Adaptive Shot Technology To Address Severe Lithography Challenges For Advanced FOPLP

Fan-out wafer level packaging (FOWLP) is a popular new packaging technology that allows the user to increase I/O in a smaller IC size than fan-in wafer level packaging. Market drivers such as 5G, IoT, mobile and AI will all use this technology. According to Yole Développement’s analysis, the fan-out packaging market size will increase to $3 billion in 2022 from $2.44 hundred million in 2014, validating the market requirement for fan out packaging. While FOWLP has been used for many years, there is still a relentless drive to reduce the cost, and fan-out panel level packaging (FOPLP) has been proposed as one possible solution. FOPLP allows users to put more chips on a substrate, meaning more product output and a higher substrate utilization percentage. According to Yole’s analysis, the FOPLP market size will increase to $2.79 hundred million with 79% CAGR, showing that more people are adopting FOPLP.

FOPLP has many advantages and low cost potential, but it faces significant process challenges, such as die placement error and substrate warpage control. One of the key challenges is the trade-off between overlay, yield, and throughput during the lithography processing steps. A user exposes multiple dies per exposure shot to increase throughput, but this can result in lower overlay yield because of “pick and place” die placement error. To overcome the low yield issue, each die needs to be aligned, but this impacts throughput, so a compromise is required. To find the balance point between throughput and overlay is one of the biggest challenges for FOPLP.  

In this paper we address the tradeoff between throughputs and overlay yield, we demonstrate an integrated feedforward adaptive shot solution. This feedforward approach uses a third party metrology system to measure reconstituted panel die location data and sends the data to the stepper via a network. With feedforward algorithm technology, the stepper uses smart adaptive shot technology to generate an optimized variable shot size layout. This layout ensures the overlay yield is within specification with the minimum number of exposure steps. With feedforward adaptive shot technology, the user can maximize the throughput of the stepper and ensure the overlay yield at the same time.

Key words: advanced packaging, die placement error, FOWLP, FOPLP, overlay, yield, feedforward.