Deep Trench Isolation and through Silicon via Wetting Characterization by High-Frequency Acoustic Reflectometry

Abstract

Wetting efficiency of microstructures or nanostructures patterned on Si wafers is a real concern in integrated circuits manufacturing. We present here a high-frequency acoustic method which enables the local determination of the wetting state of a liquid on real DTI and TSV structures. Partial wetting states for non-hydrophobic surfaces or low surface tension liquids are detectable with this method. Filling time of TSV structures has also been measured.

Assessment and Interpretation of Surface Wettability Based on Sessile Droplet Contact Angle Measurement: Challenges and Opportunities

“…An alternative acoustic method based on the principle of high‐frequency acoustic echography has been presented to study the solid–liquid interaction and degree of liquid imbibition in the micro‐ and nanostructures . The acoustic wave is generated by a piezoelectric transducer integrated on the backside of the substrate under analysis on which the droplet is deposited .…”

Polydimethylsiloxane Micro-Channels Application for the Study of Dynamic Wetting of Nano-Etched Silicon Surfaces Based on Acoustic Characterization Method

“…The DTI [1,7] (Deep Trench isolation) silicon wafer is an etched silicon structure with trenches width of 200 nm, organized as a network of rectangles. Although the DTI wafer is made of silicon, there are two additional layers which are silicon dioxide (SiO2) and silicon nitride (Si3N4) of several tens of nanometers in thickness, present uniquely on the top surface of the trenches.…”

“…The characterization acoustic method that we developed [2] is represented in Fig. 3; it consists of sending an incident volume wave generated by a piezoelectric transducer (ZnO disc of 75 µm diameter) which is fabricated on the back of the wafer by lithography process.…”

“…4, which will be used to calculate the fluid film thickness (h); then we will take our micro-channel height as 2h to achieve the same fluid flow profile, since it is a closed channel compared to the open jet system used in cleaning industrial wafers. Different aspect ratios of DTI [1,7] within silicon wafers, and covered by a PDMS micro-channel, have been tested and subjected to different hydrodynamic conditions. Table 1 show the hydrodynamic conditions on 300 mm flat wafer and the corresponding pressure loss calculated using Eq.…”

“…With these increasing aspect ratios it's becoming more and more difficult to achieve wet cleaning of these etched silicon structures [1] and to remove non-desired particles which can lead to defective electronic products. We developed an acoustic method [2,3] using ultra-high frequency (5 GHz) to detect the penetration of the liquid to the bottom of the etched structure and hence get information about the efficiency of the wetting (cleaning) states. Our previous results have been obtained under static wetting conditions (droplet based) while the industrial cleaning process uses a liquid dispensed in a form of jet on a rotating wafer.…”