Modeling HfO2 atomic layer chemical vapor deposition on blanket wafer, via, and trench structures using HfCl4∕H2O

Abstract

Atomic layer chemical vapor deposition ͑CVD͒ of HfO 2 on blanket wafer, trench, and via structures using a HFCl 4 /H 2 O chemistry has been modeled. The feature modeling uses a Monte Carlo model ͑three-dimensional Papaya͒ as well as calculation results from CVD reactor and molecular dynamics chemistry models. Added to the feature scale model, Papaya, is the capability to input time dependent fluxes from the CVD reactor model as well as specify a multistep process for tens of cycles. HCl products from HfCl 4 + OH-and H 2 O + Cl-reactions are more likely to react within a feature than at the field which reduces the OH coverage within feature, limiting maximum coverage achievable with a pulse. Given the particulars of the cross flow reactor's design, features downstream of the inlet during the H 2 O pulse will have a higher percentage of the HCl reaction product to the surface and desorption of HfCl 4 causing differences in the coverage fraction and deposition rate across the wafer. Characterized are the minimum pulse times sufficient for surface reaction saturation on blanket wafers versus deposition on trench and via features. The Cl fraction in the deposit is greater at the surface than in the bulk, reaches a steady state after tens of cycles, has reduced minimum and maximum values as coverage is reduced, and total is reduced as feature aspect ratio is increased.