U.S. patent application number 10/212786 was filed with the patent office on 2002-12-12 for burn-in apparatus and semiconductor wafer.
This patent application is currently assigned to NEC CORPORATION. Invention is credited to Okabe, Fumihiro.
Application Number | 20020186032 10/212786 |
Document ID | / |
Family ID | 13368337 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020186032 |
Kind Code |
A1 |
Okabe, Fumihiro |
December 12, 2002 |
Burn-in apparatus and semiconductor wafer
Abstract
A semiconductor wafer has a device zone and a peripheral edge
zone. Semiconductor devices to be screened are formed in a matrix
form on the device zone of the semiconductor wafer. A plurality of
wires connected to the semiconductor devices are formed on the
device and peripheral edge zones. In the device zone, the wires are
formed among lines of the semiconductor devices. A burn-in
apparatus comprises a holder, a thermal controller, a signal
generator, and interconnection members. The holder holds a
plurality of the semiconductor wafers in order to install them in a
room. The thermal controller controls temperature in the room to
heat the semiconductor wafers up to a predetermined temperature.
The signal generator generates a test pattern signal for screening
the semiconductor devices. Each of the interconnection members has
a plurality of electrodes formed so as to contact the ends of the
wires, and presses the electrodes into the wires to establish
complete connection between the electrodes and the wires.
Inventors: |
Okabe, Fumihiro; (Tokyo,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037-3213
US
|
Assignee: |
NEC CORPORATION
|
Family ID: |
13368337 |
Appl. No.: |
10/212786 |
Filed: |
August 7, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10212786 |
Aug 7, 2002 |
|
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09525766 |
Mar 14, 2000 |
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6459285 |
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Current U.S.
Class: |
324/750.05 ;
324/762.05 |
Current CPC
Class: |
G01R 31/2862 20130101;
G01R 31/287 20130101; G01R 31/2863 20130101; G01R 31/2831
20130101 |
Class at
Publication: |
324/760 ;
324/765 |
International
Class: |
G01R 031/02; G01R
031/26 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 1999 |
JP |
11-068250 |
Claims
What is claimed is:
1. A burn-in apparatus comprising: a holder which holds plurality
of semiconductor wafers each having an inner zone prepared for
arranging thereon a plurality of semiconductor devices to be
screened, and a peripheral edge zone around said inner zone, in
order to install the plurality of semiconductor wafers in a room; a
thermal controller which controls temperature of the room so as to
heat the plurality of said semiconductor wafers up to a
predetermined temperature; a signal generator which generates a
test pattern signal for screening said semiconductor devices on the
plurality of said semiconductor wafers which have been heated up to
the predetermined temperature; and interconnection members which
electrically interconnects said signal generator and each of said
semiconductor devices, in order to provide said semiconductor
devices respectively with the signals generated by said signal
generator.
2. The burn-in apparatus according to claim 1, wherein said holder
holds said semiconductor wafers each having a plurality of pathways
which are formed across said inner and peripheral edge zones for
supplying the test pattern signal to said semiconductor devices;
and each of said interconnection members has a plurality of
electrodes being connected to said signal generator, and presses
said electrodes so that said electrodes contact said pathways.
3. The burn-in apparatus according to claim 2, wherein each of said
interconnection members comprises; a first board on which said
semiconductor wafer is vacuum fixed; and a second board which
collaborates with said first board to provide said electrodes with
pressure for making contact with said pathways.
4. The burn-in apparatus according to claim 3, wherein the
plurality of said electrodes are arranged so as to contact both
ends of said pathways which are formed among lines of said matrix
formed semiconductor devices on said semiconductor wafer.
5. The burn-in apparatus according to claim 4, wherein the
plurality of said electrodes are grouped by ends of said pathways
being connected to, and said electrodes in the same group are
connected to each other by wires while one of said electrodes in
the group is connected to said signal generator.
6. A semiconductor wafer comprising: a device zone which is
prepared for forming semiconductor devices thereon, and a
peripheral zone which is prepared around said device zone; a
plurality of semiconductor devices which are formed on said device
zone to be subjected to screening; and a plurality of wires which
are formed across said device and peripheral zones in order to
supply signals for screening respectively to the plurality of said
semiconductor devices, wherein said wires are straight while being
parallel to each other in said device zone.
