O'Boyle MAPLD 2005/P1023 1 Digital Design Obsolescence John O’Boyle For MAPLD September 2005 ilitary, Aerospace, and High Reliability IC Manufacture
Jan 14, 2016
O'Boyle MAPLD 2005/P10231
Digital Design Obsolescence
John O’BoyleFor MAPLD September 2005
Military, Aerospace, and High Reliability IC Manufacturer
O'Boyle MAPLD 2005/P10232
Defense Programs Still Need OLD ICs
• 30 Year Old ICs Are Still in Use in many modern High Reliability, Military, and Aerospace applications.
• Combining New Technologies and older devices leave Mil/Aero OEMs challenged with IC sourcing due to obsolescence.
• The Fabrication of Obsolete ICs Is Not Attractive due to low returns and matching original designs.
O'Boyle MAPLD 2005/P10233
Issue : Diminishing Supply• In Some Cases the Parts
Just Vanish:– Take, for example, the Dual
RS-422 Line Drivers to the right
– National Semi unilaterally discontinued the supply of these devices on April 21, 2005.
– Why? Because they simply ran out, no close monitoring of the supply
– This means even the best managed programs may be vulnerable.
O'Boyle MAPLD 2005/P10234
TODAY’s Key Challenge
How Does a Mil/Aero OEM Obtain Reliable, Accurate Reproduction of
Older Parts?
or
How Do They Entice the IC Foundry to Build Such Replacement Parts?
O'Boyle MAPLD 2005/P10235
Factors for Consideration• Buy Entire Remaining Inventory; But that’s
very expensive and many various Gov’t regs limit requisition quantities. – And, as a corollary to the RS-422 example, that is still
no guarantee; demand can outstrip supply.
• Use Commercial Parts From the Beginning; But they, too, are diminishing and are not suitable in all applications.
• So, do we look to the foundry for a solution?
Let’s See …
O'Boyle MAPLD 2005/P10236
1. Foundry : Low VolumesA Fundamental Disconnect
• An Illustration – Teledesic (the early days)– Almost 1000 satellites (Close enough for this
illustration)– Assume 100 “Identical” parts per satellite, balance
are other hi-rel.– Build them all in one year (Not realistic, but suitable
for this example).– Spares at 100% of original build.– Complex die, Estimate die size 5 by 6 mm.– Technology: 0.25 Micron on 8-inch wafers.– Total fab, assembly, test yield = 85%.
O'Boyle MAPLD 2005/P10237
• 1000 x 100 = 100k devices• Plus 100% spares = 200k• Total die needed: 200k/85% =
236k round to 250k die• Gross die per wafer 1000• Total 250k/1000 = 250 wafers• In 1996 top 10 IDMs
(Integrated Device Mfr.) were 20 million wafers per year
• 250/20 million = 0.00125 % • Bottom line: Volume is
insignificant for the foundries
Low Volumes = Low Profitability for IC Mfg This is Reality
O'Boyle MAPLD 2005/P10238
2. Lack of Process Knowledge• Modern designers use tools with IP
embedded – they place blocks with 100s of transistors, or more.– Plus, design rules prohibit changes.
• Important when designing a complex digital device or the time to complete would be prohibitive doing “Stick” designs.
• Designers today enjoy no real process knowledge– No understanding of the nuances of the process used
to make their design at the foundry.
O'Boyle MAPLD 2005/P10239
“Lack” – is a Real GapAn Example:
• Temp compensated bias driver – As temp changed, reference voltages A, B, and C remain unchanged.
• Why? – The process had very linear negative TC for VBE which was used in a ratio between D3 and Q6 to afford ideal positive compensation.
• A new designer tried to “Copy” the part but did not understand the process so the part failed to work.
O'Boyle MAPLD 2005/P102310
3. Foundry : Economic Imperatives• Wafer Throughput and Yield
– Large scale manufacturing economics drive the foundries and fabs.
– The fixed costs are very high and short term variable costs are significant, too.
– The factories must produce many wafers just to reach breakeven.
• Cardinal Rules:1. “Fill the Fab”2. Minimize process variations: wafers out/wafers
started 100% (or As Close As Possible “Cut the Scrap”)
O'Boyle MAPLD 2005/P102311
Incredibly High Investments• Over 68 foundries listed by FSA (Fabless
Semiconductor Association) today, not counting firms like Toshiba (not listed).
• Today a 130/90 nm Fab Costs $3 to $4 Billion. Plus expendables.
