Method for treating substrate that support catalyst particles for plating processing

Abstract

The present invention provides a method for treating a substrate that supports metal fine particles for forming a plating layer on a circuit pattern or TSVs in various substrates, in which further micronization treatment is enabled compared with the conventional methods, and the formation of a stable plating layer is enabled. The present invention is a method for treating a substrate, the method including bringing a substrate into contact with a colloidal solution containing metal particles in order to support the metal particles that serve as a catalyst for forming a plating layer on the substrate, in which the colloidal solution contains metal particles formed of Pd and having a particle size of 0.6 nm to 4.0 nm and a face-to-face dimension of the (111) plane of 2.254 or more. When an organic layer such as SAM is formed on a surface of the substrate before this treatment, the binding force of the Pd particles can be increased.

Claims

1. A method for treating a substrate, the method including bringing a substrate into contact with a colloidal solution containing metal particles in order to support the metal particles that serve as a catalyst for forming a plating layer on the substrate, wherein the colloidal solution contains metal particles formed of Pd and having a particle size of 0.6 nm to 4.0 nm and a face-to-face dimension of a plane 111 of 2.254 or more but 2.388 or less.

2. The method for treating a substrate according to claim 1, wherein the method comprising a step of forming an organic layer formed from an organic substance, on a surface of the substrate before the contacting with the colloidal solution.

3. The method for treating a substrate according to claim 2, wherein a self-assembled monolayer (SAM) is formed as the organic layer.

4. The method for treating a substrate according to claim 3, wherein the step of forming a self-assembled monolayer is applying a silane coupling agent on the substrate.

5. The method for treating a substrate according to claim 2, wherein a film comprising a polyimide, polyethylene terephthalate, or polyethylene naphthalate is formed as the organic layer.

6. The method for treating a substrate according to claim 1, wherein the concentration of the metal particles in the colloidal solution is adjusted to 9.310.sup.6 to 3.810.sup.1 mol/L.

7. The method for treating a substrate according to claim 1, wherein the substrate is a substrate having one or more via holes formed therein, and at least one aspect ratio of the via holes is 3 to 50.

8. The method for treating a substrate according to claim 2, wherein the step of forming an organic layer is applying a silane coupling agent on the substrate.

9. The method for treating a substrate according to claim 3, wherein a film comprising a polyimide, polyethylene terephthalate, or polyethylene naphthalate is formed as the organic layer.

10. The method for treating a substrate according to claim 4, wherein a film comprising a polyimide, polyethylene terephthalate, or polyethylene naphthalate is formed as the organic layer.

11. The method for treating a substrate according to claim 2, wherein the concentration of the metal particles in the colloidal solution is adjusted to 9.310.sup.6 to 3.810.sup.1 mol/L.

12. The method for treating a substrate according to claim 3, wherein the concentration of the metal particles in the colloidal solution is adjusted to 9.310.sup.6 to 3.810.sup.1 mol/L.

13. The method for treating a substrate according to claim 4, wherein the concentration of the metal particles in the colloidal solution is adjusted to 9.310.sup.6 to 3.810.sup.1 mol/L.

14. The method for treating a substrate according to claim 5, wherein the concentration of the metal particles in the colloidal solution is adjusted to 9.310.sup.6 to 3.810.sup.1 mol/L.

15. The method for treating a substrate according to claim 2, wherein the substrate is a substrate having one or more via holes formed therein, and at least one aspect ratio of the via holes is 3 to 50.

16. The method for treating a substrate according to claim 3, wherein the substrate is a substrate having one or more via holes formed therein, and at least one aspect ratio of the via holes is 3 to 50.

17. The method for treating a substrate according to claim 4, wherein the substrate is a substrate having one or more via holes formed therein, and at least one aspect ratio of the via holes is 3 to 50.

18. The method for treating a substrate according to claim 5, wherein the substrate is a substrate having one or more via holes formed therein, and at least one aspect ratio of the via holes is 3 to 50.

19. The method for treating a substrate according to claim 6, wherein the substrate is a substrate having one or more via holes formed therein, and at least one aspect ratio of the via holes is 3 to 50.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1(a) and 1(b) illustrate a TEM observation image and the results for an X-ray diffraction analysis of the Pd particles of a first embodiment.

