We report on the first use of optical low coherence reflectometry (OLCR) for Edge Defined Film-Fed Growth (EFG) silicon characterization. This OLCR sensor system has been used to measure horizontal profiles of silicon thickness and flatness to an accuracy of 1.5 Rim with the sensor head positioned 1 cm away from the silicon. The use of this noninvasive sensor for EFG silicon growth monitoring may lead to more efficient solar cell manufacturing processes.

Plasma etching of GaInAs and AlInAs has been carried out in a system which consists of an electron cyclotron resonance (ECR) source and an rf-powered stage. Since the ECR source can generate a plasma with low ion energy, dry etching induced damage is expected to be minimal. In this study, Schottky diodes and transmission lines were fabricated on the etched GaInAs surface. The diode and transmission line characteristics were evaluated as a function of etch conditions. For the etching of GaInAs and AllnAs, C12 and Ar were used as the etch gases. In addition to the ratio of the two gases, microwave power, rf power, pressure, and source distance were varied and their effects on etch rate, morphology, and surface damage were analyzed. Etch rate increased monotonically with microwave power, rf power, and C12 percentage. Etch rate decreased with increasing distance and reached a maximum for a pressure of 1 mTorr. The etch conditions for the damage study were chosen to maintain smooth morphology. One of the most important factors influencing damage was the ion energy which can be limited by using low rf power and short source distance. Minimum damage was obtained at 1 mTorr which provides the optimal balance between high etch rate and low ion energy. Besides limiting ion energy, the addition of Cl2 reduced etch-induced damage. The specific contact resistivity and sheet resistivity obtained from transmission line measurements of dryetched n-GaInAs were lower than the wet-etched samples. Schottky diode analysis show reduction in barrier height and breakdown voltage after Ar sputtering. Addition of 10% C12 is sufficient for full recovery of the diode characteristics.

A Scanning Electron Microscopy method called Dark Voltage Contrast (DVC) was applied for the first time to investigate on a microscale, the narrow depletion region of a Zener diode. Zener diodes were fabricated by the Sprague Semiconductor Corp. using conventional boron diffusion into a n-type wafer with phosphorus.

Zener diodes were chosen because of the presence of a shallow p-n junction and for the ability of Zeners to work in the breakdown regime where the dynamics of the current might influence the field distribution in the p-n junction. The samples were examined in the SEM with a beam current below 50 pA to minimize injection of electrons into the depletion region.

Reverse and forward biased diodes were examined and potential distribution information was obtained, using Dark Voltage Contrast software. Doping information and C-V measurements were used to double check DVC depletion region measurements.

The main results of these studies include measurements of electrical field for three regimes of operation: forward, reverse, and breakdown, with almost ideal field distribution in some Zeners, and fluctuations in others. The field irregularities are related to the defects in the junction area. However the amount of charge build-up appears to depend on the current flow in the dynamic regime for the breakdown. The typical measurements of depletion region width were Wf=.14 μm when forward biased, Wr=0.35 μm at 3-4 volts when reverse biased and Wbr=0.44 gm for 6 v of breakdown. This data helps to reconstruct the diffusion profile.

The growth of ternary semiconductor compounds Cd1-ZZnx. Te leads to possible uses of this material like optoelectronic devices. In the present work we report the structural characterization of Cd0.96Zn0.04Te obtained by modified - Bridgman technique. Structural studies were carried out using Scanning Electron Microscopy (SEM) and Conventional and High Resolution Electron Microscopy (TEM and HREM, respectively). Selected Area Electron Diffraction (SAED) was used to determine local variations in composition. Characteristics of the growth of the bulk samples were observed and structural details that might be related with the stability of ternary phase were derived.

We discuss an approach to iron concentration determination in silicon, based on wafer-scale surface photovoltage measurement of the minority carrier diffusion length in the millimeter range. The approach combines two novel aspects: it overcomes the diffusion length to wafer thickness ratio limitation of previous SPV methods, and it employs iron separation from other recombination centers using rapid photo-dissociation of iron-boron pairs. The wafer thickness limitation was eliminated by using the correct theoretical SPV wavelength dependence instead of simplified asymptotic diffusion length form adopted in all previous treatments and valid only for diffusion lengths much shorter than the wafer thickness. Photo-dissociation of Fe-B pairs and measurement of the corresponding decrease of the L value (caused by creation of iron intersticials) enables iron detection in typical silicon wafers in times of seconds with a sensitivity in the low 108 atoms/cm3 range.

Triple crystal x-ray diffraction (TCXD) is a non-destructive structural characterization tool capable of the separation and direct observation of the dynamic (perfect crystal) and the kinematic (imperfect crystal) components of the total intensity diffracted by a crystal. Specifically, TCXD can be used to measure the magnitude of the diffuse scattering arising from defects in the crystal structure in the immediate vicinity of a reciprocal lattice point. In this study, the effects of BC13 reactive ion etching (RIE) on the near-surface region of GaAs were investigated by analyzing the changes in the diffuse scattering using both the symmetric 004 reflection as well as the highly asymmetric and more surface sensitive 113 reflection. While the results from the 004 reflections revealed little difference between the unetched and the BC13-etched samples, maps of the diffracted intensity around the 113 reflections showed an unexpected and reproducible decrease in the extent of the diffuse scattering in the transverse direction (perpendicular to the < 113 > direction) as the RIE bias voltage was increased. This decrease suggests that the degree of etch damage induced in the GaAs near-surface region is reduced with increasing bias voltage and ion energy. Additionally, the symmetry and orientation of the kinematic scattering was altered. Possible mechanisms for these results willbe discussed.

