Wim Fyen

Saturation effects in TXRF on micro-droplet residue samples

Total reflection X-ray fluorescence spectrometry (TXRF) is a well-accepted technique for ultra-trace analysis of ultra-pure reagents and silicon wafers. Nevertheless, the technique’s linear range is not well characterized. In this paper, the upper limits of the linear range of TXRF on micro-droplet residues are identified and the origin of the non-linear effect is investigated. It is observed experimentally that a systematic decrease in the accuracy occurs as a function of the metallic content, starting from amounts above 3–10 ng, depending on the sample composition. A mass-absorption model for thin films is re-formulated for the micro-droplet residue samples and the model parameters are tested on the experimental observations. The calculations are in good agreement with the experimental data. Finally, solutions to deal with these saturation effects are discussed and a method to extend the dynamic range of TXRF is proposed.

Removal of Submicrometer Particles from Silicon Wafer Surfaces Using HF-Based Cleaning Mixtures

We have studied the particle removal efficiency of HF-based cleaning mixtures used to clean wafer surfaces during semiconductor manufacturing. SiO 2 , Si 3 N 4 , and metallic oxide (Al 2 O 3 , TiO 2 ) particles can he easily removed from silicon wafers using a HF-based clean, whereas the removal of metallic particles and especially Si and polymeric particles is much more difficult. This is explained in terms of surface hydrophobicity effects For thermal oxide wafer substrates, a low removal efficiency is observed for the positively charged Si 3 N 4 and Al 2 O 3 particles. This has been explained previously by redeposition of the particles from the carry-over layer during the final rinse [R. Vos, I. Cornelissen, M. Meuris, P. Mertens, and M. Heyns, in Cleaning Technology in Semiconductor Device Manufacturing VI, J. Ruzyllo, T. Hattori, and R. E. Novak, Editors, PV 99-36, p. 461, The Electrochemical Society Proceedings Series, Pennington, NJ (1999)]. Surfactants are found to increase the removal of Si and polymeric particles from silicon substrates. This is attributed to the elimination of hydrophobic attraction forces. In addition, the surfactant is also successful in preventing the particles from redepositing during the final rinse treatment, because during the rinse, both the particle and the substrate have the same surface charge.

Single magnetic particle detection: Experimental verification of simulated behavior

In the past, magnetoresistive sensor based biosensors, using superparamagnetic particles, have shown to be promising candidates for highly sensitive biosensors. These sensors can detect a single micron-sized magnetic particle. For single particle detection, research groups have developed models to predict the signal per particle. In these models, the separation distance plays an important role for the quantitative determination of the signal. However, mostly only the passivation layer thickness is included as the separation distance. In this paper, we describe a detection system based on a magnetic spin-valve sensor that is capable of giving position-time information of the magnetic behavior of one single bead. The results obtained with this system for the detection of a single particle signature are then compared with simulations. For this comparison, we developed a model where an additional particle-substrate separation distance is included. This distance is determined by a force balance of the perpendi...

Integration of Cu and low- k dielectrics: effect of hard mask and dry etch on electrical performance of damascene structures

Abstract In this work we discuss the importance of selecting the hard mask material and choosing the optimum dry etch and post-CMP clean processes on the integration of Cu and organic low-k dielectrics. The hard mask material plays an important role in the interline capacitance and in the effective dielectric constant of the interconnects. One generation of effective k can be gained simply by replacing the hard mask material by one with a lower dielectric constant, instead of moving to a more advanced low-k material. Interline leakage is not affected by the hard mask material and low values (∼10−9 A/cm2) are obtained at electric fields of 1 MV/cm for structures with spacing down to 0.2 μm. A non-optimized dry etch process for trench definition can result in undercutting, which affects the Cu filling of the trenches. From our results it is clear that the process conditions (lithography, etch, CMP) affect the geometry of the structures, which has a big impact on the effective dielectric constant of the interconnects.

Enhanced magnetic particle transport by integration of a magnetic flux guide : Experimental verification of simulated behavior

In the past, magnetic biosensors have shown to be promising alternatives for classical fluorescence-based microarrays, replacing the fluorescent label by a superparamagnetic particle. While on-chip detection of magnetic particles is firmly established, research groups continue to explore the unique ability of manipulating these particles by applying controlled magnetic forces. One of the challenging tasks in designing magnetic force generating structures remains the generation of large forces for a minimal current consumption. Previously, a simple transporting device for single magnetic particles has been demonstrated using a magnetic field that is generated by two tapered current carrying conductors [R. Wirix-Speetjens, W. Fyen, K. Xu, J. De Boeck, and G. Borghs, IEEE Trans. Magn. 41(10), 4128 (2005)]. We also developed a model to accurately predict the motion of a magnetic particle moving in the vicinity of a solid wall. Using this model, we now present a technique that enhances the magnetic force up to...

