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Pharmaceutical & Biopharmaceutical Development Services

EAG brings unparalleled expertise to the development and commercialization of small molecule drugs, biopharmaceuticals, antibody-drug conjugates (ADCs), drug-device combination…

EAG brings unparalleled expertise to the development and commercialization of small molecule drugs, biopharmaceuticals, antibody-drug conjugates (ADCs), drug-device combination products and other therapies. From designing IND-enabling studies to delivering full CMC analytical and QC support, we join your R&D team as a true partner. EAG scientists take time to understand both your commercial goals and the unique characteristics of your compound. We provide expert guidance to balance regulatory expectations with expediency and cost, and approach technical challenges with flexibility and resolve.

Materials Testing & Analysis

When it comes to understanding the physical structure, chemical properties and composition of materials, no scientific services company offers the breadth of experience, diversity…

When it comes to understanding the physical structure, chemical properties and composition of materials, no scientific services company offers the breadth of experience, diversity of analytical techniques of technical ingenuity of EAG. From polymers to composites, thin films to superalloys—we know how to leverage materials sciences to gain a competitive edge. At EAG, we don’t just perform testing, we drive commercial success—through thoughtfully designed investigations, technically superior analyses and expert interpretation of data.

Environmental Testing & Regulatory Compliance

Having helped develop the test methods that shape current regulatory guidelines, EAG chemists, biologists and toxicologists have evaluated the environmental impact of thousands of…

Having helped develop the test methods that shape current regulatory guidelines, EAG chemists, biologists and toxicologists have evaluated the environmental impact of thousands of active ingredients and formulations—from pesticides and pharmaceuticals to industrial chemicals and consumer products. Whether you are exploring “what if” scenarios, registering a new active ingredient or formulation, responding to a data call-in or seeking to understand the latest guidance, turn to EAG for technical excellence, sound advice, GLP-compliant study execution and expert interpretation.

Microelectronics Test & Engineering

Whether connecting the internet of things, guiding surgical lasers or powering the latest smart phone, integrated circuits and microelectronics touch nearly every aspect of human…

Whether connecting the internet of things, guiding surgical lasers or powering the latest smart phone, integrated circuits and microelectronics touch nearly every aspect of human life. In the world of technology, innovation and continuous improvement are imperatives—and being able to quickly and reliably test, debug, diagnose failures and take corrective action can make the difference between a doomed product launch and building a successful global brand. EAG offers you the world’s largest and most diverse collection of specialized analytical instrumentation, capacity to perform a variety of microelectronic tests in parallel, and the multi-disciplinary expertise required to draw true insight from data.

Custom Synthesis & Radiolabeling

No contract service provider has more experience performing custom synthesis and producing isotopically labeled compounds to support product development in life science, chemical…

No contract service provider has more experience performing custom synthesis and producing isotopically labeled compounds to support product development in life science, chemical and related industries than we do. From 14C and 3H radiolabeled clinical trial materials synthesized under cGMP, to stable-labeled active ingredients for metabolism and environmental fate/effects testing, turn to EAG. We have extensive experience with multi-step and other complex synthesis projects, and our comprehensive, in-house analytical services ensure quick turnaround of purity and structural confirmation.

Crop Biotechnology & Development

EAG combines biotechnology and protein characterization expertise with more than 50 years' experience analyzing chemical compounds in plant and environmental matrices to address…

EAG combines biotechnology and protein characterization expertise with more than 50 years’ experience analyzing chemical compounds in plant and environmental matrices to address the growing needs of the biotechnology crop industry. We offer a wide range of techniques required to fully characterize the event insertion and expressed proteins, as well as the various studies required to confirm the food, feed and environmental safety of products that represent the trait. From early-stage protein confirmation to GLP-compliant EDSP and allergenicity testing, we help you make faster, more informed development decisions and comply with evolving global regulations of genetically engineered crops.

