Implicit modified enthalpy method with application to thin film melting

During the thermal processing of thin films in which low intensity line heat sources are used, extended processing times are often required to reach steady state (˜15 sec). In addition, the melting of the film may occur some time after processing has begun, and therefore there is no initial melting condition within the film. In such cases, computer simulations may become very time consuming, and the development of an efficient computational method which incorporates the initial formation of the melt during processing is necessary. A general technique was developed to accurately model two‐dimensional heat conduction in a multilayer film structure with one‐dimensional phase change in one of the thin films. These conditions frequently exist in thin film thermal processing when the thermal gradient through the thickness of the melting film can be considered negligible. The method involves an implicit formulation of the modified enthalpy method. The solid/liquid interface energy‐balance equation is taken into account which allows the exact location of the interface to be tracked within a control volume. A comparison is made between the explicit and implicit modified methods to test efficiency and accuracy. The implicit method is then applied to the zone‐melting recrystallization of a silicon thin film in a multilayer structure.