Handbook of Strata 235 Dual-Beam SEM, FIB electron microscope

Handbook of precautions, basic functions and features of the

“DualBeam Strata 235 SEM-FIB electron microscope”

Name: Nauman Mithani (Chemistry major) Professor: Dr. Karen Kavanagh (Nano-imaging, Physics) Date: April 21st, 2007 Term: 1071 (January - April 2007) Object: Co-op work term report Title: Handbook of precautions, basic functions and features of the “DualBeam Strata 235 SEM-FIB electron microscope”

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● General information........................................................................................................................................................................................................pg ii ● Chapter 1: Precautions and conditions...........................................................................................................................................................................pg 1 ● Chapter 2: Starting procedures.......................................................................................................................................................................................pg 2 ● Chapter 3: Imaging chapter 3.1: Commencement and the first images............................................................................................................................................pg 4 chapter 3.2: Image adjustment and optimisation...............................................................................................................................................pg 5 chapter 3.3: Free analysis of the sample...........................................................................................................................................................pg 7 ● Chapter 4: 'EDX' mode (determination of elemental composition)..................................................................................................................................pg 9 ● Chapter 5: 'FIB' mode (milling and etching of arrays or patterns) chapter 5.1: Preparation....................................................................................................................................................................................pg 13 chapter 5.2: Application 1: milling custom patterns...........................................................................................................................................pg 18 chapter 5.3: Application 2: measurement of height, depth or thickness............................................................................................................pg 19 ● Chapter 6: End of session..............................................................................................................................................................................................pg 20 ● Bibliography....................................................................................................................................................................................................................pg 21

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Disclaimer: This is to serve as a handbook of reminders and is by no stretch of the imagination the definitive collection of instructions for the

operation of this instrument. The science behind this electron microscope, micro and sub-micro scale imaging is to be sought elsewhere. Initial training, introduction and familiarisation must be provided by the supervisor.

Universal rules: Always be gentle, in all aspects of operation of the instrument (the further the size of an object from that of an every-day object, the

rarer, more sensitive and expensive it is). Key:-

● {?} represents a physical button e.g. {Off} means a physical 'Off' button on a panel somewhere. ● [?] represents a button, feature or drop-down menu in a software e.g. [Vent] means the 'Vent' button/feature/option in the software

that may be accessed by clicking on it using the mouse ● ((?)) represents a physical knob.

Recommendations:

● Screenshots of the software, its functions and features may be consulted in the official “Reference Guide”. ● Preferably, the user should save the transfer images of the sample analysis in a personal USB drive or removable device. Once a

particular project or experiment is concluded, all pertinent data should be removed from both computers (a procedure is stated in box no. 31.2).

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1 Laboratory apparel

Do not wear clothes with loose threads.

Any foreign substance in the main chamber is a contamination. If a thread falls on the sample, to say the least, the user may obtain undesirable images. If a thread falls between the chamber door and the chamber wall, the essential vacuum shall not occur due to an incomplete seal.

2 ... and the hair Use Rubber-bands, hair-bands, fellow user's hands etc. to keep them from the sample.

As above.

3

Sample condition

The sample must be clean, dry and must not be something that may out-gas significantly; it must not be a magnetic substance. These conditions are to be met in the sample preparation.

The electron beam must reach the sample un-interrupted. Secondly, a magnetic substance may bend/deflect the electron beam.

4 Sample preparation Please use another, appropriate laboratory other than the Nano-imaging Facility.

The Nano-imaging Facility wishes to avoid any lingering odours or spills.

5 Handling the sample Wear nitrile or latex gloves. Minimising sample contamination.

6

Check the {STBY}, {OFF}, {Vacuum}, {High Tension} and

{ON} lighted switches

These are physical, translucent buttons, located on a panel before the stage motion joystick. Check (but do not touch) that the {STBY}, {OFF}, {Vacuum}, {High Tension} buttons are lit, and the dark green {ON} button is not lit. If not, the supervisor is to be alerted immediately.

The instrument shall not function properly or at all. So, do not proceed.

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7 The primary electron

microscope computer. Press {1} on the 'Raritan Compuswitch' box on top of the ultra-sensitive (pico) ammeters.

