SONOS Memory Sidewall Oxide Protection via Spacer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The isotropic nature of wet etching in semiconductor manufacturing leads to lateral etching issues, damaging the top oxide layers in SONOS memory structures, which compromises the stability and performance of memory storage.
Innovation Solution
A method is introduced where a first oxide layer and a silicon oxynitride layer are deposited, followed by dry etching of the silicon oxynitride layer and wet etching of the first oxide layer, with a second oxide layer grown to form a spacer that protects against sidewall oxide loss during subsequent wet processes, ensuring the stability of the memory structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching is used to remove the first oxide layer, then the etching process can be performed with high selectivity and without plasma damage, but lateral etching occurs due to isotropic nature, damaging the top oxide layers and reducing memory stability
Solution Approach 1:
A second oxide layer is grown in advance on the silicon oxynitride layer before the wet etching step. This preliminary action creates a protective barrier that prevents lateral etching damage to the top oxide layers during the subsequent wet etching process, while still allowing the wet etching to effectively remove the first oxide layer.
2Productivity
If wet etching is used to remove the first oxide layer, then the process is simple and effective, but the isotropic etching causes lateral erosion of the top oxide layers, compromising memory storage stability
Solution Approach 1:
The second oxide layer is grown beforehand to provide protective spacers on the sidewalls. This preliminary protective measure allows the wet etching to proceed efficiently without compromising the reliability of the memory structure, as the spacers prevent lateral erosion that would otherwise damage the top oxide layers.
Solution Approach 2:
The second oxide layer acts as an intermediary protective layer between the wet etching process and the top oxide layers. It mediates the interaction by providing a barrier that prevents the harmful lateral etching from reaching the critical memory structure, while allowing the etching process to continue effectively.
3Manufacturing precision
If the second oxide layer is grown early to protect sidewalls, then lateral etching damage is prevented, but the conforming rate and reliability are reduced without proper timing
Solution Approach 1:
The growth timing of the second oxide layer is dynamically adjusted based on the process stage. It is grown at the optimal moment before wet etching to provide protection, and its thickness and growth conditions are optimized to ensure both sidewall protection and high conforming rate, resolving the contradiction between precision and reliability.
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 method effectively prevents film loss and damage to the oxide layers during wet etching, enhancing the stability and performance of the SONOS memory by modifying the growth sequence of the second oxide layer, thereby improving the conforming rate and reliability of the device.
Implementation Method 1
removing the silicon oxynitride layer 13 in the logic area by means of dry etching
Implementation Method 2
removing the first oxide layer 12 in the logic area by means of wet etching
Implementation Method 3
growing a second oxide layer 14 on silicon oxynitride layer 13 and on logic area
Data Source
AI summary
The present invention provides a method for making SONOS memory, comprising the following steps: depositing silicon oxide layer and silicon oxynitride layer in sequence on underlayer; coating a layer of photoresist on the silicon oxynitride layer; removing part of the photoresist and form the logic area; removing silicon oxynitride layer in the logic area; removing the bottom oxide layer in the logic area; growing top oxide layer on the silicon oxynitride layer and logic area; removing the top oxide layer in the logic area; growing gate oxide layer; forming device structure of SONOS and logic area. The present invention can avoid the damage of top oxide layer and lateral etching in wet etching so as to improve the defect-free rate of devices.