Study of a clamping process with no deformation for a thin substrate using a freezing pin chuck system

• Published in: Precision engineering 2020-07, Vol.64, p.45-52
• Main Authors: Yoshitomi, Kenichiro, Une, Atsunobu, Tada, Kazuki
• Format: Article
• Language: English
• Subjects: Fixation liquid; Freezing pin chuck; Non-deformation clamping; Quartz glass wafer; Thin substrate; Warp
• ISSN: 0141-6359; 1873-2372
• DOI: 10.1016/j.precisioneng.2020.03.008

In planarizing a thin substrate, it has been difficult to remove warp or waviness as such substrates are forcibly deformed by conventional clamping methods. To clamp a thin substrate with no deformation, we have developed a freezing pin chuck system that fixes a thin substrate by freezing the fixation liquid on many pins. This paper describes the precision and fixing characteristics of this newly developed clamping process. The process consists of temperature control of the chuck, a spraying method to form droplets having concurrently uniform height on all pins, and a placing and fixing method that uses melting and refreezing steps so as to not impart shock on a wafer. Fixing strength in the shearing direction achieved more than 110 kPa, and the maximum deformation using the proposed clamping process achieved only 10 μm for a wafer 300 mm in diameter, 1.2 mm in thickness, and 100 μm in warp. Additionally, it is shown theoretically that the cause of slight deformation in this clamping method is the attraction imparted by the meniscus force. •This study can contribute to the achievement of machining to remove a warp or an undulation of a thin substrate.•Freezing pin chuck can greatly reduce the wafer deformation in comparison with a conventional clamping method.•Maximum deformation achieved only 10 μm for a wafer that has 300 mm in diameter, 1.2 mm in thickness, and 100 μm in warp.•Fixing strength in the shearing direction achieved more than 110 kPa.