U.S. patent application number 13/214571 was filed with the patent office on 2011-12-08 for non-volatile memories, cards, and systems including shallow trench isolation structures with buried bit lines.
Invention is credited to Wook Hyun KWON.
Application Number | 20110302363 13/214571 |
Document ID | / |
Family ID | 39885905 |
Filed Date | 2011-12-08 |
United States Patent
Application |
20110302363 |
Kind Code |
A1 |
KWON; Wook Hyun |
December 8, 2011 |
NON-VOLATILE MEMORIES, CARDS, AND SYSTEMS INCLUDING SHALLOW TRENCH
ISOLATION STRUCTURES WITH BURIED BIT LINES
Abstract
A non-volatile memory device can include a buried bit line in a
substrate of a non-volatile memory device and a self-aligned
shallow trench isolation region in the substrate that is
self-aligned to the buried bit line.
Inventors: |
KWON; Wook Hyun; (Kyung-Ki
Do, KR) |
Family ID: |
39885905 |
Appl. No.: |
13/214571 |
Filed: |
August 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12109761 |
Apr 25, 2008 |
8022462 |
|
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13214571 |
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Current U.S.
Class: |
711/103 ;
257/314; 257/315; 257/E29.255; 257/E29.3; 711/E12.008 |
Current CPC
Class: |
H01L 29/7881 20130101;
H01L 29/42336 20130101; H01L 27/115 20130101; H01L 27/11521
20130101; G11C 16/0416 20130101; H01L 21/76224 20130101 |
Class at
Publication: |
711/103 ;
257/314; 257/315; 257/E29.255; 257/E29.3; 711/E12.008 |
International
Class: |
G06F 12/00 20060101
G06F012/00; H01L 29/788 20060101 H01L029/788; H01L 29/78 20060101
H01L029/78 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2007 |
KR |
10-2007-0041430 |
Claims
1. A non-volatile memory device comprising: a buried bit line in a
substrate of a non-volatile memory device; and a self-aligned
shallow trench isolation region in the substrate self-aligned to
the buried bit line.
2. The non-volatile memory device according to claim 1 further
comprising: a gate structure having the buried bit line
self-aligned thereto, wherein the gate structure includes a
protruding portion that extends into the substrate beyond a lower
surface of the buried bit line.
3. An electronic system comprising: a processor configured to
coordinate operations of an electronic system; a volatile memory,
electrically coupled to the processor, configured to store and
retrieve data responsive processor operations; a system interface,
electrically coupled to the processor, configured to provide
communications between the processor and external systems; and a
non-volatile memory, electrically coupled to the processor,
including at least one non-volatile memory device comprising: a
buried bit line in a substrate of a non-volatile memory device; and
a self-aligned shallow trench isolation region in the substrate
self-aligned to the buried bit line.
4. The electronic system according to claim 3 further comprising: a
gate structure having the buried bit line self-aligned thereto,
wherein the gate structure includes a protruding portion that
extends into the substrate beyond a lower surface of the buried bit
line.
5. A memory card comprising: a non-volatile memory controller
configured to coordinate operations of the memory card; and a
non-volatile memory, electrically coupled to the non-volatile
memory controller, including a non-volatile memory comprising: a
buried bit line in a substrate of a non-volatile memory; and a
self-aligned shallow trench isolation region in the substrate
self-aligned to the buried bit line.
6. The memory card according to claim 5 further comprising: a gate
structure having the buried bit line self-aligned thereto, wherein
the gate structure includes a protruding portion that extends into
the substrate beyond a lower surface of the buried bit line.
7. The memory card according to claim 6 wherein the gate structure
comprises a U-shaped floating gate electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. application Ser.
No. 12/109,761, filed Apr. 25, 2008 in the United States Patent and
Trademark Office, and claims priority from Korean Patent
Application No. 10-2007-0041430, filed on Apr. 27, 2007, in the
Korean Intellectual Property Office, the entire contents of all of
which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of electronics,
and more particularly, to methods of forming non-volatile memories
and the devices so formed.
BACKGROUND
[0003] Non-volatile memory devices are widely used in various kinds
of electronic products such as mobile telephones, etc. One type of
non-volatile memory that has become popular is what is commonly
referred to as NOR type flash memory. It is recognized that in
conventional NOR flash memory, the metal contact employed in
source/drain regions may use a significant area of the integrated
circuit. Accordingly, one approach, sometimes referred to as buried
bit line, has been used to avoid the formation of contacts in NOR
type flash memory.
