US 5,506,499 A · Multiple probing of an auxilary test pad which allows for reliable bonding to a primary bonding pad

Abstract

Each touchdown of a probe card during wafer-sort testing of integrated circuits can leave a gouge in the pad metal. These gouges reduce the reliability of any wire bond to that pad as voids can be left in the bond where the gouges are. A second auxiliary test pad is adjacent to the primary bonding pad. This second auxiliary test pad is electrically connected to the primary bonding pad. Thus probes can land on the second auxiliary pad rather than the primary pad. Gouges are made on the second pad rather than the primary pad. This second test pad allows for multiple probing. Multiple probing is needed for testing large embedded memories on large logic chips such as video controllers. The yield of large memories is increased by laser repair. Probing and testing is required both before and after laser repair using a memory test machine. However, a logic test machine is used to test the logic controller portion of the IC, but cannot generate the millions of test vectors needed to fully test the embedded memory. Only the pins that are used for both memory testing and logic testing need the second auxiliary pads. Thus the probes can land on the second test pads multiple times while the wire bond is made to the primary bonding pad.

Claims19

Dependent claims

A large-scale integrated circuit comprising:

a plurality of bonding pads;
a logic controller connecting to each of the plurality of bonding pads;
a memory embedded in the large-scale integrated circuit, the memory being accessed by the logic controller but not directly accessible by the plurality of bonding pads in a normal mode of operation;
a subset of shared pads in the plurality of bonding pads;
auxiliary test pads having a length and width sufficiently large for probing by a wafer sort tester but insufficiently large for forming a wire bond to the auxiliary test pad;
wherein each shared pad in the subset of shared pads is electrically connected to a different auxiliary test pad;
and
multiplexer means, connected to the shared pads, for connecting the shared pads to the logic controller during the normal mode of operation but connecting the shared pads directly to the memory during a memory test mode;
whereby the auxiliary test pads have a size sufficient for wafer-sort probing, but the bonding pads electrically connected to the auxiliary pads must be used for wire bonding.

6 more elements

A method for testing a complex integrated circuit having a logic portion and an embedded memory, the method comprising:

applying sufficient force to a first probe card to make electrical contact with auxiliary test pads on a die on a wafer, the die containing the complex integrated circuit;
testing the embedded memory on the die on the wafer using the first probe card to connect the die to a memory test machine, the memory test machine applying voltages representing test inputs to the die and comparing expected outputs to voltages output from the die;
transporting the wafer from the memory test machine to a logic test machine;
applying sufficient force to a second probe card to make electrical contact with primary bonding pads on the die on the wafer, each auxiliary test pad being electrically connected on the die to one of the primary bonding pads;
testing the logic portion of the die on the wafer using the second probe card to connect the die to the logic test machine, the logic test machine applying voltages representing test inputs to the die and comparing expected outputs to the voltages output from the die;
sawing the wafer into individual die and separating out good die that did not fail when tested on the logic test machine and did not fail when tested on the memory test machine;
and
bonding wires to the primary bonding pads of the good die but not bonding to the auxiliary test pads,
whereby the auxiliary test pads are used for testing the embedded memory.

6 more elements

Dependencies are inferred from the claim text.

Multiple probing of an auxilary test pad which allows for reliable bonding to a primary bonding pad

Life of this patent

Multiple probing of an auxilary test pad which allows for reliable bonding to a primary bonding pad

Life of this patent

Abstract

Claims19