SEM MERLIN Manual

EPFL Center of MicroNanoTechnology SEM MERLIN Users Manual

November, 2013 1/14

SEM MERLIN Manual

Reservation Policy:

2 booking slots maximum per day and per person (i.e. 1h).

6 booking slots maximum per week and per person (i.e. 3h).

Reservation names must correspond to the operators

Contents:

I. System description

a. Overview

b. The GEMINI II column

c. Available detectors

II. Access conditions

III. Basic operations

a. Starting with the ZeissSmartSEM software

b. Loading – Unloading

c. Stage motions

d. Sample observation

e. Useful keyboard shortcuts


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I. System description

a. Overview

1. Electron optical column GEMINI II

2. Specimen chamber

3. Semi-automatic loadlock

4. Control monitors

5. Dual joystick

6. Control panel

The CMi SEM MERLIN is composed of a GEMINI II column, a process chamber with a 5-axes

motorized stage (X, Y, Z, Tilt and Rotation) and a semi-automatic airlock. The stage is eucentric,

which means that all rotation axes intersect the same point. The specimen surface is located at the

eucentric point, where the tilt axis meets the beam axis. This guarantees that the focus is maintained

when the specimen is tilted at a certain working distance.

Three different holders are available: mono samples, cleaved samples and full 4inch wafer.

1

2 3

4

5

6


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The SEM is controlled by the ZeissSmartSEM software operated via a graphical user interface. The

system is also fitted with a dual joystick for stage control and specimen navigation and with a main

keyboard control panel for direct access to 14 of the most frequently used functions on the SEM.

b. The GEMINI II column

The GEMINI II column is the area of the Field Emission SEM, where electrons are emitted,

accelerated, bundled, focused and deflected. Main characteristics of the GEMINI II optics are the so-

called beam booster and an objective lens that consists of a combined electrostatic/electromagnetic

lens doublet.

A Schottky field emitter serves as gun (1). Electrons are emitted from the heated filament while an

electrical field is excited by applying the extractor (Uext) voltage. To suppress unwanted thermoionic

emission from the shank of the Schottky field emitter, a suppressor voltage (Usup) is applied as well.

The emitted electrons are accelerated by the acceleration voltage (Ueht).


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The beam booster (Ub, booster voltage), which is always at a high potential when the acceleration

voltage is at most 20kV, is integrated directly after the anode. This guarantees that the energy of the

electrons in the entire beam path is always much higher than the set acceleration voltage. This

considerably reduces the sensitivity of the electron beam to magnetic stray fields and minimizes the

beam broadening.

Column mode Characteristics Beam path

High Resolution

High resolution

imaging

The upper condenser (1) has a low excitation which is varied in order to adjust the probe current in a limited range.

Electrons interaction effect is minimized

High spatial resolution is guaranteed

Probe current range is limited

Analyzer

Non-

conductive materials and

polymers imaging

The upper condenser (1) focuses the beam and creates a crossover above the ebeam-limiting anode aperture (2). The upper condenser is adjusted to modify the probe current. The lower condenser (3) is used for aperture matching of the objective lens (4) for optimum spatial resolution.

Whole probe current range is accessible

Depth of Field

High topography

imaging

The upper condenser (1) focuses the beam and creates a crossover above the ebeam-limiting anode aperture (2). The upper condenser is adjusted to modify the probe current. The lower condenser is operated at a higher excitation than in the two modes describes above. This results in a smaller aperture semi-angle. Thus, the depth of field is increased with a slightly reduced spatial resolution.

Provide a high depth of field

Useful to investigate high aspect ratio samples or to navigate on a tilted specimen

Fish-eye

Overall view of the sample

This mode enables you to view the entire 4inch wafer with electrons (EHT on). Useful for finding you sample or test patterns on the wafer

c. Available detectors

The interaction products most frequently used for generation of images in scanning electron

microscopy are secondary electrons (SEs) and backscattered electrons (BSEs). For that purpose,

three different detectors are fitted to the system.

Detectors Typical application

In-Lens (annular detector)

Surface structure

HE-SE2 (Everhart-Thornley detector)

Topography

EsB with filtering grid (in-column detector)

Pure material contrast


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The In-Lens detector is a high efficiency detector for high resolution SE imaging. It is located

above the objective lens and detects directly in the beam path.

