Built-in reliability through sodium elimination

Minute amounts of sodium can cause semiconductor devices to fail. Wafer processors have steadily reduced sodium content to increasingly low levels in the gate oxide area. However, levels as high as 5E18 cm/sup -3/ are still commonly detected around metal layers in the industry. The industry has until now relied on the BPSG layer to prevent penetration into the active gate area. This approach is usually effective, but not bulletproof. Pinholes or thin spots in BPSG film still allow sodium ions to seep through. This protective or inter-dielectric layer. As part of a strong commitment to achieve built-in reliability, Siliconix launched a project to totally eliminate sodium from its products. As reported in this paper. We have successfully reduced the presence of sodium down to the SIMS detection level.<>