Manjin J. Kim

Direct W–Ti contacts to silicon

We have studied the contact resistance in a metallization system that employs a direct contact between a tungsten–titanium alloy and shallow junctions in silicon. The values obtained in the present study are all within acceptable limits (<100 Ω μm2) for very large scale integration applications. The metal–silicon system has been subjected to moderate heat treatments, similar to those required in processing two‐level metallization schemes. No detrimental effects on the electrical properties of these contacts have been observed.

Inhibition of acid etching of Pt by pre‐exposure to oxygen plasma

Platinum etching characteristics in aqua regia have been studied. It was found that prior exposure to an oxygen plasma inhibits the dissolution of platinum in aqua regia. Oxygen, far more abundant in the exposed platinum than in the unexposed platinum, plays a key role in forming an inhibition layer, such as PtO2, which prevents chlorine ion attack. This inhibition layer appears to retard platinum etching effectively in chlorine‐based etch solutions. The layer has been observed to form at a fast rate, and it is insensitive to the oxygen partial pressure in the plasma chamber. The insoluble characteristics of both the inhibited platinum and the platinum silicide in aqua regia make it feasible to form an unframed contact interconnection for applications of very large scale integration.

Advanced analog CMOS technology

The emergence of fine geometry CMOS technology augmented with analog capability presents a powerful tool for the VLSI system designer. In this paper, the authors will review major milestones in the evolution of analog/CMOS technology. Included in this discussion will be an overview of the multilevel metal 1.2 micron analo-gechnology which incorporates molybdenum resistors and isolated metal-to-metal capacitors. The technical presentation will highlight the development of the isolated capacitor and its comparison to a two level polysilicon implementation. Performance data on various types of analog functions fabricated in this process will be presented.

Direct molybdenum contacts to silicon

Stringent requirements on the electrical and metallurgical properties of metallization systems for use in advanced, very large scale integrated circuits have created the need to study new metal‐silicon systems. We have conducted a study of the Mo/Si direct contact system. The choice of molybdenum stems from its desirable electrical and metallurgical properties. To date, however, its contact properties to silicon were not examined in detail. Results of the present study show that Mo can result in low resistivities (<5 Ω μm2) for both contacts to heavily doped p+‐Si and n+‐Si, provided appropriate care is taken in opening the contact windows. Further, we found the Mo/Si contact system to be stable under extended heat treatments at temperatures of up to 650 °C.

Mo 2 N/Mo gate MOSFET's

Molybdenum nitride coatings on molybdenum, from a direct reaction of molybdenum with ammonia, are used to improve the gate electrode properties of Mo gate self-aligned MOSFETs. A Mo2N double-layer gate shows resistance against oxidation and processing reagents, and improved ion-implantation masking. The work function of the double-layer film was determined to be 4.69 ± 0.03 eV, which is independent of the nitride thickness and annealing conditions. The projected range of boron implantation is smaller in Mo2N than in Mo. A Mo2N coating of 870 Å over 2130- Å Mo masks up to 60-keV11B and 120-keV75As. The implantation study covers the energy range from 15 to 70 keV for boron and from 40 to 160 keV for arsenic.