—Standard physical vapor deposition systems are large, expensive, and slow. As part of an on-going effort to build a fab-on-a-chip, we have developed a chip-scale, low cost, fast physical vapor deposition system consisting of two MEMS devices: a chip-scale thermal evaporator and a mass sensor that serves as a ﬁlm thickness monitor. Here, we demonstrate the functionality of both devices by depositing Pb thin-ﬁlms. The thermal evaporator was made by fabless manufacturing using the SOIMUMPs processs (MEMSCAP, inc). It turns on in 1:46 s and reaches deposition rates as high as 7:2˚As1with1 mm separation from the target. The mass sensor is a re-purposed quartz oscillator (JTX210) that is commercially available for less than one dollar. Its resolution was measured to be 2:65 fg or 7.79E-5 monolayers of Pb. Index Terms —Physical Vapor Deposition (PVD), Evaporation, Fab-on-a-chip, MEMS, Mass sensor, Quartz Oscillator, Film Thickness Monitor, Phased Locked Loop I. I NTRODUCTION PHYSICAL vapor deposition (PVD) is a widely used method for thin ﬁlm growth in which material is va- porized from a source, transported as a vapor, and con- densed onto a target [1]–[3]. It is used in a wide range of applications including coatings [4], diffusion barriers [5], micro/nanoelectronics [6], [7], magnetic ﬁlms for data storage [8]–[10], synthesis of 2D materials [11], [12], synthesis of quench condensed superconductors [13]–[16], and synthesis of nano/micro patterned metal structures [17]–[20]. Generally, these systems are large, expensive, and slow to start and stop deposition. They make up for it by being able to process many devices at a time. As part of an on-going effort to build a fab-on-a-chip (FoC) [21], we have developed a chip-scale, rapid, and inexpensive PVD system that has advantages for certain applications. The system is composed of two microelectromechanical systems (MEMS) based devices: a chip-scale thermal evaporator and a mass sensor made from a commercial quartz oscillator. These two devices combine into a PVD system that can start/stop deposition in less than 1:5 s, and has a volume of less than 1 cm3(not including a necessary vacuum system). It also consumes less than 200 mW of power inside the vacuum chamber which is an important measure because it puts an upper limit on the amount of heat generated within the system. This work was supported in part by DARPA Atoms to Product (A2P) Program/Air Force Research Laboratory (AFRL) under Grant FA8650-15-C- 7545, the National Science Foundation under Grants EEC-1647837, ECCS- 1708283, and a SONY Faculty Innovation Award L. K. Barrett, R. Lally, N. E. Fuhr, and A. Stange are with the Division of Materials Science, Boston University, Boston, MA 02215 USA (e-mail: blawrenc@bu.edu; rlally@bu.edu; fuhrnick@bu.edu; stange@bu.edu). D. J. Bishop is with the Division of Materials Science, Electrical and Com- puter Engineering Department, Physics Department, Department of Mechan- ical Engineering, Department of Biomedical Engineering, Boston University, Boston, MA 02215 USA (e-mail: djb1@bu.edu). Manuscript received ???Additionally the system is low-cost. The thermal evaporator is made by fabless manufacturing [22], [23] using a multi- user commercial foundry process, and the mass sensor is a commercially available device costing less than one dollar. These characteristics give the chip-scale system advantages over over traditional PVD systems in certain applications. For example, because of the low power consumption, the system is safer, and produces less heat. The decreased heat production allows the system to be used with heat-sensitive targets such as certain organic ﬁlms and heat-sensitive environments such as a cryostat. The low power output also decreases thermal drift without the need for active temperature controls which is particularly important in dynamic stencil lithography [24], [25]. Here, we test the chip-scale PVD system by depositing Pb. The thermal evaporator was measured to produce a ﬂux of 7:2˚As1at a separation 1 mm from the mass sensor. To pro- duce this ﬂux, the thermal evaporator consumed ( 176:7 mW of power and used a low voltage ( 9:5 VDC). The evaporator also has a modest footprint ( 0:25 mm2) which opens the possibility of putting many evaporators on the same substrate and evaporating multiple materials in parallel. This potential capability is particularly of interest for combinatorial material preparation for new material discovery [26]. MEMS based thermal evaporators have been demonstrated previously by Imboden et al. and Han et al. [21], [27]. They used a surface micro-machining process (PolyMUMPs by MEMSCAP, inc.) to produce ﬂoating silicon plates