Characteristics of In_0.7Ga_0.3As MOS Capacitors with Sulfur and Hydrazine Pretreatments

Abstract

This paper proposes an effective pretreatment process that combines wet ammonium sulfide ((NH 4 ) 2 S) dipping and hydrazine (N 2 H 4 ) vapor treatment before high dielectric constant (κ, kappa) deposition to reduce native oxide and elemental arsenic (As) before atomic layer deposition of ammonium oxide (Al 2 O 3 ) gate dielectrics on n-doped indium gallium arsenide (In 0.7 Ga 0.3 As) layers to form metal oxide semiconductor capacitors (MOSCAPs). X-ray photoelectron spectroscopy (XPS) analysis confirms that sulfuration of In 0.7 Ga 0.3 As surface by (NH 4 ) 2 S solution dipping can effectively reduce indium-oxygen (In-O), gallium-oxygen (Ga-O), arsenic-oxygen (As-O) bonds while elemental As still exist at the high-κ/In 0.7 Ga 0.3 As interface. Furthermore, N 2 H 4 treatment on sulfurated In 0.7 Ga 0.3 As can effectively suppress the native oxides and elemental As. Accordingly, the obtained data indicate that the combination of chemical sulfur pretreatment and N 2 H 4 treatment is advantageous to passivate the trap states on In 0.7 Ga 0.3 As metal-oxide-semiconductor capacitors (MOSCAPs). Moreover, forming gas annealing (FGA) process could further improve the capacitance-voltage (C-V) characteristics and the interface trap density (D it ) of In 0.7 Ga 0.3 As MOSCAP could be reduced significantly, achieving a value of 1.2 × 10 12 cm −2 eV −1 .