We report on the application of optical methodologies to detect problems related to the deposition of nonparticulate contaminants on and in wafers that occurs during silicon semiconductor wafer processing. At issue is the problem of heavy metal contaminants such as Fe being deposited into the bulk of the wafer. The application of optical methodologies to detect these problems will be examined. We will also show how these techniques can be used for post-processing assessment of contaminant build-up and instrument qualification or monitoring, and how they will be used for future ULSI.

The adsorption of an anionic and a cationic surfactant onto a silicon surface was investigated using the technique of ATR (Attenuated Total Reflection) FT-IR at pH values of 2.5 and 9.5. The surface charge development on silicon samples conditioned in these surfactant solutions was investigated using a SPV (Surface Photovoltage) technique. The adsorption of DTAB was found to be much higher at pH equals 9.5 than at pH equals 2.5. In contrast, adsorption of SDS was independent of pH. The surface charge of HF-last cleaned silicon p(100) wafers was almost the same as that of the as-received wafer. After conditioning in surfactant solutions, negatively charged silicon wafers showed an excess of positive charge except of silicon wafers conditioned in DTAB solution at pH equals 9.5. After a DI water rinsing step, the surface charge was returned to its original value.

Single Photon Ionization Time-of-Flight Mass Spectroscopy (SPI-TOFMS) is used as an in situ optical characterization technique to monitor chemical reactions occurring at semiconductor surfaces during molecular beam epitaxial (MBE) growth be detecting gaseous species. In this approach, 118 nm (10.5 eV) laser photons are generated and passed on front of a semiconductor substrate in the ultra-high vacuum (UHV) chamber. Here, the photons ionize the gaseous scattered and desorbed growth species which are detected by time-of-flight mass spectroscopy. The photons are produced by frequency tripling the fundamental Nd:YAG output to 355 nm and tripling again in a static cell of Xe/Ar to 118 nm. The 10.5 eV photons have sufficient energy to ionize III-V species of interest, but not fragment them, allowing simple interpretation of mass spectra. Gated boxcars allow for rapid data acquisition of growth species in real time. SPI-TOFMS has been used to study As_n/Si(100) desorption kinetics and, more recently, MBE growth of GaAs. Results are presented on the real-time monitoring of Ga_n and As_n growth species. Simultaneous monitoring of growth with Reflection High-Energy Electron Diffraction (RHEED) is also discussed. Future work includes SPI_TOFMS studies of Si delta-doping in GaAs and surfactant-enhanced epitaxy of Ge on Si. SPI-TOFMS is an in situ UHV optical probe used to study the growth chemistry of semiconductor surfaces. This noninstrusive, species-specific real-time monitor of growth can be applied to increase the quality of device manufacturing.

Computer Generated Holograms (CGHs) are attractive devices because of their capacity to reconstruct any wavefront defined by a mathematical function, within the limits of the fabrication techniques. That wavefront modulation can combine or divide an input beam (fan-in and fan-out element): multiple phase functions can be coded in the plane of the CGH, as optimized numerically, doing different task during the same time, without multiplex holograms recorded in the thickness of the element. This feature is particular to CGH of diffractive optical element with surface relief modulation and permits easy copying for mass production. Also, we will present a device for sequence addressing produced by our simple technique, giving about 50% of efficiency with only one mask by simulated misfocussing.

A measurement system being developed for noncontact, nondestructive evaluation of package and module interconnects will be discussed. The system is capable of detecting interconnect faults in packages and module substrate layers. Low frequency impedance profiles of interconnects are also extracted. The potential advantages of this system over TDR systems result from the utilization of thermal signals obtained with an IR camera. Hence, they are noncontact measurements (requiring no probe fixtures) that are electrically passive and locally isolated even in an intact circuit. The main disadvantage of this testing method is that the interconnect under test must be planner with the traces exposed and visible to the camera. Therefore, in multilayer substrate structures, this method requires the testing to be conducted separately for each layer prior to assembly during substrate manufacture.

