Method for no-silane electroless metal deposition using high adhesive catalyst and product therefrom
11098407 · 2021-08-24
Assignee
Inventors
Cpc classification
B01J37/0219
PERFORMING OPERATIONS; TRANSPORTING
C23C18/1893
CHEMISTRY; METALLURGY
C23C18/1653
CHEMISTRY; METALLURGY
C23C18/1639
CHEMISTRY; METALLURGY
B01J33/00
PERFORMING OPERATIONS; TRANSPORTING
B01J37/0217
PERFORMING OPERATIONS; TRANSPORTING
International classification
B01J33/00
PERFORMING OPERATIONS; TRANSPORTING
C23C18/16
CHEMISTRY; METALLURGY
C23C18/32
CHEMISTRY; METALLURGY
Abstract
A method for electroless metal deposition and an electroless metal layer included substrate are provided. The method for electroless metal deposition includes steps as follows. a) cleaning a substrate, applying a hydrofluoric acid onto the substrate; and then applying a modifying agent onto the substrate to form a chemical oxide layer on the substrate; b) a catalyst layer is formed on the chemical oxide layer, wherein, the catalyst layer includes a plurality of colloidal nanoparticles, and each of the plurality of colloidal nanoparticles includes a palladium nanoparticle and a polymer which encapsulates the palladium nanoparticle, and c) depositing a metal on the catalyst layer through an electroless metal deposition to form an electroless metal layer.
Claims
1. A method for electroless metal deposition, comprising: a) cleaning a substrate, applying a hydrofluoric acid onto the substrate, and then applying a modifying agent onto the substrate to form a chemical oxide layer on the substrate; b) forming a catalyst layer on the chemical oxide layer, wherein the catalyst layer includes a plurality of colloidal nanoparticles, and each of the plurality of colloidal nanoparticles includes a palladium nanoparticle and a polymer which encapsulates the palladium nanoparticle, and c) depositing a metal on the catalyst layer through an electroless metal deposition to form an electroless metal layer; wherein, the polymer and the palladium nanoparticle have a weight ratio of 0.5:1 to 2:1.
2. The method for electroless metal deposition as claimed in claim 1, wherein in the step a), the modifying agent is selected from the group consisting of: ozone, nitrate, hydrofluoric acid, mixture of sulfuric acid and hydrogen peroxide, and mixture of nitrate and hydrofluoric acid.
3. The method for electroless metal deposition as claimed in claim 1, wherein the protective agent is the polymer, and the precursor is a palladium ion.
4. The method for electroless metal deposition as claimed in claim 1, wherein each of the plurality of colloidal nanoparticles has a particle size ranging from 6 nm to 10 nm.
5. The method for electroless metal deposition as claimed in claim 1, wherein the polymer encapsulating the palladium nanoparticle is a polyvinyl alcohol polymer, a polyvinyl alcohol acid polymer, a poly(vinyl alcohol-co-ethylene) polymer, or a poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) polymer.
6. The method for electroless metal deposition as claimed in claim 1, wherein the polymer is a low-degree-polymerization polyvinyl alcohol polymer with a weight-average molecular weight ranging from 20000 to 30000.
7. The method for electroless metal deposition as claimed in claim 1, wherein in the step c), the metal deposited on the catalyst layer in the electroless metal deposition is nickel or copper.
8. The method for electroless metal deposition as claimed in claim 1, wherein the colloidal nanoparticles is formed by reacting a precursor, a protective agent, and a reducing agent in an alkaline environment.
9. The method for electroless metal deposition as claimed in claim 8, wherein the precursor is a palladium ion, the protective agent is the polymer, and the reducing agent is a formaldehyde solution.
10. The method for electroless metal deposition as claimed in claim 8, wherein the precursor is at least one palladium nanoparticle, the protective agent is at least one polymer, and the at least one polymer encapsulates the at least one palladium nanoparticle to form at least one colloidal nanoparticle.
11. The method for electroless metal deposition as claimed in claim 10, wherein the at least one polymer encapsulating the at least one palladium nanoparticle is a polyvinyl alcohol polymer, a polyvinyl alcohol acid polymer, a poly(vinyl alcohol-co-ethylene) polymer, or a poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) polymer.
12. A method for metal deposition, comprising: a) cleaning a substrate, applying a hydrofluoric acid onto the substrate, and then applying a modifying agent onto the substrate to form a chemical oxide layer on the substrate; b) forming a catalyst layer on the chemical oxide layer, wherein the catalyst layer includes a plurality of colloidal nanoparticles, and each of the plurality of colloidal nanoparticles includes a palladium nanoparticle and a polymer which encapsulates the palladium nanoparticle, and d) conducting an electroless metal deposition to form a metal layer on the catalyst layer; wherein, the polymer and the palladium nanoparticle have a weight ratio of 0.5:1 to 2:1.
