Transparent Transfer Substrate Die Bonding Without Mechanical Handling
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Solution Overview
Problem
Conventional die-to-wafer bonding processes face challenges in achieving high throughput and precise placement accuracy below 5 μm interconnect pitch due to mechanical handling of individual dies, which is time-consuming and prone to air entrapment/voiding, especially when transitioning from solder-based to hybrid or dielectric bonding techniques.
Innovation Solution
A method involving a light-releasable temporary bonding layer on a rigid transparent transfer substrate allows for the alignment and release of dies onto a carrier substrate without mechanical handling, using laser or other light sources to detach dies from the transfer substrate, enabling precise alignment and contact without deformation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional mechanical handling process is used for die-to-wafer bonding, then individual dies can be transferred to carrier substrate, but the process is time-consuming and results in low throughput
Solution Approach 1:
Multiple dies are attached simultaneously to a single transfer substrate, and multiple dies are released simultaneously onto the carrier substrate through a single illumination step. This merges multiple individual handling operations into one collective operation, dramatically increasing throughput while eliminating the time-consuming sequential mechanical handling of each die.
Solution Approach 2:
The patent replaces the mechanical handling system (pick-and-place machines, clamps, and manual manipulation) with an optical system. A light-releasable bonding layer is used to attach dies to the transfer substrate, and illumination with light of a specific wavelength releases the dies simultaneously. This substitution eliminates the time-consuming mechanical operations while maintaining precise control over the release process.
2Manufacturing precision
If conventional mechanical handling is used for die transfer, then dies can be positioned on carrier substrate, but placement precision below 5 μm is difficult to achieve
Solution Approach 1:
The patent replaces mechanical positioning and alignment systems with an optical release mechanism. The light-releasable bonding layer ensures that dies are released at precisely controlled locations corresponding to the carrier substrate's bonding sites. This optical control mechanism achieves sub-5 μm placement accuracy without the complexity of high-precision mechanical alignment systems.
Solution Approach 2:
The transfer substrate acts as an intermediary carrier that maintains precise spatial relationships between multiple dies and their corresponding bonding sites on the carrier substrate. The light-releasable bonding layer serves as a mediator that enables controlled release at the exact intended positions, achieving high placement precision without complex mechanical positioning.
3Reliability
If mechanical handling of individual dies is performed, then dies can be transferred to carrier substrate, but air entrapment and voiding occur at bond interface
Solution Approach 1:
The patent replaces mechanical die transfer with an optical release mechanism. The dies remain attached to the transfer substrate during alignment, and are released simultaneously onto the carrier substrate through illumination. This eliminates the mechanical manipulation that causes air entrapment and voiding, resulting in superior bonding quality with no air pockets at the bond interface.
Solution Approach 2:
The bonding surfaces are prepared and aligned while the dies are still securely attached to the transfer substrate. The light-releasable bonding layer maintains die position stability during the entire alignment process, preventing premature movement that could trap air. Only after perfect alignment is achieved are the dies released simultaneously, ensuring void-free bonding.
4Productivity
If light-releasable bonding layer is used for die attachment, then simultaneous release of multiple dies is achieved, but additional layer complexity is introduced
Solution Approach 1:
The light-releasable bonding layer utilizes changes in the optical properties of materials. The bonding layer is designed to be transparent or translucent to a specific wavelength of light, allowing the light to pass through and trigger the release mechanism. This parameter-based control (optical transparency at specific wavelength) enables simultaneous release of multiple dies without adding significant structural complexity.
Solution Approach 2:
The light-releasable bonding layer serves as an intermediary material that provides both attachment and release functions. It bonds the dies to the transfer substrate during alignment and then releases them simultaneously upon illumination. This single intermediary layer performs multiple functions without requiring complex multi-layer structures.
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 method enhances throughput and precision by eliminating mechanical handling, reducing the risk of die deformation and air entrapment, and facilitates high-accuracy bonding at sub-5 μm pitches, suitable for hybrid and dielectric bonding techniques.
Implementation Method 1
a light-releasable temporary bonding layer on a rigid transparent transfer substrate allows for the alignment and release of dies onto a carrier substrate without mechanical handling, using laser or other light sources to detach dies from the transfer substrate
Data Source
AI summary
The present disclosure provides that a plurality of dies are temporarily attached to a rigid transfer substrate through a light-releasable temporary bonding layer. The transfer substrate is a rigid substrate that is transparent for the type of light that is capable of releasing the dies, i.e. the type of light that is capable of removing or releasing the light-releasable layer. This may be laser light or other visible or invisible light such as UV, IR or LED light. The assembly comprising the transfer substrate and the dies is positioned relative to a carrier substrate with the dies facing respective interface areas on a surface of the carrier substrate. By illuminating a die through the back side of the transfer substrate, the die is released and transferred to the carrier substrate. The method is suitable for bonding dies to a carrier without any mechanical handling of individual dies.