U.S. patent application number 16/808450 was filed with the patent office on 2021-03-04 for semiconductor storage device.
This patent application is currently assigned to Kioxia Corporation. The applicant listed for this patent is Kioxia Corporation. Invention is credited to Hiroshi KANNO.
Application Number | 20210066340 16/808450 |
Document ID | / |
Family ID | 1000004691361 |
Filed Date | 2021-03-04 |
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United States Patent
Application |
20210066340 |
Kind Code |
A1 |
KANNO; Hiroshi |
March 4, 2021 |
SEMICONDUCTOR STORAGE DEVICE
Abstract
The semiconductor storage device of an embodiment includes a
first conductive layer, a stack disposed above the first conductive
layer and including a plurality of second conductive layers in a
first direction, and a columnar body that extends in the first
direction through the stack, and includes a semiconductor layer and
a charge storage film provided between the plurality of conductive
layers and the semiconductor layer. A first conductive layer out of
the plurality of conductive layers is connected to the
semiconductor layer, and the semiconductor layer includes a first
region in which a concentration of an n-type impurity is higher
than a concentration of a p-type impurity, a second region in which
a concentration of a p-type impurity is higher than a concentration
of an n-type impurity, and a third region contacted to the first
conductive layer and disposed closer to the first region than the
second region in the first direction.
Inventors: |
KANNO; Hiroshi; (Yokkaichi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kioxia Corporation |
Minato-ku |
|
JP |
|
|
Assignee: |
Kioxia Corporation
Minato-ku
JP
|
Family ID: |
1000004691361 |
Appl. No.: |
16/808450 |
Filed: |
March 4, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/1041 20130101;
H01L 27/11582 20130101 |
International
Class: |
H01L 27/11582 20060101
H01L027/11582; H01L 29/10 20060101 H01L029/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2019 |
JP |
2019-157156 |
Claims
1. A semiconductor storage device, comprising: a first conductive
layer; a stack disposed above the first conductive layer and
including a plurality of second conductive layers stacked in a
first direction; and a columnar body that extends in the first
direction through the stack, and includes a semiconductor layer and
a charge storage film disposed between the plurality of conductive
layers and the semiconductor layer, the first conductive layer is
in contact with the semiconductor layer, the semiconductor layer
includes a first region in which a concentration of an n-type
impurity is higher than a concentration of a p-type impurity, a
second region in which a concentration of the p-type impurity is
higher than a concentration of the n-type impurity, and a third
region contacted to the first conductive layer and disposed closer
to the first region than the second region in the first
direction.
2. The semiconductor storage device according to claim 1, wherein
the first region extends from the boundary between the first
conductive layer and the semiconductor layer in the first
direction.
3. The semiconductor storage device according to claim 1, wherein
the semiconductor layer further includes a third region, and the
third region does not contain the n-type impurity and the p-type
impurity or has a lower concentration of the p-type impurity and
the n-type impurity than the second region.
4. The semiconductor storage device according to claim 1, wherein a
concentration of the n-type impurity at the boundary between the
first conductive layer and the semiconductor layer is higher than a
concentration of the n-type impurity at a boundary between the
first region and the second region.
5. The semiconductor storage device according to claim 1, wherein
the concentration of the n-type impurity of the semiconductor layer
decreases with distance from the boundary between the first
conductive layer and the semiconductor layer in the first
direction.
6. The semiconductor storage device according to claim 1, wherein
the concentration of the p-type impurity of the semiconductor layer
decreases with distance from the boundary between the first
conductive layer and the semiconductor layer in the first
direction.
7. The semiconductor storage device according to claim 1, wherein
the first conductive layer includes a first portion and a second
portion, the first portion contains the n-type impurity, the second
portion contains the p-type impurity, and at least a portion of the
second portion is disposed between the first portion and the
semiconductor layer.
8. The semiconductor storage device according to claim 7, wherein
the first conductive layer further includes a third portion, the
third portion contains a carbon element, and at least a portion of
the third portion is disposed between the first portion and the
second portion.
9. The semiconductor storage device according to claim 7, wherein
the first portion further contains a carbon element.
10. The semiconductor storage device according to claim 1, wherein
the stack includes a second conductive layer closest to the first
conductive layer, and at least a portion of the second region falls
within a range of a height of the second conductive layer in the
first direction.
11. The semiconductor storage device according to claim 1, wherein
the stack includes a first stack and a second stack in order of
proximity to the first conductive layer, and at least a portion of
the second region falls within a range of a height of the first
stack in the first direction.
12. The semiconductor storage device according to claim 1, wherein
the first region is an n-type semiconductor.
13. The semiconductor storage device according to claim 1, wherein
the second region is a p-type semiconductor.
14. The semiconductor storage device according to claim 1, wherein
the n-type impurity contains phosphorus.
15. The semiconductor storage device according to claim 1, wherein
the p-type impurity contains boron.
16. The semiconductor storage device according to claim 1, wherein
the stack is disposed on a logic circuit.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2019-157156, Aug. 29,
2019; the entire contents of which are incorporated herein by
reference.
FIELD
[0002] An embodiment of the present invention relates to a
semiconductor storage device.
BACKGROUND
[0003] A NAND-type flash memory in which memory cells are laminated
three-dimensionally is known.
[Patent Document]
[0004] [Patent Document 1] Specification of U.S. Pat. No.
9,520,407
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a block diagram illustrating a circuit
configuration of a semiconductor storage device according to a
first embodiment.
[0006] FIG. 2 is a circuit diagram of a memory cell array of the
semiconductor storage device according to the first embodiment.
[0007] FIG. 3 is a layout diagram of the semiconductor storage
device according to the first embodiment.
[0008] FIG. 4 is a plan view of the vicinity of a cell array region
according to the first embodiment.
[0009] FIG. 5 is a cross-sectional view along plane A-A' in FIG.
4.
[0010] FIG. 6 is an enlarged cross-sectional view illustrating the
vicinity of a memory pillar of the semiconductor storage device
according to the first embodiment.
[0011] FIG. 7 is an enlarged cross-sectional view obtained by
cutting the vicinity of the memory pillar of the semiconductor
storage device according to the first embodiment along a conductive
layer.
[0012] FIG. 8 is an enlarged cross-sectional view illustrating a
feature portion of the semiconductor storage device according to
the first embodiment.
[0013] FIG. 9 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0014] FIG. 10 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0015] FIG. 11 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0016] FIG. 12 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0017] FIG. 13 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0018] FIG. 14 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0019] FIG. 15 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0020] FIG. 16 is a cross-sectional view illustrating an example of
a method of manufacturing the semiconductor storage device
according to the first embodiment.
