Allen McTeer

SIMS/ARXPS—A New Technique of Retained Dopant Dose and Profile Measurement of Ultralow-Energy Doping Processes

A newly developed surface analysis technique, which combines secondary ion mass spectrometry with angle-resolved X-ray photoelectron spectroscopy, was used to achieve more accurate results of the retained impurity doses and profiles for ultralow-energy implants, including conventional beamline implant and plasma immersion ion implantation (PIII). Using this method, it has been found that the B2H6 (diborane) PIII demonstrates thicker native oxide and much more B dose loss during rapid thermal processing and surface-cleaning treatments than conventional beamline ion implantation, due to the higher surface B concentration. In order to match the electrical parameters of the device, PIII must consider higher nominal dose to compensate the B loss.

Comparative Study of Self-Sputtering Effects of Different Boron-Based Low-Energy Doping Techniques

Angle-resolved X-ray photoelectron spectroscopy method was used to study self-sputtering effects of different p-type (boron-based) low-energy doping techniques, including conventional monoatomic 11B beam-line ion implant, molecular beam-line ion implants, cluster B beam-line ion implant, and plasma doping (PLAD). It has been found that the self-sputtering effects of the beam-line implants correlate with the mass of ion species except for BF2 implant. Cluster B implant shows severe self-sputtering effect and surface roughness due to its very heavy and very large cluster ions. BF2 implant shows severe sputtering/etching effect but comparable roughness due to a combination of the physical sputtering and reactive ion etching. PLAD processes using B2H6 and BF3 gas species have no sputtering effects but have deposition under certain process conditions.

Device Performance Improvement of PMOS Devices Fabricated by

It has been shown that plasma immersion ion implantation (PIII)/plasma doping (PLAD) processing offers unique advantages over conventional beam-line ion implant systems, including system simplicity, lower cost, higher throughput, and device performance improvements. A 78-nm channel length PMOS device, which is fabricated by a B2H6/H2 PIII/PLAD process on source/drain doping, can offer better device performance that includes a 50% lower contact resistance (RCS), 11%-16% higher drive current (IDS), and transconductance (KL) than those fabricated by beam-line implantation. The physical mechanisms behind the device performance improvement can be correlated to the much lower RCS, which in turn results from the unique dopant profiles of the PIII/PLAD process.

\hbox{B}_{2}\hbox{H}_{6}

A Johnsen–Rahbek (J-R type) type electrostatic chuck (ESC) was found to be more sensitive to wafer conditions than classic ESC, including backside dielectric quality and thickness and doping level. The wafer backside dielectric may reduce the clamp force and increase the declamping time, depending on dielectric quality, dielectric thickness, and ESC configurations. These issues and their mechanisms are studied extensively and potential solutions are proposed.

PIII/PLAD Processing

Comparing with conventional spreading resistance profiling and differential Hall effect (DHE) methods, the continuous anodic oxidation technique/DHE (CAOT/DHE) technique may achieve more reasonable profiles of carrier concentration nh(x), mobility muh(x), and resistivity rho(x) and more reasonable carrier dose and xj in Si substrate. It has been successfully used to study ultralow energy doping techniques including B beam-line implant and B2H6 plasma doping (PLAD). CAOT/DHE data support the fact that the devices fabricated by PLAD achieve improvement to those fabricated by beam-line implant because PLAD offered higher surface carrier concentration and carrier dose. CAOT/DHE data quantitatively verify the so-called solid solubility limit activation theory - the carrier profiles and secondary ion mass spectrometry (SIMS) B impurity profiles under BSS are very well consistent on both beam-line and PLAD implants. As a cheaper and standard metrology, the SIMS/ARXPS method with the solid solubility limit activation theory may be used to quantitatively or semiquantitatively study the doping and activation processes.

