ABSTRACT

It is clear that 193 nm lithography photoresists and scanner optical components, as well as masks, are far more sensitive to airborne molecular contaminants (AMC) than those used in earlier lithography generations. However, even older equipment can be significantly affected by AMC. Additionally, although a fab may have AMC levels under control, excursions in the ambient environment or tool pressure differentials may impact process and equipment and, over time, may result in a significant effect on lithographic illumination power or uniformity. Therefore, accurate, reliable, real-time AMC measurements at scanner manufacturer specification levels are the natural direction for monitoring critical environments.

This article discusses various realtime monitors, their advantages and limitations, and proposes strategies and applications for each.

Introduction

Over the past several years, we have experienced a steep learning curve providing many insights into the dynamics and impacts of airbor ne chemical contamination on highly sensitive processes and manufacturing equipment. Furthermore, we have realized that chemical filtration in previous generations of lithography equipment was developed under historical concerns with the primary goal of removing ammonia, and organics removal being added as an after-thought. Instead, ongoing research actually indicates that acidic contaminants pose just as serious a threat as ammonia or a large range of organic contaminants, particularly silicon-containing compounds. In the engineering world, these findings resulted in improved chemical filtration to remove alkaline, organic and acid components collectively. These enhanced methodologies have since been incorporated into newer scanner equipment design, with backwards compatibility for existing systems as well.

It is well known that airborne molecular contaminants (AMC) inside sensitive lithography equipment can come from many sources. These sources include outgassing from resist processes or materials of construction, ambient cleanroom contamination, or from purge gas streams. Evidence shows that the presence of increased AMC levels can result in thin films being deposited on surfaces inside litho scanners and can also reduce the effective lifetime of chemical filtration systems. Further, very high UV exposure doses can lead to decomposition of components, which then may undergo further chemical reactions.

It is well understood that stringent control of contaminant concentration levels of both the equipment environment and purge gases are required to maximize optics lifetime. In addition, replacement of consumable chemical filtration components at their end of life is critical. Negligence in either of these two areas increases the risk for contamination which can lead to increased equipment downtime for troubleshooting and reactive maintenance. In order to thoroughly understand the impact of contamination excursions and maintenance trends, the real-time monitoring of ammonia, acid gases, amines, and condensable organics is essential. Real-time monitoring enables determination of events that will put the equipment at risk. It can also provide real-time insight on chemical filter lifetimes, and a history of data that can be used for troubleshooting, compliance proof, and predictive diagnostics.

Most often, chemical sampling of the fab environment is done with grab sampling, which provides only a snapshot in time using an analytical lab for Ion Chromatography (IC) and Thermal Desorption & Gas Chromatography-Mass Spec (TD GCMS) analyses. While this method of testing is highly selective, very sensitive, and provides a detailed identification of each chemical detected, there are some key limitations. When taking a grab sample, it is very difficult to capture random events and AMC excursions such as chemical spills. In addition, AMC trends in a fab environment over a period of time can be hard to detect. Most importantly, however, the data analysis takes a significant amount of time, typically several days between sampling and report, and provides data after the fact. Thus, vital correlation of trends or excursions to actual optical impacts becomes a very long and costly process.

Several monitoring systems were investigated for this article, and equipment from two manufactures, the AiM® monitor from Particle Measuring Systems and the ppBRAE from RAE Systems, were evaluated at depth.

This article discusses various findings regarding these real-time monitoring techniques, including elements such as functionality, technical advantages, and potential limitations in their application.

Real-Time Monitor Options

Several manufacturers offer real-time detection methods that provide analytical chemical distinction for monitoring lithography scanner and other related equipment exposed to AMC. For instance, RAE Systems has a handheld Photo-Ionization Detector (PID) called ppB RAE, which detects volatile organic contaminants at parts per billion (ppb; 109 mol per mol) quantities. Particle Measuring Systems offers next generation AiM®-200, a monitor using a Surface Acoustic Wave (SAW) sensor to detect surface molecular contamination as ng/cm2 output which can be correlated to sub-ppb levels.(3) Further, Particle Measuring Systems also offers their Molecular Contaminations brand ion mobility spectrometry (IMS) for ppb level monitoring of acids and bases. This technique can also be coupled with a photo-acoustic organic analyzer. Finally, Entegris's Extraction brand monitor employs a chemiluminescence based system for analysis of Total Molecular Base (TMB, sum of all nitrogen containing bases) with ppb level sensitivity. The advantages and associated challenges of each of these methods will be contended next.

