U.S. patent application number 15/088855 was filed with the patent office on 2016-07-28 for integrated circuits with non-volatile memory and methods for manufacture.
The applicant listed for this patent is Cypress Semiconductor Corporation. Invention is credited to Kuo Tung CHANG, Chun Chen, Shenqing Fang.
Application Number | 20160218113 15/088855 |
Document ID | / |
Family ID | 50929930 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160218113 |
Kind Code |
A1 |
CHANG; Kuo Tung ; et
al. |
July 28, 2016 |
Integrated Circuits with Non-Volatile Memory and Methods for
Manufacture
Abstract
Semiconductor devices and methods of manufacturing thereof are
described. According to an example embodiment, a semiconductor
device comprises: a substrate comprising a core region and a
peripheral region, where the core region is adjacent to the
peripheral region; a memory array comprising non-volatile memory
cells that are located in the core region of the substrate; a
high-voltage control logic comprising high-voltage transistors that
are located in the peripheral region of the substrate; and a
low-voltage control logic comprising low-voltage transistors that
are located in the peripheral region of the substrate.
Inventors: |
CHANG; Kuo Tung; (Saratoga,
CA) ; Chen; Chun; (San Jose, CA) ; Fang;
Shenqing; (Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cypress Semiconductor Corporation |
San Jose |
CA |
US |
|
|
Family ID: |
50929930 |
Appl. No.: |
15/088855 |
Filed: |
April 1, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14484417 |
Sep 12, 2014 |
9368588 |
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15088855 |
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13715565 |
Dec 14, 2012 |
8836006 |
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14484417 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/11568 20130101;
H01L 29/66833 20130101; H01L 27/11573 20130101; H01L 29/401
20130101; H01L 29/40117 20190801; H01L 29/42344 20130101 |
International
Class: |
H01L 27/115 20060101
H01L027/115; H01L 29/423 20060101 H01L029/423 |
Claims
1. A semiconductor device, comprising: a substrate comprising a
core region and a peripheral region, wherein the core region is
adjacent to the peripheral region; a memory array comprising
non-volatile memory cells, wherein the non-volatile memory cells
are located in the core region of the substrate; a high-voltage
control logic comprising high-voltage transistors, wherein the
high-voltage transistors are located in the peripheral region of
the substrate; and a low-voltage control logic comprising
low-voltage transistors, wherein the low-voltage transistors are
located in the peripheral region of the substrate.
2. The semiconductor device of claim 1, wherein the non-volatile
memory cells comprise split-gate non-volatile memory cells.
3. The semiconductor device of claim 1, wherein the high-voltage
control logic is configured to control portions of the memory
array.
4. The semiconductor device of claim 1, wherein the low-voltage
control logic is configured to control the operation of the
semiconductor device.
5. The semiconductor device of claim 1, wherein the low-voltage
control logic includes a micro-controller.
6. The semiconductor device of claim 1, wherein the substrate
comprises a particular area that includes the core region and the
peripheral region.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 14/484,417 filed on Sep. 12, 2014,
which is a divisional of and claims priority to U.S. patent
application Ser. No. 13/715,565 filed on Dec. 14, 2012, all of
which are hereby incorporated by reference in their entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] This disclosure relates generally to improved embedded
semiconductor products and methods and apparatus for making such
semiconductor products.
[0004] 2. Related Art
[0005] A non-volatile memory cell in a non-volatile core array is
programmed using, for example, hot carrier injection to place
charge into a storage layer. High drain and gate voltages are used
to facilitate the programming process, and the memory cell conducts
relatively high current during programming, which can be
undesirable in low voltage or low power applications.
[0006] A split-gate non-volatile memory cell is a type of
non-volatile memory cell, in which a select gate is placed adjacent
a memory gate. During programming of a split-gate non-volatile
memory cell, the select gate is biased at a relatively low voltage,
and only the memory gate is biased at the high voltage to provide
the vertical electric field necessary for hot-carrier injection.
That makes hot-carrier injection more efficient during programming
operation compared to conventional non-split gate memory cell. A
split-gate non-volatile memory cell may be programmed using
techniques other than hot-carrier injection, and depending on the
technique, any advantage over the conventional non-volatile memory
cell during programming operation may vary.
[0007] Fast read time is another advantage of a split-gate
non-volatile memory cell. Because the select gate is in series with
the memory gate, the erased state of the memory gate can be near or
in depletion mode (i.e., threshold voltage, Vt, less than zero
volt). Even when the erased memory gate is in such depletion mode,
the select gate in the off state prevents the channel from
conducting substantial current. With the threshold voltage of the
erased state near or below zero, the threshold voltage of the
programmed state does not need to be very high while still
providing a reasonable read margin between erased and programmed
states. Accordingly, the voltages applied to both select gate and
memory gate in read operation can be less than or equal to the
supply voltage. Therefore, not having to pump the supply voltage to
a higher level makes the read operation faster.
[0008] It is common to monolithically incorporate multiple types of
field-effect devices on the same substrate as the memory cells.
Those devices perform, for example, decoding, charge-pumping, and
other functions related to memory operations. The substrate may
also include devices to provide functions that are not related to
memory operations. Such non-memory devices incorporated on the same
substrate as the memory cells may include transistors tailored for
high-speed operations, while other transistors are tailored for
handling high operating voltages. Integrating the processing of
memory cells, such as a split-gate non-volatile memory cell, with
the processing of one or more types of non-memory transistors on
the same substrate is challenging as each requires different
fabrication parameters. For example, for high speed performance
requirement, the gate length of the non-memory transistors needs to
be shorter such that it requires thinner gate stack for easier
processing. However, for non-memory transistors to handle higher
operating voltages, the junction of the transistors needs to be
more graded. This usually is accomplished by higher implantation
energy during the junction formation. Thicker gate stack is needed
to prevent implant penetration. Therefore, it is desirable to have
a method to have different gate stack thickness for different
non-memory transistors and integrate with non-volatile memory cells
on the same semiconductor device. Accordingly, there is a need for
device and methods for integrating a memory cell and other devices
with different electrical requirements on the same substrate to
facilitate improved cost, performance, reliability, or
manufacturability.
