A bath for electroplating copper for blind microvia filling and method of use

Abstract

The application relates to the technical field of C23C18 / 38, in particular to a plating copper bath for filling blind micro-via holes and a use method thereof, which at least comprises a leveling agent solution of 12-16 mL / L, a brightener solution of 10-15 mL / L, sulfuric acid of 60-80 g / L, copper sulfate of 160-180 g / L, hydrochloric acid of 40-55 mg / L, an oxidizing agent of 1.0-8.0 g / L, and ultrapure water supplementing to 1L. The plating copper bath has excellent hole filling performance, good filling and left-right effects for blind micro-via holes, and a bright and smooth appearance of the plating layer.

Description

Technical Field

[0001] This invention relates to the field of C23C18 / 38 technology, specifically to an electroplating copper bath for filling blind micro-vias and its application method. Background Technology

[0002] High-density interconnect (HDI) printed circuit boards achieve interlayer connections through methods such as buried vias, blind vias, and through-hole vias. Currently, the demand for HDI printed circuit boards is increasing daily, and the quality of via metallization technology directly affects the quality of the circuit board.

[0003] Current copper plating for via filling generally employs a DC copper plating process. Specifically, leveling agents, brighteners, and wetting agents are added to the basic working solution for copper plating to fill blind holes with a dielectric layer thickness of 40-100μm. The physical properties of the copper plating layer are ensured by controlling the cathode current density. For example, Chinese patent application (application number CN112458504A) discloses an electroplating copper bath and its application method for copper plating via filling in electronic circuits. A combination of polyquaternary ammonium salt, SPS, and polyether is added to the basic working solution for copper plating to fill blind holes to achieve a good filling effect. The plating layer has strong impact resistance. However, on the one hand, the copper plating layer is easily affected by carbon dioxide, sulfides, and chlorides in humid air, which leads to discoloration of the copper plating layer. On the other hand, the efficiency of copper plating for via filling is affected by the copper plating additives and needs to be further improved. Summary of the Invention

[0004] The present invention provides an electroplating copper bath for filling blind micro-holes, comprising at least 12-16 mL / L of leveling agent solution, 10-15 mL / L of brightener solution, 60-80 g / L of sulfuric acid, 160-180 g / L of copper sulfate, 40-55 mg / L of hydrochloric acid, 0.5-8.0 g / L of oxidant, and pure water to a total of 1 L.

[0005] As a preferred technical solution, the brightener solution, by mass percentage, comprises at least the following components: brightener 0.08-0.12%, sulfuric acid 0.6-1.0%, copper sulfate pentahydrate 0.3-0.5%, and water to make up the balance.

[0006] As a preferred technical solution, the sulfuric acid is sulfuric acid with a mass fraction of 98%.

[0007] As a preferred technical solution, the brightener is a combination of a polysulfide organic sulfonate brightener and a sulfur-based compound. The mass ratio of the polysulfide organic sulfonate brightener to the sulfur-based compound is (2-5):1.

[0008] As a preferred technical solution, the polysulfide organic sulfonate brightener is at least one of sodium disulfide dipropane sulfonate and sodium phenyl disulfide propane sulfonate. Preferably, the polysulfide organic sulfonate brightener is a combination of sodium disulfide dipropane sulfonate and sodium phenyl disulfide propane sulfonate; the mass ratio of sodium disulfide dipropane sulfonate to sodium phenyl disulfide propane sulfonate is (1-2):(0.5-1).

[0009] As a preferred technical solution, the sulfur-based compound is at least one selected from 2-mercaptobenzimidazole and ethylidene thiourea. Preferably, the sulfur-based compound is 2-mercaptobenzimidazole.

[0010] The brightener introduced in this invention is a combination of sodium polydisulfide dipropane sulfonate, sodium phenyl polydisulfide dipropane sulfonate, and 2-mercaptobenzimidazole, combined with a specific leveling agent, to refine the grain size of the copper plating layer, improve its brightness and levelness, and simultaneously increase the cathode pulse current density, accelerate particle deposition rate, and improve the efficiency of through-hole copper plating and the microhardness of the copper plating layer. In particular, when the mass ratio of polysulfide organic sulfonate brightener to sulfur-based compound in the system is (2-5):1, it effectively ensures the levelness and brightness of the plating layer while avoiding burrs, scorching, or white haze phenomena in the copper plating layer.

