Patent ID: 8564087

Claim:
A photodiode manufacturing method comprising: a step of preparing a silicon substrate having a semiconductor substrate having a first principal surface and a second principal surface opposed to each other, an insulating layer provided on the second principal surface of the semiconductor substrate, a first impurity region of a first conductivity type provided on the insulating layer, and a low-concentration impurity region of the first conductivity type provided on the first impurity region and having a lower impurity concentration than the first impurity region; a step of forming a photosensitive region including an impurity region of a second conductivity type, in the low-concentration impurity region; a step of shaping the first impurity region and the low-concentration impurity region into a mesa shape to form a semiconductor mesa portion including the photosensitive region; a step of forming a second impurity region of the first conductivity type having a higher impurity concentration than the low-concentration impurity region, on a surface of the semiconductor mesa portion and forming a third impurity region of the first conductivity type having a higher impurity concentration than the low-concentration impurity region, on a side face of the semiconductor mesa portion, to electrically connect the first impurity region, the second impurity region, and the third impurity region; a step of thinning a portion in the semiconductor substrate corresponding to the photosensitive region, from the first principal surface side, while leaving a surrounding region around the thinned portion; a step of irradiating the thinned portion of the silicon substrate with a pulsed laser beam from the first principal surface side to form an irregular asperity; a step of subjecting the silicon substrate to a thermal treatment, after the step of forming the irregular asperity; and a step of, after the step of subjecting the silicon substrate to the thermal treatment, forming a first electrode on the semiconductor mesa portion so as to be electrically connected to the impurity region of the photosensitive region and forming a second electrode on the semiconductor mesa portion so as to be electrically connected to the second impurity region.