U.S. patent application number 14/948569 was filed with the patent office on 2016-03-17 for traceable integrated circuits and production method thereof.
This patent application is currently assigned to STMicroelectronics S.r.l.. The applicant listed for this patent is STMicroelectronics S.r.l.. Invention is credited to Alberto Pagani.
Application Number | 20160079181 14/948569 |
Document ID | / |
Family ID | 43567950 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160079181 |
Kind Code |
A1 |
Pagani; Alberto |
March 17, 2016 |
TRACEABLE INTEGRATED CIRCUITS AND PRODUCTION METHOD THEREOF
Abstract
An embodiment of a method for producing traceable integrated
circuits includes forming on a wafer of semiconductor material
functional regions for implementing specific functionalities of
corresponding integrated circuits, forming at least one seal ring
around each functional region of the corresponding integrated
circuit, and forming on each integrated circuit at least one marker
indicative of information of the integrated circuit. Forming on
each integrated circuit at least one marker may include forming the
at least one marker on at least a portion of the respective seal
ring that is visible.
Inventors: |
Pagani; Alberto; (Nova
Milanese, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STMicroelectronics S.r.l. |
Agrate Brianza |
|
IT |
|
|
Assignee: |
STMicroelectronics S.r.l.
Agrate Brianza
IT
|
Family ID: |
43567950 |
Appl. No.: |
14/948569 |
Filed: |
November 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13194197 |
Jul 29, 2011 |
9224694 |
|
|
14948569 |
|
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Current U.S.
Class: |
438/626 ;
438/618 |
Current CPC
Class: |
H01L 2223/54433
20130101; H01L 2223/5448 20130101; H01L 21/76877 20130101; H01L
23/53238 20130101; H01L 2223/54413 20130101; H01L 23/562 20130101;
H01L 21/7685 20130101; H01L 23/544 20130101; H01L 2223/54406
20130101; H01L 2223/54473 20130101; H01L 2924/0002 20130101; H01L
21/7684 20130101; H01L 21/3212 20130101; H01L 23/585 20130101; H01L
21/268 20130101; H01L 2924/00 20130101; H01L 2924/0002
20130101 |
International
Class: |
H01L 23/544 20060101
H01L023/544; H01L 21/268 20060101 H01L021/268; H01L 23/532 20060101
H01L023/532; H01L 21/321 20060101 H01L021/321; H01L 23/58 20060101
H01L023/58; H01L 21/768 20060101 H01L021/768 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2010 |
IT |
MI2010A001415 |
Claims
1. A method, comprising: forming on a wafer of semiconductor
material including a plurality of die locations a functional region
at each die location for implementing specific functionalities of a
corresponding integrated circuit; forming a seal ring around the
functional region of each integrated circuit, and forming on a top
surface of each seal ring at least one marker that provides die
information.
2. The method of claim 1, wherein the die information identifies a
position of the die location within the wafer.
3. The method of claim 1, wherein forming the seal ring comprises
forming a stack of interconnected layers, said stack including a
top layer having a thickness; and wherein forming at least one
marker comprises forming a groove in a top surface of said top
layer, said groove positioned in between and away from an inner and
outer perimeter edge of the seal ring and having a depth that is
less than said thickness.
4. The method of claim 3, further comprising depositing a
passivation layer on the top surface of the seal ring and within
said groove.
5. The method of claim 1, wherein forming the seal ring comprises:
forming a stack of interconnected layers, said stack including a
top layer made of a first metal material having a first visible
color; and forming a cover layer of a second metal material having
a second visible color different from the first visible color and
having a thickness; and wherein forming at least one marker
comprises forming a groove in the cover layer, said groove
positioned in between and away from an inner and outer perimeter
edge of the seal ring and having a depth that is at least said
thickness.
6. The method of claim 5, further comprising depositing a
passivation layer on the cover layer and within said groove.
7. The method of claim 5, wherein the first metal material is
copper and the second metal material is aluminum.
8. The method of claim 1, wherein forming the at least one marker
includes forming a plurality of grooves on the top surface of the
seal ring, each groove being associable with one between a first
value and a second value of a binary number system, and wherein
locations without grooves are associated with the other between the
second value and the first value.
9. The method of claim 1, further comprising performing a
chemical-mechanical polishing of the top surface of the seal
ring.
10. The method of claim 1, further comprising depositing a
passivation layer on the seal ring, said passivation layer
protecting said at least one marker.
11. The method of claim 1, wherein forming the seal ring comprises:
forming a plurality of conductive layers in a stack; and forming
spacers between adjacent conductive layers.
