Shallow Trench Isolation with Region-Specific Thickness Control

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Solution Overview

Problem

Current shallow trench isolation (STI) techniques in semiconductor manufacturing face challenges in optimizing electrical isolation for different device regions with varying functions, as existing methods do not adequately address the need for tailored isolation thicknesses to prevent leakage currents and enhance device performance.

Innovation Solution

The method involves creating shallow trench isolations (STIs) with varying thicknesses by etching trenches of different depths and filling them with dielectric materials, followed by planarization, to provide tailored electrical isolation for different semiconductor device regions, allowing for optimized device characteristics such as device dimensions, driving currents, and threshold voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If uniform thickness isolation structures are used for all device regions, then manufacturing process is simplified, but electrical leakage prevention is insufficient for different device functions

Engineering Contradiction:

Improveelectrical isolation effectivenessVSAvoidisolation structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements isolation structures with different thicknesses tailored to specific device regions. First isolation structures are formed with a first thickness for logic device regions, while second isolation structures are formed with a second thickness for memory device regions. This local differentiation optimizes electrical isolation effectiveness for each device type's specific requirements without requiring complete redesign of the entire isolation system.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If trenches of different depths are etched to achieve varying isolation thicknesses, then device performance is optimized, but manufacturing process complexity increases

Engineering Contradiction:

Improveisolation thickness precisionVSAvoidtrench etching process complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent divides the isolation formation process into separate stages: first trenches are etched to a first depth and filled with dielectric material to form first isolation structures, then second trenches are etched to a second depth and filled with dielectric material to form second isolation structures. This segmentation allows each trench etching step to be optimized independently for its specific depth requirement, improving manufacturing precision while managing process complexity through modular processing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary trench etching and dielectric filling to establish the first isolation structures before proceeding to create the second isolation structures. This preliminary action ensures that the first isolation structures are already in place with precise thickness control, providing a stable foundation for subsequent processing steps and enabling better overall manufacturing precision.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If thicker isolation structures are used to prevent leakage currents, then electrical isolation is improved, but device dimensions and performance characteristics are compromised

Engineering Contradiction:

Improveleakage current preventionVSAvoiddevice dimensions

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent applies different isolation thicknesses to different device regions based on their specific electrical isolation requirements. Logic device regions receive first isolation structures with a first thickness optimized for their leakage prevention needs, while memory device regions receive second isolation structures with a second thickness optimized for their requirements. This prevents the need to use uniformly thick isolation structures that would unnecessarily compromise device dimensions in regions where thinner isolation is sufficient.

Inventive Principle:

Principle #3Local quality

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 optimized electrical isolation for various semiconductor devices, reducing leakage currents and improving device performance by providing suitable isolation thicknesses for different device regions, such as logic, memory, and CMOS image sensor regions.

Implementation Method 1

The trenches are filled with a dielectric material. The dielectric material helps to reduce electrical current leakage between the semiconductor devices.

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Data Source

PatentUS11923235B2Method for forming semiconductor device having isolation structures with different thicknesses

Publication Date: 2024.03.05 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes forming a first trench and a second trench in a semiconductor substrate; forming a first mask over the semiconductor substrate, wherein the first mask is disposed in a first portion of the first trench and exposes the second trench and a second portion of the first trench; after forming the first mask, deepening the second trench and the second portion of the first trench; after deepening the second trench and the second portion of the first trench, removing the first mask; and after removing the first mask, filling a dielectric material in both the first and second trenches.