Fabricating semiconductor lasers on silicon has been a long-held but challenging goal for the semiconductor industry. Researchers at the Data Storage Institute (DSI) of Singapore’s Agency for Science, Technology and Research (A*STAR) claim to have developed a cheap, simple, and scalable method for manufacture them. The researchers detailed their method in an ACS Photonics article.
These hybrid lasers promise inexpensive and mass-producible optical devices that integrate photonic elements and microelectronic components on a silicon chip. Potential applications for these lasers range from short-distance data communication to high-speed, long-distance optical transmission.
Existing production processes fabricate lasers on separate III–V wafers before individually aligning them to each silicon device, a costly and time-consuming process. This aligning process limits the number of lasers that can be placed on a chip.
Data Storage Institute of A*STAR Develops Fabrication Technique
Doris Keh-Ting Ng and her colleagues at the A*STAR Data Storage Institute devised a technique for producing a hybrid III–V semiconductor and silicon-on-insulator (SOI) optical microcavity, that they claim overcomes these limitations. According to the researchers, the method greatly reduces the complexity of the fabrication process and results in a more compact device.
“It is very challenging to etch the entire cavity,” said Ng. “Currently, there is no single etch recipe and mask that allows the whole microcavity to be etched, and so we decided to develop a new approach.”
They first use a SOI interlayer thermal bonding process to attach a thin film of III–V semiconductor to a silicon oxide (SiO2) wafer. This strong bond also eliminates the need for strong oxidizing agents, such as hydrofluoric acid or Piranha solution.Then, a dual hard-mask technique etches the microcavity that confined etching to the intended layer, thereby eliminating the need to use multiple overlay lithography and etching cycles.
Chee-Wei Lee et al, ‘Fabrication and Demonstration of III–V/Si Heterocore Microcavity Lasers via Ultrathin Interlayer Bonding and Dual Hard Mask Techniques’, ACS Photonics (2016) 3 (11), p2191. DOI: 10.1021/acsphotonics.6b00794.