12. The method of claim 11, wherein a top surface of a last
conductive layer of said plurality of conductive layers receives
the at least one marker.
13. The method of claim 11, further comprising forming at least one
extension protruding from at least one of said plurality of
conductive layers, and wherein forming the at least one marker
comprises forming said at least one marker on said extension.
14. The method of claim 11, wherein a last one of said plurality of
conductive layers is made of a first conductive material, further
comprising: depositing on said last one of the conductive layers a
coating layer made of a second conductive material different from
the first conductive material; and wherein forming the at least one
marker comprises forming said at least one marker on said coating
layer.
15. The method of claim 14, wherein forming said at least one
marker on said coating layer comprises forming at least one probe
mark on the coating layer.
16. The method of claim 14, wherein the first conductive material
includes copper and the second conductive material includes
aluminum.
17. The method of claim 1, wherein forming the at least one marker
comprises forming a grooves by means of a laser technique.
18. A method, comprising: forming on a wafer of semiconductor
material including a plurality of die locations a functional region
at each die location for implementing specific functionalities of a
corresponding integrated circuit; forming a seal ring around the
functional region of each integrated circuit, said seal ring
including a stack of interconnected layers, said stack including a
top layer having a thickness; and forming a groove in a top surface
of said top layer, said groove positioned in between and away from
an inner and outer perimeter edge of the seal ring and having a
depth that is less than said thickness, said groove providing die
information.
19. The method of claim 18, wherein said die information identifies
a position of the die location within the wafer.
20. A method, comprising: forming on a wafer of semiconductor
material including a plurality of die locations a functional region
at each die location for implementing specific functionalities of a
corresponding integrated circuit; forming a seal ring around the
functional region of each integrated circuit, said seal ring
including a stack of interconnected layers including a top layer
made of a first metal material having a first visible color;
forming a cover layer on the top layer, said cover layer made of a
second metal material having a second visible color different from
the first visible color and having a thickness; and forming a
groove in the cover layer, said groove positioned in between and
away from an inner and outer perimeter edge of the seal ring and
having a depth that is at least said thickness, said groove
providing die information.
21. The method of claim 20, wherein said die information identifies
a position of the die location within the wafer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application from U.S.
patent application Ser. No. 13/194,197 filed Jul. 29, 2011, which
claims priority to Italian Patent Application No. MI2010A001415,
filed Jul. 29, 2010, the disclosures of which are incorporated
herein by reference.
TECHNICAL FIELD
[0002] An embodiment generally relates to integrated circuits; in
particular, an embodiment relates to integrated circuits provided
with markings for traceability thereof downstream of their
production processes.
BACKGROUND
[0003] Typically, each integrated circuit or chip (e.g., an
integrated electronic circuit) includes a substrate of
semiconductor material on which a functional region is integrated
(typically, functional components and metal layers for the
corresponding electrical connections) for implementing specific
functionalities of the chip. The chips are formed in large number
within a wafer of semiconductor material through a production
process typically executed in a sequence of stages, after which the
wafer includes a plurality of identical chips. Each chip also
includes a respective perimeter protection ring (seal ring), which
has the purpose of both mechanically strengthening the chip
(especially, in order to avoid subsidence of the same during the
cutting operation of the wafer for separating the various chips
formed thereon) and minimizing risks of contamination and inclusion
of foreign bodies within the functional region of the chip.
Adjacent chips within the wafers are spaced apart from each other
by separation regions called scribe lines, which typically act as
cutting lines along which the chips are separated from each other
by cutting operations (through a suitable saw or laser); once the
chips have been separated, they are encapsulated in respective
packages.
[0004] In case that the integrated circuits are found to be
defective before or during their use, they are returned to the
manufacturer in order to perform failure analysis; therefore, the
possibility of tracing the original position of the chip within the
corresponding wafer (or other significant parameters) is of
strategic importance for the management of quality of the
production process. In fact, performance and reliability of each
chip may also vary considerably depending on its position within
the corresponding wafer (or other parameters relating or having
reference to the production process). For this reason, it may be
important for the manufacturer to know at which level of the
production process to act for improving the quality thereof.
[0005] To such purpose, in the production process of integrated
circuits there are also provided marking operations of the same so
as to keep track of the positions (and/or of other identification
parameters) of the corresponding chips within the wafer also
downstream of the corresponding production process. To this
purpose, in the state of the art it is possible to identify
substantially two different approaches for performing said markings
and obtaining traceable chips.
