Electroplating patterning method for preventing photoresist bleeding and applications thereof

Abstract

The application provides a plating patterning method for preventing photoresist liquid penetration and application thereof, and the plating patterning method comprises the following steps: providing a substrate, coating photoresist and performing patterning; covering a protective coating, preparing the protective coating and covering the surface of the patterned photoresist, wherein the protective coating covers at least the top surface and the sidewall of the photoresist; wherein the protective coating comprises one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polyimide and parylene; selectively removing the protective coating; plating; and removing the protective coating and the photoresist. The application covers the protective coating with good bonding force on the surface of the photoresist, selectively exposes the seed layer, prevents the plating liquid from penetrating into the photoresist through the protective coating, does not affect the pattern precision of the photoresist, reduces the production cost, significantly improves the yield of the plating product, and improves the surface quality and long-term reliability of the plating structure.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology, and specifically relates to an electroplating patterning method for preventing photoresist seepage and its application. Background Technology

[0002] In the fields of micro-nano fabrication and semiconductor manufacturing, photoresist-assisted selective electroplating is a widely used key process technology. However, this process faces a long-standing technical problem that has not been completely solved in actual production—the photoresist seepage problem. Specifically, during the electroplating process, the electroplating solution (electroplating solution) has a certain corrosiveness to the photoresist. The solvent, ions and additives in the electroplating solution may penetrate into the photoresist-covered area along the interface between the photoresist and the seed layer, or seep in through the micropores, cracks and other defects in the photoresist itself. This seepage phenomenon will lead to the following serious consequences: (1) plating nodules; (2) rough coating; (3) loss of yield.

[0003] Existing technologies employ various countermeasures, mainly including: (1) using chemically resistant photoresists; (2) air-curing processes; (3) using topcoats or overcoats; and (4) secondary photoresist coating processes. However, existing technologies have significant shortcomings in preventing electroplating defects caused by photoresist seepage, either increasing costs or failing to solve existing problems. A new solution is urgently needed that can effectively block the seepage path of the electroplating solution while maintaining process compatibility and cost-effectiveness. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an electroplating patterning method and its application for preventing photoresist seepage.

[0005] To achieve the above objectives, in a first aspect, the technical solution provided by the present invention is: an electroplating patterning method for preventing photoresist seepage, comprising the following steps:

[0006] S1 provides a substrate with a seed layer deposited on its surface;

[0007] S2, Coating and patterning photoresist: Photoresist is coated on the surface of the seed layer, and a preset pattern opening is formed on the photoresist through photolithography.

[0008] S3, Apply a protective coating: Prepare a protective coating and apply it to the surface of the patterned photoresist, wherein the protective coating covers at least the top surface and sidewalls of the photoresist; wherein the protective coating comprises one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polyimide, and parylene;

[0009] S4, selectively remove the protective coating, remove the protective coating located at the bottom of the pattern opening to expose the seed layer below, and retain the protective coating covering the top surface and sidewalls of the photoresist.

[0010] S5, electroplating, electroplating is performed on the exposed seed layer to form the desired metal coating;

[0011] S6, remove the protective coating and photoresist.

[0012] In one feasible embodiment, the substrate includes a silicon wafer, a glass substrate, or a ceramic substrate.

[0013] In one feasible embodiment, the seed layer is made of one or more of copper, gold, silver, nickel, titanium, and titanium-tungsten alloy.

[0014] In one feasible embodiment, the seed layer is deposited by sputtering, evaporation, chemical vapor deposition, or atomic layer deposition.

[0015] In one feasible embodiment, in step S3, the thickness of the protective coating is 10 nm to 5000 nm.

[0016] In one feasible embodiment, in step S3, the protective coating is applied to the photoresist by spin coating, spraying, PVD or CVD.

[0017] In one feasible embodiment, in step S4, an anisotropic etching process is used to selectively remove the protective coating.

[0018] In one feasible embodiment, the anisotropic etching process employs dry etching.

