U.S. patent application number 13/189054 was filed with the patent office on 2013-01-24 for fused buss for plating features on a semiconductor die.
The applicant listed for this patent is Kevin J. Hess, George R. Leal, Trent S. Uehling. Invention is credited to Kevin J. Hess, George R. Leal, Trent S. Uehling.
Application Number | 20130023091 13/189054 |
Document ID | / |
Family ID | 46507887 |
Filed Date | 2013-01-24 |
United States Patent
Application |
20130023091 |
Kind Code |
A1 |
Leal; George R. ; et
al. |
January 24, 2013 |
FUSED BUSS FOR PLATING FEATURES ON A SEMICONDUCTOR DIE
Abstract
A method for forming a semiconductor structure includes forming
a plurality of fuses over a semiconductor substrate; forming a
plurality of interconnect layers over the semiconductor substrate
and a plurality of interconnect pads at a top surface of the
plurality of interconnect layers; and forming a seal ring, wherein
the seal ring surrounds active circuitry formed in and on the
semiconductor substrate, the plurality of interconnect pads, and
the plurality of fuses, wherein each fuse of the plurality of fuses
is electrically connected to a corresponding interconnect pad of
the plurality of interconnect pads and the seal ring, and wherein
when each fuse of the plurality of fuses is in a conductive state,
the fuse electrically connects the corresponding interconnect pad
to the seal ring.
Inventors: |
Leal; George R.; (Cedar
Park, TX) ; Hess; Kevin J.; (Austin, TX) ;
Uehling; Trent S.; (New Braunfels, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Leal; George R.
Hess; Kevin J.
Uehling; Trent S. |
Cedar Park
Austin
New Braunfels |
TX
TX
TX |
US
US
US |
|
|
Family ID: |
46507887 |
Appl. No.: |
13/189054 |
Filed: |
July 22, 2011 |
Current U.S.
Class: |
438/132 ;
257/E21.602 |
Current CPC
Class: |
H01L 2224/45124
20130101; H01L 2924/00014 20130101; H01L 2924/01074 20130101; H01L
2924/01005 20130101; H01L 2224/03001 20130101; H01L 2224/05556
20130101; H01L 2224/94 20130101; H01L 2924/01029 20130101; H01L
24/05 20130101; H01L 2924/12042 20130101; H01L 23/5256 20130101;
H01L 23/585 20130101; H01L 24/03 20130101; H01L 2224/45124
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2224/48 20130101; H01L 2924/12042 20130101; H01L 2924/00 20130101;
H01L 2224/94 20130101; H01L 2224/03 20130101 |
Class at
Publication: |
438/132 ;
257/E21.602 |
International
Class: |
H01L 21/82 20060101
H01L021/82 |
Claims
1. A method for forming a semiconductor structure, comprising:
forming a plurality of fuses over a semiconductor substrate;
forming a plurality of interconnect layers over the semiconductor
substrate and a plurality of interconnect pads at a top surface of
the plurality of interconnect layers; and forming a seal ring,
wherein the seal ring surrounds active circuitry formed in and on
the semiconductor substrate, the plurality of interconnect pads,
and the plurality of fuses, wherein each fuse of the plurality of
fuses is electrically connected to a corresponding interconnect pad
of the plurality of interconnect pads and the seal ring, and
wherein when each fuse of the plurality of fuses is in a conductive
state, the fuse electrically connects the corresponding
interconnect pad to the seal ring.
2. The method of claim 1, further comprising: while each fuse of
the plurality of fuses is in the conductive state, providing
current through the seal ring and through each of the plurality of
fuses to each of the plurality of interconnect pads to electroplate
a conductive layer on each of the plurality of interconnect
pads.
3. The method of claim 2, further comprising: after the step of
providing current to electroplate the conductive layer, providing
current through at least a subset of the plurality of interconnect
pads to change a state of the fuses electrically connected to the
subset of the plurality of interconnect pads to a non-conductive
state.
4. The method of claim 3, further comprising: sequentially applying
currents through different subsets of the plurality of interconnect
pads to change a state of the fuses electrically connected to the
different subsets of the plurality of interconnect pads to a
non-conductive state until each fuse of the plurality of fuses is
in a non-conductive state.
5. The method of claim 1, wherein the plurality of interconnect
pads, plurality of fuses, and the seal ring are formed within a
first die of a semiconductor wafer, the method further comprising:
forming a second plurality of fuses; forming a second plurality of
interconnect pads at the top surface of the plurality of
interconnect layers; and forming a second seal ring, wherein the
second seal ring surrounds second active circuitry formed in and on
the semiconductor substrate, the second plurality of interconnect
pads, and the second plurality of fuses, wherein each fuse of the
second plurality of fuses is electrically connected to a
corresponding interconnect pad of the second plurality of
interconnect pads and the second seal ring, wherein when each fuse
of the second plurality of fuses is in a conductive state, the fuse
electrically connects the corresponding interconnect pad of the
second plurality of interconnect pads to the second seal ring, and
wherein the second plurality of interconnect pads, the second
plurality of fuses, and the second seal ring are formed within a
second die of the semiconductor wafer adjacent the first die.
6. The method of claim 5, further comprising: forming a seal ring
interconnect which electrically connects the first seal ring to the
second seal ring, wherein the seal ring interconnect is formed in a
scribe street between the first and second die.
7. The method of claim 6, further comprising: while each fuse of
the plurality of fuses and the second plurality of fuses is in the
conductive state, providing current through the seal ring, the
second seal ring, each of the plurality of fuses, and each of the
second plurality of fuses to each of the plurality of interconnect
pads and each of the second plurality of interconnect pads to
electroplate a conductive layer on each interconnect pad of the
plurality of interconnect pads and second plurality of interconnect
pads.