Critical issues in the integration of copper and low-k dielectrics

Single and dual damascene Cu/low k processes are evaluated. Critical integration issues are discussed. Good Cu continuity is obtained over long meanders. The via resistance in dual damascene structures is optimized and the values obtained are almost three times lower than those achieved for a conventional Al/W metallization process. The interline capacitance was evaluated for various etch and strip procedures. The effect of the Cu/low k process on a front end of line 0.25 /spl mu/m n-MOS process is investigated. The metallization process does not affect the performance of either transistors or field transistors.

Point of Use HF Purification for Silicon Surface Preparation by Ion Exchange

The point of use (POU) HF purification performance of an ion exchange membrane (IEM) is evaluated in this paper. First, no cationic extractable (i.e., Cu, Fe, and Ni) from two IEMs was detected in HF 0.5% which makes these membranes compatible with sub-ppb grade HF The IEM purification performance was evaluated with 0.5% HF spiked with 10 ppb of Fe, Ni, and Cu nitrates. The results show that after less than five turnovers through an IEM, the impurity concentration drops below 1 ppb. The decrease rate can be fitted to a model assuming the experimental tanks to be continuously stirred tank reactors and that the impurity concentration after the membrane is a function of the single -pass purification efficiency of the IEM, the concentration before purification, and the metals desorbed from the IEM. The concentration after purification was investigated up to a cumulative Fe loading of 300 ppb in the 23 liter recirculated loop. It increases linearly vs. cumulative loading and can be explained by the Langmuir theory resulting in a purification efficiency at the equilibrium of close to 99.5% in this loading regime. This suggests that the capacity of the membrane is high enough to ensure an adequate lifetime. Finally, a POU IEM can reduce the Cu concentration in the bath resulting in less Cu outplating. No impact was noticed on particle and organic deposition, on surface roughness, and on 5 nm gate oxide integrity.

A detailed study of semiconductor wafer drying

Publisher Summary In this chapter, the performance of several drying techniques commonly used in the semiconductor manufacturing industry is evaluated. This is done by measuring the residues on a wafer onto which a solution containing metal salts acting as tracer elements has been dispensed and dried. To correctly interpret the experimental data, the results are compared with predictions from a theoretical model. This model assumes two distinct mechanisms for deposition: adsorption and evaporative deposition. The first mechanism is a result of attractive interactions between the contaminant and the wafer surface, while the second mechanism is due to liquid evaporation during drying. For the latter case, the evaporated film thickness is introduced as a figure of merit for the drying process under study. In the tests, tests, spin drying was compared with two types of Marangoni based drying: on a vertically moving wafer and on a horizontally rotating wafer. The results show that for spin drying two consecutive phases occur: during the first seconds of spinning convective removal of liquid is the dominant mechanism, followed by a phase where evaporation takes over. This behavior is confirmed by models reported in the literature describing photo-resist coating. The amount of liquid evaporating during spin drying is inversely proportional to the square root of the rotation speed. This suggests that entrainment of liquid by the gas flow over the wafer surface is the dominant mechanism for evaporation. This finding is in agreement with fluid dynamics models describing the flow of gas entrained with a rotating substrate.

Chapter 19 – A Detailed Study of Semiconductor Wafer Drying

In this chapter, the performance of several drying techniques commonly used in the semiconductor manufacturing industry is evaluated. This is done by measuring the residues on a wafer onto which a solution containing metal salts acting as tracer elements has been dispensed and dried. To correctly interpret the experimental data, the results are compared with predictions from a theoretical model. This model assumes two distinct mechanisms for deposition: adsorption and evaporative deposition. The first mechanism is a result of attractive interactions between the contaminant and the wafer surface, while the second mechanism is due to liquid evaporation during drying. For the latter case, the evaporated film thickness is introduced as a figure of merit for the drying process under study. In the tests, spin drying was compared with two types of Marangoni based drying: on a vertically moving wafer and on a horizontally rotating wafer. The results show that for spin drying two consecutive phases occur: during the first seconds of spinning convective removal of liquid is the dominant mechanism, followed by a phase where evaporation takes over. This behavior is confirmed by models reported in the literature describing photo-resist coating. The amount of liquid evaporating during spin drying is inversely proportional to the square root of the rotation speed. This suggests that entrainment of liquid by the gas flow over the wafer surface is the dominant mechanism for evaporation. This finding is in agreement with fluid dynamics models describing the flow of gas entrained with a rotating substrate.