Abstract:
A semiconductor integrated circuit comprising: a first voltage generator configured to generate a first voltage in response to activation of a first enable signal, wherein the first enable signal is generated by detecting a level of the first voltage; and a second voltage generator configured to generate a second voltage in response to activation of at least one of the first enable signal and a second enable signal, wherein the second enable signal is generated by detecting a level of the second voltage.

Description:
RELATED APPLICATIONS 
   This application is a continuation of U.S. Pat. No. 7,362,164, filed Sep. 11, 2006, the subject matter of which application is incorporated herein by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates to a semiconductor integrated circuit and a method of controlling an internal voltage of the same. 
   2. Related Art 
   A semiconductor integrated circuit uses various voltage levels, and power can be divided into two main types: external power (VDD and VSS) and internal power (VPP and VBB). 
   In other words, external power is supplied by an apparatus having a semiconductor integrated circuit mounted thereon, and internal power is supplied by converting the external power in the semiconductor integrated circuit. 
   In ascending order, the voltage levels are VPP, VDD, VSS, and VBB. VBB is a reverse bias voltage having an absolute value larger than that of the ground voltage VSS. 
   VPP is essentially used in a word line driver and a data-out driver in order to compensate for threshold voltage loss in a transistor constituting a memory cell of an integrated circuit. VPP is generated by boosting VDD and has a value larger than the sum of VDD and the threshold voltage VT. 
   The stability of the above-mentioned internal power has a great impact on the reliability and current consumption of a semiconductor integrated circuit. Therefore, in the design of a semiconductor integrated circuit, it is important to provide a stable supply of power within a predetermined range by controlling the power supply. 
   Hereinafter, a semiconductor integrated circuit according to the related art will be described with reference to  FIGS. 1 to 4 . 
     FIG. 1  is a block diagram showing the structure of a semiconductor integrated circuit according to the related art.  FIG. 2  is a circuit diagram showing the internal structure of a VBB detector  14  of  FIG. 1 .  FIG. 3  is a cross-sectional view showing a well bias of the semiconductor integrated circuit.  FIG. 4  is a waveform view showing change in VPP and VBB according to the related art. 
   In the semiconductor integrated circuit according to the related art, as shown in  FIG. 1 , a structure for controlling VPP and a structure for controlling VBB are separate from each other. 
   The structure for controlling VPP includes a elevated voltage detector (hereinafter, referred to as a VPP detector)  11 , a VPP oscillator (VPP OSC)  12 , and a elevated voltage pump (hereinafter, referred to as a VPP pump)  13 . 
   The VPP detector  11  detects whether the level of VPP is lower than a predetermined value and outputs an enable signal PPEN (for example, a high-level signal) to drive the VPP pump  13 . 
   The VPP oscillator  12  generates a pulse during a period when the enable signal PPEN output by the VPP detector  11  is at a high level. 
   The VPP pump  13  performs a pumping operation using a pulse OSCPP output from the VPP oscillator  12  so as to raise the level of VPP. 
   The structure for controlling VBB includes a substrate bias voltage detector (hereinafter, referred to as a VBB detector)  14 , a VBB oscillator (VBB OSC)  15 , and a substrate bias voltage pump (hereinafter, referred to as a VBB pump)  16 . 
   The VBB detector  14  detects whether the level of VBB is higher than a predetermined value, and outputs an enable signal BBEN (for example, a ‘high-level’ signal) to drive the VBB pump  16 . 
   An example of the internal structure of the VBB detector  14  is shown in  FIG. 2 , and is composed of two PMOS transistors P 1  and P 2  and two inverters IV 1  and IV 2 . The VBB detector  14  is operated so that a control signal for the PMOS transistor P 2  varies depending on the VBB level and the state of the output signal BBEN is determined to be ‘high’ or ‘low’ according to a difference between the control signals for PMOS transistors P 1  and P 2 . 
   The VBB oscillator  15  generates a pulse OSCBB during a period when the enable signal BBEN output by the VBB detector  14  is at the high level. 
