Intaglio techniques include engraving, etching, and drypoint. These surfaces can be created by etching or using lithography. Fluorine is the main etchant in the silicon etching process. Silicon is machined using various etching processes. Mezzotint is often combined with other intaglio techniques, usually etching and engraving. Compared to intaglio techniques like etching and engraving, only low pressure is required to print. However, the photographic developer used for photoresist resembles wet etching. CMP cleaning is a hybrid process to smooth surfaces using both etching and mechanical polishing. Sometimes, photolithography is used to create structure without any kind of post etching. BCl is also used in plasma etching in semiconductor manufacturing. Gas assisted deposition and FIB etching process are shown below. Steel is growing in popularity as an etching substrate. Such anisotropy is maximized in deep reactive ion etching. It can be fabricated in an additive fabrication combined with etching and nanoimprint methods. Dry etching can combine chemical etching with physical etching or ion bombardment.