Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick...

39
On-Wafer Measurements in RFIC Design Rick Campbell Designer Portland State University

Transcript of Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick...

Page 1: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

On-Wafer Measurements in RFIC Design

Rick CampbellDesigner

Portland State University

Page 2: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Abstract:

This talk will cover three closely related topics: a quick overview of the different roles of high frequency on-wafer probing in engineering and production test; some details of high frequency calibration; and practical approaches to on-wafer measurement as an engineering tool during the design and development of mm-wave and sub-mm wave RFICs.We begin by discussing the need to probe engineering prototype RFICs in an era when package models are routinely included in IC design software. Why not just design everything right the first time, and use on-wafer tests to discard bad parts and wafers before packaging?Having established the need for measuring engineering prototypes, we move on to some issues with calibration, starting with a very quick review of the fundamentals: What is Cal? Why a 50 ohm environment?Why is it hard at high frequencies? Finally we turn to practical issues of on-wafer measurements at mm and sub-mm waves, including the high cost of everything, the need for mechanical precision, and high losses in interconnecting cables and waveguides. These daunting challenges may appear insurmountable in an RFIC business unit working its way up through the frequency spectrum, but these advanced measurements are now routinely practiced in advanced development labs.

Page 3: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Three uses of on-wafer probing:

Traditional

1. Modeling

Measure new devices, structures, processes to obtain constants and statistics for math models

Designers use models in simulators to develop circuits

For expensive processes, long fab times, and complex circuits, designers are totally dependent on the simulator

When things don’t work, it’s not a problem with the simulator...

Page 4: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Test Structure

Page 5: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Three uses of on-wafer probing:

Traditional

2. Production test

Multi-chip modules and expensive packages require Known Good Die

Economics favor testing simple ICs in plastic packages anddiscarding bad ones

But when die are delivered as the product, or used in-house as components of hybrid modules, tested die are needed

Page 6: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Three uses of on-wafer probing:

Less traditional:

3. RFIC Design and development -- This Talk

Engineering prototype integrated circuits historically wirebonded to prototype boards and connected to stacks of manual test equipment for evaluation

After functionality confirmed, small prototype run packaged for engineering evaluation, test circuit development, apps engineering, etc.

...this does not work at high frequency

Page 7: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Typical UHF RFIC circa 2000

Die connected to outside world using 1nH inductors

bond wire 1nH1 GHz j6.28 ohms10 GHz j62.8 ohms100 GHz j628 ohms

Page 8: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Some things a designer needs to know:

It is expensive--do we really have to do it?

1. Justify expense

OK, I’m convinced...but I don’t know anything about it. What are the basics, what is “cal” and how do I interpret results

2. Understand the basics

My company has never done anything above 30 GHz... does anything really work up there?

3. Enough experience to believe it works

Page 9: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

10k

100n

12t T37-6

1n

510

47

10

51

2020

L1

L2

1p

16.7 MHz+2 dBm in

L1, L3

12t : 2t T37-6L2, L4

2N5179

12 v 5 mA

50.1 MHz

50.1 MHz+12 dBm out

120

51 chip

2020

L3

L4

1p

J310

12 v 6 mA

jumper or key

100k

1n

1n

10

Typical VHF Circuit

Near-perfect grounds

Page 10: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Typical VHF Circuit

Near-perfect grounds

Note: FR-4 is a viable RFIC substrate

Page 11: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Three circuit elements that don’t exist at higher frequency:

Wire

Ground

DC sources

It really isn’t all about the transistors!!!