(2) FIG. 2 is a photograph of the cross-section of a substrate via hole obtained after the supporting of the Pd particles according to the first embodiment.

(3) FIG. 3 is a photograph of the cross-section of a substrate via hole obtained after a NiB electroless plating processing according to the first embodiment.

(4) FIG. 4 is a diagram illustrating the Pd particle adsorption density on the substrate surface and on the inner walls of the via holes according to a second embodiment.

(5) FIG. 5 is a photograph of the cross-section of a substrate via hole obtained after a CoWB electroless plating processing according to the second embodiment.

DESCRIPTION OF EMBODIMENTS

(6) Hereinafter, suitable embodiments of the present invention are described.

First Embodiment

(7) In the present embodiment, Pd particles and a metal colloidal solution were produced, a substrate having TSVs formed therein was treated by immersing the substrate in this metal colloidal solution, and a plating layer was formed by electroless plating.

(8) [Production of Pd Particles]

(9) 1500 mL of pure water was introduced into a separable flask having a capacity of 5 L, and 5.87 g of a Pd chloride powder (Pd content: 32.89 mmol) was introduced into this flask. The Pd chloride at this time is insoluble in water, and the solution is in a turbid state. While a sodium chloride solution obtained by dissolving 9.61 g of sodium chloride (5 times the molar equivalent of Pd) in 1000 mL of pure water was added to this solution, the mixture was stirred. During this operation, the solution acquired transparency and turned brown, and after stirring for 50 minutes, an orange-colored transparent aqueous solution was obtained.

(10) An aqueous solution of PVP (obtained by dissolving 10.5 g of PVP in 1000 mL of pure water) was added to this aqueous solution of Pd chloride, and 875 mL of ethanol was further added thereto as a reducing agent. Then, the reaction liquid was stirred in a constant temperature tank at 110 C., and the reaction liquid was heated to reflux for 3 hours at 90 C.

(11) The reaction liquid after reduction was cooled, subsequently filtered, and concentration in a rotary evaporator, and thus ethanol was removed. The residue was subjected to filtration and ultrafiltration. A filter having a fractionation molecular weight of 10,000 was used for the ultrafiltration. Thereafter, the filtrate was filtered again, and thus Pd particles were collected. These Pd particles were observed with TEM (transmission electron microscopy), and the particle sizes were measured. Also, measurement of the face-to-face dimension of the (111) plane of Pd was carried out by X-ray diffraction (source of radiation: CuK radiation).

(12) FIGS. 1(a) and 1(b) show a TEM image (FIG. 1(a)) of Pd particles, and a diffraction line of X-ray diffraction (2: 35 to 45, FIG. 1(b)). The average particle size of the Pd particles obtained from the measurement based on the TEM image was 2.2 nm. Furthermore, the face-to-face dimension of the (111) plane calculated from the peak positions of the diffraction line of X-ray diffraction was 2.293 .

(13) [Production of Pd Colloidal Solution]

(14) The Pd particles collected as described above were diluted with pure water to obtain a Pd colloidal solution. The Pd concentration of the Pd colloidal solution was adjusted to 0.1 wt %.

(15) [Substrate]

(16) In the present embodiment, a Si substrate having a thickness of 100 m was used. This substrate had via holes (hole diameter: 2 m, depth: 30 m; aspect ratio: 15) formed by reactive etching according to the Bosch process. This substrate had a SiO.sub.2 layer (200 nm) formed by thermal oxidation after the formation of via holes. Also, the substrate was subjected to washing and degreasing before a SAM was formed thereon.

(17) [SAM Formation]

(18) The aforementioned substrate was immersed in a 3-aminopropyltriethoxysilane solution (solvent: toluene), and a SAM was formed thereon. This treatment was carried out for 1 hour at 60 C. After this silane coupling treatment, the substrate was washed with ethanol and further subjected to a calcination treatment for 1 hour at 110 C. Thus, the SAM was activated.

(19) [Substrate Treatment by Means of Pd Colloidal Solution]

(20) The substrate having a SAM formed thereon was immersed in the Pd colloidal solution produced as described above. The treatment temperature at this time was adjusted to 25 C., and the immersion time was set to 10 minutes. Through this treatment, the Pd particles bind to the amino groups at the ends of the SAM.