Since the CMOS Latchup phenomena is due to parasitic bipolar elements in the monolithic structure, this failure potential is always present and may return with each new circuit design or shrink of a proven design. Industry standard tests do not always identify latchup problems and/or pinpoint the exact latchup sites. laser scanning during electrical test has been shown to dot both, however, the expense of existing laser scanning systems has prevented widespread application of the procedure. This paper describes a system which features very low cost components including a semiconductor laser diode and an acoustic detection scheme which allows detection of all sites and a qualitative estimate of latchup susceptibility. if routinely used, the method could perhaps allow a smoother evolution of design rules.

A prototype optical profilometer providing automated surface profile measurements utilizing multiple virtual styli with micron height resolution has been developed. Measurement applications illustrated in this paper include TAB Inner Lead Bond (ILB) height and planarity, surface curvature of die mounted in ceramic packages, and MCM flipchip substrate post flatness.

Using femtosecond pulses from a Kerr-lens Mode-Locked Ti:Sapphire laser to generate second harmonic from a series of native-oxidized Si(001)/SiO₂ samples prepared with systematically varied etch- induced interfacial microroughness, we demonstrate rapid, noncontact, noninvasive measurement of Angstrom-level Si(001)/SiO₂ interface roughness. These measurements were performed in air and correlated with atomic force microscopy (AFM) measurements. We also demonstrate in-situ second harmonic monitoring of Si epitaxy in two growth regimes: high temperature (approximately equals 925 K) ultra high-vacuum chemical vapor deposition (UHV-CVD) growth mode and a cyclic atomic layer epitaxy (ALE) growth mode. During UHV-CVD growth of Si on ALE-grown Si_0.9Ge_0.1(001), we observed interference of the second harmonic signals between the growing Si surface and the buried Si_0.9Ge_0.1(001) interface. In the ALE growth mode, we monitored several key stages during a full cycle of growth of a partial (approximately equals 0.42) Si monolayer on Si(001) from a disilane (Si₂H₆) precursor.

A scanning laser computer assisted microscope in which the sample is scanned electromagnetic is used to produce images from semiconductor devices using photo induced current. We obtained 2D and 3D images which were analyzed in connection with current-reverse voltage (I-V_R) characteristics of the semiconductor devices. Images are stored in digital memories in real time and then processed with the different programs in order to obtain the required information. Our scanner offers the possibility 2D or 3D images ('map' or graphs) and pixelated images too. The localization of the different defects of the semiconductor devices was made.

Grain boundary contributions to optical second harmonic generation from polycrystalline silicon samples have been investigated. An extremely high second harmonic signal, oppose to that from the single crystal silicon samples, was observed in undoped poly-Si samples. The high intensity of SHG signal is attributed tot he nonlinear susceptibility modulated by the electric-dipole contribution of dangling bonds at grain boundaries. This explanation is confirmed by the dependence of SHG signal on polysilicon processed with hydrogen plasma treatment and high temperature annealing. The effect of dopant segregation at grain boundaries on the SHG has been investigated on different grain structures.

Optical second harmonic generation (SHG) method has been applied to the investigation of mechanical stress condition of BESOI (bonded and etched-back silicon on insulator) wafers. SHG scanning of SOI wafers show drastic variations, which are explained, in the case of thin film BESOI, by the mechanical stress arising from the bonding of rough surfaces, and, in the case of thick film BESOI wafer, by the presence of polish-induced strain that results from the thinning process of the wafer. SHG rotational dependence was observed for BESOI wafers, and its symmetry preservation indicates essentially sound silicon film quality despite a high level of mechanical stress. Mechanical stress effect on the SHG signal is also demonstrated through externally applied stress on the BESOI wafer. SHG method is shown to be able to characterize mechanical stress of BESOI wafers and may even identify the sources of the stress.

The photocurrent response of Silicon wafers scanned by laser beams of variable wavelength and intensity is evaluated to assess process-induced defects in their lateral and in-depth distribution, as well as in their chemical nature. Large-area transparent contacts to bare wafers, for current collection and surface passivation, are made by electrolyte chambers (ELYMAT principle). The application of the analytical technique is discussed for a variety of process development tasks, among them evaluation of quartz quality impact on bulk minority carrier lifetime and surface-near defect formation, intrinsic gettering and DZ characterization, as well as oxide interface quality.