[0006] In particular, a first approach provides for electrically
writing significant information within suitable dedicated memory
circuits (e.g., non-volatile memories) formed within each chip;
however, the solutions using such approach may be affected by a
relatively large waste in terms of area occupation of the chip
(having to integrate also such memory circuits within the
corresponding functional region), with resulting increase of the
production costs of the integrated circuit. Moreover, such
solutions may not be applicable to chips having a fully analog
functional region, both because of problems of compatibility of
interface between the latter and the (digital) memory circuits, and
because of the need of specific technological processes to make
such memory circuits. Moreover, the information reading, being
indirect (but requiring proper reading circuits), may be difficult
and slow.
[0007] Another approach provides for making a physical marking on
each chip that may be read directly and from which information
about the chip may be quickly deduced.
[0008] For example, in U.S. Pat. No. 3,562,536, which is
incorporated by reference, such marking includes bar codes made
within the scribe lines and obtained by etching processes; however,
the cutting operation along the scribe lines may damage such bar
codes, thus making the information encoded by them inaccessible;
moreover, typically it may be preferred to allocate the entire
surface of the scribe lines to functional structures (called TEG,
or Test Element Group) through which it is possible to perform
parametric measurements of the production process.
[0009] Alternatively, typically the marking may be executed by
forming (numeric or alphanumeric) codes or maps during the
production process of the chips through proper photolithographic
masks; however, such solution is may not be applicable for the
current production processes. In fact, with the increase of the
size of the wafers and with the increase of the capacity of
integration of the integrated circuits, each step of the production
process of the chips (through the corresponding photolithographic
mask) may not be carried out by a single step over the entire
surface of the wafer, but is typically carried out step by step on
different portions of the wafer; at each step the mask acts on a
corresponding area of the wafer in which, at the end of the
process, a corresponding group of chips will be made (with each
chip of the group having its own marking); the same operation is
repeated to apply the same mask on the entire surface of the wafer.
In this way, chips of different groups in the same relative
position will have the same marking; as a consequence, auxiliary
markings will be needed for distinguishing the different groups of
chips in the wafer from each other. Moreover, such solution makes
the marking within the region of the chip bounded by the respective
seal ring, i.e., wherein the corresponding functional components
are integrated; this may imply a significant increase of the
overall area occupation of the chip, especially if the markings
include codes (or maps) being long and complex and/or requiring
auxiliary markings.
[0010] Another solution, disclosed in U.S. Pat. No. 6,063,685,
which is incorporated by reference, provides for making the marking
in regions not used (for electrical connections) of a last metal
layer of the functional region of the respective chip through
laser-writing techniques and equipment; however, such marking,
being made within inner regions of the seal ring, does not exclude
the possibility that the corresponding functional region is
accidentally damaged during writing, with resulting loss of
production yield of the chips; moreover, in case that the
availability of such inner regions of the seal ring is not ensured
for marking, this could represent a further design parameter, with
consequent possible cost increases.
SUMMARY
[0011] An embodiment overcomes the above-cited drawbacks.
[0012] More specifically, an embodiment is a method for producing
traceable integrated circuits. The method includes forming on a
wafer of semiconductor material functional regions for implementing
specific functionalities of corresponding integrated circuits,
forming at least one seal ring around each functional region of the
corresponding integrated circuit, and forming on each integrated
circuit at least one marker indicative of information of the
integrated circuit. In an embodiment, the step of forming on each
integrated circuit at least one marker includes forming the at
least one marker on at least one portion of the respective seal
ring visible external to the integrated circuit.
[0013] Another embodiment is a corresponding integrated
circuit.
