KX240Ge · Czochralski crystal puller
Germanium Crystal Growth Furnace KX240Ge
The KX240Ge is a germanium crystal growth furnace that grows Ge single crystals up to 12 inch in diameter by the Czochralski method, with a dedicated germanium hot zone, a 450 kg charge capacity and a camera-based vision system for pulling.
Where does the KX240Ge sit in a germanium wafer and blank line?
The germanium crystal growth furnace is the first machine in the chain. It turns high-purity germanium feedstock into a single-crystal ingot. Everything downstream, from cropping to polishing, works on what this furnace produces, so crystal diameter, length and quality set the limits for the rest of the line.
After growth, the ingot is cropped to length, then sliced into wafers or blanks on our SOM multi-wire saws. For thicker optical blanks, see our notes on germanium blank cutting. Because we supply both the crystal puller and the slicing and finishing equipment, ingot size and wafer format can be planned together from the start.
How does a Czochralski furnace grow a 12-inch germanium crystal?
In the Czochralski process, germanium is melted in a crucible inside a sealed, argon-purged chamber. Germanium melts at about 938 °C, far below silicon, so the thermal design of the hot zone is different from a silicon puller.
A seed crystal on the seed lift is brought into contact with the melt surface. The seed is then raised slowly while seed and crucible rotate. Melt freezes onto the seed with the same crystal orientation, and the crystal grows in length as it is pulled.
The diameter is set by the balance between pull speed and melt temperature. The furnace widens the crystal in the shoulder stage, holds it constant through the body, and then tapers it at the end. The crucible lift raises the crucible as the melt level drops, so the growth interface stays in the same position relative to the heaters.
For a broader look at the stages and temperature control, see how a crystal growing furnace works.
What makes the hot zone specific to germanium?
A silicon puller cannot simply be run at a lower setpoint. A germanium crystal growth furnace needs a hot zone configured for germanium from the start, and that is how the KX240Ge is built.
Dedicated 26-inch Ge hot zone
A 26-inch germanium hot zone with a graphite crucible, sized together with the 1,100 mm main chamber, gives room for the charge needed to grow large-diameter Ge crystals.
Purge tube for 330 mm crystals
The argon purge tube is sized for crystals up to 330 mm across. It guides argon flow over the growth interface. Argon flow is adjustable from 4 to 200 slpm.
Main and bottom heaters
A main heater and a bottom heater shape the thermal field together. The main heater is rated at 150 kW peak and 50 kW continuous, and the bottom heater at 50 kW peak and 20 kW continuous. Heat from below as well as from the side gives more control over temperature distribution in the melt.
±0.5 °C temperature control
Stable melt temperature is what keeps the diameter steady and limits defects. The control system holds temperature to within ±0.5 °C, with vacuum down to 25 mtorr and a leak rate specification of 50 mtorr/hr for a clean growth atmosphere.
How is diameter held steady over a full-length pull?
The KX240Ge is equipped with a mature camera-based vision system. The operator can run crystal pulling from the camera view, and the system measures diameter with a resolution of about ±0.05 mm.
The measured diameter feeds back into pull speed and temperature control. According to our specification, diameter control accuracy is:
| Stage | Diameter control accuracy |
|---|---|
| Shoulder (crown) | ±6 mm |
| Body, full length | ±2.5 mm |
| Body, per 100 mm length | ±1 mm |
A tight body diameter means less material is ground away before slicing, which matters for an expensive material like germanium.
Seed and crucible motion
Long, large-diameter germanium crystals need long, smooth travel on both axes. The seed lift has a maximum travel of 5,655 mm with a 3.0 m receiving chamber. Seed and crucible are driven independently:
| Axis | Travel | Lift speed | Rotation |
|---|---|---|---|
| Seed lift | 5,655 mm max | 0–600 mm/hr | 0–30 rpm |
| Crucible lift | 650 mm | 0–127 mm/hr | 0–30 rpm |
The crucible lift carries a load of up to 500 kg, which covers the 450 kg charge plus crucible and fixtures.
Who uses a germanium crystal growth furnace?
