Thursday, June 20, 2013

Low temp or high temp in ALD, we've got you covered

We've been learning a lot about what's really needed in ALD, and we've found that aside from using QCMs for in-situ, real-time monitoring for precursor development, wafer production, and exhaust maintenance, there's a need for both a temperature controlled AND a non-temperature controlled sensor. It really depends on the user's needs, and it's heavily dependent on their temperature limits.

For example, most users can put a non-temperature-controlled, Phoenix sensor head and Eon-LT controller (or monitor) into their basic ALD system, and it will do all they need in wafer production. The sensor housing is operational to 500C without a need for a separate heating/cooling control, and the electronics will provide high resolution (higher than competitor) at an extremely high rate with exceptional accuracy. The key here will be the crystal cut and coating of the resonator (many cannot have gold or copper anywhere within a chamber, for example). Cut matters, as it determines how high the temperature can go before a crystal phase change begins. We recommend our patented RC crystal for up to 300C (most applications), HT for between 300-400C, and SQ for 400C+.

If, however, the user needs to control temperature, raising and lowering (for handling) the sensor up to 700C, then the Cadillac of systems is necessary--Tempe and Eon.  Many users need this premium system for precursor development and exhaust maintenance, both of which can exceed the 500C temperature limit and require careful control of substrate temperature. Eventually, the majority of systems will get to this point, but for now, most research institutions and commercial operations only need a "Basic" system as they learn how to use QCM in a variety of ways for low-cost, real-time, in-situ measurement.

So, how are they different?

Well, there are a lot of similarities in features, as we built both systems to be robust, but the key difference is the ability-inability to control temperature. Tempe/Eon CAN; Phoenix/Eon-LT CANNOT. You might think it's not such a big deal to control the temp or get to higher temperatures, but not only are parts a lot more expensive, the science it took to create a system to withstand such high temperatures (just in springs and integrated heater, for example) took 3 years and millions of dollars to achieve. It's complicated, trust me. And let's not start about what it takes to write the software to correct for frequency vs. temperature! Ach, the algorithms!

So, if you need to reach temperatures above 500C or if you need to control temperature for other reasons, we recommend the Tempe/Eon system with software optimized for ALD. But, if your process is relatively low temperature, and you have no plans to exceed 500C, plus you don't need to control sensor temperature, a basic Phoenix/Eon-LT is all you need. You may even need 3-5 for optimal, large-wafer uniformity. The beauty of the Phoenix/Eon-LT system is that it's only about 1/4 the cost of the full-featured Tempe/Eon system.

You realize that makes it the same cost as those other guys, right? With support...and without the politics.

You know you want one. Or three.

+1 480-634-1449 today

Friday, June 14, 2013

How are QCMs different from optical film thickness measurement systems?

Today I came across a press release from a competitor for an in-situ, thin film metrology tool, called ICE, specifically designed for MOCVD. It's an optical tool, and there are apparently quite of few of those around. According to our CTO, Scot Grimshaw, they've been around for decades, and even if there are some advancements in features, those are more or less like "putting lipstick on a pig". In his words, "they just don't work."

Well, that wasn't good enough for me. As a marketer, I want to know if our potential customers see optical methods as a real possibility they might choose over QCM. When you read the PR, it seems optical film thickness measurement is comparable, when what really counts to process engineers isn't.

For example, optical methods claim to do the following:
  • Multiple Simultaneous Real-Time Measurements
  • Auto-Calibration
  • Integrated Electronics and Optics
  • Dynamic Signal Intensity Control
  • Flexible, Upgradeable Optical Enclosure Options    
Sounds good, right?

Not so fast. While it may sound like they're doing the equivalent to QCM, with the benefits of being in-situ, the truth is not so simple. For one, optical methods are not nearly as accurate. In fact, according to Scott, "the accuracy of our QCM is 100X finer than optics," so if you need high precision in your coatings, optical methods "just don't work."

Specifically, optical methods are:
  • Expensive
  • Usually for thick films only
  • Difficult to use and difficult to calibrate
  • Useful on limited substrate types (light doesn't pass through foil, e.g.)
  • Give inconsistent results due to the necessity of a clear path length*

The fact remains that for simple, in-situ, real-time film thickness measurement with high accuracy and at lower cost, your best bet is still a quartz crystal microbalance. If you need it for high temperature or super high accuracy, then a Colnatec QCM is your only solution, as I've mentioned before.

*Optical methods require light passing through a film, which requires you input light at some point into your chamber. That requires optics and a clear path length. If your system doesn't have a clear path length for the light to travel, then you'll need additional optics and fixturing. For more information on how optics work (or don't), read up on "optical absorption" or "reflectance phenomena". Scholarly articles on the subject are too numerous to cite (but you can start here).

Sunday, June 2, 2013

How are your sensors useful during ALD precursor development?

Primarily for cost savings--you can eliminate wasted substrates in your initial precursor development, for starters. Put another way, you can use the QCM as a substitute "wafer", saving hundreds of dollars per wafer.

Additionally, it assists in developing ALD process chemistry by estimating kinetic parameters involved in the ALD gas-surface reactions.

And, the Colnatec Tempe sensor system is not only high temperature, it also is materials-sensitive. In other words, it can work in most hot process and harsh or corrosive environments without degrading or contaminating the reactor. Our sensors are made of 304SS and use air cooling, so as to not foul the reactor. Stainless steel allows us to heat the sensor beyond what is possible with an aluminum head, and air cooling prevents the need for water, which is problematic in most ALD systems (water cooling is also incapable of achieving--or controlling--high temperatures beyond 100C).

Finally, the beauty of a truly "heated" sensor (not just "bakeable") is that the sensor and the substrate are at the same temperature. Our sensors are independently heated via an integrated element and controlled with software to maintain any temperature you need them to be (up to 500C). "Bakeable" sensors use ambient chamber heat to raise temperature, which is completely uncontrollable and unreliable. Most bakeable sensors are also unable to reach the high temperatures a Colnatec sensor can reach, let alone consistently hold that temp for any reliable time frame.

Saturday, June 1, 2013

What are the benefits of using your high temp QCM for ALD?

The benefits of using a real-time, in-situ, heated sensor are significant:
  • Reduction in ex-situ metrology where applicable:
    • Reduction in metrology samples and time associated with measurements
    • Reduction in demonstration and/or development test / set up
  • Increased efficiency--cost savings:
    • Reduction in time and materials waste due to the capability of the QCM to assist in design of experiment (DOE)
    • Reduction in scrapped runs (substrates) due to real time information as to process and or reactor conditions
    • More consistently accurate film deposition per wafer or per run
    • Increase in film quality due to in-situ process monitor
    • Savings in engineering, operator and maintenance technician time
Competitor QCMs, such as those made by Inficon, are unheated and therefore unable to withstand the high temperatures and corrosive environments of most ALD reactors. Most optical methods, such as those made by Filmetrics, KLA-Tencor, and Woolam, are very costly, difficult to use, difficult to calibrate, bulky, and largely inconsistent with results. Ellipsometry is even more expensive and awkward, plus they're ex-situ. Laser methods can be more accurate, but they too are expensive and oversize, and they require highly trained personnel to prepare calculation tables.

Simply said...

The use of the Colnatec high temperature QCM is the most powerful and cost effective method for examining an in-situ ALD process.