Patent Publication Number: US-7916566-B2

Title: Voltage control apparatus and method of controlling voltage using the same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 11/822,358, filed Jul. 5, 2007 now U.S. Pat. No. 7,502,268 , the subject matter of which application is incorporated herein by reference in its entirety. 
     This application claims the benefit of Korean Patent Application No. 10-2006-0099652, filed on Oct. 13, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a semiconductor integrated circuit. More particularly, the present invention relates to a voltage control apparatus using a burn-in test where a stress test is applied to weak cells and peripheral logics so as to detect defective elements in advance, and a method of controlling a voltage using the same. 
     2. Related Art 
     In general, semiconductor integrated circuits, for example, dynamic random access memories (DRAMs) are subjected to a burn-in test process that applies a stress to the DRAMs at a voltage higher than an operation voltage and a high temperature so as to detect defective elements in advance before a packaging process. If the burn-in test process is performed, it is possible to detect defective cells and logic circuits. 
     Further, during the burn-in test process, an excessive stress is applied to a dielectric film of storage capacitors of cells where a data signal is stored at a high potential so as to screen out defective cells therefrom. The stress is applied to a gate oxide film of cell transistors so as to determine whether electric breakdown occurs in the gate oxide film. 
     In order to perform the burn-in operation, a DRAM needs to have an active-write-precharge operation pattern. The operation of the DRAM is divided into a row-fast (X-Fast) operation and a column-fast (Y-Fast) operation according to row address (X-Address) and column address (Y-Address) scan methods. 
       FIG. 1  is a conceptual diagram illustrating an address proceeding direction and an address pattern according to a row-fast (X-Fast) operation, and  FIG. 2  is a conceptual diagram illustrating an address proceeding direction and an address pattern according to a column-fast (Y-Fast) operation. 
     In  FIGS. 1 and 2 , A 0  to A(N) indicate active commands, W 0  to W(N) indicate write commands, and P 0  to P(N) indicate precharge commands. 
     When comparing structures shown in  FIGS. 1 and 2 , the number of times of active-precharge during a row-fast (X-Fast) operation is n times larger than that during a column-fast (Y-Fast) operation. This means that an amount of peak current is large during an active operation or a precharge operation. 
     That is, in the case of the column-fast (Y-Fast) operation, according to an active-precharge method, after a row address is activated, a write operation is performed such that the number of times of the write operation is as many times as the number of columns, and a precharge operation is performed. For this reason, a peak current according to the operation of a word line WL during the column-fast (Y-Fast) operation becomes 1/N times smaller than that during the row-fast (X-Fast) operation. 
       FIG. 3  is a timing diagram illustrating an active-precharge method when a voltage control apparatus according to the related art performs a row-fast (X-Fast) operation. 
     As shown in  FIG. 3 , in the general voltage control apparatus, if an active command ACT is input, an active signal ACTIVE is generated, and a potential of the word line WL is increased to a level of a bootstrapping voltage VPP according to the active signal ACTIVE. Since the word line WL that is discharged to a ground voltage VSS needs to be charged to the level of the bootstrapping voltage VPP, a large amount of current is instantaneously consumed. 
     In  FIG. 3 , reference character A indicates an instantaneous peak current that is generated according to the operation of a word line WL during an active operation, and reference character B indicates a peak current that is generated during a precharge operation. Reference character C indicates a peak current that is generated according to the operation of a sense amplifier. 
     However, as the capacity of a DRAM increases, the amount of operation current that flows through the DRAM increases. In particular, in the case of the burn-in test where an active-precharge operation is repeated for 48 to 72 hours with an external voltage VDD higher than an operation voltage, a large amount of peak current is generated during a row-fast (X-Fast) operation. The large amount of peak current causes a solder ball functioning as an external signal terminal to be melted during a packaging process of a semiconductor memory apparatus, which lowers a package yield and damages a burn-in socket. 
