U.S. patent application number 14/985623 was filed with the patent office on 2017-07-06 for integrated circuits with electrostatic discharge protection.
The applicant listed for this patent is Globalfoundries Singapore Pte. Ltd.. Invention is credited to Chien-Hsin Lee, Xiangxiang Lu, Manjunatha Prabhu.
Application Number | 20170194311 14/985623 |
Document ID | / |
Family ID | 59191877 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170194311 |
Kind Code |
A1 |
Lu; Xiangxiang ; et
al. |
July 6, 2017 |
INTEGRATED CIRCUITS WITH ELECTROSTATIC DISCHARGE PROTECTION
Abstract
Integrated circuits and methods of producing such integrated
circuits are provided. In an exemplary embodiment, an integrated
circuit includes a first common line and a second common line. A
first electrostatic discharge line is in electrical communication
with the first and second common lines. The first electrostatic
discharge line includes a first diode and a first clamping
device.
Inventors: |
Lu; Xiangxiang; (Singapore,
SG) ; Prabhu; Manjunatha; (Singapore, SG) ;
Lee; Chien-Hsin; (Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Globalfoundries Singapore Pte. Ltd. |
Singapore |
|
SG |
|
|
Family ID: |
59191877 |
Appl. No.: |
14/985623 |
Filed: |
December 31, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/0255 20130101;
H01L 27/0251 20130101 |
International
Class: |
H01L 27/02 20060101
H01L027/02 |
Claims
1. An integrated circuit comprising: a first common line; a second
common line; a first electrostatic discharge line in electrical
communication with the first common line and in electrical
communication with the second common line, wherein the first
electrostatic discharge line comprises a first diode and a first
clamping device in series; and a second electrostatic discharge
line in electrical communication with the first common line and in
electrical communication with the second common line, wherein the
second electrostatic discharge line comprises a second diode and a
second clamping device in series.
2. (canceled)
3. The integrated circuit of claim 1 wherein the first diode is
configured to allow current to flow from the first common line to
the second common line and to block current flow from the second
common line to the first common line, and wherein the second diode
is configured to allow current to flow from the second common line
to the first common line and to block current flow from the first
common line to the second common line.
4. The integrated circuit of claim 1 further comprising: a third
common line; and a third electrostatic discharge line electrically
connected to the third common line and electrically connected to
one of the first common line or the second common line, wherein the
third electrostatic discharge line comprises a third diode and a
third clamping device.
5. The integrated circuit of claim 1 wherein the first clamping
device is selected from the group consisting of a field effect
transistor, a PNP transistor, an NPN transistor, a silicon
controlled rectifier, or a combination thereof.
6. The integrated circuit of claim 1 wherein the first diode has a
first turn-on voltage, and wherein the first electrostatic
discharge line has a first discharge voltage greater than the first
turn-on voltage.
7. The integrated circuit of claim 1 wherein the first clamping
device comprises a first source, a first drain, and a first gate,
and wherein the first drain is electrically connected to the first
common line, the first source is electrically connected to the
second common line, and the first gate is electrically connected to
the second common line.
8. The integrated circuit of claim 7 wherein the first diode is
configured to allow current to flow from the first common line to
the second common line and to block current flow from the second
common line to the first common line.
9. The integrated circuit of claim 1 where the first electrostatic
discharge line is configured to transmit about 1.4 amps or more of
electrical current.
10. The integrated circuit of claim 1 wherein the first clamping
device has a first clamping device switch voltage and the first
electrostatic discharge line has a first discharge voltage, wherein
the first clamping device switch voltage is within about 10 percent
of the first discharge voltage.
11. The integrated circuit of claim 1 wherein a cathode of the
first diode is electrically connected to a drain of the first
clamping device.
12. The integrated circuit of claim 1 wherein an anode of the first
diode is electrically connected to a source of the first clamping
device.
13. An integrated circuit comprising: a first common line; a second
common line; and a first electrostatic discharge line electrically
connected to the first common line and electrically connected to
the second common line, wherein the first electrostatic discharge
line blocks current flow when a voltage drop between the first
common line and the second common line is below a first discharge
voltage, and wherein the first electrostatic discharge line
comprises a single first diode having a first turn-on voltage less
than the first discharge voltage.
