Diode-Protected Copper Plating for TSV Defect Control
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Solution Overview
Problem
The copper plating process using an insoluble anode results in reverse electric currents that alter the characteristics of additives, leading to defects such as voids and irregularities in the copper film, particularly in high aspect ratio recesses like TSVs, due to the imbalance between suppressor and accelerator in the plating solution.
Innovation Solution
A plating method that involves using a copper sulfate plating solution with additives, applying a predetermined voltage, and employing a diode or resistor to prevent reverse electric currents, or controlling the additive concentration and applying a forward voltage to minimize reverse electric currents, thereby maintaining the balance between suppressor and accelerator and ensuring bottom-up plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insoluble anode is used for copper plating, then the anode surface remains clean without black film deposition, but reverse electric current flows causing additive reduction and plating defects
Solution Approach 1:
The patent extracts the harmful reverse electric current from the system by introducing a diode that blocks current flow in the reverse direction. This allows the insoluble anode to maintain its cleaning advantage while preventing the reverse current from reaching the substrate and causing additive reduction and plating defects.
Solution Approach 2:
The diode acts as an intermediary component between the power source and the plating circuit. It selectively allows forward current to pass while blocking reverse current, thereby mediating the electrical flow to prevent harmful effects on the plating process while maintaining the benefits of using an insoluble anode.
2Manufacturing precision
If a soluble anode is used for copper plating, then reverse electric current is minimized, but black film deposits on the anode surface causing plating defects
Solution Approach 1:
The patent removes the harmful reverse electric current from the system using a diode, which eliminates the need to use soluble anodes solely for preventing reverse current. This allows the use of insoluble anodes while maintaining copper film quality through directional current control.
3Manufacturing precision
If additives are used to achieve bottom-up plating in high aspect ratio recesses, then metal deposition is controlled, but reverse electric current reduces the additives causing loss of control and plating defects
Solution Approach 1:
The diode extracts and blocks the reverse electric current that would otherwise flow back through the plating solution and reduce the additives. This preservation of additive concentration maintains the controlled bottom-up plating process in high aspect ratio recesses without the harmful effects of additive depletion.
Solution Approach 2:
The diode provides a form of feedback control by continuously blocking reverse current flow, thereby preventing the reduction of additives and maintaining the chemical balance necessary for controlled bottom-up plating in complex substrate geometries.
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 prevents the generation of electrolyte components that inhibit bottom-up plating, resulting in a more uniform and defect-free copper film deposition by controlling reverse electric currents and maintaining the additive balance.
Implementation Method 1
shutting off a reverse electric current, which flows from the insoluble anode to the substrate via the plating power source, by a diode disposed between the insoluble anode and the substrate
Implementation Method 2
copper ions are reduced on the substrate W and a copper film is formed on the substrate W
Implementation Method 3
electrolysis of water occurs on the anode 101
Implementation Method 4
an additive, including a suppressor for suppressing the deposition of the metal, is used to prevent the deposition of the metal in an area around an opening of the recess 110
Data Source
AI summary
A method of plating a substrate, such as a wafer, by applying a voltage between the substrate and an anode is disclosed. The plating method includes: preparing a substrate having a recess formed in a surface thereof, a conductive layer being formed in at least a part of the recess; placing an insoluble anode and the substrate in contact with a copper sulfate plating solution containing an additive; applying a predetermined plating voltage between the substrate and the insoluble anode by a plating power source to plate the substrate; and shutting off a reverse electric current, which flows from the insoluble anode to the substrate via the plating power source, by a diode disposed between the insoluble anode and the substrate when the predetermined plating voltage is not applied.