Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2002-07-30
2004-07-06
Karlsen, Ernest (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S754090
Reexamination Certificate
active
06759861
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for providing electrical contacts. More specifically, the present invention relates to membrane probe cards used in making a large number of electrical components.
BACKGROUND OF THE INVENTION
As more and more capability is being designed into electronic components, such as microprocessors, the components are becoming increasingly complex. The more complex an electrical component becomes, the greater number of semiconductor device fabrication steps needed to form the electrical component. Semiconductor devices, such as microprocessors, are generally made from a wafer of semiconductive material. Many individual semiconductor devices are formed on a single wafer. All of the devices are made simultaneously on the wafer. Hundreds of individual semiconductor processes, which include deposition of material, ion implantation, etching, and photolithographic patterning, are conducted on a wafer to form a number of individual semiconductor devices. The wafers are sizeable. As a result, the effectiveness of each semiconductive process on each device may vary somewhat. In addition, each step or semiconductive process used to form the devices is not necessarily uniform. Generally, the semiconductive process has to perform within a desired range. The end result due to variations in the semiconductive processes as well as the variation in position is that the semiconductive devices formed may vary from one wafer to another. In addition, the semiconductive devices may vary from other semiconductive devices on the wafer.
The current practice is to test all the semiconductor devices on a wafer prior to singulation. Generally, two tests are conducted. The first test is conducted to determine if any of the individual semiconductive devices on the wafer are bad. A second test is conducted to determine a performance parameter for the good semiconductive devices on the wafer. For example, currently wafers have up to 300 microprocessors. Of course, the number of devices formed on a wafer will be higher in the future. Each of these microprocessors is tested to determine if the microprocessor is good. The speed of the microprocessor is determined in a second test. Once measured, the speed of the microprocessor is saved and the location of the microprocessor on the wafer is noted. This information is used to sort the microprocessors based on performance at the time the wafer is sliced and diced to form individual dies, each of which has a microprocessor thereon.
Each semiconductive device formed on a wafer has a number of electrical contacts. To test all the semiconductive devices on a wafer at once, many, if not all of the electrical contacts, have to be contacted. For example, testing a number of individual contacts on a wafer commonly requires upwards of 3000 different individual contacts to be made across the surface of the wafer. Testing each contact requires more than merely touching each electrical contact. An amount of force must be applied to a contact to break through any oxide layer that may have been formed on the surface of the contact. Forming 3000 contacts which are not all at the same height and not all in the same plane is also difficult. As a result, a force has to be applied to the contacts to assure good electrical contact and to compensate for the lack of planarity among the contacts.
FIG. 1
shows a membrane probe card
100
which is currently used to conduct high frequency sort and test procedures. The membrane probe card
100
includes a rigid substrate
110
and a plurality of probes
120
. The probes
120
include an attached end
122
and a free end
124
. The free end
124
of the probe
120
is used to contact an individual die
130
. More specifically, the free end
124
of the probe
120
is used to contact individual electrical contacts
132
on the die
130
. Only one die
130
is shown in FIG.
1
. It should be noted that a wafer includes many dies that have not been sliced or diced into individual dies. The probe
120
includes a sharp bend
126
and also includes a more gentle bend
128
. The more gentle bend
128
allows the probe
120
to act as a leaf spring. As shown in
FIG. 1
, the electrical contacts
132
of the die
130
have just come into contact with the individual probe
120
and specifically the free end
124
of the probe
120
.
To overcome nonplanarity among the contacts
132
and to assure good electrical contact by passing through any oxidation layer on the contacts
132
, the die is over driven into the rigid substrate
110
. In other words, the die
130
or device under test is pressed into the probes
120
to assure that the each electrical contact
132
is contacted by a probe tip
124
, and to assure that the oxidation layer has been punctured, so that good electrical contact is made. As shown by the phantom lines in
FIG. 1
, the device under test
130
is more closely spaced with respect to the substrate
110
so that the probes deflect and produce a larger force at the contacts
132
.
The currently used membrane probe card system has a number of shortcomings. Among the shortcomings is the difficulty in controlling the amount of force produced by the probe tip. The amount of force produced at the probe tip
124
is related to the deflection of the spring shaped probe
120
. If the planarity of the contacts
132
varies widely, the deflection of individual probes
120
also varies. In turn, the force at each probe tip
124
also varies widely and is difficult to control. Overdriving the probe cards not only causes variation in the force produced by the probe
120
, but also causes damage to both the probe tip
124
and the product or device under test
130
.
FIG. 2
shows a side view of a prior art membrane probe card
200
. The membrane probe card includes a substrate
210
and a membrane
230
. The membrane
230
is attached to the substrate
210
. Attached to the membrane are a plurality of contacts
220
. The contacts
220
are short and do not accommodate a lack of planarity. Any lack of planarity is accommodated by the membrane
230
. Membrane probe card cards
200
also have shortcomings. The shortcomings include the fact that the membrane
230
may be damaged when the device under test is overdriven into the membrane probe card
200
.
Thus, there is a need for a probe card which allows for force control at the probe tips so that the components of the probe card or the device under test are not damaged during testing. There is also a need for a probe card that has a more uniform or constant force at the probe tip.
REFERENCES:
patent: 2918648 (1959-12-01), Ludman et al.
patent: 4112364 (1978-09-01), Katz
patent: 4340858 (1982-07-01), Malloy
patent: 5825192 (1998-10-01), Hagihara
patent: 5926029 (1999-07-01), Ference et al.
patent: 6084421 (2000-07-01), Swart et al.
Intel Corporation
Karlsen Ernest
Schwegman Lundberg Woessner & Kluth P.A.
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