14. The integrated circuit of claim 13 further comprising: a second
electrostatic discharge line electrically connected to the first
common line and electrically connected to the second common line,
wherein the second electrostatic discharge line blocks current flow
when a voltage drop between the second common line and the first
common line is below a second discharge voltage, wherein the second
electrostatic discharge line comprises a single second diode having
a second turn-on voltage less than the second discharge voltage,
wherein the first diode is configured to allow current to flow from
the first common line to the second common line and to block
current flow from the second common line to the first common line,
and wherein the second diode is configured to allow current to flow
from the second common line to the first common line and to block
current flow from the first common line to the second common
line.
15. The integrated circuit of claim 14 wherein the second
electrostatic discharge line comprises a single second clamping
device.
16. The integrated circuit of claim 13 wherein the first
electrostatic discharge line is configured to transmit about 1.4
amps of current or more.
17. The integrated circuit of claim 13 wherein the first
electrostatic discharge line comprises a first clamping device,
wherein the first clamping device comprises a first clamping device
switch voltage such that when the voltage drop between the first
common line and the second common line is about 10 percent less
than the first clamping device switch voltage a first clamping
device resistance is about 1,000 ohms or greater, and the first
clamping device resistance is about 1 ohm or less when the voltage
drop between the first common line and the second common line is
about equal to or greater than the first clamping device switch
voltage.
18. The integrated circuit of claim 17 wherein the first
electrostatic discharge line comprises one first clamping
device.
19. The integrated circuit of claim 17 wherein the first clamping
device comprises a first source, a first drain, and a first gate,
and wherein the first drain is electrically connected to the first
common line, the first source is electrically connected to the
second common line, and the first gate is electrically connected to
the second common line.
20. (Withdrawn, Currently amended) A method of producing an
integrated circuit comprising: forming a first common line; forming
a second common line; forming a first electrostatic discharge line
in electrical communication with the first common line and in
electrical communication with the second common line, wherein the
first electrostatic discharge line comprises a first diode and a
first clamping device; and forming a second electrostatic discharge
line in electrical communication with the first common line and in
electrical communication with the second common line, wherein the
second electrostatic discharge line comprises a second diode and a
second clamping device in series.
Description
TECHNICAL FIELD
[0001] The technical field generally relates to integrated circuits
with electrostatic discharge protection and methods of producing
the same, and more particularly relates to integrated circuits with
electrostatic discharge protection that activates after a
predetermined discharge voltage is reached, and methods of
producing the same.
BACKGROUND
[0002] The semiconductor industry is continuously moving toward the
fabrication of smaller and more complex microelectronic components
with higher performance. The production of smaller integrated
circuits requires the development of smaller electronic components,
and closer spacing of those electronic components within the
integrated circuits. Circuit designs that reduce the number of
components used for a required function can reduce circuit
component crowding.
[0003] Many integrated circuits include a plurality of common lines
(including ground lines), and these common lines are typically
electrically connected together with protective electrostatic
discharge lines. Theses electrostatic discharge lines (ESD lines)
are often provided in pairs, where one ESD line is configured for
current flow in one direction between a pair of common lines, and
the other mated ESD line is configured for current flow in the
opposite direction. Diodes are typically used to configure an ESD
line for a desired direction of flow, where a diode allows current
to flow in one direction but not in the other.
[0004] The electrical connection of different common lines can lead
to current leakage from one common line to another, where this
current leakage is commonly referred to as "noise." Noise is
typically produced by a voltage spike in one common line that
results in current being transferred to another common line. Noise
can be limited by establishing a discharge voltage for the ESD
line, where current is not transferred through the ESD line if the
voltage drop between the common lines is less than the discharge
voltage, but current is allowed to flow if the voltage drop is
greater than the discharge voltage. Typically, a preset voltage is
required for a single diode to allow current flow, so when a
discharge voltage that is higher than the preset voltage is
desired, a plurality of diodes are positioned in series. The preset
voltage is typically about 0.5 volts for many types of diodes used
in the ESD lines. Therefore, if the desired discharge voltage is 4
time higher than the preset voltage, 4 diodes are connected in
series in each of the two mated ESD lines. If the desired discharge
voltage is 8 times higher than the preset voltage, then 8 diodes
are included in each of the two mated ESD lines. Forming ESD lines
with several diodes uses valuable space in an integrated circuit,
and extra components provide more opportunities for failure.
