J.C.H. Phang

Failure analysis of integrated devices by scanning thermal microscopy (SThM)

High power densities dissipated in smaller and faster devices are leading to major thermal problems of semiconductor devices. The resulting local heat dissipation can induce deleterious effects like accelerated degradation or the destruction of the integrated circuits. Due to the shrinking feature sizes of modern devices and the small local extension of electrical failures the exact localization of these defects using established thermal failure analysis techniques like infrared thermometry becoming more and more difficult. Temperature measurements on passivated electronic devices with a sensitivity of 5 millikelvin by the use of a scanning thermal microscope (SThM) in contrast demonstrate the possibilities to use this system as a tool for failure analysis. Hot spot imaging with a spatial resolution of less than 150 nm, investigations on the backside of ULSI devices as well as a comparison with complementary established analysis techniques are presented.

DETERMINATION OF SECONDARY ELECTRON YIELD FROM INSULATORS DUE TO A LOW-KV ELECTRON BEAM

A technique for the accurate determination of secondary electron (SE) yield of insulators due to low-kV electron beam is presented. It is based on a capacitatively coupled charge measurement by subjecting the insulating film to a controlled pulsed electron beam in a scanning electron microscope. SE emissions from several insulating materials employed in integrated circuit manufacturing including wet and sputtered silicon dioxide (SiO2), polyimide, and AZ1350J photoresist, have been investigated for a range of primary energies between 0.5 and 2.5 keV. Comparisons are made between experimental data for SiO2 and polyimide with previous results. The dependence of SE emission on incidence angle and topography for SiO2 was investigated. Experimental results indicate that the dependence of SE emission on surface tilt for SiO2 is in good agreement with the power law for tilt angles below 70°, while emission saturation is observed at higher tilt angles. The SE yield from sputtered oxide was found to be higher than...

Design considerations for refractive solid immersion lens : Application to subsurface integrated circuit fault localization using laser induced techniques

With fast scaling and advancement of integrated circuit (IC) technology, circuitries have become smaller and denser. New materials and more sophisticated designs have evolved. These changes reduced the effectiveness of conventional laser induced fault localization techniques. Since IC fault localization is the most critical step in failure analysis, there are strong motivations to improve both spatial resolution and sensitivity of such systems to meet the new challenges from advanced technology. Refractive solid immersion lens (RSIL) is well known to enhance the laser spot size which directly affects resolution and sensitivity in back side fault localizations. In practice, it is difficult to operate RSIL at the ideal configurations to obtain the smallest spot resolution. It is necessary to understand the resolution performance at the other design focal planes. Besides resolution, there are also other factors that affect sensitivity in a RSIL enhanced system. This paper identifies and characterizes key RSIL design parameters to optimize RSIL performance on laser induced techniques. We report that the most efficient conditions are achieved close to aplanatic RSIL design to within 20-25 microm (for a 1 mm diameter lens), and the backing objective should be the minimum numerical aperture required for optimum resolution performance. The size of the mechanical clear aperture opening should be large enough (>80%) to exploit the advantage of aplanatic RSIL. RSIL is developed on a laser scanning optical microscope in this work, and a resolution of 0.3 microm (for a wavelength of 1340 nm) was achieved over a range of operating conditions. A quantitative resolution of 0.25 microm is achieved and a pitch structure of 0.4 microm is easily resolvable. Close to 15 times enhancement in laser induced signal is obtained.

A High-Sensitivity Photon Emission Microscope System with Continuous Wavelength Spectroscopic Capabi

A new spectroscopic photon emission microscope system (SPEMS) with high-sensitivity and continuous wavelength spectroscopic capability is presented. With the specially-designed light collection and transmission optics, high- resolution spectral characteristics can be acquired from very low-level light emissious. Two new wavelength parameters have been introduced to describe the bias-dependent spectral variation. The potential use of these two parameters as well as the spectral characteristics to identify failure mechanisms is also discussed.

Single contact optical beam induced currents (SCOBIC)-a new failure analysis technique

The Single Contact Optical Beam Induced Currents (SCOBIC) is a new failure analysis technique. By connecting the substrate or power pins of an integrated circuit to the current amplifier, many junctions can be imaged. In contrast, in the optical beam induced current (OBIC) technique, only the junction directly connected to the current amplifier is imaged. The implementation of the SCOBIC approach is discussed and experimental results which validates the SCOBIC approach is presented. Application of the SCOBIC technique for CMOS devices is also discussed.

The properties of 2.7 eV cathodoluminescence from SiO2 film on Si substrate

Cathodoluminescence (CL) spectra from a silicon dioxide (SiO2) film on silicon (Si) substrate were studied. The temperature-dependent results of the 2.7 eV peak suggest that the quantum efficiency increases but the build-up of electron-beam-irradiation-induced luminescence centres decreases upon specimen cooling. The voltage-dependent behaviour of the 2.7 eV peak does not show any luminescence enhancement from the SiO2-Si interface.

Single contact electron beam induced currents (SCEBIC) in semiconductor junctions. Part I: Quantitative verification of SCEBIC model

Abstract Single contact electron beam induced current (SCEBIC) transients have been obtained from a semiconductor junction for varying electron beam currents. The transients are shown to match a previously proposed model that postulates the existence of a parasitic capacitance between the unconnected junction region and the electrostatic ground. An experimental method to quantitatively verify the SCEBIC model and to extract relevant parameters is presented. The limitations of the model are discussed.

Quantitative imaging of local defects in very thin silicon dioxide films at low bias voltage by true oxide electron‐beam‐induced current

A new low‐voltage contrast mechanism due to electron‐hole pairs generated in the oxide by an electron beam was observed at electric fields lower than 3.5 MV/cm. This is in addition to the tunneling current microscopy (TCM) contrast mechanism observed at electric fields higher than 3.5 MV/cm. The new contrast mechanism is opposite in sign to the TCM contrast mechanism such that the image of a local thinning defect in the oxide is dark at low bias voltage and bright at higher bias voltage. Good contrast can be obtained at electric field as low as 2.4 MV/cm. Applications include large area imaging of oxide defects and quantitative mapping of small oxide thickness variations.

True oxide electron beam induced current for low‐voltage imaging of local defects in very thin silicon dioxide films

A new low‐voltage contrast mechanism due to electron hole pairs generated in the oxide by an electron beam was observed at an electric field lower than 3.5 MV/cm in addition to the tunneling current microscopy (TCM) contrast mechanism at electric fields higher than 3.5 MV/cm. The new contrast mechanism is opposite in sign to the TCM contrast mechanism. Good contrast can be obtained at an electric field as low as 2.4 MV/cm, which is two to three times smaller than that needed for TCM contrast. Potential applications include large area imaging and quantitative imaging of oxide defects.

Unconnected junction contrast in ion beam induced charge microscopy

A new contrast mechanism in ion beam induced charge imaging in semiconductors is reported. Junctions not directly connected to the charge collection preamplifier were found to give rise to significant charge collection signals. Imaging with these signals is carried out, thus enabling the mapping of junctions not directly connected to the charge collection amplifier.