3D Memory Metal Contacts With Liner Removal for Stress Relief
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Solution Overview
Problem
Conventional 3D memory devices experience stress issues with metal contacts, leading to weakness, cracking, and bending, which affect the alignment and connectivity of conductive structures, and result in increased parasitic capacitance.
Innovation Solution
A stress mitigation process involving a non-conformal liner deposition on dielectric walls, followed by metal filling and liner removal to create a stress-relieved metal contact structure, using materials like carbon or carbon with boron, and titanium nitride or tungsten silicide as metal barriers, to reduce stress and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal contacts are formed in conventional 3D memory devices, then electrical connectivity is achieved, but stress accumulation causes weakness, cracking, and bending of the metal contacts
Solution Approach 1:
A liner is introduced as an intermediary layer between the dielectric wall and the metal contact. The liner has a composition correlated to the metal composition, creating a gradual transition that reduces stress concentration at the interface. This intermediary layer prevents direct contact between the metal and dielectric, eliminating the stress mismatch that causes cracking and bending.
Solution Approach 2:
The stress state of the metal contact is changed by controlling the liner composition to be correlated with the metal composition. This parameter change in material composition creates a stress-matched interface, transforming the stress profile from high-stress concentrated at sharp interfaces to a more distributed and manageable stress state throughout the contact structure.
2Reliability
If conventional metal contact structures are used, then connectivity is established, but parasitic capacitance increases due to stress-induced structural issues
Solution Approach 1:
The liner acts as a mediator that prevents stress-induced deformation of the metal contact. By eliminating bending and cracking through the stress-matched interface, the physical integrity of the contact is maintained, which in turn reduces unwanted capacitive coupling between adjacent conductive structures that would otherwise be distorted by stress.
3Ease of manufacture
If metal contacts are formed without stress mitigation, then manufacturing is simpler, but structural integrity deteriorates due to stress-induced cracking and bending
Solution Approach 1:
The liner is formed in advance before the metal contact is deposited. This preliminary action of creating the stress-matched interface layer beforehand ensures that when the metal is subsequently formed, it inherits the stress-relieved structure, preventing alignment issues and structural defects without requiring complex post-processing steps.
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 solution effectively reduces stress on metal contacts, enhances their reliability, and minimizes parasitic capacitance, leading to improved structural integrity and operational efficiency in 3D memory devices.
Implementation Method 1
the liner having a liner composition correlated to the metal composition such that removal of the liner reduces stress on the metal composition
Data Source
AI summary
A variety of applications can include apparatus having a memory device structured with a three-dimensional array of memory cells and one or more vertical metal contacts extending through levels of the memory device, where the one or more vertical metal contacts are formed with reduced stress. Each of the one or more vertical metal contacts can be constructed by forming a liner on walls of an opening in a dielectric, where the opening extends through the levels for the memory device, and forming a metal composition adjacent the liner and filling the opening with the metal composition. The liner can be removed from at least a portion of the walls of the dielectric, where the liner has a composition correlated to the metal composition such that removal of the liner reduces stress on the metal composition.