We describe successful algorithms for rapid alignment of the Bragg planes normal to the incidence plane in a high resolution X-ray diffraction experiment. One is appropriate to the surface symmetric geometry and uses a technique of rotation about the specimen normal.

From an experimental study of the rocking curve shape as a function of tilt, we have developed a new algorithm which uses tilting about an axis formed by the intersection of the specimen and incidence planes. This has been shown to be reliable for rapid optimization of the diffraction conditions for wafers cut up to 15° off the (001) plane and for asymmetric reflections. Additionally algorithms are outlined which permit rapid location of the maximum of the Bragg peak and deduction of the mean wafer curvature from the X-ray data

It has been have demonstrated that synchrotron white beam x-ray topography can be used to characterize IR detector materials at nearly every stage in the manufacturing cycle, including: as-grown CdZnTe single crystal boules; substrate wafers cut from different positions in the boules; thin films grown on characterized wafers; and HgCdTe focal plane arraystructures. Special diffraction geometries have been developed, taking advantage of the broad wavelength spectrum, large beam size, and high intensity of the synchrotron radiation source, to enable rapid and non-destructive assessment of defect densities and strain distributions after each processing step. This diagnostic method has important implications for increasing the producibility of focal plane arrays. Boule characterization can reveal defects, grain orientation, interfaces and strains, and provides guidance for optimal slicing. Wafer characterization produces multiple topographic images, providing both defect mapping and depth profiling in a single exposure. Finally, x-ray topography of HgCdTe focal plane array test articles reveals subsurface damage not observable by optical or IR microscopy. The applicability of this technique to evaluate yield, quality, and reproducibility will be discussed.

We have attained extremely smooth etched surfaces on GaAs using a hydrogen plasma pretreatment before etching. The resultant morphology exhibits smooth surfaces since the etching proceeds uniformly through the GaAs without micromasking effects arising from a nonuniform surface oxide. We report the effects of hydrogen plasma treatments before RIE of GaAs in two different reactors using a SiCI4 plasma. Optimization of H2 plasma pretreatments has produced improvements in RMS roughness greater than 1 order of magnitude (22.4 to 1.51 nm).

This work introduces a new dry etching simulation technique of the sputtering component of Reactive Ion Etching (R.I.E.) and presents experimental verifications for GaAs. The final objective is to correlate the etch rate to the plasma reactor parameters, which can be incorporated into a computer-simulation program.

Reactive ion etching of GaN grown by electron-cyclotron-resonance, microwave plasma-assisted molecular beam epitaxy on (0001) sapphire substrates was investigated. A variety of reactive and inert gases such as CC12F2, SF6, CF4, H2/CH4 mixtures, CF3Br, CF3Br/Argon mixtures and Ar were investigated. From these studies we conclude that of the halogen radicals investigated, Cl and Br etch GaN more effectively than F. The etching rate was found to increase with decreasing pressure at a constant cathode voltage, a result attributed to larger mean free path of the reactive species.

The effects of SF6 and NF3 gas plasma treatments, and succesive rapid thermal anneal (RTA) treatment for the recovery of modified silicon surface due to CHF3/C2F6 plasma have been investigated using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS analyses have revealed that NF3 and SF6 plasma treatments are effective for the removal of residue layer. SIMS results show that penetrated impurities in the contaminated silicon substrate reduce through the additional RTA treatment. The effects of NF3, SF6 plasmas, and additional RTA treatments for the recovery of reactive ion etched silicon surface has been also studied by measuring the electrical performance of the silicon devices.

Reactive ion etching of features down to 100 nm in linewidth in tungsten has been studied using an SF6 based chemistry. The studies were carried out in a PlasmaTherm 500 etcher operated at low pressure (2 mTorr) and power (100 mWatts/cm2). Key processing parameters have been identified to achieve the resolution and aspect ratio required for high contrast x-ray masks. The critical parameters include sample temperature, gas dilution and end point detection. However, even with all of these parameters optimized, additional sidewall passivation is required to obtain the necessary 6.5:1 aspect ratio. A novel method of achieving such passivation based on an intermittent etching process is described.

It is known that one of the main shortcomings of chemically amplified resist systems is their sensitivity to airborne base contaminants. The contaminants cause unpredictable linewidth variations deeming the resist incompatible with manufacturing. Besides other issues, this drawback has greatly contributed to the slow introduction of DUV into manufacturing and discouragcd most semiconductor manufactures from including DUV in their strategic plans. In this paper, we present a new positive tone chemically amplified photoresist system which is resilient to airborne base contaminants and it shows stable linewidth for more than 24 hours delay between exposure and development. This resist has high sensitivity (17-18 mj/cm2), high contrast (7), high resolution (0.35 um with λ = 248 rm and NA = 0.37) and large process latitude in deep-UV lithography. This resist also exhibits high resolution (0.1 um in 0.35 um thick resist) in E-beam lithography at a sensitivity of about 10 uC/cm2. Both lithographic systems (deep-UV and E-beam) yield nearly vertical profiles in the resist images.