U.S. patent application number 11/209415 was filed with the patent office on 2006-01-12 for decoupling capacitor for high frequency noise immunity.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Arup Bhattacharyya.
Application Number | 20060007633 11/209415 |
Document ID | / |
Family ID | 25482429 |
Filed Date | 2006-01-12 |
United States Patent
Application |
20060007633 |
Kind Code |
A1 |
Bhattacharyya; Arup |
January 12, 2006 |
Decoupling capacitor for high frequency noise immunity
Abstract
Systems and methods are provided for an on-chip decoupling
device and method. One aspect of the present subject matter is a
capacitor. One embodiment of the capacitor includes a substrate, a
high K dielectric layer doped with nano crystals disposed on the
substrate, and a top plate layer disposed on the high K dielectric
layer. According to one embodiment, the high K dielectric layer
includes Al.sub.2O.sub.3. According to other embodiments, the nano
crystals include gold nano crystals and gold nano crystals. One
capacitor embodiment includes a MIS (metal-insulator-silicon)
capacitor fabricated on silicon substrate, and another capacitor
embodiment includes a MIM (metal-insulator-metal) capacitor
fabricated between the interconnect layers above silicon substrate.
The structure of the capacitor is useful for reducing a resonance
impedance and a resonance frequency for an integrated circuit chip.
Other aspects are provided herein.
Inventors: |
Bhattacharyya; Arup; (Essex
Junction, VT) |
Correspondence
Address: |
Schwegman, Lundberg, Woessner & Kluth, P.A.;Attn: Marvin L. Beekman
P.O. Box 2938
Minneapolis
MN
55402
US
|
Assignee: |
Micron Technology, Inc.
|
Family ID: |
25482429 |
Appl. No.: |
11/209415 |
Filed: |
August 23, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10752351 |
Jan 6, 2004 |
6955960 |
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11209415 |
Aug 23, 2005 |
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09944986 |
Aug 30, 2001 |
6700771 |
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10752351 |
Jan 6, 2004 |
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Current U.S.
Class: |
361/306.2 ;
257/E21.009; 257/E21.021; 257/E27.05; 257/E29.255 |
Current CPC
Class: |
H01L 28/75 20130101;
B82Y 10/00 20130101; H01L 21/3115 20130101; H01L 29/513 20130101;
H01L 21/02186 20130101; H01L 21/02266 20130101; H01L 21/02274
20130101; H01L 29/518 20130101; H01L 21/02271 20130101; H01L
21/02189 20130101; H01L 21/3162 20130101; H01L 21/02192 20130101;
H01L 21/02183 20130101; H01L 28/55 20130101; H01L 29/94 20130101;
H01L 21/0228 20130101; H01L 29/78 20130101; H01L 21/3143 20130101;
H01L 27/0811 20130101; H01L 21/28194 20130101; H01L 21/02178
20130101; H01L 21/02197 20130101; H01L 28/56 20130101; H01L 29/517
20130101 |
Class at
Publication: |
361/306.2 |
International
Class: |
H01G 4/228 20060101
H01G004/228 |
Claims
1. A method, comprising: applying a voltage across a high K
dielectric, and controlling conductance through the high K
dielectric using a tailored amount of nano crystals uniformly
dispersed in the high K dielectric.
2. The method of claim 1, wherein applying a voltage across a high
K dielectric includes applying a voltage across alumina
(Al.sub.2O.sub.3).
3. The method of claim 1, wherein controlling conductance through
the high K dielectric includes using a tailored amount of gold nano
crystals uniformly dispersed in the high K dielectric to provide a
controlled resistance.
4. The method of claim 1, wherein controlling conductance through
the high K dielectric includes using a tailored amount of silver
nano crystals uniformly dispersed in the high K dielectric to
provide a controlled resistance.
5. The method of claim 1, wherein applying a voltage across a high
K dielectric includes applying a voltage across a dielectric
selected from the group consisting of: a tantalum oxide, a titanium
oxide, a tantalum nitride, a tantalum silicate, a zirconium oxide,
a zirconium nitride, a zirconium silicate, a hafnium oxide, a
hafnium nitride, a hafnium silicate, a praseodymium oxide, a
praseodymium nitride and a praseodymium silicate.
6. The method of claim 5, wherein applying a voltage across a high
K dielectric includes applying a voltage across a high K dielectric
doped with a complex high K dielectric selected from the group
consisting of: barium strontium titanate (BST), a transition metal,
and a metal oxide.
7. The method of claim 6, wherein the metal oxide is selected from
the group consisting of a tantalum oxide, a zirconium oxide and a
praseodymium oxide.
8. The method of claim 1, wherein applying a voltage further
comprises applying a potential to a titanium nitride layer in
contact with the aluminum oxide layer.
9. The method of claim 8, wherein applying a potential to a
titanium nitride layer includes applying a potential to a metal
layer in contact with the titanium nitride layer.
10. The method of claim 1, wherein applying a voltage further
comprises applying a potential to a silicon rich nitride layer in
contact with the aluminum oxide layer.
