Capacitor With Extended Nitride Dielectric Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional IC capacitors with ONO dielectric structures suffer from defects and leakage current issues due to concentrated electric fields at the lateral edges, leading to failures, especially under high voltage applications.
Innovation Solution
A capacitor structure is developed with a nitride layer extending beyond the lateral edge of the upper poly layer, forming an oxide-nitride-oxide (ONO) structure, and a spacer is used to protect the nitride layer from etching, ensuring it extends laterally beyond the edge, thereby reducing field concentration and potential failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dielectric layer is confined within the lateral edges of the conductive plates, then the capacitor structure is compact and manufacturing is simpler, but electric fields concentrate at the edges causing defects and leakage current
Solution Approach 1:
The dielectric layer is configured with different lateral extents in different regions: within the conductive plates it is confined to maintain compactness, but beyond the lateral edges it extends to prevent field concentration. This local variation in dielectric coverage resolves the contradiction by applying different quality requirements to different spatial zones of the capacitor structure.
Solution Approach 2:
The solution extends the dielectric layer configuration into the lateral dimension beyond the conductive plate edges, rather than keeping it strictly confined. This dimensional extension creates an overlap region that distributes electric fields laterally, preventing concentration at sharp edges while maintaining overall structural compactness.
2Ease of manufacture
If the nitride layer is etched completely at the edges, then the manufacturing process is simpler, but the breakdown voltage decreases and failures occur at lower voltages
Solution Approach 1:
The nitride layer is selectively removed (taken out) from specific regions where it is not needed - specifically from areas beyond the conductive plate edges where it would cause field concentration problems. This selective extraction maintains manufacturing simplicity while preserving the breakdown voltage by retaining the nitride layer in critical regions.
Solution Approach 2:
The etching process parameters are modified to achieve selective removal of the nitride layer. By controlling etch depth, etch selectivity, and etch conditions, the process removes nitride from edge regions while preserving it in central regions, thus changing the spatial distribution parameter of the nitride layer to resolve the contradiction between manufacturing simplicity and breakdown voltage.
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 design enhances the breakdown voltage while maintaining capacitance, reducing the likelihood of failures and improving the reliability of the capacitors by distributing electric fields more evenly.
Implementation Method 1
a terminal edge of the dielectric layer extends beyond a lateral edge of the upper conducting layer... distributing electric fields more evenly
Implementation Method 2
Silicon nitride has a high dielectric constant, and may thus be used to increase the breakdown voltage of the capacitor, while keeping the capacitance the same
Data Source
AI summary
A capacitor structure may include a lower conducting layer (e.g., poly 1 layer) and an upper conducting layer (e.g., overlying poly 2 layer), which define an anode and cathode, and a dielectric layer (e.g., an ONO layer stack) located between the upper conducting layer and the lower conducting layer, wherein a portion of the dielectric layer (e.g., at least the nitride layer of the ONO layer stack) extends beyond a lateral edge of the upper conducting layer. A method forming such capacitor structure may utilize a spacer adjacent the lateral edge of the upper conducting layer and over the first portion of the dielectric layer, performing an etch to remove a first portion of the dielectric layer but protect a second portion located below the spacer and extending laterally beyond an edge of the upper conducting layer.