AVS 52nd International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS-WeM

Paper PS-WeM6
Investigation of Fluorocarbon Polymer Formation in Polysilicon Etching on Metal Gate

Wednesday, November 2, 2005, 10:00 am, Room 304

Session: Advanced Gate Stack Fabrication
Presenter: E. Luckowski, Freescale Semiconductor, Inc.
Authors: E. Luckowski, Freescale Semiconductor, Inc.
B.W. Chan, TSMC
S. Rauf, Freescale Semiconductor, Inc.
A. Martinez, Freescale Semiconductor, Inc.
Correspondent: Click to Email
It is well known that control of critical dimension and profile for ULSI devices with conventional polysilicon gates below the 90-nm technology node requires a detailed understanding of chemical etching and by-product deposition mechanisms in a plasma system. Carbon-containing feedstock gases such as CF4 are typically used in mixtures of Cl2, HBr, and/or SF6 to achieve a balance between deposition and etching required for profile control that also meet selectivity requirements for thin dielectric layers in MOSFET devices. Impact of chamber walls and contribution of species from masking materials can play an important role in the overall balance, as well as other additives such as O2 and N2. For advanced gate stacks, as conventional polysilicon gates are being replaced by metal gates to overcome polysilicon depletion effects, the impact of these various mechanisms on metal gate patterning must also be considered. In this work, we investigated the impact of polymer formation in polysilicon etch processes on the profile of polysilicon/transition metal gate stacks on high-K dielectrics. For fluorocarbon etching in particular, the C/F ratio has been found to strongly impact the final profile of polysilicon/metal gate stacks. OES and in-situ reflectometry were used to characterize composition and changes in the plasma conditions, while polymer formation and etch rate were characterized by SEM/TEM. Plasma modeling was also done using a 2D integrated equipment-feature scale model to improve understanding of the interaction between polysilicon and metal gate etch processes.