R. R. Hart

TEMPERATURE DEPENDENCE OF LATTICE DISORDER CREATED IN Si BY 40 keV Sb IONS.

The temperature dependence of lattice disorder created in Si by 40‐keV Sb ions was studied by energy analysis of the yield of backscattered 1‐MeV He ions incident along 〈111〉 and 〈110〉 axes. Doses of ∼ 1 × 1013 Sb ions/cm2 were used so that the disorder level was below that representing an amorphous layer. The disorder per incident ion decreases strongly with implant temperature above 50°C. This is approximately 100°C lower than the region of corresponding decrease in the anneal of a low‐dose room‐temperature implantation. For implantation temperatures less than 50°C, the disorder per ion was only mildly temperature‐dependent.

Impurity‐peak formation during proton‐enhanced diffusion of phosphorus and boron in silicon

The formation of a phosphorus or boron impurity peak in silicon has been observed following irradiation with monoenergetic protons. In this study we used a sample temperature of 700 °C, proton‐beam energies of 50–140 keV, proton‐beam current densities of ∼1 μA/cm2, and proton‐bombardment times of 3 min to 3 h. The resultant impurity profiles were obtained using Schottky‐barrier differential C‐V techniques.

LATTICE DISORDER PRODUCED IN Si BY 40-KeV BORON AND ITS EFFECT ON ELECTRICAL BEHAVIOR.

The lattice disorder produced by 40 keV boron ions in Si at implant temperatures of −120 and 23°C has been measured by means of the channeling technique for a 140‐keV proton beam. At −120° there are ∼ 650 displaced Si atoms per incident boron ion for random and 〈111〉 aligned implants, respectively. In contrast to the mild dependence noted earlier for Sb implants, there is a marked dependence of residual lattice disorder upon implant temperature for boron implants in this temerature range. Hall effect measurements on the implanted layers indicate that, in the dose range for boron investigated here, the electrical yield (number of acceptors per implanted ion) after a 600°C anneal increases with the amount of disorder contained in the implanted layer, with the greatest yield occurring in implants containing a fully amorphous layer. The major effect of implant temperature is to determine the amount of residual disorder.

CHANGES OF OPTICAL REFLECTIVITY (1.8 TO 2.2 eV) INDUCED BY 40-keV ANTIMONY ION BOMBARDMENT OF SILICON.

We have measured the fractional change in the optical reflectivity of silicon in the 1.8–2.2 eV photon energy band as a function of 40‐keV antimony ion dose (1011–1015 Sb/cm2 at various implant temperatures (− 160–405°C). Approximate agreement is found between the change of reflectivity and previous measurements of lattice disorder as determined by backscattering of 1‐MeV He ions.

Effects of Al Films on Ion‐Implanted Si

Ion‐implanted amorphous regions of Si in the presence of Al films 300–700 A thick are found to recrystallize between 325 and 350°C. This recrystallization occurs at a temperature significantly below both the epitaxial regrowth of the amorphous Si (∼ 600°C) and the Al–Si eutectic of 577°C. In the case of the 300‐A metallizations, the enhanced low‐temperature reordering of the damaged layer is simultaneously accompanied by an interfacial migration which results in Si transport to the surface of the sample. The observed phenomena are analyzed as a function of anneal temperature by 280‐keV α‐particle backscattering and 1.8–6.2‐eV optical reflectance measurements.

High current density Ga+ implantations into Si

The lattice disorder produced in Si by a 59‐keV Ga+ ion beam focused to a diameter of 1200 A and having a current density of 1.2 A/cm2 was compared to that produced by broad area implantations of 59‐keV Ga+ at a current density of 0.4 μA/cm2. Based on 140‐keV proton backscattering, the disorder produced at the high‐dose rate was found to be comparable although deeper than that produced by the low‐dose‐rate implantations. The depth profile of Ga implanted at 1.2 A/cm2 to a dose of 1.5×1015/cm2 was determined by 280‐keV He++ backscattering to be basically consistent with projected range calculations.

Enhanced Migration of Implanted Sb and In in Si Covered with Evaporated Al

Amorphous layers of Si produced by the bombardment of Sb+ and In+ and covered with ∼400 A of Al show pronounced migration of the implanted atoms to the Si–Al interface and the Al surface after a 350°C anneal. This enhanced migration occurs simultaneously with the recrystallization of the amorphous layer. Low‐temperature migration effects are not seen in uncoated amorphous Si, nor on reordered Si covered with evaporated Al. The depth distribution of the implanted atoms is measured by backscattering analysis with 280‐keV α particles.

High-fluence implantations of Ge into 〈111〉 Si

Abstract The annealing of radiation damage produced by room-temperature and 300°C implantations of 60 keV 72 Ge to fluences greater than 10 16 /cm 2 into 〈111〉 Si was investigated by backscattering and channeling analyses of 280 keV alpha particles. Implantation at room-temperature produced an amorphous layer which only partially reordered after anneal at 850°C. However, implantation at 300°C did not produce an amorphous layer, and after annealing at 1000°C, resulted in an essentially perfect crystalline alloy of SiGe having a uniform Ge concentration of 6 at.% over a depth of 1000 A. These results are also consistent with optical reflectivity data obtained on the sample surfaces in the 3–5.5 eV spectrum.

Backscattering Analysis and Electrical Behavior of SiC Implanted with 40 keV Indium

Based on backscattering analysis of SiC implanted with 40 keV In+, we have shown that an amorphous layer is formed at 23°C after a dose of 1 • 1014 In+/cm2. After 1200°C anneal the amorphous layer is largely recrystallized, and ~60% of the In atoms are along the [001] atomic rows of α-SiC. Although the measured projected range of the In+ agrees with that calculated by Johnson and Gibbons, the standard deviation in range is over three times greater than the calculated value. Little residual disorder remains after a 450°C implant of 3 • 1014, 40 keV In+/cm2 into β-SiC, and ~90% of the In atoms are substitutional following a 1200°C anneal. Although the disorder profile produced by the 23°C implant is comparable to the In distribution, the disorder profile obtained after the 450°C implant indicates a small disorder peak at depths near the maximum penetration of the In. No p-type conduction of the layers implanted at 23°C was observed after anneals up to 1700°C. However, a sample implanted with In+ at 350°C did show weak p-type behavior after implantation and after anneals of 1000°C or less. Following anneals of 1200°C no p-type conduction was observed, but rather i-layers of thickness comparable to that of the In+ penetration were formed in all the implanted samples. The lack of p-type conduction is attributed to donor type defects which persist to 1800°C. The i-layer thickness changed with anneal temperature, suggesting the presence of mobile defects which anneal at 1600°C.

Effects of Implantation on Thin Layers of Aluminium Metallization on Silicon

Evaporated aluminum layers 300 to 1500 A thick on silicon have been bombarded with 28Si+, 31P+, and 75As+ ions at energies from 70 to 150 keV. The implantations were performed at target temperatures 23 and -196 °C with subsequent isochronal anneals from 100 to 650°C. Rutherford backscattering results suggest that diffusion and migration are occuring between the metallization and the implanted semiconductor at temperatures significantly below the Al-Si eutectic of 577 °C. These enhanced effects are influenced primarily by the presence of an amorphous layer at the interface; the dopant characteristics of the ion and the electrical properties of the semiconductor play a minor role. Furthermore, the data indicate a recrystallization of the amorphous region at temperatures as low as 350°C. Implanted planar devices also show similar results; however, ion penetration of aluminum metallization residing on silicon-dioxide interfaces do not exhibit the above phenomena.