This letter presents a systematic investigation of charge in HfO 2 gate stacks. Assuming that the majority of charge is associated with the stack interfaces, it is found that the charge at the HfO2/interfacial layer (IL) interface is negative while the charge at the Si/IL interface is positive. In general, the calculated charge densities at both interfaces are of order 1012 cm -2. A forming gas anneal (FGA) reduces the interface charge greatly at both interfaces. However, the FGA temperature does not have much effect on the charge density. The effects of post deposition anneal at various temperatures and under various atmospheres are also studied. Its found that a high temperature dilute oxidizing atmosphere anneal reduces the charge at both interfaces.
Bibliographical noteFunding Information:
Charge in the HfO gate stacks with a damage-free gate process has been evaluated. Due to compensation from the charge at the two interfaces, charge measurements must be done carefully. Forming gas anneals (FGA) reduce the interface charges greatly at both the HfO /IL interface and the Si/IL interface. Neither reducing nor inert atmosphere PDAs help reduce the interface charge densities, while high temperature dilute oxidizing atmosphere anneals reduce the charge at both interfaces. Since these interfacial charges are very close to the channel, they may have a significant effect on inversion layer mobility. The authors wish to acknowledge IBM and the Semiconductor Research Corporation for support of this work through contract #1060.
- Gate dielectric
- Metal gate electrode
- Work function