Reduce or eliminate IMC cracking in post wire bonded dies by doping aluminum used in bond pads during Cu/Low-k BEOL processing
View Patent ↗A bond pad structure which includes an aluminum bond pad which include one or more dopants that effectively control the growth of IMC to a nominal level in spite of high tensile stresses in the wafer. For example, aluminum can be doped with 1–2 atomic % of Mg. Alternatively, Pd or Si can be used, or elements like Cu or Si can be used as the dopant in order to reduce the overall tensile stresses in the wafer. This can control the abnormal growth of IMC, thus arresting the IMC crack formation. A combination of dopants can be used to both control the tensile stresses and also slightly alter the gold-Aluminum interface thus enabling a uniform and thin IMC formation. This tends to reduce or eliminate any voiding or cracking which would otherwise occur at the wire bond transfer.
1. A bond pad structure for engaging a gold ball, comprising:
a layer of copper;
a layer of aluminum disposed above the copper layer and configured for engagement with the gold ball, wherein said layer of aluminum is doped only with Si.
2. The bond pad structure as recited in claim 1 , wherein the layer of aluminum is doped such that the growth of intermetallic compound (IMC) is controlled to a nominal level in spite of high tensile stresses on the wafer.
3. The bond pad structure as recited in claim 1 , wherein the layer of aluminum is doped with Si, thereby reducing the overall tensile stresses, wherein the gold-aluminum interface is altered, thus enabling a uniform and thin intermetallic compound (IMC) formation.