| AVS 54th International Symposium | |
| Plasma Science and Technology | Monday Sessions |
| Session PS2+MS-MoM |
| Session: | Plasma Etching for Advanced Interconnects I |
| Presenter: | F.L. Buzzi, University of Wisconsin-Madison |
| Authors: | F.L. Buzzi, University of Wisconsin-Madison Y.-H. Ting, University of Wisconsin-Madison A.E. Wendt, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
The energy distribution of bombarding ions during plasma etching of dielectrics for microelectronics manufacturing affects both selectivity to photoresist and the profile shape of the etched feature. Here we examine the role of ion bombardment making use of an ability to produce either a narrow ion energy distribution (IED) at a specified energy, or a two-peaked distribution in which the energy and relative flux of the two peaks can be controlled. A system has been developed for manipulating the IED at the substrate during plasma etching by controlling the voltage bias waveform of the RF bias applied to the substrate. The output of a waveform generator drives a broadband power amplifier connected to the electrode, and is programmed in an iterative process to produce the desired substrate wave form. The iterative feedback process has recently been automated so that arbitrary waveforms can be quickly achieved. Waveforms to produce ions at the substrate with energies greater than 500 eV in single-peaked or two-peaked IEDs are now routinely produced, and are applied to etching of silicon dioxide in fluorocarbon-based gas mixtures. Prior studies with a single-peaked IED at energies below 200 eV showed significant improvements in etch selectivity compared to a sinusoidal bias producing a broad IEDF (Wang and Wendt, 2001, Silapunt et al., 2003). In this study, we will report on a systematic characterization of IED effects on blanket and patterned wafers. Results include the following: 1) effect of ion energy on photoresist and oxide etch rates for the narrow single-peaked IED at high energy, 2) effect of ion energy on photoresist roughening/distortion, to explore evidence of improved performance with higher energy ions, and 3) systematic study of the asymmetric bimodal IEDs as a function of the relative ion fluxes at the two energies, to examine the effect on etch rates for oxide and photoresist and etched feature profiles. The plasma system is equipped with a helicon plasma source operating at 13.56 MHz. The substrate electrode accommodates 4" diameter wafers, and is equipped with helium backside cooling and a thin film laser interferometer to monitor etch rates of blanket films. The chamber walls are heated externally to minimize process drift associated with wall temperature changes during plasma operation.