Ester type negative polyimide photoresist as well as preparation method and application thereof

Abstract

The invention discloses an ester type negative polyimide photoresist as well as a preparation method and application thereof, and belongs to the technical field of photoetching. The preparation method comprises the following steps: mixing dianhydride, diamine containing carboxylic acid sites and an organic solution, stirring and reacting to obtain a polyamide acid solution; heating and stirring the polyamide acid solution, carrying out sedimentation purification through methanol, and carrying out vacuum drying on the purified product to obtain a polyimide solid; the preparation method comprises the following steps: dissolving a polyimide solid in an organic solvent, then adding a photo-crosslinking group with hydroxyl sites and a photoinitiator, and carrying out esterification reaction to obtain the ester type negative polyimide photoresist, the photo-crosslinking group with the hydroxyl site comprises any one of cinnamyl alcohol; carrying out a specific photoetching process on the obtained photoresist to obtain a photoetching pattern; by introducing photosensitive group molecules into polyimide, a good photoetching effect can be obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photoetching technology, and particularly relates to an ester type negative polyimide photoresist and a preparation method and application thereof. BACKGROUND

[0002] In the field of microelectronic manufacturing, the evolution of semiconductor technology is always closely related to the innovation of functional materials. With the continuation of Moore's law, chip manufacturing has broken through from micron to atomic scale, and advanced packaging technologies such as fan-out, system-in-package (SiP) and three-dimensional integration (3D IC) have become the key path to continue the performance improvement of chips. These technologies have put forward unprecedented requirements for photoetching materials: not only high-precision patterning at sub-micron scale is needed, but also the structural integrity needs to be maintained in complex processes such as high-temperature post-process (such as metallization, passivation layer deposition), chemical mechanical polishing (CMP) and the like. The ester type negative polyimide photoresist gradually becomes the core material to meet the above requirements due to its unique molecular architecture.

[0003] The technical essence of the ester type negative polyimide photoresist lies in the deep integration of the high thermal stability and mechanical strength of polyimide with the patterning capability of photoetching technology. The molecular main chain takes imide ring as a rigid unit, and a photosensitive group (such as o-nitrobenzyl, coumarin derivative) is introduced through a side chain, which undergoes crosslinking reaction under ultraviolet light irradiation, and a stable pattern is formed in the unexposed area after development. Compared with traditional positive photoresist, the negative system shows significant advantages in thick film (>10 μm) applications: the crosslinked polyimide network can withstand heat treatment of more than 300 ℃, while maintaining low dielectric constant and excellent chemical corrosion resistance, becoming the preferred material for redistribution layer (RDL), electromagnetic shielding layer and flexible circuit substrate.

[0004] However, the existing ester type negative polyimide photoresist technology still faces multiple technical contradictions. First, the balance between photosensitivity and material purity has not been broken through. Traditional photosensitizers are prone to release acidic substances during the crosslinking process, causing stress concentration in the cured film and inducing crack propagation; at the same time, the compatibility of photosensitive groups with polyimide precursors is insufficient, resulting in an increase in residues after development, which affects the electrical properties. Second, the adaptability of the solvent system and the process flow is limited. Some formulations rely on high-boiling-point solvents (such as NMP), which are prone to produce interface defects in non-fluorine etching or low-temperature development processes, resulting in increased contact resistance or pattern edge roughness. In addition, the batch stability problem in large-scale production is prominent. The synthesis of polyimide involves multiple steps (such as polycondensation of diamine and dianhydride, imidization), and small fluctuations in raw material purity, reaction temperature and time will cause the molecular weight distribution to become wide, which in turn affects the coating uniformity and exposure sensitivity of the photoresist, making it difficult for the product to pass the rigorous authentication of the wafer factory for 2-3 years.

