Qualification of design-optimized multi-zone hotplate for 45nm node mask making

The demand for ever smaller features in integrated circuit manufacturing continues to put more stringent requirements on photomask fabrication, particularly with respect to critical dimension (CD) control. A high resolution process for making attenuated-phase-shift masks (attPSM) for the 45nm node with a negative-tone chemically amplified resist (nCAR), utilizing a new precision bake system, was evaluated. This process showed a significant performance improvement in critical dimension uniformity (CDU), respective to an established process based on an APB5500 system. A CD-uniformity improvement from 2.1nm CD 3σ to 1.3nm CD 3σ (40%) was achieved on a demanding layout. The new precision bake system utilizes an improved multi-zone hotplate design and control algorithm, which enables highly precise temperature controllability, facilitating a superior temperature ramp-up performance, as well as significantly improved temperature setpoint stability, as has been measured with a 25-point sensor mask for a 95°C bake process. The new precision bake system shall now be introduced to the market within the HamaTech MaskTrack series.