Phosphorus Concentration Profiles Research Articles

Measurement of phosphorus concentration profiles in chemically vapour-deposited phosphosilicate glass by precision etching

The etch rate technique was used to determine distributions of phosphorus concentration within thin phosphosilicate glass (PSG) layers. The profiles evaluated by the etch rate technique were compared with those determined by neutron activation. Etch conditions ensuring good reproducibility of etch rate measurements are described. The decrease in the etch rate at the PSG-silicon interface and the sensitivity of the etch rate to changes in temperature were studied in detail. The results presented confirmed that the etch rate technique can be successfully used to monitor the distribution of the phosphorus concentration in PSG.

The Concentration Profiles of Phosphorus, Arsenic and Recoiled Oxygen Atoms in Si by Ion Implantation into SiO2–Si

The concentration profiles of phosphorus, arsenic and recoiled oxygen in Si after high dose implantations through SiO2 films have been measured using Secondary Ion Mass Spectrometry (SIMS). The characteristics such as the standard deviation or the slopes of the exponential tails of the concentration profiles of the projectiles were found to agree with those directly implanted into bare Si within experimental errors, with the exception of a shifting of the concentration peak position. The concentration level and the maximum penetration depth in Si for recoiled oxygen relative to the projectiles are discussed in correlation with ion mass, ion energy and SiO2 film thickness.

Asymmetrical Profiles of Ion Implanted Phosphorus in Silicon

The concentration profiles of phosphorus implanted into amorphous Si at energies ranging from 150 to 300 keV have been studied by using Secondary Ion Mass Spectrometry (SIMS). It is found that the phosphorus profiles in amorphous Si deviate from Gaussian distributions in the surface region. The concentration profiles are shown to be well fitted by the joined half-Gaussian distributions using the values of the projected ranges, the standard deviations and the third central moments obtained from the measured profiles. The experimental projected ranges are about 10 to 15% smaller than those theoretically calculated. From the data of the projected ranges measured, the electronic stopping power coefficient is evaluated to be 1.4KL.

The concentration profiles of projectiles and recoiled nitrogen in Si after ion implantation through Si3N4 films

The concentration profiles of ion-implanted boron, phosphorus, and arsenic, and recoil-implanted nitrogen atoms after ion implantation through Si3N4 films on Si have been measured using secondary ion mass spectrometry. The concentration profiles of the implanted ions in Si after ion implantation through Si3N4 films were found to agree with those implanted into bare Si within experimental errors, with the exception of a shifting of the concentration peak position. The concentration profiles of recoil-implanted nitrogen in Si are generally composed of high-concentration regions with steeply decaying distributions near the silicon surface and the exponential tails whose slopes are independent of ion mass, energy, dose, and film thickness. The concentration level of recoil-implanted nitrogen and maximum penetration range relative to the implanted ion range depend strongly on ion mass, film thickness, and ion energy. It was demonstrated that the concentration profiles for recoiled nitrogen in Si calculated using the Thomas-Fermi interaction potential agree better with the measured profiles than those calculated using 1/r2 potential, such as presented in the theory by Moline et al.

Spectrophotometric evaluation of phosphorus profiles in silicon

A new method for the determination of phosphorus concentration profiles in semiconductor silicon slices makes use of spectrophotometry for concentration measurements and anodic oxidation for sectioning. Silicon layers in the 5–50-nm range can be removed reproducibly. The profile determination of phosphorus doping is possible for concentrations as low as 10 19 atoms P cm -3. Measurements of these profiles by the proposed procedure give excellent agreement with electrical evaluations. The method is simple and reliable, and expensive apparatus is not required. A medium-depth profile is normally completed in eight hours.

