Vertical Photomask Alignment for Low-Distortion Optical Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor devices continue to shrink in size, gravitational sagging of photomasks during lithography processes leads to reduced usable depth of focus and image distortion, affecting manufacturing yield and cost.
Innovation Solution
An optical lithography system with a vertically aligned photomask chuck, pressurized chamber, vacuum chamber, and curved wafer chuck to reduce photomask sagging, maintaining uniform depth of focus and reducing image distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photomask is used in optical lithography system, then patterning function is achieved, but gravitational sagging causes image distortion and reduces patterning precision
Solution Approach 1:
The patent applies anti-gravity force through a magnetic levitation system that generates an upward magnetic force to counterbalance the gravitational force acting on the photomask. This counterweight approach prevents sagging by creating an opposing force that maintains the photomask in a stable, horizontal position during lithography exposure, thereby preserving patterning precision.
Solution Approach 2:
The patent replaces the traditional mechanical support system (physical contact with support structures) with a magnetic field-based levitation system. This substitution eliminates mechanical contact points that could cause deformation or instability, allowing the photomask to be suspended in mid-air and maintain its intended geometry without gravitational distortion.
2Manufacturing precision
If photomask is held in horizontal position, then patterning accuracy is maintained, but gravitational sagging occurs reducing depth of focus
Solution Approach 1:
The magnetic levitation system generates an upward magnetic force that counterbalances gravity, preventing the photomask from sagging downward. This maintains the photomask's intended flat or curved shape throughout the exposure process, ensuring uniform depth of focus across the entire wafer surface and preserving manufacturing precision.
Solution Approach 2:
The patent employs a dynamic control system that continuously adjusts the magnetic field strength and distribution to compensate for any deviations in photomask position or shape. This dynamic adjustment ensures the photomask maintains its optimal orientation and curvature throughout the lithography process, preserving depth of focus and patterning accuracy.
3Productivity
If conventional lithography system is used, then manufacturing process is simple, but image distortion reduces device yield
Solution Approach 1:
The patent replaces conventional mechanical support systems with magnetic levitation technology, eliminating physical contact that causes image distortion. This substitution preserves the integrity of the projected image pattern, ensuring accurate pattern transfer to the wafer and thereby increasing device yield by reducing defects caused by imaging errors.
Solution Approach 2:
The magnetic field acts as an intermediary between the photomask and the support structure, transmitting the necessary holding force without direct mechanical contact. This intermediary approach prevents the transmission of mechanical stresses and deformations to the photomask, maintaining image fidelity and reducing distortion-related defects that would otherwise reduce yield.
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
Improves device performance and yield by enabling finer, more accurate patterning while reducing manufacturing costs through reduced photomask sagging and image distortion.
Implementation Method 1
An optical lithography system may include a pressurized chamber below the photomask, which uses gas pressure to tune the photomask surface curvature (e.g., tuning the photomask curvature from concave to convex) and reduce sagging of the photomask due to gravitational effects.
Implementation Method 2
An optical lithography system may include a vacuumed chamber above the photomask, which uses a vacuumed environment to tune the photomask surface curvature (e.g., tuning the photomask curvature from concave to convex) and reduce sagging of the photomask due to gravitational effects.
Implementation Method 3
An optical lithography system may include a vertical mask chuck that aligns the photomask such that a patterned major surface of the photomask is parallel to the force of gravity, reducing sagging of the photomask due to gravitational effects.
Data Source
AI summary
In an embodiment, an apparatus includes an energy source, a support platform for holding a wafer, an optical path extending from the energy source to the support platform, and a photomask aligned such that a patterned major surface of the photomask is parallel to the force of gravity, where the optical path passes through the photomask, where the patterned major surface of the photomask is perpendicular to a topmost surface of the support platform.