I 'S well Imown rac t that propert ies or bydrogenat ed carbon (C : H ) rums are strongly influenced by deposit ion cond.i t ions or the rums [1]. This allow us use C:H rums ror d.irrerent applica— t ions , but we must understand how composition and propert ies or the rums are corinec t ed. with them clepos it ion conch t ions . In the work we will consider results or optical investigation or 0:11 rilms, prepared by RF sputtering, and try to explain results ob tained on the base or model ror "graphite—like" components con densation regimes on surrace or growing rum.

P-type wafers with oxygen concentration in two ranges near 30 ppma and 33 ppma, respectively, were processed through key thermal cycles. These processes were designed to denude the surface of oxygen, begin nucleation, and precipitate a portion of the oxygen in the bulk for intrinsic gettering. The samples were evaluated using nondestructive optical production profiling (OPP), and the results compared with surface photovoltage (SPV) measurements and cleave-and-etch inspection. The denuded zone depth (DZ) and bulk microdefect density (BMD) measured by OPP gave reasonable correlation with the diffusion lengths determined by SPV. The OPP data also showed the same general trends as the cleave- and-etch data. The shallower DZ and higher BMD reported by OPP in contrast to cleave-and-etch, however, are presumably due to the greater sensitivity of OPP to small defects.

An instrument is described which is designed as a production monitor for silicon wafer damage and contamination in the surface interface. The technique functions by putting the wafer are under test into a controlled depth of inversion. Then, the lifetime is measured by determining how much the inversion condition depletion width is affected by short wavelength light. The advantages of this technique, as implemented, over related methods include: (1) Only the interface region is measured. (2) The instrument measures simultaneously: Doping concentration, Oxide Charge, Interface trap density as well as surface lifetime, Ts. (3) The measurement of Ts is not affected by the wavers oxide charge since the instrument induces a compensating surface charge to put the wafer surface into a known depth of inversion. This is in contrast to other methods which require chemical manipulation of the wafer surface for a measurement if the oxide happens to have a charge which puts the semiconductor in the state of accumulation. Data is reported showing correlation of this technique with microwave PCD measurements and with measured Fe contamination values.

Hologram recording geometry using total internal reflection (TIR) from a photo sensitive material surface was used to achieve 0.5 micron resolution at (lambda) equals 457 nm with a readout of reconstructed image on photoresist. Such a geometry has demonstrated stability to parallel displacement within the illuminated area, and a rotation of +/- 2 degrees. The TIR recording system provided double fringe sets for each plane component inside the volume hologram. Therefore, diffraction efficiency as high as 80% was observed. The result is applicable to high volume submicron lithography and can be expanded for an eight-inch semiconductor submicron pattern. The use of a large aperture, well collimated laser beam provides us with much higher throughput than existing lightography machines have.

Iron doped p- and n-type samples were prepared using Czochralski method. The effect of pairing of iron with acceptors B and Al on the minority carrier lifetime was studied using the Surface Photovoltage (SPV) and DLTS methods. The effect of resistivity on the minority carrier lifetime in iron doped samples was investigated over 1 to 60 ohmcm resistivity range. The minority carrier lifetime dominated by Fe_i was found to be independent of resistivity. On the other hand, the lifetime controlled by FeB pairs increased by a factor of approximately town on increasing the resistivity from 1 ohmcm to 60 ohmcm. The data were analyzed using the Shockley-Reed-Hall model (SRH). The results indicate that the acceptor level of FeB pair at E_{c(subscript 0.29 eV is the main recombination level of iron in p-Si. The partitioning of iron between FeB and FeAl pairs in silicon samples codoped with B and Al was found to depend upon the relative concentrations of the two acceptors. Although minority carrier lifetime values dominated by Fe(subscript i} in B and Al doped samples were similar, FeAl pair was found to be approximately five times more effective as a lifetime-killer than FeB. FeAl pairs can be dissociated optically.

We discuss the determination of oxide charge from simultaneous noncontact measurement of the surface potential barrier, V_s, (via surface photovoltage) and the voltage drop across the oxide, V_ox, (via contact potential vibrating probe). These two measurements enable us to separate the contributions from total charge and oxide charge. In combination with corona charging and low temperature stress, this approach can be used for wafer-scale determination of the mobile Na⁺ concentration. The principles of the approach are presented and typical results are given which contrast the effects of ion drift and charge injection in the oxide. Experimental results also illustrate the noncontact, wafer-scale mapping of the mobile ion distribution.

