The diffusion of boron in ion implanted LPCVD polycrystalline silicon is shown to be dominated by grain boundary diffusion at low and moderate concentrations. The diffusion coefficient is 2 to 3 orders of magnitude larger than its value in crystalline silicon. In preannealed polysilicon, the boron diffusion coefficient is found to be 30% smaller than in polysilicon annealed after implantation. This reflects the effect of the grain size in the diffusion coefficient since preannealed polysilicon has larger grains and smaller density of grain boundaries per unit area.

Gettering by the dislocation network caused by P-diffusion into the back surface of Si wafers at 950° C for 1 hr. is often used for VLSI. However, transistors with sub-micron gates are jeopardized at 950°C because of possible source-drain punch through by lateral P-diffusion. The temperature dependence of gettering by P-diffusion has been investigated at 950, 900, and 850°C. Gettering by P-diffusion was found to be marginal at 900°C and totally ineffective at 850°C.

Recently published data on the solubility and diffusivity of interstitial oxygen in Czochralski-grown Si has been used to develop a simple out-diffusion model for denuded zone formation during thermal oxidation. Comparison with experimental observations on samples with high interstitial SiO2 concentration [Oi]0, exposed to dry oxidation at 1100° C for various times up to 8 hrs. and followed by 24 hr. anneals in N2 at 700°C and 1050°C, reveal that SiO2 precipitation occurs when the supersaturation ratio exceeds 4.7. The model implies an optimum denuding temperature near 100° C for a dry oxidation time of 4 hrs. The bulk defect density was also observed to decrease more than a factor of 5 as the denuding time was increased from 0 to 8 hrs.

Intrinsic gettering by SiO2 precipitates in Czochralski-grown silicon has been evaluated over a wide range of initial interstitial oxygen concentrations 15 < [Oi]0 < 22 ppma with and without a HI-LO-HI pre-process annealing cycle. Among samples of approximately 100 p-n junctions per wafer, reductions of 1–3 orders of magnitude in reverse leakage at 5 volts were achieved in the worst 10% of 500 μm square devices on wafers that were exposed to the HI-LO-HI heat treatment. Intrinsic gettering is most effective when [Oi]0 22 ppma, but leakage reduction among the worst diodes is achieved at the expense of a 2 or 3-fold increase in median leakage.

The continued reduction of VLSI circuit geometries together with increasingly higher levels of circuit integration create the demand for new circuit fabrication technologies. One of the limitations of current IC fabrication technology is the use of high temperature processing. High temperatures severely distort silicon wafers, causing loss of geometry control and a subsequent reduction of device yield. Excimer laser technology, at very short ultra-violet wavelengths offers the possibility of extremely low temperature processing, including the following major applications: Photoresist exposure, photoresist ablation over alignment marks, annealing and etching. In addition, applications in circuit personalization and fiber optics appear as very promising new applications for excimer laser technology in the electronics industry.

Si/In203 diodes have been prepared by e-beam evaporation of In203 tablets. Annealing of these devices was carried out in N2 and H2 /N2 mixture at 1 atm. in the temperature range of 400–800°C. Experimental data indicated a large increase in the Schottky barrier height and growth of interfacial oxide during annealing. The interface state density was reduced by a factor of 2, but the results indicated the increase in the barrier height to be mainly due to reduction of positive fixed charge density.

Preliminary characterization of two native insulators on germanium is reported. A technique for preparing oxide by a room temperature chemical technique (wet chemical oxidation) is described. Compositional data based on IR transmission and ellipsometry, as well as characteristics of MOS capacitors based on this film are given. Also, compositional and electrical characterization of nitrided atmospheric pressure oxides are reported here. These films have very low fixed charge and interface state densities, and show excellent potential for use as gate insulators in a germanium MOS technology.

The Field Emission Microscope has been extensively used in the study of metal and semiconductor surfaces. The process of Field Emission is, itself, of great interest and a considerable amount of both theoretical and experimental work has been carried out in this field. The Field Emission Microscope also yields useful information of a more practical nature, such as the nature of bulk and surface impurity, diffusion, chemisorption and surface potential barriers. It is essential that the surface to be studieg can be prepared in the form of a high curvature tip, with a radius of 10−5cm and can be cleaned sufficiently well for a symmetrical reproducible pattern to be observed.

