Tapered Conductive Wire End Portion for Low Resistance Memory Contacts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In three-dimensional cross-point memory devices, it is challenging to form lead-out sections of word lines and bit lines without increasing the device area, particularly in forming contacts that maintain low electrical resistance while avoiding short circuits and maintaining high storage capacity per chip area.
Innovation Solution
The memory device incorporates conductive wires with end portions that taper in width, featuring a first portion with the shortest distance from the contact's outer peripheral surface and a second portion extending from it, allowing for a longer contact distance and reduced aspect ratio in contact holes, which facilitates embedding of contact members to minimize resistance without increasing the device area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of lead-out sections is increased to form contacts, then contact resistance is reduced, but device area increases and storage capacity per chip area decreases
Solution Approach 1:
The contact structure transitions from a planar configuration to a three-dimensional tapered configuration. The contact hole diameter varies along the depth direction, with the upper end having a larger diameter than the lower end. This dimensional change allows the contact to achieve lower resistance through increased effective contact area at the upper end while maintaining compact footprint at the chip surface, thereby resolving the contradiction between reducing contact resistance and minimizing device area.
Solution Approach 2:
The contact hole geometry is modified by changing the diameter parameter along the depth direction. Instead of a uniform cylindrical contact hole, the diameter gradually decreases from the upper end to the lower end, creating a tapered shape. This parameter change optimizes the contact resistance by providing a larger effective contact area at the upper end where the conductive wire connects, while the smaller lower end maintains compact device footprint.
2Reliability
If the contact hole aspect ratio is reduced to facilitate embedding, then contact resistance decreases, but the contact hole dimensions must be increased which may increase device area
Solution Approach 1:
The contact hole is designed with a tapered geometry where the diameter varies along the depth dimension. The upper end has a larger diameter that facilitates easier embedding of the conductive wire, effectively reducing the aspect ratio at the critical upper region. This dimensional variation allows optimal embedding conditions at the upper end while maintaining compact overall dimensions, thus reducing contact resistance without significantly increasing device area.
Solution Approach 2:
Different regions of the contact hole have different diameters tailored to specific functional requirements. The upper end has a larger diameter optimized for conductive wire embedding and electrical contact, while the lower end has a smaller diameter to minimize device footprint. This local differentiation of geometric quality allows the contact to achieve low resistance through improved embedding at the upper region without proportionally increasing the overall device area.
3Ease of manufacture
If the lead-out sections are formed with standard geometry, then manufacturing is simplified, but contact resistance increases and embedding becomes difficult
Solution Approach 1:
The contact hole geometry is modified by changing the diameter parameter along the depth direction to create a tapered shape. The upper end diameter is optimized for easy embedding of conductive wires, providing sufficient clearance and reducing aspect ratio effects that would otherwise hinder embedding. This parameter optimization facilitates manufacturing by improving embeddability without requiring excessive overetching or complex processing, while simultaneously reducing contact resistance through better contact formation.
Data Source
AI summary
According to one embodiment, a memory device includes a substrate, a conductive wire provided above the substrate to extend in a first direction and including an end portion decreases in width toward a distal end, and a contact connected to the conductive wire at least a side surface of the end portion. The end portion includes, in the contact, a first portion having a shortest distance from an outer peripheral surface of the contact and a second portion extending from the first portion and having a distance from the outer peripheral surface of the contact longer than the shortest distance.