Corrosion-Susceptible Bonding Layer for Low-Force Wafer Debonding
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Solution Overview
Problem
The wafer debonding process in semiconductor fabrication is challenging due to thermal stress, warping, cracking, and strong bonding interfaces, which can lead to breakage and micro-cracks, especially in thin wafers, impacting manufacturing yield and device performance.
Innovation Solution
Introduce a corrosion-susceptible metal or dielectric layer in the bonding structure, which is corroded during debonding using corrosive gases or electrical breakdown, facilitating separation by forming corrosion regions or dielectric breakdown to weaken the bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If strong bonding interface is used to ensure reliable wafer bonding, then bonding strength is improved, but debonding difficulty increases
Solution Approach 1:
The bonding interface is segmented into multiple layers: a strong bonding layer for reliable bonding and a separate corrosion-susceptible layer for easy debonding. This segmentation allows each layer to perform its specific function - the bonding layer provides strong adhesion while the corrosion layer enables controlled separation without damaging the wafers.
Solution Approach 2:
A corrosion-susceptible intermediate layer is introduced between the bonding interface and the wafer surfaces. This intermediary layer acts as a sacrificial element that can be selectively removed through corrosion, facilitating debonding while protecting the underlying wafer structures from damage.
2Ease of operation
If mechanical force is applied to separate bonded wafers, then debonding is achieved, but wafer damage occurs
Solution Approach 1:
The mechanical debonding process is replaced with a chemical corrosion process. Instead of applying mechanical force that could damage thin wafers, a corrosive environment is used to selectively remove the corrosion-susceptible layer, enabling separation through chemical rather than mechanical means and thus preserving wafer integrity.
Solution Approach 2:
The corrosion-susceptible layer serves as an intermediary that absorbs the separation process. By targeting this intermediate layer for corrosion, the separation force is distributed and controlled, preventing direct mechanical stress on the fragile wafer structures.
3Force
If thermal stress is used during debonding, then separation force is reduced, but warping and cracking occur
Solution Approach 1:
Thermal stress-based debonding is replaced with chemical corrosion-based debonding. While thermal stress can reduce separation force, it causes warping and cracking due to differential expansion. The chemical corrosion approach achieves low-force separation without thermal cycling, thus avoiding deformation issues.
Solution Approach 2:
The debonding mechanism is changed from thermal-parameter-based to chemical-parameter-based. By controlling chemical corrosion parameters (corrosive gas composition, temperature, exposure time) rather than thermal parameters, separation is achieved with minimal mechanical stress and no thermal-induced deformation.
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 easier and more reliable wafer debonding with reduced force requirements, improving manufacturing yield and device reliability by minimizing damage to the wafers.
Implementation Method 1
a corrosion-susceptible metal layer is buried below a thin metal bonding layer that is disposed on either one of a carrier wafer or a product wafer. During the debonding process, an edge region of the bonded wafers can be exposed to corrosive gases to trigger the buried metal layer chemical reaction.
Implementation Method 2
a voltage can be applied on the buried dielectric layer, at the bonded wafer edge and through the one or more vias, to cause dielectric break down in the dielectric layer. The dielectric layer break down weakens a strengthen of the buried dielectric layer and facilitates a following wafer debonding process.
Data Source
AI summary
A bonded semiconductor structure including a product wafer having a first metal layer disposed on a first frontside surface of the product wafer, and a carrier wafer having a second metal layer disposed on a second frontside surface of the carrier wafer and a third metal layer disposed under the second metal layer, wherein the first metal layer is bonded to the second metal layer by metal-metal bonds disposed at a bonding interface between the first frontside surface and the second frontside surface, and wherein the third metal layer includes a corrosion portion extending from an edge of the carrier wafer to a center of the carrier wafer.