摘要:

The ability to pattern silicon with sub‐micron linewidths has resulted in the need to measure junction depths less than 100 nm. Analysis of shallow junctions using secondary ion mass spectrometry (SIMS) is complicated by distortions due to primary ion beam mixing, the equilibration zone required for the primary species, and surface roughness. Abrupt dopant profiles can be obtained with low energy primary beams. The pre‐equilibrium region can be moved with deposition of a silicon overlayer, and topography effects can be reduced by sample rotation during bombardment. SIMS cannot provide part‐per‐million to part‐per‐billion detectability for present feature sizes. Imaging depth profiles and SIMS test areas designed into the grid regions between chips assist in the analysis of production wafers.

ISSN:1071-1023    

DOI:10.1116/1.586353

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Accurate measurement of shallowpnpemitter depths requires secondary ion mass spectrometry analysis with optimized depth resolution. This work characterized depth resolution at different beam energies for monomer, dimer and trimer species from a N2O ion source, specifically for enhancing depth resolution of abrupt boron profiles in silicon. At high beam energies, (5.5 keV), the depth resolution of the trimer is favorable to that of the dimer, as the initial ion energy is split in thirds when the molecule disassociates. At sub‐keV energies, the low velocity of the sputtering ion greatly increases the scattering cross section of the target, reducing the momentum transfer to the subsurface dopant species. At 2 keV/molecule, the trimer ion beam yields 0.67 keV/atom, and has significantly enhanced depth resolution compared to the dimer ion species.

ISSN:1071-1023    

DOI:10.1116/1.586354

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We have used secondary ion mass spectrometry (SIMS) as an analytical tool to measure the depth distribution of 2–10‐keV focused ion beam Ga implants into crystalline Si. Depth profiling was carried out by SIMS using 2‐keV Cs+bombardment at 60° with respect to normal and monitoring positive secondary ions. Implant ranges correlate well with those calculated bytrimbut are shallower by 20–25 Å; in contrast ΔRpvalues are identical to those calculated bytrim. Rapid thermal annealing has been used to electrically activate the Ga and SRP measurements have been used to determine junction depths.

ISSN:1071-1023    

DOI:10.1116/1.586355

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This article describes the shape of secondary ion mass spectrometry (SIMS) depth profiles from ultra thin ‘‘δ layers’’ in silicon, and its dependence on the impurity species and the primary beam energy. The impurities studied are boron, antimony, and germanium in epitaxial layers grown by molecular beam epitaxy. The use of the data for the assessment of depth resolution and the quantification or synthesis of SIMS profiles from thicker layers and distributions is discussed. Possible limits to deconvolution are explored.

ISSN:1071-1023    

DOI:10.1116/1.586282

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The accurate determination of dopant concentrations in the near‐surface region of secondary ion mass spectrometry (SIMS) depth profiles is often complicated by surface ion yield transients. These ion yield transients, which result mainly from the implantation of the ion yield enhancing primary ion beam, can lead to errors in the quantification of impurity species as well as distortions in the dopant profile shape. Polyencapsulation, oxygen flooding, and matrix normalization have each proven to be useful in the reduction and elimination of these surface ion yield transients. The use of low primary beam energies has been shown to have the additional benefit of reducing profile broadening due to cascade mixing. In this study, three methods of transient reduction were evaluated in the SIMS characterization of ultra‐shallowp+ junctions in Si (<1000 Å) using oxygen bombardment and positive secondary ion detection.

ISSN:1071-1023    

DOI:10.1116/1.586356

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This article discusses the utilization of profiling data from an end‐user’s viewpoint and emphasizes some requirements of profiling techniques for the modeling of present and future integrated circuit technologies. In the development and characterization of diffusion model, we have to fit both the measured profile shape and integrated dose for each dopant. We will present the evaluation of secondary ion mass spectrometry (SIMS) and spreading resistance (SRP) profiling techniques against this criterion and the selection of SIMS data as the standard for model parameter extraction. We will then discuss the methodology and results of model characterization which is a step‐by‐step application of SIMS data for the calibration of SUPREM III model parameters. To validate the characterized model for technology development, we will talk about the checking against available SRP, sheet resistance,C–V, and deviceI–Vdata. Finally, we want to bring up the need of profiling data for the characterization of two‐dimensional shallow junctions and dopant diffusion in polysilicon.