[0005] Accordingly, it is desirable to provide integrated circuits
with ESD lines that have fewer components than an ESD line with
multiple diodes, and methods of producing the same. In addition, it
is desirable to provide integrated circuits with ESD lines where
the discharge voltage can be set at a wide variety of values
without requiring additional diodes for higher discharge voltages.
Furthermore, other desirable features and characteristics of the
present embodiment will become apparent from the subsequent
detailed description and the appended claims, taken in conjunction
with the accompanying drawings and this background of the
invention
BRIEF SUMMARY
[0006] Integrated circuits and methods of producing such integrated
circuits are provided. In an exemplary embodiment, an integrated
circuit includes a first common line and a second common line. A
first electrostatic discharge line is in electrical communication
with the first and second common lines. The first electrostatic
discharge line includes a first diode and a first clamping
device.
[0007] An integrated circuit is provided in another embodiment. The
integrated circuit includes a first common line and a second common
line. A first electrostatic discharge line is electrically
connected to the first and second common lines. The first
electrostatic discharge line blocks current flow when a voltage
drop between the first and second common lines is below a first
discharge voltage. The first electrostatic discharge line includes
a single first diode having a first turn on voltage, where the
first turn on voltage is less than the first discharge voltage.
[0008] A method of producing an integrated circuit is provided in
yet another embodiment. The method includes forming a first common
line and a second common line. A first electrostatic discharge line
is formed in electrical communication the first and second common
lines, where the first electrostatic discharge line includes a
first diode and a first clamping device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present embodiments will hereinafter be described in
conjunction with the following drawing figures, wherein like
numerals denote like elements, and wherein:
[0010] FIGS. 1 and 2 illustrate a portion of an integrated circuit
schematic in accordance with exemplary embodiments; and
[0011] FIG. 3 illustrates a portion of an embodiment of the
integrated circuit of FIGS. 1 and 2 and methods for its fabrication
in a sectional perspective view.
DETAILED DESCRIPTION
[0012] The following detailed description is merely exemplary in
nature and is not intended to limit the various embodiments or the
application and uses thereof. Furthermore, there is no intention to
be bound by any theory presented in the preceding background or the
following detailed description. Embodiments of the present
disclosure are generally directed to integrated circuits and
methods for fabricating the same. The various tasks and process
steps described herein may be incorporated into a more
comprehensive procedure or process having additional steps or
functionality not described in detail herein. In particular,
various steps in the manufacture of integrated circuits are
well-known and so, in the interest of brevity, many conventional
steps will only be mentioned briefly herein or will be omitted
entirely without providing the well-known process details.
[0013] A "common line," as used herein, means an electrically
conductive line in electrical communication with a power supply
neutral point, or with an electrical ground, or with both a power
supply neutral point and an electrical ground. Various circuits or
sub-circuits are typically completed by electrically connecting to
the common line. Electrical circuits typically include a power
supply hot line and a common line, where the hot line has a higher
voltage or potential than the common line such that current
generally flows from the hot line to the common line. "Electrical
communication" between two or more components, as used herein,
means electrical current can flow between the different components,
where the current may or may not flow through additional components
between the two or more components. "Electrical connection" between
two or more components, as used herein, means electrical current
can flow directly between the different components, such that the
different components are either directly connected together or a
conductive line directly connects the different components together
with no intervening components between the different components
that are electrically connected. As used herein, an "electrically
conductive material" is a material with a resistivity of about
1.times.10.sup.-4 ohm meters or less and an "electrically
insulating material" is a material with a resistivity of about
1.times.10.sup.4 ohm meters or more.
