Abstract:
An ESD protection circuit design incorporating a single, or a plurality of, parallel inductor and capacitor, also known as LC tank(s), to avoid power loss by parasitic capacitance in ESD circuits. The first design described incorporates a LC tank structure. The second includes two LC tank structures. These structures can be expanded to form ESD protection circuit structures stacked with n-stages LC tanks. The last design described is ESD protection circuits formed by stacking the first design. These designs can avoid power gain loss from parasitic capacitance of ESD, because the parameters of LC tank can be designed to resonant at a desired operating frequency. Each of these designs can be altered slightly to create variant designs with equal identical ESD protection capabilities.

Description:
BACKGROUND OF THE INVENTION 
   Field of Invention 
   This invention is related to an electrostatic discharge (ESD) protection circuitry. More particularly, the invention relates to an electrostatic discharge (ESD) protection circuitry that can be used in a radio frequency (RF) circuitry for electrostatic discharge protection. 
   Electrostatic discharge (ESD) is a transient process of high-energy transfer from integrated circuit (IC) outside to inside when the IC is floated. On-chip ESD protection circuits are constructed into the IC to withstand such destructive currents. The total discharge process takes about ˜1 μs for a human-body-model (HBM). In addition to HBM, there is also charged-device model (CDM) and machine model (MM). Several hundred volts are transferred during such ESD stresses. Voltage transition of this magnitude will make the gate oxide of input stage breakdown and render an IC mailfunction. As the thickness of gate oxide is scaled down constantly with advancements in sub-micrometer-fabrication processes, it is vital to improve the design of ESD protection circuits. 
   A traditional ESD protection design is a two-staged protection structure for digital IC, which is shown in  FIG. 1 . Between a primary stage  10  and a secondary stage  20  of an input ESD protection circuit, a resistor  15  is added to limit the ESD current flowing through a short-channel NMOS  25  in the secondary stage  20 . The resistance value of the resistor  15  is dependent on the turn-on voltage of the ESD clamp device in the primary stage  10  and the current I t2  (secondary breakdown current) of the short-channel NMOS  25  in the secondary stage  20 . Such a two-staged ESD protection design can provide high ESD level protection for digital input pins. However, the large series resistance and the large junction capacitance in the ESD clamp devices will cause a long RC timing delay to the input signal. Therefore, this design is not suitable for analog pins, especially for radio frequency (RF) signal applications. 
   Due to the features of the high frequency applications, parasitic capacitance of the ESD protection device will degrade the power gain performance of RF circuits. In order to solve this problem, the prior art tried to minimize the area of the ESD protection device to reduce the parasitic capacitance of the ESD protection device. This solution, however, also degrades the ESD protection level, so it is necessary to minimize the effects of the parasitic capacitance of the ESD clamp devices for the RF circuits. 
   Some protection circuits have been proposed to achieve the above objectives, as follows. 
   Reversed-Biased Diodes with V DD -to-V SS  Power-Rail Clamp Circuit 
   In order to reduce the loading capacitance to an input pin of RF circuits, diodes in the ESD protection circuits are designed with a small device dimension. With a small device dimension, the NDIO (PDIO) diode under the PS-mode (ND-mode) ESD stress (shown in  FIG. 2 ) operates in the junction breakdown to discharge the ESD current. Typically, the diode under breakdown operation can only offer a low-level ESD protection. To avoid the small diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, and thus limit the ESD protection level of the entire circuit, a turn-on efficient ESD clamp circuit is inserted between the power rails to significantly increase the overall ESD protection level. The ESD circuit structure is shown in  FIG. 3 . 
   When the RF input pin is zapped with NS-mode (PD-mode) ESD stress, the NDIO (PDIO) diode operates under a forward-biased condition to discharge the ESD current. The diodes operating under the forward-biased condition can sustain a much higher ESD level than those operating under a reverse-biased breakdown condition. The RC-based ESD detection circuit  30  is used to trigger on the MNESD device, when the RF INPUT PAD  400  is zapped with the PS-mode or ND-mode ESD stress. The ESD current paths in this RF ESD protection design, under the PS-mode and ND-mode ESD stresses, are respectively illustrated by the dashed lines ESD in  FIG. 4  and  FIG. 5 . Because the NDIO diode in the PS-mode ESD stress is not operating under the breakdown condition, the ESD current is bypassed through the forward-biased PDIO diode and the turned-on MNESD between the VDD/VSS power rails. Similarly, the ND-mode ESD current is discharged as the dashed line illustrates in  FIG. 5  with the NDIO diode operating under a forward-biased condition and the turned-on MNESD between the V DD /V SS  power rails. The MNESD is especially designed with a larger device dimension to sustain a high-level ESD. Although the large-dimension MNESD has a large junction capacitance, the capacitance does not contribute to the RF INPUT PAD  400 . By using this ESD protection design, the RF INPUT pin can sustain much higher ESD levels under the four modes of ESD stresses, but only with small diodes connected to the RF INPUT PAD  400 . This can reduce the loading capacitance generated from the ESD protection devices to the RF INPUT PAD  400 . 
   Use of Inductor as an ESD Device 
   The Leuven University proposed a paper about LNA circuits with inductors and V DD -to-V SS  dual stacked diodes to against the ESD discharge. The inductor is a metallic low-pass passive device and is suitable for ESD protection devices. However, since the inductor is connected from the input to the ground, it will cause DC leakage from the input to the ground directly. Therefore, it needs to be coupled with a capacitor, in series, to block the input PAD and the input gate. 
   Distributed ESD Protection Device for High-Speed Integrated Circuits 
   Shown in  FIG. 6  and  FIG. 8  are distributed ESD protection devices for high-speed integrated circuits, which are inventions by Stanford University.  FIG. 6  shows a one-stage matching structure  45 , and  FIG. 8  shows a four-stage matching structure, including  45   a ,  45   b ,  45   c  and  45   d .  FIG. 7  shows a trace in Smith Chart of parasitic capacitance of the ESD within a one-stage distributed matching structure, and  FIG. 9  shows the same capacitance in a four-stage distributed matching structure. In  FIG. 7 , the parasitic capacitance of ESD (CA+CB) traverses down its path following the circle in Smith Chart from the origin. A transmission line TL will bring the path to the x-axis of Smith Chart. In  FIG. 9 , the parasitic capacitance (C 4 A+C 4 B) traverses down its path following the circle in Smith Chart from the origin. The transmission line TL 4  will bring the route to the x-axis of Smith Chart. The same concept can be applied to illustrate the other parasitic capacitance (C 3 A+C 3 B), (C 2 A+C 2 B), and (CIA+C 1 B). The transmission lines TL 3 , TL 2 , and TL 1  will bring their routes to the x-axis of Smith Chart.
 
