Comparative analysis of aqueous suspensions of cerium oxide and modifying additives for the process of chemical and mechanical planarization of plates with Shallow Trench Isolation

A comparative physicochemical analysis of industrial aqueous suspensions of cerium oxide abrasive particles used in the processes of chemical-mechanical planarization (CMP) of plates with shallow trench isolation (CMP STI) was carried out. IR spectroscopy and dynamic light scattering showed that the cerium oxide suspension (pH ≈ 6) with an average particle size of 120 nm additionally contains polyacrylic acid (PAA) and a second non-ionic polymer, presumably polyacrylamide (PAAM), which creates conditions for electrostatic and spatial stabilization of abrasive particles. It has been shown that the transfer of the suspension (sample 1) to the acidic pH range of 3–1.5 leads to a bimodal distribution of abrasive particles by size, where, along with aggregates ranging in size from 1200 to 4000 nm, particles with a diameter of 45–30 nm appear.The suspension (sample 2) (pH ≈ 3.5) with an average particle size of 100-120 nm does not contain polycarboxylates, and its stability is due to the presence of low molecular weight glutamic acid. Based on the known behavior of the suspensions in question in the process of CMP of STI silicon wafers, the role and mechanism of operation of the modifying additives included in them are formulated.