Quartz crystal microbalance technique dissolution

There are a number of reasons that it is important to characterize the dissolution or development rate of any given resist. The main reasons tend to be for process control purposes, given that image discrimination in resists is based on differences in dissolution rates between the image and non-image areas. The two main techniques that are used to characterize the dissolution properties of a resist are laser interferometry and quartz crystal microbalance. Each of these techniques is reviewed below. 

The use of the quartz crystal microbalance in monitoring resist dissolution rates was first reported in 1985 by W.D. Hinsberg et al. This technique is based on the equation that G. Sauerbrey developed in 1959 as a method for correlating changes in the oscillation frequency of a piezoelectric crystal with the mass... 

Recently, in addition to the in situ STM/AFM, many other surface-analysis techniques such as surface X-ray scattering (SXS) [19, 20] and electrochemical quartz crystal microbalance (EQCM) [21, 22] have also been employed to investigate the electrochemical deposition and dissolution processes at atomic resolution. Atomically controlled electrochemical epitaxial growth and layer-by-layer dissolution... 

The details of the deposition and dissolution processes of the DAB-dend-(NHCOFc) in tetra n-butyl ammonium perchorate (TBAP)/CH2Cl2 solution were investigated using the electrochemical quartz crystal microbalance (EQCM) technique as well as admittance measurement of the quartz crystal resonator by Takada etal. [77]. It was found that the oxidized form of the dendrimers deposited onto the Pt electrode likely due to the low solubility of the salt composed of the oxidized dendrimer (ferricenium form) and C104 anions. On the other hand, the reduced form of the dendrimers easily redissolved except for the first monolayer, which appeared to be strongly adsorbed. Further, the mass-transfer process, during the redox reaction of the adsorbed dendrimers in an AN solution, was found to be of the anion exchange type. The resistance measurements of the quartz crystal resonator based on the admittance also supported the results obtained by EQCM. 

By employing advanced analytical techniques, more detailed quantitative information can be gained. For example, using a conventional electrochemical cell in combination with a quartz crystal microbalance, Dam and de Bruijn (2007) studied the influence of temperature and potentials on Pt thin-film dissolution in 1 M HCIO4 solution. They detected that the Pt catalyst dissolution rate was accelerated by increasing the temperature and the dissolution potential, which agrees with the Nernst equation. When temperature was increased from 60°C to 80°C, the Pt dissolution rate increased from 0.87 ng h cm" to 1.58 igh cm 2 when exposed to a potential of 1.15 V. However, the amount of Pt dissolution was too small to measure at 40°C. 

Nonsteady behavior of electrochemical systems was observed by Fechner as early as 1828 [ii]. Periodic or chaotic changes of electrode potential under gal-vanostatic or open-circuit conditions and similar variation of current under potentiostatic conditions have been the subject of numerous studies [iii,iv]. The electrochemical systems, for which interesting dynamic behavior has been reported include anodic or open-circuit dissolution of metals [v-vii], electrooxidation of small organic molecules [viii-xiv] or hydrogen, reduction of anions [xv, xvi] etc. [ii]. Much effort regarding the theoretical description and mathematical modeling of these complex phenomena has been made [xvii-xix]. Especially studies that used combined techniques, such as radiotracer (-> tracer methods) ig. 1) [x], electrochemical quartz crystal microbalance (Fig. 2) [vii,xi], probe beam deflection [xiii], surface plasmon resonance [xvi] surface stress [xiv] etc. have contributed considerably to the elucidation of the role of chemisorbed species ( chemisorption), surface reconstruction as well as transport phenomena in the mechanism of oscillations. 

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