Basic electroplating solution for cobalt interconnection of integrated circuit as well as preparation method and application of basic electroplating solution

Abstract

The invention provides a basic electroplating solution for cobalt interconnection of an integrated circuit as well as a preparation method and application of the basic electroplating solution. The preparation method comprises the following steps: providing a cobaltous sulfate stock solution and a boric acid solution; heating the cobaltous sulfate stock solution to a supersaturated state, cooling and crystallizing to obtain high-purity cobaltous sulfate crystals; adding the cobaltous sulfate crystal into a boric acid solution, mixing and filtering to obtain the basic electroplating solution for cobalt interconnection of the integrated circuit; before the cobalt sulfate crystals are added into the boric acid solution, impurities in the boric acid solution are removed. According to the technical scheme, operation is easy, the provided basic electroplating liquid for cobalt interconnection is high in purity, and the purity requirement of the electroplating liquid for cobalt interconnection of an integrated circuit is met.

Description

Technical Field

[0001] This invention relates to the field of separation and purification technology, and in particular to a basic electroplating solution for cobalt interconnects of integrated circuits, its preparation method, and its uses. Background Technology

[0002] Since the advent of the dual damask process for integrated circuit metal interconnects, copper interconnects have become the mainstream interconnect metal material due to their excellent conductivity. Copper interconnects typically require the deposition of materials such as tantalum nitride as a barrier layer to prevent copper from electromigrating into the dielectric layer on the substrate. However, the resistivity of these barrier layers is higher than that of metals. As interconnect lines shrink, if the size of the barrier layer is not reduced, the overall resistance of the interconnect line will increase. At the same time, copper's large mean free path of electrons also leads to a sharp increase in the resistance of small-linewidth copper interconnects. Cobalt interconnects can solve these problems.

[0003] Cobalt interconnects inherit the electroplating process from copper interconnects, but require different plating solutions. For cobalt interconnect base plating solutions, not only are the chemical composition and proportions of the solution clearly defined, but the purity of the solution is also subject to extremely strict requirements. For example, key impurities such as Fe, Ni, Cu, and Pb have deposition potentials similar to or higher than cobalt, and will deposit together with cobalt during electroplating, or even preferentially deposit, thus affecting the purity of the cobalt coating and the reliability of the cobalt interconnect and devices. Furthermore, organic impurities and particulate impurities can enter the cobalt coating during electroplating, thereby increasing the resistivity of the cobalt interconnect lines.

[0004] Therefore, a high-purity base electroplating solution for cobalt interconnects in integrated circuits is needed. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a basic electroplating solution for cobalt interconnects of integrated circuits, its preparation method and application, so as to solve the problems in the prior art.

[0006] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0007] The first aspect of this invention provides a method for preparing a basic electroplating solution for cobalt interconnects in integrated circuits, comprising: providing a cobalt sulfate stock solution and a boric acid solution; heating the cobalt sulfate stock solution to a supersaturated state, cooling and crystallizing to obtain high-purity cobalt sulfate crystals; adding the cobalt sulfate crystals to the boric acid solution, mixing and filtering to obtain the basic electroplating solution for cobalt interconnects in integrated circuits; and removing impurities from the boric acid solution before adding the cobalt sulfate crystals.

[0008] Preferably, the concentration of the cobalt sulfate stock solution is 1-500 g / L. More preferably, the concentration of the cobalt sulfate stock solution is 10-250 g / L, for example, it can be 10 g / L, 50 g / L, 90 g / L, 100 g / L, 150 g / L, 200 g / L, or 250 g / L. The concentration of the cobalt sulfate stock solution is specific. If the concentration of the cobalt sulfate stock solution is too low, the time and energy required to heat to a supersaturated state will increase, resulting in high production costs. If the concentration of the cobalt sulfate stock solution is too high, crystals will spontaneously precipitate from the solution at room temperature, which is detrimental to the subsequent crystallization process.

