A mems plating solution additive for reducing dog-boning and applications thereof

Abstract

The application belongs to the technical field of MEMS electroplating solution, and particularly relates to a MEMS electroplating solution additive for reducing dog bone effect and application thereof. n H 2n+1 N + (CH3)3X ‑ , wherein n is a non-zero natural number, and X is halogen; and the B component is an unsaturated organic sulfonate salt. The additive provided by the application can significantly reduce the dog bone effect of the concave middle and the raised edge of the plating layer during electrodeposition, so that the difference in the thickness of the prepared plating layer is changed from greater than 30% to less than 2%, and other performances of the plating layer and the service life of the plating solution are not affected.

Description

Technical Field

[0001] This invention belongs to the field of MEMS electroplating solution technology, specifically relating to a MEMS electroplating solution additive that reduces the dog bone effect and its application. Background Technology

[0002] In the field of microelectronics and MEMS manufacturing, when preparing metal microstructures (typically 10 to 150 micrometers in size) by electroplating, the growth rate of the coating at the edge of the pattern, i.e., near the photoresist sidewall, is sometimes significantly greater than that in the central area of ​​the pattern. This results in the final coating cross-section having a concave center and convex edges, often referred to as the "dog bone effect".

[0003] This effect leads to uneven coating thickness. Even with subsequent chemical mechanical polishing, edge breakage, microcracks, or gaps may occur during the smoothing process. Furthermore, due to the higher edges and larger electroplating area, it becomes impossible to guarantee the consistency of coating performance during electroplating, thus jeopardizing coating reliability. Therefore, suppressing the dog-bone effect during electroplating is a core technological challenge that must be overcome in the micro-sodium processing and manufacturing.

[0004] Pulse plating is the most common method for improving the "dog bone effect," utilizing pulse intervals to promote ion diffusion or using reverse current to preferentially dissolve the raised edges, thereby achieving a leveling effect. However, pulse plating has high power supply requirements, is difficult to control the current waveform, and reduces plating efficiency, affecting production capacity. Furthermore, strict parameter control is necessary to prevent the introduction of new defects. More importantly, pulse plating has limited effectiveness in improving fine structures.

[0005] Other improvement methods, such as enhanced stirring, ultrasonic assistance, and liquid jetting, have not shown significant effects. In contrast, modifying the plating solution properties is a more thorough and efficient way to address the dog-bone effect, significantly expanding the adjustable range and making it more universally applicable. Summary of the Invention

[0006] This invention provides an additive for reducing the dog bone effect in MEMS electroplating solutions and its application, in order to solve the technical problems that current methods for solving the dog bone effect are difficult, ineffective, and lack universality.

[0007] To address the aforementioned technical problems, this invention provides a MEMS electroplating solution additive for reducing the dog bone effect, comprising component A and component B, wherein component A has the general chemical formula C. n H 2n+1 N + (CH3)3X - , where n is a non-zero natural number, X is a halogen; component B is an unsaturated organic sulfonate.

[0008] Optionally, in component A, n is 4-35 and X is Cl.

[0009] Optionally, component B is a C2-C6 unsaturated alkyl, alkenyl, or alkynyl group.

[0010] Optionally, n in component A is 8-18, and preferably component A is dodecyltrimethylammonium chloride or hexadecyltrimethylammonium chloride.

[0011] Optionally, component B is sodium allyl sulfonate, sodium vinyl sulfonate, sodium methyl allyl sulfonate, sodium propyne sulfonate, sodium propyne sulfonate, or sodium hexyne sulfonate, preferably sodium allyl sulfonate or sodium vinyl sulfonate.

[0012] Optionally, the ratio of component A to component B by mass is 1:(1-100).

[0013] The present invention also provides a MEMS electroplating solution comprising a main salt, the above-mentioned MEMS electroplating solution additives for reducing the dog bone effect, and water.

[0014] Optionally, the main salt is a rhodium salt.

[0015] Optionally, the concentration of component A is 1 mg / L to 1000 mg / L, preferably 50 mg / L to 500 mg / L.

[0016] Optionally, the concentration of component B is 0.1 g / L to 50 g / L, preferably 0.5 g / L to 5 g / L.

[0017] Optionally, when the main salt is a rhodium salt and the coating thickness is 10 micrometers or more, it also includes a brightener and a coordinating agent.

[0018] Optionally, the brightener is an aromatic ring compound containing at least one sulfonate or sulfonyl salt substituent, and the coordinating agent is a carboxylic acid compound containing two or more carboxyl groups.

