Laser-Modified Through-Hole Formation in Glass Interposers
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Solution Overview
Problem
Existing methods for forming substrates with through-holes, such as etching and laser-based techniques, often result in rugged inner walls, debris deposition, and poor electrical connectivity due to incomplete seed film formation and debris issues, hindering the formation of high-quality through-electrodes for interposer applications.
Innovation Solution
A method involving the application of a laser beam with a wavelength transmitted through the substrate to create column-shaped modified regions, followed by etching to form recesses or through-holes, and subsequent filling with conductive material to form high-quality electrodes, avoiding debris generation and ensuring uniform electrode formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If through-holes are formed by alternately repeating etching and protective film formation, then through-holes can be formed in the substrate, but the inner walls of the through-holes become rugged and it becomes impossible to uniformly form the seed film on the inner walls
Solution Approach 1:
The patent applies a preliminary action by forming a protective film on the inner walls of through-holes before etching deepens the holes. This protective film is formed in advance to prevent the substrate material from protruding onto the inner walls during subsequent etching steps, thereby maintaining smooth inner walls that enable uniform seed film formation.
2Productivity
If through-holes are formed by applying laser beam to the substrate, then through-holes can be formed quickly, but debris deposits on the substrate surface around the through-holes and is difficult to remove
Solution Approach 1:
The patent converts the harmful laser-induced debris generation into a beneficial process by using the laser to modify the substrate structure in a controlled manner. The laser treatment creates a modified region that facilitates clean etching without generating debris that would deposit on the substrate surface, thus maintaining both high productivity and surface cleanliness.
3Reliability
If silicon substrate is used as interposer with through electrodes, then chips can be interconnected, but the production cost is high and transmission loss of electrical signals is large
Solution Approach 1:
The patent replaces expensive silicon substrates with glass substrates as interposers. Glass substrates are significantly cheaper and can be produced in large sizes, thereby reducing production costs while maintaining the through-electrode interconnection functionality between chips.
4Ease of manufacture
If glass substrate is used as interposer instead of silicon substrate, then production cost is reduced and large-sized substrates can be produced, but through-holes must be formed without generating debris that affects electrical interconnection
Solution Approach 1:
The patent replaces mechanical drilling or traditional etching methods with a laser-based modified region formation followed by controlled etching. This substitution enables clean through-hole formation in glass substrates without generating debris that would compromise electrical interconnection, while maintaining the advantages of low cost and large substrate size.
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 formation of substrates with high-quality through-electrodes that facilitate effective electrical interconnection between chips, reducing transmission losses and production costs by using glass substrates, which are less expensive and easier to scale than silicon substrates.
Implementation Method 1
applying a laser beam of such a wavelength as to be transmitted through the substrate to the substrate, with a focal region of the laser beam positioned inside the substrate, to form a column-shaped modified region
Implementation Method 2
an etching step of etching the modified region to form the recess or the through-hole in the substrate
Data Source
AI summary
A recess or through-hole forming method for forming a substrate with a recess or a through-hole along a thickness direction of the substrate, the method including: a modified region forming step of applying a laser beam of such a wavelength as to be transmitted through the substrate to the substrate, with a focal region of the laser beam positioned inside the substrate, to form a column-shaped modified region which is exposed to a surface of the substrate and extends along the thickness direction of the substrate; and an etching step of etching the modified region to form the substrate with the recess or the through-hole, after the modified region forming step is performed.