Flash lamp & Pulsed laser annealing

The department has a long time experience in sub-second thermal annealing. It allows a fast heating up of solid surfaces on a time scale of nanoseconds (pulsed laser annealing) or within hundreds of microseconds to tens of milliseconds. Thereby, the achievable final temperature of the layer could be more than 2000 °C depending on the operation conditions and the optical and thermodynamic properties of the sample.

FLA Schema

Fig. 1: Basic Scheme of a FLA tool.

A typical tool for flash lamp annealing (FLA) is made by a chamber as shown in the Fig. 1 which can be flooded by an inert gas if needed. A bank of halogen lamps can preheat the wafer or another type of sample from the backside, whereas the flash itself is provided by a bank of Xe flash lamps from the front side. The reflector above the flash lamps directs the light toward the wafer and ensures a better homogeneity of irradiation. In order to protect the preheating and flash lamps they are separated from the wafer by suitable quartz windows.

PLA Schema

Fig. 2: Basic Scheme of a PLA tool.

In pulsed laser annealing (PLA) a XeCl excimer laser with a wavelength of 308 nm and a repetition rate of 10 Hz is guided onto the sample which can be moved underneath. Because of the short pulse time of 30 ns only a narrow region close to the surface is heated, whereas the backside stays at room temperature.

Main technical parameters

FLA PLA
pulse length

130 µs - 80 ms

30 ns

sample size up to 300 x 200 mm2

5 x 5 mm2 (spot size)

annealing gas

N2, Ar, O2, atmosphere

atmosphere

energy density / energy per pulse

up to 135 Jcm-2

up to 500 W per pulse

preheating

up to 900°C

no
handling mode

one flash one wafer

raster scan of the wafer

Benefits:

  • maximum temperature only at surface
  • allows temperature-sensitive substrates
  • defect annealing after implantation
  • allows dynamic physical processes like explosive crystallization
  • suppresses unwanted phenomena like diffusion or segregation
  • is energy saving and suitable for roll-to-roll applications

Applications:

  • activation of dopants and defect annealing in semiconductors and semiconductor nanostructures
  • hyperdoping, i.e. doping above the solubility limit
  • Bandgap engineering of Si or Ge, e.g. by Sn alloying
  • thermal treatment of wide bandgap materials
  • thin films on glass substrates
  • flexible and printed electronics

Projects

  • Humboldt Research Fellowship for Postdoctoral Researchers, Y. Berencén, 06/16 – 05/19
  • SAB project SiNERGY, 09/17 – 09/19
  • DFG project Dotierung mittels FLA and ALD, start 2018

Publications

  1. Subsecond annealing of advanced materials
    Skorupa and H. Schmidt (Ed.)
    Cham : Springer International Publishing, 2014
  2. A review of thermal processing in the subsecond range: semiconductors and beyond
    Rebohle, S. Prucnal, W. Skorupa
    Semiconductor Science and Technology 31(10), 103001 (2016)
    doi:10.1088/0268-1242/31/10/103001
  3. Millisecond thermal processing using flash lamps for the advancement of thin layers and functional coatings
    Skorupa, T. Schumann, L. Rebohle
    Surface & Coatings Technology 314 (2017) 169–176
  4. Doping by flash lamp annealing
    Prucnal, L. Rebohle, W. Skorupa
    Materials Science in Semiconductor Processing 62 (2017), 115-127