The computer hosting the main FEI xP analysis software is aged in every sense of the word. Hard-drive, memory and processor speed are limited, so anything and everything that that can be hosted by another computer is.

8 User log-in [File] menu then [User login] This is to maintain a trace of usage per user.

9 Reset the sample stage

position.

[Pages] menu in the top-right corner of the screen, select the [Work] page and set the [X], [Y], [Z], [T] (tilt) values to zero; location is near the centre of the page. Do press enter in each box when the values are put in to register them. If 'Z' is not available, select [Unlink Z from FWD] from the [Stage] menu. Do not set FWD to zero.

This is done to start the analysis from the zero (default) position. The zero or (for that matter) any position is relative to the sample stage. Unfortunately, there is no way to ensure a particular position of the sample stage corresponds exactly to a particular point on the sample every time it is loaded.

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Vent the main chamber (equalise the internal pressure

with that of the outside).

[Pages] menu in the top-right corner of the screen, select the [Startup] page then click on [Vent].

In order to equalise the pressure, the chamber is flooded with inert, gaseous nitrogen. Recall, air, due to its moisture content, cannot be used.

11 Opening the chamber door

Venting shall take up to five minutes approximately. Pull gently at the chamber door's horizontal bar; if the door slides open then venting has concluded, otherwise not.

To allow the user to place the sample onto the stage in the chamber. If the chamber door does not budge at the slight pull, there is yet significant pressure difference with the outside. Do not pull with force.

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12 Mounting the sample

With covered hands, place the sample onto the stage, then fix its position by inserting the hex-screw provided in the hole below the sample holding stage's surface and turning clockwise.

An uncontaminated sample is securely placed onto the sample holding stage.

13 Height check

With the help of a particular tool (the height gauge, for lack of a better name) provided in the same box as the hex-screw, check the height of the sample. If as high or higher than the limit denoted on the tool, consult the supervisor.

If the sample is too high, it would clash with the detector(s) or the tip(s) of the electron/ion column(s).

14 Re-establishing vacuum

Gently push the chamber door to close the chamber. Go to the [Startup] page and initialise the vacuum by accessing the [Pump] feature. A box may appear with further vacuum related options, click [OK]. Physically, keep the chamber door pressed at the spot where it says, for approx. a minute.

This is the procedure for establishing vacuum. The push is for facilitating a difference in air pressures to “grab” and seal the door.

15 Maximum working pressure

(air)

On the [Startup] page, towards the bottom, is an numerical indicator of the “chamber pressure”, wait until it is falls to 3.0×10-5 milli-bar.

The maximum (air) pressure is simply a working vacuum limitation of the instrument.

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16 Commencement: applying the

'High Voltage' Turn on the [HV] feature in the “Electron Column” section on the [Startup] page.

Turns on the electron beam (E-Beam) and engages the accelerating voltage to apply the driving force for the electrons.

17 'Detector' check Select, if not selected by default, [SED] from the [Detector] menu.

This is the standard detector mode; its selection is deliberate.

18 'E-Beam' HV check

(High Voltage)

To start with, select [5 kV] from the [E-Beam] menu to apply the driving force for the electrons. Most probably, it shall be selected by default.

When there may be a need to raise the accelerating voltage (e.g. when conducting analysis of elemental composition), raising it too high could cause the sample to become charged resulting in distorted/shifting images. The visible effect of a change is in the contrast of the image.

19 E-Beam mode: SRH (Search) To select the 'search' mode, [E-Beam] menu → [Imaging Mode] sub-menu → [Search]. This is the default mode.

This is the “general purpose” mode. The other modes serve more specific purposes and thus have more limitations.

20 Inaugural image acquisition

Access the [Set Continuous Scan] function from the [Scan] menu, then select the resolution. Start with a lower ‘Resolution’ such as [0.181] . If scanning does not commence, access the [Start Scan] function or press {F6} on the keyboard. This and the [Start Scan] function start/resume the continuous scanning.

Thus, the user obtains the very first image(s) of the day. The 'resolution' is the image update-time. The image(s), understandably, would hardly be of any use since the settings of contrast, brightness and focus would not be optimised.

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21

“E-Beam Link Focus”:-

linking 'Z' to 'FWD (Free Working Distance)'

A box may appear on the screen asking to link 'Z' and 'FWD' which is not be answered for the time being. The box may be put aside but do not answer it.