[0019] Optionally, the aromatic ring compound is a benzene ring or a naphthalene ring compound, the sulfonate substituent is a sodium sulfonate group or a potassium sulfonate group, and the sulfonyl salt substituent is a sulfonamide group.

[0020] Optionally, the brightener is selected from one or more of sodium o-(m-, p-)toluenesulfonate, sodium benzenesulfonate, sodium o-(m-, p-)hydroxybenzenesulfonate, sodium o-(m-, p-)formylbenzenesulfonate, sodium naphthalenesulfonate, trisodium 1,3,5-naphthalenetrisulfonate, trisodium 1,3,6-naphthalenetrisulfonate, sodium dodecylbenzenesulfonate, and p-toluenesulfonamide.

[0021] Optionally, the ligand is selected from one or more of citric acid, ethylenediaminetetraacetic acid, tartaric acid, oxalic acid, malic acid, and succinic acid.

[0022] The additive provided by this invention can significantly reduce the dog bone effect of the coating layer being concave in the middle and convex at the edges during electrodeposition, reducing the thickness difference of the coating layer from more than 30% to less than 2%, while other properties of the coating layer and the life of the plating solution are not affected. Attached Figure Description

[0023] Figure 1 This is a square optical mirror image of the MEMS electroplated part in Example 1;

[0024] Figure 2 This is the white light interference diffraction pattern of the MEMS electroplated part in Example 1;

[0025] Figure 3 This is a square optical mirror image of the MEMS electroplated part in Comparative Example 1;

[0026] Figure 4 This is a white light interference diffraction pattern of a MEMS electroplated part (compare to Example 1). Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Example 1

[0029] Prepare 1L of rhodium plating solution:

[0030] 1. Weigh 5g of rhodium sulfate and dissolve it in an appropriate amount of deionized water.

[0031] 2. Slowly add 100mL of concentrated sulfuric acid.

[0032] 3. Add 3g of brightener (its composition by mass percentage is: 40% sodium p-toluenesulfonate, 30% trisodium 1,3,5-naphthalenetrisulfonate and 30% sodium dodecylbenzenesulfonate).

[0033] 4. Add 20g of complexing agent (its composition by mass percentage is: 60% citric acid and 40% disodium EDTA).

[0034] 5. Add 50 mg of dodecyltrimethylammonium chloride and 0.5 g of sodium allyl sulfonate.

[0035] 6. Add deionized water to a final volume of 1L and stir well.

[0036] 7. Adjust the pH value to 1.0 using dilute sulfuric acid or dilute alkali solution.

[0037] A polished, degreased, acid-activated, and pre-nickel-plated brass sheet was placed as the cathode in the aforementioned plating solution at a temperature of 45°C. The cathode current density was 1.5 A / dm², the cathode was moved, and the electroplating time was approximately 2 hours. The resulting rhodium plating layer thickness was approximately 12 μm. Figure 1 and 2 As shown, the "dog bone effect" has been greatly improved, and the coating surface is white, bright, and free of cracks.

[0038] Product testing:

[0039] 1. Thickness difference: The coating thickness is tested using a white light interferometer. A single square is randomly selected and its maximum and minimum thickness values ​​are measured. The difference is always less than 2% of the total thickness.

[0040] 2. Coating hardness: The coating hardness was tested using nano-indentation. Six points were pressed on the same square, and six squares were randomly selected for testing and the average value was taken, which was 1109 HV.

[0041] Example 2

[0042] Prepare 1L of rhodium sulfate plating solution:

[0043] 1. Weigh 5g of rhodium sulfate and dissolve it in an appropriate amount of deionized water.

[0044] 2. Slowly add 100mL of concentrated sulfuric acid.

[0045] 3. Add 3g of brightener (its composition is: 40% sodium benzenesulfonate, 40% trisodium 1,3,5-naphthalenetrisulfonate, and 20% sodium dodecylbenzenesulfonate).

[0046] 4. Add 15g of complexing agent (composition: 40% citric acid, 60% disodium EDTA).

[0047] 5. Add 10 mg of cetyltrimethylammonium chloride and 1 g of sodium vinyl sulfonate.

[0048] 6. Add deionized water to a final volume of 1L and stir well.

[0049] 7. Adjust the pH value to 1.0 using dilute sulfuric acid or dilute alkali solution.

