Trench Isolation Formation via Alternating Etch and Fill

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Solution Overview

Problem

As integrated circuit sizes decrease, the narrow widths and increased depths of trench isolation features lead to structural issues such as mask feature toppling and bending due to fill material stresses, limiting the ability of photolithographic techniques to reliably form features below a certain pitch.

Innovation Solution

The method involves etching first trench lines into a semiconductor substrate, filling them with isolation material, and then etching alternating second trench lines, allowing for a wider expanse between trenches to reduce stress during fill and prevent bending, while using pitch multiplication techniques to enhance feature resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If trench widths are reduced and depths are increased to accommodate higher device density, then device packing density is improved, but mask feature stability deteriorates due to fill material stresses causing toppling and bending

Engineering Contradiction:

Improvedevice packing densityVSAvoidmask feature stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent divides the trench isolation formation process into multiple stages: first forming shallow trenches with masks, filling them with isolation material, then forming deeper trenches in the remaining spaces. This segmentation allows each stage to be optimized independently, preventing mask toppling by limiting trench depth in any single step while achieving high overall device density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary trench formation and isolation material deposition before completing the full trench depth. By pre-forming isolation structures in shallower regions first, the method creates a stable foundation that prevents mask toppling during subsequent deeper trench formation, while still achieving the required high device packing density.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If photolithographic techniques are used to pattern features, then manufacturing capability is maintained, but minimum feature pitch is limited below which features cannot be reliably formed

Engineering Contradiction:

Improvemanufacturing capabilityVSAvoidminimum feature pitch

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent transitions from two-dimensional photolithographic patterning to three-dimensional trench formation and fill processes. By utilizing vertical dimension (trench depth) and alternating trench formation sequences, the method achieves pitch multiplication, forming features at pitch dimensions below the photolithographic minimum while maintaining manufacturing capability through established etching and deposition techniques.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If pitch multiplication techniques are used to extend photolithographic capabilities, then minimum pitch limitation is overcome, but process complexity increases

Engineering Contradiction:

Improveminimum pitch capabilityVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges multiple trench formation and fill operations into an integrated process sequence. By combining alternating trench etching, isolation material deposition, and mask removal steps into a unified pitch multiplication methodology, the patent achieves extended pitch capability while managing process complexity through systematic integration of individual process modules.

Inventive Principle:

Principle #5Merging (Combining)

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 enables the formation of trench isolation structures with minimum widths of 35 nanometers or less, reducing the susceptibility to bending and improving the reliability of feature formation beyond the limitations of conventional photolithographic techniques.

Implementation Method 1

etching first trench lines into semiconductive material of a semiconductor substrate

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

filling them with isolation material

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS7846812B2Methods of forming trench isolation and methods of forming floating gate transistors

Publication Date: 2010.12.07 MICRON TECHNOLOGY INC

AI summary

A method of forming trench isolation includes etching first trench lines into semiconductive material of a semiconductor substrate. First isolation material is formed within the first trench lines within the semiconductive material. After forming the first isolation material within the first trench lines, second trench lines are etched into semiconductive material of the substrate between the first trench lines such that the first trench lines and second trench lines alternate. Second isolation material is formed within the second trench lines within the semiconductive material. Alternate and additional aspects are contemplated.