'Z' and 'FWD' represent the height and distance of the sample stage relative to the beam sources respectively (e.g. the electron beam gun). Eventually, when the beam has been focused, [OK] may be pressed.

22 Brightness and contrast

The button in the toolbar below the menus may be used to execute the initial auto adjustment of

brightness and contrast. Adjust the ((Brightness)) and ((Contrast)) on the panel before the keyboard in order to fine tune the brightness and contrast of the image.

Once these subjective parameters have been set, a sufficient contrast between the background and surface topography obtained, the user may move on to 'focus'.

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An appropriate spot:-

choosing a point for the initial focus

The user may zoom out using the central ((Magnification)) dial. One way is to use the cream-coloured joystick to the left of the panel, whilst the alternative is to double-click on the spot on the screen which one wishes to bring to the centre. The electron beam may be shifted using the ((X)) and ((Y)) knobs on the same panel that bears the ((Magnification)) dial.

One wishes to bring to the viewing area, a rugged region of the sample, one with peaks or variations in topography. Naturally, it would be awkward to bring anything into focus over a flat, unchanging, planar region. The ((X)) and ((Y)) knobs may be used for fine movements. Remember, these knobs shift the electron beam, not the sample stage.

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24 Focus

Then, set the magnification to at least '1000X', this may be done by using the ((Magnification)) dial; or typing '1000' in the box containing the magnification value on the [Work] page. Adjust the focus of the image by the ((Coarse)) and ((Fine)) focus knobs.

The '1000X' magnification value is a reasonable starting point for initial focusing. If the user intends to conduct imaging at only higher magnifications then initial focusing may be carried out at a higher magnification. Focus, akin to decimal place accuracy, is more accurate if carried out at a higher magnification.

25 Response to the 'EBeam

Confirm Focus' box

Once the image has been focused, answer the box by clicking [OK]. If the 'E-Beam Link Focus box' was [Cancel]led then 'Z' may be linked to 'FWD' by pressing the [Z=FWD] button on the [Work] page.

In a manner of speaking, a calibration has been conducted. As per the official statement, “...sample collision protection...” has been set. Now, 'Z' on the [Work] page has become 'FWD'. Remember, a change in the focus shall cause a change in the FWD (a numerical indication) value and so one may freely adjust the focus.

26 Stigmator controls

(Advanced)

((X)) and ((Y)) stigmator knobs may be used to adjust astigmatism. If before/during focus, the image seems to shift or blur in a particular direction, and if after focusing, the image seems to be blurred in a particular direction, astigmatism shall have to be adjusted.

By far, the most challenging parameter in image adjustment. In the beginning, it is advised to adjust only one knob at a time and carefully at that. Astigmatism is many a time the culprit in skewed milled patterns (Ion beam mode). There is no numerical value associated with the stigmator controls.

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27

Translational movement (viewing other areas and points

on the sample)

The sample stage may be subjected to translational movement by using the cream-coloured joystick to the left of the panel, whilst an alternative is to double-click on the spot on the screen which one wishes to bring to the centre.

28 Screen quadrants

(NOTICE) One may switch to another quadrant by a mouse-click. Switching quadrants 'freezes' scanning.

Resumption of scanning removes the image originally present in the quadrant and scans the area under viewing in the former active quadrant, and NOT the area originally displayed in the quadrant. Thus, save the coordinates often. A potential advantage of using the quadrants is viewing the same area under different imaging modes.

29 Coordinates (NOTICE)

'X' and 'Y' coordinates can be seen on the [Work] page, which update in real-time. Coordinates can be “bookmarked” by typing alphanumeric text into the rectangular text box in the ”Stage” section, above the 'R' (rotation of the stage) menu-box, and press {Enter}.

Saves coordinates include 'X', 'Y', 'T' (tilt of the sample stage) and 'R'. The user is advised to save coordinates often.

30 Single scan (NOTICE)

Firstly, focus the image under 'continuous scan'. Access the [Single Scan] feature from the [Scan] menu then choose the resolution. Start with [11.77] from the 'High' column.

