U.S. patent application number 15/053485 was filed with the patent office on 2017-08-31 for method of forming a semiconductor device structure and semiconductor device structure.
The applicant listed for this patent is GLOBALFOUNDRIES Inc.. Invention is credited to Juergen Faul, Frank Jakubowski.
Application Number | 20170250191 15/053485 |
Document ID | / |
Family ID | 59653565 |
Filed Date | 2017-08-31 |
United States Patent
Application |
20170250191 |
Kind Code |
A1 |
Faul; Juergen ; et
al. |
August 31, 2017 |
METHOD OF FORMING A SEMICONDUCTOR DEVICE STRUCTURE AND
SEMICONDUCTOR DEVICE STRUCTURE
Abstract
The present disclosure provides, in accordance with some
illustrative embodiments, a semiconductor device structure
including a hybrid substrate comprising an SOI region and a bulk
region, the SOI region comprising an active semiconductor layer, a
substrate material, and a buried insulating material interposed
between the active semiconductor layer and the substrate material,
and the bulk region being provided by the substrate material, an
insulating structure formed in the hybrid substrate, the insulating
structure separating the bulk region and the SOI region, and a gate
electrode formed in the bulk region, wherein the insulating
structure is in contact with two opposing sidewalls of the gate
electrode.
Inventors: |
Faul; Juergen; (Radebeul,
DE) ; Jakubowski; Frank; (Dresden, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GLOBALFOUNDRIES Inc. |
Grand Cayman |
|
KY |
|
|
Family ID: |
59653565 |
Appl. No.: |
15/053485 |
Filed: |
February 25, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/40114 20190801;
H01L 27/11582 20130101; H01L 21/31116 20130101; H01L 21/3065
20130101; H01L 29/40117 20190801; H01L 27/11568 20130101; H01L
27/1207 20130101; H01L 21/26513 20130101; H01L 21/308 20130101;
H01L 27/11521 20130101; H01L 28/00 20130101; H01L 29/42352
20130101; H01L 21/76283 20130101; H01L 29/42336 20130101; H01L
21/31144 20130101 |
International
Class: |
H01L 27/115 20060101
H01L027/115; H01L 21/28 20060101 H01L021/28; H01L 21/308 20060101
H01L021/308; H01L 29/423 20060101 H01L029/423; H01L 21/3065
20060101 H01L021/3065; H01L 21/265 20060101 H01L021/265; H01L 27/12
20060101 H01L027/12; H01L 21/762 20060101 H01L021/762; H01L 21/311
20060101 H01L021/311 |
Claims
1. A method of forming a semiconductor device structure, the method
comprising: providing an SOI substrate comprising a substrate
material, an active semiconductor layer positioned above said
substrate material, and a buried insulating material interposed
between said active semiconductor layer and said substrate
material; forming an insulating structure in said SOI substrate,
said insulating structure laterally separating a first substrate
portion of said substrate material from two adjacent SOI substrate
portions; after forming said insulating structure, forming a recess
in said first substrate portion, a bottom of said recess exposing
an upper surface portion of said substrate material; applying an
etching process to said recess, said etching process being
unselective with regard to said insulating structure and said
substrate material; and after applying an etching process to said
recess, forming a gate electrode inside of said recess and above
said upper surface portion of said substrate material at said
bottom of said recess.
2. The method of claim 1, further comprising forming one of a SONOS
structure, MONOS structure, and a floating gate structure inside of
said recess and above said exposed upper surface portion of said
substrate material prior to forming said gate electrode.
3. (canceled)
4. The method of claim 1, further comprising forming a masking
pattern over said first substrate portion and said recess prior to
applying said etching process, wherein said substrate material and
said insulating structure are unselectively etched in said etching
process.
5. The method of claim 4, wherein, during said etching process,
said substrate material in said first substrate portion is
partially etched back relative to substrate material covered by
said masking pattern.
6. The method of claim 1, wherein said insulating structure is
partially etched back in said etching process, said etched back
insulating structure having a recessed portion adjacent to said
substrate material in said first substrate portion.
7. The method of claim 1, wherein said etching process comprises
one of a plasma etching process and a reactive ion etch
process.
8. The method of claim 1, further comprising forming a first oxide
layer on said exposed upper surface portion of said substrate
material in said recess and subsequently forming one of a nitride
material and a floating gate material on said first oxide
layer.
9. The method of claim 8, further comprising forming a second oxide
layer on said one of said nitride material and said floating gate
material, and subsequently forming said gate electrode.
10. The method of claim 9, wherein forming said gate electrode
comprises depositing a gate electrode material over said first
substrate region and subsequently leveling said deposited gate
electrode material with said adjacent SOI substrate portions.
11. The method of claim 4, further comprising forming a PC masking
pattern on said substrate region in alignment with said masking
pattern, said PC masking pattern leaving surface regions of said
first substrate region adjacent to an upper surface of said gate
electrode exposed to further processing.
12. The method of claim 11, wherein said PC masking pattern
represents a negative to said masking pattern in said first
substrate region.
