Energy Dependence of Radiation Damage in Sb-Implanted Si(100)

Abstract

Extended defects formed by antimony ion implantation in Si͑100͒ are investigated as a function of the implant energy. After implantation, spike annealing and furnace annealing are performed to examine the evolution of defects. The amorphization/ recrystallization of the implanted layer is examined by transmission electron microscopy ͑TEM͒, photothermal characterization, and Raman spectroscopy. Secondary-ion mass spectroscopy is employed to identify the dopant distribution before and after annealing. Cross-sectional TEM reveals that, at a dose of 1 ϫ 10 14 cm −2 , 20 keV Sb implantation is sufficient to induce an amorphous-like layer in Si͑100͒. After spike annealing, the amorphous-like layer restores to the crystalline state, but defects are observed when the Sb implantation energy is greater than 50 keV. For 70 keV implantation, extended defects appear at the near-surface and the end-of-range ͑EOR͒ regions. It is observed that near-surface defects diminish after spike annealing at temperatures higher than 980°C, while the EOR defects become coarse at 1095°C. A comparison between the spike annealing and the furnace annealing for the sheet resistance and the EOR defect is also addressed.In order to achieve the reduced dimensions of state-of-the-art semiconductor devices, ultrashallow implantation in source/drain extensions is used to suppress short-channel effects as well as to meet the requirement for high-current drive capability. 1 The 90 nm technology node will require the source/drain junction depth to be below 45 nm for the contact and below 25 nm for the extension. 2 This requires the use of a low thermal budget cycle to activate the dopant and limit diffusive distances. Since electrical activation of high dopant concentration usually requires a high annealing temperature, spike annealing with a nearly zero dwell time at the peak temperature has become the method of choice for activating the dopants. Besides, increasing the ramp rate during the activation annealing also leads to the reduction of the junction depth. 3,4 Implanted antimony ͑Sb͒ exhibits lower loss of total dose and lower sheet resistance than similarly implanted arsenic ͑As͒, and therefore can be used for source/drain extensions in n-channel metal-oxidesemiconductor devices. 5 In the past two decades, extended defects formed by ion implantation and the activation anneal have been intensely investigated. 6-8 A classification scheme has been developed to group all extended defects into five types. 8 Among the best known defect type is the end-of-range ͑EOR͒ defect, which forms beneath the amorphous/ crystalline ͑a/c͒ interface in the damaged crystalline Si. It is noticed that this type of defect is introduced when an amorphous layer is formed by ion implantation. High-mass Sb ions used for ultrashallow implantation usually exhibit a low amorphization threshold. 9 The density of EOR defects is reported to be influenced by the implant species, 10,11 energy, 12 ion dose, 13,14 dose rate, 14,15 temperature, 16 and solubility. 17 The defects are ver...