Phosphosilicate Glass Passivation for ULSI Cu Metallization

Phosphosilicate glass (PSG) passivation for Cu metallization is proposed, and the Cu diffusion rate into Si substrates through various oxide structures is measured quantitatively. Cu diffusion is suppressed effectively by the PSG passivation resulting in reduction of the diffused Cu atoms to about an order of magnitude less than when passivated by nondoped SiO 2 films. The passivation is effective when the annealing temperature is less than 600 o C. The apparent activation energy of Cu diffusion for the nondoped SiO 2 /Si substrate and PSG/nondoped SiO 2 /Si is 1.2 and 1.6 eV, respectively