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Hello, this is TZ from the Sales Department.
In advanced semiconductor packaging processes, ensuring the reliability of build-up wiring is directly linked to product performance. In particular, the occurrence of bubbles (voids) during the desmear process has become a serious issue in the semiconductor industry, leading to copper wiring connection failures and reduced yields. Our degassing system "Livalley" solves this void problem and supports stable, high-quality product manufacturing. Why not consider the optimal solution now to build a void-free production line?
Reliability of Build-up Wiring in Advanced Semiconductor Packaging
In the manufacturing process of copper plated wiring for advanced semiconductor packaging, the demand for design rules and quality standards is increasingly stringent to accommodate 3D integration and chiplet technology.
Requirements include miniaturization of wiring sizes and associated high-density integration, smoothing of wiring surfaces to improve high-frequency characteristics, and larger substrate sizes due to increased package areas.
Schematic diagram of chiplets
In chiplets, an interposer with a redistribution layer (RDL) is used to connect chips over short distances for high-speed processing of massive amounts of data.
Research and development efforts are underway to reduce costs and supply products to a wider market by replacing the substrate material used in this interposer with organic substrates (resin materials) or glass substrates instead of silicon.
The size (width/spacing: L/S) of copper plated wiring in RDL is set at 2µm/2µm, and in organic interposers, this has already reached a feasible level in research and development. However, for mass production, it is necessary to establish manufacturing technologies that can achieve stable quality with higher yields on larger substrate sizes.
Formation of Build-up Wiring and SAP Process Flow
"Build-up wiring" refers to multilayer wiring where conductive patterns are formed on interlayer insulation films, which are then stacked and connected via interlayer vias. Build-up wiring is typically formed using the Semi-Additive Process (SAP) method.
The SAP process flow is as follows:
① Interlayer insulation film application
② Laser via drilling
③ Desmear treatment
④ Electroless copper plating (seed layer formation)
⑤ Resist patterning
⑥ Cu electroplating
⑦ Resist stripping
⑧ Seed layer etching
⑨ Palladium removal
The steps highlighted in red typically employ wet processes involving chemical immersion treatments. However, in recent years, there have been instances of dry processes being introduced, such as plasma treatment or photo-irradiation methods for the desmear process, and sputtering techniques for seed layer formation.
Void Formation in the Desmear Process and Countermeasures
Here, we would like to address the issue of bubbles in conventional wet processes.
In the formation of build-up wiring, interlayer insulation films composed of epoxy resin mixed with inorganic fillers (fine powder) are used. After laser drilling, the via sidewalls have an uneven surface where both resin and inorganic fillers are exposed.
Furthermore, to accommodate high-frequency transmission, it is necessary to keep the wiring surface smooth. For this purpose, inorganic fillers with smaller particle sizes are used. While this reduces the size of the surface irregularities, it increases the number of uneven areas.
Due to the nature of these interlayer insulation film materials, resin residue (smear) remains attached to the via bottom after via processing. The process of removing this residue is called desmear.
In the desmear process, the resin is etched and removed using a chemical treatment with permanganate. If the pre-treatment is insufficient, air can remain trapped in the uneven areas.
"If bubbles remain on the copper wiring at the via bottom or in the uneven areas of the sidewalls, it can lead to connection failures due to incomplete removal of resin on the copper wiring, or result in uneven etching where bubbles are present, potentially causing irregularities in the surface texture.
Furthermore, during the electroless copper plating (seed layer formation) process, any remaining bubbles can create areas without plating. This can prevent proper electrolytic plating in subsequent steps, risking the formation of voids (cavities)."
If voids remain in the finished product, the narrower the wiring width, the greater the risk of shorts due to migration, which affects the connection reliability of copper plated wiring.
As the wiring width becomes finer, the impact of minute voids known as 'microvoids' and 'nanovoids' on connection reliability can no longer be ignored.
It is extremely important to perform thorough degassing in all wet processes across the entire substrate to minimize the adverse effects of bubbles and improve yield.
We will propose the optimal deaeration system according to your production facility's capabilities.
"With our deaeration gassing system 'Livalley', by degassing the pure water used in pre-treatment, we can reliably and quickly remove bubbles from the substrate surface, minimizing the occurrence of voids.
We will calculate the required degassing capacity based on your existing production equipment's capabilities and design the optimal degassing system. We also offer demo unit rentals."
If your existing equipment does not have a treatment tank for degassing, we also design and manufacture degassing systems with integrated treatment tanks.
Remember "Tosetz" when it comes to bubble issues in the manufacturing process of packaging substrates!
"Our degassing system 'Livalley' has been adopted by many semiconductor packaging manufacturers, contributing to improved productivity and yield.
If you're experiencing bubble-related issues in your packaging substrate manufacturing process, please take this opportunity to consult with us.
We have also published the following related articles, which we encourage you to read:"
「"Livalley", a strong ally for removing air bubbles in Copper-plated via」
「"Livalley" to improve the cleaning effect of the ultrasonic cleaning process」
「Significant points in pretreatment and posttreatment of the plating process」
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