Litigation Support & Expert Testimony

When you need solid science and investigative engineering to address product failures, inform legal strategy, protect intellectual property or address product liability disputes,…

When you need solid science and investigative engineering to address product failures, inform legal strategy, protect intellectual property or address product liability disputes, turn to EAG. We’ve provided technical consulting, analysis and expert testimony for hundreds of cases involving the aerospace, transportation, medical device, electronics, industrial and consumer product industries. Our team of experts understands the legal process and your need for responsiveness, effective communication, scientifically defensible opinion and confidentiality. From professional consulting to data review to trial preparation and expert witness testimony, ask EAG.

Techniques

Chromatography

Using an array of advanced separation techniques and innovative technology, we conduct highly precise analytical chromatography for various industries. Whether you want a closer…

Using an array of advanced separation techniques and innovative technology, we conduct highly precise analytical chromatography for various industries. Whether you want a closer look at the purity of your pharmaceutical or need to better understand an agrochemical’s components, EAG has the expertise to separate and evaluate any compound.

Mass Spectrometry

Need to evaluate the molecular structure of a compound or identify its origins? EAG knows how. With state-of-the-art tools, we can separate, vaporize and ionize the atoms and…

Need to evaluate the molecular structure of a compound or identify its origins? EAG knows how. With state-of-the-art tools, we can separate, vaporize and ionize the atoms and molecules in almost any pure or complex material to detect and obtain mass spectra of the components. We rely on decades of experience in mass spectrometry to provide our clients with precise analyses and the best detection limits.

Imaging

EAG is a world leader in high-resolution imaging down to the atomic level. We offer unmatched analytical know-how, generating extremely detailed surface and near surface images…

EAG is a world leader in high-resolution imaging down to the atomic level. We offer unmatched analytical know-how, generating extremely detailed surface and near surface images for various industries, from consumer electronics to nanotechnology. Using state-of-the-art equipment and innovative techniques, we conduct expert imaging to aid in failure analysis, dimensional analysis, process characterization, particle identification and more. If you want to investigate a material with angstrom scale resolution, you can count on EAG to get the job done quickly and precisely.

Spectroscopy

EAG offers a vast array of spectroscopic techniques to clients in various industries, from defense contractors to technology pioneers. We combine unparalleled expertise and…

EAG offers a vast array of spectroscopic techniques to clients in various industries, from defense contractors to technology pioneers. We combine unparalleled expertise and methodology with cutting-edge technology to analyze your organic, inorganic, metallic and composite materials for identification, compositional, structural and contaminant information. Whether you need expert spectroscopic analysis to improve your production process or to surmount a technical challenge, EAG is up to the task.

Physical/Chemical Characterization

Need to identify your unique material? Want to analyze the thermal properties of a sample, or measure the success of a process step? If it has to be done quickly and it has to be…

Need to identify your unique material? Want to analyze the thermal properties of a sample, or measure the success of a process step? If it has to be done quickly and it has to be done right, you can count on EAG. We offer a range of adaptable techniques and innovative methods to evaluate the physical and chemical characteristics of any compound. Our highly precise testing and analytical services will improve your production process, expedite R&D and help you conquer any technical challenge.

About

A Global Scientific Services Company

One of the most respected names in contract research and testing, EAG Laboratories is a global scientific services company operating at the intersection of science, technology and…

One of the most respected names in contract research and testing, EAG Laboratories is a global scientific services company operating at the intersection of science, technology and business. The scientists and engineers of EAG apply multi-disciplinary expertise, advanced analytical techniques and “we know how” resolve to answer complex questions that drive commerce around the world.

Our Customers

Science and technology transcend industry boundaries, and so does demand for EAG’s expertise. We partner with companies across a broad spectrum of high-tech, high-impact and…

Science and technology transcend industry boundaries, and so does demand for EAG’s expertise. We partner with companies across a broad spectrum of high-tech, high-impact and highly regulated industries. We help our customers innovate new and improved products, investigate manufacturing problems, perform advanced analyses to determine safety, efficacy and regulatory compliance, and protect their brands.

