposite of a positive photoresist. The exposed part undergoes a cross-linking reaction to form a three-dimensional network structure, having stronger corrosion resistance, and the unexposed part is etched away by the developer to form a pattern. According to different specific reaction principles, positive and negative photoresists are further subdivided into different technical systems.

[0004] Positive photoresists can be classified into two major categories according to the chemical reaction principle: chemically amplified and non-chemically amplified. Among them, chemically amplified photoresists are prepared by adding photoacid generators to the photoresist. After ultraviolet light irradiation, the photoacid generators decompose to produce acid. In the post-exposure baking process, the acid acts as a catalyst to catalyze the deprotection of the film-forming resin. Moreover, after the deprotection reaction, the acid can be released again and continue to play a catalytic role. By changing the presence or absence of the protecting group, the dissolution rate of the photoresist in the developer is changed, thereby forming a pattern. Its advantages are low energy requirements, steep topography, and strong photosensitivity. The disadvantages are that the cost of photoacid generators and resins with protecting groups is high, and the post-exposure baking (PEB) process needs to be added in the process, which is very sensitive to temperature. It is usually applied to photoresists with a film thickness below 1μm. Non-chemically amplified photoresists are further subdivided into main-chain scission type and polarity transformation type. Among them, the main-chain scission type photoresist decomposes into CO2, CO, and many low-molecular-weight fragments under EUV irradiation. The solubility of these fragments in the developer is greatly increased. The advantages of this type of photoresist are high resolution and strong photosensitivity. The disadvantages are the need for an EUV extreme ultraviolet light source, high resin cost, and high requirements for environmental cleanliness. It is often used in the front-end process. The most widely used formulation system for the polarity transformation type photoresist is the phenolic resin and diazonaphthoquinone (Phthalocyanine, PAC) type photosensitizer system. The principle is that after the photoresist is irradiated with ultraviolet light from a mercury lamp, the diazonaphthoquinone (DNQ) unit of the diazonaphthoquinone type photosensitive compound (PAC) is transformed into ketene, and further transformed into indenyl carboxylic acid in water, which promotes the dissolution of the phenolic resin in the developer. The DNQ in the unexposed part inhibits the dissolution of the phenolic resin in the alkaline developer, thereby realizing patterning.

[0005] In recent years, photoresist materials have been widely used in the actual manufacturing process of advanced packaging. The main function is to provide pattern transfer for copper electroplating in the RDL process, and their material selection and structure are also diverse. A performance- excellent thick-film positive photoresist should meet the following performance requirements: high film thickness, excellent film thickness uniformity, high resolution, high steepness, and high chemical resistance, etc. However, there are many deficiencies in the current thick-film photoresists on the market: (1) The cost of the chemically amplified positive photoresist in the current thick-film photoresists on the market is relatively high, and the PEB process needs to be added (many application terminals do not have this process); (2) The positive photoresist of the phenolic resin and photosensitizer (PAC) system on the market cannot have high resolution and high steepness under the premise of meeting a thickness of 10-20μm. During the exposure process, if the photoresist film thickness is too thick, it will lead to low light absorption of the bottom photoresist, insufficient steepness, resulting in a positive trapezoidal topography, and at the same time, it will also affect the resolution. Summary of the Invention

[0006] To solve the problems in the above-mentioned prior art, the present invention provides a positive photoresist composition. The photoresist composition can be commonly used in G, H, and I line processes and is applied to the field of advanced packaging technology. On the premise of meeting a film thickness of 10 - 20 μm, it can also maintain high resolution and steepness, and has excellent plating tolerance in acidic and inorganic acid-based copper plating solutions.

[0007] The positive photoresist composition of the present invention, calculated by mass percentage, comprises the following components: 20 - 35% cresol novolak resin A, 3 - 15% cresol novolak resin B, 5 - 10 wt% photosensitizer, 0.01 - 2% additive, and 50 - 70 wt% solvent.

