Yi, Tell us a little bit about yourself.

I was born and raised in Beijing and attended graduate school in the US at Stony Brook University in Long Island, New York. At Stony Brook, I earned my Ph.D. in physical chemistry. My research was focused on mass spectrometry, instrumentation, and atmospheric new particle formation. I really enjoyed mass spectrometry and instrumentation in general. That’s why when I was looking for a job, I specifically searched for those keywords, and that’s how I found Nova on LinkedIn. I then joined Nova in March 2021. 

What was the subject area of your first and second degrees?

I studied chemistry in college and completed my master’s at the same university in Beijing. After that, I went to the US to complete my Ph.D. 

What made you decide to move to a new country to study?

My parents encouraged me to consider studying abroad, as they didn’t have this opportunity themselves.
I was a little bit hesitant to go abroad after finishing my master’s, but they really encouraged me to. And to be honest, I miss them a lot.

Tell us a little about your experience moving to a new country and studying in a different language and culture.

Moving to the USA was a big change in my life. This was not only my first time in the USA but actually my first time abroad.
I learned a lot during this journey. I had the privilege to work on my Ph.D. in a very friendly environment. The lab team, the group I joined, and my advisor were all very welcoming. In our small research group, I was the only foreign student. All of my group members were US natives, including our host, my advisor, and my fellow students. We are still in touch to this day.

My advisor, particularly, is a good friend and someone I respect greatly. He was very helpful and shared all his knowledge to support me during my PhD studies. He encouraged me to write papers and take on professional speaking engagements. This helped me build my confidence, and eventually, I became the first Ph.D. to graduate from our group.
This positive experience is what led to me joining Nova. 

What made you go into the field of chemistry?

I think I am an observant person. I tend to notice those little changes in my environment and all the details. In addition, I like doing experiments. I liked chemistry already in high school. But to be honest, before college, I was debating between chemistry and literature.
So I chose English as my double major in college. And then, I went on to earn my M.S. in chemistry.

Now that you’ve been at Nova for a year and a half, what is it that makes you choose Nova every day?

I studied mass spectrometry in graduate school and really liked it. I would like to work on mass spectrometers in my career. I choose Nova because I learn new things every day and contribute with my experience and knowledge.

Where do you see yourself in the future?

As you know, the semiconductor industry requires a lot of knowledge, skill, and experience, and I am young and still do not have much experience. In the future, my goal is one day to become an expert in the mass spectrometry instrument field. 

You just recently moved to another position. What are you going to do now?

Previously I was a tech support engineer, mainly providing support wherever I was needed. In my new position, I work as a systems engineer. In this position, I define how some functions should be performed and assure the quality of each function along the way. 

What kind of welcome did you receive at Nova when you joined?

The second most important reason I enjoy working every day is my colleagues. The team I’m working with are people I respect very much due to their kindness and hard work. They are incredibly friendly. These people have several decades of experience in this field and are willing to share their knowledge and support me in my everyday work. 

If you had to choose one thing that characterizes you most- what would it be?

Persistence.
I always feel like I just need to keep going. Especially since completing my Ph.D., I have a deeper understanding of this because sometimes you must face and resolve the problem yourself. And you simply have to be persistent enough to solve it.

Abstract

In the semiconductor industry, ion implantation process has expanded to a wide range of applications with doses and energies spanning several orders of magnitude.
Ion implantation is a very complicated process with many parameters and factors that affect the implant profile.
For example, shadowing effects from higher aspect ratio of photoresist opening, ion channeling or de-channeling effects due to implant angle variations, and dose and implant energy accuracies are all important factors in achieving uniform device performance and good product
yield. In addition, current process controls are done on test wafers with certain time intervals, where broken sample pieces are sent outside of the fab for SIMS analysis.

The turnaround time is generally long, and the results often do not reflect the actual production conditions. It is known in some cases that, while the control charts are in good standing, the product has failed to meet its specification.
The demand for consistent implantation material is becoming more and more important. Hence, the desire for better implant process control is sorely needed.