Our Company Culture

EAG’s corporate culture is firmly rooted in four guiding principles: “foster a growth mindset,” “find a better way,” “earn more loyal customers,” and “win…

EAG’s corporate culture is firmly rooted in four guiding principles: “foster a growth mindset,” “find a better way,” “earn more loyal customers,” and “win together.” Across all of our 20+ locations, you will find a true passion for science and the power of science to improve the world we live in. Hear what some of our ~1200 scientists, engineers and support personnel say about what it means to be part of EAG Laboratories.

Careers

EAG is growing, and we are always looking for talented, problem-solving oriented individuals to join our company. If you have a “we know how” spirit, we want to hear from you.…

EAG is growing, and we are always looking for talented, problem-solving oriented individuals to join our company. If you have a “we know how” spirit, we want to hear from you. Browse current openings now, and re-visit our careers page often.

How do you constantly innovate while driving down costs?

Measurement of Low Level Nitrogen in Silicon Carbide Using SIMS

WHITE PAPER

ABSTRACT

Today’s state of the art silicon carbide (SiC) growth can produce semi-insulating crystals with a background doping around 5×1015 atoms/cm3 or lower. It is essential to have an accurate tool with low enough detection limit to measure low level nitrogen concentration. Current SIMS detection limit of low E15 atoms/cm3 will provide accurate determination for nitrogen doping level of 5E16 at/cm3 or higher. In order to determine the lower nitrogen concentration, it is necessary to provide better detection limit and to remove the contribution of background nitrogen properly. The “raster changing” method provides an accurate way to determine and remove contribution of background nitrogen to the signal because secondary ion intensities and matrix ion intensities can be analyzed at same location of sample by changing primary beam raster size during a profile. We performed experiment using these techniques and were able to determine nitrogen concentration of 3.5E15 atoms/cm3 in silicon carbide with good precision.

INTRODUCTION

Due to its unique capabilities of high detection sensitivity for a variety of elements under depth profiling mode, Secondary Ion Mass Spectrometry (SIMS) is an essential tool for characterization of dopants and impurities in SiC material.

Nitrogen, which is a shallow donor in SiC, is always present as trace impurity in all SiC wafers and epi-layers. Depending on the design and its operation, a SiC growth system can contain significant amounts of nitrogen, which will lead to a fluctuating nitrogen residual doping in the grown material. A low and controlled nitrogen background is necessary for a reproducible growth of semi-insulating wafers and low doped epi-layers. SIMS feedback of nitrogen in these crystals can provide understanding of the compensation mechanism and process conditions.

For many years, SIMS has been used routinely to determine nitrogen concentration at level of E17 to E19 atoms/cm3 with good precision. Today’s state of the art SiC growth can produce semi-insulating crystals with a background doping around 5×1015 atoms/cm3 or lower. It requires SIMS to have better precision to measure low level nitrogen concentration.

With upgraded SIMS instrument (improved vacuum and better primary beam intensity) and improved analysis protocol, we can now achieve N detection limit of 2-5E15 atoms/cm3 routinely while maintain excellent depth resolution (Fig 1). While these detection limits are very good, they are not sufficient to provide a routine way for an accurate measurement of low level (<5e15 atoms/cm3) nitrogen concentration in silicon carbide. A simple background removal at these background level (2-5E15 atoms/cm3) can introduce large and un-defined error. An extremely low nitrogen background (6-8E14 atoms/cm3) is achievable, but is very time consuming and can not be guaranteed at all the times.

Figure 1 The N detection limit is 3E15 atoms/cm3. Slight amount of N contamination in Al doped layer.

