化学气相沉积分析.ppt

Hong Xiao, Ph. D. www2.austin.cc.tx.us/HongXiao/Book.htm CVD Oxide vs. Grown Oxide CVD Oxide vs. Grown Oxide Dielectric Thin Film Applications As a dielectric layer in multilevel metal interconnection Shallow trench isolation (STI) between transistors Sidewall spacer for salicide, LDD, and the source/drain diffusion buffer The passivation dielectric (PD) Dielectric ARC for feature size 0.25 mm Dielectric Thin Film Applications Inter layer dielectric, or ILD, include PMD and IMD Pre-metal dielectric: PMD normally PSG or BPSG Temperature limited by thermal budget Inter-metal dielectric: IMD USG Normally deposited around 400 ?C Dielectric Processes CVD CVD Applications CVD Figure 10.3 Deposition Process Deposition Process CVD Processes APCVD LPCVD PECVD Question A semiconductor manufacturer has its RD lab on the coast near sea level and one of its manufacturing fabs on a high altitude plateau. It was found that the APCVD processes developed in the RD lab couldn’t directly apply in that particular fab. Why? Answer On a high-altitude plateau, the atmospheric pressure is significantly lower than at sea level. Because earlier APCVD reactor didn’t have a pressure-control system, a process that worked fine in the RD lab at sea level might not work well in the high altitude fab because of pressure difference LPCVD System PECVD Step Coverage A measurement of the deposited film reproducing the slope of a step on the substrate surface One of the most important specifications Sidewall step coverage Bottom step coverage Conformality Overhang Step Coverage and Conformity Factors Affect Step Coverage Arriving angle of precursor Surface mobility of adsorbed precursor Arriving Angles Arriving Angle Corner A: 270?, corner C: 90? More precursors at corner A More deposition Form the overhang Overhang can cause voids or keyholes Void Formation Process Control of Arriving Angle Changing pressure Tapering opening Step Coverage, Pressure and Surface Mobility Arriving Angles, Contact