Selective Molybdenum Fill for Void-Free Semiconductor Contacts

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Solution Overview

Problem

As node size in semiconductor fabrication processes decreases, achieving uniform metal fill with low resistance becomes a challenge, particularly in connecting adjacent metal layers and contacts between metal layers and neighboring devices.

Innovation Solution

A method involving the formation of a molybdenum silicide layer on a substrate's recessed feature, followed by depositing a molybdenum layer and optionally converting a portion to molybdenum nitride, using nitrogen radicals, to fill the feature without voids, utilizing molybdenum halide and oxyhalide precursors with controlled temperature and pressure to ensure selective deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional metal fill is used in reduced node size features, then feature filling is achieved, but uniformity and low resistance become difficult to maintain

Engineering Contradiction:

Improveuniform metal fillVSAvoidfeature size reduction

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The metal fill process is segmented into multiple sequential steps: forming a metal silicide layer on the bottom surface, selectively depositing a first metal layer, and optionally converting to metal nitride. This segmentation allows each step to optimize for uniformity and control, resolving the contradiction between maintaining precision and adapting to smaller feature sizes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention applies different materials and treatments to different locations within the feature. The bottom surface receives a metal silicide layer while sidewalls remain untreated, creating local quality differences that ensure uniform fill from the bottom up and prevent void formation, directly addressing the uniformity challenge in reduced node sizes.

Inventive Principle:

Principle #3Local quality

2Reliability

If metal fill is deposited to connect metal layers and contacts, then electrical connectivity is achieved, but resistance increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidresistance

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention uses composite material structures including metal silicide layers combined with metal layers, and optionally metal nitride conversions. These composite structures provide both mechanical integrity and optimized electrical conductivity, reducing resistance while maintaining reliable connectivity between metal layers and contacts.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes material parameters through chemical conversion processes. The optional conversion of metal to metal nitride and the formation of metal silicide layers alter the electrical and mechanical properties of the fill material, optimizing for lower resistance and improved conductivity in the final structure.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If selective deposition is used to fill features, then void-free fill is achieved, but process complexity increases

Engineering Contradiction:

Improvevoid-free fillVSAvoidprocess steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention performs preliminary actions by forming a metal silicide layer on the bottom surface before the main metal fill deposition. This preliminary layer acts as a foundation that promotes uniform subsequent deposition and prevents void formation, achieving void-free fill while the added step is justified by the critical need for precision in the final structure.

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

This approach enables void-free, low-resistance metal fill within semiconductor features, enhancing electrical conductivity and reducing silicon diffusion, thereby improving the quality and efficiency of semiconductor devices.

Implementation Method 1

The molybdenum silicide layer is formed by reacting a molybdenum containing precursor with the bottom surface at a temperature of about 200 to about 600° C.

Methodology Applied

Scientific EffectChemical Vapour Deposition: Chemical Vapour Deposition

Implementation Method 2

A portion of the second molybdenum layer is converted to a molybdenum nitride layer when exposed to the nitrogen radicals or nitrogen-containing radicals

Methodology Applied

Scientific EffectNitridation: Nitriding

Implementation Method 3

The methods further include exposing the molybdenum silicide layer to a reducing agent prior to depositing the first molybdenum layer

Methodology Applied

Scientific EffectReduction: Reduction

Data Source

PatentUS20260022453A1Selective molybdenum fill

Publication Date: 2026.01.22 LAM RES CORP

AI summary

A molybdenum silicide layer is formed on a bottom surface in a recessed feature in a silicon or silicon-germanium substrate. The bottom surface may be a silicon or silicon-germanium. A first molybdenum lay er may be deposited on or over the molybdenum silicide layer to fill the recessed feature. In some cases, a second molybdenum layer may be formed on the molybdenum silicide layer. In some cases, the second molybdenum layer may be exposed to nitrogen radicals or nitrogen-containing radicals, forming a molybdenum nitride layer on the second molybdenum layer.