4-4

3D Integration of LSI, Plastic MEMS Switches and Organic Transistors forPrintable Communication SheetLechang Liu1, Makoto Takamiya1, Tsuyoshi Sekitani2, Yoshiaki Noguchi2, Shintaro Nakano2, Koichiro
Zaitsu2, Tadahiro Kuroda3, Takao Someya2, and Takayasu Sakurai1
1Institute of Industrial Science, University of Tokyo
4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
Phone: +81-3-5452-6253 E-mail: llch@iis.u-tokyo.ac.jp
2
Quantum-Phase Electronics Center, School of Engineering, University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan3
Department of Electronics and Electrical Engineering, Keio University
Hiyoshi 3-14-1, Kouhokuku Yokohama, 223-8522, Japan

1. Introduction
Low-power wireless communications between electronic objects scattered over tables, walls and ceiling will
form an infrastructure necessary for wireless sensor networks and ambient intelligence. This paper presents a novelcommunication method which simultaneously achieves themobility of wireless communication and the low-power
performance of wireline communication [1]. By combining
meter-scale wireline communication and μm-scale wirelesscapacitive coupling communication, the proposed communication system enables multiple electronic objects scattered over the sheet to communicate contactlessly with eachother by establishing communication paths without cumbersome physical connections.
2. Communication Sheet
TX sheet
TX LSIRX sheet
RX LSI

50pF

75μm

Wireless
capacitive coupling
between 16 pads

PadMEMS

Data
Datab

Communication
sheet for routing

17

OrganicMemory

Detectedposition

(a)
0

M

M

M

0
M

M

M

M

M

M

M

M

17
M

: MEMS switch
M : Organic memory(b)Fig. 1 (a) Overview of the communication system. (b) Communication route.

System Overview
Fig. 1(a) shows the overview of the whole system. The
point-to-point communication is achieved by combining themeter-scale wireline communication on the sheet and theμm-scale proximity communication between the sheet andthe transceiver. This work implements proximity communication by capacitively coupling the transmitter to the receiver. The transmitter drives a plate of metal on the transmitter (Tx) sheet that couples to a corresponding plate ofrouting metal on the communication sheet and the plate on
the other end of the routing metal in turn drives the receiveron the receiver (Rx) sheet. The typical pad distance for thecapacitive coupling is 75μm, which corresponds to 50pF
capacitance. In this application differential signaling is required because there is no common ground among Tx sheet,communication sheet and Rx sheet. Another two pads are
employed to compensate the sensitivity degradation due to
pad misalignment.
The communication route is dynamically formed using
the plastic micro-electromechanical-system (MEMS)
switches and the routing information is stored in the organic nonvolatile memories. As illustrated in Fig. 1(b), thesheet is composed of 8×8 units and every unit consists offour pads. The communication between each two unit isachieved by turning on the adjacent two MEMS switches
and the top two routing switches. Thus, only four switches
are required for the point to-point communication. Since
the information transmitted over the sheet is confined insmall space close to ad hoc routed paths, the system is freefrom the issues related with radio frequency band allocation
which has already been tight.
Device Structure
The device structure of the communication sheet isshown in Fig. 2(a). It consists of five low-cost printed
sheets: a 16×16 pad array for capacitive coupling, two 9×8MEMS-switching matrices for differential signal routing, a
9×8 organic nonvolatile memory array for routing information storage and a 8×8 position-sensing coil array [2, 3].
The 16×16 capacitive coupling pad arrays are fabricated on a polyimide film. The side length of the square
pad is 9.7mm and the distance between each square is 3mm

16 x 16 pads
for capacitive
coupling

20cm

9.7 mm
3.0 mm20cm

4 padsfor TX

TXsheet9 x 8 MEMS
switchesfor Data
9 x 8 MEMS
switchesfor Datab

CSlong periods of time with no AC signal. Power dissipated inthese periods is wasted. The proposed pulse detector can
alleviate this problem by having essentially zero power
dissipation for no AC input. Two unbalanced inverters areused to detect the rising edge and falling edge respectively
and the detection results are level-shifted to VDD.
4. Measurement Results

9 x 8 organic
nonvolatile memory

Typical (Equals to 52pF)
150
Distance (μm)

8 x 8 coils for
position detection

Fig. 2 Device structure of communication sheet.