[0005] From the industry application status, the penetration rate of ester type negative polyimide photoresist in high-end chip manufacturing is still limited by the above bottlenecks. For example, in the packaging of RF Front-End, the material needs to meet the low loss demand of high frequency signal transmission and the reliability requirement of high temperature bonding process at the same time, and the existing products are difficult to balance between dielectric performance and thermal stability; in the field of flexible wearable devices, the contradiction between low temperature curing demand and photoetching precision is further highlighted, and the traditional system shows poor test effect in tensile test. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide an ester type negative polyimide photoresist, a preparation method and application thereof, which solves the problems in the prior art.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A preparation method of an ester type negative polyimide photoresist, comprising the following steps:

[0009] Mixing and stirring the dianhydride, carboxylic acid site containing diamine and organic solution to obtain a polyamic acid solution;

[0010] After heating and stirring the polyamic acid solution, methanol is used for sedimentation purification, and the purified product is vacuum dried to obtain a polyimide solid;

[0011] The polyimide solid is dissolved in an organic solvent, then a hydroxyl site containing photo-crosslinking group is added to obtain a photo-crosslinking polyimide solution; then a photo initiator is added to obtain an ester type negative polyimide photoresist;

[0012] The hydroxyl site containing photo-crosslinking group includes any one of the following:

[0013] Further, the dianhydride includes any one of the following:

[0014]

[0015] Further, the carboxylic acid site containing diamine includes any one of the following:

[0016]

[0017] Further, the structure formula of the polyamic acid is:

[0018]

[0019] Among them, A1 represents dianhydride, and B1 represents carboxylic acid site containing diamine.

[0020] Further, the photo initiator comprises any one of the following:

[0021]

[0022] Further, the photo crosslinking polyimide has the following structural formula:

[0023]

[0024] wherein A1 represents a dianhydride, B1 represents a carboxylic acid site containing diamine, and C1 represents a hydroxyl site containing photo crosslinking group.

[0025] Further, the molar ratio among the dianhydride, the carboxylic acid site containing diamine and the hydroxyl site containing photo crosslinking group is 1:1:2.

[0026] An ester type negative polyimide photoresist is prepared by using the preparation method.

[0027] The application of the above ester type negative polyimide photoresist in pattern photoetching.

[0028] Further, the process of the pattern photoetching is as follows:

[0029] The ester type negative polyimide photoresist is spin-coated on a silicon wafer by using a spin coater and dried, then the silicon wafer is placed under a mask under a UV lamp for exposure, and then a mixed solution of NMP and ethanol is used for development, so that a photoetching pattern is obtained; wherein the volume ratio of NMP and ethanol is 1:2.

[0030] The beneficial effects of the present application are as follows:

[0031] 1. The present application introduces a new type of photosensitive group into polyimide, and obtains an ester type negative polyimide photoresist through esterification, which solves the problem of performance degradation of materials caused by acidic substances generated in the crosslinking process of traditional photosensitizers. The new type of photosensitive group generates a neutral byproduct after exposure, avoiding chemical erosion of the polyimide main chain, and significantly improving the crosslinking density, so that the cured film can maintain low dielectric properties while significantly improving thermal stability, which can meet the stringent requirements of high-frequency radio frequency devices and high-temperature post-processes.

[0032] 2. The dianhydride selected by the present application plays an important role in the synthesis process of the photoresist, which can significantly simplify the synthesis process, greatly improve the synthesis efficiency, and exhibit the advantages of convenient and fast synthesis. The diamine selected by the present application plays an important role in the synthesis process of the photoresist, which has the characteristics of simple and easy synthesis, can greatly shorten the synthesis period, and at the same time, due to the factors such as easy availability of raw materials, it performs excellently in cost control, and can realize the synthesis of photoresist at a lower cost.

[0033] 3. The photocrosslinking agent selected in this invention has a unique ethylamine structure. At the chemical reaction level, this structure endows it with a more efficient and faster reaction ability with polyamic acid, significantly improving the reaction rate.

