Electroplating Current Recipe Dial-In for Wafer Co-Planarity
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Solution Overview
Problem
The challenge in electroplating semiconductor substrates is achieving uniformity in metal deposition, particularly due to variations in pattern density and current distribution, leading to within-die nonuniformity and co-planarity issues.
Innovation Solution
A machine-learning approach is employed to train a model that generates a recipe for alternating cycles of forward plating and reverse de-plating currents, optimizing the plating process based on substrate and chamber characteristics to improve uniformity and co-planarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroplating is used with standard current application, then the plating process is simple and fast, but within-die nonuniformity and co-planarity issues occur due to pattern density variations
Solution Approach 1:
The patent applies periodic alternating current (AC) plating with forward and reverse current cycles instead of continuous direct current. The forward current deposits metal while the reverse current redistributes it, creating periodic action that achieves uniformity. This periodic reversal of current direction allows the system to overcome pattern density variations by continuously redistributing metal during the plating process.
Solution Approach 2:
The patent changes the electrical parameter from constant DC current to time-varying AC current with specific duty cycles, frequencies, and amplitude ratios. By adjusting these electrical parameters (forward/reverse current ratio, duty cycle, frequency), the system optimizes metal deposition and redistribution to achieve uniform within-die plating without increasing physical system complexity.
2Manufacturing precision
If multiple trial substrates are processed to optimize plating parameters, then manufacturing precision improves, but productivity decreases due to increased time and substrate consumption
Solution Approach 1:
The patent performs preliminary characterization of the substrate pattern density distribution before plating, and uses this information to pre-calculate optimal plating parameters (current amplitude, duty cycle, frequency). This preliminary action allows the system to set optimized parameters before actual plating begins, reducing or eliminating the need for trial substrates and iterative adjustments during production.
Solution Approach 2:
The patent implements a feedback mechanism where metrology data from processed substrates is fed back to adjust and optimize plating parameters for subsequent substrates. This closed-loop feedback allows continuous improvement of co-planarity while minimizing trial substrates, as the system learns from each processed substrate and automatically adjusts parameters for the next batch.
3Manufacturing precision
If uniform current density is applied across the substrate, then the plating process is simple to control, but pattern density variations cause nonuniform metal deposition
Solution Approach 1:
The patent applies local quality by using the measured pattern density distribution to determine spatially-varying plating parameters across different regions of the substrate. Areas with higher pattern density receive different current parameters compared to low-density areas, allowing each region to be plated according to its specific requirements. This local customization of plating parameters achieves uniform deposition thickness despite varying pattern densities.
Solution Approach 2:
The patent transitions from static DC current control to dynamic AC current control where parameters (amplitude, frequency, duty cycle) can be adjusted in real-time during the plating process. This dynamic control allows the system to adapt to pattern density variations across the substrate, applying appropriate current characteristics to different regions to achieve uniform deposition while maintaining manageable system complexity.
4Productivity
If forward plating current is applied continuously, then productivity is high, but within-die nonuniformity increases due to current pooling in densely patterned regions
Solution Approach 1:
The patent uses periodic AC current with alternating forward and reverse cycles instead of continuous forward current. During forward cycles, metal is deposited at high speed maintaining productivity. During reverse cycles, excess metal is redistributed from high-density to low-density regions, correcting uniformity issues. This periodic alternation allows the system to maintain high overall plating speed while achieving uniform deposition through the corrective reverse phases.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that both forward and reverse current cycles contribute to the ultimate goal of uniform deposition. The forward cycle deposits metal (useful for building thickness), while the reverse cycle redistributes metal (useful for achieving uniformity). By optimizing the duty cycle and amplitude ratio, both phases become productive contributions to the final uniform coating, rather than the reverse phase being seen as a non-productive interruption.
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 significantly reduces the number of trial substrates needed, enhances throughput, and improves the uniformity and quality of metal pillars, achieving better co-planarity and reducing waste.
Implementation Method 1
The recipe may cause a current to be applied to the plating liquid in the plating chamber to deposit a metal on exposed portions of the substrate
Implementation Method 2
The portion of the recipe may include characteristics of a forward plating current and characteristics of a reverse de-plating current
Data Source
AI summary
A method of plating substrates may include receiving characteristics of a plating chamber and characteristics of a substrate to be placed in the plating chamber to be provided as inputs to a trained model. An inference operation using the trained model may be performed to generate a recipe for the plating chamber. The recipe may include characteristics of a forward plating current and characteristics of a reverse de-plating current that may be applied in order to add and remove metal to maintain co-planarity and pillar quality. The plating operation may be performed on the substrate using the recipe that was output from the trained model to cause a current to be applied to the plating liquid in the plating chamber to deposit a metal on exposed portions of the substrate, wherein the current comprises alternating cycles of the forward plating current; and the reverse de-plating current.