TCP™ Design

Transformer Coupled Plasma™ Source Technology

Lam's patented TCP technology is employed in Lam silicon and metal etch systems. Lam's silicon etch systems, such as the 2300™ Versys Star™, are used for all silicon etch applications, such as gate, metal gate, STI, nitride spacer, and recess applications. Specifically, the 2300 Versys Star targets complex, advanced applications to sub—90 nm on 300—mm wafers for current processes and to sub—65 nm for next—generation processes. Applications include:

• All—in—one gate etch (trim, mask open, strip, and gate) in the same chamber
• Gate etch stopping on high—k gate oxides and metal gates
• Shallow trench isolation (STI) with in situ hard mask open

Metal structures, such as 150—nm aluminum interconnect, can be etched with Lam's 200—mm metal etch systems, which employ TCP technology. Geometries at sub—100 nm can be etched on Lam's 2300 Versys metal etch system, where TCP technology has been extended for 300—mm processes. With metal etch, key drivers are productivity and low overall production costs. Lam's metal etch systems incorporate proprietary technologies in their design, such as unique chamber materials and in situ cleans after each wafer is processed, to provide the required high productivity.

How It Works

Source Power
TCP technology efficiently couples RF power into a low—pressure gas to produce a partially ionized plasma (electrically excited ionized gas) at low pressures to etch nanoscale features into silicon and metal films on the wafer surface. The source power is supplied by a simple planar coil located at the top of the etch chamber. A separate power supply delivers bias voltage to the lower electrode (wafer) to provide independent control of ion energy, which influences parameters such as selectivity and CD bias.

Low Pressure
Producing plasma under low pressure is often desirable because there are fewer random collisions among the ionized and neutral species in the plasma. When there are fewer collisions, the ionized and neutral species are more uniformly distributed in the chamber above the wafer, leading to better plasma and etch rate uniformity as well as improved profile control for isolated and dense features.

Damage Control
High—density plasmas at very low pressures are known to cause physical and/or latent device damage. This type of device damage (commonly referred to as "electron shading") is related to the imbalance of electron (negatively charged) and positive ion fluxes at the bottom of high—aspect—ratio features. This imbalance can drive a net electrical current through the device as the features are being etched. A higher plasma density increases the net current and, as a result, increases the potential for device damage.

One of the main features of Lam's TCP technology is the ability to strike plasmas at various powers and pressures. Creating and maintaining the plasma at the proper pressure and density can suppress device damage while achieving the required etch characteristics.

Flexible
Lam's robust TCP source technology allows flexibility for a wide range of power, chemistry, and pressure combinations to produce the desired wafer characteristics. In addition, Lam has introduced technologies to direct gas flow and control wafer temperature that further enable control of the critical dimensions (CD) that determine a chip's usability.

Key Advantages

• Produces a uniform, high—density plasma across the wafer, center to edge, for precise profile control
• Capable of generating a high—density plasma without requiring magnetic enhancements that can cause device damage
• Enables fast and accurate changes in power to perform multiple etch steps in situ, such as gate etch (trim, mask open, strip, and gate) and STI (hard mask open and trench etch)
• Provides the process window flexibility required to etch a wide variety of advanced device structures, such as STI and gate etch stopping on high k gate oxides and metal gates with one hardware configuration