Hardened chips are often manufactured on insulating substrates instead of the usual semiconductor wafers. Nitrogen trifluoride is used in the plasma etching of silicon wafers. It is commonly used to etch glass and silicon wafers. They tubes align in regularly spaced rows on silicon wafers. The HIC detected heavy ions using stacks of single crystal silicon wafers. Germanium is the substrate of the wafers for high-efficiency multijunction photovoltaic cells for space applications. Dual junction cells can be made on Gallium arsenide wafers. Tapioca chips, thinly sliced tapioca wafers, similar to potato chips, are also popular. The silicon wafers start out blank and pure. The stress in thin film semiconductor structures results in the buckling of the wafers. The surface of epitaxial wafers may be textured to enhance light absorption. Wacker Polysilicon produces hyper-pure polysilicon for use in electronic and solar wafers. Similarly it is a cleaning agent, e.g., for steel, silicon wafers, and integrated circuits. "Stardust" was launched carrying two sets of identical pairs of square silicon wafers. Wine and unleavened wafers or unleavened bread is used.