UCLA

III-Vs like GaN and InP are the most promising substrates for high performance RF, photonics, and power electronics. However, III-V processing has been a gating factor in achieving smaller features and better devices. A primary cause of this setback has been large feature sizes resulting from limitations of older equipment. Older equipment must be used because it is compatible with III-V wafer sizes, which are smaller, costlier, and of lower quality compared to silicon wafers. To use the same cutting-edge tools and systems that silicon has immensely benefited from, III-V wafers must be made in a 300 mm format so that they can be processed in the same facilities as Si wafers. This thesis proposes and demonstrates one method of reconstituting gallium nitride (GaN) to create a large wafer that can be processed using large wafer tooling. Investigating these techniques also develops thermocompression bonding process capability that can be transferred to eventual III-V to Si vertical monolithic integration. For example, a GaN power amplifier can be vertically bonded (3D stacked) to a silicon dielet, decreasing the scale of power delivery networks by almost 1000x (from mm scale to �m scale). However, integration of gold into active silicon devices would require significant reliability study that is outside the scope of this work.

In this thesis, GaN on (111) silicon was chosen as a starting III-V material. After dicing, these dielets were bonded face-to-face to a (100) silicon handler with a gold-to-gold thermocompression bonded interface. The bulk of the dielet thickness is silicon, and it is removed with a hydrofluoric acid, nitric acid, and acetic acid etch (HNA). This leaves behind a thin (< 1 �m) film of III-V substrate, which is planarized and passivated with plasma enhanced chemical vapor deposition (PECVD) oxide and chemical mechanical planarization (CMP). The techniques developed in this thesis can be adapted to reconstitute other III-V materials, like GaN on sapphire, indium phosphide (InP), and gallium arsenide (GaAs).