A Beam Line System for a Commercial Borohydride Ion Implanter

Abstract

We describe the features of a beam line and ion source system which is being developed for a commercial ion implanter capable of meeting the challenges of high dose, low energy implants needed to fabricate integrated circuits with critical dimensions of 60 nm and less. Intense borohydride ion beams of B10Hx+ or B18Hx+ generated from the source are used to achieve commercially acceptable wafer throughputs for the low energy, high dose applications such as poly‐gate and source drain extension implants. The beam transport elements, from ion source to wafer, are designed to achieve wafer boron currents of greater than 30 pmA at an implant energy of 2–4 keV, and greater than 3 pmA at an energy as low as 200 eV. These high currents are obtained at low energy without the need for deceleration just prior to the wafer. Consequently, the beam impinging on the wafer is very pure with respect to energy, and is free of high energy components that can generally degrade shallow junction implants.After magnetic analysis the beam is parallel magnetically scanned across the wafer at a frequency in the range of 100–200 Hz. In conjunction with a serial end‐station, implants with high quality dose and angle uniformity can be achieved using a wafer mechanical scan rate as low as 0.5 Hz in a direction orthogonal to the beam scan direction.As well as the high wafer throughput performance obtained by using borohydride ions, the beam‐line is also capable of transporting conventional monatomic ions up to a maximum energy of 80 keV with a mass‐energy capability of 12.6 amu.MeV.We describe the features of a beam line and ion source system which is being developed for a commercial ion implanter capable of meeting the challenges of high dose, low energy implants needed to fabricate integrated circuits with critical dimensions of 60 nm and less. Intense borohydride ion beams of B10Hx+ or B18Hx+ generated from the source are used to achieve commercially acceptable wafer throughputs for the low energy, high dose applications such as poly‐gate and source drain extension implants. The beam transport elements, from ion source to wafer, are designed to achieve wafer boron currents of greater than 30 pmA at an implant energy of 2–4 keV, and greater than 3 pmA at an energy as low as 200 eV. These high currents are obtained at low energy without the need for deceleration just prior to the wafer. Consequently, the beam impinging on the wafer is very pure with respect to energy, and is free of high energy components that can generally degrade shallow junction implants.After magnetic analysis ...