摘要:

Cross‐sectional scanning tunneling microscopy on semiconductor structures is evolving into a technique to analyze structural, chemical, and electronic properties on the atomic and nanometer scale in all spatial dimensions, in particular, in the lateral and in‐depth spatial dimensions of the structure. This technique has been used on the ultrahigh vacuum cleaved (110) plane of (001)‐grown AlGaAs/GaAs heterostructures. Measurements of (i) interface roughness, alloy fluctuations, and ordering; (ii) the variation of electronic properties over an interface as well as fluctuations within the alloy; and (iii) the distribution of individual dopant sites are reported on.

ISSN:0734-211X    

DOI:10.1116/1.587126

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Presently, a nanometer scale capacitance–voltage (C–V) method for the quantitative measurement of the lateral dopant distribution near a semiconductor surface is being established. An atomic force microscope is used to position a nanometer scale tip at a semiconductor surface, and localC–Vmeasurements are performed. ExperimentalC–Vcurves have been performed with tips of sub‐50 nm radius on a series of silicon wafers of known dopant density. It is shown that repeatableC–Vmeasurements can be performed with nanometer scale tips, and that the capacitance change from accumulation to depletion varies monotonically with local dopant density. TheC–Vmeasurements are compared with the theoretical predictions of a simple analytical model. The experimental measurements will be described and the results will be discussed.

ISSN:0734-211X    

DOI:10.1116/1.587127

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Scanning tunneling microscopy (STM) and atomic force microscopy operating in air have been used to investigate locations of molecular‐beam epitaxially grown GaAs multiplepnjunctions cleaved and passivated with P2S5. Symmetrically and asymmetrically doped junctions were prepared within topographically delineated AlAs/GaAs marker regions for this in‐air study of electronic junction contrast. Our results indicate that the STM‐delineated junction locations do not coincide with the electrical junction locations, but rather shift into thep‐type regions.  

ISSN:0734-211X    

DOI:10.1116/1.587128

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A new technique for the two‐dimensional delineation ofP–Njunctions is presented using a scanning resistance microscope (SRM). The SRM uses a conducting probe to perform localized resistance measurements over a surface. These resistance measurements are used to delineate between regions of different doping type and concentration. Theoretical simulation shows that the SRM is able to delineate betweenp‐type andn‐type regions of a surface, and between regions of high and low dopant concentration. By using contact forces of 10−4N, the contact area is estimated to be 30 nm. Experiments have shown that this technique can localize aP–Njunction with a lateral spacial resolution of less than 35 nm, over dopant concentrations ranging from 1015to 1020atoms/cm3. In addition, during resistance measurements the SRM is capable of performing simultaneous surface topography measurements.  

ISSN:0734-211X    

DOI:10.1116/1.587129

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The electrical activity and structural properties of rapid thermal chemical vapor deposition grown, boron‐doped, strained Si1−xGexlayers were investigated for different Ge content and doping levels. Strain measurements were obtained by Rutherford backscattering experiments and show good correlation between the mismatch strain and Ge content. Differential Hall effect profiling, secondary ion mass spectroscopy, and spreading resistance profiling were used to study the electrical doping activity of boron in the strained alloy and were directly compared in this investigation for the first time. It is shown that high electrical efficiency can be achieved in the grown material with boron concentration in the range of 1019–1020cm−3. Nuclear reaction channeling experiments performed on the doped material were used to correlate the electrical behavior of the layers with structural incorporation of the dopants in the strained film. It was found that most of the dopant atoms occupy lattice sites in the strained alloy. Lower limits on the dopant solubility for the growth conditions are also reported.  

ISSN:0734-211X    

DOI:10.1116/1.587131

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Insituphosphorous‐doped Si layers have been deposited in three different ways: (i) by low‐pressure chemical vapor deposition (CVD) at 615 °C resulting in polycrystalline Si; (ii) by radio‐frequency plasma‐enhanced CVD at 250–300 °C resulting in either epitaxial Si, or (iii) in amorphous Si which is subsequently crystallized at 600 °C, resulting in epitaxially regrown Si. From secondary ion mass spectrometry and spreading resistance profile measurements, the P appears in cases (i) and (iii) to be diffused into the underlying substrate across several hundreds of nanometers, much further than normal diffusivities would forecast. An explanation of this anomalous behavior, based on precipitation of P causing supersaturated self‐interstitial concentrations is proposed.  