13. The method of claim 11, further comprising forming a sidewall
spacer structure to said gate electrode and subsequently forming at
least one of a halo, source/drain extension and deep source/drain
implantation region in said substrate material of said first
substrate portion.
14. The method of claim 13, further comprising subsequently forming
semiconductor devices in and over said adjacent SOI regions.
15. A method of forming a semiconductor device structure, the
method comprising: providing an SOI substrate comprising a
substrate material, an active semiconductor layer positioned above
said substrate material, and a buried insulating material
interposed between said active semiconductor layer and said
substrate material; forming an insulating structure in said SOI
substrate, said insulating structure laterally separating a first
substrate portion of said substrate material from two adjacent SOI
substrate portions; after forming said insulating structure,
forming a recess in said first substrate portion, a bottom of said
recess exposing an upper surface portion of said substrate
material; forming one of a SONOS structure and a floating gate
inside of said recess and above said exposed upper surface portion
of said substrate material at said bottom of said recess; and
forming a gate electrode inside of said recess and above said one
of said SONOS structure and said floating gate.
16-20. (canceled)
21. The method of claim 15, wherein forming said recess in said
first substrate portion comprises recessing a portion of said
insulating structure.
22. The method of claim 15, further comprising, after forming said
gate electrode, forming source/drain regions in said substrate
material of said first substrate portion.
23. The method of claim 1, wherein forming said recess in said
first substrate portion comprises recessing a portion of said
insulating structure.
24. The method of claim 1, further comprising, after forming said
gate electrode, forming source/drain regions in said substrate
material of said first substrate portion.
25. A method of forming a semiconductor device structure, the
method comprising: providing an SOI substrate comprising an active
semiconductor layer, a substrate material, and a buried insulating
material interposed between said active semiconductor layer and
said substrate material; forming an insulating structure in said
SOI substrate, said insulating structure laterally separating a
first substrate portion from two adjacent SOI substrate portions;
forming a recess in said first substrate portion, said recess
exposing an upper surface portion of said substrate material;
forming a first oxide layer on said exposed upper surface portion
of said substrate material in said recess; forming one of a nitride
material and a floating gate material on said first oxide layer;
forming a second oxide layer on said one of said nitride material
and said floating gate material; and forming a gate electrode in
said recess above said second oxide layer.
Description
BACKGROUND
[0001] 1. Field of the Disclosure
[0002] The present disclosure generally relates to methods of
forming semiconductor device structures and the resulting device
structures, and, more particularly, to the fabrication of
semiconductor device structures in FDSOI techniques implementing
flash devices.
[0003] 2. Description of the Related Art
[0004] In systems requiring a significant amount of non-volatile
solid state storage, flash memory devices became the dominant
memory type due to the low costs as compared to byte-programmable
EEPROM, and the relatively simple structure of flash memory cells.
As flash memories are generally a type of nonvolatile memory
storage, which may be electrically erased and programmed, recent
applications for flash memory devices aim at a replacement for hard
discs, as flash memory devices do not have the mechanical
limitations and latencies of hard drives, so a solid state drive
(SSD) implemented by flash memory devices is attractive when
considering speed, noise, power consumption and reliability.
[0005] Generally, information is stored in a flash memory via an
array of memory cells fabricated in accordance with floating gate
techniques or charge trap flash (CTF) techniques. Herein, CTF is a
term that will be used to generally refer to a semiconductor memory
technology used in creating non-volatile NOR and NAND flash memory,
a technology that differs from the more conventional floating gate
technology in that a silicon nitride film is used to store
electrons rather than the doped polycrystalline silicon typical of
a floating gate structure. In a CTF device, electrons are stored in
a trapping layer just as they are stored in the floating gate,
however, the nitride layer, in accordance with CTF being an
insulator, while the floating gate is made from a conductor.
Therefore, upon high stress being imposed on the tunnel oxide layer
of floating gate transistors (the floating gate is separated from a
general region formed between source and drain by the tunnel
oxide), disruptions in the crystal lattice of the tunnel oxide
layer are created, resulting in so-called "oxide defects." If a
large number of such disruptions are created, a short circuit is
very likely to develop between the floating gate and the
transistor's channel, causing the floating gate to no longer hold a
charge. By contrast, CTF devices are immune to such difficulties,
since charges are trapped in a nitride layer acting as a charge
trapping layer instead of the floating gate. In case oxide defects
appear in the oxide layer separating the charge trapping layer from
the channel region below, charges of the charge trapping layer will
only be drained off at regions in immediate contact with the site
of the oxide defect, leaving the other electrons in place to
continue to control the threshold voltage of a CTF transistor.
[0006] In CTF devices, electrons are moved onto the charge trapping
layer similarly to the way that floating gate NOR flash may be
programmed, i.e., through channel hot electron (CHE) injection,
which is also known as hot carrier injection. Briefly, a high
voltage is applied to the control gate, while a medium high voltage
is applied to source and drain, and a current is induced from
source to drain. As a result, electrons having sufficient energy in
traversing through the high field region near the drain will be
injected into the charge trapping layer where they come to rest.
Charges may be removed from the charge trapping layer via hot hole
injection as opposed to the well-known Fowler-Nordheim tunneling
approach used in NAND and NOR/devices for erasing information.