Traps

Absorption trap sampling has been used to take individual samples for many years, and is still effective today. Activated carbon or organic adsorbents in a sample trap are used to collect organic contaminants within a specific boiling point (molecular weight) range. Sample air is collected at low flow for a period of several hours (grab sample) and up to several months. The sample is then analyzed by TD GCMS, and results provide the average level of organic species trapped over the collection per iod. Long time accumulation enables detection of extremely low concentrations, typically not achieved with a standard 4-hour grab sample.(4)

Normally, sample inlet tubing is not required or is very short using a single point trap, eliminating line transmittance limitations. However, adsorptive traps act like gas chromatographic columns, releasing the most volatile compounds first and only retaining larger molecules. Thus, a balance between the quantity of media, sample period, and challenge concentration (input chemical concentration) needs to be considered in order to achieve valuable results.

Traps for inorganic molecules can consist of an impinger (DI water collection) or dry chemisorbent in a tube. However, water evaporation forces a similar trade-off balance between sample period and AMC concentration when using water impingers. Also, some acidic compounds, like SO2, may not be effectively captured in water. Both water and dry sample types can be analyzed by ion chromatography (IC) to provide the average concentration of each species present over the collection period.

Unlike organic traps, inorganic molecules are not lost from their respective traps, but a trap could reach saturation if the challenge concentration is too high and capacity to absorb is not adequate.

The benefit of this monitoring approach lies in sample pre-concentration of low level contaminants and the report of chemical speciation offered by GCMS and IC. However, the drawbacks of this method include potential sample deg radation due to chemical reactions or bacterial degradation in the sampling tubes, especially during long sample intervals and transport times. Also, for acidic gas monitoring, IC will report the anions present, but not the parent molecular species. For example, chloride (Cl) is measured, but it is unknown if the Cl is from Cl2 or HCl contamination; sulfate (SO42) is measured, but it is unknown if the source is H2SO4, SO2, and/or SO3 contamination.

Since this method is cumulative, whereby discrete events cannot be identified, this method is most effective for compliance evaluations and cleanliness studies, particularly for nitrogen or high purity gas lines which usually have low contaminant challenges. Monitoring these lines over a period of time would properly capture service cycles on purifiers and dryers, and the overall average concentration can be used to calculate chemical line filter unit (LFU) lifetime compared to real contaminant exposure.

Chemiluminescence

Chemiluminescence technology is used to identify specific compounds and includes a process by which light is produced as a result from a chemical reaction. Today, this technology can occur as a single stage or a twostage device to detect NO and other nitrogen-containing compounds.

One example of the two-stage technology is Entegris' Total Molecular Base Real Time Monitor (TMB-RTM) which is a 20-30 sample port system, and uses chemiluminescence to detect the sum of all nitrogen-containing contaminants an air stream. The selectivity of this method is based on an acidic scrubber that lets the system distinguish between basic compounds and the non-basic air matrix. Bases are converted to nitric oxide in a high temperature converter where the reaction of ozone with nitric oxide results in IR (infrared) emission detected by a photomultiplier tube. The reported detection limit for amines is 400 pptV (parts per trillion volume), defined as 2x RMS (root means square) noise, with a linear response across a concentration range of five orders of magnitude (analyzer manuf acture spec). The generation of excited NO2 molecules from the reaction of NO with O3 is unique. Although other substances such as CO and ethylene also react with ozone to produce photons, the wavelength of this emission is filtered out and thereby deselected by the TMBRTM to eliminate interferences. (5)

The functional schematic in Figure 1 shows how the sample train operates in two cycles controlled by valves. (6) In the first cycle, the amine scrubber is bypassed (channel 2) and all nitrogen containing species are converted to, and quantified as, NO; this is the total nitrogen value. In the second cycle, all amines are scrubbed (channel 1) the remainder is converted to and quantified as NO. The difference between the two readings is equal to the total amine concentration (including ammonia and NMP).

Calibration is automated, using customizable intervals and permeation devices for both NO2 and NH3. With a response time of approximately one minute and maintenance required on only an annual basis, operation only consists of a vacuum pump and compressed clean dry air for automatic calibration. One strength of this method is its ability to detect all amines without the need for system re-configuration. This enables immediate detection of new base compounds introduced into the fab environment, often before process engineers may be aware their negative effects.

