New Way® Air Bearings Introduces Integral Vacuum Chamber Stage Concept Reducing Volume of Chamber Required to 1000th that of Existing Chambers.
Aston, Pennsylvania, USA, July 1, 2005 – New Way Air Bearings has introduced the concept for a Vacuum Chamber Stage which would reduce the vacuum chamber to little more than the volume of the wafer in semiconductor applications…to about the volume of a teacup. The New Way stage concept would reduce the capital and operation cost of such equipment, while improving the performance of the vacuum system, the structural loop, and the metrology system.
The concept is simple: A vacuum chamber as an integral part of an air bearing precision positioning stage. This would reduce the volume of the vacuum chamber required to 1,000th of that utilized in existing chambers. The structure would employ a moving vacuum preloaded air bearing with an arrangement of differentially-pumped vacuum grooves. This would be used to achieve levels of vacuum that would be suitable for advanced patterning applications, while facilitating ultra-precision positioning of the workpiece. There would also be improvement in static and dynamic response performance of the positioning stage over existing technologies due to the significant reduction in the structural loop. Finally, both pump-down time and settling time would be dramatically reduced.
The New Way Vacuum Chamber Stage concept would provide benefits for a broad array of semiconductor applications including: Mask Writing, Ion Implantation, Ion Milling, Extreme UV Lithography, Electron Beam Lithography Writing and Inspection, and Critical Dimension Metrology.
Market Direction and Requirements
Due to the shrinking feature sizes in semiconductor wafers, greater degrees of precision are required in the positioning stages used to provide the necessary motions. Because air-bearing stages allow for higher precision, they are commonly used in semiconductor wafer patterning and inspection equipment. A point has been reached where optical techniques are limited because of the width of the wavelength of light. Extreme ultraviolet (EUV) and even Electronic Beam processing are being considered because of their shorter wavelength. A higher degree of precision is required in these processes but they also require a vacuum environment. There are many technical difficulties with large vacuum chambers, including a substantial number of components inside likely to out-gas, a high probability for mechanical contact, or even simply the large surface areas of chamber walls. The vacuum chamber stage would greatly reduce these problems.
The Vacuum Chamber Stage Concept
Instead of trying to build a stage inside a vacuum chamber or reach through a chamber wall, New Way’s concept provides for the stage itself to become the vacuum chamber (Figure 1). Having the only (or primary) vacuum chamber completely contained inside the moving stage means that all motion systems can exist outside of the vacuum. The chamber air bearing surface-pumped grooves bear directly on the plate to which the energy source is bolted.
The stage itself would be guided by its topside, which would run directly on the underside of the base reference member to which the optics, ion source, or electron source would mount. Guidance of the stage in the plane established by the X and Y-axis would be achieved with an annular air bearing separated from the vacuum section of the stage by differentially pumped groves (Figure 2).
Because vacuum chamber size would be reduced to little more than the volume of the substrate, vacuum pumping requirements and pump down times would be dramatically reduced and the requirement for a large conventional vacuum chamber is eliminated. At the same time, the structural loop between the source and the substrate (e.g. semiconductor wafer) would be dramatically shortened and stiffened, resulting in higher first order natural frequencies. Because air bearings allow for X and Y motion in a plane, it is possible to drive the stage through its center-of-mass, further improving dynamic performance. For the ultimate performance, reaction masses are relatively easy to integrate due to the planar motion of this new concept, and the fact that the reaction mass system can be placed outside of the process chamber.
Current Techniques – Effecting Motion Inside a Vacuum Chamber
Many techniques are currently employed to effect motion inside a vacuum chamber. Use of rolling element or plane bearing technology has been used, but it is difficult to achieve the precision required for semiconductor applications. Air bearing systems with differentially-pumped scavenge grooves have also been employed inside a vacuum chamber. But these stages quickly become inordinately large to provide the required travel distances. This necessitates larger vacuum chambers. It is also difficult to achieve the low pressures required in the chamber because there is so much scavenging groove perimeter.
Further, in both these methods, the drives, encoders, and services all must be contained inside the vacuum chamber, causing problems with particulation and out-gassing.
Current Technologies – Keeping Mechanization Inside the Vacuum Chamber
Methods to keep the mechanization outside of the vacuum chamber have also been previously employed. These include linear and rotary contact seals, rotary Ferro fluidic seals, and expanding and contracting bellows. Air bearing structures have also been utilized where they are separated from the vacuum chamber by integral differentially-pumped grooves that support some sort of a moving member through an aperture in the vacuum chamber wall. These approaches represent the current state of the art in ion implantation.
Attributes of the Vacuum Chamber Stage Concept
A unique attribute of the New Way Vacuum Chamber Stage Concept is that the reference plate would be both the guide surface for the plane described by the X and Y axis on one side, and on the opposite side it would be used for the mounting of the source of light, deep UV light, ions or electron beams. This would reduce the structural loop to the thickness of the reference member. Existing technologies have mounted such a source on top of or into the side of a voluminous vacuum chamber. Motion systems are typically then mounted to another wall of the chamber, or reach through another chamber wall.
Benefits of the Vacuum Chamber Stage Concept
The New Way Vacuum Chamber Stage concept would:
- Create a deep vacuum (~10-8 Torr);
- Provide a scaled-down chamber size for superior pump-down time;
- Impart a much higher total structural loop stiffness, allowing a much higher first order natural frequency of the system; and
- Reduce manufacturing and operating costs, including savings realized due to need for smaller and less costly vacuum pumps.
Concept Demonstration Unit
New Way Air Bearings plans to have a concept demonstration unit on the exhibition floor at Semicon West 2005, in the Moscone Center in San Francisco, California USA from July 12-14, 2005. Visitors to the show floor will find it in the New Way Booth, No. 3511 in Gateway Hall (Wafer Processing). Contact Tim Claffey at 610.494.6700 to schedule a ‘test drive’ of this unique new concept.
The Advantages of Porous Media
The Vacuum Chamber Stage concept is based on the application of proven New Way porous media technology. New Way’s modular air bearing products are inexpensive, robust, and easy to use. Unlike conventional orifice air bearings, New Way® Porous Media controls the airflow across the entire bearing surface through millions of holes in the material. More consistent air pressure distribution provides for superior performance.
Porous media technology has been in use for 40 years in precision applications such as coordinate measuring machines, precision machine tools, and test equipment. One advantage is that the bearing does not damage the surface it runs on should the air supply be inadvertently lost. Having no friction or wear problems, and with no lubrication requirements, air bearings are ideal for applications in demanding environments that wreak havoc on traditional contact bearings.
A Concept Supported By New Way Market Leadership
The Vacuum Chamber Stage concept is only the latest idea from New Way Air Bearings. The company offers a complete line of porous media air bearing products including flat panel conveyor air bearings, flat air bearings, cylindrical air bushings, vacuum preloaded air bearings, radial air bearings, and air bearing stages.
New Way delivers total air bearing solutions starting at their website http://www.newwayairbearings.com/, which includes the specifications for the full product range, design and installation guides, mounting hardware, air specifications, technical support, and a full range of accessories.
For more information, contact Tim Claffey, VP Sales at 610.494.6700.
New Way Air Bearings, Inc. is the market leader in the design and manufacture of modular air bearings and is the recognized provider of porous media air bearing solutions. Founded in 1994, New Way is located in Aston, Pennsylvania, USA, just fifteen minutes from Philadelphia International Airport.
High-resolution images of the New Way Vacuum Chamber Stage Demonstration Unit referenced in this release are available for use by the media. Contact Michael Wright, Director of Marketing, New Way Air Bearings at 610.364.3453 or by email at firstname.lastname@example.org.