( C 1 A+C 1 B )=( C 2 A+C 2 B )=( C 3 A+C 3 B )=( C 4 A+C 4 B )
 
   A comparison of  FIG. 7  and  FIG. 9  shows that the more matching stages in the protective circuit, the closer the last position of the route is to the origin. The distance of the position to the origin is proportional to the signal power gain. Hence, having conditions with more stages matching leads to a better power gain. But it is hard to achieve uniform ESD current distribution amongst the numerous separated ESD sections during impulsive ESD events. The first ESD section, which is the closest to the input pad, will always receive the most bulk of the ESD current before the other sections are turned on to share the current. This causes damage to the first section and, ultimately, lowers the ESD protection threshold in the IC. 
   SUMMARY OF THE INVENTION 
   Accordingly, one object of the present invention is to provide an electrostatic discharge (ESD) protection circuitry, which can be used in a radio frequency (RF) circuitry for electrostatic discharge protection. 
   Accordingly, one object of the present invention is to provide an electrostatic discharge (ESD) protection circuitry, which considers the power gain performance of the RF circuitry and the ESD level. 
   To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an ESD protection circuit device for Giga-Hertz RF integrated circuits which overcome the problems associated with prior art techniques while raising the ESD protection threshold. The new proposed ESD protection design are stacked with LC tanks in the Input/Output (I/O) port with V DD -to-V SS  power-rail clamp circuits. The values of inductance and capacitance in the LC tank can be properly selected by resonant at the RF operating frequency. 
   To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an electrostatic discharge (ESD) circuit, adaptive to a radio frequency (RF) device. The RF device includes a RF circuit with a VDD voltage RF pad, a VSS RF pad and a RF input pad. The ESD circuit comprises a ESD clamp circuit and a LC tank structure. The ESD clamp circuit includes two terminals, the first one of which is connected to the VDD voltage RF pad, and the second one of which is connected to the VSS RF pad. The LC tank structure is coupled between the two terminals of the ESD clamp circuit, and is located between the RF circuit and the RF input pad. The LC tank structure includes a first diode and a first LC tank connected in series between the first terminal of the ESD clamp circuit and the RF input pad, and a second diode and a second LC tank connected in series between the second terminal of the ESD clamp circuit and the RF input pad. 
   In the above-mentioned ESD circuit, in an alternative embodiment, an cathode terminal of the first diode is coupled to the first terminal of the ESD clamp circuit and a anode terminal of the first diode is coupled to the first LC tank, and an cathode terminal of the second diode is coupled to the second LC tank and a anode terminal of the second diode is coupled to the second terminal of the ESD clamp circuit. 
   In the above-mentioned ESD circuit, in an alternative embodiment, an cathode terminal of the first diode is coupled to the first LC tank and a anode terminal of the first diode is coupled to a terminal between the RF circuit and the RF input pad, and an cathode terminal of the second diode is coupled to the terminal between the RF circuit and the RF input pad and a anode terminal of the second diode is coupled to the second LC tank. 
   In the above-mentioned ESD circuit, in an alternative embodiment, the LC tank structure includes an inductor and a capacitor connected to each other in parallel. 
   To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an electrostatic discharge (ESD) circuit, adaptive to a radio frequency (RF) device. The RF device includes a RF circuit with a VDD voltage RF pad, a VSS RF pad and a RF input pad. The ESD circuit comprises a ESD clamp circuit and a LC tank structure. The ESD clamp circuit includes two terminals, the first one of which is connected to the VDD voltage RF pad, and the second one of which is connected to the VSS RF pad. The LC tank structure is coupled between the two terminals of the ESD clamp circuit, and is located between the RF circuit and the RF input pad, wherein the LC tank structure includes a first ESD block between the first terminal of the ESD clamp circuit and the RF input pad, and a second ESD block between the second terminal of the ESD clamp circuit and the RF input pad. 
   In the above-mentioned ESD circuit, in an alternative embodiment, the first ESD block includes a first diode and two first LC tanks connected in series, and the second ESD block includes a second diode and two second LC tanks. 
   In the above-mentioned ESD circuit, in an alternative embodiment, an cathode terminal of the first diode is coupled to the first terminal of the ESD clamp circuit and a anode terminal of the first diode is coupled to the one of the first LC tanks, and an cathode terminal of the second diode is coupled to one of the second LC tanks and a anode terminal of the second diode is coupled to the second terminal of the ESD clamp circuit. 
   In the above-mentioned ESD circuit, in an alternative embodiment, an cathode terminal of the first diode is coupled to one of the first LC tanks and a anode terminal of the first diode is coupled to a terminal between the RF circuit and the RF input pad, and an cathode terminal of the second diode is coupled to the terminal between the RF circuit and the RF input pad and a anode terminal of the second diode is coupled to the one of the second LC tanks. 