[0009] Preferably, the heating temperature is 20-100℃. More preferably, the heating temperature of the cobalt sulfate stock solution is 40-90℃, for example, 40℃, 50℃, 60℃, 70℃, 80℃, or 90℃.

[0010] Preferably, when supersaturated, the concentration of the cobalt sulfate stock solution is 300-600 g / L. More preferably, the supersaturated concentration of the cobalt sulfate stock solution is 400-550 g / L, for example, 400 g / L, 450 g / L, 500 g / L, or 550 g / L.

[0011] Preferably, the cooling rate is 0.01-600℃ / min. More preferably, the cooling rate is 0.1-200℃ / min. Even more preferably, it is 1-50℃ / min, for example, 1℃ / min, 3℃ / min, 10℃ / min, 15℃ / min, 20℃ / min, 30℃ / min, 40℃ / min, or 50℃ / min. When the cooling rate is too fast, it is conducive to the formation of crystal nuclei, resulting in poor crystal morphology and purity; when the cooling rate is too slow, although it is conducive to crystal growth and the crystal morphology and purity are better, it will reduce production efficiency and increase production costs.

[0012] Preferably, the crystallization time is 0.01-100 h. More preferably, the crystallization time of the cobalt sulfate stock solution is 0.5-40 h, for example, 0.5 h, 1 h, 4 h, 8 h, 16 h, 20 h, 32 h, or 40 h.

[0013] Preferably, the crystallization process is performed 1 to 5 times. For example, it can be single crystallization, double crystallization, triple crystallization, quadruple crystallization, or quintuple crystallization. The number of crystallizations has a significant impact on the purity of cobalt sulfate crystals. The more crystallizations, the higher the purity of the crystals. However, if the number of crystallizations is too high, the crystallization yield will decrease and the energy consumption of production will increase.

[0014] Preferably, the concentration of the boric acid solution is 1-60 g / L. More preferably, the concentration of the boric acid solution is 5-50 g / L, for example, 5 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, or 50 g / L.

[0015] Preferably, after cooling and crystallization, solid-liquid separation is performed.

[0016] Preferably, the solid-liquid separation includes one or more of centrifugation, filtration, and vacuum filtration.

[0017] Preferably, the boric acid solution is purified using an ion exchange resin.

[0018] Preferably, the ion exchange resin is a mixed-bed ion exchange resin.

[0019] More preferably, during impurity removal, the flow rate of the boric acid solution through the ion exchange resin is 0.01-1000 L / min. More preferably, it is 0.1-30 L / min, for example, 0.1 L / min, 0.5 L / min, 1 L / min, 5 L / min, 10 L / min, 20 L / min, or 30 L / min. Excessive flow rate during impurity removal results in a shorter residence time, lower ion exchange rate, and poor purification effect; while insufficient flow rate, although beneficial for purifying the boric acid solution, increases production time and energy costs.

[0020] Preferably, the mixed-bed ion exchange resin is selected from one or more of acrylic acid-based mixed-bed ion exchange resins, styrene-based mixed-bed ion exchange resins, epoxy-based mixed-bed ion exchange resins, and phenolic mixed-bed ion exchange resins. By utilizing the selectivity and adsorption properties of the ion exchange resin, key impurities such as Fe, Ni, Cu, and Pb in the boric acid solution can be specifically removed, and the separation of organic impurities in the solution can be achieved.

[0021] Preferably, the mixed-bed ion exchange resin is selected from one or more of the following technical features:

[0022] a) The cation exchange resin of the mixed bed ion exchange resin is a strong acidic H-type resin with a total volume exchange capacity of 1-6 mmol / mL.

[0023] b) The anion resin of the mixed bed ion exchange resin is an OH-type strong basic resin with a total volume exchange capacity of 0.5-5 mmol / mL;

[0024] c) The particle size range of the mixed-bed ion exchange resin is 0.1-2.0 mm.

