Semiconductor Interconnect Reservoir for Bonding Reliability
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Solution Overview
Problem
In three-dimensional vertical stack technology for integrated circuits, surface variations between wafers or dies lead to unreliable metal-to-metal bonding of metal bond pads, resulting in unreliable interconnections.
Innovation Solution
The formation of protruding metal bond pads with adjacent reservoirs allows for improved semiconductor interconnects by preventing excess metal from flowing and causing shorts during bonding, with the reservoirs designed to capture excess metal and potentially allow dielectric contact between stacked structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal bond pads are bonded directly to metal bond pads of another wafer or die, then electrical connections are made between stacked wafers or dies, but surface variations cause unreliable metal-to-metal bonding
Solution Approach 1:
The patent introduces a dielectric material as an intermediary between the metal bond pads of stacked wafers or dies. This dielectric layer compensates for surface variations and height differences, enabling reliable bonding even when surfaces are not perfectly flat. The intermediary layer ensures consistent electrical connections by providing a uniform bonding interface.
2Reliability
If metal bond pads are made to protrude above the final dielectric layer to ensure bonding contact, then bonding reliability improves, but excess metal may flow laterally during bonding causing shorts
Solution Approach 1:
The patent converts the potentially harmful lateral metal flow during bonding into a beneficial feature by providing reservoirs that intentionally capture this excess metal. Instead of allowing metal to flow uncontrollably and cause shorts, the reservoirs are designed to contain the metal flow, ensuring that bonding reliability is maintained while preventing short circuits between adjacent interconnects.
Solution Approach 2:
The reservoirs are formed in advance before the bonding process, positioned adjacent to the metal bond pads. This preliminary preparation ensures that when bonding occurs and excess metal flows laterally, the reservoirs are already in place to capture and contain the metal, preventing shorts before they can occur.
3Reliability
If reservoirs are formed adjacent to metal bond pads to capture excess metal, then short circuit prevention improves, but device structure and fabrication complexity increase
Solution Approach 1:
The patent merges the formation of reservoirs with the existing dielectric layer fabrication process. The reservoirs are created as part of the dielectric layer structure, utilizing the same material deposition and patterning steps already required for the interconnect formation. This integration minimizes additional fabrication complexity while achieving short circuit prevention.
Data Source
AI summary
A semiconductor device and method has interconnects with adjoining reservoir openings. A dielectric layer is formed as part of an uppermost of the one or more interconnect layers. Openings formed in the dielectric layer result in modified portions of the dielectric layer along portions of sidewalls of the openings. The openings are filled with a conductive material, such as metal. An exposed portion of the dielectric layer is removed to form protruding pads of the conductive material extending above the dielectric layer. Reservoir openings are formed adjacent the protruding pads by removing the modified portions of the dielectric layer. When the semiconductor device is bonded with another device, either a wafer or a die, laterally flowing metal collects in the reservoir openings and ensures that a reliable electrical connection is made between the semiconductor device and the other device.