Ultra-Fast, Simultaneous Monitoring of Critical AMC Classes with Semicon AMC Monitors

Ultra-Fast Simultaneous AMC Monitoring

Sensitive and fast detection of airborne molecular contaminants (AMCs) present in semiconductor fabrication facilities is critical to the quality and efficiency of production.  Fabs host hundreds of independent processes that can serve as contamination sources, including ventilation systems, leaks, device failures and human emissions. AMCs are comprised of a variety of chemical compound classes which are not comprehensively measured by conventional monitoring techniques. As nodes continue to advance to smaller dimensions, the presence of AMCs at trace concentrations (<10 pptV) have a greater influence on wafer defects, consequently resulting in yield loss.

AMC classes vary significantly in physicochemical properties, uniquely interacting or reacting with surfaces or other compounds. Due to the complexity of AMC composition, modern monitoring systems must comprehensively measure a wide range of compounds spanning multiple chemical functionalities and a range of vapor pressures with sufficient speed and sensitivity.

Using real-time chemical ionization time-of-flight mass spectrometry combined with proprietary fast polarity and reagent ion switching, Semicon AMC Monitors (with ABC configuration) support up to six chemical ionization chemistries. This allows for the detection of multiple AMC classes with a cycle time less than 2 seconds. Figure 1 demonstrates the ABC monitoring configuration’s response and recovery time.

Figure 1. Response and recovery time of a ClearFab AMC Monitor. Labels in the plot show target concentrations while the Y-axis shows the measured concentration of selected compounds. The upper plot shows the concentration of MEK, PGME and PGMEA measured with one chemical ionization chemistry, while the lower plot shows the simultaneous measurement of toluene with another chemical ionization channel chemistry.
Figure 1. Response and recovery time of a Semicon AMC Monitor. Labels in the plot show target concentrations while the Y-axis shows the measured concentration of selected compounds. The upper plot shows the concentration of MEK, PGME and PGMEA measured with one chemical ionization chemistry, while the lower plot shows the simultaneous measurement of toluene with another chemical ionization channel chemistry.

Using soft ionization, AMC constituents are measured with negligible fragmentation, enabling robust data quantification and straightforward mass spectra interpretation. Due to fragmentation, compounds like propylene glycol methyl ether acetate (PGMEA, 108-65-6), propylene glycol methyl ether (PGME, 107-98-2), and methyl ethyl ketone (MEK, 78-93-3) are difficult to distinguish with conventional AMC monitors. Figure 2 presents the sequential measurement and removal of these compounds to demonstrate the efficacy of the fragmentation-free detection provided by the monitor’s soft ionization.

Figure 2. Sequential measurement and removal of PGMEA, PGME and MEK demonstrating the detection of these challenging compounds without fragmentation.

Semicon AMC Monitors accurately detect single digit, part-per-trillion concentrations in real time, enabling greater contamination control and detection compared to conventional technologies. Select limits of detection (LODs) provided by the ABC configuration are presented in Table 1 and coverage linearity is presented in Figures 3 and 4.

Compound NameCASMolecule 2s LOD (ppbv)1min LOD (ppbv)
Propylene glycol methyl ether acetate (PGMEA)108-65-6C6H12O3
0.00650.0012
Propylene glycol methyl ether (PGME)107-98-2C4H10O20.0520.0094
Methyl Ethyl Ketone (MEK)78-93-3C4H8O0.4210.075
Ethyl Acetate (EA)141-78-6C4H8O20.1040.019
Cyclopentane287-92-3C5H100.1320.023
Acetone67-64-1C3H6O0.0020.0009
Toluene108-88-3C7H80.0120.003
Ammonia7664-41-7NH30.4080.072
Hydrogen fluoride7664-39-3HF0.0110.0002
Hydrochloric acid132228-87-6 HCl0.5260.095
Nitric acid7697-37-2HNO30.00720.0013
Chlorine7782-50-5Cl20.0010.0002

Table 1. Typical LODs for relevant semiconductor manufacturing compounds with a Semicon AMC Monitor configured for the monitoring of acids (corrosives), bases, and condensables.
Figure 3. Linear range of coverage for toluene
Figure 4. To demonstrate reproducibility, accuracy, and time response, three sequences of increasing concentrations of MEK, PGME and Toluene are presented. The left axis shows the measured signal while the right axis shows the measured concentration. The compounds were measured after dilution from a calibration cylinder with a total of 12 compounds, making an overall VOC concentration of ~1200 ppb.

Semicon AMC Monitors have been evaluated for a variety of fab applications, including material off-gassing, cleanroom monitoring, leak detection and FOUP quality control. Figure 5 presents a cleanroom event where a transient leaks toluene and ammonia were detected. Figure 6 presents process off-gassing measurements for an ISO 5 microtechnology evaluation.

Figure 5. Ammonia and toluene leak detected in an ISO 5 fine chemistry cleanroom.
Figure 6. Off-gassing of material in an ISO 5 microtechnology cleanroom. Material was purged with CDA and measured directly by the Semicon AMC Monitor.  Each time series shows simultaneous compound measurements with 3 different ionization chemistries for comprehensive AMC coverage.

Conclusion

Semicon AMC Monitors represent a significant advancement for contamination control and monitoring, providing simultaneous, fast, and sensitive detection of molecular classes that impact production quality and efficiency. With complete measurement cycles less than 2 seconds, and excellent time response, Semicon AMC Monitors resolve contamination challenges experienced throughout semiconductor fabrication processes and environments.