This article explores how utilizing Secondary Ion Mass Spectroscopy, (SIMS) in-line to measure peak concentration, peak depth, and dose simultaneously to provide better implant process control.

Background and Introduction

The implantation of ions, mainly Boron, Phosphorous, and Arsenic, have a long history of use in semiconductor manufacturing. By implanting ionized atoms into a semiconductor material n-wells or p-wells can be created, changing the conductivity of the material, a technique that is often used to control threshold voltages of MOSFET devices. The creation of p-n junctions via ion implantation can prevent current flow to the substrate. Alternatively, ion implantation can create contacts to lower contact resistance and prevent diode formation. In the semiconductor industry, ion implantation process has expanded to a wide range of applications, as shown in Figure 1, with doses and energies spanning several orders of magnitude. Depending on the device, a large number of implant operations may be required in the manufacturing process flow.

Figure 1. Ion implantation applications in silicon technology at various doses and implant energies1

After implantation, the concentration distribution of the implanted ions within the material will resemble a Pearson IV distribution, with the peak depth being controlled by the implantation energy and the concentration being controlled by the implantation dose. Due to the Pearson IV distribution of the implanted ions, the only metrology method capable of measuring the peak concentration, peak depth, and dose simultaneously is Secondary Ion Mass Spectroscopy, or SIMS. By sputtering down through a material, a depth profile of the implanted atoms can be measured, giving a complete look of the shape, amplitude, and depth of the implanted ion distribution.

Figure 2 shows the distribution of implanted Boron in Silicon using a TRIM/SRIM Monte Carlo simulation.

Figure 2. Using TRIM/SRIM, (a) Monte Carlo simulation of ion implantation, and (b) Distribution of implanted Boron atoms in Silicon.

Ion Implant Metrology Challenges

Ion implantation is a very complicated process with many parameters and factors that affect the implant profile. For example, shadowing effects from higher aspect ratio of photoresist opening, ion channeling or de-channeling effects
due to implant angle variations, and dose and implant energy accuracies are all important factors in achieving uniform device performance and good product yield. In addition,current process controls are done on test wafers with certain
time intervals, where broken sample pieces are sent outside of the fab for SIMS analysis. The turnaround time is generally long, and the results often do not reflect the actual production conditions. It is known in some cases that, while the control charts are in good standing, the product has failed to meet its specification. The demand for consistent implantation material is becoming more and more important. Hence, the desire for better implant process control is sorely needed.

Metrion®

Nova’s Metrion® is a 300mm wafer-level in-line SIMS metrology system developed to seamlessly integrate with an automated high-volume manufacturing (HVM) fab environment.
It is a fully automated recipe driven metrology tool utilizing a Magnetic Sector mass analyzer to provide high quality dynamic SIMS depth profiles. It has an O2 ion source that ranges from low to medium high in beam energy for a variety of applications. Because Metrion® utilizes a low voltage secondary ion extraction field, it enables stable and repeatable measurements within a 50um x 50um metrology pad on product wafers. With multiple parallel detectors, Metrion® can measure multiple species simultaneously through the entire film stack, providing high data density capable of achieving higher depth resolution.
Process automation with built-in film analysis and recipe management make the system easy to use and shorten the time to data.

B-implant Application

Boron is one of the most commonly implanted species in semiconductors. It has one fewer valence electron than Silicon, which upon implant, results in a p-type semiconductor. As shown in Fig 1, Boron implant is used in a wide range of applications, in all types of devices in both logic and memory space.

Figure 3. Metrion® vs Lab SIMS results for 1e+15 Dose B Implant in Si wafers with Implant Energies of 5, 10, 20, and 30keV.