[0008] During the experiment, the inventors found through the experimental results that if the weight-average molecular weight of the cresol novolak resin is too low, the viscosity of the obtained positive photoresist composition will become low, and the required film thickness of 10 - 20 μm cannot be achieved after processing and forming. Moreover, its development rate will increase, and its tolerance in the developer will become poor. After final forming, there will be problems such as rounded corners at the top of the side morphology of the photoresist and indentations in the middle; if the weight-average molecular weight of the cresol novolak resin is too high, the viscosity of the photoresist composition will increase significantly, thus affecting the application film thickness of the photoresist. At the same time, the development speed of the photoresist composition will also become slow, and the film cannot be developed under the processing conditions provided by the present invention. Therefore, the inventors chose to use two kinds of cresol novolak resins, cresol novolak resin A and cresol novolak resin B, and adjusted the mass ratio of the two cresol novolak resins used to stabilize the development rate of the photoresist composition within an appropriate range. Therefore, in the examples of the present invention, the weight-average molecular weight of cresol novolak resin A is 15,000 - 30,000, and the weight-average molecular weight of cresol novolak resin B is 5,000 - 10,000. The mass ratio of cresol novolak resin A to cresol novolak resin B is 9 - 6:1 - 4, and the specific ratio can be 9:1, 8:2, 7:3, 6:4, etc.

[0009] In some embodiments of the present invention, the raw materials for preparing the cresol novolak resin include m-cresol novolak resin and p-cresol novolak resin, and the following steps can be carried out: In a suitable reaction vessel, add appropriate amounts of cresol and phenol formaldehyde according to the required ratio (usually 1:1.2 - 1:1.5) for mixing. Then, while stirring, slowly add an acidic catalyst (such as hydrochloric acid) for catalysis. The addition amount of the catalyst is usually 1% - 5% of the total weight of the reactants. When carrying out the acid-catalyzed condensation reaction, the reaction temperature is usually between 70°C and 100°C, and the reaction time can be adjusted according to actual needs, usually ranging from two hours to dozens of hours. After the reaction is completed, stop heating and cool the reaction solution to room temperature. After obtaining the crude product of the cresol novolak resin, it can be purified through treatment steps such as filtration, washing, and drying to finally obtain the required product.

[0010] In some embodiments of the present invention, the main absorption wavelength of the photosensitizer is between 365 - 436 nm. This is because the lithography machine for semiconductor advanced packaging uses a mercury lamp as the excitation light source, and the energy peak bands of the mercury lamp are concentrated in three bands: 365 nm, 405 nm, and 436 nm. Correspondingly, the processing wavelength of the G-line lithography machine is near 436 nm, the processing wavelength of the H-line lithography machine is near 405 nm, and the processing wavelength of the I-line lithography machine is near 365 nm. In order to enable the thick film photoresist composition to achieve good photoreactions within the above wavelength range, the photosensitizer used in the present invention is preferably a polymer with an absorption wavelength of 365 - 436 nm.

[0011] Considering the properties of the polarity conversion type photoresist, the positive photoresist composition of the present invention utilizes the photoreaction principle of the polarity conversion type photoresist. In some embodiments of the present invention, the photosensitizer is at least one of 2,1,4-diazo sulfonate compounds and 2,1,5-diazo naphthoquinone sulfonate compounds. Preferably, the diazo naphthoquinone derivatives include at least one of 2,1,5-diazo naphthoquinone sulfonyl chloride and 2,1,4-diazo naphthoquinone sulfonyl chloride, and the derivatives of the naphthol compounds include at least one of 2,3,4-trihydroxy benzophenone, 2,4,4′-trihydroxy benzophenone, 2,2′,4-trihydroxy benzophenone, 2,3,4,4′-tetrahydroxy benzophenone, 2,2′,3,4-tetrahydroxy benzophenone, 2,4,2′,4′-tetrahydroxy benzophenone, 2,3,4-trihydroxy acetophenone, and 2,4-dihydroxy acetophenone. As an example, the photosensitizer is selected from at least one of 2,3,4,4-tetracarboxy benzophenone-1,2-diazido naphthoquinone-5-sulfonate and 2,3,4,4-tetracarboxy benzophenone-1,2-diazido naphthoquinone-4-sulfonate.

