Composite Dielectric Film for Memory Metal Gate Etch Protection
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Solution Overview
Problem
The semiconductor industry faces challenges in protecting metal gates during the fabrication of memory devices, particularly in preventing etching damage due to metal precipitates, which can lead to performance issues and yield reduction in flash memory devices like ESF3.
Innovation Solution
A composite dielectric film structure comprising a first layer of dielectric material with good adherence properties and a second layer of higher density material is applied over the metal gates in the peripheral region, providing enhanced protection against etching damage and improving the integrity of the metal gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single layer of dielectric material is used over metal gates, then the structure is simple and easy to manufacture, but the protection against etching damage is insufficient
Solution Approach 1:
The patent applies a composite dielectric film structure consisting of a first dielectric layer with good adherence properties and a second dielectric layer with higher density. This composite structure provides superior protection against etching damage compared to a single dielectric layer, while the layers are designed to work together synergistically - the first layer ensures good adhesion to the metal gate and the second layer provides enhanced etch resistance.
Solution Approach 2:
The dielectric protection film is segmented into multiple functional layers. The first dielectric layer is specifically designed with good adherence properties to bond effectively to the metal gate surface, while the second dielectric layer is designed with higher density to provide superior etching protection. This segmentation allows each layer to optimize its specific function rather than requiring a single material to perform all functions.
2Productivity
If metal gates are exposed during fabrication, then the fabrication process is simpler, but etching damage from metal precipitates occurs leading to yield reduction
Solution Approach 1:
The composite dielectric film structure is formed over the metal gates before subsequent fabrication steps that could cause etching damage. This preliminary protective action prevents metal precipitates from causing etching damage during later processing steps, thereby maintaining high fabrication yield without requiring changes to the metal gate formation process itself.
Solution Approach 2:
The composite dielectric film acts as an intermediary protective layer between the metal gates and the harmful etching environment. The first dielectric layer provides good adhesion to the metal gate surface, while the second dielectric layer with higher density provides a barrier against etching damage from metal precipitates, allowing the metal gates to remain exposed during fabrication without suffering damage.
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 composite dielectric film structure effectively prevents etching damage to the metal gates, enhancing the performance and yield of memory devices by maintaining the integrity of the metal gate structures during fabrication.
Implementation Method 1
a first layer of dielectric material with good adherence properties
Implementation Method 2
providing enhanced protection against etching damage
Data Source
AI summary
A semiconductor memory device and method of making the same are disclosed. The semiconductor memory device includes a substrate that includes a memory region and a peripheral region, a transistor including a metal gate located in the peripheral region, a composite dielectric film structure located over the metal gate of the transistor, the composite dielectric film structure including a first dielectric layer and a second dielectric layer over the first dielectric layer, where the second dielectric layer has a greater density than a density of the first dielectric layer, and at least one memory cell located in the memory region. The composite dielectric film structure provides enhanced protection of the metal gate against etching damage and thereby improves device performance.