Transfer of functional ceramic thin films using a thermal release process.

It is also being explored for new applications such as nanorods, [ 9 ] domain physics, [ 10 ] and nanodevices. [ 11,12 ] Transfer of PZT thin fi lms can allow integration of such fi lms on substrates that are incompatible with the requirements of fi lm deposition. However, transfer of functional ceramic thin fi lms has long been hampered by the diffi culty of detaching the fi lm from the growth substrate. [ 13 , 14 ] Here, we describe a transfer process for PZT fi lms grown on Ti/Pt coated Si wafers, where the fi lms are solder bonded onto a target substrate and lifted off in one step, using separation of the PZT–Pt interface by thermal stress. The transferred fi lms show low mechanical damage, ferroelectric hysteresis with an “imprinted” polarization, [ 15 ] reduced permittivity, and improved loss tangent. Generally PZT fi lms are epitaxially grown on ordered metal seed layers, such as Ti/Pt layers deposited on Si wafers, and require high-temperature processing for crystallization and poling. [ 16 ] Therefore, the transfer of these fi lms onto target substrates is important to enable them to be used in integrated structures that are not compatible with these materials or process steps, such as organic substrates. Several techniques have been reported for transfer of PZT fi lms to make devices, involving wet etching, [ 17 ] dry etching, [ 18 ] mechanical grinding and etching, [ 13 ] or laser induced forward transfer (LIFT). [ 14 ] Wet etching can be used to pattern PZT fi lms, but is not practical for the etching of some metal seed layers, such as Pt, which is normally removed by dry etching. In a typical transfer process, a metal-bumped PZT fi lm is fi rst bonded onto a target substrate and then a lift-off process is required to separate the patterned