   In the above-mentioned ESD circuit, in an alternative embodiment, the first ESD block includes a first diode and a plurality of first LC tanks connected in series, and the second ESD block includes a second diode and a plurality of second LC tanks. Alternatively, an cathode terminal of the first diode is coupled to the first terminal of the ESD clamp circuit and a anode terminal of the first diode is coupled to the one of the first LC tanks, and an cathode terminal of the second diode is coupled to one of the second LC tanks and a anode terminal of the second diode is coupled to the second terminal of the ESD clamp circuit. 
   In the above-mentioned ESD circuit, in an alternative embodiment, an cathode terminal of the first diode is coupled to one of the first LC tanks and a anode terminal of the first diode is coupled to a terminal between the RF circuit and the RF input pad, and an cathode terminal of the second diode is coupled to the terminal between the RF circuit and the RF input pad and a anode terminal of the second diode is coupled to the one of the second LC tanks. 
   To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an electrostatic discharge (ESD) circuit, adaptive to a radio frequency (RF) device. The RF device includes a RF circuit with a VDD voltage RF pad, a VSS RF pad and a RF input pad. The ESD circuit comprises an ESD clamp circuit and a LC tank structure. The ESD clamp circuit includes two terminals, the first one of which is connected to the VDD voltage RF pad, and the second one of which is connected to the VSS RF pad. The LC tank structure is coupled between the two terminals of the ESD clamp circuit, and between the RF circuit and the RF input pad. The LC tank structure includes a first diode, a first LC tank and a first ESD block connected in series between the first terminal of the ESD clamp circuit and the RF input pad, and a second diode, a second LC tank and a second ESD block connected in series between the second terminal of the ESD clamp circuit and the RF input pad. 
   In the above-mentioned ESD circuit, in an alternative embodiment, the first ESD block includes a third diode and a third LC tank connected in series. Alternatively, an cathode terminal of the third diode is coupled to the first terminal of the ESD clamp circuit and a anode terminal of the third diode is coupled to the third LC tank. Alternatively, an cathode terminal of the third diode is coupled to the third LC tank and a anode terminal of the third diode is coupled to the first LC tank. In another embodiment, the third LC tank includes an inductor and a capacitor connected to each other in parallel. 
   In the above-mentioned ESD circuit, in an alternative embodiment, the second ESD block includes a forth diode and a forth LC tank connected in series. Alternatively, an cathode terminal of the forth diode is coupled to the forth LC tank and a anode terminal of the forth diode is coupled to the second terminal of the ESD clamp circuit. Alternatively, an cathode terminal of the forth diode is coupled to the second LC tank and a anode terminal of the forth diode is coupled to the second terminal of the ESD clamp circuit. In another embodiment, the forth LC tank includes an inductor and a capacitor connected to each other in parallel. 
   It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a block diagram showing a traditional ESD protection design with a two-staged protection structure for a digital IC. 
       FIG. 2  shows four modes of ESD zapping on an I/O pin with V DD  or V SS  relatively grounded, which are positive-to-V SS  (PS) mode, negative-to-V SS  (NS) mode, positive-to-V DD  (PD) mode, and negative-to-V DD  (ND) mode. 
       FIG. 3  is a block diagram showing the traditional ESD protection design with a two-staged protection structure for a RF circuit; 
       FIGS. 4 and 5  show ESD current paths in the RF ESD protection design of  FIG. 3 , under a PS-mode and a ND-mode ESD stresses. 
       FIG. 6  and  FIG. 8  shows distributed ESD protection devices for high-speed integrated circuits, which are inventions by Stanford University. 
       FIG. 7  shows the parasitic capacitance of ESD (CA+CB) of  FIG. 6  traverses down its path following the circle in Smith Chart from the origin. 
       FIG. 9  shows the parasitic capacitance of ESD (C 4 A+C 4 B) of  FIG. 8  traverses down its path following the circle in Smith Chart from the origin. 
       FIGS. 10–17  are block diagrams showing an ESD protection design of preferred embodiments of the invention and their responding ESD current paths. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
   The present invention provides an electrostatic discharge (ESD) protection circuitry, which can be used in a radio frequency (RF) circuitry for electrostatic discharge protection. The ESD protection circuitry considers the power gain performance of the RF circuitry and the ESD level and overcomes the problems associated with prior art techniques while raising the ESD protection threshold. The new proposed ESD protection design is stacked with one or more LC tanks in the Input/Output (I/O) port with V DD -to-V SS  power-rail clamp circuits. The values of inductance and capacitance in the LC tank can be selected by resonant at the RF operating frequency. 
   For example, the values of inductance and capacitance can be selected by applying the following formula to resonant at the operating frequency of each individual RF circuit. 
   