Challenges associated with this technology include potential for noisiness in the data as a result of subtracting two large numbers to deter mine a small ppb level concentration. Further, a fairly high concentration of ozone is used for analysis, however, the gas is scrubbed internally very effectively, free of any safety concerns, enabling use of this technology in critical medical applications. The most significant limitation associated with this method is that it measures only one of three compound classes, without solution for measurement of organics and acids.

The TMB-RTM tool is effective for monitoring low ppb levels of ammonia or total amines that may impact processes, product, or equipment. It is also possible to use this method to monitor contaminant removal efficiency of chemical filters specifically targeting the removal of bases or ammonia, such as employed in coater/developer tracks.

Ion Mobility Spectroscopy

In contrast, Ion Mobility Spectroscopy (IMS) is a time-of-flight, mass spectrometry technique distinguishing between ammonia and amines using two subsequent steps; the first is gas-phase ionization at ambient pressure, while the other is ion characterization using mobility of gas-phase ions in a weak electric field.

The Particle Measuring Systems' brand IMS systems provide contaminant selectivity through the combination of selective membranes that reject interferences, enhanced ionization chemistry through the use of selective dopants, and a time-of-flight ion spectroscopy. Figure 2 illustrates how a continuous air sample drawn over a semi-permeable membrane provides the first level of contaminant selectivity.

The molecules of interest permeate the membrane, and are delivered to the region where the reaction occurs. In the reaction chamber, the sample is ionized by low-level beta radiation, emitted by a sealed nickel-63 radiation source. A selective dopant is added to the carrier gas flow to provide selective ionization. The ionized sample is then released through a pulsing shutter grid into the drift region where ions of different sizes are separated by their drift rates under the influence of an electrostatic field. At the end of the drift region, the ions collide with a detector (Faraday plate) and produce a current.

The current is amplified to produce a signal; the sum of all signals is the time-of-flight spectrum. Concentration is then determined from the ion current peak height or area.

IMS analyzers can be configured to monitor var ious contaminants simultaneously including: ammonia, NMP, total amines (excluding NMP), HCl, HF, HBr, Cl2, SO2, total acids, total organics, siloxanes, or hydrogen peroxide.

The analyzers are configured for a fixed concentration range; typically 0.1-100.0 ppb, and response times are on the order of one minute. The concentration range of the analyzer is determined by the dopant levels used, and the properties of the cell membrane. If IMS monitors are used to detect concentrations outside of their specified range, the response will become non-linear. Further, calibration is performed by an on-board permeation calibration system. In most cases, the analyzer is calibrated with the same contaminant gas species that is being monitored in the cleanroom.

For example, an ammonia monitor is calibrated with an ammonia gas standard that is dynamically generated. Non-linearity of ammonia calibration is compensated for by firmware for the set concentration range.

One drawback of this technique is the requirement for a unique cell, or analyzer, for each of the specific contaminants described previously, although, multiple analyzers can be installed in a single monitoring system. Each cell, or analyzer, is effective for monitoring a particular component or related contaminant group. Therefore, this method could be used to detect a specific chemical filter breakthrough contaminant in order to trigger filter replacement, or to monitor an area where a specific contaminant is of particular concern. Another challenge associated with this method includes ensuring that the target contaminant concentration is captured accurately within the available analytical range.

Particle Measuring Systems' AirSentry-IMS systems can also be coupled to an infrared photoacoustic sensor (PAS) to quantitate and separate methane from non-methane organic molecules and siloxanes.(9) The sample gas in the PAS method will absorb infrared light and expand as it heats. There will be a slight pressure increase with the expansion, and a subsequent decrease as light is chopped. This creates a sound wave that is detected by sensitive microphones connected to the gas cell. The analyzer then uses narrow band interference filters specific to both CH and Si-O bonds. Data has shown that larger condensables appear under-represented in a fab air sample, and thus, may be lost in the tubing from the sample locations.

A summary of the comparison between the TMB and IMS methods for amine detection in the semiconductor industry is presented in the Table 1. One challenge common to multi-point sampling systems is that large organic molecules and acids will not transmit through many feet of Teflon tubing for reliable concentration determination. Moreover, users must be aware of sample purge times when transitioning from a high concentration sample point to a low concentration sample point. For example, sampling a location with 5-30 ppb of ammonia, and then switching the manifold to a location with 0.5 ppb ammonia will require a several minutes for the high concentration to be flushed from the system before accurate readings at the lower concentration can be taken. Another common limitation is the number of samples per day for each location. Cycle times may be 10-20 minutes depending on the desired level of the final signal. For example, with a 60 sample point manifold, and 10 minutes sampling for each sample line, there are only roughly 2 measurements at each location per day.

