Aligning of large single crystals for processing

Processing large single crystals for wafer production is a key to success in the semiconductor and crystal  industry. During sawing and grinding, the control of the orientation ensures a good product quality.

Synthetic single crystals for industrial applications are often large and heavy and require special adaptations for sample holders and supports. The main purpose of XRD measurements on such materials is to identify and control the orientation of the crystal lattice during several work steps. Technical crystals are often cut into wafers, e.g. semiconductor crystals like Si, Ge, GaAs or SiC. The processing takes several steps of sawing and grinding, during which the crystals must to be aligned in the target orientation.

An example for an adjustable crystal holder is a device for stacking oriented ingots. Using an ingot stack instead of shorter single pieces helps to use the available sawing equipment more efficiently. After an Omega Scan the orientation of an ingot in the crystal holder is known. The software calculates the necessary adjustments to reach a given target orientation. The user is then presented with detailed instructions how to operate the adjustment screws of the equipment. Due to the quick measurement, a sequence of repeated orientation and controlling steps does not require too much time.

For some applications it is important to determine the orientation with respect to the actual surface. By measuring the inclination of this surface versus the rotation axis of the crystal, the Omega/Theta instrument can provide a correction for the error resulting from the surface misalignment.