AVS 49th International Symposium
    Plasma Science Friday Sessions
       Session PS-FrM

Paper PS-FrM11
Ar@super +@/XeF@sub 2@ Beam Etching of Si: What about Doping?

Friday, November 8, 2002, 11:40 am, Room C-103

Session: Plasma Surface Interactions II
Presenter: A.A.E. Stevens, Eindhoven University of Technology, The Netherlands
Authors: A.A.E. Stevens, Eindhoven University of Technology, The Netherlands
E. Te Sligte, Eindhoven University of Technology, The Netherlands
H.C.W. Beijerinck, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
To circumvent the complexity of plasma etching, well-defined beams of Ar@super +@ ions and XeF@sub 2@ etch precursor gas are used to study the fundamentals of the etch process of silicon. Ellipsometry has been applied in the beam etching experiment in an attempt to bridge the gap between beam etching and plasma etching. The ellipsometric properties of Si(100) (n-type (P), resistivity = ~ 10 @OMEGA@ cm) during physical sputtering by Ar@super +@ ions, spontaneous etching by XeF@sub 2@ and ion-assisted etching have revealed basic information regarding the reaction layer dynamics and composition. Sputtering by Ar@super +@ ions results in an ion damage layer that consists of amorphous silicon (a-Si) with a surface roughness of less than 0.3 nm. The thickness of the a-Si layer can be described well with TRIM simulations. Spontaneous etching by XeF2 is found to cause a rough reaction layer up to 13 nm thick that can be thought of as a rough and (partially) fluorinated silicon (SiF@sub x@) surface. Ion-assisted etching is a combination of sputtering by Ar@super +@ions and etching by XeF@sub 2@, which resembles the actual etch process in plasmas. The reaction layer in this case is a mixture of rough a-Si and SiF@sub x@ layer on top of an a-Si layer. In order to obtain a reliable comparison between ellipsometry measurements and simulations the surface roughness has to be known. Atomic force microscopy has been applied to study the surface roughness evolution of Si for various etching conditions, which has been used as input in the ellipsometry simulations. This more detailed description of the reaction layer dynamics and composition has enabled the study of n- and p-doped Si(100) samples with various types of dopants (As, Sb, P, B) and doping concentration (resistivity = 0.001-10 @OMEGA@ cm). New information regarding the still unanswered question of the effect of doping on the etch mechanism will be presented.