Shaping Semiconductor Ceramic Insulation Substrates: Methods and Innovations
- Iva Leung
- Jan 17, 2024
- 3 min read
Semiconductor-grade ceramic insulation substrates are pivotal in the realm of semiconductor devices, especially for high-power semiconductor devices. As semiconductor devices continue to evolve towards higher power and frequencies, there is an increasing demand for enhanced performance from ceramic insulation substrates. The shaping process is a critical aspect of ceramic substrate manufacturing and represents a significant challenge.
This article delves into several substrate forming methods, including roll-to-roll forming, gel injection molding, and innovative 3D printing. It analyzes the characteristics, advantages, and technical challenges of each method. Additionally, it provides insights into the current research status of ceramic substrate forming both domestically and internationally, offering a glimpse into future developments and applications.
In recent years, the rapid development of semiconductor devices towards high power, high frequency, and integration has highlighted the crucial role of ceramic substrates. The heat generated by semiconductor devices is a key factor leading to malfunctions, and the thermal conductivity of insulation substrates is paramount for effective heat dissipation. Compared to traditional resin-based materials, ceramics exhibit superior thermal conductivity and mechanical properties, making them an excellent material for high-end semiconductor devices, particularly as substrates for high-power semiconductor equipment.
In practical applications, the flatness, surface roughness, and dimensional stability of ceramic substrates are critical factors affecting subsequent circuit coating and corrosion. The substrate forming process imposes stringent requirements, and the manufacturing cost directly impacts its application and market competitiveness. Therefore, choosing the right forming method is crucial for ensuring the quality and cost-effectiveness of ceramic substrates.
This article provides a detailed exploration of commonly used ceramic substrate forming methods, including roll-to-roll forming, gel injection molding, and innovative 3D printing. By summarizing the characteristics of these methods, it offers a forward-looking perspective on the future development and application of ceramic substrate forming.
Ceramic Substrates: Key Components in Semiconductor Devices
As a critical component bearing semiconductor chips and their interconnections, ceramic insulation substrates should possess the following qualities:
Excellent insulation and resistance to electrical shock.
High thermal conductivity directly impacting the operational performance and lifespan of semiconductors.
Thermal expansion coefficient matching other materials within the packaging.
Smooth surface, consistent thickness, facilitating circuit printing and ensuring uniformity.
Manufacturing Process of Ceramic Substrates:
The preparation of ceramic insulation substrates follows the basic steps of mixing, forming, and sintering, as illustrated in the accompanying figure. Particularly, ceramic substrates are typically ultra-thin, below 1mm and even around 0.3mm, making forming and sintering crucial and requiring subsequent steps like flattening and grinding.
Secondly, Roll-to-Roll Forming of Ceramic Substrates:
Roll-to-roll forming, also known as blade forming or belt casting, is a vital shaping method for thin films and sheet-like materials. Initially used in 1947 for the production of ceramic sheet-like materials, this method gained patent recognition in 1952. Key features of roll-to-roll forming include:
High production efficiency with continuous operation, high automation, and stable processes suitable for mass production.
Good green body density, elasticity, and toughness.
Controllable green body thickness.
Suitable for producing multi-layer ceramic electronic devices.
The basic process of ceramic substrate roll-to-roll forming includes preparing the casting slurry, vacuum degassing, casting, and degelling. Obtaining a high solid content and suitable slurry is critical for roll-to-roll forming.
Based on the solvent type, roll-to-roll forming can be categorized into non-aqueous roll-to-roll and aqueous roll-to-roll. Non-aqueous roll-to-roll uses organic solvents such as ethanol, toluene, xylene, and organic additives like binders and plasticizers that are easily soluble in organic solvents, facilitating the production of high-quality casting slurry. It is a commonly used solvent system in roll-to-roll processes.
Researchers, such as Xu Lei and others, have utilized a mixed solution of polyethylene glycol, anhydrous ethanol, trichloroethylene, and anhydrous ethanol as a solvent to formulate casting slurry. They manufactured black alumina ceramic substrates with good color and strength by adding ceramic colorants and sintering at low temperatures. These black alumina substrates offer light-blocking properties and can be applied to new semiconductor components with significant photosensitivity.
Chen Bai and others used a binary mixed solvent of ethanol and butanone in non-aqueous roll-to-roll forming technology to prepare zirconia/alumina (ZTA) ceramic substrates. By reinforcing alumina with added zirconia, they achieved substrates with improved mechanical properties. Gutierrez and colleagues utilized triethyl phosphate as a dispersant to control the total content and ratio of binders and plasticizers, obtaining non-aqueous roll-to-roll sheets of silicon nitride.
Non-aqueous roll-to-roll is the mainstream solvent system for batch production. However, both toluene and xylene in non-aqueous solvent systems are strong carcinogens, posing adverse effects on human health and environmental protection. Additionally, organic solvents are costly, presenting challenges that need urgent resolution. Hence, water-based roll-to-roll has become a hot research topic.
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