11. The method of claim 10, wherein applying a potential to a
silicon rich nitride layer includes applying a potential to a
polysilicon layer in contact with the silicon rich nitride
layer.
12. A method, comprising: applying a voltage across an aluminum
oxide dielectric layer; and controlling conductance through the
aluminum oxide layer to provide a controlled resistance using a
tailored amount of gold nano crystals uniformly dispersed in the
aluminum oxide layer.
13. The method of claim 12, wherein applying a voltage further
comprises applying a potential to a titanium nitride layer in
contact with the aluminum oxide layer.
14. The method of claim 13, wherein applying a potential to a
titanium nitride layer includes applying a potential to a metal
layer in contact with the titanium nitride layer.
15. The method of claim 12, wherein applying a voltage further
comprises applying a potential to a silicon rich nitride layer in
contact with the aluminum oxide layer.
16. The method of claim 12, wherein applying a potential to a
silicon rich nitride layer includes applying a potential to a
polysilicon layer in contact with the silicon rich nitride
layer.
17. A method, comprising: applying a voltage across an aluminum
oxide dielectric layer; and controlling conductance through the
aluminum oxide layer to provide a controlled resistance using a
tailored amount of silicon nano crystals uniformly dispersed in the
aluminum oxide layer.
18. The method of claim 17, wherein applying a voltage further
comprises applying a potential to a titanium nitride layer in
contact with the aluminum oxide layer.
19. The method of claim 18, wherein applying a potential to a
titanium nitride layer includes applying a potential to a metal
layer in contact with the titanium nitride layer.
20. The method of claim 17, wherein applying a voltage further
comprises applying a potential to a silicon rich nitride layer in
contact with the aluminum oxide layer.
21. The method of claim 17, wherein applying a potential to a
silicon rich nitride layer includes applying a potential to a
polysilicon layer in contact with the silicon rich nitride
layer.
22. A method, comprising: reducing a resonance frequency and a
resonance impedance for an integrated circuit chip, including
applying a voltage across a lossy capacitor coupled to an
integrated circuit load; wherein applying a voltage across a lossy
capacitor includes: applying a voltage across a high K dielectric,
and controlling conductance through the high K dielectric to
provide a controlled resistance using a tailored amount of nano
crystals uniformly dispersed in the high K dielectric.
23. The method of claim 22, wherein the high K dielectric includes
an aluminum oxide.
24. The method of claim 22, wherein the high K dielectric includes
a tantalum oxide.
25. The method of claim 22, wherein the high K dielectric includes
a titanium oxide.
26. The method of claim 22, wherein the high K dielectric includes
a tantalum nitride.
27. The method of claim 22, wherein the high K dielectric includes
a tantalum silicate.
28. The method of claim 22, wherein the high K dielectric includes
a zirconium oxide.
29. The method of claim 22, wherein the high K dielectric includes
a zirconium nitride.
30. The method of claim 22, wherein the high K dielectric includes
a zirconium silicate.
31. The method of claim 22, wherein the high K dielectric includes
a hafnium oxide.
32. The method of claim 22, wherein the high K dielectric includes
a hafnium nitride.
33. The method of claim 22, wherein the high K dielectric includes
a hafnium silicate.
34. The method of claim 22, wherein the high K dielectric includes
a praseodymium oxide.
35. The method of claim 22, wherein the high K dielectric includes
a praseodymium nitride.
36. The method of claim 22, wherein the high K dielectric includes
a praseodymium silicate.
37. The method of claim 22, wherein the nano crystals include gold
nano crystals.
38. The method of claim 22, wherein the nano crystals include
silicon nano crystals.
39. An integrated circuit, comprising: an integrated circuit load;
means for applying a voltage across a high K dielectric connected
to the integrated circuit load to lower a resonance impedance and a
resonance frequency of the integrated circuit; and means for
controlling conductance through the high K dielectric using a
tailored amount of nano crystals uniformly dispersed in the high K
dielectric to lower the resonance impedance.
40. The integrated circuit of claim 39, wherein the high K
dielectric includes aluminum oxide and the nano crystals include
silicon nano crystals.
41. The integrated circuit of claim 39, wherein the high K
dielectric includes aluminum oxide and the nano crystals include
gold nano crystals.
42. The integrated circuit of claim 39, wherein the high K
dielectric includes a dielectric selected from the group consisting
of: a tantalum oxide, a titanium oxide, a tantalum nitride, a
tantalum silicate, a zirconium oxide, a zirconium nitride, a
zirconium silicate, a hafnium oxide, a hafnium nitride, a hafnium
silicate, a praseodymium oxide, a praseodymium nitride and a
praseodymium silicate.
43. The integrated circuit of claim 42, wherein the high K
dielectric is doped with a complex high K dielectric selected from
the group consisting of: barium strontium titanate (BST), a
transition metal, and a metal oxide.
44. The integrated circuit of claim 43, wherein the metal oxide is
selected from the group consisting of a tantalum oxide, a zirconium
oxide and a praseodymium oxide.