Accordingly, erasing information in CTF devices rather uses an
electric field than a current that is necessary for Fowler-Nordheim
tunneling, to move holes towards the charge trapping layer.
[0007] Manufacturing floating gate devices and CTF devices is very
similar as both techniques use a stacked gate structure in which a
floating gate or charge trapping layer lies immediately above the
channel and below a control gate. In both techniques, an oxide
layer is formed in between the floating gate or charge trapping
layer and the channel, and between the control gate and the
floating gate or charge trapping layer. Therefore, aside from the
storage layer made of a conductive material in the case of a
floating gate or of nitride in the case of CTF, the materials for
all the remaining layers of the stacked gate structure are actually
very similar in both approaches.
[0008] Currently, fully depleted silicon-on-insulator (FDSOI) is a
favorite basis for next generation technologies in the fabrication
of semiconductor devices at 22 nm and beyond. Herein, a
semiconductor device, such as a MOSFET, is formed on a
semiconductor layer having a thickness such that a depletion region
covers the whole semiconductor layer and a buried oxide layer (BOX)
is interposed between the semiconductor layer and a substrate
material. Although FDSOI techniques are simple (when compared to
3-dimensional techniques, such as FINFETs and the like), the
implementation of flash devices in FDSOI techniques raises several
challenges, such as an excessive topography.
[0009] In view of the above, it is desirable to provide a method of
forming a semiconductor device structure and a semiconductor device
structure that allow the implementation of flash memory in FDSOI
techniques at advanced technology nodes.
SUMMARY OF THE DISCLOSURE
[0010] The following presents a simplified summary of the
disclosure in order to provide a basic understanding of some
aspects of the invention. This summary is not an exhaustive
overview of the invention. It is not intended to identify key or
critical elements of the invention or to delineate the scope of the
invention. Its sole purpose is to present some concepts in a
simplified form as a prelude to the more detailed description that
is discussed later.
[0011] In one illustrative embodiment disclosed herein, a method of
forming a semiconductor device structure is disclosed. In
accordance with some illustrative embodiments herein, the method
includes providing an SOI substrate comprising an active
semiconductor layer, a substrate material, and a buried insulating
material interposed between the active semiconductor layer and the
substrate material, forming an insulating structure in the SOI
substrate, the insulating structure laterally separating a first
substrate portion from two adjacent SOI substrate portions, forming
a recess in the first substrate portion, the recess exposing an
upper surface portion of the substrate material, and forming a gate
electrode in the recess.
[0012] In another illustrative embodiment disclosed herein, a
method of forming a semiconductor device structure is disclosed. In
accordance with some illustrative embodiments herein, the method
includes providing an SOI substrate comprising an active
semiconductor layer, a substrate material, and a buried insulating
material interposed between the active semiconductor layer and the
substrate material, forming an insulating structure in the SOI
substrate, the insulating structure laterally separating a first
substrate portion from two adjacent SOI substrate portions, forming
a recess in the first substrate portion, the recess exposing an
upper surface portion of the substrate material, forming one of a
SONOS structure, a MONOS structure and a floating gate in the
recess, and subsequently forming a gate electrode in the
recess.
[0013] In yet another illustrative embodiment disclosed herein, a
semiconductor device structure is provided. In accordance with some
illustrative embodiments herein, the semiconductor device structure
includes a hybrid substrate comprising an SOI region and a bulk
region, the SOI region comprising an active semiconductor layer, a
substrate material, and a buried insulating material interposed
between the active semiconductor layer and the substrate material,
and the bulk region being provided by the substrate material, an
insulating structure formed in the hybrid substrate, the insulating
structure separating the bulk region and the SOI region, and a gate
electrode formed in the bulk region, wherein the insulating
structure is in contact with two opposing sidewalls of the gate
electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The disclosure may be understood by reference to the
following description taken in conjunction with the accompanying
drawings, in which like reference numerals identify like elements,
and in which:
[0015] FIGS. 1a-1o schematically illustrate, in cross-sectional
views, a fabrication process of forming a semiconductor device
structure in accordance with some illustrative embodiments of the
present disclosure.
[0016] While the subject matter disclosed herein is susceptible to
various modifications and alternative forms, specific embodiments
thereof have been shown by way of example in the drawings and are
herein described in detail. It should be understood, however, that
the description herein of specific embodiments is not intended to
limit the invention to the particular forms disclosed, but on the
contrary, the intention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the
invention as defined by the appended claims.
DETAILED DESCRIPTION
[0017] Various illustrative embodiments of the invention are
described below. In the interest of clarity, not all features of an
actual implementation are described in this specification. It will
of course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions must be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming, but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure.
[0018] The present disclosure will now be described with reference
to the attached figures. Various structures, systems and devices
are schematically depicted in the drawings for purposes of
explanation only and so as to not obscure the present disclosure
with details which are well known to those skilled in the art.
