Pitch scaling of interconnects is required for 3D system integration with the industry shifting to bumpless bonding technology. However, hybrid metal/dielectric bonding requires tight process control of planarity after chemical mechanical polishing (CMP) to avoid bonding voids. Due to its sub-angstrom resolution, atomic force microscopy (AFM) is typically used to assess the nano-topography but conventional systems suffer from increased noise floor at high scanning speeds making it unsuitable for high-volume manufacturing (HVM). Here, we validate a novel in-line high-throughput AFM system (QUADRA) by reporting the topographical parameters of 250 nm and 1 μm size copper nano-pads at high scanning speeds that reach tens of wafers per hour throughput.
Wafer-to-wafer hybrid bonding is a key technology for achieving high-density three-dimensional interconnections in semiconductor devices. This technology directly bonds Cu pads formed on the surface of two wafers, where the surface height of the Cu pad compared to the SiCN surrounding the Cu pad have to be within a few nm. We have developed a method to measure the Cu pad surface height with sub-nm precision by using a top-view scanning electron microscope image. The proposed method is based on the physical principle that the difference in the backscattered electron (BSE) signals of the opposing detectors is dependent on the slope. It estimates the slope of the target with the BSE signal and then calculates the height of the target on the basis of this slope. We compared the Cu pad height measurement results by this method with those by atomic force microscopy and found that ours provided measurement precision on the sub-nm order and demonstrated the capability for evaluation of layout dependency and intra-wafer distribution. Because of its speed and alignment capability, our proposed method is promising for Cu height control in wafer-to-wafer hybrid bonding.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.