AVS 46th International Symposium
    Plasma Science and Technology Division Tuesday Sessions
       Session PS-TuM

Invited Paper PS-TuM1
Probing Surface Layers during Inductively Coupled Plasma Etching using Laser-Thermal Desorption and Other Optical Techniques

Tuesday, October 26, 1999, 8:20 am, Room 609

Session: Plasma-Surface Interactions I
Presenter: I.P. Herman, Columbia University
Authors: I.P. Herman, Columbia University
J.Y. Choe, Columbia University
N.C.M. Fuller, Columbia University
V.M. Donnelly, Bell Laboratories, Lucent Technologies
M.V. Malyshev, Bell Laboratories, Lucent Technologies
K.H.A. Bogart, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
The etching of Si, Ge, and InP by an inductively coupled plasma (ICP) of chlorine is investigated by analyzing both the composition of the surface and the plasma during etching. The surface is probed by using laser-induced thermal desorption with an XeCl laser (308 nm) to desorb the steady-state adlayer and optical methods to detect these desorbed species. The development of a new method to detect optically these laser desorbed (LD) species is detailed, that of examining transient changes in the plasma-induced emission (PIE). This LD-PIE method is seen to be more universal than the previously reported detection by laser-induced fluorescence (LD-LIF), but is seen to require more calibration due to varying electron density and temperature with varying plasma conditions. This is detailed for Si etching, for which LD-PIE and LD-LIF results are compared. The calibration methods are seen to be valid when the surface is analyzed as the rf power supplied to the reactor is varied. A more complete picture of the etching process requires detailed characterization of the plasma through measurements of the constituents of the plasma. Neutral Cl@sub 2@ and Cl densities are determined by optical emission actinometry; Cl@sub 2@@super +@ and Cl@super +@ densities are determined by LIF and Langmuir probe measurements; and electron densities - needed for LD-PIE calibration - are measured by microwave interferometry. An improved understanding of the etching mechanism is obtained by combining the results of each of these measurements. This work was supported at Columbia by NSF Grant No. DMR-98-15846.