U.S. patent application number 11/426517 was filed with the patent office on 2006-11-02 for semiconductor substrate cleaning.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Gary Chen.
Application Number | 20060244026 11/426517 |
Document ID | / |
Family ID | 23534990 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060244026 |
Kind Code |
A1 |
Chen; Gary |
November 2, 2006 |
SEMICONDUCTOR SUBSTRATE CLEANING
Abstract
Methods for removing titanium-containing layers from a substrate
surface where those titanium-containing layers are formed by
chemical vapor deposition (CVD) techniques. Titanium-containing
layers, such as titanium or titanium nitride, formed by CVD are
removed from a substrate surface using a sulfuric acid
(H.sub.2SO.sub.4) solution. The H.sub.2SO.sub.4 solution permits
selective and uniform removal of the titanium-containing layers
without detrimentally removing surrounding materials, such as
silicon oxides and tungsten. Where the titanium-containing layers
are applied to the sidewalls of a hole in the substrate surface and
a plug material such as tungsten is used to fill the hole,
subsequent spiking of the H.sub.2SO.sub.4 solution with hydrogen
peroxide (H.sub.2O.sub.2) may be used to recess the
titanium-containing layers and the plug material below the
substrate surface.
Inventors: |
Chen; Gary; (Boise,
ID) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Micron Technology, Inc.
|
Family ID: |
23534990 |
Appl. No.: |
11/426517 |
Filed: |
June 26, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10930211 |
Aug 31, 2004 |
7087534 |
|
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11426517 |
Jun 26, 2006 |
|
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|
10342853 |
Jan 15, 2003 |
6815368 |
|
|
10930211 |
Aug 31, 2004 |
|
|
|
09388660 |
Sep 2, 1999 |
6509278 |
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10342853 |
Jan 15, 2003 |
|
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Current U.S.
Class: |
257/296 ;
257/E21.251; 257/E21.309; 257/E21.583; 257/E21.585 |
Current CPC
Class: |
H01L 21/76865 20130101;
H01L 21/76883 20130101; H01L 21/31111 20130101; H01L 21/32139
20130101; H01L 21/7684 20130101; H01L 21/32136 20130101; H01L
21/76877 20130101; H01L 21/32135 20130101; H01L 21/02074 20130101;
H01L 21/32134 20130101 |
Class at
Publication: |
257/296 |
International
Class: |
H01L 29/94 20060101
H01L029/94; H01L 27/108 20060101 H01L027/108; H01L 29/76 20060101
H01L029/76; H01L 31/119 20060101 H01L031/119 |
Claims
1. An electronic device, comprising: a semiconductive substrate; a
patterned dielectric layer disposed upon the semiconductive
substrate including a plurality of openings in the patterned
dielectric layer having at least a sidewall surface and a bottom
surface; a dielectric anti-reflective coating disposed on at least
a portion of a top surface of the patterned dielectric layer; a
conductive material disposed on substantially the entirety of the
bottom surface and at least a majority of the at least one sidewall
surface of the plurality of openings in the dielectric layer; a
conductive material substantially filling a remaining portion of
the plurality of openings in the dielectric layer; and a patterned
conductive material at least connected to a top surface of the
conductive material substantially filling a remaining portion of
the plurality of openings in the dielectric layer.
2. The electronic device of claim 1, wherein the openings in the
dielectric layer expose portions of the semiconductive
substrate.
3. The electronic device of claim 2, wherein the exposed portions
of the semiconductive substrate include a metal silicide layer
substantially covering the entirety of the exposed portion of the
semiconductive substrate at the bottom surface of the plurality of
openings in the dielectric layer.
4. The electronic device of claim 1, wherein the conductive
material includes titanium.
5. The electronic device of claim 1, further comprising an adhesion
promoting layer disposed upon substantially all of the conductive
material.
6. The electronic device of claim 5, wherein the adhesion promoting
layer includes titanium nitride.
7. The electronic device of claim 1, wherein the conductive
material substantially filling the remaining portion of the
plurality of openings in the dielectric layer comprises
tungsten.
8. The electronic device of claim 1, wherein the conductive
material substantially filling the remaining portion of the
plurality of openings in the dielectric layer ends at a location
below a top surface of the patterned dielectric layer.