     According to another method in the related art, an amount of peak current is reduced by using an active-precharge method during a column-fast (Y-Fast) operation. However, when the burn-in test is performed through the column-fast (Y-Fast) operation, a peri-transistor formed in a peripheral region may be deteriorated, and it is difficult to accurately screen out defects of the peri-transistor. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention may provide a voltage control apparatus that is capable of preventing a high concentration of a peak current. 
     Another embodiment of the invention may provide a method of controlling a voltage that is capable of allowing a burn-in test process to be performed without causing elements to be deteriorated. 
     An embodiment of the present invention may provide a voltage control apparatus. The voltage control apparatus may include a signal generator that outputs a burn-in control signal and a burn-in precharge signal in response to an all bank precharge command, and a voltage controller that may supply either a first voltage or a second voltage lower than the first voltage to a word line in response to the burn-in control signal and the burn-in precharge signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating an address proceeding direction and an address pattern according to a row-fast (X-Fast) operation of a general DRAM; 
         FIG. 2  is a conceptual diagram illustrating an address proceeding direction and an address pattern according to a column-fast (Y-Fast) operation of the general DRAM; 
         FIG. 3  is a timing diagram illustrating an active-precharge method in a case where a voltage control apparatus according to the related art performs a row-fast (X-Fast) operation; 
         FIG. 4  is a block diagram illustrating an exemplary voltage control apparatus according to an embodiment of the present invention; 
         FIG. 5  is an internal circuit diagram of an exemplary signal generating unit shown in  FIG. 4 ; 
         FIG. 6  is an internal block diagram of an exemplary control signal generating unit shown in  FIG. 4 ; 
         FIG. 7  is an internal circuit diagram of an exemplary first control signal generating portion shown in  FIG. 6 ; 
         FIG. 8  is an internal circuit diagram of an exemplary second control signal generating portion shown in  FIG. 6 ; 
         FIG. 9  is an internal circuit diagram of an exemplary voltage supply unit shown in  FIG. 4 ; and 
         FIG. 10  is a timing diagram illustrating an active-precharge method in a case where a voltage control apparatus according to an embodiment of the present invention performs a row-fast (X-Fast) operation. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENT 
     Embodiments of the present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to an embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. 
     Referring to  FIG. 4 , a voltage control apparatus according to an embodiment of the present invention may include a signal generator  100  and a voltage controller  200 . 
     The signal generator  100  generates a burn-in control signal CTRL_BI and a burn-in precharge signal PCG_ALL_BI in response to an all bank precharge command (not shown). This signal generator  100  includes a first signal generating unit  110  and a second signal generating unit  130 . 
     The first signal generating unit  110  outputs the burn-in control signal CTRL_BI in response to a burn-in test mode signal TM_BI and a control signal CTRL. The first signal generating unit  110  includes a first NAND gate ND 1  that receives the burn-in test mode signal TM_BI and the control signal CTRL. Further, the first signal generating unit  110  includes a first inverter IV 1  that inverts an output signal of the first NAND gate ND 1  to output the inverted signal as the burn-in control signal CTRL_BI. The first signal generating unit  110  may be composed of a logic element that receives the burn-in test mode signal TM_BI and the control signal CTRL and performs an AND operation on the received signals, that is, an AND gate. The burn-in test mode signal TM_BI is activated during a burn-in test mode, and the control signal CTRL is activated when an all bank precharge command is input and may be a specific address signal. 
     The second signal generating unit  130  outputs the burn-in precharge signal PCG_ALL_BI in response to the second precharge signal PCG_ALL and the active signal ACTIVE. The second signal generating unit  130  includes a second inverter IV 2  that inverts the active signal ACTIVE, a second NAND gate ND 2  that receives the second precharge signal PCG_ALL and an output signal of the second inverter IV 2 , and a third inverter IV 3  that inverts an output signal of the second NAND gate ND 2  and outputs it as a burn-in precharge signal PCG_ALL_BI. 
