Damage created by high-current-density implants of phosphorus into 〈100〉 and 〈111〉 silicon wafers

Abstract

The damage left by high-current-density, ∼9 μA/cm², implants of 120 keV phosphorus into 〈100〉 and 〈111〉 silicon oriented substrates was investigated as a function of the fluence in the range 4×10¹⁵–1.5×10¹⁶/cm². The samples were analyzed by 2 MeV He⁺ channeling and transmission electron microscopy. Initially a buried amorphous layer forms at low fluences until the wafer temperature saturates at ∼450 °C at a fluence of ∼4.5×10¹⁵/cm². As the fluence is further increased ion-assisted regrowth of this initial buried amorphous layer takes place and is 2 to 2.5 times faster (with respect to ion fluence) for 〈100〉 substrates than for 〈111〉 substrates. At higher fluences, most of the residual damage is located at a depth equal to the sum of the projected range and of the straggling. In the regrown layers twins are found in both orientations, and in some cases a hexagonal silicon phase is present at high fluences. The results are compared with the ion assisted regrowth of amorphous layers at well defined temperatures in the 250°–400 °C range.