U.S. patent application number 14/080112 was filed with the patent office on 2014-03-13 for probe card for testing integrated circuits.
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 | 20140070834 14/080112 |
Document ID | / |
Family ID | 40315632 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140070834 |
Kind Code |
A1 |
PAGANI; Alberto |
March 13, 2014 |
PROBE CARD FOR TESTING INTEGRATED CIRCUITS
Abstract
An embodiment of a probe card adapted for testing at least one
integrated circuit integrated on a corresponding at least one die
of a semiconductor material wafer, the probe card including a board
adapted for the coupling to a tester apparatus, and a plurality of
probes coupled to the said board, wherein the probe card comprises
a plurality of replaceable elementary units, each one comprising at
least one of said probes for contacting externally-accessible
terminals of an integrated circuit under test, the plurality of
replaceable elementary units being arranged so as to correspond to
an arrangement of at least one die on the semiconductor material
wafer containing integrated circuits to be tested.
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: |
40315632 |
Appl. No.: |
14/080112 |
Filed: |
November 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12809964 |
Aug 11, 2010 |
8604816 |
|
|
PCT/EP2008/068047 |
Dec 19, 2008 |
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14080112 |
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Current U.S.
Class: |
324/756.03 ;
324/762.03 |
Current CPC
Class: |
G01R 1/0491 20130101;
G01R 31/2889 20130101; G01R 1/07342 20130101; B62M 25/04 20130101;
G01R 1/06727 20130101 |
Class at
Publication: |
324/756.03 ;
324/762.03 |
International
Class: |
G01R 1/04 20060101
G01R001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2007 |
IT |
MI2007A002399 |
Claims
1. A probe card, comprising: a board configured to enable coupling
an integrated circuit to a tester apparatus; a plurality of probes
coupled to the board; and a replaceable elementary unit, the
replaceable elementary unit including at least one of the plurality
of probes, the replaceable elementary unit corresponding to an
arrangement of at least one semiconductor die of a wafer of
semiconductor dies.
2. The probe card of claim 1, wherein the replaceable elementary
unit comprises at least one second semiconductor die configured for
coupling the probe card to the board; and wherein the at least one
second semiconductor die is configured according to a selected
configuration among: a first configuration wherein the at least one
second semiconductor die is electrically coupled to the board with
a conductive path comprising at least one through via crossing the
second semiconductor die using a flip-chip design; a second
configuration wherein the at least one second semiconductor die is
coupled to the board with a resin layer and the at least one probe
is coupled to the corresponding conductive path with a
corresponding wire bond; and a third configuration wherein the at
least one second semiconductor die is housed in a substrate and is
electrically coupled to the board with a conductive path comprising
at least one through via crossing the substrate.
3. The probe card of claim 1, wherein the replaceable elementary
unit is configured to have a one-to-one relationship with the at
least one die.
4. The probe card of claim 1, wherein the replaceable elementary
unit is configured to have at least two relationships with at least
two dies.
5. The probe card of claim 1, further comprising a second
replaceable elementary unit configured to correspond to a second
die of the semiconductor wafer.
6. The probe card of claim 2, wherein the second semiconductor
material includes a second integrated circuit configured to be used
during the testing of the integrated circuit on the corresponding
at least one die.
7. The probe card of claim 1, wherein the at least one probe
comprises a Micro Electro Mechanical Systems probe.
8. The probe card of claim 1, further comprising at least one
ceramic material layer, the ceramic material layer disposed between
the second semiconductor material die and the board, the conductive
path comprising a through via crossing the ceramic material layer
and configured to couple the probe to the corresponding conductive
path.
9. The probe card of claim 2, further comprising at least one
ceramic material layer, the ceramic material layer disposed between
the at least one second semiconductor die and the board, the
conductive path comprising at least one further through via
crossing the ceramic material layer and at least one wire bond
configured to couple the at least one second semiconductor die to
the corresponding further through via.
10. The probe card of claim 1, further comprising the substrate is
configured to house at least one control chip having at least one
circuit configured to test the integrated circuit.
11. The probe card of claim 2, wherein the at least one second
semiconductor die comprises at least one further integrated circuit
configured to test the integrated circuit.
12. The probe card of claim 11, wherein the at least one further
integrated circuit comprises at least one among: a circuit
configured to sense signals received from the integrated circuit;
and a circuit configured to generate signals provided to the
integrated circuit.
13. The probe card of claim 2 wherein the at least one second
semiconductor die is configured according to a third configuration
and the substrate is adapted to house at least one control chip
integrating at least one circuit configured to test the integrated
circuit.
