Polysilicon Oxidation Control for Semiconductor Isolation
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Solution Overview
Problem
Highly integrated semiconductor devices face reliability issues due to inadequate device isolation structures, which can lead to leakage currents and reduced electrical characteristics, particularly when polysilicon layers are oxidized without a preceding oxide layer, causing interface traps and charge leakage.
Innovation Solution
A method involving the formation of a first oxide layer using atomic layer deposition, followed by a polysilicon layer and a second oxide layer through oxidation, with a gap-fill layer to fill recess regions, ensuring that a portion of the polysilicon remains between the oxide layers, thereby preventing charge leakage and enhancing device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polysilicon layer is oxidized directly without a preceding oxide layer, then oxidation process is simplified, but interface traps are generated and charge leakage occurs
Solution Approach 1:
A first oxide layer is formed on the substrate before forming the polysilicon layer. This preliminary oxide layer prevents direct contact between the polysilicon and the substrate during oxidation, eliminating interface traps and charge leakage while maintaining process simplicity.
2Reliability
If complete oxidation of polysilicon layer is performed, then oxide layer coverage is improved, but polysilicon consumption increases and device characteristics deteriorate
Solution Approach 1:
The oxidation process is controlled to create different oxidation states in different regions. The first oxide layer provides complete coverage, while the second oxide layer formed by selective oxidation of the polysilicon layer creates a gradient structure that maintains adequate coverage without excessive polysilicon consumption.
Solution Approach 2:
Instead of complete oxidation of the polysilicon layer, a controlled partial oxidation is performed to form a second oxide layer. This partial action provides sufficient oxide coverage for device reliability while preserving the polysilicon layer thickness and active region area.
3Device complexity
If recess regions are not filled, then manufacturing complexity is reduced, but leakage currents increase and electrical characteristics worsen
Solution Approach 1:
Recess regions are filled with a gap-fill layer before final device assembly. This preliminary filling action prevents leakage currents and improves electrical characteristics without adding significant manufacturing complexity, as the filling is performed as an integrated step in the fabrication sequence.
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 approach improves the electrical characteristics of semiconductor devices by reducing charge leakage and maintaining the original active region area, increasing the reliability of semiconductor devices by controlling the oxidation of polysilicon and using a gap-fill layer to fill recess regions effectively.
Implementation Method 1
the first oxide layer may be formed by using an atomic layer deposition process
Implementation Method 2
forming a second oxide layer by oxidizing the polysilicon layer
Data Source
AI summary
A method of manufacturing a semiconductor device includes forming a plurality of recess regions on an upper surface of a substrate, forming a first oxide layer in the recess regions, forming a polysilicon layer on the first oxide layer, forming a second oxide layer by oxidizing the polysilicon layer, and forming a gap-fill layer on the second oxide layer to fill the recess regions, wherein at least a portion of the polysilicon layer remains between the first oxide layer and the second oxide layer after forming the second oxide layer.