[0021] FIG. 17 is a diagram schematically illustrating a band
structure of a semiconductor layer in a memory cell array according
to a comparative example.
[0022] FIG. 18 is a diagram schematically illustrating a band
structure of a semiconductor layer in the memory cell array
according to the first embodiment.
[0023] FIG. 19 is an enlarged cross-sectional view illustrating a
feature portion of a semiconductor storage device according to a
first modification example.
[0024] FIG. 20 is an enlarged cross-sectional view illustrating a
feature portion of a semiconductor storage device according to a
second modification example.
[0025] FIG. 21 is an enlarged cross-sectional view illustrating a
feature portion of a semiconductor storage device according to a
third modification example.
DETAILED DESCRIPTION
[0026] A semiconductor storage device of an embodiment includes: a
first conductive layer; a stack disposed above the first conductive
layer and including a plurality of second conductive layers stacked
in a first direction; and a columnar body that extends in the first
direction through the stack, and includes a semiconductor layer and
a charge storage film disposed between the plurality of conductive
layers and the semiconductor layer. The first conductive layer is
in contact with the semiconductor layer. The semiconductor layer
includes a first region in which a concentration of an n-type
impurity is higher than a concentration of a p-type impurity, a
second region in which a concentration of the p-type impurity is
higher than a concentration of the n-type impurity, and a third
region contacted to the first conductive layer and disposed closer
to the first region than the second region in the first
direction.
[0027] Hereinafter, a semiconductor storage device of an embodiment
will be described with reference to the accompanying drawings. In
the following description, components having the same or similar
functions are denoted by the same reference numerals and signs.
Repeated description of these components may be omitted. The
drawings are schematic or conceptual, and a relationship between
the thickness and the width of each portion, a size ratio between
the components, and the like are not necessarily identical to those
in reality. In the present specification, the term "connection" is
not limited to a case of physical connection, and also includes a
case of electrical connection. In the present specification, the
wording "extend in an A direction" means that, for example,
dimensions in an A direction are larger than the smallest
dimensions out of respective dimensions in an X direction, a Y
direction, and a Z direction to be described later. The "A
direction" is any direction.
[0028] In addition, first, the X direction, the Y direction, the Z
direction will be defined. The X direction and the Y direction are
directions that are approximately parallel to the surface of a
substrate to be described later (see FIG. 1). The X direction is a
direction in which a slit to be described later extends. The Y
direction is a direction that intersects (that is, for example,
approximately orthogonal to) the X direction. The Z direction is a
direction that intersects (that is, for example, approximately
orthogonal to) the X direction and the Y direction and is away from
a substrate 30. These expressions are for convenience only, and do
not specify the direction of gravity. In the present embodiment,
the Z direction is an example of a "first direction."
First Embodiment
[0029] FIG. 1 is a block diagram illustrating a system
configuration of a semiconductor memory 1. The semiconductor memory
1 is a non-volatile semiconductor storage device, and is, for
example, a NAND-type flash memory. The semiconductor memory 1
includes, for example, a memory cell array 10, a row decoder 11, a
sense amplifier 12, and a sequencer 13.
[0030] The memory cell array 10 includes a plurality of blocks BLK0
to BLKn (n is an integer equal to or greater than 1). The block BLK
is a set of non-volatile memory cell transistors MT (see FIG. 2).
The memory cell array 10 is disposed with a plurality of bit lines
and a plurality of word lines. Each of the memory cell transistors
MT is connected to one bit line and one word line. The detailed
configuration of the memory cell array 10 will be described
later.
[0031] The row decoder 11 selects one block BLK on the basis of
address information ADD received from an external memory controller
2. The row decoder 11 applies a desired voltage to each of the
plurality of word lines, to thereby control a write operation and a
read operation of data for the memory cell array 10.
[0032] The sense amplifier 12 applies a desired voltage to each bit
line in accordance with write data DAT received from the memory
controller 2. The sense amplifier 12 determines data stored in the
memory cell transistor MT on the basis of the voltage of a bit
line, and transmits the determined read data DAT to the memory
controller 2.
[0033] The sequencer 13 controls the operation of the entirety of
the semiconductor memory 1 on the basis of a command CMD received
from the memory controller 2.
[0034] A combination of the semiconductor memory 1 and the memory
controller 2 described above may constitute one semiconductor
device. The semiconductor device is a memory card such as, for
example, an SD (registered trademark) card, a solid-state drive
(SSD), or the like.
[0035] Next, the electrical configuration of the memory cell array
10 will be described. FIG. 2 is a diagram illustrating an
equivalent circuit of the memory cell array 10, and shows one
extracted block BLK. The block BLK includes a plurality of (for
example, four) string units SU0 to SU3.
[0036] Each of the string units SU0 to SU3 is a set of a plurality
of NAND strings NS. One end of each NAND string NS is connected to
any of bit lines BL0 to BLm (in is an integer equal to or greater
than 1). The other end of each NAND string NS is connected to a
source line SL. NAND string NS respectively includes a plurality of
(for example, eighteen) memory cell transistors MT0 to MT17, a
first selection transistor S1, and a second selection transistor
S2.
[0037] The plurality of memory cell transistors MT0 to MT17 are
electrically connected to each other in series. The memory cell
transistor MT includes a control gate and a charge storage film,
and stores data in a non-volatile manner. The memory cell
transistor MT stores charges in the charge storage film in
accordance with a voltage applied to the control gate. The control
gate of the memory cell transistor MT is connected to any of
corresponding word lines WL0 to WL17. The memory cell transistor MT
is electrically connected to the row decoder 11 through the word
line WL.
[0038] The first selection transistor S1 in each NAND string NS is
connected between the plurality of memory cell transistors MT0 to
MT17 and any of the bit lines BL0 to BLm. The drain of the first
selection transistor S1 is connected to any of the bit lines BL0 to
BLm. The source of the first selection transistor S1 is connected
to the memory cell transistor MT17. The control gate of the first
selection transistor S1 in each NAND string NS is connected to any
of selection gate lines SGD0 to SGD3. The first selection
transistor S1 is electrically connected to the row decoder 11
through the selection gate line SGD. When a predetermined voltage
is applied to any of the selection gate lines SGD0 to SGD3, the
first selection transistor S1 connects the NAND string NS and the
bit lines BL.