[0004] Non-volatile memories are also discussed in, for example,
U.S. Patent Publication No. 2004/0169238 A1 to Lee et al., U.S.
Patent Publication No. 2006/0180851 A1 to Lee et al., U.S. Pat. No.
5,526,307 to Yiu et al., U.S. Pat. No. 6,858,906 B2 to Lee et al,
and U.S. Pat. No. 7,072,214 B2 to Jeong et al.
SUMMARY
[0005] Embodiments according to the invention can provide
non-volatile memory devices, systems, and cards that include
shallow trench isolation structures with buried bit lines. Pursuant
to these embodiments, a non-volatile memory device can include a
buried bit line in a substrate of a non-volatile memory device and
a self-aligned shallow trench isolation region in the substrate
that is self-aligned to the buried bit line.
[0006] In some embodiments according to the inventive concept, an
electronic system can include a processor that is configured to
coordinate operations of an electronic system and a volatile
memory, that is electrically coupled to the processor, and that is
configured to store and retrieve data responsive processor
operations. A system interface, can be electrically coupled to the
processor, and can be configured to provide communications between
the processor and external systems and a non-volatile memory, can
be electrically coupled to the processor, and can include at least
one non-volatile memory device that includes a buried bit line in a
substrate of a non-volatile memory device and a self-aligned
shallow trench isolation region in the substrate that is
self-aligned to the buried bit line.
[0007] In some embodiments according to the inventive concept, a
memory card can include a non-volatile memory controller that is
configured to coordinate operations of the memory card and a
non-volatile memory, that can be electrically coupled to the
non-volatile memory controller, and can include a non-volatile
memory, which can include a buried bit line in a substrate of a
non-volatile memory and a self-aligned shallow trench isolation
region in the substrate that is self-aligned to the buried bit
line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic illustration of an equivalent circuit
representing a NOR type flash memory array in some embodiments
according to the invention.
[0009] FIG. 2 is a schematic representation of a layout of a
highlighted area of the NOR type flash memory array shown in FIG. 1
in some embodiments according to the invention.
[0010] FIG. 3 is a perspective view of a NOR type flash memory
device including buried bit lines with self aligned shallow trench
isolation structures formed therein in some embodiments according
to the invention.
[0011] FIGS. 4-13 are perspective views that illustrate methods of
forming a NOR type flash memory including buried bit lines in self
aligned shallow trench isolation structures in some embodiments
according to the invention.
[0012] FIG. 14 is a perspective view of a NOR type flash memory
including buried bit lines and self aligned shallow trench
isolation structures and protruding floating gate structures in
some embodiments according to the invention.
[0013] FIG. 15 is a perspective view of a flash memory including
buried bit lines and self aligned shallow trench isolation
structures with tunneling insulating patterns in some embodiments
according to the invention.
[0014] FIGS. 16-23 are cross-sectional views that illustrate
methods of forming a NOR type flash memory including buried bit
lines and self aligned shallow trench isolation structures with
U-shaped floating gates in some embodiments according to the
invention.
[0015] FIG. 24A is a schematic illustration of an equivalent
circuit of a NOR type flash memory array formed according to some
embodiments of the present invention.
[0016] FIG. 24B is a table that illustrates typical operating
parameters associated with NOR type flash memories formed according
to embodiments of the present invention.
[0017] FIG. 25 is a block diagram illustrating memory cards and/or
systems including various components and non-volatile memory with
NOR type flash memory devices formed according to some embodiments
of the present invention.
DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION
[0018] The present invention is described more fully hereinafter
with reference to the accompanying drawings, in which embodiments
of the invention are shown by way of example. The present invention
may, however, be embodied in many different forms and should not be
construed as limited to the example embodiments set forth herein.
Rather, these example embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the present invention to those skilled in the art.
Moreover, each embodiment described and illustrated herein includes
its complementary conductivity type embodiment as well.
[0019] It will be understood that when an element is referred to as
being "connected to," "coupled to" or "responsive to" (and/or
variants thereof) another element, it can be directly connected,
coupled or responsive to the other element or intervening elements
may be present. In contrast, when an element is referred to as
being "directly connected to," "directly coupled to" or "directly
responsive to" (and/or variants thereof) another element, there are
no intervening elements present. Like numbers refer to like
elements throughout. As used herein, the term "and/or" includes any
and all combinations of one or more of the associated listed items
and may be abbreviated as "/".
