Continuous Overlay Mark Layout for Accurate Wafer Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional overlay marks in photolithography processes often include pattern interruptions that are damaged during processing, leading to inaccurate overlay measurements and reduced quality of semiconductor devices.
Innovation Solution
The development of overlay marks with continuous patterns that maintain optical contrast without interruptions, allowing for more robust and reliable measurements by using an array of columns with parallel bar marks and space marks, where each line extends continuously from the uppermost to the lowermost region, and the orientation of lines alternates between regions to create detectable contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional overlay marks include pattern interruptions to generate optical contrast, then optical contrast is improved, but the marks become damaged during processing leading to reduced reliability
Solution Approach 1:
The patent changes the geometric parameters of the overlay mark pattern by replacing interrupted patterns with continuous patterns. The continuous lines maintain optical contrast through their geometry and arrangement rather than through interruptions, thereby improving durability while preserving detectability
Solution Approach 2:
Instead of using interruptions (absence of pattern) to create contrast, the patent inverts the approach by using continuous patterns where the presence and arrangement of material creates the necessary optical contrast for measurement
2Reliability
If overlay marks use continuous patterns without interruptions, then mark durability is improved, but optical contrast may be reduced affecting measurement precision
Solution Approach 1:
The patent adjusts geometric parameters including line width, spacing between lines, and arrangement of continuous patterns to optimize optical contrast. These parameter changes ensure that continuous patterns maintain sufficient contrast for precise overlay measurements
Solution Approach 2:
The overlay mark design incorporates asymmetric arrangements of continuous lines and patterns that create distinctive optical signatures. This asymmetry enhances detectability and measurement precision while maintaining pattern continuity
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 solution provides more accurate overlay measurements and enhances the durability of overlay marks, resulting in higher quality semiconductor devices by eliminating the need for pattern interruptions and maintaining detectability during processing.
Implementation Method 1
Conventional optical methods of measuring overlay typically include using an optical microscope and measuring an optical spectrum and/or a diffraction pattern
Data Source
AI summary
A method for determining overlay measurements includes orienting a wafer to align portions of lines of a pattern of an overlay mark with a direction in which a source emits light at the wafer and align other portions of the lines of the pattern to extend in a direction perpendicular to the direction in which the illumination source emits light at the wafer. The method includes capturing at least one image of the wafer via an imager sensor. The method also includes determining contrasts of regions of the overlay mark and determining a location of the overlay mark. Overlay marks include a pattern defining an array of columns. Each column includes a set of continuous lines oriented parallel to each other and extending in a first direction within a first region of a column and extending in a second different direction in a second region of the column.