14. The probe card of claim 1 wherein the at least one second
semiconductor die includes a plurality of further semiconductor
dies, each further semiconductor die electrically coupled to the
board through a respective conductive path comprising at least one
respective through via crossing the substrate.
15. A method for testing an integrated circuit, the method
comprising: providing a probe card including a board configured for
the coupling an integrated circuit to a tester apparatus, the board
including a plurality of probes; providing at least one replaceable
elementary unit having a second semiconductor die, the replaceable
elementary unit including at least one probe of the plurality of
probes; arranging the at least one replaceable elementary unit in
correspondence with the integrated circuit, wherein the integrated
circuit is disposed on a semiconductor die on a wafer, the
arranging in accordance with a selected configuration among: a
first configuration wherein the second semiconductor die is
electrically coupled to the board with a conductive path comprising
at least one through via crossing the second semiconductor die
using a flip-chip design; a second configuration wherein the second
semiconductor die is coupled to the board with a resin layer and
the at least one probe is coupled to the corresponding conductive
path with a corresponding wire bond; and a third configuration
wherein the second semiconductor die is housed in a substrate and
is electrically coupled to the board with a conductive path
comprising at least one through via crossing the substrate;
contacting the integrated circuit with a respective probe; at the
test apparatus, generating at least one first test signal;
providing said at least one first test signal to the integrated
circuit through the respective probe; and providing to the test
apparatus at least one second test signal generated by the
integrated circuit according to the received at least one first
test signal.
16. A test apparatus, comprising: a probe card, having: a plurality
of probes coupled to a board; and a replaceable elementary unit,
the replaceable elementary unit including at least one of the
plurality of probes, the replaceable elementary unit corresponding
to at least one semiconductor die of a wafer of semiconductor dies
to be tested.
17. The test apparatus of claim 16, wherein the replaceable
elementary unit comprises at least one second semiconductor die
configured for coupling the probe card to the board.
18. The test apparatus of claim 17 wherein the at least one second
semiconductor die is electrically coupled to the board with a
conductive path comprising at least one through via crossing the
second semiconductor die using a flip-chip design.
19. The test apparatus of claim 17 wherein the at least one second
semiconductor die is coupled to the board with a resin layer and
the at least one probe is coupled to the corresponding conductive
path with a corresponding wire bond.
20. The test apparatus of claim 17 wherein the at least one second
semiconductor die is housed in a substrate and is electrically
coupled to the board with a conductive path comprising at least one
through via crossing the substrate.
Description
PRIORITY CLAIM
[0001] The present application is a Continuation of copending U.S.
patent application Ser. No. 12/809,964, filed Aug. 11, 2010; which
application is a national phase application filed pursuant to 35
USC .sctn.371 of International Patent Application Serial No.
PCT/EP2008/068047, filed Dec. 19, 2008; which further claims the
benefit of Italian Patent Application MI2007A002399, filed Dec. 20,
2007; all of the foregoing applications are incorporated herein by
reference in their entireties.
TECHNICAL FIELD
[0002] An embodiment of the present disclosure relates to systems
for testing Integrated Circuits (ICs), and in particular it relates
to probe cards for testing ICs.
BACKGROUND
[0003] ICs are typically manufactured many at a time in the form of
dies on a semiconductor material wafer. After manufacturing, the
semiconductor wafer is diced, so as to obtain a plurality of IC
chips.
[0004] Before being packaged and shipped to the customers, and
installed in various electronic systems, the ICs are tested for
assessing their functionality, and in particular for ensuring that
they are not defective. In particular, during the test, information
regarding global or local physical faults (such as undesired
presence of short circuits and break-down events) and more
generally the operation of the IC on each die under test, may be
detected (for example, by checking the waveform of one or more
output signals generated by the IC on each die under test) so that
only the dies that meet predetermined requirements proceed to the
subsequent manufacturing phases (such as lead bonding, packaging
and final testing).
[0005] According to a known testing technique, the IC dies are
tested before the semiconductor wafer is diced into the individual
chips. The test conducted at the wafer level is referred to as
"wafer sort" or, as it is sometimes called, EWS (acronym for
Electrical Wafer Sort)
[0006] For example, in the case of non-volatile semiconductor
memory devices (such as Flash memories) the EWS is performed on
each die wherein the memory device is formed, in order to verify
the correct operation thereof.
[0007] For performing the test, a testing apparatus is used
comprising a tester, which is coupled to the semiconductor wafer
containing the dies to be tested, by means of a probe card, which
is used for interfacing the semiconductor wafer to the tester.