BRIEF SUMMARY OF THE INVENTION
[0009] According to an embodiment, a method of manufacturing a
semiconductor device that includes a first region, a second region,
and a third region is provided. According to the method, a first
gate dielectric is formed on substrate. A select gate dielectric is
formed in the first region after removing the first gate dielectric
from the first region. A select gate can be formed in the first
region and a first logic gate is formed in the second region. The
select gate dielectric which is not covered by the select gate in
the first region was removed. A charge trapping dielectric may then
be disposed. The charge trapping dielectric and the first gate
dielectric can then be removed from the third region and a gate
conductor layer disposed. The gate conductor layer may be removed
(e.g., etched) to define a memory gate on a sidewall of the select
gate and a second logic gate in the third region. The removal of
gate conductor layer may further include deposition and etch of
hard mask stack prior to removal of gate conductor layer.
[0010] According to embodiments, a semiconducting device is
provided. The semiconducting device includes a select gate formed
in a first region, a first logic gate formed in a second region,
and a second logic gate formed in a third region. The thickness of
the first logic gate may be the same or different from the second
logic gate. In case the first logic gate thickness is different
from that of the second logic gate, each of the first logic gate
and second logic gate are formed separately by a single layer of
gate material. Additionally, the device includes a memory gate
formed on a sidewall of the select gate, wherein the memory gate
has a width that is substantially similar to the thickness of the
second logic gate.
[0011] Further features and advantages of embodiments of the
invention, as well as the structure and operation of various
embodiments of the invention, are described in detail below with
reference to the accompanying drawings. It is noted that the
invention is not limited to the specific embodiments described
herein. Such embodiments are presented herein for illustrative
purposes only. Additional embodiments will be apparent to a person
skilled in the relevant art(s) based on the teachings contained
herein.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGS
[0012] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying schematic
drawings in which corresponding reference symbols indicate
corresponding parts. Further, the accompanying drawings, which are
incorporated herein and form part of the specification, illustrate
embodiments of the present invention, and, together with the
description, further serve to explain the principles of the
invention and to enable a person skilled in the relevant art(s) to
make and use the invention.
[0013] FIG. 1 depicts a cross-section of a split-gate non-volatile
memory cell according to various embodiments.
[0014] FIG. 2 is a circuit diagram of a memory cell in a memory
array according to various embodiments.
[0015] FIG. 3 depicts a cross-section of a semiconductor device
according to various embodiments.
[0016] FIG. 4 is a functional block diagram of a semiconductor
device according to various embodiments.
[0017] FIGS. 5A-5J depict a cross-section of a semiconductor device
at several points during its manufacture according to
embodiments.
[0018] FIGS. 6A-6D depict a cross section of a semiconductor device
at several points during its manufacture according to
embodiments.
[0019] FIG. 7 is a flowchart depicting a method of manufacturing a
semiconductor device according to embodiments.
[0020] FIG. 8 is a flowchart depicting a method of manufacturing a
semiconductor device according to embodiments.
[0021] FIG. 9 is a flowchart depicting a method of manufacturing a
semiconductor device according to embodiments.
[0022] FIG. 10 is a flowchart depicting a method of manufacturing a
semiconductor device according to embodiments.
[0023] The features and advantages of embodiments of the present
invention will become more apparent from the detailed description
set forth below when taken in conjunction with the drawings. In the
drawings, like reference numbers generally indicate identical,
functionally similar, and/or structurally similar elements.
DETAILED DESCRIPTION OF THE INVENTION
[0024] This specification discloses one or more embodiments that
incorporate the features of this invention. The disclosed
embodiment(s) merely exemplify the present invention. The scope of
the present invention is not limited to the disclosed
embodiment(s). The present invention is defined by the claims
appended hereto.
[0025] The embodiment(s) described, and references in the
specification to "one embodiment," "an embodiment," "an example
embodiment," etc., indicate that the embodiment(s) described may
include a particular feature, structure, or characteristic, but
every embodiment may not necessarily include the particular
feature, structure, or characteristic. Moreover, such phrases are
not necessarily referring to the same embodiment. Further, when a
particular feature, structure, or characteristic is described in
connection with an embodiment, it is understood that it is within
the knowledge of one skilled in the art to affect such feature,
structure, or characteristic in connection with other embodiments
whether or not explicitly described.
[0026] Before describing the various embodiments in more detail,
further explanation shall be given regarding certain terms that may
be used throughout the descriptions.
[0027] The term "etch" or "etching" is used herein to generally
describe a fabrication process of patterning a material, such that
at least a portion of the material remains after the etch is
completed. For example, it should be understood that the process of
etching silicon involves the steps of patterning a masking layer
(e.g., photoresist or a hard mask) above the silicon, and then
removing the areas of silicon no longer protected by the masking
layer. As such, the areas of silicon protected by the mask would
remain behind after the etch process is complete. However, in
another example, etching may also refer to a process that does not
use a mask, but still leaves behind at least a portion of the
material after the etch process is complete.
[0028] The above description serves to distinguish the term
"etching" from "removing." When etching a material, at least a
portion of the material remains behind after the process is
completed. In contrast, when removing a material, substantially all
of the material is removed in the process. However, in some
embodiments, `removing` is considered to be a broad term that may
incorporate etching.
[0029] During the descriptions herein, various regions of the
substrate upon which the field-effect devices are fabricated are
mentioned. It should be understood that these regions may exist
anywhere on the substrate and furthermore that the regions may not
be mutually exclusive. That is, in some embodiments, portions of
one or more regions may overlap. Although up to three different
regions are described herein, it should be understood that any
number of regions may exist on the substrate and may designate
areas having certain types of devices or materials. In general, the
regions are used to conveniently describe areas of the substrate
that include similar devices and should not limit the scope or
spirit of the described embodiments.
[0030] The terms "deposit" or "dispose" are used herein to describe
the act of applying a layer of material to the substrate. Such
terms are meant to describe any possible layer-forming technique
including, but not limited to, thermal growth, sputtering,
evaporation, chemical vapor deposition, epitaxial growth,
electroplating, etc. According to various embodiments, for
instance, deposition may be performed according to any appropriate
well-known method. For instance, deposition can comprise any
process that grows, coats, or transfers material onto a substrate.
