A method of monitoring a temperature of a plurality of regions in a substrate during a deposition process, the monitoring of the temperature including: forming, in the monitored plurality of regions, a plurality of metal structures each with a different metal pattern density, where each metal pattern density corresponds to a threshold temperature at or above which metal voids and surface roughness are formed in the plurality of metal structures, and detecting metal voids and surface roughness in the plurality of metal structures to determine the temperature of the monitored plurality of regions.