Cross-sectional samples for Transmission Electron Microscopy (TEM) have been made without the use of mechanical polishing and ion beam milling. Instead of traditional methods, we have used a combination of electron beam (e-beam) lithography for metal lift-off and reactive ion etching (RIE) to produce TEM samples of selected areas. The sample integrity for handling, dropping and ease of use is excellent, and the large amount of transparent area available for study is nearly 2 orders of magnitude larger than that given by traditional methods. The thickness of the samples is somewhat extreme, on the order of 0.50–1.0μm, but efforts are being made to reduce this dimension in order to make the method applicable to the whole range of materials used in silicon technology.

In this work we present the first SiGe-base PNP ECL circuit results. The SiGe-base PNP circuit technology includes extended Ge-profile designs for low collector doping levels, a self-aligned transistor structure on deep and shallow trench isolation, and in situ doped polysilicon emitter contacts. Circuit transistors are ob tained wilh oood Gummel characteristics, a current gain of 40, a low emitter resistance of 9 /spl Omega/, a pinched base sheet resistance of 9.5 k/spl Omega///spl square/, and a peak fT of 3 1 GHz at a VRC of 3 volts. The circuit transistors have low parasitics resulting in a peak fmax of 38 GHz at a VBC of 3 volts. An ECL ring oscillator delay of 44 ps was measured at 2.7 mW.

A bipolar isolation structure with the capability of significantly reducing collector-base capacitance and base resistance is presented. Partial SOI, with SOI surrounding the collector opening, can be used to reduce the collector window width in combination with any emitter-base self-aligned bipolar device structure, and in particular for device structures that feature sublithographic emitter width. Near-ideal transistor Gummel characteristics and a minimum ECL gate delay of 24 ps have been achieved with a nonoptimized lateral device layout, and simulations suggest that sub-20-ps delay at reduced switch current will be possible by using the optimized partial-SOI isolation structure.<>

An ECL (emitter coupled logic) circuit with an AC-coupled active pull-down emitter follower configuration is described. An unloaded ring oscillator gate delay of 13.2 ps has been achieved at 6.2 mW, in a 50 GHz-fT ion-implanted silicon bipolar technology. This circuit could be useful as an internal gate operating at low-power and as an I/O gate to drive a large capacitive load at high-power. In both cases, this circuit offers superior power-delay performance compared to conventional ECL circuits

Reactive ion etching of aluminum oxide has been studied in CHF3 and SF6 plasmas generated by electron cyclotron resonance in conjunction with in situ ellipsometric measurement for thickness variation. Because of the involatility of etch products associated with aluminum, purely chemical reactions cannot desorb etch products at room temperatures, and ion bombardment is essential to etch Al2O3 through chemically enhanced physical sputtering. The higher the oxygen content in a film, the faster the etch rate, resulting from chemical sputtering due to volatile CO molecules in CHF3 plasmas. This dependence on composition is absent in SF6 plasma. The threshold ion energy for physi-chemical sputtering by fluorine-containing species is estimated to be about 20 eV at room temperature, while the threshold for Ar sputtering is 50 eV. In CHF3 plasmas, however, Al2O3 exhibits a larger threshold energy at a lower temperature due to passivating species which inhibit sputtering. These passivating species have a very weak binding energy of roughly 0.1 eV, which has been deduced from a temperature dependence of the threshold energy. A patterned sample always shows vertical profile without undercuts.

The plasma‐assisted etching of aluminum in chlorine containing RF glow discharges has been studied. Use of a single parallel plate reactor permitted a direct comparison of etch results between , , , and . Separation of aluminum etching into native oxide reduction and water vapor/oxygen scavenging, and metal film etching allowed the likely rate‐limiting processes in the etch cycle to be ascertained for the different etch gases. The longer initiation period observed with and compared to appeared to be due to etch gas dissociation effects. Metal etching was believed to be limited by the removal of and residues with and and by etchant generation with .

In order to quantify the contributions of atomic and molecular chlorine during the plasma etching of aluminum, a discharge-flow system was used to generate chlorine atoms upstream of a parallel-plate reactor in which aluminum samples were etched with the afterglow. Molecular dissociation in excess of 70% was achieved. Dissociation was measured in the parallel-plate reactor by gas-phase titration of the chlorine atoms with NOC1 using the chemiluminescent emission resulting from atom recombination as an end point indicator. Molecules etched aluminum at least four times faster than atoms and displayed an activation energy near zero (0.02–0.04 eV/molecule) between 35 and 150 °C. Below 25 °C etching was quenched due to the inability of products and/or contaminants to desorb. The higher molecular etch rate is believed to be the result of an enhanced sticking coefficient on the chlorinated surface. Calculation of molecular sticking coefficients based on the assumption of adsorption-limited etching are in good agreement with reported values. Temperature-dependent atom recombination on the in situ electrodes prevented accurate determination of the molecule/atom etch rate ratio and masked the activation energy for atom etching.

THIS PAPER will cover 1.2μm Si-bipolar Emitter-Couple-Logic circuits with a minimum gate delay of 73ps. The circuits were fabricated with bipolar technology (Figure 1) featuring poly-base self-alignment, poly-emitter shallow profile, walled-emitter together with silicon-filled trench isolation and polysilicon resistors. This technology was also used to implement non-threshold logic(NTL) circuits with I/I resistors. The NTL ring oscillator gate delay was found to be 44ps.

The effect of sample temperature and etch gas flow rate on the etching of aluminum in and mixtures in a parallel‐plate plasma etcher was investigated. Through the use of a thermally conductive epoxy to ensure good heat‐transfer, sample heating due to exothermic chemical reactions and plasma heating was found to result in a temperature difference of more than 100°C between bonded and unbonded samples. Thus, considerable increases in etch rate were observed for the unbonded samples. Etch nonuniformities during both the inhibition period and metal etching were studied, using different plasma conditions and a nozzle to deliver chlorine directly to the aluminum surface. Oxide etching depended upon ion flux and/or energy and upon the concentration of or . species, while concentration at the sample surface determined the relative aluminum etch rates across the aluminum sample.

Etch rates of aluminum and "native aluminum oxide" films were studied as a function of substrate temperature in a parallel plate plasma etcher using and plasmas. Differences in the inhibition period for vs. etching were attributed to the relative abilities of these etchants to scavenge oxygen and water vapor and to etch native aluminum oxide. The temperature dependence of the etch rates suggested basic differences in the rate‐controlling steps for vs. plasma etching. The surface chemistry of the electrode materials played an important role in the etch rates observed with and.