[0014] Thanks to an embodiment, it may be possible to obtain
traceable integrated circuits easily and effectively, without their
production yield being compromised; in fact, making the marking on
the seal ring may allow avoiding risks of damaging the functional
regions during the writing of the markings. Moreover, since an
embodiment of a marking method is not made through
photolithographic techniques, it may be equally valid for
integrated circuits having particularly reduced size; for the same
reason, no complex or additional markings and/or mappings are
required that could cause a relevant overall increase in terms of
area occupation of the integrated circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Features and advantages will be best understood with
reference to the following detailed description, given purely by
way of a non-restrictive indication, to be read in conjunction with
the accompanying drawings (wherein corresponding elements are
denoted with equal or similar references, and their explanation is
not repeated for the sake of exposition brevity). In this respect,
it is expressly understood that the figures are not necessarily
drawn to scale (with some details that may be exaggerated and/or
simplified) and that, unless otherwise indicated, they are simply
used to conceptually illustrate the described structures and
procedures according to one or more embodiments. In particular:
[0016] FIG. 1 schematically shows in top view the structure
obtained at an intermediate step of a production process of
integrated circuits wherein an embodiment may be applied;
[0017] FIG. 2A schematically shows in top view a generic chip of
the structure of FIG. 1 according to an embodiment;
[0018] FIGS. 2B-2D schematically show in front view some steps of
the production process of the chip of FIG. 2A according to an
embodiment;
[0019] FIG. 3A shows in top view a generic chip of the structure of
FIG. 1 according to another embodiment;
[0020] FIGS. 3B-3D show some steps of a production process of the
chip of FIG. 3A according to an embodiment;
[0021] FIG. 4A shows in top view a generic chip of the structure of
FIG. 1 according to a further embodiment;
[0022] FIGS. 4B-4D schematically show in front view some steps of a
production process of the chip of FIG. 4A according to an
embodiment; and
[0023] FIG. 5 shows in top view a generic chip of the structure of
FIG. 1 according to a still further embodiment.
DETAILED DESCRIPTION
[0024] Considering in particular FIG. 1, it schematically shows in
top view the structure obtained at an intermediate step of a
production process of conventional integrated circuits or
chips.
[0025] In particular, the integrated circuits 105 are made on a
wafer 110 of semiconductor material. As best visible in the detail
of FIG. 1, each chip 105 includes a functional region 115, wherein
electronic components (and metal layers or other materials for
their electrical connections) are integrated that implement
specific functionalities of the integrated circuit; the functional
region 115 of each chip 105 is surrounded by a respective seal ring
120, which generally accomplishes protection functions against
mechanical damages and chemical contaminations of the functional
region 115 of the respective chip 105. Adjacent chips 105, or
adjacent seal rings 120, are spaced apart from each other to form
separation regions, or scribe lines 125 of the (and on the) wafer
110 (represented in the figure with a different shading with
respect to the latter for simplicity), which scribe lines 125 (only
four shown in the figure for simplicity, and represented by dashed
lines) will be used for subsequent cutting operations of the wafer
110 (through a suitable saw or laser, not shown) thereby obtaining
the division between the different chips 105, which then may be
encapsulated in corresponding packages (not shown).
[0026] In relatively recent applications, such as that in exemplary
but not limiting described embodiment, the scribe lines 125 are
usually filled with elementary structures for test equipment group
(TEG) (not shown) for the measurement of significant parameters of
the manufacturing process, and hence typically the scribe lines 125
are not available for other uses.
[0027] It should be noted that the seal ring 120 in an exemplary
disclosed embodiment has a chamfered profile at the four corners of
the respective chip 105 so as to better preserve its integrity
during the cutting operation; in fact, each corner of the chip 105,
being subjected both to a longitudinal stress and to a transversal
stress of the saw during the cutting operation, is a region
significantly exposed to possible causes of mechanical failures.
Anyway, various shapes and configurations of the seal ring 120 are
known, which are usable indiscriminately in an embodiment without
that the protection scope of the same is amended; for this reason,
the chamfered profile for the seal ring 120 is not to be construed
in a limiting way.
[0028] Beginning from the basic structure of the known chip 105, it
may be possible to perform different markings of the same, so as to
obtain different chips according to corresponding embodiments; in
the following, for reference simplicity, similar and/or
corresponding elements of different embodiments will be denoted by
similar references but differentiated only by the first digit.
[0029] In FIG. 2A there is shown in top view a generic chip 205
according to an embodiment. The seal ring 220 includes, unlike the
seal ring 120 of the conventional implementation, one or more
markers, only three shown in an exemplary embodiment illustrated in
the figure and denoted by references 230a, 230b, 230c,
respectively; in particular, such markers are made on portions of
the seal ring 220 that are visible (since not covered by elements
of the chip) from outside of the integrated circuit also downstream
of the production process. In this regard it is noted that the
position of the markers 230a, 230b, 230c within the seal ring 220
is not to be understood in a limitative way, but only exemplarily;
in particular, depending on particular and specific requirements,
such markers 230a, 230b, 230c may be properly arranged along all
the visible surface of the seal ring 220, which may be predefined
at the design stage--for example, by properly arranging such
markers in areas having relatively low density of connection wires,
or wire bond, created during the embedding process of each chip
within the corresponding package. For example, in an alternative
embodiment, not shown, one or more of such markers may be
positioned along the chamfers of the seal ring 220, or more
generally along corner regions thereof.