[0019] Secondly, the technical solution provided by the present invention is: the application of the electroplating patterning method for preventing photoresist seepage described in the first aspect above in semiconductor manufacturing, microelectromechanical systems or micro-nano fabrication.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This invention covers the photoresist surface with a protective coating that has good adhesion, while selectively exposing the seed layer. The protective coating prevents the electroplating solution from penetrating the photoresist without affecting the pattern accuracy of the photoresist, reducing production costs, significantly improving the yield of electroplated products, and improving the surface quality and long-term reliability of the electroplated structure. Specific Implementation

[0022] To illustrate the technical content, structural features, achieved objectives, and effects of the invention in detail, the technical solutions in the embodiments of the invention are described below. Obviously, the described embodiments are merely a part of the embodiments of the invention, and not all of them. In the following description, for illustrative purposes, numerous specific details are set forth to provide a detailed description of various exemplary embodiments or implementations of the invention. However, various exemplary embodiments may also be implemented independently without these specific details or in one or more equivalent arrangements. Furthermore, the various exemplary embodiments may differ, but are not necessarily exclusive. For example, the specific shape, construction, and characteristics of the exemplary embodiments may be used or implemented in another exemplary embodiment without departing from the inventive concept.

[0023] This invention provides an electroplating patterning method to prevent photoresist seepage, the electroplating patterning method comprising the following steps:

[0024] S1 provides a substrate with a seed layer deposited on its surface;

[0025] S2, Coating and patterning photoresist: Photoresist is coated on the surface of the seed layer, and a preset pattern opening is formed on the photoresist through photolithography.

[0026] S3, Apply a protective coating: Prepare a protective coating and apply it to the surface of the patterned photoresist, wherein the protective coating covers at least the top surface and sidewalls of the photoresist; wherein the protective coating comprises one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polyimide, and parylene;

[0027] S4, selectively remove the protective coating, remove the protective coating located at the bottom of the pattern opening to expose the seed layer below, and retain the protective coating covering the top surface and sidewalls of the photoresist.

[0028] S5, electroplating, electroplating is performed on the exposed seed layer to form the desired metal coating;

[0029] S6, remove the protective coating and photoresist.

[0030] In step S1, the substrate includes a silicon wafer, a glass substrate, or a ceramic substrate. The seed layer is made of one or more of the following materials: copper, gold, silver, nickel, titanium, and titanium-tungsten alloy. The seed layer is deposited on the surface of the substrate by sputtering, evaporation, chemical vapor deposition, or atomic layer deposition.

[0031] In step S2, the photolithography process includes exposure and development. After the photolithography process, the photoresist forms a preset pattern opening on the surface of the seed layer, exposing the seed layer of the area to be electroplated, so that the metal coating can be formed on the surface of the seed layer of the electroplating area during subsequent electroplating.

[0032] In step S3, the protective coating is an inorganic coating formed from inorganic materials, an organic coating formed from organic materials, or a composite coating composed of various composite structures of inorganic compounds and organic materials. The inorganic materials include inorganic compounds such as silicon oxide, silicon nitride, aluminum oxide, and titanium oxide, while the organic materials include chemically resistant polymers such as polyimide and parylene. The protective coating is applied to the outer surface of the photoresist using a spin coating, spray coating, PVD, or CVD thin-film deposition process. The materials and deposition process of the protective coating are determined based on the corrosivity of the photoresist material and the electroplating solution, ensuring that the bonding strength between the protective coating and the photoresist meets the requirements of the electroplating process, while also facilitating the removal of the protective coating in step S4. The thickness of the protective coating ranges from 10 nm to 5000 nm, with the specific thickness determined based on the photoresist thickness, the corrosivity of the electroplating solution, and the electroplating process parameters.

[0033] A protective coating is applied to the outer surface of the photoresist, creating a reliable physical barrier between the photoresist and the electroplating solution. Even if the photoresist itself has micropores or insufficient interfacial bonding, the electroplating solution cannot penetrate the coating and seep into the non-electroplated area. This eliminates the generation of plating nodules and roughness defects at the source and solves the problem of electroplating solution seeping into the photoresist during the electroplating process, affecting the plating effect and product yield. In addition, compared with using expensive chemically resistant photoresist to prevent seepage, the material cost and process cost of the protective coating are significantly reduced.