Figure 3 compares various B-implant SIMS profiles between Metrion® and lab equipment. As can be seen, the Boron concentration vs depth profiles from Metrion® matches very well with results from lab SIMS. With a full wafer measurement capability, wafer maps can easily be generated from measurements of multiple locations on the wafers, enabling within wafer uniformity process control charts.
Figure 4 shows a wafer map example of the Boron peak concentration variation across the wafer, for the 10keV implanted B sample.

Figure 4. Wafer map of B peak concentration, 10keV Implant

As a HVM metrology tool, precision of the measurement is an important metric. In Figure 5, five profiles, which were measured at locations adjacent to each other as proxy for repeatability testing, are overlayed. As can be seen, all the profiles match very well with each other, demonstrating the stability of Metrion® SIMS measurements. For most implant dopants, a relative standard deviation (RSD) of <2% can typically be achieved.

Figure 5. Overlayed of 5x repeat B-implant profiles

Summary

Nova’s Metrion® system is an innovative SIMS platform designed for the Fab environment, seamlessly integrating into an automated factory workflow. The system is engineered to deliver wafer-based high precision metrology results for process control in logic and memory devices, as demonstrated on ion implant applications. This is enabling Statistical Process Control (SPC) of the ion implant process parameters and providing in-line data correlating to electrical performance.

Authors: Benjamin Hickey, Wei Ti Li, Sarah Okada, Lawrence Rooney, Feng Zhang

First published at SIMS 23

Hi, Shira. Let’s start by sharing a little bit about yourself.

I’m 23 years old, married, and have a toddler son named Uriel. I’ve been working in high-tech for three years now.

I studied program engineering for two years in a seminar called “Elisheva Girls” in Jerusalem.

In my previous position, I worked as a developer. Here at Nova, I transferred to automation development, and I’ve been here since December 2021. I am an Orthodox Jew and live in a warm community of like-minded people in Rehovot.

So, what are the differences between development and automation development?

Standard development involves coding the products sold by the company. However, automation development concentrates on developing the tools or assisting programs that support the product development process.
Those tools help the developer check the code’s correctness and ensure the product is functional in all its developed versions.
We, the automation developers, are running a massive number of tests, allowing us to test our product every day, according to the updated version.

What made you decide to work at Nova?

Before coming to Nova, I worked in Tel Aviv at a company that creates personalized projects for its clients. Despite the interest and the challenge, I wanted to join a more global and stable company that would encourage personal growth. During my first interview with Nova, I was pleasantly surprised to hear, “In two years, if you’d like to change your position or evolve into a new place or study a different technology, we love that, and we are open to it.” That was one of the things that drew me in. The opportunity for personal and professional development, and of course, the fact that it is a large stable company, gave me a feeling of safety. I live in Rehovot, and Nova is also very close to home for me, especially considering that there aren’t many opportunities south of Tel Aviv.

As an Orthodox religious woman, what were the things that supported your integration process?

First of all, my colleagues’ respectful behavior was helpful. In my opinion, this comes from the top down, beginning with the management. Everyone here is encouraged to show ultimate respect and support each other’s personal and professional self-actualization.
From an aesthetic point of view, the offices are gorgeous, which has been a huge benefit for me. It’s fun to work in a beautiful environment.
And there is also my personal point of view, as an Ultra-Orthodox Jewish woman: this was part of the discussion from the start, already in the first interview. They asked me to state my needs and requirements and adjusted themselves accordingly. This was astonishing and exceeded the standards of any other company I worked for. My team manager always suggests arranging one-on-one meetings with an open door, and everyone shows respect, sensitivity, and consideration of my values and religious needs.

In my opinion, everything is well-balanced here. My values and religion take priority, and Nova ultimately respects this and supports me. I asked to be seated in a certain location, and they approved it. In addition, as a new mother, I asked to leave an hour earlier every day, and it was also approved. I feel respected and appreciated, so it is very satisfying.

How is your unique background expressed in the professional aspect?

In the professional aspect, I believe I’m not different in any way from anyone. I am doing my best to be professional, just like any other team member. Thanks to the sensitivity and care for my needs, I give 100% of myself at work with the maximum professionalism, dignity, and respect to the place that treats me in such a way.

