Sacrificial Waveguide for Probeless Photonics Die Testing

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Solution Overview

Problem

Conventional methods for testing photonics dies in LIDAR systems are inefficient, often requiring large gaps between dies, risking damage, and increasing manufacturing costs, while also reducing LIDAR detection capabilities due to beam power splitting.

Innovation Solution

Incorporating sacrificial waveguides and grating couplers in the scribe lines between dies for wafer-level testing, allowing optical beam transmission and measurement without probes, and removing them during die separation to avoid damage and maintain beam integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional testing methods are used with probes inserted between dies, then die testing can be performed, but large gaps between dies are required and damage risk increases

Engineering Contradiction:

Improvedie testing reliabilityVSAvoidgap between dies

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

A sacrificial waveguide structure is introduced as an intermediary element in the scribe line between dies. This waveguide provides a controlled optical path that allows probeless testing by guiding light from a test source through the die under test to a detector, eliminating the need for direct probe insertion into gaps between dies and thereby reducing damage risk while maintaining testing reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical probe insertion system is replaced with an optical testing system using the sacrificial waveguide. Instead of mechanically inserting probes into gaps between dies, light is transmitted through the waveguide and die structures optically, eliminating mechanical contact and associated damage risks while enabling reliable die-level testing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If beam power is split for testing, then die functionality can be measured, but LIDAR detection capabilities are reduced

Engineering Contradiction:

Improvedie functionality measurementVSAvoidLIDAR beam power

Core Design Contradiction:

Measurement precisionVSPower

Solution Approach 1:

Testing is performed on the wafer before final die separation and before LIDAR system assembly. The sacrificial waveguide enables complete die functionality testing to be conducted in advance, so that when the die is integrated into the LIDAR system, full beam power is available for detection without any splitting for testing purposes

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If sacrificial waveguides are used for testing, then probeless testing is enabled, but additional manufacturing steps are required

Engineering Contradiction:

Improvetesting operationVSAvoidmanufacturing process

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The sacrificial waveguide structure is integrated into the existing scribe line regions between dies during the semiconductor manufacturing process. By merging the testing infrastructure with existing manufacturing features, the additional complexity is minimized while still enabling probeless optical testing operations

Inventive Principle:

Principle #5Merging (Combining)

4Ease of manufacture

If dies are separated without sacrificial structures, then manufacturing is simpler, but die damage risk increases during separation

Engineering Contradiction:

Improvedie separation processVSAvoiddie integrity during separation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The sacrificial waveguide structure provides a cushioning or protective mechanism during die separation. The waveguide material is designed to be removed or sacrificed during the separation process, absorbing mechanical stresses and protecting the fragile die edges from damage while enabling clean die separation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

Enables efficient die testing and separation with reduced manufacturing costs, maintaining LIDAR detection capabilities by avoiding probe insertion and beam power reduction.

Implementation Method 1

a grating coupler is provided in a neutral area of a neighboring die

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

providing a sacrificial waveguide and a grating coupler at least partially in a scribe line between dies of a wafer

Methodology Applied

Scientific EffectOptical waveguide transmission: Waveguide (optics)

Data Source

PatentUS11788929B1Techniques for wafer level die testing using sacrificial structures

Publication Date: 2023.10.17 AEVA INC

AI summary

A method of testing a photonics die at the wafer level includes providing a sacrificial waveguide and a grating coupler at least partially in a scribe line between dies of a wafer, performing one or more tests on the dies of the wafer via the sacrificial waveguide and grating coupler in the scribe line, and removing the sacrificial waveguide during separation of the dies of the wafer.