This paper describes a new infrared (IR) technique that offers sub-micron spatial resolution with a pump-probe scheme that can offer simultaneous collection of IR and Raman spectra at the same spatial resolution. The technique uses a single beam to collect both IR and Raman spectra using a technique called Optical Photothermal Infrared (O-PTIR). The O-PTIR technique provides constant spatial resolution over the entire mid-IR range due to the use of a fixed wavelength probe beam at 532 nm. The paper provides examples that highlight the advantages of the novel technique for addressing challenges that are commonly observed in the failure and contamination analysis community.

This paper discusses the use of optical photothermal infrared (O-PTIR) spectroscopy combined with Raman analysis. The new technique overcomes many of the limitations of conventional FTIR and Raman spectroscopy when used alone. It is based on an infrared-visible pump-probe system that incorporates a wavelength-tunable IR laser that emits a pulsed beam that is combined colinearly with the output of a 532-nm green laser. As the paper explains, infrared radiation is partially absorbed by the test target when the wavelength of the laser resonates with the vibrational mode of the material. This excitation process causes the area under the infrared spot to heat up, in turn, causing local expansion along with changes in the refractive indices. These photothermal effects cycle on and off in synch with the pulsed IR beam and the amplitudes of the on-off states are captured by the co-located visible beam and plotted as a function of wavelength over the tunable range of the IR laser. The diffraction limited spot size of the visible beam is approximately 416 nm, corresponding to a spatial resolution of about 1 μm, which is 30 times more precise than conventional FTIR. In addition, by measuring photothermal effects in localized regions, it is possible to identify chemicals in quantities of matter as small as 0.4 pg. By comparison, the sensitivity of transmission mode FTIR is significantly less at around 100 pg.

Rapid identification of organic contamination in the semi and semi related industry is a major concern for research and manufacturing. Organic contamination can affect a system or subsystem’s performance and cause premature failure of the product. As an example, in February 2019 the Taiwan Semiconductor Manufacturing Company (TMSC), a major semiconductor manufacturer, reported that a photoresist it used included a specific element which was abnormally treated, creating a foreign polymer in the photoresist resulting in an estimated loss of $550M [1].

Failure analysis of organics at the microscopic scale is an increasingly important requirement, with traditional analytical tools such as FTIR and Raman microscopy, having significant limitations in either spatial resolution or data quality. We introduce here a new method of obtaining Infrared microspectroscopic information, at the submicron level in reflection (far-field) mode, called Optical-Photothermal Infrared (O-PTIR) spectroscopy, that can also generate simultaneous Raman spectra, from the same spot, at the same time and with the same spatial resolution. This novel combination of these two correlative techniques can be considered to be complimentary and confirmatory, in which the IR confirms the Raman result and vice-versa, to yield more accurate and therefore more confident organic unknowns analysis.

Contamination and particle reduction are critical to semiconductor process control. Lots of failure analysis had been focused on finding the root cause of the particle and contamination. The particle and contamination effect were also easily found in circuit probing (CP) process, and therefore induced yield loss and wafer scrap. In the first part of this paper, an oven contamination case was studied. The second part of this paper focus on oven contamination monitoring. In the beginning, a die flying failure was papered at the stage of blue tape and die sawing. This event clearly indicated bad adhesion between die and plastic tape. This bad adhesion was suspected to be a particle/contamination layer formed on bad die surface. Three failure analysis (FA) approaches were performed to find out the root cause. The SEM/EDS result identified the main elements of big particle, but that is insufficient to identify the root cause. The OM/FTIR, however, showed the contamination may be related to polydimethylsiloxane (PDMS). The last failure analysis was the time of fly Secondary Ion Mass Spectrometer (TOF-SIMS), the result confirmed that there was a thin PDMS layer formed on the contaminated bad die surface. The high temperature CP process induced PDMS is believed to be the contamination root cause. In order to prevent the oven contamination event, a methodology based on contact angle and wettability of Si matrix sample was set up for regular monitor in oven operation. The details of contact angle test (CAT) sample preparation, measurement and analysis results were also discussed in this paper.

Nanoscale microscopy is an important technique in analyzing current semiconductor processes and devices. Many of the current microscopy techniques can render high resolution images of morphology and, in some cases, elemental information. However, techniques are still needed to give definitive nanoscale mapping of compound materials utilized in semiconductor processes such as Si3N4, SiO2, SiGe, and low-k materials. Photo-induced force microscopy (PiFM) combines IR spectroscopy with atomic force microscopy (AFM) to provide concurrent information on topography and chemical mapping. PiFM measures the attractive dipole-dipole photo-response between the tip and the sample and does not rely on repulsive force arising from absorption-based sample expansion. As such, PiFM works well with many of the inorganic semiconductor compounds (with low thermal expansion coefficients) as well as organic materials (with high thermal expansion coefficients) [1]. In this study, various examples of nanoscale chemical mapping of semiconductor samples (surfaces processed via directed self-assembly (DSA), strain in SiGe/SiO2 structure, photoresist, etc.) will be presented, all demonstrating ~ 10 nm spatial resolution

High resolution scanning probe microscopy techniques combined with infrared (IR) light sources offer unique solutions to combined chemical/mechanical/electrical characterization of defects in nanoscale dimensions. Previously, atomic force microscopy combined with infrared (AFM-IR) technology has demonstrated its capability to characterize nano-patterned metal/low-k dielectrics, nanoscale organic contaminants, and directed self-assembly of block co-polymers used for advanced micro/nanofabrications. In this paper, two complementary nanoscale chemical analysis techniques, photothermal AFM-IR and scattering type scanning near-field optical microscopy, are implemented to isolate and characterize microelectronic device cross-sections. It is observed that both techniques are able to detect patterned features with a half-pitch less than 15 nm.