7. The semiconductor wafer according to claim 6, wherein said wires
extend straightly from said device zone to said peripheral
zone.
8. The semiconductor wafer according to claim 6, wherein said wires
are formed so that intervals among ends of the wires on said
peripheral zone are wider than intervals among said wires on said
device zone.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor wafer on
which semiconductor devices to be screened are formed. The present
invention relates to a burn-in apparatus for screening
semiconductor devices formed on a semiconductor wafer. The present
invention relates, more particularly to a burn-in apparatus and a
semiconductor wafer which enables screening many semiconductor
devices at once without connection failures on wires.
[0003] 2. Description of the Related Art
[0004] Burn-in screening has been known as a technique for
eliminating semiconductor devices having potential failures. The
screening is usually performed under elevated temperatures, and the
devices being screened have been electrically stressed for a
predetermined time period. Thus screened device tends to induce
accelerated failures which may appear early in the device's
lifetime.
[0005] Conventional screening has been applied to devices which are
cut from the wafer and mounted into packages. Usually, the devices
are placed in the packages and then the packages go into sockets on
the burn-in boards. And then, the boards are placed in the burn-in
apparatus for screening.
[0006] Recently, demands for screening unpackaged devices have been
developing because the unpackaged devices have been widely used.
However, it is difficult to individually screen devices which have
been cut away from the wafer. Therefore, demands for wafer level
burn-in have been developing.
[0007] Such the wafer level burn-in techniques are disclosed in
Unexamined Japanese Patent Application KOKAI Publications Nos.
S63-124443, H5-121502, H6-5677, and H10-284556. The disclosures of
the above applications are incorporated herein by reference in
their entirety.
[0008] In each of the techniques disclosed in the above
applications, common conductive X-axis and Y-axis pathways for
screening are formed among a plurality of devices formed on a
wafer, and common terminals connected to the common pathways are
formed at wafer edges. More precisely, common pathways 111 are
formed among semiconductor devices, and common terminals 112 are
formed at wafer edge, as shown in FIG. 6A. During the screening
process, the wafer is stuck to a stage 113 in the burn-in apparatus
as shown in FIG. 6B. And then, a probe 114 contacts the common
terminals 112, as described in Unexamined Japanese Patent
Application KOKAI Publication No. H5-121502. Then, voltages, test
pattern signals, and the like necessary for screening are supplied
to the semiconductor devices from a power source 115 and a pulse
generator 116 via the probe 114, the common terminals 112 and the
common pathways 111. Thus, the semiconductor devices on the wafer
are screened.
[0009] FIG. 7 is a diagram for explaining the screening process
disclosed in Unexamined Japanese Patent Application KOKAI
Publication No. H10-284556. A semiconductor wafer 122 on which
semiconductor devices are formed is mounted on a stage 121 in a
burn-in apparatus, as a first step. Then, a contact sheet 123 is
placed on the wafer 122, and a base unit 124 is placed on the
contact sheet 123. One major surface of the contact sheet 123
facing the wafer 122 has terminals which has a pattern same as that
of terminals on the semiconductor devices. The other side of the
contact sheet 123 has terminals which has a pattern same as that of
terminals formed on a surface of the base unit 124 which facing the
contact sheet 123. During the screening process, a mechanical jig
125 is pressed upon the burn-in apparatus, thus, the contact sheet
123 and the base unit 124 are pressed upon the wafer 122. This
contact establishes electrical connection between the terminals on
the base unit 124 and the terminals on the semiconductor devices
while sandwiching the contact sheet 123 therebetween. A signal
generator 126 generates a test pattern signal, and supply it to the
semiconductor devices via the base unit 124 being connected to the
signal generator 126 and via the contact sheet 123. Thus, the
semiconductor devices are screened.
[0010] According to the techniques disclosed in the above mentioned
Unexamined Japanese Patent Application KOKAI Publications Nos.
S63-124443, H5-121502, and H6-5677, the x-axis and y-axis common
pathways 111 are formed among the semiconductor devices. Because
such wiring formation is very complex, the formation process is
also complex. Moreover, the above-described techniques require many
steps before carrying out the screening such as formation of the
common terminal 112 and the like. Therefore, it takes a long time
before carrying out the screening. Such the extra steps also raise
the manufacturing cost.
