Any object can be seen as a complex of different materials arranged in a defined manner in Euclidean space. The manufacture or development of such an object can be perceived as a re-arrangement of these materials by either removing or adding new ones. The most common manufacturing methods are based on assembling an entire body from separate parts. Such methods are applied to electronics as well, in which numerous circuits can be assembled by using a limited range of components: integrated circuits, wires, resistors, capacitors, etc. This method relies on standard elements, the manufacture of which involves different technological processes.

An alternative method based on standard processes was applied in the manufacture of integrated circuits. The planar process involves manufacturing solid-state devices and integrated circuits through the formation of regions with different types of conductivity in mono-crystalline semiconductors (germanium, silicon, gallium arsenide). In microelectronics based on planar technology, all structures are to be formed either near of a silicon wafer surface or coated with thin dielectric and metallic films. The depth of structures in silicon wafers and the thickness of coated films are nanometric (0,01 -1 p), so any of these layers can be approximated in terms of a two-dimensional space. The manufacture of structures is provided in specific places of a layer by etching, doping or deposition. Structure shape is performed by transfering the structural medium configuration to the object layer, via photolithography, electron — or ion — beam lithography, as well as X-ray lithography. Nevertheless, these technological processes are accompanied by so-called parasitic effects, which have been noted when planar technology was introduced in the early 1960’s. Their negative impact has become more significant with the reduction of structure sizes over the years. In 1969, these parasitic effects stimulated the search for new manufacturing methods, including self-aligning processes, which, in turn, provided the experimental background for self-formation.

A planar structure can be seen as a part of Euclidean space separated by two parallel planes and cylinder surface of any configuration. The distance between two planes is determined by the processes of insertion or by the coating rate of thin films, whereas the structure configuration in plane is to be created by the lithography process. In order to obtain a defined structural configuration in a homogeneous initial object, a structural medium is essential. The medium must be of an initial configuration and interact with the object in its distinct region. As a rule, the radiation medium (light beam, electron or ion beam, X-ray) is modulated in space. In microelectronics the object is generally a radiation — sensitive layer, known as a photoresist.

Any lithography process involves a transfer of a plane figure from medium to object and can be regarded as an example of a homeomorphic mapping where number and arrangement of figures in the object correspond adequately to the same in the medium.

The process of transfer figures from medium to object is illustrated by Fig. 1, and represents external formation, known as planar technology. The time and place of this interaction between a medium and an object are regulated by human or automatic factors.

The exposed photoresist regions initially are component parts of the object, but they will not comprise any part of the ultimate electron device. The photoresist regions merely reflect the configuration transferred from the medium, which will later define a distinct region in the wafer. Fig. 2a illustrates how these processes can be carried out in which 1 represents the silicon wafer, 2- oxide, 3- photoresist and 4- exposed photoresist.

Next step involves removing the exposed part of the photoresist by means of a developer (Fig. 2b). A window in the oxide layer is then etched through the photoresist window (Fig.

2c). The implantation of impurities through the oxide window can now be accomplished (Fig.

2d).

This is an example of how the interactions between chaotic media (liquid or gas) and a structured object produce a transfer of configuration from one object layer to another layer, which differs fundamentally from external formation. That is why these processes should be referred to as internal formation, recognised as self-alignment technology. The timing of the interaction is regulated by human or automatic factors, while interaction area is determined by the object itself.

In practice the self-formed layers will have a non-linear pattern because the layers are

three-dimensional. The oxide etching process described in Fig. 2 does not actually transfer exact vertical boundaries from the photoresist layer to the oxide layer. The points of contact between the etcher and the oxide shift perpendicularly from the surface. Consequently, the etching profile corresponds to a circular segment, as can be seen in Fig. 3a and b. If the etching process continues the plane structure begins to widen (Fig. 3c and d).

From a topological point of view a homomorpheous transformation occurs in this case because only geometrical change takes place. However, more complicated patterns can be achieved, as shown in Fig. 4,

where interaction of structured object with a chaotic medium predetermines the emerge of new patterns that didn’t exist in the initial topology. In this case non-homomorpheous

1. c-Si wafer

2. Metal

3. Polymer

4. Metal oxide

(a) Cross-section of three layered structure

(b) Top view of the same structure after metal oxidation

(c) Top view of oxidised structure (b)

(d) Top view of new figure arising by two initial structures 5 & 6 (metal) electroplating