Consistent Gas Mixtures Minimize Implant Equipment Downtime
It can be tempting to take an in-situ approach by using hydrogen (H2) generators to generate gas mixtures for ion implantation, However, the short-term savings can lead to unwanted long-term costs. An in-situ gas mixture may require additional equipment downtime – any cost savings are offset by lost production hours and maintenance.
Delivering a gas mixture to the ion source assures stability and long-term reliability of implantation equipment. The quality of gas from an H2 generator is unpredictable. It may contain impurities, including excess moisture, which can increase the likelihood of tool downtime that decreases productivity and can even lead to safety issues. However, mixtures delivered in a single cylinder are analytically certified, so impurities are less likely to negatively affect ion implantation equipment.
No matter the gas or how the mixture is stored, a key operating parameter is the ion source lifetime – the amount of time the ion source can run before it needs to be taken offline for maintenance. Preventative maintenance is preferred over repair due to equipment failure, but it is desirable to reduce any form of downtime.
Addressing the Arc Chamber to Reduce Downtime
The most common reasons for preventative maintenance are often found in the arc chamber of the ion implantation tool, which is typically made from tungsten. Fluorine is released and starts to ionize when boron trifluoride (BF3) is used. Aside from the desired ions, there are interactions between the gases and the chamber itself – the fluorine reacts with the tungsten lines to form various tungsten fluorides that are re-deposited at the cathode. The fluorine is freed to react again, and the cycle is repeated, which leads to decreased source lifetimes due to deposits causing shorts or unstable beams.
The right gas mixture delivered from a cylinder combined with H2 can increase source life. That’s because it interrupts the halogen cycle and reduces the amount of fluorine ions that are available to react with the tungsten arc chamber liner. When the source lasts longer, the ion implantation does not need to be taken offline for maintenance as often.
It’s Difficult to Generate the Right Hydrogen Gas Mixture On-Site
Generating gas mixtures in-situ creates reliability, stability, and purity issues. Onboard H2 generation does not allow real-time purity analysis. Purity can vary quite substantially over time depending on operating conditions, deionized water quality, electrolytic cell life, and many other process parameters. Too much water in the form of moisture in the gas lines in combination with corrosive BF3 or germanium tetrafluoride (GeF4) will corrode gas lines, gaskets, and other components such as valves, leading to quality and performance issues. The ion implantation equipment will inevitably need to be taken offline for maintenance so the affected parts can be replaced.
Even without the issues created by impurities, H2 generators have additional maintenance requirements and failure modes. They also experience upfront parts and labor costs for installation, tool modifications, and all necessary plumbing. Combine these challenges with the reality that using in-situ gas mixtures could have a deleterious effect on implantation, frequent preventative maintenance will be necessary, and unexpected repairs more likely. This means inevitable downtime. Less predictability is never good for productivity or profitability.
Learn How Entegris Delivers Clean Gas for Ion Implantation Applications
Cylinders that deliver gas mixtures guarantee reliability and consistency, negating the need to manage all variables that come with running a hydrogen generator within ion implantation equipment.
Entegris has a long history of providing high performance gas purification solutions to the semiconductor industry, including ion implantation, to prevent process excursions and improve device performance and reliability. Entegris VAC™ cylinders safely deliver gases and gas mixtures at sub-atmospheric pressure to prevent accidental escapes and offer consistent purity backed by a Certificate of Analysis with every lot. This extends gas purity across the entire process chain to prevent excursions, improve device performance, and reliability, thereby reducing contamination that negatively impacts semiconductor device yields.
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