Ultrapure Water For Maximum Efficiency Of Solar Cells - Mettler Toledo

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Microelectronics Perspectives in Pure Water Analytics 1 News THORNTON Leading Pure Water Analytics Ultrapure Water for Maximum Efficiency of Solar Cells In the manufacture of solar wafers and solar cells the highest purity requirements are imposed on the water used for cleaning and rinsing. High-precision, modern conductivity and TOC instruments monitor in real time the quality of ultrapure water (UPW) with regard to trace ionic and organic contamination. Ultrapure water in solar cell production Large quantities of ultra-high quality ultrapure water are required in solar cell production. After the raw wafers are cut from silicon ingots using wire saws, slurry is removed from the wafers in a cleaning process and they are then washed with UPW in a rinse step. After texturing the surface using potassium hydroxide (KOH) or mixtures of hydrofluoric acid and nitric acid (HF/HNO3), residues of the etching bath are removed with another rinse with ultrapure water. Then the p/n transition is created by phosphor diffusion. The resulting phosphor glass layer on the surface must be removed by oxide etching, which requires another rinse, before a blue antireflection coating is deposited for the purpose of reducing optical losses and for electrical surface passivation. A clean wafer surface is indispensable prior to the phosphor diffusion and coating process steps for achieving maximum efficiency of the subsequent solar cell. The clean surface of the special glass panes plays a critical role also at the time of processing the solar cells into modules in the matrix unit, before the cells are imbedded in the glass foil sandwich in the laminator. A final rinse with high-quality ultrapure water ensures that the silicon and glass surfaces are not contaminated by deposits of salts or organic compounds and thus do not negatively affect efficiency.

The quality of the ultrapure water after production and in the distribution system is monitored in-line using high-precision conductivity measurements and TOC determinations. In addition, the decision is made based on these measurements, whether low-contamination rinse water is recycled to the UPW treatment system or used otherwise (reclaimed), which can substantially reduce the not insignificant costs for water treatment. High-precision conductivity measurement The greatest demands on water purity are imposed in the semiconductor and photovoltaic industry. Water is used having a conductivity equivalent to the theoretical value of 0.005501 μS / cm at 25 C. In these industries the reciprocal value of the electrolytic conductivity, the specific resistance, is indicated for monitoring for ionic contaminants. Here the aim is a value of 18.18 MΩ 3 cm at 25 C. With a coefficient of 4 to 7 % / K the temperature behavior of ultrapure water is clearly other than with other common electrolytes (e.g. approx. 2 % / K for KCl). Therefore special algorithms for ultrapure water Publisher / Production Mettler-Toledo AG Process Analytics Im Hackacker 15 CH-8902 Urdorf Switzerland Illustrations Mettler-Toledo AG Gradts, Crashoran, Rainerplendl Dreamstime.com Subject to technical changes. Mettler-Toledo AG 12/09 Printed in Switzerland. 2 METTLER TOLEDO Microelectronics News 1 must be established for precise temperature compensation. Along with this computation the exact determination of the cell constants of the conductivity sensors is of very great significance for the accuracy of the measurement. Since 1964, Mettler-Toledo Thornton has operated very successfully in the field of ultrapure water analytics and is recognized as having the most precise measurement systems for determining specific resistance / electrolytic conductivity in pure and ultrapure water. At the Thornton manufacturing plant the cell constants of the conductivity sensors are determined with a maximum unreliability of only 1 % on the special Autoloop test rig. Here ultrapure water is used as the calibration medium which corresponds also to the later operating range of the measurement cells in UPW applications. The cell constants are, moreover, traceable to generally accepted standards such as those established by ASTM and NIST. Ingot wire sawing coating rinse Raw wafer etching Use of UPW in solar cell production The Thornton 5000TOC sensor is currently the fastest analyzer on the market. Instead of batch oxidation that requires analysis times of typically 7 to 15 minutes, the 5000TOC uses the dynamic UV oxidation process. A sample stream of the UPW permanently flows through the analyzer in the open bypass. Initially, the entry conductivity is measured, then the sample flows through a silicon glass coil and is irradiated with high-energy UV light. The exposure to strong UV-light results in any organic molecules present in the solution breaking down into carbon dioxide and water. The carbon dioxide generated during UV exposure partly dissolves in water, which in turn leads to the formation of carbonic acid. The UPW now has a slightly higher conductivity, and using the difference in conductivity before and after UV oxidation the TOC content is calculated. slurry removal rinse UPW P diffusion UPW metallization Fastest TOC determination Since, as a rule, no statement on organic contamination can be made using specific resistance, it must be monitored using a TOC analyzer. According to information from solar cell manufacturers the limit value for UPW is 1 or 0.5 ppb of carbon. rinse UPW Solar cell String Solar module Wafer texturing KOH HF/HNO3