[0011] According to the technique disclosed in Unexamined Japanese
Patent Application KOKAI Publication No. H5-121502, voltages and
signals necessary for the screening are supplied to the
semiconductor devices via the probe 114 which contacts the common
terminals 112 on the wafer. Elevated temperature in the burn-in
apparatus may expands the probe 114 itself, and then the prove 114
may fail to precise contact with the common terminals 112. That is,
the technique disclosed in the above application has a problem
which causes unsuccessful screening. Moreover, the stage 113 can
hold only one wafer. Therefore, screening efficiency is poor,
especially in a case where the wafer must be placed in a chamber
under a constant temperature for a long time.
[0012] In the case of Unexamined Japanese Patent Application KOKAI
Publication No. H10-284556, the base unit 124 and the contract
sheet 123 are pressed upon the semiconductor wafer 122 by the
mechanical jig 125. This structure permits the burn-in apparatus to
place only one wafer therein for each screening. This technique
also has poor efficiency.
SUMMARY OF THE INVENTION
[0013] The present invention has been made in consideration of the
above. It is an object of the present invention to provide a
burn-in apparatus and a semiconductor wafer for screening
semiconductor devices efficiently. It is another object of the
present invention to provide a burn-in apparatus and a
semiconductor wafer for screening semiconductor devices
successfully. A further object of the present invention to provide
a burn-in apparatus and a semiconductor wafer for screening
multiple semiconductor devices simultaneously without connection
failures on wires prepared for the screening.
[0014] To achieve the above objects, a burn-in apparatus according
to a first aspect of the present invention is a burn-in apparatus
comprises:
[0015] a holder which holds a plurality of semiconductor wafers
each having an inner zone prepared for arranging thereon a
plurality of semiconductor devices to be screened, and a peripheral
edge zone around the inner zone, in order to install the plurality
of the semiconductor wafers in a room;
[0016] a thermal controller which controls temperature of the room
so as to heat the plurality of the semiconductor wafers up to a
predetermined temperature;
[0017] a signal generator which generates a test pattern signal for
screening the semiconductor devices on the plurality of the
semiconductor wafers which have been heated up to the predetermined
temperature; and
[0018] interconnection members which electrically interconnect the
signal generator and each of the semiconductor devices, in order to
provide the semiconductor devices respectively with the signals
generated by the signal generator.
[0019] This invention realizes screening the semiconductor devices
formed on the plurality of semiconductor wafers installed in the
room. In other words, it realize efficient screening wherein many
semiconductor devices are screened.
[0020] The holder may hold the semiconductor wafers each having a
plurality of pathways which are formed across the inner and
peripheral edge zones for supplying the test pattern signals to the
semiconductor devices; and
[0021] each of the interconnection members may have a plurality of
electrodes being connected to the signal generator, and presses the
electrodes so as to contact the pathways.
[0022] Each of the interconnection members may comprise;
[0023] a first board on which the semiconductor wafer is vacuum
fixed; and
[0024] a second board which collaborates with the first plate to
provide the electrodes with pressure for making contact with the
pathways.
[0025] The plurality of the electrodes may be arranged so as to
contact both ends of the pathways which are formed among lines of
the matrix formed semiconductor devices on the semiconductor
wafer.
[0026] The plurality of the electrodes may be grouped by ends of
the pathways being connected to, and the electrodes in the same
group may be connected to each other by wires while one of the
electrodes in the group is connected to the signal generator.
[0027] A semiconductor wafer according to a second aspect of the
present invention is a semiconductor wafer comprises:
[0028] a device zone which is prepared for forming thereon
semiconductor devices, and a peripheral zone which is prepared
around the device zone;
[0029] a plurality of semiconductor devices which are formed on the
device zone to be subjected to screening; and
[0030] a plurality of wires which are formed across the device and
peripheral zones in order to supply signals for screening
respectively to the plurality of the semiconductor devices, wherein
the wires are straight while being parallel to each other in the
device zone.
[0031] The wires may extend straightly from the device zone to the
peripheral zone.
