Problem tylanbpsg 2003-08-11 23:50:09: high leak rate and MFS alarm for LTO450P

rohits at rohits at
Mon Aug 11 11:50:09 PDT 2003

Measured a high leak rate of 54.2 mtorr/min (65.4-11.2) for this recipe. From the logbook, it appears that the previous user who ran this recipe right before me also got a high leak rate of 85 mtorr/min (96.2-11.2). The deposited film looked very uniform (<3% sigma intrawafer), though the dep rate was higher than expected. Flow rates and process pressure met targets SiH4=7.8sccm, O2=87 sccm. process pressure=250 mtorr.
 Also, there is an MFS alarm during step 115 (vent - backfill). The panel at the back reads PPC.PGNTLK. Previous users have also seen this problem. This is most probably due to the furnace attempting to maintain process pressure even when the gate valve is closed and tube vented. This could be prevented by inserting PRCPR=OFF and PRCPR=0 in one of the steps after the deposition is over.

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