Hybrid TCA to allow low cost test carrier for high power burn-in and test applications
Original Publication Date: 2010-Jan-22
Included in the Prior Art Database: 2010-Jan-22
A hybrid structure for a Temporary Chip Attach (TCA) Carrier is proposed. It consists of an organic carrier base with a ceramic interposer on which a Semiconductor chip can be temporarily attached to for test purposes. This enables a Known Good Die (KGD) process in a chip manufacturing flow. The ceramic interposer matches the CTE of the die to allow reliable mounting of the die with the fragile C4 interconnect required for damage free shear of the die from the TCA post test. The organic carrier provides a low resistance path for interfacing signal and power delivery from the test socket to the ceramic interposer and up into the die.
Hybrid TCA to allow low cost test carrier for high power burn -in and test applications
In multi-chip modules (MCM) manufacturing test methodologies are required to provide known good die (KGD) for Bond and Assembly onto the MCM carriers to minimize rework of the assembled MCMs. Much of the testing to identify KGDs exist at wafer test, but in areas where reliability or performance require, a temporary chip attach (TCA) carrier may be required to expose the singulated die to extreme temperatures and voltages of Burn In. These conditions tend to cause acceleration of early life failures, so modules are not shipped with silicon that have defects that would manifest themselves as early life failures in the customer's installation. This helps minimize warranty costs and maintain customer satisfaction. In addition Burn In can be used to force NBTI (
Negative bias temperature instability) gate threshold shifts expected over the life of the
product, so that performance guardbands can be minimized as the shift is already accounted for. Burnin could be done at the MCM level, but identification of failing die after MCM bond and assembly is expensive and the tooling to support power and thermal management is much more difficult when burning in an MCM than a Single Chip Module (SCM) of which a TCA is a special manifestation of.
A cross section of a typical TCA representing the state of the art is shown in Figure 1.
A chip with C4s attached is joined to a TCA carrier such that the metallurgical (or mechanical)
between the c4 and TCA carrier will not result in damage to the c4s when the chip is sheared off. Slightly elevated temperatures during the shear operation may help accomplish this. The TCA carrier must be structurally sound enough to withstand elevated temperature testing as well as CTE (coefficient of thermal expansion) matched to the die in order that the electrical integrity of the c4 attachments is not compromised during testing. Present inexpensive materials used for TCAs include alumina with molybdenum conductors embedded for signal and power connectivity from the LGA pads on the bottom of the TCA carrier to the chip c4 connections. The alumina technology employed for this results in a very poor relationship between vertical and horizontal conduction paths. The horizontal conduction paths could be an order of magnitude higher in resistance than the vertical paths. The horizontal paths are the result of traces, meshes, or planes screened onto dielectric layers which are stacked to the thickness of the TCA. The vertical paths are vias which have significantly more cross-section than the horizontal paths. The effect of this disparity in conduction is that the
current supplied to the chip under test does not spread very much from under the...