We report on the application of optical surface photovoltage (SPV) to both quantify and qualify two problems which occur during ion implantation in CZ P-type silicon. The first issue is the problem of heavy metal contaminants such as Fe being deposited into the bulk from both the front and back sides of the wafer. Our second issue examines in-line use of SPV for monitoring the presence of nonelectrostatic charge induced by ions deposited from implant processing. Most electrostatic charge from implants has been modified by the use of an electron shower or 'flood gun'. Here we will examine how effective this tool is for modifying ionic charge. We will also show how the SPV technique can be used for postprocessing assessment of contaminant build-up and instrument qualification or monitoring.

A new small-spot, film-thickness measuring system operating near Brewster's angle, shows 0.1 Angstrom or 0.1% precision on SiO₂ films in the 10-400 Angstrom range. The illuminating beam is focussed to a e^-2 intensity diameter of 8 microns. The elliptical spot on the surface is easily placed in the center of test areas, such as a 50 micron square pad. The measurement technique takes into account the non Brewster's angle rays present within the focussed beam and the Gaussian intensity distribution of these rays. The resulting theoretical and experimental reflectance-vs.-film-thickness curves are shown to agree. Precision tests for various film-thicknesses are shown. Measurements are made in 2-3 seconds. Proper focussing and placement of the illuminating beam is achieved by autofocussing of a separate microscope viewing system.

The work contains results of irivestigatior on photoemission in thin oxide layers in WhiCh internal electric field has been generated. The samples were microscopic glasses covered on both sides by coructirç layers . The internal electric field was created by applyirg a negative polarizing voltage Upot to one of the layers (field emission electrode) , whereas the other one was emitting layer (Sr :Sb, Ti ) . As a result of Upoi. voltage ard i1 lumination, electron were released from the sample . mplite distrib.itior of imp.tlses were measuremed by ampi itie multicharinel analyser (fcr ani1 hinated ard I 1lumirited samples) . For i1 luminated emitting fi ln of Sr :Sb, the frequency of cc*.inth was several times greater then for uni1 luminated samples . For titanium fi las the interity of electron emission was several ord€r of magnitte sml ler than for Sr : Sb. For al1 samples the electron emission increases with growing Upo).. Keywords : photoemission. emission yield, semicorductor, SIS system, electric field. thin oxide layers, work function, optical properties.

Generation of thermal donors (TDs) and oxgen precipitation as a result of low tiperature annealing of boron-doped CZ-silicon under nitrogen axibient for different durations has been studied by resistivity and FTIR measurements. Donor generation rate is very rapid in the early stage of annealing and decreases later on. Prolonged annealing accelerates the process of oxygen precipitation yielding a maxiniim value of 1.97 ppme for 187 hrs. of annealing. The oxygen redu ct ion can be described by the second order kinet ics . Thermal diffusion coefficient has been estimated to be 5.52x1O' cm s and activation energy 1.089 eV. CZsilicon samples with high and mederat initial oxygen concentrations have also been annealed in air-ambient at 450 C and analysed the effect of oxygen and carbon in all the cases. Arnbients do not appear to affect the TD genera t ion kinet i Cs . The resu 1 ts of the inf luence of oxygen and carbon on donors generated by annealing at 6500C for 100 hrs in the two CZ-Si samples with initial oxygen concentration 33.5 and 34.5 ppma and carbon concentrations 1.5 and 1.0 ppma respectively, and the donors so generated as a function of oxygen and carbon reduction due to precipitation are presented and discussed. Controversial issue of the exact nuirber of oxygen atoms involved in a TD formation is debatable in view of the divergent estimates put forth by the workers. Involvement of 7-0. atms in a single TD sounds mere logical as also opined by Lindstrcm et1al. because thermal treatment creates a self-.insterstitial (Si1) and Si1 so created is surrounded by six O.-atons which become mere mobile as a result of increase in temperature. bne occupies the site vacated by silicon atom. One single TD may contain maxinum 7 nearest 0. atoms with Si as a nuclais.