Miniaturized on-chip passive devices based on self-rolled-up SiNx nanomembrane inductive tube

On-chip lumped passive devices are very important radio frequency integrated circuits (RFICs) components that are used to guide and manipulate signal generated by active devices. Current on-chip lumped passive devices are designed based on standard two-dimensional (2D) planar fabrication process, which limits the design of lumped passive devices in a 2D plane. This limitation makes lumped passive devices huge compared to the active devices and occupy most of the chip area and fabrication cost. In addition, 2D structures usually have large overlap area with the substrate, which inevitably introduces serious substrate parasitic effect that significantly increases energy loss and limit applicable maximum frequency. Recently, we have proposed a novel on chip platform for lumped passive devices based on self-rolled-up SiN_x nanomembrane tubes, aiming to solve the problems addressed above.² Compared to traditional methods that use planar semiconductor substrates as mechanical support for RFICs, multiple-turn SiN_x tube provides a three-dimensional (3D) mechanical support with super small on-chip footprint. This 3D structure provides better confinement of the electromagnetic (EM) field. With pre-patterned and rolled-up conductive layers inside the tube, the electrical performance of one tube cell is calculated to be strongly inductive rather than capacitive. As shown in Figure 1, by adjusting the distance between adjacent cells, serially connected cells can be an inductor or a transformer. To be an inductor, adjacent cells need to be separated from each other far enough to eliminate the cancelling mutual inductance. To be a transformer, adjacent cells need to be close to each other to exploit the EM coupling between each other.