9. The electronic device of claim 1, wherein the dielectric
anti-reflective coating is substantially totally removed after the
conductive material substantially filling the remaining portion of
the plurality of openings in the dielectric layer is formed.
10. The electronic device of claim 1, further comprising a
dielectric layer disposed over the patterned conductive
material.
11. A semiconductor die, comprising: an integrated circuit
supported by a base layer and having a plurality of integrated
circuit devices, wherein at least one of the plurality of
integrated circuit device has a semiconductor structure with a
patterned dielectric layer disposed above the base layer including
a plurality of openings in the patterned dielectric layer having at
least a sidewall surface and a bottom surface exposing portions of
the semiconductive substrate; a conductive material disposed on
substantially the entirety of the bottom surface and at least a
majority of the at least one sidewall surface of the plurality of
openings in the dielectric layer; a conductive material
substantially filling a remaining portion of the plurality of
openings in the dielectric layer; and a patterned conductive
material at least connected to a top surface of the conductive
material substantially filling a remaining portion of the plurality
of openings in the dielectric layer.
12. The semiconductor die of claim 11, wherein the openings in the
dielectric layer comprise at least one an electrical contact to of
a plurality of diffused regions in the base layer, and a conductive
gate disposed between adjacent ones of the plurality of diffused
regions.
13. The semiconductor die of claim 11, wherein the exposed portions
of the semiconductive substrate include a metal silicide layer
substantially covering the entirety of the exposed portion of the
semiconductive substrate at the bottom surface of the plurality of
openings in the dielectric layer.
14. The semiconductor die of claim 11, wherein the conductive
material substantially filling the remaining portion of the
plurality of openings in the dielectric layer comprises tungsten up
to a location below a top surface of the patterned dielectric
layer.
15. The semiconductor die of claim 11, further including a
dielectric anti-reflective coating on a portion of a top surface of
the patterned dielectric layer, and the dielectric anti-reflective
coating is substantially totally removed after the conductive
material substantially filling the remaining portion of the
plurality of openings in the dielectric layer is formed.
16. A memory device, comprising: an array of memory cells, wherein
at least one memory cell has a bit-line contact including a
patterned dielectric layer disposed upon a semiconductive substrate
including a plurality of openings in the patterned dielectric layer
having at least a sidewall surface and a bottom surface exposing
portions of the semiconductive substrate; a dielectric
anti-reflective coating disposed on at least a portion of a top
surface of the patterned dielectric layer; a conductive material
disposed on substantially the entirety of the bottom surface and at
least a majority of the at least one sidewall surface of the
plurality of openings in the dielectric layer; a conductive
material substantially filling a remaining portion of the plurality
of openings in the dielectric layer; and a patterned conductive
material at least connected to a top surface of the conductive
material substantially filling a remaining portion of the plurality
of openings in the dielectric layer.
17. The memory device of claim 16, wherein at least one of the at
least one memory cell comprises a floating gate disposed between a
control gate and the semiconductive substrate.
18. The memory device of claim 16, wherein the exposed portions of
the semiconductive substrate include a metal silicide layer
substantially covering the entirety of the exposed portion of the
semiconductive substrate at the bottom surface of the plurality of
openings in the dielectric layer.
19. The memory device of claim 16, wherein the conductive material
includes titanium.
20. The memory device of claim 16, further comprising an adhesion
promoting layer disposed upon substantially all of the conductive
material, wherein the adhesion promoting layer comprises titanium
nitride.
21. The memory device of claim 16, wherein the conductive material
substantially filling the remaining portion of the plurality of
openings in the dielectric layer comprises tungsten.
22. The memory device of claim 16, wherein the conductive material
substantially filling the remaining portion of the plurality of
openings in the dielectric layer ends at a location below a top
surface of the patterned dielectric layer.
23. The memory device of claim 16, further comprising a dielectric
layer disposed over the patterned conductive material.