     Meanwhile, in response to the burn-in control signal CTRL_BI and the burn-in precharge signal PCG_ALL_BI, the voltage controller  200  supplies either a first voltage VPP or a second voltage VDD lower than the first voltage VPP to a word line WL. The voltage controller  200  may further receive a first precharge signal PCG_OR and an active signal ACTIVE. That is, the voltage controller  200  outputs the first voltage VPP or the second voltage VDD in response to the first precharge signal PCG_OR, the active signal ACTIVE, the burn-in control signal CTRL_BI, and the burn-in precharge signal PCG_ALL_BI. 
     The voltage controller  200  includes a control signal generating unit  210  and a voltage supply control unit  230 . 
     The control signal generating unit  210  outputs a voltage control signal VPP_VDD_SHORTb in response to the active signal ACTIVE, the first precharge signal PCG_OR, the burn-in precharge signal PCG_ALL_BI, and the burn-in control signal CTRL_BI. The first precharge signal PCG_OR precharges a part of a plurality of banks, and the second precharge signal PCG_ALL precharges all of the plurality of banks. For example, the first precharge signal PCG_OR is activated when a precharge command PCG is input, and the second precharge signal PCG_ALL is activated when an all bank precharge command APCG is input. 
     As shown in  FIG. 6 , the control signal generating unit  210  may include a first control signal generating portion  211  and a second control signal generating portion  213 . The first control signal generating portion  211  receives an active signal ACTIVE, generates an active delay signal ACTIVE_DEL obtained by delaying the active signal ACTIVE, and an active delay pulse signal ACTIVE_DEL_PUL that responds to the active delay signal ACTIVE_DEL. 
     As shown in  FIG. 7 , the first control signal generating portion  211  includes a signal delay unit  211 - 1  and a pulse generating portion  211 - 3 . The signal delay unit  211 - 1  delays the active signal ACTIVE by a first delay time td 1  and generates the active delay signal ACTIVE_DEL. The pulse generating portion  211 - 3  generates an active delay pulse signal ACTIVE_DEL_PUL in response to the active delay signal ACTIVE_DEL. For example, the signal delay unit  211 - 1  includes a series of inverters. The pulse generating portion  211 - 3  includes an inversion delay unit  211 - 31  that inverts and delays the active delay signal ACTIVE_DEL by a second delay time td 2 , a third NAND gate ND 3  that receives the active delay signal ACTIVE_DEL and an output signal of the inversion delay unit  211 - 31 , and a fourth inverter IV 4  that inverts an output signal of the third NAND gate ND 3  and outputs it as the active delay pulse signal ACTIVE_DEL_PUL. In this embodiment, the pulse generating portion  211 - 3  includes the NAND gate and the inverter, but may include other logic elements to generate a pulse signal. 
     Meanwhile, the second control signal generating portion  213  generates the voltage control signal VPP_VDD_SHORTb in response to the first precharge signal PCG_OR, the burn-in precharge signal PCG_ALL_BI, the burn-in control signal CTRL_BI, the active delay signal ACTIVE_DEL, and the active delay pulse signal ACTIVE_DEL_PUL. 
     As shown in  FIG. 8 , the second control signal generating portion  213  includes a first signal input unit  213 - 1 , a first latch unit  213 - 2 , a second signal input unit  213 - 3 , a second latch unit  213 - 4 , and a signal driving unit  213 - 5 . 