[0020] It will be understood that, although the terms first,
second, third, etc. may be used herein to describe various
elements, components, regions, layers and/or sections, these
elements, components, regions, layers and/or sections should not be
limited by these terms. These terms are only used to distinguish
one element, component, region, layer or section from another
region, layer or section. Thus, a first element, component, region,
layer or section discussed below could be termed a second element,
component, region, layer or section without departing from the
teachings of the present invention.
[0021] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a," "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising" (and/or variants
thereof), when used in this specification, specify the presence of
stated features, integers, steps, operations, elements, and/or
components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements,
components, and/or groups thereof. In contrast, the term
"consisting of" (and/or variants thereof) when used in this
specification, specifies the stated number of features, integers,
steps, operations, elements, and/or components, and precludes
additional features, integers, steps, operations, elements, and/or
components.
[0022] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which the present
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
application, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0023] As described herein below in greater detail, shallow trench
isolation structures can be formed self aligned to, for example,
impurity regions that provide the buried bit line structures and
NOR type flash memories. In particular, forming the shallow trench
isolation structures so that they are self aligned to structures
that provide the buried bit line of the non-volatile memory (i.e.,
the impurity regions) can help to substantially equalize ranks of
the associated impurity regions (i.e., the lengths of the bit
lines). For example, the formation of the self aligned shallow
trench isolation structures can help to remove portions of the
impurity regions which may have otherwise been formed misaligned by
a conventional photolithographic process. As appreciated by the
present inventors, using a photolithographic process to form the
shallow trench isolation structures separate from the formation of
the impurity regions to provide the buried bit lines can lead to
misalignment errors thereby increasing the possibility of forming
bit lines with different lengths within the same memory sector.
[0024] In further embodiments according to the invention, the
impurity regions can be formed before the shallow trench isolation
structures. In particular, the impurity regions may be formed in
the substrate to provide immediately neighboring buried bit lines
for the device. After the formation of the impurity region (i.e.,
the buried bit lines), a shallow trench isolation region can be
formed in the substrate between the immediately neighboring buried
bit lines. As appreciated by the present inventors, this approach
can substantially equalize what may be otherwise different lengths
of the immediately neighboring buried bit lines, which may be
generated by conventional approaches. For example, as appreciated
by the present inventors, if the shallow trench isolation structure
is formed in the substrate using a standard photolithographic
process (e.g., before the formation of the impurity regions), the
subsequent formation of the impurity regions can be misaligned
relative to the shallow trench isolation structures previously
formed. Accordingly, this misalignment can lead to impurity regions
(ultimately providing the buried bit lines) having different
lengths.
[0025] FIG. 1 is a schematic illustration of an equivalent circuit
including a NOR type flash memory array in some embodiments
according to the invention. In particular, FIG. 1 shows immediately
neighboring memory cells (MC) each having respective local bit
lines (LBL) for the two separate groupings of rows (i.e., 8-16 rows
of memory cells) which are combined and provided as a global bit
line (GBL). Further, the immediately neighboring memory cells (MC)
share a source line (within each of the separated rows), which is
provided to a common source line (C/S). Each of the rows of memory
cells is coupled to a word line (W/L), which can be used to access
selected memory cells.
[0026] FIG. 2 illustrates a schematic layout of a pair of
immediately neighboring memory cells (MC) shown in FIG. 1 is some
embodiments according to the invention. In particular, FIG. 2 shows
a pair of immediately neighboring memory cells (MC) where the
source line bisects the active regions used by the immediately
neighboring memory cells (MC). Further, the floating gates of the
immediately neighboring memory cells (MC) are each coupled to a
word line (W/L). Bit lines of the immediately neighboring memory
cells (MC) are also insulated from one another by self aligned
shallow trench isolation structures (STI).
[0027] FIG. 3 is a perspective view illustrating a NOR type flash
memory including buried bit lines and self-aligned shallow trench
isolation structures in some embodiments according to the
invention. As shown in FIG. 3, a central region of a substrate 100
includes the immediately neighboring memory cells (MC) shown in
FIGS. 1 and 2. In particular, a gate pattern 200 is provided on the
active region in the substrate 100 for both of the immediately
neighboring memory cells (MC). Immediately neighboring memory cells
(MC) share a source line 101 located between the respective gate
thereof. Further, buried bit lines 120 associated with each of the
immediately neighboring memory cells MC are provided by impurity
regions formed within the substrate 100. As further shown in FIG.