8. The method of claim 7, further comprising: after forming the
conductive layer on each interconnect pad of the plurality of
interconnect pads and second plurality of interconnect pads,
changing a state of each fuse of the plurality of fuses and second
plurality of fuses to a non-conductive state.
9. The method of claim 8, wherein the step of changing the state of
each fuse of the plurality of fuses and second plurality of fuses
to the non-conductive state comprises: sequentially applying
currents to subsets of each of the plurality of interconnect pads
and second plurality of interconnect pads.
10. The method of claim 9, further comprising: after the step of
changing the state of each fuse of the plurality of fuses and the
second plurality of fuses to the non-conductive state, singulating
the first and second die.
11. A method for forming a semiconductor structure, comprising:
forming a gate electrode and a fuse over a semiconductor substrate;
forming a dielectric layer over the gate electrode and the fuse; in
the dielectric layer, forming a first portion of a seal ring, a
contact to the gate electrode, a first contact to a first terminal
of the fuse, and a second contact to a second terminal of the fuse;
forming a plurality of interconnect layers over the dielectric
layer, wherein forming the plurality of interconnect layers
comprises forming a second portion of the seal ring which
contiguously extends through the plurality of interconnect layers
and is connected to the first portion of the seal ring, wherein the
seal ring is connected to the second contact through at least one
interconnect layer of the plurality of interconnect layers; and
forming an interconnect pad over the plurality of interconnect
layers, wherein the interconnect pad is connected to the first
contact through the plurality of interconnect layers.
12. The method of claim 11, further comprising: while the fuse is
in a conductive state, providing current through the seal ring,
through the second contact, through the fuse, through the first
contact, and through the plurality of interconnect layers to the
interconnect pad to electroplate a conductive layer on the
interconnect pad.
13. The method of 12, further comprising: after the step of
providing the current to electroplate the conductive layer on the
interconnect pad, changing a state of the fuse from the conductive
state to a non-conductive state.
14. The method of claim 13, wherein the step of changing the state
of the fuse comprises: providing a current through the
electroplated conductive layer and the interconnect pad to the fuse
to change the state to the non-conductive state.
15. The method of claim 11, wherein the step of forming the gate
electrode and the fuse over the semiconductor substrate comprises:
forming a second conductive layer over the semiconductor substrate;
and patterning the second conductive layer to form both the gate
electrode and the fuse from the second conductive layer.
16. The method of claim 11, wherein the fuse is further
characterized as a polysilicon fuse.
17. The method of claim 11, wherein the gate electrode, the fuse,
the interconnect pad, and the seal ring are within a first die, and
wherein: the step of forming the gate electrode and the fuse
comprises: forming a second fuse over the semiconductor substrate
in a second die, adjacent the first die, wherein the dielectric
layer is formed over the second fuse; the step of forming the first
portion of the seal ring, the contact to the gate electrode, the
first contact to the first terminal of the fuse, and the second
contact to the second terminal of the fuse comprises: in the
dielectric layer, forming a first portion of a second seal ring, a
first contact to a first terminal of the second fuse, and a second
contact to a second terminal of the second fuse; the step of
forming the plurality of interconnect layers comprises: forming a
second portion of the second seal ring which contiguously extends
through the plurality of interconnect layers and is connected to
the first portion of the second seal ring, wherein the second seal
ring is connected to the second contact to the second terminal of
the second fuse through at least one interconnect layer of the
plurality of interconnect layers; and the step of forming the
interconnect pad comprises: forming a second interconnect pad over
the plurality of interconnect layers, wherein the second
interconnect pad is connected to the first contact of the first
terminal of the second fuse through the plurality of interconnect
layers, and wherein the second fuse, the second interconnect pad,
and the second seal ring are within the second die.
18. The method of claim 17, wherein the step of forming the
plurality of interconnect layers is performed such that the seal
ring is connected to the second seal ring through at least one
interconnect layer of the plurality of interconnect layers in a
scribe street between the first and second die.
19. The method of claim 18, further comprising: while the fuse and
the second fuse are in conductive states, providing current through
the seal ring, through the fuse, and through the plurality of
interconnect layers to the interconnect pad and through the second
seal ring, through the second fuse, and through the plurality of
interconnect layers to the second interconnect pad to electroplate
a conductive layer on the interconnect pad and the second
interconnect pad; and after the step of providing the current to
electroplate the conductive layer on the interconnect pad and the
second interconnect pad, changing a state of each of the fuse and
the second fuse from the conductive state to a non-conductive
state.
20. A method for forming a semiconductor structure, comprising:
forming a plurality of fuses on a semiconductor substrate; forming
a plurality of interconnect layers over the semiconductor substrate
and the plurality of fuses; forming a plurality of interconnect
pads at a top surface of the plurality of interconnect layers;
forming a seal ring, wherein the seal ring surrounds active
circuitry formed in and on the semiconductor substrate, the
plurality of interconnect pads, and the plurality of fuses, wherein
each fuse of the plurality of fuses is coupled between a
corresponding interconnect pad of the plurality of interconnect
pads and the seal ring, and wherein when each fuse of the plurality
of fuses is in a conductive state, the fuse electrically connects
the corresponding interconnect pad to the seal ring; while each
fuse of the plurality of fuses is in the conductive state,
providing current through the seal ring and through each of the
plurality of fuses to each of the plurality of interconnect pads to
electroplate a conductive layer on each of the plurality of
interconnect pads; and after the step of providing current to
electroplate the conductive layer, changing a state of each of the
fuses from the conductive state to a non-conductive state.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] This invention relates in general to semiconductor devices
and more specifically to electroplating interconnect pads for
semiconductor devices.