If you’d advise your friends, colleagues, or other people to join the Nova team, what would you tell them? 

First of all, I’d tell them I work here, so that’s an excellent reason for them to join (laughing). Jokes aside, I’d say to them that working at Nova gives you a sense of joy and positivity at work–which is essential, as we all know. And despite the stress and deadlines, the employee always comes first–their needs are the first priority. In my perspective, this is a distinguishing value and has led to my acceptance in the workplace.
In addition, I’d tell them about the remarkable technologies and the high level of business and tech expertise. 

What are the challenges that Orthodox women are dealing with in a technological work environment? And how is it possible to deal with such challenges?

The Orthodox woman is very modest and needs to be able to set her limits when sharing a workspace with men. Communication with men at work should be mostly business related, respectful, and clear of personal talk. An Orthodox woman wouldn’t sit in a closed room with men, but here at Nova, everything is open space, so this matter isn’t an issue.
In Orthodox houses with multiple kids, there needs to be a flexible work schedule. This, too, is addressed here because at Nova, the work is hybrid and allows flexibility in the working hours, too.

In the community you’re coming from, are there some cases where you feel judged about the fact that you’re an Orthodox woman who works in the technology industry?

In my own community, as well as among the general population, the fact that I am a working Orthodox woman is completely natural. It has been quite a common phenomenon for young Orthodox girls and women to study technology and integrate in the biggest technology companies. I have friends who work at Google, Microsoft, and more. Even though in the past it was considered deviant, nowadays, it is natural and acceptable.

What do you think is the key to this massive successful integration of Orthodox women in technology work environments?

I think that what makes it possible is the will and need of Orthodox women for professional development and self-realization, along with being able to contribute financially. Also, a certain open-mindedness has been developed both within religious institutions and high-tech companies themselves. It creates opportunities to integrate different communities that were not previously included in high-tech companies.

Amazing! How do you see the future of Orthodox women in the technology market and other markets?

I believe that the future is already here. All my female colleagues from my studies are working in great companies these days, and this phenomenon is only widening and evolving. My assessment is that this will continue to trend in that same direction, and Orthodox women will be promoted to senior and key positions. They have all the qualifications and skills for that to happen.

Last question, if you’ll allow it: Would you wish for your children to also follow your same path?

Certainly. I will encourage them to do so, to take their talents and desires and invest in them. I won’t promote high-tech if it doesn’t interest them, but I’ll absolutely encourage them to pursue the professional paths they’re passionate about. However, I would be pleased if they chose high-tech because it is my domain and I love it very much.

I am 32 years old and from Ramat Gan. I recently got married in a beautiful celebration with friends and family. I have a BSc in electrical and electronics engineering from Tel Aviv University, and I am almost finished with my master’s degree. I also love sports, and exercising helps me balance my type 1 diabetes.

I have been working at Nova for about five and a half years and currently, work as a system engineering team lead as part of the Elipson project. I started at Nova in 2017 as a student in the CTO team during the first stages of the project. At the time, we could only imagine that it was possible to make RAMAN technology commercially viable–one that could work outside of the lab and create exceptional value and benefits for our customers.

What exactly do you do as part of your job?

I manage a team of system engineers, and we are expected to be experts on the Nova Elipson system. We are responsible for developing new features for the system, improving its stability, making sure it works well according to customer’s requirements and solving the challenges that the service team brings to our table. In addition, we support all the other entities that work on the product, hardware, optics, and software, as well as the service people and product managers.

When additional customer needs arise, we come up with concepts for solutions, prepare and perform feasibility analyses for them, and eventually create requirements documentation for the hardware or software teams, defining what they need to develop.

How do you manage to maintain the level of enthusiasm after being here for five and a half years?

Simply put, my work keeps me engaged and interested. Over the years, everything here has been very dynamic. The project matured and moved departments, and I matured and moved with it and eventually got promoted. This type of environment suits my personality and character. I like change, and things here change all the time—the perfect fit for me.

