Nanotwin Copper Electroplating With Reverse Pulses for Void-Free Filling
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Solution Overview
Problem
Conventional electroplating methods struggle to deposit metal uniformly on patterned substrates with non-planar features, leading to defects such as voids and non-uniform thicknesses, especially when using nanotwin copper (NTCu), which is prone to oxidation and requires lower bonding temperatures and pressures.
Innovation Solution
A pulsed current electroplating method with a duty cycle of less than 50% is used to deposit NTCu from the bottom surface of openings, while a reverse current removes excess copper from sidewall surfaces, and a barrier layer is applied to suppress sidewall deposition, followed by annealing to stabilize the NTCu structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroplating is used on patterned substrates with non-planar features, then metal deposition occurs, but non-uniform thickness and voids are created due to varying deposition rates at different points
Solution Approach 1:
The patent applies pulsed electroplating with periodic forward and reverse current cycles. The forward current deposits metal while the reverse current removes excess metal from sidewalls, creating a self-correcting mechanism that maintains uniform deposition thickness across non-planar features and prevents void formation.
Solution Approach 2:
The patent uses reverse current plating to remove metal from sidewall surfaces after forward current deposition. This inverted approach of removing material rather than only adding it corrects the non-uniformity problem by selectively removing excess metal from areas that would otherwise be over-deposited.
2Temperature
If nanotwin copper is deposited to achieve lower bonding temperatures, then bonding efficiency improves, but oxidation resistance becomes a challenge
Solution Approach 1:
The patent performs electroplating in an inert or controlled atmosphere environment to prevent oxidation of the nanotwin copper structure during deposition. This protective environment maintains the low-bonding-temperature advantage of NTCu while preventing harmful oxidation that would otherwise occur.
Solution Approach 2:
The patent controls the electrochemical environment to convert potentially harmful oxidation reactions into beneficial processes, where the controlled electrochemical conditions actually protect the nanotwin structure from unwanted oxidation while enabling precise deposition control.
3Manufacturing precision
If pulsed current with reverse cycles is used to remove sidewall metal, then deposition uniformity improves, but process time increases
Solution Approach 1:
The patent applies partial reverse current cycles that remove only the excess metal from sidewalls rather than completely stripping the deposition. This partial action achieves the necessary uniformity correction without requiring excessive time, optimizing the balance between precision and productivity.
Solution Approach 2:
The patent optimizes pulsed current parameters including duty cycle, pulse duration, and current density to minimize process time while maintaining deposition uniformity. By carefully tuning these parameters, the reverse current removes sufficient sidewall metal for uniformity without unnecessarily extending the plating cycle.
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 ensures high-quality deposition of NTCu with minimal oxidation, allowing for lower bonding temperatures and pressures, reducing defects and improving the stability and bonding efficiency of copper in high-density integrated circuits.
Implementation Method 1
forming a metal material in the at least one opening, where the metal material is formed by two or more cycles that include delivering a forward current from a power supply through the plating bath of the electroplating chamber
Implementation Method 2
delivering a reverse current from the power supply through the plating bath of the electroplating chamber to remove some of the metal plated in the opening on the patterned substrate
Implementation Method 3
annealing the metal material formed in the at least one opening to increase the amount of the metal characterized by the nanotwin crystal structure
Data Source
AI summary
Exemplary methods of electroplating include contacting a patterned substrate with a plating bath in an electroplating chamber, where the pattern substrate includes at least one opening having a bottom surface and one or more sidewall surfaces. The methods may further include forming a nanotwin-containing metal material in the at least one opening. The metal material may be formed by two or more cycles that include delivering a forward current from a power supply through the plating bath of the electroplating chamber for a first period of time, plating a first amount of the metal on the bottom surface of the opening on the patterned substrate and a second amount of the metal on the sidewall surfaces of the opening, and delivering a reverse current from the power supply through the plating bath of the electroplating chamber to remove some of the metal plated in the opening on the patterned substrate.