Silicon depth profiles

As an example of the use of AES to obtain chemical, as well as elemental, information, the depth profiling of a nitrided silicon dioxide layer on a silicon substrate is shown in Figure 6. Using the linearized secondary electron cascade background subtraction technique and peak fitting of chemical line shape standards, the chemistry in the depth profile of the nitrided silicon dioxide layer was determined and is shown in Figure 6. This profile includes information on the percentage of the Si atoms that are bound in each of the chemistries present as a function of the depth in the film. 

A. J. Bevolo, M. L. Albers, H. R. Shanks, and J. Shinar. J. Appl. Phys. 62, 1240, 1987. VEELS in fixed-spot mode to depth profile hydrogen in amorphous silicon films to determine hydrogen mobility at elevated temperatures. 

Figure 3a Unprocessed depth profile (secondary ion intensity versus sputtering time) of a silicon sample containing a boron ion implant.

Figure 7 Depth profile of en ersenic ( As) ion implent in silicon with end without use of...

Neutron activation also has been combined with accelerator mass spectrometry and has been demonstrated to have part-per-billion sensitivities fer bulk nitrogen analysis in silicon. This combination was also used to obtain depth profile of Cl in silicon semiconductors. ... 

NAA cannot be used for some important elements, such as aluminum (in a Si or Si02 matrix) and boron. The radioactivity produced from silicon directly interferes with that ftom aluminum, while boron does not produce any radioisotope following neutron irradiation. (However, an in-beam neutron method known as neutron depth profiling C3J be used to obtain boron depth profiles in thin films. ) Another limitation of NAA is the long turn-around time necessary to complete the experiment. A typical survey measurement of all impurities in a sample may take 2-4 weeks. 

Figure 7 SIMS depth profile of Si implanted into a 1- im layer of Al on a silicon substrate for 6-keV O2 bombardment The substrate is B doped.

Fig. 5. Hydrogen depth profile of a deuterated polystyrene PS(D) film deposited on a protonated polystyrene PS(H) film on top of a silicon wafer as obtained by l5N-nuclear reaction analysis ( 5N-NRA). The small hydrogen peak at the surface is due to contamination (probably water) of the surface. The sharp interface between PS(D) and PS(H) is smeared by the experimental resolution (approx. 10 nm at a depth of 80 nm) [57], The solid line is a guide for the eye...

Fig. 6. Hydrogen depth profile of a thin film of poly(p-methylstyrene)(H)/ PS(D) diblock copolymer, PMS(H)-b-PS(D), on a silicon wafer as obtained by the l5N-NRA technique [57]. The sample has been annealed for 1 h at 140 °C. PMS(H) is largely enriched at the surface. The solid line is a guide to the eye...

Baudoin etal. [168,169] first presented qualitative depth profiles of lacquer and polymer coatings by means of r.f. GD-OES. Quantitative depth profiles were successively obtained by Payling et al. [170] on prepainted metal coated steel. Samples comprised a (rutile) pigmented silicone-modified polyester topcoat over a polymer primer, on top of an aluminium-zinc-silicon alloy coated steel substrate. With GD-OES in r.f. mode, it was possible to determine the depth profile through the polymer topcoat, polymer primer coat, metal alloy coating, and alloy layer binding to the steel substrate with a total depth of 50 im, all in about 60 min on the one sample. GD-OES depth profiles of unexposed and weathered silicone-modified polyesters were also reported [171]. Radiofrequency GD-OES has further been used to... 

McPhail (1989) gives a detailed account of the experimental approach to depth profiling of semiconductors, including the quantification of the data. He illustrates the analysis of a silicon epilayer grown by molecular beam epitaxy (MBE) in which 11 boron-rich layers were incorporated by co-evaporation of boron. The intended structure is shown in Figure 4.8, and it was desirable to establish the concentration of boron in the layers, the inter-peak concentration and the sharpness of the doping transitions. 

An ion-implanted standard and the MBE sample were depth profiled under the same conditions, and the secondary ions were analysed in a quadrupole mass spectrometer. The data from the ion-implanted standard was used to find the useful ion yield and thus the instrumental sensitivity for boron-in-silicon in the MBE sample. The quantified data appear in Figure 4.9. 

Zink et al. used a blend of polystyrene (hPS) and its deuterated counterpart (dPS), both of molecular weight 1.95 x 106 (abbreviated 1.95 M). The average volume fraction (4>dPS) of deuterated polystyrene was 30%. The polymers were dissolved in toluene and spin cast on thin silicon wafers (about 10 x 10 mm), the resulting film thickness being about 300 nm. The samples were annealed at 245°C for 8 days, and the measurement of the resulting depth profiles was conducted by NRA using a monoenergetic 700 keV 3He beam. The nuclear reaction employed can be written ... 

Depth profiles of ultrashallow implanted P in silicon have been determined by Kobayashi and Gibson (1999) using NRA. Quantitative analysis of this type is... 

Fig. 2. Depth profiles of the free-electron (or donor) concentration in n-type silicon before and after hydrogenation (H, 130°C, 50 min).

Fig. 4. Depth profiles of the donor concentration in Schottky-barrier diodes on n-type silicon (a) before and after hydrogenation (130°C, 60 min) and (b) after a post-hydrogenation anneal at 60°C with and without a reverse bias of 4 V (Zhu el at, 1990).

Fig. 7. Depth profiles of deuterium in n-type (P-doped) silicon after deuteration in a remote plasma system at 150°C (a) entire profile after a 120 min deuteration and (b) near-surface profiles after different durations of deuteration. Also shown is the uniform P concentration.

Equation (10.1) can be used to determine the doping density of a silicon substrate and its depth profile, even if the flat band potential is not known accurately. Diffusion doping, ion implantation or the growth of an epitaxial layer are common methods of producing doped regions in semiconductor substrates. The dopant concentration close to the surface can be measured by SRP or capacitance-... 

The SNMS depth profile (ion intensity as a function of sputter time) for the matrix elements of a Ba07Sr03TiO3 layer on a silicon substrate with Pt/Ti02/Si02 buffer layers is illustrated in Figure 9.8. Inhomogeneity of the perovskite layer was detected especially for Sr. Furthermore, an interdiffusion of matrix elements of the Ba07Sr03TiO3 layer and of the Pt barrier layer was observed. 

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