Description
RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/752,351, filed Jan. 6, 2004; which is a divisional of
U.S. patent application Ser. No. 09/944,986 filed on Aug. 30, 2001;
each of which is incorporated herein by reference.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates generally to integrated circuits and,
more particularly, to decoupling capacitors for reducing resonance
frequency and impendence in high-frequency chip designs.
BACKGROUND OF THE INVENTION
[0003] Goals for integrated circuit design include progressively
scaling the design to achieve smaller feature sizes, and using
faster clock frequencies beyond 1 GHz. Problems encountered in
achieving these goals include the increasing voltage droop and the
inductive noise of the active switching nodes, and further include
the increasing power supply oscillations and the resulting noise
that is generated and transmitted across the chip.
[0004] These problems are addressed by incorporating on-chip
decoupling capacitors into the integrated circuit design. On-chip
decoupling capacitors provide a uniform power supply voltage supply
(VDD) to fast switching nodes and offset the voltage droops caused
by resistive and inductive losses in the integrated circuit load.
As such, as will be described in more detail below, on-chip
decoupling capacitors reduce .DELTA.I and .DELTA.V noises in CMOS
circuits.
[0005] The resonance impedance (Z.sub.RES) of the chip is directly
proportional to the inductive component and inversely proportional
to the chip RC as represented by the following equation: Z RES
.varies. L ( R C + R DC ) + ( C C + C DC ) . ##EQU1## The values
R.sub.C and C.sub.C represent the resistance and capacitance of the
chip, respectively. The values R.sub.DC and C.sub.DC represent the
resistance and capacitance of the decoupling capacitor,
respectively. The resonance frequency (F.sub.RES) of the chip is
inversely proportional to the square root of L+C as represented by
the following equation: F RES .varies. 1 L + ( C C + C DC ) .
##EQU2## The V.sub.DD oscillation and the V.sub.DD noise can be
suppressed by a significant and simultaneous lowering of both
Z.sub.RES and F.sub.RES.
[0006] Conventionally, on-chip decoupling capacitors are fabricated
using silicon dioxide (SiO.sub.2) capacitance in the form of Metal
Oxide Silicon (MOS) capacitors. SiO.sub.2 has a low dielectric
constant (K.apprxeq.3.9), i.e. a low capacitance per unit area,
such that a relatively large amount of silicon area is required for
a given capacitance. Thus, the use of SiO.sub.2 adversely affects
both density and yield.
[0007] Conventional capacitors that are constructed with
defect-free silicon dioxide are characterized as "loss-less"
capacitors because, when used as decoupling capacitors, they
provide added capacitance to the chip but provide no resistive
component. As such, a separate series resistor is often fabricated
with conventional on-chip decoupling capacitors to reduce
Z.sub.RES.
[0008] It is desirable for a decoupling capacitor to have a
controlled and large value of capacitance per unit area, i.e. a
high K value, to provide an effective capacitance (C.sub.DC) in a
relatively small area and to have a built-in controlled resistance
(R.sub.DC) in order to control the resonance impedance and the
resonance frequency. Thus, it is desirable to provide controlled
and effective "lossy" decoupling capacitor structures and processes
that provide a significantly larger value of capacitance per unit
area and overcome high frequency design challenges.
[0009] One known on-chip decoupling capacitor that has an
adjustable Z.sub.RES includes two thin layers of SiO.sub.2 between
a silicon substrate and a doped polysilicon plate, and further
includes a thin layer of "injector" quality silicon-rich-nitride
(SRN), which is described below, between the two thin layers of
SiO.sub.2. For example, a known capacitive device includes an
insulating layer of SiO.sub.2 having a thickness of 25 .ANG., an
SRN layer having a thickness of 50 to 85 .ANG., and an SiO.sub.2
layer having a thickness of 15 .ANG.. A known process sequence for
forming this device includes growing 25 .ANG. of SiO.sub.2 on a
silicon substrate. SRN is deposited to a thickness of 50-85 .ANG.
using Low Pressure Chemical Vapor Deposition (LPCVD) or Plasma
Enhanced Chemical Vapor Deposition (PECVD). A Rapid Thermal Anneal
(RTA) in O.sub.2 ambient is performed, and the top oxide and SRN
layers are patterned and etched such that the SRN layer is left
only over N-well regions in the silicon substrate for subsequent
capacitor formation. The bottom oxide is removed to form field
effect transistor (FET) gate regions and gate oxide is grown.
Polysilicon is deposited, doped and patterned to simultaneously
form FET gates and the top plate of the capacitor device.
[0010] The above-described known on-chip decoupling capacitor is
limited by the scalability of the SiO.sub.2 film thickness, and
requires a large silicon area to provide a significant value of
capacitance due to the inherently low dielectric constant of
SiO.sub.2. Furthermore, even though superior to conventional oxide,
this known on-chip decoupling capacitor has a defect, yield and
reliability impact similar to thin SiO.sub.2 gate films.
[0011] Therefore, there is a need in the art to provide a system
and method that overcomes these problems. The present invention
overcomes the above limits of scalability, yield and reliability
and provides design solutions for significantly higher frequency
ranges, lower voltages, and smaller feature sizes for future
generations of integrated circuit design.