[0011] As a preferred technical solution, the leveling agent solution, by mass percentage, includes at least 0.5-1.5% sulfuric acid, 1.5-2.0% polyethylene glycol, 0.05-0.10% leveling agent, and water to make up the balance.

[0012] As a preferred technical solution, the average molecular weight of the polyethylene glycol is 2000-12000; preferably, the polyethylene glycol is a combination of PEG10000 and PEG2000; the mass ratio of PEG10000 to PEG2000 is 1:(4-6).

[0013] As a preferred technical solution, the leveling agent is tetrahydrothiazolylthione.

[0014] Based on the system of this invention, tetrahydrothiazolium thiophene is used as a leveling agent, combined with polyethylene glycol with an average molecular weight of 2000-12000. Through a pulse copper plating process, the provided copper plating layer is smooth, bright, fine, and has good adhesion. The porosity of the copper plating layer is low, preventing it from oxidizing and discoloring in humid air. During the research process, the inventors found that, especially when the polyethylene glycol in the system is a combination of PEG10000 and PEG2000 in a mass ratio of 1:(4-6), it works synergistically with tetrahydrothiazolium thiophene, sodium polydithiopropane sulfonate, sodium phenyl polydithiopropane sulfonate, and 2-mercaptobenzimidazole in the system to effectively improve the density and thickness uniformity of the copper plating layer, and enhance the thermal shock resistance of the copper plating layer.

[0015] The oxidant is ferrous sulfate.

[0016] Another aspect of the present invention provides a method for using a copper plating bath for filling blind micro-holes, wherein a leveling agent solution, a brightener solution, sulfuric acid, copper sulfate, hydrochloric acid, an oxidant and ultrapure water are added to a copper plating bath in the prescribed amounts, the blind hole plate to be plated is added to the copper plating bath, and the electroplating is performed by controlling the reverse pulse power supply parameters.

[0017] As a preferred technical solution, the reverse pulse power supply parameters are: forward current density of 1.0-3.0 A / dm². 2 The forward plating time is 15-20 seconds; the reverse current density is 4-6 A / dm³. 2 The reverse electroplating time is 1-2 seconds.

[0018] As a preferred technical solution, the hole depth of the blind hole plate to be plated is 60-100μm and the hole diameter is 100-120μm.

[0019] Beneficial effects

[0020] 1. This invention provides an electroplating copper bath for filling blind micro-vias, which has excellent filling performance, good filling effect for blind micro-vias, and a bright and smooth plating appearance.

[0021] 2. The copper plating bath for blind micro-via filling provided by the present invention introduces a combination of sodium polydisulfide dipropane sulfonate, sodium phenyl polydisulfide dipropane sulfonate and 2-mercaptobenzimidazole as a brightener in the system, and in combination with a specific leveling agent, to refine the grains of the copper plating layer, improve the brightness and levelness of the copper plating layer, and at the same time help to increase the pulse current density of the cathode, accelerate the particle deposition rate, improve the copper plating efficiency of the hole filling and the microhardness of the copper plating layer.

[0022] 3. In this invention, by controlling the mass ratio of polysulfide organic sulfonate brightener to sulfur-based compound in the brightener to be (2-5):1, the leveling and brightness of the coating are effectively guaranteed, while avoiding burrs, burning or white fog in the copper plating layer.

[0023] 4. Based on the system of this invention, tetrahydrothiazolyl thiophene is used as a leveling agent, combined with polyethylene glycol with an average molecular weight of 2000-12000, and a pulse copper plating process is used to make the copper plating layer smooth, bright, fine and with good adhesion. The copper plating layer has low porosity, which prevents it from oxidizing and discoloring in humid air.

