The core layer deposition accomplished typically with PECVD is a key step in HJT processing. When it comes to equipment supply of HJT PECVD, TaiyangNews's recent report on HJT has deeply covered the key equipment suppliers along with the details of the respective solutions. However, description has gotten so extensive that it will be presented in two parts. The tools platforms from leading Chinese tool vendors are discussed in this first half.
S.C New Energy, a leading turnkey and production equipment supplier for standard technology from China, has started developing every processing tool required for HJT, including PECVD. China's Maxwell, a world leading screen printer maker, has now not only started offering a turnkey solution for HJT production, but also single PECVD devices. Swiss based H2GEMINI – while still a young company but backed from experienced solar experts – is also offering a turnkey solution as well as single tools. Leading module equipment supplier Jinchen is cooperating with H2GEMINI for PECVD. Not only have new companies entered the segment, longtime established PECVD supplier from China, Ideal Energy and HJT manufacturer turned equipment solution provider GS-Solar have also improvised their product platforms.
Maxwell is perhaps the most successful of the lot. The company has won several HJT equipment supply bids. As mentioned in the previous report, Maxwell is one of the vendors selected to supply its PECVD system to Tongwei. Later, the company also provided a turnkey solution for startup Huasun and also won an order for its subsequent 2 GW expansion project. Very recently, Indian conglomerate RIL, which has taken over REC, an early bird to enter mass production with HJT, has ordered 4.8 GW worth of key HJT processing tools from Maxwell.
The key attribute of Maxwell's PECVD tool is its very high throughput. While the company has not responded to our enquiry regarding the details of its technology, a few experts on the subject have provided some insights on the condition of anonymity. What is very clear is that the company has adopted a very special design, based on the principle that each layer is built in several chambers.
The general practice is to deposit one layer in one chamber, but Maxwell makes a single layer in a few chambers – the secret sauce for such a high throughput. For example, the tools from other companies use one chamber to deposit intrinsic amorphous silicon layer (i-layer), whereas Maxwell's tools are designed to use 4 chambers even to deposit this very thin 2 nm i-layer, thus speeding up the process. To realize this layered deposition, Maxwell developed a so-called "inline multi-chamber quasi dynamic PECVD coating technique," according to a technical spec sheet of the company for its Maxwell MV-LH06. The technology is based on PECVD multilayer showerhead discharge cathode design coupled with composite tray design. Quick RF ignition, real-time monitoring of plasma glow and inline corrosion-resistant magnetic fluid and vacuum transfer for large size tray are the other key aspects of the design. The exact spec for the throughput is 14,400 half wafers of G12 (105 x 210 mm) per hour, and 8,000 half pieces of M10. The tool has a rated 90% uptime and the spec for mechanical breakage is given as 0.25%.
On the flip side, this approach also makes the process slightly unstable and the tool itself quite long. Another limitation is that the deposition is superfast, and the film is built-up with several layers in multiple steps, which may not be suitable for applying microcrystalline. There is also a chance of causing interfacial issues between the layers of one stack, ultimately limiting the platform's role in the deposition of microcrystalline films. That said, Maxwell has also started offering PECVD tool that supports deposition of microcrystalline.
Ideal Energy Sunflower (IES), on the other hand, already has a good amount of experience with the microcrystalline silicon deposition for HJT. This may also be the reason why Huasun, which evaluated PECVD tools from both Maxwell as well as IES in its first 500 MW line and is happy with Maxwell's solution, again ordered PECVD from IES for its second phase, albeit not in equal quantities (in MW metric).
In fact, IES is the oldest PECVD supplier for HJT in China with a track record of about a decade in developing such solutions. By the end of 2021, the company had supplied PECVD tools to 12 HJT makers including big names such as LONGi, Tongwei, Huasun, Risen and Hanergy. The company has led the development of PECVD reactor design through several generations. The basic reactor design for all the generations remains the same. The first-generation reactor is designed to process a G5 carrier with 56 wafer pockets. This early design has a rated throughput of 1,500 wafers per hour. In mid-2019, the company developed a second-generation reactor, which is nothing but stacking one reactor over another (multi-layer), so that two reactors are installed in the footprint of one. The Gen 2 reactor has a throughput of about 3,000 wafers per hour. One advantage of this stacked design is that it enables sharing of utilities, such as the gas supply system and vacuum pumps, ultimately reducing costs. Ideal Energy's PECVD system has seven chambers in the following order – load lock, preheater, transfer chamber, i-layer deposition, transfer chamber, n-layer deposition and unloading.
