CMP Slurry pH Tuning for Dense Semiconductor Interconnects
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) processes face challenges in handling devices with varying densities, as higher density devices near each other can suffer from inadvertent shortcomings due to interactions with oxidizing slurries, leading to reliability issues in semiconductor fabrication.
Innovation Solution
A method involving a series of CMP processes with tailored slurries and chemical agents to create a dishing profile in conductive features, followed by the formation of high-density dielectric layers with uneven topography, selectively removing portions to prevent metal ion entrapment and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a CMP process utilizing an oxidizing slurry is used to remove materials, then material removal efficiency is improved, but devices with higher densities suffer from inadvertent shortcomings and reliability issues
Solution Approach 1:
The patent applies different slurries with different pH levels to different regions of the substrate based on device density. High-density regions receive a first slurry with a first pH level, while low-density regions receive a second slurry with a second pH level. This local differentiation allows optimized material removal for each region type, maintaining reliability in high-density areas while achieving efficient removal in low-density areas.
Solution Approach 2:
The patent changes the pH parameter of the slurry based on the device density of the target region. By adjusting the pH level of the slurry, the chemical reactivity and material removal characteristics are modified to suit different device densities, thereby preventing reliability issues in high-density regions while maintaining productivity in low-density regions.
2Adaptability or versatility
If devices with different densities are fabricated in nearby regions, then device functionality is improved, but fabrication processes become more difficult to accommodate varying device characteristics
Solution Approach 1:
The patent implements region-specific processing by applying different pH-level slurries to different device density regions. This local quality approach allows the fabrication process to accommodate varying device characteristics without requiring entirely different process flows, thereby managing complexity while maintaining adaptability.
Solution Approach 2:
The patent segments the substrate into different regions based on device density characteristics and applies tailored slurries to each segment. This segmentation strategy simplifies the overall fabrication process by breaking it down into manageable region-specific steps, reducing the complexity of handling varying device characteristics across the entire substrate.
3Manufacturing precision
If oxidizing slurry is applied to high-density devices, then material removal is achieved, but metal ion entrapment and time-dependent dielectric breakdown occur
Solution Approach 1:
The patent changes the pH parameter of the slurry when processing high-density regions. By using a first slurry with a first pH level specifically for high-density regions, the chemical environment is optimized to prevent metal ion entrapment and subsequent time-dependent dielectric breakdown, while still achieving the necessary material removal precision.
Solution Approach 2:
The patent applies a specifically formulated slurry with appropriate pH level to high-density regions before material removal begins, creating a protective chemical environment that prevents metal ion entrapment from occurring in the first place. This preliminary anti-action approach addresses the harmful effect before it can manifest.
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 allows for the simultaneous fabrication and planarization of conductive features with different sizes and packing densities, reducing reliability issues like time-dependent dielectric breakdown and voltage breakdown, while maintaining structural integrity.
Implementation Method 1
perform a first chemical mechanical polishing (CMP) process to a first conductive feature disposed in a first interlayer dielectric (ILD) layer, resulting a first recess in the first conductive feature
Implementation Method 2
perform a second CMP process to second conductive features disposed in the first region, wherein the second CMP process completely removes portions of the second ILD layer disposed in the second region
Data Source
AI summary
A method of forming a semiconductor structure includes removing a top portion of a conductive feature disposed in a first dielectric layer and over a semiconductor substrate to form a first recess, depositing a second dielectric layer over the first dielectric layer, where the second dielectric layer includes a first region disposed vertically above the first recess and a second region disposed adjacent the first region, and forming a third dielectric layer over the second dielectric layer. The method further includes subsequently forming openings in the third dielectric layer that extend to expose the second dielectric layer, depositing a conductive material in the openings, and planarizing the conductive material to form conductive features in the first and the second regions, where the planarizing completely removes portions of the third dielectric layer disposed in the second region.