Wafer dependence of Johnsen–Rahbek type electrostatic chuck for semiconductor processes

PLAD (plasma doping) is promising for both evolutionary and revolutionary doping options because of its unique advantages which can overcome or minimize many of the issues of the beam-line (BL) based implants. In this talk, we present developments of PLAD on both planar and 3D device structures. Comparing with the conventional BL implants, PLAD shows not only a significant production enhancement, but also a significant device performance improvement and 3D structure doping capability, including an 80% contact resistance reduction, more than 25% drive current increase, and conformal doping on non-planar device structures. In PLAD developments and applications, the conventional metrologies are not suitable for PLAD process because of their limits and PLADs unique properties. Novel diagnostic metrologies for PLAD process have been developed and are also presented in this talk.

Study of Low-Energy Doping Processes Using Continuous Anodic Oxidation Technique/Differential Hall Effect Measurements

The differential Hall effect CAOT permits rapid accurate measurement of mobility, resistivity, and carrier concentration. For single crystal structures with carrier concentrations less than 1E20 B cm−3 the resistivity‐carrier concentration tracks the A.S.T.M. F‐723 algorithm relationship. Above ∼1E20 B cm−3, a scattering defect mobility component is added to the phononic and coulombic components. This component is significantly greater for beamline implantation than for plasma doping for both single crystal junctions and polysilicon films.

PLAD (Plasma Doping) on 22nm Technology Node and Beyond - Evolutionary and/or Revolutionary

New carrier drift mobility data for boron-, phosphorus-, and arsenic-doped Si in a low-energy high-dose implant regime are measured and studied using a continuous anodic oxidation technique/differential Hall effect technique. The data show that, when the doping concentration is >; 1020/cm3, both the hole and electron mobility values are lower than the conventional model predictions, and the electron mobility of the As-doped Si is lower than that of the P-doped ones. The data also show that, when the doping concentration is >; 1021/cm3 the hole mobility in the B-doped Si and the electron mobility in the P-doped Si are almost equal and reach as low as ~40 cm2/V · s, and the electron mobility of the As-doped Si is the lowest and reaches ~30 cm2/V · s. These mobility data are much lower than the conventional model predictions and are also lower than the previously published data. For the ULSI device and circuit analyses, simulations, and designs, these new mobility data need to be taken into consideration.

The Application of the Continuous Anodic Oxidation Technique for the Evaluation of State‐of‐the‐Art Front‐End Structures

An ambient-controlled scanning spreading resistance microscopy (AC-SSRM) apparatus is utilized for one-dimensional (1D) and two-dimensional doping profiling measurement. 1D SSRM profiling on a blanket (vertical) B-doped Si wafer is conducted to obtain a spreading resistance profile SR(x). Modeling is used to convert SR(x) to carrier profile n(x). Replacing the average mobility (μ) with a calibration using μ(x), the carrier (hole) profile n(x) is more accurate. This is especially pronounced near the surface and junction depth (xj) and is consistent with the continuous anodic oxidation technique/differential Hall effect (CAOT/DHE) measured carrier profiles. The model based on AC-SSRM data obtained xj = 103.4 nm, which was consistent to secondary ion mass spectrometry results of xj = 104.0 nm. Calibrated hole dose using μ(x) is 9.6 × 1014/cm2 and is relatively closer to DHE hole dose 1.4 × 1015/cm2. In addition, a fairly good consistency of sheet resistance (RS) values among 4 point probe (4PP), CAOT/DHE, an...

Study of Carrier Mobility of Low-Energy High-Dose Ion Implantations

Angle-resolved X-ray photoelectron spectroscopy method was used to study self-sputtering effects of different n-type low-energy doping techniques, including conventional monoatomic 75As and 31P beam-line ion implants and AsH3 plasma doping (PLAD). It has been found that the self-sputtering effects of the beam-line implants correlate with the mass of ion species. As beam-line implant shows more serious self-sputtering effect than monoatomic P and B beam-line implants. Very low energy P implants show surface-swelling phenomena. PLAD process using AsH3 gas species has no sputtering effects but has slight deposition under current process condition.