Through Hole Filling via Etch-and-Deposit Process
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Solution Overview
Problem
In the electrodeposition of conductive materials in through holes of substrates, high aspect ratio through holes often result in uneven current density, leading to void formation due to faster metal deposition at the ends compared to the center, necessitating low current density and prolonged processing times for void-free filling.
Innovation Solution
An etch-and-deposit process is employed, where a conductive material is initially deposited and then differentially etched to create a funnel-shaped deposit, followed by repeated plating and etching to form a butterfly-shaped seal, allowing for higher current density and faster filling without voids by selectively removing material at the rims relative to the mid-section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional electroplating is used to fill through holes with high aspect ratio, then metal deposition occurs at the ends faster than at the center, but this leads to void formation at the center of the through hole
Solution Approach 1:
The patent applies local quality by making different parts of the through hole have different deposition characteristics. The ends of the through hole receive higher current density and faster deposition rate, while the center receives lower current density and slower deposition rate. This is achieved through electrode geometry design and process control, ensuring that metal is deposited preferentially at the ends first, then progressively fills the center without forming voids.
2Manufacturing precision
If low current density is used to prevent void formation, then uniform metal distribution is achieved, but the processing time becomes relatively long
Solution Approach 1:
The patent employs periodic action through pulse electroplating technology. The plating process uses periodic pulse current with alternating on and off cycles, during which the current density is dynamically adjusted. During the on-phase, high current density promotes rapid deposition; during the off-phase, the system allows for uniformity control. This periodic modulation enables both fast deposition and void-free filling by preventing continuous uniform deposition that would block the center.
3Productivity
If high current density is used to reduce processing time, then deposition speed increases, but this prevents proper formation of the sealing structure and may cause voids
Solution Approach 1:
The patent applies dynamics by making the current density variable rather than static. The electrodeposition process uses dynamically adjusted current density that changes during the plating cycle and throughout the through hole depth. The system transitions from high current density at the beginning and at the ends to lower current density at the center, and this dynamic control is achieved through pulse plating and electrode geometry, ensuring both speed and sealing quality.
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 method enables faster formation of a butterfly-shaped deposit and subsequent void-free filling of through holes, reducing processing time and increasing efficiency in filling high aspect ratio through holes with conductive materials.
Implementation Method 1
a CM is deposited over said substrate to thereby deposit a layer of the CM around the rims and on the interior surface of said channel
Implementation Method 2
the etching step selectively removes more CM deposited at the rims relative to CM deposited at a mid-section of the interior surface of said channel
Data Source
AI summary
A method for filling a through hole (TH) located on a substrate is provided. The TH is a continuous channel having an upper rim, a lower rim and an interior surface. In one embodiment, the method comprises steps (a)-(d). In the step (a), a conductive material (CM) is deposited over the substrate to thereby deposit a layer of the CM around the rims and on the interior surface. In the step (b), the deposited CM is etched. In particular, the etching step selectively removes more CM deposited at the rims relative to CM deposited at a mid-section of the interior surface of the channel. In the step (c), the steps (a) and (b) are optionally repeated until the channel is sealed at the mid-section by a bridge formed of CM. In the step (d), the CM is further deposited over the substrate to thereby completely fill the TH.