Effects of Diffusion‐Induced Strain and Dislocation on Phosphorus Diffusion into Silicon

The diffusion‐induced strain and dislocation effects on the diffusion of phosphorus into silicon have been investigated. When phosphorus is diffused singly, the diffusion coefficient of phosphorus increases considerably at high concentrations. While, when phosphorus and germanium are diffused simultaneously, fewer dislocations are observed and the diffusion‐induced strain is compensated. In strain‐compensated diffusion, concentration profiles of phosphorus agree well with the theoretical curves (erfc). It is shown that the enhancement of the diffusion coefficient of phosphorus at high concentrations is attributed to the diffusion‐induced strain. Besides, dislocations retard the diffusion front by absorbing excess vacancies, showing the opposite effect of strain.

Depth distribution of knock-on nitrogen in Si by phosphorus implantation through Si3N4 films

The concentration profiles of phosphorus and knock-on nitrogen in silicon after phosphorous implantations into Si3N4-Si systems have been investigated by using secondary ion mass spectrometry (SIMS). The tails were found on the phosphorus distribution in silicon after the implantation through Si3N4 films. The concentration profiles of knock-on nitrogen in silicon have been determined by measuring both the in-depth profiles of knock-on nitrogen and those of nitrogen after additional nitrogen implantation into a bare silicon embedded with knock-on nitrogen. The concentration profiles of knock-on nitrogen show a very high concentration near the surface and extending tails. It was found that the tails were observed at the deeper portion in silicon as energy increased, for a given Si3N4 layer.

Excess vacancy generation by E-center dissociation in the case of phosphorus diffusion in silicon

Phosphorus diffusion equations in silicon are proposed taking into account the following: Phosphorus diffuses as E centers; an E center is formed by pairing a negatively ionized vacancy with a positively ionized phosphorus atom; with increasing phosphorus concentration, the equilibrium concentration of negatively ionized vacancies increases and the ionization rate of phosphorus decreases. The equations are solved numerically under the boundary conditions of constant surface concentrations of total phosphorus atoms and negatively ionized vacancies. The phosphorus diffusion coefficient depends not only on the vacancy concentration but also on its gradient. The excess vacancies are generated by the E-center dissociation. The concentration and the distribution of the excess vacancies are good enough to explain qualitatively the anomalous diffusion of phosphorus, except the kink in the phosphorus concentration profile.

Application of neutron activation analysis for the determination of implantation profiles of phosphorus in semiconductor grade silicon

A method of the determination of concentration profiles of phosphorus in silicon by neutron activation has been elaborated. The lower limit of determination is of the order 10−11 g P. Two groups of errors have been discussed. The suitability of autoradiography to the determination of concentration profiles has been demonstrated. Some applications of the method have been suggested.

Complex refractive index and phosphorus concentration profiles in P +31 ion implanted silicon by ellipsometry and auger electron spectroscopy

Ellipsometrically measured complex retractive index profiles in high energy P + 31 ion implanted silicon have been compared with the phosphorus concentration profiles determined by in-depth profiling of the implanted surface using Auger electron spectroscopy in conjunction with in-situ ion sputtering. Structure was observed in the phosphorus profile which corresponds to structure in the complex refractive index profiles of unannealed specimens. This implies that the complex refractive index profile of the unannealed surface is sensitive to the concentration of the implanted species as well as the amount of structural disorder in the implanted layer. These results also indicate that the implanted phosphorus tends to build up in the more highly damaged regions, possibly through a radiation enhanced self-diffusion mechanism.

Model of doped-oxide-source diffusion in silicon

A new theory of the doped oxide diffusion technique in silicon has been developed. Compared to the existing theories, it uses fore physically realistic boundary conditions. The theory was satisfactorily evaluated with radio phosphorus diffusion into (111) silicon. Between 1100 and 1275°C the transfer of phosphorus into silicon was found to be controlled by a surface barrier process and not by segregation between the oxide and silicon. The kinetics of the interfacial conductance process has been shown to involve chemically transformed elemental dopant and a probable vacancy-related defect. Phosphorus concentration profiles, controlled by its diffusivity in the mixed oxide, were processed to produce surface-induced intrinsic diffusivities. In contrast to the single defect-controlled diffusion processes known in most materials, it is seen that in silicon, under non-oxidizing conditions, the nature of the defect responsible for diffusion of dopants depends on the process employed. Technologically important quantities of surface concentration, junction depth and profile shape by the doped oxide process can bow be predicted accurately for the first time.