[0032] The wires may be formed so that intervals among the ends of
the wires on the peripheral zone are wider than intervals among the
wires on the device zone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] These objects and other objects and advantages of the
present invention will become more apparent upon reading of the
following detailed description and the accompanying drawings in
which:
[0034] FIG. 1 is a diagram showing a state where semiconductor
devices on a semiconductor wafer according to a first embodiment
are being screened;
[0035] FIG. 2 is a diagram showing a state where the semiconductor
wafer according to the first embodiment is held by a wafer
holder;
[0036] FIG. 3A is a diagram showing the structure of the
semiconductor wafer according to the first embodiment, and FIG. 3B
is a diagram showing connection between the semiconductor devices
on the semiconductor wafer shown in FIG. 3A and a burn-in
controller;
[0037] FIG. 4A is a plan view showing the structure of the wafer
holder, FIG. 4B is a cross sectional view along a B-B' line in FIG.
4A, and FIG. 4C is a diagram showing connection between an
electrode chip of the wafer holder and on-board pathways on the
semiconductor wafer;
[0038] FIG. 5 is a diagram showing the structure of a semiconductor
wafer according to a second embodiment;
[0039] FIG. 6A is a diagram showing the structure of a conventional
semiconductor wafer, and FIG. 6B is a diagram showing a state where
semiconductor devices on the semiconductor wafer shown in FIG. 6A
are being screened; and
[0040] FIG. 7 is a diagram showing the structure of a conventional
burn-in apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIRST EMBODIMENT
[0041] A semiconductor wafer according to a first embodiment of the
present invention will now be described with reference to
accompanying drawings.
[0042] FIG. 1 shows a state where semiconductor devices on the
semiconductor wafer according to the first embodiment are being
screened in a burn-in apparatus.
[0043] As shown in FIG. 1, the burn-in apparatus comprises an
isothermal chamber 11, wafer holders 12, a slot array 13, a
controller 14, and bridge lines 15.
[0044] The isothermal chamber 11 has a gateway 17 through which
semiconductor wafers 16, on which semiconductor devices to be
screened are formed, are installed in the isothermal chamber 11,
and is equipped with a heater (not shown) or the like which heats
the installed semiconductor wafers 16 up to a predetermined
temperature and maintains it.
[0045] The wafer holders 12 hold the semiconductor wafers 16, and
electrically interconnect the semiconductor devices on the wafers
16 and the bridge lines 15. The structure of the wafer holders 12
will be described later.
[0046] The slot array 13 is prepared in the chamber 11 to hold a
plurality of wafer holders 12 holding the wafers 16.
[0047] The controller 14 generates a source voltage, a control
signal, and the like necessary for screening, and supplies them to
the semiconductor devices on the wafers 16 via the bridge lines 15.
The controller 14 also controls the temperature in the isothermal
chamber 11 and the burn-in apparatus in accordance with a given
program or the like.
[0048] The bridge lines 15 electrically interconnect the controller
14 and wafer holders 12. Thus, the source voltage, control signal
or the like for the screening are supplied to the wafers 16 in the
isothermal chamber 11 from the controller 14.
[0049] The structures of the wafer holder 12 and the semiconductor
wafer 16 will now be described.
[0050] FIG. 2 shows a state where the semiconductor wafer 16 is
held by the wafer holder 12.
[0051] As shown in FIG. 3A, semiconductor devices 21, on-board
pathways 22, and burn-in controllers 23 are formed on the wafer
16.
[0052] A plurality of the semiconductor devices 21 are formed on an
inner zone of the wafer 16 (hereinafter, referred to as a device
zone) in matrix form. The formed semiconductor devices 21 will be
screened by the burn-in apparatus.
[0053] Each of the on-board pathways 22 has several (for example,
four) wires as a unit. (Note that only three wires of four are
shown in FIG. 3A.) The on-board pathways 22 are arranged among
lines of the semiconductor devices 21 unit by unit, and the
arranged pathways 22 are straight. That is, the pathways 22 are
formed in simple wiring patterns. This means that the on-board
pathways 22 can be formed by a simple method such as a reduction
projection step and repeat exposure. For the sake of connection to
the bridge lines 15 via the wafer holder 12 (the structure thereof
will be described later), the on-board pathways 22 straightly
extend to edge of the wafer 16, that is, extend to joint portions
which will be connected to the wafer holder 12. To avoid wire break
and short circuit of the on-board pathways 22, appropriate gauge
and intervals are given to the wires. For the same purpose, the
wires are shielded on the device zone while the wire ends at the
wafer edge are exposed for contact.
