Direct-Bonded Stacked Dies for Low-Stress 3D Integration
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Solution Overview
Problem
Conventional methods for die thinning and 3D integration face challenges such as damage from stresses during assembly, alignment issues, and thermal/chemical bonding difficulties when stacking integrated device dies with different thicknesses and materials, leading to limited yield and increased package height.
Innovation Solution
A method involving the mounting of integrated device dies on a carrier, thinning them while applying a protective material to prevent edge damage, and using direct bonding techniques without adhesives, allowing for the stacking of dies with arbitrary thicknesses and materials, and subsequent planarization to expose interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional die thinning and stacking methods are used, then integrated device dies can be stacked in 3D integration, but stresses during assembly damage dies and limit product yield
Solution Approach 1:
The patent applies preliminary thinning to the integrated device dies before stacking them in 3D integration. By reducing the thickness of the dies in advance, the mechanical stresses during assembly are significantly reduced, preventing damage to the dies and improving product yield. This preliminary action addresses the core issue of stress-induced damage in conventional stacking methods.
2Adaptability or versatility
If dies with different thicknesses and materials are stacked, then design flexibility is improved, but alignment and bonding become challenging
Solution Approach 1:
The patent introduces an intermediary material layer between dies with different thicknesses and materials. This intermediary layer serves as a buffer that compensates for thickness variations and provides a uniform bonding surface, enabling precise alignment during stacking. The intermediary material facilitates bonding between dissimilar dies while maintaining manufacturing precision, thus resolving the conflict between design flexibility and alignment accuracy.
3Ease of manufacture
If adhesive bonding is used for die stacking, then assembly is simplified, but thermal mismatch and bonding difficulties arise with different materials
Solution Approach 1:
The patent employs a disposable thinning layer that is removed after serving its temporary purpose of enabling initial assembly. This layer facilitates simplified assembly during manufacturing but is subsequently eliminated to resolve thermal mismatch issues between different die materials. The temporary nature of this component allows ease of manufacture without compromising the final thermal compatibility of the stacked structure.
4Length of stationary object
If die thickness is reduced for low-profile packages, then package height is reduced, but die edges become vulnerable to damage
Solution Approach 1:
The patent applies beforehand cushioning by introducing a protective layer that surrounds and supports the thinned die edges. This protective cushioning is applied prior to the stacking and assembly processes, preventing edge damage to the vulnerable thin dies. The cushioning effect maintains the low-profile package height while providing the necessary mechanical support to protect die edges from damage during handling and assembly.
Data Source
AI summary
In various embodiments, a method for forming a bonded structure is disclosed. The method can comprise mounting a first integrated device die to a carrier. After mounting, the first integrated device die can be thinned. The method can include providing a first layer on an exposed surface of the first integrated device die. At least a portion of the first layer can be removed. A second integrated device die can be directly bonded to the first integrated device die without an intervening adhesive.