The efficiency of the In-Lens detector is mainly determined by the electric field of the electrostatic

lens, which is decreasing exponentially with the distance. Thus, the working distance WD is one of

the most important factors affecting the signal-to-noise ratio of the In-Lens. As the tilt angle of the

specimen surface affects the emission angle of the electrons, you should avoid strong specimen

tilting.

The HE-SE2 detector is sensitive to SEs as well as BSEs.

Electrons moving to the detector are attracted by the collector and directed to the scintillator. The

collector voltage can be varied in the range between -1000V and +1000V. The collector voltage

generates an electrical field in front of the detector thus directing the low energy SEs towards the

scintillator. For all standard applications, the collector bias should be set at +300V.

Selecting a negative collector voltage generates a field deflecting the low energy SEs so that they

cannot reach the scintillator and do not contribute to the signal. Only high-energy BSEs contribute to

the image generation. This produces a so-called pseudo-backscattered inage, which shows

pronounced topography, but largely cancels surface properties (edge contrast).

The EsB detector is an Energy Selective Backscattered detector suitable for compositional

contrast. It is an annular in-column detector that is located above the In-Lens detector. It can

detect SEs and BSEs.

The SEs and BSEs generated at the impact point of the primary electron beam are intercepted by the

low electrical field of the column. These electrons are accelerated by the field of the electrostatic lens.

A small amount of SEs passes through the hole of the In-Lens detector and would be observed by the

EsB detector. To prevent detection of the SEs, a filtering grid is installed in front of the EsB detector.

By switching on the filtering grid voltage, the SEs will be rejected and only BSEs will be detected.

Below a landing energy of 1.5kV, the filtering grid has the additional function of selecting the desired

energy of BSEs. The operator can select the threshold energy of inelastically scattered BSEs to

enhance contrast and resolution.

EsB

In-Lens

Plasma

cleaner

EDX

HE-SE2


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II. Access conditions

1. The CMi SEM MERLIN is reserved to the regular CMI users.

2. It is exclusively reserved to the control of processes which have been done with the CMI

installation.

3. The maximal booking time per day is 1 hour (so 2 slots).

4. Saved pictures are available on STI network (EPFL local or VPN): "\\sti1files\cmi-

transfert\Z15-Zeiss-Merlin".

5. SEM training is focused on safe loading/unloading + main possibilities of the SmartSEM User

Interface + basic alignments procedures for quick and easy imaging. Images + detector

settings optimizations are not part of the training. Also, EDX analysis is only possible upon

additional training and only after SEM imaging is fully confirmed.

III. Basic operations

a- Starting with the ZeissSmartSEM software

First, the tool needs to be activated by logging onto CMi Zone15 computer with personal access rights.

On the SEM local computer, the Windows operating system is always open and running through

standard CMi session.

The EM Server, implementing the internal communication between software and hardware, is always

running too. It is sometimes minimized to a small element (icon) on the right side of the Windows task

bar.

Note: If the EM Sever was closed by the last User, Starting the ZeissSmartSEM software will first

reload the EM server and recover software/hardware communication.


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Double click on ZeissSmartSEM icon.

Alternatively, select Start/Programs/SmartSEM/SmartSEM User Interface. The EM Server Lon

On dialogue appears.

By logging, the SmartSEM user interface opens and is ready to operate the tool. By default, a TV

view inside the specimen chamber is shown.

Data zone Annotation bar

Status bar

Tool bar

SEM control tabs


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The data zone is a special and useful group of annotation objects which are used to display useful

parameters. If it is not open, select View/Data Zone/Show Data Zone from the menu.

Alternatively, type <Ctrl+D> to toggle the data zone

All icons from the toolbar run a specific action on the tool:

Specimen change via the loadlock

Left click Middle click

Live scanning Continuous averaging 2

Pixel averaging 3 Continuous averaging 4

Pixel averaging 6 Continuous averaging 6

Pixel averaging 9 Frame integration 5

Frame integration 7 Frame integration 9

Faster and slower scanning command

Freeze / Unfreeze command

Normal scanning command

Reduced area activation

Screen splitting to get two detectors viewing on the same window

Brightness and contrast adjustment (with mouse)

Chamber scope (TV view) activation

Toggle In-Lens / SE2 detectors

Magnification and focus adjustment (with mouse)

Save image to folder


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b- Loading

Press Exchange on the keyboard.

