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Case Study 1: Qualification after preventive maintenance (PM) routine
Process engineers, in a customer site, have used plasma fingerprinting to detect post-PM catastrophic fails, such as failures induced by changes to hardware or recipe configurations, or by the use of defective parts. Standard post-PM qualification checks, performed on test wafers, may not always pick up these problems. The possibility of significant yield loss exists unless these problems are discovered in some way before electrical test or sort. Since the ImPrint software compares the current post-PM fingerprint to archived post-PM fingerprints, its use means greater sensitivity to hardware and software configurations, and therefore the ability to isolate major post-PM problems.
Following any PM, engineers compare a post-PM fingerprint to its baseline. This method has the capability of finding the installation of, for example, an incorrect focus ring that will impact device yield through increased defect density because of increased particles. The conservative estimate of savings for this type of fail ~$9,000/chamber/quarter.
Case Study 2: Process chamber fault classification
Engineers at a customer site were experiencing etch rate fail problems on an etch tool during standard production runs. Instead of relying on best known methods (i.e., checking all tool parameters that affect etch rate, including etch gas flow, the RF generator, the match unit, pressure, and spacing), Straatum used fingerprinting to an established baseline. Trends in some of the RF parameters pointed toward a change in pressure. In this case, the engineer was quickly able to determine that a pressure manometer was defective. Looking at improvement in mean time to repair this fault, savings were conservatively estimated at ~$10,000/chamber/quarter.
Case Study 3: Process chamber fault classification
Chamber-to-chamber differences are a common problem in many fabs. In a leading foundry one particular chamber difference manifested itself as an "RF abort" fail during a process etch step on a Lam Research 4520Xle chamber. The problem meant that this tool would frequently abort during production, resulting in manual interjection and scrapping of a product wafer. This fault often occurred several times a day.
Engineers generated an impedance fingerprint of the problem chamber and three other similar chambers in the fab, generating real, imaginary, and vector impedance values for a standard production process recipe. The problem chamber showed lower impedance relative to the others, meaning the match unit experienced sporadic problems in tuning to this impedance - thus the RF aborts
With impedance identified as the problem, process engineers used chamber matching to determine the plasma-less impedance of each chamber. Noting a similar large difference, this indicated that the problem was hardware, not plasma or chemistry.
Next, they examined the circuitry and design of the problem chamber, quickly finding (in a few hours) that the impedance difference was likely due to a fault in an input filter board on the power delivery line. Once this board was replaced, chamber impedance of the problem chamber was much closer to the line average and the RF abort problem disappeared.
For this specific example of chamber matching, the customer conservatively estimates savings/chamber/quarter of more than $2,000.
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Straatum Launches Imprint MX3 with
Multiple Advanced Sensors, Portable Fault Libraries &
Real-time, Yield Enhancing FDC for Chipmakers
Read more
Irish Software Association
Honors Straatum with Technical
Innovation Award
for Imprint MX2
Read more
Straatum Launches Imprint MX2,
World’s First Truly Scalable Yield-Enhancing Real-Time
FDC System for Chipmakers
Read more
Straatum gets third round funding
from ACT, Intel, Vision
Read more
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