MOCVD OF BASRTIO3 FOR ULSI DRAMS

The CVD of high permittivity materials such as BaSrTiO3 presents new challenges to the semiconductor equipment and materials industries. The electrical properties of the material are a strong function of composition, microstructure and dopant concentration (electronic and ionic). However, the source reagents are typically low vapor pressure liquids, solids or solids dissolved in liquids which are challenging to manufacture with ultra-high purity and difficult to deliver with high accuracy and precision. Reactor walls must be heated to avoid condensation of the source materials and deposition temperatures are high where radiative heat transfer becomes significant. Reaction products are difficult to remove by standard dry chemical etching techniques because the halides of many of the metals are involatile inorganic salts. Design strategies to overcome these challenges and the resulting properties of BaSrTiO3 films will be discussed.