Multi Cap Layer Stress Engineering for Damascene Interconnects

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Solution Overview

Problem

In damascene interconnect processes, the compressive stress of traditional cap layers causes line distortion and water absorption, leading to Kelvin via opens, which compromise the reliability and electrical performance of copper damascene interconnects.

Innovation Solution

A multi cap layer comprising a tensile stress layer and a protecting layer, where the tensile stress layer is thicker than the protecting layer, is used to prevent line distortion and water absorption, thereby preventing Kelvin via opens. This multi cap layer is formed using deposition processes like PECVD or LPCVD, with specific RF power settings to achieve desired stress levels and prevent water ingress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a traditional cap layer with compressive stress is used, then the cap layer provides structural support, but line distortion occurs and water absorption leads to Kelvin via opens

Engineering Contradiction:

Improvestructural supportVSAvoidKelvin via open prevention

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The cap layer is segmented into multiple layers with different stress characteristics. The first cap layer has compressive stress while the second cap layer has tensile stress, allowing each layer to perform its specific function independently. This segmentation resolves the contradiction by separating the structural support function from the water barrier function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cap structure uses composite material design by combining materials with different stress properties. The first cap layer uses a material providing compressive stress for structural support, while the second cap layer uses a material providing tensile stress to counteract water absorption and prevent Kelvin via opens.

Inventive Principle:

Principle #40Composite materials

2Strength

If a traditional cap layer with compressive stress is used, then the cap layer provides structural support, but line distortion occurs in the ULK layer

Engineering Contradiction:

Improvestructural supportVSAvoidline distortion

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The second cap layer with tensile stress acts as a counterweight to the first cap layer's compressive stress. This counterbalancing stress configuration prevents line distortion in the ULK layer while maintaining the structural support provided by the compressive stress layer.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The stress parameter of the cap layer system is changed from purely compressive to a combination of compressive and tensile stresses. By adjusting the stress parameters through material selection and layer configuration, the system achieves both structural support and distortion prevention.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the cap layer directly contacts the ULK layer, then the structure is simplified, but water absorption and desorption cause Kelvin via opens

Engineering Contradiction:

Improvecap layer structureVSAvoidelectrical performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The multi-layer cap structure acts as an intermediary system between the ULK layer and the external environment. The specific arrangement of compressive and tensile stress layers creates a barrier that prevents water from reaching and damaging the ULK layer, thereby protecting electrical performance without significantly increasing structural complexity.

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

The multi cap layer effectively prevents line distortion and Kelvin via opens, improving the electrical performance and reliability of damascene interconnects by buffering compressive stress and blocking water absorption.

Implementation Method 1

the tensile stress layer is thicker than the protecting layer, is used to prevent line distortion and water absorption, thereby preventing Kelvin via opens. This multi cap layer is formed using deposition processes like PECVD or LPCVD, with specific RF power settings to achieve desired stress levels and prevent water ingress.

Methodology Applied

Scientific EffectStress buffering:

Implementation Method 2

the tensile stress layer is thicker than the protecting layer, is used to prevent line distortion and water absorption, thereby preventing Kelvin via opens

Methodology Applied

Scientific EffectWater absorption blocking:

Data Source

PatentUS8084357B2Method for manufacturing a dual damascene opening comprising a trench opening and a via opening

Publication Date: 2011.12.27 UNITED MICROELECTRONICS CORP

AI summary

A method for manufacturing a multi cap layer includes providing a substrate, forming a multi cap layer comprising a first cap layer and a second cap layer formed thereon on the substrate, forming a patterned metal hard mask layer on the multi cap layer, and performing an etching process to etch the multi cap layer through the patterned hard mask layer and to form an opening in the second cap layer.