[0054] The burn-in controllers 23 are formed on the wafer 16 so as
to be adjacent to the semiconductor devices 21 respectively. Each
of the burn-in controllers 23 supplies a source voltage, a control
signal, and the like from the controller 14, to its corresponding
semiconductor device 21.
[0055] FIG. 3B shows the structure of connection between the
semiconductor device 21 and the burn-in controller 32.
[0056] As shown in FIG. 3B, a unit of the on-board pathways 22 runs
through lined burn-in controllers 23. Each wire unit contains lines
such as a power line 31, a ground (GND) line 32, a signal line 33,
and a gate line 34. Each semiconductor device 21 has pads 38, 40
and 42, and switching transistors (hereinafter referred to as
switching Tr) 37, 39 and 41.
[0057] The switching Tr 37, 39 and 41 interconnect the pads 38, 40
and 42 with the power line 31, the GND line 32, and the signal line
33 respectively. The pads 38, 40, and 42 work as terminals of a
circuit (not shown) of the semiconductor device 21. Those terminals
will be used in practical use.
[0058] As shown in FIG. 3B, the power line 31 is connected to one
source/drain of the switching Tr 37 via a diode 35 and a resistance
36, while the other source/drain is connected to the pad 38. This
pair of the diode 35 and resistance 36 functions as an
anti-overcurrent device. That is, if the semiconductor device 21 is
broken during the screening, the corresponding anti-overcurrent
device prevents an overcurrent from being applied to other
semiconductor devices 21.
[0059] The GND line 32 is connected to one source/drain of the
switching Tr 39. The other source/drain of the switching Tr 39 is
connected to the pad 40.
[0060] The signal line 33 is connected to one source/drain of the
switching Tr 41. The other source/drain of the switching Tr 41 is
connected to the pad 42.
[0061] Gates of the switching Tr 37, 39 and 41 are connected to the
gate line 34 via a fuse 43, while being connected to the substrate
of the semiconductor device 21 via diodes 44, 45 and 46
respectively. Purpose of the diodes 44, 45 and 46 is to maintain a
gate potential in a predetermined range during the practical use.
The potential of the substrate is restricted, for example, so as to
be lower than threshold voltages of the switching Tr 37, 39 and
41.
[0062] The structure of the wafer holder 12 will now be
described.
[0063] FIGS. 4A, 4B and 4C are diagrams showing the structure of
the wafer holder 12. FIG. 4A is a plan view showing the wafer
holder 12, and FIG. 4B is a cross sectional view along a line B-B'
in FIG. 4A. FIG. 4C shows the structure of connection between the
wafer holder 12 and the on-board pathways 22 on the wafer 16.
[0064] As shown in FIGS. 4A and 4B, the wafer holder 12 comprises a
stage board 51, a chuck 52, a vacuum outlet 53, an interconnection
ring 54, electrode chips 55, common pathways 56, a pressure board
57, and fixer clasps 58.
[0065] The stage board 51 comprises the chuck 52 and the vacuum
outlet 53 which are prepared for fixing the wafer 16 on the stage
board 51. That is, a vacuum pump (not shown) or the like vacuums
out the air in the chuck 52 through the vacuum outlet 53, thus the
wafer 16 is stuck to the stage board 51.
[0066] The interconnection ring 54 comprises the electrode chips 55
and the common pathways 56. The interconnection ring 54 is placed
on the stage board 51 after the wafer 16 is stuck on the stage
board 51. The electrode chips 55 are arranged at inner side of the
interconnection ring 54 so as to contact ends of the on-board
pathways 22 on the wafer 16. That is, positions of the electrode
chips 55 when the wafer 16 is mounted on the wafer holder 12
substantially coincide with positions of ends of the on-board
pathways 22. As shown in FIG. 4A, the electrode chips 55 are
classified into two groups by the ends of the on-board pathways 22
being connected to, and the electrode chips 55 in the same group
are connected to each other by the common pathways 56. Further, one
of the electrode chips 55 in the group is connected to the bridge
line 15.