Nevertheless, the attached drawings are included to describe and
explain illustrative examples of the present disclosure. The words
and phrases used herein should be understood and interpreted to
have a meaning consistent with the understanding of those words and
phrases by those skilled in the relevant art. No special definition
of a term or phrase, i.e., a definition that is different from the
ordinary or customary meaning as understood by those skilled in the
art, is intended to be implied by consistent usage of the term or
phrase herein. To the extent that a term or phrase is intended to
have a special meaning, i.e., a meaning other than that understood
by skilled artisans, such a special definition shall be
expressively set forth in the specification in a definitional
manner that directly and unequivocally provides the special
definition for the term or phrase. For example, the person skilled
in the art will appreciate after a complete reading of the present
disclosure that the expression "A over B" is not limited to the
understanding that A is directly disposed on B, i.e., A and B being
in physical contact.
[0019] The present disclosure shows, in accordance with some
illustrative embodiments of the present disclosure, the fabrication
of semiconductor devices structures, such as a plurality of MOSFET
or MOS devices integrated on a chip. When referring to MOS devices,
the person skilled in the art will appreciate that, although the
expression "MOS device" is used, no limitation to a
metal-containing gate material and/or to an oxide-containing gate
dielectric material is intended. Accordingly, a semiconductor
device structure may be understood as comprising at least two MOS
devices of at least one of a P-type and an N-type.
[0020] Semiconductor devices of the present disclosure may concern
devices which may be fabricated by using advanced technologies,
i.e., the semiconductor devices may be fabricated by technologies
applied to approach technology nodes smaller than 100 nm, for
example, smaller than 50 nm or smaller than 35 nm, e.g., at 22 nm
or below. After a complete reading of the present application, a
person skilled in the art will appreciate that, according to the
present disclosure, ground rules smaller or equal to 45 nm, e.g.,
at 22 nm or below, may be imposed. The present disclosure proposes
semiconductor devices that may have structures of minimal length
dimensions and/or width dimensions smaller than 100 nm, for
example, smaller than 50 nm or smaller than 35 nm or smaller than
22 nm. For example, the present disclosure may provide
semiconductor devices fabricated by using 45 nm technologies or
below, e.g., 22 nm or even below.
[0021] The semiconductor devices disclosed herein may be fabricated
as P-channel MOS transistors or PMOS transistors and N-channel
transistors or NMOS transistors; both types of transistors may be
fabricated with or without mobility-enhancing stressor features or
strain-inducing features. It is noted that a circuit designer can
mix and match device types, using PMOS and NMOS devices, stressed
and unstressed, to take advantage of the best characteristics of
each device type as they best suit the semiconductor device under
design.
[0022] Furthermore, semiconductor devices as disclosed herein may
be formed as bulk devices and/or SOI (semiconductor-on-insulator)
devices. The expression SOI is not intended as being limited to a
special kind of conventional semiconductor-on-insulator device,
but, in general, SOI devices as disclosed herein have an active
semiconductor layer disposed on a buried insulating material layer,
which, in turn, is formed on a base substrate material. In
accordance with some illustrative embodiments herein, the active
semiconductor layer may comprise one of silicon, germanium, silicon
germanium and the like. The buried insulating material layer may
comprise an insulating material, e.g., silicon oxide or silicon
nitride. The base substrate material may be a base material that
may be used as a substrate as known in the art, e.g., silicon and
the like.
[0023] In accordance with at least some of the herein disclosed
illustrative embodiments employing FDSOI substrates, the active
semiconductor layer may have a thickness of about 20 nm or less,
while the buried insulating material layer may have a thickness of
about 145 nm or, in accordance with advanced techniques, the buried
insulating material layer may have a thickness in a range from
about 10-30 nm. For example, in some special illustrative
embodiments of the present disclosure, the active semiconductor
layer may have a thickness of about 3-10 nm.
[0024] As to a crystalline plane orientation of the base substrate
material, similar to that of an ordinary silicon device, an SOI
substrate having a surface with a face (100) may be used. However,
in order to improve the performance of a PMOS semiconductor device,
a surface of the PMOS semiconductor device may be used as a face
(110). Alternatively, a hybrid plane orientation substrate whose
surface may be mixed by a face (100) and a face (110) may be used.
In alternative embodiments, the base substrate material may be of
an N-type when N-accumulation and/or N-inversion devices are
considered (otherwise P-type for P-accumulation and/or
P-inversion).
[0025] FIG. 1a schematically illustrates, in a cross-sectional
view, an SOI substrate 100 comprising an active semiconductor layer
102, a substrate material 104, and a buried insulating material 106
interposed between the active semiconductor layer 102 and the
substrate material 104. In accordance with some illustrative
embodiments of the present disclosure, the active semiconductor
layer 102 may comprise a semiconductor material, such as silicon,
germanium, silicon germanium, and the like, while the buried
insulating material 106 may be a buried oxide material (e.g., BOX),
a buried nitride material and the like. The substrate material 104
may be formed by a known bulk substrate, such as a silicon bulk
substrate, a germanium bulk substrate, a silicon germanium bulk
substrate and the like.
[0026] In accordance with some illustrative embodiments of the
present disclosure, the SOI substrate 100 may be provided at an
early stage during fabrication. In accordance with some
illustrative examples, the SOI substrate 100 may be formed by known
fabrication methods, such as SIMOX or smart cut techniques.