[0008] The tester is adapted to manage signals that are employed
for performing the test. Hereinafter, such signals will be referred
as test signals and will be intended to include test stimuli (e.g.,
commands, addresses of memory locations, data to be written into
the memory device) which are generated by the tester and are sent
to each die to be tested by the probe card, and test response
signals, which are generated by the ICs integrated in each die
under test in response to the received test stimuli. The test
response signals are sent by the IC integrated in each die under
test to the tester, which processes them to derive an indication of
the proper or improper operation of the ICs in the dies under
test.
[0009] Probes are employed for the electrical coupling, through a
physical contact, of the probe card with the dies to be tested,
necessary for accomplishing the test signal exchange. For this
purpose, the probe card consists of a PCB (Printed Circuit Board),
which is connected to mechanical probes, which are adapted to
physically contact input/output contact pads of each die to be
tested.
[0010] In particular, each input/output contact pad consists of an
enlarged metallization region surrounded and partially overlapped
by a passivation layer.
[0011] During the testing, the metal contact pad is scrubbed by the
mechanical scrubbing action of the probe tip. In such a way, the
exchange of the test signals between the tester and the die to be
tested may be accomplished.
[0012] Several probe card parameters contribute to improve the
performance of the testing apparatus. Among the relevant probe card
parameters, the planarity takes an important role. The planarity is
the vertical distance (i.e., the distance along the Z-axis
indicated in FIG. 1) between the highest and lowest probe tips of
the probe card. The planarity affects the alignment between the
probe tip and the contact pad so that, for example, a poor
planarity may cause the scrub mark length and depth to be different
from the desired scrub mark length and depth; this may modify the
position in the plane defined by the X-axis and Y-axis in FIG. 1 as
time passes. Another important parameter is the probe alignment
accuracy, that is the position of the center of the scrub mark in
the plane defined by the X-axis and Y-axis with respect to the
center of the pad. In detail, scrub marks that are too long, or
probe tips contacting the pad near the pad edge, may cause the
passivation layer to be broken, while excessively deep scrub marks
may damage the pad metallization region to the extent that the pads
are then unusable for the testing and also for the normal operation
of the IC. Damages to the input/output contact pads may also cause
problems in the packaging phase of the die, since the input/output
contact pads which are used for the testing are also used for
bonding the die to the package.
[0013] The probe card parameters vary depending on the type of the
probe cards.
[0014] Cantilever probe cards usually comprise a ring (for example
made of aluminium, special alloys, or ceramic material) to which an
epoxy holder is attached. Such epoxy holder is adapted to hold a
plurality of testing elements in the form of resilient probes, made
of an alloy having good electrical and mechanical properties. In
particular, each cantilever probe includes a beam which is attached
at only one of its ends to the epoxy holder, and at the other end
the beam includes a tip which in use is intended to abut against a
contact pad of the die with the IC to be tested.
[0015] A drawback of these probe cards is that some of their probe
card parameters are unsatisfactory, so that, for example, alignment
errors (such as an X-axis error, and/or an Y-axis error and/or a
rotational error) between the probes' tips and the contact pads
(that is, between wafer and probe card) may take place, with
consequent potential problems of passivation layer breakage and
with a negative impact on quality.
[0016] More specifically, the X-axis error and the Y-axis error
represent the misalignment of the probes along the X and the Y
directions, respectively, with the contact pads to be contacted.
Due to the X-axis and Y-axis errors, the scrub mark on the contact
pad may be off-center along the X direction and/or the Y
direction.
[0017] In particular, during the testing of each die, rows of
contact pads placed on opposite sides of the die are often
contacted by the probes tips. In case of X-axis and Y-axis errors,
all the probes may be misaligned in the same direction (X or Y),
causing a displacement of the scrub marks along the X or the Y
direction.
[0018] When the scrub marks of the contact pads on one side of the
die are displaced towards the outer die edge, whereas the scrub
marks of the contact pads on the other side of the die are
displaced towards the inside of the die, a rotational error
exists.
[0019] Such errors are emphasized by the fact that the cantilever
probes are typically made based on mechanical techniques, so that
the probes are different from each other. Such difference may
further impair the values of the probe-card mechanical
parameters.
[0020] In addition, this type of probe card may have some other
limitations; for example, they may have a reduced parallel testing
capacity: indeed, when several dies have to be tested at the same
time, the number of mechanical probes significantly increases, and
it may happen that the electrical contacts between the contact pads
and the probes are not good and electrical discontinuities may take
place.