24. A memory module, comprising: a support; a plurality of leads
extending form the support; a command link coupled to at least one
of the plurality of leads; a plurality of data links, wherein each
data link is coupled to at least one of the plurality of leads; at
least one memory device contain on the support and coupled to the
command link, including at least one memory cell having a contact
including a patterned dielectric layer disposed upon a
semiconductive substrate including a plurality of openings in the
patterned dielectric layer having at least a sidewall surface and a
bottom surface exposing portions of the semiconductive substrate; a
dielectric anti-reflective coating disposed on at least a portion
of a top surface of the patterned dielectric layer; a conductive
material disposed on substantially the entirety of the bottom
surface and at least a majority of the at least one sidewall
surface of the plurality of openings in the dielectric layer; a
conductive material substantially filling a remaining portion of
the plurality of openings in the dielectric layer; and a patterned
conductive material at least connected to a top surface of the
conductive material substantially filling a remaining portion of
the plurality of openings in the dielectric layer.
25. The memory module of claim 24, wherein the memory device
comprises at least one non-volatile memory cell.
26. The memory module of claim 24, wherein the exposed portions of
the semiconductive substrate include a metal silicide layer
substantially covering the entirety of the exposed portion of the
semiconductive substrate at the bottom surface of the plurality of
openings in the dielectric layer.
27. The memory module of claim 24, further comprising a titanium
nitride layer disposed upon substantially all of the conductive
material.
28. The memory module of claim 24, wherein the conductive material
substantially filling the remaining portion of the plurality of
openings in the dielectric layer comprises tungsten.
29. The memory module of claim 24, wherein the conductive material
substantially filling the remaining portion of the plurality of
openings in the dielectric layer ends at a location below a top
surface of the patterned dielectric layer.
30. The memory module of claim 24, further comprising a dielectric
layer disposed over the patterned conductive material.
Description
[0001] This application is a Continuation of U.S. application Ser.
No. 10/930,211, filed Aug. 31, 2004, which is a Divisional of U.S.
application Ser. No. 10/342,853, filed Jan. 15, 2003, now U.S. Pat.
No. 6,815,368, which is a Divisional of U.S. application Ser. No.
09/388,660, filed Sep. 2, 1999, now U.S. Pat. No. 6,509,278, all of
which are incorporated herein.
FIELD OF THE INVENTION
[0002] The present invention relates to semiconductor substrate
cleaning or etching methods used in the fabrication of
semiconductor devices. More particularly, the present invention
pertains to a method for removing chemical vapor deposition (CVD)
titanium and titanium nitride on a semiconductor substrate
surface.
BACKGROUND OF THE INVENTION
[0003] Many electronic systems include a memory device, such as a
Dynamic Random Access Memory (DRAM), to store data. A typical DRAM
includes an array of memory cells. Each memory cell includes a
capacitor that stores the data in the cell and a transistor that
control access to the data. The capacitor typically includes two
conductive plates separated by a dielectric layer. The charge
stored across the capacitor is representative of a data bit and can
be either a high voltage or a low voltage. Data can be stored in
either the memory cells during a write mode, or data may be
retrieved from the memory cells during a read mode. The data is
transmitted on signal lines, referred to as digit lines, which are
coupled to input/output (I/O) lines through transistors used as
switching devices. Typically, for each bit of data stored, its true
logic state is available on an I/O line and its complementary logic
state is available on an I/O complement line. Thus, each such
memory cell has two digit lines, a digit and digit complement.
[0004] Typically, the memory cells are arranged in an array and
each cell has an address identifying its location in the array. The
array includes a configuration of intersecting conductive lines and
memory cells are associated with the intersections of the lines. In
order to read from or write to a cell, the particular cell in
question must be selected, or addressed. The address for the
selected cell is represented by input signals to a word line
decoder and to a digit line decoder. The word line decoder
activates a word line in response to the word line address. The
selected word line activates the access transistors for each of the
memory cells in communication with the selected word line. The
digit line decoder selects a digit line pair in response to the
digit line address. For a read operation the selected word line
activates the access transistors for a given word line address, and
data is latched to the digit line pairs. In order for there to be
memory cells there must be a semiconductor fabrication process
which produces a variety of thin films.
[0005] A large variety of thin films are used in the fabrication of
semiconductor devices. Chemical vapor deposition (CVD) is a widely
used method for depositing such thin films for a large variety of
materials. In a typical CVD process, reactant gases (often diluted
in a carrier gas) enter a reaction chamber containing a deposition
surface. The gas mixture may be heated by absorbing radiation as it
approaches the deposition surface. Near the surface, thermal,
momentum and chemical concentration boundary layers form as the gas
stream heats, slows down due to viscous drag, and changes in
chemical composition. Heterogenous reactions of the source gases or
reactive intermediate species (formed from homogenous pyrolysis)
occur at the deposition surface, thus forming the deposited
material. Gaseous reaction by-products are then transported or
vented out of the reaction chamber.
