Sang-chul Shin

Considering physical mechanisms and geometry dependencies in 14nm FinFET circuit aging and product validations

We report the extensive 14nm FinFET reliability characterization work and provide physical mechanisms and geometry dependencies. BTI, HCI variability related to #of Fin used in design along with self-heat considerations are critical for product design and qualifications. We show that along with increased AFs and optimized product HTOL stress conditions, 5-10x more efficiency in time has been achieved. In addition, external mechanical strain on Fin reliability will be discussed.

New insights into 10nm FinFET BTI and its variation considering the local layout effects

In this paper, BTI variation of 10nm FinFET is experimentally studied taking into account of the local layout effects. Although Fin shape is further optimized in 10nm compared with 14nm, the BTI and its variation show no obvious differences from the previous node. And this result is further confirmed by SRAM level reliability characterizations. In addition, the impacts of local layout effects on reliability are also investigated. Through Si data, BTI and its variation are not very sensitive to the layout effects which show within about 10% of the differences and the adopted structure for qualification can cover with all the different structures. Moreover, the results are also helpful for the accurate reliability modeling and circuit simulation.

Effects of front-end-of line process variations and defects on retention failure of flash memory: Charge loss/gain mechanism

Retention fails on flash memory were comprehensively characterized and fault-isolated for the formulation of failure mechanism. Using in-depth TEM and SIMS characterizations based on electrical findings, we found that FEOL process variations such as contact misalignment (spacer encroachment) and defects (ONO instability and stacking fault), result in retention fail of flash memory. In this paper, the failure mechanism of retention fail governed by charge loss/gain in a same cell is explicated and knobs for robust reliability and decent production are proposed from design and process perspectives.

Characterization of plate-like Ni-Sn intermetallic compounds in Sn-Ag solder bump

We characterized plate-like Ni-Sn IMCs in the Sn-2.3wt.%Ag solder bump using high-resolution 3D X-ray microscopy and transmission electron microscopy. Two types of plate-like IMCs (type 1 and 2) were observed in the solder bump. The type 1 is composed of NiSn4, Ni3Sn4 IMCs and Ni. Type 2 is only composed of plate-like NiSn3 IMC. The crystal structures of meta-stable NiSn4 and NiSna IMCs are orthorhombic (oC20) and tetragonal (I4/mcm), respectively. A significantly difference is that both type 1 and type 2 had a distribution of Ni and Sn. Ni and Sn are partially segregated (Ni-rich and Sn-rich) on the mixture of plate-like NiSn4 IMC and Ni, while Ni and Sn are uniformly distributed on the plate-like NiSn3 IMC.

Scenario-based set-level HTOL test (ASH III) for product quality and reliability qualifications on high-speed APs

In a succession of the set level stress test for high speed mobile application processor (AP) reliability [1], At-Speed HTOL (ASH) incorporated by user conditions was employed to realistically project the field failure rate of product. Using the worst case-scenario test with different frequency and operation duty, the failure modes veiled behind the conventional HTOL can be surfaced and then reconciled, which is further evolved as a failure screening technique during volume production. In addition, the simulation methodology to determine product Vmin-guardband (GB) in pre-silicon phase is also developed and compared to the Product Vmin-GB results. The results of ASH with scenario test can extend our understanding of an effective methodology to ensure robust design from design for test (DFT) and to achieve decent field failure target.

Reliability characterizations of display driver IC on High-k/ metal-gate technology

Display Driver IC is used to operate the display panel of mobile devices, such as handheld smartphones and tablets. Low power consumption becomes very important in mobile segments, thus High-k (HK)/ metal-gate (MG) process was used to fabricate DDI products. In this paper, an abnormal leakage increase observed during HTOL will be discussed along with the physical mechanism and superb HTOL results after process fixes have been implemented. As result, final DDI product showed an excellent reliability results through 1500hrs of HTOL exceeding product end of life (EOL).

Systematic reliability characterizations on Average Output Voltage (AVO) shift of Display Driver IC by HTOL

HTOL study on Display Driver IC (DDI) using 70nm process technology node is presented in this work. DDI is an IC that controls the display color pixels. The Average Voltage Output (AVO) and Deviation Voltage Output (DVO) are the two critical parameters for reliability that determines the quality of display. We report the fails observed in early product HTOL testing due to Vt mismatch of transistors in the amplifier design after aging and fixes implemented to significantly improve product reliability.

Interfacial degradation mechanism of Au-Al bonding in quad flat package

We have studied the interfacial degradation mechanism of Au-Al bonding in epoxy encapsulated quad flat package (QFP) induced by the high temperature storage (HTS) test conditions. In a way of root cause analysis to elucidate the degradation mechanism, atomic force microscope (AFM), SEM-EDX (energy disperse X-ray) and Auger electron spectrometry (AES) are used. It is found that the bonding strength of the wire pull and ball shear decreases with increasing depth profile of preexisting contamination layer and surface roughness. The plasma cleaning on the Al pad prior to an epoxy molding, however, enhances initial wire pull and ball shear strength. We firstly report the appearance of Sb on Auger spectrum from the fractured surface of Au-Al bonding. In the case of alloy-Al bonding, Pd retards the growth of intermetallics. The life time of Au-Al ball encapsulated with BP resin is much longer than that of OCN under the HST conditioned at 150 and 170/spl deg/C. It is also found that lessening in the wire pull and ball shear strength is correlated to the interfacial degradation coupled with the material of wire and EMC.