Revolutionizing SiC manufacturing with advanced crystal orientation measurement systems

Precision is critical in the wafer fabrication process. The crystal tolerances of wafers and ingots are now being revolutionized by the most recent developments in crystal orientation measuring equipment. 

Furthermore, by facilitating exact orientation transfer to grinding and slicing, these sophisticated technologies not only monitor the quality of the most recent process completed but also feed forward into the subsequent operation. 

In addition to this quality advantage, its capacity to align many ingots onto a single wire-saw frame improves process tool use and expedites production.

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Precision is critical in the wafer fabrication process. The crystal tolerances of wafers and ingots are now being revolutionized by the most recent developments in crystal orientation measuring equipment. Furthermore, by facilitating exact orientation transfer to grinding and slicing, these sophisticated technologies not only monitor the quality of the most recent process completed but also feed forward into the subsequent operation. In addition to this quality advantage, its capacity to align many ingots onto a single wire-saw frame improves process tool use and expedites production.

The crystal orientation solutions combine three features with ingot, wafer and shaped crystal applications in mind to ensure real-time quality control during processing. These systems utilize three main value drivers:

  • Optical metrology for notch/flat and wafer/ingot dimensions.
  • X-ray diffraction (XRD) algorithms to precisely measure crystal axes’ tilt, magnitude and direction.
  • Workflow-adapted stages that enable the operator to transfer the measured information to their processing tools.

Malvern Panalytical stands at the forefront of delivering XRD solutions to various needs across academic, research and industrial settings. It offers automation capabilities for batch processing, workflow-adapted sample transfer and a user-friendly software interface for controlling and analyzing data. Key features include the ability to check 100,000 wafers per year on a single tool, ensuring accurate orientation before growth, grinding and subsequent processing steps. Their systems address challenges like variations in crystal quality and provide comprehensive solutions for semiconductor fabrication facilities.

SiC Wafer and Frontend Technology

In SiC device manufacturing, misalignment between crystal orientation or wafer geometry and a process tool reference system can lead to suboptimal process performance or even failure in the front end. For example, misalignment in respect to the crystal axes during lithography or implantation can result in poor device processing, affecting functionality and yield for MOSFET products.

In MOSFET processes, trenches are crucial for accommodating differently-doped materials. Kosugi et al. conducted a study deliberately rotating these trenches concerning the wafer crystal axis. They subsequently filled the trenches using metal-organic chemical-vapor deposition. This deliberate orientation variation explores the impact of crystal orientation on device performance, offering insights into optimizing MOSFET fabrication for improved functionality and efficiency.

Recent advancements in crystal orientation measurement systems are revolutionizing silicon carbide wafer production for high-power devices like MOSFETs.  Cutting-edge systems, such as state-of-the-art X-ray technology showcased by leading innovators, provide unparalleled accuracy and speed in measuring the orientation and quality of SiC wafers and boules during their processing from seed to boule to wafer via growth, grinding, slicing and polishing. By employing a combination of lasers, X-ray sources and sophisticated optical algorithms, these systems determine reliably the orientation of crystal axes, flatness, and edge profiles of SiC wafers. Substrate reliability is the first step towards successful SiC implementation.

X-ray diffraction

XRD is a highly regarded analytical technique that employs its capabilities to reveal the intricate composition and structure of materials. XRD is an emerging non-destructive technique utilized to analyze a wide range of samples’ physical characteristics—including phase composition.

In the context of wafer characterization, XRD can be utilized to determine the orientation of crystal planes relative to the wafer surface, including the offcuts. Three fundamental elements comprise XRD instrumentation: an X-ray source, a sample holder and a detector. The sequence of events commences with X-rays emitted from the source illuminating the sample before being refracted and detected. Through manipulation of the apparatus to alter the diffraction angle, intensity data is gathered, which serves as the basis for subsequent analysis.

The scope of X-ray scattering is expanded even further by employing techniques like grazing incidence. SISSAXS and GISAXS are both small-angle X-ray scattering techniques. In conjunction with X-ray reflectometry and total scattering, these methods explore the non-crystalline constituents of substances, thereby expanding the analytical scope.

In addition to its precision, XRD is also attractive due to its efficiency. XRD is a dependable and expeditious method for characterizing materials, as its analysis times are typically less than 20 minutes. 

Furthermore, progress in analytical software has optimized the process of data analysis, rendering it feasible for individuals lacking expertise in the field. Automated analyses are advantageous to industrial processes because they guarantee quality control without requiring specialized knowledge.

[Figure 1 AR240325-sic-manufacturing-crystal-orientation.jpg] Figure 1 AR240325-sic-manufacturing-crystal-orientation.jpg

Figure 1: Example of measurement unit—static diffraction setup 

Crystal orientation control: azimuthal scan method 

The traditional approach of using XRD methods, while effective, has its limitations. Rocking curve scans, for instance, are known for their accuracy but are inherently slow, requiring considerable time and resources. In contrast, the azimuthal scan method offers a remarkable breakthrough in both speed and precision.