[0006] Another popular technique for depositing thin films is
physical vapor deposition (PVD). PVD processes deposit thin films
on a substrate by such techniques as sputtering, vacuum deposition,
or laser ablation from a solid source or target having the desired
composition of the deposited film.
[0007] Because of a fundamental difference between CVD and PVD
processes, i.e., gaseous reactants versus solid sources, the
resulting films tend to have different chemical characteristics
even when the desired resultant film is the same, e.g., a titanium
or titanium nitride film produced by CVD or PVD. These differing
chemical characteristics often lead to differences in how the
resultant films react to downstream processing, such as etching, or
cleaning, of the substrate surface.
[0008] Cleaning of the substrate surface is often desirable after
some bulk removal of material from the substrate surface. As an
example, material containing one or more layers may be formed on a
substrate surface to fill a hole or recess. A chemical-mechanical
planarization (CMP) technique may be used to abrade the material
from the surface, substantially leaving only that portion of the
material contained in the hole or recess. CMP techniques must be
tightly controlled to remove all of the surface material without
detrimentally abrading away the substrate surface. This often
results in patches or islands of the material remaining on the
substrate surface. Such patches or islands are typically cleaned
from the substrate surface by some chemical etchant. In the case of
forming contacts, vias or interconnects in a hole or recess,
removal of such islands is desirable to reduce the risk of
electrical shorts.
[0009] Hydrofluoric acid (HF)-based solutions are popular chemical
etchants in semiconductor processing. While such HF-based solutions
are generally effective at uniform removal of titanium-containing
films deposited by PVD processes, they generally result in pitting
of titanium-containing films deposited by CVD processes. There is a
need in the art for alternative methods for removing the CVD
titanium and/or CVD titanium nitride.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIGS. 1A-1H are cross-sectional views of a semiconductor
structure at various processing stages.
[0011] FIG. 2 is a cross-sectional view of a portion of a memory
device.
[0012] FIG. 3 is a block diagram of an integrated circuit memory
device.
[0013] FIG. 4 is an elevation view of a wafer containing
semiconductor dies.
[0014] FIG. 5 is a block diagram of an exemplary circuit
module.
[0015] FIG. 6 is a block diagram of an exemplary memory module.
[0016] FIG. 7 is a block diagram of an exemplary electronic
system.
[0017] FIG. 8 is a block diagram of an exemplary memory system.
[0018] FIG. 9 is a block diagram of an exemplary computer
system.
DESCRIPTION OF THE DRAWINGS
[0019] In the following detailed description of the invention,
reference is made to the accompanying drawings which form a part
hereof, and in which is shown, by way of illustration, specific
embodiments in which the invention may be practiced. In the
drawings, like numerals describe substantially similar components
throughout the several views. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention. Other embodiments may be utilized and structural,
logical, and electrical changes may be made without departing from
the scope of the present invention.
[0020] The terms wafer and substrate used in the following
description include any base semiconductor structure. Both are to
be understood as including silicon-on-sapphire (SOS) technology,
silicon-on-insulator (SOI) technology, thin film transistor (TFT)
technology, doped and undoped semiconductors, epitaxial layers of a
silicon supported by a base semiconductor structure, as well as
other semiconductor structures well known to one skilled in the
art. Furthermore, when reference is made to a wafer or substrate in
the following description, previous process steps may have been
utilized to form regions/junctions in the base semiconductor
structure, and terms wafer or substrate include the underlying
layers containing such regions/junctions. The following detailed
description is, therefore, not to be taken in a limiting sense, and
the scope of the present invention is defined only by the appended
claims.
[0021] The method of substrate cleaning will be illustrated in the
context of the formation of a contact in a semiconductor device. It
will be apparent that other semiconductor structures may be formed
and utilized with the invention.