[0034] In step S4, an anisotropic etching process is used to selectively remove the protective coating without affecting the original pattern accuracy and resolution of the photoresist. The photoresist still serves as the primary electroplating mask, ensuring clear boundaries between the electroplated and non-electroplated areas, which is beneficial for forming high-precision, steep electroplated metal structures. Dry etching is preferably used, as it allows for precise control of the removal depth and direction, avoiding lateral drilling that may occur with wet etching and ensuring the integrity of the protective coating on the photoresist sidewalls.

[0035] In step S6, depending on the materials of the protective coating and the photoresist, a stripping solution for the protective coating and a removal solution for the photoresist are used to remove the protective coating and the photoresist, thereby obtaining a metal coating.

[0036] This electroplating patterning method is compatible with existing photolithography and electroplating equipment and processes, without requiring large-scale modifications to the production line. It is applicable to various substrate materials, photoresist types, and electroplating systems. The protective coating prevents the electroplating solution from penetrating into the interface between the photoresist and the seed layer, thereby avoiding defects such as nodules and roughness caused by seepage. It significantly improves the yield of electroplated products and enhances the surface quality and long-term reliability of electroplated structures.

[0037] This invention also provides the application of an electroplating patterning method for preventing photoresist seepage in semiconductor manufacturing, microelectromechanical systems (MEMS), or micro / nano fabrication. The electroplating patterning method for preventing photoresist seepage is stable and has good repeatability, and can be directly applied to semiconductor manufacturing, MEMS, or micro / nano fabrication, significantly improving the yield and reliability of electroplated patterned products, and possessing extremely high industrial application value.

[0038] The present invention further illustrates the electroplating patterning method for preventing photoresist seepage through the following embodiments.

[0039] Example 1 (The protective coating is an organic coating)

[0040] Step 1: Provide the substrate

[0041] A TiW barrier layer (100 nm thick) and an Au seed layer (300 nm thick) were sequentially deposited on the surface of a 4-inch silicon wafer using magnetron sputtering.

[0042] Step 2: Apply photoresist and pattern it

[0043] A positive photoresist (such as AZ 4620) with a thickness of 10 μm is spin-coated onto the seed layer. After pre-baking, exposure (wavelength 365nm i-line), and development, an electroplating window pattern is formed, exposing the seed layer.

[0044] Step 3: Applying the protective coating

[0045] A polyimide (PI) precursor solution was spin-coated onto the patterned wafer surface at 2000 rpm to a thickness of approximately 500 nm, followed by soft baking at 150°C to form a dense coating. The coating completely covered the top and sidewalls of the photoresist.

[0046] Step 4: Selectively remove the coating

[0047] Reactive ion etching (RIE) was employed, using an O2 / CF4 mixed gas for anisotropic etching. The etching time was controlled to completely remove the PI coating at the bottom of the opening, exposing the Au seed layer. During the etching process, due to the anisotropy of the etching, the coating at the bottom of the pattern opening was mainly removed, while the PI coating on top of the photoresist was thinned but retained as a whole.

[0048] Step 5: Electroplating

[0049] The wafer was placed in a gold plating bath for electroplating at a current density of 1 A / dm² for 30 minutes, forming gold bumps approximately 20 μm thick on the exposed seed layer. During the electroplating process, the PI coating effectively prevented contact between the plating solution and the photoresist, and no leakage was observed.

[0050] Step 6: Remove the protective coating and photoresist.

[0051] The PI coating is removed sequentially using a PI stripping solution, followed by the removal of the photoresist using acetone and isopropanol, resulting in a smooth, nodule-free gold bump structure. (The PI stripping solution needs to have a different composition than the photoresist remover solution; it should be less alkaline and primarily composed of alcohol and ether solvents.)

[0052] Example 2 (The protective coating is an inorganic coating)

[0053] Steps 1-2: Same as in Example 1.

