Silicon Oxide Plug for Insulating Trench Stray Capacitance
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Solution Overview
Problem
Existing insulating trench structures in semiconductor substrates suffer from high stray capacitance and risk of short-circuits due to thin gate insulator layers and topography of conductive material, leading to manufacturing challenges, especially in deep trench insulation where upper surfaces of trench fill materials are not at the same level.
Innovation Solution
A method involving forming trenches in a semiconductor substrate, coating with insulating layers, filling with doped polysilicon, and creating a silicon oxide plug that protrudes above the substrate surface, reducing stray capacitance and preventing short-circuits by ensuring the oxide plug's lower surface is at the substrate level, thus aligning upper surfaces of fill materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gate insulator layer thickness is reduced to increase transistor performance, then the transistor switching speed is improved, but the risk of short-circuits between gate and conductive material increases
Solution Approach 1:
An oxide plug is formed in advance within the conductive material filling the trench, positioned to extend above the substrate surface. This preliminary structure creates a built-in insulation barrier that prevents short-circuits before they can occur during device operation, allowing the use of thinner gate insulator layers without compromising reliability.
Solution Approach 2:
The oxide plug acts as an intermediary insulating element between the conductive material and the gate structure. This intermediate layer provides electrical isolation, enabling the gate insulator to be made thinner while maintaining adequate insulation and preventing direct contact between conductive material and gate.
2Reliability
If deep trenches are formed to increase isolation effectiveness, then the insulation performance is improved, but the manufacturing complexity and difficulty increase
Solution Approach 1:
The oxide plug is formed within the conductive material filling before final trench depth adjustments are made. This preliminary formation of the insulating element simplifies subsequent manufacturing steps, as the critical insulation function is already established, reducing the overall manufacturing complexity despite the deep trench requirement.
3Reliability
If the upper surfaces of trench fill materials are at different levels to accommodate varying trench depths, then the insulation effectiveness is maintained, but the difficulty of implementing photolithography methods increases
Solution Approach 1:
The oxide plug is formed to extend above the substrate surface in advance, creating a reference level that facilitates subsequent planarization processes. This preliminary elevation of the insulating structure allows for easier achievement of flat upper surfaces across different trench regions, improving photolithography implementation.
Solution Approach 2:
By extending the oxide plug vertically above the substrate surface rather than keeping all materials at substrate level, the invention creates a new dimensional reference plane. This vertical extension allows for better control of surface topology and facilitates photolithography processes that require flat, accessible surfaces.
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 method significantly reduces stray capacitance and prevents short-circuits by maintaining a substantial thermal oxide thickness between conductive materials and gates, while ensuring the upper surfaces of oxide plugs and insulating materials are at the same level, enhancing manufacturing precision and reliability.
Implementation Method 1
performing a thermal oxidation to form said oxide plug from said upper portion
Data Source
AI summary
A method of manufacturing an insulating trench including the successive steps of: a) forming, on a semiconductor substrate, a first masking structure including a layer of a first selectively-etchable material and etching a trench into the substrate; b) forming an insulating coating on the trench walls and filling the trench with doped polysilicon; c) forming a silicon oxide plug penetrating into the trench substantially all the way to the upper surface of the substrate and protruding above the upper surface of the substrate; and d) removing the layer of the first material.