Integrated circuits are generally formed on a substrate of semiconductor material out of a variety of active and passive devices. Active devices may include such devices as complementary metal oxide semiconductor (CMOS) transistors (either NMOS transistors or PMOS transistors) and may be formed from part of the semiconductor material within the substrate along with additional structures formed in conjunction with the semiconductor material. These active devices may then be interconnected using a series of conductive and insulative layers that may be formed over the active devices.
Passive devices may include such devices as resistors. These resistors may be formed to have a desired resistance to help control the desired path and functioning of the integrated circuit. The desired resistances for the resistors may be obtained by providing a desired amount of conductivities within the material of the resistors. For example, a precise amount of dopants may be introduced into a resistor that is made from a material such as polysilicon.
However, as integrated circuits and their active and passive devices have been reduced in size over the years (and as they are continuing to be miniaturized even further in the years ahead), the precision required for the manufacturing and operation of the resistors has increased. Additionally, the materials and processes used to manufacture the resistors has not kept up with the demand for high precision resistors as desired for further miniaturization while also maintaining the ease of integration for the manufacturing process that is desired for the mass production of integrated circuits.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.