Under bump metal film comprising a stress relaxation layer and a diffusion-resistant layer
View Patent ↗An under bump metal film formed on a substrate includes a diffusion-resistant barrier layer made of a platinum group metal film, and an aluminum-based stress relaxation layer formed under the diffusion-resistant barrier layer.
1. An under bump metal film on a pad electrode formed on a substrate, the under bump metal film comprising:
a stress relaxation layer having a lower surface and an upper surface opposite to the lower surface, the lower surface being joined to the pad electrode, the stress relaxation layer being aluminum-based; and
a diffusion-resistant barrier layer made of a platinum group metal film provided on the upper surface of the stress relaxation layer.
2. The under bump metal film of claim 1 , wherein
the diffusion-resistant barrier layer is made of nickel and has a thickness of at least 800 nm and at most 2000 nm.
3. The under bump metal film of claim 2 , wherein
the stress relaxation layer is at least half and at most 1.5 times as thick as the diffusion-resistant barrier layer.
4. The under bump metal film of claim 1 , wherein
the platinum group metal is at least one of platinum and palladium.
5. The under bump metal film of claim 1 , wherein the diffusion-resistant barrier layer is formed substantially entirely on the upper surface of the stress relaxation layer.
6. The under bump metal film of claim 1 , further comprising an adhesive layer joining the lower surface of the stress relaxation layer to the electrode, the adhesive layer being made of titanium.