When I started working at Nova as a bachelor’s student in electrical engineering, I worked in the CTO team on the Nova Elipson project. It actually started as a prototype, and then we progressed to the alpha and beta stages, eventually producing it as a live commercial product.

Today we are already at an advanced stage, and the production and service teams are operating more or less independently. So, the challenges I face are constantly changing, creating the dynamic environment I enjoy.

You mentioned sports earlier. You have another line of work that is related to this, right?

That is true! Before I started working at Nova,  between my military service and college, I was looking for a job, and my girlfriend (now my wife) suggested that I sign up for a basketball refereeing course. I liked the idea, but then I realized that I was more interested in soccer refereeing because it’s a sport that I live and breathe and am incredibly enthusiastic about. I completed a course, and at the beginning of my soccer-referring journey, I refereed games for young children aged 10-12. I gradually progressed to my position today as an assistant referee in the Israeli Premier League and a FIFA international assistant referee in Europe.

Since I have had diabetes since childhood, regular physical activity helps me balance my sugar levels. At every game, I have candies in my pocket in case my blood sugar levels drop.

And what are your goals for the future in this field?

I aspire to reach the top, as I’ve always aspired to reach the highest level in everything I do.

My ambition is to continue improving and working as a referee in the leading games in the Israeli Premier League and advance as far as possible in Europe.

Amazing! Do you see yourself at some point working only in this field?

No! I really enjoy this combination of the two worlds together, which are the two worlds I really like. I think the variety helps me succeed in both of them separately. Being a football referee and working as an engineer at Nova reinforce each other. At the most basic level, when I have a bad day, either at work at Nova or refereeing a bad game, I tell myself that I have the other job to cheer me up. That reminds me everything will be fine.

Being a referee also keeps me fit, which contributes to my health. On the other hand, working at Nova helps to keep my mind sharp. It allows me to constantly learn new things and evolve as a professional in the field of science, engineering, and technology, so it also keeps both my mind and body sharp.

How do you deal with having to travel a lot?

Both of my careers require travel, and this year was a little complex as I needed to travel quite a bit for Nova and for soccer.

On one occasion, I had a series of three flights to games in Europe, and then I flew to the USA on behalf of Nova. After that, I only wanted a little time to rest without traveling. But in the end, it’s an interesting experience. I get to experience new places and meet interesting people, so it is for the best. At Nova, they support my second career, so I’m able to combine both my passions.

How do your friends react to you being a soccer referee?

Everyone is very supportive and encouraging, and I really appreciate it.

Occasionally people recognize me from the stands or I get a close-up on TV during games, and then I immediately receive lots of supportive calls and messages. It’s funny because, in practice, I’m not part of the game–in my opinion, I’m a function of the game. My goal is to keep the game fair, honest, and professional.

 

 

Performing these measurements in the semiconductor fab, rather than in a cost-and-time intensive laboratory setting, provides faster results, which reduces scrap and improves yield.

First, what is the Nova Metrion®? 

The Metrion® is a SIMS tool. SIMS stands for Secondary Ion Mass Spectrometry, a technique widely used in the semiconductor industry to study material composition and depth profiling of semiconductor wafers at the atomic level. To accomplish this feat Metrion determines the concentration of various chemical species vs. distance from the surface of an IC wafer film by sputtering the surface of the wafer, capturing and analyzing the secondary ions.

Conventionally, SIMS equipment has only been available in metrology laboratories that specialize in measuring and characterizing semiconductor devices. In keeping with Nova’s ‘lab to fab’ philosophy, the Nova Metrion® has been intentionally designed to be used in-line in high-volume manufacturing (HVM).

Let’s examine the Metrion SIMS process in more detail.