     
       
         
           
             jwL 
             // 
             
               1 
               jwC 
             
           
           = 
           ∞ 
         
       
     
     
       
         
           
             1 
             
               
                 1 
                 jwL 
               
               + 
               jwC 
             
           
           = 
           ∞ 
         
       
     
     
       
         
           
             
               1 
               jwL 
             
             + 
             jwC 
           
           = 
           0 
         
       
     
     
       
         
           
             w 
             2 
           
           = 
           
             1 
             LC 
           
         
       
     
     
       
         
           w 
           = 
           
             1 
             
               LC 
             
           
         
       
     
   
   This prevents the loss of signals to ground due to the infinite resistance seen by signals. In the formula, w represents the operating frequency of the RF circuit. The values of the inductance and capacitance of the LC tank will also determine the loss of power gain, so simulation tools are used to select the optimal values. In the ESD condition, the ESD current will be discharged through the ESD device and the inductor. The inductors are made of the top thick metal in general and are metal lines with low parasitic resistance. Thus, in the proposed designs, the novel LC tank ESD circuits will result in higher-level ESD protection for RF circuits. 
   In the following figures from  FIG. 10  to  FIG. 17 , several embodiments are introduced for the invention, including ESD protection devices stacked with one or more LC tanks in the I/O port with V DD -to-V SS  power-rail clamp circuits. 
   ESD Circuit Stacked with A LC Tank Structure 
   Please refer to  FIG. 10 , which depicts a RF circuit device  1000  with an ESD circuit stacked with a LC tank structure  1060  (ESD BLOCK N 1  and ESD BLOCK P 1 ) of a preferred embodiment of the invention. The RF circuit device  1000  includes a RF circuit  1010  with a VDD voltage RF pad  1020 , a VSS RF pad  1030  and a RF input pad  1040  is provided in  FIG. 10 . Between the RF circuit  1010  and the RF input pad  1040  is the ESD circuit. The ESD circuit includes a V DD -to-V SS  power-rail clamp circuit  1050  and a LC tank structure  1060 . The LC tank structure  1060  includes two ESD blocks, including ESD BLOCK N 1  and ESD BLOCK P 1 . 
   The ESD BLOCK N 1  and ESD BLOCK P 1  respectively includes a diode NDIO, a diode PDIO and two LC tanks LC TANK N and LC TANK P, which are connected in series. Each of the LC tanks LC TANK N and LC TANK P includes an inductor and capacitor, which are connected in parallel. The diode PDIO includes an cathode terminal coupled to a first terminal A of the ESD clamp circuit  1050  and a anode terminal coupled to the LC TANK P. The diode NDIO includes an cathode terminal coupled to LC TANK N and a anode terminal coupled to a second terminal B of the ESD clamp circuit  1050 . A terminal C between the RF circuit  1010  and the RF input pad  1040  is connected to both of the LC tanks LC TANK N and LC TANK P. 
   When the LC tank is resonant to the RF frequency, there is infinite impedance, thus minimizing the power gain loss. The ESD current will be discharged through the inductors and the ESD diodes, as the bold dash lines shown in the  FIG. 10 . To avoid the diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, which results in a lower ESD protection level, a turn-on efficient V DD -to-V SS  ESD clamp circuit  1050 , between the power rails, is constructed into the ESD protection circuit. This V DD -to-V SS  ESD clamp circuit can significantly increase the overall ESD protection. 
   When the RF INPUT pad  1040  is zapped with one of the four ESD stress modes, the NDIO diode or the PDIO diode operates under a forward-biased condition with the corresponding inductor to discharge the ESD current. Diodes operating under forward-biased condition can sustain a much higher ESD level than those operating under reverse-biased breakdown condition. The V DD -to-V SS  ESD clamp circuit  1050  is turned on when the RF INPUT PAD  1040  is zapped with PS-mode or ND-mode ESD stresses. The ESD current is bypassed through the forward-biased PDIO diode and the turned-on V DD -to-V SS  ESD clamp circuit  1050  between the V DD /V SS  power rails, because the NDIO diode, in PS-mode ESD stress, does not operate under the breakdown condition. Similarly, the NDIO diode and the corresponding inductor operates under the forward-biased condition with the V DD -to-V SS  ESD clamp circuit  1050 , between the V DD /V SS  power rails, to safely discharge the ND-mode ESD current. 
   The V DD -to-V SS  ESD clamp circuit  1050  is especially designed with a larger device dimension to sustain a high-level ESD. Although the large-dimension V DD -to-V SS  ESD clamp circuit  1050  has a large junction capacitance, this capacitance does not contribute to the RF INPUT PAD  1040 . By applying this ESD protection design, the RF INPUT pin can sustain much higher levels of ESD in the four ESD stress modes (as shown in  FIG. 2 ). Therefore, the loading capacitance generated from the PDIO diode and the NDIO diode of the ESD protection device to the RF INPU PAD  1040  can be significantly avoided by the insertion of the LC tank. Hence, there will be no significant degradation of performance in the RF IC. 
