## 3 Results and Discussion  
Figure 3a shows \(\rm N_{p,total}\) and \(\rm V_{p,total}\) calculated from the number distributions of particles measured by the portable AMC monitoring system at different sub-locations in the university's cleanroom. All the \(\rm N_{p,total}\) are less than \(1\times 10^{5}\)/cm\({}^{3}\), which represents very low AMC concentration in the cleanroom air, compared to that for 1 ppb SO\({}_{2}\) reported in our previous publication [7]. Based on the results in Figure 3a, most sub-locations in Bay 1 generally show more AMC concentrations in terms of \(\rm N_{p,total}\) than other locations (Corridor and Bay 2). However, Bay 1-3 has the lowest \(\rm N_{p,total}\) than all other sub-locations, which can be understood that the sub-location, Bay 1-3, was the cleanest one in the  
Figure 2: Details of the sub-locations as the monitoring sites for AMC in (**a**) Bay 1 and (**b**) 2 of the cleanroom at the University of Minnesota. The cleanroom air was well conditioned at 40% relative humidity (RH), 21 \({}^{\circ}\)C.  
cleanroom during the measurements. An open door next to Bay 1-3 for entering to the utility area with lower air pressure than Bay 1 might cause the lowest value. Figure 3b depicts V\({}_{\text{p,total}}\) calculated from the volume distributions of particles converted from the measured number distributions of particles. In this case, Bay 1-3 shows higher value than the sub-locations in Corridor and Bay 2, even though it was still the cleanest one in Bay 1 in terms of V\({}_{\text{p,total}}\). This difference of the trends in the relative AMC concentrations among the sub-locations between N\({}_{\text{p,total}}\) and V\({}_{\text{p,total}}\) was caused by the particle size converted from AMC. Although the total number concentration for Bay 1-3 was lower than those for the sub-locations in Corridor and Bay 2, the sizes of  
Figure 3: (**a**) Total particle number and (**b**) volume concentrations measured at different sub-locations in the cleanroom at the University of Minnesota by the portable AMC detector through soft X-ray radiolysis. particles converted from AMC through the soft X-ray radiolysis in Bay 1-3 were larger than those in Corridor and Bay 2. As the soft X-ray radiolysis is a gas-to-particle conversion, which is a mass- (or volume-) based conversion, using V\({}_{\text{p,total}}\) (the density for the particles are unknown) in Figure 3b is more appropriate for estimating AMC concentration in the cleanroom air [7]. Figure 4 represents the equivalent SO\({}_{2}\) concentrations corresponding to V\({}_{\text{p,total}}\) in Figure 3b, which were calculated through the Equation (1) and all of them are lower than 15 pptV. Interestingly, Bay 2 for PR processing shows lower concentration than Bay 1. Even though many chemicals were used in Bay 2 areas, the total number concentrations of nanoparticles converted from AMC in the cleanroom air were not exceeding those measured in Bay 1. This can be explained that the air with AMC was well-evacuated, thus reducing N\({}_{\text{p,total}}\) and V\({}_{\text{p,total}}\) in Figure 3a,b. Especially, the difference between Bay 1 and 2 was more apparent in terms of V\({}_{\text{p,total}}\), because the size of the nanoparticles converted from the AMC in Bay 2 was smaller than Bay 1. This might be achieved by the hood system for the PR processes, which was well equipped and operated. If the chemical properties of AMC in Bay 2 were all organics and Bay 1 had more acidic and basic AMCs than Bay 2, the conversion rates from the organic AMCs in Bay 2 could be slower than AMCs in Bay 1. Then, the particle or haze formation problems could be lower in Bay 2 than Bay 1, even though Bay 2 had more AMC sources. We developed this portable AMC monitoring system for determining AMC hot spots in real-time, and analyzing the chemical composition of the AMC was out of the scope of this study. In addition, one of the main issues of AMC is gas-to-particle or haze conversion due to photochemical processes with UV in the lithography processes.