Critical Thickness Threshold in Hf02 layers

摘要

Wet etch ability of H102 high k layers in diluted HF solutions is very attractive to achieve anefficient selective removal with respect to silicon consumption and metal gate compatibility foradvanced technology node. Unfortunately in most cases Hf02 layers can not be etched in a wetmixture after the gate stack formation and dry etch. This behavior is now clearly correlated to themonoclinic crystalline phase [1;2]. This phase can be either an "as deposited" state in the case ofhigh temperature deposition mode such as MOCVD, or a post integration state related to addedthermal budget as for ALCVD. In this study, the Hf02 etch rate with a diluted HF/HCI chemicalsolution was tightly monitored as a function of both ALCVD and MOCVD deposition modes, underdifferent annealing conditions and different deposited thicknesses.