     FIG. 11  depicts a RF circuit device  1100  with an ESD circuit stacked with a LC tank structure  1160 , which includes two ESD blocks ESD BLOCK N 2  and ESD BLOCK P 2 , in another preferred embodiment of the invention. In the alternative design, compared with elements in the  FIG. 10 , the positions of the LC tank LC TANK P 2  and the diode PDIO are switched and the positions of the LC tank LC TANK N 2  and the diode NDIO are also switched. The RF circuit device  1100  includes a RF circuit  1110  with a VDD voltage RF pad  1120 , a VSS RF pad  1130  and a RF input pad  1140  is provided in  FIG. 11 . Between the RF circuit  1110  and the RF input pad  1140  is the ESD circuit. The ESD circuit is constructed by a V DD -to-V SS  power clamp circuit  1150  and the LC tank structure  1160 . The LC tank structure  1160  includes two ESD blocks, ESD BLOCK N 2  and ESD BLOCK P 2 . 
   The ESD BLOCK N 2  includes a LC tank LC TANK N 2  and a diode NDIO. The ESD BLOCK P 2  includes a LC tank LC TANK P 2  and a diode PDIO. The two LC tanks and the diodes are connected in series. Each of the LC tanks LC TANK N 2  and LC TANK P 2  includes an inductor and capacitor, connected in parallel. The diode PDIO includes an cathode terminal coupled to the LC tank LC TANK P 2  and a anode terminal connected to a terminal C between the RF circuit  1110  and the RF input pad  1140 . The diode NDIO includes an cathode terminal coupled to the terminal C between the RF circuit  1110  and the RF input pad  1140  and a anode terminal coupled to the LC tank LC TANK N 2 . The other terminal of the LC TANK P 2  opposite to the terminal connected to the PDIO is connected to a first terminal A of the ESD clamp circuit  1150 . The other terminal of the LC TANK N 2  opposite to the terminal connected to the NDIO is connected to a second terminal B of the ESD clamp circuit  1150 . 
   When the LC tank is resonant to the RF frequency, there is infinite impedance, thus minimizing the power gain loss. The ESD current will be discharged through the inductors and the ESD diodes, as the bold dash lines shown in the  FIG. 11 . To avoid the diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, which results in a lower ESD protection level, a turn-on efficient V DD -to-V SS  ESD clamp circuit  1150 , between the power rails, is constructed into the ESD protection circuit. This V DD -to-V SS  ESD clamp circuit can significantly increase the overall ESD protection. 
   The V DD -to-V SS  ESD clamp circuit  1150  is especially designed with a larger device dimension to sustain a high-level ESD. Although the large-dimension V DD -to-V SS  ESD clamp circuit  1150  has a large junction capacitance, this capacitance does not contribute to the RF INPUT PAD  1140 . By applying this ESD protection design, the RF INPUT pin can sustain much higher levels of ESD in the four ESD stress modes (as shown in  FIG. 2 ). Therefore, the loading capacitance generated from the PDIO diode and the NDIO diode of the ESD protection device to the RF INPUT PAD  1140  can be significantly avoided by the insertion of the LC tank. Hence, there will be no significant degradation of performance in the RF IC. 
   ESD Circuit Stacked with Stacked LC Tank Structure 
   To consider the parasitic effect of inductors and capacitors implemented on the chip, a LC tank structure with LC tanks stacked in series is provided in the invention to achieve higher impedance at resonation. By such implementation, the power gain performance of the RF circuitry and the ESD level are considered. Please refer to  FIG. 12 , which depicts a RF circuit device  1200  with an ESD circuit stacked with a LC tank structure  1260  of a preferred embodiment of the invention. The RF circuit device  1200  includes a RF circuit  1210  with a VDD voltage RF pad  1220 , a VSS RF pad  1230  and a RF input pad  1240  is provided in  FIG. 12 . Between the RF circuit  1210  and the RF input pad  1240  is the ESD circuit. The ESD circuit includes a V DD -to-V SS  power clamp circuit  1250  and a LC tank structure  1260 . The LC tank structure  1260  includes a first stacked LC tank block  1260 SLCP, a ESD diode PDIO, a second stacked LC tank block  1260 SLCN and another ESD diode NDIO connected in series. Each of the stacked LC tank blocks includes at least two LC tanks stacked in series together. The diode PDIO includes an cathode terminal coupled to a first terminal A of the ESD clamp circuit  1250  and a anode terminal coupled to the first stacked LC tank block  1260 SLCP. The diode NDIO includes an cathode terminal coupled to the second stacked LC tank block  1260 SLCN and a anode terminal coupled to a second terminal B of the ESD clamp circuit  1250 . A terminal C between the RF circuit  1210  and the RF input pad  1240  is connected to both of the first stacked LC tank block  1260 SLCP and a second stacked LC tank block  1260 SLCN. 
