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During optimization, it is very important to know the power didribution within a proeerSOL Thns. However, the other levels are eontrolled by the circuit designer. To overcome this problem, the devices should be scaled properly. This is due to the improvement of the current drive capabilities; rn Rednced capacitances throngh small geometries and junction capacitances; I Improved interconnect technology; Availability of multiple and variable threshold devices. This iesults in good management o f active and standby power trade-off; and 1 Higher density of integration.

It was shown that the integration of 8 whole system, into a single chip, provides orders of magnitude in power savings. Some techniques are:. Higher frequencies are generated with on-chip phbse locked loop; and High-level of integration. In this book we have tried to cover the basics, from the process technologies and device modeling t o the architecture level, of VLSl system. T h e fundamentals of pow- dissipation in CMOS Circuits are presented to provide the readers with Juffieient badrgranod to be famdiaz with the low-power defign world.

Several practical eheuit examples and low-power techniqucs, mainly in CMOS technology, me discussed. This book also provides an extensive study of advanced CMOS subsystem design. Finally, the book includes a rich list of references, treating advanced topics, at the end of each chapter. This allows the readers to study, in depth, any topier they find interesting. This book is orgganiad into eigth chapters. The first chapter i s an introduction to low-power design. The other chapters m e presented in the following sections. Bipolar technology with emphasir on advanced stmetme.

The topic of the isolstion techniques wed for both bipolar and CMOS is addressed. The design rules of a 0. Finally, SO1 technology is reviewed for low-voltage and low-power spplieatianr. It introduces commonly used models of both MOS and bipolar devices. In this chapter we consider simple analytical models which EM be used for circuit malysir and design of deep-rubmicromete. This should help the reader to appreciate the meaning of the model parameters as well as to analyse the power and delay of the low-voltage cirenits presented throughout the book.

Supply voltage scaling, due to reliability and power dissipation issnes, is presented. The sauces of power dissipation in these circuits are reviewed. Simple models for delay and power dissipation estimation m e presented. The concept of switching activity is introduced and examples are given.

The power dissipation due to spurious transitions is described. Guidelines for low-power physical design presented. Other circuit variations of the static complementary CMOS, which are suitable for low-power applications, are discussed. Also an overview of clocldng strategy in VLSI systems is covered. Finally, techniques to reduce static and dynamic power components for CMOS design are also reviewed. This chapter is intended to provide the readers sufficient background in low-power circuit design.

The chapter starts with the introdoction of the conventional BiG MOS totem-pole gate which was used in 5 V applications. The degradation of this gate, with supply voltage scsJing, is demonstrated. It is shown that it provides better performance and delay-power product than CMOS, at these voltages, even a t low fan-out. Other logic families, for low power supply voltage operation, are also discussed. These techniqoes are applicd to the architectural and dreuit levels. Several advanced circuit structures and memory organisstions are described.

Circuits, operating at a power supply as low as 1 V, are dm discussed. Their low-power aspects ere investigated. Several options of each subsystem are presented with power dbripation emphasis. Lowering the power supply voltage while maintaining the performance is one technique for power reduction addressed extensively in this chapter. It is shown that low-power techniques at the high-level algorithmic and architectural of the design lead to a power saving of several orders of magnitude. Several exxamples are included to give the reader a desr picture of low-power design aspects.

In addition, the powestimation techniqnes, at the G c n i t , logical, architectural and behavioral Levels, 61e overviewed. The goal of powa estimation is to opt-e power, meet requirements and know the power distribution through the chip. Dobberpuhl et al. Solid-State Circuits, vol. Bowhill et d. Bearden, et d. Charms, ot al. Gerosa, et d. Beehade, et al. Yeung, Y-H. Sutu, T. Su, E. Pak, C-C Chao, 5. Akki, D. Yau, and R. IOI [13] 5. Lipoff and A. Stork, "Toehaalogy Leverage for U1L.

October Section 2. In Section 2. Finally, in Section 2. In the O's, it was widely acknowledged that CMOS is the technology for VLSI because of its unique advantyes, such as low power, high noise margin, wider temperature and voltage operntion range, overall circuit simplification and layout effie. The development of VLSI in tho 80's has driven the integration density to millions of transistors on B single chip.

