SEMICONDUCTOR BUMP-BONDED X-RAY IMAGING DEVICE
A high pixel density intraoral x-ray imaging sensor includes a direct conversion, fully depleted silicon detector bump bonded to a readout CMOS substrate by capillary bump bonds.
1 . An intraoral x-ray imaging sensor, comprising:
a silicon (Si) detector substrate with detector pixels thereon, said Si detector substrate for converting incident radiation directly to an electronic signal;
a readout substrate with readout pixel circuits thereon for receiving, storing and reading said electronic signals;
rigid bump bonds that interconnect said Si detector substrate and readout substrate to one another.
2 . An x-ray imaging device comprising:
a direct conversion detector substrate having detector pixels for collecting electronic signals generated in response to incident radiation; a readout substrate having readout pixels for receiving said electronic signals; and
capillary bump bonds connecting said detector pixels and readout pixels.
3 . An x-ray imaging device according to claim 2 , wherein a center to center distance ( 300 ) between the capillary bump bonds is less than or equal to 75 um and a post bonding height ( 310 ) is more than or equal to 5 um.
4 . An x-ray imaging device according to claim 2 , wherein a center to center distance ( 300 ) between the capillary bump bonds is less than or equal to 25 um and a post bonding height ( 310 ) is more than or equal to 8 um.
5 . An x-ray imaging device according to claim 2 , wherein the capillary bump bonds comprise a rigid bump leg ( 8 ) and a bump solder hat ( 6 ) positioned on top of the bump leg.
6 . An x-ray imaging device according to claim 5 , wherein a height of the bump leg ( 8 ) is 5 um or more.
7 . An x-ray imaging device according to claim 5 , wherein the bump leg comprises copper (Cu).
8 . An x-ray imaging device according to claim 5 , wherein the bump solder hat ( 6 ) comprises Tin (Sn), Bismuth Tin (BiSn), Lead Tin (PbSn), or Silver Tin (AgSn).
9 . An x-ray imaging device according to claim 1 , wherein,
the rigid bonds comprise capillary bonds, said capillary bonds being comprised of i) a rigid bump leg ( 8 ) and ii) a bump solder hat ( 6 ) positioned on top of the bump leg, and
the bump leg being sufficiently rigid that during a bonding process at a temperature from 70 C to 250 C with the bump solder hat being squeezed, the bump leg stays rigid and maintains an initial height of the bump leg.
10 . An x-ray imaging device according to claim 9 , wherein, the bump solder hat has a cross-section shape of a compressed spherical shape, with upper and lower surfaces that are generally flat and parallel, and arcuate end surfaces connecting the upper and lower surfaces.
11 . An x-ray imaging device according to claim 9 , wherein, the bump solder hat has a cross-section shape of a cross-section shape of a compressed ellipsoidal structure compressed along a minor axis, with upper and lower surfaces that are generally flat and parallel, and arcuate end surfaces connecting the upper and lower surfaces.
12 . An x-ray imaging device according to claim 9 , wherein,
each rigid bond further comprises a pad ( 12 ), a passivation layer ( 11 ) on the pad ( 12 ), the passivation layer having openings to the pad ( 12 ), said opening having a first diameter (g), a bump seed adhesion layer ( 10 ) on the passivation layer, the bump seed adhesion layer ( 10 ) having with an inner second diameter (h) and an outer third diameter (i), a bump seed bulk metal ( 9 ) with a fourth diameter (i), wherein the rigid bump leg ( 8 ) is mounted in contact on the bump seed bulk metal ( 9 ), a bump pedestal layer ( 7 ) with a fifth diameter (b) in contact on the rigid bump leg, and the bump solder hat in contact on the bump pedestal layer ( 7 ),
a width of the pad ( 12 ) and a width of the passivation layer ( 11 ) are the same, and
and a width of the rigid bump leg ( 8 ) is less than the width of the pad ( 12 ) and the width of the passivation layer ( 11 ).
13 . An x-ray imaging device according to claim 12 , wherein,
said Si detector substrate comprises, for each said rigid bond, a detector pad ( 1 ), through the detector pad the signal from the direct conversion of x-ray to electron-hole pairs is collected, a detector passivation layer ( 2 ) in contact on the detector pad ( 1 ), an under bump metalization (UBM) adhesion layer ( 3 ) on the detector passivation layer ( 2 ), a bulk under bump metalization layer ( 4 ) against the under bump metalization (UBM) adhesion layer ( 3 ), and a solder pad ( 5 ) contacting the bulk under bump metalization layer ( 4 ) and the bump solder hat,
the solder pad ( 5 ) having a sixth diameter (c), the sixth diameter (c) being greater than the fifth diameter (b).
14 . An x-ray imaging device according to claim 13 , wherein,
a center to center distance ( 300 ) between most-adjacent capillary bump bonds is less than or equal to 75 um,
and a post bonding height ( 310 ) between opposite surface of the silicon detector substate and the readout substrate is within a range of 5 um to 8 um.
15 . An x-ray imaging device according to claim 13 , wherein,
a center to center distance ( 300 ) between most-adjacent capillary bump bonds is less than or equal to 25 um, and
a post bonding height ( 310 ) between opposite main surfaces of the silicon detector substate and the readout substrate is more than or equal to 5 um.
16 . An x-ray imaging device according to claim 15 , wherein,
the post bonding height of the bump leg ( 8 ) is 8 um,
the post bonding height of the solder hat ( 6 ) is less than 6.5 um, and
the post bonding height of the bump pedestal ( 7 ) is 1.6 um.
17 . An x-ray imaging device according to claim 15 , wherein the post bonding height of the bump leg ( 8 ) is 5 um.
18 . An x-ray imaging device according to claim 10 , wherein,
a center to center distance ( 300 ) between most-adjacent capillary bump bonds is less than or equal to 25 um, and
a post bonding height ( 310 ) between opposite main surfaces of the silicon detector substate and the readout substrate is between 10 um and 15 um, and
the post bonding height of the bump leg ( 8 ) is between 5 um and 8 um.
19 . An x-ray imaging device according to claim 11 , wherein,
a center to center distance ( 300 ) between most-adjacent capillary bump bonds is less than or equal to 25 um,
a post bonding height ( 310 ) between opposite main surfaces of the silicon detector substate and the readout substrate is between 10 um and 15 um, and
the post bonding height of the bump leg ( 8 ) is between 5 um and 8 um.
20 . An x-ray imaging device according to claim 9 , wherein,
a center to center distance ( 300 ) between most-adjacent capillary bump bonds is less than or equal to 25 um, and
a post bonding height ( 310 ) between opposite main surfaces of the silicon detector substate and the readout substrate is 10 um to 15 um.