Since several years, the use of Beamline ion implantation has been proven to allow optimization of doping profiles needed for the fabrication of crystalline silicon (c-Si) solar cells while ...simplifying the process flow. Nevertheless the cost and complexity of such tools, associated to the difficulty to keep a small thermal budget to make high quality Boron doping for N-type cells, has slowed down the industrial introduction of ion implantation in high volume solar cell fabrication fabs.Thanks to an implant time independent to the implanted surface, and a simple tool architecture, Plasma Immersion Ion Implantation (PIII) offers an economically efficient alternative to Beamline Ion Implantation.In this paper, after having presented PULSION®-Solar, the IBS PIII tool dedicated to solar cell fabrication, we will demonstrate state of the art characteristics on different cells type either on c-Si but also on multi crystal Si where the beneficial gettering capability allowed by POCl 3 is also obtained using PIII phosphorus implantation. We will also show how the PIII doping process, thanks to its unique energy distribution, can even be more efficient than beam line, especially for boron doping, allowing lower thermal budget and co-anneal with phosphorus, simplifying even more the process flow for n-type PERT solar cells.
In order to achieve the requirements for P+/N junctions for < 45 nm ITRS nodes, ultra low energy and high dose implantations are needed. Classical beamline implantation is now limited in low ...energies, compared to Plasma Immersion Ion Implantation (PIII) which efficiency is no more to prove for the realization of Ultra-Shallow Junctions (USJ) in semiconductor applications : this technique allows to get ultimate shallow profiles (as implanted) due to no lower limitation of energy and high dose rate. Electrical activation is also a big issue since it has to afford high electrical activation rate with very low diffusion. Laser annealing is one of the candidates for the 45 nm node. This paper presents electrical and physico-chemical characterizations of junctions realized with BF3 PIII followed by laser thermal processing with aim to obtain ultra-shallow junctions. Different implantation conditions (acceleration voltage/dose) and laser conditions (laser types, fluence/number of shots) are used for this study. Pre-amorphization is also used to confine the junction depth, and is shown to have a positive effect on junction depth but leads in higher junction leakage due to the remaining of EOR defects. The characterization is done using Optical characterization tool (SEMILAB) for sheet resistance and junction leakage measurements. SIMS is used for Boron profile and junction depth.
Strain engineering was introduced in the microelectronics industry almost two decades ago to improve the carrier mobility due to the modification of the band structures in the Metal Oxide Field ...Effect Transistor (MOSFET) channel 1, 2. One method to induce local strain in the transistor channel consists in using Contact Etch Stop Layer (CESL) as stress liner. In order to improve both n-MOS and p-MOS performance, the use of a dual stressed liner (DSL) integration is a solution that combines tensile and compressive films on the same wafer 3. However, the poor mechanical stability of the compressive PECVD nitride layer when exposed to a high thermal budget, combined with the increased integration complexity, limits the interest of the DSL approach. An alternative solution to tackle these limitations consists in locally transforming the tensile CESL nitride into compressive by Plasma Immersion Ion Implantation (PIII).
For this study, PIII processes were performed on 300mm silicon bare wafers capped with a 35nm tensile PECVD nitride. Various species (Hydrogen (H), Helium (He) and Nitrogen (N)) implanted at various acceleration voltages (increasing from 1 to 6 in arbitrary units) and doses (A<B<C) were studied using a Pulsion® tool manufactured by IBS. After these processes, the samples were characterized by various techniques such as ellipsometry, bow measurement, Scanning Electron Microscopy observations, Secondary Ion Mass Spectrometry or FTIR analysis.
The stress of the various nitride layers was determined by the Stoney formula, using the curvature measurements and the layer thickness determined by ellipsometry, assuming the shift of the bow results only from the change in nitride stress. Results show that, for all the species studied, the PIII process provides the capability to change the nitride stress from initially tensile to neutral or even compressive when increasing the dose and the acceleration voltage (Fig.1). The largest stress modifications were achieved with nitrogen and hydrogen. For the latter however, the blistering of the nitride layer is observed for the highest doses due to an excessive hydrogen concentration, which is prohibitive for further process integration. By using helium PIII process, the stress change is less for identical process parameters (Fig.1), leading to a neutrally stressed nitride layer. Increasing the helium dose to modify the nitride stress further leads to a consumption of the layer, which limits the use of helium only to the reversal of the mechanical stress.
