Low-Temperature Hybrid Bonding for Semiconductor Stacking
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Solution Overview
Problem
Conventional wafer bonding techniques face issues such as lack of electrical contacts in fusion bonds, high compressive forces and temperatures in eutectic bonds, and mechanical stresses and oxidation in hybrid bonds, leading to poor accuracy and damage.
Innovation Solution
A low-temperature hybrid bonding process is implemented, using an oxide-oxide or silicon-silicon fusion-type interface instead of a metal-metal eutectic-type interface, with metal layers aligned and bonded at temperatures below 100°C, reducing mechanical stresses and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If eutectic bonding is used to achieve adhesion between substrates, then bonding strength is improved, but high compressive forces and temperatures cause poor accuracy and mechanical damage
Solution Approach 1:
The patent changes the bonding parameters by using fusion bonding at low temperatures (below 100°C) instead of eutectic bonding at high temperatures. This parameter change resolves the contradiction by achieving adequate bonding strength without the high compressive forces and temperatures that cause poor accuracy and mechanical damage.
Solution Approach 2:
The patent replaces the mechanical eutectic bonding system (requiring high compressive forces and temperature control) with a chemical fusion bonding system activated by plasma or chemical treatment. This substitution eliminates the need for high mechanical loads while achieving reliable bonding, thereby improving manufacturing precision.
2Ease of manufacture
If fusion bonding is used to bond substrates, then manufacturing simplicity is improved, but no electrical contacts are provided between substrates
Solution Approach 1:
The patent merges fusion bonding with eutectic bonding features by incorporating metal layers into the fusion bonding process. The metal layers serve dual purposes: they facilitate the bonding process and provide electrical interconnection between substrates, thereby resolving the contradiction between manufacturing simplicity and electrical reliability.
Solution Approach 2:
The metal layers in the patent serve multiple functions: they act as bonding interfaces for fusion bonding and simultaneously provide electrical contacts between substrates. This multi-functionality resolves the contradiction by maintaining process simplicity while adding electrical interconnection capability.
3Reliability
If hybrid bonding is used to combine fusion and eutectic bonds, then bonding reliability is improved, but mechanical stresses and oxidation problems occur
Solution Approach 1:
The patent extracts the problematic elements from hybrid bonding by using only fusion bonding mechanisms. By eliminating the eutectic bonding component that causes mechanical stresses and oxidation, the patent achieves reliable bonding through chemical activation and low-temperature fusion, thereby resolving the contradiction between reliability and harmful factors.
Solution Approach 2:
The patent converts the potential harm of metal oxidation into a benefit by using metal layers that are intentionally oxidized or chemically activated to facilitate fusion bonding. The oxidation that would normally be harmful becomes the bonding mechanism itself, resolving the contradiction between reliability and oxidation problems.
4Strength
If conventional bonding techniques are used, then substrate adhesion is achieved, but further costly processing is required to achieve interconnection of metal layers
Solution Approach 1:
The patent merges substrate bonding and metal layer interconnection into a single fusion bonding step. The metal layers are bonded simultaneously with the substrates through the fusion bonding process, eliminating the need for separate interconnection processing steps and thereby reducing device complexity and cost.
Solution Approach 2:
The patent performs preliminary preparation of metal layers (such as adding metal layers or forming bump structures) before bonding, so that the interconnection function is already in place. This preliminary action allows the bonding process to simultaneously achieve both adhesion and interconnection, reducing further processing requirements.
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
The low-temperature hybrid bonding process enhances bonding accuracy, reduces mechanical stresses, and minimizes the loading associated with polishing, resulting in a more reliable and precise semiconductor device fabrication.
Implementation Method 1
Fusion bonding is the adhesion of two substrates placed in direct contact with each other. At room temperature, the substrates bond to one another following a chemical or plasma activation step.
Implementation Method 2
Eutectic bonding is the adhesion of two substrates, having a eutectic metal layer positioned between them, where the metal transforms directly from a solid to liquid state, or vice versa, at a specific composition and temperature.
Data Source
AI summary
A method of fabricating a semiconductor device includes providing a first substrate comprising a first conductive element exposed at a surface of the first substrate; forming a patterned photoresist layer atop the first conductive element, whereby the patterned photoresist layer provides openings exposing the first conductive element; forming a first metal layer in the openings and directly atop the first conductive element; forming a first insulator layer over the first metal layer and the first substrate; and polishing the first metal layer and the first insulator layer, resulting in a first interface surface over the first substrate wherein the first interface surface includes part of the first metal layer and the first insulator layer.