[0012] In some embodiments of the present invention, the preparation raw materials of the photosensitizer include diazo naphthoquinone sulfonyl chloride, hydroxybenzophenone, dioxane, triethylamine, etc., and can be carried out according to the following steps: In a suitable reaction vessel, add an excessive amount of dioxane as the solvent background, add an appropriate amount of hydroxybenzophenone and diazo naphthoquinone sulfonyl chloride according to the required ratio (usually 1:2 - 1:3), and mix. Then, under stirring, heat up to 40 °C for dissolution. Within 1 hour, gradually add triethylamine in an equimolar amount to the diazo naphthoquinone sulfonyl chloride. After reacting for half an hour, observe the reaction phenomenon and the color of the solution, detect that the pH is between 6 - 8 and then conduct TCL detection. Then disperse the solution in the aqueous phase at a ratio of 1:4, quickly stir and disperse for 5 hours, precipitate, filter, wash with water, and then dry to obtain the corresponding photosensitizer.

[0013] In the present invention, the developing principle of the positive photoresist composition lies in that: after the diazonaphthoquinone structure of the photosensitizer is irradiated with ultraviolet light, it is transformed into ketene, and the ketene is further transformed into indenyl carboxylic acid in water. The appearance of indenyl carboxylic acid promotes the dissolution of cresol novolak resin in the developer, while the photosensitizer in the unexposed area inhibits the dissolution of the cresol novolak resin in the alkaline developer, ultimately achieving patterning. During the experimental stage, the inventors found that if the dosage of the photosensitizer in the positive photoresist composition is too high, on the one hand, the excessive photosensitizer at the top absorbs most of the light energy, and the ultraviolet light cannot reach the bottom, resulting in insufficient exposure of the positive photoresist composition at the bottom layer. Eventually, the pattern profile formed presents a positive trapezoid with a narrow top and a wide bottom, and even the bottom cannot be dissolved, causing situations such as non-opening of the film. On the other hand, when the diazonaphthoquinone structure in the positive photoresist composition is exposed and developed under alkaline conditions, a large-scale diazo coupling will occur with the excessive photosensitizer, and eventually, eagle horns will appear at the top of the pattern profile. On the other hand, since the photosensitizer will release a small amount of N2 during the exposure process, in the presence of a relatively high film thickness and a relatively high content of the photosensitizer in the positive photoresist composition, situations such as cracking of the resist film will occur. If the dosage of the photosensitizer is too low, the resistance of the unexposed area to the developer will be reduced, the formed pattern will have a concave middle part, and the actual processing exposure amount is too high relative to the exposure amount required for the thick-film positive photoresist composition, resulting in the passive exposure of the photoresist in the unexposed area. Eventually, the formed colloidal line width becomes narrower, which does not match the expected line width, thus affecting the process stability.

[0014] In summary, in some embodiments of the present invention, the dosage of the photosensitizer is preferably 5-10 wt%, more preferably 7-9 wt%.

[0015] In some embodiments of the present invention, the solvent is a commonly used solvent in the art, and its function is to dissolve and disperse the resin, achieve the coating function and improve the uniformity of the photoresist. It can be selected from polar and non-polar organic solvents. Preferably, the solvent is at least one of propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, propylene carbonate, benzyl alcohol, and ethane-3-ethoxypropionate; more preferably, the solvent is at least one of propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, and propylene carbonate.

[0016] In some embodiments of the present invention, according to the type of the photosensitizer, the solvent is selected as a mixture obtained by mixing propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether in any ratio, and the mixing ratio of the two can be adjusted adaptively according to the characteristics of other components.