[0054] Step 3: Deposition of protective coating

[0055] A SiO2 coating with a thickness of 100 nm was deposited on the patterned wafer surface using plasma-enhanced chemical vapor deposition (PECVD). The coating uniformly covered all exposed surfaces of the photoresist.

[0056] Step 4: Selectively remove the coating

[0057] Anisotropic etching was performed using an ICP etching system with CF4 / Ar as the etching gas to remove the SiO2 coating at the bottom of the opening. Etching parameters: pressure 10 mTorr, power 300 W, etching time 30 seconds.

[0058] Steps 5-6: Basically the same as in Example 1, except that the SiO2 coating is removed with diluted hydrofluoric acid (1:100 HF).

[0059] Upon inspection, the surface roughness Ra of the electroplated gold bumps was ≤0.1μm, with no visible bud defects, and the electroplating yield was improved by about 15% compared with the conventional process.

[0060] Example 3 (The protective coating is a multi-layer composite coating)

[0061] For electroplating solutions with strong corrosive properties (such as copper plating solutions with low pH or containing strong complexing agents), composite coating solutions can be used.

[0062] Steps 1-2: Same as in Example 1.

[0063] Step 3: Apply a protective coating

[0064] First, a layer of PI (200nm thick) is spin-coated as a base layer, and then SiO2 (50nm thick) is deposited by PECVD as a top layer. The composite coating combines the flexibility of organic materials with the density of inorganic materials, providing a better seepage prevention effect.

[0065] The other steps are the same as in Example 1.

[0066] Upon inspection, the surface of the electroplated gold bumps was smooth and free of visible defects such as bud formation.

[0067] In summary, this invention covers the photoresist surface with a protective coating that has good adhesion, while selectively exposing the seed layer. The protective coating prevents the electroplating solution from penetrating the photoresist without affecting the pattern accuracy of the photoresist, reducing production costs, significantly improving the yield of electroplated products, and improving the surface quality and long-term reliability of the electroplated structure.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope. The scope of protection of the present invention is defined by the appended claims, specification, and their equivalents.

Claims

1. A method for electroplating patterning to prevent photoresist seepage, characterized in that, Includes the following steps: S1 provides a substrate with a seed layer deposited on its surface; S2, Coating and patterning photoresist: Photoresist is coated on the surface of the seed layer, and a preset pattern opening is formed on the photoresist through photolithography. S3, Apply a protective coating: Prepare a protective coating and apply it to the surface of the patterned photoresist, wherein the protective coating covers at least the top surface and sidewalls of the photoresist; wherein the protective coating comprises one or more of silicon oxide, silicon nitride, aluminum oxide, titanium oxide, polyimide, and parylene; S4, selectively remove the protective coating, remove the protective coating located at the bottom of the pattern opening to expose the seed layer below, and retain the protective coating covering the top surface and sidewalls of the photoresist. S5, electroplating, electroplating is performed on the exposed seed layer to form the desired metal coating; S6, remove the protective coating and photoresist.

2. The electroplating patterning method according to claim 1, characterized in that, The substrate may include a silicon wafer, a glass substrate, or a ceramic substrate.

3. The electroplating patterning method according to claim 1, characterized in that, The seed layer is made of one or more of the following materials: copper, gold, silver, nickel, titanium, and titanium-tungsten alloy.

4. The electroplating patterning method according to claim 3, characterized in that, The seed layer deposition methods include sputtering, evaporation, chemical vapor deposition, or atomic layer deposition.

5. The electroplating patterning method according to claim 1, characterized in that, In step S3, the thickness of the protective coating is 10 nm to 5000 nm.

6. The electroplating patterning method according to claim 1, characterized in that, In step S3, the protective coating is applied to the photoresist by spin coating, spraying, PVD, or CVD.

7. The electroplating patterning method according to claim 1, characterized in that, In step S4, an anisotropic etching process is used to selectively remove the protective coating.

8. The electroplating patterning method according to claim 7, characterized in that, The anisotropic etching process described herein employs dry etching.

9. The application of the electroplating patterning method for preventing photoresist seepage as described in any one of claims 1 to 8 in semiconductor manufacturing, microelectromechanical systems, or micro / nano fabrication.