[0021] Moreover, when the contact pads are located close to each
other, it may be very difficult to ensure a good physical contact
of the mechanical probes with the pads. Such problem may be
emphasized when the pads are small in size and/or a large number
thereof is present on each die.
[0022] In addition, even if only one probe is damaged, it may be
necessary to replace the entire epoxy holder, and this negatively
contributes to the increase of the overall cost of the test
apparatus, and eventually of the ICs.
[0023] As an alternative to the cantilever probe cards, other known
probe cards include a plurality of vertical (or pseudo-vertical)
probes consisting of conductive wires passing through respective
holes formed in a probe card head. In detail, the probe card head
includes a top guide plate stacked on a bottom guide plate, which
are suitably separated by an air gap. Each probe has a tip, which
protrudes from the bottom guide plate and is adapted to
electrically contact the corresponding contact pad of the die to be
tested. A contact interface known as a "space transformer" (that is
one of the possible contact interface types) is connected to the
top guide plate and is adapted for electrically coupling the probes
to the PCB (by means of corresponding wires) so that the exchange
of the testing signal between the tester and the die under test may
be accomplished.
[0024] A drawback of these probe cards is that they may have a poor
scrubbing action on the contact pads, which may cause a reduced
electric yield. In other words, the probes may not be able to
adequately scrub the contact pad surface, that could have a metal
oxide layer (and sometimes diffusion residuals) over the contact
pad metallization region; the resulting probe scrub mark may not be
able to ensure a good electrical contact between probe and pad, and
if this happens the testing of the IC functionalities may be
impaired.
[0025] Moreover, also in this case, when the contact pads are close
to each other, it may be difficult to ensure a good physical
contact of the probes with the pads. Such problem is emphasized
when the pads are small in size and/or a large number thereof is
present on each die.
[0026] A further drawback is that, similarly to the cantilever
probe cards, when a probe breaks, it may be necessary to replace
the whole probe head, thereby increasing the overall cost of the
test apparatus.
[0027] Moreover, also in this case the probes are typically made
based on mechanical techniques, so that the probes are different
from each other. Such difference may further impair the probe card
planarity.
[0028] Probe cards are also known which include
MicroElectroMechanical Systems (MEMS) probes.
[0029] The probe cards having MEMS probes include of a multilayer
ceramic head to which the MEMS probes are coupled. Each MEMS probe
includes a base with contact features (such as a tip) adapted to
contact the pad, and a beam, which is attached at on only one end
thereof to the multilayer ceramic head and has the other end
connected to the base.
[0030] Each MEMS probe is obtained by means of lithographic
techniques, in particular a trench into a sacrificial substrate is
formed (for example, by means of etching processes) and then filled
with conductive material (e.g., gold) so as to obtain a base of the
MEMS probe adapted for contacting the contact pad. The conductive
material is then deposited on a portion of the sacrificial
substrate in order to obtain the beam of the MEMS probe. Then, the
MEMS probes are bonded to the multilayer ceramic head by means of
wire bonds or other techniques and the sacrificial substrate is
eliminated (for example, by an etching process). Finally, the
multilayer ceramic head is connected to the PCB.
[0031] A drawback of MEMS probe cards is that even if only one MEMS
probe is damaged, it may be necessary to replace the whole
multilayer ceramic head, and this may be very expensive.
[0032] Other, different types of cantilever, vertical and MEMS
probe cards are also known.
SUMMARY
[0033] An embodiment of a probe card overcomes these and other
problems of known probe cards.
[0034] An embodiment of a probe card comprises a set of replaceable
elementary probe card units which comprise one or more MEMS
probes.
[0035] In detail, according to an embodiment of the present
disclosure, a probe card is provided adapted for testing at least
one integrated circuit integrated on corresponding at least one die
of a semiconductor material wafer. The probe card includes a board
adapted for the coupling to a tester apparatus, and a plurality of
probes coupled to the said board. The probe card comprises a
plurality of replaceable elementary units, each one comprising at
least one of said probes for contacting the integrated circuit. The
replaceable elementary units of said plurality are arranged so as
to correspond to an arrangement of the at least one die on the
wafer to be tested.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] These and other features and advantages of embodiments of
the disclosure will be made apparent by the following detailed
description of one or more embodiments, provided merely by way of
non-limitative example, and such description will be conducted
making reference to the attached drawings, wherein:
[0037] FIG. 1 schematically shows a cross-sectional view of test
equipment wherein a test apparatus according to an embodiment of
the present disclosure is used;
[0038] FIG. 2 schematically shows a probe card according to an
embodiment of the present disclosure;
[0039] FIG. 3 schematically shows a probe card according to another
embodiment of the present disclosure;
[0040] FIG. 4 schematically shows a card according to still another
embodiment of the present disclosure; and
[0041] FIG. 5 schematically shows a probe card according to still
another embodiment of the present disclosure.