[0017] In some embodiments of the present invention, the first additive is a low-molecular-weight polyhydroxy aromatic compound, which functions to improve the photosensitivity of the photoresist, regulate the development dissolution rate of the phenolic resin, and increase the dissolution rate contrast between the exposed area and the unexposed area, thereby effectively improving the resolution. During the experimental stage, the inventors found that in the positive photoresist composition, if the dosage of the first additive is too high, the small molecule compound will simultaneously increase the overall dissolution rate of both the exposed area and the unexposed area, increasing the film loss of the unexposed area of the photoresist in the developer, thus failing to reach the corresponding preset film thickness and affecting the subsequent process. If the dosage of the first additive is too low, the effect of increasing the dissolution rate contrast between the exposed area and the unexposed area cannot be achieved. The first additive is preferably bisphenol A, 4,4'-(1-methylethylidene)bis(2-methylphenol), 4-(2-phenylpropan-2-yl)benzene-1,3-diol, 4-[(4-hydroxy-3,5-dimethylphenyl)-(2-hydroxyphenyl)methyl]-2,6-dimethylphenol, 4-[(4-hydroxy-2,5-dimethylphenyl)-(2-hydroxyphenyl)methyl]-2,5-dimethylphenol, 4,4-methylenebis(2,6-dimethylphenol), etc. More preferably, it is at least one of 4,4-methylenebis(2,6-dimethylphenol) and 4,4'-(1-methylethylidene)bis(2-methylphenol).

[0018] In some embodiments of the present invention, the second additive is a long carbon chain substituted secondary alcohol or a fluorinated long carbon chain acrylic acid, which functions to improve the leveling property and film-forming uniformity of the photoresist, reduce the surface tension of the photoresist, improve the wettability and the dispersibility of the solid, and prevent the generation of stripes during the spin coating process. During the experimental stage, the inventors found that in the positive photoresist composition, if the dosage of the second additive is too high, on the one hand, the second additive is expensive and the cost will increase significantly, and on the other hand, the excessive second additive will accumulate on the surface of the photoresist layer, affecting the optical path during the exposure process and thus affecting the morphology of the photoresist. If the dosage of the first additive is too low, the effect of improving the leveling property and film-forming uniformity of the photoresist cannot be achieved. It is preferably ethoxylated C12-14 secondary alcohols, a-[3,5-dimethyl-1-(2-methylpropyl)hexyl]-w-hydroxy poly(oxy-1,2-ethanediyl), a copolymer of partially fluorinated alcohol-substituted ethylene glycol and perfluoroalkanesulfonamidoacrylate polyalkenyl acrylate, etc. More preferably, it is at least one of a copolymer of perfluoroalkanesulfonamidoacrylate polyalkenyl acrylate and partially fluorinated alcohol-substituted ethylene glycol.

[0019] The above-mentioned positive photoresist composition of the present invention is applied in advanced packaging technology and is applicable to G-line, H-line, and I-line lithography machines.

[0020] In some embodiments of the present invention, when the positive photoresist composition is applied to advanced packaging technology, the film thickness after the photoreaction is 10 - 20 μm. This is because in the electroplating process of RDL, the metal grows in the gaps of the patterned photoresist from the electroplating solution through chemical deposition. In the electroplating process, it is required that the height of the photoresist layer is at least 2 - 3 μm higher than the grown metal layer to ensure the morphology of the electroplated metal wires and prevent the newly formed metal from emerging from the photoresist layer and causing metal connection, which may lead to short circuits in the subsequent device tests. In advanced packaging technology, the height of the copper wires used is generally 5 - 10 μm. To cover and deposit the copper wire layer in the photoresist, the formed photoresist film thickness should not be lower than the height of the copper wire layer. In the present invention, after the photoreaction of the positive photoresist composition is completed and patterned under the irradiation of a light source, in order to obtain a high resolution (less than 10 μm) and a high aspect ratio (the ratio of film thickness to resolution) simultaneously, it is necessary to control the film thickness formed by the positive photoresist composition to be between 10 - 20 μm.

[0021] In some embodiments of the present invention, the positive photoresist composition may further contain other specific additives. The additives may include, but are not limited to: imidazole ultraviolet absorbers, silicone adhesives, etc. In order to improve the adhesion of the positive photoresist to the substrate and the product stability in the actual process, the type of the additives can be selected according to the situation, and the dosage of the additives can be adjusted by increasing or decreasing the dosage of the solvent, which is not strictly limited in the present invention.