   The VBB pump  16  performs a pumping operation using the pulse OSCBB output from the VBB oscillator  15  such that the level of VBB is lowered. In other words, since VBB is a reverse bias, the pumping operation is performed such that the level of VBB increases in a negative direction. 
   The VPP pump  13  is designed to have a size larger than the VBB pump  16  so as to generate a VPP having a level higher than that of VDD (external voltage). Furthermore, the response time of the VBB detector  14  is longer than that of the VPP detector  11 . That is, the response of the VBB detector  14  is later than that of the VPP detector  11 . 
   A well bias of the semiconductor integrated circuit is configured as shown in  FIG. 3 . That is, an N-well to which the VPP is applied and a P-well to which the VBB is applied are adjacent to each other. 
   Therefore, the probability that coupling noise of VPP and VBB will occur due to a junction capacitor between the adjacent wells is very high. 
   In other words, as shown in  FIG. 4 , the VPP level rises when the VPP pump  13  operates, is gradually lowered after the operation of the VPP pump stops, rises when the VPP pump  13  operates again due to the set value detection of the VPP detector  11 , and is then gradually lowered over time. This procedure is repeated. 
   When the level of VPP rises in sections A and B due to the operation of the VPP pump  13 , the level of VBB also rises due to the above-mentioned coupling noise. 
   Even though the VBB pump  16  operates in section B to lower the level of VBB, since the VPP pump  13  is still operating, the VBB level increases a little. The level of VBB normally drops in section C, when the operation of the VPP pump  13  completely stops, until the operation of the VBB pump  16  stops. 
   In the semiconductor integrated circuit according to the related art, the size of the VPP pump  13  is larger than that of the VBB pump  16  and the response speed of the VBB detector  14  is slower than that of the VPP detector  11 . Furthermore, coupling noise occurs due to a junction capacitor formed between the power supplies of the internal power supplies applied to adjacent regions. 
   As a result, when a high-level power supply voltage VPP rises, a relatively low-level substrate bias voltage VBB rises together with the high-level power supply voltage to deviate from a target value, resulting in an unstable power supply voltage. 
   Therefore, the semiconductor integrated circuit according to the related art has the following problems: 
   First, the operational reliability of the semiconductor integrated circuit deteriorates. 
   Second, current loss of a transistor constituting a memory cell of the semiconductor integrated circuit increases. 
   SUMMARY OF THE INVENTION 
   Accordingly, embodiments of the present invention provide a semiconductor integrated circuit with improved reliability by preventing the level of the substrate bias voltage from rising together with a elevated voltage level according to the variation of the elevated voltage level, and a method of controlling an internal voltage of the same. 
   Embodiments of the present invention also provide a semiconductor integrated circuit with minimal current loss, and a method of controlling an internal voltage of the same. 
   According to a first embodiment of the invention, a semiconductor integrated circuit uses, as internal voltages, a substrate bias voltage VBB and an elevated voltage VPP obtained by converting an external voltage. The semiconductor integrated circuit includes: an elevated voltage detector that outputs an elevated voltage pump enable signal; an elevated voltage pump that is driven by the elevated voltage pump enable signal to pump the elevated voltage; a substrate bias voltage detector that outputs a substrate bias voltage control signal when at least one of the elevated voltage pump enable signal and a substrate bias voltage pump enable signal for driving a substrate bias voltage pump changes to an active state; and the substrate bias voltage pump that is driven by the substrate bias voltage control signal to pump the substrate bias voltage. 
   According to a second embodiment of the invention, a semiconductor integrated circuit is provided that uses, as internal voltages, a substrate bias voltage VBB and a elevated voltage VPP obtained by converting an external voltage. The semiconductor integrated circuit includes: an elevated voltage detector that outputs an elevated voltage pump enable signal; an elevated voltage pump that is driven by the elevated voltage pump enable signal to pump the elevated voltage; a pulse generating unit that generates a pulse synchronized with the elevated voltage pump enable signal; a substrate bias voltage detector that outputs a substrate bias voltage control signal when at least one of the elevated voltage pump enable signal and a substrate bias voltage pump enable signal for driving a first substrate bias voltage pump changes to an active state; the first substrate bias voltage pump that is driven by the substrate bias voltage control signal to pump the substrate bias voltage; and a second substrate bias voltage pump that pumps the substrate bias voltage according to the pulse generated by the pulse generating unit, and outputs the pumped substrate bias voltage through an output node where the first and second substrate bias voltage pumps are connected to each other. 
