Receiving Substrate Pad Stack for UBM-Free Hybrid and Solder Bonding
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Solution Overview
Problem
Existing semiconductor bonding methods require complex process steps and risk damage to hybrid bonded dies when transitioning from hybrid to solder bonding, as they involve the formation of under bump metallization (UBM) pads on the receiving substrate.
Innovation Solution
A receiving substrate is prepared with contact pads embedded in dielectric layers, featuring a two-layer structure for hybrid and solder bonding, where the bottom layer slows intermetallic compound formation with solder, allowing direct solder application without UBM pads, and additional pads for testing and wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hybrid bonding is applied first followed by solder bonding on the same receiving substrate, then both bonding techniques can be utilized, but additional process steps (UBM pad formation) are required which increase process complexity and risk damaging hybrid bonded dies
Solution Approach 1:
The receiving substrate is divided into distinct first landing areas for hybrid bonding and second landing areas for solder bonding. Contact pads in hybrid bonding areas are configured for direct dielectric-to-dielectric and metal-to-metal bonding, while contact pads in solder bonding areas are designed to receive solder material directly without requiring UBM pad formation. This spatial segmentation allows both bonding techniques to be applied on the same substrate without interfering process steps.
Solution Approach 2:
Different landing areas on the receiving substrate are given different local properties: hybrid bonding landing areas have contact pads suitable for direct hybrid bonding, while solder bonding landing areas have contact pads specifically configured to receive solder material directly. This local differentiation eliminates the need for universal UBM pad formation across the entire substrate, reducing process complexity while maintaining versatility.
2Adaptability or versatility
If UBM pads are formed on the receiving substrate after hybrid bonding, then solder bonding can be performed, but this may lead to potential damaging of the hybrid bonded dies
Solution Approach 1:
The substrate is segmented into dedicated solder bonding landing areas where contact pads are pre-configured to receive solder material directly. This eliminates the need to form UBM pads on areas where hybrid bonding has already been performed, thereby preventing potential damage to hybrid bonded dies while still enabling solder bonding capability.
Solution Approach 2:
The contact pads in solder bonding landing areas are prepared in advance during substrate fabrication to be ready for direct solder material application. This preliminary configuration eliminates the need for subsequent UBM pad formation steps that could damage previously bonded hybrid dies, as the solder-ready contact pads are already in place before any bonding operations begin.
3Adaptability or versatility
If different bonding techniques are applied on the same receiving substrate, then chip type flexibility is improved, but process steps such as plating UBM pads increase manufacturing complexity
Solution Approach 1:
The receiving substrate features contact pads with different local configurations: those in hybrid bonding landing areas are designed for direct hybrid bonding, while those in solder bonding landing areas are designed to receive solder material directly. This local quality differentiation eliminates the need for universal UBM pad plating operations, simplifying manufacturing while maintaining the ability to accommodate both hybrid and solder bonded chip types.
Solution Approach 2:
The substrate surface is segmented into distinct landing areas with specialized contact pad configurations. Hybrid bonding landing areas have contact pads suitable for direct bonding, while solder bonding landing areas have contact pads optimized for direct solder reception. This segmentation allows different chip types to be bonded using appropriate techniques without requiring complex universal preparation steps across the entire substrate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables seamless transition between hybrid and solder bonding without additional process steps, reducing damage to hybrid dies and simplifying the bonding process, while ensuring robust electrical connections.
Implementation Method 1
the bottom layer being formed of a material exhibiting slower intermetallic compound formation when reacting with solder than the material of the top layer
Implementation Method 2
under the influence of an annealing temperature and possibly a mechanical pressure
Data Source
AI summary
In one aspect, a receiving substrate is produced, configured to receive thereon one or more dies by hybrid bonding in one or more first landing areas and one or more dies by solder bonding in one or more second landing areas. In the two types of landing areas, contact pads are formed which are embedded in a dielectric layer or a stack of dielectric layers, enabling hybrid bonding in the hybrid bonding landing areas. The contact pads in the solder landing areas are configured to receive solder material directly on the contact pads after bonding of the hybrid bonded dies, without requiring the formation of under bump metal pads. In another aspect, at least the solder contact pads include two layers, a bottom layer and a top layer, the bottom layer being formed of a material exhibiting slower intermetallic compound formation when reacting with solder than the material of the top layer. In another aspect, additional contact pads are incorporated in a stack of dielectric material into which the hybrid and solder contact pads are embedded, in a manner that enables revealing the additional contact pads after hybrid and solder bonding. The additional contact pads may be configured for electrical testing of bonded dies or dies within the receiving substrate, or for wire bonding of further dies.