[0027] As schematically depicted in FIG. 1a, a process of forming
an insulating structure may be initiated by forming a masking
pattern 107' over the SOI substrate 100 as indicated by broken
lines in FIG. 1a. The masking pattern 107' may be formed by known
lithographical methods and may comprise a resist mask or a hard
mask. In accordance with some illustrative embodiments of the
present disclosure, the masking pattern 107' may comprise a
patterned nitride material layer formed over the SOI substrate
100.
[0028] FIG. 1b schematically illustrates the SOI substrate 100 at a
more advanced stage during fabrication, after an insulating
structure 108 is formed in the SOI substrate 100, the insulating
structure 108 laterally separating a substrate portion 110 from
adjacent SOI substrate portions 109. After a complete reading of
the present disclosure, the person skilled in the art will
appreciate that the substrate portion 110 may be a first substrate
portion as referred to in the first and second aspects above.
Alternatively or additionally, the person skilled in the art will
appreciate after a complete reading of the present disclosure that
the substrate portion 110 may represent a portion which is to be
prepared as a bulk region as referred to above in the third aspect
of the present disclosure.
[0029] In accordance with some illustrative embodiments of the
present disclosure, the insulating structure 108 may be formed by a
process comprising: forming the masking pattern 107' (see FIG. 1a),
anisotropically etching the SOI substrate 100 through the masking
pattern 107' for forming trenches (not illustrated) in the SOI
substrate 100, filling the trenches with an insulating material,
e.g., one of an oxide material and a nitride material, and
planarizing the insulating material to form the insulating
structure 108 as depicted in FIG. 1b. In accordance with some
illustrative embodiments herein, the masking pattern 107' may be
one of a resist mask or a hard mask, e.g., a nitride hard mask. The
person skilled in the art will appreciate that, in accordance with
some illustrative examples, the masking pattern 107' may be formed
in accordance with known lithographical techniques.
[0030] In accordance with some special illustrative embodiments of
the present disclosure, the insulating structure 108 may be formed
in accordance with known techniques for forming shallow trench
isolations (STIs), wherein the trenches are etched for partially
exposing an upper surface of the substrate material 104.
Alternatively, the trenches may be etched to partially extend into
the substrate material 104 such that the resulting insulating
structures (i.e., insulating structure 108 in FIG. 1b) may be
partially embedded into the substrate material 104. Accordingly,
the person skilled in the art will appreciate that the illustrated
embodiments are only illustrative in this regard and no limitation
as to the length of the insulating structure 108 extending into the
substrate material 104 is intended.
[0031] With regard to FIG. 1b, a masking pattern 107 may be
subsequently formed, the masking pattern 107 leaving an upper
surface US1 of the substrate region 110, i.e., the active
semiconductor layer 102, exposed to further processing, while
substrate regions 109 are covered by the masking pattern 107. In
accordance with some special illustrative embodiments of the
present disclosure, the masking pattern 107 may be based on the
masking pattern 107' in FIG. 1a, wherein the masking pattern 107'
may be patterned via known patterning techniques so as to expose
the upper surface US1. Alternatively, the masking pattern 107 may
be formed after completely removing the masking pattern 107'.
[0032] FIG. 1c schematically illustrates the substrate portion 110
and the SOI substrate portions 109 at a more advanced stage during
fabrication, after the active semiconductor layer 102 and the
buried insulating material layer 106 are removed in the substrate
portion 110 in accordance with the masking pattern 107 and a recess
R is formed in the substrate portion 110 relative to the SOI
substrate portions 109. Herein, an etching process (not
illustrated) may be performed, optionally comprising plural etching
steps, for anisotropically and sequentially etching the active
semiconductor layer 102 and the buried insulating material layer
106. Accordingly, an upper surface US2 of the bulk semiconductor
material 104 is exposed in the substrate portion 110 in alignment
with the masking pattern 107 and the insulating structure 108.
[0033] FIG. 1d schematically illustrates a top view of the
substrate portion 110, the insulating structure 108 and the SOI
substrate portions 109, where a cross-section according to line A-A
corresponds to the cross-sectional view as depicted in FIG. 1c.
[0034] After a complete reading of the present disclosure, the
person skilled in the art will appreciate that a shape of the
substrate portion 110 and the insulating structure 108 may deviate
from the depicted rectangular shape and that no limitation on a
specific shape is intended. Furthermore, the person skilled in the
art will appreciate that the figures are only schematic and no
limitation on scalings, distances, ratios of size and distance, and
the like is intended. Particularly, no limitation on a ratio of a
width of the insulating structure 108 to a width of the substrate
portion 110 and/or a ratio of a surface area of the substrate
portion 110 and a surface area of the insulating structure 108 is
intended.
