Chapter/Index: Introduction | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Appendix
| ASML had developed a first-generation MBI tool capable of simultaneously scanning multiple electron beams (in this case, 9 beams), for 5 nm and beyond, on semiconductor wafers. This is a front-end inspection tool in semiconductor manufacturing. Such multi-beam systems are designed to significantly increase inspection throughput compared to traditional single-beam electron microscopy tools. With 9 beams, throughput could increase by 600%. The tool involves an advanced electron optical system, which is responsible for creating and controlling multiple primary electron beams. These primary beams are used to scan the wafer surface, and the system then collects and processes the resulting secondary electron emissions to detect defects. The system is designed to minimize beam cross-talk (interference between the multiple beams) to less than 2%. Cross-talk reduction is crucial for maintaining high-quality inspection results, especially as feature sizes continue to shrink. The tool features a high-speed stage, that is, the mechanism moves the wafer under the beams for scanning. The system also includes a high-speed computational architecture, essential for processing the massive streams of data generated by multi-beam inspections in real-time.
Figure 4b shows the schematic of e-beam system in ASML tool. The variation of the beam current is very stable (variation was less than 1% in 10 days) [4].
In the system in Figure 4b, the energy filter detector selectively filters electrons based on their energy. In this case, different electron energies can carry different types of information about the sample. That is, by filtering electrons to select those with specific energy levels, the system can enhance contrast, reduce noise, and improve the quality of the information obtained from the sample. This capability is particularly important for differentiating between various material layers or detecting subtle defects. The bottom detector, which is more suitable for detecting backscattered electrons, is positioned to capture electrons that have been deflected back towards the source after interacting with the sample. The images, formed by backscattered electrons, generally carry information about the atomic number of the material, with higher atomic number elements scattering more electrons back. The relationship between defect size and throughput in E-beam inspection is generally inverse (page5), meaning smaller defect sizes typically result in lower throughput due to the increased inspection time required. Furthermore, ASML and HMI (Hermes Microvision, Inc.) have a close relationship, primarily because ASML acquired HMI in 2016. HMI is a leading company in the field of electron beam (e-beam) inspection technology, which is critical for identifying defects during semiconductor manufacturing. In 2016, ASML acquired HMI for approximately $3.1 billion. The acquisition was strategic, allowing ASML to integrate HMI's advanced e-beam inspection technology into its portfolio of semiconductor manufacturing equipment. The collaboration between ASML and HMI has led to the development of multi-beam inspection (MBI) tools, which are designed to meet the growing demands for higher inspection throughput at advanced nodes (e.g., 5 nm and beyond). The integration of HMI’s e-beam expertise with ASML’s broader semiconductor equipment technology has resulted in innovative solutions like the MBI tools. By combining ASML’s lithography expertise with HMI’s inspection technology, the companies have been able to offer comprehensive solutions that improve both the manufacturing process and defect detection capabilities, which are critical for the production of high-quality semiconductor devices. Figure 4c shows a HMI's multibeam electron optics design. Essential elements of an efficient MBI system comprise [3]: a) an electron optics system that can generate and manipulate multiple beamlets, along with the capability to collect and process the returning electrons, b) a high-speed stage, and c) a fast computational architecture designed for detecting defects on a wafer using multiple beamlets. The electron optic (EO) system, illustrated in Figure 4c, comprises two columns:
The beam separator in Figure 4c takes a single electron beam and the split it into multiple beams, e.g. 9 or 25 beams in ASML systems. With 25 beams, the eScan 1100 increases throughput by up to 15 times compared to single e-beam inspection tools. [5, 6] Figure 4d shows the electron optics (EO) system which is the key technology leading to MBI success. The primary beam module operates similarly to a single-beam system, but controlling the travel paths of multiple beamlets required several innovations:
Then, a Wien filter is incorporated into the primary beam module to redirect the secondary electrons into the SE projection module. Figure 4e presents the schematic of the SE projection module [1], which is significantly more complex than that of a single-beam system. The secondary electrons from the various beamlets must be projected onto a detector array with minimal crosstalk so that it keeps the beamlet SE paths independent. Each image are taken independently, using
the in-lens detector located in the primary column. [4] HMI’s unique design is able to independently adjust
stigmatism for each beamlet.
For a single e-beam inspection system, 400 Mbps is the fastest data rate offered by HMI for image processing and defect detection, while the data rate is 50 Gbps for multi beam systems.
[1] Weiming Ren, et al, United State patent, US 9,691,588 B2.
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