ISSN:0734-211X    

DOI:10.1116/1.587132

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The diffusion of boron in single crystal silicon has been modeled following a BF2or boron implant in a polysilicon layer deposited on a single crystal silicon substrate. The effective concentration‐dependent diffusivities of boron in single crystal have been extracted using Boltzmann–Matano analysis from the experimental boron diffusion profiles measured using secondary ion mass spectrometry. The effective boron diffusivities are found to be independent of the implant dose. A new analytical model for concentration‐dependent boron diffusivities has been implemented in the PEPPER simulation program to accurately model the boron diffusion profiles in single crystal silicon for a polysilicon‐on‐single‐crystal‐silicon structure. The model has been verified for a wide range of furnace anneal conditions (800–950 °C, from 30 min to 6 h), and implant conditions (BF2doses varied from 5×1015to 2×1016cm−2at 70 keV and boron dose of 5×1015cm−2at 20 keV).

ISSN:0734-211X    

DOI:10.1116/1.587133

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

This article presents results obtained using microwave reflection between 26.5 and 36.5 GHz for measuring the sheet resistance of doped layers in semiconductors. The advantage of the technique is that it is nondestructive and has a dynamic range and spatial resolution similar to what it can be obtained with four point resistivity probes. Using this technique, we have been able to measure the sheet resistance of shallow implanted layers on silicon wafers implanted with doses in the range of 1016–1012ions/cm2. The sheet resistance measured was between 30 and 80 000 Ω/⧠.

ISSN:0734-211X    

DOI:10.1116/1.587134

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Ultra‐shallow, boxlike impurity profiles are produced using gas immersion laser doping (GILD) and then analyzed by spreading resistance profilometry (SRP) and secondary ion mass spectrometry (SIMS) to determine the impurity distribution. At high concentrations, the profiles obtained by SRP exhibit the expected boxlike shape over the entire range of junction depths: The measured concentration within the junction region is uniform while the dopant gradient at the junction exceeds 1 decade/5 nm. In comparison, the same profiles analyzed using high primary ion energy SIMS show a broader transition at the metallurgical junction. Caused by knock‐ons and ion mixing during the sputtering process, the inaccuracy is markedly reduced by lowering the acceleration energy of the primary Cs+ion beam. At lower concentrations (<1019/cm3), profiles analyzed by SRP exhibit shallower junctions than expected. Electrical measurements of diodes and Hall structures show that high‐quality, ultra‐shallown+p,np, andpnjunctions are fabricated with good dose control using GILD. For complete characterization of GILD, accurate measurement of both chemical and electrically active dopant profiles are required. At present, neither SIMS nor SRP provides an entirely accurate impurity profile.

ISSN:0734-211X    

DOI:10.1116/1.587135

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A plasma is produced in 1–10 mTorr Ar using 200–700 W of power at 2.45 GHz in a 20‐cm‐diam vessel. Electron cyclotron resonance (ECR) conditions are produced with an array of permanent magnets arranged over the surface of the dielectric waveguide window. No electromagnet coils are used. The microwave circuit is nonresonant and can be easily matched to the power source using an E–H waveguide tuner. The 20‐cm‐diam plasma is 16 cm long, and is surrounded mainly by grounded metal walls. The plasma expands from the ECR source region at the window and completely fills the chamber. Measurements of the electron density, electron temperature, and plasma space potential have been made as functions of spatial position using Langmuir probes. The density ranges up to 6×1011cm−3and the electron temperature is in the 2 eV range. The density axial and radial profiles are described by an ambipolar diffusion model which accounts for ionization in the bulk plasma. By applying the same permanent magnet arrangement to a rectangular waveguide, rectangular modules can be made which can be arranged in an array to produce a large‐area plasma source with independent power control for each waveguide channel.

ISSN:0734-211X    

DOI:10.1116/1.587136

出版商:American Vacuum Society    

年代:1994

数据来源: AIP