Metrion SIMS uses an oxygen primary ion beam to sputter a small area on the surface of a silicon wafer. As this primary ion beam sputters through the material on the wafer film, secondary ions are ejected from the surface and are collected and analyzed by a mass spectrometer, which sorts the ions based on tiny differences in their weight.  The Metrion’s mass spectrometer utilizes multiple detectors to sort the ions, and the raw data is displayed in a compositional profile showing counts of the secondary ions versus the time frame in which they are detected.  Using film analysis software that is built into the Metrion process recipes, the data is quantified, converting counts into concentration and collection time into depth for each measured species.

Another key feature of Metrion is the ability to create maps of entire 300mm wafers with as few as 5 measurement points.   These wafer contour maps provide a useful visual representation of within-wafer and wafer-to-wafer uniformity differences.

The numerical data from Metrion is collected and automatically uploaded to the factory host computer where it can be used by fab technical personnel to tune their semiconductor manufacturing processes through a complex mathematical technique called Statistical Process Control. This technique can generate insights that allow users to optimize costs, time, and product yield. By using Metrion as a prevention-based real-time quality control measure, fab personnel can detect trends or changes in their manufacturing process before these result in non-conforming products or scrap. 

Why is semiconductor material composition so important?

As the requirements for modern electronic equipment become more complex, semiconductor chips and therefore the films built onto silicon wafers must become more complex as well. Two important types of semiconductors that vary significantly in composition and structure are logic semiconductors (used in data processing) and memory semiconductors (used in data storage). SIMS measurements performed by Metrion can help identify problems with both logic and memory production processes.

Let’s review how Metrion treats both logic and memory structures built onto wafers.

Logic structures for data processing are challenging to implement on silicon. In particular, the uniformity of the SiGe epitaxial layer is critical (epitaxy is the deposition of a thin layer of single-crystal material, in this case, a compound of silicon and germanium onto the surface of a silicon wafer). Besides SiGe epitaxy and residue control, other semiconductor composition priorities for logic chips include the precise control of dopant concentration, reactor matching, and process excursion prevention.

Semiconductor memory structures have generated significant manufacturer interest to control contamination and identify unwanted chemical residues that could reduce yield. Here, the power of SIMS to detect contamination throughout the entire device, and not just at the surface, is key. Other important SIMS functions include semiconductor material composition and thickness measurements, to improve device function.

By looking at potential diffusion, Metrion users can anticipate problems with barrier layers and source/ drain function. The deposition uniformity within wafers and from wafer to wafer is also important because this affects downstream fabrication processes. Insights in these areas provided by SIMS help to improve device performance, reduce scrap, and increase yield.

These are the main advantages of SIMS, which is used widely in metrology labs.   However, lab SIMS turnaround time is too long, meaning that the data coming from the lab SIMS measurements takes too long to translate into manufacturing process control improvements, which puts many wafers at risk. Let’s look at this in more detail.

For a lab SIMS service provider, turnaround on wafer measurements can take up to two weeks.  For an in-house metrology lab at a semiconductor production facility turnaround could be as short as one day, depending on the number of samples to be measured.  However, time-to-results at such a producer lab could suffer if the production team required a quick result. Also, if the producer lab tool goes down, SIMS results could take months to obtain. One solution is to integrate a SIMS tool such as Metrion directly into the semiconductor production line, something it would be impossible to do with a lab tool. 

What is the value of inline SIMS?

Laboratory SIMS systems only measure coupons, not full wafers.   Wafers must be broken into coupons resulting in scrap.  A single point is measured on each coupon.  A SIMS expert is required to manually set up each measurement and to analyze the data point by point. This whole process can take days (or weeks as just discussed).

Nova Metrion®, on the other hand, measures whole wafers and is fully automated.  Metrion fits seamlessly into the production line,  accepting wafers from the fab’s automated transport system, loading them into the Metrion measurement chamber, measuring the wafers, providing full profile data and wafer mapping, and automatically uploading the data to the factory host.  All this can be done within minutes. The real advantage of an inline Metrion SIMS system, then, is that the shorter time to data results in tighter process control and improved yield.

