Nanodiamond resonators fabricated on 8″ Si substrates using adhesive wafer bonding

Abstract

In this work, the adhesive wafer bonding of diamond thin films onto 8″ silicon substrates is reported. In order to characterize bonded nano-crystalline diamond layers, vibrometry and interferometry studies of micro-fabricated flexural beam and disk resonators were carried out. In particular, surface topology along with resonant frequencies, eigenmodes and mechanical quality factors were recorded and analyzed in order to obtain physical parameters of the transferred films. The vibration properties of the bonded resonators were compared to those fabricated directly on 3″ silicon substrates.

Inkjet‐Printed High‐Q Nanocrystalline Diamond Resonators

“…Quality factors from the inkjet‐printed NCD micro‐disk resonators from this work compared with the values reported by Lebedev et al for wafer‐bonded NCD disk on Si . The corresponding ( f 0 × Q ) figures of merit of the present NCD resonators are shown in Figure S5 (Supporting Information).…”

“…Figure shows the relationship between the quality factors and the resonance frequencies, and compares the obtained values with data from Lebedev et al (wafer‐bonded NCD on Si) . It can be seen that the inkjet‐printed NCD micro‐disk resonators display consistently high Q ‐factors of up to ≈1 × 10 4 for both disks, which can be understood as a consequence of the chosen dimensions (i.e., lower clamping losses due to the formation of whispering gallery modes), but mostly of material and device quality.…”

“…By controlling the printer settings, larger nanocrystalline diamond disks with 54 ± 4 µm in diameter and ≈1 µm thick were fabricated and applied as micro‐resonators after partial underetching of the Si substrates. Analysis of the frequency response showed consistently high Q ‐factors (>10 3 ) exceeding 10 4 , and ( f 0 × Q ) figures of merit up to ≈2.5 × 10 11 Hz in vacuum, which are higher than for other reported diamond disk resonators produced by conventional lithography‐based techniques . Even higher performances can be expected with further optimization of the NCD growth conditions, e.g., by adding oxygen to the gas mixture during CVD, to improve material properties and reduce intrinsic losses.…”

“…This is thanks to diamond's excellent material properties, such as high Young's modulus (up to ≈10 6 N mm −2 ), high acoustic velocity (≈1.8 × 10 4 m s −1 ), low thermoelastic damping, high thermal conductivity (>2000 W m −1 K −1 ), and low thermal expansion coefficient (≈10 −6 K −1 at 300 K) . The feasibility of using NCD for high‐performance MEMS resonators has already been demonstrated in a range of devices, including cantilever beams, tuning forks, rings, disks, and spheres . In particular, NCD MEMS structures that resonate with whispering gallery modes (WGM), such as disks and spheres, have shown much lower anchor losses and higher ( f 0 × Q ) figure of merit .…”

“…The grown NCD film needs then to be patterned by traditional photo‐/e‐beam lithography and lift‐off techniques, which add substantial complexity and cost of fabrication. As a solution to circumvent low seeding density and plasma uniformity issues during growth of the NCD layer, Lebedev et al proposed wafer‐to‐wafer bonding of pregrown NCD films onto another wafer to fabricate NCD disk resonators with high Q ‐factors (i.e., Q > 10 3 ) . This technique however did not remove the need to pattern the diamond after it was bonded onto the wafer.…”