A conventional field effect transistor (FET), also known as a metal oxide semiconductor (MOS) transistor, generally includes a semiconductor substrate, such as silicon, having a source, a drain, and a channel positioned between the source and drain. A gate stack composed of a conductive material (a gate conductor), an oxide layer (a gate oxide), and sidewall spacers, is typically located above the channel. The gate oxide is typically located directly above the channel, while the gate conductor, generally comprised of polycrystalline silicon (polysilicon) material, is located above the gate oxide. The sidewall spacers protect the sidewalls of the gate conductor.
The formation of semiconductor devices, including field effect transistors, often requires high temperature processing steps. For example, for a given electric field across the channel of a MOS transistor, the amount of current that flows through the channel is directly proportional to a mobility of carriers in the channel. Thus the higher the mobility of the carriers in the channel, the more current can flow and the faster a circuit can perform. One way to increase the mobility of the carriers in the channel of an MOS transistor is to produce a mechanical stress in the channel. However, the formation of a strained channel typically requires a high temperature processing step sufficient to destroy a conventional photoresist mask.
Another example of a high temperature processing step is the formation of a layer that is deposited on top of the poly silicon, known as a poly cap, in the formation of semiconductor devices. While desirable from a standpoint of device performance, the temperatures needed to form a poly cap are sufficient to destroy conventional photoresist masks.
It would be advantageous to provide methods and systems facilitating the performance of high-temperature processing steps in the manufacture of semiconductor devices.