Porous membranes are provided according to the invention having desirable coefficient of thermal expansion and large surface area, for example at least about 4,000 mm2. These porous membranes may be made according to an exemplary process employing lithographic patterning of a photoresist followed by development of the photoresist and etching. In one aspect, the etch barrier layer is chosen from a material that does not react with or incorporate metal or other contaminants into the membrane layer.