Process for fabricating infrared detector arrays and resulting article of manufacture

Claim 2

The process defined in claim 1 further characterized by: patterning a thin copper film theremocompression bonded to a thin flexible sheet of high temperature plastic to form a plurality of conductors each terminating in an expanded solder pad, electroplating the copper conductors with gold, and connecting each of the conductors to a gold contact of a detector element by positioning the end of the conductor over the contact, heating the contact, and pressing the conductor against the heated contact with a heated tool applied to the other side of the high temperature plastic sheet to form a thermocompression bond between the conductor and the contact.

Claim 3

The process defined in claim 1 further characterized by: patterning a thin copper film thermocompression bonded to a thin flexible sheet of high temperature plastic to form a plurality of conductors each terminating in an expanded solder pad, electroplating the copper conductors with gold, and connecting each of the conductors to a contact on an element by an aluminum wire ultrasonically bonded to the conductor and to the contact.

Claim 4

The process for fabricating an array of very small, closely spaced semiconductor elements which comprises: bonding a thin slice of semiconductor material to a semiconductor substrate; forming a malleable etching mask on the surface of the slice having narrow slots therein, thereby exposing portions of the surface of the semiconductor material; subjecting the exposed portions of the surface to an etching fluid directed through the slots for a time sufficient to etch cavities through the semiconductor slice but not through the substrate, thereby forming a plurality of individual semiconductor elements; concurrently with the etching of said cavities, periodically bending the edges of the mask left overhanging the cavities along the sides of the undercut area, thereby partially protecting the sidewalls of the cavities from contact by the etching fluid; and electrically connecting the individual elements to form an electrically operational array.

Claim 5

The process defined in claim 5 wherein the substrate is comprises of a degenerate semiconductor material.

Claim 6

The process defined in claim 5 wherein the individual elements are electrically connected to form an electrically operational array by: forming a contact on each of the individual elements; forming a circuit sheet containing a plurality of conductors; and electrically connecting the contact on each individual element to a designated conductor on the circuit sheet.

Claim 7

The process defined in claim 7 wherein the malleable etching mask is formed from an electrically conductive material and only a portion of said mask is removed utilizing the remaining portion as an electrically conductive contact on each element.

Claim 8

The process for fabricating an array of very small, closely spaced semiconductor elements which comprises: bonding a thin slice of semiconductor material to a semiconductor substrate; separating the slice into a plurality of individual elements by forming narrow grooves extending through the slice of semiconductor material, but not through the substrate; forming a contact on each of the individual elements; patterning a metal film bonded to a thin sheet of high temperature plastic thereby forming a circuit sheet having a plurality of conductors extending to enlarged solder pads; and electrically connecting the contact on each element to a designated conductor on the circuit sheet, thereby forming an electrically operational array.

Claim 9

The process defined in claim 9 wherein the circuit sheet is patterned to form an array of conductive leads connecting each individual element to a separate lead extending outside of the circuit sheet.

Claim 10

The process for fabricating an array of very small, closely spaced semiconductor elements which comprises: bonding a thin slice of semiconductor material to a semiconductor substrate; forming narrow grooves extending through the slice of semiconductor material, but not through the substrate thereby separating the slice into a plurality of individual elements; forming a contact on each of the individual elements; patterning a copper layer thermocompression bonded to a thin flexible high temperature plastic sheet thereby formimg a circuit sheet having copper conductors thereon; plating the copper conductors with a gold layer; and electrically connecting the contact on each element to a designated conductor on the circuit sheet, thereby forming an electrically operational array.

Claim 11

The process defined in claim 11 wherein a jumper wire is thermocompression bonded to the contact on each element and to its respective conductor on the circuit sheet.

Claim 12

The process defined in claim 11 wherein the conductors on the circuit sheet are connected to the metal contacts on the individual elements by: placing a portion of each conductor against its respective contact; heating the contacts to a temperature of from about 150* C. to about 250* C.; and pressing the circuit sheet against the contact by a tool heated to a temperature sufficient to establish a thermocompression bond between the contact and its respective conductor on the circuit sheet.

Claim 13

The process for fabricating an array of very small closely spaced semiconductor elements which comprises: bonding a thin slice of semiconductor material to a semiconductor substrate; vacuum depositing a thin layer of chromium on the surface of the slice; vacuum depositing a relatively thick layer of gold on the chromium layer; vacuum depositing a second chromium layer on the gold layer; selectively removing the second chromium layer in all areas except where a gold contact is ultimately desired on the surface of the semiconductor material; forming narrow slots in the gold layer and underlying first chromium layer, thereby exposing that portion of the surface of the semiconductor material where deep narrow grooves are to be formed, separating the slice into a plurality of individual elements; subjecting the exposed area of the surface to an etching fluid directed through the slots, thereby forming cavities in the semiconductor material; concurrently with the forming of said cavity, periodically bending the edges of the mask left overhanging the cavity along the sides of the undercut area, partially protecting the sidewalls from contact by the etching fluid, and thereby forming deep narrow grooves extending through the slice of semiconductor material but not through the substrate; subjecting the slice to a selective etchant for the gold except where protected by the chromium of the second chromium layer; then subjecting the slice to a selective etchant for the chromium to remove the second chromium layer which is not protected by the gold, the remaining gold and underlying chromium forming electrical contacts for the respective elements; forming a circuit sheet which contains a plurality of conductors; and electrically connecting the contact on each individual element to a designated conductor on the circuit sheet.

