Learn More About TEM

Learn More About TEM

Scientists report the size of a SARS-CoV-2 particle to be between 50-140 nm (https://www.news-medical.net/health/The-Size-of-SARS-CoV-2-Compared-to-Other-Things.aspx). 

New microprocessor technology in devices from companies like Apple, Intel, and AMD produces chips with features as small as 5-10 nm. Shale rock that is mined for petroleum and natural gas contains a pore structure that can be as small as 5 nm.  Wow- that’s very, very small!

Virologists, Electrical Engineers, Petroleum Engineers and Geologists; these are all very different professions.  The one thing they have in common is the need to study things that are extremely small, nano-sized particles and materials.  It’s hard to imagine because this is smaller than anything we can see with only our eyes. As a quick refresher, a nanometer (nm) is one-billionth of a meter.  For reference a single human hair is ~50,000 nanometers in diameter.  Scientists and engineers who need to study nano-sized particles or structures require a unique microscope called a Transmission Electron Microscope, or TEM for short.

Before we go any further, we should take a step back and discuss a few basics of microscopy.  When we look through the eyepiece of a microscope, the magnified image we see is created by a series of lenses, each behaving like a magnifying glass.  Various lenses give us higher and higher magnification.  How well that magnified image can be resolved is dependent on the wavelength of the source used.  In a standard light microscope, the wavelength of the light is about 500 nm.  Thus, we can resolve objects that are about 250 nm or more apart.  Anything smaller than this is too fuzzy, and the objects are blurred together.  Secondly, in a light microscope the light reflects from the sample and is projected to our eyes or perhaps to a detector that generates a digital image.

To see smaller objects with clarity we need to use a source with a wavelength less than that of visible light.  This is where electrons come in! The benefit of the electron source is that the wavelength of the electrons in the beam is only a few picometers, 1 picometer = 1000 nanometers. With the electron beam as the source of the object being viewed, it can be magnified even more and the details of a material or cell that are only 0.5 or 0.25 nanometer can be seen clearly.  

As the name indicates, in a TEM the electrons are transmitted through the sample.  Fundamentally, the TEM is analogous to a slide projector.  In a slide projector, a light bulb is used as the “source.”  The beam of light is collimated and passed through a photographic slide that is transparent. Then the beam is focused and projected onto a screen.  If you grew up in the 1970s this is how you captured all your family memories and replayed them.  In a TEM the electron source replaces the light bulb, the beam of electrons is focused with a series of lenses and passed through a very thin (100 nm or less) sample of the material being studied. The electrons change a little as they pass through the sample and thus when they are focused and projected onto a special screen, they produce a picture of the object.  Below is an example of a TEM image of carbon nanotubes.  In the image you can see the details of the sub-nanometer layers that make up multi-walled tubes!

Scientists at Cerium Laboratories use TEM daily to investigate a variety of samples for our customers.  We evaluate the internal structures of microprocessors that operate your cell phone, laptop and car.  We evaluate devices used for generating solar power.  We look at geological formations to help scientists better understand where natural gas and oil deposits are located.  

We analyze the finest details that are so minute but are so critical! We have a team with extensive experience in material characterization and research and development programs, including TEM but certainly not limited to it. If you’re ready to find out exactly what we can do for you, we want to hear from you!

6 Steps to Ensure Valid Metals Analysis

6 Steps to Ensure Valid Metals Analysis

Metal contamination in a semiconductor manufacturing environment can greatly reduce wafer yield or create long term product reliability issues.  For these reasons’ manufacturers are constantly monitoring their tools for low level metal contamination.  Vapor Phase Decomposition Inductively Coupled Plasma Mass Spectroscopy (VPD-ICPMS) is the preferred analytical technique to measure trace metals on silicon wafers.  VPD-ICPMS can measure levels of metals in the parts per billion and even parts per trillion range.  However, to do this the process requires class 1 cleanroom areas and strict protocols so the samples are not contaminated in the lab prior to analysis.

Appropriate handling prior to submitting the wafers to the lab is also very critical. Below are 6 very important rules to follow to prevent cross-contamination from sources such as an unfiltered environment or human contact.

  1. Always handle wafers with vacuum wands, never with hands (gloved or not) and on the opposite side of the wafer from which you want analyzed. Touching the wafer with a gloved hand can deposit calcium and zinc on the surface.
  2. Open wafer boxes and perform all wafer movements in a cleanroom or at least in a laminar flow hood.
  3. Ship wafers in a cleaned wafer box (cassette, FOUP (Front Opening Unified Pod or Front Opening Universal Pod) or FOSB (Front Opening Shipping Box)). In our experience analyzing 1000s of wafers, single wafer carriers (aka pucks or clamshells) are dirty and result in an increased level of metals on the wafer.
  4. Place wafers in the cassette with the side to be analyzed facing up. Automated wafer preparation tools are designed to run the top surface so there is no extra handling required.
  5. After wafers are loaded in the wafer cassette, tape the cassette closed to prevent accidental opening and contamination from the outside air. Outside air can contain significant amounts of aluminum, calcium and other elements that can deposit on unprotected wafers.
  6. Double bag the cassette with plastic and seal before placing in a box for shipping.

