Conventionally, the formation of passive components, e.g. resistors and capacitors, in the back end employs one or more photolithographic masks to define the deposition of a high-resistance material in the case of resistors and the deposition of a pair of planar electrodes with a dielectric between in the case of a capacitor.
In the case of resistors, the material has a high resistivity compared with the Al or Cu of the interconnect material and therefore requires a separate deposition step and a special mask different from the mask of the nth wiring level. In the case of capacitors, there will be separate deposition steps for horizontal planar electrodes and for the dielectric between the electrodes.
Structures like these perform well enough, but the requirement of one or more additional masks means that the use of such structures incurs additional costs to have the masks made, plus yield detractors associated with the additional handling and processing steps.
The art could benefit from a method of forming passive components that does not require additional masks and/or processing steps.