TSV Copper Electrofill Waveform for Void-Free Bottom-Up Filling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge of void-free deposition of copper in through silicon vias (TSVs) with high aspect ratios is significant due to the limitations of conventional electroplating methods, which often result in seam or pocket voids, especially in substrates with high open areas.
Innovation Solution
A current waveform is employed that includes an initial pulse of high current followed by a reduction to a baseline current, with optional additional steps, to facilitate void-free filling of TSVs by promoting a bottom-up fill mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electroplating is used to fill TSVs, then the process is simple and cost-effective, but voids form in the filled TSVs reducing reliability
Solution Approach 1:
The patent applies periodic pulsed current instead of continuous current to control copper deposition in TSVs. The pulse waveform includes on-time (depositing copper) and off-time (allowing diffusion and uniformity), repeating cycles that promote bottom-up fill and prevent void formation while maintaining process simplicity
Solution Approach 2:
The patent uses dynamic current waveform parameters (variable pulse width, duty cycle, and amplitude) that adapt during the electroplating process. The current magnitude and timing are dynamically adjusted to control deposition rate and promote uniform copper fill without voids, transitioning from simple to more sophisticated control as needed
2Productivity
If high current is applied to increase fill rate, then productivity improves, but void formation increases reducing reliability
Solution Approach 1:
The pulsed current waveform provides high current during the on-time portion to maintain fast fill rates, then reduces current to zero during off-time to allow copper diffusion and prevent void formation. This periodic high-low cycling achieves both high productivity and reliability
Solution Approach 2:
The patent changes current parameters dynamically - using high current magnitude during pulse on-time for fast deposition, then reducing to zero or low magnitude during off-time. This parameter modulation allows the system to achieve high fill rates while preventing void formation through controlled deposition cycles
3Reliability
If long pulse duration is used to ensure complete fill, then reliability improves, but energy consumption increases
Solution Approach 1:
The pulsed waveform uses periodic on-off cycling where copper deposits during on-time and diffuses uniformly during off-time. This periodic action achieves complete reliable fill more efficiently than continuous current by allowing passive diffusion during off-periods, reducing total energy consumption
Solution Approach 2:
During the off-time of the pulse waveform, copper ions naturally diffuse into the TSV structures without applied current, and the previously deposited copper redistributes uniformly. This self-service diffusion process during off-periods achieves complete fill with less energy input than continuous plating
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 effectively reduces void formation and enhances fill rate and uniformity in substrates with high open areas, ensuring complete and uniform deposition of copper in TSVs.
Implementation Method 1
electroplating is a more common method of depositing copper into TSV structures
Implementation Method 2
contacting a substrate with an electroplating solution having metal ions
Data Source
AI summary
A method of electroplating metal into features of a partially fabricated electronic device on a substrate having high open area portions is provided. The method includes initiating a bulk electrofill phase with a pulse at a high level of current; reducing the current to a baseline current level; and optionally increasing the current in one or more steps until electroplating is complete.