Semiconductor Overlay Measurement Using SEM Moiré Patterns
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Solution Overview
Problem
The challenge in semiconductor manufacturing is accurately determining overlay errors between two layers in lithography operations, which is critical as the industry advances to nanometer technology process nodes.
Innovation Solution
A method using scanning electron microscopy (SEM) to analyze Moiré fringe patterns formed by overlapping periodic patterns with slightly differing pitches, allowing for precise calculation of overlay errors through curve fitting and pattern matching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional overlay measurement methods are used, then the measurement process is simple, but the measurement precision is insufficient for nanometer technology nodes
Solution Approach 1:
The overlay measurement pattern is divided into multiple periodic patterns with different pitches (first pitch P1 and second pitch P2). By segmenting the measurement into distinct pitch regions, the system can generate Moiré fringe patterns that provide higher precision overlay error measurement capability suitable for nanometer technology nodes.
Solution Approach 2:
The invention introduces a new dimension of measurement by utilizing Moiré fringe patterns generated from overlapping periodic patterns with different pitches. This transforms the overlay measurement from direct dimensional comparison to interferometric pattern analysis, achieving higher precision through the Moiré effect.
2Measurement precision
If periodic patterns with different pitches are overlapped to form Moiré fringe patterns, then the overlay error can be precisely determined, but the device complexity increases
Solution Approach 1:
The invention changes the pitch parameter of periodic patterns to create two distinct pitch values (P1 and P2). This parameter variation enables the generation of Moiré fringe patterns when the patterns are overlapped, allowing precise overlay error determination through the resulting interference pattern analysis.
Solution Approach 2:
The Moiré fringe pattern acts as an intermediary that translates the overlay error between two layers into a visually measurable interference pattern. By using the Moiré effect as a mediator, the system can precisely determine overlay errors that would be difficult to measure directly at nanometer scales.
3Measurement precision
If multiple periodic patterns with different pitches are used, then the overlay measurement precision improves, but the manufacturing complexity increases
Solution Approach 1:
The overlay measurement pattern with multiple periodic patterns of different pitches serves multiple functions: it enables overlay error measurement in both X and Y directions, generates Moiré fringe patterns for enhanced precision, and maintains compatibility with existing lithography processes. This multi-functionality justifies the increased manufacturing complexity by providing comprehensive measurement capability.
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
Enables accurate and efficient measurement of overlay errors, enhancing the precision of semiconductor manufacturing by reducing alignment discrepancies between layers.
Implementation Method 1
A Moiré fringe pattern of the lower layer pattern and the upper layer pattern is obtained by using an electron beam
Data Source
AI summary
According to an aspect of the present disclosure, in a method of manufacturing a semiconductor device, a lower layer pattern including first periodic patterns having a first pitch is formed, and an upper layer pattern including second periodic patterns having a second pitch different from the first pitch is formed. The first periodic patterns at least partially overlaps the second periodic patterns in plan view. A Moiré fringe pattern of the lower layer pattern and the upper layer pattern is obtained by using an electron beam, and an overlay error between the lower layer pattern and the upper layer pattern is obtained from the Moiré fringe pattern.