[0034] 4. The photoinitiator selected in this invention plays an important role in the field of photochemistry. Its unique feature is that when exposed to light radiation with a wavelength of 365nm, it can generate a photochemical reaction rapidly and efficiently, and has a highly sensitive photosensitive mechanism at this specific wavelength. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a photolithographic resolution image of the ester-type negative polyimide photoresist prepared in Example 1 of this invention;

[0037] Figure 2 This is a photograph of the photolithography effect of the ester-type negative polyimide photoresist prepared in Example 1 of this invention;

[0038] Figure 3 This is a diagram showing the mechanical properties of the ester-type negative polyimide photoresist prepared in Example 1 of this invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] A method for preparing an ester-type negative polyimide photoresist includes the following steps:

[0041] S1, dianhydride, diamine containing carboxylic acid sites and organic solution are mixed and stirred to react, resulting in polyamic acid (PAA) solution;

[0042] S2, after heating and stirring the polyamic acid solution, it was purified by precipitation with methanol, and the purified product was dried under vacuum to obtain solid polyimide (PI).

[0043] S3, dissolve solid polyimide in an organic solvent, then add photocrosslinking groups with hydroxyl sites to obtain a photocrosslinked polyimide solution;

[0044] S4, adding a photo initiator into the photo-crosslinking polyimide solution, and obtaining an ester type negative polyimide photoresist after mixing.

[0045] In S1, the dianhydride includes any one of the following:

[0046]

[0047]

[0048] In S1, the diamine containing a carboxylic acid site includes any one of the following:

[0049]

[0050] In S1, the polyamic acid has a structural formula as follows:

[0051]

[0052] A1 represents a dianhydride, and B1 represents a diamine containing a carboxylic acid site.

[0053] In S1 and S3, the organic solvent is one of dimethylacetamide (DMAC), dimethylformamide (DMF), and N-methylpyrrolidone (NMP).

[0054] In S3, the photo-crosslinking group having a hydroxyl site is any one of the following:

[0055]

[0056] The photo-crosslinking polyimide has a structural formula as follows:

[0057]

[0058] A1 represents a dianhydride, B1 represents a diamine containing a carboxylic acid site, and C1 represents a photo-crosslinking group having a hydroxyl site.

[0059] In S4, the photo initiator is one of the following:

[0060] The technical solutions of the present application are described in detail below through the following examples. The raw materials used in the examples are as follows:

[0061] 3,5-diaminobenzoic acid, manufacturer: Anjie CAS number: 535-87-5;

[0062] 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, manufacturer: Anjie CAS number: 1107-00-2;

[0063] ​Methylpyrrolidone, manufacturer: Sigma-Aldrich CAS No.: 872-50-4;

[0064] Hydroxyethyl methacrylate, manufacturer: Sigma-Aldrich CAS No.: 868-77-9;

[0065] Michler's ketone, manufacturer: Sigma-Aldrich CAS No.: 90-94-8.

[0066] Example 1

[0067] In this case, a new type of ester negative polyimide photoresist is disclosed, which is prepared by using commercial 3,5-diaminobenzoic acid and commercial 4,4'-(hexafluoroisopropylidene)diphthalic anhydride as an example, including the following steps:

[0068] S1, in a Schlenk reaction bottle with a stirring magnet, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (44.4g, 0.1mol) is added and stirred and dissolved in 200ml N-methylpyrrolidone for 2h, and then 3,5-diaminobenzoic acid (15.2g, 0.1mol) is added in one aliquot every 1h (a total of 5 aliquots) and then stirred for 24h to obtain a polyamic acid (PAA) solution;

[0069] The structure of the PAA solution is as follows:

[0070]

[0071] S2, after the polyimide precursor solution is heated to 170°C and stirred for 12h, methanol is used for sedimentation, a filter membrane is used for filtration, and the obtained product is vacuum dried in an oven for 12h to obtain a polyimide (PI) solid;

[0072] The structure of the polyimide solid is as follows:

[0073]

[0074] S3, the PI solid obtained above is dissolved using NMP, then hydroxyethyl methacrylate (26g, 0.2mol) is added thereto, and stirred at room temperature in the dark for 24h to obtain a photocrosslinking polyimide;

[0075] The structure of the photocrosslinking polyimide is as follows:

[0076]

[0077] S4, after the obtained photocrosslinking polyimide is added with Michler's ketone photoinitiator, an ester negative polyimide photoresist is obtained.

