Galvanic Deposition of Silver on Silicon Surfaces from Fluoride Free Aqueous Solutions

Abstract

Direct deposition of silver from fluoride-free alkaline solutions containing Ag(I) ions at pH higher than 12 onto silicon surfaces at room or elevated temperatures has been demonstrated. This deposition does not require a reducing agent, i.e. process proceeds via galvanic displacement reactions. This new process that is based on strong alkaline and fluoride-free solutions was experimentally illustrated through XRD and SEM analyses. Theoretically, it was confirmed that this process is thermodynamically favorable at room temperature, however for the real industrial applications elevated temperatures (up to 100 Semi-conductive silicon substrates are widely used in electronics industry for various applications. Metallization of silicon semiconductors with copper, silver and gold is very important in the production of integrated electronics devices. For this purpose, electrochemical methods e.g. electrodeposition or electroless deposition from aqueous solutions are very attractive since they are quite simple and relatively easy to scale up. Practical difficulties arise due to the fact that at the surface of silicon wafers oxide films of SiO 2 are formed. SiO 2 films are non-conductive, and consequently, they must be removed prior to direct metallization using the aqueous electrochemical processes. Although the metallization of silicon substrates can be achieved via autocatalytic deposition through the surface activation with SnCl 2 /PdCl 2 catalysts, 1 this process would not remove the SiO 2 film leading to an unacceptable electronic device performance. In order to remove the SiO 2 film and to deposit metals such as copper or silver from aqueous solutions directly onto silicon, various pretreatment steps are required during processing. These pre-treatment steps involve fluoride-containing solutions, 2 which can have deleterious effect on the environment. The direct deposition of copper, silver or gold from aqueous fluoride-containing solutions onto silicon substrates via the galvanic displacement reaction has been described in the literature.3-6 Reports on the deposition of copper or silver onto silicon substrates via the galvanic displacement reaction from fluoride-free aqueous solutions have not been found in the literature. The present paper describes preliminary observations on the deposition of silver onto silicon substrates via the galvanic displacement from aqueous fluoride-free solutions. Of course, significant detailed studies will be required before this process can be applied in the practice. If and when successful, this simple process may have a significant impact on the electronics industry.Experimental p-(boron doped) and n-(phosphorus doped) single crystal (100) silicon were used as substrates in the present work. As received, silicon substrates were very carefully washed with 3:1 (H 2 SO 4 -H 2 O 2 ) solution and then with water and ethanol. After the cleaning procedure, silicon substrates were immersed into respective proprietary fluoridefree solutions containing Ag(I) ions. For the deposition of sil...

Influence of Galvanic Replacement Conditions in Dmso Solutions on the Sizes of Gold Nanoparticles, Fixed on the Surface of Silicon

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Deposition of Gold Nanoparticles via Galvanic Replacement in DMSO and Their Influence on Formation of Silicon Nanostructures

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Communication—Galvanic Deposition of Gold on Silicon from Au(I) Alkaline Fluoride-Free Solutions

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