Semiconductor devices continue to be reduced in dimensions while maintaining or increasing in performance in response to an ever-increasing demand. This increasing demand is likely to continue and requires improvements in semiconductor fabrication processes and structures. Improvements in semiconductor processes permit fabrication of semiconductor devices in smaller dimensions and in higher density, quantity, and reliability. Improvements in semiconductor structures typically yield greater circuit performance, power control, and reliability.
Semiconductor devices are comprised of a number of materials, components, structures, and layers. One type of layer employed in semiconductor devices is a dielectric layer, which is comprised of dielectric material. Dielectric materials, also referred to as dielectrics, exhibit a large attractive force between the nucleus and orbiting electrons and have a net effect of a large amount of resistance to the movement of electrons. Dielectrics have low conductivity and high resistivity in contrast to conductive materials that have a high conductivity and low resistivity. Additionally, dielectrics can be divided into low-k dielectrics, which have a relatively low capacitance for a given thickness and high-k dielectrics, which have a relatively high capacitance for a given thickness. The “k” refers to the dielectric constant of particular dielectric materials. Dielectrics, particularly high-k dielectrics, are often utilized in capacitor and capacitor like structures in semiconductor devices. Such structures are formed whenever a dielectric layer is formed between two conductors. For example, capacitor structures are formed in MOS gate structures by forming a dielectric layer between metal or polysilicon layers and silicon substrates.
The properties of high-k dielectric layers or films are sensitive to the relative compositions of the materials comprising the dielectric layers or films. These properties can become even more sensitive as dielectric layers and/or films continue to shrink in thickness. Particularly problematic is the lack of control of relative compositions of materials at different locations within the depth of the dielectric layer or film. Thus, processes and systems that facilitate control of relative compositions throughout various depths of dielectric layers are desirable.