Multi-Column Lithography Alignment via Encoder Feedback

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Solution Overview

Problem

Conventional systems face challenges in achieving and maintaining proper alignment of grating patterns when producing large wire grid polarizers for flat panel displays, leading to image smearing and inefficiencies in manufacturing due to the need for precise angular alignment and cross-scan positioning of multiple optical columns.

Innovation Solution

A lithography system with multiple imaging systems on a bridge capable of moving in the cross-scan direction, using a mask with a grating pattern and alignment marks, and encoder scales to ensure accurate alignment and uniform exposure across the substrate, allowing for precise positioning and alignment of grating strips.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple optical columns are used to expose large area substrates quickly, then productivity increases, but manufacturing precision deteriorates due to alignment difficulty between columns and scans

Engineering Contradiction:

Improvemanufacturing speedVSAvoidalignment precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

An intermediary alignment system is introduced consisting of alignment marks on the mask, alignment sensors, and a feedback control mechanism. The alignment marks are imaged onto the substrate along with the grating pattern, and the alignment sensors detect the position of these marks to generate correction signals that adjust the positioning of optical columns and substrate stage, ensuring precise alignment despite the use of multiple columns and scans

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

A feedback control loop is implemented where alignment sensors continuously monitor the position of alignment marks on the substrate, compare them to reference positions, and generate real-time correction signals to adjust the positioning of optical columns and substrate stage, maintaining alignment precision throughout the multi-column, multi-scan exposure process

Inventive Principle:

Principle #23Feedback

2Productivity

If the substrate is scanned at high speed to reduce manufacturing time, then productivity increases, but manufacturing precision deteriorates due to image smearing

Engineering Contradiction:

Improvemanufacturing speedVSAvoidgrating pattern accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system transitions from static positioning to dynamic positioning control, where the positions of optical columns and substrate stage are continuously adjusted during the scanning process based on real-time feedback from alignment sensors, allowing high-speed scanning while maintaining precise grating pattern formation

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Mechanical positioning systems are supplemented or replaced with optical feedback systems using alignment sensors and software control algorithms that calculate and apply real-time position corrections, enabling high-speed scanning without the mechanical inertia and positioning errors that would cause image smearing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If angular alignment between grating lines and scan direction is made extremely precise, then manufacturing precision improves, but device complexity increases

Engineering Contradiction:

Improveangular alignment precisionVSAvoidalignment system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The alignment system is designed to be self-aligning through the use of alignment marks that are automatically imaged and detected by alignment sensors, with the feedback control system automatically calculating and applying the necessary position corrections without requiring complex manual alignment procedures or extremely precise mechanical setup

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11243480B2System for making accurate grating patterns using multiple writing columns each making multiple scans

Publication Date: 2022.02.08 APPLIED MATERIALS INC

AI summary

A lithography system for generating grating structures is provided having a multiple column imaging system located on a bridge capable of moving in a cross-scan direction, a mask having a grating pattern with a fixed spatial frequency located in an object plane of the imaging system, a multiple line alignment mark aligned to the grating pattern and having a fixed spatial frequency, a platen configured to hold and scan a substrate, a scanning system configured to move the platen over a distance greater than a desired length of the grating pattern on the substrate, a longitudinal encoder scale attached to the platen and oriented in a scan direction and at least two encoder scales attached to the platen and arrayed in the cross-scan direction wherein the scales contain periodically spaced alignment marks having a fixed spatial frequency.