Leakage and Breakdown Mechanisms of Cu Comb Capacitors with Bilayer-Structured α-SiCN/α-SiC Cu-Cap Barriers

Abstract

This work investigates the leakage and breakdown mechanisms in copper ͑Cu͒ comb capacitors with carbon-doped low-k plasmaenhanced chemical vapor deposited organosilicate glass ͑OSG; k ϭ 3) as the intermetal dielectric and an ␣-SiCN (k ϭ 5)/␣-SiC (k ϭ 4) bilayer-structured dielectric film as the Cu-cap barrier. The leakage mechanism between Cu lines is dependent on the thickness ratio of the ␣-SiCN/␣-SiC bilayer barrier. Using an ␣-SiCN/␣-SiC bilayer barrier of 40 nm/10 nm or 30 nm/20 nm bilayer thickness, the increased leakage current ͑Frenkel-Poole emission͒ between Cu lines is attributed to the large number of interfacial defects, such as cracks, voids, traps or dangling bonds at the ␣-SiC/OSG interface, which are generated by the larger tensile force of the thicker ␣-SiC film. The Cu comb capacitor with an ␣-SiCN ͑50 nm͒/␣-SiC ͑2 nm͒ bilayer barrier exhibits a much smaller leakage current. The breakdown field and time-dependent dielectric breakdown lifetime of the Cu comb capacitor reveal little dependence on the thickness ratio of the ␣-SiCN/␣-SiC bilayer barrier, and the observed breakdown of the Cu comb capacitor is presumably due to dielectric breakdown of the bulk OSG layer.As the interconnect resistance-capacitance ͑RC͒ delay becomes a dominant factor in determining the performance of integrated circuits, the advantages of Cu metal and low-k dielectrics become more remarkable. Cu metal reduces the electrical resistance of interconnection lines because of its low electrical resistivity; moreover, Cu line also exhibits a better electromigration resistance than the conventional Al-based wires. The use of low-k dielectrics in the interconnect system reduces the wire capacitance, signal-propagation delay, cross talk-noise between metal lines, and power dissipation of integrated circuits. While many low-k (k Ͻ 3) materials have been used as inter-and intralayer dielectrics ͑ILD͒, high-dielectricconstant (k Ͼ 7) silicon nitride is still the primary candidate for the Cu-cap barrier and etching stop layer ͑ESL͒ required in the Cu damascene structure. It is desirable to replace silicon nitride with dielectric materials of lower k-value (k Ͻ 5) in order to further reduce the effective dielectric constant of the Cu interconnect system. In recent years, amorphous silicon carbides ͑␣-SiC͒ and amorphous silicon-nitricarbide ͑␣-SiCN͒ deposited by plasma-enhanced chemical vapor deposition ͑PECVD͒ using organosilicate gases ͑OSG͒ are receiving extensive attention for applications as Cu-cap barriers and ESL in Cu interconnection schemes because of their lower k-value, better etching selectivity with OSG, robust chemical mechanical polishing ͑CMP͒ strength, good photoresist poisoning resistance, higher antireflective ability, and superior properties as a Cu barrier/passivation layer in terms of Cu restraint, electromigration resistance, and Cu-hillock density. 1-3 There are a number of studies on the electrical reliability of the ␣-SiC and ␣-SiCN films with respect to their integration with Cu using planar metalinsulator-se...

Model of dissipative dielectric elastomers

“…This process is known as current leakage, which is well documented in several insulator and semi-conductor systems. 17,[23][24][25][26][27] The occurrence of leakage current is a result of the transport of electrons, ions, or both, [23][24][25] and is often linked to the presence of impurities and imperfections. 23,24 In the simplest case, the leakage current density varies approximately linearly with the applied field for small electric fields (< 10 MV/m), known as the Ohmic conduction.…”

Time Dependent Dielectric Breakdown in Copper Low-k Interconnects: Mechanisms and Reliability Models

“…The effect of the top dielectric barrier layer on the leakage current and dielectric breakdown of Cu-organosilicate glass (OSG) comb capacitor test structures were compared in a series of articles [33,34,35]. In [35], silicon carbide (SiC) and silicon oxycarbide (SiOC) single barrier layers were compared by measuring the current field characteristic at different temperatures for the same OSG intra-level dielectric.…”

Integration of Low‐ k Dielectric Films in Damascene Processes

“…Therefore, the electromigration failure mode has probably more to do with the copper surface than with the presence of a low-k material in the dielectric stack. The composition of the dielectric barrier [218] in combination with pretreatments [219] (discussed in Section 5.2.2) can strongly enhance the reliability due to an improved adhesion. Alternative integration solutions, such as self-aligned metallic barriers, show extremely improved electromigration performance [220] and therefore potential to replace the conventional dielectric barriers (see paragraph 2.2.3.1).…”