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Improving Yields and Tool Uptime with Relative Humidity Sensor in Semiconductor Environments.

Abstract:  The Semiconductor fab environment is sensitive to moisture. As the technology node advances, the need for characterizing and minimizing the exposure to Relative Humidity (RH) has become critical.

Current methods for characterizing N2 Purge FOUPs present challenges. These methods are typically not real time, are time consuming, are hard to use, and are not able to take RH measurements under production conditions, therefore are not reflective of these conditions. In
addition, hand-held RH meters and single trace hand-held meters are limited to one area and cannot move throughout the process environment. Other options are hand-made alternatives such as a wafer with RH sensors simply taped on. Lastly, they are often limited without data files generated so consequently statistics and quality standards cannot be established.

These RH control requirements create a need for a wireless wafer-like humidity sensor, which simultaneously measures RH at several points across the wafer as well as throughout the entire IC manufacturing environment. CyberOptics will review the advantages of using the wireless Auto Multi Sensor (AMS) as a more efficient and effective means of measuring RH in semiconductor environments. 

The test at the customer location involved putting an RH meter inside the FOUP. The goal was to repeat the RH meter profile for testing a FOUP on one load port without the need to open the FOUP. Starting at 40% RH (cleanroom environment), the first step was to run a high purity, high volume N2 pre-purge for 4-5 minute and then take the reading. The second step was to conduct a maintenance purge to 5% and measure the results in 5 locations across the wafer. This was followed by a process purge to 20% with sample readings taken across various locations. The goal of the testing was to test the efficiency of the N2 purge FOUP diffusers to ensure that uniform purge levels were maintained.

In response to the need for a reliable easy to use method of qualifying N2 and XCDA environments, the wireless wafer-like, AMS with five RH sensors measures the RH profile across the entire wafer surface. AMS is a complete and easy-to-use system, which communicates wirelessly to the CyberSpectrum application and moves like a normal wafer to all locations in the wafer process environment providing a true characterization of the N2 purge uniformity. Such previously hard to accomplish tasks such as characterizing purge FOUP diffuser uniformity and measuring actual RH percentages are now easily accomplished with AMS.

AMS is a multi-functional device, which also measures vibration and can be used for leveling to ensure proper wafer handling. 29nm geometry fabs and smaller require well controlled
N2 and XCDA purge environments to prevent defects and yield loss. AMS simultaneously measures RH in real-time at five locations on the wafer while it transfers like a wafer to qualify N2 and XCDA environments. The AMS device significantly shortens the task of qualifying
these environments. In addition, the AMS provides vibration and leveling measurement capabilities to ensure proper wafer handling and reduced particles. The overall result for the fab is improved N2 purge environment uniformity, which results in reduced defects and reduced labor costs.

Specific, quantified results in terms of timesavings using the AMS and accompanying software vs. alternative methods will be presented.

Biography:   Vidya Vijay, product manager at CyberOptics has over 15 years of engineering and engineering management experience at companies developing sensors, operator controls and designing motion controllers at Sensata, Infineon and Allied Motion. For projects spanning industry verticals from semiconductor to heavy off-road vehicles, she is responsible for managing the programs from iickoff through production exit. She has weaved engineering, marketing, and business throughout her professional life. She is an active member of local scouting and PMI chapter.

Vidya Vijay