Quartz Coil Conductivity Sensor (1) UV Oxidation Principle of dynamic UV oxidation This method is not only especially fast but also particularly maintenance-friendly, since moving parts such as pumps, and chemicals and membranes have been eliminated. Only the UV lamp must be replaced periodically. With a detection limit of 0.025 ppb C and a response time of 1 minute the stringent requirements of the photovoltaic and semiconductor industry on the measurement system are completely satisfied. High flexibility The Thornton 770MAX transmitter is a multi-channel measurement instrument that features two analog pulse inputs and four Smart channels. The analog pulse inputs are utilized for flow measurement Conductivity Sensor (2) UV Lamp with impeller or vortex flow sensors. The Smart channels are generally populated with sensors for conductivity but sensors for pH, redox potential, dissolved oxygen and ozone can also be connected. A special feature of the Smart technology is the Plug and Measure functionality which automatically recognizes the sensors, loads their characteristic data and automatically configures the measurement system. In this fashion, the installation and startup costs are reduced to a minimum and operating errors are eliminated. Moreover, it is equipped for connection to process control or a control system via eight analog 0/4 20 mA signals, 4 switch contacts, and a digital RS 232 interface that enables integration in PROFIBUS DP networks too. Product update The 5000TOC has now been superseded by the 5000TOC e. Physical and software improvements mean that the new model is even more reliable and robust than the previous version. Summary The quality of ultrapure water is decisive for product quality of solar wafers, cells and modules. Modern ultrapure water analysis systems ensure the required water quality with regard to conductivity and TOC, and in virtue of their modular design are very versatile for utilization in system control and quality assurance. Discover more at: www.mt.com/5000TOC 770MAX transmitter and 5000TOC e sensor METTLER TOLEDO Microelectronics News 1 3

UPW Disinfection and Sanitation Ozone Measurement Technology Increased Reliability, Reduced Maintenance For facilities using ozone as a means to disinfect or sanitize ultrapure water, METTLER TOLEDO offers a proven dissolved ozone sensor designed for high performance and low cost of ownership. Instrumentation reliability is critical The use of dissolved ozone in the production of ultrapure water is commonplace in semiconductor facilities around the world. It is seen as an economical and practical approach to controlling bacteria levels in final treatment processes of ultrapure water. Microorganisms in ultrapure water can lead to increased levels of organic and particulate contamination, ultimately contributing to decreased product yields. As many plants operate around the clock, all year, it is obvious that the instrumentation used to monitor ozone be reliable, robust and low maintenance. Optimized ozone sensor In-line dissolved ozone measurement has typically been accomplished using instrumentation that ranges from sophisticated high cost, maintenance-intensive equipment giving good performance, to low cost, less reliable equipment with flow sensitive readings. Mettler-Toledo Thornton offers a proven polarographic dissolved ozone sensor, optimized for a Ozone measurement system 4 METTLER TOLEDO Microelectronics News 1 wide range of measurement, low maintenance operation, and designed to operate on both the 770MAX and M300 multiparameter instrument platforms. Convenient multi-channel measurement In most ultrapure water systems using dissolved ozone, multiple measurement points are needed to insure proper dosage and also to confirm the removal of residual after ozone-destruct UV (ultraviolet light) exposure. Proper dosage equates to effective disinfection and allows a bacteriafree ultrapure water supply to process equipment. In contrast, detection of zero ozone is critical, as any residual becomes an unwanted contaminant at point of use and can contribute to increased oxygen levels, affecting performance of the downstream de-gassification process. Thornton’s multi-parameter, multichannel measurement capability provides the benefit of lower cost per measurement point and the convenience of one instrument to operate. Straightforward, rapid sensor maintenance Mettler-Toledo Thornton’s dissolved ozone sensor offers many advantages over other ozone sensors on the market. Sensor reliability is often a function of durability designed into a device. Our ozone sensor contains materials of construction calculated to provide long-lasting performance. The sensor body is made of stainless steel, offering high corrosion resistance. The reinforced silicone membrane maintains performance while offering the durability required for applications where maintenance downtime can be extremely costly. However, all dissolved ozone sensors require periodic maintenance. This is where Mettler-Toledo Thornton’s ozone sensor design clearly separates itself from other ozone sensors. The membrane cartridge design reduces time for periodic maintenance to a few minutes. The cartridge is removed by simply unscrewing the end of the sensor body, removing the existing cartridge, refilling a new cartridge with electrolyte, installing the new cartridge into the end cap and screwing it back onto the sensor body. This is a vast improvement over other dissolved ozone sensor designs. Find out more at: www.mt.com/THORNTON