The image obtained will bear significantly lesser “noise” and thus may seem less sharp. 'Single scan' images are used as the final images/pictures of the sample and are saved in the TIFF format. Scanning shall stop once a single scan has been executed.

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Saving the images

[File] menu → [Save] menu → [Image...] to save the image. The images are to be saved in a folder under the user's or supervisor's name in the

location. Press {2} on the 'Raritan Compuswitch' box to switch to computer number 2. The images shall be found in the “UserFiles” folder in the “Sharefolder” on the desktop.

The images are saved on the second computer because the hard-disk on the main FEI computer is of very limited capacity. The second computer also has a finite capacity and so the user is requested to transfer the images from this computer onto removable media or the internet, if provided.

32 'UHR' (ultra-high resolution)

imaging mode

It may be accessed through [E-Beam] menu → [Imaging Mode] menu → [UHR mode]. Minimum magnification for operation of this mode is 1,500 times ('1.5kX'). The user may have to re-adjust the settings of contrast and brightness, focus and astigmatism.

The purpose is to obtain focused images at higher magnifications. At such higher magnifications, 'SRH' mode can be used, though the image(s) may be less sharp (lower resolution).

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33

Commence the 'EDX' mode

(Energy dispersive X-ray)

Initiate the 'EDX mode' through the [E-Beam] menu → [Imaging Mode] menu → [EDX mode]. Set the accelerating voltage to [20 kV]. If ‘continuous scanning’ stops, resume it. The user may very well have to re-adjust the settings of contrast and brightness, focus and astigmatism. 'EDX' mode has a minute window of focus and thus should be adjusted with care.

An accurate quantification shall be obtained if the accelerating voltage is set to 20 kV. The “K” ⍺-lines may not be excited if the setting is below 20 kV, and thus the spectrum would be “incomplete”. Due to a significantly lesser sharpness (lower resolution) in the 'EDX' mode, analysis should be started out at relatively low magnifications, if possible.

34 Scanning and choosing a

particular area

Simpler method: select [Freeze scanning] from the [Scan] menu or press {F6}. Other method: execute a [Single Scan]. Next, select [External Scan] from the [Scan] menu. A tick mark should appear next to it. Click on the [Blank] button in the 'Electron Column' section on the [Startup] page to turn it off (yellow to grey).

The EDX software, installed on computer 2, is a separate software that links with the main FEI xP software.

35 The 'EDX' software:-

EDAX Genesis

Press {2} on the 'Raritan Compuswitch' box to switch to computer number 2. Execute the [EDAX Genesis] software (by its icon on the desktop).

36 Image of the sample area [Image] tab → the large [Collect image] button towards the right of the screen.

The selected area of the sample will show up in a corner towards the top-left.

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37 The scan (1 of 3)

From the toolbar above the image, select the [++++] symbol (its actual colour is black) to select a point cursor. Click on a point on the image to select it for analysis.

One may analyse the elemental composition of a particular point on the sample. The other similar symbols beside it enable an area selection and respective analysis.


From toolbar below the image, click the first button from

the left, , it is the 'Start/Stop collection' button (bring the mouse over it to see the name). ...

An existing spectrum may be removed by pressing the second button from the left, . Thus the user obtains the spectrum detailing the elemental composition of the point or area selected. Note that this information needs to be further processed and filtered.


... The button may have to pressed more than once to commence the 'collection'. If the scan does not terminate in a minute, it may be stopped manually.

The longer the 'collection' scan runs, the greater the accuracy.

40 The elemental composition.

Click on the last up-down pair of arrowheads (in the right-hand side of the screen) to bring up several options/features. Click the [Peak ID] button (towards the right of the screen) to have the software assign elements to the peaks, though, not immediately. Otherwise, the user may have to click the button multiple times for an accurate assessment of elements.

The assessment of the elemental composition is not quite accurate. The major peaks are normally identified correctly but other smaller ones, including background noise peaks, may be mislabelled.

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41 Obtaining useful information:

filtering and processing

Around the [Peak ID] button are two columns containing a list of elements. The left column consists of the likely elements, whilst the right column consists of a wider range (a catalogue) of elements, most unlikely. Selecting any element will show, with a thin vertical yellow line, its place on the spectrum, and vice versa. An element may removed from the left column and thus from the spectrum by selecting it and pressing the [Delete] button.

