Self-Aligned Structural Wafer Assembly for Hybrid Bonded Die Stacks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current hybrid bonding techniques for forming 3D die stacks face challenges such as liquid interaction with metal pads leading to oxidation or corrosion, and compatibility issues during fabrication that result in misalignment or contamination of the bonding surface.
Innovation Solution
The implementation of containment features on the backside of chiplets and a structural substrate allows for self-alignment bonding without using water droplets, resolving compatibility issues and preventing liquid interaction with metal pads. This method involves bonding chiplets to a structural wafer using hydrophobic containment features and then hybrid bonding the active surfaces of the chiplets to a base wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If water droplets are used for self-alignment bonding, then alignment precision is improved, but metal pads are exposed to liquid causing oxidation or corrosion
Solution Approach 1:
The bonding surface is segmented into hydrophobic regions (containing the metal pads) and hydrophilic regions (where water droplets are placed). This segmentation allows the water droplet to self-align on the hydrophilic region without contacting the metal pads on the hydrophobic region, thus achieving precise alignment while preventing oxidation or corrosion of the metal pads.
Solution Approach 2:
The hydrophobic containment feature acts as an intermediary between the water droplet and the metal pad. It allows the water droplet to be contained and positioned accurately while preventing direct contact between the liquid and the metal pad, thereby eliminating the harmful effect of liquid exposure on the metal pad.
2Measurement precision
If containment features and metal pads are fabricated on the same surface, then self-alignment is enabled, but compatibility issues and contamination occur
Solution Approach 1:
The metal pads are recessed into the bonding surface, creating a vertical dimension separation. The hydrophobic containment feature is formed on the surface plane, while the metal pads exist in a recessed plane below. This dimensional separation eliminates compatibility issues and contamination risks between the containment feature fabrication process and the metal pad bonding surface.
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
This approach enables fast and accurate assembly of 3D die stacks with improved bond quality and reduced risk of oxidation or corrosion, while also simplifying the fabrication process by eliminating compatibility issues between containment features and metal pads.
Implementation Method 1
bonding regions surrounded by hydrophobic containment features
Implementation Method 2
evaporating the liquid droplet between a first bonding region of a structural substrate and a second bonding region of an integrated circuit (IC) die
Data Source
AI summary
Hybrid bonded die stacks, related apparatuses, systems, and methods of fabrication are disclosed. An integrated circuit (IC) die backside surface and a surface of a structural substrate each include bonding regions surrounded by hydrophobic structures. A liquid droplet is applied to the die or structural substrate bonding region and the die is placed on the bonding region of the structural substrate. Capillary forces cause the die to self-align to the bonding region, and a bond is formed by evaporating the liquid and subsequent anneal. A hybrid bond is then formed between the opposing active surface of the die and a base substrate using wafer-to-wafer bonding. IC structures including the IC die and portions of the structural substrate and base substrate are segmented from the bonded wafers and assembled.