Large contactor with multiple, aligned contactor units

Details Large contactor with multiple, aligned contactor units Large contactor with multiple, aligned contactor units

1998-11-19

2004-02-10

Abrams, Neil (Department: 2839)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C228S180220, C361S760000

Reexamination Certificate

active

06690185

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a method of fabricating a large area multielement contactor and, more particularly, to a method of mounting multiple contactor units on a support substrate with precise alignment.
BACKGROUND OF THE INVENTION
Modern integrated circuits include many thousands of transistor elements with many hundreds of bond pads disposed in close proximity to one another (e.g., 5 mils center-to-center). The layout of the bond pads need not be limited to single rows of bond pads disposed close to the peripheral edges of the die (see, e.g., U.S. Pat. No. 5,453,583). The proximity and number of pads is a challenge to the technology of probing devices.
Semiconductor devices are generally fabricated on a wafer of silicon, with many devices on a single wafer. Modern technology uses 8-inch (200-cm) wafers, and is moving to 12-inch (300-cm) wafers. Essentially every single device fabricated on a wafer needs to be tested by probing. Probing more than one device at a time is particularly advantageous.
Modern probing equipment can probe 32 or more semiconductor devices at the same time.
However, this is only a small fraction of the total number of die on a wafer. There has been great interest in developing a probing system that can contact more, preferably all die on a wafer at the same time.
Generally, previous attempts at implementing schemes for partial or full wafer-level testing have involved providing a single test substrate with a plurality of contact elements for contacting corresponding pads on the wafer being tested. This may require extremely complex interconnection substrates and may include as many as tens of thousands of such contact elements. As an example, an 8″ wafer may contain 500 16 Mb DRAMs, each having 60 bond pads, for a total of 30,000 connections. In one representative embodiment, there are 30,000 connections between the wafer under test (WUT) and the test electronics. Moreover, the fine pitch requirements of modem semiconductor devices require extremely high tolerances to be maintained when bringing the test substrate together with the wafer being tested.
To effect reliable pressure connections between contact elements and, e.g., a semiconductor device, one must be concerned with several parameters including, but not limited to: alignment, probe force, overdrive, contact force, balanced contact force, scrub, contact resistance, and planarization. A general discussion of these parameters may be found in U.S. Pat. No. 4,837,622, entitled HIGH DENSITY PROBE CARD, incorporated by reference herein, which discloses a high density epoxy ring probe card including a unitary printed circuit board having a central opening adapted to receive a preformed epoxy ring array of probe elements.
A more sophisticated probe card uses resilient spring elements to make contact with a device on a wafer. Commonly assigned parent application Ser. No. 08/789,147, now U.S. Pat. No. 5,806,181, entitled “Contact Carriers for Populating Larger Substrates with Spring Contacts”, issued Sep. 15, 1998, discloses such a probe card in connection with what in that patent is FIG. 5, which is reproduced in this disclosure as FIG.
1
A.
FIG. 1A
illustrates an embodiment of a probe card assembly
500
which includes as its major functional components a probe card
502
, an interposer
504
and a space transformer
506
, and which is suitable in use for making temporary interconnections to a semiconductor wafer
508
. In this exploded, cross-sectional view, certain elements of certain components are shown exaggerated, for illustrative clarity. However, the vertical (as shown) alignment of the various components is properly indicated by the dashed lines in the figure. It should be noted that the interconnection elements (
514
,
516
,
524
) are shown in full, rather than in section.
The probe card
502
is generally a conventional circuit board substrate having a plurality (two of many shown) of contact areas (terminals)
510
disposed on the top (as viewed) surface thereof. Additional components (not shown) may be mounted to the probe card, such as active and passive electronic components, connectors, and the like. The terminals
510
on the circuit board may typically be arranged at a 50-mil pitch. The probe card
502
is suitably round, having a diameter on the order of 12 inches.
The interposer
504
includes a substrate
512
. Resilient interconnection elements
514
are mounted to and extend downward (as viewed) from the bottom (as viewed) surface of the substrate
512
. Resilient interconnection elements
516
are mounted to and extend upward (as viewed) from the top (as viewed) surface of the substrate
512
. Various spring shapes are suitable for the resilient interconnection elements
514
and
516
. These elements preferably are composite interconnection elements with a soft core and hard shell. In another preferred embodiment, the resilient interconnection elements comprise a resilient material in a resilient shape. In one preferred embodiment, tips of interconnection elements
514
and
516
are at a pitch that matches that of the terminals
510
of the probe card
502
.
The interconnection elements
514
and
516
are illustrated with exaggerated scale, for illustrative clarity. In certain preferred embodiments, the interconnection elements
514
and
516
extend to an overall height of 20-100 mils from respective surfaces of the interposer substrate
512
.
The space transformer
506
includes a suitable circuitized substrate
518
, such as a multilayer ceramic substrate having a plurality of terminals
520
disposed on the lower (as viewed) surface thereof and a plurality of terminals
522
disposed on the upper (as viewed) surface thereof. The terminals suitably may be contact areas or pads, or other structures known in the art. In this example, the lower plurality of contact pads
520
is disposed at the pitch of the tips of the interconnection elements
516
(e.g., 50 mils), and the upper plurality of contact pads
522
is disposed at a finer (closer) pitch (e.g., 25 mils). These resilient interconnection
514
and
516
elements are preferably, but not necessarily, composite interconnection elements.
A plurality of resilient interconnection elements
524
are mounted directly to the terminals
522
and extend upward (as viewed) from the top (as viewed) surface of the space transformer substrate
518
. The resilient interconnection elements function as probes or probe elements. As illustrated, these resilient interconnection elements
524
are suitably arranged so that their tips (distal ends) are spaced at an even finer pitch (e.g., 5 mils) than their proximal ends, thereby augmenting the pitch reduction of the space transformer
506
. These resilient contact structures (interconnection elements)
524
are preferably, but not necessarily, composite interconnection elements.
A problem associated with an array of contact elements, including spring contacts, is that often the terminals of an electronic component are not perfectly coplanar or are not aligned in an X-Y direction or in angular rotational direction with the contact pad. Contact elements lacking in some mechanism incorporated therewith for accommodating these “tolerances” (gross non-planarities) will be hard pressed to make consistent contact pressure contact with the contact pads of the electronic component.
Heretofore, it has been difficult and expensive to fabricate an assembly of contact elements of arbitrary size or shape to reliably make contact with the terminals of devices having a large size or an unusual shape.
SUMMARY OF THE INVENTION
Briefly stated, a method of manufacturing a contactor is provided wherein a plurality of contactor units is mounted on a support substrate such that contact elements attached to the contactor units align with a plurality of contact pads on a device. More particularly, a method of fabricating a segmented contactor according to the present invention comprises the steps of providing a support substrate, providing a contactor unit hav

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