Other processes such ar retrogradwvell technology is not discussed. The process starts by growing an oxide on the wafer. The oxide is then patterned to open N-well windows. After removing the nitride used in the LOCOS process, a photoresist layer is deposited and is then patterned by B P-well mark new mark. A seeond ion implantation can be applied to eliminate punchthrough in the short channel device. Simiirly, the threshold voltage of the P-channel tramistor is adjusted [Fig.

A thin gate oxide is then grown and B layer of polysilicon is deposited and doped with phoaphoros. The polyailiean is patterned to form the gates of all the transistors and intereonneetion layer [Fig. Boron is used for the Pf regions of the P-channel transistors and arsenic for N-channel transistors [Fig. The photoresist is removed and a thick oxide is deposited by Chemical Vapor Deposition CVD ar an isolation layer between the polysilicon layer and the subsequent metal layer.

Contact holes are opened in the oxide layer and metal usually aluminum is deposited on the whole wafer. At this stage, the metal is patterned and annealed at d s t i v d y low-temperature C [Fig. One or two other metal layers are u m ally added. At the end, the wafer is pauivated and windows are patterned over the metal bonding pads to provide electrical contacts with pins. Strip 1eisUordde Grow gate oxide Deporitpolysilicon Apply photoresist and pattern stripresirt.

This "twin-tub" CMOS technology uses a single mmk that d o w a it to form two independently doped and self-aligned tubs [Z];hence both CMOS devices types are optimiaed independently. This tlexibility in selecting the substrate type with no change in the process flow is the major advantage of twin-tub CMOS. This technology is alro more attractive when the devices are scaled down to submicron dimensions. Low- Voltage Process Technology 17 Fig. The starting material is B lightly doped P-epitaxial material over a, Pi- substrate to reduce latch-up. In addition to the conventional N-tub process, another N-type arsenic shallow implant is used to increase the suifaee doping of the N-tub to prevent punchthrough far short channel devices.

It is also used to form the channel-stoppers' for the P-channel transistors [Fig. The photoresist is stripped and a selective oxidation of the N-tub is performed. This is followed by a second boron ion implantation for the channel-stoppers for the N-channel device [Fig, 2. The N-tub oxide is then stripped. So far only one mask N-tub mask, MASK l is required for self-aligned wells and channel-stopper processes. Both tubs are driven in. This process results in a buried-channel PMOS transistor. The pad oxide is then removed. The remaining steps are similar to those used in the N-well process where MASK 4 is needed to pattern the polysilieon [Fig.

The fabrication ofsobmicron MOS transistors requires additional process steps to avoid hot carrier effects. The electric field near the drain is reduced due to its light doping. This prevents the generation of hot carriers. The major process steps to fabricate the LDD structure are shown in Fig, 2. Ifthe threshold voltage is sealed aggressively, the subthreshold leakage current increases drastically, which causes limitations for battery applications. Hence, high-performance low-power sealed CMOS technology is needed for ultra-low voltage operation.

Also, the subthreshold cmrrent should be reduced when low threshold voltage VT5 0. Extensions and variations of standard CMOS process have been proposed to enhance the performance of devices at low-voltage [3, There devices have good short channel behavior, low junction eapadtbnce and ledwed parasitic resistance.

Reduced power supply is needed far low-power applications, but 8 deeprubmicron CMOS device with ultrathin gate oxide and low threshold voltage should be used to improve performance. Table 2. The N-well and P-well depths are very shallow and comparable to the maxmum depletion layer width in the channel. As B result, the total depletion layer width is inmeaced and low depletion capacitance, Go,is obtained. This leads to the reduction of the subthreshold slope s w Section 3. The structure of Fig. Mo W-polycide gates m e used to reduce the poly sheet resistance.

Jonction-isolation and e p i t u y techniques triggered the progress of bipolar technology. Althongh, most of the focos has been on the development of CMOS for the last ten years, yet, we find that bipolar technology has achieved significant progress as well. It was shown that advanced silicon bipolar technologies, although quite complex, eould be integrated at the LSI level and operate at frequencies above thore of CMOS circuits.