Some well-known technologies include physical vapor deposition
(PVD), chemical vapor deposition (CVD), electrochemical deposition
(ECD), molecular beam epitaxy (MBE), atomic layer deposition (ALD),
and plasma-enhanced CVD (PECVD), amongst others.
[0031] The "substrate" as used throughout the descriptions is most
commonly thought to be silicon. However, the substrate may also be
any of a wide array of semiconductor materials such as germanium,
gallium arsenide, indium phosphide, etc. In other embodiments, the
substrate may be electrically non-conductive such as a glass or
sapphire wafer.
[0032] As used herein, "mask" may comprise any appropriate material
that allows for selective removal (e.g., etching) of an unmasked
portion a material. According to some embodiments, masking
structures may comprise a photoresist such as Poly(methyl
methacrylate) (PMMA), Poly(methyl glutarimide) (PMGI), a Phenol
formaldehyde resin, a suitable epoxy, etc.
[0033] Before describing such embodiments in more detail, it is
instructive to present an example memory cell and environment in
which the present embodiments may be implemented.
[0034] FIG. 1 illustrates an example of a split-gate non-volatile
memory cell 100. Memory cell 100 is formed on a substrate 102, such
as silicon. Substrate 102 is commonly p-type or a p-type well while
a first doped source/drain region 104 and a second doped
source/drain region 106 are n-type. However, it is also possible
for substrate 102 to be n-type while regions 104 and 106 are
p-type.
[0035] Memory cell 100 includes two gates, a select gate 108 and a
memory gate 110. Each gate may comprise a gate conductor such as
doped polycrystalline silicon ("poly") layer formed by well known,
for example, deposit and etch techniques to define the gate
structure. Select gate 108 is disposed over a dielectric layer 112.
Memory gate 110 is disposed over a charge trapping dielectric 114
having one or more dielectric layers. In one example, charge
trapping dielectric 114 includes a charge trapping silicon nitride
layer sandwiched between two silicon dioxide layers to create a
three-layer stack collectively and commonly referred to as "ONO."
Other charge trapping dielectrics may include a silicon-rich
nitride film, or any film that includes, but is not limited to,
silicon, oxygen, and nitrogen in various stoichiometries. A
vertical dielectric 116 is also disposed between select gate 108
and memory gate 110 for electrical isolation between the two gates.
In some examples, vertical dielectric 116 and charge trapping
dielectric 114 are the same dielectric, while other examples form
one dielectric before the other (e.g., they can have different
dielectric properties.) As such, vertical dielectric 116 need not
include the same film structure as charge trapping dielectric 114.
After the gates have been defined, regions 104 and 106 are created
by implanting dopants using, for example, an ion implantation
technique. Regions 104 and 106 form the source or drain of the
split-gate non-volatile memory cell depending on what potentials
are applied to each. In split-gate non-volatile memory cell, for
convenience, region 104 is commonly referred to as the drain, while
region 106 is commonly referred to as the source, independent of
the relative biases. It is to be understood that this description
is meant to provide a general overview of common split-gate
architecture and that, in actual practice, many more detailed steps
and layers are provided to form the final memory cell 100.
[0036] An example write, read, and erase operation will now be
described as it relates to memory cell 100. In order to write a bit
in memory cell 100, a positive voltage on the order of 5 volts, for
example, is applied to region 106 while region 104 is either
grounded or at a certain bias such as 0.5V, and substrate 102 is
grounded. A low positive voltage on the order of 1.5 volts, for
example, is applied to select gate 108 while a higher positive
voltage on the order of 8 volts, for example, is applied to memory
gate 110. As electrons are accelerated within a channel region
between the source and drain, some of them will acquire sufficient
energy to be injected upwards and get trapped inside charge
trapping dielectric 114. This is known as hot electron injection.
In one example of charge trapping dielectric 114, the electrons are
trapped within a nitride layer of charge trapping dielectric 114.
This nitride layer is also commonly referred to as the charge
trapping layer. The trapped charge within charge trapping
dielectric 114 store the "high" bit within memory cell 100, even
after the various supply voltages are removed.
[0037] In order to "erase" the stored charge within memory cell 100
and return the state of memory cell 100 to a "low" bit, a positive
voltage on the order of 5 volts, for example, is applied to region
106 while region 104 is floated or at a certain bias, and select
gate 108 and substrate 102 are typically grounded. A high negative
voltage on the order of -8 volts, for example, is applied to memory
gate 110. The bias conditions between memory gate 110 and region
106 generate holes through band-to-band tunneling. The generated
holes are sufficiently energized by the strong electric field under
memory gate 110 and are injected upwards into charge trapping
dielectric 114. The injected holes effectively erase the memory
cell 100 to the "low" bit state.
[0038] In order to "read" the stored bit of memory cell 100, a low
voltage is applied to each of the select gate, memory gate, and
region 104 in the range between zero and 3 volts, for example,
while region 106 and substrate 102 are typically grounded. The low
voltage applied to the memory gate is chosen so that it lies
substantially equidistant between the threshold voltage necessary
to turn on the transistor when storing a "high" bit and the
threshold voltage necessary to turn on the transistor when storing
a "low" bit in order to clearly distinguish between the two states.
For example, if the application of the low voltage during the
"read" operation caused substantial current to flow between regions
104 and 106, then the memory cell holds a "low" bit and if the
application of the low voltage during the "read" operation does not
cause substantial current to flow between regions 104 and 106, then
the memory cell holds a "high" bit.
[0039] FIG. 2 illustrates an example circuit diagram 200 that
comprises a memory cell 100 including connections to various metal
layers in a semiconductor device. Only a single memory cell 100 is
illustrated, however, as evidenced by the ellipses in both the X
and Y direction, an array of memory cells may be connected by the
various lines running in both the X and Y directions. In this way,
one or more memory cells 100 may be selected for reading, writing,
and erasing bits based on the bit line (BL) and source line (SL)
used.
[0040] An example source line (SL) runs along the X direction and
is formed in a first metal layer (M1). Source line (SL) may be used
to make electrical connection with doped region 106 of each memory
cell 100 along a row extending in the X direction.