   As previously mentioned, power gain loss is minimized when the LC tanks are resonant to the RF circuit frequency. The ESD current will be discharged through the inductors and the ESD diodes, as shown in  FIG. 12 . To avoid the diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, which results in a lowered ESD protection level, a turn-on efficient V DD -to-V SS  ESD clamp circuit  1250 , between the power rails, is constructed into the ESD protection circuit. This V DD -to-V SS  ESD clamp circuit can significantly increase the overall ESD protection. 
   When the RF INPUT pad  1240  is zapped with one of the four ESD stress modes, the NDIO or PDIO diode operates under the forward-biased condition with the inductor to discharge the ESD current. Diodes operating under the forward-biased condition can sustain a much higher ESD level than those operating under reverse-biased breakdown condition. The V DD -to-V SS  ESD clamp circuit  1250  is turned on when the RF INPUT PAD  1240  is zapped with PS-mode or ND-mode ESD stresses. The ESD current is bypassed through the forward-biased PDIO diode and the turned-on V DD -to-V SS  ESD clamp circuit  1250  between the V DD /V SS  power rails, because the NDIO diode, in PS-mode ESD stress, does not operate under the breakdown condition. Similarly, the NDIO diode and inductor operates under the forward-biased condition with the V DD -to-V SS  ESD clamp circuit  1250 , between the V DD /V SS  power rails, to safely discharge ND-mode ESD current. The V DD -to-V SS  ESD clamp circuit  1250  is especially designed with a larger device dimension to sustain a high-level ESD. Although the large-dimension V DD -to-V SS  ESD clamp circuit  1250  has a large junction capacitance, this capacitance does not contribute to the RF input pad  1240 . By applying this ESD protection design, the RF input pad  1240  can sustain much higher levels of ESD in the four ESD stress modes ( FIG. 2 ). Therefore, the loading capacitance generated from the PDIO and NDIO of ESD protection devices to the RF input pad  1240  can be significantly avoided by the insertion of the LC tank. Hence, there will be no significant degradation of performance in RF IC. 
   Please refer to  FIG. 13 , which depicts a RF circuit device  1300  with an ESD circuit stacked with a LC tank structure  1360  of another preferred embodiment of the invention, which considers the parasitic effect of inductors and capacitors implemented on the chip. In the alternative design, compared with elements in the  FIG. 12 , positions of the first stacked LC tank block  1360 SLCP and the PDIO diode are switched, and positions of the second stacked LC tank block  1360 SLCN and the NDIO diode are also switched. The RF circuit device  1300  includes a RF circuit  1310  with a VDD voltage RF pad  1320 , a VSS RF pad  1330  and a RF input pad  1340  is provided in  FIG. 13 . Between the RF circuit  1310  and the RF input pad  1340  is the ESD circuit. The ESD circuit includes a V DD -to-V SS  power-rail clamp circuit  1350  and a LC tank structure  1360 . The LC tank structure  1360  includes a first stacked LC tank block  1360 SLCP and a second stacked LC tank block  1360 SLCN connected in series. Each of the stacked LC tank blocks includes at least two LC tanks stacked in series together. The diode PDIO includes an cathode terminal coupled to the first stacked LC tank block  1360 SLCP and a anode terminal connected to a terminal C between the RF circuit  1310  and the RF input pad  1340 . The diode NDIO includes an cathode terminal coupled to the terminal C between the RF circuit  1310  and the RF input pad  1340  and a anode terminal coupled to the second stacked LC tank block  1360 SLCN. The other terminal of the first stacked LC tank block  1360 SLCP opposite to the terminal connected to the PDIO is connected to a first terminal A of the ESD clamp circuit  1350 . The other terminal of the second stacked LC tank block  1360 SLCN opposite to the terminal connected to the NDIO is connected to a second terminal B of the ESD clamp circuit  1350 . 
   As previously mentioned, power gain loss is minimized when the LC tanks are resonant to the RF circuit frequency. The ESD current will be discharged through the inductors and the ESD diodes, as shown in  FIG. 13 . To avoid the diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, which results in a lower ESD protection level, a turn-on efficient V DD -to-V SS  ESD clamp circuit  1350 , between the power rails, is constructed into the ESD protection circuit. This V DD -to-V SS  ESD clamp circuit can significantly increase the overall ESD protection. 