[0024] 5. The copper plating bath for filling blind micro-holes provided by the present invention, when the polyethylene glycol in the system is a combination of PEG10000 and PEG2000 in a mass ratio of 1:(4-6), works together with tetrahydrothiazolium thione, sodium polydithiopropane sulfonate, sodium phenyl polydithiopropane sulfonate, and 2-mercaptobenzimidazole in the system to effectively improve the density and thickness uniformity of the copper plating layer and enhance the thermal shock resistance of the copper plating layer. Detailed Implementation

[0025] Example 1

[0026] In one aspect, Embodiment 1 of the present invention provides an electroplating copper bath for filling blind micro-holes, comprising 14 mL / L of leveling agent solution, 12 mL / L of brightener solution, 70 g / L of sulfuric acid, 175 g / L of copper sulfate, 45 mg / L of hydrochloric acid, 0.5 g / L of oxidant, and ultrapure water to be added to 1 L.

[0027] The brightener solution comprises, by mass percentage, the following components: brightener 0.10%, sulfuric acid 0.8%, copper sulfate pentahydrate 0.3-0.5%, and water to make up the balance.

[0028] The sulfuric acid is 98% by mass.

[0029] The brightener is a combination of a polysulfide organic sulfonate brightener and a sulfur-based compound. The mass ratio of the polysulfide organic sulfonate brightener to the sulfur-based compound is 4:1.

[0030] The polysulfide organic sulfonate brightener is a combination of sodium disulfide dipropane sulfonate and sodium phenyl disulfide dipropane sulfonate; the mass ratio of sodium disulfide dipropane sulfonate to sodium phenyl disulfide dipropane sulfonate is 1:1.

[0031] The sulfur-based compound is 2-mercaptobenzimidazole.

[0032] The leveling agent solution, by mass percentage, comprises 1.0% sulfuric acid, 1.8% polyethylene glycol, 0.08% leveling agent, and water to make up the balance.

[0033] The polyethylene glycol is a combination of PEG10000 and PEG2000; the mass ratio of PEG10000 to PEG2000 is 1:5.

[0034] The leveling agent is tetrahydrothiazolyl thiophene.

[0035] The oxidant is ferrous sulfate.

[0036] In another aspect, Embodiment 1 of the present invention provides a method for using a copper plating bath for filling blind micro-holes. The method involves adding a leveling agent solution, a brightener solution, sulfuric acid, copper sulfate, hydrochloric acid, an oxidant, and ultrapure water to a copper plating bath in the prescribed amounts. The blind hole plate to be plated is then added to the copper plating bath, and the reverse pulse power supply parameters are controlled to perform electroplating for 70 minutes.

[0037] The reverse pulse power supply parameters are: forward current density of 2.0 A / dm². 2 The forward electroplating time is 15 seconds; the reverse current density is 5.0 A / dm³. 2 The reverse electroplating time is 1 second.

[0038] The blind hole plate to be plated has a hole depth of 70μm and a hole diameter of 100μm.

[0039] Example 2

[0040] Embodiment 2 of the present invention provides an electroplating copper bath for filling blind micro-holes, comprising 16 mL / L of leveling agent solution, 10 mL / L of brightener solution, 70 g / L of sulfuric acid, 175 g / L of copper sulfate, 45 mg / L of hydrochloric acid, 0.5 g / L of oxidant, and 1 L of ultrapure water.

[0041] The brightener solution comprises, by mass percentage, the following components: brightener 0.12%, sulfuric acid 0.8%, copper sulfate pentahydrate 0.3-0.5%, and water to make up the balance.

[0042] The sulfuric acid is 98% by mass.

[0043] The brightener is a combination of a polysulfide organic sulfonate brightener and a sulfur-based compound. The mass ratio of the polysulfide organic sulfonate brightener to the sulfur-based compound is 4:1.

[0044] The polysulfide organic sulfonate brightener is a combination of sodium disulfide dipropane sulfonate and sodium phenyl disulfide dipropane sulfonate; the mass ratio of sodium disulfide dipropane sulfonate to sodium phenyl disulfide dipropane sulfonate is 1:1.

