Adding Flash to ASICs

Some applications need to combine Flash with an ASIC. Tekmos offers two approaches for doing this.

The first approach is to just use a process that supports Flash memories. While this sounds simple, it does introduce manufacturing complexities. Many Flash processes require an additional license for both the Flash process and the Flash IP. This adds to the NRE.

Once Flash has been included in the design, there is additional testing that must be done, and this testing must be done at probe. Depending on the size of the flash, it may be necessary to add redundancy to the flash to fix flash defects. And in order to test data retention, it is necessary to write a pattern into the flash, then bake it at high temperature for 24 hours, and then re-probe it to ensure that the data is still there. The probe hardware adds to the NRE costs, while the two-pass probe testing adds to the unit price. On the other hand, the addition of a probe test saves money by improving the final test yield. Whether this is a net benefit depends on the overall yield and the package cost. The question of whether the additional NRE charges are worth the advantages of embedded Flash depends on the unit volume.

A second approach to embedded Flash is to purchase a Flash die, and use a stacked die approach in the assembly of the ASIC. This approach has both advantages and disadvantages. The advantage is that you bypass all of the flash manufacturing issues and additional NREs. You can also include large amounts of flash that might not be economically possible in the process node you are using for the rest of your ASIC. And the lack of a Flash NRE allows flash to be economically included in small volume ASICs.

The disadvantages are primarily economic. You will have to buy megabytes of Flash, even if you only need a few kilobytes. The assembly cost is a function of the number of bond wires, and the interconnect between the ASIC and the Flash can double the packaging cost. This can be mitigated somewhat by using serial Flash memories which have only 8 connections. Serial Flash memories can be much less expensive than the parallel Flash memories, but they can be harder to use from a design point of view.

No matter what your Flash requirements are, Tekmos has an approach that will economically add Flash to your design.

Date

2016-09-13