Trench Isolation Filling with TEOS and Spin-On Dielectric
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Solution Overview
Problem
Conventional trench isolation methods in integrated circuit fabrication face challenges with void formation, inadequate filling, and material density in deep and narrow trenches, particularly due to the use of high density plasma deposited oxides and spin-on-dielectrics, which require additional processing steps and result in suboptimal isolation.
Innovation Solution
The method involves forming first and second isolation trenches with varying dimensions, depositing silicon dioxide using TEOS within both trenches, and applying a spin-on-dielectric only over the second trench to fill and densify it, while ensuring the first trench is not filled, thereby addressing void formation and material density issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high density plasma deposited oxides are used to fill isolation trenches, then trench filling is achieved, but void formation occurs within deep and narrow trenches
Solution Approach 1:
The patent changes the deposition parameters by switching from high density plasma deposited oxides to TEOS (tetraethyl orthosilicate) chemical vapor deposition. This parameter change allows for better conformal deposition within deep and narrow trenches without causing void formation, while still achieving adequate fill. The TEOS process provides improved flow characteristics that enable complete trench filling without the voiding problems associated with plasma deposited materials.
Solution Approach 2:
The patent employs a sacrificial oxidation barrier layer (silicon nitride) that is deposited within all trenches to prevent unwanted oxidation during steam anneal, but is then selectively removed from first trenches after oxidation. This disposable layer protects underlying material during processing and is subsequently discarded where no longer needed, enabling selective oxidation without permanent barrier structures in all areas.
2Manufacturing precision
If spin-on-dielectric is used to fill isolation trenches, then good conformal deposition is achieved, but material density is insufficient
Solution Approach 1:
The patent merges two different deposition approaches: TEOS chemical vapor deposition for the initial insulative layer and spin-on-dielectric for subsequent filling. The TEOS process provides a dense, conformal base layer that adheres well to trench walls, while the spin-on-dielectric material fills remaining volume. This combination achieves both good conformal deposition characteristics and adequate material density by leveraging the strengths of each method.
Solution Approach 2:
The patent creates a composite trench fill structure consisting of multiple materials: TEOS-deposited silicon dioxide as the primary insulative layer, spin-on-dielectric material for additional filling, and selective oxidation of underlying semiconductive material. This composite approach allows each material to contribute its advantageous properties - TEOS provides density and conformality, spin-on-dielectric provides fill volume, and oxidation provides electrical isolation - achieving overall trench isolation with both good conformal deposition and sufficient material density.
3Manufacturing precision
If deposition thickness is increased to adequately fill deep trenches, then trench filling is improved, but processing time increases
Solution Approach 1:
The patent changes the deposition methodology from requiring thick deposits to achieving adequate fill with thinner, more conformal layers. By using TEOS chemical vapor deposition, the process achieves uniform coating at lower thicknesses that adequately fills deep trenches without requiring excessive deposition time. The improved flow characteristics of TEOS allow complete trench penetration and filling at reduced thickness compared to conventional plasma deposited materials.
4Quantity of substance
If steam anneal is used to densify deposited silicon dioxide, then material density is improved, but unwanted oxide formation occurs on underlying material
Solution Approach 1:
The patent applies preliminary anti-action by depositing an oxidation barrier layer (silicon nitride) within all trenches before steam anneal to prevent unwanted oxidation of underlying semiconductive material. This barrier is then selectively removed from first trenches after the anneal process, allowing the underlying material in those trenches to be oxidized for electrical isolation while protecting other areas. The preliminary barrier deposition prevents the harmful oxidation effect during the beneficial densification process.
Solution Approach 2:
The oxidation barrier layer serves as a sacrificial, disposable component that protects underlying material during steam anneal and is then selectively removed where oxidation is desired. This temporary barrier enables the densification process to proceed without permanent unwanted oxide formation in all areas, as the barrier is discarded only where electrical isolation is needed.
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 effectively fills and densifies the second trench, reducing seam formation and material excess, improving trench isolation quality and reducing processing time by optimizing the deposition and removal of insulative materials.
Implementation Method 1
The insulative layer comprises silicon dioxide deposited from flowing TEOS to the first and second isolation trenches
Implementation Method 2
a spin-on-dielectric is deposited over the silicon dioxide deposited from flowing the TEOS within the second isolation trench
Implementation Method 3
The spin-on-dielectric is densified within the second isolation trench
Data Source
AI summary
First and second isolation trenches are formed into semiconductive material of a semiconductor substrate. The first isolation trench has a narrowest outermost cross sectional dimension which is less than that of the second isolation trench. An insulative layer is deposited to within the first and second isolation trenches effective to fill remaining volume of the first isolation trench within the semiconductive material but not that of the second isolation trench within the semiconductive material. The insulative layer comprises silicon dioxide deposited from flowing TEOS to the first and second isolation trenches. A spin-on-dielectric is deposited over the silicon dioxide deposited from flowing the TEOS within the second isolation trench within the semiconductive material, but not within the first isolation trench within the semiconductive material. The spin-on-dielectric is deposited effective to fill remaining volume of the second isolation trench within the semiconductive material. The spin-on-dielectric is densified within the second isolation trench.