Via Structure with Etch Stop Pattern for Fine-Pitch Circuit Boards
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Solution Overview
Problem
Conventional via formation techniques struggle with achieving fine-pitch via structures on circuit boards due to inclined side surfaces and difficulties in forming precise via holes, especially when the thickness of the resist layer exceeds 2 μm, limiting the integration of via structures within thick interlayer insulating layers.
Innovation Solution
A circuit board design featuring a vertically perpendicular via structure within a thick interlayer insulating layer, utilizing an etch stop pattern made of insulating material with a lower etch rate than the interlayer insulating layer, and a method involving reactive ion etching and plating processes to form via structures with integral via bodies and pads, allowing for reduced via spacing and improved manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional via formation techniques are used, then via structures can be formed in thin resist layers, but the interval between vias cannot be reduced and precise via holes cannot be formed in thick resist layers
Solution Approach 1:
The patent divides the via formation process into multiple etching stages with intermediate steps. The etch stop pattern is formed at an intermediate depth, allowing the thick resist layer to be processed in segments rather than as a single continuous etch, thereby maintaining precision throughout the full thickness
Solution Approach 2:
The etch stop pattern is formed preliminarily within the thick resist layer before completing the via hole formation. This preliminary structure provides a reference plane and etch stop point that enables subsequent precise etching operations to achieve the required via hole accuracy
2Object-affected harmful factors
If conventional via formation techniques are used, then via structures can be formed, but they have inclined side surfaces that prevent fine pitch implementation
Solution Approach 1:
The etch stop pattern is formed preliminarily to counteract the tendency toward inclined side surfaces during etching. By providing a hard stop at a specific depth, the pattern prevents further lateral erosion that would create inclination, ensuring vertically perpendicular sides in the final via structure
Solution Approach 2:
The etch stop pattern acts as an intermediary layer between the resist and the substrate during etching. It mediates the etching process by providing a controlled stop point that maintains vertical sidewalls, enabling fine pitch via structures with perpendicular sides
3Manufacturing precision
If photolithography resolution limits are exceeded, then via structures cannot be formed in thick resist layers, but manufacturing efficiency is reduced
Solution Approach 1:
The via formation process is segmented into multiple etching steps with an intermediate etch stop pattern formation. This segmentation allows each step to operate within photolithography resolution capabilities while collectively achieving via holes through thick resist layers that would otherwise be impossible
Solution Approach 2:
The etch stop pattern is formed preliminarily to establish a controlled etching boundary. This preliminary structure enables subsequent etching steps to proceed with precise control, maintaining manufacturing precision even as total via depth increases beyond simple photolithography limits
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 the formation of fine-pitch via structures with vertically perpendicular side surfaces even in thick interlayer insulating layers, reducing via spacing to less than 30 μm and improving bonding reliability and manufacturing efficiency by integrating via bodies and pads through a single plating process.
Implementation Method 1
an etch stop pattern disposed on the interlayer insulating layer in the horizontal direction perpendicular to the vertical direction to surround the via structure... The etch stop pattern may have a lower etch rate than the interlayer insulating layer
Implementation Method 2
a method involving reactive ion etching and plating processes to form via structures
Implementation Method 3
the via body and the via pad may be integrally formed by a single plating process
Data Source
AI summary
The present invention relates to a circuit board. A circuit board in accordance with an embodiment of the present invention includes a base substrate; an interlayer insulating layer covering the base substrate; a via structure passing through at least the interlayer insulating layer of the base substrate and the interlayer insulating layer in the vertical direction; and an etch stop pattern disposed on the interlayer insulating layer in the horizontal direction to surround the via structure and made of an insulating material.