Differential Contrast Plating for Coplanar Metal Pillars
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Solution Overview
Problem
Existing electroplating processes for semiconductor substrates result in non-uniform deposition of metal pillars due to varying feature depths, leading to undesirable height differences and non-planarity, which are difficult to correct without costly and time-consuming etching processes.
Innovation Solution
A method involving a pre-acceleration solution followed by an electroplating process with controlled use of accelerators and levelers to achieve differential plating rates between deep and shallow features, ensuring uniform deposition heights by saturating the substrate with accelerator compounds and using levelers to deactivate deposition in shallow features before deep features are fully filled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroplating processes are used on substrates with varying feature depths, then electroplating speed and purity can be maintained, but non-uniform deposition heights and poor co-planarity result
Solution Approach 1:
The substrate is pre-treated with an accelerator solution before electroplating to saturate the feature surfaces with accelerator compounds. This preliminary action ensures that when electroplating begins, all features regardless of depth have maximum accelerator coverage, enabling uniform initial deposition rates across varying feature depths and improving co-planarity without sacrificing plating speed
Solution Approach 2:
The electroplating bath contains both accelerator and leveler additives that create locally different deposition conditions. Accelerators enhance deposition in recessed regions while levelers suppress deposition on exposed regions, creating differential plating rates that compensate for depth variations and achieve uniform pillar heights
2Manufacturing precision
If electroplating is performed to fill deep features, then complete filling of deep features is achieved, but shallow features become over-filled and non-planar
Solution Approach 1:
The electroplating bath composition is modified by adjusting the ratio and concentration of accelerator to leveler additives. This parameter change creates a differential plating environment where the accelerator drives deposition in deep features while the leveler suppresses deposition in shallow features, enabling simultaneous filling of features with different depths to uniform heights without requiring separate processing steps
3Manufacturing precision
If within-die, within-wafer, and within-feature uniformity are optimized, then acceptable non-uniformity is achieved, but electroplating rates and purity may be compromised
Solution Approach 1:
The electroplating bath chemistry is optimized by carefully controlling the concentrations of metal ions, acid, accelerator, and leveler additives. This parameter optimization achieves the dual goal of maintaining high electroplating rates for productivity while ensuring uniform deposition across all spatial scales (within-die, within-wafer, and within-feature) through the synergistic action of accelerator and leveler compounds
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 improves co-planarity of metal pillars by ensuring uniform deposition heights across features of varying depths, enhancing within-die, within-wafer, and within-feature uniformity while optimizing electroplating speed and purity.
Implementation Method 1
exposing a surface of a substrate to a pre-acceleration solution including an accelerator compound, wherein the surface of the substrate becomes saturated with accelerator compound
Implementation Method 2
immersing at least the surface of the substrate in an electroplating solution including ions of the metal... while the surface of the substrate is immersed in the electroplating solution, electroplating the metal into the features
Implementation Method 3
the leveler reduces the plating rate of more exposed regions of the substrate surface relative to more recessed regions of the substrate surface by polarizing deposition at the more exposed regions of the substrate surface relative to more recessed regions
Data Source
AI summary
A method of electroplating a metal into features, having substantially different depths, of a partially fabricated electronic device on a substrate is provided. The method includes adsorbing accelerator into the bottom of recessed features; partially filling the features by a bottom up fill mechanism in an electroplating solution; diffusing leveler into shallow features to decrease the plating rate in shallow features as compared to deep features; and electroplating more metal into the features such that the height of metal in deep features is similar to the height of metal in shallow features.