Overlay Measuring Device Z-Axis Focus Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current overlay measuring methods in semiconductor manufacturing are inefficient due to increased measurement time and decreased workability caused by separate movements of the stage and objective lens, leading to interference between electrically activated patterns and reduced circuit performance.
Innovation Solution
An overlay measuring device and method that simultaneously moves the stage and objective lens, using a processor to obtain and store height values for each site on the wafer, allowing for controlled Z-axis movement of the objective lens based on pre-measured data to predict and adjust focal lengths, thereby reducing measurement time and improving workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the stage is moved to the position of a site to be measured on the X and Y-axis, and then the objective lens is adjusted in the Z-axis direction based on height measured through an auto focus system, then the measurement can be performed, but the measurement time increases and workability deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-measuring the height of each site on the wafer and storing this information before the actual overlay measurement process. This allows the Z-axis position of the objective lens to be predetermined based on the stored height data, eliminating the need for time-consuming real-time auto-focus adjustments during measurement. The height data is obtained in advance through a separate process and stored in memory, enabling rapid access during the measurement phase.
Solution Approach 2:
The patent merges the height measurement process with the overlay measurement process by integrating the Z-axis position control into the existing measurement system. The processor controls both the stage movement (X and Y axes) and the objective lens Z-axis movement simultaneously based on stored height data, combining what were previously separate sequential operations into a unified coordinated movement system.
2Measurement precision
If the stage is moved to the position of a site to be measured on the X and Y-axis, and then the objective lens is adjusted in the Z-axis direction, then the measurement can be performed, but the workability deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-measuring and storing the height data for each site before the overlay measurement process. This pre-prepared data is then used to automatically control the Z-axis position of the objective lens during measurement, reducing manual intervention and improving workability. The processor automatically retrieves and applies the stored height information, eliminating the need for manual focus adjustment operations.
Solution Approach 2:
The system performs self-service by automatically using the pre-stored height data to control the objective lens Z-axis position without requiring manual intervention. The processor autonomously retrieves the height information from memory and applies it to position the objective lens correctly, making the system self-sufficient and improving ease of operation.
3Manufacturing precision
If separate movements of the stage and objective lens are performed, then the measurement process can be completed, but the measurement time increases
Solution Approach 1:
The patent merges the stage movement (X and Y axes) and objective lens movement (Z axis) into a coordinated simultaneous operation. The processor controls both movements based on the stored height data, allowing the stage and objective lens to move at the same time rather than sequentially. This integration of movements directly reduces the total measurement time while maintaining measurement accuracy.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing the Z-axis position information for each site based on pre-measured height data. This advance preparation allows the objective lens to be positioned correctly without waiting for sequential adjustments during the measurement process, enabling parallel execution of stage and lens movements and thereby increasing productivity.
Data Source
AI summary
There are provided an overlay measuring device and a method for controlling a focus and a program therefor. An overlay measuring device controlling a focus in one embodiment includes an objective lens; a memory; a lens focus actuator operating the objective lens to adjust a distance between the objective lens and a wafer; and a processor controlling operations of the memory and the lens focus actuator, wherein the processor is configured to obtain a first height value in relation to each site of the wafer, match the obtained first height value and a corresponding site and store the same, and as initial measurement in relation to each site of the wafer starts, control the lens focus actuator, based on the stored first height value of the site, to control a Z-axis movement of the objective lens.