EMIB Cavity Lithography for Fine-Pitch Bridge Alignment
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Solution Overview
Problem
Existing EMIB technology faces challenges in achieving precise cavity dimensional and location tolerances due to non-uniform organic layer thickness, leading to issues like laser punch through and copper pad delamination, especially as bump pitch scales down to 30 μm or lower.
Innovation Solution
Employing lithographic processes to form sacrificial conductive layers that are etched away, creating cavities with improved dimensional and positional tolerances, using the same chrome mask for conductive features, and integrating this with lithographically defined vias to enhance precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser skiving is used to form cavities in organic substrates, then cavity formation is achieved, but dimensional and location tolerances deteriorate due to non-uniform organic layer thickness
Solution Approach 1:
A lithographically defined sacrificial layer is introduced as an intermediary element. This sacrificial layer is formed with precise thickness and dimensions through lithography, providing a stable reference for cavity formation. The sacrificial layer mediates between the laser processing step and the final cavity, enabling precise cavity dimensions even when the underlying organic substrate has thickness variations. The sacrificial layer is later removed to create the cavity, transferring the precision from the lithographic definition to the final cavity structure.
Solution Approach 2:
The sacrificial layer is formed in advance with precisely controlled dimensions through lithography before the cavity formation step. This preliminary action establishes the exact cavity location and dimensions beforehand, allowing the subsequent laser skiving or etching process to follow a pre-defined path with high precision, regardless of organic substrate thickness variations.
2Reliability
If laser skiving is used to form cavities, then cavity formation is achieved, but copper pad delamination occurs due to thermal impact and punch through
Solution Approach 1:
The lithographically defined sacrificial layer serves as a cushioning layer between the laser and the copper pads. It absorbs and distributes the laser energy, preventing direct laser-pad interaction that causes punch through and delamination. The sacrificial layer is designed with sufficient thickness to stop the laser before it reaches the copper, cushioning against thermal damage while still allowing precise cavity formation through its pre-defined geometry.
Solution Approach 2:
The sacrificial layer acts as an intermediary that decouples the cavity formation process from direct laser-copper interaction. It mediates the energy transfer, allowing cavity formation without transmitting excessive thermal energy to the copper pads, thereby preventing delamination and punch through damage.
3Length of moving object
If bump pitch is scaled down to 30 μm or lower, then finer interconnect bridges are achieved, but cavity tolerance requirements become more stringent
Solution Approach 1:
The patent replaces mechanical alignment methods with lithographic definition for cavity positioning. Instead of relying on mechanical positioning tolerances, the cavity location is defined by lithographic patterns with sub-micron precision. This substitution of mechanical alignment with optical lithography enables precise cavity placement even as bump pitch scales down to 30 μm or lower, meeting the stringent tolerance requirements.
Solution Approach 2:
The sacrificial layer is formed with precise lithographic dimensions before cavity formation, establishing the exact cavity location and size in advance. This preliminary lithographic definition provides the precision needed for fine pitch applications, allowing subsequent cavity formation to achieve the required tolerances without relying on less precise mechanical alignment methods.
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 reduces misalignment errors and thermal impacts, ensuring precise cavity formation with tolerances of +/-3 μm, minimizing copper pad delamination and enabling reliable EMIB connections with fine pitch scaling.
Implementation Method 1
the thickness of organic material layers that a laser needs to skive is not uniform. Variation of organic layer thickness within lot and even within panel is difficult to predict. As such, there is a higher chance of laser punch through (over-drilling) that damages underlying copper pads.
Data Source
AI summary
Embodiments include an electronic package with an embedded multi-interconnect bridge (EMIB) and methods of making such packages. Embodiments include a first layer, that is an organic material and a second layer disposed over the first layer. In an embodiment, a cavity is formed through the second layer to expose a first surface of the first layer. A bridge substrate is in the cavity and is supported by the first surface of the first layer. Embodiments include a first die over the second layer that is electrically coupled to a first contact on the bridge substrate, and a second die over the second layer that is electrically coupled to a second contact on the bridge substrate. In an embodiment the first die is electrically coupled to the second die by the bridge substrate.