SOI Substrate Buried Layers for Backside Bias Elimination

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Solution Overview

Problem

Silicon-on-insulator (SOI) semiconductor devices face the backside bias effect, which affects the breakdown voltage of metal-oxide-semiconductor field-effect transistors, requiring additional circuitry to minimize its impact.

Innovation Solution

Implanting an n-type buried layer and a p-type buried layer in the silicon-on-insulator substrates, separated by a distance, to eliminate the backside bias effect without using additional masks or circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional circuitry is added to minimize the backside bias effect, then the breakdown voltage stability is improved, but the device complexity increases

Engineering Contradiction:

Improvebreakdown voltage stabilityVSAvoidadditional circuitry

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the harmful backside bias effect by removing the vulnerable oxide layer and replacing it with a buried layer structure that actively compensates for bias effects. The buried layer is separated from the surface oxide, isolating the harmful electrical influence while maintaining mechanical support.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The buried layer acts as an intermediary element between the substrate and the active device region. It mediates the electrical field distribution, providing a transition zone that prevents direct coupling of backside bias to the transistor channel, thereby stabilizing breakdown voltage without complex circuitry.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If additional masks and circuitries are used to address backside bias, then the breakdown voltage control is improved, but the manufacturing process complexity increases

Engineering Contradiction:

Improvebreakdown voltage controlVSAvoidprocess complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The buried layer is formed in advance during the substrate preparation stage, before device fabrication begins. This preliminary action establishes the electrical compensation mechanism early in the process, eliminating the need for additional masks and processing steps during subsequent device fabrication.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent merges the backside bias compensation function with the substrate structure itself by integrating the buried layer into the substrate architecture. This combination eliminates the need for separate compensation circuitries and reduces the number of discrete manufacturing steps.

Inventive Principle:

Principle #5Merging (Combining)

3Loss of energy

If the oxide layer is made thinner to reduce parasitic capacitance, then the power efficiency is improved, but the backside bias effect becomes more significant

Engineering Contradiction:

Improveparasitic capacitanceVSAvoidbackside bias sensitivity

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent converts the harmful backside bias effect into a beneficial compensation mechanism. The buried layer is designed to generate an opposing electrical field that counteracts the backside bias, transforming what was previously a detrimental effect into a useful compensation feature that allows thin oxide operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the electrical parameters of the substrate by introducing a doped buried layer with specific conductivity and depth. This parameter modification alters the electrical field distribution, reducing the coupling between backside voltage and device operation, thereby enabling thin oxide designs with reduced parasitic capacitance while maintaining immunity to backside bias.

Inventive Principle:

Principle #35Parameter changes

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 increases the breakdown voltage and eliminates the backside bias effect, enhancing the performance of SOI semiconductor devices without the need for extra implants or additional circuitry.

Implementation Method 1

an n-type buried layer and a p-type buried layer are implanted in the silicon-on-insulator substrates

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Data Source

PatentUS9978867B1Semiconductor substrate structures, semiconductor devices and methods for forming the same

Publication Date: 2018.05.22 VANGUARD INTERNATIONAL SEMICONDUCTOR CORPORATION

AI summary

A semiconductor substrate structure includes a substrate having a first conductivity type, an oxide layer disposed on the substrate, and a semiconductor layer disposed on the oxide layer. The semiconductor substrate structure also includes a first buried layer disposed in the semiconductor layer, having a second conductivity type opposite to the first conductivity type. The semiconductor substrate structure further includes a second buried layer disposed in the semiconductor layer and above the first buried layer, having the first conductivity type, wherein the first buried layer and the second buried layer are separated by a distance.