Southampton Nanofabrication Centre
Southampton Nanofabrication Centre
 

High temperature annealing is needed for a number of applications, including the repair of implantation damage, the densification of deposited insulators, the diffusion of dopants, for silicide formation etc. Anneals are usually done at a high temperature (900C or above) and in a nitrogen ambient. However, if a completely inert anneal is required, anneals can also be performed in an argon ambient. The most common anneal method uses a furnace at a high temperature and an anneal time of typically one hour. However, shorter anneals are often required to minimise dopant diffusion and in this case a rapid thermal annealer can be used.

Tempress Anneal Furnaces

For silicon and other clean processes, several anneal furnaces are available, including a 200mm anneal furnace and a 150mm anneal furnace. For general processes, a 150mm anneal furnace is available. These furnaces allow automated loading of up to 25 wafers in a quartz boat and provide oxidations at temperatures between 600 and 1150C. Temperature accuracy can be controlled to better than ±1C. For alloying of metal contacts, a low temperature anneal furnace is available which uses forming gas (a mixture of hydrogen and nitrogen). An alloy anneal is typically performed at 420C for about 15 minutes and has the dual functions of providing a low resistance ohmic contact and of hydrogen passivation of the interface between silicon dioxide and silicon.

Jipelec Jetfirst 200 Rapid Thermal Annealers

Where very thin silicon dioxide layers are required, rapid thermal annealing can be used. Rapid thermal oxidation is a technique that provides a short (typically 30 seconds) anneal at a high temperature using fast lamp heaters. Two Jipelec Jetfirst 200 rapid thermal annealers are available in the clean room, one for clean silicon processing and one for general use. Temperatures between 400 and 1200C can be reached and the anneal time can be varied from 5 seconds to 10 minutes, with a ramp-up rate of 150C/s. Absolute temperature can be controlled to within ±5C. Temperature is generally measured using a pyrometer, but a thermocouple can also be used.