Silver gate electrodes and polyimide gate dielectric layers
are patterned by using inkjet printing. TheMEMS-switching matrix is formed by using inkjet printing
and screen printing. The electrodes for electrostatic attraction are patterned on a 25μm-thick polyimide membrane.
Compared to the organic FET switch, MEMS switch provides lower ON-resistance and lower parasitic capacitance,
which contributes to low energy/bit communication.
3. Transceiver Design

TX

Communication
sheet
Bias
1

Pulse detector to detect
rise edge of Datain

RXBias2

Level Shifter

Edge detector
DelayDatain
Data
Bias1

Dataout

Datab

Bias1

Bias2Pulse detector to detect
fall edge of Datain

Bias: VDD/2 generator, Bias : (VDD/2−ΔV) generator
12Fig. 3 Schematic of transceiver with data edge signaling and DC
power-free pulse detector.

A transceiver is designed and fabricated in 0.18μm
CMOS process and the schematic is shown in Fig. 3. In thisstudy the input non-return-zero (NRZ) signal is converted
into return-to-VDD/2 signal pulse to avoid the DC wander
effect. The modulated data is achieved by switching theinput data and the output of the half VDD generator. Theedge detector is used to generate the switching signal forthe selector by detecting both the rising and falling edge ofthe input data. To detect a small signal, an amplifier and acomparator is often used in the first stage of the receiver toamplify the received signal for the next demodulation. The
major disadvantage of this topology is large DC power dissipation that occurs even for no AC input. In the transmitted signal of the communication sheet, the circuit spends aMinimum ΔV (V)
0.300
0.285
0.2700.255

12510075

100kbps502502.5

5.0

7.5

Displacement (mm)Fig. 4 Measured minimum ΔV for different displacement anddistance of the pads.

For the capacitive coupling system, a critical challenge
in high-performance communication is correctly aligning
the chips. With misaligned pads, one transmitter will be
coupled to several other receivers, simultaneously reducing
the intended signal and increasing crosstalk to the otherreceiver. Fig. 4 shows the measured sensitivity requirement
for the horizontal misalignment and the vertical pad distance. For the normal 75μm pad distance, which is equal to
the sheet thickness, the sheet can operate up to 3.75mm
displacement. The maximum tolerable displacement is7.5mm, which corresponds to the 77% of the pad size.
4. Conclusions
A 20cm×20cm 3D-integaration communication sheetwith data edge signaling transmitter and DC power-freereceiver is developed. The proposed communication sheet
achieves the lowest energy 107J/bit at 100kbps in the wireless communications at a distance of 60cm in 0.18μm
CMOS and the four-pad differential signaling scheme cancompensate the one-dimension misalignment up to 77%.
Acknowledgements
This work is supported in part by CREST, JST, and MEXT.

References[1] L. Liu, et al., “A 107pJ/b 100kb/s 0.18μm capacitive couplingtransceiver for printable communication sheet,” IEEE ISSCC
Tech. Dig. Papers, pp. 292–293, Feb. 2008.
[2] T. Sekitani, et al., "Communication sheets using printed organic nonvolatile memories," IEEE IEDM Tech. Dig. Papers,
pp. 221-224, Dec. 2007.
[3] M. Takamiya, et al., "Design solutions for multi-object wireless power transmission sheet based on plastic switches," IEEEISSCC Tech. Dig. Papers, pp. 362-363, Feb. 2007.

3D Integration of LSI, Plastic
MEMS Switches and Organic
Transistors for Printable
Communication Sheet
L. Liu, M. Takamiya, T. Sekitani, Y. Noguchi,
S. Nakano, K. Zaitsu, *T. Kuroda, T. Someyaand T. Sakurai
University of Tokyo*Keio University

Ubiquitous Electronics
Convenience
Safety & Security
Healthcare

1,000~10,000
Electronic devices

Entertainment

WelfareHow to communicate effectively?
IssuesWireline
WirelessImmobility
High Power2

What is Communication Sheet?