[0041] An example bit line (BL) runs along the Y direction and is
formed in a second metal layer (M2). Bit line (BL) may be used to
make electrical connection with doped region 104 of each memory
cell 100 along a column extending in the Y direction.
[0042] It is to be understood that the circuit connections shown in
FIG. 2 are only exemplary and that the various connections could be
made in different metal layers than those illustrated. Furthermore,
although not depicted, memory cells 100 may be arrayed in the Z
direction as well formed within multiple stacked layers.
[0043] FIG. 3 illustrates an example semiconductor device 300 that
includes both memory circuitry 302 and peripheral circuitry 304 in
the same substrate 102. In this example, substrate 102 includes a
core region 302 and a periphery region 304. Core region 302
includes a plurality of memory cells 100 that may operate similarly
to those previously described. It should be understood that the
cross-section of FIG. 3 is only exemplary, and that core region 302
and periphery region 304 may be located in any area of substrate
102 and may be made up of various different regions. Furthermore,
core region 302 and periphery region 304 may exist in the same
general area of substrate 102.
[0044] Substrate 302--and indeed substrates in general as used
throughout the description--can be silicon according to various
embodiments. However, the substrate 302 may also be any of a wide
array of semiconductor materials such as germanium, gallium
arsenide, indium phosphide, etc. In other embodiments, the
substrate 302 may be electrically non-conductive such as a glass or
sapphire wafer.
[0045] Periphery region 304 may include integrated circuit
components such as resistors, capacitors, inductors, etc., as well
as transistors. In the illustrated embodiment, periphery region 304
includes a plurality of high-voltage transistors 306 and
low-voltage transistors 308. In one example, high-voltage
transistors 306 exist in a separate region of substrate 102 than
low-voltage transistors 308. High-voltage transistors 306 are
capable of handling voltages up to 20 volts in magnitude, for
example, while low-voltage transistors 308 operate at a faster
speed, but cannot operate at the same high voltages as high-voltage
transistors 306. In an embodiment, low voltage transistors 308 are
designed to have a shorter gate length than high voltage
transistors 306. High-voltage transistors 306 are commonly
characterized as having a thicker gate dielectric 310 than the gate
dielectric of low-voltage transistors 308. As shown in FIG. 3, low
voltage transistors 308 have a narrower width than high-voltage
transistors 306, but this need not be the case. According to some
embodiments, low-voltage 308 transistors can be wider than high
voltage transistors 306 or, alternatively, low-voltage transistors
308 and high-voltage transistors 306 can have the same width.
[0046] During the descriptions herein, various regions of the
substrate upon which the field-effect devices are fabricated are
mentioned. For instance, with respect to FIG. 3, core region 302
and periphery region 304 were described. It should be understood
that these regions may exist anywhere on the substrate and
furthermore that the regions may not be mutually exclusive. That
is, in some embodiments, portions of one or more regions may
overlap. Although up to three different regions are described
herein, it should be understood that any number of regions may
exist on the substrate and may designate areas having certain types
of devices or materials. In general, the regions are used to
conveniently describe areas of the substrate that include similar
devices and should not limit the scope or spirit of the described
embodiments.
[0047] FIG. 4 is a functional block diagram of a semiconductor
device 402 according to embodiments of the present invention. As
shown, semiconductor device 402 includes a non-volatile memory
array 404, high voltage control logic 406, and low voltage control
logic 408. According to various embodiments, the memory array 404
may comprise a number of memory cells 100 and may be physically
located in a core region 302 of semiconductor device 402. High
voltage control logic 406 may comprise a number of high-voltage
transistors 306, which can be used to control and/or drive portions
of the memory array 404. Additionally, the high voltage control
logic 406 may be physically located in the periphery 304 of the
semiconductor device 402. Similarly to the high voltage control
logic 406, the low voltage control logic 408 may comprise a number
of low voltage transistors 308, which can be used to control and/or
drive portions of the memory array 404. The low voltage control
logic 408 may also be located in the periphery 304 of the
semiconductor device. According to various embodiments, the high
voltage control logic 406 and the low voltage control logic 408 are
located in different portions of the periphery region 304. In
addition, the low voltage control logic 408 may also include a
micro-controller and analog circuits for control the operation of
semiconductor device 402.
[0048] FIGS. 5A-5J depict a cross-section of a semiconducting
device 500 at various points during its manufacture according to
embodiments of the present invention. FIG. 5A depicts
semiconducting device 500 after several initial features have been
formed. As depicted in FIG. 5A, the device 500 comprises a
substrate layer 502 which is divided into several regions.
[0049] A first or memory region 504 of the substrate may be used
for memory components. According to various embodiments, the first
region 504 comprises a memory core region where a plurality memory
cells 100 can be formed. For instance, according to some
embodiments, the first region may be used to form a number of
select gate 108/memory gate 110 pairs.
[0050] Logic and/or control circuitry may be formed in periphery,
which includes second and third regions 506 and 508, respectively
according to various embodiments. The second region 506 may
comprise the high voltage control logic region 406 and the third
region 508 may comprise the low voltage control logic region
408.
[0051] As shown in FIG. 5A, the gate dielectric 510a is formed
(e.g., deposited) in first region 504 and gate dielectric 510b has
been disposed in second region 506 and in third region 508.
According to various embodiments the gate dielectrics 510a and 510b
may be different thicknesses, but this need not be the case. The
gate dielectrics 510a and 510b may be formed through any well-known
method. For instance, the dielectrics 510a and 510b may be grown on
the substrate 502. The dielectric 510a in the first region 504 may
also be formed independently of dielectric 510b disposed in the
second and third regions 506 and 508. It is also possible, however,
for the gate dielectrics 510a and 510b to be disposed on the
substrate and comprise an oxide of a different material than the
substrate 502 or an oxide of the same material as the substrate
502. Additionally, dielectrics 510a and 510b may comprise the same
or different material and may be formed at the same time or at
different times according to various embodiments.
[0052] FIG. 5B depicts a cross section of device 500 after a layer
of gate conductor 512 has been disposed. The gate conductor 512 may
comprise any suitable conductor such as, for example, poly. As
shown in FIG. 5B, the gate conductor layer 512 is disposed over the
gate dielectric 510a in the first region 504 and over gate
dielectric 510b in second region 506 and the third region 508.