Improper wafer handling can lead to confusing and inaccurate data.  We take extreme measures to ensure our processes are clean. For the best results, however, the process starts at the customer site.  Following these simple steps will ensure your samples are not contaminated by secondary sources.

VPD-ICPMS vs TXRF

VPD-ICPMS vs TXRF

There is a bit of a battle in the analytical arena when it comes to the best method for measuring trace contaminants on the surface of a silicon wafer.  We described the analysis of trace metals on silicon wafers by Vapor Phase Decomposition – Inductively Coupled Plasma Mass Spectroscopy (VPD-ICPMS) in a previous blog post.  TXRF or Total Reflection X-Ray Fluorescence is another technique that is often used in semiconductor manufacturing to monitor contamination.  Where VPD-ICPMS collects the contaminants in a droplet that is then analyzed by mass spectroscopy, the TXRF instrument uses an x-ray beam to excite the wafer surface.   Elements fluoresce after being excited, the fluorescence is then measured to determine what elements are present and in what amounts.  There is considerable overlap between the two techniques, but each has its own unique features.

VPD-ICPMS on one hand is a very well-defined process and provides analysis of the top surface of the wafer, about 20 Angstroms.  Whereas TXRF is more versatile and can be used on different wafer surfaces.  Below is a comparison of the two techniques.

VPD-ICPMS TXRF
Contaminants from the entire wafer surface are collected and analyzed. Only the area excited by the X-Ray beam (~2cm spot) is analyzed.  To do the entire wafer multiple spots are required e.g., a 300 mm wafer will need 350 spot analyses to cover the full surface of the wafer.
Results are cumulative for the wafer surface, no spatial information is available. TXRF can produce maps showing the impurity distribution on the wafer surface.
10-100X greater sensitivity.
Detects light elements like Li, Na and Mg where TXRF cannot. Detects non-metals like Cl, and Ar where VPD-ICPMS cannot.
Considered destructive analysis Non-destructive analysis.
Wafer can only be analyzed 1x. Wafer can be reanalyzed as needed.
Analyzes ~20 Angstroms or thickness of oxide film. X-Ray beam penetrates ~ 500 Angstroms.
Can only analyze bare Si or Si with SiO2 films. Will analyze oxide and any amorphous or crystalline film beneath it.

VPD-ICPMS and TXRF use very different methods to analyze for contamination on wafer surfaces.  These different mechanisms however provide certain benefits for each.  In fact, chemists and engineers realized the advantages and now many semiconductor fabrication facilities use an integrated VPD-TXRF system to monitor contamination.

Frequently Asked Questions Regarding Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy

Frequently Asked Questions Regarding Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy

You’re an expert in your industry, but not the specifics and niche fields of all the science related to it. Nowhere is this more evident than when it comes to Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy. If you’ve been wanting to learn a little more about it, Cerium Labs can answer all your questions! Not only can we tell you all about it, but we can also perform it for you too. Before we get more into exactly what services we can do for you, let’s go over all the details and answer the specific questions you have relating to Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy. 

What does VPD-ICPMS stand for?

In the industry, Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy is abbreviated to VPD-ICPMS. 

How do you prepare to begin the process?

It all starts with the vapor phase decomposition sample preparation technique. During this process, trace elements on the surface of a silicon wafer are collected into a liquid sample to be analyzed by HR-ICP-MS. The silicon wafer is exposed to hydrofluoric acid vapor in a sealed chilling chamber. The hydrofluoric acid vapor forms a condensate on the chilled wafer surface. 

What is the size of the silicon wafer?

The silicon wafer can be 150, 200, or 300 mm. 

Why are you looking for the condensate?

This condensate etches the oxide layer off of the wafer surface along with any trace metals that are present. These trace metals are exactly what we’re looking for, because they hold the answers to the questions you are asking. The condensate is then collected by rolling a drop of scan solution across the surface of the wafer. 

What scan solution do you use?

The scan solution is almost always a dilute mixture of hydrogen peroxide, nitric acid, and hydrofluoric acid. The drop is transferred from the wafer surface into a clean sample vial. 

What is this method capable of measuring?

The liquid sample is analyzed for trace metals using HR-ICP-MS. The VPD technique is capable of measuring metallic contaminants at concentrations ranging from 1E6 to 1E14 atoms/cm2. 

What elements are measured?

This is particularly useful in measuring light elements on bare silicon or in hydrofluoric acid soluble thin films. The most popular light elements that can be measured this way include lithium, beryllium, boron, sodium, magnesium, and aluminum.

What instrument is used?

Cerium Labs has the instruments, knowledge, and industry experts to do this job the right way. The specific instrument we use is a gemetec automated VPD prep tool. This is a special production tool for online monitoring of metal contamination on semiconductor wafers with ultra-low detection limits.

