Many people underestimate the impact that roughness has on a surface’s functional properties. It can affect mechanical, chemical, optical, electrical, and even physical responses and material characteristics: for better or worse. In this webinar, you’ll learn how to quanitfy and analyze surface roughness so you can ensure the optimal materials are incorporated into your next project.
Covalent’s Vice President of Technology, Dr. Chris J.L. Moore, has prepared a robust overview of surface characterization methods. From optical profilometry options to electron microscopy, he’ll break down the advantages and disadvantages of measurements to help you scope the right technique for your metrology needs. Watch the 2nd episode of Covalent Academy for a crash course in surface analysis with:
And more!
This Webinar Will Answer
- Why should you care about surface roughness? What does it affect?
- How do you quantify surface roughness?
- What techniques are used to analyze surface roughness?
- What are the pro’s and con’s of those techniques?
- How should you go about selecting the right kind of analysis for your project? What are the key things to keep in mind?
Frequently Asked Questions
For white light interferometry, by high resolution how high would that be spatially?
Chris will present the answer later in the presentation. He will cover both lateral and vertical. It depends on which lens is chosen and this is covered in slide 27 and will discussed in more detail next week.
What would you recommend to be effective in measuring surface features in a optic piece, that is about 4 inches in diameter? The surface has been abliated in an unpatterned fashion.
As Chris has indicated: it depends. It depends on what you are trying to learn about your sample. We might recommend Chromatic Dispersion, AFM, or Laser Confocal. I would use a chromatic dispersion but it depends on what spatial and vertical resolution you need and over what area.
For AFM at Nanometer Z resolutions, SVOCs that are common in ambient air, like DOP, DBP, Silicones, BHT, Caprolactam can adsorb, and should then give false positive Z height error. Shouldn’t AFM be run under w C filter, ULPA, for SVOC, nanoparticle control. Is this commonly done or not?
Although environmental contamination of a surface can affect the results it is normally not a problem for Roughness as it is often in the sub- monolayer regime. It is a more significant problem for surface chemistry and composition. Placing a sample is UHV does not guarantee you have a clean surface.
Roughness is very important for Silicon wafer if etch on back side. How can I decide about roughness to my Silicon vendor?
Silicon wafer roughness is normally measured using with AFM or white light interferometry.
Don’t most AFMs handle roughness up to approx 5 microns?
It can, but other techniques might work better and faster at that level of roughness. For example, the laser confocal might give equivalent results more quickly. Depends if you are quoting Ra then the excursion are at least 3x that number which is beyond the range of most AFM’s. If you are quoting peak to valley you are correct.
What do you think about the surface roughness that can be measured by ellipsometry? Is it useful?
It can be very useful if you are looking to ranks surfaces. However, it is very difficult to correlate with other direct techniques.
What would ellipsometry methods for roughness look like in terms of reliability when compared to other techniques such as AFM or XRR?
If the samples are similar they are very reliable. If the samples change and you need to remodel you can have difficulty.
Do you care or measure changes in interfacial free energy changes induced from roughness?
This can be measured qualitatively, but need to keep in mind surface tension depends on equilibrium with the environment. Need to be able to manipulate and control environmental conditions: dry, humid, etc.
Are there preferred/common methods/values (for example you mentioned Rz can be a good cross check for Ra measurements between samples for some techniques) used to cross-check certain roughness measurements, if so, is it often instrument specific?
Considering that how Rz is calculated can differ from instrument to instrument it is difficult to use Rz. Since ra often depends on the length of scan you need to make sure you are comparing similar scans. In short yes it is very instrument dependent.
One of your slides Ra and RZ but how can I get which one is important Ra or Rz?
Both are important and which is more important depends on your process needs.
Is any other technique available other than AFM to measure sub nm surface vertical roughness?
Closest for a flat sample is White Light Interferometry but be careful on transparent materials.
Speakers:
Chris Moore
PhD, Chief Technical Officer at Covalent Metrology