[0022] In order to manufacture a contact in a substrate 20, as
illustrated in FIG. 1A, an insulator layer 12 is formed on a
substrate base layer 11 and a contact hole 14 is patterned or
etched through the insulator layer 12 to expose a portion of the
underlying base layer 11. Insulator layer 12 may be any insulative
material, but is commonly a silicon oxide material, such as silicon
dioxide or borophosphosilicate glass (BPSG). Contact hole 14 has
sidewalls defined by insulator layer 12 and a bottom defined by the
exposed portion of base layer 11.
[0023] A dielectric anti-reflection coating (DARC) layer 13
optionally may be formed on top of the insulator layer 12 prior to
patterning the contact hole 14. Such DARCs improve the resolution
of photolithographic techniques utilized to pattern the contact
hole 14 and such use is well understood in the art. Additionally,
the bottom of contact hole 14 may be etched or cleaned by a
pre-metal deposition cleaning process to improve the electrical
contact to the base layer 11.
[0024] As shown in FIG. 1B, chemical vapor deposition (CVD) is then
used to form a first CVD titanium-containing layer 15, such as
titanium. CVD permits accurately controlled formation of films,
including conformal films. CVD titanium layer 15 is formed over the
surface of insulator layer 12, as well as the sidewalls and bottom
of contact hole 14. A variety of gaseous reactants may be used to
form CVD titanium layer 15 as is well known by persons skilled in
the art.
[0025] Referring to FIG. 1C, a second CVD titanium-containing layer
16, such as titanium nitride, may be formed by a second CVD process
on CVD titanium layer 15. A CVD titanium nitride layer 16 is useful
in improving adhesion to CVD titanium layer 15 of subsequent plug
materials used for the core of the contact. As with CVD titanium
layer 15, CVD titanium nitride layer 16 is formed overlying the
surface of insulator layer 12, as well as the sidewalls and bottom
of contact hole 14.
[0026] The substrate may be annealed to form a titanium silicide
interface between CVD titanium layer 15 and the base layer 11,
where the base layer 11 contains silicon. Such silicide interfaces
reduce resistance between a silicon base layer 11 and CVD titanium
layer 15. A rapid thermal processing (RTP) annealing process may be
used to form the titanium silicide interface. The annealing process
may include heating the substrate 20 to a temperature of
approximately 600 to 800 degrees Celsius for approximately 10
seconds. The annealing process may be performed at any time after
forming CVD titanium layer 15.
[0027] Referring to FIG. 1D, a plug layer 17, such as tungsten, is
deposited on CVD titanium nitride layer 16. Plug layer 17 may
contain materials other than tungsten, particularly other metals
when forming a contact. However, the material of plug layer 17 must
be generally resistant to sulfuric acid (H.sub.2SO.sub.4), as will
become apparent below. Referring to FIG. 1E, the overriding
tungsten layer 17 is removed from the top of the substrate by using
a chemical mechanical planarization (CMP) process to form contact
24. CMP processing often utilizes changes in friction between an
abrading surface and the surface of the material being abraded.
This relative friction technique can permit use of the insulator
layer 12 as a stopping layer. An alternate method of determining a
stopping layer is to simply abrade for a defined period of time,
having previously determined the amount of time necessary to reach
the stopping layer. In either case, because of the inherent
variability in industrial processing, residual material is often
left behind on the stopping layer.
[0028] As shown in FIG. 1E, such residual material may take the
form of islands 22 on the surface of substrate 20. Note that as
FIG. 1E is not necessarily drawn to scale, the slope of islands 22
may be exaggerated. Because these islands 22 contain conductive
material, i.e., CVD titanium layer 15 and CVD titanium nitride
layer 16, they may result in undesirable electrical shorts if they
are not removed. Such removal is addressed by the various
embodiments of the invention.
