Multi-Metal CMP Planarization for Matched Semiconductor Contacts

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Solution Overview

Problem

Existing semiconductor manufacturing processes face challenges in achieving low contact resistance and high conduction speed while integrating conducting elements made of different metallic materials like ruthenium and tungsten or molybdenum, as they struggle to planarize these materials to have top surfaces at the same level.

Innovation Solution

A two-step chemical mechanical polishing (CMP) process is employed using specific polishing slurries and inhibitors to selectively remove and planarize ruthenium and tungsten or molybdenum layers, ensuring their top surfaces are at the same level by utilizing different active chemicals and inhibitors in each step to protect the underlying metal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a single CMP process is used to planarize multiple metal layers, then the process is simple and fast, but the top surfaces of different metal materials cannot be planarized to the same level

Engineering Contradiction:

Improveplanarization precisionVSAvoidCMP process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent divides the CMP process into multiple sequential steps, each with a dedicated polishing slurry formulated for specific metal materials. The first CMP step uses a slurry optimized for ruthenium, followed by a second CMP step with a slurry optimized for tungsten or molybdenum. This segmentation allows each metal layer to be planarized with appropriate parameters, achieving precise height control (within 5 nm) while managing process complexity through systematic organization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies the principle of local quality by using different polishing slurries with distinct chemical compositions and abrasive characteristics tailored to each metal material's properties. The first slurry contains chemicals and abrasives optimized for ruthenium's hardness and chemical reactivity, while the second slurry is specifically formulated for tungsten or molybdenum. This localized optimization ensures each metal layer receives the appropriate polishing treatment, achieving uniform top surfaces at the same level.

Inventive Principle:

Principle #3Local quality

2Reliability

If different metal materials are integrated to achieve low contact resistance and high conduction speed, then device performance is enhanced, but the difficulty of planarizing them to the same level increases

Engineering Contradiction:

Improvedevice performanceVSAvoidheight control precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent employs parameter changes by adjusting key CMP process variables including slurry pH, oxidant concentration, abrasive particle size and composition, and polishing pressure for each metal layer. The first CMP step uses parameters optimized for ruthenium (e.g., specific pH range, oxidant type), while the second step modifies these parameters for tungsten or molybdenum. This systematic parameter adjustment enables precise control of material removal rates, achieving height control within 5 nm despite the different mechanical and chemical properties of the metal materials.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If multiple CMP steps with different slurries are used to planarize different metals, then height precision is achieved, but the manufacturing process becomes more complex

Engineering Contradiction:

Improveheight uniformityVSAvoidmanufacturing efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies preliminary action by performing the first CMP step with a ruthenium-optimized slurry before proceeding to the second CMP step with a tungsten or molybdenum-optimized slurry. Each step is carefully controlled to remove specific thicknesses and achieve target height profiles in advance. This preliminary planning and execution of each polishing step with predetermined parameters enables the final height uniformity to be achieved efficiently, reducing the need for additional corrective steps.

Inventive Principle:

Principle #10Preliminary action

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 process effectively planarizes conducting elements made of different metals, reducing height differences to less than 5 nm, enhancing semiconductor device performance by improving conductivity and reducing contact resistance.

Implementation Method 1

performing a chemical mechanical polishing (CMP) process on a base structure including therein a first metal portion and a second metal portion

Methodology Applied

Scientific EffectChemical mechanical polishing:

Implementation Method 2

the acidic polishing slurry including an active chemical and an inhibitor which protects the first metal portion from being overpolished

Methodology Applied

Scientific EffectChemical inhibition:

Data Source

PatentUS20250316534A1Method for forming semiconductor structure with metal portions made of different materials

Publication Date: 2025.10.09 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method for forming a semiconductor structure includes: performing a chemical mechanical polishing (CMP) process on a base structure including therein a first metal portion and a second metal portion using an acidic polishing slurry, the acidic polishing slurry including an active chemical and an inhibitor which protects the first metal portion from being overpolished, a metal material of the first metal portion being different from a metal material of the second metal portion.