[0050] A polished, degreased, acid-activated, and pre-nickel-plated brass sheet was placed as the cathode in the above plating solution at a temperature of 45°C and a cathode current density of 2.0 A / dm³. 2 The cathode was moved, and the electroplating time was approximately 2 hours. The resulting rhodium plating layer was approximately 14 μm thick. The plating surface was white, bright, and free of cracks.

[0051] Product testing:

[0052] 1. Thickness difference: The coating thickness is tested using a white light interferometer. A single square is randomly selected and its maximum and minimum thickness values ​​are measured. The difference is always less than 2% of the total thickness.

[0053] 2. Coating hardness: The coating hardness is tested using nano-indentation. Six points are pressed on the same square, and six squares are randomly selected for testing and the average value is taken as 1080 HV.

[0054] Example 3

[0055] Prepare 1L of rhodium sulfate plating solution:

[0056] 1. Weigh 5g of rhodium sulfate and dissolve it in an appropriate amount of deionized water.

[0057] 2. Slowly add 100mL of concentrated sulfuric acid.

[0058] 3. Add 6g of brightener (its composition is: 40% sodium hydroxybenzenesulfonate, 30% sodium dodecylbenzenesulfonate, and 30% p-toluenesulfonamide).

[0059] 4. Add 25g of complexing agent (composition: 50% succinic acid, 50% disodium EDTA).

[0060] 5. Add 25 mg of octyltrimethylammonium chloride and 0.2 g of sodium propyne sulfonate.

[0061] 6. Add deionized water to a final volume of 1L and stir well.

[0062] 7. Adjust the pH value to 1.0 using dilute sulfuric acid or dilute alkali solution.

[0063] A polished, degreased, acid-activated, and pre-nickel-plated brass sheet was placed as the cathode in the above plating solution at a temperature of 50°C and a cathode current density of 1.0 A / dm³. 2 The cathode is moved, and the electroplating time is approximately 2 hours. The resulting rhodium plating layer is approximately 10 μm thick. The plating surface is white, bright, and free of cracks.

[0064] Product testing:

[0065] 1. Use a white light interferometer to test the coating thickness. Randomly select a single square and measure its maximum and minimum thickness values. The difference between the two values ​​should always be less than 2% of the total thickness.

[0066] 2. Coating hardness: The coating hardness was tested using nano-indentation. Six points were pressed into the same square, and six squares were randomly selected for testing and the average value was taken, which was 986 HV.

[0067] Example 4

[0068] Prepare 1L of rhodium sulfate plating solution:

[0069] 1. Weigh 2g of rhodium sulfate and dissolve it in an appropriate amount of deionized water.

[0070] 2. Slowly add 50 mL of concentrated sulfuric acid.

[0071] 3. Add 1.2g of brightener (its composition is: 40% sodium p-toluenesulfonate, 30% sodium p-hydroxybenzenesulfonate, and 30% sodium naphthalenesulfonate).

[0072] 4. Add 5g of a complexing agent (composed of 45% tartaric acid and 55% oxalic acid).

[0073] 5. Add 5 mg of octadecyltrimethylammonium chloride and 0.1 g of sodium propargyl sulfonate.

[0074] 6. Add deionized water to a final volume of 1L and stir well.

[0075] 7. Adjust the pH value to 1.0 using dilute sulfuric acid or dilute alkali solution.

[0076] A polished, degreased, acid-activated, and pre-nickel-plated brass sheet was placed as the cathode in the above plating solution at a temperature of 50°C and a cathode current density of 2.0 A / dm³. 2 Mechanical stirring and electroplating time are approximately 2 hours. The resulting rhodium plating layer is approximately 14 μm thick. The plating surface is white, bright, and free of cracks.

[0077] Product testing:

[0078] 1. Use a white light interferometer to test the coating thickness. Randomly select a single square and measure its maximum and minimum thickness values. The difference between the two values ​​should always be less than 2% of the total thickness.

[0079] 2. Coating hardness: The coating hardness is tested using nano-indentation. Six points are pressed on the same square, and six squares are randomly selected for testing and the average value is taken as 1006 HV.

[0080] Comparative Example 1

[0081] The difference from Example 1 is that dodecyltrimethylammonium chloride and sodium allyl sulfonate were not added, such as Figure 3 As shown, the sample exhibits a clear "dog bone effect".

[0082] Thickness difference: such as Figure 4 As shown, the coating thickness was tested using a white light interferometer. A single square was randomly selected, and its maximum and minimum thickness values ​​were measured. The difference accounted for 20% of the total thickness.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that dodecyltrimethylammonium chloride was not added.

