摘要:

Resonance ionization mass spectrometry of neutral atoms sputtered from GaAs/AlGaAs materials, used for heterojunction bipolar transistors (HBT), provides quantitative information about the dopant position near interfaces. The results help elucidate beryllium dopant migration because they are free of matrix effects common in secondary ionization mass spectrometry. HBT performance is shown to be associated with Be location. Quantitative analysis of Be is possible across the AlGaAs/GaAs interface without extensive use of standards. The magnitudes of dopant (Be) and matrix (Al) signals are related in proportion to their concentration.

ISSN:1071-1023    

DOI:10.1116/1.586363

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

During the last five years much work has been done in developing the spreading resistance technique. This work has led to a much clearer understanding of the strengths and weaknesses of the technique. It has been shown that it is capable of producing carrier concentration profiles which are accurate enough to be used in process control and development. A review is presented which highlights the three steps necessary to obtain such data. These are the optimization of the acquisition of raw data, the conversion of the raw data to carrier profiles, and finally the interpretation and use of the final profiles. A great emphasis is placed on the need to acquire the most accurate and reproducible data and on the methods which are used to achieve this objective. For the accurate profiling of ultrashallow layers such procedures are shown to be of paramount importance.

ISSN:1071-1023    

DOI:10.1116/1.586364

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This paper discusses carrier diffusion‐induced problems that occur in profiling certain silicon structures with the spreading resistance technique. Such structures includep‐ andn‐wells, lightly doped epitaxial layers and very thin epitaxial or diffused layers. Various methods for resolving carrier diffusion problems are discussed. A new method, which we call SRP2, is introduced. In the SRP2 process, the Poisson equation is used to calculate a spreading resistance profile from an assumed dopant profile (usually deduced from conventional spreading resistance analysis or generated by a process simulator such assupremorpredict); the calculated spreading resistance profile is then compared to a measured profile to ‘‘proof‐test’’ the assumed dopant profile. Examples of the SRP2 process will be shown for CMOSp‐ andn‐wells and for several other layers, including thin epitaxial and very shallow source‐drain layers. The limits of Poisson‐based analysis for ultra‐shallow layers will be discussed.

ISSN:1071-1023    

DOI:10.1116/1.586365

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Spreading resistance measurements are widely used to obtain carrier depth profiles in shallow silicon diffused layers. The transformation of the raw spreading resistance data into concentration data relies on the calibration of the system against standards of known resistivity. This procedure implies that, for a given carrier concentration, the analyzed sampleandthe standards have the same carrier mobility. However, this hypothesis is not verified when other carrier scattering centers, in addition to those active in a perfect silicon single crystal (lattice and ionized impurities), are present in the sample. In this case spreading resistance cannot give the correct carrier concentration and an independent measurement of carrier mobility must be performed. In addition, uniform standards are not easily available at the very high doping levels used, for instance, for the source and drain diffusion of complementary metal–oxide semiconductor devices, or for the emitter diffusion in bipolar devices. In this paper we compare the results obtained with incremental sheet resistance and sheet Hall coefficient, secondary ion mass spectrometry, and spreading resistance measurements on samples implanted with BF2at high fluence and annealed at low temperatures, and on high fluence arsenic implanted layers. Rapid thermal annealed samples, implanted with As, As and P, and BF2have been also studied, due to the present interest in this low thermal budget method for dopant activation.

ISSN:1071-1023    

DOI:10.1116/1.586366

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Accurate determination of the electrically active dopant profile from spreading resistance measurements requires the application of a carrier spilling correction scheme based on the iterative solution of the one‐dimensional Poisson–Boltzmann equation. It will be shown that the results are strongly influenced by the boundary conditions applied describing the probe–silicon contact. An exploratory and somewhat speculative new theoretical probe contact model will be presented which takes into account Schottky barrier effects, surface states on the bevel surface, band‐gap narrowing and variations of the dielectric constant due to the large probe pressures applied at the metal–silicon interface. It will be shown that this model can predict adequately the detailed behavior of an experimentally measured spreading resistance low dose implant.

ISSN:1071-1023    

DOI:10.1116/1.586367

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

In the past year, several researchers have reported on methods for extracting the true dopant profile from spreading resistance measurements. This paper reports on some theoretical aspects of the 1D Poisson analysis used in these methods. Linear perturbation analysis is used to show the origin of noise amplification when calculating the dopant profile from the measured carrier profile. Perturbations on model data are used to demonstrate the robustness and accuracy of the general noise reduction method proposed by Mathur and Thurgate, without making anyaprioriassumptions about the functional form of the dopant profile. This method successfully extracts the surface dopant profile for low‐doped ultrashallow junctions for which the on‐bevel electrical junction falls outside the sample.

ISSN:1071-1023    

DOI:10.1116/1.586368

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

This paper presents results obtained in extracting dopant profiles from spreading resistance (SR) data, with carrier spilling effects taken into account. The inversion process involves a one‐dimensional solution of Poisson’s equation, followed by the application of a multilayer analysis to calculate the spreading resistance for a planar structure whose surface is defined by the probe position on the beveled SR sample. The dopant profiles ofn/n+epitaxial andp‐well structures were recovered using the method of regularization. A detailed description is provided of the procedure employed in applying the method of regularization.

ISSN:1071-1023    

DOI:10.1116/1.586369

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Laplace based reconstruction of the carrier profile from spreading resistance measurements is adequate in the absence of carrier spilling effects provided the calibration curve is interpreted correctly through an appropriate constant (variable) contact radius and (zero) barrier calibration. It will be shown that serious disagreement between secondary ion mass spectroscopy (SIMS) and SRP profiles can arise solely due to the incorrect choice of these parameters. A universal barrier and radius calibration procedure is described which removes the above discrepancies, is applicable top‐ as well asn‐type material, for any type of calibration curve and generates accurate profiles in agreement with SIMS (also forp p+‐layers) and correct sheet resistance values.

ISSN:1071-1023    

DOI:10.1116/1.586370

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

It has become evident in recent years that carrier concentration profiles measured on beveled surfaces with a spreading resistance probe might not accurately reflect the associated vertical dopant profiles. Carrier spilling, even in the absence of surface states, can move an on‐bevel junction 1/2 micron or more from its metallurgical depth. This article describes a Poisson solver which we have developed for use in spreading resistance data reduction. It allows the calculation of dopant profiles from measured on‐bevel profiles. Examples from a variety of structures are given.

ISSN:1071-1023    

DOI:10.1116/1.586371

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The accurate measurement of shallow (<0.2 μm) electrically active profiles is complicated by the effects of carrier diffusion which in some cases causes the carrier concentration profile calculated from spreading resistance (SR) data to be different from the impurity profile. This article describes analysis of SR data collected on shallow As profiles using the new analysis programsrp2.srp2is an analysis process which compares the measured SR data with SR data calculated from an assumed impurity profile. This assumed impurity profile is adjusted until the calculated SR profile matches the measured one. Thesrp2‐calculated electrical profiles agree well with independently simulated electrical profiles obtained using models which were calibrated to secondary ion mass spectrometry (i.e., nonelectrical profiles) and sheet resistance data. The distribution of the calculated SR data beyond the junction is found to be strongly dependent upon the assumed tail of the impurity distribution, and therefore provides a means of characterizing the electrically active low‐concentration tail (below 1×1016). The variation of the calculated spreading resistance with the assumed shape of the tail is illustrated and compared with measured SR data.

ISSN:1071-1023    

DOI:10.1116/1.586372

出版商:American Vacuum Society    

年代:1992

数据来源: AIP