[0030] In an embodiment, each marker 230a, 230b, 230c is made in
such a way that it may be read directly (i.e., visually) and easily
interpreted as an appropriate binary code, i.e. a sequence or
string of binary digits (e.g., with values 0 and/or 1); such binary
code may be used for encoding information of the chip 205 that are
considered significant, such as, for example, the position of the
chip 205 in the wafer (e.g., through the use of a coordinate
system), lot number of the wafer, wafer position in the lot,
manufacturing plant of the wafer, and/or masks set used for the
making of the chip 205. In particular, each marker 230a, 230b, 230c
includes (depending on the value of the binary code to be
implemented) a plurality of dots 235 (schematically represented in
the figure as grey circles) to each of which is associated, for
example, the digit 1, and a plurality of missing dots 240
(represented in the figure as an empty position since not occupied
by a dot) to each of which is associated, for example, the digit 0.
In the examples in the figure, the marker 230a, including a dot
235, followed by two missing dots 240 and by another dot 235, is
read as binary code of value 1001; instead, the marker 230b,
including two dots 235 followed by a missing dot 240 and by two
other dots 235, is read as binary code of value 11011; finally, the
marker 230c, including two dots 235 followed by two missing dots
240 and by two other dots 235, is read as binary code of value
110011. In this regard, it is noted that, in order that the reading
of the binary code is made correctly, there may be a fixed distance
between adjacent 235 dots; as a consequence, a missing dot 240 may
be interpreted as such in the presence of an empty region of the
seal ring (i.e., not occupied by any dot 235) of extent
substantially equal to, for example, twice the fixed distance that
there is between two adjacent dots 235.
[0031] At least one reference element (for example, one or more
further dots, not shown for simplicity) may be formed for allowing
a correct reading of the binary code, for example for indicating a
reading starting point and/or a reading direction (and/or other
similar indications).
[0032] Turning to FIGS. 2B-2D, they schematically show in front
view some exemplary steps of an embodiment of a production process
of the chip 205 (of which only the portion bounded by II in FIG. 2A
is shown in section for simplicity); with particular reference to
FIG. 2B, the chip 205 is yet at an advanced stage of its production
process. In particular, the chip 205 includes a substrate 245,
i.e., a predefined portion of the wafer 105 on which there are
integrated, in a known manner, the functional region 115 (shown in
the figure as a generic block) comprising electronic components and
metal layers for the corresponding electrical connections, and the
corresponding seal ring 220 surrounding the functional region 115
to protect it.
[0033] In general, since typically the formation process of the
seal ring 220 is parallel to the formation process of the
functional region 115, such processes are usually carried out by
exploiting the same (or similar) manufacturing techniques; for this
reason, in the exemplary described embodiment, the seal ring 220
includes a stacked structure of metal layers and vertical
connections (vias, in jargon) similar to that provided (but not
shown) in the functional region 115. In particular, without
entering into excessive detail, per se well known, the seal ring
220 includes a plurality of metal layers 250, for example copper,
stacked on each other from the substrate 245; each metal layer 250
is mechanically separated from the underlying metal layer 250 (or
from the substrate 245, in the case of the first metal layer 250)
by a suitable dielectric layer 255 and electrically connected
thereto by the corresponding vias 260 obtained within the
dielectric layer 255; in other words, as it is known, the
dielectric layer 255 and the vias 260 between adjacent metal layers
250 act as corresponding spacer elements. As shown in FIG. 2C, the
last conductive layer 250 of the seal ring 220 is subjected to a
writing technique through laser incision (through a suitable laser
apparatus, not shown since per se known and, however, not limiting)
for making the desired marking (in the considered example, the dot
235 of the marker 230c). In particular, grooves are formed on
portions of the last metal layer 250 subjected to the laser action,
each one of which grooves is associable with a corresponding dot
235, whereas portions not subjected to the laser action are
associated with respective missing dots 240 (not visible in the
figure due to the illustrated portion of the chip 205 and to the
considered point of view).
[0034] In order to facilitate the writing operation and obtain dots
235 that are as homogeneous as possible to each other, before the
writing a finishing process of the exposed surface of the chip 205
(and in particular of the last metal layer 250 of the seal ring
220) may be performed; such finishing process may be performed by,
for example, a known Chemical-Mechanical Polishing (or CMP)
technique, which allows making the exposed surface of the chip 205
planar, with a very low unevenness and an excellent
selectivity.