[0039] The second selection transistor S2 in each NAND string NS is
connected between the plurality of memory cell transistors MT0 to
MT17 and the source line SL. The drain of the second selection
transistor S2 is connected to the memory cell transistor MT0. The
source of the second selection transistor S2 is connected to the
source line SL. The control gate of the second selection transistor
S2 is connected to a selection gate line SGS. The second selection
transistor S2 is electrically connected to the row decoder 11
through the selection gate line SGS. When a predetermined voltage
is applied to the selection gate line SGS, the second selection
transistor S2 connects the NAND string NS and the source line
SL.
[0040] Next, the structure of the memory cell array 10 will be
described. FIG. 3 is a layout diagram of a memory cell array of a
semiconductor storage device according to a first embodiment. The
memory cell array 10 includes a cell array region CA, a bit line
hookup region BHU, a word line hookup region WHU, a contact region
CRI, and a contact region CRE.
[0041] The number of cell array regions CA is plural, and the cell
array regions CA are arranged in a matrix in the X direction and
the Y direction. The bit line hookup region BHU is disposed between
the cell array regions CA adjacent to each other in the Y
direction. The word line hookup region WHU extends in the Y
direction, and is disposed at the end portion of the cell array
regions CA in the X direction. The contact region CRE extends in
the Y direction, and is disposed on the opposite side to the cell
array regions CA with reference to the word line hookup region WHU.
The contact region CR1 extends in the Y direction, and is disposed
between the cell array regions CA and the bit line hookup regions
BHU which are adjacent to each other in the X direction.
[0042] A plurality of bit lines BL extending in the Y direction are
arranged above the bit line hookup regions BHU and the cell array
regions CA in the X direction. Further, a plurality of word lines
WL extending in the X direction are arranged above the word line
hookup region WHU in the Y direction.
[0043] Next, the planar structure of a feature portion of the
memory cell array 10 will be described. FIG. 4 is a plan view of
the vicinity of the cell array regions CA. FIG. 4 is an enlarged
plan view of the vicinity of two cell array regions CA between
which the bit line hookup region BHU is interposed in the Y
direction.
[0044] A slit ST1 is between the bit line hookup region BHU and
each of the cell array regions CA. The slit ST1 electrically
isolates the cell array region CA from the bit line hookup region
BHU. The slit ST1 extends in the X direction and the Z direction.
The slit ST1 divides the memory cell array 10 into a plurality of
blocks BLK0 to BLKn.
[0045] Each of the cell array regions CA is with a plurality of
memory pillars MP and slits SLT. In the present embodiment, the
memory pillars MP are an example of a "columnar body." The memory
pillars MP are dotted within the cell array region CA. The
plurality of memory pillars MP are disposed, for example, in a
staggered form. The slits SLT extend in the X direction and the Z
direction. The slits SLT divide the plurality of memory pillars MP
within the cell array region CA in the Y direction.
[0046] The word line hookup region WHU is with a plurality of
contact plugs CC. Each of the contact plugs CC is electrically
connected to a plurality of word lines WL disposed above the
contact plug CC.
[0047] The bit line hookup region BHU is with a plurality of
contact plugs CP1. The plurality of contact plugs CP1 are dotted
within the bit line hookup region BHU. Each of the contact plugs
CP1 is electrically connected to a plurality of bit lines BL. Each
of the bit lines BL is electrically connected to any of the memory
pillars MP and the contact plugs CP1.
[0048] The contact region CRE is with a plurality of contact plugs
CP2. The contact plug CP2 is electrically connected to an
interconnection layer (not shown) which is another layer.
[0049] Next, the cross-sectional structure of a feature portion of
the memory cell array 10 will be described. FIG. 5 is a
cross-sectional view along plane A-A' in FIG. 4.
[0050] The memory cell array 10 shown in FIG. 5 includes the
substrate 30, a circuit layer PE, a stack 40, a cover insulating
layer 50, the bit line BL, the memory pillar MP, the contact plug
CP1, the slits ST1 and SLT, and vias V1 and V2.
[0051] The substrate 30 is, for example, a silicon substrate. There
is a plurality of element isolation regions 30A in the surface
region of the substrate 30. The element isolation regions 30A
contain, for example, a silicon oxide. There are the source region
and the drain region of a transistor Tr between the element
isolation regions 30A adjacent to each other.
[0052] The circuit layer PE is on the substrate 30. The circuit
layer PE includes the row decoder 11, the sense amplifier 12, and
the sequencer 13 of the semiconductor memory 1. The circuit layer
PE includes, for example, a plurality of transistors Tr, a
plurality of interconnection layers D0 and D1, and a plurality of
vias C1 and C2. The plurality of transistors Tr, the plurality of
interconnection layers D0 and D1, and the plurality of vias C1 and
C2 are disposed within an insulating layer E1. The insulating layer
E1 contains, for example, a silicon oxide. The via C1 connects the
source region or the drain region of the transistor Tr and the
interconnection layer D0. The via C2 connects the gate region of
the transistor Tr and the interconnection layer D1. Each of the
interconnection layer D0 and the interconnection layer D1 extends
in the X direction and the Y direction. The interconnection layer
D1 is connected to the contact plug CP1. The vias C1 and C2 and the
interconnection layers D0 and D1 contain, for example,
tungsten.
[0053] The stack 40 includes a plurality of conductive layers 41,
43, and 45 and a plurality of insulating layers 42 and 44 in the Z
direction. The conductive layers 41, 43, and 45 and the insulating
layers 42 and 44 are alternately laminated. The plurality of
conductive layers 41, 43, and 45 extend in the X direction and the
Y direction. The plurality of insulating layers 42 and 44 extend in
the X direction and the Y direction.
[0054] The conductive layer 41 is closest to the circuit layer PE
among a plurality of conductive layers. The conductive layer 41 is
an example of a first conductive layer. The conductive layer 41
includes semiconductor layers 41A, 41B, and 41C. The semiconductor
layer 41A is on the circuit layer PE. The semiconductor layer 41B
is on the semiconductor layer 41A. The semiconductor layer 41C is
on the semiconductor layer 41B. The details of the semiconductor
layers 41A, 41B, and 41C will be described later.
[0055] The conductive layer 43 is closest to the circuit layer PE
next to the conductive layer 41 among a plurality of conductive
layers. The conductive layer 43 is, for example, a metal or a
semiconductor. The metal used in the conductive layer 43 is, for
example, tungsten. The semiconductor used in the conductive layer
43 is, for example, silicon doped with phosphorus. In the
conductive layer 43, a voltage is applied to the memory pillar MP,
and positive holes are generated within the semiconductor layer.
The conductive layer 43 functions as the second selection
transistor S2.
