Unveiling crystal clarity: A recap of our introduction to crystal orientation webinar
The orientation of a crystal can have a very strong effect on its properties. It is critical for epitaxy and other processes in the semiconductor industry. We recently launched our new range of crystal orientation diffractometers with a webinar hosted by Dirk Kok.
If you missed it – no worries. You can find the recording here. We’d also like to share some of the most relevant questions we received and our answers in a recap of the Q&A session.
What are the main differences among orientation measurement of wafers, boules, or ingots? Can a single XRD machine perform this?
We can measure any single crystalline material on these machines. The only difference between measuring wafers, boules or ingots would be maybe the sample holder.
Are there any specific calibration procedures or maintenance requirements necessary to ensure the long-term reliability and accuracy of the system?
The system requires no calibration, just alignment which mostly happens at the factory. When the sample stage is changed, this will have to be aligned to be level. Other alignment is only necessary if the configuration is changed, for example if the detector is swapped. About once a year we recommend a service visit to check things like the X-ray tube.
Can you measure EPI film’s lattice orientation? Even the lattice mismatch between EPI and Si wafer substrate.
This has been done with this type of machine. It is possible to measure the orientation of both the epi-layer and the substrate.
What is your beam size range? Fixed or adjustable?
The beam size is fixed to about 1 mm diameter, depending on the exact angle of incidence.
Can you explain how you can determine the offcut of bowed wafers by XRD only or is an additional laser used to measure surface tilt?
There is indeed a laser that measures the sample surface tilt.
Will this be suitable for biomaterials (amino acids, peptides, proteins) grown on conductive substrates?
The intensity from the biomaterials themselves is probably too low, but we can measure the substrates.
Is this applicable for polycrystalline thin films?
Not really, the grains in the film are probably too small.
Two questions regarding the omega/theta tool: 1) is it possible to perform mappings of 200mm wafers? 2) How long does a single rocking curve roughly take, when you do a rocking curve mapping?
1) On the Omega-Theta we have a 290mm mapping table. If we remove the flat stop, we can map an entire 300 mm wafer, although we would only be able to say something about relative tilt direction because we don’t have a geometric reference anymore.
2) The time a rocking curve measurement will depend on the settings for the scan. About 1-2 minutes should be typical. The system can actually use an azimuthal or theta scan to first find the tilt and then perform a rocking scan around the specified peak even if it is tilted by a few degrees.
Can you elaborate on how the phi azimuthal scan measures the miscut of the out-of-plane direction?
If we take a pattern, and place the center of rotation in the middle (at the origin), we will see each point at a certain angle in the rotation. If the pattern moves slightly, and we rotate again, we will find the points at different angles in the rotation. If we know what the pattern looks like, we can calculate back how far it has shifted. We can also do this when the pattern has been rotated, because the angle difference between where we observe the points also changes.
The same holds for the asymmetric scattering peaks we record in the azimuthal scan. We need to have a model for the material and orientation we want to measure and then we can calculate the orientation of the sample from the peaks we record.
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