Si-OEIC (OPIC) for optical pickup

An optical pickup OPIC(TM) with a built-in high-speed split photodiode and new device structure, has been developed. We have successfully fabricated the OPIC with a cutoff frequency of 18.4 MHz for 780 nm radiation and 21.1 MHz for 635 nm radiation. The development of the OPIC was made possible by the high-speed photodiode, which has n-type buried diffusion regions formed in the vicinity of the P-type buried isolation diffusion regions. An anti-reflection film is formed directly on the isolation region of the split photodiode as well as on the photodiode, therefore enhancing the sensitivity. The cutoff frequency of the photodiode thus realized is 24 MHz for 780 nm radiation and 41 MHz for 635 nm radiation and reflection rate is lower than 3%. The OPIC is compatible with 12 x speed CD-ROM and DVD optical systems. In this paper, we show the structure of this new device and its fabrication process. We found that the cutoff frequency of the photodiode is lower when the isolation region is irradiated than when the center region of the photodiode is irradiated. We studied the mechanism of the above difference of the cutoff frequency of the photodiode using device simulations.