Spatially Tailored Resistive Element for Electroplating Uniformity
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Solution Overview
Problem
Semiconductor wafer electroplating faces challenges with radial and azimuthal non-uniformity of metal thickness due to terminal effects and variations in photoresist thickness, leading to non-functional chips.
Innovation Solution
An ionically resistive, ionically permeable element with spatially tailored resistivity is positioned near the substrate during electroplating, featuring varying thickness and porosity to mitigate non-uniformity by adjusting local resistivity, thereby controlling the flow of ionic current and improving plating uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electroplating is performed on a semiconductor substrate with patterned photoresist, then metal can be deposited on exposed seed layer regions, but radial and azimuthal non-uniformity of metal thickness occurs due to terminal effects and photoresist thickness variations
Solution Approach 1:
The patent applies local quality by varying the resistivity of the ionically permeable element in different spatial regions. The element has higher resistivity in regions corresponding to thicker photoresist or edge areas, and lower resistivity in other regions, thereby locally compensating for non-uniform current distribution and achieving uniform metal thickness across the substrate
Solution Approach 2:
The ionically permeable element acts as an intermediary component positioned between the electrolyte and the substrate. It modulates the ionic current flow to the substrate surface, compensating for terminal effects and photoresist thickness variations by its spatially varying resistivity, thus achieving uniform plating without modifying the electroplating process itself
2Manufacturing precision
If the ionically permeable element has uniform resistivity, then the structure is simpler, but it cannot compensate for spatial variations in current density across the substrate
Solution Approach 1:
The ionically permeable element is designed with spatially varying resistivity, where different regions have different resistivity values tailored to compensate for local current density variations. This is achieved by varying the porosity or thickness of the element in different regions, creating a complex internal structure that enables precise control of current distribution
Solution Approach 2:
The patent changes the resistivity parameter of the ionically permeable element in a spatially dependent manner. By varying porosity or thickness across the element, the resistivity is adjusted to compensate for terminal effects and photoresist variations, achieving uniform plating through parameter optimization
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
The solution achieves improved uniformity of metal deposition, reducing radial and azimuthal non-uniformity to within 5% or less, ensuring consistent chip quality by compensating for terminal effects and photoresist thickness variations.
Implementation Method 1
the element allows for flow of ionic current through the element towards the substrate during electroplating
Implementation Method 2
an ionically resistive ionically permeable element having spatially tailored resistivity that is positioned in proximity of the substrate during electroplating
Implementation Method 3
electrodeposition of metal occurs over the entirety of the substrate
Implementation Method 4
The electrolyte typically also includes an acid that provides sufficient conductivity to the electrolyte and may also contain additives
Data Source
AI summary
An apparatus for electroplating metal on a semiconductor substrate with improved plating uniformity includes in one aspect: a plating chamber configured to contain an electrolyte and an anode; a substrate holder configured to hold the semiconductor substrate; and an ionically resistive ionically permeable element comprising a substantially planar substrate-facing surface and an opposing surface, wherein the element allows for flow of ionic current towards the substrate during electroplating, and wherein the element comprises a region having varied local resistivity. In one example the resistivity of the element is varied by varying the thickness of the element. In some embodiments the thickness of the element is gradually reduced in a radial direction from the edge of the element to the center of the element. The provided apparatus and methods are particularly useful for electroplating metal in WLP recessed features.