Nova Metrion® Use Cases

Several use cases that we will explore for the Nova Metrion® system include contamination control, process excursion prevention, reactor matching, and uniformity control. The objectives of these use cases are to detect contaminants which can kill devices, improve barrier layer and source/drain function, maintain deposition uniformity that impacts downstream processes, and ensure wafer-to-wafer consistency.

Use Case #1: Dopant Concentration

The first use case to discuss is doping concentration for logic devices.  Since very small variations in Boron concentration in a logic device wafer can impact the performance of the final logic device, Metrion can be used to qualify, monitor, and match Epi chambers in the fab to keep the production process under control.

During the Epi process, Metrion can also help control some key fabrication parameters. One of these is Epi growth uniformity, measured by tracking the Germanium concentration and the ratio of Germanium to Boron (referred to as the “Germanium fraction”).

Other key parameters the Metrion can measure include dopant concentration profile, plus peak concentration and uniformity across the wafer.

In the graph below (Figure 1) we can see an example of a single measurement of Boron, Germanium, and Silicon concentration profiles.

Figure 1 Boron Concentration Profile in SiGe     

On the next graph (Figure 2 we see the tracking over time of the average Boron concentration and Germanium fraction. This data is automatically uploaded to the factory host for SPC of the Epi process.

Figure 2 Automated Epitaxy SPC

As a result of chamber qualification and matching in the fab, customers can achieve tighter process control on the challenging Epi process and higher uptime of their Epi chambers.

Use Case #2: Deposition Uniformity

The second use case we will review is controlling the uniformity of Silicon-Germanium deposition in Nanosheets. Although Gate-All-Around is beginning to replace FinFET as a transistor technology because it generates better performance with lower power consumption, there are challenges to creating these nanosheets.

One of the critical steps in the manufacturing of Nanosheets or Gate-All-Around, is the deposition of SiGe.

The concentration of the Germanium, and in particular its uniform deposition on each nanosheet, dramatically affects the selectivity of the following etch process and has a direct impact on transistor performance.

In-Line Metrion SIMS can be used to monitor within-layer and within-wafer uniformity and help optimize nanosheet manufacture.

 As an example, in the graph below (Figure 6), we see the Germanium concentration variation across each one of the three Nanosheets.  Notice also the growth difference in the first nanosheet compared to the other two.  This could mean that some of the germanium is left behind during the etch.  So, monitoring the thickness of each Epi layer is key.

Figure 3: SiGe Growth Uniformity Monitoring

In the graph below (Figure 4) the uniformity of the Germanium concentration across the entire wafer is displayed, based on a 9-point Metrion SIMS measurement.  These contour maps can be generated from as few as 5 measurement points also.

Figure 4: In-Line Germanium Deposition Uniformity Across Wafer

Use Case #3: Contamination Detection

The next use case to consider is contamination detection.  There are many applications for in-line contamination control since impurities can be device killers, resulting in valuable wafers being scrapped. The sooner contamination can be detected, the more wafers will be saved, positively affecting yield and productivity for the fab.

 The next example is a 3D NAND application where chlorine and fluorine concentrations were measured in the wafer stack, as shown in the graph below (Figure 5).

Figure 5: Cl and F Concentration-Depth Profile

Nova Metrion® generates a compositional profile through the entire wafer stack.  The next graph (Figure 6) is an example of a process excursion that was identified from data uploaded to the factory host.  Faster-time-to-data means that the production team can be alerted as soon as the excursion occurs, allowing process engineers to make adjustments and preserve some of the wafers — improving yield.

Figure 6: Fluorine SPC 

Use Case #4: Implant Control

The last Nova Metrion® use case we will review is implant control for memory devices. 

The uniformity and concentration of boron implants have a direct impact on device performance. 

With an in-line Metrion SIMS system customers can perform weekly quals, identify process excursions, match chambers and upload uniformity maps, such as the one in the lower right-hand corner.   

Gathering this data in-line takes some of the burden off the metrology labs and makes the data available for SPC via the factory host. 

In the next graph (Figure 7) we see a Metrion measurement result of the concentration profile of a boron implant.  This comparison between the Metrion and lab SIMS measurements shows excellent correlation.

Figure 7: Boron Implant Concentration Profile

In summary, Nova Metrion® offers a variety of high-value use cases that generate faster time-to-results and reduced scrap. This saves money and improves productivity, which are invaluable to semiconductor manufacturers in today’s competitive landscape.