[0053] In FIG. 5C, a mask 514a is applied to the substrate over a
portion of the gate conductor layer 512 disposed in the first
region 504. Similarly, a mask 514b is disposed over a portion of
the gate conductor layer 512 disposed in the second region 506. No
mask is disposed in the third region. According to various
embodiments, the masks 514a and 514b will be used to form a select
gate in the first region 504 and a transistor gate in the second
region 506. Masks 514a and 514b may comprise any appropriate
material that allows for selective removal (e.g., etching) of the
unmasked portion of the gate conductor layer 512. According to some
embodiments, masking structures may comprise a photoresist such as
Poly(methyl methacrylate) (PMMA), Poly(methyl glutarimide) (PMGI),
a Phenol formaldehyde resin, a suitable epoxy, etc.
[0054] FIG. 5D depicts a cross section of device 500 after the
unmasked portion of gate conductor layer 512 has been removed along
with masks 514a and 514b. As can be seen in FIG. 5D, a select gate
516 has been formed in the first region 504 over gate dielectric
510a. Additionally, a second gate 518 has been formed in the second
region 506 over gate dielectric 506. According to various
embodiments, the gate conductor layer 512 can be removed by any
appropriate method such as etching. According to various
embodiments, the removed portion of the gate conductor layer 512 is
removed using well-known etching methods. For instance, the gate
conductor layer 512 may be etched using Cl2, KOH, TMAH
(tetra-methyl-amino-hydroxyl), or using gas phase etching with, for
instance, H2, HCl, O2, H2O (vapor or gas), O3, HF, F2, and
Carbon-Fluoride compounds with Cl2 and XeF2. Additionally,
according to some embodiments, a combination of etching products
may be used.
[0055] FIG. 5E depicts a cross section of device 500 after several
additional structures have been formed according to various
embodiments. As shown in FIG. 5E, the portion of dielectric 510a
which is non-covered by SG 516 in first region was first removed,
and a charge trapping dielectric 522 was disposed over the entire
device 500. According to various embodiments, the charge trapping
dielectric comprises one or more layers of dielectric such as ONO,
as described above. For instance, the charge trapping dielectric
522 may comprise a first dielectric layer 522a, a nitride layer
522b, and a second dielectric layer 522c. According to various
embodiments the first dielectric layer 522a and the second
dielectric layer 522c may comprise any suitable dielectric, such as
an oxide. Regardless of the specific composition of the charge
trapping dielectric 522, it preferably contains at least one charge
trapping layer such as nitride layer 522b. The charge trapping
layer may be formed of a nitride, silicon rich nitride, and may
include multiple layers of different nitrides according to some
embodiments. A masking layer 520 has also been formed to cover the
first region 504 and second region 506. The charge trapping
dielectric 522 and dielectric 510b in the third region 508 were
removed by etch method. Finally, a gate dielectric 510c has been
formed over the portion of the substrate 502 disposed in the third
region 508, after masking layer 520 is removed.
[0056] FIG. 5F depicts a cross section of device 500 at a later
stage during the manufacturing process. As shown in FIG. 5F, a
second gate conductor layer 524 has also been disposed in all three
regions 505, 506, and 508 of the device 500. According to some
embodiments, the second gate conductor layer 524 is thinner than
the previously-deposited gate conductor layer 512. Additionally,
the second gate conductor layer 524 may be disposed so that it is
substantially conformal to the device 500.
[0057] FIG. 5G depicts a cross section of device 500 at a later
stage of the manufacturing process according to various
embodiments. As shown in FIG. 5G, a mask 536 has been disposed over
a portion of the second gate conductor layer 524 that is disposed
in the third region 508. The portions of the second gate conductor
524 that are disposed in the first region 504 and in the second
region 506 remain unmasked.
[0058] FIG. 5H depicts a cross section of device 500 after a
portion of the second gate conductor layer has been removed by, for
instance, etching. As shown, removal of the second gate conductor
layer 524 has formed a gate 526 over the dielectric 510c in the
third region 508. Additionally, a portion 528 of the second gate
conductor layer 524 has remained disposed on the sidewalls of the
select gate 516 and gate 518. According to various embodiments, one
of the portions 528 will be used as a memory gate for memory a
memory cell 100 in the first region 504.
[0059] FIG. 5I depicts a cross section of device 500 at a later
stage of the production process. As shown in FIG. 5I, the portion
528 disposed on the right sidewall of the select gate 516 will be
used as the memory gate for the memory cell 100 disposed in the
first region 504. Accordingly, the memory gate 528 has been masked
by mask 530 along with a portion of the third region 508 containing
the gate 526, which is formed of the second gate conductor. This
masking will allow further removal of the second gate conductor 524
from the left side of the select gate 516 (as indicated by
reference number 534) and from sidewalls of gate 518.
[0060] FIG. 5J depicts a cross section of device 500 according to
various embodiments. As shown in FIG. 5J, the remaining portion 528
of the second gate conductor 524 has been removed (e.g., etched)
from the left sidewall of the select gate 516 and from both
sidewalls of gate 518. Additionally, the charge trapping dielectric
522 has been removed from all portions of the device except the
portion of the device separating the memory gate 528 from the
substrate 502 and the select gate 516.
[0061] As can be seen in FIG. 5J, the device 500 contains a
split-gate non-volatile memory cell 532 that includes a select gate
516, a memory gate 528, and a charge trapping dielectric. As
explained above, the charge trapping dielectric may comprise
several dielectric layers. For instance, the charge trapping
dielectric may include a nitride layer sandwiched between two
dielectric layers according to various embodiments. In such a
scenario, the nitride layer may function as the charge trapping
layer. That is, the nitride layer may function to trap charge
within the dielectric to store a value for the memory cell.
[0062] Because gate 526 and memory gate 528 were formed from the
same layer of gate conductor--the second gate conductor layer 524
in this case--the height h1 of gate 526 is substantially the same
as the width w1 of the memory gate 528 at its base according to
various embodiments. Additionally, since the select gate 516 and
gate 518 are formed of the same gate conductor layer 510, they may
have substantially the same height h2 according to various
embodiments. Since gate conductor layer 512 and gate conductor
layer 524 were deposited at different time, thickness of h1 and h2
can be either the same or different. In addition, each gate
conductor layer 512 and 524 are formed by a single gate conductor
deposition separately.
