In working to improve previous generations of megasonic wafer-cleaning systems, ACM discovered how to enhance megasonic uniformity across wafers with an innovative solution called Space Alternated Phase Shift (SAPS™) technology. SAPS technology outperforms conventional megasonic cleaning products and efficiently exceeds expectations beyond removing random defects. Learn more about how ACM’s unique SAPS cleaning systems enable more efficient manufacturing, reduce chemical consumption, enable time and cost savings, and increase wafer yields.
A brief background of cleaning technologies
Many years ago, the semiconductor industry processed all wafer cleaning steps in bulk tanks placed in a bench, hence the term “wet bench.” The wafers were protected from damage by a coating of photoresist, which was subsequently stripped after backside silicon etching. Following this discovery, ultrasonic and, subsequently, megasonic cleaning systems were introduced to wet benches. However, as the power of these systems was increased, it resulted in damage to sensitive gate structures even at the 65nm node. In addition, pulling the wafers out of the tanks resulted in a pattern of residual particles on the bottom of the wafer. This was the beginning of the end of wet benches, as they did not meet particle specifications.
To reduce process steps and contamination, SEZ Group (now Lam Research) introduced the spin etcher in 1988. This technology used a Bernoulli chuck, which uses a nitrogen cushion to prevent the front side of the wafer from touching the chuck to minimize contamination and allow backside etching of the wafers. In the late ’90s, SEZ group also introduced BEOL of the line cleaning with a mechanical edge grip chuck for front side processing.
SEZ and DNS continued to introduce new single-wafer cleaning systems, and, as technology nodes shrank, there was a move to combine single wafer-cleaning systems with the binary nozzle by DNS, TEL and Lam. As well as megasonics, e.g., the Goldfinger (Akrion) and the Honda nozzle. These were evaluated by many OEMs, but none really achieved the desired performance.
A new take on megasonics for single wafer cleaning
Following on these earlier approaches, ACM Research evaluated the ProSys MegPie and found ways to improve the megasonic uniformity across the wafers by maintaining the distance between the pie and the wafers with a pure meniscus of liquid; they called this approach Space Alternated Phase Shift (SAPS™) technology. SAPS employs alternating phases of megasonic waves in the gap between a megasonic transducer and the wafer. Unlike the stationary megasonic transducers used in previous generations of megasonic wafer-cleaning systems, SAPS technology moves or tilts the transducer while the wafer rotates, enabling megasonic energy to be delivered uniformly across all points on the wafer, even if the wafer is warped.
On a microscopic level, this megasonic energy can reach every point on the wafer surface to remove random defects much more effectively and completely than conventional megasonic or jet spray processes. Radicals for removing the random defects are generated in dilute chemical solution by the megasonic energy. The mechanical force of cavitations generated by megasonic energy enhances the mass transfer rate of dislodged random defects and improves particle-removal efficiency. The megasonic action thins the boundary layer of the chemistry so the chemical can reach into 30:1 via contact and trench holes down to 10nm and remove any residue and particles; achieving cleaning performance in deep trenches that even the binary nozzle cannot effectively deliver. Additionally, SAPS can accomplish all of this in less time than conventional megasonic cleaning products, without loss of material and without roughing wafer surfaces.
Introducing Smart Megasonix™ advanced SAPS megasonic and chemical cleaning for single wafers
ACM now offers Smart Megasonix™ advanced SAPS megasonic and chemical cleaning technologies that efficiently remove random defects while enhancing process flexibility and reducing chemical consumption. Employing these systems in a fab enables resource optimization, time and cost savings, and reduced cost of ownership, as well as enhancing fabs’ sustainability.
To learn more about how Smart Megasonix and SAPS have demonstrated their advanced wafer-cleaning capabilities as nodes continue to shrink – as well as how you can increase wafer yields by using our tools to add cleaning to more steps in the manufacturing process visit us at: https://www.acmr.com/tools-and-processes/wet-processing/ultra-c-saps-cleaning/.