Probe tip card for the testing of semiconductor components

Details Probe tip card for the testing of semiconductor components Probe tip card for the testing of semiconductor components

1998-12-23

2002-03-12

Karlsen, Ernest (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S758010, C324S761010

Reexamination Certificate

active

06356090

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of semiconductor components, and, more particularly, to a probe tip card for testing components on a semiconductor wafer.
BACKGROUND OF THE INVENTION
To reduce manufacturing costs and times, a majority of tests performed on semiconductor components, i.e., integrated circuits and discrete components, are presently carried out directly on the silicon wafers when they come off the production line before the cutting operation. To perform the tests, a tester provides electrical signals to the integrated circuit chips using a probe tip card adapted to their topology. For this purpose, the silicon wafer containing the chips to be tested is moved towards the probe tip card so that the probe tips, or needles, rest on the contact pads provided on the chips. The probe tip card is part of a testing machine. A processor is used for the automatic management of the testing machine. It also provides for the running of the test sequences, the storage of the test results, and the identification of defective chips.
There are three kinds of commonly used probe tip cards. They are manufactured according to three different technologies. These technologies are known as the “cantilever” technology, the “membrane” technology, and the “vertical” technology.
A probe tip card made according to the “cantilever” technology is shown schematically in a sectional view in
FIG. 1A
, and in a top view in
FIG. 1B. A
probe tip card
10
of this kind has several needles
11
positioned horizontally, i.e., parallel to the surface of the card, and around a window
15
formed in the center of the probe tip card
10
. This type of card is generally connected to an epoxy or ceramic printed circuit support
12
. The needles
11
are fixed to the support
12
either by soldering or by bonding with an epoxy adhesive (reference
13
). Conductive wires
16
are used for the electrical connection of the needles
11
to the tester
19
by the contacts of the printed circuit.
For greater clarity, only one chip
21
to be tested is shown in the silicon wafer
20
in FIG.
1
A. This chip has contacts
22
. During the tests, the silicon wafer
20
is moved towards the probe tip card
10
so that the needles
11
are supported on the contact pads
22
, and thus provide an electrical contact between the chip
21
and the tester
19
through the probe tip card
10
.
The shape of the needles
11
allow for a certain elasticity. A retention ring
14
is used to hold the needles so that they are pointed towards the contacts
22
of the circuit to be tested. Furthermore, the ends of the needles
11
are curved to form a claw. Thus, during the tests, when the contacts
22
of the chips to be tested are pressed against the needles
11
of the probe tip card
10
, the pressure provides a side motion of the needles
11
. This side motion prompts a clawing effect on the contacts
22
. This clawing enables the removal of a surface layer of aluminum oxide that is formed over the contacts
22
, and thus enables very high quality electrical contact to be established.
A card of this kind allows for the performance of up to 700,000 tests. However, its cost of manufacture is still quite high. A major drawback related to the use of these probe tip cards
10
is that their handling requires great precautions. The needles
11
exert a large amount of force on the contacts
22
of the chips
21
. Care is needed to avoid applying excessive pressure when the chips
21
to be tested and the probe tip card
10
come into contact with each other to avoid damaging the contacts of the chips
21
. Such damage could cause the breakage of the passivation layer around the contact pads
22
. This deterioration of the contact pads
22
for the chips
21
would present problems since a chip
21
requires tests at different stages of its assembly into modules. Consequently, the number of tests are limited to prevent excessive deterioration of the chip
21
caused by the testing operation itself.
The ends of the needles
11
must be located in the same plane so that each of them can set up an electrical contact with a contact pad
22
of a chip
21
being tested. This planar characteristic may be obtained by working on the shape of the needles
11
after they have been fixed in the probe tip card
10
. The trueing, however, is a laborious and lengthy task. Furthermore, this trueing of the needles
11
often deteriorates after the needles
11
have been pressed between the contact pads
22
because they tend to buckle. As a result, constant maintenance is required.
Furthermore, even an accurate trueing of the needles
11
cannot compensate for the significant differences in the heights of the contact pads
22
of the chips
21
being tested. To compensate for these differences, greater pressure would have to be applied to enable a needle
11
to be able to set up contact with a contact pad
22
that is shorter than the others. However, in this case, such pressure would be too excessive and the other contact pads
22
, whose height is greater, would be damaged or even rendered unusable. Furthermore, the difficulty of trueing the needles
11
makes the probe tip card
10
practically impossible to repair.
Currently, the chips
21
are being increasingly miniaturized to a size where the space between the contact pads
22
is also reduced. This space is generally in the range of 200 &mgr;m, 150 &mgr;m and even less than 100 &mgr;m. To adapt to current chips and enable several of them to be tested in parallel, the probe tip cards must have inter-tip gaps of the same magnitude. The needles
11
of the cantilever cards have a conical shape with a diameter that is greater at the ends fixed to the support of the printed circuit. It would therefore be difficult to place these needles side by side. Consequently, a card manufactured according to the cantilever technology cannot be used to test several chips in parallel because it is not cost effective.
A probe tip card made according to the “membrane” technology is schematically shown in a sectional view in
FIG. 2. A
probe tip card
40
of this kind has a flexible printed circuit
41
, also called a membrane, fixed to a rigid ring support
45
. Metal bosses
42
are made on the flexible printed circuit
41
. A bias is maintained on the membrane
41
, for example, by a spring
43
held by a lid
44
. An electrical contact is set up between the bosses
42
and the contact pads
22
of the chips to be tested when pressure is applied to the silicon wafer
20
.
However, to enable constant voltage to be maintained between the metal bosses
42
, the dimensions of the membrane
41
must be limited. Furthermore, because of the significantly large size of the bosses
42
, the spacing between the bosses
42
cannot be reduced sufficiently to adapt to the small size of current chips. Consequently, the membrane type cards cannot be used to test several chips in parallel. Furthermore, the bosses
42
are all connected to one another by the membrane in such a way that they are not independent. The motion of one boss
42
causes the motion of neighboring bosses
42
. The membrane furthermore has great flexibility so that it is very difficult to maintain tension so that the bosses
42
are all parallel and located in one and the same plane. This type of card therefore does not make it possible to easily compensate for the significant differences in height between the contact pads.
Finally, forming a probe tip card of this kind is very costly. Furthermore, given that the metal bosses
42
are made by deposition directly on the flexible printed circuit
41
, they cannot be interchanged and the card can not be repaired. Finally, the lifetime of this type of card is fairly limited since it allows for only about 250,000 tests to be performed.
A probe tip card made according to vertical technology has needles positioned vertically, i.e., perpendicular to the surface of the card. Two types of cards are presently being made according to this vertical technology. One is the “cobra” card

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