[0025] In this application, the cation resin of the mixed-bed ion exchange resin is an H-type strong acid resin with a total volumetric exchange capacity of 1.8–6 mmol / mL, and the anion resin is an OH-type strong base resin with a total volumetric exchange capacity of 0.9–5 mmol / mL and a particle size range of 0.4–1.2 mm.

[0026] Preferably, the filter element used in the filtration process has a pore size of no more than 5 μm. More preferably, the filter element used in the filtration process has a pore size of no more than 0.3 μm, for example, 0.3 μm, 0.1 μm, 0.05 μm, 0.03 μm, or 0.01 μm. The filtration operation can effectively reduce particulate contaminants in the base electroplating solution, such as trace amounts of insoluble impurities in the solution and dust mixed in from the air, thereby improving the quality of the base electroplating solution.

[0027] Preferably, the filtration flow rate is 0.01-5000 L / min. More preferably, the filtration operation flow rate is 1-30 L / min, for example, 1 L / min, 3 L / min, 5 L / min, 10 L / min, 20 L / min, or 30 L / min. If the filtration flow rate is too high, the load on the filter and filter element increases, the service life is shortened, and energy consumption increases; if the filtration flow rate is too low, the impurity removal effect of the filter element decreases, and production efficiency decreases.

[0028] Preferably, the filtration time is 0.1-200h. More preferably, the filtration time is 0.5-50h, for example, 0.5h, 1h, 5h, 8h, 10h, 20h, 30h, 40h, or 50h.

[0029] A second aspect of the present invention provides a base electroplating solution for high-purity cobalt interconnects of integrated circuits, prepared by the preparation method described above.

[0030] Preferably, the Fe content in the base electroplating solution is less than 100 ppb. More preferably, the Fe content in the base electroplating solution is less than 70 ppb. Even more preferably, the Fe content in the base electroplating solution is less than 60 ppb, such as 57 ppb, 40 ppb, 20 ppb, 11 ppb, or 5 ppb.

[0031] Preferably, the Ni content in the base electroplating solution is less than 100 ppb. More preferably, the Ni content in the base electroplating solution is less than 90 ppb, such as 89 ppb, 61 ppb, 40 ppb, 20 ppb, or 5 ppb.

[0032] Preferably, the Cu content in the base electroplating solution is less than 100 ppb. More preferably, the Cu content in the base electroplating solution is less than 15 ppb. Even more preferably, the Cu content in the base electroplating solution is less than 10 ppb, such as 5 ppb or 2 ppb.

[0033] Preferably, the Pb content in the base electroplating solution is less than 100 ppb. More preferably, the Pb content in the base electroplating solution is less than 15 ppb. Even more preferably, the Pb content in the base electroplating solution is less than 10 ppb, such as 8 ppb, 4 ppb, 3 ppb, 2 ppb, or 1 ppb.

[0034] Preferably, the total organic carbon content in the base electroplating solution is less than 5 ppm. More preferably, the total organic carbon content in the base electroplating solution is less than 3.6 ppm, such as 2.7 ppm, 2.6 ppm, 2.1 ppm, or 1.8 ppm.

[0035] Preferably, the content of particles with a diameter greater than 0.1 μm in the base electroplating solution is less than 1000 pcs / mL. More preferably, the content of particles with a diameter greater than 0.1 μm in the base electroplating solution is less than 800 pcs / mL. Even more preferably, the content of particles with a diameter greater than 0.1 μm in the base electroplating solution is less than 600 pcs / mL, such as 580.0 pcs / mL, 538.1 pcs / mL, 494.9 pcs / mL, 128.6 pcs / mL, or 19.1 pcs / mL.

[0036] The third aspect of the present invention provides a basic electroplating solution as described above as a main component of an electroplating solution for cobalt interconnects in integrated circuits, used to achieve cobalt interconnect electroplating.

