Simulation of capacitively coupled Ar/O₂ discharges based on global/equivalent circuit model and an extended reaction set

Abstract Radio frequency capacitively coupled plasmas (RF CCPs) operated in Ar/O 2 gas mixtures which are widely adopted in microelectronics, display, and photovoltaic industry, are investigated based on an equivalent circuit model coupled with a global model. This study focuses on the effects of singlet metastable molecule <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msup> <mml:mi mathvariant="normal">b</mml:mi> <mml:mn>1</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">g</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> , highly excited Herzberg states <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msup> <mml:mi mathvariant="normal">A</mml:mi> <mml:mn>3</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">u</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo>,</mml:mo> <mml:msup> <mml:mi mathvariant="normal">A</mml:mi> <mml:mn>3</mml:mn> </mml:msup> <mml:msub> <mml:mo>Δ</mml:mo> <mml:mi mathvariant="normal">u</mml:mi> </mml:msub> <mml:mo>,</mml:mo> <mml:msup> <mml:mi mathvariant="normal">c</mml:mi> <mml:mn>1</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">u</mml:mi> <mml:mo>−</mml:mo> </mml:msubsup> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> , and the negative ion <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> , which are usually neglected in simulation studies. Specifically, their impact on particle densities, electronegativity, electron temperature, voltage drop across the sheath, and absorbed power in the discharge is analyzed. The results indicate that <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:msup> <mml:mi mathvariant="normal">b</mml:mi> <mml:mn>1</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">g</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> <mml:mo>−</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> exhibit relatively high densities in argon–oxygen discharges. While <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msup> <mml:mi mathvariant="normal">A</mml:mi> <mml:mn>3</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">u</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> <mml:mo>,</mml:mo> <mml:msup> <mml:mi mathvariant="normal">A</mml:mi> <mml:mn>3</mml:mn> </mml:msup> <mml:msub> <mml:mo>Δ</mml:mo> <mml:mi mathvariant="normal">u</mml:mi> </mml:msub> <mml:mo>,</mml:mo> <mml:msup> <mml:mi mathvariant="normal">c</mml:mi> <mml:mn>1</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">u</mml:mi> <mml:mo>−</mml:mo> </mml:msubsup> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> play a critical role in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:msup> <mml:mi mathvariant="normal">b</mml:mi> <mml:mn>1</mml:mn> </mml:msup> <mml:msubsup> <mml:mo>Σ</mml:mo> <mml:mi mathvariant="normal">g</mml:mi> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> production, especially at higher pressure. The inclusion of these particles reduces the electronegativity, electron temperature, and key species densities, especially the O − and O* densities. Moreover, the sheath voltage drop, as well as the inductance and resistance of the plasma bulk are enhanced, while the sheath dissipation power and total absorbed power decrease s