Multi-stage deposition system for growth of inclined c-axis piezoelectric material structures

#The present disclosure relates to structures including inclined c-axis hexagonal crystal structure piezoelectric materials such as aluminum nitride (AIN) and zinc oxide (ZnO), as well as systems and methods for producing inclined c-axis hexagonal crystal structure piezoelectric material. Inclined c-axis hexagonal crystal structure piezoelectric materials may be used, for example, in various resonators as well as in thin film electroacoustic and/or sensor devices, particularly for sensors operating in liquid/viscous media (e.g., chemical and biochemical sensors), and the like.

#Hexagonal crystal structure piezoelectric materials such as AIN and ZnO are of commercial interest due to their piezoelectric and electroacoustic properties. Beneficial properties in this regard include a high quality factor, moderate coupling coefficient, moderate piezoelectric constant, high acoustic velocity, and low propagation losses. In addition to these characteristics, AIN thin films are chemically stable and compatible with various integrated circuit fabrication technologies, thereby making AIN an attractive material for fabrication of electroacoustic devices, including bulk acoustic wave (BAW) devices such as bandpass filters and the like.

#A primary use of electroacoustic technology has been in the telecommunication field (e.g., for oscillators, filters, delay lines, etc.). More recently, there has been a growing interest in using electroacoustic devices in high frequency sensing applications due to the potential for high sensitivity, resolution, and reliability. However, it is not trivial to apply electroacoustic technology in certain sensor applications—particularly sensors operating in liquid/viscous media (e.g., chemical and biochemical sensors)—since longitudinal and surface waves exhibit considerable acoustic leakage into such media, thereby resulting in reduced resolution.

#FIG. 1 is a simplified schematic of an axial sputtering deposition apparatus arranged to eject metal atoms from a target surface toward a substrate supported by a substrate holder substantially parallel to the target surface, with central axes of the target surface and the substrate being aligned with one another.

#FIG. 2A is a schematic representation of a rocking curve measurement geometry of an AIN film structure obtained by radio frequency magnetron sputtering in a reactive gas environment in a planar sputtering system without tilting the substrate, showing zero tilt angle at the center, and a radially symmetrical variation of tilt angle of crystallites in the AIN film structure.

#FIG. 2B is a plot of tilt angle versus distance from center for the AIN film structure described in connection with FIG. 2A, showing a nearly linear variation of tilt angle with increasing distance away from a center of the AIN film structure.

#Embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing the invention. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

#It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

#Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.