Low Temperature Plasma Decapsulation of Copper-Wire-Bonded and Exposed Copper Metallization Devices

Abstract

One method of reducing costs in the packaging sector is to switch from gold bond wires to copper. Thicker copper wires (over 2 mils) can be safely decapsulated using a ratio mixture of fuming acids. Some surface etching of the copper will occur, but the wire will remain electrically viable. Microwave Plasma can provide a safer alternative for decapsulating packages with copper bondwires and exposed copper metallization. In this paper, experimental deprocessing of copper bond wire and copper metallization using laser ablation and downstream microwave plasma has found that 1 mil stressed wires can be safely exposed and examined, showing slip plane fractures in the corner wires. Topside copper metallization remains intact, even the thin protective nickel plating. Sensitive copper metal structures on top of the passivation (such as antennas) will remain electrically viable following decapsulation with plasma, but are often lost and defective following acid decapsulation.

Physical Fault Injection and Side-Channel Attacks on Mobile Devices: A Comprehensive Analysis

“…In some forensics cases, investigators may have to resort to laser or chemical decapsulation to gain hardware access for reverse engineering and/or data extraction [144]. Laser or chemical decapsulation increases the risk of destroying the device, particularly the bonding wires [68].…”

“…This damage can occur in two ways: (1), when the laser or chemical is used on the package to expose the device [68]; and (2), when the investigator manipulates the probes to contact the device during chip-on methods to read device memory or conduct physical FIAs [67]. To address this, Staller [144] (2010) proposed a method coupling electrically conductive adhesives (ECAs) and the precision of laser ablation-also known as photoablation-for the repair of damaged bonding wires and to minimise the risk of device damage.…”

Laser Focus Depth Adaptation for Decapsulation of Copper Wirebonded Devices

“…Some of these are related to the chemical etching temperature, mixed acid ratios and concentration, etc. [1][2][3][4][5][6][7].…”