Damage-free sputtering of a transparent conductive oxide using a triode plasma configuration

초록

Transparent conductive oxides (TCOs) are crucial in modern electronics, including displays, smart windows, antistatic coatings, and optoelectronic devices. Their simultaneous transparency and electrical conductivity make them especially useful in solar cells. TCOs are deposited using conventional diode-configured magnetron sputtering, which often leads to sputter damage and degrades the surface passivation of silicon heterojunction solar cells. The bombardment of highly energetic O- ions induces sputter damage, which can be partially recovered by thermal annealing but is partially irreversible. To mitigate this irreversible damage, we propose a triode plasma configuration incorporating a mesh electrode into the conventional diode-configured magnetron sputtering reactor. In contrast with the conventional diode-configured magnetron sputtering of Sn-doped indium oxide (ITO), triode-configured ITO sputtering with the negatively biased mesh electrode successfully alleviates the effect of O- ion bombardment, minimizing sputter damage. The benefits of negatively biased mesh electrode are confirmed through the material properties of the as-deposited ITO films, which exhibit higher carrier mobilities, higher refractive indices, and lower extinction coefficients than conventional diode-deposited films. Additionally, mitigating the effect of O- ion bombardment changes the preferred orientation of the ITO films from the (400) plane to (222). Because the triode configuration is compatible with conventional magnetron sputtering, it can also be applied in diverse electronics technologies, including optoelectronic devices.

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