Since then, the interest in sdvaneed bipolar processes has increased. The key features for such technologies are: i self-aligned base, ii advanced isolation techniques such 8s deep-trench, and iii polySicon emitter contact. The SICOS rtructnre is suitable for VLSI applications became of its density and low perasitics One of the features of advanced bipolar transistors is the replacanent of alnm n iU m by polysilicon for the contact of the emitter. This step has led to noticeable improvement in the current gain of bipolar transistam. For further reading on polysilicon emitter BJTs refer to [lo, 12, Any bipolar process typically starts with creating the bnried layers and the epitaxial layer.

This buried lsyer is introduced to reduce the collector resistance o f a hipolar transistor. While the epitaxial layer offers the high-quality silicon host far the bipolar transistor. The steps involved in Fig. First, an oxide lsrer is grown on the substrate and is then patterned using the buried layer mask. After etching the oxide, the exposed regions of the silicon surface are implanted by arsenic or antimony to form the Nt buried layers.

The photoresist is then removed and an annealing step is carried out. All oxide is then stripped. An N-epitariai layer is grown 'A r-irw of conrmntiond bipolar t. The thickness of this epitadal layer can he as low as 0. First, photoresist is deposited and patterned to define the collector contact region deep Nt collector sink. The resist and the oxide are then removed. A combination of 'P polysilicon and oxide layers are deposited o m the wafer. These layers are then etched 8 s shown in Fig. A CVD oxide is deposited eyer the wafer. The oxide is then dry etched using reactive ion etching RIE. The secondled of polysilicon is deposited and implanted with phosphoros that will ultimately form the diffosed emitter junction.

This is followed by the metallieation step. At the end, the metal is patterned 81 shown in Fig. B The advantage of bipolar devices is their high-speed performance. However, there are not suitable for battery backup systems because they consume high DC current. Many logic circuit techniqoes have been proposed for low-power adlow-voltage operation, particularly for telecommunications applications , Isolation in CMOS is reqnired to separate the devices electrically by elimioating the inversion layers, which might be induced by the interconnection layer between the trmsiston.

The principle of isolation in CMOS is based on a field oxide formation between two active mess [Fig, 2. The width ofthe isohtion region should be minimiied to attain dense layout and particularly for VLSI circuits. Several isolation techniques have been proposed and used. Selective epitaxy is not studied in t h s chapter. It is realivcd by forming a thick field oxide FOX between the active meas.

FOX is very thick 0. The condition for preventing an inversion layer under FOX and between two active regions is that this field threshold voltage should be higher than the highest power supply voltage used on chip. The field threshold voltage can be further increased by iaipig the doping level under the FOX, Thir can he achieved by selectively implanting the regions over which the FOX is subsequently grown. These redom are commonly knom as chonnel8toppera. A p d oxide of 40 n m is grown and is followed hy chemical vapor deposition of B nm thick nitride layer, which masks the active region.

The pad oxide is called stress-relief-oxide SRO because it protects the silicon from stress caused by the nitride during nuhsepucnt high temperature processes. Sicon nitride is used as a mask to protect the active region from oxidation. A layet of photoresist h applied to the wafer and then patterned using the mask of the active areas. The photoresist, which is used for protection against ion implantation,is sttipped and a thick thermal oxide is grown;i.

Only local oxkdstion is reahed hecanre the nitride masks the cegions heneath it.


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A typical value ofthb encroachment is 0. This encroachment limits the sealing of the active areas and the c h e l width of the MOS device. Ln this modified LOCOS process, the nitride mask thickness has been inereared t o n m snd B polysilicon streas relief buffer layer or50 nm has been added between the nitride and B 10 n m pad oxide [Fig. This srrangement prevents deep lateral extenlion ofthe field oxidc under the nitride layer [Fig.