• Opportunity cost related to stopping a running fab to insert 250 wafers for an annual buy is expensive.– This is applies to most fabs, 12-inch, 8-inch and even 6-inch.
O'Boyle MAPLD 2005/P102312
Breakeven Is High
Figure 18 Inch Revenue to Breakeven
$-
$5.0
$10.0
$15.0
$20.0
$25.0
$30.0
$35.0
5000 10000 15000 20000 25000 30000
WSM
Rev
enu
e ($
M)
8" Rev @ $1000 8" Rev @ $800 8" Rev @ $600 Breakeven
• Figure 1 (8 inch 0.18 micron fab):– At different wafer prices the monthly breakeven moves from $15
Million and 15k wafers for $1k Per wafer to $16 Million for 20k wafers at $800 each.
O'Boyle MAPLD 2005/P102313
Breakeven is Very High
Figure 212 Inch Revenue to Breakeven
$-
$10.0
$20.0
$30.0
$40.0
$50.0
$60.0
$70.0
$80.0
5000 10000 15000 20000 25000 30000
WSM
Rev
enu
e ($
M)
12" Rev @ $2500 12" Rev @ $2000 12" Rev @ $1500 Breakeven
• Figure 2 (12 inch 90 nm fab):– At $2500 per wafer the monthly breakeven Is $40 Million for 17k wafers
and at $1500 breakeven will not be achieved until the variable costs come down.
Yikes!
O'Boyle MAPLD 2005/P102314
4. Foundry : Scarce Expertise• Today’s Obsolete Device Designer relies on
modern tools and experience and knowledge about process – a True Artisan.
• Gone Are the Days of Pencil & paper and Karnaugh maps (Min-sums); Mylar Grids with Mylar transistors and hand-drawn resistors; “Digitizers” and Rubyliths; 500x cameras that floated on Hg; chrome masters and glass plate masks.
O'Boyle MAPLD 2005/P102315
Tackling Obsolescence Today– A Few Solutions
• Size Does Matter – Hi-Rel volumes too small to be attractive. So think SMALL
• Emulate – Works when no other solutions are available.
• Create – NEW APPROACH; Much closer to original and more reasonable in investment.
O'Boyle MAPLD 2005/P102316
1. Solution – Size Does Matter• The Large Foundries (TSMC, UMC, SMIC,
etc.) are out of reach to small Hi-Rel OEMs.
• Small “Research Oriented” Foundries (Typically under 10,000 wafers a year, sometimes much lower) will still run special lots.– Caution: Their processes are not as well controlled as
modern flows, but they are better than anything else available.
O'Boyle MAPLD 2005/P102317
2. Solution – Emulate …• There are a couple of approaches available which
allow a design team to emulate an obsolete part, right down to the timing delays.
• Works well for logic, the analog function is still in question, but they’re working on that too.
• There are available programmable approaches.
• May be a possible low volume obsolete parts replacement.
O'Boyle MAPLD 2005/P102318
3. NEW APPROACH: The Multi-Project Die (“MPD”)• Amortize Mask Tool Costs Across Several
Parts– Derive several different options from “MPW” Die– Metal mask programmable – Allows wafer hold at metal
and patterning to meet orders – Quick Turns
• Higher WSM (Wafer Starts per Month) figures to foundry partner
• Not constrained by Max GDPW (Gross Die Per Wafer)
• Flexible Family Sets; Memories, sequential and combinatorial logic – 34 different parts on first MPD.
O'Boyle MAPLD 2005/P102319
Options for MPD• I/Os:
– TTL Totem Pole– DTL– Multiple I/Os
• PROM – Metal Mask– Core covers major and
Minor densities in range (S, M, L)
– Fusible links next
• Foundry holds average of 24 wafers at metal. When down to 12, they start another 24.
Four Peripheral Drivers, One Wafer:QP1631, QP1632, QP1633 and QP1634
O'Boyle MAPLD 2005/P102320
Metal Options (OP 1)
Note, One ConnectionScheme in OP 1
O'Boyle MAPLD 2005/P102321
Metal Options (OP 2)
And Another
Scheme in OP 2
O'Boyle MAPLD 2005/P102322
Summary• Economies of scale are opposite between a
foundry and an obsolete device maker.– Partnering with the right manufacturing partner is key
• An obsolete device designer needs process knowledge to tailor the design to take advantage of “anomalies”.
• The obsolete designer must find creative ways to fabricate parts:– Focus on what is important to achieve performance– Target smaller foundries– Adapt designs/layout(s) for flexibility in die size while
keeping costs within reason.