[0003] 2. Description of the Related Art
[0004] To electroplate features such as interconnect or bond pads
on a semiconductor wafer, plating buses must be added to the top
surface of the wafer and then removed after the plating process is
complete. The application and removal of the buses add cost.
[0005] A replacement for Au--Al wirebonding has been sought. The
Over Pad Metallurgy (OPM) process for bond pads was developed to
enable Au--Au and Cu--Au bonding. The OPM deposition is currently
limited to electroless plating processes because a method for
connecting the individual bond pads to a plating bus has not been
conceived and traditional pattern (electro) plating processes are
cost prohibitive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The present invention may be better understood, and its
numerous objects, features, and advantages made apparent to those
skilled in the art by referencing the accompanying drawings.
[0007] FIG. 1 illustrates a top view of an embodiment of
semiconductor wafer.
[0008] FIG. 2 is a partial top view of additional detail of the
wafer of FIG. 1 according to an embodiment.
[0009] FIG. 3 is a partial side cross-sectional view of a wafer
after a phase of manufacture in accordance with an embodiment of
the present invention.
[0010] FIG. 4 is a partial side view of the wafer of FIG. 3 after
several other phases of manufacture.
[0011] FIG. 5 is a partial side view of the wafer of FIG. 4 after
another phase of manufacture.
[0012] FIG. 6 is a partial side view of the wafer of FIG. 5 after
another phase of manufacture.
[0013] FIG. 7 is a partial side view of the wafer of FIG. 6 after
another phase of manufacture.
[0014] FIG. 8 is a partial side view of the wafer of FIG. 7 after
another phase of manufacture.
[0015] FIG. 9 is a partial side view of the wafer of FIG. 8 after
another phase of manufacture.
[0016] FIG. 10 is a partial cross-sectional side view of another
embodiment the wafer of FIG. 4 after another phase of
manufacture.
[0017] FIG. 11 is a partial cross-sectional side view of another
embodiment the wafer of FIG. 4 after another phase of
manufacture.
[0018] FIG. 12 is a partial top view of the wafer of FIG. 11 after
another phase of manufacture.
[0019] FIG. 13 illustrates a top-down layout schematic view of an
embodiment of a fuse that can be used in the wafer of FIGS.
2-12.
[0020] The use of the same reference symbols in different drawings
indicates identical items unless otherwise noted. The features
shown in the Figures are not necessarily drawn to scale.
DETAILED DESCRIPTION
[0021] The following sets forth a detailed description of a mode
for carrying out the invention. The description is intended to be
illustrative of the invention and should not be taken to be
limiting.
[0022] Embodiments of a fused plating bus connection between a seal
ring or other continuous die or wafer structure and the individual
bond pads on the top surface of the die are disclosed. One
embodiment comprises a polysilicon fuse at the active layer of the
wafer proximal to the seal ring structure. The contacts of the seal
ring are directly connected to the first end of the poly fuse. A
metal/via stack electrically coupled to the topmost pad conductive
layer is connected to the second end of the fuse link. The
metal/via stack can be placed between the bond pad footprint and
the seal ring or directly under the bond pad. Seal rings of
multiple die on the wafer may be grouped together via an electrical
connection to a common metal tracing placed in the scribe street
that is later removed during the sawing process.
[0023] The current for plating flows through the common metal trace
in the scribe street, the seal ring, poly fuse, metal stack, and to
the bond pad. Once the plating process is completed, the fuse can
be blown by overdriving the fuse with a current higher than that
used for the plating process. Thus, bond pads can be
electrolytically plated and then isolated from the plating bus. The
fuse overdriving process can be performed during wafer probe test
where the fuse blowing process can be staged or sequenced to
further limit total current needed.
[0024] FIG. 1 illustrates a top view of an embodiment of
semiconductor wafer 100 with a plurality of integrated circuit (IC)
die 102 formed thereon. IC die 102 are shown cross-hatched in FIG.
1 to distinguish IC die 102 from unused portions of around the
circular edge of wafer 100. Plating traces 104 are connected to
seal rings 108 formed around the edge of each IC die 102 in a grid
pattern on wafer 100. The end of each trace 104 can extend into and
beyond edge bead region 106 to the edge of wafer 100. Metal
interconnect layers in the edge bead region 106 can be exposed by
selectively removing dielectric material using processes and tools
known in the art. Referring to FIG. 2, a partial top view of
additional detail of a portion delineated by area B of wafer 100 in
FIG. 1 according to an embodiment is shows corner portions at an
intersection of four IC dies 102 having seal rings 202, singulation
path 204, scribe streets 206, fuses 208, interconnect pads 210,
active regions 212, and seal ring interconnects 214.
[0025] Seal rings 202 are placed around the perimeter of IC dies
102 to seal the edge of IC dies 102 from contaminating ions that
affect the yield during processing and affect performance of IC die
102 after IC die 102 has been fabricated. In addition, seal ring
202 is grounded to a substrate (not shown) of wafer 200. In another
embodiment, the seal ring 202 is connected to the substrate through
a well implant (not shown). Singulation paths 204 are shown by
dashed lines in scribe streets 206 to indicate the location where a
saw and/or laser may be used to separate IC die 102 from one
another.