(21) FIG. 2 is a photograph of the cross-section of a substrate via hole obtained after the supporting of the Pd particles. It can be confirmed from FIG. 2 that the Pd particles are supported evenly at the opening and the bottom of the via hole. Furthermore, the number of Pd particles bound onto the substrate was calculated from the SEM photograph, and the number was 2.010.sup.4 particles/m.sup.2.

(22) [Formation of Metal Film by Electroless Plating]

(23) A NiB film was formed by electroless plating on the substrate obtained after the supporting of the Pd particles. For the NiB plating, an electroless plating liquid composed of 0.17 mol/L of nickel sulfate, 0.049 mol/L of dimethylaminoborane, and 0.63 mol/L of citric acid (reducing agent, complexing agent) was used. The electroless plating processing was carried out by immersing the substrate in the electroless plating liquid that had been adjusted to 70 C., for 1 hour.

(24) FIG. 3 is a photograph of the cross-section of a substrate via hole obtained after a NiB electroless plating processing. It can be confirmed from FIG. 3 that the Pd particles supported at a high density act as a catalyst, and thus a thin and continuous NiB thin film is formed. Also, it can be seen that the NiB thin film is formed to a sufficient thickness even at the bottom of the via hole.

Second Embodiment

(25) Here, the same treatment of a substrate as in the first embodiment was carried out by means of the Pd colloidal solution produced in the first embodiment, and the binding state of the Pd particles was checked in more detail. Also, a CoWB film was formed as a metal film by electroless plating.

(26) The substrate used was a Si substrate having via holes (hole diameter: 2.5 m, depth: 63 m; aspect ratio: 25) formed therein. This substrate had a SiO.sub.2 layer and a SAM formed in advance, as in the case of the first embodiment. This substrate was immersed in the Pd colloidal solution. The treatment temperature at this time was adjusted to 25 C., and the immersion time was set to 10 minutes.

(27) After the supporting of Pd particles by this immersion treatment, the Pd particle adsorption density (number of particles bound) on the substrate surface and the inner walls of the via holes was calculated from SEM photographs. The results are presented in FIG. 4. It can be confirmed from FIG. 4 that Pd particles are supported at a uniform density to the interior of the via holes by the Pd colloidal solution of the first embodiment.

(28) Next, a CoWB film was formed by electroless plating on the substrate obtained after the supporting of the Pd particles. CoWB plating was carried out by means of an electroless plating liquid composed of 0.17 mol/L of cobalt sulfate, 0.049 mol/L of dimethylaminoborane, 0.005 mol/L of tungstic acid, and 0.63 mol/L of citric acid (reducing agent, complexing agent). The electroless plating processing was carried out by immersing the substrate in the electroless plating liquid that had been adjusted to 45 C., for 15 minutes.

(29) FIG. 5 is a photograph of the cross-section of a substrate via hole obtained after an electroless plating processing. It can be confirmed from FIG. 5 that a continuous thin metal film has also been formed by CoWB plating.

Third Embodiment

(30) Here, Pd particles having different particle sizes and the face-to-face dimensions of the (111) plane of Pd were produced. 2000 mL of pure water was introduced into a separable flask, and 5.87 g of a Pd chloride powder (Pd content: 32.89 mmol) was introduced thereto. Then, while the same sodium chloride solution as that of the first embodiment was added thereto, the system was stirred. An aqueous solution of PVP (obtained by dissolving 8.75 g of PVP in 1500 mL of pure water) was added to this aqueous solution of Pd chloride, and 875 mL of methanol was added thereto. Thereafter, similarly to the first embodiment, the reaction liquid was heated, stirred and heated to reflux, and Pd particles were collected by concentration, ultrafiltration, and filtration. The Pd particles obtained by this process had an average particle size of 4 nm, and the face-to-face dimension of the (111) plane of Pd was 2.254 .

Comparative Example 1

(31) As Comparative Example for the embodiments described above, Pd particles were produced by a conventional method. The Pd particles were produced by means of dinitrodiamine Pd nitrate as a precursor of the Pd particles. 76.67 g of dinitrodiamine Pd nitrate (Pd content: 32.89 mmol) was dissolved in 2000 mL of pure water in relation to the first embodiment. At this time, dinitrodiamine Pd nitrate dissolved easily in water. Thereafter, an aqueous solution of PVP and a reducing agent were added thereto under the same conditions as in the first embodiment, and the mixture was heated to reflux. Thus, Pd particles were collected. The Pd particles at this time had an average particle size of 4 nm, and a face-to-face dimension of the (111) plane of Pd of 2.251 .