[0035] Subsequently, as shown in FIG. 2D, a passivation layer 265
is deposited on the structure thereby obtained, which passivation
layer allows protecting the chip 205 by preserving it from
contamination/corrosion by atmospheric agents or by unwanted
chemical reactions. Furthermore, the passivation layer 265, by
depositing also inside the grooves that identify the dots 235
(possibly) provided on the seal ring 220, preserves and protects
also the markers, thereby preventing alterations thereof (e.g.,
corrosions) that might distort the reading of the respective codes
encoded by them.
[0036] It is noted that, before depositing the passivation layer
265, it may be useful to perform a cleaning process of the surface
of the wafer in order to remove possible contaminating particles
deposited and/or formed thereon.
[0037] Turning now to FIG. 3A, it shows a top view of a generic
chip 305 according to another embodiment. The chip 305 is
substantially similar to the chip 205, but, unlike the latter, it
has a seal ring 320 including an additional portion 370 extending
in an area of the functional region 115 at relatively low density
of occupation of components and/or electrical connections; in this
respect, it is considered that typically, during the layout design
of the chips, it is necessary to comply with design rules, so that
areas of the functional region 115 (typically, but not necessarily,
the peripheral ones) may have a relatively low occupation. In the
exemplary but not limitative described embodiment, the seal ring
320 still includes markers 230a, 230b, 230c, and a further marker
330d made (in a way that will be described shortly) in such
additional portion of the seal ring 320.
[0038] The marker 330d of the chip 305 thereby obtained may
usefully be employed to achieve a two-dimensional encoding system,
unlike the encoding used for the markers 230a, 230b and 230c (and
identifiable as one-dimensional, since it includes an ordered
string of dots 235 and missing dots 240 to be read along a single
direction). Such two-dimensional encoding is obtained, in the
example at issue, by combining information of the marker 330d and
those of the marker 230c (or, possibly, those of the markers 230a
and 230b). For example, the marker 330d may be used for
implementing code redundancies (so as to not lose information also
in case of damages of markers in sensitive positions of the seal
ring 320), establishing a reading reference of the markers (e.g., a
direction and/or reading start point thereof), or encoding an index
according to a matrix mapping.
[0039] However, it is noted that the information contained in the
markers 230a, 230b and 230c may be properly encoded using codes
that may implement redundancy and/or codes that allow, for example,
error correction to meet specific requirements.
[0040] In order to implement the chip 305 according to the just
described embodiment, the production process is very similar to
that previously disclosed, with the difference that the making of
the seal ring 320 provides for the formation of a last metal layer
350 including the metal layer 250 and an extension of the same
protruding into the functional region 115 and that implements the
additional portion 370 of the seal ring 320 (see FIG. 3B, wherein
there is shown in front view the portion of the chip 305 indicated
by III in FIG. 3A). From this point the manufacturing process of
the chip 305 continues as that of the chip 205 above described, and
in particular with the writing of the dots 235 (two, in the example
at issue) and missing dots (not visible), and subsequent covering
through the passivation layer 265, as shown in FIGS. 3C and 3D,
respectively.
[0041] It is noted that by combining the two just-described
embodiments, it may be possible to obtain a variety of possible
implementations; for example, the extension 370 may be made on
different metal layers 250 (not necessarily on the last one).
Moreover, in the presence of specific layouts of the chip, it may
be possible to make such extension 370 protruding towards the
scribe lines 125 (since, after the cutting operation that separates
from each other the various chips in the wafer, the chip typically
may include a more or less extensive residual portion of the scribe
line 125).
[0042] Moreover, if the sizes of the seal ring and that of the dots
are sufficient, it may be possible to create an encoding system or
two-dimensional code without necessarily forming the extension 370.
It is noted that, although in the embodiment illustrated in the
figure the two-dimensional code is implemented as two strings of
dots and missing dots, actually it may be achieved even using more
than two strings.
[0043] Turning to FIG. 4A, it shows in top view a generic chip 405
according to an embodiment. The chip 405 is substantially similar
to the chip 205, but, unlike the latter, it has a seal ring 420
configured in such a way that the dots 435 and the missing dots 440
have such a color contrast to make them distinguishable in a
particularly easy and clear way during the reading operation of the
codes of the respective markers 430a, 430b, 430c.