[0026] Active regions 212 of IC die 102 are delineated by a dashed
line inside the perimeter of seal ring 202 and include circuitry
(not shown) that is used for the functionality of a semiconductor
device. For example, active regions 212 may include circuitry used
for logic or memory functions. Interconnect pads 210 are coupled to
the circuitry in active regions 212 and are typically arranged in
one or more rows around the inside perimeter of active regions 212.
Each of fuses 208 are coupled between a corresponding interconnect
pad 210 and seal ring 202. One end of each seal ring interconnect
214 is coupled to a first seal ring 202 and another end of seal
ring interconnect 214 is coupled to another seal ring 202 across
scribe street 206. Seal rings 202 are thus interconnected with one
another either directly or indirectly by seal ring interconnects
214.
[0027] FIG. 3 is a partial side cross-sectional view of wafer 200
after a phase of manufacture in accordance with an embodiment of
the present invention. Scribe street 206 and first and second
active regions 212 are delineated by vertical dashed lines. Wafer
200 includes dielectric layer 314 formed over substrate 302,
transistor having a gate electrode 304 and contact 306, and fuses
208, 320. Electrical interconnections including gate contact 306,
conductive vias 308, 310, 312, 316, 318 are formed though
dielectric layer 314 to corresponding components as further
describe herein. Gate electrode 304 is shown as an example of one
of various types of active circuitry that may be included in active
regions 212. Substrate 302 can be any suitable silicon or
silicon-on-insulator (SOI) substrate, such as bulk silicon
substrate, a gallium arsenide substrate, or the like, having an
active region 212.
[0028] A first end portion of fuses 208, 320 are positioned in
respective active regions 212 and a second end portion of fuses
208, 320 are positioned between respective active regions 212 and
scribe street 206. Via 308 is coupled to fuse 208 inside first
active region 212, while a pair of vias 310 are coupled to fuse 208
between first active region 212 and scribe street 206. Another via
(not shown) is coupled to fuse 320 inside second active region 212,
while a pair of vias 318 are coupled to fuse 320 between second
active region 212 and scribe street 206. As additional layers are
formed on substrate 302, vias 310 will form part of first seal ring
202 (FIG. 2) and via 312 will form part of a crack stop for first
IC die 102. Similarly, vias 318 will form part of second seal ring
202 (FIG. 2) and another via 316 will form part of a crack stop for
second IC die 102.
[0029] FIG. 4 is a partial side view of the wafer of FIG. 3 after
several other phases of manufacture including forming a number (N)
of interconnect layers 400, which are not shown in detail in FIG.
4, but include alternating metal interconnect layers and via layers
that may be similar to metal interconnect layer 402 and via layer
404. In one embodiment, conductive portions of metal interconnect
and via layers include copper. In another embodiment, the
conductive portions of metal interconnect layers include aluminum
and conductive portions of via layers include tungsten. Any number
of vias may be formed between conductive portions of adjacent metal
interconnect layers.
[0030] Stacked vias 306, 308, 310, 312, 316, 318 are formed
vertically through dielectric layers in interconnect layers 400, as
well as in via layers 404, 408. In the embodiment shown, layer 402
includes metal interconnect 410 coupled to stacked via 308 in
active region 212. In the region between active region 212 and
scribe street 206, layer 402 further includes metal interconnect
418 coupled to a pair of stacked vias 310; metal interconnect 422
coupled to via stack 312; metal interconnect 434 coupled to stacked
via 316; and metal interconnect 438 coupled to a pair of stacked
vias 318.
[0031] Layer 406 includes metal interconnect 414 coupled to stacked
via 308 in active region 212. In the region between active region
212 and scribe street 206, layer 406 further includes metal
interconnect 420 coupled to stacked via 310; metal interconnect 424
coupled to stacked via 312; metal interconnect 436 coupled to
stacked via 316; and metal interconnect 440 coupled to a pair of
stacked vias 318.
[0032] Additionally, layer 406 includes first and second metal
interconnects 426, 430 in scribe street 206. Layer 408 includes
vias 427, 428, 432, 433 coupled to respective metal interconnects
426, 430 in layer 406. Metal interconnect 426 and vias 427, 428
form a first scribe street contact 429 for seal ring interconnect
214 (FIG. 2). Metal interconnect 430 and vias 432, 433 form a
second scribe street contact 435 for seal ring interconnect
214.
[0033] Plating bus portion 417 is thus formed in active region 212
by stacked vias 308 coupled between fuse 208, metal interconnects
410, 414, and a pair of vias 416 coupled to metal interconnect 414.
Plating bus portion 417 couples interconnect pad 210 (FIG. 2) to
the first end portion of fuse 208 in active region 212. Additional
plating bus portions 417 are formed in active region 212 for other
interconnect pads of IC die 102, but are not shown in the figures.
Further, plating bus portions 417 are formed in active regions 212
for other IC die 102, but are not shown in the figures.
[0034] First edge seal 421 is formed in the region between first
active region 212 and scribe street 206 by the pair of stacked vias
310 connected to fuse 208 in layer 314 and extending through layers
400, 404, 408. The pair of stacked vias 310 are further connected
to metal interconnects 418, 420 in respective layers 402, 406.
[0035] First crack stop 425 is thus formed in the region between
edge seal 421 and scribe street 206 by stacked via 312 extending
from the bottom of dielectric layer 314 to the top of dielectric
layer 408 and coupled to metal interconnects 422, 424 in respective
conductive layers 402, 406.
[0036] Second edge seal 442 is thus formed in the region between
second active region 212 and scribe street 206 by the pair of
stacked vias 318 connected to fuse 320 in dielectric layer 314
extending through layers 400, 404, 408. The pair of stacked vias
318 are further connected to metal interconnects 438, 440 in
respective layers 402, 406.