[0029] In one embodiment, the substrate 20 and accompanying layers
are immersed in a sulfuric acid (H.sub.2SO.sub.4) solution to
remove the titanium-containing layers, i.e., CVD titanium layer 15
and CVD titanium nitride layer 16. Sulfuric acid solution, as used
herein, will describe a solution consisting essentially of aqueous
or anhydrous H.sub.2SO.sub.4 unless noted otherwise by subsequent
spiking or additions to the solution. In a further embodiment, the
substrate 20 and accompanying layers are exposed to H.sub.2SO.sub.4
vapors to remove the titanium-containing layers. In a still further
embodiment, the substrate 20 and accompanying layers are sprayed
with an H.sub.2SO.sub.4 solution. In one embodiment, the
H.sub.2SO.sub.4 solution is heated. In another embodiment, the
H.sub.2SO.sub.4 solution is heated to a temperature of
approximately 100-140.degree. C. In a further embodiment, the
H.sub.2SO.sub.4 solution is heated to a temperature of
approximately 120.degree. C. In one embodiment, the H.sub.2SO.sub.4
solution is anhydrous H.sub.2SO.sub.4. In another embodiment, the
H.sub.2SO.sub.4 solution is an aqueous solution containing greater
than approximately 75% H.sub.2SO.sub.4. In a further embodiment,
the H.sub.2SO.sub.4 solution is an aqueous solution containing
greater than approximately 1% H.sub.2SO.sub.4.
[0030] In the various embodiments, titanium-containing layers are
selectively and uniformly removed from the surface of substrate 20
without detrimentally removing surrounding materials, such as
tungsten layer 17 or insulator layer 12. The surface of substrate
20 includes the surface of DARC layer 13 or the surface of
insulator layer 12 if no DARC layer 13 is present. FIG. 1F depicts
the substrate 20 with resultant contact 24 following removal of CVD
titanium layer 15 and CVD titanium nitride layer 16.
[0031] Following removal of the titanium-containing layers, islands
of DARC may still remain if a DARC layer 13 was utilized in the
formation of the contact 24. To remove residual DARC, a solution of
tetramethylammonium fluoride (TMAF) and HF may be used. In one
embodiment, the TMAF/HF solution is approximately 5-50 wt % TMAF
and approximately 0.02-20 wt % HF in aqueous solution. In another
embodiment, the TMAF/HF solution is approximately 22.8 wt % TMAF
and approximately 0.28 wt % HF in aqueous solution. In a further
embodiment, tetramethylammonium hydroxide (TMAH) replaces the TMAF.
FIG. 1G depicts the substrate 20 following removal of DARC layer
13.
[0032] In some situations, it may be desirable to recess the
materials in the contact hole 14 or otherwise condition the surface
of the materials. In use with the various embodiments, the
H.sub.2SO.sub.4 solution may be spiked with hydrogen peroxide
(H.sub.2O.sub.2) which may selectively remove some CVD titanium
layer 15 and/or CVD titanium nitride layer 16 from the contact hole
14. Spiking the H.sub.2SO.sub.4 solution with H.sub.2O.sub.2 in the
present example will result in recessing of the CVD titanium layer
15, the CVD titanium nitride layer 16 and the tungsten layer 17
below the surface of the substrate 20, along with surface
conditioning of tungsten layer 17. FIG. 1H depicts the substrate 20
following recessing of CVD titanium layer 15, CVD titanium nitride
layer 16 and tungsten layer 17. Recessing may be accomplished by
immersing the substrate 20 in the solution of H.sub.2SO.sub.4 and
H.sub.2O.sub.2 for a period of about 2-120 seconds.
[0033] Those skilled in the art recognize that semiconductor
structures such as contact 24 are utilized in the formation of more
complex integrated circuitry. As one example, contact 24 may be
used as a bit-line contact in a memory device.
Memory Devices
[0034] FIG. 2 is a cross-sectional view of one such memory device.
The memory device includes an array of memory cells. The memory
cells include capacitors 230, access transistors 240, wordlines 250
and bit-line contacts 260 formed over a base layer 210, often a
silicon base layer. Those skilled in the art will recognize that
wordlines 250 in FIG. 2 are coupled to access transistors 240
outside the plane of FIG. 2. Bit-line contact 260 is used to couple
the capacitors 230 to a bit line or digit line (not shown) of the
memory device. Bit-line contact 260 may be formed in conjunction
with an embodiment of substrate cleaning described above. As such,
bit-line contact 260 may contain a CVD titanium layer 15, a CVD
titanium nitride layer 16, and a tungsten layer 17 as previously
described.
