Environmental Impact of Single Wafer Wet Tools. SESHA Mini-Conference September 28, 2014 Brian K. Raley

Transcription

1 Environmental Impact of Single Wafer Wet Tools SESHA Mini-Conference September 28, 2014 Brian K. Raley

2 Environmental Impact of SW Wet Tools Increased Chemical Usage Virgin chemical supply Onsite storage Increased Waste Generation Increased Water Usage Higher Emissions Particulates VOCs Partnership Required 2

3 Promise vs. Reality 2007 Micro article, Sony Semiconductor: SW wet cleans consumes far smaller quantities of chemicals and DI water than a traditional immersion-type RCA cleaning 2007 Micro article, Bijan Moslehi: Single-wafer tools also promise to reduce chemical and DI-water consumption, while at the same time offering the potential to improve process control and uniformity. Handbook of Silicon Wafer Cleaning Technology (2 nd Edition) 2008: Single-Wafer tools consume much less chemicals compared to immersion tools ITRS: The trend towards single wafer cleaning needs to be managed for efficient use of chemicals and resources ITRS: One trend is the migration from batch wet processing tools to single wafer systems. The throughput of a single wafer wet tool is less than batch systems and single wafer wet tools use more UPW per wafer pass. Both of these trends increase the UPW consumption of a given fab. 3

4 Estimated Chemical & Water Usage Utility/ Chemical AVG ratio Flow (ml/min) Step time (sec) Use per step (ml) Steps per wafer Wafers per year m 3 /year Gallons/ year Volume/day Sulfuric Acid ,400 6,181,625 16,936 Gal/day Hydrogen Peroxide ,850 1,545,406 4,234 Gal/day UPW ,000 3,847,500 1,016,401, MGD SPM waste NA ,250 7,727,031 21,170 Gal/day Estimates based on industry averages, intended as an average and a starting point for discussions. Many variables affect these numbers. SPM waste total is sum of used sulfuric acid and hydrogen peroxide, and does not include rinse water. Assumed advanced 300mm facility with 75K WOPM. 4

5 Sulfuric Acid Volume Standard truck shipment of virgin sulfuric: About 2,500 gallons, limited by road weight (in U.S.). Takes approx hours to offload. Based on volume estimates, this requires 7 loads (trucks) a day and 2 reserved loading bays (minimum). Storage: International Fire Code (2012) Table Detached Building Required Water Reactive, Class 2: limit is 25 tons 25 tons is approximately 3,200 gallons Based on estimates, this is less than 5 hours of usage. Therefore, detached storage is required. 5

6 SPM Waste Volume: Truck capacity is about 3,000 gallons, limited by road weight. Waste offload takes about 3 hours. Based on volume estimates, this would be about 7 loads (trucks) a day and a reserved bay. Trucks are Halar lined (due to peroxide and potential for heat generation). Therefore, expensive and limited availability. Some shipping companies ask for cost sharing for the transportation fleet. Cost estimate for offsite transport, treatment and disposal (average for one location): $7 per gallon Results in >$50M in annual disposal costs. Beneficial reuse (capacity, quality) Potential solutions: Optimize configuration and/or process to reduce demand. Provide onboard reuse/recycle capabilities. 6

7 Hazardous Waste Generation Benchmarking indicates that SPM waste becomes significantly larger and approaches 90% of hazardous waste volume as SW tool use increases. General trend: % of total Haz Waste 10% of total for little SW tools use 40% if some SW tool use 80%+ if full SW tool use Onsite reuse options are limited due to large volumes. Onboard recycle capabilities could greatly reduce this impact. ITRS Target (2015) for hazardous waste generation (all streams combined): 8 g/cm 2 Estimations for SPM alone: 76.9 g/cm 2 7

8 Water Usage ITRS 2015 Target for total UPW consumption (all uses): 6.5 L/cm 2 UPW Usage estimate for SW wet cleans alone: 6.0 L/cm 2 At these volumes, more sites will be forced to reuse/recycle wastewater from wet cleans, possibly simply due to infrastructure. Most common setup is batch collection (last rinse) and feed back to UPW manufacturing input. With a batch collection system, a single tool can contaminate the batch. Better wastewater segregation could improve reuse opportunities. Improved program drain switching based on time period (for example). Tool vendor support is needed to understand wastewater contaminant profile and to modify drain switching as needed. 8