[0037] In this invention, the initial purification of cobalt sulfate is achieved through cooling crystallization. Specifically, cooling induces crystallization in the supersaturated cobalt sulfate stock solution, causing cobalt sulfate to precipitate from the solution in crystalline form. Most metallic and organic impurities remain in the solution, thus removing key impurities such as Fe, Ni, Cu, and Pb, as well as organic impurities, from the cobalt sulfate. The cobalt sulfate crystals are then mixed with a high-purity boric acid solution treated with ion exchange resin, and further impurities are removed by filtration, ultimately yielding a high-purity base electroplating solution for cobalt interconnects in integrated circuits.

[0038] The beneficial effects of this invention are:

[0039] This invention provides a high-purity cobalt interconnect base electroplating solution, its preparation method, and its applications. The contents of Fe, Ni, Cu, and Pb elements can be controlled to be less than 100 ppb, the total organic carbon (TOC) can be controlled to be less than 5 ppm, and the particulate matter with a diameter greater than 0.1 μm can be controlled to be less than 1000 pcs / mL. This base electroplating solution can meet the purity requirements of electroplating solutions for cobalt interconnects in integrated circuits. Attached Figure Description

[0040] Figure 1 The diagram shows a flow chart of the preparation method of the basic electroplating solution for cobalt interconnect of integrated circuits according to the present invention. Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0042] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0043] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0044] In the following embodiments of the present invention, the styrene-based mixed-bed ion exchange resin ZGER8420 was purchased from Zhejiang Zhengguang Industrial Co., Ltd.; and the 0.1μm and 0.05μm filter cartridges were purchased from Hangzhou Kebaite Filter Material Co., Ltd.

[0045] Example 1

[0046] This embodiment provides a specific basic electroplating solution for cobalt interconnects in integrated circuits and its preparation method, which specifically includes the following steps:

[0047] (1) The cobalt sulfate stock solution with a concentration of 90 g / L was heated to a concentration of 550 g / L at 80℃, and then cooled to room temperature at a cooling rate of 15℃ / min for 20 h to crystallize. Then it was centrifuged at 4000 rpm for 15 min to dehydrate and obtain high-purity cobalt sulfate crystals.

[0048] (2) A boric acid solution with a concentration of 50 g / L was passed through a resin column packed with styrene-based mixed bed ion exchange resin at a flow rate of 1 L / min to remove impurities, thereby obtaining a high-purity boric acid solution.

[0049] (3) Add the high-purity cobalt sulfate crystals from step 1) to the high-purity boric acid solution from step 2) and mix them thoroughly. Pass the thoroughly mixed solution through a filter column equipped with a filter element with a pore size of 0.1 μm at a flow rate of 3 L / min for 8 hours to obtain the basic electroplating solution.

[0050] To verify the purity of the base electroplating solution, ICPMS (inductively coupled plasma mass spectrometry), TOC, and liquid particle number were tested. The analysis results are shown in Table 1.

[0051] The specific testing method of ICPMS (Inductively Coupled Plasma Mass Spectrometry) is as follows: Fe, Ni, Cu and Pb elements in the basic electroplating solution prepared in Example 1 are tested using an 8900 inductively coupled plasma mass spectrometer (Agilent Technologies). The plasma power is 1500W, the plasma gas flow rate is 15L / min, the auxiliary gas flow rate is 0.9L / min, the atomization chamber temperature is 2℃, and the oxygen flow rate is 0L / min.

[0052] The specific testing method for TOC is as follows: The total organic carbon (TOC) in the base electroplating solution is tested using a multi N / C UVHS total organic carbon analyzer (Jena). The injection volume is 5 mL, the purge time is 180 s, and the integration time is 260 s. The specific testing method for liquid particle count is as follows: The number of particles with a diameter greater than 0.1 μm in the base electroplating solution is tested using a KS-42AF liquid particle counter (Rion). The injection volume is 50 mL.

[0053] Table 1

[0054]

[0055]

[0056] Example 2

[0057] The steps are the same as in Example 1, except that the cooling rate of the cobalt sulfate stock solution in step 1) is 3°C / min.