SUMMARY OF THE INVENTION
[0012] The above mentioned problems are addressed by the present
subject matter and will be understood by reading and studying the
following specification. An on-chip decoupling device and method is
provided. A resonance impedance and a resonance frequency for an
integrated circuit chip are reduced using a lossy decoupling
capacitor that has a large capacitance per unit area (high K value)
and a built-in controlled resistance. The lossy decoupling
capacitor includes a high K dielectric layer doped with nano
crystals. The lossy decoupling capacitor has a number of variables
that can be manipulated to provide the desired capacitance and
resistance for simultaneously lowering the resonance impedance and
resonance frequency for the chip. These variables are also capable
of being manipulated for scaling purposes in high clock frequency
and high speed switching designs.
[0013] One aspect of the present subject matter is a capacitor
insulator structure. One embodiment of the capacitor insulator
structure includes a high K dielectric layer and nano crystals. The
nano crystals are dispersed through the high K dielectric.
[0014] One aspect of the present subject matter is a capacitor. One
embodiment of the capacitor includes a substrate, a high K
dielectric layer doped with nano crystals disposed on the
substrate, and a top plate layer disposed on the high K dielectric
layer. According to one embodiment, the high K dielectric layer
includes Al.sub.2O.sub.3. According to other embodiments, the nano
crystals include gold nano crystals and silicon nano crystals.
[0015] One capacitor embodiment includes a MIS
(metal-insulator-silicon) capacitor fabricated on a silicon
substrate, and another capacitor embodiment includes a MIM
(metal-insulator-metal) capacitor fabricated at lower temperature
between the interconnect layers above a silicon substrate. The MIS
capacitor directly consumes the silicon area for fabrication of the
capacitors, but potentially requires less processing steps when
appropriately integrated with the gate insulator processing. The
MIM capacitor does not directly impact silicon area and potentially
provides a large area for capacitor fabrication. However, the MIM
capacitor potentially impacts the number of required interconnect
layers which adds mask level and processing cost.
[0016] One aspect of the present subject matter is an integrated
circuit. One embodiment of the integrated circuit includes a power
source, an integrated circuit load coupled to the power source, and
a lossy decoupling capacitor coupled to the integrated circuit load
to lower the resonance impedance and the resonance frequency. The
integrated circuit load is characterized by a resonance impedance
and a resonance frequency, and includes an inductive load, a
resistive load, and a capacitive load. The lossy decoupling
capacitor has a large capacitance per unit area (high K value) and
a built-in controlled resistance. The lossy decoupling capacitor
includes a high K dielectric layer doped with nano crystals
disposed on a substrate, and a top plate layer disposed on the high
K dielectric layer.
[0017] One aspect of the present subject matter provides a method
of reducing a resonance impedance and a resonance frequency for an
integrated circuit chip. According to one embodiment of this
method, a decoupling capacitor is formed by providing a first
plate, a second plate, and a dielectric formed from a layer of
alumina (Al.sub.2O.sub.3) doped with nano crystals. The decoupling
capacitor is coupled to the integrated circuit.
[0018] These and other aspects, embodiments, advantages, and
features will become apparent from the following description of the
invention and the referenced drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a graph showing refractive index of silicon-rich
silicon nitride films versus SiH.sub.2Cl.sub.2/NH.sub.3 flow rate
ratio.
[0020] FIG. 2 is a graph showing current density versus applied
field for silicon-rich silicon nitride films having different
percentages of excess silicon.
[0021] FIG. 3 is a graph showing apparent dielectric constant K
versus refractive index for both silicon rich nitride (SRN) and
silicon rich oxide (SRO).
[0022] FIG. 4 is a lumped model illustrating the resistive and
inductive losses for an integrated circuit.
[0023] FIG. 5 is another model of the electrical behavior for an
integrated circuit.
[0024] FIG. 6 is the integrated circuit model of FIG. 7 with a
lossy decoupling capacitor.
[0025] FIG. 7 is a schematic for an on-chip decoupling device.
[0026] FIG. 8 illustrates one embodiment of a
metal-insulator-silicon (MIS) capacitor formed over an n silicon
substrate or an n-well.
[0027] FIG. 9 illustrates another embodiment of a MIS capacitor
formed over an n silicon substrate or an n-well.
[0028] FIG. 10 illustrates another embodiment of a MIS capacitor
formed over an p silicon substrate or a p-well.
[0029] FIG. 11 illustrates another embodiment of a MIS capacitor
formed over an p silicon substrate or a p-well.
[0030] FIG. 12 illustrates one embodiment of a MIS capacitor with a
metal top plate.
[0031] FIG. 13 illustrates another embodiment of a MIS capacitor
with a metal top plate.
[0032] FIG. 14 illustrates one embodiment of a
metal-insulator-metal (MIM) capacitor with gold nano crystals.
[0033] FIG. 15 illustrates another embodiment of a MIM capacitor
with silicon nano crystals.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The following detailed description of the invention refers
to the accompanying drawings which show, by way of illustration,
specific aspects and 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. 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, along with the full scope of equivalents to
which such claims are entitled.
