STI Local Oxidation to Suppress Cone Defects in Polysilicon Passives
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Solution Overview
Problem
Defects in shallow trench isolation (STI) structures, such as cone defects caused by nitride particles, can lead to oxide stress failures in polysilicon resistors or capacitors, affecting the reliability of semiconductor components.
Innovation Solution
The method involves forming a shallow trench isolation (STI) structure on a semiconductor surface layer, oxidizing the side of the STI structure, and subsequently forming a doped polysilicon structure on the oxidized side, which reduces the height of cone defects and increases the gap distance between the polysilicon structure and the silicon in the indent, thereby enhancing breakdown voltage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If STI trench etching is performed, then isolation structure is formed, but cone defects are created due to remaining nitride particles
Solution Approach 1:
A pad oxide layer is formed on the semiconductor surface before trench etching to protect against cone defects. The pad oxide layer is subsequently removed after etching, having served its protective function during the critical etching process.
Solution Approach 2:
The patent converts the harmful effect of remaining nitride particles (which cause cone defects) into a beneficial process by using the pad oxide layer as a sacrificial protective element. The nitride particles that would normally cause defects are instead allowed to remain, as their harmful effect is prevented by the oxide protection layer.
2Ease of manufacture
If cone defects are present in STI structure, then polysilicon resistors or capacitors can be formed, but oxide stress failures occur
Solution Approach 1:
The semiconductor surface is oxidized before forming the polysilicon structures to create a protective oxide layer. This preliminary oxidation prevents oxide stress failures by ensuring a robust oxide foundation exists before the polysilicon components are deposited.
Solution Approach 2:
The oxidation process changes the physical and chemical parameters of the semiconductor surface, creating a more stable and stress-resistant oxide layer that can withstand the subsequent polysilicon fabrication process without failing.
3Manufacturing precision
If additional masks or processing steps are added to prevent cone defects, then manufacturing precision improves, but process complexity increases
Solution Approach 1:
The pad oxide formation step is merged with the existing trench etching process flow, and the surface oxidation is combined with the polysilicon fabrication sequence. These protective measures are integrated into standard process steps rather than requiring separate dedicated processes.
Solution Approach 2:
The pad oxide layer serves multiple functions: it protects during trench etching, defines etch boundaries, and can be used as a sacrificial layer. The oxidation process similarly serves both defect prevention and surface preparation functions, reducing the need for separate specialized process steps.
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 breakdown voltage performance of passive components without adding additional masks or processing steps, reducing the likelihood of oxide breakdown and enhancing the reliability of semiconductor components.
Implementation Method 1
performing an oxidation process using the mask to oxidize silicon in an indent in the dielectric material of the STI structure
Data Source
AI summary
A method of manufacturing an electronic device includes forming a shallow trench isolation (STI) structure on or in a semiconductor surface layer and forming a mask on the semiconductor surface layer, where the mask exposes a surface of a dielectric material of the STI structure and a prospective local oxidation of silicon (LOCOS) portion of a surface of the semiconductor surface layer. The method also includes performing an oxidation process using the mask to oxidize silicon in an indent in the dielectric material of the STI structure and to grow an oxide material on the exposed LOCOS portion of the surface of the semiconductor surface layer.