DAMAGE AND CONTAMINATION IN LOW-TEMPERATURE ELECTRON-CYCLOTRON-RESONANCE PLASMA-ETCHING

An electron cyclotron resonance (ECR) plasma etching system has been b uilt to study the damage and contamination inherent to the high densit y ECR etching. The temperature of the substrate can be lowered to -150 degrees C by the backside cooling of the substrate with the liquid-ni trogen cooled helium. The substrate temperature during etching was mon itored by a sheathed thermocouple and IR laser interference thermometr y. Gate polysilicon etching by SF6 plasma had been carried out and the effect of the substrate temperature on the anisotropy, selectivity, a nd etch rate was examined with special emphasis on the damage and cont amination incurred by the plasma etching. Secondary ion mass spectrosc opy (SIMS) analysis shows that the depth of the contaminated layer dec reases when the substrate temperature is lowered to -120 degrees C. Al so, the measurement of the gate oxide breakdown voltage shows much les s oxide damage when the substrate temperature is lowered during ECR et ching.