| difference between the maximum value and the minimum value of a wafer thickness at each site of the wafer surface
Note 1 to entry: All sites existing within the FQA on the wafer surface possess their own LTV value.
Note 2 to entry: Measurement is performed on a clamped wafer with the reference plane as defined in IEV 561-07-27, Note 1 to entry, item 1. An example of the distribution of sites for measurement of the LTV is shown in Figure 1. The LTV is defined within each site, as illustrated in Figure 2.
Figure 1 – Example of the distribution of sites for measurement of the LTV
Figure 2 – LTV defined within each site on the wafer surface