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NEWSLETTER
By A. Marzuki
Technical Consultant of C-RAD Technologies
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Highlights&News
1. IC ranking (Fabless) in the world: Qualcomm, Broadcom , pleasesee at this URL for more info.
http://www.icinsights.com/news/bulletins/bulletins2008/bulletin20080801.html
2. Wireless Transfer Technology which was announced in 2006 byMIT is a fascinating research topic,http://www.mit.edu/~soljacic/wireless_power.html. Product basedon this technology is currently being pursued. So hopefully we cansee a product that recharge your batterys hand phone wirelessly inthe future!
3. Femtocell development is to configure each house as smallerversion of base station, it is another version of Picocell. Femtocell isthought could improve the cost and efficiency of the network, it willbe connected with broadband IP in house. It seems a lot of work needto be done to roll out this technology!
4. Lead-Free material is thought good to nature, is it so? Some say itcauses in increase on Tin usage, and we back to square one, as TinMining is not good for nature. What do you think?
5. Wireless PAN at 60 GHz for high definition TV is thought to offervery high speed, high data rate wireless connectivity, but thefrequency is one of the resonant frequencies of water. Unless we areshielded by metal, the frequency can be used at will, maybe atdifferent frequency? But we dont want to waste tremendous researcheffort on 60 GHz circuit design.
Please email your comments to [email protected]
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Circuit Techniques
1. Voltage reference circuit which is much smaller than standardband-gap circuit employs PTAT and CTAT current sources.
Ref1: A voltage reference circuit for current source of RFIC block,http://www.emeraldinsight.com/10.1108/13565360810889593Ref2: Low Power Bandgap Circuit, WIPO, WO 03/050847 A2
Please email your comments to [email protected]
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II. EXPERIMENT PROCEDURE
Figure 1 shows the top view and the cross-section of Si3N
4MIM capacitor. Top view shows the
bottom and top metal named metal 2 and metal 3 respectively, while the cross-section viewillustrated the thickness of the metal and insulator for the device with Si
3N
4as passivation of the
device. It consist of 100 m of GaAs substrate, 0.12 m thickness of Si 3N4 sandwiched betweenthe metal 2 and metal 3 with thicknesses 0.4 m and 3.12 m respectively. The complete
capacitor is covered by a layer of nitride with a thickness of 0.12 m which passivate the wholestructure.
New equivalent circuit is proposed to show the performance of Si3N
4MIM capacitor, but this
circuit is still in the beginning stage of the modeling process. Equivalent circuit of Si3N
4MIM
capacitor is depicted in Figure 2. Cm2
represent the parasitic effect associated with the bottom
metal or metal 2. C is the required value for the capacitor and Rloss
is the parasitic loss that
associated to C. Cm3
and Rm3
are the parasitic effect associated with the top metal or metal 3.
Finally, Csub
and Rsub
are the parasitic effect that associated with the substrate. Parasitic effect
description is explained in Table 1.
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Device measurement was performed in S-parameter environment using in-house microprobestation. The measurement result was then imported into S2P component in ADS window to
perform smith-chart plot and compared it with the proposed equivalent circuit model using thelumped elements through two port schematic simulation. Si
3N
4MIM capacitor measurement as
depicted in Figure 3 is connected to RF pad.
Table 1: Equivalent circuit descriptionDevice Description
Cm2
Capacitance between bottom metal (metal 2) and substrate
C Main value of capacitance
Rloss
Dielectric loss
Cm3
Capacitance between bottom metal and substrate
Rm3
Resistance between bottom metal and substrate
Csub
Substrate capacitance
Rsub
Substrate resistance
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III. RESULT AND DISCUSSION
S-parameter simulation result for Si3N
4MIM capacitor 70 m x 70 m is shown in Figure
4, 5 and 6 below. S(1,1) is to obtain the value of the measured data and S(3,3) indicates
the value of simulation using the proposed equivalent circuit model. In Figure 4, the dataof S(3,3) is similar to S(1,1) from 2 GHz to 15 GHz, but it starts to disperse from S(1,1)
at frequency near to 15 GHz up to 38 GHz, this situation is depicted in Figure 5. This
happens due to the value of Rsub
and Csub
which are optimized. At frequency is between
45 GHz to 50 GHz, the measured Si3N
4MIM capacitor device resonates 2 times, and we
can see that S(3,3) of the proposed equivalent circuit cannot be modelled S(1,1) precisely.
Figure 6 shows that the Si3N
4MIM capacitor is working as a capacitor solely without
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having inductance behaviour. The capacitance value for 70 m x 70 m Si3N
4MIM
capacitor is obtained through the imaginary admittance value as defined in ADS 2005 as
explained from (1) to (3), and the values are 2.157 pF for the measured device and 2.3737pF for the proposed equivalent circuit.