[0014] Referring to FIG. 1, an integrated circuit 10 includes a
first common line 12 and a second common line 14. As used herein,
the term "integrated circuit" means a circuit of electronic
components, such as transistors, resistors, and capacitors,
constructed on and/or in a semiconductor wafer or chip, in which
the electronic components are interconnected to perform a given
function, wherein at least some of the electronic components are
positioned within about 50 microns or less from each other. The
first and second common lines 12, 14 may be electrically connected,
such as at a neutral point 17 of a power supply 18, but in many
embodiments the first and second common lines 12, 14 are employed
in the service of different sub-circuits (not illustrated) within
the integrated circuit 10. The different sub-circuits served by the
first and second common lines 12, 14 may be virtually any
sub-circuits included in the integrated circuit 10, where a
sub-circuit includes one or more electronic components such as
transistors, resistors, capacitors, diodes, etc. In an exemplary
embodiment, the first and second common lines 12, 14 are not
electrically connected for at least most of the length of the first
and second common lines 12, 14, such as about 95 percent of the
length of the first and second common lines 12, 14. The first
and/or second common lines 12, 14 may be employed in more than one
sub-circuit, where a common line may carry current from more than
one sub-circuit to the power supply 18. The power supply 18 also
includes a hot line 19, where the hot line 19 has a higher voltage
than the neutral point 17 and the first and second common lines 12,
14.
[0015] The integrated circuit 10 also includes a first
electrostatic discharge line 20 that is in electrical communication
with the first and second common lines 12, 14. In some embodiments,
the first electrostatic discharge line 20 is electrically connected
(i.e., directly connected) to one or both of the first and second
common lines 12, 14. The first electrostatic discharge line 20
includes a first diode 22 and a first clamping device 24 in series,
and may include a first conductive line 26 electrically connecting
two or more of the first diode 22, the first clamping device 24,
and the first and second ground lines 12, 14. As used herein a
"clamping device" is a device that allows current flow when a
voltage drop across the clamping device is above a set value, and
blocks current flow when the voltage drop across the clamping
device is below the set value. As used herein, reference to a
component or components "allowing" current flow indicates the
component or components have a resistance of about 1 ohm or less,
or about 0.5 ohms or less, or about 0.1 ohm or less in various
embodiments when allowing current flow, and a component or
components "blocking" current flow indicates a resistance of about
100 ohms or greater, or about 1 megaohms (Mohms) ohms or greater,
or about 100 Mohms or greater in various embodiments. The first
diode 22 and the first clamping device 24 may be directly
physically connected together and may directly connect to the first
and second common lines 12, 14, in which case the first optional
conductive line 26 would not be present. The first electrostatic
discharge line 20 is configured to transfer a preset amount of
current, for example about 1.4 amperes (amps) of current or more to
drain sufficient charge from the first or second common lines 12,
14 to provide protection for electrical surges. The first diode 22,
the first clamping device 24, and the optional first conductive
line 26 are components of the first electrostatic discharge line 20
and are connected in series, so each component is capable of
transferring the preset amount of current e.g. 1.4 or more amps
each. In alternate embodiments, the preset amount of current may be
about 2 amps or more or about 10 amps or more.
[0016] In an exemplary embodiment, the first diode 22 is configured
to allow current to flow from the first common line 12 to the
second common line 14, but blocks current flow from the second
common line 14 to the first common line 12. As such, the first
diode 22 has an anode in electrical communication with the first
common line 12, and the first diode 22 has a cathode in electrical
communication with the second common line 14. The first diode 22
may have a first turn-on voltage, where the first diode 22 blocks
current flow in both directions when the voltage drop (potential
difference) across the first diode 22 is less than the first
turn-on voltage. The first diode 22 allows current flow in one
direction when the voltage drop across the first diode 22 is equal
to or greater than the first turn-on voltage (as long as the higher
voltage is on the anode of the first diode 22). In an exemplary
embodiment, the first turn-on voltage is about 0.5 volts.
[0017] The first diode 22 can be any type of diode that allows
current to flow in one direction while blocking current flow in the
other direction. In the embodiment illustrated in FIG. 1, the first
diode 22 is positioned between the first clamping device 24 and the
first common line 12, but the position of the first diode 22 and
the first clamping device 24 can be switched in some embodiments
such that the first clamping device 24 is between the first diode
22 and the first common line 12.
