A method of monitoring the temperature of a rapid thermal annealing (RTA) process and a test wafer for use in this process are disclosed. The method includes the step of forming a distorted surface region in a crystalline semiconductor wafer and the mounting of the wafer in a process chamber for performing the RTA process in a reaction gas containing ambient. The distorted surface region of the semiconductor wafer enables higher diffusion rates of reaction gas components into the wafer surface and therefore a higher growth rate of a reaction product film. The increase of the reaction product film thickness enables an increase of the film thickness measurement accuracy and thus the accuracy in determining the RTA temperature homogeneity. In one embodiment, a distorted surface region in a crystalline silicon test wafer is produced by implanting ions at low doses into a wafer substrate up to a pre-amorphization level of the surface crystalline lattice. As a low dose of heavy ions is sufficient for producing the distorted surface region, the test wafers are produced at low costs. Additionally, a method of reworking test wafers that have been used in an RTA monitoring method is presented. By reworking the test wafers and preparing for the next RTA-monitoring the wafer costs can be efficiently reduced.