ISSN:1071-1023    

DOI:10.1116/1.586357

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

As device dimensions decrease and packing densities increase, the need for accurate mapping of dopant profiles in at least two dimensions is becoming ever more acute. Such data are required to establish the limitations of very large scale integrated manufacture, and to verify and refine the process simulators which have been devised. However, direct measurements of dopant atom distributions, using analytical techniques such as secondary ion mass spectrometry, are not possible owing to the limited analyte volume available at high spatial resolutions. The technique described here uses a specially fabricated sample which allows material to be collected from a large number of similar volumes, thus improving the sensitivity. The geometry magnifies the lateral spread many times increasing the lateral resolution achieved with a probe of a given diameter. Relatively low energy probes may be used to obtain high depth resolutions. In subsequent processing, sensitivity, depth, and lateral resolution may be mutually traded to optimize the profile for a given application.

ISSN:1071-1023    

DOI:10.1116/1.586358

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The problem of measuring two‐dimensional (2D) diffusion profiles in silicon is a critical one. Several very different methods for 2D dopant profiling have been proposed recently, but the methods are often applied only by specialists to selected problems and wide acceptance of these methods is yet to take place. This article presents a comprehensive review of methods for the measurement of 2D dopant profiles, along with a complete bibliography. The goal is to compare the various methods on the basis of some common factors, and to begin to establish some criteria for selecting 2D dopant profiling methods. First, some issues are raised which, in addition to criteria such as resolution and sensitivity, form a basis for differentiating between various methods. The methods described in the literature to date are then classified and discussed briefly. All reported methods and their variations are at least mentioned with appropriate references. Finally, a comparison of various methods is presented, focusing on specific issues such as resolution, accuracy, complexity of sample preparation, and the complexity of equipment required for the measurement.

ISSN:1071-1023    

DOI:10.1116/1.586359

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Two‐dimensional doping profiles can be determined from multiple one‐dimensional secondary ion mass spectrometry (SIMS) profiles using computed tomography techniques. The chemical nature of SIMS enables the measurement of both as‐implanted and annealed profiles with this technique. Mechanical lapping was done of multiple samples to expose different faces of the substrates followed by one‐dimensional SIMS measurements. Doping profiles of 0.4 μm boron junctions have been measured and reconstructed using the maximum likelihood estimation algorithm. Issues of sample alignment, SIMS depth resolution and SIMS sensitivity are discussed with respect to the application of this technique to sub 100 nm junctions.

ISSN:1071-1023    

DOI:10.1116/1.586360

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Two relatively new methods of sensitive and quantitative depth profiling are described. They both rely on efficient photoionization of sputtered neutral atoms and molecules, followed by mass spectrometry. This is in contrast to the commonly used technique of secondary ion mass spectrometry (SIMS) where only the charged sputtered particles are observed. The prime reason for examining theneutralsputtered component is that it typically represents the overwhelming majority of the sputtered flux, and therefore this decoupling of sputtering and ionization can readily result in a much more quantitative and sensitive measure. The two methods that probe the neutral component are distinguished by whether selective or nonselective photoionization is used. These two approaches are discussed briefly and some examples of the nonselective approach (surface analysis by laser ionization, SALI) are shown along with comparisons to SIMS. These examples demonstrate a substantial reduction of matrix effects for SALI at buried interfaces and at surfaces of ultrashallow implants.

ISSN:1071-1023    

DOI:10.1116/1.586362

出版商:American Vacuum Society    

年代:1992

数据来源: AIP