Conductive Pillar Contact for Aluminum Gate Reliability

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Solution Overview

Problem

The challenge in integrated circuit manufacturing is achieving reliable electrical contacts to aluminum gate electrodes while avoiding issues with aluminum oxide layers and etch polymer removal, particularly for large gate electrodes, which can lead to dishing of semiconductor structures during chemical mechanical polishing.

Innovation Solution

The introduction of electrically conductive pillars with workfunction adjustment and/or barrier materials within the aluminum structures ensures that contacts are established with these materials, reducing the formation of unwanted oxide layers and improving the robustness of the contact process, and allowing for larger aluminum features by reducing dishing during chemical mechanical polishing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If aluminum is used as gate electrode material, then electrical conductivity and charge carrier density are improved, but formation of aluminum oxide layers and difficulty in establishing reliable electrical contacts occur

Engineering Contradiction:

Improveelectrical contact reliabilityVSAvoidaluminum oxide layer formation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A contact opening is introduced as an intermediary structure that selectively accesses the aluminum gate electrode through the aluminum oxide layer. The contact opening is positioned and dimensioned to establish electrical connection while minimizing exposure to oxygen, thereby reducing further oxide formation. This mediator structure enables reliable electrical contact without directly exposing the aluminum to harsh contact conditions that would accelerate oxidation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If larger aluminum gate electrodes are formed, then device performance is improved, but dishing occurs during chemical mechanical polishing

Engineering Contradiction:

Improvedevice performanceVSAvoidsurface flatness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The gate electrode structure is designed with non-uniform thickness distribution, creating a cambered profile where the center is thicker than the edges. This local variation in geometry compensates for the dishing effect during chemical mechanical polishing - the thicker center material provides excess that can be removed, while the thinner edges are protected from over-removal. The result is a flatter final surface after polishing, enabling larger aluminum gate electrodes to be manufactured with acceptable surface precision.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If etch polymers are removed aggressively, then cleaning is improved, but aluminum gate electrodes are attacked and interfacial layers are formed

Engineering Contradiction:

Improveetch polymer removalVSAvoidaluminum gate electrode damage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The contact opening structure serves as a protective intermediary during etch polymer removal. By confining the cleaning process to within the contact opening boundaries, the aluminum gate electrode is shielded from aggressive cleaning chemicals. The contact opening walls act as a physical barrier that prevents direct contact between the aluminum surface and harmful cleaning agents, allowing thorough polymer removal while preserving the aluminum integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Device complexity

If contacts are made directly to aluminum gate electrodes, then manufacturing simplicity is maintained, but contact robustness is reduced due to oxide layers

Engineering Contradiction:

Improvecontact structure complexityVSAvoidcontact robustness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The contact opening is formed and positioned in advance, before final electrical contact establishment. This preliminary structuring creates a controlled access path to the aluminum gate electrode that is optimized for subsequent contact formation. By pre-defining the contact geometry and location, the process ensures that contacts will reliably penetrate through existing oxide layers and establish robust electrical connection, while maintaining manufacturing simplicity through a standardized contact opening formation process.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9466685B2Semiconductor structure including at least one electrically conductive pillar, semiconductor structure including a contact contacting an outer layer of an electrically conductive structure and method for the formation thereof

Publication Date: 2016.10.11 GLOBALFOUNDRIES US INC

AI summary

A semiconductor structure includes a substrate, at least one electrically conductive pillar provided over the substrate and an electrically conductive structure provided over the substrate. The electrically conductive pillar includes an inner portion and an outer layer that is provided below the inner portion and lateral to the inner portion. The electrically conductive structure also includes an inner portion and an outer layer that is provided below the inner portion and lateral to the inner portion. The electrically conductive structure annularly encloses each of the at least one electrically conductive pillar. The outer layer of each of the at least one electrically conductive pillar contacts the outer layer of the electrically conductive structure. The outer layer of the at least one electrically conductive pillar and the outer layer of the electrically conductive structure are formed of different metallic materials.