The channel of metal-oxide-semiconductor (MOS) transistors at different modes of operation has been characterized using dynamic backside laser reflectance modulation technique for different NMOS and PMOS transistors with different channel lengths. The reflectance modulations contain a primary peak near the drain-end when the MOS transistor is in saturation mode. Comparison studies with a Pseudo-Two-Dimensional analytical model support the hypothesis that the observed peak corresponds to the pinch-off point.

In this paper, a mobile Diffractive Solid Immersion Lens (mDSIL) design is proposed to enhance spatial resolution for backside laser fault isolation techniques. By allowing for multiple failure sites analysis using a single DSIL, this design improves conventional static DSIL directly fabricated on silicon substrate. The feasibility of mDSIL is demonstrated experimentally and the resolution performance is shown to be comparable to a static DSIL.

Dynamic Laser Stimulation (DLS) fault isolation techniques involve using an Automated Test Equipment (ATE) to run the device under certain test patterns together and a scanning laser beam to localize sites sensitive to laser stimulation. Such techniques are proven effective for localizing soft failures. In this paper, we demonstrate the feasibility of using such dynamic techniques for functional hard failures and design debug applications. We illustrate experimentally the significance of achieving sufficient signal to noise ratio (SNR) before such applications can be realized effectively, due to the large irregular noise that couples through as the functional pattern is run. We adopted a combination of hardware noise reduction and test program modification to overcome this challenge.

The capability of the Scanning Electron Acoustic Microscopy (SEAM) technique for high resolution non-destructive subsurface imaging at different depths for a multi-level integrated circuit is assessed. Experimental results using a beveled DRAM IC sample are used to quantify the effect of the electron beam energy and modulation frequency on contrast, spatial resolution and depth of focus of SEAM amplitude and phase images.

A Laser Timing Probe (LTP) system which uses a noninvasive 1.3 µm continuous wave (CW) laser with frequency mapping and single point measurement capabilities is described. The frequency mapping modes facilitate the localization of signal maxima for subsequent single point measurements. Measurements of waveforms with long delays and 50 ps response time from NMOS and PMOS transistors are also shown.

The effect of Refractive Solid Immersion Lens (RSIL) parameters on the enhancement to laser induced fault localization techniques are investigated. The experimental results of the effect on a common laser induced technique, namely Thermally Induced Voltage Alteration (TIVA), and imaging are presented. A signal enhancement in the peak TIVA signal of close to 12 times has been achieved.

In this paper, the application of scanning near-field photon emission microscopy for imaging photon emission sites is demonstrated. Photon emissions generated by a Fin-FET test structure with one metallization layer are imaged with spatial resolution of 50 nm using scattering dialectic probe. The potential applications and limitations of the technique are discussed.

The spatial resolution and sensitivity of laser induced techniques are significantly enhanced by combining refractive solid immersion lens technology and laser pulsing with lock-in detection algorithm. Laser pulsing and lock-in detection enhances the detection sensitivity and removes the ‘tail’ artifacts due to amplifier ac-coupling response. Three case studies on microprocessor devices with different failure modes are presented to show that the enhancements made a difference between successful and unsuccessful defect localization.

Spectral analysis of near IR photon emissions was performed on unstrained as well as uniaxial tensile strained nMOSFETs with physical gate length of 60 nm. The significant differences in the observed spectra could be attributed to the strain-induced bandgap narrowing. This shows that photon emission spectroscopy could potentially be used as a tool to monitor strain in the nMOSFET channel.

In this paper, the application of pulsed-TIVA for the localization of Cu/low- k interconnect reliability defects in comb test structures is described. Two types of subtle dielectric defects which are otherwise not detectable with conventional TIVA can be detected with pulsed-TIVA.

This paper describes a pulsed laser induced digital signal integration algorithm for pulsed laser operation that is compatible with existing ac-coupled and dc-coupled detection systems for fault localization. This algorithm enhances laser induced detection sensitivity without a lock-in amplifier. The best detection sensitivity is achieved at a pulsing frequency range between 500 Hz to 1.5 kHz. Within this frequency range, the algorithm is capable of achieving more than 9 times enhancement in detection sensitivity.

In this paper, scanning thermal conductivity microscopy is used to characterize interconnect defects due to electromigration. Similar features are observed both in the temperature and thermal conductivity micrographs. The key advantage of the thermal conductivity mode is that specimen bias is not required. This is an important advantage for the characterization of defects in large scale integrated circuits. The thermal conductivity micrographs of extrusion, exposed and subsurface voids are presented and compared with the corresponding topography and temperature micrographs.

In thermal microscopy, temperature error arises whenever a constant emissivity value is assumed for different materials. In this paper, we propose a new approach to eliminate these undesirable effects resulting from the ambiguous surface emissivity of materials. This method enables the compensated (true) temperature distribution of a device under test to be obtained from the measured temperature image. A transfer function that relates the measured and true temperature is formed to estimate the actual temperature distribution of a biased device to an accuracy of approximately 0.3-0.7K.

This article describes a series of experiments that were conducted on flash memory devices to correlate the defects that are detected by photon emission microscopy (PEM) and laser-induced techniques. Currently, there are two main categories of fault localization techniques for failure analysis, namely passive and active techniques. The article discusses defect localization by PEM and SOM. Three types of defects are described: Type 1 defects are those that can be accurately localized by both PEM and laser-induced techniques; Type 2 defects are defects which can only be detected with PEM and are not observable with laser-induced techniques; and Type 3 defects are those that are detectable with laser-induced techniques but cannot be detected by PEM. While PEM is able to capture the symptoms of existing leakage defects, laser-induced techniques can precisely localize temperature sensitive defects.

A spectroscopic photon emission microscope (SPEM) which is capable of high resolution spectroscopy for a continuous wavelength range between 300 nm to 1700 nm has been developed. Photon emissions were observed at energy levels below silicon bandgap from pn junctions and MOSFET devices at different biases. The experimental results indicate significant emission activity in this range. It was also found that the spectra is closely correlated to the electric fields present in the devices.

In this paper, the temperature distributions around interconnect defects due to electromigration are presented. A method to overlay the temperature distribution over the optical microscope image of the physical defect has also been developed. This allows a direct correlation of the temperature distribution and the physical structure of the defect.

Thermal beam induced techniques such as Thermally Induced Voltage Alteration (TIVA), Seebeck Effect Imaging (SEI) [1] and Optical Beam Induced Resistance Change (OBIRCH) [2] have been used for localization of reliability related faults in integrated circuits over the last few years. In this paper, we describe several approaches to optimize the detection of thermal beam induced phenomenon. In the first method, we have improved control of the laser scanning system to define a specific dwell time at each pixel. Secondly, we utilized a voltage source in series with an inductor to detect the induced voltage changes as the laser is scanned across the device. Finally, we employed a pulsed laser and a lock-in signal processing technique to increase the signal-tonoise ratio.

Temperature measurements on passivated electronic devices and the determination of the local thermal conductivity using the Scanning Thermal Microscope demonstrate promising possibilities to use this system as a tool for thermal diagnostics as well as for the failure analysis. Since doping concentration affects the thermal conductivity (k) due to the free carriers introduced, we propose the SThM as a potential dopant-profiling tool. To correlate doping concentration and thermal conductivity, we have mapped out the thermal conductivity of decreasing Boron-doped and Phosphorus-doped staircase silicon substrates and compared these data to the corresponding doping profile from ID Secondary ion mass spectroscopy (SIMS). To demonstrate the ability of the SThM technique to analyze both thermal features - temperature distribution and quantitative thermal conductivity - of an electronic device, we investigated properties of an NMOS device.