[0063] According to some embodiments, an alternative to the process
shown in FIG. 5G may be performed subsequent to the process step
depicted in FIG. 5F. This alternative "hard mask" process is
described with respect to FIGS. 6A-6D. FIG. 6A depicts device 500
after the steps described with respect to FIG. 5F have been
performed. Additionally, a first hard mask layer 542 is formed on
top of gate conductor layer 524. A second hard mask layer 544 can
be formed over the first hard mask layer 542. Together, hard first
and second hard mask layers 542 and 544 can be termed a "hard mask
stack." A mask 546 is formed to cover the third region 508. As
shown in FIG. 6A, mask 546 covers the entirety of the third region,
but this need not be the case.
[0064] In FIG. 6B depicts a cross section of device 500 after the
portion of the second hard mask 544 that was not itself masked by
mask 546 has been removed by, e.g., etching.
[0065] FIG. 6C depicts a cross section of device 500 after the mask
layer 546 has been removed. Additionally, the portion of the hard
mask stack 542 and 544 that was in the first and second regions 504
and 506 has been removed. That is, the hard mask stack 542 and 544
only remains in the third region 508.
[0066] FIG. 6D, depicts a cross section of device 500 after the
forming of a mask 536 over the remaining hard mask layers 542 and
544 in the third region 508. The portions of the second gate
conductor 524 that are disposed in the first region 504 and in the
second region 506 remain unmasked and can be removed at later steps
illustrated in FIG. 5H.
[0067] FIG. 7 is a flowchart depicting a method 700 of
manufacturing a semiconductor device 500 according to various
embodiments of the invention. Method 700 will be described with
simultaneous reference to FIGS. 5A-5J for ease of understanding. It
should be understood, however, that method 600 is not so limited to
the embodiments depicted in FIGS. 5A-5J.
[0068] As shown in FIG. 7, a gate dielectric is formed at step 702.
According to various embodiments, the gate dielectric 510b is
formed on entire surface of semiconductor device 500. A masking and
etch step is performed to remove gate dielectric 510b from the
first region 504, and followed by gate dielectric growth 510a in
first region 504. At this step, both the second region 506 and
third region 508 have gate dielectric 510b, while first region 504
has gate dielectric 510a. Additionally, the gate dielectric formed
in each of the regions could be the same or different. For
instance, according to some embodiments the gate dielectric 510a
formed in the first region 504 could be thinner than the gate
dielectric 510b. However, it is also possible to form a gate
dielectric that is consistent throughout all of the three regions
504, 506, and 508.
[0069] At step 704, a first layer of gate conductor 512 is disposed
on the semiconductor device 500. As noted above, the first layer of
gate conductor 512 may be disposed using any appropriate method
such as through deposition. According to some embodiments, the gate
conductor layer 512 can be disposed conformally over the
already-formed structures. For instance, the gate conductor layer
512 can be disposed conformally over gate dielectric 510a in the
first region 504 and over 510b in the second region 506 and third
region 508.
[0070] At step 706, a select gate 516 and a logic gate 518 are
defined from the first gate conductor layer 512. According to
various embodiments, this can be accomplished by forming a mask
514a in the first region 504 over the first gate conductor layer
512 and forming a mask 514b over the first gate conductor layer
512. The masks 514a and 514b can be used to define the select gate
and logic gate, respectively, as the first gate conductor layer 512
is masked.
[0071] At step 708, a charge trapping dielectric 522 is formed on
device 500. According to various embodiments, the charge trapping
dielectric may be formed over all three regions 504, 506, and 508
of device 500. Additionally, the charge trapping dielectric may be
formed of one or more dielectric layers. For instance, the charge
trapping dielectric 522 may comprise a first dielectric layer 522a,
a nitride layer 522b, and a second dielectric layer 522c.
Regardless of the specific composition of the charge trapping
dielectric 522, it preferably contains at least one charge trapping
layer such as nitride layer 522b. The charge trapping layer may be
formed of a nitride, silicon rich nitride, and may include multiple
layers of different nitrides according to some embodiments. Prior
to forming the charge trapping dielectric 522 it is possible to
remove the portion of dielectric 510a left uncovered by select gate
516 from the first region.
[0072] At step 710, a second gate conductor layer 524 can be
disposed in all three regions 504, 506, and 508 by, for instance,
deposition. The second gate conductor layer 524 may be thinner than
the first gate conductor layer 512. The second gate conductor layer
524 can then be removed (e.g., etched) at step 712 to define a
second logic gate 526 in the third region 508. Additionally a
memory gate 528 may be defined from the second gate conductor layer
524. Preferably, the memory gate 526 is formed on the sidewall from
of the select gate 516 and is separated from the select gate 516 by
the charge trapping dielectric 522. Additionally, the memory gate
526 is separated from the substrate 502 by charge trapping
dielectric 522. Together the select gate 516, charge trapping
dielectric, and the memory gate 526 form a split-gate non-volatile
memory cell 532. Additionally, because the memory gate 528 and the
logic gate 526 were formed from the same layer of gate conductor
524, the height of gate 526 is substantially the same as the width
of the memory gate 528 at its base. Similarly, because select gate
516 and gate 518 were formed from the same layer of gate conductor
512, they have substantially the same height according to various
embodiments. Step 610 may also include a masking and etch step is
in order to cover the first and second region, and remove the
charge trapping dielectric layer 522 and gate dielectric 510b from
the third region.
[0073] FIG. 8 is a flowchart depicting a method 800 of
manufacturing a semiconductor device 500 according to various
embodiments of the invention. Similarly to the description of
method 700, method 800 will be described with simultaneous
reference to FIGS. 5A-5J for ease of understanding. It should be
understood, however, that method 800 is not so limited to the
embodiments depicted in FIGS. 5A-5J.
