Mihaela Balseanu

Advanced metal and dielectric barrier cap films for Cu low k interconnects

Multi-layer SiN barrier film with high breakdown and low leakage is developed for Cu low k interconnects and is compared with the SiCNH barrier film used at previous technology nodes. Ultra-thin SiN barrier cap film also provides high conformality and fills recess in Cu lines observed post CMP. A significant enhancement in electro migration (EM) performance was obtained by selectively depositing Co on top of Cu lines followed by conformal multi-layer SiN barrier film. Further EM lifetime improvement is obtained by using a Co liner to form a wrap around structure with completely encapsulated Cu. An integrated in-situ preclean/ metal/dielectric cap chamber was used to avoid any oxidation of Cu/Co layers. Kinetic studies of CVD Co liner/Co cap samples show significant increase in EM activation energy (1.7 eV) over samples with dielectric only barrier film (0.9-1 eV). The complete wrap around structure with Co liner and Co cap shows improved device reliability.

A Self-Aligned Two-Step Reactive Ion Etching Process for Nanopatterning Magnetic Tunnel Junctions on 300 mm Wafers

We demonstrated a self-aligned two-step reactive ion etching (RIE) process to pattern high density magnetic tunnel junction (MTJ) arrays. We did the RIE for the top electrode (TE) and stop in the middle of the tunnel barrier. A nitride conformal film was coated on the device pillars as a dielectric spacer. The conformal spacer protects the tunnel barrier from shorting by redeposition and provides a mask for the bottom electrode (BE) RIE. We used this process and completed perpendicular MTJ devices with our process flow. We tested the devices by measuring magnetic field switching and spin transfer torque switching. We get tunneling magnetoresistance (TMR) up to 100%, switching current as low as 60 μA at 100 ns, switching current density Jc0 as low as 2.5 × 106 A/cm2 and endurance above 109 for devices as small as 50 nm in diameter. The results are compared with devices from a TE RIE only process, and we find minimum damage was made by the BE RIE. We also discuss the size dependence of MTJ parameters such as TMR and free layer coercive field and offset field, which is very related to the RIE process.

Novel Hardmask for Sub-20nm Copper/Low K Backend Dual Damascene Integration

As device nodes move below 20nm and increasing concerns for low k damage during plasma etch, alternative metal hardmask (HM) schemes have gained tractions for back-end-of-line (BEOL) integration. Conventional TiN hardmask has been in high volume manufacturing since the 90nm technology node, however, TiN faces many challenges, such as defectivity, line bending, and manufacturing robustness, which can only be overcome at the expense of shrinking the overall process window. A novel boron nitride (BN) based HM material was developed using a conventional CVD approach to address these issues.

Theoretical modeling on hydrogen evolution in ultraviolet light-treated hydrogenated silicon nitride

Ultraviolet light illumination is shown experimentally to be able to induce hydrogen evolution in hydrogenated amorphous silicon nitride (a-SixNyHz) film and the total hydrogen (H) removal percentage depends strongly on the composition with a maximum with balanced silicon-hydrogen and nitride-hydrogen single bonds (Si–H/N–H ratio equals to 1). We developed a general model for analyzing H removal in such alloyed glass system. Our statistical Monte Carlo models reveal that H2 evolution is the result of highly selective chemical reactions among nearest neighbor SiH and NH bonds in a-SiNxHy, which leads to formation of Si–N bonds. This process is sensitive to its local chemical environment. The nearest neighbor coordination number and the presence of SiH2 and NH2 groups in a-SixNyHz network have impact on the total H removal. Our model gives quantitative measures for all the corresponding reaction constants, consistent with experimental observations.

Post Deposition Ultraviolet Treatment of Silicon Nitride Dielectric: Modeling and Experiment

Simulation and FTIR analysis of the UV treatment impact on bond strengths of PECVD deposited silicon nitride films

Development, characterization and integration of a novel boron nitride process for application as a Cu diffusion barrier

The properties of boron nitride (BN) films cyclically-deposited by means of PECVD have been studied. Cyclical deposition is critical to improve the density and reduce the k of the material. When compared to conventional SiCN barriers, this material demonstrates greatly reduced leakage, superior mechanical properties and better etch selectivity. Therefore, BN is a promising candidate as a low k dielectric copper barrier and etch stop.