[0035] FIG. 1e schematically illustrates the recess R in the
substrate portion 110, the insulating structure 108 and the SOI
substrate portions 109 at a more advanced stage during fabrication,
after a masking pattern 113 (see hatching in the top view as
depicted in FIG. 1e) is formed, the masking pattern 113 being
partially formed in the recess R. In accordance with some
illustrative embodiments of the present disclosure, the masking
pattern 113 may cover the SOI portions 109, may partially cover the
insulating structure 108, and may partially cover the upper surface
US1 in FIG. 1c such that an upper surface portion US2 of the upper
surface US1 is exposed to further processing. After a complete
reading of the present disclosure, the person skilled in the art
will appreciate that the masking pattern 113 may not be limited to
the configuration as illustrated in FIG. 1e, and that the masking
pattern 113 may be provided instead via two masking strips
supplementing the masking pattern 107 so as to expose the upper
surface portion US2 of the substrate portion 110 to further
processing.
[0036] FIG. 1f schematically illustrates the substrate portion 110,
the insulating material 108 and the SOI substrate portions 109 in a
cross-sectional view along the line B-B in FIG. 1e at a more
advanced stage during fabrication, when an etching process 115 is
performed in accordance with the masking pattern 113 in the recess
R. In accordance with some illustrative embodiments of the present
disclosure, the etching process 115 may be unselective with regard
to the insulating structure 108 and the substrate material 104 in
the substrate portion 110.
[0037] In accordance with some illustrative embodiments of the
present disclosure, the etching process 115 may be a plasma etching
process, e.g. (without limitation), a dry plasma etching process,
or a reactive ion etching (RIE) process and the like. In accordance
with some special (but not limiting examples), the etching process
may comprise a fluorocarbon gas, e.g., CF.sub.x (x=1, 2, 3, 4)
and/or C.sub.2F.sub.6 and/or CHF.sub.3 and/or CH.sub.2F.sub.2
and/or C.sub.3F.sub.8 and/or C.sub.4F.sub.8, where fluorocarbon
gases with high C/F ratio have a good selectivity against Si, while
maintaining a high etch rate of SiO.sub.2 in semiconductor devices.
In accordance with some illustrative examples herein, at least one
additive gas may be provided, such as at least one of O.sub.2 and
H.sub.2. For example, including O2 at an amount in the range from
about 0-10% (relative to CF.sub.4), a relative etch rate of poly to
siliconoxide from less than 0.2 to about 1.0 may be achieved, while
in the range from about 10-60%, the relative etch rate of poly to
oxide decreases from about 1.0 to about 0.2 (the plot of the amount
of O.sub.2 (x-axis) to the relative etch rate (y-axis) shows a peak
at about 0.2% of about 1.0). In some illustrative examples,
including H.sub.2 in the amount of 0-60% shows an etch rate of
SiO.sub.2 from about 50-60 nm/min to an etch rate slightly above 40
nm/min, while poly may be etched at a rate of about 40-45 nm/min
(at about 0%) to about 0-5 nm/min (at about 60%) when adding
H.sub.2. Accordingly, etch rates may be tuned when adding one of
O.sub.2 and H.sub.2 in low amounts to CF.sub.4 in dry plasma
etching processes, for example.
[0038] FIG. 1g schematically illustrates the substrate portion 110
at a more advanced stage during fabrication, after the etching
process 115 is completed and the insulating structure 108 and the
substrate material 104 are unselectively etched and partially
recessed. Accordingly, an etched insulating structure 108' and an
etched substrate material 112, having an upper surface portion US3
relative to substrate material 108 covered by the masking pattern
113 and relative to insulating structure 108 covered by the masking
pattern 113 may be provided. The substrate material 112 in the
recess R may be partially etched back relative to the substrate
material 104 in the substrate portion 110 covered by the masking
pattern 113. Similarly, the insulating structure 108 may be
partially etched back in the exposed region of the masking pattern
113 relative to the insulating structure 108 being protected by the
masking pattern 113. In accordance with the schematic illustration
in FIG. 1g, a recessed portion 117 of the insulating structure 108'
is formed in accordance with the masking pattern 113. After a
complete reading of the present disclosure, the person skilled in
the art will appreciate that the recessed portion 117 may have a
stepping towards the material of the insulating structure 108
covered by the masking pattern 113.
[0039] FIG. 1h schematically illustrates the substrate portion 110
at a more advanced stage during fabrication, after a process 119 is
performed. In accordance with some illustrative embodiments of the
present disclosure, the process 119 may be a thermal oxidation
process or may be a rapid thermal oxidation (RTO) process. In the
case of a thermal oxidation, the process 119 may be performed in a
furnace having an oxygen-containing atmosphere at about
600-800.degree. C., e.g., in a time interval of about 0.5-30
minutes. Alternatively, the process 119 may be implemented as an
RTO and may be performed in an oxygen-containing atmosphere at
about 800-1000.degree. C., e.g., in a time interval of about 5-60
seconds. During the process 119, an oxide layer 121 may be formed
on the substrate material 112 in alignment with the insulating
structure 108'.
[0040] After a complete reading of the disclosure, the person
skilled in the art will appreciate that, in accordance with some
illustrative embodiments of the present disclosure, the masking
pattern 113 may have been removed at the stage as depicted in FIG.
1h, that is, the substrate material 104 and the substrate material
112 in the substrate portion 110 may be exposed to the process 119.
