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  • 1.  Non-destructive CVD thickness measurement

    Posted 02-16-2026 18:30

    When using CVD to deposit polycrystalline diamond onto a silicon carbide base, there are instances where one must measure the deposition layer (say about 10 micron) without cross-sectioning the finished product or applying the same coating to a sample that can be destructively measured. There must be a way aerospace or automotive suppliers do this, possibly with x-ray absorbance or wavelength bounceback. 



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    John Merrill
    Principal Engineer
    EagleBurgmann | Freudenberg
    Matthews NC
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  • 2.  RE: Non-destructive CVD thickness measurement

    Posted 02-17-2026 10:23
    Hello John,

    To the best of my knowledge, there are three techniques that are commonly used for this type of measurement:
    1. X-Ray reflection. Suited for thin films in nm range. More involved but used in semiconductor manufacturing when there are multiple deposits.
    2. X-Ray fluorescence. Used in micron range in the coating and plating industry. 
    3. X-Ray Diffraction: Since the width of a diffracted beam is related to crystallite size on the sample surface and assuming that the single crystals span the thickness of the coating, one can measure the thickness of the film using X-Ray diffraction equipment. The 10 micron thickness is in the range of this technique.

    Good Luck!

    Ratnesh Dwivedi, Ph.D.
    RKD ENGG, LLC



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  • 3.  RE: Non-destructive CVD thickness measurement

    Posted 02-18-2026 12:54

    We have utilized confocal Raman spectroscopy to measure the film thickness of a CVD coating applied to a stainless steel substrate. It is a nondestructive and relatively quick analysis with the right instrumentation and expertise. Resolution is on the order of 1-3 microns in depth. The film and the base substrate need to be spectrally different for this analysis to be effective.  



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    Greg Borgard
    Sr. Engineering Advisor
    Eli Lilly and Company
    Carmel IN
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  • 4.  RE: Non-destructive CVD thickness measurement

    Posted 02-21-2026 09:05

    Thank you for the response, Ratnesh.

     

    I will contact some of the instrument manufacturers of these types and see if they have a commercial solution.

     

    John

     




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  • 5.  RE: Non-destructive CVD thickness measurement

    Posted 02-21-2026 09:28

     

    Another technique I've used in the past is to put a magnet under the substrate and put fine iron powder on top of the substrate but over the magnet. This masks the deposited film and can be removed just by removing the magnet. Neodymium, and samarium cobalt magnets have curie temperatures of 300+C and 700+C respectively. Depending on the deposition conditions the iron powder can remain even if the magnetism is lost.

     

    S.H. Astaneh, C. Sukotjo, C.G. Takoudis, and A. Feinerman, "Simple masking method for selective atomic layer deposition of thin films," Journal of Vacuum Science & Technology B 38, 025001 (2020); https://doi.org/10.1116/6.0000146




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  • 6.  RE: Non-destructive CVD thickness measurement

    Posted 02-18-2026 15:59

    One of our consultants sent this back to me. All we do is CVD diamond films.

    You might also look at attending ICMCTF in San Diego in April.

    Hope this helps.

    Ed

    This is pretty easy stuff. Semiconductor industry has been doing this of decades! They use ellipsometry or reflectometry to measure films down to nm thick nondestructively. Examples are below.

    Thin-Film Thickness Measurement | Thin-Film Metrology | KLA Instruments

    kla.com

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    https://www.angstec.com/?gad_source=1&gad_campaignid=20937964969&gbraid=0AAAAAD_CVvYA-rvByCESH614tNP5Y7X9w

    The 

    NanoSpec is a non-contact optical metrology tool that determines the thickness of transparent thin films (e.g., oxides, photoresists) on silicon wafers by measuring light reflection. It uses spectro-reflectometry to analyze how light waves interfere within the film, typically operating across the 370–800nm range to calculate thicknesses from 100 Å to 

    .



    I used to measure thickness on Nanospec in 1985!



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    Edward Francis
    VP Imagineering
    Crystallume
    Santa Clara CA
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  • 7.  RE: Non-destructive CVD thickness measurement

    Posted 02-21-2026 09:02

    Thank you for the response, Ed.

     

    I will dig into this deeper. I am not sure if our diamond layer is transparent. It looks dark grey compared to the silicon carbide substrate which is a brighter grey.

     

    John

     




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  • 8.  RE: Non-destructive CVD thickness measurement

    Posted 02-20-2026 15:24

     

    A former colleague pointed out to me that a 10 micron diamond film is too rough for reliable optical measurement. Some companies can make very smooth diamond films but their low transparency still makes optical thickness measurements challenging.

     

    A major synthetic diamond film manufacturer always loaded Silicon witness chips alongside the production wafers. After deposition, the witness chips could be cleaved to expose the cross-section of the film. The thickness can then be measured using an optical microscope (SEM is not strictly necessary), typically with less than 10% error.

     

    Another approach is to place a smaller masking chip on top of a larger witness chip during loading. After deposition, the step created by the masking chip can be measured using a profilometer to determine film thickness.

     

    X-ray-based methods may offer higher precision, but they are generally time-consuming and less accessible compared to the approaches above.

     




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  • 9.  RE: Non-destructive CVD thickness measurement

    Posted 02-21-2026 18:46

    Hi John

    It would be helpful to know the roughness and transparency of these films as ellipsometry is a very useful technique with low absorbance and low scattering films. 

    Regarding X-ray diffraction, the application of peak broadening using the Scherer equation is only valid up to crystallite sizes of about 100 nm, and then only after instrumental peak broadening has been quantified and removed.  

    I look forward to hearing what you find to be useful here.

    Harold



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    Harold Ackler
    Clinical Associate Professor
    Micron School of Materials Science and Engineering
    Boise State University, Boise ID
    408-230-7277 cell
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    Original Message


  • 10.  RE: Non-destructive CVD thickness measurement

    Posted yesterday

    I haven't worked hands-on with CVD specifically but I do know that, in the "normal" coatings industry, like for example paints, people use eddy current probes and they can resolve to 10 microns. I used to work somewhere where we applied a nominal paint thickness of .001" (25 microns) and we used these probes for QC all the time. Eddy current is a very sensitive technique (in fact, that's an Achilles heel when using it for NDE purposes, since you need to watch out for false positives).

    This is way beyond what you'd need but just for kicks - if you ever need to resolve down to angstroms, you can use what's called a QCM, or quartz crystal microbalance. It's a probe that takes a small quartz wafer about the size of a dime and electrically excites it to a certain frequency, such as 6 megahertz (quartz is piezoelectric). The wafer is exposed in the chamber while the coating deposition process is occurring, so the wafer gets coated along with the parts. As the wafer gets coated, it gets heavier, and this will retard its vibration frequency, say from 6.0 MHz to 5.99. The probe can measure this and, using calculations with a few inputs about the coating material (such as its density), it can calculate a film thickness. We used to use these at a thin film lab I worked at in college; I'm not aware that anyone's using them in a non-academic context but in theory you could. In this case it wouldn't be used to directly measure coating thickness on parts after the fact, it would be a representative sample.



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    Sean Piper
    Technical Market Development Specialist
    CBMM North America
    Houston TX
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