Topography Evolution of Si (001) Substrate Fabricated by Ar + Ion Beam Sputter Etching
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Topography Evolution of Si (001) Substrate Fabricated by Ar+ Ion Beam Sputter Etching Hyung Seok Kim, Ju Hyung Suh, and Chan Gyung Park Department of Materials Science & Engineering Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea ABSTRACT Self-formed nanopatterns on Si (001) substrates fabricated by ion beam sputter etching were investigated by atomic force microscopy (AFM). The ion beam sputtering was performed with an Ar+ ion beam produced from a Kaufman type ion gun. In order to fabricate the periodic nanoscale patterns on Si surface, the effects of sputter parameters such as ion energy, flux, incident angle and etching time on surface morphology was investigated. As a result, nanometer scale ripples and 3-dimensioal nanodots were formed uniformly after ion beam sputtering. The surface morphology of Si was significantly dependent on incident angle and ion beam flux. INTRODUCTION Ion beam sputtering is a widespread experimental technique used in a large number of applications such as thin film deposition, sputter etching, substrate cleaning and surface analysis [1]. Recently, it has been reported that ion sputtering produces periodic nanopatterns and 3-dimensional nanodots on semiconductor surfaces under certain etching conditions [2, 3]. Ion sputtered nanopatterns are very important for the development of optoelectronic and quantum devices because of the low cost and efficient mass production of nanometer scale surface structures [4]. The formation mechanism of these nanopatterns was suggested by Bradley and Harper’s model (B-H model) [5]. According to the B-H model, if there is unevenness on surface, regular patterns form due to differences of momentum, which is transferred from accelerated ions to the substrate in the concave and convex surface regions. However, the exact formation mechanisms of nanopatterns in various materials have not been ascertained yet due to the insufficient understanding of ion beam dynamics and the collision process of energetic ions. The effects of sputter etching parameters such as ion energy, flux and incident angle on surface morphology should be ascertained in order to the successfully apply ion beam etching to surface treatment. In the present study, Si (001) substrates were irradiated by an Ar+ ion beam produced by a 3 cm Kaufman type ion gun and the change in surface morphology was
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then investigated by atomic force microscopy (AFM). The effects of ion energy, flux, incident angle and etching time on surface morphology was investigated. Nanometer scale patterns such as ripples and 3-dimensioal nanodots were formed uniformly after ion beam sputtering. The topography of Si was significantly dependent on ion beam flux and incident angle, however, it was independent of ion beam energy and etching time. EXPERIMENTAL An ion beam sputtering system with a Kaufman type ion beam source was employed for surface etching [6, 7]. The Kaufman type ion gun has a 3 cm ion beam diameter. Figure 1 shows the schematic of the ion beam sputter system a
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