1.4 - Technologies for Fast Blue and IR PIN Diodes
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings OPTO 2011
- O1 - Components for Sensing and Detection
- D. Sommer, K. Bach - X-FAB Semiconductors Foundry AG, Erfurt (Germany)
- 33 - 39
Photo detector integrated circuits (PDIC) for Bluray data storage require high sensitivity and high bandwidth photo diodes. Carriers are generated close to the surface because the used wavelength of 405nm is very short. Standard photo diodes have a low sensitivity for blue light. The latest generation of Blu-ray data storage devices supports 6x to 8x speeds. Next-generation devices will need 12x speed, which requires diode bandwidth of >800MHz, and support for legacy CD and DVD , as well as appropriate sensitivity and bandwidth for 650nm and 780nm.
X-FAB has developed a PIN diode on its 0.35μm technology platform that fulfils all requirements of a triple wavelength photo diode for Blu-ray, and supports sensitivity and bandwidth for 12x speed Blu-ray applications.
A special optical window etched on top of the photo diode and the deposition of an Anti Reflecting Coating (ARC) optimized for the Blu-ray wavelength of 405nm increases the sensitivity to 0.3A/W, resulting in a quantum efficiency of 98%. As there is still a high sensitivity for DVD (650nm) with 0.44A/W and for CD (780nm) with 0.4 A/W, the photo diode supports triple wavelength applications.
A PIN diode solution is used comply with the high bandwidth requirements. Using low doped wafer material allows for a high-speed photo diode without impacting the CMOS behaviour of the circuit. A special cathode implant reaches a deeper electrical field. Most of the carriers can drift, and only a few diffuse. This means the photo detection becomes very fast to address high bandwidth applications.
A PDIC includes additional critical components beside the PIN diode. Optimizing the interfaces and the components themselves requires high simulation effort. A model of the PIN diode is supported for simulation. The accuracy of the model for sensitivity and bandwidth has been silicon-proven by measurement.