Page 12: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Low DC Power 40m ReceiverRick Campbell 15 Mar 2009

H1 7 MHz 50 ohm quadrature hybrid: 18 turns bifilar on T37-2 (1.1 uH) and two 220 pF capacitors. L1 and L2 12 turns FT37-43. T1 8 turns trifilar on FT37-43. JFET Hartley VFO component values determined experimentally: see many examples in EMRFD. Gain from antenna input to 50 ohm head-phone output is 50 dB: use good antenna and sensitive headphones

This receiver was designed and built as an exercise in sustainable radio engineering: minimum DC power requirements with fundamental concepts, components and techniques that have been around for 50 years and will still be useful for another 50. Performance falls in the wide gap between minimalist designs and good basic receivers such as the microR2. The major performance compromises to achieve ultra-low DC power with common components are opposite sideband suppression, gain, and 2nd and 3rd order dynamic range. Gain and dynamic range limitations may be addressed by using a full-sized elevated dipole antenna fed with ladder line and a high Q impedance matching network such as a Johnson Matchbox. Suppression of an interfering signal or carrier on the opposite sideband may be achieved by adjusting the input Pi network and IQ balance pot to null the offending signal. Experiments are in progress to reduce the power consumption of the Local Oscillator.

L3

730pF

51

2uH

C1 2.7

J310

1N4148100n

1002.2k

33mH

12k

3.9k

680p

2N3904

2N3904

3

1

2

7

5

6

1.8k27k

27k

3.3k430p

768k

487k

+

+

33u

33u

1u680n

3.9mH

100u+

22k

10k

22n

2N3906

2N3906

12k

3.9k

680p

2N3904

2N3904

1.8k27k

27k

3.3k430p

196k

124k

+

+

33u

33u

1u680n

3.9mH

22k

10k

22n

2N3906

2N3906

2Q4

+100u

1k8

10 390

270

4.5v

4v

220k

220k

33u

+ 1.5uF

T1

10nF

51

730pF10nF

T2

H1

L1

L2

1N4148

1M

C2

9v 4 mA

IQ Diode Detector

Local Oscillator

B&W

4v 2.5 mA

10k

This single sideband receiver does not have any amplifiers at the signal frequency. It can be built at 7 MHz or 700 GHz

Frequency Scalable Receiver Architecture

Page 13: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

MF to UHF transformers and inductors

Page 14: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Inductors and transformers are easier at higher frequencies

Page 15: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Frequency Scaling Works -- but there are limits:

1mm square LNA die at 1 GHz

1um square die at 1 THz

It really isn’t all about the transistors!!!

with 650um bond wires -- 650 pH

with 650nm bond wires -- 650 fH

Page 16: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Frequency Scaling--walking up the bands

Circuit board at 2.3 GHz -- 1mm square die at 60 GHz

Page 17: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Signal In Signal Outsignal path on die

DC and control

DC and control

sub-mm wave RFIC die

Page 18: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Probe in and out

Bond Die to board

DC and control

Works at 500 GHz

Page 19: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

App circuit mimics wafer probes

Signal In Signal Out

Page 20: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

What an RFIC Designer really needs to know about on-wafer measurements...

...so he can explain it to managment

Page 21: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

0.10.1

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0.20.2

0.2

0.30.3

0.3

0.40.4

0.4

0.50.5

0.5

0.6

0.6

0.6

0.7

0.7

0.7

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0.8

0.9

0.9

0.9

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1.0

1.0

1.2

1.2

1.2

1.4

1.4

1.4

1.6

1.6

1.6

1.8

1.8

1.8

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2.0

3.03.0

3.0

4.04.0

4.0

5.05.0

5.0

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0.20.2

0.20.2

0.40.4

0.40.4

0.60.6

0.60.6

0.80.8

0.80.8

1.01.0

1.01.0

20-20

30-30

40-40

50-50

60-60

70-70

80-80

90-90

100-100

110-110

120-120

130-130

140

-140

150

-150

160

-160

170

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180

±

90-9

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80-8

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75-7

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65-6

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40-40

35-35

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25-25

20-20

15-15

10-10

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0.04

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0.05

0.06

0.06

0.070.07

0.080.08

0.090.09

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0.120.120.13

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0.150.15

0.160.16

0.170.17

0.180.18

0.190.19

0.20.2

0.210.21

0.22

0.220.23

0.230.24

0.24

0.25

0.25

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0.27

0.27

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0.29

0.3

0.3

0.31

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0.330.34

0.340.35

0.350.36

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0.37

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0.39

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0.4

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0.45

0.45

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0.47

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0.48

0.48

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0.010.050.10.20.30.40.50.60.70.80.91

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[dB]

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ORIGIN

Black Magic Design

The Complete Smith Chart

Gaaaahhhh!

