Bias Stress Induced Conduction Mechanism Evolution in Silica Based Inter-Metal Dielectrics
The real-time conduction mechanism evolution during bias stress of three silica based inter-metal dielectrics in Cu damascene structures was investigated. Capacitance measurements at 1 MHz and I-V measurements were intermittently inserted into the process of bias stress to monitor the conduction mechanism evolution with time. All experiments show that the capacitance is constant and the I-V curve slope decreases with bias stress and converges to the half of the initial value. Based on these findings, we conclude that the conduction mechanism changes from a normal Frenkel-Poole emission to an "abnormal" Frenkel-Poole emission with bias stress
Time-Dependent Dielectric-Constant Increase Reliability Issue for Low Dielectric-Constant Materials
The stability of low dielectric-constant (low-k) materials during electric-field stress was studied. The dielectric constants (k-values) were found to increase sharply under bias-temperature stress. This time-dependent dielectric-constant increase (TDDI) was estimated for a practical operating condition by extrapolation. The extrapolated TDDI lifetimes and k-value increases for tested materials (k = 2.3-3.2) ranged from 30 days to 1,000 years and from 0 to 23%, respectively. Considering the estimated TDDI, new criteria for reliable low-k materials are proposed. The criteria were used successfully to identify those low-k materials that show high stability during electric-field stress.
The Role of Nonclassroom Spaces in Living-Learning Communities.
A body of research suggests that learning communities provide a range of academic benefits by increasing social connectedness. Researchers have also hypothesized that informal learning spaces -- nonclassroom spaces (NCSs) -- can facilitate learning by supporting social connectedness. This study uses qualitative methods to explore the way nonclassroom spaces facilitate learning-related activities within a recently established learning community at State University. Our findings suggest that NCSs function as social hubs, help make intellectual and creative work visible to the larger learning community, and provide access to important resources. More generally, NCSs help to facilitate community formation and identity.