Plasma doping implant depth profile calculation based on ion energy distribution measurements

Abstract

International audienceIn traditional beamline implantation, the incident ion mass and energy are well known parameters and simulation programs are available to predict the implant profiles. In plasma based ion implantation, all ionized species present in the plasma are extracted and implanted by applying negative voltage pulses to the wafer. Therefore, prediction of implant profile is more complicated since it requires the knowledge of relative abundance of each ion species as well as their energy distribution prior to entering the wafer surface. This information is not readily available using conventional plasma characterization techniques because most of them measure plasma bulk properties. In order to collect the information needed for predicting plasma implant profiles, an ion mass and energy spectrometer is installed at the wafer level to allow in situ measurement of ion mass and energy distribution. In this paper, BF3 plasma in the pressure range from 30 to 250 mTorr is studied. The relative flux and energy distribution of B+, BF+, BF2 +, and BF3 + ions striking the wafer surface with energies up to 1 keV are measured. As expected, no energy contamination was observed during a plasma doping implantation and the maximum energy of the ions is defined by the cathode voltage. Based on the spectrometer data, a series of simulations was performed to calculate the boron and fluorine dopant depth profiles. The calculated profiles were in good agreement with secondary ion mass spectrometry (SIMS) results and give some additional explanations of the unique surface-peaked SIMS profile of plasma doping implantatio

Tailoring carbon nanotips in the plasma-assisted chemical vapor deposition: Effect of the process parameters

“…As a result, the energy of ions, which is a complex function of the ratio / L, 47 is also changed. The results of Godet et al 48 show that / L decreases with increasing gas pressure; hence, ion energy is reduced, which leads to the lower deposition rate and the sputtering yield. 49 However, the diffusion of the ions deposited on the surface may be enhanced; this is quantified by the weaker effect of the term ‫ץ͑‬ 3 / ‫ץ‬l 3 ͒sec as more carbonaceous ions arrive to the surface.…”

Ion energy distributions measured inside a high-voltage cathode in a BF3pulsed dc plasma used for plasma doping: experiments andab initiocalculations

“…The EQP analyzer is gated by a TTL pulse starting 20 µs after the beginning of the PLAD voltage pulse and stopping at its end. As described in [12], 20 µs is the time required to ensure stabilization of the ion flux to the cathode. With this setup, we measure during the ON pulse ion distributions with energy ranging from 0 to 1000 eV.…”

“…Therefore, the energy distribution of the ions reaching the cathode after acceleration inside the high-voltage sheath is expected to be strongly affected and to spread to lower energy. Figures 6 and 7 of [12] show the IEDs of the different ions striking the highvoltage cathode under different gas discharge pressures during 1 kV and 500 V implantation (figure 5…”

“…In this work we have developed an in situ technique to measure energy distribution of different dopant ions reaching the silicon surface after their acceleration inside the high-voltage sheath. These measurements allow for the prediction of the dopant depth profile [11,12]. Over the last few years several papers have been published concerning BF 3 PLAD [11,[13][14][15][16][17][18][19][20][21][22][23][24][25].…”

“…The doped zone has been characterized and studied in detail in many papers. However, most often the plasma has not been characterized and a few works are dedicated to plasma characterization and process understanding [12,[26][27][28][29][30][31][32][33][34][35][36]. The study presented here provides the practical and theoretical underpinnings upon which the technique of PLAD can be built.…”