Field Emission technique has been applied to study the behaviour of thin overlayers of gold on GaAs. Using Fowler-Nordheim plots, change in the work function φ, is examined for temperatures, T=77K and T=300K. φ changes slightly for low doses of gold and significantly for larger ones {φ=4.3 − 3.7 eV}. Desorption of gold is also examined and the results indicate two different adsorbed states in Au-overlayers formed at room temperature. Finally, a brief description of sample preparation is also included.

Ion beam mixing has been used to form layers of titanium disilicide on Si wafers. Doses of Ge+ up to 1×1016 ions/cm2 were implanted at 140 keV through 51 nm of sputtered Ti. The substrate was held at different temperatures; 150°C, 300°C and 400°C. In addition, some samples were processed without temperature control. Two rapid thermal annealing cycles were used, 800°C for 10 s and 650°C for 50 s in an N2 ambient to form stoichiometric TiSi2. As-implanted samples showed an increase in the number of mixed Ti and Si atoms with higher implant temperature and larger dose. In addition, a thin layer with a Ti/Si ratio of 1:1 as seen in some samples indicating possible TiSi phase formation. Lower implant temperatures, higher doses and higher anneal temperatures all produced greater TiSi2 thicknesses. Ion beam mixing yields thicker. silicide layers than those formed without mixing. The silicide interface smoothness was improved by ion beam mixing although some residual implant damage was observed after annealing. The implanted Ge+ accumulated below the silicide/Si interface and in the surface Ti oxide layer.

Model parameters have been measured to characterize the exposure and development of Microposit 2400 resist exposed by a new deep UV wafer stepper at 248 nm. Resist profiles are obtained from the model for equal line/space patterns. The observed non-vertical wall profiles are correctly predicted by the simulation. These profiles result from the strong absorption of the resist and lack of photobleaching at 248 nm.

Derivatives of 2,6-bis(4-azidobenzylidene) cyclohexanone are frequently used as photosensitizers in photoresists. These compounds are generally considered to be quite thermally stable. However, there have been reports of thermal degradation occurring at temperatures as low as 60'C.

Experiments done here suggest that the thermal stability of the azide is adversely affected by the presence of unsaturated material in the formulation. Data from IR spectroscopy show that, by itself, 2,6-bis(4-azidobenzylidene) 4-methylcyclohexanone is thermally stable in a polyamic acid film at 75–80° C. However, addition of a monomeric aminoacrylate to the formulation results in a significant decay in the absorption of the azide moiety in just a few hours at these same temperatures. This decay is attributed to reaction of the sensitizer with the acrylate double bonds. In a thick film, which might require a 1–2 hour prebake, this thermal addition could result in a significant degree of crosslinking and thus to decreased contrast in the final pattern.

We describe the use of a novel organosilicon novolac as a base resin component of bi-level resist systems for both photo and electron-beam lithography. The lithographic evaluation of the new material demonstrates submicron resolution and high aspect ratio images with little linewidth loss after reactive ion etching (RIE). The optimization of the RIE conditions will be also discussed.

The polydiacetylene with urethane substituents, P4BCMU, has been investigated under e-beam irradiation. A thin, ∼ (100nm), coating can be applied to a silicon wafer by spin coating from a solution in chloroform. E-beam exposure of around 20μC/cm2 renders the polymer insoluble and resistant to a CF4 /O2 plasma etch and a RIE with freon 112. Features down to .2μm have been drawn and etched in this way. X-ray Photoelectron Spectroscopy indicates only a slight change in stoichiometry and suggests the irradiated polymer has tertiary amide characteristics. Fourier Transform Infra Red and Raman spectroscopies indicate that the unsaturated carbon bonds in the backbone of the polymer are not destroyed by e-beam irradiation. Rather the main changes occur in the N-H and the C=O (carbonyl) bonds of the urethane group.

We have studied some of the physical and mechanical properties of cyclized polybutadiene (CBR) dielectrics by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetry, infrared analysis, and differential scanning calorimetry. Of interest is the difference in properties between thin (<30 μm) films which have been cured under vacuum and those which have been cured in air. Our results indicate that curing under vacuum prevents oxidation and reduces crosslinking. Vacuum cured films have 20% smaller moduli and 200 lower glass transition temperature than do films produced in air.