Comparison Between Chemical and Plasmatic Treatment of Seeding Layer for Patterned Diamond Growth
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1203-J17-53
Comparison between chemical and plasmatic treatment of seeding layer for patterned diamond growth A. Kromka1, O. Babchenko1,2, B. Rezek1, K. Hruska1, A. Purkrt1,2, Z. Remes1 1 Institute of Physics AS CR, v.v.i., Cukrovarnicka 10, CZ-16253 Praha 6, Czech Republic 2 Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, CZ-12000 Praha 2, Czech Republic ABSTRACT We employ UV photolithographic and electron beam lithographic patterning of diamond seeding layer on SiO2/Si substrates for the selective growth of micrometer and sub-micrometer diamond patterns. Using bottom-up strategy, thin diamond channels (470 nm in width) are directly grown. Differences between wet chemical and plasma treatment on the patterned diamond growth are studied. We find that the density of parasitic diamond crystals (outside predefined patterns) is lowered for gas mixture CF4/O2 plasma than for rich O2 plasma. After CF4/O2 plasma treatment, the density of parasitic crystals is 106 cm-2 which is comparable to the wet chemical treatment. Introducing sandwich-like structure, i.e. photoresist-seeding layer-photoresist, and its treatment (lift-off and CF4/O2 plasma) further reduces the density of parasitic crystals down to 105 cm-2. The advantage of this novel treatment is short processing time, simplicity, and minimal damage of the substrate surface. INTRODUCTION An increased interest in nano-crystalline diamond (NCD) films for diverse applications requires also development of techniques suitable for diamond structuring. Such structuring is the key technological step for fabrication of simple as well as sophisticated microelectronic devices [1,2]. Common strategy uses a post-growth plasma treatment in which the fabrication of diamond-based devices consists of at least three technological steps: a) nucleation and/or seeding of non-diamond substrates, b) chemical vapor deposition (CVD) of diamond layer and c) postgrowth structuring which is mostly realized by implementing lithographical steps followed by dry etching [3-5]. Limited number of works can be found where very fine and well defined diamond structures (i.e. features far under 1 µm) were realized by reaction ion etching [6]. However, such process is more complex and requires using of plasma-resistive masking material (e.g. SiNx or Al2O3). Finally, the number of technological steps increases and the total processing time is also prolonged. A selective area deposition (SAD) of NCD structures has been proposed as a promising alternative where the third step, i.e. dry plasma etching of diamond films, is omitted. In SAD, the diamond seeding or nucleation layer is patterned already prior to the diamond growth. This is typically done by photolithographic processing. The SAD was recently achieved also by a direct printing of diamond seeds onto a silicon and quartz substrate with feature sizes of 70 µm [7]. The oldest techniques for the SAD predefined the growth area by a deposition of protection layer (i.e. a masking material used as a sa
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