[0056] The plurality of conductive layers excluding the conductive
layers 41 and 43 are a plurality of conductive layers 45. The
plurality of conductive layers 45 are above the conductive layer
43. Each of the conductive layers 45 is interposed between the
insulating layers 44. The conductive layers 45 contain, for
example, a conductive metal. The conductive metal is, for example,
tungsten. The conductive layers 45 may be, for example, polysilicon
doped with impurities. Each of the plurality of conductive layers
45 is connected to one of the plurality of word lines WL through
the contact plug CC. Each of the plurality of conductive layers 45
functions as the gate electrodes of the memory cell transistors MT.
Conductive layers 45 located lower among the plurality of
conductive layers 45 (for example, several conductive layers from
the bottom) may function as the second selection transistor S2. The
number of conductive layers 45 is arbitrary.
[0057] The insulating layer 42 is between the conductive layer 41
and the conductive layer 43. The plurality of insulating layers 44
are between the conductive layers 43 and 45 next to each other in
the Z direction. The insulating layers 42 and 44 contain, for
example, a silicon oxide. The insulating layers 42 and 44 insulate
between the conductive layers 41, 43, and 45 adjacent to each
other. The number of insulating layers 44 is determined according
to the number of conductive layers 45.
[0058] The cover insulating layer 50 is on the insulating layer 44
which is an uppermost layer of the stack 40. The cover insulating
layer 50 insulate between the stack 40 and the bit lines BL. The
cover insulating layer 50 includes, for example, a first layer 51
and a second layer 52. The cover insulating layer 50 contains, for
example, a silicon oxide.
[0059] The plurality of bit lines BL are on the cover insulating
layer 50. In addition, as shown in FIG. 4, the bit lines BL are
electrically connected to any of the memory pillars MP and the
contact plugs CP1. In FIG. 5, the bit line BL is connected to the
memory pillar MP through the vias V1 and V2. The vias V1 and V2
contain, for example, tungsten. The via V1 is within the first
layer 51 of the cover insulating layer 50. The via V2 is within the
second layer 52 of the cover insulating layer 50.
[0060] The contact plug CP1 extends in the Z direction. The contact
plug CP1 electrically connects the bit line BL and the
interconnection layer D1 of the circuit layer PE. The contact plug
CP1 includes a conductive part 71 and insulating layers 72 and 73.
The insulating layer 72 coats the outside surface of the conductive
part 71. The insulating layer 73 coats the outside surface of the
insulating layer 72 at a height position overlapping the conductive
layers 41 and 43 in the Z direction. The conductive part 71
contains, for example, tungsten. The insulating layers 72 and 73
contain, for example, a silicon oxide.
[0061] The slits SLT and ST1 extend in the Z direction. The slits
SLT and ST1 extend from the uppermost surface of the stack 40 to
the conductive layer 41. The inner portions of the slits SLT and
ST1 are insulators. The insulators contain, for example, a silicon
oxide.
[0062] The memory pillar MP is within the stack 40. The memory
pillar MP extends in the Z direction. The memory pillar MP extends
from the uppermost surface of the stack 40 to the conductive layer
41.
[0063] FIG. 6 is an enlarged cross-sectional view illustrating the
vicinity of the memory pillar MP of the semiconductor memory 1
according to the first embodiment. FIG. 7 is a cross-sectional view
obtained by cutting the vicinity of the memory pillar MP of the
semiconductor memory 1 according to the first embodiment along the
conductive layer 45. FIG. 6 is a cross section obtained by cutting
the memory pillar MP along a YZ plane, and FIG. 7 is a cross
section obtained by cutting the memory pillar MP along an XY plane.
The memory pillar MP is within a memory hole MH formed in the stack
40.
[0064] The memory pillar MP includes a core 60, a semiconductor
layer 61, and a memory film 62. The core 60, the semiconductor
layer 61, and the memory film 62 are within the memory hole MH in
order from the inner side. The memory pillar MP is, for example,
circular or elliptical when seen from the Z direction.
[0065] The core 60 extends in the Z direction, and is columnar. The
core 60 contains, for example, a silicon oxide. The core 60 is
inside the semiconductor layer 61.
[0066] The semiconductor layer 61 extends in the Z direction. The
semiconductor layer 61 is a bottomed cylinder. The semiconductor
layer 61 coats the outside surface of the core 60. The
semiconductor layer 61 contains, for example, silicon. The silicon
is, for example, polysilicon obtained by crystallizing amorphous
silicon. The semiconductor layer 61 is a channel of each of the
first selection transistor S1, the memory cell transistor MT, and
the second selection transistor S2. The channel is a flow channel
of carriers between the source side and the drain side.
[0067] The memory film 62 extends in the Z direction. The memory
film 62 coats the outside surface of the semiconductor layer 61.
The memory film 62 is between the inner surface of the memory hole
MH and the outside surface of the semiconductor layer 61. The
memory film 62 includes, for example, a tunnel insulating film 63,
a charge storage film 64, and a cover insulating film 65. The
tunnel insulating film 63, the charge storage film 64, and then the
cover insulating film 65 are in this order near the semiconductor
layer. A portion of the memory film 62 is missing at a position
connected to the semiconductor layer 41B. The memory film 62 is not
disposed between the semiconductor layer 41B and the semiconductor
layer 61. The semiconductor layer 41B and the semiconductor layer
61 are in contact with each other without going through the memory
film 62.
[0068] The tunnel insulating film 63 is between the charge storage
film 64 and the semiconductor layer 61. The tunnel insulating film
63 contains, for example, a silicon oxide, or a silicon oxide and a
silicon nitride. The tunnel insulating film 63 is a potential
barrier between the semiconductor layer 61 and the charge storage
film 64.
[0069] The charge storage film 64 is between each of the conductive
layer 45 and the insulating layer 44 and the tunnel insulating film
63. The charge storage film 64 contains, for example, a silicon
nitride. A portion at which the charge storage film 64 and each of
the plurality of conductive layers 45 intersect each other
functions as a transistor. The memory cell transistor MT holds data
depending on the presence or absence of charges within portions
(charge storage parts) at which the charge storage film 64
intersects the plurality of conductive layers 45 or the amount of
charges stored. The charge storage part is between each of the
conductive layers 45 and the semiconductor layer 61, and surrounds
the periphery with an insulating material. The charge storage part
is a so-called floating gate structure.
[0070] The cover insulating film 65 is between, for example, each
of the insulating layers 44 and the charge storage film 64. The
cover insulating film 65 contains, for example, a silicon oxide.
