Pad-out structure for semiconductor device and method of forming the same
The present disclosure provides a method of fabricating a semiconductor device. The method can include bonding a first die and a second die face to face, the first die including a substrate, transistors formed on a face side of the first die over a semiconductor layer with an insulating layer between the substrate and the semiconductor layer, and a first contact structure on the face side of the first die extending through the insulating layer. The method can also include exposing the first contact structure from the back side of the first die, forming, from the back side of the first die, a contact hole in the insulating layer to expose the semiconductor layer, and forming, on the back side of the first die, a first pad-out structure connected with the first contact structure and a second pad-out structure, on the contact hole, conductively connected with the semiconductor layer.
1. A method for fabricating a semiconductor device, comprising:
bonding a first die and a second die face to face, the first die including a first substrate, an insulating layer on a face side of the first substrate, a first contact structure on the face side of the first die extending through a first portion of the insulating layer, and a semiconductor layer on a face side of a second portion of the insulating layer, a portion of the insulating layer being disposed between the first contact structure and the semiconductor layer, and the portion of the insulating layer being in direct contact with the first contact structure and a side surface of the semiconductor layer that faces the first contact structure;
exposing the first contact structure from a back side of the first die by removing the first substrate from the back side of the first die;
forming, from the back side of the first die, a contact hole in the second portion of the insulating layer, the contact hole exposing the semiconductor layer; and
forming, on the back side of the first die, a first pad-out structure conductively connected with the first contact structure and a second pad-out structure on the contact hole that is conductively connected with the semiconductor layer.
2. The method of claim 1 , wherein forming the first pad-out structure and the second pad-out structure further comprises:
forming, from the back side of the first die, a first conductive layer over the first contact structure and the semiconductor layer, the first conductive layer filling the contact hole; and
patterning, from the back side of the first die, the first conductive layer to form the first pad-out structure conductively connected with the first contact structure and the second pad-out structure conductive connected with the semiconductor layer.
3. The method of claim 2 , wherein forming the first pad-out structure and the second pad-out structure further comprises:
forming a second conductive layer on a back side of the insulating layer, the second conductive layer interfacing the first conductive layer and the first contact structure and interfacing the first conductive layer and the semiconductor layer; and
patterning the second conductive layer using a same photomask as the first conductive layer.
4. The method of claim 3 , wherein:
the first conductive layer is made of a first metal material; and
the second conductive layer is made of a second metal material.
5. The method of claim 4 , wherein:
the first conductive layer comprises at least aluminum; and
the second conductive layer comprises at least titanium.
6. The method of claim 1 , wherein exposing the first contact structure from the back side of the first die further comprises:
removing an etch stop layer after removing the first substrate, the etch stop layer being sandwiched between the first substrate and the insulating layer.
7. The method of claim 1 , wherein:
the first die further includes memory cells formed on the face side of the semiconductor layer; and
the second die includes peripheral circuitry for the memory cells on a face side of a second substrate.
8. The method of claim 7 , wherein bonding the first die and the second die face to face further comprises:
bonding a first bonding structure connected with the first contact structure in the first die with a second bonding structure connected to an input/output circuit in the peripheral circuitry in the second die.
9. The method of claim 7 , wherein the second pad-out structure is configured to provide an array common source for the memory cells.
10. The method of claim 1 , wherein:
the second die includes memory cells disposed on the face side of the second die; and
the first die further includes peripheral circuitry for the memory cells.
11. A semiconductor device, comprising:
a first die and a second die bonded face to face, the first die including an insulating layer on a back side of the first die, a first contact structure extending from a face side of the first die through a first portion of the insulating layer, a semiconductor layer on a face side of a second portion of the insulating layer, and first transistors formed on a face side of the semiconductor layer, a portion of the insulating layer being disposed between the first contact structure and the semiconductor layer, and the portion of the insulating layer being in direct contact with the first contact structure and a side surface of the semiconductor layer that faces the first contact structure;
a first pad-out structure disposed on the back side of the first die, the first pad-out structure being electrically coupled with the first contact structure; and
a second pad-out structure disposed on the back side of the first die, the second pad-out structure being electrically coupled with the semiconductor layer.
12. The semiconductor device of claim 11 , wherein:
the first transistors include memory cells formed over the semiconductor layer on the face side of the first die; and
the second die includes a substrate and peripheral circuitry that is formed on the face side of the substrate for the memory cells.
13. The semiconductor device of claim 12 , wherein the memory cells comprise:
a stack of alternating word line layers and insulating layers; and
a plurality of channel structures extending through the stack, a channel structure including a channel layer surrounded by one or more insulating layer.
14. The semiconductor device of claim 13 , wherein:
the first die further includes a plurality of contact structures formed in a staircase region of the stack, the plurality of contact structures being coupled with the word line layers, the staircase region being on a boundary or in a middle of the stack.
15. The semiconductor device of claim 12 , wherein:
the first pad-out structure is coupled with an input/output circuit of the peripheral circuitry via the first contact structure, a bonding interface between the first die and the second die, and a corresponding second contact structure in the second die; and
the peripheral circuitry is coupled with the memory cells via corresponding third contact structures in the first die, the bonding interface, and corresponding fourth contact structures in the second die.
16. The semiconductor device of claim 12 , wherein the second pad-out structure is configured to provide an array common source for the memory cells.
17. The semiconductor device of claim 11 , wherein:
the second die further includes memory cells formed on a face side of a substrate;
the first transistors include peripheral circuitry, formed on the face side of the first die, for the memory cells;
the first pad-out structure is coupled with an input/output circuit of the peripheral circuitry via the first contact structure; and
the peripheral circuitry is coupled with the memory cells via corresponding contact structures in the first die, a bonding interface between the first die and the second die, and corresponding contact structures in the second die.
18. The semiconductor device of claim 11 , wherein:
the first pad-out structure includes a first portion of a first conductive layer;
the second pad-out structure includes a second portion of the first conductive layer;
the first portion of the first conductive layer is spaced apart from the second portion of the first conductive layer; and
the first conductive layer is made of a first metal material.
19. The semiconductor device of claim 18 , wherein:
the first pad-out structure further includes a first portion of a second conductive layer disposed between the first contact structure and the first portion of the first conductive layer;
the second pad-out structure further includes a second portion of the second conductive layer disposed between the semiconductor layer and the second portion of the second conductive layer;
the first portion of the second conductive layer is spaced apart from the second portion of the second conductive layer; and
the second conductive layer is made of a second metal material.
20. The semiconductor device of claim 19 , wherein:
the first metal material is made of aluminum; and
the second metal material is made of titanium.