4 TYPES AND ORIGINS OF TRANSIENT SI WAFER DEFORMATION WITH FURNACE INSERTION AND WITHDRAWAL

Several types of transient deformations (200-1000 mum) of silicon wafe rs, observed when the wafers are inserted into or withdrawn from a hot horizontal furnace, are shown to be due to small asymmetries (2-10 mu m) in the actual wafer shapes. Saddle-type deformation during the inse rtion process is categorized in two types along axes which are at righ t angles. The type of deformation depends on a small difference (asymm etry) between the extent of deformation in two crystallographically eq uivalent (100) directions with the same Young's modulus. During withdr awal, two kinds of bowl-type deformations (concave and convex) are obs erved. This is also due to small inherent deformations (asymmetry) in the original wafers.