[0037] Second crack stop 437 is thus formed in the region between
edge seal 442 and scribe street 206 by stacked via 316 extending
from the bottom of dielectric layer 314 to the top of dielectric
layer 408 and coupled to metal interconnects 434, 436 in respective
conductive layers 402, 406.
[0038] Seal rings 202 surround the periphery of respective active
regions 212 and can include a respective edge seal 421, 442 and,
optionally, crack stop 425, 437. Although example seal rings 202
for two adjacent IC die 102 on wafer 100 have been described,
additional seal rings 202 are formed around the periphery of IC die
102 to prevent moisture from penetrating into active regions 212 of
respective IC dies 102 as well as to provide conductive
interconnects to fuses 208 and 320. Additional crack stops 425, 437
may be formed to prevent cracks created when respective IC dies 102
are singulated (e.g., by a saw or laser) from penetrating into
active regions 212.
[0039] FIG. 5 is a partial side view of the wafer of FIG. 4 after
another phase of manufacture during which conductive interconnect
pad 502 is formed in active region 212 over vias 416 of plating bus
portion 417. During the same process, plating bus contacts 504, 508
are formed over respective seal rings 202 and vias 427, 433; and
seal ring interconnect 506 is formed over vias 428 and 432, thereby
conductively interconnecting seal rings 202, fuses 208, 320,
plating bus portions 417, and interconnect pad 502.
[0040] Passivation layer 510 is then formed over dielectric layer
408 and interconnect pad 502, plating bus contacts 504, 508, and
seal ring interconnect 506. Passivation layer 510 is removed over
portions of interconnect pad 502 and plating bus contacts 504, 508,
but is left over seal ring interconnect 506.
[0041] FIG. 6 is a partial side view of the wafer of FIG. 5 after
another phase of manufacture in which conductive layers 602, 604,
606 are formed or electroplated on interconnect pad 502 and plating
bus contacts 504, 508 using conventional electroplating methods. In
some embodiments, conductive layers 602, 604, 606 are formed by
electroplating interconnect pad 502 and plating bus contacts 504,
508. A potential is applied to seal rings 202 (also referred to as
traces 104 in FIG. 1) to provide the required electric current for
the electroplating process. The electroplating process can be used
to plate metals such as Ni, Ni--Au, Ni--Pd--Au, Cu, Cu--Pd or other
metals in various embodiments. A metal ring for contacting the
electroplating tooling can be formed in the wafer fab process using
commonly practiced wafer edge processing methods known to one
skilled in the art. Interconnect pad 502 and seal rings 202 are
electrically coupled. The current used during the electroplating
process is less than the current required to overload fuses 208,
320. For example, for 90 nm CMOS technology, current in the range
of 2 to 10 microAmps can be used during electroplating a single
contact pad whereas a current in the range of 40-150 milliAmps is
required to blow fuses 208, 320.
[0042] FIG. 7 is a partial side view of the wafer of FIG. 6 after
another phase of manufacture in which current is supplied to
interconnect pad 502 through test probe 702 which contacts
conductive layer 602. A ground connection to enable current flow
through fuse 208 can be made by contacting conductive layer 604 in
the seal ring 202. The current is greater than the current required
to overload fuse 208, thus causing fuse 208 to fail and create an
open circuit 704 between circuitry in active region 212 and seal
ring 202. For example, for 45 nm CMOS technology, a fuse with body
dimensions of 0.15 um width and 1.0 um length can be overloaded by
100 milliAmps of current applied by a 5 microsecond pulse at 1.5
Volts.
[0043] FIG. 8 is a partial side view of the wafer of FIG. 7 after
another phase of manufacture during which overload current was
applied to an interconnect pad (not shown) connected to fuse 320.
The failure of fuse 320 creates an open circuit 802 between
circuitry in respective active region 212 and seal ring 202.
[0044] Overload current can be applied to each interconnect pad 502
in sequence via a respective conductive layer 602. The amount of
current required to overload fuses 208, 320 is less than the
current required to damage active circuitry on IC die 102.
[0045] FIG. 9 is a partial side view of the wafer of FIG. 8 after
another phase of manufacture after which IC die 102 have been
singulated and are ready to package including attaching IC die 102
to a lead frame or other package substrate (not shown), adding wire
bonds between conductive layer 602 and conductive leads on the lead
frame or other package substrate, and encapsulating IC die 102 in a
protective coating, for example.
[0046] FIG. 10 is a partial cross-sectional side view of another
embodiment of the wafer of FIG. 6 after another phase of
manufacture during which conductive interconnect pad 502 is formed
in active region 212 over vias 416 of plating bus portion 417.
During the same process, plating bus contacts 504, 508 are formed
over respective seal rings 202 and vias 427, 433; and seal ring
interconnect 506 is formed over vias 428 and 432, thereby
conductively interconnecting seal rings 202, fuses 208, 320,
plating bus portions 417, and interconnect pad 502.
[0047] Passivation layer 1004 is then formed over dielectric layer
408 and metal interconnect layer 1002 including interconnect pad
502, plating bus contacts 504, 508, and seal ring interconnect 506.
Passivation layer 1004 is removed over a portion of interconnect
pad 502 but is left over plating bus contacts 504, 508, and seal
ring interconnect 506. Thus, the surface of seal ring interconnect
506 is not exposed during the plating process. The advantage of not
plating metal onto the surface of seal ring interconnect 506 is
that no additional metal is formed in the scribe street. Metal in
the scribe street can cause damage to the die during the wafer
sawing process.