To verify that the stress change will remain during the subsequent process steps, curvature measurements were performed after a consequent thermal budget, equivalent to PMD deposition, applied after the PIII processes. The results show no significant change of the stress level.
We demonstrated the capability of PIII processes to turn a tensile CESL nitride layer into a compressive one in a reasonable processing time thanks to the high beam current achievable with PIII process, without any consumption of the layer and without the need of a post implantation thermal treatment. Complementary analysis are on-going to fully characterize the impact of each species on the CESL physicochemical properties and thereby understand its stress evolution. Thanks to these encouraging results, the most promising conditions of all the species mentioned above will be experimented on electrical structures to quantify the related static performance gain.
This project (OCEAN12) has received funding from the ECSEL Joint Undertaking (JU) under grant agreement No 783127. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and France, Germany, Austria, Portugal, Greece, Spain, Poland.
1 S. Ito, et al, “Mechanical Stress Effect of Etch-Stop Nitride and its Impact on Deep Submicron Transistor Design”, 2000 IEDM Tech. Dig., p. 247
2 T.K. Kang, IEEE ELECTRON DEVICE LETTERS, VOL. 33, NO. 6, JUNE 2012.
3 H. S. Yang, “Dual Stress Liner for High Performance sub-45nm Gate Length SO1 CMOS Manufacturing”, IEDM 2004
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Thanks to its high throughput and low cost of ownership Plasma Immersion Ion Implantation (or Plasma Doping) has been widely used for Memory device fabrication. Its ability to implant very high doses ...in shallow layers, makes it a perfect tool for new material modification applications needed for advanced logic devices. Nevertheless, few works are reported for its uses in power device fabrication. The aim of this paper is to present several application cases where we studied the use of our PULSION® PIII tool for implantation in silicon, silicon carbide and gallium nitride power devices. Benefits of PIII and challenges to overcome will be discussed for the following applications in silicon devices: High dose phosphorus and boron implantation for polysilicon gate doping and low dose doping of deep trench superjunction applications, contact plug doping for Silicon SFET devices and wall doping of deep shallow trenches for IGBTs. In addition possible applications for wide band gap materials will be discussed with an example of doping application for GaN HEMT, where PIII allowed to make the first demonstration of a normally-off device. Finally some doping and material modification applications on SiC are presented
The development of new architectures, as well as the new materials needed for <; 10 nm nodes, open new challenging applications for ion implantation where PIII (or plasma doping) will have an ...important role to play, either for doping or for material modification. We demonstrated that our PULSION® tool was ready to address these new challenges thanks to its ability to implant on 3D structures, to do hot implantation, reducing amorphization depth and to efficiently dope III-V materials. Due to its ability to implant high dose at low energies, PULSION® is also very well adapted for material modification applications and its use for NiSi improvement has been demonstrated. Finally scalability toward 450 mm was also proven. We would like to express sincere thanks to all the Laboratories and Companies that have worked with us to generate these data. We also want to thank the Public Authorities in France, as well as by the ENIAC Joint Undertaking for their financial support through PLACES2BE and E450EDL R&D projects.
Due to its mechanical properties and low density, the Ti-6Al-4V titanium alloy is used in hip prostheses. But the tribological behavior of Ti-6Al-4V sliding against ultra high molecular weight ...polyethylene involves wear degradations. The wear behavior of (Ti-6Al-4V/UHMWPE) couple can be improved by ion implantation of nitrogen. After a characterization study to find the optimal parameters for classic ion implantation, this study presents an analysis of wear behavior in comparison with chemical composition, microhardness and adhesion work for a new implantation technique, plasma immersion ion implantation.
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