Page 22: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Simplified

Can study basics just using S11

Page 23: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Hi ZLow Z

Inductance

Capacitance

length = mag S11

Ignore all the lines

The Smith Chart is just a polar plot of S11

Page 24: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Series X

Shunt X

Transmission Line

Start anywhere

add:seriesshuntTL

MeasuredData presented on the Smith Chart show the Designer how to fix things

Page 25: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Manager view of Smith Chart

very useful

1.0

20 dB Return Loss

0.80.6

0.40.2

10 dB Return Loss1.00.80.60.40.20.0

0.

00

Page 26: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Bad Design

Page 27: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Good Design

Note the spread: Solutions on the Smith Chart are not points. They show statistical variations and how results vary with frequency.

Page 28: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Manager view of Smith Chart

The Sky is Falling!

Verymisleading!

...which leads us to...

Page 29: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

What an RFIC Designer really needs to know about calibration...

...so he can explain it to managment

Page 30: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Open with 1dB attenuator

Open

Cal is your friend

Frequency sweep of a 1 dB attenuator and an open circuit length of transmission line

Page 31: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Open with 1dB padcalibrated outand small errors

Multiply magnitude of S11 by 1.58489 at every frequency

That’s silly--it was measured data--too many decimal places

After cal, the entirely passive system appears to be unstable

Page 32: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Measurements of entirely passive systems with open and/or short circuits and lossy transmission lines often wander beyond the edge of the Smith Chart.

The sky is not falling.

Page 33: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

SeriesInductor

ShuntCapacitor

Cal is beyond complex

The effect of stray Inductors,Capacitors, transmission line lengths depend not only onfrequency, but also where you start on the Smith Chart

Page 34: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

SeriesInductor

ShuntCapacitor

Why 50 ohms?convenient transmission lines

at low Zinductance dominates

at high Z capacitance dominates

Page 35: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

On-Wafer Measurements at sub-mm waves:

Different Behavior Dominated by Electromagneticsand the physical size of electrical degrees:

Small, precision mechanical pieces are expensive...

Page 36: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Coax and Connectors

Garden variety SMA connectors ~22 GHz

0.5mm Coax Connectors good to 110 GHz

~$1k per mated pair, limited life

Coax 20mil coax single mode to 270 GHz

but attenuation many dB per inch...

Page 37: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Above 110 GHz

waveguide to probes, coax or waveguide to membrane tip

At 300 GHz, free space half-wave dipole is 500 microns long...

250 microns is halfway around the Smith Chart

Where you land on a set of 100 micron bond pads can make large excursions on Smith Chart--need to land exactly the same place on cal structure as on test structure

Page 38: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

At what freq can you start to see granularity of photons?

1 Hz bandwidth1Kelvin1.38x10^-23 Joule/K

1 photon per second6.626×10−34 Joule-Seconds

hf = kT

solve for f

at 1K f=20.8 GHz

at 3K cosmic background 62 GHz

at room temperature 6 THz

green light 538nm frequency 560 THz

Wait... are sub mm-waves photons? Little billiard balls that pop out of the probe tip one at a time?

Page 39: Rick Campbell Designer Portland State Universityweb.cecs.pdx.edu/~campbell/CompassRLC.pdf · Rick Campbell Designer Portland State University. Abstract: This talk will cover three

Conclusions:

The sky is not falling when statistical variations in cal coefficients and measured data take us beyond the edge of the Smith Chart

mm-wave hardware is expensive but capable

We need on-wafer measurements as part of RFIC Design at high frequencies

The fundamentals are pretty basic

Cal is complex, but simple to understand