   According to a third embodiment of the invention, a method of controlling the internal voltages of a semiconductor integrated circuit is provided that uses, as the internal voltages, a substrate bias voltage VBB and an elevated voltage VPP obtained by converting an external voltage. In the method, the level of the substrate bias voltage is pumped when a voltage control signal becomes active. In addition, the voltage control signal is in an active state for a period when at least one of an elevated voltage pump enable signal, for an elevated voltage pumping operation, that is output when the elevated voltage reaches a first predetermined value, and a substrate bias voltage pump enable signal, for a substrate bias voltage pumping operation, that is output when the substrate bias voltage reaches a second predetermined value, is active. 
   According to a fourth embodiment of the invention, a method of controlling internal voltages of a semiconductor integrated circuit is provided that uses, as the internal voltages, a substrate bias voltage VBB and an elevated voltage VPP obtained by converting an external voltage. In the method, the level of the substrate bias voltage is pumped when a voltage control signal becomes active. In addition, the voltage control signal is in an active state for a period where at least one of a elevated voltage pump enable signal, for an elevated voltage pumping operation, that is output when the elevated voltage reaches a first predetermined value, and a substrate bias voltage pump enable signal, for a substrate bias voltage pumping operation, that is output when the substrate bias voltage reaches a second predetermined value, is active, or is activated by a pulse that is activated in synchronization with the elevated voltage pump enable signal and is inactivated before the active period of the elevated voltage pump enable signal ends. 
   Therefore, according to embodiments of present invention, it is possible to improve the operational reliability of a semiconductor integrated circuit, and to reduce the current consumption by minimizing the current loss of a transistor constituting a cell. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the structure of a semiconductor integrated circuit according to the related art; 
       FIG. 2  is a circuit diagram showing the internal structure of a VBB detector of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view showing a well bias of the semiconductor integrated circuit; 
       FIG. 4  is a waveform diagram showing change in VPP and VBB according to the related art; 
       FIG. 5  is a block diagram showing the internal structure of a semiconductor integrated circuit according a first embodiment of the invention; 
       FIG. 6  is a circuit diagram showing the internal structure of a VBB detector of  FIG. 5 ; 
       FIG. 7  is a timing chart illustrating the operation of each unit of  FIG. 5 ; 
       FIG. 8  is a waveform diagram showing change in a VPP and a VBB according to the first embodiment shown in  FIG. 5 ; 
       FIG. 9  is a block diagram showing the structure of a semiconductor integrated circuit according to a second embodiment of the invention; 
       FIG. 10  is a circuit diagram showing the internal structure of a pulse generating unit of  FIG. 9 ; 
       FIG. 11  is a circuit diagram showing the internal structure of a VBB detector of  FIG. 9 ; 
       FIG. 12  is a timing chart illustrating the operation of each unit of  FIG. 9 ; and 
       FIG. 13  is a waveform diagram showing change in VPP and VBB according to the second embodiment shown in  FIG. 9 . 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Hereinafter, embodiments of a semiconductor integrated circuit and a method of controlling an internal voltage of the same according to the invention will be described with reference to the accompanying drawings. 
     FIG. 5  is a block diagram showing the structure of a semiconductor integrated circuit according to a first embodiment of the invention.  FIG. 6  is a circuit diagram showing the internal structure of a VBB detector  21  shown in  FIG. 5 .  FIG. 7  is a timing chart illustrating the operation of each unit of  FIG. 5 .  FIG. 8  is a waveform diagram showing change in a VPP and a VBB according to  FIG. 5 .  FIG. 9  is a block diagram showing the structure of a semiconductor integrated circuit according to a second embodiment of the invention.  FIG. 10  is a circuit diagram showing the internal structure of a pulse generator of  FIG. 9 .  FIG. 11  is a circuit diagram showing the internal structure of a VBB detector of  FIG. 9 .  FIG. 12  is a timing chart illustrating the operation of each unit of  FIG. 9 .  FIG. 13  is a waveform diagram showing change in a VPP and a VBB according to  FIG. 9 . 