Surface Acoustic Wave

Surface Molecular Contamination (SMC) has been adopted as the term that quantifies how gas-phase contamination interacts with critical surfaces and is typically represented as a mass per unit area (ng/cm2 or ng/ cm2/min).(13) Monitoring molecular contamination deposited on surfaces offers the advantage of being able to see the net effect of complex air chemistries, environmental conditions, and the chemical/physical nature of the surface and provides data that complements traditional test wafer monitoring.(12) Surface Acoustic Wave (SAW) sensor technology can measure the amount of SMC deposition.

Particle Measuring Systems developed a tool, AiM-200 (Figure 3), which uses SAW technology to monitor ambient air, or closed piped (flow-through) locations and are designed for monitoring environment within a temperature range of 15°C to 35°C. This SAW equipment employs piezoelectric quartz crystals in which the crystal oscillates when electricity is passed through it. If a contaminant adsorbs to the surface of the crystal sensor, the crystal's frequency of oscillation will be less than that of an uncontaminated cr ystal (on-board sealed reference crystal). The acoustic waves from the oscillations travel along the surface of the crystal. Then a frequency shift is observed and recorded as mass increases (contaminants are deposited) on the sensor surface. The AiM proprietary software (firmware) calculates the difference in frequency between the exposed sensor chip and the sealed reference chip, as well as the mass of the contamination based on that change in frequency. (13) Output signals are reported in ng/cm2, a mass of the contamination per area.

The AiM-200 is effective for detecting organics and siloxane compounds using SiO2 sensors and provides a Total Organic Carbon (TOC) value. Metallic coated sensors are available and can detect a variety of acid gasses with the copper sensor used for detecting halogenated compounds such as HCl, HF, and HBr, and the silver sensor used for detecting NOx, and SOx; together providing a "total acid" value. (14) The monitor may be calibrated after an equilibration period using a software command which takes the following 10 samples, averages them for a baseline, and sets the baseline to zero for a new mass accumulation starting point. Once equilibrated, the sensor shows response to contamination events within seconds. Sensors are consumables and are replaced based on quantity of contamination accumulated; generally 6 months to one year for a low concentration ambient environment. Table 2 offers a qualitative model provided by Particle Measuring Systems with guidelines for output detection vs. cleanliness.

One drawback we found is that when this system is used outside the relative humidity operation range (20-50&per;), the standard equilibration period of several hours, can be upwards of several of days for very dry air streams (15) before the system can report meaningful data.

Another challenge is that AiM sensors may respond var iably to different chemicals, with some contaminants appearing to contribute more to the surface contamination sensor response than others. Larger, more polarized molecules with higher boiling points may elicit a larger response than smaller, less polarized molecules with lower boiling points. Even though the technology responds well to specific calibration gases, it is not selective in a complex air matrix such as that found in clean rooms. The most significant challenge for this technology is that the output needs to be interpreted along with other parameters in order to obtain semi-quantitative and semicalibrated concentration information.

Our evaluation determined that the AiM-200 monitor is highly sensitive to concentration changes and affords stability over a long period of time, yet requires long equilibrium periods. This combination makes it applicable for use as a long-term monitor for general air quality where total organic or total acid values are sufficient, such as for filter lifetime determination. This system could be used to monitor an ambient space or high purity line in order to react to unspecified contamination levels, or for understanding fluctuations of contaminants dur ing repetitive maintenance events, or for recording random events such as spills. It could also be used to determine end of filter life using a trigger point of filter removal efficiency, where efficiency is calculated from the average TOC and total acid contamination rate. That rate could then be monitored using software, and when it trends beyond the user defined threshold, filters would require replacement. It is not recommended that this equipment be used for measurement periods shorter than a few days due to the time associated with sensor equilibration and the need for establishing a baseline contamination rate.

Photo-ionization Detector

RAE Systems, Inc, has a handheld monitor, ppB RAE, (Figure 4) that mainly detects total volatile organic compounds (VOC) and is based on classic PID technology. The monitor employs a UV lamp to break chemical bonds, thereby generating positive and negative ions (ionization) which are easily separated by an electric field, and collected by electrodes. The resulting current detected is amplified by firmware algorithms and displays the output value as a concentration in ppb of a specific gas, like isobutylene, to which the sensitivity of the detector is calibrated.