[0067] The electrode chips 55 are pressed upon the on-board
pathways 22 as the interconnection ring 54 is pressed upon the
stage board 51. More precisely, each of the electrode chips 55 has
contact electrodes 59, as shown in FIG. 4C, which contact the wires
in the unit of the on-board pathways 22. That is, the contact
electrodes 59 are arranged at intervals which coincide with
intervals of the wires. Each of the contact electrodes 59 is
connected to the bridge line 15 or the common pathways 56.
Accordingly, electric connection between the on-board pathways 22
and the bridge lines 15 will be established when the
interconnection ring 54 is pressed upon the stage board 51. This
structure realizes successful screening, because the connection
between the on-board pathways 22 and the electrode chips 55 is
established at the ends of the on-board pathways 22, thus, it is
easy to see connection status. The number of wires in a unit of the
common pathways 56 and a unit of the bridge lines 15 is the same as
that of the wires in the unit of the on-board pathways 22.
[0068] The pressure board 57 is placed on the interconnection ring
54. The fixer clasps 58 tighten the pressure board 57 so that the
pressure board 57 and the stage board 51 press the interconnection
ring 54, thus the contact electrodes 59 contact the on-board
pathways 22 completely.
[0069] Since the semiconductor wafers 16 are mounted on the wafer
holders 12 as described above, common terminals (pads) which have
been employed in the conventional techniques are unnecessary.
Moreover, complete connection between the bridge lines 15 and the
on-board pathways 22 is established. Those features prevent
connection failures caused by thermal expansion during the
screening process from appearing, thus, successful screening is
realized. Further, the above structures of the wafers 16 with the
wafer holders 12 allow the isothermal chamber 11 to contain stacked
multiple wafers 16 as shown in FIG. 1. This feature realizes
screening the mass of semiconductor devices 21 simultaneously in a
small space.
[0070] Steps of screening the semiconductor devices 21 on the
semiconductor wafers 16 by the above described burn-in apparatus
will now be described.
[0071] First, pre-test for find out short circuit and the like of
the semiconductor devices 21 is carried out, by which semiconductor
devices 21 having failures unsuitable for screening are eliminated.
More precisely, the fuses 43 of such the unsuitable devices 21 are
cut by laser beam or the like, thus they will not be screened.
[0072] And then, the semiconductor wafers 16 are mounted on the
wafer holders 12. In this step: the wafers 16 are placed on the
stage boards 51 of the wafer holders 12; and sets of the stage
board 51 and the pressure boards 57 are tightened by the fixer
clasps 58. Thus, the electrode chips 55 contact the on-board
pathways 22, and this contact electrically interconnects the bridge
lines 15 and the semiconductor devices 21 on the wafer 16.
[0073] The plurality of the wafer holders 12 on each of which the
wafer 16 is fixed are attached to the slot array 13. The bunch of
wafers 16 and wafer holders 12 are loaded into the isothermal
chamber 11 through the gateway 17.
[0074] After the loading, the controller 14 starts to elevate the
temperature in the isothermal chamber 11 in accordance with a given
program and the like, in response to an instruction given by an
operator of the apparatus or the like.
[0075] When the temperature in the isothermal chamber 11 reaches a
predetermined level, the controller 14 activates the switching Tr
37, 39 and 41 by providing the gate lines 34 with control signals
having a predetermined level. The controller 14 also provides the
semiconductor devices 21 with source voltages via the power lines
31 in order to drive the semiconductor devices 21. And then, the
controller 14 provides the semiconductor devices 21 with test
pattern signals via the signal lines 33, thus, the semiconductor
devices 21 are screened.
[0076] After the screening, the bunch of the wafer holders 12 is
unloaded from the isothermal chamber 11 through the gateway 17. In
the same manner, following bunches of the semiconductor devices 21
are subjected to the screening one after another. Finally, the
semiconductor devices 21 which passed the screening are diced to be
products.
