Hybrid Copper Interconnect Structure with Dual Impurity Levels

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Solution Overview

Problem

Current copper back-end-of-the-line (BEOL) interconnect structures face challenges in reducing resistance and capacitance, and maintaining reliable signal transmission, particularly due to limitations in copper purity levels and overburden within these structures.

Innovation Solution

A hybrid copper interconnect structure is fabricated using a combination of physical vapor deposition for low impurity copper regions and electroplating for high impurity copper regions, with copper reflow to completely fill re-entrant profiles and reduce overburden, allowing for different impurity levels within the same opening.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If electroplating is used to fill copper regions, then the opening can be completely filled, but overburden increases and copper resistivity increases due to high impurity levels

Engineering Contradiction:

Improvecompletely filling openingVSAvoidcopper resistivity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The copper fill is divided into two distinct regions: an electroplated copper region at the bottom of the opening and a PVD copper region at the top. This segmentation allows each region to have optimized properties - the electroplated region provides complete fill and adhesion, while the PVD region provides low resistivity and low impurity content.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different copper regions within the same opening are assigned different impurity levels and deposition methods. The bottom region uses electroplating with higher impurity tolerance, while the top region uses PVD with strict impurity control to achieve low resistivity. This local quality differentiation resolves the contradiction between complete filling and low resistivity.

Inventive Principle:

Principle #3Local quality

2Reliability

If physical vapor deposition is used for copper regions, then copper resistivity is lowered, but the opening cannot be completely filled and re-entrant profiles remain

Engineering Contradiction:

Improvecopper resistivityVSAvoidcompletely filling opening

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The electroplated copper region is formed first as a preliminary structure that completely fills the bottom of the opening and addresses re-entrant profiles. This preliminary action creates a foundation that enables subsequent PVD copper deposition to achieve low resistivity without compromising complete filling.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If conventional copper interconnect structures are used, then manufacturing is simplified, but resistance and capacitance reduction becomes increasingly challenging

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidresistance and capacitance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The interconnect structure uses a composite copper system with two distinct copper regions having different impurity levels and deposition characteristics. This composite approach enables simultaneous optimization of electrical properties (low resistance) and manufacturing feasibility, addressing the challenges of conventional single-material copper interconnects.

Inventive Principle:

Principle #40Composite materials

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 effectively lowers copper resistivity, reduces overburden, and enhances the reliability of interconnect structures by utilizing dual material liners and varying impurity levels, improving signal speed and reducing crosstalk.

Implementation Method 1

utilizing a combination of physical vapor deposition of a copper region having a low impurity level

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 2

copper reflow, with electroplating another copper region

Methodology Applied

Scientific EffectCopper reflow: Melting

Implementation Method 3

electroplating another copper region having a high impurity level

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS8525339B2Hybrid copper interconnect structure and method of fabricating same

Publication Date: 2013.09.03 GLOBALFOUNDRIES US INC

AI summary

A hybrid interconnect structure containing copper regions that have different impurities levels within a same opening is provided. In one embodiment, the interconnect structure includes a patterned dielectric material having at least one opening located therein. A dual material liner is located at least on sidewalls of the patterned dielectric material within the at least one opening. The structure further includes a first copper region having a first impurity level located within a bottom region of the at least one opening and a second copper region having a second impurity level located within a top region of the at least one opening and atop the first copper region. In accordance with the present disclosure, the first impurity level of the first copper region is different from the second impurity level of the second copper region.