Phosphorus concentration profiles in p-doped silicon dioxide measured using Auger spectroscopy

The depth distribution of phosphorus in silicon dioxide formed by reacting phosphine and silane with oxygen at 480°C, has been measured with Auger spectroscopy using (i) ramp-etched silicon dioxide films and (ii) in situ ion milling. Quantitative Auger analysis showed the phosphorus concentration to be 0.5 at.% throughout most of the oxide. However, when grown directly on silicon, a phosphorusrich oxide, [sine wave] 30 Å thick and containing > 3 at.% phosphorus, was first deposited, followed by a phosphorus-depleted region, [sine wave] 150 Å thick; both regions formed within the first minute of deposition and probably resulted from a rapid initial reaction of phosphine with the silicon surface. Neither region is formed when the doped oxide is deposited on silicon dioxide, and undoped oxides < 200 Å thick were successfully used to eliminate the phosphorus-rich layer. There was negligible diffusion (≲100 Å ) of phosphorus from a doped oxide containing 0.5 at.% phosphorus into steam oxide after heating for 30 min at 1000°C.

Electron microprobe analysis of iron content of incisor enamel in some species of rodentia

Enamel from maxillary incisors of six species was analysed. In those species where pigmentation was observed in the outermost layer of enamel, a corresponding iron-rich zone was demonstrated by elemental analysis. The enamel of squirrel and beaver contained about 10 per cent of iron close to the enamel surface and the concentration gradually decreased to less than 0.1 per cent within 20–30 μm from the surface. Through the same zone, the calcium and phosphorus concentration profile lines showed a gradual increase until a plateau was reached (about 36 per cent calcium and 17 per cent phosphorus) at the point where iron had decreased below a detectable level. This inverse relationship between iron on one hand and calcium and phosphorus on the other was clearly seen in incisor enamel of hamster and mouse which contained a maximum of 5–6 per cent iron near the enamel surface, but was not observed in the lemming (maximum 3 per cent iron). In the non-pigmented enamel of the guinea-pig, iron was not detected at the 0.1 per cent level, and the calcium and phosphorus profile lines followed a horizontal course through the entire width of the enamel. The sum of iron, calcium and phosphorus was approximately equal in all analysed areas. The results indicate that a clear relationship exists between pigmentation and iron content of rodent incisor.

Diffusion and defect annealing in silicon doped by phosphorus ion implantation

Conductivity profiles and impurity concentration of silicon implanted with 30 keV phosphorus ions (implantation dose 6 Cm−2) were studied. The defect annealing has been found to terminate practically during the first minutes at Tann = 600 to 900°C. Diffusion redistribution of implanted atoms becomes appreciable after 6 h at 600°C, after 2 h at 800°C, and after 2 to 5 min at 900°C. The annealing process at 900°C is accompanied by a considerable change of the defect concentration and therefore of the coefficient D of the radiation-induced diffusion. A calculation of D(x, t) basing on the variation of the phosphorus concentration profile shows that initially the diffusion coefficient in the region of maximum defect concentration is 2 to 2.5 orders of magnitude higher than the coefficient for ordinary diffusion. [Russian Text Ignored].

Phosphorus Concentration Profile and Phase Segregation in Phosphosilicate Glass on SiO2 Films

The phosphorus distribution in phosphorus diffused films has been determined by means of neutron activation. The general shape of the profile is in good agreement with the results by Fränz et al. (4), who used the P32 isotope. In the phosphosilicate region occasional strong fluctuations of the P concentration were observed, usually accompanied by changes in the etch rate in opposite to the expected dependence of etch rate on P concentration. The fluctuations were tentatively attributed to phase segregation in the phosphosilicate glass. Confirmation was obtained from related experiments in which polycrystalline films of composition (and possibly were obtained and identified by electron diffraction.