[0042] FIG. 6 is a schematic system level view of a probe card
according to an embodiment of the present disclosure.
[0043] FIGS. 7-11 are cross sectional views of a portion of the
probe card of FIG. 6 according to different embodiments of the
present disclosure.
DETAILED DESCRIPTION
[0044] Throughout the following description, identical or similar
elements in the drawings are denoted by same reference
numerals.
[0045] Referring to FIG. 1, a cross-sectional view of an embodiment
of test equipment 100 is schematically shown, in which an exemplary
structure and the positioning of a probe card 105 according to an
embodiment of the present disclosure and of a semiconductor wafer
110 to be tested is visible.
[0046] The semiconductor wafer 110 to be tested is placed on a
chuck 115, which is capable of movement in the three orthogonal
directions "x", "y" and "z" schematically indicated in the drawing.
The chuck 115 may also be rotated and tilted, and it may be further
capable of other movements, so that once the semiconductor wafer
110 is placed on the chuck 115, the latter is moved so that the
dies 145 of the wafer 110 to be tested are brought close to the
probe card 105, for enabling communication therewith.
[0047] In the example at issue, the probe card 105, in one of its
embodiments, includes a PCB 125 forming a support board for pseudo
silicon wafer 130--herein referred to as test silicon wafer--made
up of a plurality of pseudo-dies 135 each one forming an elementary
probe unit.
[0048] The PCB 125 comprises all the circuitry which is employed
for the communication between the tester (not shown in figure) and
the wafer 110 under test. For example, the PCB 125 comprises
data/signal processing circuits that control the overall operation
of the probe card 105, and which may operate under the control of a
software stored in a storage unit (e.g., one or more memories which
are also included in the PCB 125).
[0049] A top view of the probe card 105 (including the test silicon
wafer 130) and the semiconductor wafer 110 is also shown in the
drawing.
[0050] Fiducial signs 140 may be provided on the PCB 125, or on the
test wafer 130, for allowing the correct alignment between the
probe card 105 and the semiconductor wafer 110.
[0051] As shown, the elementary probe units 135 are arranged in the
test silicon wafer 130 in order to form a two-dimensional
arrangement which corresponds to the arrangement of dies on the
semiconductor wafer 110 under test. In particular, the test silicon
wafer 130 comprises an array of the elementary probe units 135
which reproduce a shape of the wafer 110 to be tested. In an
embodiment of the present disclosure, each of the elementary probe
units 135 of the test wafer 130 belonging to the probe card 105 is
adapted to establish a one-to-one communication relationship with a
corresponding die of the semiconductor wafer 110 to be tested, by
means of a number of MEMS probes adapted to contact the pads of an
IC.
[0052] In particular, as better described in the following, each
elementary probe unit 135 is formed starting from a silicon die,
individually diced and finally assembled with the other elementary
probe units 135 in order to form the test silicon wafer 130 having
a shape corresponding to the semiconductor wafer 110 to be
tested.
[0053] Referring to FIG. 2, a portion of the probe card 105 is
shown. In particular, FIG. 2 shows an elementary probe unit 135
according to an embodiment of the present disclosure. The
elementary probe unit 135 includes a silicon die 205 which is
connected, e.g. by flip-chip techniques, to the PCB 125. In
particular, contact bumps 210 are provided in order to connect a
top surface 215 of the silicon die 205 to the PCB 125. Through
Silicon Vias (TSV) 220 are provided crossing the silicon die 205 in
order to connect the top surface 215 to a bottom surface 221 of the
silicon die 205. A plurality (for example, two as shown in figure)
of mechanical elements forming probes 225 (particularly of MEMS
type), are connected to the bottom surface 221 of the silicon die
205. In particular, the TSVs 220 are adapted to electrically
connect the MEMS probes 225 to the top surface 215 of the silicon
die 205 and thus to the PCB 125, by means of a conductive path that
may also include one or more layers of TSVs, vias, and metal
strips.
