Conductive Contact via Segmented Plug and Spacer
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Solution Overview
Problem
The increasing integration of memory arrays in integrated circuitry poses challenges in making suitable connections from peripheral circuitry to tightly packed wordlines and bitlines, as conventional methods consume substantial semiconductor real estate and are prone to issues like copper diffusion and conductive stringers.
Innovation Solution
A method involving the formation of electrically conductive contacts using a conductive plug with a copper core and a titanium nitride barrier, recessed below a tungsten layer, which is then coupled with a spacer to create a narrow upper region for connecting to tightly pitched wordlines and bitlines, avoiding copper diffusion and stringer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional connection methods are used to connect peripheral circuitry to tightly packed wordlines and bitlines, then electrical connection is achieved, but substantial semiconductor real estate is consumed
Solution Approach 1:
The connection structure is divided into multiple functional segments: a copper plug at the bottom for low-resistance connection, a tungsten layer in the middle section, and a metal cap at the top. This segmentation allows each material to perform its optimal function while minimizing overall footprint and consuming less semiconductor real estate compared to conventional single-material contacts.
Solution Approach 2:
The patent employs a nested structure where the copper plug is positioned within the opening, the tungsten layer is deposited over and around the copper plug, and the metal cap is formed over the tungsten layer. This nested arrangement of multiple materials within a single vertical column achieves reliable electrical connection while minimizing lateral footprint.
2Reliability
If copper is used directly in contact with insulative material, then good electrical conductivity is achieved, but copper diffusion and conductive stringer formation occur
Solution Approach 1:
A titanium nitride barrier layer is introduced as an intermediary between the copper plug and the surrounding insulative material. This barrier layer prevents copper atoms from diffusing into the insulator and forming conductive stringers, while maintaining good electrical conductivity through the copper plug itself. The tungsten layer serves as an additional intermediary protective layer.
Solution Approach 2:
The contact structure uses a composite material approach, combining copper (for conductivity), titanium nitride (for diffusion barrier), and tungsten (for structural support and additional barrier). This composite structure achieves reliable electrical connection while preventing the harmful effects of pure copper exposure.
3Productivity
If wordlines and bitlines are tightly packed to increase integration, then integration density improves, but making suitable connections becomes increasingly difficult
Solution Approach 1:
The patent transitions from lateral connection approaches to a vertical connection architecture. The multi-material contact structure extends vertically through the insulative material, allowing connections to be made in the vertical dimension rather than requiring extensive lateral routing. This enables tightly packed wordlines and bitlines while maintaining manufacturable connection structures.
Solution Approach 2:
The connection structure employs local quality by using different materials at different vertical positions: copper at the bottom for conductivity, titanium nitride at the interface for barrier properties, and tungsten in the middle for structural support. This localized material optimization makes the connection structure both compact and manufacturable.
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 allows for efficient electrical coupling between highly integrated structures and peripheral circuitry without consuming semiconductor real estate, improving contact uniformity and reducing the risk of shorts, thus enhancing the integration density of memory arrays.
Implementation Method 1
The electrically conductive plug is directly against an electrically insulative material. An electrically insulative spacer is over and directly against the electrically conductive plug... avoiding copper diffusion and stringer formation
Data Source
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AI summary
Some embodiments include methods of forming electrically conductive contacts. An opening is formed through an insulative material to a conductive structure. A conductive plug is formed within a bottom region of the opening. A spacer is formed to line a lateral periphery of an upper region of the opening, and to leave an inner portion of an upper surface of the plug exposed. A conductive material is formed against the inner portion of the upper surface of the plug. Some embodiments include semiconductor constructions having a conductive plug within an insulative stack and against a copper-containing material. A spacer is over an outer portion of an upper surface of the plug and not directly above an inner portion of the upper surface. A conductive material is over the inner portion of the upper surface of the plug and against an inner lateral surface of the spacer.