Low Resistivity Metallic Films by Thermal Atomic Layer Deposition for MEMS and Sensor Applications
ABSTRACT
High quality conductive films have myriad applications in MEMS and sensors. Thin, high quality, and conformal metal films have been used as electrodes for piezoelectric MEMS and capacitor places for electrostatic actuators. As device designs scale and push toward more intricate 3D architectures and higher aspect-ratio structures, conformal thin metal films can reduce interconnect (metal line) resistance, provide selective sidewall patterning, or facilitate metal gap-fill. Advancements such as these can lead to improvements in a range of devices from micromirrors, microactuators, microswitches, resonators and filters, and position sensors. Unfortunately, current standard processes for high quality metal films are limited to line-of-site techniques, chemical vapor deposition (CVD) or physical vapor deposition (PVD), limiting possible device architectures. Fortunately, atomic layer deposition, ALD, can produce high density and low resistivity metal films, both as compound, such TiN and TaN, and elemental, such as Ru and Pt, films. Adoption of ALD of metals has been slow as there are significant drawbacks, traditional ALD reactors can be too slow and inefficient for production requirements or require plasma for sufficient film quality. Forge Nano has single wafer thermal ALD technology to improve the speed and efficiency and exploit unique surface chemistry to improve film properties of ALD metal films. A novel TiN thermal ALD process has been developed which decreases the as-deposited, 300°C, resistivity from ~1200 to <300 uΩ·cm at a deposition rate >1 nm/min. TiN has been used as a novel ultra-thin, ~50nm, membrane-based sensor for pressure and viscosity in bioMEMS sensors or as a conductive layer in diaphragm MEMS acoustic sensors. In addition, a high-quality Ru film has been developed that has resistivity values <30 uΩ·cm and can be deposited on SiO2, HfO2, Pt, and TiN, with good adhesion. Thus, this Ru film can be used as a charge dissipation layer in inertial sensors and as a conductive layer in FBAR devices. Both films are conformal over 10:1 aspect ratio feature and when used together have shown success as a Cu barrier/seed stack for Cu electrofill in trenches as shown in Figure 1. This will enable next generation via fill for non-line-of-site metal interconnects, critical to MEMS and sensor device scaling. In this talk, I will briefly discuss the basics of ALD, how the Forge Nano technology is differentiated from batch and PEALD tools, discuss the improvement and implementation of low resistivity TiN at 300°C and Ru at 250°C, and discuss potential MEMS and sensor applications for these films.
BIOGRAPHY
Dr. Matt Weimer is Director of R&D at Forge Nano who specializes in object and semiconductor applications for atomic layer deposition (ALD). He received his B.S. and Ph.D. in chemistry from the University of Washington and the Illinois Institute of Technology, with a joint guest graduate appointment at Argonne National Laboratory (ANL), respectively. After completing a postdoctoral appointment at ANL in fundamental battery research, he joined the R&D deposition group at Lam Research developing novel vapor deposition semiconductor solutions. At Lam, Matt used multiple deposition techniques to find solutions for a range of applications in both logic and memory.
Since coming to Forge Nano, Matt has led R&D efforts to identify and develop novel ALD solutions over a range of device applications in the semiconductor space, including MEMS and Sensors. His research interests include modification and control of surface chemistry, thin film growth and characterization, and technology commercialization.
Matt has multiple papers, patents, and talks in the fields of synthetic chemistry, ALD, and CVD and is on the executive board of the Rocky Mountain Chapter of the American Vacuum Society. In his spare time, he is an avid racquetball player, hiker, and traveler.