Effect of La Doping of Ceria Abrasives for STI CMP

Abstract

The nitride removal rate by ceria abrasives in presence of amino acids is altered by the purity of ceria. Commercial ceria obtained from Sigma-Aldrich with low purity (<90%) and with high purity (99.95%) were employed in the study. Polishing experiments showed that in presence of lanthanum in the abrasive, proline does not suppress nitride removal. In order to verify that the effect is mainly due to presence of lanthanum, ceria particles were synthesized with and without lanthanum doping. Three types of amino acids viz. proline, alanine and glutamic acid were used with the ceria particles. The removal rate results show that proline is sensitive to presence of lanthanum impurity in abrasive, while alanine and glutamic acid suppress the nitride removal irrespective of the purity of the abrasives. The abrasives were characterized using XRD. The adsorption of amino acids on abrasive was characterized by differential thermal analysis.

Effect of Potassium on Sol-Gel Cerium and Lanthanum Oxide Catalysis for Soot Combustion

“…The presence of Ce 3+ , poorly appreciated, associated with the surface anion vacancies could be a consequence of the removal of oxygen during the sample pretreatment. The reported BE of La 3d between 830 eV and 870 eV [36] and La 3d 5/2 at 834.9 eV for surface La 3+ indicates that the obtained values of 835.1 and 835.4 eV shifted towards higher BE, indicating the presence of only La 3+ [38]. This is the expected result considering no other stable oxidation state of lanthanum occurs when combined with oxygen.…”

“…The C1s emission was used as reference. According to Praveen et al [36] and Fleming et al [37], the BE range of Ce between 875eV and 925 eV indicates a mixture of surface Ce 3+ and Ce 4+ . The obtained BE values of Table 3 of Ce 3d 5/2 at 883.0 eV and Ce 3d 3/2 at 900 eV have a relationship with 13% and 12% of Ce 3+ for the K/3%CeO 2 -Al 2 O 3 and K/5%CeO 2 -Al 2 O 3 catalysts, respectively.…”