1. Field
Embodiments disclosed herein generally relate to plasma processing systems and materials and apparatus for controlling plasma uniformity in plasma processing systems.
2. Description of the Related Art
Plasma processing chambers are regularly utilized in various electronic device fabrication processes, such as etching processes, chemical vapor deposition (CVD) processes, and other processes related to the manufacture of electronic devices on substrates. However, sometimes it is not desirable or cost effective to generate a plasma in the chamber processing the substrate. In such cases, a remote plasma source (RPS) can be used.
Conventional RPS designs traditionally use a closed loop RF source configuration having windings that are wrapped around a closed magnetically permeable core that surrounds a portion of the plasma-generating region. Recently, open loop RF source configurations have been developed. The open loop RF source configurations use an annular processing volume surrounding a magnetically permeable core, such as a magnetically permeable linear rod, with windings wrapped around the magnetically permeable core. Open loop designs have the advantage of being able to create a plasma 360 degrees around the magnetically permeable core, which can increase efficiencies relative to closed loop designs.
Although the open loop design has advantages, obtaining targets for plasma uniformity can be challenging. For example, in open loop designs using an annular plasma chamber surrounding a linear magnetically permeable core that extends in a first horizontal direction, the plasma density in the RPS can have one or more peaks that are skewed in that first horizontal direction. When the plasma density is not centered or uniform across the horizontal direction relative to center of the annular plasma chamber, then the plasma-containing or radical containing gas will not be uniformly supplied to the process chamber, which creates non-uniformities in the process results achieved on the substrate being processed in the process chamber. Furthermore, when minor adjustments to the configuration of the RPS hardware are made, such as adjustments to the coil position relative to the plasma chamber, dramatic shifts in the uniformity of the plasma density in horizontal directions are often observed.
Therefore, there is a need for an open loop RF source configuration that improves the plasma uniformity in the plasma chamber.