Some knowledge of the elemental composition of the sample is required in order to discern the plausible elements from the non-existent or unlikely.

42 Manual detection

Pressing the [EPIC] button brings up the periodic table with orbital energy values assigned to each element. Clicking on each element will display the values; Clicking on the spectrum will display the constants for that point (in the status bar below the spectrum). If the 'Eng'...

The user may manually filter the plausible elements present. Secondly, the 'Eng' value is of consequence.

43 ... ... values are out of the range of the spectrum then select the [L] option.

44 Quantification of the

composition

Click the [Q] button in the same toolbar as the 'Start/Stop collection' button to bring up a box displaying the percentage elemental composition of analysed spot.

The 'At%' (atomic percentage) and 'Wt%' (weight percentage) values are to be noted.

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45 a

Saving pictures of the spectrum

[File] menu → [Save as] then select the location and type(s) of data to save. Another method is to save screenshots of the display, this may be done by the [Screen capture] function from the [Edit] menu then selecting the sections from the right-hand side and pressing the [Copy] button. The image may then be “pasted” in any application that can handle images such as Microsoft Paint, Word, Powerpoint, etc.

45 b

Saving the spectrum data

Switch to the main [Spectrum] tab. Execute a ‘collection’ scan (the buttons are at the top) and from the [File] menu, access the [Save as] function, select the format, file name and location and [Save].

The spectrum may be saved in the multi-platform, text-based 'csv' format from the main [Spectrum] tab. The spectrum and the image of the sample may be saved as images from the [Image] tab.

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46 Imaging mode Switch to the default [SRH] mode.

The main purpose of the gallium ion beam is to mill/etch, not image; however, it is, possible to do so but with undesirable side-effects including sample damage. Milling/etching under the 'UHR' mode at higher magnifications is not an option since this is technical constraint.

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'Eucentric height':-

aligning the E-Beam and I-Beam.

(Step 1)

Set the magnification to at least '1000X' with the 'FWD' at 5. Since this procedure requires focusing, it is best to centre the cursor on an appropriate point. Select [Zero Beam Shift] from the [Stage] menu. If the cursor shifts, centre it again on the desired reference point; then, de-select [Update FWD after a Z stage move] from the [Stage] menu. Set the tilt to 15° by typing “15” (and press {Enter}) in the 'T' box on the [Work] page. The reference point shall then shift. After re-adjusting the brightness, contrast (do not adjust the focus), keep the black button on the stage motion joystick pressed whilst using the joystick to bring the reference point under the cursor. The other way is to adjust the ((Z)) knob on the chamber door. Do not move the joystick laterally.

Setting the eucentric height sets the E-Beam and the I-Beam to focus on the same point. The little black knob on the joystick pad, if pressed, allows for adjustment of the stage height; if not pressed, translational motion would occur. Moving the joystick laterally, when the little black button is pressed, will cause tilting of the sample stage.

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48 ‘Eucentric height'

(step 2) Set the tilt to 30°, 45° then 52° to align the reference point with the cursor each time.

The joystick is not as sensitive and skips often, therefore, be patient and careful.

49 'Eucentric height'...

(step 3) Set the tilt back to 0° and check the offset of the cursor relative to the reference point.

An offset of 1 to 2 µm is ideal. If the offset is less than 5 µm, the user may move on, if the offset is between 5 and 10 µm, it is permissible that the user may move on but if the offset is greater than 10 µm then the eucentric height needs to be set again.

50 'Eucentric height'

(step 4)

Select [Update FWD after a Z stage move] from the [Stage] menu then select [Stage is at Eucentric height] from the [Stage] menu.

Eucentric height has been set and registered. 'FWD' will then be registered at 5 mm.

51 Starting up the 'Focused Ion

Beam'

Press the [Source] button in the 'Ion Column' section of the [Startup] page, wait for the 'Ion Emission Current' to fall between 2.1 µA and 2.3 µA inclusive, 2.2 µA being the desired value, then press the [HV] button in the 'High Voltage' section below the 'Ion Column' section.

If the 'Ion Emission Current', displayed in the 'Status' section near the bottom of the [Startup] page, is below 2.1 µA or beyond 2.3 µA, the supervisor is to be notified. The [Beams On] button activates both, the E-Beam and the I-Beam. The I-Beam imaging mode is to be engaged later.

