Specific Process Knowledge/Thin film deposition/Deposition of Zinc: Difference between revisions
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*It is better to use a crucible rather than a W boat to heat small Zn pellets, as the pellets sometimes jumped out of the boat when they got hot. | *It is better to use a crucible rather than a W boat to heat small Zn pellets, as the pellets sometimes jumped out of the boat when they got hot. | ||
*Do the deposition in manual mode as the power level for evaporation was not consistent and the rate was not constant even at a constant power level. | *Do the deposition in manual mode as the power level for evaporation was not consistent and the rate was not constant even at a constant power level. | ||
*We needed about 12-13 % power on the Lesker Thermal evaporator to get Zn evaporation. It is best to soak for a long time(e.g., ramping and soaking for | *We needed about 12-13 % power on the Lesker Thermal evaporator to get Zn evaporation. It is best to soak for a long time(e.g., ramping and soaking for more than 5-8 minutes). | ||
*The thickness /rate measurement may not have been accurate as the crystal monitor looked irregularly coated after the deposition. | *The thickness /rate measurement may not have been accurate as the crystal monitor looked irregularly coated after the deposition. | ||
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When we asked other labs about Zn evaporation, they mostly said to try to avoid it and perhaps to try to cool the substrate. An employee at the UCSB Nanofabrication Facility had tried thermal evaporation of Zn and says that their chamber now has status as Zn contaminated, but they have had no user complaints and it is now a long time since they did the deposition. Their chamber is mostly used for III-V materials. They used wires of Zn rather than pellets. | When we asked other labs about Zn evaporation, they mostly said to try to avoid it and perhaps to try to cool the substrate. An employee at the UCSB Nanofabrication Facility had tried thermal evaporation of Zn and says that their chamber now has status as Zn contaminated, but they have had no user complaints and it is now a long time since they did the deposition. Their chamber is mostly used for III-V materials. They used wires of Zn rather than pellets. | ||
More information can be found on the O-drive of the Thin film group under PVD/Thermal evaporator (for Danchip staff only). | More information can be found on the O-drive of the Thin film group under PVD/Thermal evaporator (for Danchip staff only). | ||
===Further lessons based on work by Chanju Kim=== | |||
''Depositions carried out in October 2018.'' | |||
Small Zn pellets (Lesker) were evaporated from an alumina crucible in Source 1 of the Lesker Thermal evaporator onto InP dummy substrates and InGaP substrates. | |||
It was possible to use an automatic program after some adjustments. A stable deposition rate of 0.5 Å/s was obtained with a max. power of 14.5 % after approx. 15 min of ramping and soaking. The final PID parameters were P 15, I 2 and D 1. | |||
It is important not to use too high power as this will give a very fast increase in the deposition rate once the evaporation is started. | |||
For new Zn pellets, an oxide removal run is recommended before the actual deposition. The max power needs to bel slightly adjusted for this run (slightly higher than for already-melted pellets). | |||
Frequently exchange the QCM crystal (quartz crystal monitor) which is used to measure the thickness of the deposited film. After about 1 micron accumulated deposition, the crystal severely underestimated the thickness, whereas a fresh sensor measured accurately (film thickness verified with Dektak profilometry). | |||