Key takeaways:
Jerry Liao from Leadmicro described the transition from TOPCon to back-contact as an upgrade pathway that builds on existing manufacturing infrastructure
BC processing requires additional deposition steps, making throughput and tool utilization key factors in controlling equipment costs
Hybrid process approaches and upgrades in ALD, EPD, and laser systems are emerging as practical tools to support the transition toward TBC
There are 2 common routes to achieving tunnel oxide and doped polysilicon layers for TOPCon: LPCVD and PECVD. With back-contact (BC) technology gaining popularity, these routes are being evaluated for integrating and upgrading existing TOPCon lines to TOPCon back-contact (TBC) lines.
Jerry Liao, CTO of Leadmicro, presented the company’s solutions at the TaiyangNews High-Efficiency Solar Technologies Conference 2025. He explained how equipment development is evolving as the industry looks beyond TOPCon toward BC technologies. The talk focused on the practical question many manufacturers face today: how can existing TOPCon production lines be upgraded to BC without completely rebuilding factories? Rather than presenting BC as an immediate replacement, he framed it as a gradual transition, with equipment flexibility and process compatibility playing key roles.
TOPCon has rapidly replaced PERC and remains the dominant cell technology, with a large share expected to continue in the coming years. At the same time, BC is gradually gaining attention, especially as manufacturers search for the next efficiency step. From an equipment perspective, this creates a challenge because many factories have already invested heavily in TOPCon tools. The key question, therefore, is how to adapt those investments for future BC production.
Liao explained that BC manufacturing can still be based on established processes such as LPCVD, but it requires additional steps compared to TOPCon. For manufacturers already using PECVD-based TOPCon processes, Leadmicro proposed an intermediate route combining PECVD and LPCVD methods. In this approach, mature processes are used for both n-type and p-type regions, allowing a gradual upgrade path rather than a complete technology switch. He also discussed the company’s ongoing work on PECVD-based p-type polysilicon, aimed at reducing reliance on LPCVD and simplifying future BC integration. According to the data presented, key technical barriers such as passivation quality, blistering, uniformity, and doping control are being addressed, although full industrial validation still depends on production-scale integration and yield.
A large part of the presentation focused on equipment improvements to reduce investment costs for BC lines. As BC processing often requires thicker films and repeated deposition steps, throughput becomes a critical factor. Liao described modifications in LPCVD tools designed to increase throughput and improve loading methods, helping reduce the number of tools required per gigawatt of capacity. Similar efforts were described for PECVD systems, where capacity and uniformity improvements are aimed at supporting the front-side appearance and process stability required for BC cells.
ALD was another key topic, since BC and future TOPCon variants increasingly require double-sided deposition. This creates a capacity challenge compared to earlier single-sided processes. Liao explained that batch-type ALD becomes necessary in such cases, and capacity improvements are being pursued to offset the higher equipment demand. He also touched on related processes such as edge passivation deposition (EPD) and laser patterning, which are becoming more important as the industry moves toward finer cell cuts and more complex BC structures.
Overall, Liao’s presentation centered around how equipment innovation is enabling a more practical transition from TOPCon to BC. Instead of a single solution, he outlined multiple pathways, including traditional LPCVD routes, hybrid approaches, and newer PECVD-based options, depending on a manufacturer’s starting point. He emphasized that BC development is progressing not only through cell design but also through continuous adjustments to deposition, patterning, and interconnection equipment, aimed at reducing complexity and investment risk as the industry prepares for the next phase of high-efficiency solar manufacturing.