Profiles of boron implantations in silicon measured by secondary ion mass spectrometry

Abstract

M. de Grefte (1973) Profiles of boron implantations in silicon measured by secondary ion mass spectrometry, Radiation Effects, 17:1-2, 83-90,The concentration of boron implanted in silicon as a function of depth has been measured by using secondary ion mass spectrometry. In this method the silicon substrate is sputtered continuously by ion bombardment and the boron secondary ion current is measured as a function of time.tion profile are formulated and have been checked by a number of experiments. It has been found, that under certain precautions, this is a reliable and fast method for the measurement of boron profiles.paid to the range and range straggling as well as to the existence of a small tail on the profile.The requirements that must be fulfilfed to ensure that this time-dependent current represents the true concentra-A number of boron profiles in the energy range 30-75 keV have been measured and are discussed. Attention is

Depth profiling by secondary ion mass spectrometry

“…This change, which takes place over a depth approximately equal to the implantation range of the primary beam ions, has to be taken into account for precision depth measurements (Schulz et al 1973). Crystal damage by preirradiation can also lead to a change in sputter rate (McDonald and Haneman 1966) but this effect is usually very small ( Baruch et al 1975a, Hofker et al 1973a. The second cause of change of erosion rate at the surface is preferential sputtering (Mayer andPoate 1978, Shimizu et al 1973, Zinner 1978.…”

“…In addition, ions can be selected only from the central portion of the swept area which is exposed to a uniform current density. This selection is accomplished either by the so-called stop-scan method (Tamura et al 1974), by masking the sample with a diaphragm made of noninterfering material (Hofker et al 1973a(Hofker et al , 1973c, by imaging the secondary ions onto an aperture (Hofker et al 1973a, 1973c or by electronically gating the secondary ion counting system such that it accepts counts only during the time the primary beam is scanned over the…”

“…Because of the extensive use of SIMS depth profiling for the measurement of dopants implanted into semiconductors a considerable number of investigations has been devoted to the question whether the ion yield of impurities depends on their concentration. This has been done for B in Si (Hofker et al 1973a, 1973b, 1973c,Schwarz et al 1973, Asin Si (Lurrabee andDobrott 1979, Tsai et al 1973), B in diamond (Blanchard et al 1976) andP in Si (Larrubee andDobrott 1979). In all these cases ion yields are constant for impurity concentrations of up to 2-3 x 102' ~m -~.…”

“…Possible contaminants in the primary beam are implanted into the sample, resulting in a background. Material sputtered from the crater rims or the halo zone may be redeposited on the crater bottom ( Croset 1972, Hofker et al 1973a, Schilling and Burger 1978. A memory effect Burger 1978, Werner 1976) can result from the sputtering by secondary electrons of elements deposited in the sample chamber and finally, the residual gas may contribute to recontamination of the sample surface (Morabito and Lewis 1975).…”

“…In order to understand the capabilities and limitations of SIMS depth profiling and to optimize the results close attention has to be paid to the basic principles and the instrumental operations have to be carefully controlled. Previous authors have dealt with factors affecting depth measurements ( Colby 1975, Liebl 1975, McHugh 1975a, Werner 1974a, 1974b, have outlined optimum conditions for measuring implantation profiles (Hofker et al 1973a, Werner 1976, as well as summarized various applications (Colby 1975, McHugh 1975b, Morabito and Lewis 1975 and given comparisons with other depth profiling techniques (Coburn and Kay 1975, Evans 1975, Morabito andLewis 1975. The first part of this review is concerned with the basic principles of SIMS depth profiling, the second part with applications.…”