[0018] The first clamping device 24 serves as a switch that blocks
current flow (or has a high resistance, as described above) when
the voltage drop across the first clamping device 24 is less than a
first clamping device switch voltage. When the voltage drop across
the first clamping device 24 is equal to or greater than the first
clamping device switch voltage, the resistance of the first
clamping device 24 drops significantly to allow current flow. For
example, if the first clamping device 24 is exposed to a voltage
drop about 10 percent less than the first clamping device switch
voltage, the first clamping device blocks current flow with a high
first clamping device resistance, such as about 100 ohms, about
1,000 ohms, or about 5,000 ohms. If the first clamping device 24 is
exposed to a voltage drop about equal to or greater than the first
clamping device switch voltage, the first clamping device 24 allows
current flow with a low first clamping device resistance, such as
about 1 ohm, about 0.5 ohms, or about 0.1 ohms. The change in
resistance of the first clamping device 24 occurs rapidly at about
the first clamping device switch voltage. A wide variety of
electronic components can serve as a clamping device, including but
not limited to a field effect transistor, an NPN transistor, a PNP
transistor, and a silicon controlled rectifier. In an exemplary
embodiment with a transistor (a field effect transistor, an NPN
transistor, or a PNP transistor), a drain of the transistor is in
electrical communication with the first ground line 12, and a
source and a gate of the transistor are both in electrical
communication with the second common line 14. The type and design
of the first clamping device 24 may be selected to provide a
desired first clamping device switch voltage.
[0019] The first electrostatic discharge line 20 has a first
discharge voltage, where the first electrostatic discharge line 20
(including the first diode 22, the first clamping device 24, and
the optional first conductive line 26) allows current flow when the
voltage drop between the first and second common lines 12, 14 is
equal to or greater than the first discharge voltage. The first
electrostatic discharge line 20 blocks current flow when the
voltage drop between the first and second common lines 12, 14 is
less than the first discharge voltage. The voltage drop between the
first and second common lines 12, 14 is the difference in voltage
between the first and second common lines 12, 14. In an exemplary
embodiment, the first clamping switch voltage is within about 10
percent or less of the first discharge voltage, so the first
clamping switch voltage largely determines the first discharge
voltage. The first discharge voltage may be somewhat higher than
the first clamping switch voltage in some embodiments because of
resistance, such as resistance from the first diode 22 or the
optional first conductive line 26. Reference to the first
electrostatic discharge line allowing current flow when the voltage
drop is greater than the first discharge voltage only applies when
the first common line 12 has a higher voltage than the second
common line 14, and does not apply with the second common line 12
has a higher voltage than the first common line 12, because the
first diode 22 blocks reverse current flow.
[0020] In some embodiments and referring again to FIG. 1, a second
electrostatic discharge line 30 is similar to the first
electrostatic discharge line 20, except the second electrostatic
discharge line 30 is configured to allow current to flow from the
second common line 14 to the first common line 12 (i.e., in the
opposite direction as the first electrostatic discharge line 20.)
The second electrostatic discharge line 30 includes a second diode
32, a second clamping device 34, and an optional second conductive
line 36, and the first and second common lines 12, 14 are in
electrical communication with the second electrostatic discharge
line 30. In some embodiments, the second electrostatic discharge
line 30 directly contacts the first and/or second common line 12,
14, so the second electrostatic discharge line 30 may be
electrically connected to the first and/or second common line 12,
14. The second clamping device 34 has a second clamping device
switch voltage that may be within about 10% of a second discharge
voltage of the second electrostatic discharge line 30, as described
above for the first electrostatic discharge line 20. The second
electrostatic discharge line 30, when combined with the first
electrostatic discharge line 20, balances the electrostatic
discharge protection of the first and second common lines 12,
14.
[0021] In some embodiment and referring now to FIG. 2, the
integrated circuit 10 may include a third common line 16, wherein
the third common line 16 is similar to the first and second common
lines 12, 14 described above. In the illustrated embodiment, the
third common line 16 is electrically connected to a ground 48
instead of to the neutral point 17 of the power supply 18, but
other embodiments are also possible. A third electrostatic
discharge line 40 and a fourth electrostatic discharge line 50 are
in electrical communication (and optionally in electrical contact)
with the third common line 16 and one or more of the first and
second common lines 12, 14. The third electrostatic discharge line
40 includes a third diode 42, a third clamping device 44, and an
optional third conductive line 46, and the fourth electrostatic
discharge line 50 includes a fourth diode 52, a fourth clamping
device 54, and an optional fourth conductive line 56, as described
above for the first and second electrostatic discharge lines 20,
30. The integrated circuit 10 may include additional common lines
(not illustrated) and additional electrostatic discharge lines (not
illustrated) in alternate embodiments.
