CNC Knowledge: [Technologie MEMS]Detailed explanation of the glass micromachining process

As a common material, glass shines brightly in the fields of micro-nano-mechanical systems (MEMS), micro-nano-fluidic devices and optical MEMS due to its unique physical and chemical properties. Its excellent transparency, mechanical strength and dielectric properties make glass an ideal substrate material for these demanding, high-precision applications. However, although glass exhibits extraordinary properties at the macro scale, it faces many challenges during precise processing at the micron and even nanoscale. This article will provide an in-depth introduction to the glass micromachining process and understand its technical status, challenges and future development directions.

In the field of MEMS, glass is preferred because it can easily be seamlessly connected to silicon substrates through an anodic bonding process, and the connection interface has excellent airtightness and high bonding strength. . This combination not only simplifies the manufacturing process, but also significantly improves the reliability and stability of the equipment. However, microprocessing of glass materials is much more difficult than that of semiconductor materials like silicon.

TEMPAX glass, as a type of glass commonly used in micromachining, has a complex composition, containing approximately 75% SiO₂ and various additives such as Na₂O and CaO. While these additives give the glass unique properties, they also increase the complexity of its microprocessing. Compared to pure SiO₂, TEMPAX glass exhibits different etch rates during the etch process, resulting in problems such as low aspect ratio, low etch rate, limited mask selectivity, and roughness. high surface area, which have become the standard in glass micromachining.

In order to overcome the difficulties of glass micromachining, researchers have developed various technical means, including drilling, milling, laser processing, sandblasting, wet etching, dry etching and glass casting technology. Each technology has its unique advantages and limitations and is suitable for different application scenarios.

(1) Drilling and milling: These two methods are generally used to process larger patterns or structures, but they cannot achieve micron-level precision.

(2) Laser processing: although it can achieve high precision processing, the cost is high and it has a certain thermal impact on the material.

(3) Sandblasting technology: With its advantages of simplicity, low cost and precise directional engraving, it occupies a place in glass micro-machining. However, as mentioned earlier, sandblasting technology faces problems such as difficulty in dealing with small patterns, rough etching surfaces and residual particles.

(4) Wet and dry etching: Wet etching can remove material through the reaction of chemical solution and glass surface, and can obtain smooth side walls, but the aspect ratio is limited and dimensional reproducibility is poor. Dry etching achieves more precise micromachining, but it still faces challenges in etch speed, mask selectivity, and depth etch quality.

(5) Glass casting technology: including glass blowing and glass remelting, it is a microsystem manufacturing technology with great potential. Through high-temperature thermal deformation, glass can be shaped into complex three-dimensional structures, such as microlens arrays and wine glass resonators. However, this technology requires high process control and is difficult to produce narrow patterns.

Among the many glass micromachining technologies, sandblasting technology has attracted much attention because of its unique processing mechanism. The sandblasting machine accelerates fine powder particles through high-pressure airflow and blasts them toward the glass surface, using the impact force of the particles to remove the material. This type of mechanical erosion makes sandblasting excellent for machining harder materials.

However, sandblasting technology is not perfect. First, due to the resolution limitations of dry films and the large size of powder particles, sandblasting technology is unable to process small sub-micron patterns. Second, the rough etching surface and tapered etching profile produced during the sandblasting process are unacceptable for high-precision applications. Additionally, powder particles such as Al₂O₃ remaining on the etched surface can also harm subsequent processes.

In order to overcome these problems, researchers are constantly exploring new solutions. For example, the precision and surface quality of sandblasting processing can be improved by optimizing the sandblasting process parameters (such as spray speed, workbench moving speed, etc.), improving materials and resistance processes and developing post-treatment cleaning technology.

With the rapid development of nanotechnology and the continued emergence of new materials, people will be able to develop new materials and processes that are more suitable for glass microprocessing. For example, by regulating the composition and structure of glass to improve its engraving performance; using advanced nanoprocessing technologies (such as focused ion beam etching, electron beam etching, etc.) to achieve higher precision processing and combining multiple processing technologies; to form a composite processing system, etc. With the widespread application of MEMS technology and the acceleration of the trend of intelligence, the position of glass as a MEMS substrate material will become more stable.

In the future, glass microprocessing technology will be more combined with sensor technology, microfluidic technology, optical technology, etc. to form multifunctional and highly integrated microsystem solutions. These microsystems will be widely used in biomedical, environmental monitoring, aerospace, intelligent manufacturing and other fields.

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