Emitter Dip Effect by Low Temperature Heat‐Treatment of Arsenic‐Diffused Layer

Abstract

When arsenic is used as the emitter diffusant in a n-p-n silicon transistor, it is well known that the emitter dip effect is not observed. However, it was found that the diffusion of boron underneath the arsenic emitter was accelerated during heat-treatment at 500~176This phenomenon is related to abnormal behavior of arsenic in silicon. The diffusion of arsenic is enhanced by such treatment. The anomalous diffusion of arsenic depends on treatment time, and is remarkable in the beginning of the treatment. The diffusivity is extremely large in comparison with the normal one extrapolated from high temperature data. It is considered that this anomaly is caused by the generation of excess vacancies during such treatment. The emitter dip effect is also caused by these excess vacancies during heat-treatment at relatively low temperature.Arsenic is generally used as the emitter diffusant for a microwave n-p-n silicon transistor. The arsenic emitter avoids the emitter dip effect, and the carrier profile is suitable in comparison with phosphorus. The covalent radius of arsenic is nearly equal to that of silicon. Therefore, the lattice strain is considerably reduced as compared to phosphorus.However, the authors (1) reported that the diffusion of arsenic was accelerated by low temperature heattreatment and that this caused the emitter dip effect. Such a phenomenon may be due to the excess vacancies formed during these treatments. Large decreases in the conductivity of arsenic-doped silicon during 500~176 heat-treatments were reported by Schwenker et al.(2). They suggested that the effect was due to the formation of As-As clusters. Miyamoto et al (3) also reported using the x-ray double crystal diffraction technique that the lattice constant of the arsenic-doped silicon was increased after heat-treatment at low temperature. They explained that this lattice expansion and the increase of resistivity were due to arsenic atom precipitation and SiAs formation. Osvenskii et al. (4) made an electron microscopic investigation of the structure of silicon single crystals doped with arsenic to a concentration of 5 • 1020 cm-S and observed the formation of prismatic dislocation loops during annealing at 800~ They concluded that the observed dislocation loops were formed by the decrease of a solid solution of arsenic in silicon. Furthermore, Haskell et al. (5) investigated the channeling measurements in arsenic-doped silicon using a He + ion backscattering technique, and both silicon-and arsenic-aligned yields increased in the arsenic-diffused samples during low temperature annealing. They suggested the model of the formation of the complex on substitutional lattice sites.Arsenic, which is a relatively normal diffusant in silicon at high temperature, shows the complicated behavior described above by low temperature annealing.In this paper, the emitter dip effect in a n-p-n transistor using arsenic for the emitter impurity by low temperature heat-treatments is reported. The previous paper (1) suggested that such emitter dip effect was due...

Measurement of Active Dopant Distribution and Diffusion in Individual Silicon Nanowires

“…Fair et al, have shown that this effect increases the diffusivity at 600 °C by 4 orders of magnitude relative to the value extrapolated from high temperatures; they have also shown that this enhancement will be even larger at lower temperatures. H. Shibayam et al have reported on boron and arsenic diffusivities reaching values of ∼ 1 × 10 −20 m 2 s −1 in the temperature range of 500−800 °C and with no sign for temperature dependence. They associated this enhancement to a generation of excess vacancies at low temperatures.…”

Enhanced Diffusion of Implanted Arsenic and Boron in Silicon by Low‐Temperature Heat‐Treatment

“…SIMS profiles were determined with the CAMECA IMS 300 using a 5. 5 As: 10 ~8 em-~ 60 keY, 24 rain 990~ Ni mary beam. Oxygen gas was introduced into the sample chamber at a pressure of about 3 X 10-~ Torr, except for one arsenic profile, which was measured in the 10 -7 Torr residual vacuum.…”

Nano-Scale Measurements of Dopants and Electronic Impurities in Individual Silicon Nanowires Using Kelvin Probe Force Microscopy

“…It was shown (Fair and Tsai 1977) that this effect increases the diffusivity at 600ºC by four orders of magnitude relative to the value extrapolated from high temperatures; they have also shown that this enhancement will be even larger at lower temperatures. It was reported (Shibayama, Masaki et al 1976) that Boron and Arsenic diffusivities can reach values of ~ 1x10 -20 m 2 s -1 in the temperature range of 500-800ºC and with no sign for temperature dependence. They associated this enhancement to a generation of excess vacancies at low temperatures.…”