The RAE unit requires a short, two-step calibration procedure, but is ready to initiate sampling immediately after calibration. Calibration involves creating a baseline (zero) for the air stream sampled using a sealed glass tube (zero tube) containing carbon filtration media fitted to the ppB RAE probe. Then, a target gas (isobutylene) is used for a "span" calibration to set the detection slope. (16) Subsequently, because this instrument has a tendency for calibration to drift after a few days, the span gas may then be used to check the slope setting, and the zero tube can be used to check the zero level. Recalibration requirements are dependent on exposure to and the quantity of contaminants, and the level of desired accuracy. Calibration accuracy can be extended on RAE units by utilizing a special pump-cycling feature (duty cycle). Re-calibrating a RAE unit during the sampling period will reset "zero" for more accurate readings. Like the AiM unit, the ppB RAE is also a non-selective monitor and has a limit to the range of compounds and quantity of data points it can accumulate. Its 10.6 eV lamp used in our evaluation is effective for organic molecules with ionization energies less than 10.6 eV; higher than 10.6 eV may not be detected. Although a higher energy lamp is available, both its shelflife and lifetime are very limited. We also found that run times are limited to about one week due to limited battery life and data storage capacity.

The potential for calibration drift over time limits the application of this equipment to "event" situations, for example, troubleshooting source contamination or spills, or gaining visibility to fluctuating contaminant levels during a specific event, like repetitive maintenance. Further, it is possible that pre- and post-filtration point readings using ppB RAE could provide useful values for filter efficiency calculations. In addition, it is not recommended that this equipment be used even for a short period of time on high pressure facility lines, unless a check valve is used, because of back flow potential.

Output interpretation is application dependent. If used for a spill where the contaminant is known, the actual quantity of the known contaminant can be accurately determined from RAE Technical Note #106; (17) whereas in the case of unknown or mixed contaminants, the output may only be compared on a relative basis, as in filter efficiency calculation. It also appeared that there were some contaminant interferences that were not necessarily organic compounds, which resulted in a signal.

Even though PID detectors can be used in combination with separating gas chromatographs, the ppB RAE system is mostly limited in its ability to give specific AMC information.

Conclusions

Although lower wavelengths and higher energies on exposure tools increase the potential for more significant negative effects due to trace AMC, the semiconductor industry is rightly trending toward improved AMC prevention and control. Fabs are becoming cleaner with respect to ammonia and total organics levels, mainly due to increased awareness and enhanced chemical filtration, both in purge gas supply and in clean room HVAC systems. Excursions in high purity clean, dry air (CDA) and N2 purge gases are far less critical due in part to point-of-use chemical filtration. Additionally, increased emphasis has been placed on getting rid of "bad players" within the fab, such as ammonia, silicon-containing compounds, and sulfates. Nikon recognized this critical issue early on and for several years has been shipping litho scanners with complex chamber integrity features, including detailed environmental control systems, as well as special chemical filters to clean the fab air before it enters the scanner to ensure lens quality is maintained over the life of the product. In addition major lens assemblies are purged with nitrogen to eliminate lens degradation caused by fab contamination. These features protect exposed optics and enable relaxation of some ambient AMC control requirements.

Reliable monitoring is the next technical challenge toward characterizing and preventing AMC before it manifests itself as a visible result, such as power degradation, illumination unifor mity changes, flare, and degradation in processes or equipment. Single instrument set-itand- forget-it technology that measures a comprehensive suite of acid, base, and organics contamination would be ideal, but is not currently available due to technology limitations, cost, and maintenance or operation requirements.

Further, physical sampling constraints drive the need for reasonably priced, portable systems capable of collecting point-of-use samples. Scanner environmental requirements require very low detection limits, and, in many cases, require speciated results. Technological advancements in the monitoring equipment provide the capability to satisfy requirements for stable ammonia and base quantitation today, whereas acids and organics detection are only met at minimal real-time monitoring levels. However, although advanced technology for AMC measurement is available and mature (for example, online GC/MS or IC systems), proven solutions for fast, cost-effective, low maintenance, and reliable online monitoring of acids and organics are still lagging.