[0022] An exemplary embodiment of the first electrostatic discharge
line 20 is illustrated in a perspective sectional view in FIG. 3,
with continuing reference to FIG. 1. The first electrostatic
discharge line 20 is electrically connected to the first and second
common lines 12, 14. The first diode 22 is formed in a substrate
60, and the first clamping device 24 is formed with a first drain
64 and a first source 66 within the substrate 60 and a first gate
68 overlying the substrate 60, but other embodiments are also
possible. The first conductive line 26 is formed in an interlayer
dielectric 62 overlying the substrate 60, and the first and second
common lines 12, 14 are formed in the interlayer dielectric 62. As
used herein, the term "overlying" means "over" such that an
intervening layer may lie between the first electrostatic discharge
line 20 and the substrate 60, and "on" such that the first
electrostatic discharge line 20 physically contacts the substrate
60. As used herein, the term "substrate" will be used to encompass
semiconductor materials conventionally used in the semiconductor
industry from which to make electrical devices. Semiconductor
materials include monocrystalline silicon materials, such as the
relatively pure or lightly impurity-doped monocrystalline silicon
materials typically used in the semiconductor industry, as well as
polycrystalline silicon materials, and silicon admixed with other
elements such as germanium, carbon, and the like. Semiconductor
material also includes other materials such as relatively pure and
impurity-doped germanium, gallium arsenide, zinc oxide, glass, and
the like. In an exemplary embodiment, the semiconductor material is
a monocrystalline silicon substrate. The silicon substrate may be a
bulk silicon wafer or may be a thin layer of silicon on an
insulating layer (commonly known as silicon-on-insulator or SOI)
that, in turn, is supported by a carrier wafer. The interlayer
dielectric 62 is an electrically insulating material overlying the
substrate 60, such as silicon dioxide, silicon nitride, or other
materials.
[0023] The first clamping device 24 is illustrated in FIG. 3 as a
field effect transistor with the first drain 64 and the first
source 66 formed in the substrate 60, and the first gate 68 formed
overlying the substrate 60 between the first source 66 and the
first drain 64, but the first clamping device 24 may be other types
of electronic components in alternate embodiment as described
above. The first drain 64 of the first clamping device 24 is
electrically connected to the first diode 22 through the first
conductive line 26, and the first diode 22 is electrically
connected to the first common line 12 through a contact 70. The
first source 66 and the first gate 68 are electrically connected to
the second common line 14 through additional contacts 70. The
second diode 32 and second clamping device 34 are not visible in
FIG. 3. Contacts 70 are formed through the interlayer dielectric 62
to electrically connect the various components. The contacts 70 may
provide essentially vertical electrical connections between various
underlying components and horizontal portions of the first
conductive line 26. Contacts 70 may generally provide an electrical
connection between components that are vertically separated.
Different types of diodes, clamping devices, and conductive lines
may be used in alternate embodiments.
[0024] The first and second electrostatic discharge lines 20, 30
allow for controlled current flow between the first and second
common lines 12, 14, where current flow at low voltages can be
blocked or controlled. In this manner, voltage variations in one
common line may be blocked from leaking to another common line,
even when the two common lines are in electrical communication
through the electrostatic discharge lines. As such, the first and
second electrostatic discharge lines 20, 30 protect the first and
second common lines 12, 14 from voltage surges while limiting
unintended current transfer ("noise"). The first and/or second
electrostatic discharge lines may each include a single diode
and/or a single clamping device, as illustrated, so two electrical
components (the diode and clamping device) per electrostatic
discharge line are sufficient to provide voltage surge protection
for a common line.
[0025] While at least one exemplary embodiment has been presented
in the foregoing detailed description, it should be appreciated
that a vast number of variations exist. It should also be
appreciated that the exemplary embodiments are only examples, and
are not intended to limit the scope, applicability, or
configuration of the application in any way. Rather, the foregoing
detailed description will provide those skilled in the art with a
convenient road map for implementing one or more embodiments, it
being understood that various changes may be made in the function
and arrangement of elements described in an exemplary embodiment
without departing from the scope, as set forth in the appended
claims.
* * * * *