Industry Support ASTM International Committee Mettler-Toledo Thornton Participation Water Committee standards from ASTM are widely used in the industries utilizing pure waters such as microelectronics, as well as the pure water treatment industry itself. Mettler-Toledo Thornton contributes to this important work, enabling customers to benefit from optimized measurements. Globally respected body ASTM International, originally known as the American Society for Testing and Materials (ASTM), was formed in 1898. Today it continues to develop voluntary consensus standards with input from expert producers, users, consumers, government and academia. The concept of consensus is effectively built into the standards approval process. All committee members have a voting interest and all objections must be addressed fairly and objectively by the group. As a result, the ASTM plays a respected leadership role in addressing the standardization needs of the global marketplace. Water Committee Of special interest to Mettler-Toledo Thornton and its customers is the ASTM Committee D19 on Water. It was formed in 1932 and currently has approximately 340 members in nearly 30 countries, with jurisdiction of over 300 standards documents. Key areas of committee interest are the development of standard methods for sampling, identification, and analysis of water and materials dissolved or suspended in water. In addition, it develops standards on the performance of water treatment materials and the determination of the corrosivity or deposit-forming properties of water. Water Committee standards are widely used in the industries utilizing pure waters including microelectronics, power and pharmaceutical, as well as the pure water treatment industry itself. ASTM Standards take the form of: Methods for measurement, calibration and accuracy determination; Specifications for the purity or other characteristics of water or treatment materials; Practices that outline accepted procedures; and Guides that describe a variety of approaches to measurements. Thornton conductivity / resistivity sensors for pure water measurements are all manufactured, factory calibrated and certified in accordance with ASTM standards D1125 and D5391 which define standard conductivity solutions and the techniques for handling pure water measurements. Thornton high purity pH and dissolved oxygen sensors are designed and operate in accordance with ASTM standards D5128 and D5462 respectively. Sharing expertise These standards not only provide widely accepted means for industry standardization, they also serve as important learning tools to those new to particular measurement or testing technologies. For over 15 years, Mettler-Toledo Thornton has sponsored its personnel in participating in the ASTM Water Committee with industry colleagues, contributing in their areas of expertise. These areas have included continuous conductivity measurement and temperature compensation in high purity waters, total organic carbon determination, pH measurement (especially in low conductivity waters), oxidation-reduction (redox) potential measurement, dissolved oxygen measurement in ppb ranges, ozone measurement, plus related pure water treatment methods and materials. At the same time, their participation keeps Thornton personnel up to date with new treatment methods, user-developed measurement techniques and industry trends. Participants on the Committee have found it to be a rewarding, on-going challenge to articulate technology into clear and concise standards and to keep them up to date. In addition, the work has helped enable Thornton and Thornton customers to benefit from optimized measurement techniques over the years. www.mt.com/THORNTON METTLER TOLEDO Microelectronics News 1 5

Total Organic Carbon TOC Measurement in UPW Systems for the Semiconductor Industry As integration on silicon chips becomes greater, so does the necessity for ever purer water. With fast, accurate measurement down to 0.025 ppbC, the 5000TOC e sensor is the perfect measurement instrument. Ever-increasing integration Over the past four decades advances in chip architecture, the reduction in line width and the increase in the number of transistors on semiconductor wafers has exponentially increased on silicon chips. The increase in the number of circuits has significantly decreased the line-widths on the wafers and the advances in design continue with the recent announcement of the 22 nm SRAM chip and work beginning on 16 – 15 nm and even 8 nm chips. The 22 nm SRAM chip puts 364 million bits of SRAM memory and more than 2.9 billion transistors packed into an area the size of a fingernail. This advancement increases by magnitudes the requirements for sensitive, accurate and continuous measurement and control of the UPW system. The semiconductor manufacturing process has the most stringent specifications and requirements for ionic, particulate and organic contamination in their pure and ultrapure water systems. Managing and measuring these contaminants in their UPW systems has assisted and enabled semiconductor manufacturers to improve product quality and maximize yields. Advances in water purification technology and innovations in instrumentation for monitoring these contaminants have played a significant role in improving and measuring the quality of ultrapure water. These advances, in turn, have driven lower 6 METTLER TOLEDO Microelectronics News 1 specifications for all contaminant levels in UPW systems. Vital measurement In-line, real-time analysis of total organic carbon (TOC) is a powerful and critical technique for monitoring organic contaminants in ultrapure water and for maintaining the ’health’ of the UPW system. To accurately and quickly measure contamination in the single ppb and ppt range requires instruments that are not only accurate at that level but also calibrated to perform in the required range. The Mettler-Toledo Thornton 5000TOC e is designed and calibrated for this specific critical application. Monitoring the TOC in the UPW system after the deionization (electro-deionization) and polishing stage is an important checkpoint for organics to prevent them from entering the polishing and distribu- 5000TOC e sensor tion loop. Additional measurements upstream and downstream can help diagnose where the organics are breaking through, e.g. whether it is reverse osmosis membrane failure or ion exchange resin deterioration or a pump failure. Further measurement in the distribution loop reduces the risk of organic contamination in the production process. Value and limitations The key to understanding the value and limitations of TOC data lies in understanding the great potential variety of organic impurities in water and in the relationship between the TOC level and the various organic compounds potentially present in ultrapure water. The percentage of carbon in organic compounds found in water can vary from less than 5 % to more than 80 %. Therefore, water with a reported TOC level could contain any combination of natural and