Figure 2 illustrates this point. In a fab with 50,000 wafer starts per month, and a turnaround time for SIMS data of 2 hours, less than 200 valuable wafers will be placed at risk. But if it takes 24 hours to get the SIMS data back from a lab, the number of wafers at risk increases dramatically to 1600. The key point here is that the faster the time to obtain results with Metrion SIMS the more wafers are saved and therefore more money is saved by improving yield.

Figure 1: Wafers at Risk by Hour for 50K Wafer Starts per Month (WSPM)

Not all the wafers have to be scrapped, so let’s imagine a scenario where there is a 3% yield loss due to some problem in the manufacturing process and, further, that this problem is identified by SIMS.

How much would a 3% increase in yield save a fab in one day?  Would it save the fab $500, $5,000 or $50,000? (our assumptions are that the fab has 50,000 wafer starts per month and the cost per wafer is $1,000) The answer is that a 3% yield increase could save a fab $7,500 in a single day, a significant amount.

Now let’s imagine that a catastrophic event occurs where all of the wafers at a certain process step are lost, or if  50% of the wafers in a deposition step are lost. That’s going to have a huge financial impact.  

Why can’t these savings be achieved by inline metrology today?

There are in-line solutions available, such as LEXES (Low energy Electron Induced X-ray Emission Spectrometry), Ellipsometry, 4-point probe, and XRD (X-Ray Defraction).  But these techniques have to be correlated. In other words, no single metrology option exists that will provide a comprehensive picture of what is happening on the wafer.

Nova Metrion® can replace these in-line metrology options because it performs direct measurements of material composition through the entire wafer stack.  Metrion also produces full wafer maps of thickness and uniformity based on several points across a wafer. Additionally, the data is automatically uploaded to the factory host for statistical process control.  

What makes Nova Metrion® unique?

The Nova Metrion® includes several key features that make it well-suited for high-volume manufacturing.   For example, Metrion uses an oxygen ion beam, which is fast, contamination-free, and safe for use in production.

Metrion uses multiple ion detectors, which enable multiple chemical species to be measured simultaneously. It also delivers superior depth resolution and higher data density.

Additionally, Metrion utilizes multiple modes of operation to detect a broad range of species through complex stacks, including dielectric layers.

To reduce the impacted measurement area on a wafer, Metrion utilizes a small, die-sparing raster zone, enabling SIMS measurements on product wafers without damaging valuable dies.

Lastly, the Metrion is fully automated. Offering much more than automated wafer handling Metrion has built-in film analysis recipes, recipe management, factory host communication, and compatibility with automated wafer transport.

Why is contamination from SIMS a concern?

The ultimate goal for Metrion is to measure product wafers and then feed those same wafers back into the production process, without impacting yield.

A contamination study using a Nova VeraFlex® XPS system was recently completed. The goal was to determine if Germanium ions redeposit on the surface of a wafer as a result of a SIMS measurement.

While the XPS system did pick up Germanium in the sidewall of the crater produced on the wafer surface by the SIMS primary ion beam (which is what we would expect because we’re exposing some of the SiGe layer on the edges of the crater), there was no Germanium detected in any of the other locations, including the crater center.

The conclusion from this test was that no Germanium ions were redeposited on the wafer surface during the SIMS measurement. Therefore, the Metrion did not cause any contamination and should be considered safe to use on product wafers.

What is the meaning of full automation?

Full automation means more than just wafer handling with an EFEM (Equipment Front End Module) transfer system. It includes pattern recognition to locate a specific measurement area on a pattern wafer,  wafer transport, tool recipe management, and factory host communication for statistical process control.  These built-in standard features enable Metrion to be used by a trained operator, rather than an experienced SIMS scientist in a laboratory setting running the film analysis on the tool.

The Nova applications team develops what are called recipes in the Metrion system.  Those recipes include the film analysis and quantification, which can be set up to run automatically by the trained operator simply and quickly.

