Defect‐Guarded Rapid Thermal Processing

Abstract

Pattern‐induced thermal nonuniformities, arising during rapid thermal processing, are not radially symmetric. So the pattern‐induced part of the thermal nonuniformities cannot be reduced by conventional methods such as multiple bank control, circular lamp arrangement, or wafer rotation. A new approach to the reduction of the transient thermal nonuniformities is described. The approach utilizes a digital control of the heating power in addition to the pyrometer control. The power absorbed by the wafer in any time period of processing can be controlled, limited, or ramped according to a defined recipe. Independent top and bottom heater bank control enables step by step changeable asymmetrical heating. These features allow better process design by reduction of any transient nonuniformities, especially during heating up. The additional power control, together with a new back‐radiant silicon ring design allows defect‐guarded processing.