A circuit substrate includes a first terminal connected to a storage device, a second terminal to which voltage higher than voltage which is applied to the first terminal is applied, and a third terminal. In preferred embodiments, these methods are optimized for producing Group III-N compound semiconductor wafers and specifically for producing GaN wafers. Therefore, the scrambling apparatus is simplified, and the interference between scrambling signals is eliminated. Further, the second section can be torn off along the perforated line to reveal the information on the first section with minimal labor.