Abstract Contamination in the gate oxide layer is the most common effect which cause the gate oxide integrate (GOI) issue. Dynamic Secondary Ion Mass Spectrometry (SIMS) is a mature tool for GOI contamination analysis. During the sample preparation, all metal and IDL layers above poly should be removed because the presence of these layers added complexity for the subsequent SIMS analysis. The normal delayering process is simply carried out by soaking the sample in the HF solution. However, the poly surface is inevitably contaminated by surroundings even though it is already a practice to clean with DI rinse and tape. In this article, TOFSIMS with low energy sputter gun is used to clean the sample surface after the normal delayering process. The residue signals also can be monitored by TOF SIMS during sputtering to confirm the cross contamination is cleared. After that, a much lower background desirable by dynamic SIMS. Thus an accurate depth profile in gate oxide layer can be achieved without the interference from surface.

Abstract This paper described a gate oxide failure case which affected the electrical parameters such as Vt and Idsat of both HV N&P MOS. A systematic problem solving approach combined with several FA techniques was applied to find the root-cause to be arsenic outgas cross-contamination.

Abstract Threshold Voltage (Vt) of MOSFET controls transistor’s on and off state. Vt is usually depends on gate oxide thickness and operating temperature. Systematic failure analysis for a Vt shift issue, should also consider the channel doping which affects the inversion layer formation. In this article, the failure case of a shift in the Vt of a Power MOSFET V is studied. Secondary Ion Mass Spectrometry (SIMS) is found to be the most direct way for detecting any abnormality in the channel doping profiles. A comprehensive simulation is performed showing that the Phosphorus level diffusion from substrate was so high that it affects the doping concentration of channel.

Abstract In this paper, we will describe a low yield case which revealed itself as leakage failures near the wafer edge. A systematic problem solving approach was used based on the application of a variety of FA techniques such as electrical curve tracing, Spreading Resistance Probing (SRP), Secondary Ion Mass Spectrometry (SIMS), and Chemical Analysis coupled with extensive Fab investigations. These techniques transformed an invisible defect into a visible one, leading to a full resolution of the issue with good understanding of the failure mechanism and the root cause. We will show that the wafer edge leakage was the result of N-type contamination of the substrate due to Phosphorus outgassing from the V-ring during the high temperature Argon anneal process.

Abstract In this paper, two failure analysis case studies are presented to demonstrate the importance of sample preparation procedures to successful failure analyses. Case study 1 establishes that Palladium (Pd) cannot be used as pre-FIB coating for SiO2 thickness measurement due to the spontaneously Pd silicide formation at the SiO2/Si interface. Platinum (Pt) is thus recommended, in spite of the Pt/SiO2 interface roughness, as the pre-FIB coating in this application. In the second case study, the dual-directional TEM inspection method is applied to characterize the profile of the “invisible” tungsten residue defect. The tungsten residue appears invisible in the planeview specimen due to the low mass-thickness contrast. It is then revealed in the cross-sectional TEM inspection.

Abstract A particular failure analysis case where phosphorous contamination occurred in arsenic-implanted Si is presented. Time-of-Flight secondary ion mass spectroscopy (TOF-SIMS) can be used for fast diagnosis of this contamination which shows 300% surface density change relative to the baseline. It is found that the cause of the phosphorous contamination is due to a combination of implanter chamber re-deposit cross contamination and rapid thermal annealing (RTA) process induced drive-in effect.