manmade organic compounds and the concentration of those compounds can vary widely in the UPW. TOC measurements do not provide analytical detail of the organics in the water or the concentration of a specific impurity. Instead, the TOC measurement provides a baseline for the total organic contamination in the UPW stream. Improving the accuracy of the TOC measurement will help insure that the organic level is well within the required specifications for today’s critical wafer production. The 5000TOC e and 770MAX are specifically designed and calibrated for use in the measurement of UPW in a semiconductor facility. The 5000TOC e undergoes a stringent special calibration in a UPW system that is high resistivity (18.178 MΩ 3 cm) and ultra low TOC 2 ppb. This special system calibration of the 5000TOC e and 770MAX assures the fastest and most accurate measurement of TOC in UPW systems. Measurement of TOC in UPW systems Microbial contamination can result in the loss of millions of dollars in defective wafers and chips. While a direct correlation between organics in the water system and microbial contamination is difficult, organic levels are a significant indicator of the ’health’ of the water system. Organics provide a food source for any bacteria that may exist in the distribution system, storage tanks, and the process technology or treatment modules. Accurate, fast and convenient measurement of the organic level in a UPW system can save millions of dollars in lost product. The 5000TOC e sensor provides the performance needed to meet these requirements, while offering the added benefits of continuous in-line measurement in a low-maintenance, industrial package with proven multi-parameter technology. The 5000TOC e sensor interfaces directly with the 770MAX instrument, which provides additional measurement parameter capability. The 770MAX is the ’gold measurement standard’ for the semiconductor industry and the 5000TOC e sensor increases the significance of this multiparameter platform. Standard parameter TOC testing has been a standard for the Semiconductor industry for many years but because of the cost and inconvenience of some analyzers it was employed in only a limited number of points on the UPW skid and distribution loop. The 5000TOC e sensor and 770MAX multi-parameter instrument package make multiple testing points not only economical but critical investments for risk reduction and improved yields. Using the 5000TOC e sensor throughout the UPW skid to monitor the integrity of reverse osmosis membranes, the effectiveness of TOC destruct UV lamps, resin bed and electro-deionization performance and organics shedding is a cost-effective way to improve the performance of the UPW pad. Pure and ultrapure water production requires the monitoring of organic contamination throughout the treatment process. The 5000TOC e sensor provides continuous, fast, and reliable monitoring of TOC levels from post RO waters to point-of-use. With continuous in-line measurements, the 5000TOC e sensor ensures TOC excursions will not be missed. Flexible solution The Thornton 5000TOC e sensor with 770MAX multi-parameter instrument provides the ideal combination of accuracy, speed and capability in one analytical package. The 770MAX can accept three other analytical sensors in addition to a TOC sensor, including conductivity / resistivity, pH, ORP or dissolved oxygen, plus pressure, tank level or two flow sensors. The 770MAX can also interface with two 5000TOC e sensors, leaving two additional channels for conductivity, pH or DO measurement and two pulsed flow channels are also available. Find out more at: www.mt.com/THORNTON METTLER TOLEDO Microelectronics News 1 7

Comprehensive Website The Information you Want is at www.mt.com/pro The METTLER TOLEDO Process Analytics website contains a vast amount of up-to-date information on all our products and services. A typical Product page: with Features Content is localized for your country and tailored to suit your selections. and Benefits and quick access to relevant application information, related products and downloads Simple layout allows you to quickly find the information and features you are looking for. 8 METTLER TOLEDO n Learn about our most recent product developments n Register for free webinars n Request further information on products and services n Obtain a quote quickly and easily n Download our latest white papers n Read case studies relevant to your industry n Access buffer and electrolyte solution certificates n and more. Microelectronics News 1

