MOCVD OF BASRTIO3 FOR ULSI DRAMS

The CVD of high permittivity materials such as BaSrTiO3 presents new c hallenges to the semiconductor equipment and materials industries. The electrical properties of the material are a strong function of compos ition, 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 manuf acture with ultra-high purity and difficult to deliver with high accur acy and precision. Reactor walls must be heated to avoid condensation of the source materials and deposition temperatures are high where rad iative heat transfer becomes significant. Reaction products are diffic ult to remove by standard dry chemical etching techniques because the halides of many of the metals are involatile inorganic salts. Design s trategies to overcome these challenges and the resulting properties of BaSrTiO3 films will be discussed.