Sapphire Wafer Sorter

Device for automatic measurement and subsequent sorting of crystal orientation and warp&bow of sapphire wafers

This new device measures and sorts C- and R-oriented sapphire wafers, which are deposited in cassettes or loaded manually. Wafer sizes can range from 2" to 8". Cassettes are standard type.

After measurement, a wafer may be put back to the location from where it was taken or it can be put in a free slot in another cassette. The processing of one or more cassettes can be arranged in advance so that after start the remaining procedures run automatically. The bar code read from the cassettes may be used for flow control of single wafers or whole batches. Depending on size, up to five cassettes can be loaded for processing.

Determination of the crystal orientation is performed with the omega-scan method. It gives high-precision orientation results even for large misorientations (~2°). During an omega-scan, the turntable, on which the wafer is placed, is rotated at constant speed. One rotation (scan) takes about 5 seconds. If several scans are overlayed for better measurement statistics the overall processing time is longer by the relatively short overtime it takes for the extra rotations.

The present machine setup is for C- and R-oriented sapphire wafers only. However, in principle, the method can be extended to cover A- and M-wafer orientations.

Synchronously to the x-ray measurements a laser optical determination of the surface normal is performed. Crystal orientation values are usually reference to the surface normal.

The position of the wafer mark (flat or notch) is determined optically. This is achieved with a camera taking images of the wafer during the other measurements. After real-time image analysis the deviation of the mark from its target value is available and is journaled together with the other measurement results.

A special feature of the machine is the warp&bow determination of the wafer surface. For that purpose a line laser is used. The projection of the line laser on the wafer is measured during rotations of the measurement turntable. As a primary result the 3D-topology of the wafer surface is calculated. In sorting applications, limiting values for bow&warp can be used in the selection strategy.

Machine Features

• C-/R-sapphire wafers 2"-8"
• Manual wafer measurement
• Automatic processing after customizable program scheme
• 1-3 Standard cassettes per slide; max. 3 loading slides
• Integrated bar code reader
• Principle(Orientation): Omega-scan and surface normal laser measurement
• Principle(Bow&warp): linie laser measurement
• Principle(Marks): illumination bar and optical imaging/processing
• Typical cycle time per wafer 1'15"
  
• Typical precision of crystal orientation 0.01°
• Typical precision of bow&warp 10micrometers
• Typical precision of mark position 0.1°

Machine Specifications

• Radiation full-protection device
• X-ray generator max. 1.2 kW
• X-ray tube, Cu anode, max. 1.5 kW
• Modern control computer with monitor
• Control software with intuitive GUI
• Diode light bar and optial camera for imaging
• Integrated linie laser sensor/module
• Dimensions 1700 x 880 x 2050 mm
• Weight 350 kg
• Power supply 230 V / 50 Hz
• Max. power consumption 2.5 kW
• Cooling water (~20°C, 4l/Min, ~0,3MPa)
• Pressured air (0,6-0,8MPa, dry, oil-free)

Measuring unit and two slides on the transport tacks.

Illuminated wafer in measuring position.

Linie laser for bow&warp determination.

Graphical display of the 3D wafer surface.

Total view of the machine .

Weitere Informationen:

• Prospectus of the wafer sorter