A photoresist patterning method for improving edge effect of electroplating

Abstract

The application relates to a photoresist patterning method for improving plating edge effect, which comprises the following steps: 1, designing and preparing a photoetching mask plate with a microstructure at the edge of a pattern, the microstructure being selected from one or more of the following: sawtooth, wave, periodic groove, micropore array, island-shaped protrusion and sinusoidal; the feature size of the microstructure is 0.1-10 mu m, and the repeat interval is 0.1-5 mu m; 2, coating photoresist on the surface of a plating substrate to form a photoresist layer; 3, exposing and developing the plating substrate by using the photoetching mask plate to form a photoresist residual layer at the bottom of the edge of the photoresist pattern, the photoresist residual layer being consistent with the profile of the microstructure; the thickness of the photoresist residual layer is 20-500 nm, and the extension range is 30-500 nm; 4, performing plasma activation and acid washing treatment on the plating substrate, and then performing metal plating deposition. The microstructure at the edge of the pattern is matched with the photoresist residual layer, the plating edge effect is effectively improved, and the problems of uneven plating layer thickness and pattern distortion are relieved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and in particular to a photoresist patterning method for improving the edge effect of electroplating. Background Technology

[0002] In electroplating processes involving planar structures and high aspect ratio structures, the edge effect of electroplating is a critical issue affecting product quality. This manifests as a much faster plating rate at the edges of the pattern compared to the center, leading to uneven plating thickness, pattern distortion, and even bridging between adjacent patterns, resulting in short circuits.

[0003] Existing technologies for improving edge effects mainly employ chemical or process control approaches, such as optimizing electroplating bath additives (e.g., leveling agents), adjusting electroplating parameters (pulse current, reverse pulse), and improving pre-plating treatment processes. However, these methods require extensive experimental screening of additives or parameter adjustments, resulting in high costs and long cycles. Furthermore, the obtained additives or process parameters often exhibit specificity and narrow process windows, leading to ineffective edge effect control when the photoresist or plating bath type is changed, thus exhibiting poor versatility.

[0004] Therefore, how to provide a photoresist patterning method that is independent of electroplating formulations and parameters and has strong versatility to improve the edge effect of electroplating is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a photoresist patterning method to improve the edge effect of electroplating, thereby solving the above-mentioned technical problems.

[0006] To address the aforementioned technical problems, this invention provides a photoresist patterning method for improving electroplating edge effects, comprising the following steps:

[0007] Step 1: Design and fabricate a photomask with microstructures at the edge of the pattern. The microstructures are selected from one or more of the following: serrated, wavy, periodic grooves, micro-hole arrays, island protrusions, and sinusoidal. The feature size of the microstructures is 0.1~10μm, and the repeating interval is 0.1~5μm.

[0008] Step 2: Coat the surface of the substrate to be electroplated with photoresist to form a photoresist layer;

[0009] Step 3: Using the photomask prepared in Step 1, expose and develop the substrate to be electroplated with the photoresist layer to form a photoresist residue layer at the bottom edge of the photoresist pattern that is consistent with the microstructure outline; the thickness of the photoresist residue layer is 20~500nm, and the epitaxial range is 30~500nm.

[0010] Step 4: Perform plasma activation and acid pickling on the substrate to be electroplated, followed by metal electroplating deposition.

[0011] Preferably, the substrate to be electroplated is a silicon wafer or an aluminum wafer.

[0012] Preferably, the thickness of the photoresist residue layer is controlled by the development time.

[0013] Preferably, the thickness of the photoresist residue layer is 50~200nm.

[0014] Preferably, the epitaxial range of the photoresist residue layer is 50~200nm.

[0015] Preferably, the plasma activation power is 50~200W and the processing time is 30~120s.

[0016] Preferably, the pickling process includes washing in dilute sulfuric acid for 1 minute and then washing in pure water for 30 seconds.

[0017] Preferably, the concentration of dilute sulfuric acid is 3% to 10%, and the temperature is 15 to 35°C.