Other techniques to solve the problem of the bird's beak encroachment can be found in [24, 25, This technology has been accepted relatively quickly b the industry [Z'f]. The advmtages of the trench isolation m e : i no bird's beak encroachment, ii latch-up fiee structure, and iii planar sorfacc. Fig 2. First, the pad oxide, the nitride and the thick oxide layers are patterned using the mask of the active areas. The thick oxide series ar s mask in the trench processing [Fig. A deep trench is formed by dry etching RLE. The top thick oxide is removed, and the trench sidewds are oxidived [Fig.

The polysilicon is deposited over the whole wafer, filling the trenches.

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The polysilicon is used as the trench dielectric because it uniformly fills the trenches better than other dielectrics. The surface polysilicon is then etched to yield the stroetore shown in Fig. The wafer is oxidized using the nitride as a mask. The nitride is finally removed as illustrated in Fig. At this stage, conventional processing can be used to integrate the CMOS devices. Although trench isolation permits reduction of the separation between the active regions; it has several drawbacks: i it is a costly process because of the large number of processing steps, and fi it can not be used BE an isoletian region for the inactive parts of the chip.

T h e description of other trench isollrtion processes c m be found in [28]. The N-wells N collectors ofthe adjacent transistors were separated by Pt isles, which are deeply diffused to reach the P-type substrate. By tying these ides and the robstrate to the most negative voltage, thejunctions between them and the N-type collectors are revuse biased. Grow oxidelnitrideloxide Pattern a l i v e region.. RIE trench Implant boron. The area conmmed by the isolation isles is large relative to the tramsirtor area.

An additional advantage of LOCOS isolation is the reduction of the parasitic collector-substrate capacitance. As the epitaxial thickness is being reduced for higher device performance the oxide isolation area becomes smaller, which means that LOCOS may become a practical isolation technique for advanced bipol-1 and BiCMOS technologies. A photoresist layer is applied and patterned with M isolation mark [Fig. Boron implant is performed to form the ehannel-stopper [Fig.

The photoresist is then removed and the wafer i s oxidized to grow the thick isolation oxide. This oxide is called recessed ozide. The resulting strocture is almost planar. These techniques reduced the collector-substrate capacitance and increased the packing density. We have seen that epitaxial and buried layers hsvc been used for CMOS to mute the latch-up. The use of polysilicon for creating selfaligned MOS transistors was later adapted for self-digned poly emitter bipolar transistors.

Another uample of the convergence between bipolar and CMOS is the use of oxide spacers in CMOS for formation of LDD regions, while, it has been osed in bipolar to reduce the reparation between the base contact and the emitter. The convergence of both technologies made the attractive ides of merging bipolar and CMOS seem more rational and feasible than ever. Some examples of there steps are: 1. The polysilicon can be used for the CMOS gatos and for the emitter contacts; 4. The final annealing s t e p match. However, as more steps me being shared by t h e different devices, the device charactedstics have to be compromised.

There is L tradeoff between the process complexity and device quality. With the technological progresr achieved in r-t ycarr, this idea has been revived. There are many techniques t o merge bipolar and CMOS devices as reported in the literature [33, 34, 35, 36, 37, One way ih to classify them according to the baseline process. In both eases, the added device would have to be compromired, which means that its characteristics can not be optimired. In this regard, three categories can be identified: Low- Voltage Process Technology 37 1. Low-cost; 2. Medium-performance; and 3. High-performance high-speed.

The first one represents B low-cost proeers. The third example illnstrbter a high-performsnce process in which polydicon emitter and self-aligned structures are used. A typical N-we! The base is implanted in a separate step using an additional mask. The process complexity is comparable to that of the CMOS. Howeuer, there me many trade offs in designing the emitter, base, and collector of the NPN. If the CMOS proccss is optimbed, some of the bipolar device parameters, suuh as the breakdown voltage and the gain, may be satisfactory, but many others are degraded.

For example, due to the absence of the buied layer and the deep Nt collector in the NPN, the collector resistance is high.

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Hence, the cut-off frequency is low, the current drive is poor, and the collector-emitter saturation voltage is high. A thin epitaxial layer 1 pm - 2 p m is used to increase the cutoff frequency of the NPN transistor and to reduce the required width of the isolation islea between the bipolar transistors. In this process an aluminum emitter contact is used.

