Removable Opaque Coating for Transparent Film Topography

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Solution Overview

Problem

Optical topography measurements on transparent films in semiconductor wafers are inaccurate due to interference from light reflections from underlying layers, making existing correction models complex and time-consuming for high-volume manufacturing environments.

Innovation Solution

A highly reflective, removable opaque coating is deposited on the top surface of the wafer, allowing for accurate measurement of the topography by differentiating light reflections and subsequently removed without causing stress or damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If correction models are used to compensate for transparent films effects, then measurement accuracy is improved, but measurement time and process complexity increase significantly

Engineering Contradiction:

Improvetopography measurement accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

An opaque coating is deposited on the wafer surface before measurement to eliminate transparent film effects in advance. This preliminary action ensures that subsequent optical measurements are not affected by light transmission through transparent films, thereby improving measurement accuracy without requiring complex correction models during the measurement process itself.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The opaque coating acts as an intermediary layer between the optical measurement system and the wafer surface. By introducing this intermediate layer, the measurement system interacts with a surface that does not transmit light, thereby eliminating the complex optical path issues caused by transparent films and enabling direct, accurate topography measurements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If correction models are used to compensate for transparent films effects, then measurement accuracy is improved, but device and process complexity increase

Engineering Contradiction:

Improvetopography measurement accuracyVSAvoidcorrection model complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The opaque coating is applied beforehand to prevent transparent film interference, eliminating the need for complex correction algorithms. This transforms a software-intensive solution into a simple physical preparation step, significantly reducing process complexity while maintaining measurement accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The opaque coating serves as a physical intermediary that simplifies the optical measurement environment. By blocking light transmission through transparent films, it creates ideal measurement conditions that do not require complex computational corrections, thereby reducing both device and process complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If physical contact measurement methods are used, then measurement is simplified, but wafer damage risk increases

Engineering Contradiction:

Improvemeasurement simplicityVSAvoidwafer damage

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The opaque coating acts as a sacrificial intermediary layer that protects the underlying wafer surface during measurement. Optical measurement systems can interact with this coating without risking damage to the delicate wafer structures, thereby maintaining measurement simplicity while eliminating wafer damage risks.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The opaque coating is a temporary, disposable layer applied specifically for measurement purposes. It serves its function as a protective intermediary during the measurement process and is then removed, preventing any potential damage to the wafer while allowing straightforward optical measurements to be performed.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 method enables precise and efficient optical topography measurements by enhancing light reflectivity and avoiding physical contact, reducing measurement time and preventing wafer damage.

Implementation Method 1

measuring topography on the highly reflective coating... the highly reflective coating reflects at least twenty percent of incident light

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS11049720B2Removable opaque coating for accurate optical topography measurements on top surfaces of transparent films

Publication Date: 2021.06.29 KLA CORP

AI summary

A method of using removable opaque coating for accurate optical topography measurements on top surfaces of transparent films includes: depositing a highly reflective coating onto a top surface of a wafer, measuring topography on the highly reflective coating, and removing the highly reflective coating from the wafer. The highly reflective coating includes an organic material. The highly reflective coating comprises a refractive index value between one and two. The highly reflective coating comprises a complex wavelength greater than one at six-hundred and thirty-five nanometers. The highly reflective coating reflects at least twenty percent of incident light. The highly reflective coating when deposited maintains an underlayer pattern topography at a resolution of forty by forty micrometers. The highly reflective coating does not cause destructive stress to the wafer.