Stray Light Evaluation Techniques
Measuring stray light, optics cleaning, optics replacement and monitoring stray light have been shown to increase yields by 5% and reduce reworks by 10%.
An often overlooked area for improving CD control has been the issue of stray light. Stray light, Flare, or Scattered light are all names used to describe the same optical effect. Measuring stray light, optics cleaning, optics replacement and monitoring stray light have been shown to increase yields by 5% and reduce reworks by 10%. Of course, these results are both product and process dependent.
Stray light is defined as unwanted light that degrades the image contrast (poor CD control) caused by internal optical component – mounting reflections, scattered light resulting from particles on optical element surfaces, and external reflections from reticle chrome or wafer substrate. There are two basic types of stray light: Short Range and Long Range. Basically short range stray light impacts the region in the “dark” (under the reticle chrome) non-image areas 0 to 10 um from the image, mid-range 10 – 100um, while long range stray light impacts regions 100 to 500 um or greater from the image.
Stray light impacts DUV tools greater than i-line tool and many tests have been to monitor the DUV Stray light. These tests include FireFly (long range), SAMOS (short mid range) and Kirk (short range).
Simax has developed additional techniques for functionally evaluating the impact of stray light on i-line and DUV photoresist Critical Dimensions. The impact is photoresist type dependent with lower contrast materials having the greatest sensitivity.
Please contact Simax Applications Engineering at simaxlithography.com for assistance in developing a custom stray light monitoring application for your process.
Steve Brainerd is a Senior Applications Engineer with Simax Lithography. With over 30 years “hands-on” wafer fabrication experience concentrated in semiconductor wafer, MEMs, thick photoresist, solar, and LCD fabrication manufacturing processes, Steve uses his strong analytical skills to develop robust processes for customers. His knowledge and experience include process-equipment startup, process development, process modeling, anti-reflection coating design/modeling, cost reduction, yield improvement, and capacity increases
ASML 5500/100 Yield Improvement: Stray Light Evaluation Techniques
Process improvement defines a process engineer’s value to the corporation. Everyday a photolithographic process engineer is working on projects to improve CD, overlay, throughput, and defect reduction, with the end result being increased yield and profits.An often overlooked area for improving CD control has been the issue of stray light. Stray light, Flare, or Scattered light are all names used to describe the same optical effect. Measuring stray light, optics cleaning, optics replacement and monitoring stray light have been shown to increase yields by 5% and reduce reworks by 10%. Of course, these results are both product and process dependent.
Stray light is defined as unwanted light that degrades the image contrast (poor CD control) caused by internal optical component – mounting reflections, scattered light resulting from particles on optical element surfaces, and external reflections from reticle chrome or wafer substrate. There are two basic types of stray light: Short Range and Long Range. Basically short range stray light impacts the region in the “dark” (under the reticle chrome) non-image areas 0 to 10 um from the image, mid-range 10 – 100um, while long range stray light impacts regions 100 to 500 um or greater from the image.
Stray light impacts DUV tools greater than i-line tool and many tests have been to monitor the DUV Stray light. These tests include FireFly (long range), SAMOS (short mid range) and Kirk (short range).
Simax has developed additional techniques for functionally evaluating the impact of stray light on i-line and DUV photoresist Critical Dimensions. The impact is photoresist type dependent with lower contrast materials having the greatest sensitivity.
Please contact Simax Applications Engineering at simaxlithography.com for assistance in developing a custom stray light monitoring application for your process.
Steve Brainerd is a Senior Applications Engineer with Simax Lithography. With over 30 years “hands-on” wafer fabrication experience concentrated in semiconductor wafer, MEMs, thick photoresist, solar, and LCD fabrication manufacturing processes, Steve uses his strong analytical skills to develop robust processes for customers. His knowledge and experience include process-equipment startup, process development, process modeling, anti-reflection coating design/modeling, cost reduction, yield improvement, and capacity increases