The first metallization layers 205 are formed over the first substrate 203 and the first active devices and are designed to connect the various active devices to form functional circuitry. In an embodiment the first metallization layers 205 are formed of alternating layers of dielectric and conductive material and may be formed through any suitable process (such as deposition, damascene, dual damascene, etc.). In an embodiment there may be four layers of metallization separated from the first substrate 203 by at least one interlayer dielectric layer (ILD), but the precise number of first metallization layers 205 is dependent upon the design of the first semiconductor device 201.
The first contact pads 207 may be formed over and in electrical contact with the first metallization layers 205. The first contact pads 207 may comprise aluminum, but other materials, such as copper, may alternatively be used. The first contact pads 207 may be formed using a deposition process, such as sputtering, to form a layer of material (not shown) and portions of the layer of material may then be removed through a suitable process (such as photolithographic masking and etching) to form the first contact pads 207. However, any other suitable process may be utilized to form the first contact pads 207. The first contact pads may be formed to have a thickness of between about 0.5 μm and about 4 μm, such as about 1.45 μm.