NCF (Non Conductivity Film) is a material used for under-fill purpose in the TSV (Through Silicon Via) process, and is a key material for ensuring TSV 3D Package (PKG) reliability. Among the types of defects generated by the NCF, the most typical type is delamination. Particularly in NCF delamination frequently occurs during reliability test, we analyzed chemical state change of NCF according to reliability test step/condition by utilizing FTIR and TMA. Through these studies, we clarify the cause of Delamination.

Atomic force microscopy infrared (AFM-IR) technology combines the best of both worlds of AFM and IR spectro-microscopy offering high spatial resolution chemical characterization. Recent developments in the AFM-IR technique, such as tapping AFM-IR pushes the spatial resolution limit below 10 nm, making it ideal for chemically characterizing directed self assembly (DSA) components and defects for failure analysis. This paper demonstrates the chemical characterization of DSA nanopatterns using tapping AFM-IR technology with spatial resolution beyond 10 nm. Tapping AFM-IR experiments is performed on different block copolymers routinely used to fabricate directed self-assemblies on Si wafers. Along with chemical mapping, mechanical properties, such as relative stiffness and damping yielding complete chemical and mechanical property information in nanoscale to achieve material contrast, can be simultaneously probed.

Spectroscopic characterization of interconnects and circuits in semiconductor devices has become increasingly complicated as dimensions for breakthroughs and failure analysis are continuously shrinking. To achieve high spatial resolution infrared (IR) spectroscopic information, a pulsed infrared laser can be coupled to an atomic force microscope in the atomic force microscopy IR (AFM-IR) technique. The combination of AFM-IR and Lorentz contact resonance AFM (LCR-AFM) has great potential for providing high spatial resolution chemical and mechanical analysis. To demonstrate the feasibility of the AFM-based techniques, AFM-IR spectrum and images were obtained from the interlayer dielectrics of a test structure at a length scale shorter than the IR wavelength. Using the LCR-AFM technique, the relative mechanical properties of the components could be mapped distinctively by observing the contact resonance of the AFM probe. Finally, preliminary data suggest there may be AFM-IR spectral differences between contamination and the bulk material on a liquid crystal display.

This paper deals with real-time FTIR (Fourier Transform Infrared Reflectometry) etch depth measurements performed on passive integrated silicon substrates. High-density trench capacitors are non-destructively characterized using an FTIR Michelson type spectrometer. Based on effective medium approximations, an effective index associated to the capacitor layer is introduced which allows a good evaluation of the capacitor hole depth. Obtained results correlate well with those from SEM (Scanning Electron Microscopy) measurements performed on cross-sections, on a range going from 12µm to 30µm depth.

Two instances of BGA package level failures were identified during in-circuit electrical test. The electrical opens occurred as a result of contamination issues originating at the board supplier. Analytical techniques including optical inspection, SEM/EDS, Raman and FTIR were key in identifying photoresist on the board surface in the first case study and nickel carbonate contamination on the board surface in the second case study. In the first case study, resolution was achieved with a Plasma etch process. In the second case study, CCAs were cleaned with a wet chemical etch process formulated specifically to attack the nickel carbonate.

A failure analysis flow is developed for surface contamination, corrosion and underetch on microchip Al bondpads and it is applied in wafer fabrication. SEM, EDX, Auger, FTIR, XPS and TOF-SIMS are used to identify the root causes. The results from carbon related contamination, galvanic corrosion, fluorine-induced corrosion, passivation underetch and Auger bondpad monitoring will be presented. The failure analysis flow will definitely help us to select suitable methods and tools for failure analysis of Al bondpad-related issues, identify rapidly possible root causes of the failures and find the eliminating solutions at both wafer fabrication and assembly houses.

This article introduces several analytical chemistry techniques that are extremely useful in the electronics failure analysis (FA) laboratory, but are not normally found in FA laboratories. It presents the techniques in simple language and makes a case for the inclusion of chemists in the rapidly evolving and ever-shrinking world of microelectronic failure analysis. The article discusses the following techniques in terms of their applications, advantages, and operating principles: gel permeation chromatography, gas chromatography-mass spectrometry, Fourier transform-infrared spectroscopy, and electron spectroscopy for chemical analysis (ESCA). As we move into the world of nanotechnology, these techniques will become key in analyzing failures that cannot be visualized using traditional FA methods.

