Buried Gate Semiconductor Device Stress Management
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Solution Overview
Problem
The mechanical stress caused by nitride films in buried gate structures of semiconductor devices deteriorates cell-transistor characteristics, particularly refresh characteristics, in semiconductor memory devices.
Innovation Solution
A semiconductor device with a buried gate structure that includes a recess with multiple capping insulation films: a first silicon nitride film with a higher nitrogen ratio, a partially oxidized oxide film, and a third silicon nitride film with nitrogen implantation, which reduces mechanical stress by adjusting the silicon-to-nitrogen ratio and filling the recess.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitride film is used as a capping insulation film in a buried gate structure, then gate isolation is achieved, but mechanical stress deteriorates cell-transistor characteristics
Solution Approach 1:
The single nitride film capping insulation layer is divided into multiple layers with different materials and compositions. The patent employs a multi-layer structure including silicon nitride films with varying nitrogen ratios and oxide films, where each layer contributes differently to stress management while collectively providing gate isolation functionality.
Solution Approach 2:
The patent changes the compositional parameters of the capping insulation films by using silicon nitride films with different nitrogen ratios (higher and lower than standard Si3N4) and incorporating oxide films. This parameter variation allows control over the mechanical stress characteristics of each layer, enabling stress reduction while maintaining isolation properties.
2Object-affected harmful factors
If the nitrogen ratio in silicon nitride film is increased, then mechanical stress is reduced, but film composition control becomes more complex
Solution Approach 1:
Instead of attempting to control nitrogen ratio in a single film, the patent segments the capping insulation into multiple films with different nitrogen ratios. This allows each layer to be optimized independently, with higher nitrogen ratio films providing stress reduction and lower nitrogen ratio films providing other functional benefits, thereby simplifying the overall control strategy.
Solution Approach 2:
The patent creates a composite capping insulation structure combining silicon nitride films with different nitrogen ratios and oxide films. This composite approach leverages the complementary properties of each material, where the combination achieves stress reduction functionality that would be difficult to obtain with a single uniform material composition.
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 solution effectively improves refresh characteristics by reducing mechanical stress and enhancing the performance of semiconductor devices by adjusting the composition of the capping insulation films.
Implementation Method 1
configured to reduce mechanical stress caused by a nitride film by subtracting the volume of the nitride film from a capping insulation film formed over a buried gate
Implementation Method 2
The second capping insulation film may include an oxide film in which the first capping insulation film is partially oxidized
Implementation Method 3
a third capping insulation film formed over the second capping insulation film so as to fill the recess
Implementation Method 4
a third silicon nitride film with nitrogen implantation, which reduces mechanical stress by adjusting the silicon-to-nitrogen ratio
Data Source
AI summary
An embodiment of the semiconductor device includes a recess formed in an active region, a gate buried in a lower part of the recess, a first capping insulation film formed over the gate, a second capping insulation film formed over the first capping insulation film, and a third capping insulation film formed over the second capping insulation film. In the semiconductor device including the buried gate, mechanical stress caused by a nitride film can be reduced by reducing the volume of a nitride film in a capping insulation film formed over a buried gate, and the ratio of silicon to nitrogen of the nitride film is adjusted, so that mechanical stress is reduced, resulting in improvement of operation characteristics of the semiconductor device.