Single-crystal germanium is used where its infrared transmission or its electronic properties matter. Typical KX240Ge users include:
Infrared optics makers
Germanium is a standard material for thermal-imaging lenses and windows. Large-diameter crystals allow larger optical blanks.
Substrate producers
Germanium wafers are used as substrates, for example for multi-junction solar cells used in space applications.
Detector and electronics makers
Germanium is also used in radiation detectors and specialty semiconductor devices.
Research institutes
Labs developing Ge-based materials and processes that need their own crystal growth capacity.
For how germanium compares with silicon, GaAs and other materials in furnace design, read our guide to crystal growing furnace materials.
Technical specifications
Key data of the KX240Ge germanium crystal growth furnace. Figures are from our specification.
| Item | KX240Ge |
|---|---|
| Growth method | Czochralski (CZ) |
| Max crystal diameter | 12 inch |
| Charge capacity | 450 kg |
| Main chamber inner diameter | Φ1,100 mm |
| Hot zone | 26-inch germanium hot zone, graphite crucible |
| Purge tube | For crystals up to 330 mm |
| Receiving chamber height | 3.0 m |
| Main heater power | 150 kW peak / 50 kW continuous |
| Bottom heater power | 50 kW peak / 20 kW continuous |
| Seed lift | 5,655 mm max travel; 0–600 mm/hr; 0–30 rpm |
| Crucible lift | 650 mm travel; 0–127 mm/hr; 0–30 rpm; 500 kg load |
| Temperature control | ±0.5 °C |
| Diameter measurement resolution | approx. ±0.05 mm |
| Diameter control | Shoulder ±6 mm; body ±2.5 mm full length, ±1 mm per 100 mm |
| Vision system | Camera-based; pulling from camera view |
| Ultimate vacuum | 25 mtorr |
| Leak rate | 50 mtorr/hr |
| Argon flow | 4–200 slpm |
| Machine weight | 6,062 kg |
| Noise | < 70 dB |
| Growth rate, throughput, crystal quality | Contact us with your target crystal |
KX240Ge or another crystal puller: which fits your material?
Each furnace in our range is built around one material. Choose by what you grow:
| Model | Material | Method | Key figure |
|---|---|---|---|
| KX240Ge | Germanium | Czochralski | Up to 12 inch, 450 kg charge |
| KX360MCZ | IC-grade silicon | MCZ (horizontal superconducting magnet) | 12 inch (300 mm) |
| CCz-1600 | Silicon | Continuous Czochralski | 1,000 kg charge, up to 10 inch |
| KY-125 | Sapphire | Kyropoulos | 125 ± 25 kg crystal |
If you grow silicon, the KX240Ge is not the right machine: go to one of the silicon pullers above. See the full crystal growing furnace range, or browse germanium growth furnaces.
Utilities, installation and safety
Power supply, cooling water, argon supply and site requirements depend on your plant. They are confirmed with your order. Please ask us for a site-preparation list.
The KX240Ge is CE certified.
Warranty and after-sales support
Every KX240Ge germanium crystal growth furnace comes with a 1-year warranty. Our engineers respond to service requests within 12 hours.
See the KX240Ge in operation
Questions we get on the KX240Ge
What is the largest germanium crystal the KX240Ge can grow?
Up to 12 inch in diameter, from a charge of up to 450 kg.
Can the KX240Ge also grow silicon?
The KX240Ge is configured with a germanium hot zone. For silicon, we recommend the KX360MCZ or CCz-1600.
Which growth method does it use?
The Czochralski (CZ) method: a seed crystal is pulled from the germanium melt while seed and crucible rotate.
How does the operator monitor the pull?
Through a camera-based vision system. Crystal pulling can be run from the camera view, and diameter is measured with a resolution of about ±0.05 mm.
What are the power and utility requirements?
They are confirmed with each order according to your site. Contact us for a site-preparation list.
Planning a germanium crystal growth line?
Send us your target crystal diameter, length and annual output for the germanium crystal growth furnace. We will reply with a KX240Ge configuration and, if you need it, a matching cropping, slicing and polishing line.
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