[0074] As shown in FIG. 8, the gate dielectric 510b is formed at
step 802 over entire surface of semiconductor device 500. A masking
and etch step is performed to remove gate dielectric 510b from the
first region 504, and followed by gate dielectric growth 510a in
first region 504. At this step, both the second region 506 and
third region 508 have gate dielectric 510b, while first region 504
has gate dielectric 510a. Additionally, the gate dielectric formed
in each of the regions could be the same or different. For
instance, according to some embodiments the gate dielectric 510a
formed in the first region 504 could be thinner than the gate
dielectric 510b. However, it is also possible to form a gate
dielectric that is consistent throughout all of the three regions
504, 506, and 508.
[0075] At step 804, a first layer of gate conductor 512 is disposed
on the semiconductor device 500. As noted above, the first layer of
gate conductor 512 may be disposed using any appropriate method
such as through deposition. According to some embodiments, the gate
conductor layer 512 can be disposed conformally over the
already-formed structures. For instance, the gate conductor layer
512 can be disposed conformaly over gate dielectric 510a in the
first region 504 and over 510b in the second region 506 and third
region 508.
[0076] At step 806, a select gate 516 and a logic gate 518 are
defined from the first gate conductor layer 512. According to
various embodiments, this can be accomplished by forming a mask
514a in the first region 504 over the first gate conductor layer
512 and forming a mask 514b over the first gate conductor layer
512. The masks 514a and 514b can be used to define the select gate
and logic gate, respectively, as the first gate conductor layer 512
is masked.
[0077] At step 808, a charge trapping dielectric 522 is formed on
device 500. According to various embodiments, the charge trapping
dielectric may be formed over all three regions 504, 506, and 508
of device 500. Additionally, the charge trapping dielectric may be
formed of one or more dielectric layers. For instance, the charge
trapping dielectric 522 may comprise a first dielectric layer 522a,
a nitride layer 522b, and a second dielectric layer 522c.
Regardless of the specific composition of the charge trapping
dielectric 522, it preferably contains at least one charge trapping
layer such as nitride layer 522b. The charge trapping layer may be
formed of a nitride, silicon rich nitride, and may include multiple
layers of different nitrides according to some embodiments. Prior
to forming the charge trapping dielectric 522 it is possible to
remove the portion of dielectric 510a left uncovered by select gate
516 from the first region.
[0078] At step 810, the charge trapping dielectric 522 can be
removed from the third region 508. According to various
embodiments, the portion of the charge trapping dielectric 522 that
is to be removed can be removed by masking and etching to cover the
first and second regions 504 and 508 and to remove the charge
trapping dielectric 522 and gate dielectric 510c from the third
region 508.
[0079] At step 812, a second gate conductor layer 524 can be
disposed in all three regions 504, 506, and 508 by, for instance,
deposition. The second gate conductor layer 524 may be thinner than
the first gate conductor layer 512.
[0080] At step 814, a hard mask may be employed to protect the
third region 508. The hard mask may comprise any appropriate
material or combination of materials such as amorphous carbon, SiN,
SiON, SiO2, or some combination thereof. As an example, as shown in
FIGS. 6A-6D, amorphous carbon as first hard mask layer 542 is
deposited over the entire gate conductor layer 524, followed by
deposition of SiON as second had mask layer 544. A masking step 546
is used to cover the third region, and the SiON 544 at the first
and second regions 504 and 506 is removed. The SION 544 at third
region is used as a mask to protect the amorphous carbon 542 at
third region and to etch the amorphous carbon 542 in first and
second region. The masking layer 546 is also removed during the
removal of mask 542 in the first and second regions. At this step,
only the amorphous carbon 542 and SiON 544 at third region are
remained
[0081] At step 816, the second gate conductor layer 524 can then be
removed (e.g., etched) to define a second logic gate 526 in the
third region 508 by using masking layer 536. Additionally a memory
gate 528 may be defined from the second gate conductor layer 524.
Preferably, the memory gate 528 is formed on the sidewall of the
select gate 516 and is separated from the select gate 516 by the
charge trapping dielectric 522. Additionally, the memory gate 528
is separated from the substrate 502 by charge trapping dielectric
522. Together the select gate 516, charge trapping dielectric, and
the memory gate 528 form a split-gate non-volatile memory cell 532.
Additionally, because the memory gate 528 and the logic gate 526
were formed from the same layer of gate conductor 524, the height
of gate 526 is substantially the same as the width of the memory
gate 528 at its base. Similarly, because select gate 516 and first
logic gate 518 were formed from the same layer of gate conductor
512, they have substantially the same height according to various
embodiments.
[0082] FIG. 9 is a flowchart depicting a method 900 of
manufacturing a semiconductor device 500 according to various
embodiments. Method 900 will be described with reference to FIGS.
6A-6D. As shown in FIG. 9, a first hard mask layer 542 may be
formed at step 902 on top of the gate conductor layer 524. A second
hard mask layer 544 may be formed at step 904. At step 906, the
third region 508 is masked with mask 546. As shown in FIG. 6A, mask
546 covers the entirety of the third region, but this need not be
the case.
[0083] At step 908, the portion of the second hard mask 544 that
was not itself masked by mask 546 has been removed by, e.g.,
etching. A subsequent etching step may also be employed to remove
the portion of first hard mask 542 from first and second region by
using the remaining hard mask 544 in the third region. The mask
layer 546 is also removed either at the same step or prior to
removal of 542 in first and second region. At this step, only the
third region had mask 542 and 544 remain.
[0084] At step 910, the logic gate mask 536 is formed over the
remaining hard mask layers 542 and 544 in the third region 508. The
portions of the second gate conductor 524 that are disposed in the
first region 504 and in the second region 506 remain unmasked and
can be removed at later steps illustrated in, for instance, FIG.
5H.
[0085] FIG. 10 is a flowchart depicting a method 1000 of
manufacturing a semiconductor device 500 according to various
embodiments of the invention. Similarly to the description of
methods 700 and 800, method 1000 will be described with
simultaneous reference to FIGS. 5A-5J for ease of understanding. It
should be understood, however, that method 1000 is not so limited
to the embodiments depicted in FIGS. 5A-5J.
[0086] As shown in FIG. 10, gate dielectric is formed at step 1002.
