12-in. wafer imprinting using soft mold and gas pressure mechanism

In this paper, a new concept and mechanism has been developed, the PDMS mold is used and the gas pressure mechanism is employed for 12-in. wafer nanoimprint. As illustrated in Fig. 1, the gas pressurized imprinting process consists of four steps: (1) placing the substrate with resist onto the stamper of chamber B, which is then placed above a heating/cooling plate; (2) enclosing the chamber B and vacuuming, and then heating the substrate/mold stacker; (3) blowing the gas into the chamber A to exert gas pressure uniformly over the substrate, forcing it into the mold and imprinting resist; (4) exhausting the chamber A gas and blowing the chamber B gas, and then opening the chamber A to get the substrate with patterns. In experiment process, PDMS mold was cast and assembled. The resist used was PMMA. Nitrogen gas was used as pressing media. The seal film/PDMS mold/wafer stack is placed in a closed chamber. Then the gas is introduced into the chamber for pressing the stack. Excellent contact and uniform imprinting pressure throughout the whole area can be achieved. The experiment was carried out at temperature of 180°C with a gas pressure of 30 bar. The gas pressure was held constant for 5 minutes. Results showed that the patterns were reproduced in the PMMA resist (Fig. 2). This paper has reported an innovative method and mechanism for large area imprinting using direct gas pressure to press the soft mold and substrate. Successful replication of submicron features on fully 12-in. wafer by one imprinting step and it can achieve high replication throughput at, potentially, low cost.