Outlines 3/12/2011. Vacuum Chamber. Inside the sample chamber. Nano-manipulator. Focused ion beam instrument. 1. Other components of FIB instrument

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1 Focused ion beam instruments Outlines 1. Other components of FIB instrument 1.a Vacuum chamber 1.b Nanomanipulator 1.c Gas supply for deposition 1.d Detectors 2. Capabilities of FIB instrument Lee Chow Department of Physics University of Central Florida 2.a Imaging 2.b Milling/sputtering 2.c Deposition 2.d Enhanced etching 3/4/2011 Lecture 6 2 Focused ion beam instrument Vacuum Chamber For source and ion column, vacuum at torr isrequired. For sample and stage chamber, a vacuum of torr is required. 3/4/2011 Lecture 6 3 3/4/2011 Lecture 6 4 Inside the sample chamber Nano-manipulator W probe with a tip radius of 500 nm and a 13 taper angle for maximum life time. Shank diameter is (0.508 mm). 3/4/2011 Lecture 6 5 3/4/2011 Lecture 6 6 1

2 Gas injection system Tungsten deposition 3/4/2011 Lecture 6 7 The gas nozzle is ~ 300 m from the substrate. The gas pressure is typically Pa in the chamber, but locally can be much higher. The beam spot size is around ~ 7 nm. The deposited tungsten film can contain ~ 30% of Ga. 3/4/2011 Lecture 6 8 Many charged and uncharged particles were produced due to the bombardments of primary ions (Ga + ). Charged particles, both secondary electrons and secondary ions can be used for imaging, Comparison of secondary electron and secondary ion images of bonded pad on IC device (a) SE image induced by primary ion beam. (b) Secondary ion image of the same structure as in (a). (c) Secondary ion image with flood e gun. 3/4/2011 Lecture 6 9 3/4/2011 Lecture 6 10 Comparison between e-beam and ion beam columns Capabilities of FIB instrument 1. Imaging 2. Milling 3. Deposition 3/4/2011 Lecture /4/2011 Lecture

3 Topographic contrast of semiconductor surface B. B. Rossie, Lucent Technologies 3/4/2011 Lecture /4/2011 Lecture 6 14 Because of channeling on the left, less electrons were produced, so the left grain is darker. 3/4/2011 Lecture /4/2011 Lecture 6 16 Aluminum grain size GRAIN ORIENTATION CONTRAST Grain size and grain boundary can be determined by imaging at different incident angles. J. Cargo, Lucent Technologies 3/4/2011 Lecture /4/2011 Lecture

4 3/4/2011 Lecture /4/2011 Lecture 6 20 Chemical contrast Material contrast In certain cases, FIB SI images show greatly enhanced chemical contrast which is readily interpretable, such as in the presence of oxygen at the grain boundaries of metallic samples. 3/4/2011 Lecture /4/2011 Lecture 6 22 Material contrast 3/4/2011 Lecture /4/2011 Lecture

5 Milling and sputtering 3/4/2011 Lecture /4/2011 Lecture /4/2011 Lecture /4/2011 Lecture /4/2011 Lecture /4/2011 Lecture

6 Deposition 3/4/2011 Lecture /4/2011 Lecture 6 32 Deposition system 3/4/2011 Lecture /4/2011 Lecture 6 34 Ion beam induced CVD 3/4/2011 Lecture /4/2011 Lecture

7 Ion beam induced CVD The importance of process parameters The gas is introduced by a nozzle which is positioned a few hundreds of microns above the area of interest. The gas is then adsorbed on the surface of the material. When the FIB hits the surface, secondary electrons with energy ranging from a few ev to a few hundreds of ev are generated. These secondary electrons will break chemical bonds of the adsorbed gas molecules which will separate into different components 3/4/2011 Lecture /4/2011 Lecture 6 38 The importance of process parameters The importance of milling strategy If the FIB remains too long onto the same point, the freshly deposited material will be sputtered away. Every time the gas is being consumed, it needs to be replenished in order to maintain a net positive yield. For this reason, once the beam has used the majority of the adsorbed gas, it moves to another location before coming back to the same point. The time between two subsequent visits is called the refresh time. Once some new molecules have been adsorbed on the surface, the beam can revisit the same point and then increase the deposition thickness. A pillar structure created with the same dose and the same ion beam current setting but different milling strategies. 3/4/2011 Lecture /4/2011 Lecture /4/2011 Lecture /4/2011 Lecture

8 3/4/2011 Lecture /4/2011 Lecture 6 44 Enhanced etching 3/4/2011 Lecture /4/2011 Lecture /4/2011 Lecture /4/2011 Lecture

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