[0044] As in the foregoing, in order to illustrate the main steps
of an embodiment of a production process of the chip 405, there is
shown in front view a significant portion of the latter (delimited
by IV in FIG. 4A); with particular reference to FIG. 4B, on the
last metal layer 250, for example of copper, a coating conductive
layer 475 (e.g., of aluminum) is deposited, for example, with a
thickness lower with respect to the conductive layer 250 below. In
such configuration, the corresponding dots 435 and missing dots 440
may be formed by exploiting the color difference between the copper
(typically reddish, but white painted for simplicity) and the
aluminum (typically silver) of which the metal layers 250 and the
coating conductive layer 475 are formed, respectively. In
particular, in this case a dot 435 may be obtained by incising
(e.g., again through laser techniques) only the coating conductive
layer 475 and leaving intact the metal layer 250 below it (as
visible in FIG. 4C), whereas a missing dot 440 (not visible) is
correspondingly associated with a missed incision of the coating
conductive layer 465.
[0045] Therefore, unlike the previously described embodiments, the
dot 435 may be better distinguished (from the missing dot 440)
thanks to the color difference between the copper (of the last
metal layer 250) uncovered by the incision and the aluminum (of the
residual coating conductive layer 475 around it). Moreover, the
marking operation or code writing may have a briefer duration,
since the incision of the coating conductive layer 475, having to
be performed for a lower depth, needs a lower time; such
implementation, moreover, is also remarkably versatile, since the
aluminum coating conductive layer 475, having a reduced thickness,
may be effectively drilled also using a mechanical tool; for
example, by pressure using a suitable probe (e.g., of the
cantilever type), it may be possible to leave a probe mark
functionally equivalent to the groove to which the dot is
associated.
[0046] The process then continues in FIG. 4D, with the deposition
of the passivation layer 265, in a quite similar manner as
previously described.
[0047] In a variant not shown, having in this example used aluminum
for the coating conductive layer 475 on the copper metal layer 250,
the passivation layer 265 may be possibly opened at least in a
portion of the seal ring 420 (in a quite similar manner to how is
done for an interconnection terminal or pad of the chip 405), and
therefore the marking operation may occur also after the deposition
of the passivation layer 265. This may be useful for adding further
information during the production process. In a further variant not
shown, the coating layer 475, rather than being of a conductive
material, may be formed by using materials with such features that
they are able to store information; for example, it may be possible
to use chalcogenide alloys or heat-sensitive or photosensitive
materials, which may vary one of their characteristics (e.g., their
status or color or other chemical and physical properties) locally
in response to a given procedure (e.g., a thermal and/or optical
one). Since the passivation layer 265 is typically transparent, the
marking operation may also occur after the deposition of the
passivation layer 265 itself, depending on the material used and on
the characteristic subjected to variation.
[0048] As outlined in the foregoing, also such embodiment may be
combined, even partially, with those previously described, also
jointly with conventional techniques, so as to obtain a large
variety of implementations based on a principle of exploiting the
seal ring as an element on which to make the markings, for example,
in the form of binary code.
[0049] A different approach for making the markings by exploiting
the seal ring is shown in FIG. 5; in particular, such figure shows
in top view a generic chip 505 according to an embodiment. The chip
505 has a seal ring 520 structurally equivalent to the seal ring
120, but, unlike the latter, it has at least one conductive layer
(for example, the last one) visible in reading with a cantilevered
structure having a shaped side profile according to the information
to be encoded. Such shaped profile identifies a marker 530
including bumps 535 and missing bumps 540 (functionally analogous
to the dots and missing dots previously described), which may be
read, for example, as a binary digit 1 and binary digit 0 (in the
example at issue, the marker 530 encodes a binary string of value
101001). It is noted that such marker 530 is defined
lithographically (i.e., it is obtained by a proper
photolithographic mask that allows directly making the conductive
layer with the shaped profile), and obtained by means of, and
during, the normal photolithographic process by which the chips 505
are made within the wafers; therefore, such marker 530 is typically
able to encode only fixed information (i.e., according to the
corresponding mask used), and therefore it is advantageously usable
as a marker for encoding auxiliary information that are usually
shared by each chip of a same wafer 110 (such as for example
details about the masks set used and the like), or in combination
with other encoding systems for facilitating the reading thereof.
Therefore, such embodiment may be particularly suitable for use in
combination with, for example, the embodiments described above (or
possibly in combination with conventional techniques), so as to
obtain markers with encoding systems being advanced, complete and
readily identifiable and readable, and at the same time involving a
reduced area occupation.
[0050] Moreover, it is noted that the shape of the bumps 535 and
missing bumps 540 is not limitative, as they may be, for example,
rectangular (as in the exemplary embodiment shown in the figure),
triangular, semicircular, polygonal, any combination thereof, or
any other shape.
