Papers by Keyword: Particle Removal Efficiency

Abstract: Recently the reduction of the devise sizes causing the semiconductor processes more complicated and becoming more and more sensitive to the particle contamination [1]. Numerous studies have been carried out to improve the device yield with high particle removal efficiency (PRE) and Wet cleaning process along with megasonic is one of the well-established techniques used for particle removal in the semiconductor industry [1, 2]. However as the pattern size is reduced bellow 60 nm this method is not effective to improve the PRE. Recently, two-flow jet spray cleaning process became popular in semiconductor manufacturing processes due to its many advantages [2]. In this process, micron size water droplets are jetted onto a wafer surface at high velocity, which can remove the particles which are on the wafer surface. It consists of two separate nozzles for liquids and carrier gases which are concurrently delivered on the wafer surface during cleaning process. However, there is still lot of scope to improve the PRE during jet spray wet cleaning process by optimizing the process parametrs. Hence in the present study we focused on the jet spray wet cleaning parameters such as nozzle distance from the wafer and the flow rate of the carrier gas to improve the PRE with minimum pattern damage.

Abstract: Megasonic cleans have been applied to remove defects such as particles and polymer/resist residues in silicon wafer fabrication of IC devices. However, with the shrink of device technology node, megasonic cleans are being challenged to maintain high cleaning efficiency promoted by streaming force of stable cavitation for the smaller particles without producing pattern collapse caused by violent implosions of transient cavities [. S. Kumari et al. reported that CO₂-dissolved water (CO₂ DIW) was potentially able to suppress wafer damage during megasonic exposure by minimizing unrestrained explosion of transient cavities. This is accomplished through the study on Sonoluninescence (SL), the phenomenon of release of light when liquid is irradiated by sound wafers of sufficient intensity, as a sensitive indicator of cavitation events [2, . This paper compares the effects of CO₂ dissolution on particle removal efficiency (PRE) and pattern collapse in a range of megasonic power with >100nm-size Si₃N₄ particles and 2xnm node line/space-pattern, respectively to N₂-gasified water (N₂ DIW).

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: Brush cleaning can trigger both mechanical and chemical reaction to efficiently remove the adsorbed particles on the wafer. However, the removal mechanism of nanosized particles by brush cleaning is far from clear because no direct experimental data, such as the friction and contact force of the interface between brush and wafer surface, are available to back up the theoretical models in the literature. In this paper, we set up a monitoring system to measure the friction force of the interface between brush and wafer surface during brush cleaning to investigate the effect of the brush nodule structure having different nodule heights and nodule gaps on particle removal efficiency. To confirm the mechanical effect of the brush nodule structure, an oxide wafer contaminated with Polystyrene latex (PSL) particles (mean diameter: 300 nm) was cleaned with each PVA brush having different brush nodule structures using de-ionized water (DIW). The silica particle (mean diameter: 22 nm) and chemical solution (NH₄OH, 0.1 wt%) were also used to investigate the chemical-aided particle removal. The remaining particles were measured with a Surfscan 6420 (KLA Tencor) and the friction force monitoring was conducted by using a Cleaner812-L (G&P Technology). The results indicated that a higher brush nodule height produced lower friction force, resulting in lower particle removal efficiency. When the nodule gap became smaller, the contact area between brush nodule and wafer surface became larger, resulting in higher particle removal efficiency. However, the experimental results using silica particles and 0.1 wt% of NH₄OH showed different trends under each condition. The particle removal mechanism with silica particle and NH₄OH was also verified by measuring the zeta potential between the particle and wafer.

Abstract: In IC manufacturing, particle removal from a wafer's back side (BS) has become as important as that from the front side (FS). For example, during lithography, BS particles can cause a variation on the topside surface topography. This may result in a focus-spot failure due to the reduced process window for depth of focus (DOF) as shown in Fig. 1. This problem increases as the feature size decreases. BS particles may cause other problems in wet benches, where BS particles can be transferred to the adjacent front side of wafers. Fig. 2 shows these FS particles, which usually appear as flow or streak patterns on the wafer [.

Abstract: In this work the dynamics of particle removal by aerosol spray is investigated. Local dwell time of spray cleaning is calculated numerically from the process conditions, and some striking topological similarities between the particle removal efficiency and dwell time profiles are observed. The particle removal rates, defined as the normalized speed of particle removal, are not constant during a typical process, with the highest removal rate for the first tens of milliseconds and a temporal decay as time elapses. Increasing N₂ flow rate results in an enhancement in both the particle removal efficiency and the particle removal rate.

Abstract: The local particle removal efficiency (PRE) of nano particles in megasonic cleaning experiments is studied. This approach makes it possible to quantify non uniform cleaning effects over the wafer and to look into the dynamics of particle removal at different areas on the wafer. A direct correlation between PRE and megasonic induced damage of device structures demonstrates that a considerable amount of damage is already formed at less efficiently cleaned areas of the wafer.