13. The method of claim 12, wherein the step d) further includes conducting an electro-plating process to increase the thickness of the metal layer.
14. The method of claim 12, wherein the step b) further includes using the polymer and a palladium ion to form the catalyst layer on the chemical oxide layer.
15. An electroless metal layer included substrate, comprising: a chemical oxide layer formed on a surface of a substrate by cleaning the substrate, applying a hydrofluoric acid onto the substrate, and then applying a modifying agent onto the substrate; a catalyst layer disposed on the chemical oxide layer, and the catalyst layer including a plurality of colloidal nanoparticles, and each of the plurality of colloidal nanoparticles including a palladium nanoparticle and a polymer which encapsulates the palladium nanoparticle, and an electroless metal layer formed by conducting an electroless metal deposition to deposit a metal on the catalyst layer; wherein, the polymer and the palladium nanoparticle have a weight ratio of 0.5:1 to 2:1.
16. The electroless metal layer included substrate as claimed in claim 15, wherein each of the plurality of colloidal nanoparticles has a particle size ranging from 6 nm to 10 nm.
17. The electroless metal layer included substrate as claimed in claim 15, wherein the polymer encapsulating the palladium nanoparticle includes a polyvinyl alcohol polymer, a polyvinyl alcohol acid polymer, a poly(vinyl alcohol-co-ethylene) polymer, or a poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) polymer.
18. The electroless metal layer included substrate as claimed in claim 15, wherein the polymer is a low-degree-polymerization polyvinyl alcohol polymer with its weight-average molecular weight ranging from 20,000 to 30,000.
19. The electroless metal layer included substrate as claimed in claim 15, wherein the metal includes nickel or copper.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(11) Embodiments disclosed in the instant disclosure are illustrated via specific examples as follows, and people familiar in the art may easily understand the advantages and efficacies of the instant disclosure by disclosure of the specification. The instant disclosure may be implemented or applied by other different specific examples, and each of the details in the specification may be applied based on different views and may be modified and changed under the existence of the spirit of the instant disclosure. The figures in the instant disclosure are only for brief description, but they are not depicted according to actual size and do not reflect the actual size of the relevant structure. The following embodiments further illustrate related technologies of the instant disclosure in detail, but the scope of the instant disclosure is not limited herein.
First Embodiment
(12) Please refer to
(13) Please refer to
(14) Firstly, a substrate 1 (a silicon substrate is illustrated in the instant disclosure) is provided, and the substrate 1 is cleaned using an RCA cleaning method. The RCA cleaning method is a standard procedure for wet cleaning in the industry. RCA-1 and RCA-2 are two reagents used in the RCA cleaning method. The ingredients of RCA-1 are NH.sub.4OH, H.sub.2O.sub.2, and H.sub.2O (also known as APM), and the RCA-1 is used to remove organic particles on a surface. The ingredients of RCA-2 are HCl, H.sub.2O.sub.2, and H.sub.2O (also known as HPM), and the RCA-2 is used to remove metals on a surface. In the instant disclosure, an APM solution of the RCA cleaning method is used in the cleaning procedure to clean the organic particles on the surface. The cleaning procedure includes the following steps. The substrate 1 is soaked in the APM solution for 20 minutes at 80° C., and the APM solution has a ratio of NH.sub.4OH:H.sub.2O.sub.2:DI=1:1:5 (DI is deionized water). After being cleaned, the substrate 1 is then soaked into a 2% hydrofluoric acid (HF) aqueous solution to remove an oxide layer formed in the RCA cleaning method on the surface. Then, a sulfuric peroxide mixture (SPM), or an ozone is used to conduct a hydroxide surface modification on a surface of the substrate 1, and the substrate 1 is soaked into the SPM (H.sub.2SO.sub.4—H.sub.2O.sub.2) with a volume ratio of 3:1 for 10 minutes, so as to hydroxylate the surface of the substrate 1 and to form an uniform and hydroxylated chemical oxide layer 2 on the surface (as shown in the leftmost figure of
(15) Next, the surface modified substrate 1 is soaked in a PVA-Pd (polyvinyl alcohol polymer-palladium) solution for 5 minutes at 40° C., and the PVA-Pd is attached to the chemical oxide layer 2 of the surface of the substrate 1, so as to form a catalyst layer 3 (as shown in the middle figure of
(16) Please refer to
(17) Then, as shown in
(18) Please refer to
(19) Each of the colloidal nanoparticles 31 of this embodiment is such that, at least one protective agent encapsulates at least one precursor. Specifically, the protective agent is at least one polyvinyl alcohol polymer 312 and the precursor is at least one palladium nanoparticle 311, and the at least one polyvinyl alcohol polymer 312 encapsulates the at least one palladium nanoparticle 311 to form at least one colloidal nanoparticle 31 as shown in
(20) Each of the colloidal nanoparticles 31 of this embodiment has a particle size ranging from 6 nm to 10 nm, and the protective agent and the precursor in each of the colloidal nanoparticles 31 have a weight ratio of 0.5:1 to 2:1, for example, 1:1. The at least one polyvinyl alcohol polymer 312 could be a low-degree-polymerization polyvinyl alcohol polymer with its weight-average molecular weight ranging from 20000 to 30000, and the alcoholysis degree of polyvinyl alcohol polymer 312 could be 80% to 90%, for example, 88%.
