“ALD is slow and expensive,” is what critics might argue. So how do we begin to make ALD feasible for industry?
ALD found its original niche in the semiconductor manufacturing industry where it was first introduced in 2000 by Micron Technology to assist in the fabrication of their DRAM memory devices. The extreme precision afforded by ALD enabled device manufacturers to exponentially decrease the scale of their components, offering smaller, faster and more efficient electronics. However, while ALD provided the only viable fabrication method for nanoscale device architecture, the technique has two main drawbacks against widespread industrial adoption: ALD is slow and ALD is expensive.
Imagine how long it takes to put a fitted sheet on a bed. Now do that hundreds of times to hundreds of beds. It could take a while, right? The essence of ALD is the buildup of material one, perfectly conformal, atomic layer at a time. Inevitably, the deposition method has a slow growth rate. Typical ALD processes have growth rates around 0.1 nm/cycle, which, even in the fastest systems, reach only 300 nm per hour of growth. For depositing thick films, this growth rate is too slow for single substrate processing to be economical. Additionally, capital equipment cost is often a limiting factor for parties interested in adopting ALD. Even the simplest tools for performing atomic layer deposition processes are comprised of sophisticated heating components, numerous engineered valves, robust vacuum and filtration systems, and demanding electrical requirements. Depending on the tool, the cost can range from 100s of thousands to over 1 million Euros. Oftentimes, the throughput achieved with ALD cannot offset the cost of ownership of the tool. So how does one begin to make ALD feasible for industry?
Introduction of batch ALD
ALD has been traditionally performed in single-wafer or single-substrate tools where only one sample is coated at a time. In the past decade, innovations surrounding ALD tools has allowed coating experts to drastically increase the throughput of ALD by introducing a batch process. Rather than performing depositions on a single substrate, batch ALD offers the ability to coat multiple samples at the same time. The isotropic nature of ALD means the process will coat all surfaces in a reaction chamber, so in theory, one could pack any number of substrates into a chamber and coat them all at once. This was originally used as a strategy for increasing production volume of wafer processing tools. Rather than coating one wafer at a time, stacks of silicon slices could be processed in the same chamber during one deposition run.
Many cluster-integratable, 300 mm ALD tools utilize this strategy for maintaining high fab throughput. This solution is simple and offered new life to industrially viable ALD. With batches as large as 150 wafers, now up to 15 wafers/hour could be processed compared to barely 1 per hour in traditional crossflow and showerhead systems. But this was just the beginning for batch ALD processing.
Thick film solutions
ALD is synonymous with very thin films, or films with thicknesses only on the order of single or dozens of nanometers. Batch ALD and throughput breakthroughs for wafer fabrication benefitted from the small scale of film thicknesses needed. However, other industries soon realized that conformality and uniformity was also desirable for film stacks on a larger scale, in the micron range. This presented new challenges for tool manufacturers. Increasing the film thickness exponentially increases the process time exponentially and current batch systems were no longer economical. To make ALD a contender for depositing thick film stacks, the batch size needed to also be exponentially larger. Achieving such a process required engineering mastery for scaling fluid dynamics in the chamber, optimization of batch location in the reactor and scalable precursor introduction, for example, all while maintaining a clean deposition process.
Enter the Beneq P-Series.
The BENEQ P-Series
The Beneq P-Series is comprised of three tools dedicated to 3D and batch ALD: the P400A, P800 and P1500. The product line benefits from over 35 years of experience in industrially-relevant and scalable batch ALD. The P-Series is uniquely engineered to live at the intersection of batch size, deposition rate, and uniformity, and they are all about increasing throughput. Features of the P-Series include:
- Reaction chamber volumes spanning over 3 orders of magnitude
- Switchable chamber configuration to maximize tool uptime
- Pre-heating oven to cut down on heating process time
- High-capacity precursor sources for thick film stacks
- Modular vacuum pump and precursor deactivation system
This line of ALD tools offers the most control over batch production. Whether you are a high or low volume manufacturer, have substrates ranging different sizes or need films from nano to micro scale, the Beneq P-Series has a tool that will be optimized for your production needs. Some of our customers hottest use cases for batch ALD are below.
Use Case #1: Y2O3 for Anticorrosion Coatings
Here, Process Engineer Lassi Leppilahti explains the scale up process for large batches of Y2O3 coatings. Y2O3 coatings offer superior corrosion resistance for semiconductor manufacturing equipment, like showerheads or liners in a PECVD chamber. As technology nodes get smaller, the tolerance for metal contamination also decreases, making etch resistance in plasma chambers paramount. Batch ALD in the Beneq P800 provides an economical path towards coating semiconductor equipment parts and increasing yield in fabs.
Use Case #2: Freeform Optical Coatings
In this talk, Process Engineer John Rönn speaks on the use of batch ALD for coating batches of freeform optical components. Our ALD process affords highly conformal deposition without the need to rotate or manipulate complex 3D objects and allows deposition of thick, high-quality optical films. Batch ALD in the Beneq P-Series not only supercharges throughput but provides a more straightforward coating alternative to PVD without sacrificing film uniformity.
With some of the largest and most robust batch ALD tools on the market, our experts will help you find the solution best suited to your throughput and manufacturing desires. We want to know how batch ALD can help make your coating processes more economical or kickstart a coating solution workflow into your production line. Drop us a line here to speak with a Beneq representative about your batch ALD inquiry.