This process uses only 3 extra masks to form the bipolar transistor. The first mask is needed for N t buried layer. The collector resistance is low in comparison to the lowcost proecsr exsmple 1. For a 0. One mtra mask is required to open the emitter window of the bipolar transistor. As shown in Fig. LOCOS is developed to isolate the devices. The deep collector N t is implanted and driven in, and the P-baseiS then patterned and implanted. The threshold voltages of the MOS transistors are adjusted hy additional ion implantations.

After the gate oxide growth, a thin polysilicon is deposited as shown in Fig. The emitter window is then pettermed and a second polysilicon layer is deposited [Fig. The polysilicon is then doped by implantation and patterned to define the CMOS gates and polyrilieon emitter [Fig. The BJTs realiaed in the presented high-performance BiCMOS process have low collector resistance because of the buried layer and deep sink , high current gain becsuse of the poly emitter contact and low parasitic capacitances because of the self-alignment.

BiCMOS technology k a relatively high cost and complexity, because it requires a total of 15 masks for snbmicron process. Recently one idea [40] has resulted in low-cost 0. This technology is suitable for 3. The applications of these technologies are, for example, for low-voltage 3 V and s u b 3 V and high-speed logic circuits. Bipolar devices can be used for high-frequency and highspeed parts with low-power innovative circuits, and CMOS can be used for low-speed ultra-low-power parts.

Moreover far wireless applications, where high-speed m d Im-power charactelistics are iequired, CBiCMOS technology is one of the solution. The Pi buried layer is only used for isolation isles between NPN transistors. The emitters of the NPN and the PNP are formed by the self-aligned contact doping technique to simplify the process flow.

go Finally, the metal is deposited and patterned. The corresponding device parameters are presented in Chapter 3. The rest of the masks are generated automatically. The corresponding graphical representation of design rules is illustrated in Plate 1. Polyrilicon PO The PO mark defines the gate and the emitter electrodes, and the polysilicon interconnect layer. Metal 1 Ml The M1 mark interconnects.

Metal 2 M2 The M2 mask interconneets. N-weU NW 1. Metal 2 Ma Via VIA This is due to the reduction of the cost and improvement of its performance a t lower voltage. Many techniqnes existent to grow silicon on insolator [HI. It is fabricated simply by the formation of buried oxide SiOl implantation of oxygen underneath the surfsce of the silicon as illustrated in Fig. Dose and energy of oxygen ions are as high as 2 x 10'8m-2 and KeV respectively.

A subaqaent thermal annealing at high temperature is performed to improve the qoality of the silicon overlayer. The buried oxide can be several hundreds of n m thick and the thin silicon layer can have several tens of n m thickness. It is due mainly to the floating sobstrate of an NMOS device. An explanation of this phenomena c a n be found in [51]. V with an access time less than 5 nr. The process starts by the formation of buried oxide in silicon wafer ar explained above in [Fig. Then, an oxide is grown on the surface silicon and 8 nitride hyer is deposited.

Silicon nitride is used as n mark to protect the active region from oxidation. At the end, the nitridejoxide layers are removed. A thin gate oxide is then gmvn and a layer of polyrilicon is deposited and doped with phosphorus. A thick oxide is then deposited BS an isolation layer between the polysilicon and the subsequent metd layer.

The oxide is etched at contact locations. Finally, the metal is etched and annealed. It has been discovered that if the silicon containing the devices is made sufficiently thin Unfortunately, the technology hsr minor disadvantages such sr floating body effects which rault in i floating body induced threshold voltage lowering and ii low drain-tusauce breakdown voltage. For 1 V power supply this is not a problem.

However for 3 V operation this could be an important limitation. Also, the threshold voltage is very sensitive to the thickness uniformity of the superficial silicon. In addition. Therefore technological improvements are still needed to mlve there Limitations. W e have shown that the advanced CMOS and bipolar processes me converging, and many process techniques can be shsred for the fabdestion of both devices. The different options for merging bipolar and CMOS devices are then discussed.

Wanlans, and C. Parrillo, R. Payne, R.

