This system, available stand-alone or as an add-on to the basic COREMA - WT
setup, extends the analytic capability of the capacitive measurement to include
evaluation of carrier mobilities µ > 1000 cm2/Vs, in particular for
GaAs and InP. Because the full set of electric transport parameters is obtained,
the conventional Hall measurement is obsolete. Although intensively used for
many years, the classic Hall approach is hampered by destructive, time consuming
sample preparation, difficult ohmic contacting, slow measurement procedure and
complicated evaluation.
The patented COREMA - RM procedure is based on the magnetoresistance effect. The
magnetic field is generated by a specially designed arrangement of high
performance permanent magnets. The sample resistivity is measured with and
without magnetic field. The mobility is calculated from the difference of the
resistivity data.
Clearly this procedure is more demanding and also somewhat more time-consuming
than a single resistivity measurement. On the other hand, inquiries have
confirmed that topographic measurements of mobility with high lateral resolution
is not required. Therefore, automated wafer translation is not provided, but
measurement points may be chosen arbitrarily on the entire wafer area by manual
shifting. The total measurement time is essentially
determined by the time needed for manual wafer loading.
Again user-friendly, dedicated software supports the entire data acquisition,
evaluation and presentation procedure.
In
summary, COREMA - RM realizes a breakthrough in production-control oriented
wafer characterization technology. In addition to the advantage of
non-destructive evaluation of standard wafers, order-of-magnitude improvements
with respect to cost, measurement speed, reproducibility and lateral resolution
are achieved.
