Media Coverage and Awards
Technology Innovation Showcase: Metrology
Paula Doe, SEMI, San Jose – Semiconductor International, 5/18/2007
As expanding computing power increasingly makes new kinds of measurements possible, and shrinking chip geometries increasingly make them necessary, this year’s Technology Innovation Showcase highlights some ways to better control chemical composition on product wafers, wafer position in the chamber, and moisture levels in the gas distribution system.
The volunteer committee of equipment and materials veterans who selected these technologies to feature at SEMICON West 2007 aimed to help introduce innovations that will be useful to the industry, especially those from somewhat outside the mainstream. “Our goal is to showcase things that will have an impact,” said Ralph Kirk, director of Technology Programs at SEMI North America. “These crusty old industry guys go out and look for things that are important.” This year, they found ReVera (Sunnyvale, Calif.) with inline process control, CyberOptics Semiconductor’s (Beaverton, Ore.) on-board wafer vision system that allows a window into the process chamber, and GE Sensing’s (Billerica, Mass.) low-cost, fast-acting moisture sensors — all promising to make a difference in improving yields
ReVera
Improved throughput and better small-spot capabilities are starting to extend compositional metrology beyond nitrogen in logic gate dielectrics to patterned wafers, memory and implants. ReVera reports its second-generation X-ray photoelectron spectroscopy (XPS) tool VeraFlex is now being used for inline process control on product wafers. While device makers are primarily using it to control nitrogen levels in gate silicon oxynitride (SiON) films, they’re also developing inline applications for memory dielectrics and ion and plasma implant monitoring. The XPS technique uses low-energy X-rays to generate a signal from the top 100 Å of the substrate, and directly identifies and quantifies the elements present by the characteristic photoelectrons they emit. It also measures film thickness, calculated by the attenuation of the signal from the known material underneath. But the first-generation tool worked only on monitor wafers.
The company has now figured out how to focus the X-ray beam down to a 50 × 50 µm box so that it can be used on patterned wafers while maintaining the precision and throughput needed for production-level metrology. The second-generation VeraFlex tool focuses the X-rays by first generating much higher X-ray fluxes than the previous system, then using compound, precisely shaped single-crystal X-ray optics to focus the beam on the metrology box. John Samuels, director of marketing, said that some VeraFlex customers are using the XPS measure as their primary metrology technique for SiON gate dielectrics for film thickness, as well as for nitrogen content. Also driving interest are more challenging memory cell dielectrics for both flash, DRAM and doped high-k/metal gate stacks.
XPS measurement of BF3 plasma implant shows both boron concentration (left)
and SiO2 thickness (right). (Source: ReVera)
General surface contamination control is another new application area. STMicroelectronics (Geneva, Switzerland) has reported using ReVera’s in-fab XPS to monitor fluorine contamination in its metallization processes, as well as de-scum effectiveness in post-implant cleans. ReVera also believes it can directly measure high dopant concentrations in ultrashallow junctions, in addition to surface oxide and any contaminates present.
This article was edited from the published version to exclude sections on additional companies. The full article is available on Semiconductor.net.