Monthly Archives: July 2012

The Elephant Has Left the Room – 450 mm is a Go!

It’s the day before Semicon opens up, and we have had a slew of announcements on 450 mm, the biggest of which was the joint ASML/Intel notice that Intel will be taking a share of ASML as a way of funding 450 mm and EUV R&D. Simultaneously imec released that the Flemish government would invest in their upcoming 450-mm facility, and imec and KLA-Tencor declared that a 450-mm capable SP3 450 unpatterned wafer defect inspection tool had been installed at imec.

ASML announced it as a “co-investment program” in which Intel would invest EUR829 million (about $1B) over the next five years, EUR553M of which would be in 450 mm R and D. Intel focused more on the R and D and described the financial details later.

They cited the classic economics of doubling the wafer size, and the potential die cost reduction:

All of which is logical, but ASML has been notably reticent about making any comments on 450-mm R and D in the past, to the point where some industry watchers (including me) have wondered if we would ever get there; if the biggest litho vendor isn’t on board, there won’t be any 450-mm fabs even if all the other equipment companies are ready.

Which brings me to the elephant in the title. Last year at Semicon there was a 450 mm panel, and everyone was pontificating wisely, until Bob Johnson of Gartner commented on "the elephant in the room – ASML has no 450-mm program, so why are we bothering to even talk about it?" (my paraphrasing). Which kind of shut the whole thing down.

However, that particular pachyderm has clearly moved on, and we have an ASML roadmap with both 450 mm and EUV in it:

We won’t have any production tools until 2018, but at least a huge barrier to adoption is lifted; now there are just the simple engineering tasks of getting a substrate the size of a turkey platter exposed with patterns with feature sizes of 14nm or smaller. Has anyone said that this industry is crazy?

By coincidence Mike Splinter of Applied Materials was speaking at the imec Technology Forum, and he commented that 300-mm had just about paid off its development costs as of now, roughly 14 years after the launch of the first systems. He guesstimated the costs for developing 450 mm as $15 – 20B, with an as yet unknown payoff time. (Has anyone said that this industry is crazy?) However,  he also said this time last year that Applied would spend over $100M on 450 mm and that "450 mm is going to happen."

Clearly Intel has recognised that if it wants 450 mm to go forward, then it has to pony up some cash to encourage the litho side, and it is already invested in the consortium being set up at Albany. For anyone interested in the financial side of the deal, check out the press releases linked above, or watch ASML CFO Peter Wennink in a video.

Looks like 450 mm is actually going to happen!

Sony’s PS Vita Uses Chip-on-Chip SiP – 3D, but not 3D

At the tail end of last year Sony released their PlayStation Vita, and it was duly torn down by iFixit and others. In due course we took it apart too, though we didn’t post it on our teardown blog.

Sony CXD5315GG in the PlaySation Vita

Inside we found the usual set of wireless chips, motion sensors, and memory, but the key to the increased performance of the PS Vita is the Sony CXD5315GG processor, a quad-core ARM Cortex-A9 device with an embedded Imagination SGX543MP4+ quad-core GPU.

Above I said that we found memory, but actually the only discrete memory that we found on the motherboard was 4 GB of Toshiba flash; and Sony’s specification states that there is 512 MB (4 Gb) regular RAM, plus 128 MB (1 Gb) VRAM (video RAM). In a phone that would tell me that there is memory in a package-on-package (PoP) configuration, mobile SDRAM in the top part and the processor in the bottom part.

However, when we took the part off the board and did a set of x-rays, the side view proved me wrong – it’s a stack, and the close-up shows that there appear to be five dies in there, a thick die at the base, a thinner one immediately on top and three smaller die on top of that. The second die down could be a spacer, since there don’t seem to bond wires going to it.

Side x-ray images of Sony CXD5315GG

This immediately led us to speculate – if the second die up is the VRAM, is it wide I/O DRAM, and is it using through-silicon vias (TSVs)? Time for a real cross-section to check that out, and almost predictably we were disappointed:

Sony CXD5315GG package cross-sectioned

This type of face-to-face connection showed up back in 2006 in the original Sony PSP, and Toshiba had dubbed it “semi-embedded DRAM”, now they are calling it “Stacked Chip SoC”. The ball pitch is an impressive ~45 µm, almost as tight as TI’s copper pillars, but they are staggered to achieve 40-µm pitch.

So what are the five chips that are in the stack? At the base we have the processor chip; face to face with it is a Samsung 1-Gb wide I/O SDRAM; and the top three dies comprise two Samsung 2-Gb mobile DDR2 SDRAMs, separated by a spacer die, and conventionally wire-bonded. The base die is ~250 µm thick, and the others ~100 – 120 µm.

When we look at the die photos of the processor and the 1-Gb memory, we can see that they are purposely laid out for the stacked-chip configuration, since in the centres of both is an array of matching bond pads.

Die photos of the Sony CXD5315GG (left) and Samsung 1-Gb wide I/O SDRAM with bond pad arrays annotated

Close examination reveals that there are 1080 pads in two blocks of 540 (2 sub-blocks of 45 rows of 6 pads), so likely 2 x 512 bit I/O operation, possibly sub-divided into 4 x 128.

Wide I/O bond pad arrays in Sony CXD5315GG (top) and Samsung SDRAM

Last year at ISSCC Samsung described a similar wide I/O DRAM using TSVs [1], claiming a data bandwidth of 12.8 Gb/s, four times the bandwidth of an equivalent LPDDR2 part. I doubt that the authors expected their design to be in a volume consumer device before the end of the year, but that seems to be what happened!

Chip architecture of Samsung 1Gb Wide-I/O DRAM and SEM image of microbumps (Source: Samsung/ISSCC)

This uses similar I/Os, but not the same as, the JEDEC wide I/O standard issued earlier this year (which calls for 50 rows of 6 pads in each block), and of course it predates it by about a year.

By combining the processor with the different memories in the same package in the Vita, Sony and Toshiba have produced one of the few true system-in-package (SiP) parts that we have seen. And I would call it 3D, even though industry convention is now restricting that term to TSV-based parts – so it’s not 3D, in our current argot.
In a way this device highlights the commercial barriers to introducing TSVs into the SiP world, since not only do the corresponding parts have to be designed to suit the I/Os, but at least for a two-stack the technology is already there; so the performance cost/benefit has to be critical enough to require TSVs for that third and more die. Admittedly the demands on mobile devices are increasing at an astounding pace, but it still seems a while before we’ll see TSVs in commercial devices. Time will tell!

[1] J-S. Kim et al., A 1.2V 12.8GB/s 2Gb Mobile Wide-I/O DRAM with 4Ã??128 I/Os Using TSV-Based Stacking, ISSCC 2011, pp. 496 – 498.