Method for monitoring the performance of an ion implanter using reusable wafers

Abstract

Low-mass implants, for example hydrogen and helium ions, are used in place of more typical dopants like boron, phosphorus, and arsenic for testing the performance of ion implanters. Consistency between ion implantation test runs with the low-mass ions may be used to provide information about the proper operation of ion implanters. Lower-mass ions do not transfer as much of their energy to the wafer as heavier ions. Consequently, high energy ion implantations with low-mass ions do not repair wafer surface damage to the same degree as ion implantations with high-mass ions. When sufficient surface damage exists, a thermawave tool can detect the damage and provide information about the performance of the ion implanter. This determination can be made in a one-step method. An additional advantage to implanting the test wafers with low-mass ions is being able to reuse the wafers for subsequent test runs. When low-mass implants are used (such as hydrogen and helium), a thermal anneal subsequent to the ion implantation can repair any damage to the crystal and at the same time dissociate the low-mass dopants from the silicon crystal. The crystal is returned in its original condition after the escape of the low-mass dopants. If reusability is the highest priority, silicon ions may be used as the test species. Implanted silicon ions can cause measurable damage to the surface of the wafer. A calibration state of the ion implanter may then be determined by examining the surface damage. A subsequent thermal anneal can repair the damage to the surface and return the crystal to its original state.

Dependencies are inferred from the claim text.