Semiconductor Print Check Alignment via Coarse Fine Stages
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Solution Overview
Problem
Conventional alignment techniques in semiconductor wafer fabrication require multiple scans to properly align multiple reference dies to a master die and are not robust, often failing to align images within acceptable thresholds, especially for detecting smaller defects in sub-7 nm design rule devices.
Innovation Solution
A system and method that aligns multiple reference dies from multiple die rows to a master die in a single scan using a combination of coarse and fine alignment processes, with a single coarse alignment offset value to improve robustness and reduce scan-to-scan variation, enabling more accurate and efficient image alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alignment techniques are used to align multiple reference dies to a master die, then alignment can be achieved, but multiple scans are required and the process is not robust, often failing to align images within acceptable thresholds
Solution Approach 1:
The system performs preliminary coarse alignment using a single coarse alignment offset value calculated from alignment targets identified in training images before fine alignment. This preliminary action establishes a robust initial alignment that enables subsequent fine alignment to achieve acceptable alignment thresholds within a single scan, eliminating the need for multiple scans required by conventional techniques.
Solution Approach 2:
The system introduces alignment targets as intermediary elements that facilitate the alignment process. These alignment targets are identified in training images and used to calculate the coarse alignment offset value, serving as a mediator between the reference die images and the master die, enabling more robust and accurate alignment within acceptable thresholds.
2Measurement precision
If conventional alignment techniques are used, then alignment process is simple, but the system fails to properly align images within acceptable alignment thresholds, especially for smaller defects in sub-7 nm devices
Solution Approach 1:
The alignment process is segmented into two distinct stages: coarse alignment and fine alignment. The coarse alignment stage uses a single coarse alignment offset value to establish initial alignment, while the fine alignment stage refines the alignment to achieve acceptable thresholds. This segmentation enables the system to handle both large initial misalignments and precise final alignment requirements, improving success rate for sub-7 nm devices.
Solution Approach 2:
The system changes alignment parameters by using a single coarse alignment offset value for the entire die row rather than individual offsets for each reference die. This parameter change simplifies the alignment process while maintaining accuracy, and the offset value is dynamically calculated based on alignment targets identified in training images, adapting to specific sample characteristics.
3Measurement precision
If multiple scans are performed to achieve proper alignment, then alignment accuracy can be improved, but scan-to-scan variation increases and throughput decreases
Solution Approach 1:
The system performs preliminary identification of alignment targets in training images before the actual alignment scan. This preliminary action allows the coarse alignment offset value to be pre-calculated, enabling accurate alignment to be achieved within a single scan without requiring multiple scans, thereby maintaining high throughput while ensuring alignment accuracy.
Solution Approach 2:
The system uses feedback from alignment targets identified in training images to calculate the coarse alignment offset value. This feedback mechanism ensures that the alignment process is adaptive to the specific characteristics of each sample, achieving consistent alignment accuracy across different scans without requiring multiple scans, thus maintaining high inspection throughput.
Data Source
AI summary
A system includes a controller communicatively coupled to an optical inspection sub-system, the controller configured to: receive training images of a sample; identify alignment targets in the master die; receive a first set of reference images of a first die row of a sample, the first die row including a master die and a first set of reference die; align the first set of reference die to the master die via fine alignment processes to generate a first set of aligned reference images of the first row; receive a second set of reference images of a second die row of the sample; align the second set of reference die to the master die based on the alignment targets and the training images using a course alignment offset value; and align the second set of reference die to the master die via a fine alignment process.