Particle Metrology in CMP Slurries - Potential and Limitations of Relevant Measuring Methods

Abstract

ABSTRACTThe design of nanostructured materials like CMP slurries on an industrial scale requires the control of disperse systems of nanoparticles as well as of single isolated "bad" particles . It is well known that slurry abnormalities resulting from large abrasive particles and abrasive particles agglomeration can cause defects on wafer surfaces during CMP.Particle-particle interactions generate secondary nanometer structures, clusters or agglomerates, which can dominate the relevant properties of the bulk material. Size and structure of these particle agglomerates/structures are the result of a dynamic equilibrium between agglomeration and desagglomeration. There is still a lack of understanding of these secondary soft nano- up to micro- particles because no adequate characterization methods are established.Dilution and other preparation treatment to enable analysis by laboratory methods like TEM or AFM will distort the interparticle forces and will generate artifacts. Hence characterization methods are under investigation which can tolerate a high number of particles in the sensing zone. These high concentration methods often deliver ambiguous results. Consequently different physical principles have to be combined to get unambiguous information on the disperse state.Performance characteristics of ultrasonic spectroscopy, photon correlation spectroscopy, analytical photo-centrifugation method combined with the high spatial resolution as well as special single particle optical counters are discussed on examples.