[0077] As described above, the present invention prevents contact
failures caused by thermal expansion, because the electrode chips
55 of the wafer holder 12 completely contact the on-board pathways
22 of the semiconductor wafer 16. This feature realizes successful
screening for the semiconductor devices 21. Since the realized
screening is so secure, only the semiconductor devices 21 actually
having rich reliability will pass the screening. Moreover, the
present invention reduces the steps of the screening, because
preparation of common terminals (pads) on the wafers 16 is
unnecessary. Such the elimination is realized by the complete
connection between the electrode chips 55 and the on-board pathways
22 featured in the present invention.
[0078] Furthermore, multiple stacked semiconductor wafers 16 can be
screened simultaneously, because the on-board pathways 22 are
electrically connected to the bridge lines 15 via the electrode
chips 55. That is, the present invention has an advantage over the
conventional techniques because it realizes screening
simultaneously the mass of semiconductor devices 21 in a small
space.
SECOND EMBODIMENT
[0079] A semiconductor wafer according to a second embodiment of
the present invention will now be described with reference to
accompanying drawings.
[0080] A semiconductor wafer according to the second embodiment is
similar to the semiconductor wafer 16 described in the first
embodiment. This embodiment features the structure of wafer edge
which differs from the wafer 16 of the first embodiment. More
precisely, intervals among the ends of the on-board pathways 22 at
the edge of the wafer 16 of this embodiment are wider than
intervals among them in the device zone of the wafer 16 (inner zone
where the semiconductor devices are formed) as shown in FIG. 5. In
other words, the ends of the wires of the on-board pathways 22 are
scattered at the wafer edge.
[0081] The arrangement of the electrode chips 55 of the wafer
holder 12 will be modified as the structure of the wafer 16 is
modified. That is, the electrode chips 55 are arranged on the
interconnection ring 54 so as to contact the wires of the on-board
pathways 22 respectively. In this case, the electrode chips 55 are
grouped by ends of the on-board pathways 22 being connected to, and
the electrode chips 55 in the same group are connected to each
other by the common pathway 56. For example, the electrode chips 55
being connected to one ends of the power lines 31 are connected to
each other via one common pathway 56; and the electrode chips 55
being connected to one ends the signal lines 33 are connected to
each other via another common pathway 56. In the same manner, the
electrode chips 55 being connected to the other ends of the
on-board pathways 22 are connected to each other via their
corresponding common pathway 56.
[0082] Other structures of the wafer 16, and the structure of the
burn-in apparatus are substantially the same as those described in
the first embodiment. The steps of screening the semiconductor
devices 21 described in the first embodiment are also employed in
this embodiment.
[0083] Aforementioned wide intervals among the ends of the on-board
pathways 22 at the wafer edge are helpful to form the electrode
chips 55 so that the electrode chips 55 themselves coincide with
the positions of the ends of the on-board pathways 22. In other
words, each of the electrode chips 55 does not require its own
minute contact elements (contact electrodes 59 in the first
embodiment) to be respectively connected to the wires of the
on-board pathways 22. As a result, precise mounting of the wafer 16
on the wafer holder 12 can be done without any difficulties in
processing and adjusting.
[0084] The wafer holders 12 described in the above embodiments may
employ other structures which enable the electrode chips 55 to
contact the on-board pathways 22. For example, the wafer holder 12
may have fixer clamps instead of the pressure board 57, which bind
the stage board 51 and the interconnection ring 54. Or, the wafer
holder 12 may have clothespin-like clips which pinches the wafer 16
to hold it. In this case, one side of contact surface of the clip
has the electrode chips 55. The clip has dual function of holding
and connecting. That is, the clip can connect the electrode chips
55 to the on-board pathways 22 completely while holding the wafer
16.
[0085] Various embodiments and changes may be made thereunto
without departing from the broad spirit and scope of the invention.
The above-described embodiments are intended to illustrate the
present invention, not to limit the scope of the present invention.
The scope of the present invention is shown by the attached claims
rather than the embodiments. Various modifications made within the
meaning of an equivalent of the claims of the invention and within
the claims are to be regarded to be in the scope of the present
invention.
[0086] This application is based on Japanese Patent Application No.
H11-068250 filed on Mar. 15, 1999 and including specification,
claims, drawings and summary. The disclosure of the above Japanese
Patent Application is incorporated herein by reference in its
entirety.
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