Memory device structure and fabrication method
A 3D memory device includes a complementary metal-oxide-semiconductor (CMOS) structure having a page buffer region and a string driver region respectively corresponding to a cell region and a string region in an array structure, wherein the CMOS structure further includes a plurality of page buffers in a folded structure formed in the page buffer region; and string driver circuits formed in the string region.
1 . A three-dimensional (3D) memory device, comprising:
a complementary metal-oxide-semiconductor (CMOS) structure having a page buffer region and a string driver region respectively corresponding to a cell region and a string region in an array structure,
wherein the CMOS structure further includes a plurality of page buffers in a folded structure formed in the page buffer region; and string driver circuits formed in the string region, wherein
each page buffer of the plurality of the page buffers includes at least two unfolded portions and at least one folding portion; and
the plurality of page buffers in the folded structure are aligned at a first device pitch, and the unfolded portions of the page buffers are aligned at a second device pitch, the first device pitch being greater than the second device pitch.
2 . The 3D memory device according to claim 1 , wherein:
the 3D memory device further includes the array structure combined with the CMOS structure; and
the array structure includes a plurality of memory cells formed in the cell region, and a string structure formed in the string region.
3 . The 3D memory device according to claim 2 , wherein:
the array structure is an array wafer and the CMOS structure is a CMOS wafer;
the array wafer and the CMOS wafer are combined via a bonding interface between an array joint layer of the array wafer and a CMOS joint layer of the CMOS wafer, and
the array joint layer of the array wafer to the CMOS joint layer of the CMOS wafer are bonded together and one or more joint structures on the array joint layer of the array wafer and one or more joint structures on the CMOS joint layer of the CMOS wafer are bonded together for electrical connection.
4 . The 3D memory device according to claim 3 , wherein the 3D memory device further comprises:
an insulating layer formed over the array wafer;
at least one through substrate contact penetrating the array wafer; and
one or more array pads in contact with the at least one through substrate contact.
5 . The 3D memory device according to claim 1 , wherein the array structure has a plurality of bit lines formed in the cell region aligned at a bit line pitch.
6 . The 3D memory device according to claim 5 , wherein the first device pitch of the page buffers in the folded structure is measured as the bit line pitch multiplied by a first pre-determined number.
7 . The 3D memory device according to claim 6 , wherein
the second device pitch of the unfolded portions of the page buffers is measured as the bit line pitch multiplied by a second pre-determined number; and
the first pre-determined number is greater than the second pre-determined number.
8 . The 3D memory device according to claim 7 , wherein the first pre-determined number is twice of the second pre-determined number.
9 . The 3D memory device according to claim 8 , wherein the first pre-determined number is 8, and the second pre-determined number is 4.
10 . The 3D memory device according to claim 7 , wherein each of the plurality of page buffers includes a plurality of devices and wiring channels, the devices are aligned at the second device pitch, and the wiring channels are aligned at the first device pitch.
11 . The 3D memory device according to claim 10 , wherein the devices include sources, drains, and gates of CMOS transistors, and the at least one folding portion includes shared sources and/or drains.
12 . The 3D memory device according to claim 11 , wherein the CMOS transistors are fin field-effect transistors having different fin heights.
13 . The 3D memory device according to claim 7 , wherein:
each of the page buffer of the plurality of the page buffers has three unfolded portions and two folding portions; and
the first pre-determined number is three times of the second pre-determined number.
14 . A memory system, comprising:
a 3D memory device, including a complementary metal-oxide-semiconductor (CMOS) structure having a page buffer region and a string driver region respectively corresponding to a cell region and a string region in an array structure, a plurality of page buffers in a folded structure formed in the page buffer region; and string driver circuits formed in the string region, wherein
each page buffer of the plurality of the page buffers includes at least two unfolded portions and at least one folding portion; and
the plurality of page buffers in the folded structure are aligned at a first device pitch, and the unfolded portions of the page buffers are aligned at a second device pitch, the first device pitch being greater than the second device pitch;
a memory controller coupled to the 3D memory device for controlling the 3D memory device; and
an external interface for communicating with a host for storing information in the 3D memory device.
15 . The memory system according to claim 14 , wherein:
the 3D memory device further includes the array structure combined with the CMOS structure; and
the array structure includes a plurality of memory cells formed in the cell region, and a string structure formed in the string region.
16 . The memory system according to claim 14 , wherein the external interface includes one of universal serial bus (USB), secure digital (SD), compact flash (CF), solid state drive (SSD), and embedded multi-media-card (eMMC).
17 . A method for forming a three-dimensional (3D) memory device, comprising:
forming an array wafer having a cell region and a string region, including: providing a first substrate having the cell region and the string region; forming a plurality of memory cells on the first substrate in the cell region; and forming a string structure on the first substrate in the string region;
forming a complementary metal-oxide-semiconductor (CMOS) wafer having a page buffer region and a string driver region respectively corresponding to the cell region and the string region, including: providing a second substrate having the page buffer region and the string driver region; forming a plurality of page buffers in a folded structure in the page buffer region; and forming string driver circuits in the string region, wherein
each page buffer of the plurality of the page buffers includes at least two unfolded portions and at least one folding portion; and
the plurality of page buffers in the folded structure are aligned at a first device pitch, and the unfolded portions of the page buffers are aligned at a second device pitch, the first device pitch being greater than the second device pitch;
bonding the array wafer and the CMOS wafer at a bonding interface; and
forming the 3D memory device based on the bonded array wafer and CMOS wafer.
18 . The method according to claim 17 , wherein:
forming the array wafer further comprises:
forming a plurality of bit lines in the cell region in connection with the plurality of memory cells, wherein the bit lines are aligned at a bit line pitch; and
the first device pitch of the page buffers in the folded structure is measured as the bit line pitch multiplied by a first pre-determined number.
19 . The method according to claim 18 , wherein
the second device pitch of the unfolded portions of the page buffers is measured as the bit line pitch multiplied by a second pre-determined number; and
the first pre-determined number is greater than the second pre-determined number.
20 . The method according to claim 19 , wherein forming a plurality of page buffers in a folded structure in the page buffer region further comprises:
forming a plurality of devices and wiring channels in each of the plurality of page buffers, wherein the devices are aligned at the second device pitch, and the wiring channels are aligned at the first device pitch.