Stepped Via Holes in Multilayer Electronic Structures
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Solution Overview
Problem
Current interconnect structures, particularly those using the 'drill & fill' method, face limitations in achieving high-density, high-reliability vias with varying sizes and shapes due to rough sidewalls, tapering, and difficulties in uniform copper filling, which restricts miniaturization and increases costs.
Innovation Solution
The development of multilayer electronic structures with stepped holes fabricated using a sacrificial stack of metal layers and dielectric material, where the sacrificial stack is etched away to create holes with varying dimensions and shapes, allowing for precise alignment and filling of copper via posts in a dielectric matrix, enabling the creation of complex geometries and high-density interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser drilling is used to create via holes, then via holes can be created through dielectric material, but the side walls become rough and tapered, reducing effective diameter and electrical contact quality
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure with the desired via geometry before creating the final via hole. The mandrel is formed with smooth, non-tapered walls and precise dimensions, and then used as a template to define the via hole geometry through subsequent processing steps, eliminating the need for direct laser drilling of the via walls.
Solution Approach 2:
The patent introduces a mandrel as an intermediary structure that mediates between the desired via geometry and the final via hole. The mandrel serves as a temporary structure that defines the via shape and is later removed, leaving a via hole with the precise geometry defined by the mandrel rather than by direct drilling.
2Ease of manufacture
If electroplating is used to fill via holes, then copper can be deposited, but dimpling or overfill occurs, creating difficulties for subsequent via stacking
Solution Approach 1:
The patent applies preliminary action by forming a mandrel with the exact desired via geometry and dimensions before filling. The mandrel is precisely controlled to ensure uniform wall thickness and proper via dimensions, which allows subsequent filling processes to achieve uniform results without dimpling or overfill, as the mandrel provides a precise template for the final via structure.
3Reliability
If drill & fill technology is used, then via holes can be created and filled, but the throughput rate is limited and fabrication costs become prohibitive for high-density substrates
Solution Approach 1:
The patent merges multiple via formation steps into a unified process. Instead of individually drilling and filling each via, the method forms mandrels for multiple vias simultaneously, then performs unified filling operations. This consolidation of steps significantly increases throughput while maintaining via quality, as the same process equipment and parameters can be used across multiple via locations.
Solution Approach 2:
The patent applies universality by creating a mandrel structure that serves multiple functions: it defines the via geometry, provides alignment references for subsequent layers, and acts as a template for uniform filling. This multi-functional approach eliminates the need for separate precision operations for each function, improving overall process efficiency and throughput.
4Adaptability or versatility
If different sized via channels are drilled and filled, then various via sizes can be created, but they fill at different rates causing exacerbated dimpling or overfill issues
Solution Approach 1:
The patent applies preliminary action by forming mandrels with precisely controlled dimensions for each via size requirement before filling. Each mandrel is formed with the exact diameter and geometry needed for its specific via, allowing subsequent filling to proceed uniformly across all via sizes. The mandrels ensure that even small vias have sufficient wall thickness and proper geometry, eliminating the fill rate problems that occur when trying to fill vias of vastly different sizes simultaneously.
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 the fabrication of high-density, reliable interconnects with precise control over via dimensions and shapes, overcoming the limitations of traditional drill & fill methods by allowing for a wide range of via sizes and shapes, improving electrical performance, and reducing manufacturing costs.
Implementation Method 1
the sacrificial stack is etched away to create holes with varying dimensions and shapes
Implementation Method 2
the vias created thereby may be referred to as 'drilled & filled vias'... subsequent filling with a metal, usually copper, that is deposited therein by a plating technique
Data Source
AI summary
A multilayer electronic structure comprising a plurality of layers extending in an X-Y plane consisting of a dielectric material surrounding metal via posts that conduct in a Z direction perpendicular to the X-Y plane, wherein at least one multilayered hole crosses at least two layers of the plurality of layers and comprises at least two hole layers in adjacent layers of the multilayer composite electronic structure, wherein the at least two holes in adjacent layers have different dimensions in the X-Y plane, such that a perimeter of the multilayered hole is stepped and where at least one hole is an aperture to a surface of the multilayer electronic structure.