[0035] FIG. 3 is a simplified block diagram of a memory device
according to one embodiment of the invention. The memory device 300
includes an array of memory cells 302, address decoder 304, row
access circuitry 306, column access circuitry 308, control
circuitry 310, and Input/Output circuit 312. The memory can be
coupled to an external microprocessor 314, or memory controller for
memory accessing. The memory receives control signals from the
processor 314, such as WE*, RAS* and CAS* signals. The memory is
used to store data which is accessed via I/O lines. It will be
appreciated by those skilled in the art that additional circuitry
and control signals can be provided, and that the memory device of
FIG. 3 has been simplified to help focus on the invention. At least
one of the memory cells has a bit-line contact formed in accordance
with the invention. It will be recognized that other contacts, vias
and interconnects may be used in conjunction with a portion of
memory device 300 and formed in accordance with the invention.
[0036] It will be understood that the above description of a DRAM
(Dynamic Random Access Memory) is intended to provide a general
understanding of the memory and is not a complete description of
all the elements and features of a DRAM. Further, the invention is
equally applicable to any size and type of memory circuit and is
not intended to be limited to the DRAM described above. Other
alternative types of devices include SRAM (Static Random Access
Memory) or Flash memories. Additionally, the DRAM could be a
synchronous DRAM commonly referred to as SGRAM (Synchronous
Graphics Random Access Memory), SDRAM (Synchronous Dynamic Random
Access Memory), SDRAM II, and DDR SDRAM (Double Data Rate SDRAM),
as well as Synchlink or Rambus DRAMs and other emerging DRAM
technologies.
[0037] As recognized by those skilled in the art, memory devices of
the type described herein are generally fabricated as an integrated
circuit containing a variety of semiconductor devices. The
integrated circuit is supported by a substrate. Integrated circuits
are typically repeated multiple times on each substrate. The
substrate is further processed to separate the integrated circuits
into dies as is well known in the art.
Semiconductor Dies
[0038] With reference to FIG. 4, in one embodiment, a semiconductor
die 710 is produced from a wafer 700. A die is an individual
pattern, typically rectangular, supported by a substrate or base
layer and containing circuitry, or integrated circuit devices, to
perform a specific function. At least one of the integrated circuit
devices has a semiconductor structure formed in accordance with the
invention. A semiconductor wafer will typically contain a repeated
pattern of such dies containing the same functionality. Die 710 may
contain circuitry for the inventive memory device, as discussed
above. Die 710 may further contain additional circuitry to extend
to such complex devices as a monolithic processor with multiple
functionality. Die 710 is typically packaged in a protective casing
(not shown) with leads extending therefrom (not shown) providing
access to the circuitry of the die for unilateral or bilateral
communication and control.
Circuit Modules
[0039] As shown in FIG. 5, two or more dies 710 may be combined,
with or without protective casing, into a circuit module 800 to
enhance or extend the functionality of an individual die 710.
Circuit module 800 may be a combination of dies 710 representing a
variety of functions, or a combination of dies 710 containing the
same functionality. One or more dies 710 of circuit module 800
contain at least one semiconductor structure formed in accordance
with the invention.
[0040] Some examples of a circuit module include memory modules,
device drivers, power modules, communication modems, processor
modules and application-specific modules, and may include
multilayer, multichip modules. Circuit module 800 may be a
subcomponent of a variety of electronic systems, such as a clock, a
television, a cell phone, a personal computer, an automobile, an
industrial control system, an aircraft and others. Circuit module
800 will have a variety of leads 810 extending therefrom and
coupled to the dies 710 providing unilateral or bilateral
communication and control.
[0041] FIG. 6 shows one embodiment of a circuit module as memory
module 900. Memory module 900 contains multiple memory devices 910
contained on support 915, the number depending upon the desired bus
width and the desire for parity. Memory module 900 accepts a
command signal from an external controller (not shown) on a command
link 920 and provides for data input and data output on data links
930. The command link 920 and data links 930 are connected to leads
940 extending from the support 915. Leads 940 are shown for
conceptual purposes and are not limited to the positions shown in
FIG. 6.
Electronic Systems
[0042] FIG. 7 shows an electronic system 1000 containing one or
more circuit modules 800. Electronic system 1000 generally contains
a user interface 1010. User interface 1010 provides a user of the
electronic system 1000 with some form of control or observation of
the results of the electronic system 1000. Some examples of user
interface 1010 include the keyboard, pointing device, monitor or
printer of a personal computer; the tuning dial, display or
speakers of a radio; the ignition switch, gauges or gas pedal of an
automobile; and the card reader, keypad, display or currency
dispenser of an automated teller machine. User interface 1010 may
further describe access ports provided to electronic system 1000.
