* '''Select the appropriate sample holder:''' There are several different sample holders available for the SEM, each adapted for a particular sample size or function, such as a full 2 inch wafer holder, cross-sectional sample holder etc. Generally, you should use the smallest sample holder that will accommodate your sample. This will give you the greatest range of tilt. The PC-SEM software knows about the geometry of the different sample holders, and will automatically set the safe tilt angles for you, and prevent you from accidentally running the sample holder into the pole-piece.
* '''Select the appropriate sample holder:''' There are several different sample holders available for the SEM, each adapted for a particular sample size or function, such as a full 2 inch wafer holder, cross-sectional sample holder etc. Generally, you should use the smallest sample holder that will accommodate your sample. This will give you the greatest range of tilt. The PC-SEM software knows about the geometry of the different sample holders, and will automatically set the safe tilt angles for you, and prevent you from accidentally running the sample holder into the pole-piece.
* '''Attach the sample:''' The 2 inch wafer holder allows for the attachment of samples to the holder via clips, and the cross-sectional sample holders alow the samples to be either clamped in place or mounted with a screw. For the remaining sample holders, and adhesive must be used, e.g. carbon tape, graphite paste, or silver conducting paste. Most users use the carbon tape. It is easy to use, and to remove, but due to the elastic nature of the tape, some drift may occur at high magnification. If this is a problem, or you have fragile samples that may break when removed from the adhesive tape, you can try the graphite paste. It has lower adhesion, but also more electrically resistive. There are two pastes available, one suspended in water solution, and the other in isopropanol. Apply only a small dot to the sample holder surface and place your sample over it, press down gently on the sample and then leave it to try for about 5 minutes. Test whether the sample is well attached to the sample holder before loading. Note: Do not use for full wafers.
* '''Attach the sample:''' The 2 inch wafer holder allows for the attachment of samples to the holder via clips, and the cross-sectional sample holders alow the samples to be either clamped in place or mounted with a screw. For the remaining sample holders, and adhesive must be used, e.g. carbon tape, graphite paste, or silver conducting paste. Most users use the carbon tape. It is easy to use, and to remove, but due to the elastic nature of the tape, some drift may occur at high magnification. If this is a problem, or you have fragile samples that may break when removed from the adhesive tape, you can try the graphite paste. It has lower adhesion, but also more electrically resistive. There are two pastes available, one suspended in water solution, and the other in isopropanol. Apply only a small dot to the sample holder surface and place your sample over it, press down gently on the sample and then leave it to try for about 5 minutes. Test whether the sample is well attached to the sample holder before loading. Note: Do not use for full wafers.
* '''Set the sample height:''' The sample must be attached to the sample holder such that its surface protrudes slightly from the edge of the sample holder when viewed from the side. The height of this protrusion is known as the sample surface offset. If the sample surface is below the edge of the sample holder, it must be adjusted. In the case of the 12.5 mm sample holder (see figure), this is done by loosening the two retaining screws on the side of the holer, and then screwing the large screw on the underside of the holder. This adjusts the height of the central stub to which the sample is attached.
* '''Set the sample height:''' [[File:Sample holder.png|right|400px|The 12.5 mm sample holder as seen from the side and from below.]] The sample must be attached to the sample holder such that its surface protrudes slightly from the edge of the sample holder when viewed from the side. The height of this protrusion is known as the sample surface offset. If the sample surface is below the edge of the sample holder, it must be adjusted. In the case of the 12.5 mm sample holder (see figure), this is done by loosening the two retaining screws on the side of the holer, and then screwing the large screw on the underside of the holder. This adjusts the height of the central stub to which the sample is attached.
