Barry Lewis Chambers

Germanium ion implantation efficiency improvement with use of germanium tetrafluoride

Ion implantation of germanium in silicon wafers is often troubled by reduced ion source life due to use of germanium tetrafluoride (GeF₄) as a source material. The problem is mainly due to tungsten re-deposition, a result of a fluorine-induced halogen cycle initiated within the ion source. The halogen cycle is particularly pronounced in the case of GeF₄ by easy fragmentation of the molecule, as well as low utilization of germanium due to wide isotopic distribution of natural abundance GeF₄. Through isotopic enrichment of ⁷²GeF₄, benefits such as enhanced ion implantation beam current, lower gas flow, and longer source life can be achieved versus natural GeF₄. Additional benefits can be realized when using mixtures of GeF₄ with hydrogen (H₂). Data are presented that show the effect of H₂ content on beam current as well as on tungsten transport. Lastly, thermodynamics and stability results are presented for a single cylinder mixture of GeF₄ with H₂.

Gas cylinder release rate testing and analysis

There are varying cylinder technologies employed for the storage of gases, each resulting in a potentially different hazard level to the surroundings in the event of a gas release. Subatmospheric Gas delivery Systems Type I (SAGS I) store and deliver gases subatmospherically, while Subatmospheric Gas delivery Systems Type II (SAGS II) deliver gases subatmospherically, but store them at high pressure. Standard high pressure gas cylinders store and deliver their contents at high pressure. Due to the differences in these cylinder technologies, release rates in the event of a leak or internal component failure, can vary significantly. This paper details the experimental and theoretical results of different Arsine (AsH3) gas cylinder release scenarios. For the SAGS II experimental analysis, Fourier Transform Infrared Spectroscopy (FTIR) was used to determine the spatial concentration profiles when a surrogate gas, CF4, was released via a simulated leak within an ion implanter. Various SAGS I and SAGS II cylind...

Source and beam performance improvement for carbon implantation with carbon monoxide (CO) gas

Carbon co-implantation has been widely adopted for better Ultra-Shallow Junction formation in the fabrication of advanced semiconductor devices. Currently, carbon dioxide (CO2) is the primary feed gas for carbon implantation. The primary disadvantage of CO2 is the high oxygen content, which causes significant oxidation of the implant source components resulting in rapid degradation of the source performance. Usually the C+ beam starts to degrade quickly while running continuously with carbon dioxide. Also, some other species’ implants, especially boron, are significantly affected after a short duration of CO2 usage. Carbon monoxide (CO) is described here as an alternative carbon source material to CO2. In our testing, CO has demonstrated significant improvements compared to CO2 for both source life and beam performance. Additionally, this paper describes a subatmospheric delivery option for CO. The cylinder package with reliability information is provided.Carbon co-implantation has been widely adopted for better Ultra-Shallow Junction formation in the fabrication of advanced semiconductor devices. Currently, carbon dioxide (CO2) is the primary feed gas for carbon implantation. The primary disadvantage of CO2 is the high oxygen content, which causes significant oxidation of the implant source components resulting in rapid degradation of the source performance. Usually the C+ beam starts to degrade quickly while running continuously with carbon dioxide. Also, some other species’ implants, especially boron, are significantly affected after a short duration of CO2 usage. Carbon monoxide (CO) is described here as an alternative carbon source material to CO2. In our testing, CO has demonstrated significant improvements compared to CO2 for both source life and beam performance. Additionally, this paper describes a subatmospheric delivery option for CO. The cylinder package with reliability information is provided.

EnrichedPLUS 72Germanium Tetrafluoride (EnPLUS 72GeF4) and Hydrogen (H2) Mixture for Implanter Performance Improvement

In the manufacturing process of advanced node semiconductor devices, germanium tetrafluoride (GeF4) gas is used for pre-amorphization implantation (PAI) of the silicon crystal structure. This germanium implant is required for controlling channeling and reducing Transient Enhanced Diffusion (TED) for better ultra-shallow junction formation. Fluoride gases, including GeF4, have a long history of poor ion source life performance due to tungsten transport from halogen cycling inside the arc chamber of the implant tool. Also, running long periods of GeF4 negatively impacts the arc chamber, which can affect subsequent dopant processes. This paper will demonstrate the advantages of mixing hydrogen (H2) with EnPLUS 72GeF4 gas to increase implanter source life, extend the length of the beam campaign, improve beam performance, and eliminate post beam purge time.

Utilization of SAGS Type 1 delivery systems in novel doping applications

The advent of new technologies is driving the emergence of alternative doping methods. For instance, plasma doping is potentially a critical enabler for three-dimensional (3D) devices in the integrated circuit (IC) market, requiring flow rates much higher than those of traditional planar structures. Unlike traditional beam-line ion implantation, dopants are typically not introduced from an on-board gas box within the tool; rather they are distributed from a remote gas delivery system. This is possible given that the gas delivery system is held at the same potential as the tool and there is no high voltage gap to overcome. Similarities exist in other markets such as solar, flat panel display, and power electronics, in terms of needing to deliver high gas flows from a remote delivery source. This requirement poses significant hurdles in terms of process safety, installation considerations, and the ability to enable high gas conductance through proper flow component selection. This paper details how each of these factors affects the performance of the system and the ability to achieve the required process flow rates. Theoretical flow modeling is used to estimate overall system conductance and gas utilization and these results are compared to empirical data to show that system attributes can be predicted. This capability coupled with a gas delivery cabinet that is designed to enable the performance and safety of SAGS Type1 delivery systems, provides a robust solution to material delivery needs for novel doping applications.