A Chip Integrity Monitor for Evaluating Long-term Encapsulation Performance Within Active Flexible Implants

Abstract

One key obstacle in employing silicon integrated circuits in flexible implants is ensuring a long-term operation of the chip within the wet corrosive environment of the body. For this reason, throughout the years, various biocompatible insulating materials have been proposed, yet, evaluating their long-term encapsulation performance on representative silicon samples still remains to be the main challenge. For this aim, in this work, a sensitive platform is introduced that can track the integrity of the chip against water and ion ingress. This platform is developed to be used for long-term monitoring of chip integrity and study of encapsulation layers in wet environments. The platform comprises a sensing array and a measurement engine and operates by tracking the changes in the inter-layer dielectric resistance within the chip. The proposed system uses a novel charge/discharge-based time-mode resistance sensor that can be implemented using simple yet highly robust circuitry. The sensor array is implemented together with the measurement engine in a standard 0.18 µm 6-metal CMOS process. For chip validation, dry and wet measurements in saline are presented in this paper.

Long-term Encapsulation of Platinum Metallization Using a HfO2 ALD - PDMS Bilayer for Non-hermetic Active Implants

“…In addition, to fully characterize the use of the proposed bilayer for packaging active implants, its encapsulation performance on implantable CMOS chips would also have to be investigated. To this end, we have previously reported a CMOS sensor array for monitoring moisture/ion ingress [15], which we intend to utilize to gain further insight on the encapsulation properties of the proposed bilayer.…”

A Chip Integrity Monitor for Evaluating Moisture/Ion Ingress in mm-Sized Single-Chip Implants

“…In this work we propose and present the implementation of an in-situ sensor array for early detection of moisture/ion infiltration within a CMOS chip. The measurement principle employed for such a sensor array, supported by a proof of principle, was first presented in [34]. Here, in this extended manuscript, previously unpublished circuit analysis and details on the design and implementation of the proposed sensor are reported.…”