Patterning: Principles and some new developments

This article provides an overview of various patterning methodologies, and it is organized into three major sections: generation of patterns, replication of patterns, and three-dimensional patterning. Generation of patterns from scratch is usually accomplished by serial techniques that are able to provide arbitrary features. The writing process can be carried out in many different ways. It can be achieved using a rigid stylus; or a focused beam of photons, electrons, and other energetic particles. It can also be accomplished using an electrical or magnetic field; or through localized add-on of materials such as a liquid-like ink from an external source. In addition, some ordered but relatively simple patterns can be formed by means of self-assembly. In replication of patterns, structural information from a mask, master, or stamp is transferred to multiple copies with the use of an appropriate material. The patterned features on a mask are mainly used to direct a flux of radiation or physical matter from a source onto a substrate, whereas a master/stamp serves as the original for replication based on embossing, molding, or printing. The last section of this article deals with three-dimensional patterning, where both vertical and lateral dimensions of a structure need to be precisely controlled to generate well-defined shapes and profiles. The article is illustrated with various examples derived from recent developments in this field.