[0022] Beneficial effects: Compared with the prior art, the present invention adjusts the film thickness and the development rate of the positive photoresist composition in the developer by selecting cresol novolak resin A and cresol novolak resin B, the weight average molecular weights of the two resins and their usage mass ratios, so as to increase the contrast between the exposed area and the non-exposed area and achieve the purpose of adjusting the morphology. Based on the weight average molecular weights and dosages of the cresol novolak resin A and cresol novolak resin B, the dosage of the photosensitizer is preferably adjusted and used in combination with the cresol novolak resin A and cresol novolak resin B, so that the photoresist composition can be applied to the advanced packaging technology process, and finally the following are achieved: under the condition of ensuring a film thickness of 10 - 20 μm, the film thickness uniformity is less than 5%, and can reach about 3%; the pattern resolution reaches 5 - 10 μm, and the aspect ratio can reach at least 2:1; the steepness of the pattern side morphology reaches 83° and above; and it has excellent electroplating tolerance in inorganic acid-based copper electroplating solutions. Description of the Drawings

[0023] Figure 1 : The line width morphology of the photoresist obtained in Example 1;

[0024] Figure 2 : The line width morphology of the photoresist obtained in Example 2;

[0025] Figure 3 : Line width topography of the photoresist obtained in Example 3;

[0026] Figure 4 : Line width topography of the photoresist obtained in Comparative Example 1;

[0027] Figure 5 : Line width topography of the photoresist obtained in Comparative Example 2;

[0028] Figure 6 : Line width topography of the photoresist obtained in Comparative Example 3;

[0029] Figure 7 : Line width topography of the photoresist obtained in Comparative Example 4;

[0030] Figure 8 : Line width topography of the photoresist obtained in Comparative Example 5. Detailed Description of the Specific Embodiments

[0031] The content of the present invention can be more easily understood by referring to the following detailed description of the preferred embodiments of the present invention and the included examples. Unless otherwise defined, the technical and scientific terms used herein have the same common meaning as those in the field to which the present invention belongs.

[0032] As used herein, terms such as "comprising", "including", "having", etc. or other variations, for example, a composition, step, method, article, or device containing the listed elements need not be limited to those elements, but may include other elements not explicitly listed or requirements inherent in such composition, step, method, article, or device.

[0033] As used herein, the equivalents, concentrations, or other values or parameters are all ranges formed by any pair of a range, a preferred range, or a series of upper preferred values and lower preferred values and any lower limit or preferred value of the range, regardless of whether the range is separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include ranges "1 to 2", "1 to 3", "1 to 4", "1 to 2 and 2 to 4", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0034] Unless otherwise stated, the singular form includes plural discussion objects. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and this description includes the case where the event occurs and the case where the event does not occur.

[0035] Approximate terms in the specification and claims are used to modify quantities, indicating that the present invention is not limited to the specific quantity, but also includes modified parts that are close to the quantity and acceptable without causing changes to the relevant basic functions. Accordingly, modifying a numerical value with "about", "approximately", etc. means that the present invention is not limited to the exact numerical value. In some examples, the approximate term may correspond to

[0036] In addition, the indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the singular form of the element or component also includes the plural form, unless the quantity specifically refers to the singular form.

[0037] The present invention is illustrated below by specific embodiments, but the present invention is not limited to the specific examples given below. Table 1 shows the raw materials and their proportions of the positive photoresist compositions described in Examples 1-6 and Comparative Examples 1-7:

[0038] Table 1 Raw materials and their proportions of the photoresist compositions in Examples 1-6 and Comparative Examples 1-7

[0039]

[0040]

[0041]

[0042]

[0043] Mix the above Examples 1-6 and Comparative Examples 1-7 evenly according to the formula given in Table 1, and then perform processing and patterning. The specific operation process is as follows:

[0044] 1. Coat the positive photoresist compositions obtained from the above Examples 1-6 and Comparative Examples 1-7 on a 4-inch PVD sputtered copper sheet, select and adjust to an appropriate spin coating speed. For example: first use a speed of 800 rpm / 5 s to spread the positive photoresist composition, and then use 1200 rpm / 60 s as the main speed to adjust the photoresist film thickness to 15 μm;