52 Tilting the sample Tilt the sample stage to 52°.

The I-Beam column is positioned at an angle of 38°; the E-Beam column at an angle of 90°. In order to view the sample from straight up, the stage has to be tilted to 52°, perpendicular to the I-Beam column.

53 Ion beam mode

Shift to an area which the user can afford to have altered; this area may be the edge of the sample or away from it. The I-Beam may be engaged through the [DB Control] menu by accessing the [Primary Beam - I] function.

The image should have to be focused. The only method described thus far has been by way of 'continuous scanning'. Gallium ions which comprise the ion beam, however, carry significantly more momentum, and thus continuous scanning in the I-Beam mode causes milling/erosion of the sample in the viewing area. The higher the focus or the larger the 'Ion Column Aperture', the greater the rate of milling/erosion.

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54 'Ion Column Aperture' Start with an aperture setting of [10 pA 30kV] from the [I-Beam] menu.

This is the default setting. It controls the strength of the beam. The higher the aperture setting, the more ions pass through, thus, the wider (since the ions are more spread out) the milling. Focusing under one aperture setting and milling under another is discouraged as contrast-brightness and focus do not remain constant.

55 Focusing

Set the magnification to a higher magnitude (one or two clockwise shifts of the ((Magnification)) dial or more if so desired) than the one the user intends to mill at. Engage the continuous scanning and focus the image. Carefully, adjust the stigmator controls.

As previously stated, the higher the magnification when focusing, the more thorough and more accurate the focus. Adjust the stigmator controls regardless, if not to adjust then to at least confirm the lack of astigmatism. Lack of focus and especially presence of astigmatism, will cause the milled patterns to be skewed.

56 Choice of area

Switch to 'E-Beam' mode from the [DB Control] menu → [Primary Beam - E], browse over the sample to choose the desired spot for milling; then execute a single 'I-Beam' scan by the [Grab 1I] function from the [Scan] menu. This shall execute a quick, single scan of the area in 'I-Beam' mode whilst in the 'E-Beam' mode then freeze the scanning. Return to the 'I-Beam' mode.

The switch to 'E-Beam' mode is made so as to harmlessly browse over the sample without suffering passive Ga ion milling (of the whole area in view). The quick 'I-Beam' scan is carried out to obtain the final image of the area before the milling.

57 Milling:-

simple shapes

Simple shapes to be milled may be selected from the [Patterning] menu → [Create] sub-menu, and then drawn on the screen. When ready to mill, execute the [Start Patterning] function from the same menu.

This particular menu contains a few more features and settings that are self-explanatory. If any errors along the lines of “…excessive number of points…” appear, refer to row 61. If the errors persist, draw a smaller pattern or switch to higher magnifications.

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58 'Stream files'

(NOTICE)

Stream files (describing a repeating pattern) may be generated by multiple means e.g. stream files may be created indirectly through MATLAB ®. Refer to the webpage: http://schottky.phys.sfu.ca/research/splasmons/, more specifically, the “Stream Files” section, for another means to generate a stream file and for further vital information. Another resource on stream files is “Generation of stream files” by Samantha Grist of SFU ENSC, accessible through Dr. Karen Kavanagh of SFU Physics. Generating stream files (extension: str) from custom images is described in chapter 5.2.

These are text-based files which are used to create patterns with the FIB e.g. an array of circles or a custom drawing. The file is comprised of information of coordinates, magnitude of magnification, dwell-time, loop-count and number of points (max. 1 million).

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Milling:- 'stream files':

(NOTICE: location)

The stream files must be present in drive (any location in this drive) of computer 1 for the FEI xP software to load them.

The stream files shall have to be shifted from the . The user is asked to keep the files organised and not

leave them in the root directory.

60 Milling the stream file

[File] menu → [Open] menu → [Pattern Data] to load the stream file. Select the material file corresponding to the base material of the sample; this may be from the [Material File] drop-down menu (towards the top-right) on the [Work] page. From the [Patterning] menu, execute the [Start Patterning] function to commence the milling.

If the exact material file cannot be found, consult the supervisor for the closest match. If any errors along the lines of the pattern/points not fitting in the screen appear, refer to row 61.