The cover insulating film 65 protects the charge storage film 64
from etching during processing. The cover insulating film 65 may
not be present, or may be used as a block insulating film with a
portion thereof left between the conductive layer 45 and the charge
storage film 64.
[0071] In addition, as shown in FIGS. 6 and 7, a block insulating
film 45a and a barrier film 45b may be included between the
conductive layer 45 and the insulating layer 44 and between the
conductive layer 45 and the memory film 62. The block insulating
film 45a suppresses back-tunneling. Back-tunneling is a phenomenon
in which charges return from the conductive layer 45 to the memory
film 62. The barrier film 45b improves adhesion between the
conductive layer 45 and the block insulating film 45a. The block
insulating film 45a is, for example, a silicon oxide film or a
metal oxide film. An example of a metal oxide is an aluminum oxide.
For example, in a case where the conductive layer 45 is tungsten,
the barrier film 45b is a laminated structure film of a titanium
nitride and titanium as an example.
[0072] FIG. 8 is an enlarged cross-sectional view illustrating a
feature portion of the semiconductor memory 1 according to the
first embodiment. The semiconductor layer 61 includes, for example,
a first region 61A, a second region 61B, and a third region 61C.
The first region 61A, the second region 61B, and then the third
region 61C are in the order the semiconductor layer 41B in the Z
direction.
[0073] The first region 61A is a lower portion of the semiconductor
layer 61. The first region 61A extends from, for example, a
boundary 61a between the semiconductor layer 61 and the
semiconductor layer 41B in the Z direction. The first region 61A is
surrounded by, for example, the conductive layer 41, the insulating
layer 42, and a portion of the conductive layer 43 in the XY
direction. The height position of a boundary 61b between the first
region 61A and the second region 61B is, for example, in a range of
the height of the conductive layer 43 in the Z direction. The range
of the height of the conductive layer 43 is a range of height
interposed between the upper surface and the lower surface of the
conductive layer 43.
[0074] The first region 61A contains both an n-type impurity and a
p-type impurity. In the first region 61A, the concentration of the
n-type impurity is higher than the concentration of the p-type
impurity. The concentration of the n-type impurity at the boundary
61a between the semiconductor layer 61 and the semiconductor layer
41B is higher than the concentration of the n-type impurity at the
boundary 61b between the first region 61A and the second region
61B. The concentration of the p-type impurity at the boundary 61a
between the semiconductor layer 61 and the semiconductor layer 41B
is higher than the concentration of the p-type impurity at the
boundary 61b between the first region 61A and the second region
61B.
[0075] The first region 61A is an n-type semiconductor. The first
region 61A is formed of, for example, an n.sup.+-type semiconductor
and an n.sup.--type semiconductor. For example, in the first region
61A, a portion close to the semiconductor layer 41B is an
n.sup.+-type semiconductor, and a portion distant therefrom is an
n.sup.--type semiconductor. The n-type impurity is, for example,
phosphorus. The p-type impurity is, for example, boron. The
concentration of the n-type impurity in the first region 61A is,
for example, equal to or greater than 1.times.10.sup.19
cm.sup.-3.
[0076] The second region 61B is between the first region 61A and
the third region 61C. The second region 61B is farther from the
boundary 61a between the semiconductor layer 41B and the
semiconductor layer 61 than the first region 61A in the Z
direction. At least a portion of the second region 61B falls within
a range of the height of the conductive layer 43 in the Z
direction. The second region 61B falls within, for example, a range
of the height of the conductive layer 43 in the Z direction. The
second region 61B overlaps the conductive layer 43, for example,
when seen from the X direction or the Y direction. The second
region 61B is surrounded by the conductive layer 43, for example,
in the XY direction.
[0077] The second region 61B contains a p-type impurity. The second
region 61B contains, for example, an n-type impurity and a p-type
impurity. The second region 61B can be divided into, for example, a
region close to the first region 61A and a region distant from the
first region 61A. The region close to the first region 61A contains
both an n-type impurity and a p-type impurity, and the region
distant from the first region 61A contains only a p-type impurity.
The second region 61B is a p-type semiconductor. The concentration
of the p-type impurity in the second region 61B is, for example,
equal to or greater than 1.times.10.sup.18 cm.sup.-3 and equal to
or less than 1.times.10.sup.19 cm.sup.-3.
[0078] The third region 61C is on the opposite side to the first
region 61A with reference to the second region 61B. The third
region 61C is farther from the boundary 61a between the
semiconductor layer 41B and the semiconductor layer 61 than the
second region 61B in the Z direction. At least a portion of the
third region 61C is surrounded by, for example, any of the
conductive layers 45 in the XY direction.
[0079] The third region 61C has a lower concentration of a p-type
impurity and an n-type impurity than the second region 61B. The
third region 61C has, for example, an impurity concentration equal
to or less than 1.times.10.sup.18 cm.sup.-3. The third region 61C
is, for example, an intrinsic semiconductor containing few n-type
impurities and few p-type impurities.
[0080] In the semiconductor layer 61, the concentration of the
n-type impurity decreases with distance from the boundary 61a
between the semiconductor layer 41B and the semiconductor layer 61
in the Z direction. In the semiconductor layer 61, the
concentration of the p-type impurity decreases with distance from
the boundary 61a between the semiconductor layer 41B and the
semiconductor layer 61 in the Z direction.
[0081] The concentration of the n-type impurity and the
concentration of the p-type impurity in the semiconductor layer 61
can be measured using, for example, secondary ion mass spectrometry
(SIMS).
[0082] The conductive layer 41 includes, for example, the
semiconductor layer 41A, the semiconductor layer 41B, and the
semiconductor layer 41C as described above. The semiconductor layer
41A is on the circuit layer PE. The semiconductor layer 41A is, for
example, an n-type semiconductor. The semiconductor layer 41A is,
for example, polysilicon doped with impurities. The semiconductor
layer 41B is on the semiconductor layer 41A. The semiconductor
layer 41B is in contact with the semiconductor layer 61 of the
memory pillar MP. The semiconductor layer 41B is, for example, an
epitaxial film doped with impurities. The semiconductor layer 41C
is on the semiconductor layer 41B. The semiconductor layer 41C is,
for example, an n-type or non-doped semiconductor.
[0083] The semiconductor layer 41B includes, for example, a first
layer 41Ba and a second layer 41Bb. The first layer 41Ba extends
into the XY plane. The first layer 41Ba contains an n-type
impurity. The first layer 41Ba contains, for example, phosphorus.
The first layer 41Ba is an n-type semiconductor. The first layer
41Ba is an example of a first portion.
