Detection of low energy single ion impacts in micron scale transistors at room temperature

Abstract

[7]. Donor electron and nuclear spins are promising candidates for implementation of quantum bits in silicon [7]. The detection of low energy single ion impacts for device integration has been accomplished via detection of secondary electrons [2,4,9], or by collection of electron holepairs in optimized diodes [3]. It is also well known that high energy (MeV) single ion impacts can upset device currents [10], and an extension of this approach to low energy ions was recently outlined in Ref. 11. Also, random telegraph noise due to switching occupancies of single Coulomb scattering centers [12] has long been observed in sub-micron transistors, and it can thus be expected that the impact of lower energy (<100 keV) single ions, which is accompanied by the generation of multiple charged defects, can also be sensed in FETs.In this letter we report on the detection of low energy (50 to 70 keV) antimony and xenon ion impacts in FETs with channel areas of 4 μm 2 at room temperature. FETs were formed for development of single donor spin readout techniques, and spin dependent neutral donor scattering was recently observed in transport studies with similar devices used here [13]. Single ions change transistor channel mobilities through formation of defects upon impact, enabling precision placement of defined numbers of dopants into transistor channels. Upon further reduction of the beam current to ~0.1 ions/s, pulses contain mostly no ions, and current steps from single ion hits are recorded (Figure 2 c)). The probability for multiple ion hits in one pulse under these conditions of reduced beam current was less then 3%.During exposures with ions of different impact energies and charge states we found that the sensitivity to ion impacts, i. e. the magnitude of current steps, was gradually reduced with increasing implant dose. Further, variations in step heights at the given noise level did not allow us to confidently discriminate multiple hits from single ion hits based on the step heights. Due to the degrading sensitivity, it was also difficult to investigate charge state effects on the single ion induced current step height. It can be expected that the localized deposition of potential energy of multiply and highly charged ions [21] contributes significantly to the formation of defects in the gate oxide and at the Si-SiO 2 interface, and future work aims at quantifying this effect.Following a series of exposures with an accumulated dose of ~10 11 cm -2 , devices were annealed for damage repair and dopant activation. Rapid thermal annealing (RTA) was performed in an AGA Heatpulse at 900º C for 20 s in Argon, followed by another 30 min. N 2 /H 2 -forming gas anneal at 400º C. In figure 3, we show a series of I-V curves of a pristine A-FET 5 (Fig. 3 a) and NMOS-FET (Fig. 3 b), after FIB processing and forming gas anneal, and then after monitored implantation with noble gas and Sb ions and the consecutive anneals, demonstrating that devices were functional transistors after the full process sequence. The threshold voltages, V...

Single ion implantation for single donor devices using Geiger mode detectors

“…The state-of-the-art for low energy single ion detection using a built-in p-i-n diode is signal-to-noise limited to an energy of ~10 keV P ions producing ~10 3 e-h pairs per implanted ion [7]. Batra et al, [10] and Shinada et al, [11] have alternatively demonstrated successful single ion detection by monitoring changes in transistor current after implanting Si, P, Xe, or Sb donors, 30 -70 keV energies, into the channel of micron scale Si transistors. Increased sensitivity to lower energy ions is desirable to decrease straggle below the range of ~10 nm [6,7] for single atom devices such as solid-state quantum bits [12].…”

Single Ion Implantation into Si-Based Devices

“…[10] Single ion implantation and detection has been reported by a number of groups. [11][12][13][14][15][16][17][18][19] These works are compared in Table I. The table shows the energy and type of implanted ion as well as the target type and detection scheme used.…”

“…Low energy single dopant implantation into both micron-scale and nano-scale devices has been reported (indicated by the bold text in Table I). [11,15,19] Deterministic P implantation was achieved by the detection of the electron-hole (e-h) pairs created by the ion impact with an integrated PiN structure.…”

“…Low energy single dopant implantation into both micron-scale and nano-scale devices has been reported (indicated by the bold text in Table I). [11,15,19] Deterministic P implantation was achieved by the detection of the electron-hole (e-h) pairs created by the ion impact with an integrated PiN structure. [11] This scheme has resulted in a device where the timeresolved control and transfer of a single electron between two deterministically implanted P atoms was observed.…”

“…Low energy single dopant implantation into both micron-scale and nano-scale devices has been reported (indicated by the bold text in Table I). [11,15,19] Deterministic P implantation was achieved by the detection of the electron-hole (e-h) pairs created by the ion impact with an integrated PiN structure.[11] This scheme has resulted in a device where the timeresolved control and transfer of a single electron between two deterministically implanted P atoms was observed.[20] Other detection schemes are based on ion impact signals from secondary electrons [14,16,18] a These values represent the percentage of the total energy lost to ionization and nuclear recoils, respectively as calculated with SRIM. Additional energy loss occurs via phonon generation.…”