However, this does not pose any limitation to the present
disclosure and the substrate material 104 in the substrate portion
110 may remain covered. The person skilled in the art will
appreciate that, in any case, the SOI substrate portions 109 may
remain protected during the process 119 by the masking pattern 107.
For example, after the stage illustrated in FIG. 1g, a removal
process (not illustrated) for removing the masking pattern 113 may
be performed, optionally including a cleaning process. However, as
pointed out above, this does not pose any limitation on the present
disclosure, and the person skilled in the art will appreciate that
the masking pattern 113 may remain (not illustrated in FIG. 1h and
following).
[0041] FIG. 1i schematically illustrates the substrate portion 110
at a more advanced stage during fabrication, during and after a
process 123 is performed and completed. In accordance with some
illustrative embodiments of the present disclosure, the process 123
may comprise a process for depositing a nitride material on the
oxide layer 121. In accordance with some illustrative examples
herein, the process 123 may comprise a decoupled plasma nitridation
(DPN) using an inductive coupling to generate a nitrogen plasma and
to incorporate a high level of nitrogen uniformly into the top
surface of the oxide layer 121. For example, the process 123 may be
performed in a vacuum chamber (not shown), and a gas mixture of
nitrogen and an inert gas (e.g., He) may be introduced into the
vacuum chamber (not illustrated). Herein, the vacuum chamber (not
illustrated) may be maintained at a preselected pressure during the
process 123. During the DPN, an RF power may be impressed on RF
coils (not illustrated) within the vacuum chamber (not illustrated)
to energize and maintain a plasma (not illustrated). Upon applying
an appropriate RF bias to the substrate 100, a potential difference
between the plasma (not illustrated) and the substrate 100 may be
achieved and nitrogen may be incorporated into the oxide layer 121
for forming the nitride layer 125. After the DPN, a post
nitridation annealing process may be performed at about
700-1100.degree. C. in an inert or oxidizing ambient. After a
complete reading of the present disclosure, the person skilled in
the art will appreciate that, in accordance with the process 123
comprising DPN, a CTF device may be provided.
[0042] In other illustrative embodiments of the present disclosure
in which a floating gate device is to be formed, a conductive
material may be deposited in the process 123 on the oxide layer 121
to form a floating gate layer 125. In accordance with some
illustrative embodiments herein, a polysilicon material or the like
may be deposited.
[0043] FIG. 1j schematically illustrates the substrate portion 110
at a more advanced stage during fabrication, after a gate
insulating material layer 129 is deposited in a process 127. The
gate insulating material layer 129 may comprise an oxide material,
a high-k material and the like. In case that the gate insulating
material 129 corresponds to a material used to form the insulating
structure 108, the person skilled in the art will appreciate that
the gate insulating material 129 and the insulating structure 108'
may be supplemented without an interface between the two layers,
while the interface may be present in case that two different
materials are employed. This is indicated in FIG. 1j and the
following by a broken line. In accordance with some special
illustrative examples herein, the insulating structure 108' may be
formed by an oxide material, and the gate insulating material layer
129 may be formed by a gate oxide material.
[0044] FIG. 1k schematically illustrates the substrate portion 110
at a more advanced stage during fabrication where a process 131 is
performed and a gate electrode material 133 is deposited. In
accordance with some illustrative examples herein, the gate
electrode material 133 may be one of amorphous silicon, polysilicon
and a gate metal, such as titanium, aluminum and the like.
[0045] FIG. 1l schematically illustrates the substrate portion at a
more advanced stage during fabrication, after a polishing process
(not illustrated) is completed and the deposited gate electrode
material 133 is leveled relative to the masking pattern 107. In
accordance with some illustrative examples herein, the polishing
process may comprise a CMP process with end point detection at the
masking pattern 107.
[0046] FIG. 1m schematically illustrates the substrate portion 110
in a top view at a more advanced stage during fabrication, after a
masking pattern 135, e.g., a strip mask, is formed for patterning
the gate structure in the substrate region 110. In accordance with
some illustrative embodiments of the present disclosure, the
masking pattern 135 may be formed in accordance with known
lithographical masking techniques employing resist or hard masking
techniques. In accordance with some special illustrative examples
herein, the masking pattern 135 and the masking pattern 107 may be
related such that the masking pattern 135 may represent the
negative of the masking pattern 107 in the substrate portion
110.
[0047] After a complete reading of the present disclosure, the
person skilled in the art will appreciate that a gate electrode
(see gate stack 138 in FIG. 1n) to be subsequently formed in the
substrate portion 110 is in contact with the insulating structure
108 at two opposing sidewalls of the gate electrode (see FIG. 1m,
wherein the masking pattern 135 contacts the insulating structure
108 at two opposing sides of the masking pattern 135).
[0048] FIG. 1n schematically illustrates the substrate portion 110
in a cross-section view along the line C-C in FIG. 1m at a more
advanced stage during fabrication, while a process 136 is
performed. The process 136 may comprise, in accordance with some
special illustrative examples, an anisotropic etching process as
employed in the art for patterning gate stacks. Accordingly, a gate
stack 138 comprising the material layers 121, 125, 129, 133 and the
masking pattern 135 may be formed in the substrate region 110,
leaving upper surface regions of the substrate material 104
exposed.
