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The Rigakubu News
The Rigakubu News, Sep. 2025.
Research Student Communicates to Faculty >
Visualizing the Effects of Antiplatelet Drugs
Hiroaki Tamaru (Professor, Photon Science Research Institute)
ISome organisms have flourished by acquiring abilities that most others lack, thereby opening up new ecological niches. Understanding the mechanisms by which such novel abilities arise has long been a central concern in evolutionary biology, and strange flowers that emit odors reminiscent of rotten meat to deceive flies into pollinating them provide an excellent example. Recently, we succeeded in uncovering how multiple plant lineages independently acquired the ability to produce such foul odors, showing that this specialized form of evolution can, contrary to expectation, occur through relatively simple steps.
Traditionally, semiconductor manufacturing referred to the front-end process, in which pre-designed fine circuit patterns were transferred onto silicon wafers using a technique known as photolithography. However, as circuits became more miniaturized and chip areas larger, the defect rate in the front-end process increased significantly, making it impractical to manufacture highly miniaturized, large-scale semiconductors on a single chip. To address this, the chiplet architecture has recently been adopted. In this approach, silicon chiplets of appropriate sizes are manufactured for each function, and only the good ones are interconnected on a substrate, thereby realizing ultra-fine, large-scale circuits.
This method, however, requires highly advanced back-end (packaging) technologies, since enormous numbers of fine terminals formed on the chiplet surfaces must be wired with high precision. Currently, wiring widths of several to several tens of micrometers are used depending on the application, while through-holes connecting the front and back of the substrate typically range from several tens to 100 micrometers in diameter. On the front-end side, photolithography using extreme ultraviolet (EUV) light with a wavelength of 13.5 nm has been introduced to achieve higher resolution. At the same time, to meet demands such as AI applications, larger chips (e.g., 120 mm × 120 mm) are required. Yet, wiring accuracy is limited by factors such as substrate flatness and differences in thermal expansion coefficients. As a result, glass substrates, which can provide higher flatness and thermal expansion compatibility with silicon, are now attracting attention. For next-generation substrates, via-hole drilling requires further miniaturization. However, glass is difficult to process and prone to cracking, so various processing methods are currently being explored.
In this study, we fabricated fine through-holes in a high-performance glass substrate called EN-A1, developed by AGC for its excellent electrical and thermal properties, using only laser processing (see figure). By employing an ultrashort-pulse deep ultraviolet laser, we succeeded in drilling holes with diameters of less than 10 μm through the glass. The aspect ratio (hole depth to diameter) reached approximately 20. While conventional acid etching methods have struggled to achieve such high aspect ratios, direct machining with deep UV lasers enabled crack-free processing with high aspect ratios. Moreover, since this method does not involve any chemical treatments, it reduces environmental impacts such as wastewater disposal.
This achievement represents an important milestone as a through-hole drilling technology for glass substrates, which are expected to replace conventional core materials and interposers in the back-end processes of next-generation semiconductor manufacturing. The technology is expected to contribute to further miniaturization of semiconductors and to the advancement of increasingly complex chiplet technologies.
These results were presented at the 2025 IEEE 75th Electronic Components and Technology Conference (ECTC), held in Dallas, USA, on May 30, 2025.
Conceptual diagram of this research