Trap Induction and Breakdown Mechanism in SiO2 Films

Abstract

Dielectric breakdown in SiO, films is derived from trap filling of clusters of large density of deep neutral electron traps within the interface regions of the films. The real existence of such clusters is supported by some well known experimental results about microdefects, interface region trap densities, and hopping current measurements in SiO, films. The supposed mechanism of dielectric breakdown starts with electron injection via tunnel or hopping transitions from the negative electrode into these clusters. There the trapped charge causes local internal fields which may be large enough to induce further traps. If trap induction by the local field exceeds a critical value it increases avalanche like so that local current densities pass over to the final phase of thermal breakdown. As a proof the theory derived can explain the increase of breakdown field strength with decreasing film thickness as a direct consequence. Der dielektrische Durchbruch in Si0,-Schichten wird aus der Fiillung von Clustern hoher Dichte tiefer, neutraler Elektronenhaftstellen in den Randzonen der Schichten hergeleitet. Das reale Vorhandensein solcher Cluster wird durch einige bekannte experimentelle Ergebnisse iiber Mikrodefekte, Trapdichten in Randzonen und Hoppingstrom-Messungen in Si0,-Schichten gestiitzt. Der angenommene Mechanismus des dielektrischen Durchbruchs wird durch Elektroneninjektion auf dem Wege von Tunnel-oder Hoppingiibergangen von der negativen Elektrode in diese Cluster eingeleitet. Dort fiihrt die getrappte Ladung zu lokalen inneren Feldern, die stark genug sein konnen um weitere Haftstellen zu induzieren. Wenn diese Induktion von Haftstellen durch das lokale Feld einen kritischen Wert iibersteigt, wachst sie lawinenartig an, so da13 die lokalen Stromdichten in die Endphase des thermischen Durchbruchs iibergehen. Als Priifung ihrer Tragfahigkeit kann die entwickelte Theorie die Zunahme der Durchbruchfeldstarke mit abnehmender Schichtdicke als direkte Konsequenz erklaren.

Degradation and Breakdown of Gate Oxides in VLSI Devices

“…The first one, developed by Harari [5, GI, postulates that the breakdown is due to the progressive accumulation of negative charge in the oxide bulk that increases the anode field until a critical value is reached. The critical anode field is high enough to break Si-0 bonds, create new traps [ 7 ] , and trigger the final runaway process. The second one, presented by Hu and co-workers [8 to 101, proposes a positive feedback mechanism of local enhancement of the cathode field.…”

High-Frequency Capacitor with Working Substance "Insulator-Undoped Silicon-Insulator"

“…The electrical voltage of the external field on the whole structure should not exceed breakdown field voltage of silicon dioxide (SiO 2 ) U bd , where U bd is the experimentally measured threshold breakdown voltage of SiO 2 of thickness L ox . Thus, the voltage U must satisfy the condition U < U bd , where U bd ≈ 0.4-1 kV for silicon dioxide of thickness L ox = = 1 µm at a stationary external breakdown electric field strength E bd = 4-10 MV/cm [29][30][31].…”