Electron Beam Lithography Alignment Mark Detection
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Solution Overview
Problem
The challenge in semiconductor manufacturing is achieving high precision in aligning patterns on substrates, particularly for phase shifting masks and extreme ultra-violet (EUV) substrates, due to variations in alignment mark location accuracy and differing amplification factors required for different materials, which complicates the use of a single electron beam lithography apparatus.
Innovation Solution
An electron beam lithography apparatus with a detector and amplifier system that uses pre-stored initial gain values for amplifying detection signals, allowing for precise alignment mark location measurement and adjustment, and distinguishing between PSM and EUV substrates by using separate files for initial gain and level values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks are arranged around the main pattern outside the lithography accuracy compensation region, then the alignment marks can be positioned for detection, but the positional accuracy of the alignment marks becomes inferior compared to the main pattern
Solution Approach 1:
The patent introduces a multi-layer substrate structure where alignment marks are placed on different layers (first alignment mark on substrate surface, second alignment mark on overlay layer). This dimensional separation allows both marks to be within the lithography accuracy compensation region while serving different alignment functions, resolving the contradiction between detectability and positional accuracy.
2Adaptability or versatility
If a single electron beam lithography apparatus is used for both PSM and EUV substrates, then device utilization is improved, but the apparatus cannot simultaneously optimize for different materials with differing amplification factors
Solution Approach 1:
The patent stores multiple sets of initial gain and level values in memory, each optimized for different substrate types (PSM or EUV). The system automatically selects the appropriate parameter set based on the substrate being processed, allowing a single apparatus to maintain optimal detection accuracy for different materials without requiring separate devices.
3Ease of operation
If the amplifier uses fixed gain values for amplifying detection signals, then the amplifier operation is simplified, but the system cannot accommodate variations in alignment mark signals from different substrate materials
Solution Approach 1:
The system pre-calculates and stores optimal initial gain and level values for different substrate types before actual alignment mark detection. This preliminary preparation allows the amplifier to quickly switch between different substrate types without requiring real-time adjustment or complex calculations during operation, maintaining simplicity while achieving adaptability.
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 approach improves alignment mark detection accuracy and reduces the number of search scan failures by using optimized initial values for specific substrates, enabling precise alignment between patterns and accommodating different materials and structures.
Implementation Method 1
detecting charged particles emitted when the alignment mark is scanned by the charged particle beam
Implementation Method 2
an amplifier configured to amplify the detection signal based on an initial gain value selected from a plurality of initial gain values stored in advance in a memory
Data Source
AI summary
In one embodiment, a charged particle beam lithography apparatus includes an irradiator 201 to irradiate substrates with charged particle beams, each of the substrates being provided with a predetermined mark, and a detector 114 to detect charged particles emitted when the predetermined mark is scanned by a charged particle beam and output a detection signal. The apparatus further includes an amplifier 124 to adjust and amplify the detection signal and output an amplified signal, and a measurement circuitry 211 to measure a location of the predetermined mark based on the amplified signal. The apparatus further includes storage 128 to store initial gain values of the amplifier for amplifying the detection signal, the initial gain values corresponding to conditions of the scan. The amplifier amplifies the detection signal based on an initial gain value selected from the initial gain values according to a condition of the scan.