Shankar Venkataraman

Dual Discharge Modes Operation of an Argon Plasma Generated by Commercial Electronic Ballast for Remote Plasma Removal Process

An argon plasma generated between the cone-shaped electrode powered by commercial electronic ballast and grounded plane electrode has been investigated. Since the electronic ballast has positive and negative cycle in a period, two different discharge modes of remote plasma-the normal glow discharge mode and the hollow cathode discharge mode-have been observed. It is noted that the hollow cathode discharge mode has wider operation window in gas pressure than the glow discharge one. The glow discharge started to be extinguished at pressure higher than 4.1 torr and turned to the hollow cathode discharge mode in the holes on ground plate, while the hollow cathode discharge mode kept growing until 10 torr. These results show that the stable operation window of the system could be defined by the glow discharge mode rather than the hollow cathode discharge mode and could be improved by optimizing the applied voltage waveform and electrode configuration.

Residual Stress Effects on the Fracture of Tantalum Nitride Films

In this study, continuous microscratch testing was used to determine the effects of compressive residual stresses on the fracture of thin tantalum nitride films. The films were sputter deposited at room temperature onto single crystal sapphire substrates to a thickness of 600 nm. Some films were left in the as-deposited condition while the remaining films were vacuum annealed at 300°C. The only discernible change in structure was a surface rearrangement of atoms into parallel arrays of striations on the vacuum annealed samples revealing a high compressive residual stress in the films. These stresses had a strong effect on fracture as shown by the as-deposited films which buckled readily during scratch tests forming uniform-width and circular blisters while the vacuum annealed films exhibited a much lower susceptibility to fracture. Application of mechanics-based models for film buckling defined the levels of compressive residual stress and their effect on interfacial fracture.

Optimization of hollow cathode discharge electrode for damage free remote plasma removal process for semiconductor manufacturing

Cone-shaped hollow cathode electrode configuration for a damage free remote plasma removal process has been optimized for given pressures based on Paschen characteristic curves, voltage–current characteristics and time-resolved discharge observations as well as oxide film removal performances. Remote plasmas have been generated in two types of cone-shaped electrodes with mixtures of He, NF3, and NH3 for pressure range of 1–30 Torr. Paschen characteristic curves and voltage–current (V–I) characteristics define an operating pressure for low breakdown voltage and the hollow cathode effect to minimize the particles. Sinusoidal voltage waveform and asymmetry electrode configuration alternate the glow discharge and hollow cathode discharge modes in a cycle. The current and infrared emission intensity from the glow discharge increases together for both cone-shaped electrodes with increasing pressure, whereas the hollow cathode discharge plasma emits strong infrared only when pD condition is satisfied. For the wide cone electrode configuration, high voltage operation at higher pressure results in particle contamination on the processed wafer by high energy ion bombardment. Operating at optimum pressure for a given electrode configuration shows faster oxide etch rate with better uniformity over a whole 300 mm wafer.

Conformal doping of 3-D structures using sub-atmospheric CVD films

Applicability of SACVD for doping of 3-D structures was assessed on both flat substrates as well as patterned structures focusing on the optimization of dopant profile within the SACVD film. Boron and phosphorous doped ultra-shallow junctions of 6 and 10nm respectively are obtained with surface concentration in excess of 1E21 at/cc for this intrinsically conformal and damage-free technique

Dual plasma modes operation of hollow cathode electrode system for remote plasma removals for semiconductor manufacturing

Summary form only given. A remote plasma source for selective removal process in semiconductor device fabrication has been investigated. Plasma has been generated between the cone-shaped electrode powered by commercial electronic ballast and the grounded plane electrode with noble gases of argon, helium or a mixture gas of He+NF3+NH3 for the pressure range from 1 Torr to 30 Torr. Sinusoidal voltage waveform and asymmetry electrode configuration alternate the glow discharge and the hollow cathode discharge modes in a cycle - two different discharge modes in a cycle. It is noted that the operating pressure windows of the hollow cathode discharge mode was wider than the glow discharge mode. The glow discharge started to extinguish at relatively higher pressure while the hollow cathode discharge mode kept growing. These results show that the stable operation window of the system could be limited by the glow discharge mode rather than the hollow cathode discharge mode and could be improved by optimizing the applied voltage waveform and electrode configuration.

Improved electrical performance for 65nm node and beyond through the integration of HARP O 3 /TEOS oxide films for STI, PMD, and thin film applications

In this paper, we discuss the HARPtrade (high aspect ratio process) 03/TEOS oxide film. A complete film property characterization is presented and a comparison with an HDP-CVD process is made. For 65 nm node and beyond, the HARP films can be used for multiple applications, including STI fill, PMD fill, and stress memorization.

Feature Evolution During Sub 100NM Gap-Fill and Etch

Inductively coupled plasma (ICP) reactors are being used at low gas pressure ( 1013 /cm2 ) processes in semiconductor fabrication. In these reactors plasma is generated by inductively coupled electric field while positive ions are accelerated anisotropically by applying a negative bias RF to the substrate. Semiconductor manufacturers face many challenges as wafer size increases while device geometries decrease. Two key challenges for both process design and electronics processing equipment design are (a) scale up of process from 200mm to 300mm diameter substrate, and (b) deposition and etching features with high aspect ratios. A unified phenomenological model to explain profile evolution trend as a function of aspect ratio for deposition (gap fill) and trench etch using ICP reactors is presented. Trends for feature evolution as a function of pressure for gap fill and trench etch are reviewed and explained. The article emphasizes importance of low pressure for sub-100nm gap-fill and trench-etch applications in ICP processing reactors.Copyright

Hydrogen Effects on the Fracture of Thin Tantalum Nitride Films

In this study we used nanoindentation and continuous microscratch testing to determine the effect of hydrogen on the work of adhesion and fracture toughness of thin tantalum nitride films. These films were sputter-deposited on sapphire substrates to a thickness of 600 nm followed by the heating of some films in deuterium and some in vacuum at 300°C. Deuterium was used in this study because it is much easier to detect and measure than hydrogen. Ion beam spectroscopy showed that exposure to deuterium produced a uniform internal deuterium concentration of 2000 appm. Nanoindentation showed that exposure to deuterium at 300°C and vacuum annealing at 300°C had little effect on elastic modulus and hardness values of these films at room temperature. In contrast, the microscratch tests at room temperature revealed that the work of adhesion decreased from 24.5 J/m 2 after vacuum annealing to 9.1 J/m 2 after deuterium charging and demonstrated that tantalum nitride films have a strong susceptibility to hydrogen embrittlement.