No abstract

Ion implants of 1 keV B+11 and 5 keV BF2+, to a dose of 1×1015/cm2 at a tilt angle of 0°, were implanted into preamorphized (Si+,70 keV, 1×1015/cm2) wafers. These samples were rapid thermal annealed in an ambient of 33 ppm of oxygen in N2 at very short times (<0.1 s spike anneals) at 1000 and 1050 °C to investigate the effects of the fluorine in BF2 implants on transient enhanced diffusion (TED). By using a relatively deep preamorphization of 1450 Å, any difference in damage between the typically amorphizing BF2 implants and the nonamorphizing B implants is eliminated because the entire profile (<800 Å after annealing) is well contained within the amorphous layer. Upon annealing, the backflow of interstitials from the end-of-range damage from the preamorphization implant produces TED of the B in the regrown layer. This allows the chemical effect of the fluorine on the TED of the B in the regrown Si to be studied independent of the damage. The secondary ion mass spectroscopy results show that upon annealing, the presence of fluorine reduces the amount of B diffusion by 30% for the 1000 °C spike anneal, and by 44% for the 1050 °C spike anneal. This clearly illustrates there is a dramatic effect of F on TED of B independent of the effects of implant damage. Analysis of the temperature dependence of the enhancement factors point to transient enhanced diffusion not boridation as the source of the interstitials.

Cobalt silicide layer formation on ultra-shallow junctions (< 100 nm deep) was studied as a function of junction doping species and concentration over the range from below the electrical activation limit to above it. The silicide thickness, as measured by XRF, was uniform to within 2-3% (1 sigma) and did not depend on the junction doping.XTEM measurements showed that the silicide microstructure was unaffected by doping.N o discernible effect of doping or species could be observed on the silicide sheet resistance, where the standard deviation of the resistance variation across a 200 mm wafer was 3-496.Silicides formed on substrates which were initially amorphized by the junction implant were slightly smoother than those formed on undoped wafers or B junctions.A large fraction (8040%) OP the junction dose was lost to the growing silicide,

It is known that boron transient enhanced diffusion (TED) is influenced by the existence of fluorine. This paper further investigates this phenomenon by separating the damage effect of fluorine from the chemical effect of fluorine. To accomplish this goal, a u)Ne+ implant with equivalent energy and dose was selected to simulate the fluorine damage (F has an amu of 19). Three types of samples were investigated. First was a 5keV BF2 implant. The second sample created the same damage profile but the B and F implants were separated using a 1.94keV 2e15 Ft followed by 1.2keV le15 B+ implant. The third sample used a 2keV 1.8e15 Ne+ implant to create the amorphous layer followed by a 1.2keV le15 B+ implant. All three implant sets were then subjected to the same rapid thermal annealing conditions (RTA) between 950°C and 1050°C for lOsec in a controlled 300ppm 0 2 in N2 ambient. It was found that FF plus B+ resulted in the least amount of B diffusion with AXj=20a at 950°C and loo.& at 1050°C. BF2+ and Ne+ plus B+ implants showed AXj>lOOdi for all temperatures. Damage behavior was also studied by using transmission electron microscopy (TEM). The defect structure of F+B implant is similar to that of Ne+B implant and different from the BF2 implant. Results indicate that the chemical effect of fluorine on boron diffusion dominates over the implant damage effect.

The evaluation of the doping process requires the ability to measure accurate depth profiles. In this study, the accuracy of electrical measurement techniques is evaluated for the measurement of ultra-shallow dopant profiles. The methods investigated are spreading resistance profiling, electrochemical capacitance-voltage profiling, differential Hall effect profiling, tapered-groove profilometry, and a new method called microwave surface impedance profiling. The focus of this article is the comparative study of the different methods and an evaluation of the accuracy of the profiles. The study points out details of the measurements and analysis which are important in obtaining consistent and accurate measurements of ultra-shallow junctions.