Embodiments of the present disclosure relate to apparatus and methods for forming films having uniformity of thickness on substrates. Embodiments of the present disclosure may be used to measure thickness or other properties of films being deposited on a substrate without knowing beforehand the surface properties of the substrate. Embodiments of the present disclosure may be used to measure thickness or other properties of a plurality of layers being formed. For example, embodiments of the present disclosure may be used in measuring thickness of vertical memory stacks.