Papers by Keyword: Megasonic

Abstract: In the semiconductor wafer cleaning, ammonium hydroxide based APM (ammonium peroxide mixture) has been widely used to remove particles and organic contaminants [. However as the film thickness and line width of semiconductor structure scales down rapidly, the material losses by etching reaction of alkaline chemicals can cause serious problem in yield loss due to electric failure. The presence of H₂O₂ could enhance the material loss on silicon wafer. Very dilute alkaline chemicals might be of interest since it could minimize any possible ionic contamination or chemical residues from chemicals as long as we control the surface roughness and particle removal efficiency. Also the characterization of these very dilute alkaline chemicals will be very useful for particle removal in gas dissolved DI water.

Abstract: Ultraviolet based nanoimprint lithography (UV-NIL) technology is widely used in nanosized fine pattern transfer. NIL, which uses low pressure and low temperature, makes it possible to fabricate 3-dimensional pattern [. So, UV-NIL is one of the techniques with great potential as a new manufacturing process. But, UV-NIL process uses an expensive quartz substrate for transmission of UV light. Therefore, quartz substrate needs to be recycled to reduce the manufacturing cost. Usually, UV-NIL uses UV curable resins, whose chemical bonding and structure could be altered during UV light exposure which would result in crosslinking between the polymers. This UV cured resin with cross-linked structure is very hard to remove from the quartz substrate [. Conventionally, UV cured resin is removed by treating with sulfuric acid-hydrogen peroxide mixture (SPM) followed by ammonium hydroxide-hydrogen peroxide mixture (APM). One of the major drawbacks in using SPM-based treatment is the chemical haze formation and particle contamination on the quartz substrate [. Thus, an alternative cleaning composition will be of interest.

Abstract: Current work describes development, testing and verification of a single wafer megasonic cleaning method utilizing a transducer design that meets the extreme particle neutrality, Particle Removal Efficiency (PRE), and repeatability requirements of production scale wafer bonding and other applications requiring extremely low particle levels.

Abstract: When fabricating flat panel displays (FPDs), cleaning process is important in the preparation of next steps. A megasonic system for cleaning FPD which can remove smaller particles with lower power and lower consumptions of chemical and UPW was designed and manufactured. The anti-resonance frequency of the lead zirconate titanate (PZT) actuator was measured, and the value was 992 kHz. The impedance graph of the cleaning system was analyzed using commercial finite element method (FEM) analysis software Ansys, and the obtained value was 992 kHz. This agreed well with the measured value of 989 kHz. The performance of the developed system was evaluated by comparing the acoustic pressures with the conventional product. As a result, the acoustic pressures of the developed system were three times larger than that of the commercial system (conventional type: 13.9 kPa, the developed one: 43.1 kPa). In addtion, the PRE test was performed and the 83% particles were removed using 64% reduced power and 80% reduced chemical consumptions.

Abstract: It has been shown that megasonics can accelerate strip processes such as doped and plasma treated photoresist [1]. However, applied megasonic energy can also damage sensitive semiconductor devices. It was shown that adding a solvent such as IPA or lowering the temperature helps to control cavitation in semi-aqueous fluids [2]. Sonochemical reactions have been observed in various industries, however, there are no published observations in semiconductor cleaning. Ions may form in megasonic driven bubble collapse impacted by the characteristics of a gas or liquid that enters the bubble from the bulk liquid. Lower ionization potential gases or liquids may form ions earlier in the bubble collapse, so as to use up some of the total available energy through sonochemical reactions and possibly reducing the cavitations implosive energy. Here, tests are conducted to vary the liquid and gas type based on ionization potential to look into the impact this would have on cleaning and damage. It is shown that lower ionization or liquid additives lower the device damage.

Abstract: Since the introduction of megasonic cleaning in semiconductor industry a debate has been going on about which physical mechanism is responsible for the removal of particles. Because of the high frequency range it was believed that acoustic cavitation could not occur and cleaning was attributed to phenomena like Eckart and Schlichting streaming or pressure build-up on particles [1,2]. Recently it was shown however, that the removal of nanoparticles is closely related to the presence of acoustic cavitation in megasonic cleaning systems [3]. The dependence of particle removal efficiency on the concentration of dissolved gas and the presence of sonoluminescence are clear (but indirect) indications that the underlying mechanism is related to bubble dynamics. As the requirements for cleaning in semiconductor processing are ever more stringent, it becomes necessary to obtain a thorough understanding of the physical behavior of acoustically driven microbubbles in contact with a solid wall. In particular, the forces exerted thereby which might clean or damage a substrate are of interest. Here, a step in this direction is taken by visualization of both the removal of nanoparticles and the sub-microsecond timescale dynamics of the cavitation bubbles responsible thereof.

Abstract: T type megasonic waveguide was analyzed by finite element method (FEM), acoustic pressure measurements and particle removal efficiency for the single wafer cleaning application. Compared to conventional longitudinal waves, a transverse waves were generated in a T type waveguide. Not like longitudinal waves, transverse waves showed changes of direction and phase which increased the cleaning efficiency.