Serious Overburning of Epitaxial Dislocation
Epitaxial dislocation is a common issue for semiconductor devices which involves a defect in the growth of epitaxial material/film onto a wafer or other substrate. This defect can occur during either the growth or etching process of the epitaxial layer. It is characterized by an abrupt change in the electrical properties of the interface between two adjacent layers such as a metal and dielectric layer. The defect is usually caused by a mismatch in the crystalline structures of the two materials; it can also be caused by a lack of crystalline order in the growth of the material.
Epitaxial dislocation can cause several problems in several areas, including electrical and mechanical properties, dielectric breakdown, and thermal performance. This problem is often the result of an imbalance between the atoms that form the crystallites in the epitaxial material. While some dislocation types are harmless and can be negated by high-temperature processing, other types of dislocation can result in catastrophic failure and ultimately, short circuits or device and package failure.
One of the most noteworthy causes of epitaxial dislocation is serious overburning of the epitaxial layer. Overburning occurs when a growth process of the epitaxial layer is too active and results in a surface that is highly defective. This overburning causes significant structural damage to the atoms in the epitaxial material, resulting in a highly disordered structure instead of a single crystal. This disordered structure is usually characterized by misaligned or missing lattice planes, leading to the development of interstitials and vacancies within the material.
To avoid this issue, the epitaxial growth process should be carefully monitored and adjusted to ensure that it is not too active and that the temperatures used are appropriate. Operators also need to be aware of the fact that different materials have different limitations when exposed to high temperatures. Once an overburning process has occurred, the effectiveness of subsequent repair and/or correction process is significantly reduced. To repair the material properly, the epi layer needs to be completely stripped, and the underlying layers need to be etched away to reduce the number of interstitials left in the material.
Epitaxial dislocation, caused by serious overburning, is the source of numerous issues and defects in microelectronic devices. It is essential to be aware of what can cause this issue and to be able to identify it quickly in order to take corrective action. By understanding the underlying cause and being able to adjust the process accordingly, manufacturers and designers can avoid this issue and reduce device failure and scrap.
