Sputtered Multi-Layer Electrode for Semiconductor Devices

The patent employs a composite electrode structure consisting of multiple metallic layers with distinct functions: a nickel-chromium alloy layer providing corrosion resistance and adhesion, a copper layer providing electrical conductivity, and a silver layer providing low contact resistance. This composite structure resolves the contradiction by combining materials that individually address different requirements, achieving both ease of manufacture through sputtering and superior corrosion resistance against lead-free solder.

The electrode is segmented into multiple functional layers, each performing a specific function: the nickel-chromium layer handles adhesion and corrosion protection, the copper layer provides bulk conductivity, and the silver layer ensures low contact resistance. This segmentation allows each layer to be optimized for its specific function while collectively solving the contradiction between manufacturing ease and corrosion resistance.

The patent replaces the traditional thermal firing process with a physical vapor deposition process (sputtering). Instead of using high-temperature firing to sinter metal particles, the sputtering process directly deposits dense, adherent metallic layers through physical bombardment. This substitution eliminates the need for complex firing schedules while producing electrodes with superior aging characteristics and reliability.

The patent changes the fundamental process parameters from thermal processing (firing temperature, time, atmosphere) to physical processing (sputtering power, gas pressure, deposition rate). This parameter change enables the formation of electrodes with controlled thickness, composition, and microstructure that provide excellent aging resistance without requiring complex thermal processing equipment or procedures.

The patent converts the harmful chemical plating process into a beneficial physical deposition process. By using sputtering instead of electroless plating, the harmful cyanide chemicals are eliminated entirely, replaced by a clean vacuum process using inert gases. The adhesion benefits of nickel plating are achieved through the nickel-chromium sputtered layer, which provides equivalent or superior adhesion without any toxic substances.

The nickel-chromium alloy layer serves as an intermediary between the ceramic substrate and the copper electrical contact layer. This intermediate layer provides both adhesion to the substrate and a diffusion barrier, while the sputtering process itself acts as a clean intermediary method that avoids direct chemical contact with harmful substances, eliminating the need for cyanide-based plating solutions.