Contact printing resolution

The ultimate resolution capability of the terpolymers was determined by electron beam irradiation (20kv, 5X10 C/cm ). Figure 4a depicts O.Siim and l/im lines and spaces printed in P(M-OM-CN) (69 16 15). Optical contact printing exposures (200-400 nm) are illustrated by Figure 4b which shows 0.75fim lines and spaces, and Figure 4c which depicts profiles of Ijim lines and spaces. These results are typical of all the materials examined. 

Proximity printing, a variation of contact printing, preserves a minimum gap of approximately 10-30 xm between the silicon wafer and the mask. Although the problem of particulate contamination is avoided, light distortion is enhanced, and a loss in resolution results. 

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...

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. 

Micro-contact printing can be used in plastic electronics to form high-resolution source/drain electrodes with short channel lengths [14]. Depositing an organic semiconductor on top of these electrodes yields a transistor with a layout like that... 

During the early years of the microelectronics industry, the imaging process used to define the layers of patterned conductor, insulator, and semiconductor materials that constitute active devices was accomplished by using contact printing in conjunction with resists based on photo-induced cross-linking to generate differential solubility. The resolution of the processes in... 

In this equation, is half the grating period, s is the gap between the mask and the photoresist surface, X is the wavelength of the exposing radiation, and d is the photoresist thickness. For contact printing s = 0 and from equation (3.1), with X = 400 nm and a 1 /zm thick resist, the maximum resolution is slightly... 

On the basis of equation (3.2), for a gap of 10 iim, using 400 nm exposing radiation, the resolution limit is about 3 /u,m which is poorer than that of contact printing. 

Practical and technical difficulties associated with contact printing led to a modification of the latter technique, such that the mask and the wafer were separated by a small, accurately controlled gap of 10-25 p,m during exposure. Introduced in the early 1970s, this technique, known as proximity printing, minimizes mask and wafer damage caused by contact, but at the expense of resolution. This gap, however, limited resolution because of diffraction. The theoretical resolution of proximity printing is given by... 

In contact printing [see Fig. 13.24(a)] the mask and the photoresist-coated substrate are in direct contact during exposure, with the mask held chrome-side down on the resist film. Patterns on the mask are transferred to the entire wafer hy broadband radiation. The theoretical resolution hmit of contact printing is given by ... 

However, due to the defectivity problem associated with contact printing, as discussed above, the first noncontact aligners, called proximity aligners, were introduced in 1973 by Kasper Instruments. In proximity printing mode, the mask does not come into direct physical contact with the wafer [see Fig. 13.24(a)]. Rather, it is held 10-25 p.m above the upper surface of the resist-coated wafer. This gap, however, limited resolution on account of diffraction. The theoretical resolution limit of proximity printing is given by the expression... 

Shown in Lig. 15.4 are 80-nm contacts printed with SCALPEL technology, illustrating the resolution capability of this technology. 

Contact printing The resolution is the limited by the optical skin depth of the mask material. 

Nanoimprinting A master stamp is used directly for hot embossing of a substrate, usually made of a polymer. This allows the stamp to produce many patterned substrates. Although there is no diffraction hmit here, hot embossing has been applied mainly for low-resolution applications, in various fields such as miniaturized total-analysis Systems (p.TAS), microfluidics, and microoptics. UV-nanoimprint lithography corresponds to contact printing with UV exposure. 

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