M. Schuhmacher

Advanced secondary ion mass spectroscopy quantification in the first few nanometer of B, P, and As ultrashallow implants

This article presents investigation on secondary ion mass spectroscopy (SIMS) profile quantification for ultrashallow profiles. New configuration for the cesium and oxygen sources on the CAMECA IMS Wf tool-provides SIMS profiling capability at 150 eV impact energy with sputter rates of 1 and 2 nm/min for the Cs+ and O2+ primary beams, respectively. Results for as-implanted B, P, and As profiles using extremely low impact energy (EXLIE) sputtering conditions are reported. They are compared with high resolution Rutherford backscattering spectroscopy and elastic recoil detection analysis profiles. The overall results confirm that the use of EXLIE conditions minimizes near surface (depth <5 nm) artifacts but data quantification still requires dedicated postanalysis data treatment to take into account matrix effects between Si and SiO2.

Depth scale calibration of SIMS depth profiles by means of an online crater depth measurement technique

The depth scale calibration of a SIMS depth profile requires to determine the sputter rate used for the analysis from the crater depth measurement. An in situ crater depth measurement system based on the heterodyne laser interferometer has been developed. Experimental results demonstrate that crater depths can be measured from nanometers to micrometers range with an accuracy better than 5% in different matrices and a repeatability of 1%.

LEXES and SIMS as complementary techniques for full quantitative characterization of nanometer structures

Abstract A new technique, the Low energy Electron induced X-ray Emission Spectroscopy (LEXES) is used to determine dose of shallow dopants and film thicknesses; it is element selective and can resolve depth in the nanometer range. CAMECA has developed a specific instrumentation—called ‘Shallow Probe’—which adapts the LEXES to the requirements of the semiconductor industry in terms of sensitivity and reproducibility of dose and thickness measurements. The presented work reports performance of the shallow probe applied to a wide variety of dopants implanted into silicon wafers, nitrogen quantification in oxynitride barriers, as well as characterization of Si1−xGex structures.

Shallow As dose measurements of patterned wafers with secondary ion mass spectrometry and low energy electron induced x-ray emission spectroscopy

Secondary ion mass spectrometry (SIMS) and low energy electron induced x-ray emission spectroscopy (LEXES) are both well established technologies. SIMS tools are the ultimate reference for depth profiling and direct measurement of dopants with highest sensitivity and dynamic range. The LEXES-based shallow probe is a versatile, sensitive, in-line metrology tool for thin layer elemental composition and dopant dosimetry in semiconductor production. In this contribution, the ability of LEXES and SIMS techniques to differentiate nominal dose differences among three different 300mm patterned wafers are compared. In each die, several test pads were available for dose measurements. Five neighboring dies were measured by LEXES and afterward by SIMS. The repeatability measurements of both techniques (<0.5%) is suitable to determine dose nonuniformity from die to die and to discriminate nominal dose between wafers as small as 3%.

Automated Dose and Dopant Level Monitoring by SIMS

Full wafer SIMS without breaking the 300mm wafer has the advantage of saving cost and speeding‐up response time. A variety of performance examples for B, As and P implants in Si and for B levels in SiGe is shown for both Cameca tools, the quadrupole based SIMS 4600 and the magnet based IMS Wf. Dose mapping and dose monitoring with an RSD around 0.5% are demonstrated and the added value of dopant profiles is illustrated.

Accurate in depth profiling of As and P shallow implants by secondary ion mass spectroscopy

The challenge for secondary ion mass spectroscopy is to accurately measure the profile shape for low-energy implants within the first few nanometers as well as to precisely determine the junction depth in the structure after any thermal treatment. Even if knowledge of the exact profile shape is not required for dose measurement, this information becomes essential for process modeling. This article presents results on the accurate determination in depth distribution of shallow As and P implants in Si. Sub-keV impact energy is investigated for O2+ and Cs+ primary ions. An in situ laser interferometer providing a real-time record of the sputter rate is used for the depth scale calibration. Fundamental and instrumental effects limiting the depth resolution, the sensitivity, and the accuracy are discussed.

Quantitative low energy depth profiling of SiGe laterally nonuniform structures

This work explored quantitative analyses of SiGe layers, either grown on bulk Si wafers or in a confined space of different dimensions within the N28 node technology. Dynamic secondary ion mass spectrometry (SIMS) measurements were performed with a magnetic sector CAMECA IMS Wf, using low impact energy O2+ sputtering and recording the Ge containing molecular ions. It was concluded that the molecular ions protocol, called “self-focusing” SIMS, is capable of providing an accurate characterization of SiGe composition with Ge content up to 90%.

Sims analytical technique for PV applications

This paper presents analytical performance provided by SIMS tools for the development and manufacturing of new solar cells. Results for two main applications are presented: trace element analysis in PV Si feedstock with detection limits from the ppm down to the ppb range (depending on the species to be analyzed) for light elements (C, O, N), main Si dopants (B, P, As) and metals ; in-depth distribution of main components and trace elements in CIGS thin films.