[0035] Silicon-rich nitride (SRN), or more particularly, injector
SRN was referenced in the Background of the Invention. SRN is a
subset of silicon rich insulator (SRI). Another subset of SRI is
silicon rich oxide (SRO), or more particularly, injector SRO. FIGS.
1-3, described below, are included to elaborate on the
characteristics of SRN, including injector SRI.
[0036] FIG. 1 is a graph showing refractive index of silicon-rich
silicon nitride films versus SiH.sub.2Cl.sub.2/NH.sub.3 flow rate
ratio (R). This figure is provided herein to illustrate the known
relationship between the silicon amount and the refractive index in
the film. The graph indicates that the index of refraction
increases linearly with increasing silicon content. As such, the
index of refraction of the films can be used as an indication of
the silicon content of the films.
[0037] FIG. 2 is a graph showing current density versus applied
field for silicon-rich silicon nitride films having different
percentages of excess silicon. The current density (J) is
represented in amperes/cm.sup.2, and log J is plotted against the
electric field E (volts/cm) for Si.sub.3N.sub.4 layers having a
SiH.sub.2Cl.sub.2NH.sub.3 flow rate ratio R of 0.1, 3, 5, 10, 15
and 31. This figure is provided herein to illustrate the known
relationship between the amount of silicon and the conductivity of
the film. The plot shows that the Si.sub.3N.sub.4 layers having
small additions of silicon (R=3 and 5) exhibit a relatively small
conductivity increase over stoichiometric Si.sub.3N.sub.4. The plot
further shows that increasing silicon content at or above R=10
substantially increases or enhances the conductivity.
[0038] Silicon-rich nitride films having an R greater than 10 (or,
more specifically, having an index of refraction greater than 2.3)
are referred to as an injector medium. A silicon-rich
Si.sub.3N.sub.4 (SRN) injector provides appreciably enhanced charge
conductance without providing significant charge trapping similar
to the characteristics of semi-metals.
[0039] Silicon nitride injectors are preferred over silicon oxide
injectors because the two-phase nature of the interface is believed
to provide a localized electric field distortion and an associated
high current. At elevated processing temperature, silicon readily
diffuses within silicon oxide and changes the size and geometry of
silicon crystals, which disrupts the injection threshold by
reducing the localized field distortions. However, silicon does not
readily diffuse within Si.sub.3N.sub.4. Furthermore, SRN is
chemically passive against chemical solutions as well as an
effective barrier against n or p type dopant diffusion; that is,
against phosphorus or boron respectively.
[0040] FIG. 3 is a graph showing apparent dielectric constant K
versus refractive index for both silicon rich nitride (SRN) and
silicon rich oxide (SRO). The SRN and SRO plotted in this graph
were provided using a Low Pressure Chemical Vapor Deposition
(LPCVD) process. The SRO was fabricated at approximately
680.degree. C., and the fabricated structure included 100 .ANG.
oxide and 150 .ANG. SRO. The SRN was fabricated at approximately
770.degree. C., and the fabricated structure included 45 .ANG.
oxide and 80 .ANG. SRO. As shown in the graph, the dielectric
constant of silicon is around 12. Materials with a higher K than
silicon are conventionally termed a high K material, and materials
with a lower K than silicon are conventionally termed a low K
material. Injector SRN are those that have a refractive index of
2.5 or greater and injector SRO are those that have a refractive
index of 1.85 or greater. Injector SRN and injector SRO have
apparent dielectric constants that are greater than 12. Injector
SRI includes both high K SRO and high K SRN.
[0041] Thus, as illustrated by FIGS. 1-3, injector SRN provides
enhanced charge conductance. Controlling the dispersion and amount
of silicon in injector SRN controls the resistivity of the film in
which the injector SRN is deposited.
[0042] FIG. 4 is a lumped model illustrating the resistive and
inductive losses for an integrated circuit. The model includes a
power source 410 and an integrated circuit load 412. The power
source 410 is represented by both a voltage source 414 and a
current source 416. The integrated circuit load 412 has a resistive
component 418, an inductive component 420, and a capacitive
component 422. These are represented in this model as a lumped
resistance, a lumped inductor and a lumped capacitor connected in
series. The lumped resistance contributes to signal loss as
represented by .DELTA.V.sub.R. The lumped inductor also contributes
to signal loss as represented by .DELTA.V.sub.L.
[0043] FIG. 5 is another model of the electrical behavior for an
integrated circuit. This model also includes a power source 510 and
an integrated circuit load 512. The power source 510 is represented
by both a voltage source 514 and a current source 516. The
integrated circuit load 512 has a resistive component 518, an
inductive component 520, and a capacitive component 522. The
resistive component 518 is attributable to the resistance of the
chip/substrate. The inductive component 520 is attributable to the
inductance in the substrate and interconnect. In this model, the
resistive component and capacitive component are connected in
series with each other, and are connected in parallel with the
inductive component.
