Selective and deep plasma etching of SiO2: Comparison between different fluorocarbon gases (CF4, C2F6, CHF3) mixed with CH4 or H2 and influence of the residence time

Abstract

Articles you may be interested inDifferences in erosion mechanism and selectivity between Ti and TiN in fluorocarbon plasmas for dielectric etch J. Vac. Sci. Technol. B 30, 041811 (2012); 10.1116/1.4736979 Wettability and thermal stability of fluorocarbon films deposited by deep reactive ion etching J. Vac. Sci. Technol. A 23, 434 (2005); 10.1116/1.1875232 Langmuir probe measurements in an inductively coupled plasma: Electron energy distribution functions in polymerizing fluorocarbon gases used for selective etching of SiO 2Residence time effects on SiO 2 /Si selective etching employing high density fluorocarbon plasma SiO 2 is a well suited material for integrated optic applications and is also attractive for microelectromechanical system and micro-optical electromechanical system fabrication. Such optical components require deep oxide etching ͑several microns͒ and subsequent high selectivity with respect to the mask. In this article, we describe the influence of various process parameters ͑gas mixture, pressure, plasma power, and residence time͒ on the selective etching of SiO 2 with respect to Si in inductively coupled plasma ͑ICP͒ fluorocarbon with the aim of finding the best compromise between high selectivity and high oxide etch rate. Oxide etch rate is improved by decreasing pressure or increasing source power within the acceptable process windows, respectively, 3-20 mTorr and 1000-2000 W, but the gain in selectivity is low (ϫ1.5). Adding methane rather than more commonly usual hydrogen resulted in higher selectivity without significant decrease in the oxide etch rate. A relatively good correlation is found between the selectivity and the (CϩH)/F ratio of the precursor molecule. However, we show that varying the hydrofluorocarbon mixture does not allow us to improve both oxide etch rate and selectivity. In this regard, the residence time is the most significant parameter: choosing the appropriate amount of methane mixed with C 2 F 6 , and decreasing t R leads to an improvement in both the selectivity (ϫ7) and the oxide etch rate (ϫ1.5). Finally, the influence of these parameters on pattern transfer is investigated.

Integrated optics based on plasma processed dielectric materials

“…Afterwards, waveguide patterns are printed by UV-lithography on a positive resin spread by spin coating. In order to shape SiO x C y H z core waveguides, the plasma polymer (uncoated with the resin) and unexposed resin are then etched by a CHF 3 plasma in an Inductively Coupled Plasma (ICP) reactor [40]. Etching is performed at low pressure (5 mTorr equivalent to a total gas flow rate inferior to 40 sccm), 1500 W RF power and 150 V (200 W) substrate bias.…”

Photonics integrated circuits on plasma-polymer-HMDSO: Single-mode TE00-TM00 straight waveguides, S-Bends, Y-Junctions and Mach-Zehnder Interferometers

“…Afterwards, waveguides patterns are printed by UV-lithography on a positive resin spread by spin coating. The plasma polymer (uncoated with the resin) and unexposed resin are then etched by a CHF 3 plasma in an Inductively Coupled Plasma (ICP) reactor [14]. Etching is performed at low pressure (5 mTorr equivalent to a total gas flow rate inferior to 40 sccm), 1500 W RF power and 150 V (200 W) substrate polarization.…”

Positive sheath behaviour in low pressure Argon plasma

“…Sheath acts as the transition between plasma and surface, and is therefore a crucial element in many fields of plasma applications like tokamak (ITER), etching [1], plasma immersion for ion implantation (PIII) [2,3]. If dynamics of the sheath is dominated by one specie (electron or ion) it is called space charge limited or Child-Langmuir (CL) sheath.…”