According to various embodiments, the gate dielectric 510b is
formed on entire surface of semiconductor device 500. A masking and
etch step is performed to remove gate dielectric 510b from the
first region 504, and followed by gate dielectric growth 510a in
first region 504. At this step, both the second region 506 and
third region 508 have gate dielectric 510b, while first region 504
has gate dielectric 510a. For instance, a gate dielectric 510a
could be formed in a first region 504 of the semiconductor device
500, a gate dielectric 510b could be formed in a second region 506
of the semiconductor device 500, and no gate dielectric formed in a
third region 508 of the semiconductor device. However, according to
some embodiments, gate dielectric could be formed in all of the
first region 504, the second region 506, and the third region
508.
[0087] At step 1004, a first layer of gate conductor 512 is
disposed on the semiconductor device 500. As noted above, the first
layer of gate conductor 512 may be disposed using any appropriate
method such as through deposition. According to some embodiments,
the gate conductor layer 512 can be disposed conformally over the
already-formed structures. For instance, the gate conductor layer
512 can be disposed conformally over gate dielectric 510a in the
first region 504 and over 510b in the second region 506. If no gate
dielectric has been formed in the third region 508, then the gate
conductor layer 512 can be disposed directly on top of substrate
502 in the third region 508. However, if a gate dielectric 510c has
been formed in the third region 508, then the gate conductor layer
512 is disposed over the gate dielectric 510c.
[0088] At step 1006, a select gate 516 and a logic gate 518 are
defined from the first gate conductor layer 512. According to
various embodiments, this can be accomplished by forming a mask
514a in the first region 504 over the first gate conductor layer
512 and forming a mask 514b over the first gate conductor layer
512. The masks 514a and 514b can be used to define the select gate
and logic gate, respectively, as the first gate conductor layer 512
is masked.
[0089] At step 1008, a charge trapping dielectric 522 is formed on
device 500. According to various embodiments, the charge trapping
dielectric may be formed over all three regions 504, 506, and 508
of device 500. Additionally, the charge trapping dielectric may be
formed of one or more dielectric layers. For instance, the charge
trapping dielectric 522 may comprise a first dielectric layer 522a,
a nitride layer 522b, and a second dielectric layer 522c.
Regardless of the specific composition of the charge trapping
dielectric 522, it preferably contains at least one charge trapping
layer such as nitride layer 522b. The charge trapping layer may be
formed of a nitride, silicon rich nitride, and may include multiple
layers of different nitrides according to some embodiments. Prior
to forming the charge trapping dielectric 522 it is possible to
remove the portion of dielectric 510a left uncovered by select gate
516 from the first region.
[0090] At step 1010, the charge trapping dielectric 522 can be
removed from the third region 508. According to various
embodiments, the portion of the charge trapping dielectric 522 that
is to be removed can be removed by masking and etching to cover the
first and second regions 504 and 508 and to remove the charge
trapping dielectric 522 and gate dielectric 510c from the third
region 508.
[0091] At step 1012, a second gate conductor layer 524 can be
disposed in all three regions 504, 506, and 508 by, for instance,
deposition. The second gate conductor layer 524 may be thinner than
the first gate conductor layer 512.
[0092] At step 1014, a hard mask stack may be employed to protect
the third region 508. The hard mask may comprise any appropriate
material or combination of materials such as amorphous carbon, SiN,
SiON, SiO2, or some combination thereof. As an example, as shown in
FIG. 6A-6D, SiN as first hard mask layer 542 is deposited over the
entire second gate conductor layer 524, followed by deposition of
second hard mask layer 544 SiO2. A masking step 546 is used to
cover the third region and remove the SiO2 544 in the first and
second region. After the removal of mask layer 546, hard mask 542
in the first and second regions 504 and 506 can be removed by using
the remaining mask 544 in the third region to mask. At this step,
only the hard mask stack 542 and 544 only remains in the third
region.
[0093] The second gate conductor layer 524 can then be removed
(e.g., etched) at step 1016 to define a second logic gate 526 in
the third region 508. According to embodiments, the second logic
gate 526 is defined by forming a logic gate mask 536 over the
remaining hard mask layers 542 and 544 in the third region 508.
Additionally a memory gate 528 may be defined from the second gate
conductor layer 524. Preferably, the memory gate 526 is formed on
the sidewall from of the select gate 516 and is separated from the
select gate 516 by the charge trapping dielectric 522.
Additionally, the memory gate 526 is separated from the substrate
503 by charge trapping dielectric 522. Together the select gate
516, charge trapping dielectric, and the memory gate 526 form a
split-gate non-volatile memory cell 532. Additionally, because the
memory gate 528 and the logic gate 526 were formed from the same
layer of gate conductor 524, the height of gate 526 is
substantially the same as the width of the memory gate 528 at its
base. Similarly, because select gate 516 and gate 518 were formed
from the same layer of gate conductor 512, they have substantially
the same height according to various embodiments.
[0094] It is to be appreciated that the Detailed Description
section, and not the Summary and Abstract sections, is intended to
be used to interpret the claims. The Summary and Abstract sections
may set forth one or more but not all exemplary embodiments of the
present invention as contemplated by the inventor(s), and thus, are
not intended to limit the present invention and the appended claims
in any way.
[0095] Embodiments of the present invention have been described
above with the aid of functional building blocks illustrating the
implementation of specified functions and relationships thereof.
The boundaries of these functional building blocks have been
arbitrarily defined herein for the convenience of the description.
Alternate boundaries can be defined so long as the specified
functions and relationships thereof are appropriately
performed.
[0096] The foregoing description of the specific embodiments will
so fully reveal the general nature of the invention that others
can, by applying knowledge within the skill of the art, readily
modify and/or adapt for various applications such specific
embodiments, without undue experimentation, without departing from
the general concept of the present invention. Therefore, such
adaptations and modifications are intended to be within the meaning
and range of equivalents of the disclosed embodiments, based on the
teaching and guidance presented herein. It is to be understood that
the phraseology or terminology herein is for the purpose of
description and not of limitation, such that the terminology or
phraseology of the present specification is to be interpreted by
the skilled artisan in light of the teachings and guidance.
[0097] The breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims and
their equivalents.
* * * * *