   When the RF INPUT pad  1340  is zapped with one of the four ESD stress modes, the NDIO or PDIO diode operates under the forward-biased condition with the inductor to discharge the ESD current. Diodes operating under the forward-biased condition can sustain a much higher ESD level than those operating under reverse-biased breakdown condition. The V DD -to-V SS  ESD clamp circuit  1350  is turned on when the RF INPUT PAD  1340  is zapped with PS-mode or ND-mode ESD stresses. The ESD current is bypassed through the forward-biased PDIO diode and the turned-on V DD -to-V SS  ESD clamp circuit  1350  between the V DD /V SS  power rails, because the NDIO diode, in PS-mode ESD stress, does not operate under the breakdown condition. Similarly, the NDIO diode and inductor operates under the forward-biased condition with the V DD -to-V SS  ESD clamp circuit  1350 , between the V DD /V SS  power rails, to safely discharge ND-mode ESD current. The V DD -to-V SS  ESD clamp circuit  1350  is especially designed with a larger device dimension to sustain a high-level ESD. Although the large-dimension V DD -to-V SS  ESD clamp circuit  1350  has a large junction capacitance, this capacitance does not contribute to the RF input pad  1340 . By applying this ESD protection design, the RF input pad  1340  can sustain much higher levels of ESD in the four ESD stress modes ( FIG. 2 ). Therefore, the loading capacitance generated from the PDIO and NDIO of ESD protection devices to the RF input pad  1340  can be significantly avoided by the insertion of the LC tank. Hence, there will be no significant degradation of performance in RF IC. 
   In alternative embodiment as shown in  FIG. 14 , a LC tank structure with n-stage LC tanks stacked in series is provided to achieve higher impedance at resonation. By such implementation, the power gain performance of the RF circuitry and the ESD level are both considered. In  FIG. 14 , which depicts a RF circuit device  1400  with an ESD circuit stacked with a LC tank structure  1460 . The RF circuit device  1400  includes a RF circuit  1410  with a VDD voltage RF pad  1420 , a VSS RF pad  1430  and a RF input pad  1440 . Between the RF circuit  1410  and the RF input pad  1440  is the ESD circuit. The ESD circuit includes a V DD -to-V SS  power clamp circuit  1450  and a LC tank structure  1460 . The LC tank structure  1460  includes a first n-stage stacked LC tank block  1460 SLCP, a ESD diode PDIO, a second n-stage stacked LC tank block  1460 SLCN, and a ESD diode NDIO connected in series. Each of the stacked LC tank blocks includes at least two LC tanks stacked in series together. The diode PDIO includes an cathode terminal coupled to a first terminal A of the ESD clamp circuit  1450  and a anode terminal coupled to the first n-stage stacked LC tank block  1460 SLCP. The diode NDIO includes an cathode terminal coupled to the second n-stage stacked LC tank block  1460 SLCN and a anode terminal coupled to a second terminal B of the ESD clamp circuit  1450 . A terminal C between the RF circuit  1410  and the RF input pad  1440  is connected to both of the first n-stage stacked LC tank block  1460 SLCP and a second n-stage stacked LC tank block  1460 SLCN. 
   In further embodiment as shown in  FIG. 15 , a LC tank structure with n-stages LC tanks stacked in series is provided to achieve higher impedance at resonation. In the alternative design, compared with elements in the  FIG. 14 , positions of the first n-stage stacked LC tank block  1560 SLCP and the PDIO diode are switched, and positions of the second n-stage stacked LC tank block  1560 SLCN and the NDIO diode are also switched. As shown in  FIG. 15 , which depicts a RF circuit device  1500  with an ESD circuit stacked with a LC tank structure  1560 , which considers the parasitic effect of inductors and capacitors implemented on the chip. The RF circuit device  1500  includes a RF circuit  1510  with a VDD voltage RF pad  1520 , a VSS RF pad  1530  and a RF input pad  1540  is provided in  FIG. 15 . Between the RF circuit  1510  and the RF input pad  1540  is the ESD circuit. The ESD circuit includes a V DD -to-V SS  power clamp circuit  1550  and a LC tank structure  1560 . The LC tank structure  1560  includes a first n-stage stacked LC tank block  1560 SLCP and a second n-stage stacked LC tank block  1560 SLCN connected in series. Each of the stacked LC tank blocks includes at least two LC tanks stacked in series together. 
   ESD Devices with Stacked LC Tank and Diode (ESD Block) Structures 
   Applying the same principle of the incorporation of LC tanks into a ESD protection device and the fact that stacked ESD devices decreases the parasitic capacitance, it is provided in an alternative embodiment to create designs of ESD protection devices by stacking similar ESD blocks (ESD BLOCK P 1  and ESD BLOCK N 1  as shown in  FIG. 16 ), herein is denoted as a “stacked ESD block structure”. Using these designs, the power gain loss is reduced by stacked LC tanks and the power gain loss affected by the stacked ESD diodes is also decreased. This significantly lowers the total power gain loss by the introduction of ESD circuits into RF circuits. 
     FIG. 16  depicts the ESD circuit stacked with a stacked ESD block structure  1660 . The RF circuit device  1600  includes a RF circuit  1610  with a VDD voltage RF pad  1620 , a VSS RF pad  1630  and a RF input pad  1640  is provided in  FIG. 16 . Between the RF circuit  1610  and the RF input pad  1640  is the ESD circuit coupled therebetween. The ESD circuit includes a V DD -to-V SS  power clamp circuit  1650  and a stacked ESD block structure  1660 . The stacked ESD block structure  1660  includes two portions between the ESD clamp circuit  1650  and a terminal C located between the RF circuit  1610  and the RF input pad  1640 . 