[0058] The basic electroplating solution prepared in Example 2 was subjected to ICPMS (inductively coupled plasma mass spectrometry), TOC, and liquid particle number tests, using the same methods as in Example 1. The impurity content analysis results of the basic electroplating solution prepared in Example 2 are shown in Table 2.

[0059] Table 2

[0060]

[0061] Example 3

[0062] Similar to Example 1, except that in step 3), a filter element with a pore size of 0.05 μm is used to filter the thoroughly mixed solution.

[0063] The basic electroplating solution prepared in Example 3 was subjected to ICPMS (inductively coupled plasma mass spectrometry), TOC, and liquid particle number tests, using the same methods as in Example 1. The impurity content analysis results of the basic electroplating solution prepared in Example 3 are shown in Table 3.

[0064] Table 3

[0065]

[0066] Example 4

[0067] Similar to Example 1, except that the cooling rate of the cobalt sulfate stock solution in step 1) is 30°C / min.

[0068] The basic electroplating solution prepared in Example 4 was subjected to ICPMS (inductively coupled plasma mass spectrometry), TOC, and liquid particle number tests, using the same methods as in Example 1. The impurity content analysis results of the basic electroplating solution prepared in Example 4 are shown in Table 4.

[0069] Table 4

[0070]

[0071] Example 5

[0072] Similar to Example 1, except that after obtaining high-purity cobalt sulfate crystals in step 1), water is added to dissolve them into a cobalt sulfate stock solution with a concentration of 90 g / L. The cobalt sulfate stock solution with a concentration of 90 g / L is then heated to a concentration of 550 g / L at 80°C. After cooling to room temperature at a cooling rate of 15°C / min, the solution is crystallized for 20 h. Then, it is centrifuged at 4000 rpm for 15 min to dehydrate. The above crystallization steps are repeated once to obtain high-purity cobalt sulfate crystals that have been crystallized 3 times.

[0073] The basic electroplating solution prepared in Example 5 was subjected to ICPMS (inductively coupled plasma mass spectrometry), TOC, and liquid particle number tests, using the same methods as in Example 1. The impurity content analysis results of the basic electroplating solution prepared in Example 5 are shown in Table 5.

[0074] Table 5

[0075]

[0076] Comparative Example 1

[0077] Similar to Example 2, except that the boric acid solution in step 2) is not purified by an ion exchange resin. The results of the impurity content analysis of the basic electroplating solution prepared in Comparative Example 1 are shown in Table 6.

[0078] Table 6

[0079]

[0080] The results showed that the Fe, Ni, and TOC impurities in the base electroplating solution prepared in Comparative Example 1 were too high, failing to meet the purity requirements for electroplating solutions used in cobalt interconnects of integrated circuits. This was because the high Fe, Ni, and TOC content in the boric acid solution, resulting from the lack of purification with ion exchange resin, further led to high Fe, Ni, and TOC content in the obtained base electroplating solution.

[0081] Comparative Example 2

[0082] Similar to Example 2, except that the solution thoroughly mixed in step 3) was not filtered. The results of the impurity content analysis of the basic electroplating solution prepared in Comparative Example 2 are shown in Table 7.

[0083] Table 7

[0084]

[0085] The results showed that the number of particles larger than 0.1 μm in diameter in the base electroplating solution prepared in Comparative Example 2 was too high, failing to meet the purity requirements for electroplating solutions used in cobalt interconnects of integrated circuits. This was because the mixed solution was not filtered, resulting in an excessively high number of particles larger than 0.1 μm in the obtained base electroplating solution.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a base plating solution for cobalt interconnects of integrated circuits, characterized in that The application provides a preparation method of a high-purity cobalt sulfate solution. The cobalt sulfate solution is heated to a supersaturated state, and then cooled to crystallize, so as to obtain high-purity cobalt sulfate crystals. The cobalt sulfate crystals are added into a boric acid solution, and then filtered after mixing, so as to obtain the basic plating solution for integrated circuit cobalt interconnection. The boric acid solution is impurity-removed before the cobalt sulfate crystals are added into the boric acid solution.

