Harold Persing

Noninvasive, real-time measurements of plasma parameters via optical emission spectroscopy

Plasma process control applications require acquisition of diagnostic data at a rate faster than the characteristic timescale of perturbations to the plasma. Diagnostics based on optical emission spectroscopy of intense emission lines permit rapid noninvasive measurements with low-resolution (∼1 nm), fiber-coupled spectrographs, which are included on many plasma process tools for semiconductor processing. Here the authors report on rapid analysis of Ar emissions with such a system to obtain electron temperatures, electron densities, and metastable densities in argon and argon/mixed-gas (Ar/N2, Ar/O2, Ar/H2) inductively coupled plasmas. Accuracy of the results (compared to measurements made by Langmuir probe and white-light absorption spectroscopy) are typically better than ±15% with a time resolution of 0.1 s, which is more than sufficient to capture the transient behavior of many processes, limited only by the time response of the spectrograph used.

A novel plasma-based technique for conformal 3D FINFET doping

A novel plasma based conformal doping technique was developed in this work and process characterization was conducted for arsenic doping in terms of doping conformality, residual silicon fin damage, sheet resistance and effect of doping process parameters. Doping conformality, the ratio of doping at then fin sidewall and top, was characterized by cross-section transmission electron spectroscopy (XTEM) and through-fin secondary ion mass spectroscopy (SIMS) on fin structures. The residual post-anneal damage was also evaluated. Sheet resistance (Rs) was used for the matching to beam line implant. The effect of main doping process parameters on silicon fin amorphization was also studied.

Comparison of surface vacuum ultraviolet emissions with resonance level number densities. II. Rare-gas plasmas and Ar-molecular gas mixtures

Vacuum ultraviolet (VUV) emissions from excited plasma species can play a variety of roles in processing plasmas, including damaging the surface properties of materials used in semiconductor processing. Depending on their wavelength, VUV photons can easily transmit thin upper dielectric layers and affect the electrical characteristics of the devices. Despite their importance, measuring VUV fluxes is complicated by the fact that few materials transmit at VUV wavelengths, and both detectors and windows are easily damaged by plasma exposure. The authors have previously reported on measuring VUV fluxes in pure argon plasmas by monitoring the concentrations of Ar(3p54s) resonance atoms that produce the VUV emissions using noninvasive optical emission spectroscopy in the visible/near-infrared wavelength range [Boffard et al., J. Vac. Sci. Technol., A 32, 021304 (2014)]. Here, the authors extend this technique to other rare-gases (Ne, Kr, and Xe) and argon-molecular gas plasmas (Ar/H2, Ar/O2, and Ar/N2). Results...

Comparison of surface vacuum ultraviolet emissions with resonance level number densities. I. Argon plasmas

Vacuum ultraviolet (VUV) photons emitted from excited atomic states are ubiquitous in material processing plasmas. The highly energetic photons can induce surface damage by driving surface reactions, disordering surface regions, and affecting bonds in the bulk material. In argon plasmas, the VUV emissions are due to the decay of the 1s4 and 1s2 principal resonance levels with emission wavelengths of 104.8 and 106.7 nm, respectively. The authors have measured the number densities of atoms in the two resonance levels using both white light optical absorption spectroscopy and radiation-trapping induced changes in the 3p54p→3p54s branching fractions measured via visible/near-infrared optical emission spectroscopy in an argon inductively coupled plasma as a function of both pressure and power. An emission model that takes into account radiation trapping was used to calculate the VUV emission rate. The model results were compared to experimental measurements made with a National Institute of Standards and Techn...

B2H6 PLAD Doped PMOS Device Performance

Plasma doping (PLAD) achieves high wafer throughput by directly extracting ions across the plasma sheath. PLAD profiles are typically surface peaked instead of retrograde as obtained from beamline (BL) implant. It may require optimization of PLAD energy and dose in order to match BL doping results. From device optimization point of view, it is necessary to understand the impact of doping parameters to device characteristics. In this paper we present the PMOS device performance with the poly gate and source drain (SD) implants carried out using B2H6 PLAD. The BL control conditions are 2–5 keV 11B+ 4–6×1015 cm−2. Equivalent device performance for p+ poly gate doping is obtained using PLAD with B2H6 / H2. In SD doping using same gas mixture, nearly 50% reduction in SD contact resistance is observed in the PLAD splits. The reduction in SD contact resistance leads to 10–15% increase in device on‐current, hence demonstrating the process advantages of using PLAD in addition to having a high wafer throughput.

Process Control in Production‐Worthy Plasma Doping Technology

As the semiconductor industry continues to scale devices of smaller dimensions and improved performance, many ion implantation processes require lower energy and higher doses. Achieving these high doses (in some cases ∼1×1016 ions/cm2) at low energies (<3 keV) while maintaining throughput is increasingly challenging for traditional beamline implant tools because of space‐charge effects that limit achievable beam density at low energies. Plasma doping is recognized as a technology which can overcome this problem. In this paper, we highlight the technology available to achieve process control for all implant parameters associated with modem semiconductor manufacturing.

Plasma doping: production worthy solution for 65nm and beyond technology nodes

65nm and beyond advanced logic and DRAM devices will require decreasing junction depths and poly thickness at increasing doses. Present beam-line technology will suffer decreasing throughput during this transition as a result of space charge effects. Plasma doping is a well characterized alternative to beam-line technology that meets the doping requirements for <65nm ITRS technology nodes. This is accomplished at superior throughput levels which are largely energy insensitive. The simplicity of the plasma doping tool design and maturing process control features offer a promising future for production worthiness of this technique. Varians PLAD tool has demonstrated advanced logic USJ SDE/SD formation as well as advanced DRAM poly and SD doping capability. In this paper we present as-implanted and annealed SIMS profiles to highlight the sub-kV doping capability of the PLAD system for PMOS transistor fabrication and its impact on the R/sub s/ vs. X/sub J/ figure of merit. TEM data will also be presented to show lack of residual damage after a high nominal dose implant which agrees well with low junction leakage observed on PLAD doped devices. The production worthiness of the processes mentioned above is demonstrated with uniformity, repeatability, metals purity and particle performance comparable to that attainable with beam-line implants.