[0049] FIG. 1o schematically illustrates the substrate portion 110
at a more advanced stage during fabrication, after implantations
for forming source/drain regions 150 in the substrate material 104
within the substrate region 110, and a sidewall spacer structure
139 to the gate stack 138, and a gate cap 141 are formed. The
person skilled in the art will appreciate that the sidewall spacer
structure 139 may be formed in accordance with known techniques
after the masking pattern 135 is removed. Accordingly, source/drain
extension regions 152 may be formed in alignment with the gate
stack 138 and deep source/drain regions 153 may be formed in
alignment with the spacer structure 139 as known in the art.
Optionally, HALO regions 154 may be formed within the substrate
material 104 for adjusting the threshold voltage.
[0050] After a complete reading of the present disclosure, the
person skilled in the art will appreciate that the process flow as
described above with regard to FIGS. 1a-1o schematically shows, in
accordance with some illustrative embodiments of the present
disclosure, processes for fabricating a semiconductor device
structure, comprising a hybrid substrate comprising an SOI region
(see 109 in FIG. 1o) and a bulk region (see 110 in FIG. 1o), the
SOI region comprising an active semiconductor layer (see 102 in
FIG. 1o), a substrate material (see 104 in FIG. 1o), and a buried
insulating material (see 106 in FIG. 1o) interposed between the
active semiconductor layer and the substrate material, and the bulk
region being provided by the substrate material; an insulating
structure (see 108 in FIG. 1o) formed in the hybrid substrate, the
insulating structure separating the bulk region and the SOI region;
and a gate electrode (see 138 in FIG. 1n) formed in the bulk
region, wherein the insulating structure is in contact with two
opposing sidewalls of the gate electrode.
[0051] The process flow as described above with regard to FIGS.
1a-1o may be continued by a gap-fill (e.g., HDP, HARP, etc.), and a
polishing process for polishing down to the masking pattern 107.
Furthermore, the fabrication process may be continued in accordance
with standard process flows by removing the masking pattern 107
over the SOI substrate regions 109, forming semiconductor devices
over the SOI substrate regions 109, performing a contact module for
performing contacts to the substrate region 110 and the SOI regions
109, etc. In accordance with some special illustrative examples
herein, an early nickel silicidation or a late nickel silicidation
process may be performed.
[0052] According to the process flow as described above with regard
to FIGS. 1a-1o, a buried flash device may be fabricated in a bulk
region of an FDSOI substrate 100, wherein the flash device may be
formed prior to the fabrication of SOI devices. In accordance with
some illustrative embodiments of the present disclosure as
discussed above, a planar surface topography may be obtained
because the gate stack 138 and the adjacent insulating structure
108/108' may be substantially planar relative to the remaining SOI
substrate surface. In accordance with some illustrative embodiments
of the present disclosure, a modular process flow may be provided
such that a buried flash device fabrication module may be at hand,
which may be dropped in and taken out of implemented standard
process flows on demand.
[0053] The person skilled in the art will appreciate that the gate
stack 138 of FIG. 1n may be formed in accordance with CTF
techniques or floating gate techniques. In case of CTF techniques,
the gate stack 138 may comprise one of a SONOS structure, and a
MONOS structure, such as a TANOS or a THNOS structure. In
accordance with some illustrative embodiments of the present
disclosure as discussed above, the modular process for fabricating
the gate stack 138 may only employ three masks, wherein an optional
fourth mask may be formed when fabricating flash contacts in a
contact module during late nickel silicidation for only contacting
flash devices.
[0054] In accordance with some illustrative embodiments of the
present disclosure, a contacting of a flash gate electrode may be
achieved via a logic gate stack using a masked high-k dielectric
removal on top of flash gates (optionally implanting contact
through high-k removal mask into top of flash poly gate), and the
deposition of a metal/poly material stacked directly on top of the
poly material.
[0055] In accordance with some illustrative embodiments of the
present disclosure, a flash cell may be fabricated in accordance
with a process comprising process steps as described above with
regard to FIGS. 1a-1o, the flash cell optionally being wired as a
NAND flash or a NOR flash or may be used as a single bit
storage.
[0056] In accordance with some illustrative embodiments of the
present disclosure, the gate stack 138 may be connected with a
logic PC poly as a word line in subsequent processing (not
illustrated).
[0057] The particular embodiments disclosed above are illustrative
only, as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. For example, the process steps
set forth above may be performed in a different order. Furthermore,
no limitations are intended to the details of construction or
design herein shown, other than as described in the claims below.
It is therefore evident that the particular embodiments disclosed
above may be altered or modified and all such variations are
considered within the scope and spirit of the invention. Note that
the use of terms, such as "first," "second," "third" or "fourth" to
describe various processes or structures in this specification and
in the attached claims is only used as a shorthand reference to
such steps/structures and does not necessarily imply that such
steps/structures are performed/formed in that ordered sequence. Of
course, depending upon the exact claim language, an ordered
sequence of such processes may or may not be required. Accordingly,
the protection sought herein is as set forth in the claims
below.
* * * * *