Lateral spread of high energy implanted ions studied by electronic test structures

The lateral spread of high-energy implanted ions in Si is studied by electronic test structures. It is shown that the ions implanted through thick overlying layers spread significantly in the substrate. The lateral spread of boron ions is estimated to be about 1 mu m at a 650-keV implantation energy for 650-nm-thick dielectric film. The spread measured with the test structures shows rough agreement with simulation but with a slight difference. When it is required to separately control the threshold voltage of neighboring transistors in small-dimension devices using high-energy ion implantation, the neighboring transistors should be separated at least by the space determined by the spread of ions.<>