[0054] In particular, for electrically contacting the input/output
contact pads of the die to be tested and exchanging the test
signals between the input/output contact pads and the tester (not
shown in figure), the PCB 125 provides corresponding conductive
paths 230, which electrically couple the tester to the silicon die
205 and thus to the probes 225. In particular, for testing the dies
in order to assess the functionality of the ICs integrated therein,
the tester is adapted to generate test signals to be fed to the ICs
integrated on the dies belonging to the semiconductor wafer 110;
the tester is coupled by means of the PCB 125 to the elementary
probe units 135, each one of which is adapted to be fed by the
tester trough the conductive paths 230 with the test signals, and
the power supply necessary for its operation.
[0055] In other words, the MEMS probes 225, the TSVs 220, the bumps
210 and the conductive paths 230 are adapted to establish a
bi-directional link between the tester and each die (or groups of
dies) of the semiconductor wafer 110 under test. The probe card 105
receives the test input signals from the tester and transmits them
to the dies to be tested by using the MEMS probes 225. The test
signals are then used to test the IC integrated on the die
belonging to the semiconductor wafer 110; test response signals are
generated in response to the test input signals. The test response
signals are transmitted to the probe card 105, and then sent to the
tester, which processes them to assess the functionality of the IC
integrated on the die under test.
[0056] Referring to FIG. 3, an elementary probe unit 135 (also in
this case coupled to the PCB 125) according to another embodiment
of the present disclosure is shown.
[0057] The elementary probe unit 135 includes the silicon die 205,
which is attached by means of a resin layer or sticky layer 305 to
the PCB 125. Wire bonds 310 are provided for electrically
connecting the silicon die 205 to the conductive paths 230 formed
on the PCB.
[0058] Referring to FIG. 4, an elementary probe unit 135 according
to a still another embodiment of the present disclosure is
shown.
[0059] In this embodiment, a multilayer ceramic material 405 is
interposed between the PCB 125 and the silicon die 205. The
multilayer ceramic material 405 is employed for improving the
performance of the probe card 105 when it is subjected to high
temperatures. For example, the multilayer ceramic material 405
allows preventing the thermal expansion of the PCB 125 during the
exposure of the probe card 105 to high temperature.
[0060] Through vias 410 and 415 are provided, respectively crossing
the silicon die 205 and the multilayer ceramic material 405. The
through vias 410 and 415 may also be replaced by a more complex
conductive path scheme inside the multilayer ceramic material 415
and the silicon die 205. The bumps 210 connect the through vias 410
to corresponding through vias 415 so that a conductive path is
formed between the PCB 125 and the MEMS probes 225.
[0061] Finally, referring to FIG. 5, an elementary probe unit 135
according to still another embodiment of the present disclosure is
shown. In this case, a multilayer ceramic material 505 is
interposed between the PCB 125 and the silicon die 205. Wire bonds
510 are provided for connecting the silicon die 205 to the
multilayer ceramic 505. In particular, the wire bonds 510 are
connected to through vias 515 crossing the multilayer ceramic 505.
The through vias 515 may also be replaced by a more complex
conductive path scheme inside the multilayer ceramic. In such a
way, a conductive path formed by the wire bonds 510, the trough
vias 515 and the paths 230 is formed so that the test signals may
be exchanged between the tester and the silicon wafer to be tested
by means of the probe card 105 according to an embodiment of the
present disclosure.
[0062] It should be noted that, according to an embodiment of the
present disclosure, the probe card 105 may be formed by connecting
in different way one or more silicon dies 205. In particular,
depending on the shape of the wafer to be tested, each elementary
probe unit 135 may be arranged in order to form a test silicon
wafer 130 having a shape similar to that of the wafer under
test.
[0063] In particular, according to an embodiment of the present
disclosure, the probe card 105 may be formed by a plurality of
basic and replaceable elementary units (the elementary probe units
135) so as to obtain a modular and flexible structure which is
easily usable for any semiconductor wafer to be tested,
irrespective of the type of ICs integrated therein. In other words,
depending on the semiconductor wafer to be tested, the elementary
probe units 135 may be arranged in different ways and shapes. In
such a way, the probe card 105 has a high flexibility, and,
therefore, may be adaptable to any wafer to be tested and the
overall cost of the testing of different several wafers is
significantly reduced.
[0064] Moreover, such modular and flexible structure allows, in
case one of the elementary probe units 135 is damaged, to replace
it without changing the entire test silicon wafer 130.
[0065] Additionally, the use of a silicon die for manufacturing the
elementary probe unit 135 allows further reducing the overall cost
of each probe which is employed in the testing apparatus.
[0066] In other words, the test system according to the described
embodiments of the present disclosure may be significantly less
expensive than those using the conventional probe cards, since the
elementary probe units are manufactured by lithographic techniques
starting from a silicon wafer.