[0045] 2. Place the PVD Cu wafer with the photoresist film on a contact hotplate for soft baking at 100 °C for 300 s. Measure the film thickness with a film thickness gauge. By adjusting the spin coating speed, ensure that the dry film thickness of the photoresist is within 15.0 ± 0.5 μm. Randomly select several different positions on the entire photoresist film and measure the film thickness at the selected positions. Calculate the uniformity of the obtained photoresist film thickness (uniformity %) = (maximum film thickness - minimum film thickness) / (average film thickness * 2). If uniformity % < 5%, it is regarded as good film thickness uniformity; conduct photolithography tests on the photoresists obtained from the formulations of the above Examples 1-6 and Comparative Examples 1-7 on a year-on-year basis;

[0046] 3. Expose the PVD Cu wafer coated with the photoresist on a G, H, I-Line Stepper lithography machine (SSB 500 / 40M) with an energy intensity of 1000 mJ / cm 2 , let it stand for about 30 min, and develop it with a Mark8 device, continuously spraying 2.38% TMAH for 480 s;

[0047] 4. Cut the photoresist into slices, and use a Thermo Fisher Scientific ultra-high resolution field emission scanning electron microscope Verios5XHR SEM to measure the side tilt angle (photoresist sidewall morphology) of the photoresist obtained from the sliced samples of Examples 1-6 at a film thickness of 15 μm and the upper and lower bottom line widths of the photoresist obtained from the sliced samples of Comparative Examples 1-7 at a film thickness of 15 μm, and observe the minimum line CD (Critical Dimension, abbreviated as CD), which is regarded as the resolution of the photoresist. The aspect ratio is obtained by dividing the film thickness by the resolution; repeat the test 3 times for each formulation.

[0048] The sidewall morphology after the photochemical reaction of the positive photoresist composition described in the above examples and comparative examples is shown in the attached Figure 1-8 :

[0049] Table 2 Film thickness uniformity, resolution, and corresponding morphology diagrams of the photoresists obtained from Examples 1-6 and Comparative Examples 1-7

[0050]

[0051] From the data in Table 2 and the corresponding side morphology diagrams, it can be seen that for the positive photoresists prepared from the formulations of the positive photoresist compositions described in Examples 1-6 at a film thickness of 15 μm: the film thickness uniformity is all lower than 5%, and the lowest can reach 2.6%; the resolution of the formed pattern is 6-7 μm; the steepness of the line width is not less than 83°. Respectively: the steepness of the sidewall morphology of the photoresist obtained in Example 1 is 90° (see Figure 1 ), and the steepness of the sidewall morphology of the photoresist obtained in Example 2 is 86° (see Figure 2), the steepness of the sidewall topography of the photoresist obtained in Example 3 is 83° (see Figure 3 ). The steepness of the sidewall topography of the photoresist obtained in Example 4 is 89°, the steepness of the sidewall topography of the photoresist obtained in Example 5 is 84°, and the steepness of the sidewall topography of the photoresist obtained in Example 6 is 87° (the SEM images obtained in Examples 4-6 are extremely similar to the SEM images obtained in Examples 1-3. Therefore, in the drawings, Figure 1-3 is used to represent the sidewall topography obtained in Examples 4-6).

[0052] In Comparative Example 1, compared with Example 1, the weight-average molecular weight of the cresol novolak resin A used is relatively low (Mw = 12,000). Although the final formed photoresist has good film thickness uniformity and resolution, the line width of the formed sidewall topography is relatively narrow (see Figure 4 ). This is because the cresol novolak resin with a relatively low weight-average molecular weight makes the positive photoresist composition obtained in Comparative Example 1 less tolerant to the developer, resulting in overdevelopment. In addition, the relatively low molecular weight of cresol novolak resin A leads to a relatively fast development rate, and the photoresist in the non-exposed area is also corroded by the developer, ultimately resulting in a narrower line width.

