AVS 46th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS2-MoA

Invited Paper AS2-MoA5
Photoelectron Spectroscopic Investigation of Interfaces and Thin Layers for Microelectronics: Composition and Chemistry as a Function of Depth

Monday, October 25, 1999, 3:20 pm, Room 6A

Session: Applied Surface Science for Microelectronics
Presenter: R.L. Opila, Bell Labs, Lucent Technologies
Authors: R.L. Opila, Bell Labs, Lucent Technologies
J.P. Chang, Bell Labs, Lucent Technologies
J. Eng, Jr., Bell Labs, Lucent Technologies
M. Du, Bell Labs, Lucent Technologies
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As dimensions shrink in microelectronics, the role of interfaces between materials becomes more important and the characteristic dimensions of microelectronics approach the escape depth of photoelectrons. Two strategies to examine thin layers and their interfaces will be described. First, the overlayer will slowly be deposited, the specimen will be transferred in vacuo, after which the photoelectron spectrum is recorded. This strategy has proven to be particularly useful in determining how metals react with polymers, which are being considered as low dielectric constant interlayers between conductors. Because it is desirable to use copper despite its poor adhesion, barrier layers of more reactive metals and their nitrides must be incorporated. We have successfully used photoelectron spectroscopy to study the chemistry that occurs between a series of low dielectric constant materials, including fluoropolymers and aerogels, and titanium, tantalum and their nitrides. The relative reactivity at the interface controls the morphology of the growing overlayer. The interface between the barrier metal and the copper seed layer has been studied. In another application of photoelectron spectroscopy, the composition and chemistry of oxide layers for use as gates in transistors or as dielectrics in capacitors have been studied. The thickness of the dielectric layer is comparable to the escape depth of the photoelectrons. Thus, we have been able to identify certain chemical states as those likely to act as defects in the electronic device. Moreover, using angle resolved photoemission, the composition of the dielectric overlayer has been determined as a function of depth for silicon oxynitrides and tantalum pentoxide. A maximum entropy algorithm to transform the angle resolved data to elemental and chemical depth profiles will be described. Reactions that occur at the buried interfaces between the dielectic and the underlying electrode will also be described.