VLSI , devices

Although the majority of NAA applications have been in the area of bulk analysis, some specialized uses need to be mentioned. One such unique application is the measurement of phosphorus in thin films (about 5000 A) of phosphosilicate (PSG) or borophosphosilicate (BPSG) glasses used in VLSI device fabrication. In this case,... 

The development of low-dielectric-constant materials as ILDs is crucial to achieve low power consumption, reduce signal delay, and minimize interconnect cross-talk for high-performance VLSI devices. In one of the multilevel interconnect process routes, metal lines (e.g., A1—Cu or Cu) are patterned through reactive ion etching, and then dielectric films are filled in the trenches formed between these lines. These trenches can have widths in the sub-0.5 pm range and aspect ratios greater than 3. Therefore, small gap-filling capability is also required for such dielectrics. 

Plot of the power delay product vs. year and cost per bit vs. year for commercially available VLSI devices. 

Materials that exhibit enhanced solubility after exposure to radiation are defined as positive resists. The mechanism of positive resist action in most of these materials involves either main-chain scission or a polarity change. Positive photoresists that operate on the polarity change principle have been widely used for over three decades in the fabrication of VLSI devices and they exhibit high resolution and excellent dry etching resistance. Ordinarily, the chain scission mechanism is only operable at photon wavelengths below 300 nm where the energy is sufficient to break main chain bonds. 

The continual progress in VLSI device development is placing increasing demands on the lithographic technologies used for their manufacture. At the present time, almost all commercial devices are made by photolithography utilizing... 

Materials that exhibit enhanced solubility after exposure to radiation are defined as positive resists. Positive acting materials are particularly attractive for the production of VLSI devices because of their high resolution properties. The chemistry of these systems generally involves either chain-scission or solution-inhibition mechanisms. 

Y. Taur and T. H. Ning, Fundamentals of Modern VLSI Devices, Cambridge University Press, New York, 1998, Chaps. 4 and 5. 

Resist requirements for microfabrication are similar, regardless of the exposure technology. While the general requirements have been discussed in many articles (2,3) it is instructive here to review the more important requirements, particularly in view of the special limitations imposed by the need to fabricate fine line VLSI devices. 

A focused ion beam (FIB) can be used instead of a conventional ion mill to mill a sample. In such cases, especially targeted regions of a sample can be thinned for observation in the TEM. This technique requires expensive instrumentation but is becoming extremely popular in the age of VLSI devices and nanostructured components, where precise thinning of specific areas is necessary. 

When working with this type of resist to make VLSI devices there are several problems that come up, particularly the need for improved thermal stability from the resist images emd a method to control light that is reflected or scattered in a nonimagewise manner. The function of a development enhancement agent is to increase the dissolution rate of the photoresist so that polymers with better physical properties but slow dissolution rates may be used. The dyes... 

Tong Q, Lee T-H, Kim W-J, Tan T, Gosele U. Feasibility study of VLSI device layer transfer by CMP PETEOS direct bonding. Proceedings of IEEE International SOI Conference 2001. p 36-37. 

Enhancement of Gold—Aluminum Wirebond Reliability in Plastic Encapsulated Very Large Scale Integration (VLSI) Devices Through C—Br Bond Stabilization... 

Identifying and addressing issues related to high T materials required to process components for both small- and Jarge-scale demonstration projects should be undertaken. For example, the growth, pattern generation and transfer of specific material structures with fully optimized properties for VLSI devices must be... 

The resistivity of the bulk material is at 22 pQ cm, but resistivities measured for TiN films are substantially higher with values in the range of 40 to more than 1000 pQ cm. In this context, it should be mentioned that resistivity requirements for adhesion or barrier layers in VLSI devices should be less than 600 pQ cm [73]. 

As the VLSI device fabrication efforts intensify over the next few years, it is becoming very clear that the trench technology will become a dominant feature and the trench isolation an integral part in most of those VLSI device and circuit structures. 

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