[19p-S423-1~17] 13.4 Si wafer processing /Si based thin film /MEMS/Integration technology

[19p-S423-6] Effect of Additives to Neutral Electroless Copper Plating Solution

〇(M1)HITOSHI UTSUNO¹, Osamu Sugiura² (1.Chiba Inst. of Tech., graduate school of eng., 2.Chiba Inst. of Tech., fac. of eng.)

Keywords:electroless plating,copper plating,neutral electroless copper plating

Time dependence of resistivity of plating film was evaluated from the thickness and the sheet resistivity of the film which was deposited on the electrode of the quartz crystal microbalance sensor. The resistivity will be large if the film has rough surface. From the time dependence of resistivity, it can be estimated when film deposition mode changed from island growth to two dimensional growth. We applied the evaluation method to neutral electroless copper plating using cobalt (II) complex as reducing agent. When the copper film were plated without additives to plating solution, the resistivity were decreased up to about 150nm thickness. But it was almost constant when the film was thicker than 150nm. It showed that uniform film requires at least 150nm thick without additives plating solution. When polyethylene glycol was added to the copper plating solution, the resistivity reached the constant value at 80nm thickness. Film deposition mode seems to change to two dimensional growth in thinner condition than no additive solution. It can be said that polyethylene glycol is effective to make the film uniform even in neutral electroless copper plating solution. In plating without additives in the solution, the dependence of film thickness to plating time was linear. However, there was nonlinear relationship when polyethylene glycol was added to the solution. Plating rate decreased after thick film was plated.