Feature sizes

For tire purjDoses of tliis review, a nanocrystal is defined as a crystalline solid, witli feature sizes less tlian 50 nm, recovered as a purified powder from a chemical syntliesis and subsequently dissolved as isolated particles in an appropriate solvent. In many ways, tliis definition shares many features witli tliat of colloids , defined broadly as a particle tliat has some linear dimension between 1 and 1000 nm [1] tire study of nanocrystals may be drought of as a new kind of colloid science [2]. Much of die early work on colloidal metal and semiconductor particles stemmed from die photophysics and applications to electrochemistry. (See, for example, die excellent review by Henglein [3].) However, the definition of a colloid does not include any specification of die internal stmcture of die particle. Therein lies die cmcial distinction in nanocrystals, die interior crystalline stmcture is of overwhelming importance. Nanocrystals must tmly be little solids (figure C2.17.1), widi internal stmctures equivalent (or nearly equivalent) to drat of bulk materials. This is a necessary condition if size-dependent studies of nanometre-sized objects are to offer any insight into die behaviour of bulk solids. 

Further reduction in feature size to achieve nanoscale stmctures by photohthography will necessitate the use of ever smaller wavelengths of light. 

Process Feature Size Equipment Remote handling Corrosion resistance... 

FIGURE 4.14 Feature size on mieroeleetronie deviees has steadily deelined over the years as improved ehemieal etching processes have been developed. This graph shows feature size as a function of the year in which the device with the smallest feature size was first produced. Courtesy, AT T Bell Laboratories. 

According to the international technology roadmap for semiconductors, chips with a wafer diameter of450 mm and a feature size of 0.05 /xm by 2011 will serve to decrease manufacturing costs [29]. In the integrated circuit (IC) manufacture process as shown in Fig. 21 [30], dielectric stacks have been formed by the ion etching on the coating of dielectric material formed on the silicon surface (Fig. 21 (a)). 

The diameter of the spot is greater than 55% of the feature size. 

Figure 12.1. Silicon-integrated circuit nominal feature size over the years.

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