   First Embodiment 
   As shown in  FIG. 5 , a semiconductor integrated circuit according to the first embodiment includes: a high-voltage detector (hereinafter, referred to as a VPP detector)  11 , which detects whether an elevated voltage VPP exceeds a predetermined value and outputs a VPP pump enable signal PPEN according to the detection result; a substrate bias voltage detector (hereinafter, referred to as a VBB detector)  21  that detects whether a substrate bias voltage VBB exceeds a predetermined value and outputs a substrate bias voltage control signal BBEN on the basis of at least one of the output signal PPEN of the VPP detector  11  and a VBB pump enable signal BBEN 0  ( FIG. 6 ) according to the detection result; a VBB oscillator  22  that generates a pulse OSCBB for a period where the substrate bias voltage control signal BBEN output by the VBB detector  21  is ‘active (high)’; and a substrate bias voltage pump (hereinafter, referred to as a VBB pump)  23  that pumps the substrate bias voltage level by using the pulse OSCBB output from the VBB oscillator  22  and outputs the pumped substrate bias voltage. 
   The VBB oscillator  22  can be integrally formed in the VBB pump  23 . The VPP oscillator  12  and the VPP pump  13  have well-known structures, and thus a description thereof will be omitted. The VPP oscillator  12  may also be integrally formed in the VPP pump  13 . 
   As shown in  FIG. 6 , the VBB detector  21  includes a first transistor P 1 , a second transistor P 2 , first and second inverters IV 1  and IV 2 , and an OR gate  21 - 1 . The drain of the first transistor P 1  is connected to the source of the second transistor P 2 . A ground voltage VSS is applied to the gate of the first transistor P 1 , and an external voltage VDD is applied to the source of the first transistor P 1 . The substrate bias voltage VBB is applied to the gate of the second transistor P 2 , and the ground voltage VSS is applied to the drain of the second transistor P 2 . The first and second inverters IV 1  and IV 2  buffer an output signal of a node where the drain of the first transistor P 1  is connected to the source of the second transistor P 2 . The OR gate  21 - 1  is a logic gate that performs the logic sum operation of an output BBEN 0  of the second inverter IV 2  and an output PPEN of the VPP detector  11 . 
   According to the entire circuit design, the number of inverters IV 1  and IV 2  may increase or decrease. 
   The operation of the semiconductor integrated circuit having the above-mentioned structure will be described in detail. 
   First, as shown in  FIG. 7 , the VBB detector  21  outputs the enable signal BBEN that is obtained by performing a logic sum operation of the output signal PPEN of the VPP detector  11  and the output signal BBEN 0  of the second inverter IV 2  by means of the OR gate  21 - 1 . 
   The output signal PPEN is an enable signal for driving the VPP pump  13  to prevent the level of the voltage VPP from dropping below a predetermined value. The output signal BBEN 0  is an enable signal for driving the VBB pump  23  to prevent the level of the voltage VBB from rising over a predetermined value. 
   The VBB oscillator  22  outputs the pulse OSCBB when the signal BBEN is in an active (high) state. 
   The VBB pump  23  performs a pumping operation using the pulse OSCBB such that the VBB level drops, that is, the VBB level increases in the negative direction. 
   In this way, when the VPP pump  13  performs a pumping operation using the output signal PPEN of the VPP detector  11 , the VBB pump  23  also operates so as to prevent the VBB level from abnormally rising. 
   In the related art, as shown in  FIG. 4 , since the VBB pump does not operate when the VPP pump performs the pumping operation, the VBB level also rises. However, according to the first embodiment of the invention, since the VBB pump  23  also operates when the VPP pump  13  operates, a rising gradient of the VBB is markedly reduced, as shown in  FIG. 8 . 