[0084] The second layer 41Bb coats at least a portion of the first
layer 41Ba. The second layer 41Bb contains a p-type impurity. The
second layer 41Bb contains, for example, boron. The second layer
41Bb is, for example, a p-type semiconductor, and an n-type
semiconductor containing a p-type impurity. The second layer 41Bb
is an example of a second portion. A portion of the second layer
41Bb is between the first layer 41Ba and the semiconductor layer
61. The thickness of the second layer 41Bb is, for example, equal
to or greater than 1 nm and equal to or less than 10 nm.
[0085] Next, a method of manufacturing a portion of the cell array
region CA of the semiconductor memory 1 according to the first
embodiment will be described. The following FIGS. 9 to 16 are
cross-sectional views illustrating an example of a method of
manufacturing the cell array region CA. The following FIGS. 9 to 16
show only portions located above the conductive layer 41.
[0086] First, the element isolation region 30A is formed within the
substrate 30, and the transistor Tr is formed within the circuit
layer PE (see FIG. 1). The transistor Tr can be manufactured using
a well-known method. In addition, in the circuit layer PE, a
plurality of interconnection layers D0 and D1 and a plurality of
vias C1 and C2 which are electrically connected to the transistor
Tr are formed within the insulating layer E1. The plurality of
interconnection layers D0 and D1 and the plurality of vias C1 and
C2 can be manufactured using a well-known method.
[0087] Next, as shown in FIG. 9, the semiconductor layer 41A, an
intermediate film 81a, a sacrificial film 81b, an intermediate film
81c, the semiconductor layer 41C, the insulating layer 42, and the
conductive layer 43 are laminated on the circuit layer PE in this
order. The intermediate film 81a and the intermediate film 81c
contain, for example, a silicon oxide. The sacrificial film 81b is,
for example, p-type doped silicon, n-type doped silicon, or
non-doped silicon. The semiconductor layer 41A, the semiconductor
layer 41C, the insulating layer 42, and the conductive layer 43 are
the same as described.
[0088] Next, as shown in FIG. 10, the insulating layer 44 and a
sacrificial film 85 are alternately laminated on the conductive
layer 43. As described above, the insulating layer 44 contains, for
example, a silicon oxide. The sacrificial film 85 contains, for
example, a silicon nitride.
[0089] Next, as shown in FIG. 11, the memory hole MH is formed in a
stack. The memory hole MH extends from the upper surface of the
stack halfway to the semiconductor layer 41A. The memory hole MH is
manufactured by etching. For example, anisotropic etching is
performed from the upper surface of the stack to the semiconductor
layer 41A. The anisotropic etching is, for example, reactive ion
etching (RIE).
[0090] Next, as shown in FIG. 12, the memory film 62, the
semiconductor layer 61, and the core 60 are formed within the
memory hole MH in this order. The memory hole MH is buried in the
memory film 62, the semiconductor layer 61, and the core 60. The
memory pillar MP is formed within the memory hole MH.
[0091] Next, as shown in FIG. 13, the slit SLT is formed in the
stack. The slit SLT extends from the upper surface of the stack
halfway to the sacrificial film 81b. The slit SLT is formed by
anisotropic etching. A stopper film 86 is formed on the inner wall
of the slit SLT. The stopper film 86 is, for example, a silicon
nitride film.
[0092] Next, as shown in FIG. 14, the sacrificial film 81b is
isotropically etched through the slit SLT. The sacrificial film 81b
is removed by isotropic etching. The isotropic etching is performed
using an etchant capable of etching n-type doped silicon or
non-doped silicon earlier as compared with a silicon oxide and a
silicon nitride. In addition, a portion of the memory film 62 is
also removed by etching. In the memory film 62, the sacrificial
film 81b is removed, and an exposed portion is removed. The memory
film 62 is etched using an etchant capable of etching a silicon
oxide earlier as compared with a silicon nitride. The intermediate
films 81a and 81c are removed simultaneously with the memory film
62. A space Sp is formed between the semiconductor layer 41A and
the semiconductor layer 41C.
[0093] Next, as shown in FIG. 15, the inner portion of the space Sp
is buried with semiconductors through the slit SLT. First, the
second layer 41Bb is formed within the space Sp. The second layer
41Bb is formed at a boundary between the space Sp and the
semiconductor layer 41A or the semiconductor layer 41C. Next, the
first layer 41Ba is formed inside the second layer 41Bb. Materials
of the first layer 41Ba and the second layer 41Bb are as described.
The first layer 41Ba contains an n-type impurity, and the second
layer 41Bb contains a p-type impurity.
[0094] Next, as shown in FIG. 16, the sacrificial film 85 is
replaced with the conductive layer 45. First, the stopper film 86
and the sacrificial film 85 are removed through the slit SLT. The
stopper film 86 and the sacrificial film 85 are removed by
isotropic etching. In the isotropic etching, an etchant capable of
etching a silicon nitride earlier as compared with a silicon oxide
and polysilicon is used. Thereafter, a portion in which the
sacrificial film 85 is removed is buried with a conductive
material, and the conductive layer 45 is formed. Finally, the inner
portion of the slit SLT is buried with an insulator.
[0095] The cell array region CA is manufactured by the above
processes. The manufactured cell array region CA is heated in a
post-process. The n-type impurity of the first layer 41Ba and the
p-type impurity of the second layer 41Bb are diffused to the
semiconductor layer 61 by heating. Since the second layer 41Bb is
closer to the semiconductor layer 61 than the first layer 41Ba, and
the diffusion rate of the p-type impurity is faster than the
diffusion rate of the n-type impurity, the p-type impurity is
diffused to a position farther from the semiconductor layer 41B
than the n-type impurity. The first region 61A and the second
region 61B of the semiconductor layer 61 are formed by, for
example, thermal diffusion of an n-type or p-type impurity through
heating. The manufacturing processes shown herein are an example,
and other processes may be inserted between the processes.
[0096] According to the semiconductor memory 1 of the first
embodiment, it is possible to achieve an improvement in the speed
of an erasure operation of data. The memory cell array 10 stores
data using charge stored in the charge storage film 64. When holes
are injected into the charge storage film 64, data is erased. The
holes are supplied from the semiconductor layer 61 to the charge
storage film 64.
[0097] During the erasure operation, the semiconductor layer 61
generates holes due to a phenomenon called gate-induced drain
leakage (GIDL). In a case where the first region 61A is an n-type
semiconductor, when a negative voltage is applied to the conductive
layer 43 against the conductive layer 41, an electric field occurs
in the semiconductor layer 61 extending from the first region 61A
to the third region 61C and pairs of electrons and holes are
generated. The semiconductor layer 61 is charged by these holes
being stored in the semiconductor layer 61. When the semiconductor
layer 61 is sufficiently charged with holes, an electric field
occurs between the semiconductor layer 61 and the charge storage
film 64, and holes are injected into the charge storage film 64.