[0045] The sulfur-based compound is 2-mercaptobenzimidazole.

[0046] The leveling agent solution, by mass percentage, comprises 1.0% sulfuric acid, 1.5% polyethylene glycol, 0.10% leveling agent, and water to make up the balance.

[0047] The polyethylene glycol is a combination of PEG10000 and PEG2000; the mass ratio of PEG10000 to PEG2000 is 1:5.

[0048] The leveling agent is tetrahydrothiazolyl thiophene.

[0049] The oxidant is ferrous sulfate.

[0050] Embodiment 2 of the present invention provides a method for using a copper plating bath for filling blind micro-holes. The method involves adding a leveling agent solution, a brightener solution, sulfuric acid, copper sulfate, hydrochloric acid, an oxidant, and ultrapure water to a copper plating bath in the prescribed amounts. The blind hole plate to be plated is then added to the copper plating bath, and the reverse pulse power supply parameters are controlled to perform electroplating for 70 minutes.

[0051] The reverse pulse power supply parameters are: forward current density of 2.0 A / dm². 2 The forward electroplating time is 15 seconds; the reverse current density is 5.0 A / dm³. 2 The reverse electroplating time is 1 second.

[0052] The blind hole plate to be plated has a hole depth of 70μm and a hole diameter of 100μm.

[0053] Example 3

[0054] In one aspect, Embodiment 3 of the present invention provides an electroplating copper bath for filling blind micro-holes, comprising 12 mL / L of leveling agent solution, 14 mL / L of brightener solution, 70 g / L of sulfuric acid, 175 g / L of copper sulfate, 45 mg / L of hydrochloric acid, 0.5 g / L of oxidant, and 1 L of ultrapure water.

[0055] The brightener solution comprises, by mass percentage, the following components: brightener 0.08%, sulfuric acid 0.8%, copper sulfate pentahydrate 0.3-0.5%, and water to make up the balance.

[0056] The sulfuric acid is 98% by mass.

[0057] The brightener is a combination of a polysulfide organic sulfonate brightener and a sulfur-based compound. The mass ratio of the polysulfide organic sulfonate brightener to the sulfur-based compound is 4:1.

[0058] The polysulfide organic sulfonate brightener is a combination of sodium disulfide dipropane sulfonate and sodium phenyl disulfide dipropane sulfonate; the mass ratio of sodium disulfide dipropane sulfonate to sodium phenyl disulfide dipropane sulfonate is 1:1.

[0059] The sulfur-based compound is 2-mercaptobenzimidazole.

[0060] The leveling agent solution, by mass percentage, comprises 1.0% sulfuric acid, 2.0% polyethylene glycol, 0.08% leveling agent, and water to make up the balance.

[0061] The polyethylene glycol is a combination of PEG10000 and PEG2000; the mass ratio of PEG10000 to PEG2000 is 1:5.

[0062] The leveling agent is tetrahydrothiazolyl thiophene.

[0063] The oxidant is ferrous sulfate.

[0064] Embodiment 3 of the present invention provides a method for using a copper plating bath for filling blind micro-holes. The method involves adding a leveling agent solution, a brightener solution, sulfuric acid, copper sulfate, hydrochloric acid, an oxidant, and ultrapure water to a copper plating bath in the prescribed amounts. The blind hole plate to be plated is then added to the copper plating bath, and the reverse pulse power supply parameters are controlled to perform electroplating for 70 minutes.

[0065] The reverse pulse power supply parameters are: forward current density of 2.0 A / dm². 2 The forward electroplating time is 15 seconds; the reverse current density is 5.0 A / dm³. 2 The reverse electroplating time is 1 second.

[0066] The blind hole plate to be plated has a hole depth of 70μm and a hole diameter of 100μm.

[0067] Comparative Example 1

[0068] Comparative Example 1 of the present invention provides an electroplating copper bath for filling blind micro-holes and its application method. The specific implementation method is the same as that of Example 1, except that the brightener is sodium polydisulfide dipropane sulfonate.