[0048] A conductive layer 1006 can then be formed on interconnect
pad 502 by electroplating interconnect pad 502. Direct potential is
applied to seal rings 202 to provide the required electric current
for the electroplating process. The interconnect pad 502 is
electrically coupled to the seal rings 202. The current used during
the electroplating process is less than the current required to
overload fuses 208, 320.
[0049] Once the electroplating process is complete, current is
applied to interconnect pad 502 through a wafer test probe, such as
probe 702 (FIG. 7) which contacts conductive layer 1006, as well as
to other interconnect pads (not shown). The current is applied to
the interconnect pads in a sequence such that the maximum
instantaneous current applied to the wafer can be controlled. A
current greater than the current required to overload fuse 208 is
applied to cause fuse 208 to fail and create an open circuit
between circuitry in active region 212 and seal ring 202. A ground
connection to enable current flow through fuse 208 can be made by
contacting conductive layer 1006 of another interconnect pad
electrically coupled to seal ring 202 that is not coupled to the
seal ring through an intervening fuse 208. The testing and
subsequent induced fuse failure processes are repeated for each
interconnect pad/fuse combination for each die 102. IC die 102 can
then be singulated and packaged as previously described.
[0050] FIG. 11 is a partial cross-sectional side view of another
embodiment of the wafer of FIG. 6 after an electroplating phase of
manufacture during which metal interconnect 602 is formed over
interconnect pad 502, metal interconnects 604, 606 are formed over
plating bus contacts 504, 508, and scribe street plating buss
contact 1202 is formed over seal ring interconnect 506.
[0051] FIG. 12 is a partial top view of the wafer of FIG. 1 showing
scribe street plating buss contacts 1202 spaced at intervals along
continuous seal rings 202. Plating buss contacts 1202 provide a
plurality of contacts for applying the plating current uniformly
across the wafer during the electroplating process.
[0052] Once the electroplating process is complete, a current
greater than the current required to overload fuse 208 is applied
to conductive layer 602 via wafer test probe, such as probe 702 of
FIG. 7, as well as to other interconnect pads (not shown) in a
sequence such that the maximum instantaneous current applied to the
wafer can be controlled. A ground connection to scribe street
plating buss contact 1202 can be made to enable current flow
through fuse 208. The testing and subsequent induced fuse failure
processes are repeated for each interconnect pad/fuse combination
for each die 102. IC die 102 can then be singulated and packaged as
specified.
[0053] FIG. 13 illustrates a top-down layout view of an embodiment
of fuse 208 that can be used in the wafer of FIGS. 2-12. Fuse 208
includes first end portion 1302, center portion 1304, and second
end portion 1306. Center portion 1304 has a narrower cross-section
than end portions 1302, 1306. First and second end portions 1302,
1306 include respective contacts 308, 310 to provide an electrical
connection between interconnect pad plating bus portion 417 and
edge seal plating buss portion 421 (FIG. 4). Note that although six
contacts 310 and three contacts 308 are shown to form each
electrical connection, any number and shape of contacts can be used
to provide the electrical connections. For example, in another
embodiment, the electrical connections to the one or more end
portions may be made by bar contacts. Fuse 208 is blown by driving
a high enough current through it to result in fuse 208 being
changed to a nonconductive state, thereby eliminating the
electrical connection between end portions 1302, 1306.
[0054] By now it should be appreciated that there has been provided
methods and structures for forming and using polysilicon fuses 208,
320 coupled to seal rings 202 and interconnect pads 502-508 as
electroplating busses for semiconductor devices. One end of fuses
208, 320 is coupled to respective edge seals 421, 442 and another
end of fuses 208, 320 is coupled to respective interconnect pads
502. In one embodiment, one end of fuses 208, 320 is located under
respective edge seals 421, 442 and another end of fuses 208, 320 is
located under respective interconnect pads 502. The addition of
fuses 208, 320 therefore should not affect the size of IC die 102.
In another embodiment, one end of the fuses 208, 320 is coupled to
respective edge seals 421, 442 but not located below the seal ring
202. In still another embodiment, another end of fuses 208, 320 is
coupled to the respective interconnect pad 502, but is not located
below the interconnect pad 502. In yet another embodiment, the
fuses 208, 320 may be formed within a layer of the plurality of
interconnect layers 400.
[0055] Currently known electroplating processes use a large number
of steps that are not required in the methods and structures
disclosed herein. For example, with currently known methods, the
steps include fabricating a wafer, applying an electroplating buss,
applying photoresist, exposing and developing the elements to be
electroplated, electroplating the elements, stripping the
photoresist, removing the plating buss, testing electrical
connections and functionality of the wafer, and singulating the IC
die.
[0056] In contrast, embodiments of the electroplating process for
the present disclosure include fabricating the wafer with fuses
208, 320 coupled to seal rings 202, electroplating the exposed
elements, applying current to blow fuses 208, 320 coupled to an
electroplated element, testing electrical connections and
functionality of the IC die on the wafer and singulating the wafer
into individual IC die. Embodiments of the novel fused
electroplating buss structure can be fabricated using the same
processes as required to create active circuitry and seal rings 202
currently being performed and requires no additional area on the IC
die. The novel process of blowing the fuses after interconnect pads
502 are electroplated disconnects active circuitry and interconnect
pads 502 from the seal rings 202. Thus embodiments of structures
and methods disclosed herein provide the advantages of
electroplating while eliminating most of the process steps and cost
associated with electroplating.
