Method for Transporting Rough-Edge Wafers into Prober by Stacking on Drilled Carrier.
Original Publication Date: 2009-Oct-01
Included in the Prior Art Database: 2009-Oct-01
The proposed idea uses drilled holes in a flat, hard surface, e.g. solderless silicon wafer, to allow vacuum to pass through to a smaller or partial wafer that it would carry on top of it. Through use of this, the test wafer is held flat, so it can be properly transported, aligned and contacted on an automated wafer prober.
Method for Transporting Rough-Edge Wafers into Prober by Stacking on Drilled Carrier .
Disclosed is a device for the transportation of a rough-edged wafer or piece of wafer that uses holes in the device to pass the vacuum to the test wafer. An embodiment may consist of a solderless wafer to transport another, smaller wafer.
The problem addressed by this invention is to transport a wafer, or part of a wafer into a prober, if it would not be able to do so on its own. Some wafers have rough edges as a consequence of processing, which does not allow the optical sensor used by the prober to align the wafer properly, and therefore does not bring the wafer onto the chuck. The partial wafers have a similar problem, as they cannot be safely transported from the wafer table into the machine, and no alignment can be made.
This is mainly a problem if the wafer's edge become compromised or if the edge
is rough to begin with. It also becomes a problem when only a single chip or fragment of a wafer needs to be tested. At the current time, the method for solving this problem has been to tape the wafer or fragment to the top of a 300 mm wafer. This has some serious drawbacks. Since a standard 300 mm wafer has solder bumps, the tested wafer does not stay flat if taped to the top. This causes difficulties in the fine alignment, which is done by an optical sensor. If a solderless wafer is used and the wafer to be tested is taped to the top, this still does not solve the problem, as both the support and test wafer have warping characteristics. This can especially be a problem with thin wafers. These problems also surfaces when the prober attempts to contact the wafer. Since the tested wafer does not lay flat, it deflects when the prober makes contact, so the connection made is not very strong. The additional solution is required because a strong connection is needed in order to accurately test the chips on the wafer.
The basic concept of this idea is to create a 300mm circular carrier out of a hard, flat material with holes in it, e.g. alter an existing 300mm wafer without solder bumps, to allow vacuum to pass through to the 200mm wafer that is sitting on top. Holes will be drilled out of the carrier in specific points where the vacuum holes are on the chuck (what holds the wafer while inside the prober).
Some of the advantages of the proposed solution are:
The idea allows for the 200mm wafer to sit flat on top of the 300mm
Since the 200mm wafer is flat, good contact will be made by the prober.
The 300mm circular carrier could be a recycled wafer that has been
stripped of its solder bumps or a new wafer that has n...