Backside Silicon Milling Endpoint Detection via Electrical Strain Feedback

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing semiconductor failure analysis methods require the removal of backside silicon to enable imaging and interrogation of field effect transistor layers, but lack an in-situ endpoint detection system, leading to a high risk of device destruction during mechanical milling.

Innovation Solution

An assembly and method using a piezoelectric mechanism to monitor the power draw of field effect transistors during backside milling, detecting endpoint strain changes to prevent device damage by adjusting milling parameters in real-time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If backside silicon is removed to enable imaging and interrogation, then analysis capability is improved, but device integrity deteriorates due to risk of damage during milling

Engineering Contradiction:

Improveimaging capabilityVSAvoiddevice integrity

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The patent implements real-time feedback by monitoring power draw changes of field effect transistors during milling. The system continuously measures electrical characteristics and uses this feedback to detect endpoint conditions, allowing dynamic adjustment of milling parameters to prevent device damage while achieving sufficient silicon removal for imaging

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces purely mechanical endpoint detection methods with electrical measurement-based detection. By monitoring power draw and electrical characteristics of the device under test, the system detects milling endpoint conditions without relying on mechanical measurement techniques that require removing the device from the milling machine

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If milling process is paused and device removed for thickness measurement, then endpoint detection accuracy is improved, but productivity deteriorates

Engineering Contradiction:

Improveendpoint detection accuracyVSAvoidmilling efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent enables continuous milling operation by implementing in-situ electrical characteristic monitoring. The system continuously measures power draw and electrical parameters during the milling process without interruption, eliminating the need to pause and remove the device for thickness measurements, thereby maintaining continuous productive action

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent introduces electrical characteristic measurements as an intermediary method to detect milling progress and endpoint conditions. Instead of directly measuring silicon thickness mechanically, the system uses changes in electrical properties (power draw, conductivity) as indirect indicators of milling depth and endpoint conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If milling force is applied to remove silicon, then material removal rate is improved, but device strain increases risking damage

Engineering Contradiction:

Improvematerial removal rateVSAvoiddevice strain

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The patent implements dynamic control of milling parameters by continuously monitoring electrical characteristics and adjusting milling force, speed, or other parameters in real-time. This dynamic adaptation allows the system to maintain high material removal rates while adjusting conditions to prevent excessive strain on the device

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies beforehand cushioning by using electrical monitoring to detect early signs of excessive strain or approaching endpoint conditions. The system prepares for potential damage by detecting precursor changes in electrical characteristics and preemptively adjusting milling parameters to cushion against device damage

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 safe and accurate removal of backside silicon without damaging the underlying circuit, allowing for effective failure analysis while preserving the integrity of the semiconductor device.

Implementation Method 1

uses a piezoelectric mechanism to monitor changes in power draw of field effect transistors

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS20260018471A1Assembly and method for performing in-situ endpoint detection when backside milling silicon based devices

Publication Date: 2026.01.15 BATTELLE MEMORIAL INST

AI summary

An assembly for monitoring a semiconductor device under test comprising a mill configured to mill the device, a sensor configured to measure an electrical characteristic of the device, and a computer configured to determine the amount of strain in the device from the electrical characteristic when the mill is milling the device and detect an endpoint of milling at a circuit within the device. In use the endpoints of the milling process of the semiconductor device are detected measuring an electrical characteristic of the device with a sensor during milling determining the amount of strain in the device from the electrical characteristic and detecting an endpoint of the milling process within the device based on the amount of strain.