     The first signal input unit  213 - 1  changes a potential of a first node S 1  in response to the first precharge signal PCG_OR, the burn-in control signal CTRL_BI, the active delay signal ACTIVE_DEL, and the active delay pulse signal ACTIVE_DEL_PUL. The first signal input unit  213 - 1  includes a fifth inverter IV 5 , a first transistor P 1 , a second transistor N 1 , a third transistor N 2 , a sixth inverter IV 6 , and a fourth transistor P 2 . The fifth inverter IV 5  inverts the first precharge signal PCG_OR, and the first transistor P 1  switches a second voltage VDD according to an output signal of the fifth inverter IV 5 . The second transistor N 1  transmits the voltage of the first node S 1  to the third transistor N 2  in response to the burn-in control signal CTRL_BI, and the third transistor N 2  transmits a voltage supplied by the second transistor N 1  to a ground terminal VSS in accordance with an active delay signal ACTIVE_DEL. The sixth inverter IV 6  inverts the active delay pulse signal ACTIVE_DEL_PUL, and the fourth transistor P 2  transmits the second voltage VDD to the first node S 1  in accordance with the output signal of the sixth inverter IV 6 . 
     The first latch unit  213 - 2  latches a potential of the first node S 1 . The first latch unit  213 - 2  includes seventh and eighth inverters IV 7  and IV 8 . 
     The second signal input unit  213 - 3  changes a potential of the second node S 2  in response to the burn-in precharge signal PCG_ALL_BI, the burn-in control signal CTRL_BI, and the active delay signal ACTIVE_DEL. The second signal input unit  213 - 3  includes a ninth inverter IV 9 , a fifth transistor P 3 , a sixth transistor N 3 , and a seventh transistor N 4 . The ninth inverter IV 9  inverts the active delay signal ACTIVE_DEL, and the fifth transistor P 3  transmits the second voltage VDD to the second node S 2  in response to the output signal of the ninth inverter IV 9 . The sixth transistor N 3  transmits a voltage of the second node S 2  to the seventh transistor N 4  in response to a burn-in control signal CTRL_BI, and the seventh transistor N 4  transmits a voltage supplied by the sixth transistor N 3  to a ground terminal VSS in response to the burn-in precharge signal PCG_ALL_BI. 
     The second latch unit  213 - 4  latches a potential of the second node S 2 . The second latch unit  213 - 4  includes a tenth inverter IV 10  and an eleventh inverter IV 11 . 
     In response to the active delay signal ACTIVE_DEL, the signal driving unit  213 - 5  drives either an output signal of the first latch unit  213 - 2  or an output signal of the second latch unit  213 - 4  to output it as the voltage control signal VPP_VDD_SHORTb. The signal driving unit  213 - 5  includes a twelfth inverter IV 12 , a first switching element PG 1 , a second switching element PG 2 , and a thirteenth inverter IV 13 . The twelfth inverter IV 12  inverts the active delay signal ACTIVE_DEL, and the first switching element PG 1  transmits an output signal of the first latch unit  213 - 2  to the third node S 3  in response to the active delay signal ACTIVE_DEL and the output signal of the twelfth inverter IV 12 . The second switching element PG 2  transmits the output signal of the second latch unit  213 - 4  to the third node S 3  according to the active delay signal ACTIVE_DEL and the output signal of the twelfth inverter IV 12 . The thirteenth inverter IV 13  inverts a signal of the third node S 3  and outputs it as the voltage control signal VPP_VDD_SHORTb. In this embodiment, each of the first switching element PG 1  and the second switching element PG 2  is composed of a pass gate, each of the first transistor P 1 , the fourth transistor P 2 , and the fifth transistor P 3  is composed of a PMOS transistor, and each of the second transistor N 1 , the third transistor N 2 , the sixth transistor N 3 , and the seventh transistor N 4  is composed of an NMOS transistor. 
     Meanwhile, the voltage supply control unit  230  supplies either the first voltage VPP or the second voltage VDD lower than the first voltage VPP to the word line WL in response to the voltage control signal VPP_VDD_SHORTb. The second voltage VDD may be an external supply voltage supplied from the outside, and the first voltage VPP may be a voltage that is generated by pumping the second voltage VDD. As shown in  FIG. 9 , the voltage supply unit  230  may be composed of an eighth transistor P 4  that shorts the first voltage VPP and the second voltage VDD in response to the voltage control signal VPP_VDD_SHORTb. The eighth transistor P 4  may be replaced by a switching element that shorts the first voltage VPP and the second voltage VDD in response to the voltage control signal VPP_VDD_SHORTb. 