   Second Embodiment 
   As shown in  FIG. 9 , a semiconductor integrated circuit according to a second embodiment of the invention includes a high-voltage detector  11  (hereinafter, referred to as a VPP detector), a pulse generating unit  31 , a substrate bias voltage detector  32  (hereinafter, referred to as a VBB detector), a first VBB oscillator  33 , a first substrate bias voltage pump  34  (hereinafter, referred to as a first VBB pump), a second VBB oscillator  35 , and a second substrate bias voltage pump  36  (hereinafter, referred to as a second VBB pump). 
   The VPP detector  11  detects whether an elevated voltage VPP exceeds a predetermined value and outputs a VPP pump enable signal PPEN according to the detection result. The pulse generating unit  31  generates a pulse PPEND having a narrow width that becomes active in synchronization with a rising edge of the output signal PPEN of the VPP detector  11  and becomes inactive before an active period of the output signal PPEN ends. The VBB detector  32  detects whether the substrate bias voltage VBB exceeds a predetermined value and outputs a substrate bias voltage control signal BBEN 1  on the basis of at least one of the output pulse PPEND of the pulse generating unit  31  and a VBB pump enable signal BBEN 0  ( FIG. 11 ) according to the detection result. The first VBB oscillator  33  generates a pulse OSCBB 1  for a period where the substrate bias voltage control signal BBEN 1  output by the VBB detector  32  is in an active state. The first VBB pump  34  pumps the level of VBB by using the pulse OSCBB 1  output by the first VBB oscillator  33  and outputs the pumped VBB. The second VBB oscillator  35  generates a pulse OSCBB 2  for a period where the output pulse PPEND of the pulse generating unit  31  is in an active (high) state. The second VBB pump  36  pumps the level of the VBB by using the pulse OSCBB 2  output from the second VBB oscillator  35  and outputs the pumped VBB through a node where the first and second VBB pumps  34  and  36  are connected to each other. 
   The first and second VBB oscillators  33  and  35  may be integrally formed inside the first and second VBB pumps  34  and  36 , respectively. The VPP oscillator  12  and the VPP pump  13  have well-known structures, and thus a description thereof will be omitted. The VPP oscillator  12  may also be integrally formed inside the VPP pump  13 . 
   The pulse generating unit  31  generates the pulse PPEND that has a width narrower than the enable signal PPEN and becomes active in synchronization with the enable signal PPEN such that the first and second VBB pumps  34  and  36  operate together at the beginning of the operation of the VPP pump  13 . 
   The pulse generating unit  31  includes a low pulse generator  31 - 1 , a latch  31 - 2 , a phase inversion delay unit  31 - 3 , and first and second inverters IV 1  and IV 2 , as shown in  FIG. 10 . The low pulse generator  31 - 1  generates a low pulse when the output signal PPEN of the VPP detector  11  changes to a high level. The latch  31 - 2  maintains a predetermined signal level (high) according to the output of the low pulse generator  31 - 1 . The phase inversion delay unit  31 - 3  inverts the phase of the output signal of the latch  31 - 2 , delays the inverted signal by a predetermined amount of time, and feeds back the delayed signal to the latch  31 - 2 . The first and second inverters IV 1  and IV 2  buffer the output of the latch  31 - 2 . 
   The latch  31 - 2  has a first NAND gate ND 1  and a second NAND gate ND 2 . The output of the low pulse generator  31 - 1  is input to a first input terminal of the first NAND gate ND 1 . The output of the first NAND gate ND 1  is input to a first input terminal of the second NAND gate ND 2 , and the output of the phase inversion delay unit  31 - 3  is input to a second input terminal of the second NAND gate ND 2 . The output of the second NAND gate ND 2  is input to a second input terminal of the first NAND gate ND 1 . 
   According to the entire circuit design, the number of inverters V 1  and V 2  may increase or decrease. 
