Might have an IC design coming up, depends on whether we can squeeze it all in, and on other external parameters. Anyhow, is there a table that compares capacitance per square micrometer between the various CMOS processes out there? Like a top 10 chart?
I am not an IC guy and only (somewhat) familiar with the XH-035 XFab process which clocks in at just under 4fF/um^2 for poly-diffusion. But less than 1fF/um^2 for poly-poly :-(
The electrical stuff won't be very demanding, one microwatt level 405MHz TX and the rest all audio and below. But I can't have discrete decoupling C's, need two caps >300pF and it looks like one of them has to be poly-poly. The whole chebang can't be larger than 0.2mm by 1mm, caps, circuitry, contact pads. The smallest one I had to deal with so far was 0.4mm by 2.5mm, so this would be even more interesting.
(1) Why XH-035? High voltage? (2) Seems like a waste to use up that much silicon just to get a capacitor.
What I've done in "have to" situations is use gate oxide... 5V devices have, typically, 2.5-3fF/um^2. I've used them regularly as compensation capacitors for LDO's. The only caution is to make sure the "channel" is conductive to avoid large series resistance. I usually roll my own square geometry (all drain, or source, call it what you want)... that geometry dramatically drops the effective R. ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Here's a set of subcircuits that accurately reflect how this capacitor behaves, capacitance and resistance, substitute the MOS model of your choice (P or N-type), and watch the wrap....
************ .SUBCKT NSQCAP1 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP2 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP3 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} X3 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP4 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} X3 G COM B NSQCAP PARAMS: E={E} X4 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP5 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} X3 G COM B NSQCAP PARAMS: E={E} X4 G COM B NSQCAP PARAMS: E={E} X5 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP6 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} X3 G COM B NSQCAP PARAMS: E={E} X4 G COM B NSQCAP PARAMS: E={E} X5 G COM B NSQCAP PARAMS: E={E} X6 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP7 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} X3 G COM B NSQCAP PARAMS: E={E} X4 G COM B NSQCAP PARAMS: E={E} X5 G COM B NSQCAP PARAMS: E={E} X6 G COM B NSQCAP PARAMS: E={E} X7 G COM B NSQCAP PARAMS: E={E} .ENDS
************ .SUBCKT NSQCAP8 G COM B PARAMS: E=10u X1 G COM B NSQCAP PARAMS: E={E} X2 G COM B NSQCAP PARAMS: E={E} X3 G COM B NSQCAP PARAMS: E={E} X4 G COM B NSQCAP PARAMS: E={E} X5 G COM B NSQCAP PARAMS: E={E} X6 G COM B NSQCAP PARAMS: E={E} X7 G COM B NSQCAP PARAMS: E={E} X8 G COM B NSQCAP PARAMS: E={E} .ENDS
************ ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
What does that have to do with "low power"? ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Thanks, Jim. This post came in with a delay here for some reason. Will try on the weekend, the missus called. Dinner, and she is a really good cook. Then margaritas :-)
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I did some poking thru my XFAB libraries... I have them all ;-)
I don't use poly-diffusion caps because of the about 50% parasitic on one end to substrate... or one end is actually AT substrate.
Excluding that, I'm finding generally that poly-poly caps are all right around 1.87fF/um^2... except on XH-035, where the oxide thickness is larger... don't use it if you don't need HV, use XC-06 (my favorite).
I see some MIM caps at 2.5fF/um^2... but that's an extra process step, and you're cheap, cheap, cheap... ;-) I almost always have that process module, because I like RPOLYH resistors to keep the power (and space) down. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Only if it's special "thinned" oxide. Field oxide is quite thick, comparatively. MIM caps are made from thin oxide, but require extra process steps. Multi-layered ones end up having strays to substrate which can be a pain. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Color me stupid concerning CMOS processes; if an area can be isolated (think DI), then a substrate-iso-metal-iso-metal config with top metal tied to substrate can give a hell of a lot of capacitance per square micrometer.
I take most of my "walk-ins" to XFAB processing... good bunch of people.
Why do you need such a large value... coupling audio on chip ?>:-}
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Wish they would send some Thuringian sausage with shipments. I love those.
Can't talk about that yet, but I really need some capacitance. If we have to lower it we can but it'll come with some penalties for us. It's all at a feasibility stage right now, to see if we can do this with an IC at all. The challenge is the space it has to go into, the 0.2mm width requirement is a hard limit.
Are you doing "chip-on-board", or is that the package size?
Maybe you should have a pro look at your custom I/C needs ?>:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
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| 1962 | I love to cook with wine. Sometimes I even put it in the food.
COB, and the stated dimensions are for the bare die. Aside from passivation it may also have to be protected from the elements but that won't add much if it is a coating.
Eventually yes. I am certainly not getting myself into IC design. It may likely be IP blocks to a large extent but still, that ain't my turf.
We are lucky, we've got a German butcher in Sacramento. It's a bit of a drive but the air-dried Landjaeger alone is worth it. He said he can't even get them completely air-dried because they fly off the shelves. So we dry them here. Last time I bought 30, surgeon general's nightmare.
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