[0051] Finally, it is noted that, similarly to that previously
described, the chip 505, and hence the marker 530, is covered by
the passivation layer 260 (not shown in the figure) for preserving
it from external contaminations.
[0052] Naturally, in order to satisfy local and specific
requirements, one may apply to one or more of the above-described
embodiments many logical and/or physical modifications and
alterations. More specifically, although one or more embodiments
have been described with a certain degree of particularity, it is
understood that various omissions, substitutions and changes in the
form and details as well as other embodiments may be possible. In
particular, different embodiments may even be practiced without the
specific details (such as the numeric examples) set forth in the
preceding description for providing a more thorough understanding
thereof; on the contrary, well known features may have been omitted
or simplified in order not to obscure the description with
unnecessary particulars. Moreover, it is expressly intended that
specific elements and/or method steps described in connection with
any disclosed embodiment may be incorporated in any other
embodiment as a matter of general design choice.
[0053] Moreover, an embodiment lends itself to be implemented with
an embodiment of a method (by using similar steps, removing some
steps being not essential, or adding further optional steps); the
steps may be performed in different order, concurrently or in an
interleaved way (at least partly).
[0054] The type of marker is not limitative; in particular, an
embodiment of the marker may be implemented by alphanumeric codes
(i.e., by letters and numbers), possibly in combination with binary
codes. Moreover, for manufacturing reasons, different portions of
the same seal ring may have corresponding markers implemented by
encoding systems different from each other.
[0055] Different seal rings, even with different heights, may be
provided around each functional region; in such condition, an
embodiment may be applied in a similar manner on one or more of
such seal rings. The seal ring may have any shape and size. In
addition, the seal ring may be provided with sacrificial structures
(for example, for reinforcing the chip corners), which, although
being intended with good probability to be lost during the cutting
operation of the wafer, may in any case be provided with markings
analogous or similar to those previously described.
[0056] In addition, the protruding extension or additional portion
may be formed on more than one metal layer, and such extensions may
be staggered between each other (e.g., extending alternately
towards the functional region and towards the scribe lines) so as
to be all visible during the reading of the markings. Analogous
considerations apply of course also for the cantilevered
structure.
[0057] Nothing prevents the coating conductive layer from including
a multi-layer structure, in order to obtain suitable color and
hardness characteristics for distinguishing the dots from the
missing dots and performing the incision according to desired modes
and times. In this respect, it is noted that the last metal layer
(as well as at least part of those below it) may be made of
aluminum, whereas the coating conductive layer may be made of
copper.
[0058] Furthermore, the formation of a dot by pressure of a
suitable probe may also be performed in an embodiment that does not
provide for the formation of the coating layer on the last metal
layer; in this respect, the last metal layer, or the one that
defines the readable portion to be marked, may be formed with a
thickness thin enough to ensure the erosion thereof in the event of
even relatively slight pressure by the probe or other mechanical
means.
[0059] Moreover, the shape of the dots is not limitative and it is
also possible to use dots having different shapes on the same seal
ring for example for implementing a proper code. It may be useful,
for example, to use a dot having an elongated shape to be more
visible even in case that wire bonds are provided. Anyway, by using
particular focusing optical techniques, the dots may be visible
even in the presence of wire bonds; for this reason, embodiments
are not limited to regions of the seal ring not covered by wire
bonds.
[0060] Similar considerations apply if the chip has a different
structure or includes equivalent elements; in addition, the
elements may be separated from each other or combined together, in
whole or in part. For example, each element of the integrated
circuit may have any shape and/or size, and may be made of any
other material.
[0061] It is understood that the proposed structure may be part of
the design of an integrated circuit. The design may also be created
in a programming language; moreover, if the designer does not
manufacture the integrated circuits or the masks, the design may be
transmitted by physical means to others. In any case, the resulting
integrated circuit may be distributed by its manufacturer in raw
wafer form, as a bare die, or in packages. Moreover, the proposed
structure may be integrated with or coupled to other circuits on
the same die or in the same chip, or it may be mounted in
intermediate products (such as mother boards) and may be, e.g., a
controller such as a processor, or may be coupled with one or more
other chips (e.g., a controller such as a processor). In any case,
the integrated circuit may be suitable to be used in complex
systems (such as automotive applications or microcontrollers).
[0062] From the foregoing it will be appreciated that, although
specific embodiments have been described herein for purposes of
illustration, various modifications may be made without deviating
from the spirit and scope of the disclosure. Furthermore, where an
alternative is disclosed for a particular embodiment, this
alternative may also apply to other embodiments even if not
specifically stated.
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