SNF began as a device foundry, but is continually evolving to accommodate changing research requirements. This page outlines the current, base policies that have governed materials and processing rules at SNF for the last couple of decades. As new equipment, ProM requests, and capabilities are incorporated to meet labmembers' needs, we are gradually adopting the new materials/contamination policy.
Here is a general overview of the current policy. This document describes how this applies to equipment groups in the lab. Please note that there are many process- and equipment- specific exceptions. A couple of the general exceptions are listed below -- but you should always make sure to review the specific rules for each piece of equipment or station you use. As always, if you have ANY questions about materials processing, contact the ProM (Process and Materials) Committee, which not only approves new materials and processes, but is also a resource for helping you to develop your processes: firstname.lastname@example.org
The three contamination classes of equipment/processes at SNF are:
Clean: Most restrictive level, compatible with front-end CMOS processing.
Semi-clean: Less restrictive, compatible with backend electronics process. Substrates with standard metals (Al, W, Ti) are acceptable.
Gold-Contaminated: Least restrictive, covering non-standard materials (however, any new material must be approved before processing.)
One-way travel: Substrates may be processed in order of equipment belonging to the groups "Clean" -> "Semi-Clean" -> "Gold-Contaminated“ without process review. However, substrates run in semiclean equipment are then considered semiclean, even if no metalss are on the wafer. Likewise, wafers run in gold-contaminated equipment are then considered gold-contaminated. But there are two standard exceptions, as follows.
Depending on the materials and processes involved, some substrates can be decontaminated so that they can, for example, travel from "semiclean" equipment to "clean" equipment. Refer to the Lab User Guide and Policies for documented procedures. Submit a ProM request for a new process.
All Equipment Group
Some equipment, generally, most analytical and litho tools, belong to all three categories. While it's not really true that there is no cross-contamination at these stations, the standard required resist and pre-deposition/furnace cleans minimize the risk of cross-contamination at the process steps that really matter.