Davis, G. Ratlinger, and R. Tam et al. Lee et al. TaLeuchi et al. Yamaeaki, K. Goto, T. Fukano, Y. Nara, T. Oyamatsu, K. Kinugawa, and M. Yoshimma, F. Mdatsooka, and M. Uehino, T. Shiba, T. Kikuehi, Y. Tamaki, A. Watansbe, Y. Kiyota, and M. Ning, and D. Tang, "Bipolar Trends," Proe. IEEE, vol. Nabamnra, T. Miyslaki, S. Takahashi, T. Kure, T.

Ohabe, end M. Ning, and R. Kspoor and D. Ota and R. Solid-state Circuits, vol. Wilhelm and P. Kooi, J. Van Lierop, and J. Rung, H. Momore, and Y. Yamaguchi, S. Morimoto, G. K-wamoto, H. Park, and G. Eiden, "High-speed Latch-up Free 0. December Mikashiba, T. Homma, and K. Chapman, et al. Chiu, R. Fsng, J. Lin, and J. Chin, J. Moll, and J. ED, pp. Aui, P. Vande Voorde and J. Yamamoto, 0. Mieuno, T. Kubota, M. Nakamae, A. Shiraki, and Y. Tamaki, T. Shiba, N. Honma, S. Miauo, and A.

Tang, P. Solomon, T. Ning, R.

Practical Low Power Digital VLSI Design

Isaac, and R. Burger, "1. SC, pp. Lin, J. Ro, R. Iyer, and K. Electron Devices, " ED, no. Ikeda, A. Watanabe, Y. Nishio, I. Mwuda, N. Tamba, M. Okada, and K. Momose, K. Cham, C. Drowley, H. Fu, "0. Teplik, D. Hnlsemh, H. Bastani, C. Wong, J. Small, R. Lahri, L. Bouknight, T. Bowman, J. Y-guchi and T.

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Yoshida, H. Suziki, Y. Kinoshita, K. Imai, T. Ahnoto, K. Toksshiki, and T. Sung et al. Embabi, A. BeUaouar, M. Elmarry, andR. Hiraki, K. Mioami, K. Sato, N. Matsumki, A. Watanabe, T. Nirhida, K. Seb, "A 1. Kobayashi, C. Yamaguchi, Y. Amemiya, and T. Higashitmi, H. Honda, K. Ueda, M. Hatanalra, and S. Maeda, K. Ishimaru, and H. Burger, C. Lage, B. Landau, M. DeLong, and J. Small, "An Advanced 0.

Sun, et al. Electron Dev i e r , " Ikeda, T. Naksrhima, S. Kubo, A. Jonba, and M. Izumi, M. Doken, and H. Shahidi, T. Dennard and B. SSDM, Japan. I Y. Kado, T. Ohm, M. Harada, K. Deguchi, and T. Digest, pp. Fujishima, K. Omura and K. Ohno, Y. Hsrada, and T. Yamaguchi, A. Ishibarhi, M. NiPhimura, K. Tsu ;amoto. Aoric, and Y. Electron Devices, vol. Electron Device Letters, pp. IEEE J. Sturm, K. Tokunaga, and J. Omura, S. Nakashima, K. Pumi, and T. It is intended to review the basics of the MOS transistor, which is a prerequisite for Chapters 4.

In this chapter we consid- simple analytical models which can be used for circuit analysis and deign of deeprubmicrometer MOSFET's at low-voltage. The more sophisticated SPICE device models are also presented to d w the reader to appreciate the meaning of the model parameters as well as the capabilities and limitations of there models The SPICE parameters for the 0. In Seetion 3. By applying a positive voltage on the gate Vos,. Fnrther increase in VoS results in a surface inversion layer. This charge is positive. T h e width of the depletion layer in the bulk W D is given by 3. This condition also defines what is known as the strong inversion'.

At the onset of strong inversion we can assumc that Qs ii: Q B. To get a reasonable VTo,the device rnrface is implanted with boron. Typical values of the VT are For low-voltage CMOS they a m 0. When VGs Vm, the channel is formed and a drain current flowsfrom the dm. Vco The voltage drop between the pinchoff point and the wmce is VDS,. If we assume that the distance between the piacbaff point and the drain is extremely small compared with the overall length.

