Tunable Grating Shrinkage via Grey-Tone Mask Lithography

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional lithography technologies face challenges in fabricating surface relief gratings (SRGs) with high or low duty cycles due to critical dimension limitations, and existing methods are expensive and time-consuming, especially when trying to achieve variable duty cycles without double patterning techniques and 193-nm immersion technology.

Innovation Solution

The use of a grey-tone mask with a non-uniform light transmittance profile to selectively adjust the critical dimensions of lithography-defined features by configuring a varying duty cycle profile, allowing for the fabrication of SRGs with a broad range of duty cycles from 0.1 to 0.9 without the need for new lithography masks or changing lithography conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional lithography technologies are used to fabricate surface relief gratings, then the manufacturing process is simple, but the critical dimension control is limited and cannot achieve high or low duty cycles effectively

Engineering Contradiction:

Improvecritical dimension controlVSAvoidlithography process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

A shrink material layer is introduced as an intermediary substance between the photoresist pattern and the final grating structure. This shrink material contains photobase generator that reacts with the photoresist upon exposure to activating radiation, causing the shrink material to shrink and thereby precisely control the critical dimensions of the grating features, enabling duty cycles from 0.1 to 0.9

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the physical and chemical parameters of the system by using a shrink material that undergoes volume contraction when exposed to activating radiation. The shrink material's properties (solubility, shrinkage ratio, photobase generator content) are specifically tuned to enable precise critical dimension control and achieve the desired duty cycle profile without requiring complex lithography equipment

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If double patterning techniques or 193-nm immersion technology are used to achieve variable duty cycles, then the critical dimension precision is improved, but the production cost and time increase significantly

Engineering Contradiction:

Improveduty cycle precisionVSAvoidproduction efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The shrink material is applied and configured before the final exposure step, with the photobase generator pre-distributed throughout the shrink material layer. This preliminary configuration allows the entire duty cycle profile to be established in a single lithography exposure, eliminating the need for multiple patterning steps or specialized immersion lithography equipment

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The shrink material system serves multiple functions: it acts as a spacer, a source of photobase generator, and a shrinking agent all in one material layer. This multi-functionality enables the fabrication of gratings with varying duty cycles using standard lithography equipment, making the process universally applicable without requiring specialized techniques

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If standard lithography masks are used, then the device complexity is low, but the adaptability to create varying duty cycle profiles is insufficient

Engineering Contradiction:

Improveduty cycle profile flexibilityVSAvoidmask and process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The shrink material layer is configured with spatially varying properties, including non-uniform thickness and/or non-uniform photobase generator concentration, to create different duty cycle profiles in different regions of the grating. This local variation in shrink material quality enables the fabrication of gratings with complex duty cycle profiles using a single standard lithography mask

Inventive Principle:

Principle #3Local quality

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 the definition of much smaller critical dimensions for various devices, including nano-sized features, improving illuminance uniformity in light guide display systems by allowing for the fabrication of SRGs with a broad variation of duty cycles, reducing production costs and time.

Implementation Method 1

exposing the photoresist pattern with the shrink material to the radiation transmitting through the grey-tone mask to cause a reaction between the shrink material and the photoresist pattern

Methodology Applied

Scientific EffectPhotochemical reaction: Photopolymerisation

Data Source

PatentUS20230160820A1Tunable shrinkage and trim process for fabricating gratings

Publication Date: 2023.05.25 META PLATFORMS TECHNOLOGIES LLC

AI summary

A method is provided. The method includes forming a shrink material layer over a substrate including a photoresist pattern. The method also includes exposing the substrate with the shrink material layer to an activating radiation via a grey-tone mask that provides a predetermined light transmittance profile for the activating radiation. The method also includes removing at least a portion of the shrink material layer.