[0044] FIG. 6 is the integrated circuit model of FIG. 5 with a
lossy decoupling capacitor. The lossy decoupling capacitor 624 is
coupled in parallel with the chip capacitive component 622 of the
integrated circuit load 612. The model for the lossy decoupling
capacitor 624 includes a decoupling capacitor (C.sub.DC) 626
coupled in parallel with a decoupling resistor (R.sub.DC) 628. As
provided earlier, increasing C.sub.DC and R.sub.DC lowers the
resonance impedance (Z.sub.RES) and the resonance frequency
(F.sub.RES) and suppresses the V.sub.DD oscillation and the
V.sub.DD noise.
[0045] FIG. 7 is a schematic for an on-chip decoupling device
according to the present subject matter. A substrate 730 is
provided with isolation regions 732. Control devices 734 are formed
between isolation regions 732. Each control device 734 includes a
gate 736 and two diffused regions 738 in the substrate 730. A gate
insulator 740 separates the gate 736 from the diffused regions 738.
An n-well 742 is formed between the two control devices 734. A
decoupling capacitor plate 744 is formed over the n-well, and is
separated from the n-well by a capacitor insulator structure 746.
This capacitor insulator structure 746 provides the characteristics
for the lossy decoupling capacitor. According to one embodiment,
the fabrication of the insulator structure 746 is integrated with
the processing of the gate insulator 740 of the control devices
734.
[0046] There are a number of variables that may be manipulated
during the fabrication of the decoupling capacitor to achieve the
desired values for the resistive and capacitive component (R.sub.DC
and C.sub.DC) of the decoupling capacitor. One of these manipulated
variables, as taught by the present subject matter, is the K value
of the dielectric used in the capacitor insulator structure 746.
Other manipulated variables taught by the present subject matter
include the distribution of nano crystals in the capacitor
insulator structure 746 and the composition of the nano crystals.
The nano crystals control the resistivity of the high K dielectric.
Those of ordinary skill in the art will understand, upon reading
and comprehending this disclosure, how to manipulate these and
other variables to achieve the desired R.sub.DC and C.sub.DC for a
decoupling capacitor.
[0047] FIG. 8-13 illustrate various embodiments of a MIS
(metal-insulator-substrate) capacitor. The gate oxide for the
capacitor insulator structure is a high K dielectric containing
tailored amounts of nano crystals. According to various
embodiments, these nano crystals are uniformly distributed or
dispersed in the high K dielectric. According to one embodiment,
the high K dielectric includes alumina (Al.sub.2O.sub.3). In one
embodiment, silicon or gold nano crystals are uniformly distributed
in Al.sub.2O.sub.3 by simultaneous sputtering, by implant, by
ion-beam deposition or by vapor phase deposition. In one
embodiment, silicon-rich alumina is deposited by chemical vapor
deposition (CVD) technique to create a two phase insulator
consisting of desired silicon nano crystals uniformly dispersed in
Al.sub.2O.sub.3.
[0048] If the capacitor plate is a silicon plate, the insulator is
capped with a thin (5 nm, for example) layer of injector SRN which
adds an increased resistive component with negligible impact on
capacitance. This is because, as was stated above, injector SRN
provides appreciably enhanced charge conductance without providing
appreciably enhanced charge trapping. Additionally, the injector
SRN layer prevents dopant and impurity migration during subsequent
high temperature processing. If the capacitor plate is a metal
plate, one embodiment provides a thin layer of titanium nitride
(TiN) to provide a diffusion barrier between the insulator and the
metal interface. One embodiment uses the TiN layer as the top plate
of the capacitor.
[0049] According to various embodiments, the capacitance of the
decoupling capacitor is further enhanced by doping transition
metals into the high K dielectric material. These transition metals
include, but are not limited to, hafnium (Hf), tantalum (Ta),
zirconium (Zr), and praseodymium (Pr). Additionally, a complex high
K dielectric is used as the dielectric for the capacitor, or is
doped with the high K dielectric for the capacitor. One such
complex high K dielectric is barium strontium titanate ((BaSr)
TiO.sub.3) which is also known as BST. Other complex high K
dielectrics include, but are not limited to, tantalum pentoxide
(Ta.sub.2O.sub.5), titanium dioxide (TiO.sub.2), tantalum nitride
(TaN), zirconium oxide (ZrO.sub.2) which is also known as zirconia,
and praseodymium oxide (Pr.sub.2O.sub.3).
[0050] FIG. 8 illustrates one embodiment of a MIS capacitor formed
over an n silicon substrate or an n-well. According to this
embodiment, a layer 850 of gold-doped Al.sub.2O.sub.3 is disposed
on the substrate 830 and functions as the capacitor insulator
structure 846. Gold-doped Al.sub.2O.sub.3 is Al.sub.2O.sub.3 doped
with gold nano crystals. An injector layer 852, such as an injector
SRN layer, is disposed on the gold-doped Al.sub.2O.sub.3. The top
plate 844 of the capacitor is formed from n+ polysilicon.