Second Embodiment
(21) Please refer to
(22) 1) Rinsing: firstly, after being cleaned, the substrate 1 is placed into the 2% hydrofluoric acid (HF) aqueous solution for 2 minutes to remove an oxide layer which is generated in the RCA cleaning process and/or generated naturally. Subsequently, the substrate 1 is soaked into the SPM with a volume ratio of H.sub.2SO.sub.4:H.sub.2O.sub.2 being 3:1 for 10 minutes at about 70° C. to 80° C., so as to conduct the hydroxide surface modification on the surface of the substrate 1 to form an uniform and hydroxylated chemical oxide layer 2 on the surface of the substrate 1. In the second embodiment, the SPM also can be replaced with ozone (O.sub.3), nitrate (HNO.sub.3), or a mixture of nitrate (HNO.sub.3) and hydrofluoric acid (HF; 500 ppm).
(23) 2) Soaking: after the chemical oxide layer 2 formed substrate 1 is taken out from the SPM, the surface of the substrate 1 of the chemical oxide layer 2 is rinsed with deionized water, and the chemical oxide layer 2 formed substrate 1 is soaked in the PVA-Pd solution for 5 minutes at 40° C., such that a center of the palladium of the PVA-Pd may interact with hydroxyl groups and the PVA-Pd may absorb on the surface of the substrate 1 of the chemical oxide layer 2, so as to form a catalyst layer 3.
(24) 3) Electroless-nickel deposition: the chemical oxide layer 2 and catalyst layer 3 formed on the substrate 1 is placed into the electroless nickel plating solution having a pH of 4.9 (or about pH of 4.5 to 5.0) at 80° C. (or about 75° C. to 85° C.) to conduct the electroless metal deposition for 1 minute. During the process of electroless metal deposition, the catalyst PVA-Pd on the surface of the chemical oxide layer 2 and catalyst layer 3 formed on the substrate 1 may effectively decrease an active energy which is required for a reaction, so as to facilitate hypophosphite ions and nickel ions to generate redox reactions on the surface of the chemical oxide layer 2 and catalyst layer 3 formed on the substrate 1, and an electroless nickel phosphorus layer (electroless metal layer 4) with approximately 200 nm thickness may be deposited.
(25) The 200 nm thickness of electroless metal layer 4 on the substrate 1 may not be enough for some applications. Therefore, after the electroless metal layer 4 being formed on the substrate 1 according to the instant disclosure, additional process like conventional electro-plating process may also be performed to the substrate 1 so as to deposit more metal onto the metal layer and increase the thickness of the metal layer to meet the needs of some applications.
(26) The preparation method of the PVA-Pd solution in this embodiment may be identical to that in the first embodiment, thus it is not repeated herein.
(27) The method for forming the colloidal nanoparticle 31 in this embodiment may be identical to that in the first embodiment. In addition, the PVA is used as an example in the first embodiment. In this embodiment, the polymer used to encapsulate the palladium nanoparticle may include but not limited to a polyvinyl alcohol polymer, a polyvinyl alcohol acid polymer, a poly(vinyl alcohol-co-ethylene) polymer, or a poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) polymer.
Third Embodiment
(28) In the third embodiment, the steps of the method for no-silane electroless metal deposition using the high adhesive catalyst are identical to that of the second embodiment, and also include main three steps: conducting a hydroxide surface modification on a surface of a substrate 1 to form a chemical oxide layer 2, forming a catalyst layer 3 on the chemical oxide layer 2, and conducting an electroless metal deposition to form an electroless metal layer 4. A silicon substrate is also illustrated as the substrate 1. The cleaning method of the substrate 1, the composition of the catalyst layer 3, the electroless metal deposition steps, the method for forming the colloidal nanoparticles 31 being used to the no-silane electroless metal deposition, and the composition of the colloidal nanoparticles 31 may all be identical to those of the second embodiment, thus they are not repeated herein. The difference between the third embodiment and the second embodiment is that, in the third embodiment, a RCA method is used for conducting the hydroxide surface modification on the surface of the substrate 1.
