Semiconductor Device Deep Trench Polysilicon RF Loss Reduction

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Solution Overview

Problem

The formation of a low-resistance layer between the substrate and buried oxide in semiconductor devices leads to degradation in radio frequency performance due to eddy-current losses and unacceptable insertion losses, affecting the quality factor of inductors and transmission lines.

Innovation Solution

A deep trench is formed through the low-resistance layer, and a polysilicon layer is deposited within this trench to block electron migration, thereby reducing insertion losses and eddy currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a low-resistance layer is formed between substrate and buried oxide, then electrical connectivity is improved, but radio frequency performance degrades due to eddy-current losses and insertion losses

Engineering Contradiction:

Improveelectrical connectivityVSAvoideddy-current losses and insertion losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The low-resistance layer is segmented by forming deep trenches that divide it into isolated regions. This segmentation interrupts the continuous path for eddy currents while maintaining local electrical connectivity through carefully positioned conductive structures, thereby reducing RF losses without compromising overall electrical performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the low-resistance layer are treated differently: areas beneath RF devices have trenches to reduce eddy currents, while areas requiring electrical connectivity maintain the low-resistance properties. This local differentiation allows simultaneous optimization of both RF performance and electrical connectivity in different locations

Inventive Principle:

Principle #3Local quality

2Loss of energy

If deep trenches are formed through low-resistance layer, then eddy-current losses are reduced, but device complexity increases

Engineering Contradiction:

Improveeddy-current lossesVSAvoidprocess complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

Deep trenches are formed through the low-resistance layer during the fabrication process before final device assembly. This preliminary action of creating trenches early in the process flow simplifies subsequent steps and allows for more straightforward integration of RF devices without requiring complex post-processing operations

Inventive Principle:

Principle #10Preliminary action

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

The solution effectively decreases unexpected insertion losses and eddy currents, improving the radio frequency performance of integrated circuits by blocking electron migration and reducing cross-talk between substrate and RF devices.

Implementation Method 1

a polysilicon layer is formed in the deep trench to block the migration of electrons

Methodology Applied

Scientific EffectElectron migration blocking: Diffusion Barrier

Data Source

PatentUS10090327B2Semiconductor device and method for forming the same

Publication Date: 2018.10.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Embodiments for forming a semiconductor device structure are provided. The semiconductor device structure includes a substrate and a buried oxide layer formed over the substrate. An interface layer is formed between the substrate and the buried oxide layer. The semiconductor device structure also includes a silicon layer formed over the buried oxide layer; and a polysilicon layer formed over the substrate and in a deep trench. The polysilicon layer extends through the silicon layer, the buried oxide layer and the interface layer.