TY - JOUR
T1 - Feasibility of 4 GHz half wavelength contact acoustic microscopy (HaWaCAM)
AU - Van Neer, P. L.M.J.
AU - Quesson, B. A.J.
AU - Tamer, M. S.
AU - Hatakeyama, K.
AU - Van Es, M. H.
AU - Van Riel, M. C.J.M.
AU - Piras, D.
PY - 2021
Y1 - 2021
N2 - Several methods are being researched to detect and characterize buried nanoscale structures in hard solid samples. The most common acoustic method is acoustic microscopy. An acoustic microscope is based on a single element transducer operating in pulse-echo mode. The acoustic waves are coupled into a sample using a liquid couplant (eg water) and the beam is focused using a geometric lens to obtain a good lateral resolution. Thus, the frequency is limited by the attenuation in the coupling layer (water 3.5\{dB}/{m} at 4 GHz) and the typically low transmission coefficients at the transducer-liquid couplant and liquid-sample interfaces. Here, we present a novel method for high frequency acoustic metrology of buried structures in solid samples. The concept consisted of a 4 GHz acoustic transducer integrated above the tip of a custom designed probe. It operated in pulse-echo mode, and used solid-solid contact with the sample without the need for liquid coupling layers. A prototype was built and successfully tested experimentally on samples consisting of silicon with 1D and 2D arrays ofmu\{m} sized features buried below 5-10{m} of PMMA or SiO2 top layers. Moreover, a good match was obtained between model predictions and measurements of the pulse-echo performance of the novel GHz acoustic metrology method. The technique features a penetration depth of O(10s ofmu\{m}), is nondamaging and is not hampered by optically opaque layers.
AB - Several methods are being researched to detect and characterize buried nanoscale structures in hard solid samples. The most common acoustic method is acoustic microscopy. An acoustic microscope is based on a single element transducer operating in pulse-echo mode. The acoustic waves are coupled into a sample using a liquid couplant (eg water) and the beam is focused using a geometric lens to obtain a good lateral resolution. Thus, the frequency is limited by the attenuation in the coupling layer (water 3.5\{dB}/{m} at 4 GHz) and the typically low transmission coefficients at the transducer-liquid couplant and liquid-sample interfaces. Here, we present a novel method for high frequency acoustic metrology of buried structures in solid samples. The concept consisted of a 4 GHz acoustic transducer integrated above the tip of a custom designed probe. It operated in pulse-echo mode, and used solid-solid contact with the sample without the need for liquid coupling layers. A prototype was built and successfully tested experimentally on samples consisting of silicon with 1D and 2D arrays ofmu\{m} sized features buried below 5-10{m} of PMMA or SiO2 top layers. Moreover, a good match was obtained between model predictions and measurements of the pulse-echo performance of the novel GHz acoustic metrology method. The technique features a penetration depth of O(10s ofmu\{m}), is nondamaging and is not hampered by optically opaque layers.
KW - GHz acoustic metrology
KW - half wavelength contact area
KW - half-wavelength contact acoustic microscopy
KW - HaWaCAM
KW - solid contact
UR - http://www.scopus.com/inward/record.url?scp=85122857315&partnerID=8YFLogxK
U2 - 10.1109/IUS52206.2021.9593305
DO - 10.1109/IUS52206.2021.9593305
M3 - Conference article
AN - SCOPUS:85122857315
SN - 1948-5719
JO - IEEE International Ultrasonics Symposium, IUS
JF - IEEE International Ultrasonics Symposium, IUS
T2 - 2021 IEEE International Ultrasonics Symposium, IUS 2021
Y2 - 11 September 2021 through 16 September 2021
ER -