Embodiments provide a patterning process. A photoresist layer is patterned. At least portions of the photoresist layer are converted from an organic material to an inorganic material by a deposition process of a metal oxide. All or some of the patterned photoresist layer may be converted to a carbon-metal-oxide. A metal oxide crust may be formed over the patterned photoresist layer. After conversion, the patterned photoresist layer is used as an etch mask to etch an underlying layer.