Bidirectional Substrate Rotation for Plating Uniformity
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Solution Overview
Problem
The cup-type electroplating apparatus experiences issues with the uniformity of the plating film thickness due to the solution current generated by substrate rotation and the field shielding effect caused by the paddle's reciprocating motion, especially when the frequencies align, leading to increased field shielding and reduced uniformity.
Innovation Solution
The apparatus is configured with a rotation mechanism that rotates the substrate in both forward and reverse directions, with a control device that ensures the time periods or time-integrated rotation speeds in both directions are equal, thereby canceling out the inclination of the plating film surface caused by the solution current and reducing the field shielding effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the substrate is rotated to form a solution current, then the supply of ion to the substrate is enhanced, but the conductive film becomes inclined and uniformity in thickness is reduced
Solution Approach 1:
The substrate rotation is performed periodically in forward and reverse directions with equal time periods or equal time-integrated rotation speeds. This periodic bidirectional rotation creates alternating solution currents that prevent the formation of a consistent downstream direction, thereby maintaining ion supply while preventing film inclination and ensuring uniform thickness distribution across the substrate surface.
2Quantity of substance
If the paddle reciprocates to enhance solution current, then ion supply is improved, but field shielding effect increases and uniformity in thickness is reduced
Solution Approach 1:
The paddle performs reciprocating motion with periodic forward and backward movements. By controlling the motion frequency and amplitude periodically, the system enhances solution current and ion supply to the substrate while preventing consistent field shielding at specific locations, thereby maintaining uniform plating film thickness.
3Stability of the object's composition
If the rotation speed of substrate and frequency of paddle are synchronized, then the plating process is stable, but field shielding effect is significantly increased
Solution Approach 1:
The system intentionally creates asymmetry in the timing and frequency relationships between substrate rotation and paddle reciprocation. By avoiding synchronized frequencies and using non-integral multiple relationships, the paddle beam does not consistently stop at identical substrate locations, thereby reducing field shielding effect while maintaining overall process stability through controlled periodic motion.
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 configuration enhances the uniformity of the plating film thickness by canceling out the inclination caused by the solution current and reducing the field shielding effect, resulting in a more uniform plating process.
Implementation Method 1
rotating the substrate holder and the substrate forms a solution current in the vicinity of the surface of the substrate
Implementation Method 2
a phenomenon that the conductive film is inclined in a direction of the solution current is likely to occur
Implementation Method 3
a voltage is applied between the substrate and an anode, so that a conductive film (plating film) deposits on the surface of the substrate
Data Source
AI summary
An object is to reduce the field shielding effect of a paddle during plating. There is provided an apparatus for plating that is configured to plate a substrate and comprises a plating tank; an anode placed in the plating tank; a rotation mechanism configured to rotate the substrate in a first direction and in a second direction that is opposite to the first direction; and a control device configured to control the rotation mechanism, such that a time period when the substrate is rotated in the first direction becomes equal to a time period when the substrate is rotated in the second direction or such that a time integrated value of a rotation speed in the first direction becomes equal to a time integrated value of a rotation speed in the second direction.