[0018] Preferably, the metal deposited by electroplating is selected from gold, copper, nickel, tin, silver, platinum, rhodium and their alloys.

[0019] Compared with existing technologies, the photoresist patterning method for improving electroplating edge effects provided by this invention has the following advantages:

[0020] 1. This invention effectively improves the edge effect of electroplating by combining the microstructure of the pattern edge with the photoresist residue layer, alleviates the problems of uneven coating thickness and pattern distortion, and improves the quality of electroplating.

[0021] 2. The process method provided by this invention does not require modification of the electroplating solution composition and electroplating operation parameters, is compatible with various substrate materials such as silicon wafers and aluminum wafers, and can also meet the electroplating processing needs of different types of metals, with good versatility;

[0022] 3. The overall process of this invention is simple and mature, and the supporting plasma activation and pickling processes are stable and reliable, which can effectively reduce the production defect rate. Detailed Implementation

[0023] To illustrate the technical solutions of the invention in more detail, specific embodiments are listed below to demonstrate the technical effects; it should be emphasized that these embodiments are used to illustrate the invention and not to limit the scope of the invention.

[0024] The photoresist patterning method for improving electroplating edge effects provided by this invention includes the following steps:

[0025] Step 1: Design and fabricate a photomask with microstructures at the edge of the pattern. The microstructures are selected from one or more of the following: serrated, wavy, periodic grooves, micro-hole arrays, island protrusions, and sinusoidal. The feature size of the microstructures is 0.1~10μm, and the repeating interval is 0.1~5μm.

[0026] Step 2: Coat the surface of the substrate to be electroplated (such as a silicon wafer or aluminum sheet) with photoresist to form a photoresist layer.

[0027] Step 3: Using the photomask prepared in Step 1, expose and develop the substrate to be electroplated with the photoresist layer in Step 2 to form a photoresist residue layer at the bottom edge of the photoresist pattern that is consistent with the microstructure contour; the thickness of the photoresist residue layer is 20~500nm, and the specific thickness can be controlled by the development time, preferably 50~200nm; the epitaxial range is 30~500nm, preferably 50~200nm.

[0028] Step 4: The substrate to be electroplated is subjected to plasma activation and acid pickling treatment, followed by metal electroplating deposition. The metal to be electroplated can be selected from gold, copper, nickel, tin, silver, platinum, rhodium, and their alloys. Specifically, the plasma activation power is 50~200W, and the treatment time is 30~120s. The acid pickling treatment includes first rinsing in dilute sulfuric acid for 1 min, and then rinsing in pure water for 30 s; the concentration of dilute sulfuric acid is 3%~10%, and the temperature is 15~35℃.

[0029] The mechanism of action of this invention is as follows:

[0030] An extremely thin residual layer of photoresist can weaken the concentrated distribution effect of electric field lines at the edge of the pattern, thereby reducing the metal deposition rate at the edge of the pattern.

[0031] Flow field control: Edge structures with specific edge patterns can reduce the mass transfer rate of metal ions at the edge of the pattern, thereby slowing down the replenishment of metal ions at the edge of the pattern and the deposition rate of metal at the edge of the pattern.

[0032] The process steps and technical effects of the present invention will be described in detail below through a set of comparative examples and three sets of embodiments.

[0033] Comparative Example 1

[0034] Step 1: Select a conventional photomask with a circular pattern of 50μm in diameter and smooth edges without microstructure.

[0035] Step 2: The substrate to be electroplated is a silicon wafer, and a photoresist layer is formed by coating the surface of the wafer.

[0036] Step 3: Complete the conventional exposure and development process. The development conditions are standard development. There is a smooth photoresist residue layer with an epitaxial range of about 30nm and a thickness of 50nm remaining at the edge of the pattern.

[0037] Step 4: Perform plasma activation using 100W power for 60s; select 5% dilute sulfuric acid, pickle at 25℃ for 1min, rinse with pure water for 30s, and then carry out nickel metal electroplating.

