IN-SITU OXIDE REMOVAL IN A LPCVD FURNACE SYSTEM
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-27
Several problems arise when working with polysili- con films in the fabrication of high density BiCMOS circuits, demonstrated in the attached figure. The first involves the contact made between the deposited polysili- con layer and the emitter opening in the NPN transistor. A native oxide exists on the single crystal surface and gets covered by the polysilicon deposit. This interfacial oxide film has several negative effects on the bipolar device performance. One is emitter contact resistance which will adversely effect the speed of the device. Another is the control of the electrical parameter, beta or current gain. By having the native oxide between the poly and single crystal surface, breakup of the oxide during subsequent heat treatments controls the uniformity of this parameter instead ofthe base and emitter dopant profiles.