Search by Product or by Application n Read the latest product news n Access our Newsletter archive n Find out when our next Trade Show or Exhibition is in your area n Register for free webinars presented by our industry experts Application pages help guide you to the n Download our White Papers products that are right for your processes METTLER TOLEDO Microelectronics News 1 9

The THORNTON Solution One Transmitter for Multi-Parameters for TOC, pH, Conductivity, DO THORNTON solution Wide range of instruments for your processes Mettler-Toledo Thornton is the market leader in critical ultrapure and pure water analytics. Our 770MAX instrument is a multiparameter meter with a broad range of measurement sensor options. The in-line 5000TOC rapidly detects organic contamination in real time. As well as TOC, THORNTON produces sensors for monitoring pH / ORP, DO2 / DO3, conductivity, flow and pressure. 770MAX multi-parameter transmitter 5000TOC sensor for continuous Total Organic Carbon measurements pH for ultrapure water applications 2-electrode, 4-electrode and inductive conductivity sensors Flow Sm ar t pH / ORP DO2 / DO3 10 METTLER TOLEDO Microelectronics News 1

THORNTON benefits All-in-one supplier with sensors for all your pure water analytics needs Multi-parameter transmitter capabilities saves panel space and lowers costs per parameter 5000TOC allows a real-time TOC measurement, in-line, all the time No gases or reagents to handle, store or replace for TOC sensor; absence of moving parts minimizes routine maintenance Smart Sensor technology offers “Plug and Measure” communication from sensor to transmitter Sterilizable sensors designed for exceptionally long lifetime Pressure / Tank level Transmitter 770MAX ar t Sm ar t Sm ar t Sm Conductivity TOC METTLER TOLEDO Microelectronics News 1 11

Get in-line with METTLER TOLEDO Take Conductivity to a Digital Level With measurement technology built into each sensor, Intelligent Sensor Management (ISM) conductivity sensors from Mettler-Toledo Thornton have the ability to store unique sensor identity, measurement, configuration and calibration data, all within the sensor! Installation and startup are effortless when utilizing pre-calibrated ISM technology. Each sensor automatically communicates via an electronic “handshake” to the transmitter providing quick and consistent installation for simple Plug and Measure performance. Sensors send digital signals to the transmitter with less ambient noise and interference, extending cable lengths and improving measurement performance. When simplicity and installation speed are important, think ISM conductivity sensors from Mettler-Toledo Thornton. www.mt.com/cond Mettler-Toledo Thornton, Inc. 36 Middlesex Turnpike Bedford, MA 01730, USA Tel: 1 781 301 8600 Fax: 1 781 271 0214 Toll Free (USA): 1 800 510 PURE Email: mtprous@mt.com www.mt.com/pro Visit for more information

time the quality of ultrapure water (UPW) with regard to trace ionic and organic contamination. Ultrapure water in solar cell pro-duction . Specifications for the pu-rity or other characteristics of water or treatment materials; Practices that outline accepted procedures; and Guides that describe a variety of approaches to .

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Ultrapure water system 11 6. Intended use MicroPure ultrapure water systems are a reaction to actual user needs, the continually increas-ing requirements that water of ultrapure quality must fulfill, the increasingly strict demands re-sulting from technological advances and the need for user-friendly systems and complete solu-tions.

water quality standards and ensure the best reproducible results in their class. Up to 120 l of consistently high-quality ultrapure water with a conductivity of 0.055 µS/cm (0 18.2 MO cm) can be dispensed each hour. The ultrapure water is virtually microorgan-ism-free when a Sartopore 2 150 end filter is used.

The Therno Scientific Barnstead Ultrapure water Systems complies with the following standards and directives: Low Voltage Directive 2014/35/EC EMC Directive 2014/30/EU ASTM D1193-6 RoHs 2011/65/EU Additionally, the ultrapure water system is in compliance with many other international standards, regulations and directives not .

water, dry the system and take out the cartridges. Pack the ultrapure cartridges into a bubble wrap and/or packaging foam and put it into the package of the Smart2Pure Pro ultrapure water system. DANGER: Do not pull the plastic foil over your head. Risk of suffocation. Use the plastic foil only for packaging.

Exchange capacity for 18.2 MΩ cm ultrapure water relative to CaCO3 [Grain] [Equivalent] Analytical Kit 965 1.25 Biological Kit 1,14 1.48 Elemental Kit 1,268 1.64 Universal Kit 965 1.25 Order number Description H2O-A-PACK Analytical Kit, Arium Pro cartridge set for biological, chemical-analytical and standard ultrapure water applica-tions .

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