Azimuthal scans involve rotating the sample 360° and recording intensity peaks, providing comprehensive data on both tilt magnitude and direction, as well as in-plane directions within the crystal, all in under 10 seconds. This method not only significantly reduces measurement time but also offers unparalleled accuracy, with precision down to 0.01°.

One of the key advantages of azimuthal scan measurements is their versatility and ease of use. With minimal moving parts and robust instrumentation, these measurements can be seamlessly integrated into various stages of the wafer production process. From checking seed quality before crystal growth to transferring orientation during grinding and cutting stages, azimuthal scan measurements streamline operations and ensure the highest level of accuracy and quality control.

The azimuthal scan method finds applications across various stages of semiconductor production. It ensures the correct orientation of seed crystals, facilitates accurate grinding and cutting of ingots into wafers and enables thorough quality inspection of semiconductor materials. Crystal orientation measurement devices, such as the Omega Theta diffractometer and the Wafer XRD 200/300 high-throughput wafer metrology machines, are seamlessly integrated into semiconductor manufacturing equipment. These devices enhance automation and improve overall production efficiency.

[Figure 2 AR240325-sic-manufacturing-crystal-orientation.jpg] Figure 2 AR240325-sic-manufacturing-crystal-orientation.jpg

Figure 2: Azimuthal scan principle 

Wafer XRD 200 and 300

XRD solutions utilize magnets and optical sensors to precisely measure the orientation of crystals. These systems can determine the orientation of crystals on both flat and curved surfaces, providing valuable data for optimizing grinding and slicing processes. By integrating this technology into cutting and grinding machines, manufacturers can achieve unparalleled precision in their operations.

For smaller crystals, such as SiC, innovative stacking techniques have been developed to streamline the slicing process. By arranging multiple crystals in an oriented fashion on a sine beam, manufacturers can significantly increase slicing efficiency, reducing production time from weeks to just one day.

After rough-cutting the wafers, advanced metrology solutions come into play for precise examination and quality control. Optical measurement systems with laser alignment capabilities ensure accurate notch and flat alignment, eliminating human error and ensuring consistent results. Additionally, mapping stages equipped with high-resolution imaging technologies enable detailed characterization of crystal quality and orientation across the wafer surface.

In high-throughput production environments, the Wafer XRD 200 sorting system offers rapid and automated quality assessment of wafers. Wafer XRD 200 is designed for wafer sorting based on crystal orientation and geometry parameters, setting a new standard in efficiency and accuracy.

Combining X-ray orientation measurements with optical sensors, this system can analyze a standard cassette of 25 wafers in just 10 minutes, facilitating efficient sorting and quality control processes.

The system’s fully automated handling and sorting capabilities further enhance productivity, streamlining your quality control process. With detailed data transmission tools, it seamlessly integrates into your workflow, providing effortless connectivity with MES and SECS/GEM interfaces.

Key measurements provided by the Wafer XRD 200 include crystal orientation, notch position and characteristics, diameter, flat position and length, as well as resistivity. With a typical standard deviation tilt of less than 0.003° for azimuthal scan—e.g., Si(100)—it offers unparalleled accuracy for critical measurements.

These advancements in metrology technologies extend beyond the semiconductor industry, with applications in various fields, such as aerospace and optics.

Versatility is a hallmark of the Wafer XRD 200, capable of analyzing a wide range of materials, including silicon, SiC, aluminum nitride, aluminum oxide (sapphire), gallium arsenide, quartz, lithium niobate and barium borate. Whether in research or production environments, it adds tangible value by facilitating easy and rapid analysis of numerous samples.

The Wafer XRD 300 is another cutting-edge XRD module by Malvern Panalytical tailored for 300-mm wafer production, offering precise insights into crystal orientation and geometric features like notches and flats. Its proprietary scan technology ensures ultra-fast and high-precision measurements within seconds, optimizing throughput and productivity. With easy connectivity to MES and SECS/GEM interfaces, this module effortlessly integrates into new or existing processes, making it a versatile and powerful solution for your metrology needs. Elevate your wafer production with the Wafer XRD 300’s advanced capabilities.

Looking beyond SiC

Crystal orientation measurement techniques are not limited to silicon-based semiconductors but apply to various single crystalline materials. Advancements in this field drive innovation and enhance semiconductor manufacturing processes. In optoelectronic edge emitter applications like indium phosphide lasers, precise measurement of crystal orientation ensures lithography masks align parallel to the cleavage plane, crucial for cleaving laser bars. 

Potential failures late in the process can incur significant costs. Various use cases, from XXL Si Ingot processing to optical crystals like CaF2 or Quartz technology, are linked by crystal anisotropy defining material and device properties. Accurate control of crystal orientation is vital for high-quality semiconductor materials with consistent properties. 

Adopting advanced crystal orientation measurement techniques offers benefits in efficiency, precision, and overall product quality in semiconductor manufacturing.


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