Lastly, we have automated tuning and calibration as discussed in the previous section.

All of these things equal full automation.

What is the value of full automation offered by Metrion?

It is true that fully automated systems like Metrion cost more than manual lab SIMS systems, with higher maintenance costs as well.

However, a common misconception is that capital equipment expenses and maintenance costs are the biggest drivers of ownership costs.  Rather, the largest components of the entire cost to own a metrology tool like Metrion are consumables costs and uptime.

Fully automated systems have much higher availability than manual systems, usually 90% or higher.  Manual systems typically have 50% or even lower availability.

And these are generous assumptions because of the manual adjustments required to set up a lab SIMS, including beam alignment, magnet settings, and switching between oxygen and cesium sources.   These manual procedures, taken together with manual film analysis, can take two to four days on a lab SIMS, resulting in significant tool downtime.  A fully automated system such as the Nova Metrion® has much higher availability.

We still need to factor in labor costs.

The Metrion has lower labor costs than manual laboratory systems because SIMS experts are not required to run the system. Also, the automated recipe management means that measurement jobs can be set up to run on their own.  An expert operator is not needed to attend the tool 100% of the time.

The Metrion sample measurement recipes can be loaded remotely through the factory host.  And the numerical data resulting from the measurements is automatically uploaded to the factory host upon completion of a job.

Compared to a manual laboratory SIMS, then, the Metrion demonstrates higher productivity.

So, what does this mean? It means that the Metrion potentially has a 20% lower cost of ownership compared to laboratory SIMS systems. With such advantages, it is clear why semiconductor fabrication facilities could benefit from Nova Metrion® SIMS.   

How does Nova Metrion® achieve better depth resolution than lab SIMS and why is it important?

Now we’re going to review some of the data we have generated with the Metrion to explain its technical advantages.

Lab SIMS typically have a single detector.  To collect data on multiple species during a single data acquisition run, the detectors must undergo a mass switching cycle.  This means that some data will be missed because data can only be collected on one species at a time.

Metrion detectors monitor the species of interest continuously during the acquisition, resulting in higher data density and better depth resolution.

Why is a small analysis area important?

Recall that the goal for Metrion is to measure product wafers inline.  For this to be viable in HVM, Metrion must be able to measure within a 50µm x 50µm² metrology pad or scribe line.  This die-sparing SIMS measurement strategy limits damage to the wafer and preserves as much of the wafer as possible so that usable die can be built on the remaining surface.  Minimizing the analysis area also reduces the data acquisition time.

By comparison, the minimum measurement area for most lab SIMS is 150µm x 150µm². Therefore, measurement runs take longer than with Metrion, data acquisition times are longer, and damage to the on-wafer die can occur. All these add to the total cost of ownership.

Summary: Why is the Metrion important?

Metrion provides wafer-level SIMS data that semiconductor manufacturers can rely on for high-volume manufacturing SPC. Metrion provides fully automated hardware and measurement sequences, with recipe-driven to support 300mm wafers. HVM worthy, Metrion provides convenient fab connectivity for SPC. Metrion offers high throughput, accuracy, and repeatability with a robust algorithm suite for material information analysis.

Metrion is only one part of Nova’s growing product portfolio.  The critical metrics that all fabs must monitor include composition and thickness, homogeneity, uniformity, as well as strain, and crystallinity.  Along with Metrion, Nova offers a full suite of products for materials metrology to quantify these metrics. The Nova VeraFlex® system is optimized for composition and thickness measurements, Elipson was designed to measure strain and crystallinity, and Metrion measures materials composition, uniformity, and thickness.

Creating and supporting such a complex and extensive product portfolio requires a substantial team effort. For example, the Metrion product team, comprised of scientists, engineers, production experts, and support personnel spent many hours together to make Metrion a success. And customers appreciate the effort.

In the second part of this blog post, we explore some widely applicable use cases where Metrion solved critical customer wafer fab issues successfully.