Hybrid Near-Field Scanning Microwave Microscope with an Optical Confocal Sensor

There are a number of micro-and nanometer-scale manufacturing processes, which demand or would highly benefit from tools allowing high-spatial-resolution quality control for identification of defect spots and defective parts. These may include, for example, fabrication of microfluidic components or micro-electro-mechanical systems (MEMS) as well as certain processes and technological steps in semiconductor and electronics industries. Addressing this need, we have developed a scanning probe microscope that utilizes optical confocal distance sensor and near-fields of microwaves to probe and image samples and parts with a sub-micrometer spatial resolution, which exceeds the resolution of the available optical tools. The near-field microwave probe remains out of contact with the part/sample surface during imaging to prevent or dramatically reduce the probe damage and wear-out. The main foreseen use of the microscope is high-spatial-resolution inspection of parts with varying surface shape and/or electrical properties (dielectric constant and conductivity). As demonstrate in Fig. 1, the lateral spatial resolution of the microwave near-field probing of the tool is better than $1 \mu \mathrm{~m}$, which exceeds the resolution of about $2 \mu \mathrm{~m}$ of far-field optical systems currently employed in industry. The tool can be used for inand off-line inspection of topographic features, such as channels and protrusions in microfluidic systems and MEMS. Due to the ability of microwaves to penetrate through dielectric materials the microscope can be utilized for imaging of buried structures, for example, metal lines or voids in a dielectric material (see, e.g., the review [1]), which can find applications in non-destructive failure analysis of semiconductor device packaging.