Plasma-based method for delayering of circuits
The present invention relates to methods of delayering a semiconductor integrated circuit die or wafer. In at least one aspect, the method includes exposing a die or wafer to plasma of an etching gas and detecting exposure of one or more metal layers within the die. In one aspect of the invention, the plasma of the etching gas is non-selective and removes all materials in a layer at about the same rate. In another aspect of the invention, two different plasmas of corresponding etching gases are employed with each plasma of the etching gas being selective, thus necessitating the sequential use of both plasmas of corresponding etching gases to remove all materials in a layer.
1 . A method comprising:
providing a die, the die including:
a device layer;
a conductive layer including:
a first metal layer in proximity to a back-side surface of the conductive layer, the first metal layer including:
a first metal portion; and
a first intralayer dielectric;
a second metal layer in proximity to a front-side surface of the conductive layer, the second metal layer including:
a second metal portion; and
a second intralayer dielectric;
a plurality of first vias disposed between the first metal layer and the second metal layer; and
a first interlayer dielectric disposed between the first metal layer and the second metal layer; and
a contact layer including:
a passivation layer;
a third metal layer; and
a second interlayer dielectric disposed between the second metal layer and the third metal layer;
wherein the conductive layer is disposed between a front-side surface of the device layer and a back-side surface of the contact layer;
etching at least a portion of a front-side surface of the contact layer to expose at least a portion of the second metal layer, thereby providing an etched die;
exposing the etched die to a first inductively coupled plasma employing a first etching gas, the first inductively coupled plasma employing the first etching gas producing a first plasma etch, the first plasma etch chemically and physically removing at least a portion of the second metal layer, the first plasma etch being non-selective, the first plasma etch adapted to remove the second metal portion and the second intralayer dielectric at about the same rate;
exposing the etched die to a second inductively coupled plasma employing a second etching gas, the second inductively coupled plasma employing the second etching gas producing a second plasma etch, the second plasma etch chemically and physically removing at least a portion of the plurality of first vias and a portion of the first interlayer dielectric, the second plasma etch being non-selective, the second plasma etch adapted to remove the plurality of first vias and the first interlayer dielectric at about the same rate; and
detecting exposure of the first metal layer, thereby providing a delayered die.
2 . The method of claim 1 , wherein the etching step includes removing at least a portion of the passivation layer or at least a portion of the third metal layer.
3 . The method of claim 1 , wherein the etching step includes polishing at least a portion of the front-side surface of the contact layer to remove at least a portion of the passivation layer or at least a portion of the third metal layer.
4 . The method of claim 1 , wherein at least one of the first etching gas and the second etching gas includes at least one of a hydrocarbon, a halogen, a fluorocarbon, a carbonyl, and an acetate.
5 . The method of claim 1 , wherein the contact layer further includes a planarization layer disposed on a front-side surface of the passivation layer.
6 . The method of claim 1 , further comprising, after the providing step:
depositing a planarization layer on a front-side surface of the contact layer;
wherein the etching step includes etching at least a portion of the planarization layer.
7 . The method of claim 1 , further comprising, after the detecting exposure step:
exposing the delayered die to a third inductively coupled plasma employing a third etching gas, the third inductively coupled plasma employing the third etching gas producing a third plasma etch, the third plasma etch chemically and physically removing at least a portion of the first metal layer, the third plasma etch being non-selective, the third plasma etch adapted to remove the first metal portion and the first intralayer dielectric at about the same rate.
8 . The method of claim 7 , wherein the conductive layer further includes:
a plurality of third vias disposed between the device layer and the first metal layer; and
a third interlayer dielectric disposed between the device layer and the first metal layer.
9 . The method of claim 8 , further comprising, after the exposing the delayered die to a third plasma etch step:
exposing the delayered die to a fourth inductively coupled plasma employing a fourth etching gas, the fourth inductively coupled plasma employing the fourth etching gas producing a fourth plasma etch, the fourth plasma etch chemically and physically removing at least a portion of the plurality of third vias and a portion of the third interlayer dielectric, the fourth plasma etch being non-selective, the fourth plasma etch adapted to remove the plurality of third vias and the third interlayer dielectric at about the same rate.