Kevin Sanchez

Delay variation mapping induced by dynamic laser stimulation

We present a novel technique based on dynamic laser stimulation (DLS) to characterize CMOS structures and to highlight time margin alterations by delay variation mapping. We used photoelectric laser stimulation (PLS) or thermal laser stimulation (TLS) to perturb CMOS transistor characteristics in order to affect propagation delays. The proposed methodology further extends the capabilities of DLS techniques such as soft defect localization (SDL) and laser assisted device alteration (LADA) to characterize defective ICs.

Dynamic Thermal Laser Stimulation Theory and Applications

Thermal laser stimulation (TLS) techniques have demonstrated their ability to detect and locate defects in integrated circuits (IC). Optical beam induced resistance change (OBIRCH) and all derivatives are based on the same physical principle: local laser heating of integrated circuits. The purpose of this paper is to synthesize the extensive work done in this area in order to highlight the essential physical principles. With this knowledge dynamic thermal laser stimulation (D-TLS) applications can then be tackled, optimizing parameters such as laser dwell time for sufficient heating. Finally, applications are presented on 180nm, 120nm and 90nm, comparing the sensitivity of dynamic thermal laser stimulation with respect to light emission

Frequency mapping in dynamic light emission with wavelet transform

Abstract Dynamic photon emission microscopy is an efficient tool to analyse today’s integrated circuit. Nevertheless, the reduction of transistor’s dimensions leads to more complex acquisitions where many spots can be seen. A frequency characterization of the whole acquired area can help to have a better understanding of it. With that purpose in mind, a new methodology to draw frequency mapping of dynamic light emission acquisition is reported. It is fully automated and based on wavelet transform and autocorrelation function. Regarding the possible use in an industrial context, the suggested method can help to localize abnormal emission activity and it gives some perspectives on automatic databases comparison.

Optical probing (EOFM / TRI): A large set of complementary applications for ultimate VLSI

Electro Optical Techniques (EOFM: Electro Optical Frequency Mapping and EOP: Electro Optical Probing) and Dynamic Light Emission Techniques (TRE: Time Resolved Emission and TRI: Time Resolved Imaging) are dynamic optical probing techniques widely used at IC level for design debug and defect localization purpose. They can pinpoint the origin of timing issue or logic fault in up to date CMOS devices. Each technique has its advantages and its drawbacks allowing a common set of applications and more specific ones. We have been involved in the development of the most advanced techniques related to EOFM and TRI on various devices (down to 28nm technology). What we can expect with each technique, which one to choose, what are the limitations are questions that must be answered regarding tooling cost and skills involved. Based on the understanding of the bases of each technique, their complementarities and their limitations have been identified. Even if these techniques can solve most of the issues we encountered, we can wonder if they can be applied on future technologies and this aspect will also be discussed.

Improvement of signal to noise ratio in electro optical probing technique by wavelets filtering

Electro Optical Probing (EOP) technique is an efficient backside contactless technique to measure waveforms in modern VLSI circuits. The signal related intensity variation of the reflected beam is very weak therefore, to acquire a signal with enough Signal to Noise Ratio, averaging techniques are usually performed. Resulting acquisition time for one waveform is too long to implement point to point probing to image mode. To overcome this limitation, we have developed a new filtering by wavelets approach to keep a good SNR while significantly reducing this acquisition time. It opens the doors to new multipoint probing applications. In this paper, we describe the technique, its efficiency in terms of SNR, execution time and limits.

Unsupervised image processing scheme for transistor photon emission analysis in order to identify defect location

Abstract. The study of the light emitted by transistors in a highly scaled complementary metal oxide semiconductor (CMOS) integrated circuit (IC) has become a key method with which to analyze faulty devices, track the failure root cause, and have candidate locations for where to start the physical analysis. The localization of defective areas in IC corresponds to a reliability check and gives information to the designer to improve the IC design. The scaling of CMOS leads to an increase in the number of active nodes inside the acquisition area. There are also more differences between the spot’s intensities. In order to improve the identification of all of the photon emission spots, we introduce an unsupervised processing scheme. It is based on iterative thresholding decomposition (ITD) and mathematical morphology operations. It unveils all of the emission spots and removes most of the noise from the database thanks to a succession of image processing. The ITD approach based on five thresholding methods is tested on 15 photon emission databases (10 real cases and 5 simulated cases). The photon emission areas’ localization is compared to an expert identification and the estimation quality is quantified using the object consistency error.

New statistical post processing approach for precise fault and defect localization in TRI database acquired on complex VLSI

Timing issue, missing or extra state transitions or unusual consumption can be detected and localized by Time Resolved Imaging (TRI) database analysis. Although, long test pattern can challenge this process. The number of photons to process rapidly increases and the acquisition time to have a good signal over noise ratio (SNR) can be prohibitive. As a result, the tracking of the defect emission signature inside a huge database can be quite complicated. In this paper, a method based on data mining techniques is suggested to help the TRI end user to have a good idea about where to start a deeper analysis of the integrated circuit, even with such complex databases.

Dynamic laser stimulation techniques for advanced failure analysis and design debug applications.

Dynamic laser stimulation (DLS) techniques have been introduced over the past few years to tackle the localization of dynamic failures. This article first reviews the principles behind DLS techniques and their implementation based on monitoring functional test mapping (pass/fail) signals and monitoring other electrical variations. The integration of DLS within a dynamic optical analysis workflow in failure analysis and design debug is then presented. Finally improvements aimed at increasing the ability of DLS techniques to solve ever-growing range of subtle soft defects issues are discussed.

Dynamic laser stimulation case studies

Dynamic Laser Stimulation (DLS) techniques based on near-infrared laser scanning are used for failure analysis, design debug, and time margin studies or critical path analysis. In failure analysis, it is applied to localize defects when static techniques can not be applied. Moving from static to dynamic laser stimulation requires a more complex electrical setup. This paper presents several DLS case studies along with the used DLS setup. It is shown that design-process related issues as well as physical defects such as resistive contacts are rapidly and precisely localized.

Automatic processing scheme for low laser invasiveness electro optical frequency mapping mode

Electro optical techniques are efficient backside contactless techniques usually used for design debug and defect location in modern VLSI. Unfortunately, the signal to noise ratio is quite low and depends on laser power with potential device stress due to long acquisition time or high laser power, especially in up to date technologies. Under these conditions, to maintain a good signal or image quality, specific signal or image processing techniques can be implemented. In this paper, we proposed a new spatial filtering by stationary wavelets and contrast enhancement which allows the use of low laser power and short acquisition time in image mode.