[0051] FIG. 9 illustrates another embodiment of a MIS capacitor
formed over an n silicon substrate or an n-well. According to this
embodiment, a layer 950 of silicon-doped Al.sub.2O.sub.3 is
disposed on the substrate 930 and functions as the capacitor
insulator structure 946. Silicon-doped Al.sub.2O.sub.3 is
Al.sub.2O.sub.3 doped with silicon nano crystals. An injector layer
952, such as an injector SRN layer, is disposed on the
silicon-doped Al.sub.2O.sub.3. The top plate 944 of the capacitor
is formed from n+ polysilicon.
[0052] FIG. 10 illustrates another embodiment of a MIS capacitor
formed over an p silicon substrate or a p-well. According to this
embodiment, a layer 1050 of gold-doped Al.sub.2O.sub.3 is disposed
on the substrate 1030 and functions as the capacitor insulator
structure 1046. An injector layer 1052, such as an injector SRN
layer, is disposed on the gold-doped Al.sub.2O.sub.3. The top plate
1044 of the capacitor is formed from p+ polysilicon.
[0053] FIG. 11 illustrates another embodiment of a MIS capacitor
formed over an p silicon substrate or a p-well. According to this
embodiment, a layer 1150 of silicon-doped Al.sub.2O.sub.3 is
disposed on the substrate 1130 and functions as the capacitor
insulator structure 1146. An injector layer 1152, such as an
injector SRN layer, is disposed on the silicon-doped
Al.sub.2O.sub.3. The top plate 1144 of the capacitor is formed from
p+ polysilicon.
[0054] FIG. 12 illustrates one embodiment of a MIS capacitor with a
metal top plate. According to this embodiment, a layer 1250 of
gold-doped Al.sub.2O.sub.3 is disposed on the substrate 1230, and a
TiN layer 1254 is disposed thereon. According to another
embodiment, a layer 1250 of silicon-doped Al.sub.2O.sub.3 is
disposed on the substrate 1230, and a TiN layer 1254 is disposed
thereon. The top plate 1244 of the capacitor is formed from a
metal.
[0055] FIG. 13 illustrates another embodiment of a MIS capacitor
with a metal top plate. According to this embodiment, a layer 1350
of gold-doped Al.sub.2O.sub.3 is disposed on the substrate 1330,
and a TiN layer 1354 is disposed thereon. According to another
embodiment, a layer 1350 of silicon-doped Al.sub.2O.sub.3 is
disposed on the substrate 1330, and a TiN layer 1354 is disposed
thereon. The TiN 1354 layer forms the top plate 1344 of the
capacitor.
[0056] FIGS. 14-15 illustrate various embodiments of a MIM
(metal-insulator-metal) capacitor. According to various
embodiments, the MIM capacitor is fabricated on top of silicon and
is appropriately connected to the VDD/Gnd nodes, clock trees and
active circuits. The insulator is a high K dielectric containing
tailored amounts of nano crystals uniformly distributed or
dispersed in the high K dielectric. Such insulator is usually
fabricated at lower temperature than corresponding MIS options. The
techniques used for fabrication include electron cyclotron
resonance-plasma enhanced chemical vapor deposition (ECR-PECVD),
atomic layer deposition (ALD), sputtering, E-Beam and Ion-Beam
deposition of thin films.
[0057] According to one embodiment, the high K dielectric includes
Al.sub.2O.sub.3. In one embodiment, ALD aluminum is deposited on
top of a tungsten nitride (TiN), a tungsten (W) or tungsten
silicide (WSi) electrode and subsequently oxidized in ozone plasma
at low temperature. In one embodiment, silicon or gold nano
crystals are uniformly distributed in Al.sub.2O.sub.3 by
simultaneous sputtering, or by implant, or by vapor phase
deposition. In one embodiment, silicon-rich alumina is deposited by
CVD technique to create two phase insulator consisting of desired
silicon nano crystals uniformly dispersed in Al.sub.2O.sub.3.
According to various embodiments, the metal top plate is any metal
such as titanium nitride (TiN), copper (Cu) or aluminum (Al).
[0058] According to various embodiments, the capacitance of the
decoupling capacitor is further enhanced by doping transition
metals into the high K dielectric such as Al.sub.2O.sub.3. These
transition metals include, but are not limited to, hafnium (Hf),
tantalum (Ta), zirconium (Zr), praseodymium (Pr). Additionally, a
complex high K dielectric is used as the dielectric for the
capacitor, or is doped with the high K dielectric for the
capacitor. One such complex high K dielectric is barium strontium
titanate ((BaSr) TiO.sub.3) which is also known as BST. Other
complex high K dielectrics include, but are not limited to,
tantalum pentoxide (Ta.sub.2O.sub.5), titanium dioxide (TiO.sub.2),
tantalum nitride (TaN), zirconium oxide(ZrO.sub.2) also known as
zirconia, and praseodymium oxide (Pr.sub.2O.sub.3).