9 Particulate Emissions Segregated acid and caustic exhaust systems. Industry moved to segregated exhaust systems as a result of NH 4 OH use in wet cleans in the 1980s, mainly due to particulate (salt) formation. Introducing NH 3 to an acid exhaust system created ammonium salts. Ammonium chloride (and others salts) are thermodynamically favorable and the NH 3 will react to completion (assuming no limitation by reaction kinetics). Ammonium fluoride is also formed, but has a higher equilibrium vapor pressure. Opacity: In the US, there are specific Federal opacity (visible emission) limits. In addition, visible emissions in any location can draw additional regulatory and neighbor concern. Typical US limit: 20% maximum 6 minute average. 9

10 Particulate Emissions (cont.) NH 3 concentrations 1 ppm in an acid scrubber inlet can cause particulate and opacity at the stack. (Most common recommendation from tool vendors has been acid exhaust system.) Tests have shown some SW wet sinks have NH 3 exhaust concentrations near 1,000 ppm (in the exhaust directly from the sink). A couple SW wet tools could theoretically cause some opacity at a stack! Potential Solutions: There are integrated switching exhaust options, but they have many drawbacks: cost, space, exhaust demand and between 4 and 10% crossover Tool vendors should provide emissions testing or estimates to support assessment of potential issues or required infrastructure. 10

11 VOC Emissions SW wets tools are sometimes used for IPA cleans. US (major source thresholds): tons per year of VOCs (Volatile Organic Compounds). Threshold varies regionally based on attainment status. Threshold exceedance results in a different permitting regime, more restrictive requirements, a more lengthy and complex permitting and permit modification process. With recent Supreme Court decision (UARG vs EPA), being a major source for VOCs would also make a fab a major source for GHGs. The Court has ruled that a source cannot be major for GHGs only, but becomes major for GHGs if it is also a major source for conventional pollutant(s). Tool vendors should support with testing data or estimates. 11

12 VOC Emissions (cont.) Based on emissions testing for one scenario, just a couple tools could approach this threshold. (Many variables play into this.) Some tool suppliers don t offer a 3-way switching exhaust option. With up to 10% crossover for a switching exhaust option, a set of tools could still be problematic (if left unabated). Unabated VOCs to acid/corrosive exhaust. Corrosives to an uncoated VOC exhaust, particulate to an RCTO. Switching exhaust significantly increases overall exhaust requirements. Even if using point-of-use abatement (assume 98% efficiency), 20 tools (for example) could be problematic. Therefore, even higher efficiencies would be required. Single Tool IPA Emissions 12

13 Summary of Impacts Significant potential regulatory impact. Stack opacity VOC emission limits and resulting requirements for exceeding In addition to standard infrastructure support for wets (>$100M): Exhaust modifications: $15M Chiller Plant upgrades (make-up air): $40M HPM Dispense Buildings: >$50M Operating costs: SPM waste disposal >$50M/year. UPW and wastewater total costs: >$15M/year. Virgin sulfuric, peroxide supply $$$. Chiller Plant operations $$. Testing emissions on site after install is disruptive. Increase in risk during transportation/handling of chemicals and wastes due to significant volumes. Company and industry resource conservation goals are significantly impacted (waste generation, water use etc.) 13

14 Tool Vendor Partnership Required Credible expedited plan for enabling resource conservation: Reduce chemical and water use Improve water segregation capabilities Reduce exhaust volumes Support with emissions testing. Improved exhaust segregation solution. SEMATECH is holding a Single Wafer Wet Tool Workshop on October 15th to strengthen the industry partnership around these issues, identify potential solutions, and commit to a path forward. 14

15 Acknowledgements Todd Dietrich Joel Rouillard, Albert Franzi, Jim Mussgnug Kristen Fitzpatrick Tom Huang 15

16 Thank you. Trademark Attribution GLOBALFOUNDRIES, the GLOBALFOUNDRIES logo and combinations thereof, and GLOBALFOUNDRIES other trademarks and service marks are owned by GLOBALFOUNDRIES Inc. in the United States and/or other jurisdictions. All other brand names, product names, or trademarks belong to their respective owners and are used herein solely to identify the products and/or services offered by those trademark owners GLOBALFOUNDRIES Inc. All rights reserved. 16