Secondary ion mass spectrometry analysis of ultrathin impurity layers in semiconductors and their use in quantification, instrumental assessment, and fundamental measurements

Abstract

The subject of this review is the secondary ion mass spectrometry (SIMS) analysis of ultrathin or delta layers of impurity in a semiconductor matrix and their use in establishing the limitations of SIMS depth profiling, exploring the fundamental processes occurring during analysis, and enhancing the quantification of SIMS data. Methods for extracting accurate information for the grower (concerning the material) and the analyst (concerning the SIMS instrument) are described. It is demonstrated that sets of SIMS profiles obtained over a range of analytical conditions are desirable if accurate information is required. In this context, the observation of dopant interaction occurring in codoped samples during SIMS analysis is reported for the first time. It is shown that quite large discrepancies exist between different measurements of decay length and associated parameters for the same impurity/matrix combination. These need to be explained before attempting to relate delta profile shape to primary ion beam induced mass transport mechanisms. The concept of the delta profile as a response function and the use of deconvolution as a complete quantification method are discussed. The use of delta profiles in setting up models of the ion–solid interaction such as IMPETUS is illustrated.

Carbon-13 labeling for improved tracer depth profiling of organic materials using secondary ion mass spectrometry

“…The observed convolution-type arises primarily from ion-induced mixing of the 13 C and 12 C matrix and implantation of the 13 C further into the film (tailing) [18]. Analogous behavior has been observed for 30 Si implants in a 28 Si matrix [18]. Here we employ a simplified version of a convolution scheme that has been outlined previously [18,19].…”

“…Analogous behavior has been observed for 30 Si implants in a 28 Si matrix [18]. Here we employ a simplified version of a convolution scheme that has been outlined previously [18,19]. It combines a Gaussian with a standard deviation eff that accounts for ion-induced mixing and sources of uncorrelated convolution, such as sample roughness, and an exponential for the observed tailing, which has a characteristic decay length d .…”

Si1-xGex/Si Interface Profiles Measured to Sub-Nanometer Precision Using uleSIMS Energy Sequencing

“…If F Sample (z) is known, or can be approximated to a simple analytical function, as in the case of a δ-layer, then the response function for the given measurement conditions can be determined. Such an approach has been used in previous studies exploiting boron δ-layers in Si, which have been used to determine a generic SIMS response function capturing the essential ion-sample interactions [21]. Conversely, if R(E, z) were known precisely, then F Sample (z) could be obtained from a single SIMS profile by calculating explicitly the convolution R(E, z) ⊗ F Sample (z) for different models of the sample profile.…”

“…The ρ u/d parameters are not linked directly to any physical ion-sample interactions. Broadly, however, ρ d (E P ) will be related to the depth of the ion induced distribution within the altered layer and the surface escape probability whilst ρ u (E P ) is related to the depth of any surface features, including effects such as surface roughening due to ion bombardment and the effective escape depth [21]. It is expected that ρ u (E P ) is small and tends towards 0.…”

GaAs delta-doped layers in Si for evaluation of SIMS depth resolution GaAs

“…It has been suggested that a SIMS profile of a delta-doped layer can be described with an exponential trailing edge, a Gaussian-like rounded top and an exponential rising part. 4 The SIMS depth resolution could be evaluated with three parameters such as the intrinsic width and the growth and decay lengths up and down . In this report, GaAs delta-doped multilayers in Si were made and proposed as a delta-doped multilayer reference material for evaluation of SIMS depth resolution.…”