[0078] Example 2

[0079] In this embodiment, the new ester type negative polyimide photoresist prepared in Example 1 is used for pattern photolithography, and the specific steps are as follows:

[0080] The photoresist is dropped on the silicon wafer using a spin coater, and then spin-coated at 1000 r / min for 10 s and then at 3000 r / min for 1 min. The silicon wafer is placed in a temperature of 80°C for 5 min for soft baking. The silicon wafer is exposed to UV light under a mask for 5 min, and then developed using a NMP / ethanol mixed solution (volume ratio 1:2) for 10 s, and a photolithographic pattern is obtained.

[0081] The effect of the new ester type negative polyimide photoresist prepared in Example 1 for photolithography is shown in Figure 2 It can be seen that the new ester type negative polyimide photoresist prepared in the application has very excellent photolithographic effect.

[0082] Example 3

[0083] In this embodiment, the new ester type negative polyimide photoresist prepared in Example 1 is observed under an optical microscope, and the photolithographic resolution effect is shown in FIG. 1. It can be seen that the resolution of the negative polyimide photoresist prepared in the application can reach 22 microns.

[0084] The new ester type negative polyimide photoresist obtained in Example 1 is applied to a glass plate, which is placed in an oven with a gradient temperature rise to form a film. The obtained film is processed into small strips of 10 mm x 5 mm, and a tensile test is performed in a tensile testing machine. The test standard is GB / T 1040.2

[0085] The tensile test results of the new ester type negative polyimide photoresist in Example 1 are shown in Figure 3 It can be seen that the fluorine-free transparent negative polyimide prepared in the application has extremely excellent tensile strength, and is therefore less likely to break when subjected to external force.

[0086] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0087] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for preparing an ester-type negative polyimide photoresist, characterized in that, Includes the following steps: A polyamic acid solution is obtained by mixing and stirring dianhydride, diamine containing carboxylic acid sites, and an organic solution. The polyamic acid solution was heated and stirred, then purified by precipitation with methanol, and the purified product was dried under vacuum to obtain solid polyimide. Polyimide solid is dissolved in an organic solvent, and then photocrosslinking groups with hydroxyl sites are added to obtain a photocrosslinked polyimide solution; then a photoinitiator is added to obtain an ester-type negative polyimide photoresist. The photocrosslinking group with hydroxyl sites includes any one of the following:

2. The method for preparing an ester-type negative polyimide photoresist according to claim 1, characterized in that, The dianhydride includes any of the following:

3. The method for preparing an ester-type negative polyimide photoresist according to claim 1, characterized in that, The diamine containing the carboxylic acid site includes any one of the following:

4. The method for preparing an ester-type negative polyimide photoresist according to claim 1, characterized in that, The structural formula of the polyamic acid is: In this context, A1 represents dianhydride, and B1 represents diamine containing a carboxylic acid site.

5. The method for preparing an ester-type negative polyimide photoresist according to claim 1, characterized in that, The photoinitiator includes any one of the following:

6. The method for preparing an ester-type negative polyimide photoresist according to claim 1, characterized in that, The structural formula of the photocrosslinked polyimide is: In this context, A1 represents dianhydride, B1 represents diamine containing a carboxylic acid site, and C1 represents a photocrosslinking group with a hydroxyl site.

7. The method for preparing an ester-type negative polyimide photoresist according to claim 1, characterized in that, The molar ratio between the dianhydride, the diamine containing a carboxylic acid site, and the photocrosslinking group with a hydroxyl site is 1:1:

2.

8. An ester-type negative polyimide photoresist, characterized in that, Prepared using the preparation method described in any one of claims 1-7.

9. The application of the ester-type negative polyimide photoresist according to claim 8 in pattern lithography.

10. The application according to claim 9, characterized in that, The process of pattern photolithography is as follows: Using a spin coater, the ester-type negative polyimide photoresist is spin-coated onto a silicon wafer and dried. The silicon wafer is then placed under a photomask and exposed to ultraviolet light. Finally, a mixed solution of NMP and ethanol is used for development to obtain the photolithographic pattern. The volume ratio of NMP to ethanol is 1:2.

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