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61

Milling:- 'stream files' and the ”RunScript” software

Run the 'RunScript' program on computer 1 by the [RunScript] icon on the desktop. Do not select the loop count option to retain the loop count value specified in the stream file. Access the [File] menu → [Script 1] to select the script file for the program, its name and location is

. Upon loading the script file, the milling may be commenced by [Run] menu → [Start].

Other options produce no noticeable effect. When milling commences, a dialogue box shall appear in the FEI xP software. Once the milling is completed, a few script-related error notices may pop up, which may be dismissed.

62 Viewing the result The user may switch to 'E-Beam' mode, in the same or another quadrant, to view the milled pattern.

Recall, this would be an angled view.

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63 The software: “Patterns” This software translates the custom pattern/image into a stream file; it may be accessed from the start menu.

The pattern must exist as an image in the bitmap format containing a monochrome (black and white) pattern/drawing/image (extension: bmp). When preparing the image, it is better to remove, if possible, any blank parts of the image. The software does not recognise any other image format.

64 The procedure

Select the [MS Windows .BMP] option at the top. Set the magnification in the [Magnification] box; set the milling time in the [Pattern Time, mins] box; select the [Save Data] option. Press the [Calculate] button at the bottom to select and load the bitmap file. Press the button again to bring up the box for the saving of the translated stream file. If a box pertaining to bitmap file(s) comes up, select the [Cancel] option to bring up the desired stream file box.

If unsure of the pattern milling time, set it to 2 minutes. The extension is also to be typed along with the desired name of the stream file. This software can pick up a file from the 'SharedFolder' but remember to save the translated stream file in drive of computer 1.

65 Visualising a stream file From the [File] menu, access the [Load .str] function to choose and visualise a stream file.

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66 Cross-sectioning

by slicing

Access [Patterning] menu → [Create] menu → [Regular Cross Section], then draw out the box such that the top, horizontal edge would slice the protrusion in half. If one intends to simply gauge the thickness of the covering layer then the box may be drawn over a flat section of the viewing area. In this case, it's no more than digging by ion milling to see how deep it goes.

The pattern to be drawn is a trench with a sloping base, deepest at the upper face. It is outlined by the main edges of the box. Reduce the size of the box if the software gives an error related to an excess number of points; the depth of the milling is of importance here, not the area. It is assumed that the user has accounted for the preliminaries of angle of tilt, choice of area, focusing, ion column aperture (row 46-57, 61), etc. Once the milling is complete, switch to another quadrant (and 'E-Beam' mode) for viewing so as to preserve the box; in case the depth of the trench is insufficient to view the layer-base interface (on the upper, vertical face of the trench), with the user intending to mill again.

67 Cleaning the cross section

If the trench does not appear clean enough, especially the upper face, the 'cleaning cross section' feature may be used. [Patterning] menu → [Create] sub-menu → [Cleaning Cross Section].

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68 Cessation of scanning

Stop the scanning by the {F6} key or [Freeze Scanning] from the [Scan] menu, then set the accelerating voltage of the E-Beam to [5 kV], the [Spotsize] to 3 (if adjusted during the session); set the 'Ion Column Aperture' to [10pA...].

69 Turning the beams off Turn both beams off by accessing the [Beams Off] button in the 'System' section, towards the top-right on the [Startup] page.

70 Vent Refer to box 2 of row 9

71 Sample stage to zero position Whilst the chamber is open set the [X], [Y], [Z], [T] (tilt), [R] (rotation) values to zero.

72 Unload the sample Insert the hex-screw below the sample stage surface and gently turn anti-clockwise (two or three turns ought to be enough).

73 Re-establishing vacuum:

pumping Close the chamber. Access the [Pump] function on the [Startup] page.

74 Log-out [File] menu → [User Logout] function.

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• FEI Company, xP DualBeam Workstation User's Guide, 1999.

• (Dr. Karen) Kavanagh group, http://schottky.phys.sfu.ca/research/splasmons/, SFU Physics dept.

• Grist, Samantha, “Generation of stream files”, SFU ENSC dept., 2007.

Documents

Handbook of Strata 235 Dual-Beam SEM, FIB electron microscope