In failure analysis of wafer fabrication it is difficult to identify possible sources of carbon-related contaminants as most of them are from polymers, organic and complex compounds. In this paper, the fingerprints of EDX, FTIR, XPS and TOFSIMS techniques will be introduced so as to identify sources of carbon-related contaminants. For example, Si peak (1.740 keV) can be used as a fingerprint of EDX technique to identify the ink-related contaminant from the other carbon-related contaminants. FTIR spectra of more than 10 possible materials from wafer fab and assembly processes are discussed, which may be used as the fingerprints of FTIR technique to identify carbon-related contaminants. The C=O functional group and the PDMS (PolyDimethylSiloxane) are recommended as the fingerprints of XPS and TOF-SIMS techniques to identify source of carbon-related contaminants, respectively. In this paper, some application cases will be also discussed.

Airborne molecular contamination poses a serious problem for advanced wafer fabrication as the devices are continually scaled down. The amount of this contamination may be only a few monolayers, which are extremely difficult to detect by the commonly used analytical techniques, such as FTIR. ToF-SIMS has extremely high surface sensitivity for the analysis of trace contaminants on wafer surfaces. The high mass resolution of ToF-SIMS is also a powerful tool for the identification of the contaminants. In the current study, ToF-SIMS is used to monitor the build-up of airborne amine contamination on Black Diamond1 surfaces. It has been found that cleaning of the Black Diamond surfaces using wet chemicals can lead to photoresist poisoning. Thermal desorption-GC-MS analysis revealed that wet cleaning would result in the accumulation of hydrocarbons on the Black Diamond surfaces. ToF-SIMS shows that amines can build up gradually on the Black Diamond surfaces after wet cleaning, probably via airborne molecular contamination. For the Black Diamond wafers which did not go through the wet cleaning process, there was no significant increase of amines on the wafer surfaces. The amount of amines on the Black Diamond surfaces depends on the chemicals used in the cleaning processes and the wafer storage conditions. The level of amine contamination can be significantly reduced after the samples are heated up to 300°C for a few minutes in inert atmosphere.

A comparison of the electrical performance and effect of different types of flux to Micro Ball Grid Array (ìBGATM) solder ball quality was conducted. The units using no clean flux were found to exhibit opens failures during off-board testing and programming. Initial analysis conducted showed that the failures were due to contact problems between the solder balls and the test/programming sockets resulting from the presence of a transparent residue on the solder balls. In-depth failure analysis, in parallel with experiments conducted in the assembly line, was performed to determine the root cause of the solder ball contamination. Three failure analysis techniques were employed, namely: Scanning Electron Microscopy (SEM), Energy Dispersive Xray Analysis (EDX), and Fourier Transform Infrared (FTIR) Spectroscopy. An initial experiment was conducted to isolate the cause of the contamination by examining the different modules in the ìBGATM assembly. Failure analysis and experimental data proved that the opens failures were due to the no clean flux residue that was deposited on the surface of the solder ball after the reflow process.

A technique is presented for mapping the logic states of CMOS integrated circuits by observing their static infrared emission. Application of the technique is shown in two case studies. The technique has the advantages of being non-invasive, having high observability and reduced complexity compared with dynamic probing techniques.

Terahertz time-domain spectroscopy (THz-TDS) is a promising new technology which provides a relatively simple means of generating and detecting single-cycle pulses of far-infrared (or terahertz) radiation. One of the most interesting aspects of this system is its insensitivity to the thermal background. This obviates the need for cryogenic apparatus; as a result, this may be the first portable far-infrared spectrometer. Recent work has demonstrated the possibility of tomographic imaging using THz-TDS. In this imaging mode, a reflected pulse train is used to construct a three-dimensional representation of a composite material, using the timing between reflected pulses to determine the spacing between adjacent dielectric interfaces. Here, the transverse resolution is determined by the diffraction-limited focus of the THz beam, and is typically ~300 microns. The longitudinal (depth) resolution of ~100 microns is determined by the coherence length of the radiation, although the location of isolated surfaces can be determined with far higher precision. Since many common packaging materials have high transparency in the THz range, this suggests the possibility of exploiting this new imaging system for non-invasive testing and on-line monitoring. The operation of the THz “T-ray” imaging system will be described, and several examples will be provided which illustrate its capabilities and limitations.

In this paper, we report on a non-destructive technique, based on IR emission spectroscopy, for measuring the temperature of a hot spot in the gate channel of a GaAs metal/semiconductor field effect transistor (MESFET). A submicron-size He-Ne laser provides the local excitation of the gate channel and the emitted photons are collected by a spectrophotometer. Given the state of our experimental test system, we estimate a spectral resolution of approximately 0.1 Angstroms and a spatial resolution of approximately 0.9 μm, which is up to 100 times finer spatial resolution than can be obtained using the best available passive IR systems. The temperature resolution (<0.02 K/μm in our case) is dependent upon the spectrometer used and can be further improved. This novel technique can be used to estimate device lifetimes for critical applications and measure the channel temperature of devices under actual operating conditions. Another potential use is cost-effective prescreening for determining the 'hot spot' channel temperature of devices under normal operating conditions, which can further improve device design, yield enhancement, and reliable operation. Results are shown for both a powered and unpowered MESFET, demonstrating the strength of our infrared emission spectroscopy technique as a reliability tool.