Temporary Wafer Bonding Materials with Mechanical and Laser Debonding Technologies for Semiconductor Device Processing

Abstract

Advanced wafer-level packaging (WLP) techniques, mainly driven by high-performance applications in memory and mobile market, have been adopted for large-scale manufacturing in recent years. Temporary wafer bonding and debonding technology have been widely studied and developed over the last decade for use in various WLP technologies, such as package on package, fan-out integration, and 2.5-D and 3-D integration using through-silicon-via. Temporary bonding technology enables handling of thinned substrates (<100 μm), which can no longer self-support during backside processing and packaging. Moreover, some applications require the temporary bonding materials to withstand temperatures up to 250°C in high-vacuum conditions, and even up to 350°C or higher during the dopant activation step required for manufacturing power devices. Therefore, a simple yet effective temporary bonding process and material that can survive all the backside processes is highly desired. In this study, a series of formulations based on polar thermoplastics was developed for temporary wafer bonding applications. These materials target high-temperature survivability and improved adhesion to prevent the premature delamination during downstream wafer processing. All these materials provide high thermal stability up to 250°C or higher, and are able to be bonded to carrier wafers treated with release layers, which can be selectively debonded by either mechanical or laser release after backside processing. The material left on device wafer after debonding can be easily cleaned using common industrial solvents. Wafers bonded with these materials demonstrate lower overall stack total thickness variation (<5 μm) after grinding and have successfully passed a 200°C plasma-enhanced chemical vapor deposition (PECVD) process without any delamination during grinding and PECVD processes.

Direct Bonding and Debonding Approach of Ultrathin Glass Substrates for High Temperature Devices

“…The direct bonding is performed at room temperature under ambient atmosphere using rigid glass carrier to provide sufficient mechanical support of the ultrathin glass without using of intermediate adhesive agents or polymer bonding materials. The alignment and the contact force between the UTG and the corresponding carrier glass are programmed using a dedicated lamination tool (pressure of 0.5 x10 6 Pa, speed of 40 mm.s -1 ). For practical convenience, the size of the carrier glass needs to be carefully considered.…”

“…Finally, it must have a very short time and gentle debonding process without imparting damage to the thinned wafer or the features of its active components. There are several options for debonding of thin wafers from the organic temporary glues [4], [5], [6]: mechanical separation, ultraviolet (UV) or heat curing and release, thermal sliding-off, chemical activation or solvent swelling and laser activation with UV or infrared (IR) sources.…”

Cleaning and Particle Challenges in the Temporary Bonding and Debonding Process

“…Several types of integrated technologies such as fan-out wafer-level packaging (FOWLP), 2.5D interposer, 3D through-silicon vias (TSVs), and package-on-package (PoP), have all been developed with expected advantages of high integration, low power consumption, miniaturization, and high reliability [1][2][3]. As many of these current integration process flows require backside processing or thinning of the device wafer, the use of temporary bonding and debonding (TBDB) systems have proven necessary for enabling these current technologies [4][5][6][7][8][9][10]. During TBDB, wafers are temporarily adhered to a more rigid carrier wafer using a temporary bonding material (TBM) for mechanical support during handling and processing [8,11].…”