[0057] Accordingly, in some embodiments, as shown in FIGS. 1-13 and
described herein, a method for forming a semiconductor structure
comprises forming a plurality of fuses 208 over a semiconductor
substrate; forming a plurality of interconnect layers 400-408 over
the semiconductor substrate and a plurality of interconnect pads
502 over the plurality of interconnect layers. A seal ring 202 is
formed around active circuitry formed in and on the semiconductor
substrate 302, interconnect pads 502, and fuses 208, 320. Each fuse
208, 320 is electrically connected to a corresponding interconnect
pad 502 and the seal ring 202. When each fuse 208 is in a
conductive state, the fuse 208 electrically connects the
corresponding interconnect pad 502 to the seal ring 202.
[0058] In another aspect, while each fuse 208 is in the conductive
state, current is provided through the seal rings 202 and through
each of the fuses 208 to each of the interconnect pads 502 to
electroplate a conductive layer 602 on each of the interconnect
pads 502.
[0059] In a further aspect, after the step of providing current to
electroplate the conductive layer 602, current is provided through
at least a subset of the interconnect pads 502 to change a state of
the fuses 208 electrically connected to the subset of the
interconnect pads 502 to a non-conductive state.
[0060] In a further aspect, currents are sequentially applied
through different subsets of the interconnect pads 502 to change a
state of the fuses 208 electrically connected to the different
subsets of the interconnect pads 502 to a non-conductive state
until each fuse 208 is in a non-conductive state.
[0061] In a further aspect, the interconnect pads 502, fuses 208,
and the seal ring 202 are formed within a first die 102 of a
semiconductor wafer. A second plurality of fuses 320 are formed. A
second plurality of interconnect pads 502 are formed at the top
surface of the interconnect layers 400-408. A second seal ring 202
is formed that surrounds second active circuitry formed in and on
the semiconductor substrate 302, the second interconnect pads 502,
and the second fuses 320. Each fuse 320 is electrically connected
to a corresponding interconnect pad 502 and the second seal ring
202. Each of the second fuses 320 is in a conductive state. The
fuse 320 electrically connects the corresponding interconnect pad
502 of the second interconnect pads 502 to the second seal ring
202. The second interconnect pads 502, the second fuses 320, and
the second seal ring 202 are formed within a second die 102 of the
semiconductor wafer adjacent the first die 102.
[0062] In a further aspect, a seal ring interconnect 214 is formed
which electrically connects the first seal ring 202 to the second
seal ring 202. The seal ring interconnect 214 is formed in a scribe
street 206 between the first and second die 102.
[0063] In a further aspect, while each fuse 208 and the second
fuses 320 are in the conductive state, current is provided through
the seal ring 202, the second seal ring 202, each of the fuses 208,
and each of the second fuses 320 to each of the interconnect pads
502 and each of the second interconnect pads 502 to electroplate a
conductive layer 602 on each of the interconnect pads 502 and the
second interconnect pads 502.
[0064] In a further aspect, after forming the conductive layer 602
on each of the interconnect pads 502 and each of the second
interconnect pads 502, a state of each fuse 208 and second fuses
320 is changed to a non-conductive state.
[0065] In a further aspect, the step of changing the state of each
fuse 208 and second fuses 320 to the non-conductive state comprises
sequentially applying currents to subsets of each of the first and
second interconnect pads 502.
[0066] In a further aspect, after the step of changing the state of
each fuse 208 and second fuses 320 to the non-conductive state, the
first and second die 102 are tested and singulated.
[0067] In another embodiment, as shown in FIGS. 1-13 and described
herein, a method for forming a semiconductor structure comprises
forming a gate electrode 304 and a fuse 208 over a semiconductor
substrate 302; forming a dielectric layer 314 over the gate
electrode 304 and the fuse 208; in the dielectric layer 314,
forming a first portion of a seal ring 202, a contact 306 to the
gate electrode 304, a first contact 308 to a first end or terminal
of the fuse 208, and a second contact 310 to a second end or
terminal of the fuse 208; forming interconnect layers 400-408 over
the dielectric layer 314, wherein forming the interconnect layers
400-408 comprises forming a second portion of the seal rings 202
which contiguously extends through the interconnect layers 400-408
and is connected to the first portion of the seal ring 202, wherein
the seal ring 202 is connected to the second contact 310 through at
least one interconnect layer of the interconnect layers 400-408;
and forming an interconnect pad 502 over the interconnect layers
400-408, wherein the interconnect pad 502 is connected to the first
contact 308 through the interconnect layers 400-408.
[0068] In another aspect, while the fuse 208 is in a conductive
state, current is provided through the seal ring 202, through the
second contact 310, through the fuse 208, through the first contact
308, and through the interconnect layers 400-408 to the
interconnect pad 502 to electroplate a conductive layer 602 on the
interconnect pad 502.
[0069] In a further aspect, after the step of providing the current
to electroplate the conductive layer 602 on the interconnect pad
502, the state of the fuse 208 is changed from the conductive state
to a non-conductive state.
[0070] In a further aspect, the step of changing the state of the
fuse 208 comprises: providing a current through the electroplated
conductive layer 602 and the interconnect pad 502 to the fuse 208
to change the state to the non-conductive state.
[0071] In a further aspect, the step of forming the gate electrode
304 and the fuse 208 over the semiconductor substrate 302 comprises
forming a second conductive layer over the semiconductor substrate
302; and patterning the second conductive layer to form both the
gate electrode 304 and the fuse 208 from the second conductive
layer.
[0072] In a further aspect, the fuse 208 is further characterized
as a polysilicon fuse 208.
