Blank Mask Light-Blocking Layer Grain Size Control
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Solution Overview
Problem
As semiconductor devices become more highly integrated, it becomes difficult to precisely control the shape of light-blocking pattern layers, leading to increased defect occurrence and pseudo-defect detection during high-sensitivity defect inspections, which degrades the accuracy of photomask resolution and increases the defective rate.
Innovation Solution
A blank mask and photomask with a light-blocking layer composed of a transition metal and either oxygen or nitrogen, featuring an average grain size of 14-24 nm and controlled etching speeds, are developed to improve defect detection accuracy and etching precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-blocking layer with conventional grain structure is used, then the photomask can block light effectively, but pseudo-defects are detected during high-sensitivity defect inspections
Solution Approach 1:
The patent applies local quality by controlling the grain size distribution specifically at the surface of the light-blocking layer (14-24 nm average grain size) while maintaining effective light-blocking properties in the bulk material. This localized control of surface morphology reduces pseudo-defect detection during defect inspections while preserving the light-blocking functionality.
2Measurement precision
If the light-blocking layer has finer grain structure, then pseudo-defect detection is reduced, but manufacturing precision control becomes more difficult
Solution Approach 1:
The patent employs parameter changes by optimizing the average grain size to a specific range (14-24 nm) and controlling the number of grains (20-55 grains per 0.01 μm²). These parameter specifications balance the reduction of pseudo-defects with the maintainability of manufacturing precision for light-blocking pattern shapes.
3Measurement precision
If a light-blocking layer with controlled grain size is used, then defect inspection accuracy improves, but etching speed control becomes more challenging
Solution Approach 1:
The patent applies dynamics by differentiating etching speeds between multiple light-blocking layers. The first light-blocking layer has an etching speed of 0.56 Å/s or more with argon gas, while the second layer has an etching speed of 0.3-0.5 Å/s with argon gas. This dynamic control allows selective etching while maintaining the controlled grain structure that improves defect inspection accuracy.
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
The solution enables high-resolution photomasks with reduced pseudo-defect detection and improved etching speed control, enhancing the precision and accuracy of defect inspection and patterning processes.
Implementation Method 1
a blocking portion including the light-blocking layer blocks the exposure light
Implementation Method 2
The attenuated exposure light has a phase difference compared to the exposure light passing through the transmissive portion
Implementation Method 3
the light-blocking layer may be formed using a sputtering target including 0.0001 to 0.035 parts by weight of Fe based on a total of 100 parts by weight of the transition metal
Data Source
AI summary
A blank mask includes a light transmissive substrate, and a light-blocking layer, disposed on the light transmissive substrate, comprising a transition metal and either one or both of oxygen and nitrogen. An average value of grain sizes of a surface of the light-blocking layer ranges from 14 nm to 24 nm.