SCM (Scanning Capacitance Microscopy) and SMM (Scanning Microwave Microscopy): Principles and complementarity of semiconductor electrical properties detection

We learned about the "ultimate puzzle" of semiconductor inspection - eSPM (Electrical Scanning Probe Microscope). While traditional electron microscopes (TEM/SEM) can only see the physical structure clearly, eSPM can take a colorful "electrical distribution map" of the microscopic world.

Among the intricate electrical indicators inside the chip, there is an extremely critical parameter:Carrier (doping) concentration. It is like the "blood concentration" inside the chip, which directly determines whether the transistor can switch normally.

In order to see the distribution of these "bloods" clearly, there are currently two absolute "star players" in the field of semiconductor failure analysis (FA):SCM (Scanning Capacitance Microscopy)andSMM (Scanning Microwave Microscope)。

Not only do they have similar names, they also haveNon-destructive testingTheir excellent characteristics also have a high degree of overlap in application fields. Today, we will deeply analyze the principles of these two non-destructive testing technologies and how they bridge each other and perfectly complement each other.

If detecting carriers in semiconductors is compared to photography, then SCM is like a "standard digital camera" that is simple to operate, widely known to the public, and highly popular.

The core principle of SCM is to use an extremely sharp conductive probe to contact the chip surface and measure the semiconductor surface by applying an AC voltage.Microscopic capacitance changes, thereby inferring the internal carrier type (P type or N type) and concentration distribution.

As the most commonly heard name in semiconductor wafer fabs and failure analysis laboratories, SCM has a very high industry status:

• 🏆Advantage 1: There is a large amount of domestic equipment and high awareness.
  Over the past decade, SCM has become the “standard” for semiconductor doping analysis. Whether it is a foundry or an IC design company, engineers have a very high degree of acceptance and recognition of SCM reports.

• 🏆 Advantage 2: The technology is extremely mature and the images are of higher quality.
  Thanks to years of technology iteration, SCM, combined with mature sample preparation processes and powerful software algorithms, can output two-dimensional pseudo-color images with extremely high contrast, extremely smooth and beautiful appearance. For qualitative analysis that requires visual display of the PN junction outline and finding obvious abnormal junction depths, SCM's "image output" is perfect.

If SCM is a universal camera that takes beautiful photos, then SMM, which has suddenly emerged in recent years, is like a "precision microwave radar" that can obtain deeper multi-dimensional information.

SMM works on a more general principle, emitting a beam of microwave signals through a probe into the sample. After the microwave interacts with the semiconductor material, the reflected signal not only contains capacitance information, but also contains extremely rich impedance and other data.

In addition to having the same characteristics of non-destructive testing, SMM’s “precision radar” masters several advanced skills:

• 🚀 Advantage 1: Obtain more dimensions of information.
  Because of the high-frequency characteristics of microwave signals, a single scan of SMM can not only see the carrier distribution clearly, but also obtain more dimensional material physical information such as local dielectric constant and microwave impedance at the same time. The data it can "see" is richer than traditional capacitance measurement.

• 🚀 Advantage 2: Linear doping signal, more accurate quantitative analysis.
  Engineers familiar with SCM know that the signal of SCM is nonlinear, which makes it difficult to accurately tell you "what is the specific doping concentration here." andThe response of SMM to doping concentration exhibits an excellent linear relationship, which makes the "quantitative analysis" of semiconductors more accurate and reliable!

  

SMM multi-modal imaging example

Seeing this, many engineers will ask: SMM obtains more information, so will it replace SCM?

Not really.SCM and SMM are by no means an either-or competition, but are “golden partners” in semiconductor electrical characterization.。

In complex semiconductor inspection actual combat, different application scenarios require different weapons:

• When customers needQuickly and intuitively see the PN junction morphology, when you need to submit a report that meets common industry standards and has extremely beautiful images,Mature SCM is the obvious choice。

• When customers face extremely complex advanced processes or need to extractMulti-dimensional material impedance information, it is necessary to carry out the micro-regionFor accurate quantitative analysis of doping concentrations, accurate SMM can provide powerful fire support.

Many times, advanced failure analysis laboratories will useSCM (intuitive qualitative, large-scale confirmation of morphology) + SMM (multi-dimensional quantitative, in-depth exploration of details)combination. Only by bridging the two can the leakage and doping anomalies hidden deep in the nanometers be hidden.

Whether it is SCM with a profound foundation or SMM with a sharp edge, there is only one ultimate goal:Help Chinese semiconductor companies see through the "soul" of chips and improve yield rates。

In the detection of the microscopic world, there is no magic trick that is popular all over the world, only precise enemy control for different application scenarios.

As a professional micro electrical analysis team,Shanghai Guozhiwei TechnologyAlso master core eSPM technologies such as SCM and SMM. We not only have advanced equipment, but also accumulated rich experience in sample preparation and data analysis.

Whether you need the ultimate in SCM images or non-destructive quantitative data from SMM, we can provide you with the best-matched test solution.

Let professionals do the most professional things. Your next chip analysis may require this "double sword" solution!