Arun Vijayakumar

Polishing mechanism of tantalum films by SiO 2 particles

Dishing and erosion are major problems in conventional chemical mechanical planarization of copper/barrier layers. Understanding the polishing mechanism of the different materials involved can assist in providing a solution to these issues. Chemical mechanical polishing of tantalum was performed using alumina and silica particles dispersed in deionized water at pH 6. Tantalum shows a higher removal rate in silica slurry compared to alumina slurry. To examine the polishing mechanism of tantalum in silica slurry, the surface structure of the film was investigated by X-ray photoelectron spectroscopy (XPS). Various electrochemical techniques were used to characterize the surface film formation, dissolution and the interaction between silica particles and tantalum film. XPS and electrochemical results indicate that tantalum film may react with silica particles to form Ta-O-Si bonds on the surface. The mechanical tearing of Ta-O-Si bonds leads to the removal of Ta2O5 as a lump, resulting in higher removal rates of tantalum in silica slurry.

Amorphous-SiCBN-Based Metal–Semiconductor–Metal Photodetector for High-Temperature Applications

A photodetector (PD) with metal-semiconductor-metal (MSM) structure has been developed using an amorphous SiCBN film. The amorphous SiCBN film was deposited on the silicon substrate using reactive RF magnetron sputtering. The optoelectronic performance of the SiCBN MSM devices has been examined through photocurrent measurements. Temperature effect, with respect to photocurrent ratios, has been studied. The detector sensitivity factor, which is determined through the PD current ratio, was greater than five at room temperature. Furthermore, the device showed an excellent current sensitivity factor that is greater than two even at a higher temperature of 200 oC . The improved performance of the device at higher temperatures could open avenues for high-temperature PD applications.

In Situ High Temperature Electrical Characterization of RF Sputtered SiCBN Thin Films

Electrical properties of reactively sputtered SiCBN thin films were studied at high temperature conditions. In situ electrical characterization was performed through sheet resistance measurements in the temperature range from room temperature to 900°C. The electrical properties were observed to be extremely sensitive with respect to variations in the chemical composition, and bonding structure of the SiCBN films. The film stoichiometry, obtained with no N 2 gas flow, showed very interesting electrical characteristics that have been correlated with the chemical structure of the material. Multiple heating and cooling cycles show uniquely stable resistance readings. This is presumed to be due to the formation of a stable surface passivation oxide layer leaving the bulk of the thin film unaffected. This was further confirmed through secondary ion mass spectroscopy depth profile. The thermal stability and stable reproducible electrical properties indicate potential for low cost high temperature thin film applications.

Effect of N2/Ar gas mixture composition on the chemistry of SiCBN thin films prepared by RF reactive sputtering

In this work we report the deposition and characterization of amorphous thin films of silicon boron carbon nitride (SiCBN). The SiCBN thin films were deposited in a radio frequency (rf) magnetron sputtering system using reactive cosputtering of silicon carbide (SiC) and boron nitride (BN) targets. Films of different compositions were deposited by varying the ratios of argon and nitrogen gas in the sputtering ambient. Surface characterization of the deposited films was performed using X-ray photoelectron spectroscopy and optical profilometry. Studies reveal that the chemical state of the films is highly sensitive to nitrogen flow ratios during sputtering. Surface analysis shows that smooth and uniform SiCBN films can be produced using this technique.

Oxygen Annealing Characterization of Reactively Sputtered SiCBN Thin Films by X-Ray Photoelectron Spectroscopy

Amorphous thin films of silicon boron carbon nitride (SiCBN) were deposited in a multigun radio frequency magnetron sputtering system using reactive co-sputtering of silicon carbide (SiC) and boron nitride targets. Films of different compositions were obtained by varying the ratios of argon and nitrogen gas in the sputtering ambient. The films were annealed in dry oxygen ambient in the temperature range 300-900°C. Subsequent surface characterization of the annealed films was performed using X-ray photoelectron spectroscopy to investigate the chemical composition and oxidation kinetics at the different annealing temperatures. Studies revealed that the carbon and nitrogen concentrations in the films are highly sensitive to annealing temperatures. Higher annealing temperatures lead to broken C-N bonds, resulting in the loss of C and N content. Temperatures beyond 700°C lead to complete loss of nitrogen, and the silicon and boron in the films interacted with oxygen to form SiO 2 and B 2 O 3 .

Effect of Hydrogen Peroxide on Oxidation of Copper in CMP Slurries Containing Glycine and Cu Sulfate

This study compares the oxidative dissolution, passivation, and polishing behavior of copper chemical mechanical polishing in the presence of hydrogen peroxide, glycine and copper sulfate. High purity discs were used to study the dissolution and oxidation kinetics under static and dynamic conditions at pH 4 with varying H 2 O 2 concentrations. Changes in surface chemistry of the statically etched copper-disc were investigated using X-ray photoelectron spectroscopy (XPS). With the addition of glycine and copper sulfate to the slurry, the copper removal rates increased significantly and the maximum removal rate shifted to a H2O2 concentration of 3%. Electrochemical investigation indicates an enhanced dissolution of copper, which might be due to the strong catalytic activity of Cu(II)-glycine complexes in decomposing H 2 O 2 to yield hydroxyl radicals. XPS results suggest that the passivation at higher H 2 O 2 concentrations in the presence of glycine and copper sulfate is provided by the OH radicals adsorbed on Cu surface.

Development of a Transparent Heater to Measure Surface Temperature Fluctuations for Pool Boiling and Spray Cooling

A heater designed to monitor surface temperature fluctuations during pool boiling and spray cooling experiments while the bubbles are simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or synthetic fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 μm wide and overlapped to form a 25 μm by 25 μm junction. TFTC voltages were recorded by a DAQ at a sampling rate of 50 kHz. A high-speed CCD camera recorded bubble images from below the heater at 2000 frames/second. From these images, the bubble outer diameter and contact ring diameter were clearly visible. A trigger sent to the camera by the DAQ program synchronized the bubble images and the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were made. The 1–2°C temperature drops occurred as the contact ring moved over the TFTC junction during bubble growth and as the contact ring moved back over the TFTC junction during bubble departure.Copyright