Rapid Thermal Annealing

Question 1

What is RTP/RTA used for?

Answer 1

Implant annealing, oxidation, CVD, epitaxial growth.

Question 2

What are the main objectives of RTA?

Answer 2

Heating and cooling the wafer uniformly, and measuring the temperature

Question 3

Which three classes can RTA be devided into?

Answer 3

Adiabatic, thermal flux and isothermal RTA

Question 4

Why is quartz used to rest wafers on during RTA?

Answer 4

Because of its chemical stability and low thermal conductivity

Question 5

Name the four types of heat transfer central to SC processing.

Answer 5

• Conduction (diffusion of heat through solid or gas)
• Convection
• Forced flow (caused by an externally applied pressure gradient)
• Radiation (Planck’s radiation law ~ T⁴ (dominant at high T))

Question 6

What is a typical exposure time and temperature for RTA?

Answer 6

2-60s and 600-1200ᵒC

Question 7

Name different methods for measuring the temperature of the wafer during RTA

Answer 7

• Pyrometer (measuring radiant energy assuming known emissivity)
• Thermal expansion (interferometer from gratings on wafer surface or measuring wafer thickness)
• Acoustic temperature measurement (velocity of sound in SI is linear as a function of wafer temperature)
• Low temp (<600ᵒC): Bandgap measurements