SIMS measurement of hydrogen and deuterium detection limits in silicon: Comparison of different SIMS instrumentation

Abstract

Hydrogen is the most abundant element in the universe, but it cannot be detected by many analytical techniques. This element is used to improve interface quality and reduce the impact of defects in silicon technology. Knowledge of the amount and distribution of hydrogen is of significant interest for many technologies, such as ZnO and glass manufacturing. Secondary ion mass spectrometry (SIMS) can provide analysis for hydrogen and the isotopes deuterium and tritium. Lower instrument vacuum will improve the hydrogen detection limit. Vacuum conditions can be optimized by methods such as overnight pumping of samples and sample holder heating. Adsorption of hydrogen from the vacuum environment during analysis can be minimized with use of high sputtering rate. The species monitored may be atomic or molecular, such as H− or Cs2H+. The latter species provides a practical means for hydrogen profiling in dielectric films in magnetic sector instruments with conventional charge compensation. It is of interest to compare the detection limit that can be obtained for various SIMS instrument configurations under typical operating conditions. Time of flight, magnetic sector, and quadrupole analyzers were used to analyze hydrogen and deuterium ion implanted silicon. The detection limits varied for the different analyzers used and were in the 1018–1019 atoms/cm3 range for hydrogen and as low as 1016 atoms/cm3 for deuterium.

Improvement of hydrogen detection limit for quadruple SIMS tool

“…The 3.1×10 19 atoms/cm 3 detection limit with 5 keV Cs + bombardment was higher than expected considering the very low base pressure for the instrument, especially when comparing to the magnetic sector and time-of-flight SIMS tools at higher bass pressure. [5] Fig. 1 Quadrupole hydrogen SIMS depth profiles.…”

“…[5] Although quadrupole SIMS tool can reach about 2 orders lower vacuum pressure, magnetic sector SIMS achieved the best detection limit. [5] The instrumental background of quadrupole SIMS tool has been discussed in reference [1]. There is high noise blast peak at mass zero because the RF and DC fields of the filter collapsed and all negatively charged particles are transmitted.…”

“…And higher sputter rate could be reached by high sputtering current and smaller raster size, which will minimize the hydrogen reabsorption during analysis. [1,5,6] Hydrogen detection limit in silicon has been compared between magnetic sector, quadrupole and time of flight SIMS instrumentation. [5] Although quadrupole SIMS tool can reach about 2 orders lower vacuum pressure, magnetic sector SIMS achieved the best detection limit.…”

“…[2] The detection limit of hydrogen using SIMS has been explored with various methods, including improving instrument vacuum, increasing sputtering rate, and reducing raster size during analysis. [1,[3][4][5][6] Early studies showed that better vacuum system pressure improved the hydrogen detection limit. [1,3] That is because hydrogen is the primary component under ultrahigh vacuum pressures ranging from 10-7 to 10-10 mbar, [7] which is the typical pressure for SIMS instrument.…”

“…[1,5,6] Hydrogen detection limit in silicon has been compared between magnetic sector, quadrupole and time of flight SIMS instrumentation. [5] Although quadrupole SIMS tool can reach about 2 orders lower vacuum pressure, magnetic sector SIMS achieved the best detection limit. [5] The instrumental background of quadrupole SIMS tool has been discussed in reference [1].…”