[0053] In Comparative Example 2, compared with Example 1, the weight-average molecular weight of the cresol novolak resin A used is relatively high (Mw = 40,000). The film thickness uniformity of the final formed photoresist becomes poor, and the photoresist composition at the bottom does not develop, making it impossible to form a clear pattern (see Figure 5 ), and no development means the resolution is 0. This is because the cresol novolak resin with a relatively high weight-average molecular weight significantly improves the resistance of the positive photoresist composition obtained in Comparative Example 2 to the developer, and its development rate in the developer becomes slower. Within the processing energy and development time provided by the present invention, the photoresist composition at the bottom cannot be developed to the bottom, thus unable to develop and form a pattern.

[0054] In Comparative Example 3, compared with Example 1, in the cresol novolak resin used, the mass ratio of cresol novolak resin A to cresol novolak resin B is less than 1:1, that is, the amount of cresol novolak resin B is greater than that of cresol novolak resin A. Although the final formed photoresist has good film thickness uniformity and pattern resolution, in the line width sidewall topography presented, a rounded corner is formed at the top (see Figure 6 ). - This is because the dissolution rate of cresol novolak resin B is relatively faster than that of cresol novolak resin A. A high proportion of cresol novolak resin B will cause the development rate of the positive photoresist composition obtained in Comparative Example 3 to accelerate during the exposure and development processes. Within the same development time, the photoresist in the unexposed area at the top layer is corroded by the developer for a long time, thus forming a rounded corner.

[0055] In Comparative Example 4, compared with Example 1, the dosage of the photosensitizer is relatively low (3 wt%), and although the film thickness uniformity and resolution of the finally obtained photoresist are good, upon careful observation, it is found that there is still an increasing trend of 1-2 μm in resolution compared with Examples 1-6, and the middle part of the side profile of the line width is concave (see Figure 7 ). This is because the resistance of the positive photoresist composition in Comparative Example 4 to the developer in the non-exposed area is reduced, and the processing exposure amount provided by the present invention is much greater than the exposure amount required by the photosensitizer contained in the positive photoresist composition in Comparative Example 4. Therefore, the photoresist in the non-exposed area is passively affected by exposure, and the finally formed line width becomes narrower. The slight difference in resolution is, on the one hand, due to the inappropriate dosage of the photosensitizer, and on the other hand, it may also be caused by fluctuations in various processing process factors. In addition, the results obtained in Comparative Example 6 are similar to those in Comparative Example 4.

[0056] In Comparative Example 5, compared with Example 1, the dosage of the photosensitizer is relatively high (12 wt%), and the film thickness uniformity and resolution of the finally obtained photoresist are good, but the side profile of the line width is narrow at the top and wide at the bottom, showing a positive trapezoid (see Figure 8 ). This is because the excessive photosensitizer at the top of the photoresist absorbs most of the light energy, making it impossible for ultraviolet light to reach the bottom ideally, resulting in insufficient exposure of the photoresist composition at the bottom.

[0057] In Comparative Example 7, compared with Example 4, the dosage of the photosensitizer is too high (14 wt%), and the film thickness uniformity formed by the obtained positive photoresist composition is good, but the film is not opened at the bottom, resulting in poor sidewall morphology, and this result is very similar to that in Comparative Example 2. This is because the excessive photosensitizer at the top of the photoresist absorbs most of the light energy, making it impossible for ultraviolet light to reach the bottom ideally, resulting in too low exposure of the photoresist composition at the bottom. Within the same developing time under the same conditions, the photoresist cannot be developed and opened. In addition, by combining Comparative Example 7 and Comparative Example 2, it is found that the molecular weights of cresol novolak resin A and cresol novolak resin B and the dosage of the photosensitizer in the present application have equally important effects on the sidewall morphology of the photoresist that can be formed by the positive photoresist composition. Any change in the parameters of either of them will seriously affect the exposure degree of the positive photoresist composition, resulting in poor sidewall morphology of the obtained photoresist.

