Buried Bond Pad Structure to Prevent Low-K Dielectric Peeling
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Solution Overview
Problem
Conventional bond pad structures in integrated circuits (ICs) suffer from poor bonding with low-K dielectric materials, leading to peeling issues that result in device failure and resource wastage during manufacturing.
Innovation Solution
The implementation of buried bond pad structures within the interconnect structure of ICs, providing a larger contact surface area and stronger bonding by having bond pads in direct contact with metal layers further from the light source, reducing the likelihood of peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional bond pad structures are used with low-K dielectric materials, then manufacturing process is simpler, but bonding strength is poor leading to peeling issues
Solution Approach 1:
The bond pad structure transitions from a surface-level configuration to a three-dimensional embedded structure within the interconnect layers. The bond pad is formed by extending conductive material through multiple dielectric layers and metal interconnects, creating a volumetric bonding interface rather than a planar one. This dimensional transformation increases the bonding surface area and mechanical interlocking, thereby improving bonding strength without simply scaling up the surface footprint.
Solution Approach 2:
The bond pad structure employs a composite configuration combining multiple materials including conductive metal layers (e.g., copper, aluminum), low-K dielectric materials, and barrier/adhesion layers. This composite structure allows each material to perform its optimized function: the metal provides electrical conductivity and bonding strength, the low-K dielectric provides electrical isolation with minimal signal interference, and the barrier layers prevent diffusion and enhance adhesion. The synergistic combination resolves the contradiction by integrating material properties rather than relying on a single material solution.
2Reliability
If bond pads are placed on the IC surface, then bonding access is easier, but peeling occurs due to poor bonding with low-K dielectric
Solution Approach 1:
The bond pad structure implements a nested configuration where the conductive bond pad material is embedded within successive layers of dielectric and metal interconnects. The bond pad nucleus is formed in an initial layer, then subsequent dielectric and conductive layers are deposited and patterned around it, creating a nested structure similar to Russian dolls. This nesting provides mechanical anchoring through multiple interfaces, preventing peeling while maintaining electrical functionality. The nested design also allows the bond pad to be accessed from the top surface after planarization, preserving ease of bonding access.
Solution Approach 2:
The bond pad structure is prepared in advance during the interconnect fabrication process before the final bonding step. Conductive material is extended through dielectric layers and metal interconnects during standard CMOS or BCMA manufacturing sequences, creating pre-formed bonding surfaces with enhanced adhesion. This preliminary formation of the bond pad structure, including any required planarization or surface preparation, is completed during normal fabrication flow, so that when bonding occurs, the structure is already optimized for reliable attachment without requiring additional specialized processing steps.
3Strength
If bond pad contact area is increased, then bonding strength improves, but device area is consumed
Solution Approach 1:
The solution moves the bonding interface from a two-dimensional surface contact to a three-dimensional volumetric structure. By extending the bond pad conductive material vertically through multiple dielectric and metal layers, the effective bonding surface area is increased without proportionally increasing the horizontal footprint on the IC surface. The volumetric nature of the embedded bond pad provides additional bonding area through side walls and internal interfaces, achieving enhanced bonding strength while maintaining compact lateral dimensions and preserving valuable IC real estate for active devices.
Data Source
AI summary
Some embodiments relate an integrated circuit (IC) including a first substrate. An interconnect structure is disposed over the first substrate. The interconnect structure includes a plurality of metal features that are stacked over one another. A lowermost metal feature of the plurality of metal features is closest to the first substrate, an uppermost metal feature of the plurality of metal features is furthest from the first substrate, and intermediate metal features are disposed between the lowermost metal feature and the uppermost metal feature. A recess extends into the interconnect structure and terminates at a bond pad. A lower surface of the bond pad directly contacts an upper surface of the lowermost metal feature.