This is the first in a series of informal interviews, speaking with technologists about new, innovative products, their technology, and market impact. This month, we have selected Dr. Kevin McLaughlin, Technical Marketing Manager, at SCP Global Technologies about a new single-wafer cleaning tool.

Paul Nesdore: Chief Editor, A2C2: In general, tell me about your product and why and where single wafer processing makes sense.

Kevin McLaughlin: What we are introducing to the marketplace is a tool called Emersion, a megasonic immersion-style wafer processor. We are focusing this product for front-end-of-line (FEOL) critical cleans in the IC industry. The idea of having this tool is to supplement the application spaces already currently supported by both batch wet tools as well as spin spray single wafer tools.

PN: Can you get a bit more specific?

KM: After talking to, and doing testing with, numerous customers we decided to target 65nm and below technology. We discovered that there were areas of cleaning such as particularly exposed polysilicon around the gate stack, which were not being adequately cleaned with either batch or single-wafer spin technologies. We found that either there were unacceptable levels of damage by the existing tools running at the limits, or if the tools were run without megasonics, the cleaning capability was too low for acceptable operations.

PN: What are the main advantages of single wafer processing?

KM: One basic advantage is that with single wafer processing you can tailor the fluid flow, temperature, and megasonic energy profile to that individual wafer rather than to the entire batch.

PN: Let’s talk about the process itself.

KM: If you looked at the tool itself, you would see a very thin immersion style process vessel (See Figure 1). The megasonics that we use have three independent transducers that are located at different points in the vessel so that we can create a megasonic energy field primarily at the interface where wafer, liquid, and air (or nitrogen blanket) come together. We sweep the wafer through the megasonic field, resulting in very short contact times between individual features of the wafer and the energy field. We also are able to use a very low energy density relative to typical batch or single wafer tools.

PN: So you are combining lower energy and shorter exposure?

KM: Precisely. The defining rule for us was to maintain a 30 second goal for any individual process. We are essentially able to get off the curve everyone seems to be on, which is that lower damage equals lowers particle removal or conversely higher particle removal equals higher damage. We have actually been able to demonstrate cleaning without damage on 65nm and below type wafer structures with high particle removal efficiency.

PN: What is unique about your process?

KM: Our patented process is not the actual transducer itself. We purchase these from an existing vendor, trying to maintain as few unique parts as we can. The patent is on the design—where the transducers are placed, the angle at which they are placed, and the location within the vessel.

PN: Tell me something about how the process is controlled.

KM: We have a tool and process controller on board the tool capable of setting any number of process parameters including megasonic energy to each of the transducers as well as their on/off duration. The transducers are at a fixed frequency but are operated at variable energy (wattage) levels. Also controllable are the other parameters enabling us to have the capability to run SC1, SC2, HCl and other chemistries.