suspended by two compliant springs [28]. The plates were heated by run- ning a current through the springs. Materials were deposited onto the plates using a traditional PVD system and then re- evaporated from the plates in a controlled manner. The thermal evaporator presented in this work is similar in design and function to the evaporators presented Imboden et al. and Han et al but are larger scale, thus addressing an application space unmet by these previous systems or traditional PVD systems. For clarity, throughout the rest of the work, we will refer to the evaporators presented by Imboden et al. and Han et al. as microscale evaporators and the new evaporator presented here as a mesoscale evaporator. Like the microscale evaporator, the mesoscale evaporator consists of a ﬂoating plate supported by two compliant springs that also serve as heating elements. Differently, the mesoscale evaporator is made using a silicon-on-insulator (SOI) process (SOIMUMPs by MEMSCAP, inc.) [29]. Consequently, the heating elements and plate on the mesoscale evaporator are about ten times thicker than the microscale evaporators. Stem- ming from this difference, there are several trade-offs between the microscale and mesoscale evaporators. The microscale evaporators have faster thermal time con- stants owing to their lower mass ( <10 ms ), and they have a SUBMISSION 2 (a) (b) (c) (d) Fig. 1: Simulation data (Comsol Multiphysics) for the temperature proﬁle of a mesoscale evaporator with 15 V and10 V potential difference from one side to the other. At high temperatures, the proﬁle remains relatively uniform because of the nature of blackbody radiation (a) Color plot of the surface temperature of the micro-source at 15 V . (b) Plot of the difference between peak heater temperature and average plate temperature vs. the average plate temperature. The red line indicates the melting point of silicon. (c) Image of a heating element and part of plate with blue squares indicating the points plotted in (d). (d) Plot of the temperature at the points indicated in (c) vs. the position of the point along the path with the ﬁrst point being at 0. The dotted line indicates the edge of the plate. smaller footprint. Mesoscale evaporators can hold >100the material that has been demonstrated for microscale evaporators (>12 000 000 µm3vs.110 000 µm3). Additionally, due to their increased mechanical rigidity, they can be loaded by mechanically placing material onto the plate with tweezers, a probe station or a pick-and-place system, obviating the need to use a traditional PVD system to load the plate. When used at low temperatures ( <10 K ), microscale evap- orators deposit quench condensed thin ﬁlms that show no evidence of island growth. This is attributed to the adatoms having little or no mobility when they land on the target, and it is different than quench condensed ﬁlms deposited with traditional PVD systems [14], [30]. This behavior opens up the possibility of using microscale evaporators as a material source in a FoC single atom lithography system. Currently, it remains an open question whether mesoscale evaporators can reproduce this unique behavior. Microscale evaporators have also been used to deposit eight different materials (Al, Ag, Au, Cu, Fe, In, Pb and Sn) [27]. While mesoscale evaporators have only been demonstrated with Pb, we expect that mesoscale evaporators will work withall of these materials, but it has not been demonstrated to date. The mesoscale thermal evaporator is only half of the system. The other half is a mass sensor that can measure the the depo- sition rate in situ. Mass sensors have been extensively studied both using MEMS [31]–[36] and NEMS [37]–[40]. In addition to being used as ﬁlm thickness monitors, mass-sensors are also can be used as chemical, biological, and gas sensors. Single atom resolution or better has been demonstrated using carbon nanotubes as resonators [37], [38]. Custom MEMS mass sensors have also been used as ﬁlm thickness monitors in FoC systems [21], [27]. Here, we demonstrate that a mass sensor can be made from a commercial device (JTX210) [41]. Using a commercial device gives advantages both in terms of cost and ease of implementation. It may be the ideal solution for laboratory scale setups where an adequate mass sensor is needed quickly and reliably. The minimum Allan deviation was found to be 21:9µHzwith 3 stime averaging. This corresponds to 2:65 fg and 7.79E-5 monolayers of Pb. SUBMISSION 3 (a) (b) (c) (d) (e) Fig. 2: Simulation data (Comsol Multiphysics) for various designs of heaters and plates (a) Graph of average plate surface temperature vs. maximum stress in the heater. The legend