Method for depositing polysilicon with discontinuous grain boundaries

摘要

A method for depositing a polysilicon layer on a substrate is provided. The method is performed in a LPCVD reaction chamber at a temperature of between 580° C. to 650° C. During the LPCVD process, at least two different silicon source gases, such as silane (SiH. sub.4), disilane (Si.sub.2 H.sub.6), trisilane (Si.sub.3 H.sub.8) or dichlorosilane (SiH.sub.2 Cl.sub.2) are absorbed onto the substrate to form random surface conditions. This grows the polysilicon layer with grain boundaries that are discontinuous and randomly oriented. The different silicon source gases can be injected into the reaction chamber at the same time or separately. In addition, a dopant gas such as phosphine (PH.sub.3), arsine (AsH.sub.3) or diborane (B.sub.2 H.sub.6) can also be injected into the reaction chamber to dope the polysilicon layer in situ.