[0058] From the results of Comparative Examples 1-7, it can be analyzed that both the cresol novolak resin and the photosensitizer contained in the positive photoresist in the present invention have an important impact on the sidewall morphology of the formed photoresist. Changing the parameters of any one of the two components can cause adverse changes in the sidewall morphology of the photoresist. Moreover, when the parameters of the photosensitizer remain unchanged, changing the resin ratio of the weight-average molecular weights of cresol novolak resin A and cresol novolak resin B will result in poor film thickness uniformity and resolution of the photoresist. When the parameters of the resin ratio of the weight-average molecular weights of cresol novolak resin A and cresol novolak resin B remain unchanged, changing the dosage of the photosensitizer may cause poor resolution of the photoresist, but the impact on film thickness uniformity can be ignored.

[0059] In summary, by adjusting the weight-average molecular weights, usage mass ratios of cresol novolak resin A and cresol novolak resin B, the dosage of the photosensitizer, and the dosage of the additive in the present invention, the positive photoresist composition can be adapted to the lithography machine with G, H, I-Line mixed-line light sources, and under the special advanced packaging technology process conditions and on the premise of ensuring the film thickness is 10-20 μm, technical effects such as a film thickness uniformity of less than 5%, a pattern resolution of 5-10 μm, an aspect ratio of not less than 2:1, and a sidewall topography steepness of the line width reaching 83° or more are achieved, and excellent plating tolerance in inorganic acid-based copper plating solutions is obtained.

[0060] The above is only an embodiment of the present invention and does not impose any form of limitation on the present invention. Although the present invention has been disclosed as above by way of examples, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, may make some changes or modifications by using the above-disclosed methods and technical contents as equivalent embodiments of equivalent changes. However, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A positive photoresist composition, characterized in that: The invention comprises the following components in percentage by mass: 20-35% cresol novolac resin A, 3-15% cresol novolac resin B, 5-10wt% photosensitizer, 0.01-2wt% additive and 50-70wt% solvent; wherein the weight average molecular weight of the cresol novolac resin A is 15000-30000, and the weight average molecular weight of the cresol novolac resin B is 5000-10000.

2. The positive photoresist composition according to claim 1, characterized in that: The mass ratio of cresol novolac resin A to cresol novolac resin B is greater than 1:

1.

3. The positive photoresist composition according to claim 2, characterized in that: The mass ratio of the cresol novolac resin A to the cresol novolac resin B is 9-6:1-4.

4. The positive photoresist composition according to claim 1, characterized in that: The absorption wavelength of the photosensitizer is 365-436nm.

5. The positive photoresist composition according to claim 4, characterized in that: The photosensitizer is at least one of a 2,1,4-diazonaphthoquinone sulfonate compound and a 2,1,5-diazonaphthoquinone sulfonate compound.

6. The positive photoresist composition according to claim 5, characterized in that: The amount of the photosensitizer used is 7-9wt%.

7. The positive photoresist composition according to claim 1, characterized in that: The solvent is at least one of propylene glycol methyl ether acetate, propylene glycol methyl ether, ethyl lactate and propylene carbonate.

8. The positive photoresist composition according to claim 7, characterized in that: The solvent is a mixture of propylene glycol methyl ether acetate and propylene glycol methyl ether in any proportion.

9. The positive photoresist composition according to claim 7, characterized in that: The additive includes at least one of a first additive and a second additive.

10. The positive photoresist composition according to claim 9, characterized in that: The first additive is a low molecular weight polyhydroxy aromatic compound, specifically preferably at least one of bisphenol A, 4,4'-(1-methylethylene)bis(2-methylphenol), 4-(2-phenylprop-2-yl)benzene-1,3-diol, 4-[(4-hydroxy-3,5-dimethylphenyl)-(2-hydroxyphenyl)methyl]-2,6-dimethylphenol, 4-[(4-hydroxy-2,5-dimethylphenyl)-(2-hydroxyphenyl)methyl]-2,5-dimethylphenol, and 4,4-methylenebis(2,6-dimethylphenol).

11. The positive photoresist composition according to claim 9, characterized in that: The second additive is at least one of long carbon chain substituted secondary alcohols and fluorine-containing long carbon chain acrylic acid.

12. Use of the positive photoresist composition according to any one of claims 1 to 11 in the field of advanced packaging technology.

13. Use of the positive photoresist composition according to claim 12 in the field of advanced packaging technology, characterized in that: The thickness of the formed photoresist film is 10-20 μm.

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