3, immediately neighboring buried bit lines 120 located between
immediately neighboring memory cells (MC) are separated by a
self-aligned shallow trench isolation structure pattern 160.
[0028] As further shown in FIG. 3, the gate pattern 200 coupled to
each of the immediately neighboring memory cells (MC) includes a
number of layers. In particular, each of the gate patterns 200 can
include a gate insulating pattern 201, a floating gate pattern 202
formed thereon, an inter-gate dielectric layer formed thereon, a
control gate pattern formed thereon, and a hard mask pattern 205.
It will be understood that the control gate pattern 204 can provide
the word line (W/L) described above in reference to FIGS. 1 and
2.
[0029] FIGS. 4-13 are perspective views that illustrate methods of
forming a NOR type flash memory with buried bit lines and self
aligned shallow trench isolation structures in some embodiments
according to the invention. According to FIG. 4, a lower pattern
110 is formed on the substrate 100. The lower pattern 110 can be
provided by forming a series of layers on the substrate 100
followed by either separately patterning each of the layers or
patterning the complete collection of layers together.
[0030] According to FIG. 4, the lower pattern 110 includes a gate
insulating pattern 111, a lower conductive pattern 112 formed
thereon, and the capping pattern 113 formed on the lower conductive
pattern 112. In some embodiments according to the invention, the
gate insulating pattern 111 can be SiO2, SiON, and/or a high-K
material. In some embodiments according to the invention, the lower
conductive pattern 112 can be any conductive material, such as
polysilicon. In some embodiments according to the invention, the
capping pattern 113 may be silicon nitride.
[0031] The layers described above are patterned to provide
pluralities of openings 114 to define the lower pattern 110.
Accordingly, the openings 114 expose respective portions of the
substrate 100. Impurities are implanted into the exposed portions
of the substrate 100 via the openings 114 to form impurity regions
120. It will be understood that the impurity regions 120 can
provide buried bit lines for the NOR type flash memory in some
embodiments according to the invention.
[0032] According to FIG. 5, a dielectric material 130 is formed on
the substrate 100 including in the openings 114 to cover the
impurity regions 120. In some embodiments according to the
invention, the deposition of the dielectric material 130 is limited
to the openings 114. In other embodiments according to the
invention, the dielectric material 130 fills the openings 114 and
is deposited on an upper surface of the lower pattern 110 and is
subsequently planarized to again expose the upper surface of the
lower pattern.
[0033] According to FIG. 6, a photo-resist pattern 150 is formed on
the lower pattern to have openings 155 therein. In some embodiments
according to the invention, the photo-resist pattern 150 having the
openings 155 can be formed on a mask pattern 140. As shown in FIG.
6, the openings 155 are formed above the regions of the substrate
that lie between selective ones of the impurity regions 120 that
have the dielectric layers thereon. For example, the openings 155
are formed above regions of the substrate 100 wherein the self
aligned shallow trench isolation structures are to be formed.
Accordingly, the openings 155 should be formed between immediately
neighboring local bit lines provided by the impurity regions 120.
In some embodiments according to the invention, the mask pattern
140 and photo resist pattern 155 are formed using conventional
photo lithographic processes.
[0034] According to FIG. 7, selected portions of the lower pattern
110 are removed via the openings 155 to expose sidewalls of the
dielectric layers 130 to which the shallow trench isolation
structures are to be self aligned in the substrate 100. As further
shown in FIG. 7, and as appreciated by the present inventors, the
respective lengths, L3 and L4, of the different impurity regions
120 can be unequal.
[0035] As shown in FIG. 8, portions of the substrate 100 underlying
the openings 155 and having respective portions of the lower
pattern 110 formed thereon are etched to form self aligned trenches
160 and the substrate 100. The self aligned trenches 160 are self
aligned to the side walls of the dielectric layers 130 formed
thereon the impurity regions 120 to ultimately provide the buried
bit line structures for immediately neighboring pairs of memory
cells (MC). Further, because of the self aligned nature of the
trench 160, the respective lengths of the immediately adjacent
impurity regions 120 can be substantially equalized.
[0036] According to FIG. 9, an isolation layer 170 is formed on the
upper surface of the lower pattern 110 and in self aligned trenches
160. In some embodiments according to the invention, the isolation
layer 170 can be HDP, SOG, MTO, HTO, and/or undoped SiGe. In some
embodiments according to the invention, the mask pattern 140
described above in reference to FIGS. 6 and 7 may remain beneath
the isolation layer 170 rather than be removed.
