Quantitative Depth Profiling of B and P in Borophosphosilicate Glass

Borophosphosilicate glass (BPSG) is used in the semiconductor industry for two purposes: (1) as a top passivation layer on electronic devices and (2) as an intermetal dielectric (typically between aluminum and polysilicon) [1,2]. The advantages of BPSG over undoped Si0₂ is its ability to reflow within device-compatible temperature ranges [3,4] and its formation of better aluminum contact step coverage [5]. In addition, the presence of phosphorus in the passivation layer serves to getter impurities and minimizes the penetration of alkali metals into the device [6]. Although these advantages are significant, the high P concentration in BPSG, coupled with its high porosity and hygroscopicity (related to P contents), is a major cause of corrosion of aluminum runs in devices [7,8]. As a consequence, it is necessary to have a thin phosphorus free glass layer between the BPSG and A1.