Selective Cobalt-Copper Fill for Semiconductor Interconnects

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Solution Overview

Problem

In semiconductor interconnects, filling features of varying sizes with cobalt results in poor electrical properties due to higher line resistances, particularly as feature sizes decrease below 10 nm.

Innovation Solution

A method involving the deposition of a cobalt layer followed by heating to fill narrower features with cobalt while simultaneously depositing copper to fill wider features, using a combination of chemical vapor deposition and physical vapor deposition processes within a cluster tool to optimize fill materials for different sized features.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If cobalt is used to fill all features regardless of size, then manufacturing process is simple, but electrical properties deteriorate with higher line resistances

Engineering Contradiction:

Improvefilling process simplicityVSAvoidelectrical properties

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by selectively filling narrow features with cobalt and wide features with copper based on feature width. A liner layer is deposited first, then cobalt is deposited and selectively retained in narrow features through size-selective filling, while wide features are subsequently filled with copper. This local differentiation optimizes electrical properties for each feature type.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The filling process is segmented into multiple sequential steps: (1) depositing a liner layer in all features, (2) depositing cobalt material, (3) selectively removing excess cobalt from wide features, and (4) filling remaining wide features with copper. This segmentation allows different materials to be optimally placed in different feature types.

Inventive Principle:

Principle #1Segmentation

2Reliability

If copper is used to fill wide features, then electrical conductivity improves, but manufacturing complexity increases

Engineering Contradiction:

Improveelectrical conductivityVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by first depositing a liner layer in all features before selective filling. The liner layer is prepared in advance to provide a uniform base for subsequent cobalt and copper deposition, simplifying the overall process by establishing a common foundation before differentiation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The liner layer acts as an intermediary between the substrate and the selective cobalt/copper filling process. It provides a uniform starting point that facilitates controlled material deposition and selective removal, mediating the complexity of size-selective filling.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 line resistance in features of varying sizes by preferentially growing cobalt in narrow features and copper in wider features, enhancing the electrical properties of metal interconnects in semiconductor devices.

Implementation Method 1

depositing a cobalt layer to a first thickness atop the barrier layer within the first plurality of features and the second plurality of features, wherein the cobalt layer is deposited using a chemical vapor deposition process

Methodology Applied

Scientific EffectChemical vapor deposition: Chemical Vapour Deposition

Implementation Method 2

heating the substrate to a first temperature to fill the first plurality of features with cobalt material

Methodology Applied

Scientific EffectThermal diffusion: Diffusion

Implementation Method 3

simultaneously depositing a copper material on the substrate via a physical vapor deposition process to fill the second plurality of features

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS10014179B2Methods for forming cobalt-copper selective fill for an interconnect

Publication Date: 2018.07.03 APPLIED MATERIALS INC

AI summary

Methods for processing a substrate include: (a) depositing a cobalt layer to a first thickness within a first plurality of features and a second plurality of features formed in a substrate, wherein each of the first plurality of features and each of the second plurality of features comprises an opening, and wherein a width of the openings of the first plurality of features is less than a width of the openings of the second plurality of features; and (b) heating the substrate to a first temperature to fill the first plurality of features with cobalt material while simultaneously depositing a fill material on the substrate to fill the second plurality of features.