[0037] According to FIG. 10, the portion of the isolation layer 170
remaining on the upper surface of the lower pattern 110 is removed
to once again expose the upper surface of the lower pattern 110.
Accordingly, as shown in FIG. 10, the deposition of the isolation
layer 170 in the self aligned trench 160 provides for the formation
of self aligned shallow trench isolation structures 175.
[0038] According to FIG. 11, the capping layer 113 included in the
lower pattern 110 is removed to expose upper surface of the lower
conductive pattern 112. The dielectric layer 130 is recessed (along
with the isolation material 175) to expose side walls of the lower
conductive pattern 112 above the impurity regions 120 that provide
the buried bit lines. As further shown in FIG. 11, a portion of the
dielectric layer 130 remains on the impurity regions 120 to reduce
any subsequent coupling between an upper conductive layer and the
impurity regions 120.
[0039] According to FIG. 12, an upper layer 180 is formed on the
lower conductive pattern 112. The upper layer 180 includes an
intergate dielectric layer 181 formed on the lower conductive layer
112, an upper conductive layer 182 formed on the intergate
dielectric layer 181, and an upper hard mask layer 183 formed on
the upper conductive layer 182. In some embodiments according to
the invention, the upper conductive layer can be polysilicon,
silicide, metal and/or a multi-layered upper conductive layer
including any of these materials or combinations thereof. In some
embodiments according to the invention, the intergate dielectric
layer can be SiOx/SxiNy/SiOx, SiOx, SixNy, Al203, HfAIOx, HfAION,
HfSiOx, HfSiON. According to FIG. 13, the upper layer is patterned
to provide an upper layer pattern 200 that can provide word lines
for the memory cells (MC).
[0040] FIG. 14 is a perspective view and illustrates the
non-volatile memory device including buried bit lines with self
aligned shallow trenched isolation (STI) structures with gate
structures 190 protruding into the substrate 100. According to FIG.
14, the substrate 100 can be patterned to define groves therein,
into which a gate insulating pattern 201 can be deposited.
Subsequently, when the lower conductive pattern 202 is formed, a
portion is deposited in the groove to provide a protruding portion
of a floating gate structure 190 that extends into the substrate
100. Accordingly, a channel developed by the gate 190 may the
reduced short channel effects using such a structure.
[0041] According to FIG. 15, the gate pattern 210 is formed on the
substrate 100. The gate pattern 210 can include a tunnel insulating
pattern 211 formed to a thickness of about 30 to about 100 .ANG..
In some embodiments according to the invention, the tunnel
insulating pattern can be SiO2, SiON, SixNy, Al2O3, HfAlON, HfSiOx,
and/or HfSiON. In some embodiments according to the invention, the
gate pattern 210 includes a charge storage pattern 212 formed on
the tunnel insulating pattern 211. The charged storage pattern can
be formed to a thickness of about 30 to about 100 .ANG. and can be
SixNy, Al2O3, HfAlOx, HfAlON, HfSiOx, and/or HfSiON. The gate
pattern 210 can also include a blocking insulating pattern 213
formed on the charge storage pattern 212. The blocking insulating
pattern 213 can be formed to a thickness of about 50 to about 200
.ANG. and can be made from SiOx/SixNy/SiOx, SiOx, SixNy, Al2O3,
HfAlOx, HfAlON, HfSiOx, and/or HfSiON. Further, the gate pattern
210 can include a control gate pattern 214 formed on the blocking
insulating pattern 213. The control gate pattern 214 can be formed
of a metal that has a work function of at least four electron volts
(eE). In some embodiments according to the invention, the metal
used to provide the control gate pattern 214 can be, TaN, W, WN,
Ti, TiN, Ta, Hf, Nb, Mo, RuO2, Mo2N, Ir, Pt, Co, Cr, RuO, and/or
Ti3Al.
[0042] FIGS. 16-23 are cross sectional views that illustrate
methods of forming a non-volatile memory including buried bit lines
and self aligned shallow trench isolation structures with U shaped
floating gate electrodes in some embodiments according to the
invention. According to FIG. 16, the lower pattern 110 is formed on
the substrate 100 including openings 106 to expose underlying
portions of the substrate 100. First impurities are implanted into
the substrate 100 via the openings 106 to form lightly doped
regions 121.
[0043] According to FIG. 17, a side wall spacer pattern 99 is
formed on side walls of the lower pattern 110 in the openings 106.