[0067] It is pointed out that, in some embodiments of the
disclosure, the test silicon wafer 130 may include a number of
elementary probe units 135 lower than the number of dies of the
semiconductor wafer 110 to be tested (in which case, groups of dies
of the wafer are tested in parallel), or the number of elementary
probe units 135 may be even greater than the number of dies 105 of
the specific wafer 110 under test (in which case, only a subset of
the elementary probe units 135 are exploited for testing the whole
wafer).
[0068] Moreover, an embodiment of the present disclosure allows
testing at the same time the whole semiconductor wafer 110, or at
least groups of dies 145 on the wafer 110. In this way, a
significant reduction of the test time may be attained, with a
corresponding productivity improvement.
[0069] Referring to FIG. 6, a system level view of a probe card
105' according to an embodiment of the present disclosure is shown.
The probe card 105' includes a test wafer 130' comprising a set of
probe units 135' each including a respective set of one or more
silicon dies 205' sharing a same substrate 610. Each silicon die
205' is provided with one or more probes 225' (particularly of the
MEMS type) adapted to interact with pads on at least one die 145 in
the semiconductor wafer 110 to be tested.
[0070] The test wafer 130' is supported by a PCB 125', which may
comprise all the circuitry employed for the communication between
the tester and the wafer 110 under test. In the same way as for the
PCB 125 of the previous embodiments, the PCB 125' may comprise
data/signal processing circuits that control the overall operation
of the probe card 105', and which may operate under the control of
software stored in a storage unit (e.g., one or more memories which
may also be included in the PCB 125').
[0071] A main purpose of a probe unit's substrate 610 is to house
the silicon dies 205' of said probe unit 135', for providing a
robust mechanic support and at the same time electrically
insulating each silicon die 205' from the others. Thus, the
substrate 610 may be formed by a proper insulating material, such
as a resin or a polymer.
[0072] FIG. 7 is a cross-sectional view of a portion of the probe
card 105' illustrated in FIG. 6. Particularly, FIG. 7 shows a probe
unit 135' according to an exemplary embodiment of the present
disclosure. The probe unit 135' includes a substrate 610 having a
top surface 615 facing the PCB 125' (not illustrated in FIG. 7) and
a bottom surface 620. The probe unit 135' further includes a set of
silicon dies 205' (in the example at issue, two) each having a top
surface 215' covered by the substrate 610 and an exposed bottom
surface 221'. MEMS probes 225' are connected to the bottom surface
221' of the silicon dies 205', for electrically contacting the
input/output contact pads of one or more dies 145 on the
semiconductor wafer 110 to be tested. Each silicon die 205' is
adapted to be electrically connected to the PCB 125'. For this
purpose, the substrate 610 includes through vias 220' connecting
the top surface 615 with the bottom surface 620; the through vias
220' are connected at the top surface 615 with contact bumps 625
adapted to be connected in turn to the PCB 125'. Moreover, metal
lines 630 are provided on the bottom surface 620 of the substrate
610 for connecting each through vias 220' to the bottom surface
221' of a corresponding silicon die 205'. In this way, a
bi-directional link between the tester and each die 145 on the
semiconductor wafer can be established through the MEMS probes
225', the metal lines 630, the through vias 220' and the bumps
625.
[0073] Since, thanks to the presence of the substrate 610, a single
probe unit 135' may include more than one silicon die 205', it is
possible to reduce the global costs by using smaller silicon dies
205', which may be also reused for testing different devices.
Moreover, this solution allows one to better exploit the area of
the probe unit 135'.
[0074] According to an alternative embodiment of the present
disclosure, the silicon dies 205' may be provided with silicon
through vias each electrically coupled with a respective through
via 220' crossing the substrate 610.
[0075] FIG. 8 is a cross-sectional view of a portion of the probe
card 105' illustrated in FIG. 6, which shows a probe unit 135'
according to a further exemplary embodiment of the present
disclosure. Particularly, the set of silicon dies included in the
probe unit 135' are adapted to electrically contact the
input/output contact pads of a plurality of dies 145 on the
semiconductor wafer 110 to be tested. Making reference to the
example at issue, a first silicon die 205'(1) is provided with MEMS
probes 225' for electrically contacting the input/output contact
pads of a first die 145(1) in the semiconductor wafer 110; a second
silicon die 205'(2) is provided with first MEMS probes 225' for
electrically contacting the input/output contact pads of the first
die 145(1) and second MEMS probes 225' for electrically contacting
the input/output contact pads of a second fie 145(2) in the
semiconductor wafer 110; finally, a third silicon die 205'(3) is
provided with MEMS probes 225' for electrically contacting the
input/output contact pads of the second die 145(2). In other words,
thanks to the proposed embodiment, it may be possible to implement
complex structures, wherein the through vias 220' crossing the
substrate 610 may be placed in the available areas between adjacent
silicon dies 205', and a die 145 in the semiconductor wafer 110 may
be contacted by MEMS probes 225' of more than one silicon die
205'.
