Deposition Efficiency Study on Wafer Level Gold Plating based on Cyanide-free Electrolyte

Gold plating process is widely used in semiconductor industry. Due to environmental and safety issues, more and more wafer packaging factories began to devote themselves to the development of cyanide-free gold plating process. However, the current efficiency is a big challenge for the cyanide-free electrolyte plating process. This study focused on the increase of gold deposition efficiency on entire wafer. The gold plating process is achieved on the mass production tool from ACM with the mass production type electrolyte from EEJA. The gold film deposition efficiency is investigated by using various Paddle agitation speed. In the experiment, the motor speed was set to 0mm/s (no extra agitation), 120mm/s, 240mm/s, and 360mm/s. It was found that the agitation of paddle helped to increase the deposition thickness of the gold film, which reached a maximum when the paddle motion velocity was 240mm/s. Besides the above, 13 points were also measured on the whole wafer for plating uniformity. According to the experimental results, the agitation of the paddle also improved the uniformity of electroplating, achieving the best uniformity at a paddle speed of 240mm/s. The above improvement in current efficiency and electroplating uniformity can be attributed to the fact that paddle stirring accelerates the supplement of Au
⁺
on the wafer surface and makes the distribution of Au
⁺
concentration on the wafer surface more uniform.