Access ports are used to connect an electronic system to the more
tangible user interface components previously exemplified. One or
more of the circuit modules 800 may be a processor providing some
form of manipulation, control or direction of inputs from or
outputs to user interface 1010, or of other information either
preprogrammed into, or otherwise provided to, electronic system
1000. As will be apparent from the lists of examples previously
given, electronic system 1000 will often contain certain mechanical
components (not shown) in addition to circuit modules 800 and user
interface 1010. It will be appreciated that the one or more circuit
modules 800 in electronic system 1000 can be replaced by a single
integrated circuit. Furthermore, electronic system 1000 may be a
subcomponent of a larger electronic system.
[0043] FIG. 8 shows one embodiment of an electronic system as
memory system 1100. Memory system 1100 contains one or more memory
modules 900 and a memory controller 1110. Memory controller 1110
provides and controls a bidirectional interface between memory
system 1100 and an external system bus 1120. Memory system 1100
accepts a command signal from the external bus 1120 and relays it
to the one or more memory modules 900 on a command link 1130.
Memory system 1100 provides for data input and data output between
the one or more memory modules 900 and external system bus 1120 on
data links 1140.
[0044] FIG. 9 shows a further embodiment of an electronic system as
a computer system 1200. Computer system 1200 contains a processor
1210 and a memory system 1100 housed in a computer unit 1205.
Computer system 1200 is but one example of an electronic system
containing another electronic system, i.e., memory system 1100, as
a subcomponent. Computer system 1200 optionally contains user
interface components. Depicted in FIG. 9 are a keyboard 1220, a
pointing device 1230, a monitor 1240, a printer 1250 and a bulk
storage device 1260. It will be appreciated that other components
are often associated with computer system 1200 such as modems,
device driver cards, additional storage devices, etc. It will
further be appreciated that the processor 1210 and memory system
1100 of computer system 1200 can be incorporated on a single
integrated circuit. Such single package processing units reduce the
communication time between the processor and the memory
circuit.
Conclusion
[0045] Methods of cleaning substrates are disclosed, particularly
cleaning or removal of titanium-containing layers from a substrate
surface where those titanium-containing layers were formed by
chemical vapor deposition (CVD) techniques. The various embodiments
use sulfuric acid solutions to remove titanium-containing layers
without detrimentally removing surrounding materials, such as
tungsten or silicon oxide materials. The sulfuric acid solutions
consist essentially of aqueous or anhydrous sulfuric acid.
Integrated circuit devices produced in accordance with embodiments
of the invention have a reduced tendency for electrical shorts
caused by residual titanium-containing layers on the surface of the
substrate.
[0046] In devices where physical vapor deposition (PVD) techniques
were used to form the titanium-containing layers, hydrofluoric acid
(HF)-based solutions could be used to remove the
titanium-containing layers without detrimentally removing a
tungsten layer. However, due to the differences in the chemical
characteristics of CVD layers, these prior cleaning solutions are
generally ineffective at removing the titanium-containing layers.
Ineffective removal of the titanium-containing layers increases the
likelihood of metal shorts in resulting semiconductor devices.
[0047] Titanium-containing layers retained in the resultant device,
where those titanium-containing layers were formed by CVD
techniques, have improved surface characteristics over such
titanium-containing layers exposed to traditional HF-based cleaning
solutions. Such improved surface characteristics are the result of
more uniform removal and reduced pitting of the surface.
[0048] Piranha baths, solutions containing H.sub.2SO.sub.4 and
H.sub.2O.sub.2, are generally effective at removing
titanium-containing layers deposited by CVD or PVD, but they also
tend to remove tungsten at rates too high to permit removal of the
titanium-containing layer without detrimentally removing tungsten.
The embodiments of substrate cleaning methods provided herein
facilitate selective and uniform removal of CVD titanium-containing
layers while leaving the tungsten substantially un-attacked.
[0049] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement which is calculated to achieve the
same purpose may be substituted for the specific embodiment shown.
This application is intended to cover any adaptions or variations
of the present invention. Therefore, it is manifestly intended that
this invention be limited only by the claims and equivalents
thereof.
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