[0076] According to a further embodiment of the present disclosure,
each probe unit 135' may be provided with a respective local PCB,
adapted to be used for increasing the pitch between adjacent
through vias 220' so as to simplify the assembly of the various
probe units 135' to the probe card 105'. For example, as
illustrated in FIG. 9, the top surface 615 of the substrate 610 may
be directly connected to a local PCB 910 provided with a conductive
path 920 per through via 220' that crosses the substrate 610.
Particularly, each through via 220' is electrically connected to a
respective conductive path 920 in the local PCB 910; each
conductive path 920 ends on a top surface 930 of the local PCB 910
with a contact bump 940 adapted to be connected to the PCB 125. In
this way, instead of directly connecting the probe unit 135' to the
PCB 125' using contact bumps connected to the top ends of the
trough vias 220'--and, thus, very close to each other--the probe
unit 135' of FIG. 9 may be connected to the PCB 125 through more
spaced contact bumps 940.
[0077] The same considerations may apply if the local PCB 910 is
replaced with a ceramic layer, or with equivalent means.
[0078] According to a further embodiment of the present disclosure,
the silicon dies 205' included in the probe units 135' may include
integrated circuits--identified in FIG. 6 with the reference
IC--adapted to be used during the test of the dies 145 on the
semiconductor wafer 110. For example, said integrated circuits IC
may include circuits adapted to sense/generate very low power
signals or pre-process signals received from/provided to the tested
dies 145 and so on.
[0079] Moreover, the substrate 610 of a probe unit 135' may be
advantageously exploited for housing other electronic devices
useful for the operation of the probe card 105'. For example, FIG.
10 is a cross-sectional view of a portion of the probe card 105',
which shows a probe unit 135' in which the substrate 610 thereof
houses a supply filter capacitor 1000.
[0080] According to a further embodiment of the present disclosure,
the substrate 610 of a probe unit 135' may house a dedicated
control chip--identified in FIG. 6 with the reference
ICM--integrating circuits adapted to manage the operations
performed by the probe unit 135' and control the traffic of the
signals generated by/provided to the silicon dies 205' connected to
MEMS probes 225'. Moreover, the control chip ICM may be used for
integrating additional circuits to be shared among the silicon dies
205' of the probe unit 135'. For example, the control chip ICM may
integrate a digital to analog converter that can be shared by more
than one silicon die 205' of the probe unit 135'. FIG. 11 is a
cross-sectional view of a portion of the probe card 105', which
shows a probe unit 135' in which the substrate 610 thereof houses a
control chip ICM which is connected to the through vias 220'--and,
thus, to the silicon dies 205'--by means of the metal lines
630.
[0081] Naturally, in order to satisfy local and specific
requirements, a person skilled in the art may apply to the
embodiments described above many modifications and alterations.
Particularly, although embodiments of the present disclosure have
been described, it should be understood that various omissions,
substitutions and changes in the form and details as well as other
embodiments are possible; moreover, it is expressly intended that
specific elements and/or method steps described in connection with
any disclosed embodiment of the disclosure may be incorporated in
any other embodiment as a general matter of design choice.
[0082] For example, although in the preceding description reference
has been made to an elementary unit having only one ceramic layer,
it is possible to have a ceramic layer in common among different
silicon dies.
[0083] Moreover, although in the preceding description reference
has been made to elementary units equal each other, an embodiment
of the present disclosure may be applied also in case the
elementary units 135 are different from each other, such as
manufactured with different material or having a different
structure.
[0084] An embodiment according to the present disclosure may be
applied in such a way that a silicon die 205 may test only a
portion of a die 145 of the semiconductor wafer 110.
[0085] The conductive path routing may be accomplished partly in
the test dies 135 and/or partly in the multilayer ceramic material
and/or partly in the PCB using for example one or more layers of
TSVs, through vias and metal strips.
[0086] Moreover different techniques may be used to assemble the
silicon die 135 on the multilayer ceramic and/or on the PCB.
[0087] Also, different techniques may be used to assemble the
multilayer ceramic on the PCB.
[0088] 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.
* * * * *