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Video Training Script for the SEM

Part1: Overview of Scanning Electron Microscope

The Hitachi 3500H series scanning electron microscope offers high resolution imaging in a vacuum.

With the SEM, the maximum sample size is 150mm in diameter. However, when dealing with large samples it is possible to crash the sample into the objective lens when tilting the sample.

Let’s now introduce our lab users.

Part 2: Parts of SEM

There are various parts for the Scanning Electron Microscope.

The chamber door is located on the front of the machine. When the machine is vented, the chamber door opens up to reveal the stage, which is located just behind the chamber door.

The lens is inside of the chamber. It is important to not crash a sample into the lens.

The x and y knobs are used to move the stage from left to right and from forward to back.

The z-axis moves the stage up and down.

The tilt handle rotates the stage from zero to 60 degrees. Be careful when tilting large samples. It is possible to crash the sample into the lens.

The EDS probe selector is located above the chamber. It is used to set the mode of the EDS probe. For our training video, the EDS probe will be set to imaging.

The control box has various knobs to change the magnification, contrast, brightness, and focus. The knobs on the top right are used to adjust the stigmation in the x and y directions when the stigmation screen is open. The two knobs on the top left, which are called the image shift/multi function x/k1 y/k2 knobs have different uses. Their use is defined in the k1, k2 display area of the status bar in the SEM software.

Part 3: Mounting a Sample

Mounting samples will be located in a plastic box near the SEM. You can mount samples of all different sizes with the maximum size being 150mm in diameter. As stated before, remember that working with large samples greatly increases the risk of crashing the sample into the lens.

The sample that you use in the SEM cannot be an insulator. If the sample is an insulator it must be coated with gold using the gold sputter coater. Silicon is okay to use in the SEM. We will show the effects of using an insulator later on in this video.

We will begin by showing how to mount a small sample. We put the mounting screw through the lock ring, the mounting shaft into the base, put the lock ring into the base, and then we put this top into the mounting shaft.

We place a small piece of a double-sided conductive carbon tape onto the stub. We then stick the sample to the stub.

We want to use our height gauge to make sure that the height of the mounted sample is leveled even in one of two ways. The first way is to use the black line on the gauge. This indicates that you will use the black scale on the z-axis. The second way to align our mounted sample is with the top of the height gauge. This indicates that you will use the red scale on the z-axis. These two scales are used for setting your working distance. Later in this video, we will show the scales on the z-axis.

WARNING: Do not throw the tape backing on the floor. Please use the trashcans that are readily available throughout the clean room. If you do not throw away your tape backing, good lab users like Joel will be forced to get down on their hands and knees in order to vacuum your trash.

If we want to look at the edge of a sample, we use the stub with an angled top. We place a piece of tape on the top, and mount our sample so that the edge we want to look at is on the tip of the stub. Make sure the tip of the stub is below the line on the post.

If we want to mount an entire 4 inch wafer, we use the large mounting stub. Mount the sample using the tape the same way in which we mounted the other samples.

Part 4: Venting the Chamber

Before we begin using the SEM, we must make sure that the LUT Copy 32 software is running. If it is not running, we must open the application. We can find it by going to start, programs, and then startup.

Start the SEM software by clicking the icon on the desktop. Once it has loaded, we must make sure that the high voltage is off. Do not leave the high voltage on when venting the chamber.

The software is now initialized and we must now make sure that the hardware is set properly.

We need to make sure the stage inside of the chamber set to the loading position. The loading position has the tilt set to zero, the Y-axis set to 25, and the X-axis set to 60. We then adjust the Z-position so that the black arrow is pointing to 30 on the black numbers or 25 on the red numbers. When you are moving your sample in the chamber, remember which scale you used when aligning the height of your sample with the height gauge. Using the wrong scale can crash your sample into the lens.

In case you forget, the exchange position sticker on the right side of the SEM has the venting positions listed on it.

When we are doing imaging in the SEM, we want to make sure the EDS probe is set to imaging. There is an arrow on the scale showing the correct position for imaging. Rotate the knob until the arrows line up.

We are now ready to vent the chamber. Remember to make sure that the high voltage is turned off. Vent the chamber by pressing the EVAC OFF button on the front of the machine. After pressing the button, the red light will come on indicating that the chamber is now venting. It takes a few minutes for the chamber to vent. The chamber door will open by itself when it reaches atmospheric pressure. The bar on the software indicates when the chamber has been vented completely as well. If the software indicates the chamber being vented but it does not open, the lock screw located on the base of the chamber door might be tightened. Loosen the lock screw for the door to open.

WARNING: Never pull on the chamber door. It will open by itself when it reaches atmospheric pressure.

Part 5: Loading a Sample

Carefully put the stub into the stage. Make sure to put the stub in straight. Do not tilt it. Put it in and gently slide it in. If you feel any resistance, do not force it. You can crush the metal sleeve inside of the mounting hole. Make sure the stub is fully seated once you put it in.

If you are using the 45-degree stub, place the stub so that the angled edge is facing to the left. This is done so that then when the stage is tilted, the edge of the sample will be perpendicular to the objective lens, allowing us to look at the edge of the sample.

Be careful when tilting the stage into the large wafer. Tilting the stage can crash the sample into the lens. Be sure to lower the stage when tilting a large sample.

The tilting of the sample when the chamber door is open is only for demonstrational purposes only. The stage must be in the loading position when the chamber door is closed. Remember, the exchange position sticker on the right side of the SEM has the venting positions listed on it.

After loading our sample, we are ready to close the chamber. Push and hold the chamber door closed and press the EVAC ON button. When the vacuum pump starts, we can let go of the door.