You can trust our processes, which means you can trust our results too. Do you have any further questions? Reach out to us today to learn more about what our scientists can do for you! Call us at (866) 770-7752 or email sales@ceriumlabs.com to get started.

Understanding Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy

Understanding Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy

In the industry, Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy is abbreviated to VPD-ICPMS. If you’ve been wanting to learn a little more about it, Cerium Labs is happy to help! Not only can we tell you all about Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy but we can also perform the service for companies who need it professionally done as well. Before we get more into exactly what we can do for you, let’s go over the details of Vapor Phase Decomposition Inductively Coupled Mass Spectroscopy more specifically. 

It all starts with the vapor phase decomposition sample preparation technique. During this process, trace elements on the surface of a silicon wafer are collected into a liquid sample to be analyzed by HR-ICP-MS. The silicon wafer, which can be 150, 200, or 300 mm, is exposed to hydrofluoric acid vapor in a sealed chilling chamber. The hydrofluoric acid vapor forms a condensate on the chilled wafer surface. This condensate etches the oxide layer off of the wafer surface along with any trace metals that are present. These trace metals are exactly what we’re looking for, because they hold the answers to the questions you are asking.

After this step, the condensate is then collected by rolling a drop of scan solution across the surface of the wafer. The scan solution is almost always a dilute mixture of hydrogen peroxide, nitric acid, and hydrofluoric acid. It’s just a tiny drop, so don’t worry! The drop is transferred from the wafer surface into a clean sample vial. 

Lastly, the liquid sample is then analyzed for trace metals using HR-ICP-MS. The VPD technique is capable of measuring metallic contaminants at concentrations ranging from 1E6 to 1E14 atoms/cm2. It is particularly useful in measuring light elements on bare silicon or in hydrofluoric acid soluble thin films. The most popular light elements that can be measured this way include lithium, beryllium, boron, sodium, magnesium, and aluminum.

Even if you wanted to, this isn’t something you can do on your own. If nothing else, you probably don’t have a gemetec automated VPD prep tool needed to perform the procedure! That’s okay, because Cerium Labs has the instruments, knowledge, and industry experts to do this job the right way. You can trust our processes, which means you can trust our results too. 

We offer an extensive array of material analysis techniques including surface science, trace metal testing, electron imaging, mass spectroscopy, as well as chemical analysis. Our team solves problems for some of the world’s leading companies, including semiconductors, pharmaceuticals, medical devices, alternative energy manufacturers, and many more. Do you think we can help you? We do too! Reach out to us today to learn more about what our scientists can do for you! Call us at (866) 770-7752 or email sales@ceriumlabs.com to get started.

What’s in the water – analytical chemistry helps everyone

What’s in the water – analytical chemistry helps everyone

Analytical chemistry of water

What do you think of when you hear the term “Inductively Coupled Plasma Mass Spectroscopy”?  A CSI episode? College Chemistry? Or maybe nothing at all? Most likely you are not familiar with Inductively Coupled Plasma Mass Spectroscopy or ICPMS for short.  But one type of analysis performed with ICPMS is highly relevant to our health and safety and that is the analysis of metals in water.

While you may not have heard of ICPMS, you probably have heard of lead, the soft, malleable silvery gray metal.  Lead poisoning has been documented for centuries but not until the early 1970’s did the US government start to regulate lead to reduce its effect on the environment and wildlife.  In the last few decades regulations for cleaner gasoline, use of lead-free plumbing and paints and many other products have greatly reduced the problem, but not completely. This is because in many cases, old infrastructure is still in use, older buildings are being gentrified and antique items with the original lead-based paints are now chic. These are just some of the ways lead could be ingested or leak into the water supply.

Science tells us that even low-level lead exposure can cause neurological and cardiovascular disease, infertility, and decreased kidney function. Higher than healthy amounts of lead have been linked to learning and behavioral problems, lower IQ, and other health issues in young children. These adverse health effects can last a lifetime! This is why health experts agree that any level of lead in one’s blood, no matter how small, is cause for concern. This is where Inductively Coupled Plasma Mass Spectroscopy can help. ICPMS can measure lead at extremely low levels in water, soil, or other materials like paint.

The ICPMS technique can measure a long list of metallic contaminants in the part per trillion concentration range.  To visualize how minute this is, think of 1 drop of water in 10,000,000 gallons of water!  An Olympic size swimming pool holds 660,000 gallons of water so 1 part per trillion is 1 drop in about 15 full Olympic size pools.  Furthermore, some elements, Pb included, can be measured in the parts per quadrillion range!

You cannot taste, see, or smell low levels lead in the water, which makes it pretty scary.  But knowing that scientists have a method of “seeing” it should make us all feel a little safer.  With the help of a professional lab you can be sure your house, soil, child’s toy or grandma’s antique armoire are not sources of lead in your home.  Inductively Coupled Plasma Mass Spectroscopy is actually highly relevant to protecting ourselves and our children’s health!