Preparation and properties of electroless deposited NiP, NiWP as barrier layer on p-type Si

In this study, we used electroless deposition of NiP, NiWP on p-type Si as the barrier layer to prevent the diffusion of Cu into Si. We added different amount of W into the layer, wt% is 11.89% (NiWP-1) and 25.36% (NiWP-2). After annealed at various temperatures, thermal stability of the Si/Ni(W)P/Cu layers were evaluated by measuring the changes of resistance of the samples, using four-point probe method. XRD was applied to detect the formation of Cu₃Si, which symbolizes Cu has diffused into Si, to evaluate the barrier performance of the layers. The results of XRD of the stacked Si/NiP/Cu, Si/NiWP-1/Cu, Si/NiWP-2/Cu films reveal that Cu atom could diffuse through NiP barrier layer at 450 °C, Cu could diffuse through NiWP-1 layer at 550 °C, while Cu could hardly diffuse through NiWP-2 layer. This means that with W added in the layer, the barrier performance is improved. Although the resistance of Si/NiWP-1 and Si/NiWP-2 are higher than that of Si/NiP, the resistance of stacked layers of Si/NiWP-1/Cu and Si/NiWP-2/Cu are close to that of Si/NiP/Cu. This means that using NiWP as barrier layer is acceptable.