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Figure 7, 8 and 9 show the S-parameter simulation for 100 m x 100 m Si3N
4MIM capacitor.
From the figures, the function of S(1,1) and S(3,3) are similar to 70 m x 70 m Si3N
4MIM
capacitor. In Figure 7, S(3,3) of the proposed equivalent circuit model behaves similarly to themeasured S(1,1) data. This means that the proposed equivalent circuit model performance is very
good for larger device and higher frequency. Figure 8 shows the close up simulation of 100 m x100 m Si
3N
4MIM capacitor at frequencies above 15 GHz. From the figure, it is obtained that the
device starts to resonate at 16.88 GHz. Figure 9 shows that Si3N
4MIM capacitor is working as a
capacitor solely without having inductance effect. The capacitance values that are defined usingthe same technique stated in (1) to (3) are 4.372 pF for the measured device and 4.2905 pF for the
proposed equivalent circuit.
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The proposed Si3N
4MIM capacitor equivalent circuit model value using lumped elements is
explained in Table 2. The prime capacitance value for 70 m x 70 m is 2.3737 pF and for 100m x 100 m is 4.2905 pF. The proposed equivalent circuit model used for 70 m x 70 m doesnot perform very well at higher frequency than 15 GHz, hence the elements value of R
suband C
sub
which give the effect for high frequency must be tuned and optimized accordingly.
Table 2 Optimization results of Si3
N4
MIM capacitor equivalent circuit
Device 70 m x 70 m 100 m x 100 um
Cm2
3 fF 0.001 fF
C 2.3737 pF 4.2905 pF
Rloss
0.472 4.547
Cm3
0.1 fF 0.001 fF
Rm3
4 k 91.876
Csub
4 fF 16.4218 fF
Rsub
697 436
IV. CONCLUSION
S-parameter simulation of the proposed equivalent circuit model representing Si3N
4MIM
capacitor performed very well at high and low frequency if compared to measure Si3N
4MIM
capacitor device especially device with dimension 100 m x 100 m. Hence, some modificationof equivalent circuit model for smaller dimension (< 70 m x 70 m) Si
3N
4MIM capacitor will
be performed in the near future.
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ACKNOWLEDGEMENT
The author would like to thank TM R&D Sdn. Bhd. for providing the grant for this work underProject No: R05-0607-0. The help from Advanced RF systems Cluster is greatly appreciated for
guidance in using ADS-Momentum Simulator.
REFERENCES
[1] M. Engels and R.H. Jansen, Rigorous 3D EM Simulation and An Efficient Approximate Model of
MMIC Overlay Capacitors with Multiple Feedpoints, IEEE MTT-S International Microwave Symposium
Digest, 14-18 Jun 1993, Page(s): 757-760 vol.2.
[2] Piquet, J.; Cueto, O.; Charlet, F.; Thomas, M.; Bermond, C.; Farcy, A.; Torres, J.; Flechet, B,
Simulation and Characterization of High-frequency Performances of Advanced MIM Capacitors, Solid-
State Device Research Conference, 12-16 Sept. 2005, Page(s):497 500
[3] Masa Asahara, A Novel Approach to Modeling Metal-Insulator-Metal Capacitors Over Vias With
Significant Electrical Length, IEEE Transaction on Microwave Theory and techniques, Vol. 55, No. 4,
April 2007, Page(s) : 709 714
[4] Liu Lintao, Wnag Jiniang, Feng-Chang Lai, A New Equivalebt Circuit Model of MIM Capacitor for
RFIC, Microwave and Milimeter Wave Technology, pp. 1 3, April 2007.[5] Anders Mellberg, Jorgen Stenarson, An Evaluation of Three Simple Scalable MIM Capacitor Models,
Microwave and Techniques, vol. 54, no. 1, pp. 169 172, January 2006
[6] Lombard, P.; Arnould, J.-D.; Exshaw, O.; Eusebe, H.; Benech, P.; Farcy, A.; Torres, J.; MIM
capacitors model determination and analysis of parameter influence, IEEE International Symposium on
Industrial Electronics, Vol 3, Page(s):1129 1132, June 2005
Rasidah Sanusi received her B. Eng. degree in Electrical
and Electronic Engineering from University Putra
Malaysia (UPM) in 2002. Upon graduation she worked as a
Graduated Research Assistant (GRA) at UPM. She is
currently pursuing her Masters degree in Electronics at
the same university. In 2004, she joined TelekomResearch & Development Sdn. Bhd. as an assistant
researcher in the Microelectronis and Nano technology
group. She is currently involved in the MMICs
application design based on III-V material.
About CTDMM:A not for profit group with interest in Circuit Technique, Design Methodologyand Modeling.Contact: [email protected]
About CTDMM Newsletter: Newsletter which cover news and articles from industry andacademia. The main purpose is to share knowledge and news within the Microelectronics
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