Liquid phase epitaxi (LPE)
Parc Sud Galaxie
1, rue des Tropiques - BP 344
38435 ECHIROLLES Cedex - France
Push rod translation mechanism and load lock

The configuration has the following features.

An heavy duty stainless steel glove-box and a load lock.
A double quartz tube reactor and a three or four zones (option) horizontal low inertia furnace.
Horizontal movements of the furnace and of the quartz tube reactor are either manual or motorized (option).
The slider displacement is actuated through a quartz push rod connected to a high precision translation stage .
........It is especially modified to avoid potential pollution of the glove-box by lubricants.
The vacuum station consists of a set of dry primary and turbo molecular pump. It is connected to the computer.
A high level gas purification system equipped with flow meters (N2 , H2 , other on request).
For safety an independent unit monitors hydrogen concentration in the glove-box and in the furnace hood.
........It is connected to an efficient interlock network.
In the unlikely event of a leak, the complete machine is flushed by the neutral gas and placed in a safe state.
The equipment is fully controlled by an industrial PC computer. It runs a dedicated LPE growth software.
.......The software has also a special module for tailoring thermal distribution and for testing important parts of the
....... machine.
Power stages of heaters are switching DC power supplies for minimum vibrations and improved stability.
Temperature controllers are high precision 2704 units from Eurotherm (one per heating zone). They can
........control the furnace in either the single loop mode or the cascade mode.
One overheating detector per zone.
A laser printer is provided for data for plotting.
The machine is also equipped with an uninterruptible power supply (UPS). In case of a power failure, provides enough power in order to place the equipment in a safe state.

For the II-IV crystals, Cyberstar also manufactures THM (traveling heater furnace), Bridgman furnace, annealing and rocking furnaces.

The LPE furnace
Pictures shown :

Top : The LPE furnace.
Bottom : Push rod translation mechanism and load lock.

Following our commitment to infrared materials production, Cyberstar has developed a Liquid Phase Epitaxy installation for II-VI crystals. It is mainly studied for deposition of device quality Cadmium Telluride, other II-VI binary and ternary compounds or other III-V compounds.  The process involves the popular graphite boat slider technique. The furnace is optimised for high stability and low thermal inertia and is able to heat up homogeneously the large graphite boat necessary for handling a 40 x 60 mm2 sample.


Standard blank graphite boats can be provided, for the following sample dimensions :
20 x 25 mm2 , 36 x 38 mm2 and 40 x 60 mm2 (other boats on request).


Glove-box, load lock
  heavy duty stainless steel (316L) construction,
  double access windows,
  flushed by the neutral gas : overpressure adjustable from 7 to 50 mbar,
  load lock equipped with a fully expendable drawer (outside and then inside).

  high purity quartz,
  external diameter 110 mm,
  cantilever geometry,
  boat supported by the very stiff internal tube (no flexion),
  well studied gas circulation for optimum uniformity around the boat,
  opens inside the glove-box,
  safe and easy to use : locking features on the flange,
  slides on a sturdy and clean translation (no lubricant).

Main flange - exhaust
  quartz tubes of the reactor are held on the main flange,
  for minimum dead corners and limited length of pipes connected, the turbo-molecular pump, the vacuum
........ gauges and valves are directly connected to the flange,
  water cooled,
  large ø 20 mm exhaust tube,
  water cooled mercury condenser and charcoal filter.

  Four zones low inertia furnace, controlled by three temperature controllers and three power stages (standard)
........ or four (option).
..... In the case of the three temperature controllers configuration, the two central zones of the furnace are connected
........ in series.
  Decreasing temperature speed (measured in the graphite boat) :
.....10 °C / minute at 600 °C,
.....5 °C / minute at 250 °C,
  Water cooled internal screens.

Horizontal translation of the push rod
  adjustable from 0.06 up to 60 mm/second,
  acceleration ramp,
  entirely stainless steel and aluminum alloy. It is lubricant tight to avoid, with mercury, the build-up of dangerous
........ chemicals.

Furnace and reactor translations
For fast cooling down of the graphite boat, the furnace can be translated. It is moved manually or by an electric motor (option).
The push rod translator is attached to the back flange of the reactor. This back flange opening gives access to the place where the graphite boat is located. When the back flange is opened, the complete push rod translator/quartz tube reactor ensemble is translated inside the glove-box.
This sturdy translation is manual and gives a complete access to the graphite boat for installation and removal. It can be controlled by an electric motor as an option.

Pumping station
  dry pump : 5.7 m3 /h
  typical ultimate vacuum : 7. 10-2 mbar
  turbo molecular pump : ISO 63 flange
  inlet pumping speed N2 : 65 l/s
..........................................H2 : 50 l/s
  ultimate vacuum : 10-6 mbar
  microprocessor controlled and connected to the PC computer.

Gas purification system
  two different gas channels N2 and H2 (other on request)
  output : oxygen content in the purified gas : better than 50 ppb for an input gas purity in the range of 1 ppm of O2
........ and/or H2O,
  maximum allowed input gas purity : 5 ppm
  flow meters on each channel : 5 normal liters per minute maximum (other range on request).

Hydrogen detectors
  hydrogen leak detector in the glove-box,
  hydrogen leak detector in the hood above the reactor and the furnace,
  hydrogen leak detector in the gas purification cabinet,
  these detectors are powered by a UPS in case of power failure.

Computer and software
  industrial PC computer,
  input/output cards and laser printer,
  software made of two main modules :
  the test module checks every unit operating the machine, motors, gauges, temperature controllers, safety
........ features, etc.
  the LPE software allows parametric drive of the multi zones furnace, the push rod, gas control, etc.
I.....IIt It is versatile enough to give the user any possibilities to adjust his process. It gives also a large information
........ storage capability.

Power modules and temperature controllers
  one power module per hot zone of the furnace : 3 kW – 50 V
  2704 Eurotherm temperature controllers and overheating detector : one set per channel,
  single loop mode or cascade mode,
  stability : ± 5. 10-5 of the reading per °C of the room temperature variation,
  resolution of the reading : ± 0.1 °C,
  worst case linearization error : < ± 0.2 °C.

Temperature probes
  three K type thermocouples per hot zone in the furnace :
- on the resistance : one measuring thermocouple and one for the overheating detector,
- inside the reactor : one thermocouple for the cascade mode,
  one Pt100 inside the graphite boat,
  temperature homogeneity along the full graphite boat : ± 0.5 °C worst case,
  extra K type thermocouples and inputs to the computer for temperature gradient uniformity measurements.



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