Multiplexed output two terminal photodiode array for imaging applications and related fabrication process

A multi-pixel photodetector array comprising:

• a semiconductor substrate;
• a plurality of Schottky photodiodes on said semiconductor substrate, each Schottky photodiode comprising a plurality of metal filled anode contacts having a depth different than a depth of metal filled anode contacts of at least one other Schottky photodiode;
• a common cathode contact coupled to said plurality of Schottky photodiodes and defining a first connection lead;
• and
• a front metallization layer adjacent said semiconductor substrate and defining a common anode collecting grid coupled to said plurality of metal filled anode contacts and defining a second connection lead.

A multi-pixel photo detector array comprising:

• a semiconductor substrate;
• a plurality of Schottky photodiodes on said semiconductor substrate, each Schottky photodiode comprising a plurality of metal filled anode contacts having a depth different than a depth of metal filled anode contacts of at least one other Schottky photodiode;
• a common cathode coupled to said plurality of Schottky photodiodes;
• and
• a common anode collecting grid coupled to said plurality of metal filled anode contacts.

A method of making a multi-pixel, photo detector array of Schottky photodiodes on a semiconductor substrate having a dopant concentration between 1018 and 1019 atoms/cm3, comprising the steps of:

• a) growing a first relatively thin epitaxial layer with a dopant concentration between 1017 and 1018 atoms/cm3 of a same type of conductivity of the dopant of the substrate, on a front side thereof;
• b) growing a second relatively thick epitaxial layer with a dopant concentration comprised between 1013 and 1015 atoms/cm3 of same type of conductivity of the dopant of the substrate and thickness between 3 and 150 μm, over the first relatively thin epitaxial layer;
• c) depositing a sacrificial metal hardmask layer;
• d) defining an array of uniformly spaced parallel openings through the sacrificial metal hardmask layer by a first lithography step of a given spacing and width of the uniformly spaced parallel openings;
• e) anisotropically etching the doped semiconductor of the second relatively thick epitaxial layer through the uniformly spaced parallel openings of the metal hardmask layer, forming trenches of a given depth, and removing residual metal of the metal hardmask layer;
• f) depositing a metal layer of Schottky contact by a conformal metal deposition technique for completely filling the trenches, and etching the deposited metal layer for removing it from a planar front surface of the photodiode;
• g) repeating steps c) d) e) and f) for each other pixel of the array for as many different depths of the metal filled trench contacts of the number of pixels of the array of respective spacing and width of the metal filled trenches;
• h) depositing a standard metal layer on the planer front surface in contact with the Schottky contact metal filler of all the trenches of all the array pixels;
• i) defining a common anode current distributor grid from the deposited standard metal layer for connecting, in common, the Schottky contact metal filler of all the trenches and forming a connectable anode terminal pad of the multi pixel array, by a second lithography step and selective wet etch process;
• j) depositing a passivating layer conformally over the planar front surface for coating the defined parts of the standard metal layer;
• k) removing the passivating layer in areas of separation among coated parallel stripes of the common anode current distributor defined over the metal filled trenches by a third lithography step and dry etch process;
• and
• l) depositing a metallization layer over the rear surface of the semiconductor substrate to define a connectable cathode terminal.

A method of making a multi-pixel photo detector array comprising:

• forming a semiconductor substrate;
• forming a plurality of Schottky photodiodes on the semiconductor substrate, each Schottky photodiode comprising a plurality of metal filled anode contacts having a depth different than a depth of metal filled anode contacts of at least one other Schottky photodiode;
• forming a common cathode coupled to the plurality of Schottky photodiodes;
• and
• forming a common anode collecting grid coupled to the plurality of metal filled anode contacts.