   The VBB detector  32  includes a first transistor P 1 , a second transistor P 2 , first and second inverters IV 1  and IV 2 , and an OR gate  32 - 1 , as shown in  FIG. 11 . A ground voltage VSS is applied to the gate of the first transistor P 1  and an external voltage VDD is applied to the source of the first transistor P 1 . The substrate bias voltage VBB is applied to the gate of the second transistor P 2  and the ground voltage VSS is applied to the drain of the second transistor P 2 . The drain of the first transistor P 1  is connected to the source of the second transistor P 2 . The first and second inverters IV 1  and IV 2  buffer an output signal from a node where the drain of the first transistor P 1  is connected to the source of the second transistor P 2 . The OR gate  32 - 1  outputs the logic sum of the output signal BBEN 0  of the second inverter IV 2  and the output signal PPEND of the pulse generating unit  31 . 
   According to the entire circuit design, the number of inverters V 1  and V 2  may increase or decrease. 
   The operation of the semiconductor integrated circuit having the above-mentioned structure will be described below in detail. 
   First, as shown in  FIG. 12 , the VBB detector  32  outputs the substrate bias voltage control signal BBEN 1  that is obtained by performing a logic sum operation of the output signal PPEND of the pulse generating unit  31  and the signal BBEN 0  detected by the VBB detector  32  by means of the OR gate  32 - 1 . 
   The first VBB oscillator  33  outputs the pulse OSCBB 1  for a period when the substrate bias voltage control signal BBEN 1  is in an active (high) state. 
   The first VBB pump  34  performs a pumping operation using the pulse OSCBB 1  so that the VBB level drops, that is, increases in the negative direction. 
   The second VBB oscillator  35  outputs the pulse OSCBB 2  for a period when the pulse PPEND is in an active (high) state. 
   The second VBB pump  36  performs a pumping operation using the pulse OSCBB 2  so as to increase the falling gradient of the level of the VBB output from the output terminal that is connected to the first pump  34 . 
   As described above, in the semiconductor integrated circuit according to the second embodiment of the invention, the first and second VBB pumps  34  and  36  are simultaneously operated at the initial period of the operation of the VPP pump  13  using the output PPEND of the pulse generating unit  31  corresponding to the initial period of the output PPEN of the VPP detector  11 . Therefore, it is possible to minimize the abnormal rising of the VBB level. Then, the first VBB pump  34  operates according to the waveform of the pulse OSCBB 1 . However, since the VBB level rises the most during the beginning of the operation of the VPP pump  13 , the second VBB pump  36  is simultaneously operated with the first VBB pump  34  for only the initial period of the operation of the VPP pump  13  such that the output level of the VBB is remarkably lowered. 
   In the related art, since the VBB pump does not operate when the VPP pump is operating, the VPP level and the VBB level increase, as shown in  FIG. 4 . However, in the semiconductor integrated circuit according to the second embodiment of the invention, since the first and second VBB pump  34  and  36  operate when the VPP pump  13  operates, the level of the VBB further drops, as shown in  FIG. 13 . 
   In  FIG. 13 , the waveform represented by a dotted line indicates a VBB gradient according to the first embodiment of the invention. As can be seen from  FIG. 13 , in the second embodiment of the invention, an increase in the VBB level is prevented, as compared to the first embodiment. 
   As described above, the second embodiment of the invention can further prevent the increase in the VBB level due to an increase in the VPP level, as compared to the first embodiment of the invention. However, the second embodiment of the invention needs to additionally have the second VBB oscillator  35  and the second VBB pump  36 . 
   Therefore, the first and second embodiments of the invention can be selectively applied in order to prevent an increase in the VBB level while reducing the number of components to a minimum, and in order to prevent an increase in the VBB level even when additional components are provided. 
   Although the present invention has been described in connection with the exemplary embodiments of the present invention, 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-described embodiments are not limitative, but illustrative in all aspects. The scope of the present invention is defined by the appended claims rather than by the description preceding them, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the claims. 
   As described above, the semiconductor integrated circuit and the method of controlling the internal voltage of the same according to any one of the embodiments of the invention can stably maintain the level of the substrate bias voltage VBB regardless of an increase in the level of the elevated voltage VPP. Therefore, the above-described embodiments may have the following effects. 
   First, it is possible to improve the operational reliability of a semiconductor integrated circuit. 
   Second, it is possible to reduce total power consumption by minimizing the current loss of the transistors constituting memory cells of a semiconductor integrated circuit.