Abstract

Silicon carbide (SiC) is a desirable material in a wide variety of semiconductor fields. The impressive thermal, chemical, and mechanical properties that make SiC an attractive material also make it very difficult to machine. New fabrication techniques are required to take full advantage of the potential of SiC. First, a new 3-dimensional (3D) non-line-of-sight (NLOS) fabrication technique using two-photon absorption is demonstrated in SiC. NLOS microchannels are shown with aspect ratios higher than 100:1. The process is the only method known, at this time, that can create truly 3D subsurface structures in SiC without direct line of sight to the etch front. Next, a toolset of metrology techniques is introduced for the imaging and characterization of complex NLOS subsurface etches in SiC. We use a combination of destructive and non-invasive techniques that can accurately image microchannels with about 3-micron resolution (for non-invasive) to sub-nanometer resolution (for destructive) depending on the imaging method. Then, the system used for the novel NLOS technique is described. It is designed to create a high photon density at a laser focus on the surface of a SiC wafer by combining a femtosecond laser with a high numerical aperture objective. A custom etch chamber creates a SiC/hydrofluoric acid interface to facilitate the electrochemical process. An XYZ-translation stage moves the chamber relative to the laser focus. Next, an ablation process for creating through wafer vias in SiC is described along with an open-air plug, electroplating technique for filling the vias with copper. It was observed that the initial blast of the laser caused significant cracking in the absence of a protective layer. A layer of Kapton tape was able to prevent damage to the SiC while still allowing easy alignment of the laser focus to existing surface features. Finally, the fabrication process for a transparent, cryogenic probe card in SiC is demonstrated. A combination of ablation techniques, electroplating processes, and traditional photolithography is used to create a probe card die with a fine pitch array of palladium tips connected by way of through wafer vias and patterned surface traces to bond pads that can be connected to in order to extract the probing signal. Compliant legs are cut into the SiC to allow for flexion of die when probing. The die is thinned to allow for close to 50 μm of flexion.

Degree

PhD

College and Department

Ira A. Fulton College of Engineering; Electrical and Computer Engineering

Rights

https://lib.byu.edu/about/copyright/