As we said last week, Chipworks’ lab staff quickly decapsulated and imaged the A4 processor chip that has received so much comment in the last few months. Inside we found an APL0398 chip, which we speculate is the next-generation processor from the APL0298 that was in the iPhone 3GS.
Die Mark on Apple A4 Processor
The die was approximately 7.3 mm square, giving a die area of 53.3 mm2, which is somewhat smaller than the 71.8 mm2 of its 65-nm predecessor that we looked at last year – a 26% shrink, so assuming comparable functionality, this could well be a 45-nm part.
Die Photo of Apple APL0398 at Top Metal
When we compare the top-metal layout, it does look rather like the APL0298, so we can probably assume that it has similar capabilities, with the possible exception of the 64-bit memory path.
Die Photo of Apple APL0298 at Top Metal
However, speculation as to the node is not evidence, so back into the lab it went, this time to do a cross-section and look at some transistors. That showed it to be fabbed in a nine-metal process, eight copper layers plus an aluminum bond pad/redistribution layer.
Zooming in a bit, we can get some idea of transistor density and the metal/dielectric structure – here we see four levels of copper with barrier layers and surrounding dielectric, the pre-metal dielectric (PMD), some transistors and shallow-trench isolation (STI).
SEM Cross-Section of Apple APL0398
Closer examination of the sample shows that the contacted gate pitch is ~190 nm, and the 1X metal half-pitch is ~83 nm, both of which are right in the range of the other 45-nm parts we have looked at in the last couple of years.
So now we’ve confirmed that the A4 is a 45-nm part; the common supposition has been that it was fabbed by Samsung, similar to its predecessors in the iPhones and iPods. As it happens, we have looked at another Samsung-fabbed 45-nm part, the Xilinx Spartan-6. Below is a similar image from our Xilinx analysis.
SEM Cross-Section of Xilinx Spartan-6
The staining is slightly different, but the metal profiles, the nature of the PMD, the way the contact etch-stop layer wraps around the transistors, and the style of STI are enough to convince me that the A4 is from the same process as the Xilinx chip.
The industry commentators appear to be right – the A4 is indeed a 45-nm part, and it’s manufactured by Samsung. Given that the associated two Gb of SDRAM and the 64 Gb of flash in the iPad are also Samsung parts, the Korean giant has achieved significant design wins, and also pushed forward their ambition to be one of the top foundries.
For those interested in the full teardown and die analysis of the iPad, it is of course on our website here.