A high brightness plasma ion source has been developed to address focused ion beam ͑FIB͒ applications not satisfied by the liquid metal ion source ͑LMIS͒ based FIB. The plasma FIB described here is capable of satisfying applications requiring high mill rates ͑Ͼ100 m 3 / s͒ with non-gallium ions and has demonstrated imaging capabilities with sub-100-nm resolution. The virtual source size, angular intensity, mass spectra, and energy spread of the source have been determined with argon and xenon. This magnetically enhanced, inductively coupled plasma source has exhibited a reduced brightness ͑␤ r ͒ of 5.4ϫ 10 3 A m −2 sr −1 V −1 , with a full width half maximum axial energy spread ͑⌬E͒ of 10 eV when operated with argon. With xenon, ␤ r = 9.1 ϫ 10 3 A m −2 sr −1 V −1 and ⌬E = 7 eV. With these source parameters, an optical column with sufficient demagnification is capable of forming a sub-25-nm spot size at 30 keV and 1 pA. The angular intensity of this source is nominally three orders of magnitude greater than a LMIS making the source more amenable to creating high current focused beams, in the regime where spherical aberration dominates the LMIS-FIB. The source has been operated on a two lens ion column and has demonstrated a current density that exceeds that of the LMIS-FIB for current greater than 50 nA. Source lifetime and current stability are excellent with inert and reactive gases. Additionally, it should be possible to improve both the brightness and energy spread of this source, such that the ͑␤ r / ⌬E 2 ͒ figure-of-merit could be within an order of magnitude of a LMIS.

The Focused Ion Beam (FIB) has become ubiquitous for site-specific cross sectioning and other sample preparation activities in the semiconductor failure analysis lab, as well as in many other research and industrial settings. Such systems use a gallium liquid metal ion source (Ga-LMIS) as the source of the ions, providing a typical beam current range of 1 pA to 20-65 nA, with a maximum material removal rate by sputtering of ~10 3 µm 3 /min for silicon at 60 nA of beam current. However, some larger structures seem beyond the reach of FIB techniques using such standard sputtering rates. For example, in semiconductor packaging, solder bumps and Through-Silicon-Vias (TSVs) which have length scales of ~100 µm, would generally be considered prohibitively large for a routine FIB cross section, resulting in mill times of hours or 10s of hours, or more.Above several 10s of nA of ion beam current, the Ga-LMIS ion beam performance becomes considerably degraded due to the ion optical properties of the source and focusing lenses. For such a high current regime new ion source technology is needed and the inductively-coupled plasma (ICP) source is a promising candidate [1,2]. While the LMIS is a point source with high brightness, the ICP is a broad source with high angular intensity, making it more suitable for high current operation (see Fig. 1). These optical properties mean that while the ICP source based FIB system does not produce as fine an ion beam as the LMIS-based FIB at low beam currents -with approx 50 nm possible compared to < 5 nm with a LMIS-based FIB -the ICP is far superior at high beam currents enabling up to several µA of ion beam current for fast material removal. The cross-over in beam spot performance between the LMIS and ICP is around 20-50 nA, above which the ICP offers the better performance. In addition, the ICP allows for a wide range of possible ion species; with Xe currently being used as the milling species of choice due to its higher mass (e.g. the sputter yield for Xe is 1.6 times higher per ion than Ga when milling Si) and favorable ion source performance parameters [1]. Therefore using a 1 µA Xe beam can have an overall milling rate for silicon some 80 times higher than a Ga beam operating at 20 nA, with enhancements of over 200 times seen for materials like Cu and epoxy [2].Two applications of the ICP based FIB are shown in Figs. 2, 3 and 4. In Fig. 2 nearly 1 million cubic microns of material was removed in less than 20 minutes to expose an accelerometer through its packaging. Figs. 3 and 4 show the cross-sectioning and imaging of copper TSVs, with both images also being acquired with the same ICP source-based FIB [3]. References[1] N.S. Smith et al., "High brightness inductively coupled plasma source for high current focused ion beam applications", J.

Temperature dependence of the work function of the Zr ∕ O ∕ W ( 100 ) Schottky electron source in typical operating conditions and its effect on beam brightness Experimental evaluation of the extended Schottky model for ZrO/W electron emission A computer modeling program that is able to imitate the polyhedral shape of the ZrO/W(100) Schottky cathode is used to compute emission parameters such as the electric field distribution and reduced brightness B r for the various observed end form shapes. This program includes the electron-electron interactions in the beam and their effect on B r . A relationship between the axial field factor b ¼ F/V e and the axial lens factor K ¼ (I 0 /J) 1/2 (where F, V e , I 0 , and J are the applied electric field, extraction voltage, beam angular intensity, and surface current density, respectively) was obtained from the data which allow b, K, and the work function to be calculated from experimental I 0 (V e ) data. In addition, an empirical relation, independent of the end form shapes, was obtained that allows B r to be calculated from the intrinsic reduced brightness. Experimental energy distribution measurements are presented which allows one to compare the energy spread and B r values for emitters with various values of b. An empirical relation, also independent of the end form shape, showing the Boersch contribution to the energy spread to be a function of b and J was obtained from the data thereby allowing the axial energy spread to be calculated from I 0 (V e ) data.

The optical performance of on-and off-axis emission from the central (001) facet of a Schottky emission (SE) source has been studied using a hybrid experimental and numerical approach, which allows for the simultaneous determination of all key performance measures. A recently developed computer modeling program was instrumental in aiding the discovery of empirical relationships that allow work function (u), b (where field factor b ¼ F=V e for emitter surface field F and extraction voltage V e ), and source brightness (B r ) to be calculated from on-and off-axis experimental angular intensity (I 0 ) data. Emission parameters F, current density (J), and u, were determined from experimental data for off-axis emission angle up to 4 in which energy spread (DE50) and I 0 were directly measured. Also included in this study was the influence of the various end-form shapes of the polyhedral SE source on the various emission parameters. Plots of B r versus DE50 for emitters over a range of b, I 0 , and off-axis angle have been constructed, which allow users of the SE source for electron optical applications to understand the tradeoff between DE50 and B r .