Comparative Example 2

(32) Similarly to Comparative Example 1, Pd particles were produced by means of dinitrodiamine Pd nitrate as a precursor of the Pd particles. 4.98 g of sodium borohydride was added as a reducing agent in relation to Comparative Example 1. Thereafter, similarly to the first embodiment, the mixture was heated to reflux, and Pd particles were collected. The Pd particles at this time had an average particle size of 15.0 nm, and a face-to-face dimension of the (111) plane of Pd of 2.243 .

(33) Evaluation was carried out by performing treatment of substrates by means of the Pd colloidal particles of the third embodiment and Comparative Examples 1 and 2 produced as described above, in the form of colloidal solutions, and performing formation of a CoWB film according to electroless plating. Regarding the substrates used, they were 10 kinds of Si substrates in which via holes having a hole diameter of 2 m and a depth of 6 to 100 m (aspect ratio: 3 to 50) were formed. Furthermore, SAMs were formed thereon in the same manner as in the first embodiment. Furthermore, the Pd concentration of the colloidal solutions for the treatment of substrates was 0.1 wt %. The conditions for electroless plating of the CoWB film were the same as in the second embodiment.

(34) In regard to this evaluation, the adsorption density of the Pd particles at the bottoms of the via holes in the substrates obtained after the treatment with a Pd colloidal solution was measured, and also, the presence or absence of the formation of a continuous metal film inside the via holes after electroless plating was investigated. These results are presented in Table 1. Furthermore, this evaluation test was also carried out for the Pd colloidal solution of the first embodiment.

(35) TABLE-US-00001 TABLE 1 First embodiment Third embodiment Comparative Example 1 Comparative Example 2 Average particle size 2.2 nm Average particle size 4.0 nm Average particle size 4.0 nm Average particle size 15.0 nm Face-to-face dimension Face-to-face dimension Face-to-face dimension Face-to-face dimension 2.293 2.254 2.251 2.243 Particle Particle Particle Particle adsorption Continuous adsorption Continuous adsorption Continuous adsorption Continuous density plated film density plated film density plated film density plated film TSV 3 aspect 5 ratio 10 12 15 20 x 25 x x x 30 x x x 40 x x x x 50 x x x x For particle adsorption density . . . 8000 particles/m.sup.2 or more to the bottoms of TSV holes . . . 4000 to 8000 particles/m.sup.2 to the bottoms of TSV holes x . . . Fewer than 4000 particles/m.sup.2 to the bottoms of TSV holes For continuous plated film . . . Continuous film was formed . . . Continuous film was formed, but via holes or voids were present x . . . Continuous film was not formed

(36) It was confirmed from the results of Table 1 that the colloidal solutions containing Pd particles of the first and third embodiments could adsorb the Pd particles to the bottoms of via holes having a high aspect ratio. Furthermore, also for the formation of a metal film, it was confirmed that continuous films without any defects were formed. On the other hand, regarding the treatment using conventional Pd colloidal solutions in Comparative Examples, it can be said that the treatment was effective for substrates having via holes with a low aspect ratio (3 to 5); however, it can be seen that when the aspect ratio was 40 to 50, the treatment was hardly effective.

(37) Furthermore, in the third embodiment, the aspect ratio of the via holes was 30 or more, and the particle adsorption density was 8000 particles/m.sup.2 or less. In the third embodiment, the target support density for the plating processing was attained, and in this test, there was no hindrance to the formation of a continuous film. Therefore, it can be said that the third embodiment can be applied to most of the use applications. However, for example, in the case of making the target film thickness of the plated film to be very thin, there is a risk of the formation of partial pinholes. In such a case, it is expected that the risk can be coped with by making the particle size of the Pd particles to be finer (for example, 3 nm or less).

INDUSTRIAL APPLICABILITY

(38) As discussed above, according to the present invention, Pd particles having high catalytic activity can be suitably dispersed, and the adhesiveness of the plating layer obtained thereafter can be made satisfactory. The present invention is useful for the plating processing for the formation of planar substrates as well as substrates for TSV having high aspect ratios. Furthermore, the present invention becomes more effective when combined with the formation of organic layers such as SAM.