The carriers which reach the pinchoff paint are swept across to the drain by the potential VDS- Vns.. From Pip. From Equation 3. Therefore, the magnitnde of Q I decreares with the distance across the channel. This is why the inversion layer is triangular a illustrated in Fig.

Equation 3. The cnrrent eqnations 3. Using linear extrapolation, VTO and k p p can he determined 8s shown in Fig. This is due to the channel length modulation phenomenon which can be explained s follows. A typical value of X is 0. However, kp or p can be used as D fitting parameter to reduce this error. This model in most suitable for preliminary analysis. Low-Voltage Device Modeling 73 3.

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A typical value of 0 is 0. To account for the effect of lateral average electnc field, the effectivemobility is related to the drhin-source voltage and the channel length by I41 3. Lou-Voltage Device Modeling 75 3. This channel length redoctian is formulated in MOS3 by Baum'r model [5]. V, marks the point between the weak and strong inversion modes. I , is related to the c u r e d of Equation 3. Therefore, the MOS3 model is not precise in simulating the intermediate region where the diffusion and drift currents are comparable.

I VDS 3. The LEVEL 3 model approximates the device physics and relies on the proper choice of the empirical pammeters t o accurately reproduce the device characteristics. The model was tested for effective channel length down to 1 p m. This model inelodes: Vertical field dependence of carder mobility; Carrier velocity saturation;. Channel VDS 3. Typical values for KI and K 2 are 1 V'lz and 0. I , is expressed BI 3.

The Subthreshold parameter n is a function of Vpbs and VB. It uses an. The model is also simple and has a s d number of parameters x Each of the bottom area and the sidewall contributes to the total depletion cap-tance. The bottom area capacitance is mesured per unit area, while the sidewall capacitance is measured per unit perimeter. Both of t h e e components are voltage dependent. As these junctioos a x normally zcyerse biased, we will consider the case when the bulk-soures and bulk-drain voltages V hand V B D m e less than 01 equal to 0. The total bull-source and hulk-drain capacitances can be expressed by the following reletions [l] The exponential factor.

Mj and Mi. C, is the zero-bias capacitance of the bottom jmction p a unit area and C;,- is the eel-bias capacitance per unit perimeter. Low- Voltage Device Modeling 83 3. Both Ccs.. They are usually given per unit width as Coso and Cooo. The channel shields the b d k and the CBpaeitance exists only between the gate and the channel.

The above described capacitance model can be used for circuit analysis and eLeuit design. This modelis bared on the mtod distribution of charge in the MOS stiuctue and its conservation. These models e. The primary goal of this sequential logic design is to optimize the speed and area by choosing the proper options available in the synthesis tool. More over the work focuses the design of FSM with more processes operates at a faster rate and the number of slices utilized in an FPGA is also reduced when compare to single process. Multipliers in DSP computations are crucial.

Thus modern DSP systems need to develop low power multipliers to reduce the power dissipation. One of the efficient ways to reduce power dissipation is by the use of bypassing technique. This paper presents the column Bypass multiplier and 2-D bypass multiplier using reversible logic; Reversible logic is a more prominent technology, having its applications in Low Power CMOS and quantum computations. The switching activity of any component in the bypass multiplier depends only on the input bit coefficients. These multipliers find application in linear filtering FFT computational units, particularly during zero padding where there will be umpteen numbers of zeros.

A bypass multiplier reduces the number of switching activities as well as the power consumption, above which reversible logic design acts to further almost nullify the dissipations. A 10 bit opamp-sharing pipeline analog-to-digital converter ADC using a novel mirror telescopic operational amplifiers opamp with dual nmos differential inputs is presented.

Reduction of power and area is achieved by completely Reduction of power and area is achieved by completely merging the front-end sample-and-hold amplifier SHA into the first multiplying digital-to-analog converter MDAC using the proposed opamp. Transistors in the opamp are always biased in saturation to avoid increase of settling time due to opamp turn-on delays.

The design targets 0. A high speed low power consumption positive edge triggered Delayed D flip-flop was designed for increasing the speed of counter in Phase locked loop, using nm CMOS technology. The designed counter has been used in the divider chip The designed counter has been used in the divider chip of the phase locked loop.

