Glass Via Etching Sequence for Higher Density and Less Undercut
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Solution Overview
Problem
Conventional single-sided wet etching processes for forming vias in glass substrates result in excessively tapered holes, limited via density, and significant undercutting, which complicates the formation of precise and uniform through-holes for electronic and photonic packaging applications.
Innovation Solution
A method involving a single-sided acidic wet etching process followed by a double-sided acidic wet etching process, using hydrogen fluoride etching compositions, to control the formation of vias, reducing undercutting and achieving a conical frustum shape with a waist within a specific thickness range, thereby improving via density and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-sided wet etching process is used to form vias in glass substrates, then the process is simple and fast, but the vias become excessively tapered with large top openings and significant undercutting
Solution Approach 1:
The etching process is divided into two separate stages: a first etching process that creates an initial opening through the damage track, and a second etching process that enlarges the opening to the final diameter. This segmentation allows each process to be optimized independently - the first process creates a controlled initial opening while the second process achieves the final via shape with minimal tapering and undercutting.
Solution Approach 2:
A damage track is created in the glass substrate before etching using laser irradiation or ion beam treatment. This preliminary action creates a localized region of modified glass structure that guides the etching process and enables precise via formation. The damage track serves as a pre-formed pathway that controls where the via will form and limits lateral etching.
2Device complexity
If a single-sided wet etching process is used, then the process complexity is low, but via density is limited due to large opening sizes
Solution Approach 1:
The two-stage etching process enables better control over via opening sizes. By separating the initial opening creation from the final enlargement step, the process can achieve smaller, more precise via openings that increase via density while maintaining manageable process complexity through systematic control of each stage.
Solution Approach 2:
The damage track created before etching serves as a precise template that limits lateral etching and controls via positioning. This preliminary structuring enables higher via density by ensuring that etching occurs only along the predetermined damage track pathway, preventing unwanted lateral expansion that would reduce via density.
3Loss of time
If a single-sided wet etching process is used, then manufacturing time is reduced, but undercutting increases which complicates subsequent metallization
Solution Approach 1:
By dividing the etching into two controlled stages, the process minimizes undercutting in both stages compared to a single long etch. The first stage creates a controlled initial opening with limited undercutting, and the second stage completes the via with precise shape control. This reduces the need for additional undercutting removal steps, maintaining efficiency while improving metallization readiness.
Solution Approach 2:
The damage track created beforehand serves as a confinement structure that directs etching vertically through the glass rather than allowing lateral undercutting. This preliminary structural modification ensures that subsequent etching follows the damage track pathway, producing vias with minimal undercutting that are ready for direct metallization without additional cleaning or preparation steps.
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
The method enhances control over via shape and size, reduces undercutting, and increases via density by making the top opening diameter less dependent on substrate thickness, facilitating easier metallization and reducing manufacturing time and costs.
Implementation Method 1
applying a single-sided acidic wet etching process to a first surface of the inorganic substrate
Implementation Method 2
The single-sided acidic wet etching process may enlarge at least a maximum width of the first end of the damage track to form a first opening
Data Source
AI summary
A method of facilitating formation of a via in an inorganic substrate may include applying a single-sided acidic wet etching process to a first surface of the inorganic substrate in a first state in which the inorganic substrate has a mask layer set covering a second surface of the inorganic substrate; and applying a double-sided acidic wet etching process to the first surface and the second surface of the inorganic substrate after completion of the single-sided acidic wet etching process and in a second state in which the inorganic substrate has had the mask layer set removed from the second surface of the inorganic substrate.