Wafer chucks are used to clamp wafers in various processes during semiconductor device manufacturing. In particular, wafer chucks are critical components in lithography scanners as they are used to not only hold the wafer, but also to flatten the wafer to minimize defocus problems resulting from wafer geometry, such as bow and warp. More recently, electrostatic chucks are being used to clamp and flatten reticles in extreme ultraviolet (EUV) lithography scanners during exposure. Similarly, electrostatic chucks will be used for clamping wafers during EUV lithography processes. Traditionally, vacuum chucks that provide approximately 80 to 90 kPa of clamping pressure have been used in photolithography tools. These pressures are generally sufficient to deform typical wafers with modest amounts of bow and warp flat and achieve complete chucking. If wafers are not chucked completely, overlay and defocus issues may arise in lithography processes.1–3 While wafer chucking is not typically considered a key challenge, recent and future changes to lithography systems and processes have increased the importance of wafer chucking. These changes include: (1) the development of EUV lithography systems that use electrostatic chucks with lower clamping pressures, (2) a move to smaller feature sizes with tighter requirements on defocus and overlay that make complete chucking, down to the nanometer level, critical, and (3) a transition to larger diameter, 450-mm wafers that are thicker and thus stiffer and more difficult to chuck. As described in 4, which reports experiments that involved the chucking of wafers and masks, the clamping pressure that is typically generated by electrostatic chucks is significantly lower (5 to 20 kPa) than that produced by vacuum chucks (). The development of EUV lithography systems has driven increased interest in characterization of different electrostatic chucking mechanisms and their capabilities, but previous reports have largely focused on mask chucking.5–7 As a result, there is a critical need to better understand the mechanics of the wafer chucking process and the role of wafer geometry in chuck performance.