High-resolution Stamps

The printing process can be separated into two parts fabrication of the stamp and use of this stamp to pattern features defined by the relief on its surface. These two processes are typically quite different, although it is possible in some cases to use patterns generated by a stamp to produce a replica of that stamp. The structure from which the stamp is derived, which is known as the master , can be fabricated with any technique that is capable of producing well-defined patterns of surface relief. This master can then be used directly as the stamp, or it can be used to produce stamps via molding or printing procedures. 

It is important to note that the technique for producing the master does not need to be fast or low in cost. It is also not essential for it to have other characteristics that might be desirable for a given patterning task it is used just once to produce a master, which is directly or indirectly used to fabricate stamps. 

Micro-contact printing (pCP) uses high resolution rubber stamps with inks (e.g. alkanethiols) that form self assembled monolayers (SAMs) on the surface (e.g. thin gold film) that is printed [13]. In one pCP approach, these SAMs act as resists for etching material in the unprinted areas, as illustrated in Fig. 10.11. 

For plastic electronics and many other systems, multiple layers must be patterned on top of each other with good overlay registration. A challenge with pCP is that the elastomeric stamps tend to deform during the printing. This deformation can alter, in ways that are difficult to control, the precise alignment of features. There are at least two simple strategies to reduce these problems  

eliminate significant mechanical manipulation of the stamp during printing 

---

Contact Printing with High-resolution Stamps... 

Fig. 10.10. Micro-contact printing process. Schematic illustration of two methods for producing high resolution stamps. The first step of both involves patterning a layer of resist on a flat substrate. This structure, known as the master , is converted to a stamp either by etching or by molding. In the first case (right frames), the resist acts as a mask for etching the underlying substrate. Removing the resist yields a stamp. This structure can be...

Fig. 10.14. High resolution stamp on a plastic substrate. Bending and resolution are illustrated.

Each of these stamps can then be used many times for printing. In a common approach for the high-resolution techniques that are the focus of this chapter, an established lithographic method, such as one of those developed for the microelectronics industry, defines the master. Figure 10.10 schematically illustrates two possible routes to stamps. Both use photolithography to define a pattern of resist on a silicon wafer. 

Nanotransfer printing (nTP) is a more recent high resolution printing technique. It uses surface chemistries as interfacial glues and release layers (rather than inks ) to control the transfer of solid material layers from relief features on a stamp to a substrate [10-12, 44], This approach is purely additive (i.e. material is only deposited in locations where it is needed) and it can generate complex two or three-dimensional structures in single or multiple layers with nanometer resolu-... 

Fig. 10.20. Ill ustration of the usage of a PDMS stamp to print a high resolution Au/Ti layer onto a flexuble subtrate. Separating the stamp from the substrate results in the transfer of the Au/Ti layer from the rised regions onto the substrate.

Zaumseil J, Someya T, Baldwin K, Bao Z, Loo Y-L and Rogers J A, Nanoscale Organic Transistors Formed by Soft Contact Lamination and Source/Drain Electrodes Supported by High Resolution Rubber Stamps , Appl Phys Lett, 2003 82 793— 795. 

Capabilities include colour matching, foil stamping, holograms, unusual die cuts, and high-resolution ink jet imaging. They can also add signature panels, bar codes, encoded magnetic stripes and individual... 

J. Zaumseil et al., Nanoscale organic transistors that use source/drain electrodes supported by high resolution rubber stamps, Appl. Phys. Lett, 82, 793, 2003. 

HCP [340]. Michel and coworkers reported a high-resolution printing technique based on transferring a pattern from an elastomeric stamp to a solid substrate by conformal contact, and described the potential for emerging micro- and nanoscale patterning technologies [91, 341]. 

---