     According to one purpose of a designer, the voltage supply unit  230  may supply either the first voltage VPP or the second voltage VDD to the word line WL in response to the voltage control signal VPP_VDD_SHORTb, in a different method from the method according to the above-described embodiment. 
     Referring to  FIGS. 4 to 10 , the voltage control apparatus according to an embodiment of the present invention stabilizes each power at a predetermined voltage level after a semiconductor device enters a burn-in test mode. And then, the voltage control apparatus receives an all bank precharge command APCG before an active signal is input and performs a dummy all bank precharge operation. The all bank precharge operation means that a precharge operation is performed once more in the voltage control apparatus, and does not affect a normal operation. During the all bank precharge operation, since the control signal CTRL is an activated pulse signal, the signal generator  100  outputs the burn-in control signal CTRL_BI that is the activated pulse signal. 
     When the all bank precharge command APCG is applied, the second precharge signal PCG_ALL is activated at a high level, and the first precharge signal PCG_OR is maintained at a low level. Meanwhile, if the precharge command PCG is input, the first precharge signal PCG_OR is activated at a high level, and the second precharge signal PCG_ALL is maintained at a low level. 
     When the all bank precharge command APCG is applied in a state where the active signal ACTIVE is at a low level, the first precharge signal PCG_OR is maintained at a low level, and the active delay signal ACTIVE_DEL and the active delay pulse signal ACTIVE_DEL_PUL is maintained at a low level. Meanwhile, since the second precharge signal PCG_ALL and the burn-in control signal CTRL_BI are activated at a high level, the second signal generating unit  130  outputs the burn-in precharge signal PCG_ALL_BI at the high level. 
     Referring to  FIG. 8 , the sixth transistor N 3  and the seventh transistor N 4  are turned on in response to the burn-in control signal CTRL_BI and the burn-in precharge signal PCG_ALL_BI. As a result, the potential of the second node S 2  is shifted to a low level and the second latch unit  213 - 4  maintains the potential of the second node S 2  at a low level. Since the active delay signal ACTIVE_DEL is at a low level, the second pass gate PG 2  is turned on, and the potential of the third node S 3  becomes a high level and the voltage control signal VPP_VDD_SHORTb is shifted to a low level. In response to the voltage control signal VPP_VDD_SHORTb, the voltage supply unit  230  shorts the first voltage VPP and the second voltage VDD and pulls down the first voltage VPP to the second voltage VDD. 
     Then, when the active command ACT is input, the active signal ACTIVE is activated to a high level. The active signal ACTIVE is delayed by the signal delay unit  211 - 1  by the first delay time td 1  and is then output as the active delay signal ACTIVE_DEL. The pulse generating unit  211 - 3  receives the active delay signal ACTIVE_DEL to output the active delay pulse signal ACTIVE_DEL_PUL that is a pulse signal having an activated interval as much as the second delay time td 2 . 
     The word line WL is activated in response to the active signal ACTIVE, and the potential of the word line WL is increased to the second voltage VDD for the first delay time td 1 . Meanwhile, when the active delay pulse signal ACTIVE_DEL_PUL is generated, the word line WL is increased to the first voltage VPP for the second delay time td 2 . 
     That is, if the active signal ACTIVE is activated during an interval where the voltage control signal VPP_VDD_SHORTb is at a low level, the word line WL is supplied with the second voltage VDD and increases to the second voltage VDD, for the first delay time td 1 . Then, since the voltage control signal VPP_VDD_SHORTb is shifted to a high level during an interval where the active delay pulse signal ACTIVE_DEL_PUL is activated, the potential of the word line WL is increased to the first voltage VPP for the second delay time td 2 . 
