The bendable silicon-based ultra-thin chips (UTCs), with thickness below 50 μm are needed to provide high-performance flexible electronics for several emerging applications ranging from flexible displays to robotic e-skin. The UTCs from standard silicon wafer are obtained by etching the bulk material from the backside of the wafer using a wet chemical etchant. During the etching process, it is imperative to protect the front processed side from the etchant as in most cases, the etchant is incompatible with the metals and other materials used in the fabrication of devices. This paper reports a new method using polydimethylsiloxane (PDMS) as the protective coating during wet etching of silicon. The silicon sample is thinned to sub-25 μm thickness using Tetramethylammonium hydroxide (TMAH), while PDMS acting as a protective coating, which is removed after thinning by using a chemical composition involving a nucleophilic attack on siloxane bond. As a bulk material with lowtemperature processing requirements, PDMS offers an interesting alternative to other commercially available materials. The presented approach offers a range of advantages compared to other polymeric materials that are being used for the abovementioned purpose.