A variety of real-time monitoring solutions is available, each with different advantages and limitations. The key to an effective monitoring plan is knowing the targets: what AMC is present, how much of it is present, for how long, and where it is present. Having an arsenal of equipment to monitor for these targets provides invaluable information regarding the overall impact of AMC to sensitive lithography processes and equipment, but is typically cost prohibitive and not widely accepted. Therefore, users may want to consider how to combine existing real-time monitoring with trap sampling for a comprehensive solution. Entegris is making grab samples easier and less expensive by introducing a portable "technician in a box" device, called the Lithoscout AMC sampler, which is as easy as a one-touch operation. A combination of real-time monitoring technologies that provide the sensitivity, dynamic range, and rapid response with continuous data stream to quickly identify abnor mal contamination conditions, and using trap sampling for speciation of contaminants at the highest accuracy and sensitivity level may actually be the most robust and probably most reliable solution in the foreseeable future.

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REFERENCES

1. A. J. Dallas et al. "Are Ambient SO2 Levels a Valid Indicator of Projected Acid Gas Filter Life?" Proc. SPIE Vol. 5375 (2004) pp. 807-818.

2. R. R. Kunz, V. Liber man, and D. K. Downs "Experimentation and Modeling of Organic Photocontamination on Lithographic Optics," Proc. SPIE Vol. 4000 (2000) pp. 474-487.

3. Akiyama, T. et al, "Monitor System for Clean Dry Environment using Surface Acoustic Wave Sensor," Proceedings of 21st Annual Tech. Meeting on Air Cleaning and Contamination Control, Japan Air Cleaning Association, April 2003, 46-48.

4. C. Atkinson, J. Hanson, O. Kishkovich, M. Alexander, A. Grayfer. "New approach to measurement of photoactive deep UV contaminants at sub parts-per-trillion levels," Proc. SPIE vol.5037 (2003) pp. 439-449.

5. Private Communication from Entegris, Gas Micro-contamination Division.

6. Courtesy of Entegris, Gas Microcontamination Division.

7. Courtesy of Particle Measuring Systems, Molecular Analytics Division.

8. T. Bacon, K. Webber, R. Carpio. Contamination Monitoring For Ammonia, Amines And Acid Gases Utilizing Ion Mobility Spectroscopy (IMS), Proc. SPIE vol.3332 (1998) pp. 550-559.

9. T. Bacon & K. Webber Monitoring For Photochemical Organic Contamination In 193 And 157 nm Processes, SEMICON West 2003. ISBN # 1-892568-78-0.

10. Communications from both Particle Measuring Systems, Molecular Analytics Division and Entegris, Gas Micro-contamination Division.

11. O. Kishkovich, et al. "Real-time methodologies for monitoring airborne molecular contamination in modern DUV photolithography facilities," Proc. SPIE Vol. 3677 (1999) pg. 362.

12. Monitoring Molecular Contamination of Critical Surfaces in Semiconductor Manufacturing
13. S. Rowley "Real-time optics contamination monitoring using surface acoustic wave technology," Proc. SPIE Vol. 5375 (2004) pp. 1033-1038.

14. A Molecular Contamination Monitoring Test Protocol for Production Environments, 09/2003.

15. Nikon internal project report. Contact author from more information.

16. Technical Note (TN-127, rev 1) "Ensuring Measurement Accuracy and Consistency of ppBRAE by Calibrating with RAE Single-Use VOC Zeroing Tube" at http://www.raesystems.com/AppTech_Notes/TN, April 2002.

17. Technical Note (TN-106, rev13d) "Correction Factors, Ionization Energies and Calibration Characteristics" at http://www.raesystems.com/AppTech_Notes/TN, May 2004.

ABOUT THE AUTHOR

Robin Danfelt is a Senior Contamination Control Engineer at Nikon Precision, USA. She co-developed chemical testing strategies to qualify fabs for equipment delivery, while also supporting investigative projects for performance improvements and enhanced cost of ownership. Robin holds a Masters of Science degree in Cellular Biology. Her experience in biotech facility monitoring and chemical clean efforts at Nikon Precision contribute to a well-rounded understanding of contamination control concepts.

Robin Danfelt
Contamination Control Engineering
Nikon Precision, Inc., 1399 Shoreway Road
Belmont, CA 94002, USA
Tel: +1 650-508-3855
E-mail: rdanfelt@nikon.com
Website: www.nikonprecision.com

AiM® is a registered trademark of Particle Measuring Systems, Inc.