Backside Optical Carrier Injection for High-Resolution IC Imaging

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing optical carrier injection methods for ICs face challenges such as substrate light absorption, time-consuming imaging processes, and limited spatial resolution due to mechanical translation stage tolerances, especially when using backside illumination with photon energy higher than the substrate bandgap.

Innovation Solution

Employing a pulsed optical beam with photon energy below the substrate bandgap for backside optical carrier injection, utilizing nonlinear optical interactions to inject carriers in the active layer, and combining mechanical and electronic beam steering for high-resolution imaging without substrate thinning or polishing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If backside optical carrier injection with photon energy higher than substrate bandgap is used, then carrier injection into active layer is achieved, but substrate absorbs light before it reaches the active layer

Engineering Contradiction:

Improvecarrier injection efficiencyVSAvoidlight absorption by substrate

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent changes the photon energy parameter to be below the substrate bandgap, allowing light to pass through the substrate without absorption while still enabling carrier injection into the active layer through nonlinear optical interactions at the focal point

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs pulsed optical excitation instead of continuous illumination, using short pulses to achieve carrier injection through nonlinear optical effects while minimizing overall energy absorption and heating in the substrate

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If frontside optical carrier injection is used, then tight focal point and high spatial resolution are achieved, but metallization traces and insulating layers interfere with the optical beam

Engineering Contradiction:

Improvespatial resolutionVSAvoidinterference from metallization traces

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the illumination direction by using backside illumination instead of frontside illumination, allowing the optical beam to pass through the substrate and reach the active layer without encountering metallization traces and insulating layers that block frontside injection

Inventive Principle:

Principle #13The other way round (Inversion)

3Measurement precision

If mechanical translation stage is used for scanning, then imaging of IC wafer is achieved, but processing time is excessive and spatial resolution is limited by stage tolerances

Engineering Contradiction:

Improveimaging resolutionVSAvoidimaging processing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical translation stage with an acousto-optic beam steering system that uses acoustic waves to deflect the optical beam, eliminating mechanical tolerance limitations and significantly reducing scanning time through faster, contactless beam positioning

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Achieves efficient carrier injection and high spatial resolution imaging of ICs without substrate alteration, reducing processing time and overcoming mechanical translation limitations.

Implementation Method 1

Photons of the optical beam are absorbed at the focal point in the active layer by nonlinear optical interactions to inject carriers at the focal point in the active layer

Methodology Applied

Scientific EffectNonlinear optical interactions:

Implementation Method 2

Optical carrier injection employs an optical beam (typically a laser beam) that is focused on a specific location of an active layer of an IC to excite electron-hole pairs at that location

Methodology Applied

Scientific EffectOptical carrier injection: Photoelectric Effect

Implementation Method 3

focusing the pulsed optical beam at a focal point in an active layer disposed on a frontside of the substrate

Methodology Applied

Scientific EffectOptical focusing: Focusing

Implementation Method 4

an acousto-optic beam steering device arranged to steer the pulsed optical beam to locations on the IC wafer or chip

Methodology Applied

Scientific EffectAcousto-optic effect: Acousto-optic Effect

Data Source

PatentUS20250290977A1Systems and methods for precise signal injection into microelectronic devices

Publication Date: 2025.09.18 BATTELLE MEMORIAL INST

AI summary

In an optical carrier injection method, a pulsed optical beam having pulse duration of 900 fs or lower is applied on a backside of a substrate of an integrated circuit (IC) wafer or chip, and is focused at a focal point in an active layer on a frontside of the substrate. Photons of the optical beam are absorbed at the focal point by nonlinear optical interaction(s) to inject carriers. The pulsed optical beam may be applied using a fiber laser in which the fiber is doped with Yb and/or Er. An output signal may be measured, comprising an electrical signal or a light output signal produced by the IC wafer or chip in response to the injected carriers. By repeating the applying, focusing, and measuring over a grid of focal points in the active layer, an image of the IC wafer or chip may be generated.