Parshuram B. Zantye

Effect of Annealing on the Structural, Mechanical and Tribological Properties of Electroplated Cu Thin Films

The increasing demand for faster and more reliable integrated circuits (ICs) has promoted the integration of Copper-based metallization. Electroplated Cu films demonstrate a microstructural transition at room temperature, known as self annealing. In this paper we intend to investigate the annealing behavior of electroplated Cu films grown on a seed Cu layer on top of the barrier layers over a single crystal silicon substrate. All the samples were undergone through a multistep annealing process. Grazing incident x-ray diffraction pattern shows stronger x-ray reflections from Cu (111) and (220) planes but weaker reflections from (200), (311) and (222) planes in all the electroplated Cu samples. Transmission electron microscopy was performed on the cross section of the samples and the diffraction pattern showed the crystalline behavior of both seed layer and electroplated Cu. Nanoindentation was performed on all the samples using the continuous stiffness measurement (CSM) technique and it was found that the elastic modulus varies from 110 to 130 GPa while the hardness varies from 1 to 1.6 GPa depending on the annealing conditions. The tribological properties of all the copper films were also measured using the Bench Top CMP tester. Subsequently, Nanoindentation was performed on the samples after polishing the top surface in order to investigate the work hardening and an increase in hardness and modulus was observed. Finite Element Modeling was performed in order to investigate the stress behavior during nanoindentation.

Investigation of the nonuniformities in polyurethane chemical mechanical planarization pads

We have investigated the spatial variation of specific gravity (nonuniformities) in full size commercial pads for chemical mechanical polishing using a previously described nondestructive ultrasound transmission (UST) technique. After UST analysis, the different regions showing relatively higher and lower ultrasound permeability, which directly correlates with material density, were isolated and subjected to further evaluation of their mechanical properties using dynamic mechanical analysis (DMA) and tribological properties using a bench top chemical mechanical planarization (CMP) tester. Though the evaluated regions did not show significant variation in their tribological properties, presence of such regions in the body of the polishing pads has the potential to induce intermittent process defect during the CMP process.

Metrology and characterization of application specific chemical mechanical polishing pads

There is a need for metrology, characterization, and optimization of chemical mechanical polishing (CMP) pad architecture before being put into service. A polishing pad which is made up of polyolefin material instead of conventional polyurethane has been developed. The surface of the pad has been modified to match the hardness of the surface of the material that is being polished. In this research, we coated the pad with tetraethylorthosilicate using plasma enhanced chemical vapor deposition for varying durations of time for optimum pad output. The pad was then extensively characterized using the several standard metrology techniques such as scanning electron microscopy, x-ray photoelectron spectroscopy, nanoindentation, etc. The CMP performance evaluation of all the candidate pads along with in situ measurement of dynamic coefficients of friction, material removal rate, and acoustic emission was done using CETR CP-4™ bench top CMP tester. There was a correlation and interdependence of the pad coating tim...

Metrology of Psiloquest's Application Specific Pads (ASP) for CMP Applications

There is a need to develop a metrology metrics for evaluation of pad CMP performance before putting them in to service. This has been attempted on Psiloquests application specific pads (ASP) in which the pad surface is tuned to match the mechanical properties of the target substrate. The ASP is made up of thermoplastic foams co extruded with condensed polyolefin. The chemical and mechanical properties of the pad-wafer interface are tuned by coating the pad with ceramic thin films by surface coating method such as chemical vapor deposition (CVD). The surface of the pad is characterized using metrology techniques such as ultra sound reflectivity, XPS and nanoindentation. The cross section of the pads was characterized using SEM. The mechanical properties of bulk pad materials were studied using Dynamic Mechanical Analysis (DMA). A test was performed on the pads to measure the static coefficient of friction (COF) and wear rate. The pads were polished using CETR CP-4 bench top CMP tester to evaluate the dynamic COF, Acoustic Emission (AE) signal and removal rate during a simulated Tungsten CMP process. The thickness of the ceramic coating on the surface of the ASP played an important role in determining these tribological properties. The results of the various static and dynamic tests performed on the pad were cross tabulated to evaluate their correlation.

Polishing Behavior of the Various Interconnect Thin Films in Cu Damascene Process with Different Slurries

Chemical Mechanical Polishing is a key technology for Cu damascene wiring process in integrated circuit (IC) manufacturing. It is important to understand the effects of mechanical and tribological properties of the coatings that form a part of Cu damascene structure on the CMP process in order to successfully evaluate and implement these materials. In this paper, we present tribological properties of different interlayer coatings (SiLK TM , Ta and Cu) during their CMP process using different Cu and barrier selective slurries. A micro CMP tester was used to study the fundamental aspects of the CMP process. The coefficient of friction (COF) and acoustic emission (AE) signals were acquired in situ to monitor the process and to see the difference in polishing behavior of these coatings. The issues of end point detection and slurry selectivity are discussed in detail.

Metrology Issues in Cu-Low-K Chemical Mechanical Planarization

Ultra low- k materials used in Cu damascene process are inherently soft and weak in nature; hence the evaluation of tribological properties of these materials is an issue of paramount importance in the field of semiconductor fabrication. Chemical Mechanical Polishing (CMP) of these films is a major challenge due to their reduced modulus and cohesive strength. The objective of this research is to develop a strong understanding of the tribological properties of Cu ultra low- k dielectric materials for successful implementation in the semiconductor devices. The Cu ultra low- k systems are polished at different conditions of load and platen rotation and their polishing behavior is compared with the standard Cu-SiO 2 system. The polishing behavior of Cu and the barrier Ta material is studied in order to effectively detect the end point of the Cu CMP process. Delamination studies, post process surface characterization using scanning electron microscopy and the reliability issues of these materials also come within the scope of this study.

Delamination Behavior of Cu-Low-k Stack Under Different Slurries

Lower mechanical strength, reduced cohesive strength and lack of compatibility with other interconnect materials, are the major challenges involved in chemical mechanical polishing (CMP) of Cu metallization with ultra low- k materials as interlayer dielectrics. In this study we have investigated the polishing behavior of patterned Cu samples with underneath different low- k materials using two different slurries and a wide range of machine parameters. CMP micro tribometer was used to polish the samples with different rotations of platen (50 to 250 RPM) and down forces (1-6 PSI). Friction co-efficient and wear behavior were also investigated at different conditions. Optical and scanning electron microscopy was used to investigate the polished surface. It was observed that the two different Cu slurries used for polishing have marked effects on the polishing of Cu-low- k stack with respect to wear and delamination.