HDP Oxide Cap Layer for Nonvolatile Memory Gate Protection
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Solution Overview
Problem
The shrinking critical dimension of nonvolatile memory cells makes it difficult to form a sufficient cap layer using traditional thermal oxidation processes, leading to insufficient protection of the control gate and increased resistivity, which hinders device integration and quality.
Innovation Solution
A high-density plasma (HDP) deposition process is used to form an oxide layer on the control gate, allowing for the creation of a cap layer with sufficient thickness, independent of the memory cell's critical dimension, and enabling the use of metal materials for the control gate while maintaining low resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal oxidation process is used to grow oxide cap layer on control gate, then the process is simple and well-established, but the cap layer thickness becomes insufficient when critical dimension shrinks
Solution Approach 1:
The patent changes the deposition process parameters from thermal oxidation to HDP (high-density plasma) deposition. This parameter change allows the cap layer thickness to be decoupled from the critical dimension scaling, enabling sufficient cap layer thickness (e.g., 600 Å) to be achieved even as device dimensions shrink, thereby resolving the technical contradiction between maintaining cap layer thickness and reducing critical dimension.
2Reliability
If metal materials are used to replace polysilicon for control gate to reduce resistivity, then resistivity problem is solved, but forming sufficient cap layer becomes more difficult
Solution Approach 1:
The patent changes the deposition method parameter from thermal oxidation to HDP deposition. This parameter change enables the formation of sufficient cap layers on metal control gates, overcoming the limitation that metal surfaces do not oxidize well through traditional thermal processes. The HDP process parameters are optimized to deposit oxide layers effectively on metal surfaces, thereby resolving both the resistivity requirement and the cap layer formation challenge.
3Productivity
If continuous device integration improvement is pursued by shrinking memory cell dimension, then device integration increases, but cap layer thickness becomes insufficient
Solution Approach 1:
The patent implements a parameter change in the deposition process from thermal oxidation to HDP deposition. This enables the decoupling of device dimension scaling from cap layer thickness, allowing continuous device integration improvement through dimension shrinking while maintaining sufficient cap layer thickness for quality assurance, thereby resolving the contradiction between productivity improvement and manufacturing precision.
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 HDP process ensures a cap layer of adequate thickness is formed, enhancing the quality and integration of nonvolatile memory cells by providing effective protection and reducing resistivity, even as device dimensions shrink.
Implementation Method 1
performing a HDP deposition process to form an HDP oxide layer on the top surface of the control gate
Data Source
AI summary
A method of fabricating a nonvolatile memory cell includes providing a substrate with a trench, with a sidewall where a tunnel oxide layer and a floating gate are successively formed, forming a control gate in the trench, performing a high density plasma deposition process to form an HDP oxide layer on the top surface of control gate.