After depositing the n-type material, the wafers are brought out and loaded onto the carrier, which is then flipped. The above process repeats again in the second PECVD tool with the only difference being that a p-layer is deposited instead of the n-layer. The company's PECVD tools feature an advanced RF plasma system, which enables plasma stabilization in 0.1 seconds with either 13.56 or 40.68 MHz. The company's production tools are equipped with cassette-to-cassette fully automated wafer transferring without using a belt. To maximize productivity, the chamber and carriers are integrated with in-line cleaning. The process chambers are also equipped with RF self-clean de-contamination apparatus to avoid opening of the chambers for cleaning.
Keeping these fundamentals the same, IES has introduced an upgraded version Gen 2.5 that has a slightly larger process chamber to accommodate larger carriers. The main feature of this tool is that it supports the processing of larger wafer formats – up to G12. The tool also features a few improvements including increased transport speed and optimized vacuum system, to support higher throughput. All these improvements enable the tool to achieve a figure of 5,000 wafers per hour for the M6 wafer size and has a rated capacity of 250 MW. Now the company has set its sights on making a GW-scale product. Even more interesting, IES is also offering a microcrystalline-ready PECVD solution. In fact, recent world records for HJT by LONGi have been achieved with IES' solution, as shared by IES' Vice President Liang Ouyang at TaiyangNews Virtual Conference on High Efficiency Solar Technologies 2021. "LONGi has set the record 3 times in 6 months based on our microcrystalline solution," said Ouyang in his presentation (watch Ideal's presentation Industrial Production-Ready PECVD Equipment for High Efficiency HJT Cells).
GS-Solar, banking on its thin-film PV equipment background and the experience it gained in establishing a 500 MW fab, has been offering HJT production equipment. The company was also one of three successful bidders in the equipment supply tender from Tongwei, and GS-Solar had the highest share of 2 PECVD and 2 PVD tools. While the company is reserved regarding the details of its processing equipment, it did provide the basic configuration details. The company is promoting two PECVD systems, mainly differing in production capacity – 350 MW and 500 MW. Both its PECVD tools are compatible with multiple wafer sizes, 166 mm and 182 mm, while G12 half wafer format is part of the standard spec now. The reactor chamber is designed to process 169 wafers of M6 size and 144 pieces of 182 mm. While these are still the same for both the tools, the loading capacity for G12 is different – the smaller tool can accommodate up to 200 wafers of half 210 mm format and 325 of the same format in the 500 MW system. Apparently, the tools are different even in their hourly throughputs. The 350 MW system has a throughput of 6,760, 5,760 and 8,000 (half-pieces) of G12, , M10 and M6 wafers, respectively. The high-capacity variant processes 10,140, 8,640 and 13,000 (half-pieces) per hour following the same order (see The Core Of HJT).
S.C New Energy is also promoting a PECVD tool for core layer deposition. While the company has not provided any input, its website does offer a few details. The reactor uses an RF frequency of 13.56 MHz with prompt response match and is based on remote plasma generation source. S.C New Energy underscores that its plasma technology is based on a self-cleaning mechanism, reducing the downtime to less than 5%. The company's PECVD system is based on an inline batch configuration. The process chamber is designed to accommodate a tray with either 10×10 pockets suitable for M6 wafers, 9×9 for 180 mm wafers or 8×8 for 210 mm wafers. S.C is offering two variants of the system – 125 MW and 250 MW. The fundamental configuration has four process chambers connected in series through a long tunnel. The first process chamber is for depositing intrinsic amorphous silicon layer, followed by the chamber for depositing n-type doped film. The wafers are then flipped to deposit the rear with the intrinsic layer first and then the p-type doped film. Depending on the required throughput, the process chambers can be added to the setup. The tool has a throughput of 5,500 wafers of M6 size per hour.
The Text is an excerpt from 3rd edition of TaiyangNews' Heterojunction Technology 2022 report, which provides an overview on the most recent production equipment developments. For more details, please read the full report, which can be accessed free of charge here.
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