[0038] Post-electroplating inspection revealed a deposition thickness of 10.52 μm and an edge creep height of 1.94 μm, representing a creep ratio of 18.44% relative to the coating thickness.

[0039] Example 1

[0040] Step 1: Prepare a photomask with a circular pattern of 50 μm in diameter. The pattern edge has a serrated microstructure with a feature size of 1 μm and a repeating interval of 1 μm.

[0041] Step 2: Select a silicon wafer as the substrate to be electroplated, and coat the surface with photoresist to form a photoresist layer.

[0042] Step 3: Use the photomask to complete exposure and development. The development conditions are standard development. There is a residual photoresist layer at the edge of the pattern that matches the contour of the serrated microstructure. The epitaxial range is about 150nm and the thickness is 120nm.

[0043] Step 4: Perform plasma activation using 100W power for 60s; pickle with 5% dilute sulfuric acid at 25℃ for 1min, rinse with pure water for 30s, and finally perform nickel metal electroplating.

[0044] Post-electroplating inspection revealed a deposition thickness of 10.05 μm and an edge creep height of 0.53 μm, representing a creep ratio of 5.3% relative to the coating thickness.

[0045] Compared with Comparative Example 1, this embodiment uses the exact same substrate, pattern size, development conditions, plasma activation parameters, pickling parameters, and nickel metal electroplating. By adding a serrated microstructure to the edge of the photomask pattern and forming a photoresist residue layer that matches the contour, the edge effect of electroplating can be effectively improved, plating creep can be suppressed, and the shape of the electroplated structure can be maintained.

[0046] Example 2

[0047] Step 1: Prepare a photomask with a rectangular pattern on it, which has a side length of 65μm and a sinusoidal microstructure at the edge of the pattern. The microstructure has an amplitude of 1μm and a period of 2μm.

[0048] Step 2: Select an aluminum sheet as the substrate to be electroplated, and coat the substrate surface with photoresist to form a photoresist layer.

[0049] Step 3: Perform exposure and development operations. The development condition is overdevelopment, which can form a photoresist residue layer at the edge of the pattern that matches the contour of the sinusoidal microstructure, with an epitaxial range of about 90nm and a thickness of 80nm.

[0050] Step 4: Activate with 100W plasma for 60s, pickle with 5% dilute sulfuric acid at 25℃ for 1min, rinse with pure water for 30s, and then perform gold electroplating.

[0051] Post-electroplating inspection revealed a deposition thickness of 6.14 μm and an edge creep height of 0.15 μm, representing a creep ratio of 2.4% relative to the coating thickness.

[0052] This embodiment employs different edge microstructure types, and even if the substrate material is changed, the development process is adjusted, or the type of electroplating metal is changed, the electroplating edge effect can still be effectively improved.

[0053] Example 3

[0054] Step 1: Prepare a photomask with a circular pattern of 50 μm in diameter. At the center of the pattern is a square deep hole structure with a pit depth of 60 μm and an opening of 18 μm. The edge of the pattern has a serrated microstructure with a feature size of 1 μm and a repeating interval of 1 μm.

[0055] Step 2: Using a silicon wafer as the substrate to be electroplated, a photoresist layer is formed by coating the substrate surface.

[0056] Step 3: Perform exposure and development operations under standard development conditions to form a photoresist residue layer that matches the contour of the serrated microstructure, with a thickness of 120nm and an epitaxial range of 150nm.

[0057] Step 4: Activate with 100W plasma for 60s; pickle with 5% dilute sulfuric acid at 25℃ for 1min; rinse with pure water for 30s; and then proceed with nickel metal electroplating.

[0058] Post-electroplating inspection revealed a deposition thickness of 16.89 μm and an edge creep height of 0.93 μm, representing a creep ratio of 5.4% relative to the coating thickness.

