SURFACE systems + technology GmbH & Co. KG
SURFACE nanometrology
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Laser Heater for Substrates

Laser heater and temperature
Substrate in PLD chamber heated by laser heater to 1170°C with exceptional temperature stability
Click to play video

Key Features

  • Two options: Diode laser or CO2 laser
  • High temperatures not limited by process atmosphere
  • Better vacuum at high temperatures
  • Virtually any temperature ramp possible
  • Flash heating, flash recrystallization

High Power Diode Laser – The Perfect UHV Heater

Temperature is one of the most important physical parameters for the epitaxial growth of thin films. Generating high temperatures in UHV applications is always a compromise between the requirements of the process and the available heat sources suitable for these temperature and process conditions. For conventional heaters, the individual vapor pressures of the component materials of the heater add up and generate a partial pressure that could limit the achievable UHV conditions and deteriorate process quality. This problem even increases with temperature and with the demand for oxidation resistance of the heater material. In addition, the heat capacity of the heater assembly limits the heating/cooling rates. These conventional radiation heaters are available from SURFACE in different sizes – for substrates from 5×5 mm2 to 150×150 mm2 – and are suitable for up to 1000°C.

SURFACE has developed a laser heating system for substrate sizes of up to 15×15 mm2, using the latest available diode laser technology with powers from 100 W to 350 W, which avoids the problems of conventional heaters mentioned above. The laser heater modules offered by SURFACE are compact, highly flexible, and ready to use, shipped with all necessary components:

  • laser module with power supply and cooling
  • optical fiber and focusing optics
  • control unit for advanced laser processing
Block Diagram
Block Diagram
Click to enlarge

The infrared laser light is guided by a fiberoptic cable to the substrate. Laser spot position and size are adjustable to fit your needs. The laser power is controlled by an integrated feed-back loop using a high speed pyrometer.

Substrate Manipulator

For PLD applications, the laser heater is integrated into a SURFACE substrate manipulator with precision, backlash-free adjustments for rotation, tilt, and height of the substrate:

MotionRange
Rotation:±90°
Tilt:±3°
Height:2"

The substrate manipulator includes a thermocouple, mounted to the substrate shutter, to calibrate the setting of the pyrometer emission coefficient.

The Main Features of Diode Laser Heating

Temperature rates
Temperature rates
Click to enlarge
  • better vacuum at high substrate temperatures: 1200°C at 10-8 mbar
  • higher temperatures – regardless of the process pressure: 1300°C, 1400°C,…
  • virtually any temperature ramp possible – only limited by substrate and film material properties
  • flash heating of thin films
  • flash crystallization of amorphous thin films
  • only suitable for small substrate sizes if high temperatures are needed
  • higher cost compared to conventional heater technology (expensive diodes and advanced cooling required)
  • sample has to absorb laser wavelength

Advanced Processing: Cleaning, Heating, Annealing

Continuous (CW) mode

  • standard laser heating of small substrates in UHV applications – especially Laser MBE
  • post process annealing at any oxygen pressure
  • for in-situ cleaning of Si substrates to remove the native oxide layer
Si and laser heater
Silicon substrate
Click to enlarge

Pulsed mode

  • flash annealing of thin films, to recrystallize a film or to modify the grain size of such a film
  • annealing of small nano-/micro-structures without heating the underlying substrate

CO2 Laser Heater

Many commonly-used oxide substrate materials such as SrTiO3, Al2O3, or rare earth scandates are transparent in the near-infrared range. If backside coating is not acceptable because of its complications and limitations, CO2 laser heating may be a suitable alternative. In combination with a beam shaper/homogenizer, a “top hat” beam profile can be achievend that will result in a homogeneous temperature of the substrate, similar to the diode laser. SURFACE can deliver a modified laser heater assembly that integrates the necessary beam line components.

Features of CO2 Laser Heating

  • wavelength of 10.6 μm
  • suitable for most oxide substrates
  • high temperatures – regardless of the process pressure: >1500°C on a 10×10 mm substrate
  • virtually any temperature ramp possible – only limited by substrate and film material properties
  • not suitable for metallic substrates (metals are highly reflective for this wavelength)
  • special ZnSe laser windows needed

Please contact us for further information.

System Specifications (Diode Laser)

Laser: CW and pulsed up to 2 kHz
Wavelength: 940 nm
Output power: 100, 140, 350 W
Optical fiber: 600 μm Ø, 5 m long
Pyrometer: single or dual wavelength, range 1.2…1.8 μm, up to 10 kHz sample rate
Controller: real time operating system, TCP/IP interface, data logging

Product Photos

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Saturday, 2014-08-23  17:18