Tunnel Oxide Layer Fabrication via In-Situ Steam Generation
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in improving data retention characteristics without compromising high-speed logic performance, primarily due to limitations in the tunnel oxide layer's quality and thickness, which affects the insulation between the gate and the silicon substrate.
Innovation Solution
A method of fabricating a tunnel oxide layer using an in-situ steam generation process combined with furnace oxidation, where reactive gases penetrate the first oxide layer to form additional oxide layers, resulting in a thicker tunnel oxide stack with optimized thickness and structure, minimizing thermal budget and avoiding nitrogen plasma nitridation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tunnel oxide layer thickness is increased to improve data retention, then data retention characteristics are improved, but high-speed logic performance is compromised
Solution Approach 1:
The tunnel oxide layer is divided into multiple segments: a first oxide layer formed by in-situ steam generation and additional oxide layers formed by furnace oxidation. This segmentation allows each layer to contribute differently to the overall structure, enabling improved data retention through increased total thickness while maintaining interfaces suitable for high-speed logic operation
Solution Approach 2:
Different regions of the oxide structure are given different qualities: the first oxide layer formed by ISSG provides a high-quality interface with the silicon substrate optimized for logic performance, while subsequent oxide layers add thickness for data retention. The reactive gas penetration creates a gradient structure where oxide quality varies through the depth, with better quality near the substrate interface
2Ease of manufacture
If conventional furnace oxidation is used to form the oxide layer, then the process is simple and well-established, but oxide defects occur and data retention is limited
Solution Approach 1:
The invention merges two oxidation approaches: in-situ steam generation (ISSG) and conventional furnace oxidation. The ISSG process forms a high-quality first oxide layer with fewer defects, followed by furnace oxidation to form additional oxide layers. This combination retains the simplicity of conventional processing while significantly improving oxide quality and data retention characteristics
Solution Approach 2:
The first oxide layer is formed by ISSG as a preliminary step before the main furnace oxidation process. This preliminary layer serves as a foundation that prevents defect formation during subsequent oxidation, enabling the furnace process to proceed without generating the same defects that would occur on bare silicon
3Reliability
If nitrogen plasma nitridation is used to enhance oxide properties, then oxide quality is improved, but thermal budget increases and process complexity increases
Solution Approach 1:
The in-situ steam generation process inherently provides nitrogen-free oxidation that self-regulates to form high-quality oxide without requiring additional nitridation steps. The reactive gases (oxygen and hydrogen) penetrate the oxide structure and self-adjust the oxidation process, eliminating the need for separate plasma nitridation equipment and process 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
This approach enhances data retention characteristics of semiconductor memory devices by reducing oxide defects and maintaining high-speed logic performance, suitable for single poly floating gate non-volatile memory applications without modifying the core logic devices.
Implementation Method 1
fabricating on a substrate a first oxide layer by an in-situ-steam-generation process
Implementation Method 2
reactive gases penetrate the first oxide layer and react with the silicon substrate to form at least a first portion of the at least one further oxide layer beneath the first oxide layer
Data Source
AI summary
A method of fabricating a tunnel oxide layer for a semiconductor memory device, the method comprising: fabricating on a substrate a first oxide layer by an in-situ-steam-generation process; and fabricating at least one further oxide layer by a furnace oxidation process, wherein during fabrication of the at least one further oxide layer, reactive gases penetrate the first oxide layer and react with the silicon substrate to form at least a first portion of the at least one further oxide layer beneath the first oxide layer.