To determine low nitrogen concentration with adequate precision, it requires [1] (a) better Signal-to-Noise ratio; (b) a proper way to subtract background contribution from the measured signal because background contribution can change over time, and can also vary from location to location in SIMS sample holder. To solve these issues, we applied SIMS “raster changing” technique on silicon carbide sample with low level of nitrogen concentration (<5e15 atoms/cm3) to determine the nitrogen concentration in the sample and to verify the precision of the results. The “raster changing” method provides an accurate way to determine and remove contribution of background nitrogen to the signal, because secondary ion intensities and matrix ion intensities can be analyzed at same location of sample by changing primary beam raster size during a profile [2]. The disadvantage of this technique is that it can be used only on uniformly doped sample or in the region of depth that concentration is uniform.

EXPERIMENTS

The experiments were performed on CAMECA IMS-4f double focusing magnetic sector instruments equipped with oxygen and/or Cs primary beam sources. The sample was sputtered by a focused Cs+ primary ion beam, which is rastered over a square area. Beam current used in the analysis are 200 to 300 nA. Secondary ions formed during the sputtering process are accelerated away from the sample surface by a sample voltage of – 4500 V. Secondary ions were energy separated by an Electrostatic Analyzer and mass separated based on their mass/charge ratio by a Magnetic Mass Analyzer. After passing through the analyzers, the ions are detected using either a Faraday cup (Matrix ions) or an Electron Multiplier (nitrogen ions). The SiC sample used in this study has low level of nitrogen uniform through out the sample.

RESULTS & DISCUSSION

First, the nitrogen concentration in the test sample was determined using traditional background subtraction method. With a brand new Cs source and a few days pumping with sample in UHV chamber, we were able to achieve nitrogen background of 5e14 atoms/cm3, determined from measurement of a piece of un-doped SiC epi sample that was loaded together with the test sample. We determined the nitrogen concentration in this test sample as 3.3E15 atoms/cm3. The precision of this value is ±14% (1σ) based on repeat measurements and sample and background.

With raster changing technique, the nitrogen concentration [N] in the SiC sample and corresponding contribution of nitrogen from instrument background [NB] can be calculated using [2],

[N] = RSF × (IN1-IN2)/(IM1-IM2)

[NB] = RSF × (IN/IM) – [N]

assuming the adsorption rate of nitrogen on sample surface is constant. Where RSF is Relative Sensitivity Factor determined from nitrogen implant standard in SiC ; IN1 and IN2 are nitrogen secondary ion intensities under two different raster sizes, and IM1 and IM2 are corresponding matrix secondary ion intensities under these two different raster sizes.

In this experiment, nitrogen concentration was determined from nitrogen (N+13C)- and matrix (Si)- secondary ion intensity at 125 μm x 125 μm raster and 50 μm x 50 μm raster (Fig. 2). Then we applied raster changing technique on this sample at different background level ranging from 1e15 atoms/cm3 to 5e15 atoms/cm3.

Figure 2 Raster change during N profile. The N shown is quantified at 50×50 μm raster.

Results of nitrogen concentration in the sample and background nitrogen levels are listed in the table below:

The average nitrogen concentration determined from three measurements is 3.5E15 atoms/cm3 with precision of ±9% (1σ ). The results show very good agreement with the data previously obtained with tremendous amount of more effort. Results also demonstrated that low level nitrogen can be measured with good precision, even at relatively high nitrogen background level, using raster changing technique.

CONCLUSION

We have demonstrated that SIMS raster changing technique can be used to determine low level nitrogen in silicon carbide sample with good precision. The measurement eliminated the problems associated with the traditional background subtraction method can be used at relatively higher nitrogen background conditions. But this technique is limited to bulk sample or thick layers (>2 μm).

ACKNOWLEDGEMENT

We would like to thank Okmetic AB, Sweden for providing samples used in this study.

 


REFERENCES

[1]       R.S. Hockett, et al., in High Purity Silicon, Vol. VI, ECS PV 2000-17, 2000, p584

[2]       A. Ishitani, et al., in Proceedings of the international Conference on Materials and Process Characterization for VLSI (ICMPC’88), 1988, p. 124.