RENA's Batch 3 N600 series batch-type wet process tool, used for texturing, single-side etching, and cleaning processes, features 6 carriers, each capable of holding up to 120 wafers per bath, and can deliver up to 15,000 wafers per hour
Its brand-new InEtchSide 4+ series inline wet process tool, which features a long bath lifetime and IP-protected water capping technology, is designed for the high-throughput removal of silicon oxide layers and doped glasses, including boron emitter etch and PSG/poly-Si Etch
RENA promotes a clustered design featuring both inline-type InEtchSide NIAK 4 and batch-type BatchEtch 3 N600 series wet process tools for gigawatt-scale TOPCon cell fabrication
Wet chemical treatment is an integral step in both TOPCon and HJT cell fabrication, ensuring proper wafer surface preparation for effective light trapping, cleaning, and etching of unwanted deposition layers. The quality of each wet chemistry process step – such as the pyramid structure of the textured surface, proper edge isolation, or etching of the polysilicon wraparound – directly contributes to efficiency gains in the cell. However, balancing quality with cost optimization remains the unique selling point (USP) for any cell tool manufacturer.
RENA, a European wet chemistry process tool manufacturer with over 3,300 machines installed globally, participated in the recently concluded TaiyangNews Annual Flagship Virtual Conference – High-Efficiency Solar Technologies 2024. Damian Brunner, Senior R&D Manager for Solar & Battery at RENA Technologies GmbH, presented a comprehensive range of wet chemistry process tools designed for cost-effective, high-efficiency cell fabrication at the TaiyangNews conference (see RENA presentation here).
For TOPCon cell fabrication, RENA offers both batch and inline wet process tools for 3 key chemical process steps: texturing, boron emitter etching, and poly etching & cleaning. The texturing process addresses inherent defects in incoming wafers, such as saw damage, and transforms the surface into a pyramid structure for better light capture. In the boron emitter etching process, single-side oxide or BSG etching, emitter etching, and subsequent cleaning are carried out. After rear-side passivation layer deposition, the poly etch & cleaning step removes unwanted polysilicon wraparound, followed by a cleaning process.
RENA’s Batch 3 N600 series wet process tool, featuring 6 carriers per bath, is used for texturing, single-side etch, and cleaning processes. This wet bench, equipped with carriers up to 710 mm in length, can process up to 120 wafers per carrier, translating to a throughput of 15,000 wafers per hour. Its pre- and post-cleaning steps are based on O3, as added by RENA. Assuming 8,280 hours of production at gross throughput per year, this tool, with its flexibility for wafer size changes, can process over 1 GW of wafer capacity in M10, G12R, or M12 sizes, reported the tool maker.
The recent introduction of RENA monoTEX H2.7 additive into the TOPCon texturing process enables the formation of smaller, pointier pyramids, resulting in an increase in Jsc of nearly 0.2 mA/cm² compared to the reference texture, according to RENA’s in-house test results. Brunner says this additive was used on TOPCon cells by a Tier-1 high-volume manufacturer, achieving approximately 25.5% efficiency.
RENA’s brand-new inline InEtchSide 4+ series wet process tool, which features a long bath lifetime and RFL (RENA Functional Layer = water capping) for improved optical yield and front-side protection, is designed for the high-throughput removal of silicon oxide layers and doped glasses, including boron emitter etch and PSG/poly-Si Etch. This tool, compatible with 12-lane (M12 and G12R wafer sizes) or 14-lane (M10 wafer size) configurations, can deliver up to 16,000 wafers per hour on a <20 m² footprint, noted Brunner. Assuming 8,280 hours of production at gross throughput per year for 25% efficient TOPCon cell production, this tool can process more than 1 GW of wafer capacity in M10, G12R, or M12 sizes.
For the single-side emitter etch process, RENA promotes a clustered tool design featuring both inline-type InEtchSide NIAK 4 and batch-type BatchEtch 3 N600 series wet process tools for gigawatt-scale TOPCon cell fabrication. The inline tool uses low, medium, or high HF concentrations at varying temperatures for BSG removal, while batch-type Si etching is done in a KOH medium. This clustered design can achieve high throughput of more than 1 GW per year, according to RENA.
RENA’s internal test data indicates that the edge isolation quality can be controlled through etching speed and different roller designs. The company has observed Jrev2 values of < 1.5 mA/cm², which serve as a key indicator for validating the quality of edge isolation in TOPCon cells using its wet chemistry process tool.
In the context of Indian TOPCon cell wet chemical processing costs (CoO), RENA highlighted a comparative analysis based on recent field data between all RENA wet tools and all-China wet tools. Although RENA’s tools come with a cost premium, their H2O2-free operation and lower consumption of KOH, HF, and DIW lead to a 30% lower CoO. This translates into savings of €3 million per 1 GW in annual running costs, explained RENA.
Additives for SHJ Cells
RENA also offers texture additives like mT H3.8 for industrial high-efficiency SHJ solar cells.