2. The base electroplating solution of claim 1, wherein, The concentration of the cobalt sulfate solution is 1-500 g / L. The heating temperature is 20-100 ℃. The concentration of the cobalt sulfate solution is 300-600 g / L when the solution is supersaturated. The cooling rate is 0.01-600 ℃ / min. The crystallization time is 0.01-100 h. The crystallization is performed for 1-5 times. The concentration of the boric acid solution is 1-60 g / L. The solid-liquid separation is performed after the cooling and crystallization. The ion exchange resin is used to remove impurities from the boric acid solution. The pore size of the filter core used in the filtering is not greater than 5 μm. The flow rate of the filtering is 0.01-5000 L / min.

3. The base electroplating solution of claim 2, wherein, The concentration of the cobalt sulfate solution is 10-250 g / L. The heating temperature is 40-90 ℃. The concentration of the cobalt sulfate solution is 400-550 g / L when the solution is supersaturated. The cooling rate is 0.1-200 ℃ / min. The crystallization time is 0.5-40 h. The concentration of the boric acid solution is 5-50 g / L.

4. The base electroplating solution of claim 2, wherein, The solid-liquid separation includes one or more of centrifugation, filtration and suction filtration. The pore size of the filter core used in the filtering is not greater than 0.3 μm. The flow rate of the filtering is 1-30 L / min. The ion exchange resin is a mixed bed ion exchange resin. The flow rate of the ion exchange resin used in the impurity removal is 0.01-1000 L / min.

5. The base electroplating solution of claim 3, wherein, The cooling rate is 1-50 ℃ / min.

6. The base electroplating solution of claim 4, wherein, The mixed bed ion exchange resin is selected from one or more of acrylic mixed bed ion exchange resin, styrene mixed bed ion exchange resin, epoxy mixed bed ion exchange resin and phenolic mixed bed ion exchange resin. The mixed bed ion exchange resin is selected from one or more of the following technical features: a) the cation resin of the mixed bed ion exchange resin is H-type strong acid resin, and the volume full exchange capacity is 1-6 mmol / mL; b) the anion resin of the mixed bed ion exchange resin is OH-type strong base resin, and the volume full exchange capacity is 0.5-5 mmol / mL; c) the particle size of the mixed bed ion exchange resin ranges from 0.1 mm to 2.0 mm. The flow rate of the ion exchange resin used in the impurity removal is 0.1-30 L / min.

7. A basic plating solution for integrated circuit cobalt interconnection, which is prepared by the preparation method of any one of claims 1-6.

8. The base electroplating solution of claim 7, wherein, The content of Fe in the basic plating solution is less than 100 ppb. The content of Ni in the basic plating solution is less than 100 ppb. The content of Cu in the basic plating solution is less than 100 ppb. and / or, the content of Pb element in the basic electroplating solution is less than 100 ppb; and / or, the content of total organic carbon in the basic electroplating solution is less than 5 ppm; and / or, the content of particles with diameter greater than 0.1 μm in the basic electroplating solution is less than 1000 pcs / mL.

9. The base electroplating solution of claim 8, wherein, the content of Fe element in the basic electroplating solution is less than 70 ppb; and / or, the content of Ni element in the basic electroplating solution is less than 90 ppb; and / or, the content of Cu element in the basic electroplating solution is less than 15 ppb; and / or, the content of Pb element in the basic electroplating solution is less than 15 ppb; and / or, the content of total organic carbon in the basic electroplating solution is less than 3.6 ppm; and / or, the content of particles with diameter greater than 0.1 μm in the basic electroplating solution is less than 800 pcs / mL.

10. Use of the basic electroplating solution prepared by the preparation method of any one of claims 1-6 or the basic electroplating solution of any one of claims 7-9 as a main component of an electroplating solution for cobalt interconnection in the field of integrated circuits to realize cobalt interconnection electroplating.

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