This paper describes concurrent reactive ion etching using micro ionic liquid ion source (ILIS) array. The system consists of micro needle emitters and a reservoir for the ionic liquid (IL) of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]-[BF4]). The ion beam etching of a (100) silicon substrate using the fabricated ILIS array was demonstrated. As a result of mass spectroscopy during the etching, the peaks of SiF+, SiF 2+, and SiF3+ were observed. The chemical reaction between the silicon and fluorine based ions from the IL was confirmed. Also, etching rate of the silicon using the ILIS array applying 5.1 kV ion-acceleration voltage was calculated from the etched dimple on the substrate and was 1.5 times larger than that of a conventional focused Ga + ion beam applying 30 kV ion-acceleration voltage.