A divide counter is required in the feedback loop to increase the VCO frequency above the input reference frequency. The proposed circuit is faster than conventional circuit as it has fast reset operation. The circuit consumes less power as it prevents short circuit power consumption. The circuit operates at 1. This work has been used in the design. Channel routing is a key problem in VLSI physical design. The main goal of the channel routing problem is to reduce the area of an IC chip. If we concentrate on reducing track number in channel routing problem then automatically the area If we concentrate on reducing track number in channel routing problem then automatically the area of an IC chip will be reduced.

Here, we propose a new algorithm to reduce the number of tracks using four layers two horizontal layers and two vertical layers. To be more specific, through this algorithm we convert a two-layer channel routing problem into a four-layer channel routing problem using VCG of the channel. Next, we show the experimental results and graphical structure of that solution.

Resonant tunneling diodes RTDs have functional versatility and high speed switching capability. The integration of resonant tunneling diodes and MOS transistor makes threshold gates and logics. The design and fabrication of linear The design and fabrication of linear threshold gates will be presented based on a monostable bistable transition logic element. Each of its input terminals consist out of a resonant tunnelling diode merged with a transistor device. Two input XOR gate is designed and tested. This paper focuses on principles of adiabatic logic, its classification and comparison of various adiabatic logic designs.

This modifications in the circuits leads to improvement of Power Delay Product PDP which is one of the figure of merit to optimize the circuit with factors like power dissipation and delay of the circuit. This paper investigates the design approaches of low power adiabatic gates in terms of energy dissipation and uses of Simple PN diode instead of MOS diode which reduces the effect of Capacitances at high transition and power clock frequency.

The impact of device parameters on the static power dissipation and delay of a CMOS inverter is presented. Fin dimensions such as Fin width and height Fin dimensions such as Fin width and height are varied. For a given gate oxide thickness increasing the fin height and fin width degrades the SCEs, while improves the performance. It was found that reducing the fin thickness was beneficial in reducing the off state leakage current IOFF , while reducing the fin height was beneficial in reducing the gate leakage current IGATE.

It was found that Static power dissipation of the inverter increases with fin height due to the increase in leakage current, whereas delay decreased with increase fin width due to higher on current. The performance of the inverter decreased with the downscaling of the gate oxide thickness due to higher gate leakage current and gate capacitance.

Due to In this paper an attempt has been made to model variation of built-in potential variation for a cylindrical surrounding gate MOSFET. The model has been verified to be working in good agreement with the variations of gate length and channel radius. Switching activity is one of the factors that affect dynamic power in a chip and several Switching activity is one of the factors that affect dynamic power in a chip and several publications have suggested various techniques to reduce the same. Reduction of switching activity in the busses attains significance as bus width, bus capacitance and the clock are recording continuous uptrend.

In this paper, we propose a technique for bus encoding, which, reduces the number of transitions on the bus and performs better than the existing methods such as bus invert coding and shift invert coding for random data in terms of switching activity, without the need for extra overhead in computation and circuit. However, irrespective of the bus width it needs three extra bits and does not assume anything about the nature of the data on the bus.

The second order modulator is designed to work at a signal band of 20K Hz at The second order modulator is designed to work at a signal band of 20K Hz at an oversampling ratio of 64 with a sampling frequency of 2. It achieves a signal to noise ratio of The CIC digital filter is designed to implement a decimation factor of 64, operating at a maximum sampling frequency of 2. A second order sigma delta modulator is implemented in 0.

The complete Sigma Delta ADC, consisting of analog block of second order modulator and digital block of decimator consumes a total power 1. In this paper, we propose a new multiplier-and-accumulator MAC architecture for low power and high speed arithmetic. High speed and low power MAC units are required for applications of digital signal processing like Fast Fourier High speed and low power MAC units are required for applications of digital signal processing like Fast Fourier Transform, Finite Impulse Response filters, convolution etc.

For improving the speed and reducing the dynamic power, there is a need to reduce the glitches 1 to 0 transition and spikes 0 to 1 transition.