Copper Alloy Recesses for BEOL Planarization

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Solution Overview

Problem

Conventional back end of line (BEOL) metallization processes face challenges with metal overburden planarization, where copper via structures coupled to active interconnects experience greater erosion, leading to issues in downstream processing and non-planar surfaces during the fabrication of multiple metal layers and insulating layers.

Innovation Solution

The introduction of a copper alloy deposited into recesses formed in copper via structures coupled to active interconnects, which eliminates further erosion and provides a planar top surface, enhancing the stability and fabrication of pillar structures by using a copper alloy limited to these recesses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If copper via structures are used in conventional BEOL metallization processes, then good electrical conductivity is achieved, but metal overburden planarization causes greater erosion leading to non-planar surfaces and downstream processing issues

Engineering Contradiction:

Improveelectrical conductivityVSAvoidsurface planarity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by depositing copper alloy selectively only in recesses of copper via structures that are coupled to active interconnects, while leaving other areas unchanged. This localized treatment addresses the erosion problem specifically where it occurs without affecting the entire via structure uniformly, thereby maintaining surface planarity while preserving the electrical conductivity of the copper via structures.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining copper and copper alloy in a single via structure. The via contains pure copper for electrical conductivity and copper alloy in recesses for erosion resistance and planarization. This composite approach allows the structure to simultaneously achieve good electrical conductivity and resistance to planarization erosion.

Inventive Principle:

Principle #40Composite materials

2Shape

If planarization processes are applied to copper via structures, then surface flatness is improved, but copper via structures experience greater erosion leading to instability in downstream processing

Engineering Contradiction:

Improvesurface flatnessVSAvoidvia structure stability

Core Design Contradiction:

ShapeVSStability of the object's composition

Solution Approach 1:

The patent employs composite materials by incorporating copper alloy into the copper via structure. The copper alloy provides enhanced stability and resistance to planarization erosion, while the copper maintains electrical conductivity. This composite structure allows the via to withstand planarization processes without excessive erosion, maintaining both surface flatness and structural stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies beforehand cushioning by pre-depositing copper alloy in recesses of the copper via structure before planarization. This copper alloy acts as a protective layer that cushions the copper against erosion during subsequent planarization and downstream processing, thereby maintaining via structure stability while achieving surface flatness.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If copper alloy is deposited into recesses of copper via structures, then erosion is eliminated and planar top surface is achieved, but process complexity increases

Engineering Contradiction:

Improveerosion resistanceVSAvoiddeposition process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by restricting copper alloy deposition to only the recesses of copper via structures coupled to active interconnects. This localized deposition approach achieves erosion resistance and planar top surfaces without requiring complex blanket deposition processes, thereby limiting process complexity to only the necessary localized steps.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses preliminary action by forming recesses in the copper via structures before depositing the copper alloy. This pre-preparation of recesses allows for controlled and simplified copper alloy deposition, reducing the complexity of the overall process compared to attempting to deposit alloy uniformly or modify existing via structures after formation.

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 prevents further erosion in downstream processing, ensures a planar top surface, and facilitates the formation of stable interconnect structures, improving the overall fabrication process and device performance.

Implementation Method 1

The introduction of a copper alloy deposited into recesses formed in copper via structures coupled to active interconnects

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS10910307B2Back end of line metallization structure

Publication Date: 2021.02.02 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Back end of line metallization structures and processes of fabricating the metallization structures generally include one or more metal filled via structures within a dielectric layer of an interconnect level, wherein at least one of the metal filled via structures includes a bulk metal and a metal alloy overlaying the bulk metal, wherein the bulk metal and metal alloy filled via is coupled to an active circuit.