[0059] FIG. 14 illustrates one embodiment of a MIM capacitor with
gold nano crystals. According to this embodiment, a first layer
1462 of TiN is disposed on the bottom metal layer 1460, a layer
1450 of gold-doped Al.sub.2O.sub.3 is disposed on the first layer
of TiN 1462, a second layer 1444 of TiN is disposed on the layer
1450 of gold-doped Al.sub.2O.sub.3, and a top plate 1444 is formed
on the second layer 1444 of TiN. According to various embodiments,
the top plate is fabricated from titanium nitride (TiN), copper
(Cu), tungsten (W) or aluminum (Al) and the bottom metal layer is
fabricated from Cu, W, Al, TiN, or tungsten silicide (WSi).
[0060] FIG. 15 illustrates another embodiment of a MIM capacitor
with silicon nano crystals. According to this embodiment, a first
layer of TiN 1562 is disposed on the bottom metal layer 1560, a
layer 1550 of silicon-doped Al.sub.2O.sub.3 is disposed on the
first layer 1562 of TiN, a second layer 1564 of TiN is disposed on
the layer 1550 of gold-doped Al.sub.2O.sub.3, and a top plate 1544
is formed on the second layer 1544 of TiN. According to various
embodiments, the top plate is fabricated from TiN, Cu, W or Al and
the bottom metal layer is fabricated from Cu, W, Al, TiN, or
WSi.
[0061] Injector SRN was provided as an example of an injector
medium in the above examples. One of ordinary skill in the art will
understand, upon reading and comprehending this disclosure, that
other materials may be used as an injector medium. These materials
include silicon-rich aluminum nitride and SRO. Al.sub.2O.sub.3 is
not an effective diffusion barrier for certain dopants like
phosphorus for an n+ gate. The injector media SRN and silicon-rich
aluminum nitride function as a diffusion barrier for doped
polysilicon gates to prevent phosphorous, for example, from
diffusing into Al.sub.2O.sub.3. A diffusion barrier is not needed
if a metal gate is used.
[0062] Al.sub.2O.sub.3 was provided as an example of a high K
charge blocking medium in the above examples. One of ordinary skill
in the art will understand, upon reading and comprehending this
disclosure, that other materials may be used as a high K charge
medium. A high K charge medium is a material that has a K greater
than the K of silicon. These materials include oxides, nitrides and
silicates of tantalum, titanium, zirconium, hafnium and
praseodymium. Additionally, these materials may further be doped
with complex high K dielectrics such as barium strontium titanate
(BST), transition metal, and metal oxides such as tantalum
pentoxide (Ta.sub.2O.sub.5), titanium dioxide (TiO.sub.2), tantalum
nitride (TaN), zirconium oxide (ZrO.sub.2), and praseodymium oxide
(Pr.sub.2O.sub.3). Furthermore, thin films of these materials can
be readily fabricated at near room temperature or at low
temperature by several techniques including sputtering, ion beam
deposition, and electron cyclotron resonance-plasma enhanced
chemical vapor deposition (ECR-PECVD).
[0063] One of ordinary skill in the art will understand, upon
reading and comprehending this disclosure, how the characteristics
of these materials provide a number of variables that are capable
of being manipulated to achieve the desired characteristics for the
decoupling capacitor. That is, one of ordinary skill in the art
will understand how to provide design solutions for significantly
higher frequency ranges, lower voltages, and smaller feature sizes
for future generations of integrated circuit design.
[0064] Furthermore, one of ordinary skill in the art will
understand, upon reading and comprehending this disclosure, how to
incorporate the decoupling capacitor into various integrated
circuit designs for various components in a larger electronic
system. Such an electronic system includes a processor or
arithmetic/logic unit (ALU), a control unit, a memory device unit
and an input/output (I/O) device. Generally, such an electronic
system will have a native set of instructions that specify
operations to be performed on data by the processor and other
interactions between te processor, the memory device unit and the
I/O devices. The memory device unit contains the data plus a stored
list of instructions. The control unit coordinates all operations
of the processor, the memory device and the I/O devices by
continuously cycling through a set of operations that cause
instructions to be fetched from the memory device and executed.
[0065] The figures presented and described in detail above are
similarly useful in describing the method aspects of the present
subject matter. One of ordinary skill in the art will understand
these methods upon reading and comprehending this disclosure.
CONCLUSION
[0066] The present subject matter provides a decoupling capacitor
for reducing resonance frequency and impedance in high frequency
designs. The capacitor insulator structure of the decoupling
capacitor includes a high K dielectric, and nano crystals dispersed
through the high K dielectric. The distribution of the nano
crystals and the composition of the nano crystals control the
resistivity of the high K dielectric. Thus, the capacitor insulator
structure provides a decoupling capacitor with a high K to provide
an effective C.sub.DC in a relatively small area and with a
built-in controlled R.sub.DC to control the resonance impedance and
the resonance frequency of an integrated circuit chip. As such,
smaller and faster integrate circuit design are achieved.
[0067] 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 adaptations or variations
of the present invention. It is to be understood that the above
description is intended to be illustrative, and not restrictive.
Combinations of the above embodiments, and other embodiments will
be apparent to those of skill in the art upon reviewing the above
description. The scope of the invention includes any other
applications in which the above structures and fabrication methods
are used. The scope of the invention should be determined with
reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled.
* * * * *