[0073] In a further aspect, the gate electrode 304, the fuse 208,
the interconnect pad 502, and the seal ring 202 are within a first
die 102, and the step of forming the gate electrode 304 and the
fuse 208 comprises forming a second fuse 320 over the semiconductor
substrate in a second die 102, adjacent the first die 102, wherein
the dielectric layer 314 is formed over the second fuse 320. The
step of forming the first portion of the seal ring 202, the contact
306 to the gate electrode 304, the first contact 308 to the first
end or terminal of the fuse 208, and the second contact 310 to the
second end or terminal of the fuse 208 comprises, in the dielectric
layer 314, forming a first portion of a second seal ring 202, a
first contact 308 to a first end or terminal of the second fuse
320, and a second contact 318 to a second end or terminal of the
second fuse 320. The step of forming the interconnect layers
400-408 comprises forming a second portion of the second seal ring
202 which contiguously extends through the interconnect layers
400-408 and is connected to the first portion of the second seal
ring 202, wherein the second seal ring 202 is connected to the
second contact 318 to the second end or terminal of the second fuse
320 through at least one interconnect layer of the interconnect
layers 400-408. The step of forming the interconnect pad 502
comprises forming a second interconnect pad 502 over the
interconnect layers 400-408, wherein the second interconnect pad
502 is connected to the first contact of the first end or terminal
of the second fuse 320 through the interconnect layers 400-408, and
wherein the second fuse 320, the second interconnect pad 502, and
the second seal ring 202 are within the second die 102.
[0074] In a further aspect, the step of forming the interconnect
layers 400-408 is performed such that the seal ring 202 is
connected to the second seal ring 202 through at least one
interconnect layer of the interconnect layers 400-408 in a scribe
street 206 between the first and second die 102.
[0075] In a further aspect, while the fuse 208 and the second fuse
320 are in conductive states, providing current through the seal
ring 202, through the fuse 208, and through the interconnect layers
400-408 to the interconnect pad 502 and through the second seal
ring 202, through the second fuse 320, and through the interconnect
layers 400-408 to the second interconnect pad 502 to electroplate a
conductive layer 602 on the interconnect pad 502 and the second
interconnect pad 502. After the step of providing the current to
electroplate the conductive layer 602 on the interconnect pad 502
and the second interconnect pad 502, changing a state of each of
the fuse 208 and the second fuse 320 from the conductive state to a
non-conductive state.
[0076] In still another embodiment, as shown in FIGS. 1-13 and
described herein, a method for forming a semiconductor structure,
comprises forming a plurality of fuses 208 on a semiconductor
substrate 302; forming a plurality of interconnect layers 400-408
over the semiconductor substrate 302 and the fuses 208; forming a
plurality of interconnect pads 502 at a top surface of the
interconnect layers 400-408; forming a seal ring 202, wherein the
seal ring 202 surrounds active circuitry formed in and on the
semiconductor substrate 302, the interconnect pads 502, and the
fuses 208, wherein each fuse 208 is coupled between a corresponding
interconnect pad 502 of the interconnect pads 502 and the seal ring
202, and wherein when each fuse 208 is in a conductive state, the
fuse 208 electrically connects the corresponding interconnect pad
502 to the seal ring. While each fuse 208 is in the conductive
state, providing current through the seal ring 202 and through each
of the fuses 208 to each of the interconnect pads 502 to
electroplate a conductive layer 602 on each of the interconnect
pads 502. After the step of providing current to electroplate the
conductive layer 602, changing a state of each of the fuses 208
from the conductive state to a non-conductive state.
[0077] Because the apparatus implementing the present invention is,
for the most part, composed of electronic components and circuits
known to those skilled in the art, circuit details will not be
explained in any greater extent than that considered necessary as
illustrated above, for the understanding and appreciation of the
underlying concepts of the present invention and in order not to
obfuscate or distract from the teachings of the present
invention.
[0078] Although the invention is described herein with reference to
specific embodiments, various modifications and changes can be made
without departing from the scope of the present invention as set
forth in the claims below. For example, polysilicon fuses may be
coupled between a seal ring and bumps to serve as electroplating
busses for flipchip semiconductor devices. Accordingly, the
specification and figures are to be regarded in an illustrative
rather than a restrictive sense, and all such modifications are
intended to be included within the scope of the present invention.
Any benefits, advantages, or solutions to problems that are
described herein with regard to specific embodiments are not
intended to be construed as a critical, required, or essential
feature or element of any or all the claims.
[0079] The term "coupled," as used herein, is not intended to be
limited to a direct coupling or a mechanical coupling. Moreover,
the terms "front," "back," "top," "bottom," "over," "under" and the
like in the description and in the claims, if any, are used for
descriptive purposes and not necessarily for describing permanent
relative positions. It is understood that the terms so used are
interchangeable under appropriate circumstances such that the
embodiments of the invention described herein are, for example,
capable of operation in other orientations than those illustrated
or otherwise described herein. Furthermore, the terms "a" or "an,"
as used herein, are defined as one or more than one. Also, the use
of introductory phrases such as "at least one" and "one or more" in
the claims should not be construed to imply that the introduction
of another claim element by the indefinite articles "a" or "an"
limits any particular claim containing such introduced claim
element to inventions containing only one such element, even when
the same claim includes the introductory phrases "one or more" or
"at least one" and indefinite articles such as "a" or "an." The
same holds true for the use of definite articles. Unless stated
otherwise, terms such as "first" and "second" are used to
arbitrarily distinguish between the elements such terms describe.
Thus, these terms are not necessarily intended to indicate temporal
or other prioritization of such elements.
* * * * *