[0069] Comparative Example 2

[0070] Comparative Example 2 of the present invention provides an electroplating copper bath for filling blind micro-vias and its application method. The specific implementation method is the same as that of Example 1, except that the polyethylene glycol is PEG20000.

[0071] Performance testing methods

[0072] 1. The blind hole boards of the examples and comparative examples were subjected to a 300°C lead-free tin furnace for 10 seconds as one thermal shock. After being removed and placed in the air for 10 seconds, it was considered a thermal shock. The thermal shock was repeated 6 times. The results were observed and analyzed by metallographic sectioning. If no fractures, cracks or hole walls were observed in the copper holes, the thermal shock resistance was recorded as "qualified". If fractures, cracks or hole walls were observed in the copper holes, the thermal shock resistance was recorded as "unqualified". The results are shown in Table 1.

[0073] 2. The filling rate of the blind hole plates after filling in the examples and comparative examples was calculated using the formula, and the results are recorded in Table 1.

[0074] Through-hole ratio = (thickness of the copper plating layer from the bottom of the blind hole to the deepest point on the hole surface / thickness of the copper plating layer from the bottom of the blind hole to the surface thickness of the copper plating layer on the board) × 100%.

[0075] 3. The blind via plates of the examples and comparative examples were subjected to SEM testing. The size range and size uniformity of the copper grains were observed and recorded. The results are recorded in Table 1.

[0076] Table 1

[0077] Thermal shock resistance Cavity filling rate (%) Size range and dimensional uniformity Example 1 qualified 98 10-15μm, good uniformity Example 2 qualified 96 8-16μm, good uniformity Example 3 qualified 95 10-20μm, good uniformity Comparative Example 1 Unqualified 90 20-35μm, poor uniformity Comparative Example 2 Unqualified 88 18-40μm, poor uniformity

Claims

1. A copper plating bath for filling blind micro-vias, characterized in that, The solution comprises at least 12-16 mL / L of leveling agent solution, 10-15 mL / L of brightening agent solution, 60-80 g / L of sulfuric acid, 160-180 g / L of copper sulfate, 40-55 mg / L of hydrochloric acid, 0.5-8.0 g / L of oxidant, and ultrapure water to a final volume of 1 L. The brightening agent solution, by mass percentage, comprises at least the following components: 0.08-0.12% brightening agent, 0.6-1.0% sulfuric acid, 0.3-0.5% copper sulfate pentahydrate, and water to make up the balance. The leveling agent solution, by mass percentage, comprises at least 0.5-1% sulfuric acid. 5%, polyethylene glycol 1.5-2.0%, leveling agent 0.05-0.10%, water to make up the balance; the brightener is a combination of polysulfide organic sulfonate brightener and sulfur-based compound in a mass ratio of (2-5):1; the polysulfide organic sulfonate brightener is a combination of sodium polydisulfide dipropane sulfonate and sodium phenyl polydisulfide dipropane sulfonate in a mass ratio of 1:1, and the sulfur-based compound is 2-mercaptobenzimidazole; the polyethylene glycol is a combination of PEG10000 and PEG2000 in a mass ratio of 1:(4-6); the leveling agent is tetrahydrothiazolylthione.

2. A method of using an electroplating copper bath for filling blind micro-vias according to claim 1, characterized in that, Add the prescribed amounts of leveling agent solution, brightener solution, sulfuric acid, copper sulfate, hydrochloric acid, oxidant, and ultrapure water to the copper plating tank. Add the blind hole plate to be plated into the copper plating tank and perform electroplating by controlling the reverse pulse power supply parameters.

3. The method of using the electroplating copper bath for filling blind micro-vias according to claim 2, characterized in that, The reverse pulse power supply parameters are: forward current density of 1.0-3.0 A / dm². 2 The forward plating time is 15-20 seconds; the reverse current density is 4-6 A / dm³. 2 The reverse electroplating time is 1-2 seconds.

4. The method of using the electroplating copper bath for filling blind micro-vias according to claim 2, characterized in that, The hole depth of the blind hole plate to be plated is 60-100μm, and the hole diameter is 100-120μm.