Direct Relaxation Measurement

A key requirement in both compound and Si semiconductor analysis is the determination of the relaxation of individual layers within a multiple layer stack. The strain and composition of the layers are critical, as this sets the performance criteria. The Jordan Valley method, developed by Bede, is a unique method which has been adopted as the standard process for monitoring relaxation in production lines.

Traditional scanning methods

• Low, broad peaks for thin layers leading to inaccurate relaxation and composition determination
• Relaxation value needs to be assumed to obtain meaningful data
• Cannot separate individual layers from a multilayer stack
• Slow measurements
• Manual interpretation required

The method developed by Bede, and now used by Jordan Valley, determines the layer relaxation without assuming anything about the structure. It uses the knowledge of the out of plane lattice parameter (from the (004) symmetric scan) to directly probe the relaxation values by scanning across relaxation in reciprocal space. With this unique method, different layers with differing out of plane lattice parameters can be probed for either relaxation or composition without the influence of other peaks obscuring the peaks of interest.

The above example is the unambiguous automated measurement of the composition and relaxation of a SiGe layer on Si. The (004) scan determines the exact start and end points of the relaxation scan in reciprocal space. As can be seen from the relaxation scan, the value for the relaxation is read directly from the peak position, with no complex interpretation required. In this example the layer is fully strained with a composition of ~ 13% Ge.