Memory Array Fabrication with Conductive Tier Openings
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Solution Overview
Problem
Current memory array fabrication methods face challenges in efficiently forming vertically-stacked memory cells with reliable control circuitry, particularly in maintaining structural integrity and ensuring proper electrical coupling of channel material to conductive tiers.
Innovation Solution
The method involves forming a conductive tier with openings, an insulator tier extending into these openings, and a stack of vertically-alternating insulative and wordline tiers, with channel material strings directly electrically coupled to the conductive tier, utilizing a 'gate-last' or 'replacement-gate' processing approach to create memory cells with charge-blocking and storage regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vertically-stacked memory cells are formed using conventional fabrication methods, then memory array structure is created, but structural integrity and electrical coupling reliability deteriorate
Solution Approach 1:
The conductive tier is formed with openings and the insulator tier is prepared in advance before the channel material strings are formed. This preliminary preparation ensures that when the channel material is deposited, it can be directly coupled to the conductive tier through the pre-formed openings, guaranteeing electrical coupling reliability without requiring complex post-processing alignment steps.
Solution Approach 2:
The insulator tier acts as an intermediary structure that extends into the openings of the conductive tier. This intermediary provides both structural support to prevent delamination and a defined interface for electrical coupling, simplifying the overall fabrication process while maintaining reliability.
2Stability of the object's composition
If insulator material extends into conductive tier openings, then structural anchoring is improved, but manufacturing precision requirements increase
Solution Approach 1:
The insulator tier is formed to extend into the openings of the conductive tier as a preliminary step. This pre-formed insulator structure provides structural anchoring that prevents delamination of the vertically-stacked memory cells. The preliminary formation allows for controlled extension into the openings without requiring high-precision alignment during subsequent processing steps.
Data Source
AI summary
A method used in forming a memory array comprises forming a conductive tier atop a substrate, with the conductive tier comprising openings therein. An insulator tier is formed atop the conductive tier and the insulator tier comprises insulator material that extends downwardly into the openings in the conductive tier. A stack comprising vertically-alternating insulative tiers and wordline tiers is formed above the insulator tier. Strings comprising channel material that extend through the insulative tiers and the wordline tiers are formed. The channel material of the strings is directly electrically coupled to conductive material in the conductive tier. Structure independent of method is disclosed.