A printed version is in a blue binder by the instrument
Responsibility
Primary
Pétur
Secondary
Nader
The JEOL 7800F is a 30 kV field emission scanning electron microscope (SEM). It is equipped with two secondary electron detectors a backscatter detector, and a EDS detector. It has a eucentric stage, a range of different sample holders depending on application requirements, and can accommodate samples of up to 50 mm in diameter. A unique feature of this SEM, is its ability to place a negative bias on the sample stage in order to decelerate incoming electrons as well as to eject secondary electrons, thereby increasing the signal-to-noise ratio. This feature is known as gentle beam (GB), and is particularly useful when working at low acceleration voltages.
Overview
The different components of the SEM are illustrated in the two figures below:
Left side of the JEOL 7800FLeft side of the JEOL 7800F
The lower electron detector (LED) is a secondary electron detector, located in the chamber, and is mostly used for overview images, or in conjunction with sample tilting or high acceleration voltages.
The upper electron detector (UED) is an in-lens secondary electron detector located in the electron beam column. It is typically used for obtaining ultrahigh resolution iamges at low acceleration voltages. It is usually used in conjunction with the gentle beam (GB).
The backscatter detector (BSD) measures the high energy electrons from the incident beam that are backscattered by the sample surface. Particularly useful for samples composed of different materials of contrasting densities. The detector is inserted by a pneumatic valve when needed by the user, but is otherwise retracted.
The EDS detector measures the x-ray wavelengths of photons generated in the sample when exposed to the electron beam. Using the measured x-ray spectrum, the sample material composition may be determined.
The chamber camera is colour sensitive, and primarily used to see the sample and sample holder in relation to the pole-piece. It can only be switched on if the gun-valve is closed, and the gun-valve cannot be opened while the camera is on.
The loadlock camera automatically takes a picture of the sample surface when the loadlock is evacuated. However, if the user is not logged in, the image will not be taken, and there is no way to take it without venting and re-evacuating the loadlock. The overview picture can be used for rough navigation of the sample.
There is a magnetic field sensor suspended adjacent the electron beam column, and is connected to a magnetic field cancellation unit in the corner of the room. If you notice interference, or feel that you are not reaching the image resolution you feel you should, check the field cancellation unit to see if it has been tripped. This happens once in a while due to vibration from foot traffic outside, etc, and the field cancellation may be restored by pressing the reset button on the unit.
The SEM has a N2 dewar for cooling the sample stage.
Sample mounting
Select the appropriate sample holder: There are several different sample holders available for the SEM, each adapted for a particular sample size or function, such as a full 2 inch wafer holder, cross-sectional sample holder etc. Generally, you should use the smallest sample holder that will accommodate your sample. This will give you the greatest range of tilt. The PC-SEM software knows about the geometry of the different sample holders, and will automatically set the safe tilt angles for you, and prevent you from accidentally running the sample holder into the pole-piece.
Attach the sample: The 2 inch wafer holder allows for the attachment of samples to the holder via clips, and the cross-sectional sample holders alow the samples to be either clamped in place or mounted with a screw. For the remaining sample holders, and adhesive must be used, e.g. carbon tape, graphite paste, or silver conducting paste. Most users use the carbon tape. It is easy to use, and to remove, but due to the elastic nature of the tape, some drift may occur at high magnification. If this is a problem, or you have fragile samples that may break when removed from the adhesive tape, you can try the graphite paste. It has lower adhesion, but also more electrically resistive. There are two pastes available, one suspended in water solution, and the other in isopropanol. Apply only a small dot to the sample holder surface and place your sample over it, press down gently on the sample and then leave it to try for about 5 minutes. Test whether the sample is well attached to the sample holder before loading. Note: Do not use for full wafers.
Set the sample height:The 12.5 mm sample holder as seen from the side and from below. The sample must be attached to the sample holder such that its surface protrudes slightly from the edge of the sample holder when viewed from the side. The height of this protrusion is known as the sample surface offset. If the sample surface is below the edge of the sample holder, it must be adjusted. In the case of the 12.5 mm sample holder (see figure), this is done by loosening the two retaining screws on the side of the holer, and then screwing the large screw on the underside of the holder. This adjusts the height of the central stub to which the sample is attached.