Follow and perform all instructions of the macro message before clicking OK.

Clicking OK will start pumping in the airlock and will open the gate.

The Vent button is used to ventilate the loadlock.

Be sure the holder is correctly loaded! Be sure to screw the rod on the holder!


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Close the door and click OK on the macro message for the pumping to start. When correct vacuum is reached, the gate will automatically open.

Check from the window when the gate is open. The light inside the chamber is automatically

switched on. Load the sample onto the stage and retract the rod all the way out. When loading, visually check from the window what you are doing!

Be sure the holder is steady on the stage and that it doesn't move when the rod is turned

counterclockwise and then retracted.

Click OK on the previous macro message and click Resume on the keyboard to close the gate.

Here, there is no need to ventilate the airlock: just click OK on this message.

Click OK to finish the loading sequence and to proceed with SEM imaging.



c- Unloading

Press Exchange on the keyboard.

Click OK on the macro message (there is no need to ventilate the airlock now).

Clicking OK will start pumping in the airlock and will open the gate.

Check from the window when the gate is open. The light inside the chamber is automatically

switched on. Unload the sample from the stage and retract the rod all the way out.

When unloading, visually check from the window what you are doing!

Be sure the holder is steady in the airlock with the rod fully retracted.

Click OK on the previous macro message and click Resume on the keyboard to close the gate. Follow instructions before clicking OK on the following message.



The Vent button is used to ventilate the loadlock.

Unload the sample.

Close the door and click Store on the airlock for the pumping to start. Validate the previous message by clicking OK.



Click OK to finish the unloading sequence.

d- Stage settings and motions

The Stage Navigation window can be used to initiate XY movement of the stage by double-clicking

on the sample holder top view. Be sure to select the correct holder from the list and to adjust the zoom

view sliding bar to your needs. All five axes coordinates are reported in this window in order to save

specific positioning on the sample if needed.

The STOP button on the Stage Navigation window or the Break button on the dual joystick can be

clicked at any time to quickly stop any engaged motion of the stage.

Finding your way on the sample is mainly done by the use of the dual joystick panel, where all five

axes can be actuated.

e- Sample observation

The following table may help to find the required settings for your application:

Detector EHT Typical

WD Detector settings Remarks

In-Lens

3kV – 20 kV 3 – 6mm

None

Avoid strong specimen

tilting.

Surface structure

100V – 3kV 2 – 3mm

100V Max 4mm

HE-SE2

1kV – 30kV Min. 4mm Collector bias adjustable from -

1000V to +1000V.

Standard applications: +300V

None.

Topography

1kV – 5kV 4 – 6mm

5kV – 30kV Min. 6mm

Left joystick (Z and T) has to be

used with great care: a risk of

damaging the tool and/or the

specimen is present if hitting the

objective lens while driving the

stage. Watch the moving stage

in TV mode.



Pseudo BSE image: -1000V to 0V

EsB

1kV – 5kV Max. 4mm EsB grid adjustable from 0V to

+1500V.

Value depends on type of

electrons to be detected (approx.):

<800V : SE +BSE

>800V: BSE

Avoid strong specimen

tilting.

Materials contrast 100V – 1kV 1 – 2mm

f- Useful keyboard shortcuts

Ctrl + d : display/hide data zone

+ (numerical keyboard) : increase the scanning rate - (numerical keyboard) : decrease the scanning rate

tab : fine/coarse mode

Ctrl + tab : center the sample when click on the picture

Ctrl + shift + tab : drag a rectangle on the picture and the system will automatically zoom in and center the sample into it

Ctrl + A : annotation tools

Please, avoid using the arrow keys at the edges of

the sliding bar when selecting column current! Use

either the slide bar, or type the desired valued in

directly.

Documents

SEM MERLIN Manual