Silicon Photonic Waveguide Fabrication with Variable Buried Oxide

Solution Overview

Problem

Current CMOS technology faces challenges in fabricating photonic and electronic devices on the same silicon substrate due to differing optimal buried oxide (BOX) thickness requirements, where photonic devices need a thicker BOX to minimize optical loss while electronic devices require a thinner BOX.

Innovation Solution

A method is developed to pattern a semiconductor substrate into regions with different BOX thicknesses for electronic and photonic devices, involving the formation of a thinner oxide layer in one region and a thicker oxide layer in another, with a donor wafer used to separate and remove substrate material to achieve the desired thicknesses, allowing for the integration of both device types on the same substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a thick buried oxide layer is used to minimize optical loss in photonic devices, then optical performance is improved, but electronic device performance deteriorates due to excessive thickness

Engineering Contradiction:

Improveoptical lossVSAvoidelectronic device performance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The substrate is divided into distinct first and second regions with different oxide layer thicknesses. The first region (for electronic devices) has a thinner oxide layer while the second region (for photonic devices) has a thicker oxide layer, allowing each device type to operate with its optimal oxide thickness

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the substrate are given different local properties - specifically, different oxide layer thicknesses tailored to the specific device type in each region. This allows photonic devices to have thick oxide for low optical loss while electronic devices have thin oxide for optimal electrical performance

Inventive Principle:

Principle #3Local quality

2Reliability

If a thin buried oxide layer is used to optimize electronic device performance, then electronic device reliability is improved, but photonic device performance deteriorates due to increased optical loss

Engineering Contradiction:

Improveelectronic device performanceVSAvoidoptical loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The substrate is divided into distinct first and second regions with different oxide layer thicknesses. The first region (for electronic devices) has a thinner oxide layer while the second region (for photonic devices) has a thicker oxide layer, allowing each device type to operate with its optimal oxide thickness

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the substrate are given different local properties - specifically, different oxide layer thicknesses tailored to the specific device type in each region. This allows photonic devices to have thick oxide for low optical loss while electronic devices have thin oxide for optimal electrical performance

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If a single uniform oxide layer thickness is used across the entire substrate, then manufacturing simplicity is maintained, but device performance deteriorates due to inability to meet different thickness requirements

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoiddevice performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The substrate is divided into distinct first and second regions with different oxide layer thicknesses achieved through selective etching, allowing each device type to operate with its optimal oxide thickness while maintaining compatibility with standard CMOS manufacturing processes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces spatial variation in the oxide layer thickness across the substrate surface, transitioning from a uniform single-dimensional specification to a multi-dimensional structure where thickness varies by location to meet different device requirements

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 direct integration of electronic and photonic devices on a silicon substrate, allowing them to operate optimally and work together in complex circuits, enhancing performance for fiber communications with improved optical channel spacing.

Implementation Method 1

an oxide layer is formed on the substrate

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

A donor wafer is subsequently placed on top of the oxide layer

Methodology Applied

Scientific EffectWafer bonding: Welding

Data Source

PatentUS9488776B2Method for fabricating silicon photonic waveguides

Publication Date: 2016.11.08 BAE SYSTEMS INFORMATION ANDELECTRONIC SYSTEMS INTEGRATION INC

AI summary

A method for fabricating electronic and photonic devices on a semiconductor substrate using complementary-metal oxide semiconductor (CMOS) technology is disclosed. A substrate is initially patterned to form a first region for accommodating electronic devices and a second region for accommodating photonic devices. The substrate within the first region is thicker than the substrate within the second region. Next, an oxide layer is formed on the substrate. The oxide layer within the first region is thinner than the oxide layer within the second region. A donor wafer is subsequently placed on top of the oxide layer. The donor substrate includes a bulk silicon substrate, a sacrificial layer and a silicon layer. Finally, the bulk silicon substrate and the sacrificial layer are removed from the silicon layer such that the silicon layer remains on the oxide layer.