 Enabling multiple electronic objects scattered over thesheet to communicate without physical connections.
 Infrastructure for the ubiquitous electronics together
with the wireless power transmission sheet.
3

Overview of Communication Sheet (CS)Low Cost, Flexible

2D Mobility

Wirelessμm-scale
wirelessmeter-scale wireline

Security,Unnecessary RF Band Allocation

Low Powercommunication

 CS enables both mobile and low power communication.
4

Capacitive-Coupling Transceiver in CS
TX sheet
TX LSIRX sheet
RX LSI

50pF

Wireless
capacitive coupling
between 16 pads

Pad

Detectedposition

75μm

MEMS
Organic
MemoryData
Datab

Communication
sheet for routing

 No common ground requires differential signaling.
 MEMS switches provides lower parasitic capacitancethan the organic FETs.

5

Dynamic Routing in CS
071M

M

M0M

M

M

M

M

MMM

M

1

7:MEMS switch
M :Organic memory
 Arbitrary 2 points are connected via 4 switches.

6

Device Structure of CS
20cm

16 x 16 pads
for capacitive
coupling
9.7 mm
3.0 mm20cm

4 padsfor TX

TX
CSsheet CS is fabricatedwith printingtechnology.

9 x 8 MEMS
switchesfor Data
9 x 8 MEMS
switchesfor Datab
9 x 8 organic
nonvolatile memory
8 x 8 coils forposition detection
7

DC Power-Free Pulse Detector Problems of conv clock-less RX: Large DC power
Voltage
Data

VDD/2bias
ADatabB
VDD/2-ΔVbias

VDD
Wp/Lp

Out

VDD
Logical VTH

Wn/Ln

VDD/2 A
VDD/2-ΔV B

Detected

ΔV

V00Time Dynamic logical VTH of the inverter achieves DC
power-free pulse detection.
8

Receiver with DC Power-Free Pulse Detector
RX
Communication
sheet

Datain

Bias
1

Bias
2

Level Shifter

Data

Dataout

TX
Datab

Bias : VDD/2
1
generator
Bias : (VDD/2−ΔV)
2generator

Bias
1Bias
2Pulse detector
9Chip MicrographsRX

0.7 mm

0.85 mm

TX

0.4 mm
25 μm

55 μm

0.4 mm

45 μm

39 μm

10

Performance Summary
Technology

0.18μm CMOS

Supply Voltage
Typ
Data RateMax
Capacitive
CommuniCoupling
cationDistanceWireline
Alignment Tolerance
TX
Power
RX
@100kbps
Total
Energy per bit
TX
Core AreaRX

1.8V
100kbps
8Mbps
150μm
60cm
7.5mm
9.73μW
0.97μW
10.7μW
107pJ/bit
2475μm2
975μm211

Capacitive-Coupling Communication on CS
RX LSITX LSI
TX
pads

Capacitive
coupling

RX pads

DatainCommunication sheet(Only pads andinterconnects)

Dataout
0110010101

100kbps60cm
12ΔV Dependence of RX

VDD-ΔV
2

Minimum detectable
RX amplitude(V0) (V)

VDD
2Pulse detector
VDD
V0

RX power (μW)

100kbps
1.6

0.3

1.2

0.2

0.8

0.1

0.4

00.15
ΔV (V)

00.3

 The tradeoff between the power and the RX sensitivity
can be tuned by ΔV.
13

ΔV dependence of Displacement
Typical (Equals to 52pF)

Distance (μm)

150

Minimum ΔV (V)
0.300
0.285
0.270
0.255

125
10075

100kbps502502.5

5.0

7.5Displacement (mm) For the 75μm distance, the sheet can operate up to
3.75mm displacement.
 The maximum tolerable displacement was 7.5mm, whichcorresponds to the 77% of the pad size.
14

Summary
The communication sheet combining the meritof wireless and wireline approachesÎAchieving both the mobility of wirelesscommunication and the low-power performanceof wireline communication.

The 100kbps 0.18μm capacitive-couplingtransceiver for the communication sheet• Low power data edge signaling and DC power-freepulse detector• The lowest energy of 107pJ/bit in the wirelesscommunications
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