X-ray diffractometer DSO-2H

Scientific Instruments

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X-ray diffractometer DSO-2H for the Specification of Silicon Ingots Orientation

X-ray diffractometer DSO-2H (fig.1) is intended for the automatic orientation measurement of big silicon single crystals, for the semi-automatic mesurement of geometric and crystallography axes misorientation, and for the manual searching of a primary flat orientation. The method of measurement is based on the analysis of reflections from a motionless crystal during the X-ray goniometer rotation, which includes a micropower X-ray source. A spatial orientation of crystal surface is specified by a laser triangulation sensor.

Fig.1. General view of DSO-2H.

Specification.

Dimensions	1400x700x1750 (height) mm
Weight	< 150 kg
Power feeding	220 V 50 Hz
Power consumption	250 W
X-ray generator power	10 W
X-ray tube	0.01BS18 – Cu
X-ray tube cooling	forced air
High voltage	25 kV
X-ray tube current	0.4 mA
Silicon orientations	100, 111, 110, 211
Diffraction angle range	30 - 57°
Crystal weight	up to 60 kg
Sample diameter	78 - 250 mm
Sample length	150 - 800 mm
Inclination range	7.5°
Measurement error for the surface or axis	± 2 arc min.
Measurement error for the primary flat	± 3 arc min.
Scintillation counter	entrance window diameter 24 mm, count rate 6x10⁵ cps
Measurement cycle duration	3 – 6 min.
Software	Radicon Device Programming Workbench (RDPW)
Radiation protection	less than 1 mSv/h (diffractometer is fully exempted from radiation inspection and registration)

Optical diagram and construction

The optical scheme of diffractometer is represented in fig.2

Рис.2. X-ray optical diagram of DSO-2H.

A cut angle orientation measurement of silicon crystals is realized by using the symmetric reflections from an ingot cut surface (fig.2). Collimator and the X-ray tube 0.01BS18Cu are mounted on a common carriage, forming a radiation monoblock XRB. The search of reflection is realized by means of scanning XRB close to the expected angle in the range up to ±7.5°. Simultaneousely a laser sensor measures a distance to the crystal surface. A reflection position is defined as the сhord center on a half maximum level. Then goniometer rotates to Phi = 90° and a reflection search is repeated. The control program records the second distance value from laser sensor. The same search is repeated on Phi = 180° and 270°. The software processes the results and outputs them to PC interface and several files (Log, Data, Inf).

Specification of crystallographic axis orientation according to geometric one is realized by a XRB scanning in two positions of Phi goniometer (0 и 180°) for three Phi angle positions of a crystal according to its geometric axis (0, 90 and 180°).

The search of a primary flat direction [110] or [100] on calibrated ingots is realized, when Theta-Theta goniometer is set in a vertical position, and XRB and detector are set in the position for measuring the reflections 440 or 400 by a definite program. The ingot on a special carriage is arranged sideways to goniometer (manually, using a rotary table). Then operator rotates a crystal manually on the carriage (on the special rollers) around a geometrical axis till a reflection will be found. Then he makes a special mark by means of a T-square or a special stencil.

The orientation definition of an executed primary flat or the testing of square cut ingots is realized similar to specification of a crystal butt-end orientation with a difference, that Theta-Theta goniometer is arranged in a vertical position.

Fig.3. General view of Theta-Theta-Phi goniometer with removed elements of the protection housing.

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