(Invited) Parylene C Based Adhesive Bonding on 6” and 8” Wafer Level for the Realization of Highly Reliable and Fully Biocompatible Microsystems

Abstract

The ongoing miniaturization and implementation of new functionalities into micro-electro-mechanical systems (MEMS) demand the development and application of new wafer bonding and encapsulation technologies with a high performance. Requirements are low process temperatures, high mechanical strengths of the bonded interface, as well as the applicability on large wafer sizes. Within the presented study, the polymer Parylene C was used as an adhesive for the bonding of 6” and 8” wafers. Doing so, the material combinations of the wafers, the Parylene thicknesses and geometries as well as the bonding parameters were varied. The properties of the wafer compounds were characterized with various methods, including mechanical tests, infrared imaging, cross-sections, hermeticity tests and the investigation of the thermal reliability. Using the Parylene C bonding process, tensile strengths of up to 35 MPa, and shear strengths of up to 80 MPa were realized. The determined helium leakage rate was lower than 1 ∙ 10-7 mbar ∙ l/s and the thermal reliability was verified to be excellent.

Low-Temperature Parylene-Based Adhesive Bonding Technology for 150 and 200 mm Wafers for Fully Biocompatible and Highly Reliable Microsystems

“…Note, that the tensile strength of the compounds bonded at 300 °C was not measurable due C•I. 30 to glue failure. All samples debonded cohesively and adhesively during the tensile test, whereas they only debonded adhesively during the shear test.…”

“…The debonding mechanism was determined to be dependent on the parylene frame width: For the C•III. 30 tensile tests, the samples with a frame width of 70 μm debonded adhesively. In contrast to this, the samples with a frame width of 200 μm debonded adhesively and cohesively.…”

“…These SEM images can be found in. 30 The described cracks at the inner bonding frame indicate the absence of epoxy, which would stabilize the substrate material during grinding. Hence, these cracks can be interpreted as an indicator for a closed and hermetic parylene frame.…”

“…This is advantageous for C•III. 30 the realization of cavities by parylene adhesive bonding. For nonpatterned parylene, the analysis with IR light transmission revealed that a homogeneous bond without any defects can be realized as well.…”

“…Tensile strength (a) and shear strength (b) of silicon-silicon (Si-P-//-Si) compounds bonded for different times, at a bonding temperature of 280 °C and a contact pressure of 2 bar. Detailed values are given in TableC•I 30.…”