   In the first portion, the first ESD block ESD BLOCK P 1 , a LC tank LC 1  and an ESD diode PDIO are connected in series. One terminal of the first ESD block ESD BLOCK P 1  is connected to a first terminal A of the ESD clamp circuit  1650  and another terminal of the first ESD block ESD BLOCK P 1  is connected to an cathode terminal of the diode PDIO. A anode terminal of the diode PDIO is connected to the LC tank LC 1 . The other terminal of the LC tank LC 1  opposite to the terminal connected to the diode PDIO is connected to terminal C. In the second portion, the second ESD block ESD BLOCK N 1 , a LC tank LC 2  and an ESD diode NDIO are connected in series. One terminal of the second ESD block ESD BLOCK N 1  is connected to a second terminal B of the ESD clamp circuit  1650  and another terminal of the second ESD block ESD BLOCK N 1  is connected to a anode terminal of the diode NDIO. An cathode terminal of the diode NDIO is connected to the LC tank LC 2 . The other terminal of the LC tank LC 2  opposite to the terminal connected to the diode NDIO is connected to the terminal C. 
   To avoid the diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, which results in a lowered ESD protection level, a turn-on efficient V DD -to-V SS  ESD clamp circuit  1650 , between the power rails, is constructed into the ESD protection circuit. This V DD -to-V SS  ESD clamp circuit can significantly increase the overall ESD protection while lowering the power gain loss of the RF circuit. 
   When the RF INPUT pin is zapped with one of the four ESD stress modes, the NDIO or PDIO diode operates under forward-biased condition with the inductor to discharge the ESD current. Diodes operating under forward-biased condition can sustain a much higher ESD level than those operating under reverse-biased breakdown condition. The V DD -to-V SS  ESD clamp circuit  1650  is turned on when the RF INPUT PAD  1640  is zapped with PS-mode or ND-mode ESD stresses. The ESD current is bypassed through the forward-biased PDIO diode and the turned-on V DD -to-V SS  ESD clamp circuit  1650  between the V DD /V SS  power rails, because the NDIO diode, in PS-mode ESD stress, does not operate under breakdown condition. Similarly, the NDIO diode and inductor operates under forward-biased condition with the V DD -to-V SS  ESD clamp circuit  1650 , between the V DD /V SS  power rails, to safely discharge ND-mode ESD current. The V DD -to-V SS  ESD clamp circuit  1650  is especially designed with a larger device dimension to sustain a high-level ESD. Although the large-dimension V DD -to-V SS  ESD clamp circuit  1650  has a large junction capacitance, this capacitance does not contribute to the RF INPUT PAD  1640 . By applying this ESD protection design, the RF INPUT pin can sustain much higher levels of ESD in the four ESD stress modes ( FIG. 2 ). Therefore, the loading capacitance generated from the PDIO and NDIO of ESD protection devices to the RF INPUT PAD  100  can be significantly avoided by the insertion of the LC tank. Hence, there will be no significant degradation of performance in RF IC. 
     FIG. 17  shows an alternative design to the said circuit by stacking ESD BLOCKs with the LC tanks and the diodes switched (ESD BLOCK P 2  and ESD BLOCK N 2 ).  FIG. 17  depicts the ESD circuit stacked with a stacked ESD block structure  1760 . The RF circuit device  1700  includes a RF circuit  1710  with a VDD voltage RF pad  1720 , a VSS RF pad  1730  and a RF input pad  1740  is provided in  FIG. 17 . Between the RF circuit  1710  and the RF input pad  1740  is the ESD circuit coupled therebetween. The ESD circuit includes a VDD-to-VSS power clamp circuit  1750  and a stacked ESD block structure  1760 . The stacked ESD block structure  1760  includes two portions. In the first portion, a first ESD block ESD BLOCK P 2 , a LC tank LC 1  and an ESD diode PDIO are connected in series. In the second portion, a second ESD block ESD BLOCK N 2 , a LC tank LC 2  and an ESD diode NDIO are connected in series. Each of the ESD block includes at least a LC tank and an ESD diode stacked in series together. In the alternative design, compared with elements in the  FIG. 16 , positions of the first ESD block ESD BLOCK P 2  and the PDIO diode are switched, and positions of the second ESD block ESD BLOCK N 2  and the NDIO diode are also switched. 
   To avoid the diodes from operating under breakdown condition during the PS-mode and ND-mode ESD stresses, which results in a lower ESD protection level, a turn-on efficient V DD -to-V SS  ESD clamp circuit  1750 , between the power rails, is constructed into the ESD protection circuit. This significantly increases the overall ESD protection while lowering the power gain loss of the RF circuits. 
   The ESD circuit with LC tank above-mentioned is constructed of two parts. First is the implementation of ESD device in the I/O port. The other is the LC tank. Regarding the ESD device, due to the minimization requirement of parasitic capacitance in RF IC, ESD devices used in this invention must possess high ESD level with small layout area. Regarding the LC tank, the inductor can be implemented on board the chip. In CMOS technology, on-chip inductors with a low Q value could cause degradation to the realistic LC resonating condition. However, there exist alternative high Q value inductors and bond-wire inductors that will limit such degradations. The capacitors used in the invention can be metal-in-metal or MOS capacitors. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.