[0059] This embodiment has the same process parameters as Embodiment 1, except that a high aspect ratio deep hole structure is added to the center of the circular pattern, which also improves the electroplating edge effect, demonstrating the adaptability of the present invention in complex microstructure electroplating scenarios.

[0060] As shown by the measured data from Comparative Example 1 and Examples 1 to 3, when using a conventional smooth-edge mask to prepare photolithographic patterns, the edge plating creep rate is as high as 18.44%, exhibiting a prominent edge effect and poor coating uniformity. This invention eliminates the need to adjust the electroplating solution formulation and electroplating electrical parameters. By setting microstructures at the edge of the photolithographic mask pattern and controlling the development time to form a photoresist residue layer of a set thickness and epitaxial range, the edge plating creep phenomenon can be significantly suppressed, reducing the creep rate to the range of 2.4% to 5.4%. Furthermore, this invention is adaptable to different substrates such as silicon and aluminum wafers, compatible with various metal plating processes such as gold and nickel, and suitable for complex pattern plating scenarios with high aspect ratio deep holes, demonstrating strong process versatility.

[0061] In summary, the photoresist patterning method for improving electroplating edge effects provided by this invention effectively improves electroplating edge effects and reduces the incidence of uneven plating and pattern distortion by setting various microstructures at the edges of the photomask pattern, forming a photoresist residue layer corresponding to the outline through exposure and development, and then combining standardized activation, acid washing, and electroplating processes. This method requires no modification to the electroplating solution formulation and electroplating operating parameters, has a wide substrate compatibility range, allows for flexible control of photoresist residue layer parameters, has a simple and easy-to-operate process flow, and can be adapted to various metal electroplating processing scenarios, demonstrating strong practicality for mass production.

[0062] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for patterning photoresist to improve the edge effect of electroplating, characterized in that, Includes the following steps: Step 1: Design and fabricate a photomask with microstructures at the edge of the pattern. The microstructures are selected from one or more of the following: serrated, wavy, periodic grooves, micro-hole arrays, island protrusions, and sinusoidal. The feature size of the microstructures is 0.1~10μm, and the repeating interval is 0.1~5μm. Step 2: Coat the surface of the substrate to be electroplated with photoresist to form a photoresist layer; Step 3: Using the photomask prepared in Step 1, expose and develop the substrate to be electroplated with the photoresist layer to form a photoresist residue layer at the bottom edge of the photoresist pattern that is consistent with the microstructure outline; the thickness of the photoresist residue layer is 20~500nm, and the epitaxial range is 30~500nm. Step 4: Perform plasma activation and acid pickling on the substrate to be electroplated, followed by metal electroplating deposition.

2. The photoresist patterning method for improving electroplating edge effects as described in claim 1, characterized in that, The substrate to be electroplated is a silicon wafer or an aluminum wafer.

3. The photoresist patterning method for improving electroplating edge effects as described in claim 1, characterized in that, The thickness of the residual photoresist layer is controlled by the development time.

4. The photoresist patterning method for improving electroplating edge effects as described in claim 3, characterized in that, The thickness of the residual photoresist layer is 50~200nm.

5. The photoresist patterning method for improving electroplating edge effects as described in claim 1, characterized in that, The epitaxial range of the photoresist residue layer is 50~200nm.

6. The photoresist patterning method for improving electroplating edge effects as described in claim 1, characterized in that, The plasma activation power is 50~200W, and the processing time is 30~120s.

7. The photoresist patterning method for improving electroplating edge effects as described in claim 1, characterized in that, The pickling process includes washing in dilute sulfuric acid for 1 minute and then washing in pure water for 30 seconds.

8. The photoresist patterning method for improving electroplating edge effects as described in claim 7, characterized in that, The concentration of dilute sulfuric acid is 3%~10%, and the temperature is 15~35℃.

9. The photoresist patterning method for improving electroplating edge effects as described in claim 1, characterized in that, The metal deposited by electroplating is selected from gold, copper, nickel, tin, silver, platinum, rhodium and their alloys.