Claim 14

The process defined in claim 14 wherein the substrate is comprised of a degenerate semiconductor material.

Claim 15

The process for fabricating a photodetector array of very small, closely spaced semiconductor detector elements which comprises: bonding a thin slice of photosensitive semiconductor material to a degenerate semiconductor substrate; separating the slice into a plurality of individual detector elements by forming narrow grooves extending through the slice of photosensitive semiconductive material, but not through the substrate; forming a contact on each of the individual detector elements; forming a circuit sheet suitable for use in a photodetector by patterning a copper layer thermocompression bonded to a thin flexible high temperature plastic sheet thereby forming an array of conductors; plating the copper conductors with a gold layer; and electrically connecting the contact on each element to a designated conductor on the circuit sheet.

Claim 16

The process defined in claim 16 wherein a jumper wire is thermocompression bonded to the contact on each element and to its respective conductor on the circuit sheet.

Claim 17

The process defined in claim 16 wherein the conductors on the circuit sheet are connected to the metal contacts on the individual elements by: placing a portion of each conductor against its respective contact; heating the contacts to a temperature of from about 150* C. to about 250* C.; and pressing the circuit sheet against the contact by a tool heated to a temperature sufficient to establish a thermocompression bond between the contact and its respective conductor on the circuit sheet.

Claim 18

The process for fabricating a photodetector array of very small, closely spaced semiconductor detector elements which comprises: alloying a thin slice of photosensitive semiconductor material to a degenerate semiconductor substrate; forming a malleable etching mask of an electrically conductive material on the surface of the slice having narrow slots therein, thereby exposing that portion of the surface of the photosensitive semiconductor material; subjecting the exposed portion of the surface to an etching fluid directed through the slots, thereby forming cavities in the semiconductor materials; concurrently with the forming of said cavities, periodically bending the edges of the mask left overhanging the cavities along the sides of the undercut area, partially protecting the sidewalls from contact by the etching fluid, and thereby forming deep narrow grooves extending through the slice of semiconductor material, but not through the substrate, separating the slice into a plurality of individual detector elements; removing only a portion of the mask to leave an electrically conductive contact on each element; patterning a metal film bonded to a thin flexible high temperature plastic sheet to form a plurality of conductors extending to enlarged solder pads, thereby forming a circuit sheet suitable for use in a photodetector; and electrically connecting the contact on each detector element to a designated conductor on the circuit sheet.

Claim 19

The process defined in claim 19 wherein the photosensitive semiconductor material is comprised of mercury-doped germanium and the semiconductor substrate is comprised of degenerate germanium.

Claim 20

The process for fabricating a photodetector array of very small, closely spaced semiconductor elements which comprises: alloying a thin slice of photosensitive semiconductor material to a degenerate semiconductor substrate; vacuum depositing a thin layer of chromium on the surface of the slice; vacuum depositing a relatively thick layer of gold on the chromium layer; vacuum depositing a second chromium layer on the gold layer; selectively removing the second chromium layer in all areas except where a gold contact is ultimately desired on the surface of the semiconductor material; forming narrow slots in the gold layer and underlying first chromium layer, thereby exposing that portion of the surface of the semiconductor material; subjecting the exposed area of the surface to an etching fluid directed through the slots, thereby forming cavities in the semiconductor material; concurrently with the forming of said cavities periodically bending the edges of the mask left overhanging the cavities along the sides of the undercut area, partially protecting the sidewalls from contact by the etching fluid, and thereby forming deep narrow grooves extending through the slice of semiconductor material, separating the slice into a plurality of individual detector elements; subjecting the slice to a selective etchant for the gold except where protected by the chromium of the second chromium layer but not through the substrate; subjecting the slice to a selective etchant for the chromium to remove the second chromium layer which is not protected by the gold, the remaining gold and underlying chromium forming electrical contacts for the respective detector elements; patterning a metal film bonded to a thin flexible high temperature plastic sheet to form a plurality of conductors extending to enlarged solder pads, thereby formimg a circuit sheet suitable for use in a photodetector; and electrically connecting the contact on each detector element to a designated conductor on the circuit sheet.

Claim 21

The process defined in claim 21 wherein the photosensitive semiconductor material is comprised of mercury-doped germanium and the semiconductor substrate is comprised of degenerate germanium.