Part 6: Acquiring an Image

Wait for the chamber to reach operating pressure. We know that its reached operating pressure when the vacuum bar turns blue and the text box states the high voltage is ready. Check the magnification and turn it to the minimum setting by using the dial on the control box.

These icons select our scan speed. The pop-up help box will tell you the results of pressing the button. We want to start in TV1.

Go to operate file and check what the rotation tilt settings are. Make sure that rotation tilt raster rotation is off. We also check image adjust. If the stigmator setting is very far from the center, click the box in the corner and it will return the setting to the center. These are the best positions when we are beginning a scan.

Now we can turn on the high voltage. You should now be able to see an image on the screen.

Click on accelerating voltage to see the accelerating voltage parameters. Check AFS, which is automatic filament saturation. This will automatically adjust the filament current to the correct setting. We can also click one of the automatic buttons, which will automatically tune the image. This should put us close to a good setting. Now we can adjust the focus for the best image quality.

The focus distance is shown on the bottom of the screen. This value should be very close to the Z-axis value.

If you don’t see this bar at the bottom, go to setup, go to data display, and check these settings. If this is not selected, the data display will be off. If we don’t want the black, we can deselect the black bar and we will get white letters superimposed on the image.

These boxes will show the working distance, the accelerating voltage, the magnification, the photo size, and the scale marker. As you can see, the working distance is 36mm. On the stage, the working distance should be 30mm, so this value should be adjusted to match up with the value on the stage. We cannot get perfect alignment, but the value should be close to the Z setting on the stage

Part 7: Refining an Image

Once the area we want to look at is in the center of the field of view, we can increase the magnification. You may need to re-center the image after we increase the magnification. If we want to look at a different area of the sample, move the stage in order to bring that section into the field of view.

If we focus the image and it appears that image is moving left and right or up and down, this means that we need to adjust the stigmation. Adjusting the stigmation is only useful if we are above 2000 magnification. One way to adjust the stigmation is to go to the operate menu, then go to alignment, and then go to stig-x. As you can see, the image is rocking. Adjust the stigmation using the control box until the image stops rocking. If we turn the knob and the rocking changes direction, that means we have adjusted too much. You can also adjust the stigmation in the y direction by selecting stig-y. As you can see, the rocking has almost been eliminated.

Do not adjust the aperture, the gun shift, or the gun tilt. Changing them can make it impossible to see any image. Now when we focus, we get a very sharp image. We can increase the magnification and still get a clear image even at 20,000 magnification. This shows the capability of the SEM if it is used properly.

For most purposes, we use an accelerating voltage of 15 kilo-volts. For very high magnification, you can go as high as 20 kilo-volts.

WARNING: Do not exceed 20 kilo-volts. Doing so can damage the machine.

As we can see, the higher accelerating voltage gives us more noise, but also gives us more contrast. This is a magnification of 35,000. If we change back to 15 kilo-volts, we have less contrast. If we go down to 10 kilo-volts, we cannot achieve the same magnification. The image is very low contrast and is fuzzy. 15 kilo-volts is the recommended all-around operating voltage.

If you have a material that is an insulator, you will not be able to get a good image even using the conducting carbon tape. This is demonstrated with a small piece of glass. When the magnification is increased to just 700 magnification, we can clearly see the image shifting on the screen. This is because the glass is acquiring a charge and is deflecting the position of the electron beam.

The charging can be prevented by coating the sample with a thin layer of gold in the gold sputter coater.

Part 8: Image Capturing

After we have adjusted our image for magnification and contrast, click on the slow scan speed. This will give us the best image quality. The button has multiple speeds. Click on the button to change the speed. The different speeds give different resolutions.

After we have selected the slow scan speed, we click on the Quartz PCI icon. This will capture an image and open the PCI Quartz software.

We can measure features on the image by using the measuring tool. The first thing we should do is compare the calibration of the measuring tool to the scale by checking the length of the scale. Align the bottom leg of the cursor with one end of the scale, hold down the left mouse button, and then drag the cursor so that the bottom leg of the cursor is aligned with the other end of the scale. In our case, the Quartz PCI thinks that this distance is 9.78 microns, which is equal to the length of the scale. If you feel this distance is not the correct value, contact MiRC staff for re-calibration.

We can also draw a line and display the length of the line on the image. If we save the image right now, we will not save the line or the distance. We must click on the overlay menu and click apply to image. This will make the scale line and the distance part of the image.

When saving, go to File, Save As, and only save on the server Grover. All files on the SEM computer will be periodically deleted. Select the type of file you wish to save it as. JPEG is recommended for it’s small size.

There are many options for drawing on your image and adding text. Remember, whenever we add anything to the image, we must make sure to apply the overlay to the image or it will not be saved.

If we want to save another image, minimize the Quartz PCI software, find an image you wish to capture, click on slow scan speed, and then click on Quartz PCI. We then need to open the window for the Quartz PCI software.

Part 9: Finishing Tasks

First begin by turning off the high voltage. Then turn the magnification down all the way by using the dial on the control box. If we have selected rastor rotation or any of the other options, we need to turn them off when we are finished.

Then return the Y-axis to 25, the X-axis to 60, the Z-axis to 30 on the black numbers, and the tilt to zero.

Vent the chamber the same way in which we did in the beginning of this video. Once you have the chamber door open, carefully remove sample and stub. Close the chamber door by holding the chamber door closed and pressing the EVAC on button.

When the chamber has pumped down, shut down the Hitachi software. Do not shut down the lut32 copy application.

Part 10: Concluding Remarks

After watching this training video, you should have a good understanding of how to:

Vent and open the chamber
Mount a sample on the provided stubs
Load a sample into the chamber
Capture an image

If you have any further questions, please direct them to the trainer for this equipment. Please do not direct your questions to Charlie.