Laser-Formed Via Hole Structure for Void-Free Substrate Filling
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Solution Overview
Problem
The formation of holes in substrates using lasers often results in defects such as narrowing via holes and protrusion of upper metal layers over lower insulation layers, leading to incomplete metal filling and reduced yield due to differences in thermal conduction and laser absorption between insulation and metal layers.
Innovation Solution
A substrate design with a via hole structure that includes a lower hole, a middle hole, and an upper hole, where the upper hole has a greater width than the lower hole, and the sidewalls of the holes have distinct angles, preventing the narrowing of the via hole and ensuring the upper metal layer does not protrude beyond the lower insulation layer, along with a manufacturing method using specific laser types to form these holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a laser is used to form holes in the substrate, then holes can be formed for electrical connection between layers, but the via hole width narrows upward and the upper metal layer protrudes beyond the lower insulation layer due to differences in thermal conduction and laser absorption
Solution Approach 1:
The via hole is divided into three distinct segments: an upper hole portion, a middle hole portion, and a lower hole portion. Each segment has different width characteristics and sidewall angles to compensate for the narrowing effect caused by laser processing and thermal conduction differences between materials.
Solution Approach 2:
Different portions of the via hole are given different local geometries: the upper hole has a wider width with a first sidewall angle, the middle hole has an intermediate width with a second sidewall angle, and the lower hole has the narrowest width with a third sidewall angle. This local variation in geometry compensates for the material-dependent narrowing effects.
2Productivity
If laser processing is used to form via holes, then electrical connections can be established, but metal layer filling becomes incomplete and yield decreases due to void formation
Solution Approach 1:
The via hole is segmented into three portions with progressively different widths, creating a tapered structure that facilitates complete metal layer filling from bottom to top, preventing void formation and ensuring reliable electrical connections.
Solution Approach 2:
Instead of forming a uniform or narrowing hole shape, the invention inverts the expected geometry by making the upper hole portion wider than the lower portion, counteracting the natural narrowing tendency caused by laser processing and thermal effects.
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 design and method prevent defects in metal layer filling within via holes, ensuring complete filling and reducing void formation by maintaining a consistent width and angle configuration throughout the hole structure, thereby enhancing the substrate's electrical connectivity and yield.
Implementation Method 1
forming a first hole by first removing the conductive layer and the insulation layer by irradiating a first laser; forming a second hole by second removing the insulation layer by irradiating a second laser; and forming a third hole by third removing the conductive layer and the insulation layer by irradiating a third laser
Data Source
AI summary
A substrate including: an insulation layer; a conductive layer disposed on the insulation layer; and a via hole configured to include a lower hole disposed in a first portion of the insulation layer and an upper hole disposed in a second portion of the insulating layer and connected to the lower hole, wherein a width of the upper hole is greater than that of the lower hole, at least a portion of the upper hole of the insulation layer has a width that is substantially equal to that of the upper hole of the conductive layer, and a first angle formed between a first direction that is parallel to a lower surface of the insulating layer and a sidewall of the lower hole and a second angle formed between the first direction and a sidewall of the upper hole are different from each other.