When holes are injected into the charge storage film 64, data is
erased. When the amount of holes generated due to GIDL is small, it
takes time to charge the semiconductor layer 61, and thus it takes
time to erase data. The memory cell array 10 according to the first
embodiment has a tendency to generate holes within the
semiconductor layer 61. Hereinafter, the reason will be
described.
[0098] FIG. 17 is a diagram schematically illustrating a band
structure of a semiconductor layer in the vicinity of a conductive
layer 43 of a memory cell array according to a comparative example.
In the comparative example, there is no region in which the
concentration of a p-type impurity in the semiconductor layer is
higher than the concentration of an n-type impurity.
[0099] The semiconductor layer shown in FIG. 17 includes a first
region 91A and a second region 91B. In FIG. 17, the first region
91A is an n-type semiconductor, and the second region 91B is an
intrinsic semiconductor. Similarly to the above-described memory
cell array 10, the n-type impurity is diffused from a contact
between the semiconductor layer 41B and the memory pillar MP. The
first region 91A is closer to the contact between the semiconductor
layer 41B and the memory pillar MP than the second region 91B. In
the first region 91A, a side close to the contact between the
semiconductor layer 41B and the memory pillar MP is an n.sup.+
semiconductor, and a side distant therefrom is an n.sup.-
semiconductor.
[0100] The left of FIG. 17 is a band structure in a thermal
equilibrium state, and the right is a band structure when a
positive voltage is applied to the conductive layer 41 and a
negative voltage is applied to the conductive layer 43 against the
conductive layer 41 with reference to the potential of the second
region 91B. FIG. 17 shows a band structure in the vicinity of a
valence band upper end Ev and a conduction band lower end Ec. When
an electric field is applied to the semiconductor layer, the band
structure of the semiconductor layer changes. The band structure
changes, for example, from the left state of FIG. 17, that is, a
thermal equilibrium state to the right state, that is, an erasing
bias application state. Since the energy level of the first region
91A in an n.sup.+ semiconductor region and the energy level of the
second region 91B in the vicinity of the conductive layer 43 are
different from each other, a band is inclined due to a difference
in the energy level between these regions and a depletion layer is
formed. When electrons e in a valence band transition to a
conduction band due to interband tunneling in the depletion layer,
holes h are generated in the valence band. The holes h flow to the
second region 91B side along an electric field in the depletion
layer, and charge the semiconductor layer.
[0101] FIG. 18 is a diagram schematically illustrating a band
structure of the semiconductor layer 61 in the vicinity of the
conductive layer 43 of the memory cell array 10 according to the
present embodiment.
[0102] As shown in FIG. 18, the semiconductor layer according to
the present embodiment includes the first region 61A, the second
region 61B, and the third region 61C. As described above, the first
region 61A is a region in which the concentration of the n-type
impurity is higher than the concentration of the p-type impurity.
In FIG. 18, in the first region 61A, a side close to the contact
between the semiconductor layer 41B and the memory pillar MP is an
n.sup.+ semiconductor, and a side distant therefrom is an n.sup.-
semiconductor. The second region 61B is a region in which the
concentration of the p-type impurity is higher than the
concentration of the n-type impurity. In FIG. 18, the second region
61B is a p.sup.- semiconductor. The third region 61C is a region
having a lower concentration of a p-type impurity and an n-type
impurity than the second region 61B. In FIG. 18, the third region
is an intrinsic semiconductor.
[0103] The left of FIG. 18 is a band structure in a thermal
equilibrium state. In FIG. 18, for the purpose of comparison, the
valence band upper end Ev and the conduction band lower end Ec in
the comparative example are shown by dotted lines. Since the second
region 61B has a p-type impurity, an energy level in the second
region 61B is higher than energy levels in the first region 61A and
the third region 61C. In addition, the energy level shown in FIG.
18 is different from the energy level in the comparative example
shown in FIG. 17. In the second region 61B, the energy level shown
in FIG. 18 is higher than the energy level in the comparative
example shown in FIG. 17. In the second region 61B, the energy
level of a valence band upper end Ev shown in the left of FIG. 18
is located closer to a Fermi level than the energy level of the
valence band upper end Ev in the comparative example shown in the
left of FIG. 17. In the second region 61B, the energy level of the
conduction band lower end Ec shown in the left of FIG. 18 is
located at a position farther from the Fermi level than the energy
level of the conduction band lower end Ec in the comparative
example shown in the left of FIG. 17.
[0104] The right of FIG. 18 is a band structure when a positive
voltage is applied to the conductive layer 41 and a negative
voltage is applied to the conductive layer 43 against the
conductive layer 41 with reference to the potential of the third
region 61C, that is, a band structure in an erasing bias
application state.
[0105] Even in the erasing bias application state, the energy level
shown in FIG. 18 is higher than the energy level in the comparative
example shown in FIG. 17. As a result, an electric field in the
depletion layer is higher than in the comparative example shown in
FIG. 17. The holes h generated in the depletion layer flow to the
third region 61C side along the electric field. When the electric
field in the depletion layer is high, the probability of occurrence
of interband tunneling of electrons e.sup.- increases, and the
holes h can be efficiently supplied to the third region 61C. That
is, in the memory cell array 10 according to the present
embodiment, the holes h can be efficiently generated in the
semiconductor layer 61, and the erasure operation of data becomes
faster.
First Modification Example
[0106] Next, a first modification example of the embodiment will be
described.
[0107] FIG. 19 is an enlarged cross-sectional view illustrating a
feature portion of a memory cell array according to the first
modification example of the first embodiment. In the memory cell
array according to the first modification example, the structure of
a conductive layer 41 is different from the structure shown in FIG.
8. Components other than those described below are the same as the
memory cell array 10 of the first embodiment.
[0108] The conductive layer 41 according to the first modification
example includes semiconductor layers 41A, 41D, and 41C. The
semiconductor layer 41D includes a first layer 41Da, a second layer
41Db, and a third layer 41Dc. The first layer 41Da is the same as
the first layer 41Ba in FIG. 8. The second layer 41Db is the same
as the second layer 41Db in FIG. 8.
