Bit Line Extension for Storage Device Contact Resistance
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Solution Overview
Problem
Existing storage devices face challenges in reducing contact resistance between bit lines and transistors, particularly when misalignment occurs, which affects the electrical connection and integration density.
Innovation Solution
The storage device incorporates a second insulating film with a lower etching rate, such as silicon nitride or titanium oxide, positioned between the first insulating film and the transistor portion, facilitating the formation of bit lines that extend beyond the barrier metal layer, enabling electrical connection through both the upper and side surfaces, thereby reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bit lines are formed to connect to transistors in conventional storage devices, then electrical connection is achieved, but contact resistance increases when misalignment occurs between bit lines and transistors
Solution Approach 1:
The bit line is extended from a single-plane connection to a three-dimensional structure that contacts the transistor from multiple surfaces (upper surface and side surface). This dimensional extension allows the bit line to maintain electrical connection even when lateral alignment is imperfect, as the vertical and side surface contacts provide alternative conduction paths.
Solution Approach 2:
The bit line structure is designed to extend through multiple layers and wrap around the transistor structure. The bit line penetrates the interlayer insulating films and barrier metal layer, then extends along the side surface of the transistor, creating a nested configuration where the bit line surrounds part of the transistor structure to ensure contact.
2Reliability
If bit lines extend beyond the barrier metal layer to reduce contact resistance, then electrical connection improves, but device complexity increases
Solution Approach 1:
The extended bit line structure serves multiple functions simultaneously: it provides the primary electrical connection path, acts as a alignment tolerance buffer, and creates redundant conduction paths through multiple contact points. This multi-functionality justifies the additional structural complexity by delivering multiple benefits from a single design feature.
Solution Approach 2:
The bit line is designed to extend beyond the barrier metal layer in advance, before final alignment is achieved. This preliminary extension ensures that even if misalignment occurs during operation, the electrical connection is already established through the extended portions, preventing connection failures.
3Reliability
If bit lines make contact through multiple surfaces (upper and side), then contact resistance decreases, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the geometric parameters of the bit line, extending its length and altering its three-dimensional trajectory to contact the transistor at multiple locations. This parameter change transforms a single-point contact (high resistance, tolerant to misalignment) into a multi-point contact (low resistance, less sensitive to misalignment).
Solution Approach 2:
The barrier metal layer and interlayer insulating films serve as intermediaries that the bit line must penetrate to reach the transistor. By designing the bit line to extend through these intermediate layers and along the side surface, the invention creates multiple intermediate contact points that collectively reduce total contact resistance while providing alignment tolerance.
Data Source
AI summary
A storage device including a transistor portion including a transistor, a plurality of interlayer insulating films provided above the transistor portion, a plurality of first conductive layers provided respectively between the plurality of interlayer insulating films, and a second conductive layer extending through the plurality of interlayer insulating films and the plurality of first conductive layers, the second conductive layer having one end electrically connected to the transistor portion, and a part that extends beyond a portion of the transistor portion.