A method of forming a glass substrate includes providing a glass substrate having alumina, translating a pulsed laser beam on the glass substrate to form one or more pilot holes, contacting the glass substrate with an etching solution, and providing agitation. The etching solution has a pH from about 0 to about 2.0, and an etch rate is less than about 3 μm/min. A glass substrate is disclosed having a first surface and a second surface opposite the first surface in a thickness direction, and at least one hole penetrating the first surface, wherein the at least one hole has been etched by an etching solution. A greatest distance d1 between (1) a first plane that contacts the first surface in regions that do not have the at least one hole or a deviation in a thickness of the substrate surrounding the at least one hole and (2) a surface of the deviation recessed from the first plane is less than or equal to about 0.2 μm.