Subsequently, second impurities are implanted into the substrate
100 through the openings 106 having the spacer pattern 99 formed
therein to form a highly doped region 122 in the substrate 100.
Accordingly, the lightly doped region 121 located beneath the side
wall spacer pattern 99 is maintained in the substrate 100. In some
embodiments according to the invention, the material used to form
the spacer pattern 99 can be the same material used to form the
lower conductive pattern 112. It will be understood that the
lightly doped region 121 and the more highly doped region 122,
taken together, can provide the impurity region 120 described
above.
[0044] According to FIG. 18, a lower interlayer dielectric layer
130 is formed in the openings 106 between the spacer pattern 99.
According to FIG. 19, selective structures within the lower patter
110 are removed as described above in reference to, for example,
FIGS. 7 and 8, to provide self aligned trenches 160 in the
substrate 100 that are self aligned to the side walls of the lower
interlayer dielectric 130.
[0045] According to FIG. 21, a shallow trench isolation material
175 is formed in the self aligned trench 160 to provide the self
aligned shallow trench isolation structures 175 that are self
aligned to the side walls of the interlayer dielectric layer 130
exposed by the formation of the self aligned trenches 160 shown in
FIG. 20.
[0046] According to FIG. 22, the capping pattern 113 is removed and
the lower inter layer dielectric 130 is recessed to expose side
walls of the lower conductive pattern 112 defined by the side wall
spacer pattern 99. Therefore, according to FIG. 22, the side wall
spacer pattern 99 and the lower conductive pattern 112 combine to
provide a U shaped floating gate electrode for the non volatile
memory.
[0047] According to FIG. 23, an upper pattern is formed on the U
shaped floating gate electrode including an inter gate dielectric
layer 203, a control gate pattern 204, and a passivation layer 205,
which together provide the upper layer 200.
[0048] FIG. 24A shows a schematic illustration of an equivalent
circuit including the neighboring memory cells (MC) described above
in reference to FIG. 1. Further, FIG. 24B includes a table that
illustrates nominal parameters associated with operations of the
memory cell (MC) shown in FIG. 24A.
[0049] FIG. 25 is a schematic representation of an electronic
system 560 including a processor circuit 530 that is configured to
coordinate overall operation of the electronic system 560 via a bus
500 that is coupled to a volatile memory system 540, an interface
system 510, and a nonvolatile memory system 550. The nonvolatile
memory system 550 can include memory devices, such as memory cards
and separate non-volatile memory devices as described herein and
including self-aligned shallow trench isolation structures in some
embodiments according to the invention and as described herein.
[0050] As described herein, shallow trench isolation structures can
be formed self aligned to, for example, impurity regions that
provide the buried bit line structures and NOR type flash memories.
In particular, forming the shallow trench isolation structures so
that they are self aligned to structures that provide the buried
bit line of the non-volatile memory (i.e., the impurity regions)
can help to substantially equalize ranks of the associated impurity
regions (i.e., the lengths of the bit lines). For example, the
formation of the self aligned shallow trench isolation structures
can help to remove portions of the impurity regions which may have
otherwise been formed misaligned by a conventional
photolithographic process. As appreciated by the present inventors,
using a photolithographic process to form the shallow trench
isolation structures separate from the formation of the impurity
regions to provide the buried bit lines can lead to misalignment
errors thereby increasing the possibility of forming bit lines with
different lengths within the same memory sector.
[0051] In further embodiments according to the invention, the
impurity regions can be formed before the shallow trench isolation
structures. In particular, the impurity regions may be formed in
the substrate to provide immediately neighboring buried bit lines
for the device. After the formation of the impurity region (i.e.,
the buried bit lines), a shallow trench isolation region can be
formed in the substrate between the immediately neighboring buried
bit lines. As appreciated by the present inventors, this approach
can substantially equalize what may be otherwise different lengths
of the immediately neighboring buried bit lines, which may be
generated by conventional approaches. For example, as appreciated
by the present inventors, if the shallow trench isolation structure
is formed in the substrate using a standard photolithographic
process (e.g., before the formation of the impurity regions), the
subsequent formation of the impurity regions can be misaligned
relative to the shallow trench isolation structures previously
formed. Accordingly, this misalignment can lead to impurity regions
(ultimately providing the buried bit lines) having different
lengths.
[0052] It will be apparent to those skilled in the art that various
modifications and variations can be made in the invention. Thus, it
is intended that the invention covers the modifications and
variations of this invention provided they come within the scope of
the appended claims and their equivalents.
* * * * *