     This will be described in detail with reference to  FIG. 8 . During an interval where the active delay pulse signal ACTIVE_DEL_PUL is activated at a high level, the fourth transistor P 2  is turned on and the first node S 1  is shifted to a high level, and the first latch unit  213 - 2  maintains the first node S 1  at a high level. Since the active delay signal ACTIVE_DEL is at a high level, the first pass gate PG 1  is turned on, and the third node S 3  maintains a low level. That is, the voltage control signal VPP_VDD_SHORTb is shifted to a high level. 
     Then, if the control signal CTRL has a dummy activation pulse according to the all bank precharge command APCG before the precharge command PCG, the first signal generating unit  110  outputs the burn-in control signal CTRL_BI as a pulse signal that is activated at a high level, and the second signal generating unit  130  outputs the burn-in precharge signal PCG_ALL_BI at the low level. When the control signal CTRL has a dummy activation pulse during a burn-in test mode, a DRAM can be operated in a normal state. For example, in  FIG. 10 , when a current mode is not a burn-in test mode as indicated by reference character D, the signal generator  100  receives the burn-in test mode signal TM_BI at the low level and the control signal CTRL at the high level, and outputs the burn-in control signal CTRL_BI at the low level as indicated by reference character E. 
     At this time, the second transistor N 1  and the third transistor N 2  are turned on in response to the burn-in control signal CTRL_BI and the active delay signal ACTIVE_DEL. As a result, the first node S 1  is shifted to a low level, and the first latch unit  213 - 2  maintains the potential of the first node Slat a low level. The first pass gate PG 1  is turned on in response to the active delay signal ACTIVE_DEL at the high level and the third node S 3  is maintained at a high level, and the voltage control signal VPP_VDD_SHORTb is shifted to a low level by the thirteenth inverter IV 13 . Since the voltage supply unit  230  shorts the first voltage VPP and the second voltage VDD in response to the voltage control signal VPP_VDD_SHORTb, the potential of the word line WL is pulled down to the second voltage VDD. Then, if the precharge command PCG is input, the active signal ACTIVE is inactivated, and the word line WL is pulled down to the ground voltage VSS in response to the active signal ACTIVE. When the precharge command PCG is input, the first precharge signal PCG_OR has a pulse signal that is activated at a high level. As a result, the first transistor P 1  is turned on and the potential of the first node S 1  is shifted to a high level, and the first latch unit  213 - 2  maintains the potential of the first node S 1  at a high level. At this time, since the active delay signal ACTIVE_DEL is maintained at a high level, the first pass gate PG 1  is turned on, and the potential of the third node S 3  is shifted to a low level. That is, the voltage control signal VPP_VDD_SHORTb is shifted to a high level. 
     As described above, when the voltage control apparatus according to an embodiment of the present invention drives the word line WL during an active operation, the voltage control apparatus increases the potential of the word line WL to the second voltage VDD, and drives the word line WL with the first voltage VPP higher than the second voltage VDD, thereby distributing a peak current. Further, the voltage control apparatus decreases the potential of the word line WL to the second voltage VDD level before performing the precharge operation and decreases the potential of the word line WL to the ground voltage VSS level, thereby distributing the peak current during the precharge operation. 
     As shown in  FIG. 10 , reference character F indicates that the peak current is distributed during an active operation, and reference character G indicates that the peak current is distributed during a precharge operation. 
     The voltage control apparatus distributes the peak current generated during the active operation and the precharge operation so as to prevent the solder ball in a package from melting due to a high concentration of peak current, thereby improving productivity of a semiconductor memory apparatus and improving a burn-in screen capability. 
     It will be apparent to those skilled in the art that various modifications and changes may be made without departing from the scope and spirit of the invention. Therefore, it should be understood that the above embodiments are not limitative, but illustrative in all aspects. The scope of the invention is defined by the appended claims rather than by the description preceding them, and therefore all changes and modifications that fall within metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the claims.