VLSI technology

The physical techniques used in IC analysis all employ some type of primary analytical beam to irradiate a substrate and interact with the substrate s physical or chemical properties, producing a secondary effect that is measured and interpreted. The three most commonly used analytical beams are electron, ion, and photon x-ray beams. Each combination of primary irradiation and secondary effect defines a specific analytical technique. The IC substrate properties that are most frequendy analyzed include size, elemental and compositional identification, topology, morphology, lateral and depth resolution of surface features or implantation profiles, and film thickness and conformance. A summary of commonly used analytical techniques for VLSI technology can be found in Table 3. 

Table 3. Analytical Techniques Used in VLSI Technology...

Electron Beam Techniques. One of the most powerful tools in VLSI technology is the scanning electron microscope (sem) (see Microscopy). A sem is typically used in three modes secondary electron detection, back-scattered electron detection, and x-ray fluorescence (xrf). AH three techniques can be used for nondestmctive analysis of a VLSI wafer, where the sample does not have to be destroyed for sample preparation or by analysis, if the sem is equipped to accept large wafer-sized samples and the electron beam is used at low (ca 1 keV) energy to preserve the functional integrity of the circuitry. Samples that do not diffuse the charge produced by the electron beam, such as insulators, require special sample preparation. 

For example, chloride and duoride ions, even in trace amounts (ppm), could cause the dissolution of aluminum metallization of complimentary metal oxide semiconductor (CMOS) devices. CMOS is likely to be the trend of VLSI technology and sodium chloride is a common contaminant. The protection of these devices from the effects of these mobile ions is an absolute requirement. The use of an ultrahigh purity encapsulant to encapsulate the passivated IC is the answer to some mobile ion contaminant problems. 

Polymer radiation chemistry is a key element of the electronics industry, in that polymer materials that undergo radiation induced changes in solubility are used to define the individual elements of integrated circuits. As the demands placed on these materials increases due to increased density, complexity and miniaturization of devices, new materials and chemistry will be required. This necessitates continued efforts to understand fundamental polymer radiation chemical processes, and continued development of new radiation sensitive materials that are applicable to VLSI Technology. 

Bock K (2005) Polytronics - electronics and systems on flexible substrates. IEEE VLSl-TS A International Symposium on VLSI Technology, Hsinchu, Taiwan, pp 53-56... 

S. M. Sze, VLSI Technology (2nd edition, McGraw-Hill Book Company, New York, 1988) p. 383. 

S. Lai, Proceedings of the International Symposium on VLSI Technology, Systems, and Applications (VLSTTSA), Taipai, Taiwan, 1993, p. 47. 

Plummer, J. D., Griffin, P. B. and Deal, M. D. Silicon VLSI Technology Fundamentals, Practice, and Modeling (Prentice Hall, 2000). 

Striny, K. M. In VLSI Technology, Second Edition Sze, S. M., Ed. McGraw-Hill New York, 1988 Chapter 13. 

This chapter gives explicit examples of how the techniques of wet (solution) chemistry can be applied to the production of integrated circuits. The quality control for processed thin films, chemicals, and pure water, along with microcontamination analysis, to resolve production problems are discussed. These examples indicate that wet chemical techniques are the only ones available for absolute standardization and measurement of trace metals and their effect on the devices produced by current very-large-scale-integration (VLSI) technology. 

Cohalt Silicides. The interest in the study of metal silicides is growing at much faster rate because of their use as interconnects and contacts in semiconductor and VLSI technology. The silicides in general have lower resistivity than polysilicon and are able to withstand high annealing temperatures than most pure metal interconnects. In the development of the metal-silicide studies the most important quantities of interest are metal/Si ratio as a function of depth, the silicide film thickness and the identification and the quantification of any contaminants present. The conventional surface analysis techniques... 

Plummer JD, Deal M, Griffin PD. (2000) Silicon VLSI Technology, D ed. Prentice Hall. 

Improvements in the performance of integrated circuits and the trend towards VLSI-technology require the replacement of polycrystalline silicon by materials with a lower resistivity for use as gate electrodes. Transition metal silicides appear to be valuable possibilities for these applications. Timgsten-silicon compounds could be suitable precursors for the precipitation of tungsten-silicide thin films. Moreover tungsten-silicon compounds are nearly unknown and of scientific interest. 

Lee HS, Park MH, Shin YG, Park T-S, Kang HK, Lee SI, Lee MY. An optimized densification of the filled oxide for quarter micron shallow trench isolation (STl). S5mposium on VLSI Technology Technical Digest June 1996. p 158-157. 

Elbel N, Gabric Z, Langheinrich W, Neureither B. A new STI process based on selective oxide deposition. Symposium on VLSI Technology, Digest of Technical Papers June 1998. p 208-209. 

---