Ammonia Pre-treatment for Memory Cell Insulating Layer
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Solution Overview
Problem
The existing manufacturing processes for nonvolatile memory cells often result in erase failures due to the formation of unintentional charge traps at the interface between the silicon oxide and silicon nitride layers, leading to failed cells that are either scrapped or require rework, thereby reducing yield and increasing costs.
Innovation Solution
A method involving pre-treating the insulating layer in a substantially ammonia atmosphere for more than 5 minutes to form a pre-treated layer, followed by depositing a silicon nitride layer, which reduces the formation of charge traps and enhances the uniformity of the interface, thereby minimizing erase failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standardized voltage is applied to erase charge in memory cells, then the erase function works for most cells, but some cells fail to erase and are designated as failed cells
Solution Approach 1:
The patent applies ammonia pre-treatment to the silicon oxide layer before depositing the silicon nitride layer. This preliminary action modifies the interface properties in advance, preventing the formation of charge traps that would later cause erase failures, thereby improving both reliability and yield
Solution Approach 2:
The patent changes the chemical composition and physical properties of the silicon oxide layer by exposing it to ammonia atmosphere. This parameter change creates a modified interface that reduces charge trap formation, leading to fewer erase failures and improved cell reliability
2Reliability
If failed memory cells are scrapped or subjected to rework, then the number of functional cells increases, but the production cost increases and yield decreases
Solution Approach 1:
By performing ammonia pre-treatment during the initial fabrication process, the patent prevents charge trap formation before it can cause failures. This eliminates the need for costly rework or scrapping of failed cells, improving both reliability and manufacturing efficiency
Solution Approach 2:
The patent converts the potentially harmful interface between silicon oxide and silicon nitride into a beneficial structure by using ammonia treatment. This transforms what would normally be a charge trap-prone interface into a reliable barrier, eliminating failures without additional rework costs
3Productivity
If the interface between silicon oxide and silicon nitride layers is formed without pre-treatment, then the fabrication process is simpler and faster, but charge traps form at the interface causing erase failures
Solution Approach 1:
The patent modifies the chemical parameters of the silicon oxide layer through ammonia exposure, creating a nitrogen-rich interface that prevents charge trap formation. This parameter change maintains fabrication efficiency while dramatically improving charge dissipation capability
Solution Approach 2:
The ammonia atmosphere acts as an intermediary that mediates the interface formation between silicon oxide and silicon nitride. It creates a transitional layer with improved properties that prevents charge trap formation without significantly extending the fabrication process
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 ammonia pre-treatment significantly reduces erase failures in memory cells by eliminating or preventing the formation of charge traps, allowing for more efficient charge dissipation and improving the reliability of memory cell fabrication.
Implementation Method 1
pre-treating an insulating layer in a substantially ammonia atmosphere for a period of more than 5 minutes to thereby form a pre-treated insulating layer
Implementation Method 2
depositing a silicon nitride layer on the pre-treated insulating layer
Data Source
AI summary
A method of manufacturing a memory cell 200. The method comprises forming a memory stack 215. Forming the memory stack includes pre-treating an insulating layer 210 in a substantially ammonia atmosphere for a period of more than 5 minutes to thereby form a pre-treated insulating layer 310. Forming the memory stack also includes depositing a silicon nitride layer on the pre-treated insulating layer.