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Rapid Thermal Annealer (RTA)

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Technique

Thermal treatments for silicon technology are critically important.They are required for removal of crystalline defects during electrical activation of the dopant species. However, the thermal budget of the treatments also heavily affects the diffusion behaviour of the dopant atoms. Thus, the chance of performing anneals with controlled, reproducible, and uniform final temperature and process timing is of high importance. In the AS-Micro annealer, samples are heated in a reproducible and uniform way using a system of 6 halogen lamps that irradiate a quartz chamber. The temperature is read by a thermocouple inserted in the chamber and in thermal contact with the samples.

Most important features

The AS-Micro annealer uses an integrated PID system, to permit real-time adjustment to the power supplied to the lamps. This helps to give a regular and uniform ramp up rate from the starting temperature to the set point. In this way, the process temperature is reached with little or no overshoot. The heating system (halogen lamps) is engineered in order to achieve heating ramp rate up to 250 °C/s. A SiC coated graphite susceptor that holds the sample helps to achieve better uniformity of the final temperature across the whole surface of the treated material. The entire system is connected to a personal computer in order to create a library of treatment receipts and store the outcome of the processes in terms of power supplied and temperature of the material as a function of the process time. This permits an accurate evaluation of the thermal budget supplied to the material during the process.

Applications

The main function of the annealer is the thermal treatment of ion implanted material to anneal out implantation damage, re-grow the layer, and activate the dopant atoms. This is mainly considered for silicon and silicon based materials but it can also be used for Ge and III-V semiconductors. The usual set-up is under flowing nitrogen. However, the equipment can run anneals in oxidizing atmosphere so as to perform RTO (Rapid Thermal Oxidation). When requested, anneals can be performed under vacuum (down to 10-3 torr) or reducing atmosphere (N2/H2).

Instrument   at ITC-irst

Annealsys AS-Micro

Temperature Treatment

0-1200 °C

Ramp up rate to temperature

0-250 °C/s

Heating System

6 tubular halogen lamps

Temperature Control

Thermocouple and fast digital PID temperature controller

Process gas

Purge (N2) + 2 gas lines (N2 and H2   or O2)

Samples

From small specimen up to 2-inch wafers

Samples holders

- Quartz holder (2-inch wafers)
  - SiC coated graphite susceptor (smaller samples)

Other characteristics

- Possible to run process under vacuum
  - Full PC control