Akihiko Sagara

Luminescence Studies of Residual Damage in Low‐Dose Arsenic Implanted Silicon after High‐Temperature Annealing

In order to prevent the degradation of device performance, it is necessary to detect and reduce residual damage remaining after ion implantation and annealing. In this study, we focused on the high‐temperature annealing process after low‐dose arsenic (As) implantation in silicon (Si) and evaluated the correlation of annealing conditions and damage by cathodoluminescence (CL) compared to Secondary Ion Mass Spectrometry (SIMS) and Junction Photo‐Voltage (JPV) results. Increasing the annealing temperature with the high‐heat‐up rate, As profile and the sheet resistance didn’t change. However, the intensity of the band‐to‐band transition increased with temperature. This implies the some kind of residual damage remains after low‐temperature annealing and it is removed with increasing annealing temperature. On the other hand, with increasing the annealing time at 1200 °C, more As was piled‐up at the SiO2/Si interface and the luminescence intensity decreased. We guess this piled‐up As is inactive and it may creat...

Thermal Behavior of Residual Defects in Low-Dose Arsenic- and Boron-Implanted Silicon After High-Temperature Rapid Thermal Annealing

We investigated the thermal behavior of defects remaining in low-dose (<;1013 cm-2) arsenic- and boron-implanted Si after high-temperature (1100 °C) rapid thermal annealing (RTA). The defects remaining after RTA were characterized as vacancy-type defects, and confirmed to be created by nonequilibrium states that occur during the extremely rapid cooling step of the RTA sequence. They were gradually removed by applying additional furnace annealing (FA) (i.e., thermal equilibrium heating process) at 300-400 °C. At the range of 500-600 °C, however, carbon- and oxygen-related point defects were newly created. These defects were confirmed to be eliminated at 700 °C, and the crystal quality was significantly improved. When using a rapid thermal process for heat treatment after low-dose impurity implantation, it is necessary to apply an equilibrium thermal treatment at >700 °C to remove residual damage as well as to activate impurities.

Thermal behavior of residual damage in low-dose implanted silicon after high-temperature rapid thermal annealing

Along with the development of the Si semiconductor industry, numerous studies have been carried out on the defects that remain after ion-implantation processes [1]. For example, in the case of high-dose (~1015 cm-2) implantation, dislocation loops can be created even after annealing. These defects are typically evaluated by transmission electron microscopy (TEM) and have been confirmed as a reason for junction leakage [2][3]. Even in low-dose (<; 1013 cm-2) implantation, some intrinsic point defects remain at relatively low annealing temperatures (<; 700 C). These defects have been conventionally analyzed and investigated by optical and electrical characterization techniques, such as photoluminescence (PL) and deep transient level spectroscopy (DLTS) [4]-[6]. In contrast, residual damage in low-dose implanted and high-temperature annealed Si has not been detected and reported. Therefore, it is believed that there is no damage remains in this condition, and, if exists, it has no influence on device performance. Little attention has been paid to the defects that remain after low-dose implantation processes.