[0109] At least a portion of the third layer 41Dc is between the
first layer 41Da and the second layer 41Db. The third layer 41Dc
contains a carbon element. The third layer 41Dc is, for example,
polysilicon doped with carbon. The third layer 41Dc is an example
of a third portion. The thickness of the third layer 41Dc is, for
example, equal to or greater than 1 nm and equal to or less than 10
nm.
[0110] A method of manufacturing a memory cell array according to
the first modification example is the same as the above
manufacturing method up to processes leading to FIG. 14. When the
space Sp is buried with semiconductors, the second layer 41Db, the
third layer 41Dc, and the first layer 41Da are formed in this
order. First, the second layer 41Db is formed within the space Sp.
The second layer 41Db is formed at a boundary between the space Sp
and the semiconductor layer 41A or the semiconductor layer 41C.
Next, the third layer 41Dc is formed inside the second layer 41Db.
Finally, the first layer 41Da is formed inside the third layer
41Dc.
[0111] With such a configuration, it is also possible to achieve an
improvement in the speed of an erasure operation similarly to the
first embodiment. In addition, the third layer 41Dc suppresses the
diffusion of an n-type impurity from the first layer 41Da to the
semiconductor layer 61. When the diffusion of an n-type impurity to
the semiconductor layer 61 is suppressed, a range in which the
first region 61A is formed becomes narrow. When the region of an
n.sup.- semiconductor in the first region 61A becomes narrow, the
inclination of the energy band in the depletion layer becomes
sharper, and the efficiency of generation of the holes h
increases.
Second Modification Example
[0112] Next, a second modification example of the embodiment will
be described.
[0113] FIG. 20 is an enlarged cross-sectional view illustrating a
feature portion of a memory cell array according to the second
modification example of first embodiment. In the memory cell array
according to the second modification example, the structure of a
conductive layer 41 is different from the structure shown in FIG.
8. Components other than those described below are the same as the
memory cell array 10 of the first embodiment.
[0114] The conductive layer 41 according to the first modification
example includes the semiconductor layers 41A, 41E, and 41C. The
semiconductor layer 41E includes a first layer 41Ea and a second
layer 41Eb. The second layer 41Eb is the same as the second layer
41Bb in FIG. 8.
[0115] The first layer 41Ea extends into the XY plane. The first
layer 41Ea contains an n-type impurity and a carbon element. The
first layer 41Ea contains, for example, phosphorus and carbon. The
first layer 41Ea is an n-type semiconductor doped with phosphorus
and carbon. The first layer 41Ea is an example of a first
portion.
[0116] A method of manufacturing a memory cell array according to
the first modification example is the same as the manufacturing
method shown in the first embodiment. When the first layer 41Ea is
formed, the first layer 41Ea is doped with carbon along with an
n-type impurity.
[0117] With such a configuration, it is also possible to achieve an
improvement in the speed of an erasure operation similarly to the
first embodiment. In addition, the carbon element applied into the
first layer 41Ea suppresses the diffusion of an n-type impurity
from the first layer 41Ea to the semiconductor layer 61. When the
diffusion of an n-type impurity to the semiconductor layer 61 is
suppressed, a range in which the first region 61A is formed becomes
narrow. When the region of an n.sup.- semiconductor in the first
region 61A becomes narrow, the inclination of the energy band in
the depletion layer becomes sharper, and the efficiency of
generation of the holes h increases.
Third Modification Example
[0118] Next, a third modification example of the embodiment will be
described.
[0119] FIG. 21 is an enlarged cross-sectional view illustrating a
feature portion of a memory cell array according to the third
modification example of the first embodiment. The memory cell array
according to the third modification example is different from the
structure shown in FIG. 8 in that the conductive layer 43 is
replaced with a first stack 46. Components other than those
described below are the same as the memory cell array 10 of the
first embodiment.
[0120] The stack 40 includes the first stack 46 and a second stack
47. The first stack 46 is closer to the conductive layer 41 than
the second stack 47. The first stack 46 includes a plurality of
conductive layers 48 and a plurality of insulating layers 49, and
has the conductive layers 48 and the insulating layers 49
alternately laminated therein. The conductive layer 48 contains,
for example, a conductive metal. The conductive metal is, for
example, tungsten. The conductive layer 48 may be, for example,
polysilicon doped with impurities. The insulating layer 49
contains, for example, a silicon oxide. The second stack 47
includes a plurality of conductive layers 45 and a plurality of
insulating layers 44, and has the conductive layers 45 and the
insulating layers 44 alternately laminated therein.
[0121] There is no clear distinction between structures of the
first stack 46 and the second stack 47. The first stack 46 is, for
example, a portion ranging from a boundary with the insulating
layer 42 in a stack having the first stack 46 and the second stack
47 combined with each other to five conductive layers 48. The
plurality of conductive layers 48 of the first stack 46 function as
the second selection transistor S2. The plurality of conductive
layers 45 of the second stack 47 function as the memory cell
transistor MT. The thickness of the semiconductor layer 41C in FIG.
21 is larger than, for example, the thickness of the semiconductor
layer 41C in FIG. 8.
[0122] A method of manufacturing a memory cell array according to
the third modification example is different from the method of
manufacturing a memory cell array according to the first embodiment
in that, after the insulating layer 42 is formed, the insulating
layer 44 and the sacrificial film 85 are alternately laminated
without forming the conductive layer 43. The semiconductor layer
41C is made thicker than the semiconductor layer 41C of the memory
cell array according to the first embodiment. The semiconductor
layer 41C functions as a stopper layer during the formation of the
slit SLT and the memory hole MH. A procedure of forming the memory
pillar MP, the slit SLT, and the semiconductor layer 41B is the
same as the method of manufacturing a memory cell array according
to the first embodiment.
[0123] With such a configuration, it is also possible to achieve an
improvement in the speed of an erasure operation similarly to the
first embodiment.
[0124] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing form the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and sprit of the
inventions.
EXPLANATION OF REFERENCES
[0125] 1 Semiconductor memory [0126] 10 Memory cell array [0127] 30
Substrate [0128] 40 Stack [0129] 41, 43, 45, 48 Conductive layer
[0130] 41A, 41B, 41C, 41D, 41E Semiconductor layer [0131] 41Ba,
41Da, 41Ea First layer [0132] 41Bb, 41Db, 41Eb Second layer [0133]
41Dc Third layer [0134] 42, 44, 49 Insulating layer [0135] 46 First
stack [0136] 47 Second stack [0137] 61 Semiconductor layer [0138]
61a Boundary [0139] 61A, 91A First region [0140] 61B, 91B Second
region [0141] 61C Third region [0142] 64 Charge storage film [0143]
MP Memory pillar [0144] PE Circuit layer
* * * * *