[0085] Thickness difference: The coating thickness is tested using a white light interferometer. A single square is randomly selected and its maximum and minimum thickness values ​​are measured. The difference accounts for 25% of the total thickness.

[0086] Comparative Example 3

[0087] The difference from Example 1 is that sodium allyl sulfonate is replaced with propynyl alcohol (commonly used as a leveling agent in nickel plating solutions).

[0088] Thickness difference: The coating thickness is tested using a white light interferometer. A single square is randomly selected and its maximum and minimum thickness values ​​are measured. The difference accounts for 28% of the total thickness.

[0089] Comparative Example 4

[0090] The difference from Example 1 is that dodecyltrimethylammonium chloride is replaced with dodecylamine hydrochloride.

[0091] Thickness difference: The coating thickness is tested using a white light interferometer. A single square is randomly selected and its maximum and minimum thickness values ​​are measured. The difference accounts for 30% of the total thickness.

[0092] Comparative Example 5

[0093] The difference from Example 1 is that sodium allyl sulfonate is replaced with sodium propyl sulfonate.

[0094] Thickness difference: The coating thickness is tested using a white light interferometer. A single square is randomly selected and its maximum and minimum thickness values ​​are measured. The difference accounts for 30% of the total thickness.

[0095] Comparative Example 6

[0096] The difference from Example 1 is that the rhodium plating solution is replaced with a nickel plating solution that also has a dog bone effect.

[0097] 1. Weigh 100g of nickel sulfate hexahydrate, 10g of sodium chloride, 30g of boric acid, and 60g of sodium sulfate and dissolve them in an appropriate amount of deionized water.

[0098] 2. Add 50 mg of dodecyltrimethylammonium chloride and 0.5 g of sodium allyl sulfonate.

[0099] 3. Add deionized water to a final volume of 1L and stir well.

[0100] 4. Adjust the pH value to 5.5 using dilute sulfuric acid or dilute alkali solution.

[0101] A polished, degreased, acid-activated, and pre-nickel-plated brass sheet was placed as the cathode in the above plating solution at a temperature of 25°C and a cathode current density of 1 A / dm³. 2 The cathode moves.

[0102] Product testing:

[0103] Thickness difference: The coating thickness was tested using a white light interferometer. A single square was randomly selected, and its maximum and minimum thickness values ​​were measured. The difference accounted for 28% of the total thickness. This additive has limited effect on improving the "dog bone effect" of other plating solutions.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An additive for reducing the dog bone effect in MEMS electroplating solutions, characterized in that, It includes component A and component B, wherein the general chemical formula of component A is C. n H 2n+1 N + (CH3)3X - , where n is a non-zero natural number, X is a halogen; component B is an unsaturated organic sulfonate.

2. The MEMS electroplating solution additive for reducing the dog bone effect according to claim 1, characterized in that, In component A, n is 4-35 and X is Cl.

3. The MEMS electroplating solution additive for reducing the dog bone effect according to claim 2, characterized in that, In component A, n is 8-18, preferably dodecyltrimethylammonium chloride or hexadecyltrimethylammonium chloride.

4. The MEMS electroplating solution additive for reducing the dog bone effect according to claim 1, characterized in that, The B component is a C2-C6 unsaturated alkyl, alkenyl, or alkynyl group.

5. The MEMS electroplating solution additive for reducing the dog bone effect according to claim 4, characterized in that, Component B is sodium allyl sulfonate, sodium vinyl sulfonate, sodium methyl allyl sulfonate, sodium propyne sulfonate, sodium propyne sulfonate, or sodium hexyne sulfonate, preferably sodium allyl sulfonate or sodium vinyl sulfonate.

6. The MEMS electroplating solution additive for reducing the dog bone effect according to claim 1, characterized in that, The ratio of component A to component B by mass is 1:(1-100).

7. A MEMS electroplating solution, characterized in that, It includes a main salt, the MEMS electroplating solution additive for reducing the dog bone effect as described in any one of claims 1-6, and water.

8. The MEMS electroplating solution according to claim 7, characterized in that, The main salt is a rhodium salt.

9. The MEMS electroplating solution according to claim 7, characterized in that, The concentration of component A is 1 mg / L to 1000 mg / L, preferably 50 mg / L to 500 mg / L.

10. The MEMS electroplating solution according to claim 7, characterized in that, The concentration of component B is 0.1 g / L to 50 g / L, preferably 0.5 g / L to 5 g / L.

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