Sulfur corrodes silver metal in a continuous reaction. This corrosion is also found in semiconductor industry processes for the application of silver into Backside Grinding & Backside Metal (BGBM). In this paper two experiments were conducted for the sulfide corrosion behavior in a Circuit Probing (CP) clean room environment. They were Mixed Flowing Gas (MFG) and clean room environment exposure test. The MFG test of this research was conducted in a testing chamber with temperature, relative humidity, and concentration of H2S were carefully controlled and monitored. The MFG test conditions included the test temperature of 25°C, relative humidity of 75 %, and H 2 S gas concentration of 10 ppb. And the MFG tests lasted for over 72 hours. The X-ray photoelectron spectroscopy (XPS) was used to analyze the elements composition and Ag 2 S film thickness of the MFG test samples. The second test of this research was the direct exposure experiment. The silicon samples deposited with appropriate silver layer thickness were exposed in CP fab clean room environment with H 2 S concentration well monitored. The XPS analysis results of the corresponding exposure test samples indicated that the Ag 2 S contamination would continue to develop and wouldn't saturate. This would be indicative for the management of Ag 2 S contamination control. The results of MFG and Exposure test were help for Ardentec to setup Ag 2 S corrosion methodology. All the managements were applied into daily operation of the BGBM semiconductor products.

Contamination and particle reduction are critical to semiconductor process control. Lots of failure analysis had been focused on finding the root cause of the particle and contamination. The particle and contamination effect were also easily found in circuit probing (CP) process, and therefore induced yield loss and wafer scrap. In the first part of this paper, an oven contamination case was studied. The second part of this paper focus on oven contamination monitoring. In the beginning, a die flying failure was papered at the stage of blue tape and die sawing. This event clearly indicated bad adhesion between die and plastic tape. This bad adhesion was suspected to be a particle/contamination layer formed on bad die surface. Three failure analysis (FA) approaches were performed to find out the root cause. The SEM/EDS result identified the main elements of big particle, but that is insufficient to identify the root cause. The OM/FTIR, however, showed the contamination may be related to polydimethylsiloxane (PDMS). The last failure analysis was the time of fly Secondary Ion Mass Spectrometer (TOF-SIMS), the result confirmed that there was a thin PDMS layer formed on the contaminated bad die surface. The high temperature CP process induced PDMS is believed to be the contamination root cause. In order to prevent the oven contamination event, a methodology based on contact angle and wettability of Si matrix sample was set up for regular monitor in oven operation. The details of contact angle test (CAT) sample preparation, measurement and analysis results were also discussed in this paper.

This paper describes the investigation of donut-shaped probe marker discolorations found on Al bondpads. Based on SEM/EDS, TEM/EELS, and Auger analysis, the corrosion product is a combination of aluminum, fluorine, and oxygen, implying that the discolorations are due to the presence of fluorine. Highly accelerated stress tests simulating one year of storage in air resulted in no new or worsening discolorations in the affected chips. In order to identify the exact cause of the fluorine-induced corrosion, the authors developed an automated inspection system that scans an entire wafer, recording and quantifying image contrast and brightness variations associated with discolorations. Dark field TEM images reveal thickness variations of up to 5 nm in the corrosion film, and EELS line scan data show the corresponding compositional distributions. The findings indicate that fluorine-containing gases used in upstream processes leave residues behind that are driven in to the Al bondpads by probe-tip forces and activated by the electric field generated during CP testing. The knowledge acquired has proven helpful in managing the problem.