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(30) 1) Rinsing: after a cleaning process, the substrate 1 is placed into a 2% hydrofluoric acid (HF) aqueous solution for 2 minutes to remove an oxide layer which is generated in the RCA cleaning process and/or generated naturally. The substrate 1 is soaked into a solvent with a volume ratio of NH.sub.4OH:H.sub.2O.sub.2:DI-water being 1:1:5 for 20 minutes at 80° C., so as to conduct the hydroxide surface modification on the surface of the substrate 1 to form a hydroxylated chemical oxide layer 2 on the surface of the substrate 1.
(31) 2) Soaking: the substrate 1 is soaked into the PVA-Pd solution for 5 minutes at 40° C., such that a center of the palladium of the PVA-Pd can interact with the hydroxyl groups and the PVA-Pd absorb onto the surface of the substrate 1 of the chemical oxide layer 2, so as to form a catalyst layer 3. The preparation method of the PVA-Pd solution in this embodiment can be identical to that in the first and second embodiments, thus it is not repeated herein.
(32) 3) Electroless-nickel deposition: the chemical oxide layer 2 and catalyst layer 3 formed substrate 1 is placed into the electroless nickel plating solution having a pH of 4.9 (or about pH of 4.5 to 5.0) at 80° C. (or about 75° C. to 85° C.) to conduct the electroless metal deposition for 1 minute. During the process of electroless metal deposition, the catalyst PVA-Pd on the surface of the chemical oxide layer 2 and catalyst layer 3 formed substrate 1 can effectively decrease an active energy which is required for a reaction, so as to facilitate hypophosphite ions and nickel ions to generate redox reactions on the surface of the chemical oxide layer 2 and catalyst layer 3 formed on the substrate 1, and an electroless nickel phosphorus layer (electroless metal layer 4) with approximately 200 nm thickness is deposited.
(33) The 200 nm thickness of electroless metal layer 4 on the substrate 1 may not be enough for some applications. Therefore, after the electroless metal layer 4 being formed on the substrate 1 according to the instant disclosure, additional process like conventional electro-plating process may also be performed to the substrate 1 so as to deposit more metal onto the metal layer and increase the thickness of the metal layer to meet the needs of some applications.
(34) In the third embodiment, the RCA method is used to conduct the hydroxide surface modification on the surface of the substrate 1, but in other embodiments, it also can be replaced with a sulfuric peroxide mixture method, an ozonation method, a hydrogen plasma method, or a nitric acid method. In addition, while the PVA is used as an example in the third embodiment, however, the polymer used to encapsulate the palladium nanoparticle may also include but not limited to a polyvinyl alcohol polymer, a polyvinyl alcohol acid polymer, a poly(vinyl alcohol-co-ethylene) polymer, or a poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) polymer.
(35) According to the embodiments mentioned previously, the substrate 1 is cleaned by the RCA cleaning method so as to remove organic particles and metals attached onto the surface of the substrate 1. After the RCA cleaning method, some hydroxide groups may be formed on the surface of the substrate 1. However, the hydroxide groups formed during the RCA cleaning method are not uniform because the cleaning to the substrate 1 and the formation of the hydroxide groups happens at the same time, and the organic particles and metals attached onto the substrate 1 would negatively impact the formation of the hydroxide groups.
(36) Therefore, the method for no-silane electroless metal deposition of the present disclosure further includes the steps of applying a hydrofluoric acid onto the substrate and then applying a modifying agent onto the substrate. In the step of applying a hydrofluoric acid onto the substrate, the hydrofluoric acid can remove the hydroxide groups formed by RCA cleaning method. In the step of applying a modifying agent onto the substrate, the modifying agent can modify the surface of the substrate 1 with new hydroxide groups to form a uniform and hydroxylaye chemical oxide layer 2.
(37) Via the method for no-silane electroless metal deposition using the high adhesive catalyst can achieve the following experimental results.
(38) <Experimental Result 1: XPS Spectrum Analysis>
(39) Please refer to
(40) As shown in
(41) <Experimental Result 2: Water Droplet Contact Angle (Hydrophilicity) Experiment>
(42) In order to understand a degree of change of the hydrophilicity of the surface of the substrate 1 after which is conducted the SPM method in the second embodiment and the RCA method in the third embodiment in this instant disclosure, the water droplet contact angle experiment is used for measurement. Please refer to
(43) <Experimental Result 3: Electroless Nickel Layer Adhesion Experiment>
(44) Please refer to
(45) The descriptions illustrated supra set forth simply the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alterations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.