Microelectronics feature size

The MOSFET, the most important microelectronic device, can be reduced in dimension to reach a minimum feature size of 0.1 micron but even lower dimensions (0.05 microns) are foreseen, as demonstrated by recent advanced experiments. 

Most microelectronic facilities can readily achieve minimum feature sizes on the order of 10 pm or better. State-of-the art facilities can produce devices with feature sizes of a few tenths of a micrometer. The lower limit is still decreasing, but the effort required expands exponentially as feature size decreases. Frequently, large numbers of devices can be simultaneously fabricated on the same substrate and subsequently separated by scoring and breaking or sawing the substrate after all processing steps are complete. While complex multilayer devices are possible, most film electrode devices reported to date involve only one or two layers. 

An integrated multi-sensor system requires precise control of sensor characteristics, and may require 10 or more sensors in close proximity. To achieve this, we have to rely on microelectronic processes in order to fabricate sensors with small and precisely controlled feature sizes on silicon. 

The microelectronics industry is continuously reducing the feature size of integrated circuits. In 2006, a DRAM halfpitch, i.e. line widths of 70 nm will be put into practice, until 2010 a reduction to 45 nm is laid down in the International Technology Roadmap for Semiconductors [1]. An integrated circuit consists of a series of patterned functional layers (insulators, metal wires). The structure of each layer is transferred from a mask via a photolithographic process followed by etching or ion implantation. These manufacturing processes must be able to produce the required feature sizes. 

Due to their small feature sizes, microelectronic circuits need protection from environmental hazards such as mechanical damage and adverse chemical influences from moisture and contaminants. Several approaches are currently in use, for example, hermetic encapsulation of the device in sealed metal or ceramic enclosures, application of soft silicone gels as a cover over integrated circuitry, and encapsulation by transfer molding, which is the topic of this report. Both silicone resins and epoxy resins are used for this purpose. As the quality and performance of the epoxy encapsulants improved, the need for the generally more expensive silicone resins diminished. The present work is exclusively devoted to epoxy transfer molding compounds. 

Miniaturization. Typical sizes of functional elements in microsystem-based sensors are on the order of micrometers. A trend to continued shrinkage of feature sizes exists, similar to but not as pronounced as in microelectronics. The overall system size is meanwhile often determined by its packaging and the need for... 

S. Y. Chou and P. R. Kranss, Imprint lithography with sub-10 nm feature size and high throughput. Microelectron. Eng., 35, 237, 1997. 

Chemical reactions initiated in gas discharges and plasmas, in particular in low-temperature, nonequilibrium plasmas, have become indispensable for the advancement of many key technologies in the past 10-15 years (see, e.g Becker et al., 1992 Garscadden, 1992). The plasma-assisted etching of microstructures and the deposition of high-quality thin films with well-defined properties have become crucial steps in the fabrication of microelectronic devices with typical feature sizes of less than 0.5 /rm. The manufacture of state-of-the-art microchips now involves hundreds of process steps, most of them serial, to yield circuits with millions of discrete elements and interconnections in an area of a single square centimeter (Garscadden, 1992). Each step is a physical-chemical interaction that must be controlled. More than one-third of the process steps rely on plasma... 

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