CN114270443A - CMOS circuit of memory - Google Patents

Abstract

The present application provides a memory CMOS circuit comprising: the high-voltage functional circuit comprises at least one MOS tube, wherein a source electrode end or a drain electrode end of one MOS tube is connected with input high voltage; the output voltage of the power supply is gradually increased and reaches the maximum value when the enable signal is effective; and the auxiliary clamping circuit is arranged between the input high voltage and the source end or the drain end of the MOS tube and is used for clamping the voltage input to the source end or the drain end of the MOS tube in the output voltage rising stage so as to enable the clamping voltage to be smaller than the input high voltage. By the aid of the storage CMOS circuit, the problem that a high-voltage functional circuit in an existing storage CMOS circuit has reliability risks is solved.

Description

CMOS circuit of memory

Cross Reference to Related Applications

The present application is filed and claimed as priority based on chinese patent application having application number 202011336570.X, filed on 25/11/2020, the entire contents of which are incorporated herein by reference.

Technical Field

The application belongs to the field of integrated circuit design, and particularly relates to a CMOS circuit of a memory.

Background

In recent years, Flash memories (Flash memories) have been developed rapidly, and have been widely used in various fields such as microcomputers and automation control, because they have the main characteristics of retaining stored information for a long time without power-on, and have the advantages of high integration, fast access speed, easy erasing and rewriting, etc. In order to further improve the Bit Density (Bit Density) of the flash memory and simultaneously reduce the Bit Cost (Bit Cost), the three-dimensional flash memory (3D NAND) technology has been rapidly developed.

In a CMOS circuit of 3D NAND, there is a problem that some functional circuits (such as a switch circuit and a level shift circuit) are operated under high voltage, which causes a MOS device therein to deteriorate due to hot carrier injection effect caused by excessive drain-source voltage at the stage of output voltage rise, thereby causing reliability risk of such high voltage functional circuits. In the prior art, in order to solve the technical problem, a MOS device with higher voltage resistance is usually used to design such a high-voltage functional circuit, so that such a high-voltage functional circuit has a larger area and a smaller current.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present application aims to provide a memory CMOS circuit for solving the problem of reliability risk of a high-voltage functional circuit in the existing memory CMOS circuit.

To achieve the above and other related objects, the present application provides a memory CMOS circuit, comprising:

the high-voltage functional circuit comprises at least one MOS tube, wherein a source electrode end or a drain electrode end of one MOS tube is connected with input high voltage; the output voltage of the power supply is gradually increased and reaches the maximum value when the enable signal is effective;

and the auxiliary clamping circuit is arranged between the input high voltage and the source end or the drain end of the MOS tube and is used for clamping the voltage input to the source end or the drain end of the MOS tube in the output voltage rising stage so as to enable the clamping voltage to be smaller than the input high voltage.

Optionally, the auxiliary clamp circuit comprises: the first depletion type high-voltage NMOS tube and the second depletion type high-voltage NMOS tube are connected, the first connection end of the first depletion type high-voltage NMOS tube is connected with the first connection end of the second depletion type high-voltage NMOS tube and is connected with the input high voltage, the second connection end of the first depletion type high-voltage NMOS tube is connected with the second connection end of the second depletion type high-voltage NMOS tube and is connected with the source end or the drain end of the MOS tube, the grid end of the first depletion type high-voltage NMOS tube is connected with a preset voltage, and the grid end of the second depletion type high-voltage NMOS tube is connected with the output end of the high-voltage functional circuit; the preset voltage is smaller than the input high voltage, and the threshold voltage of the second depletion type high-voltage NMOS tube is smaller than 0.

Optionally, the preset voltage is equal to half of the input high voltage.

Optionally, the threshold voltage of the first depletion type high-voltage NMOS transistor is less than 0.

Optionally, the auxiliary clamp circuit further comprises: the first connection end of the third depletion type high-voltage NMOS tube is connected with the first connection end of the first depletion type high-voltage NMOS tube, the second connection end of the third depletion type high-voltage NMOS tube is connected with the second connection end of the first depletion type high-voltage NMOS tube, and the grid end of the third depletion type high-voltage NMOS tube is connected with another preset voltage; and the preset voltage connected to the grid end of the third depletion type high-voltage NMOS tube is less than the preset voltage connected to the grid end of the first depletion type high-voltage NMOS tube.

Optionally, when the number of the third depletion type high-voltage NMOS tubes is greater than 1, the first connection ends of the third depletion type high-voltage NMOS tubes are connected to the first connection end of the first depletion type high-voltage NMOS tube, the second connection ends of the third depletion type high-voltage NMOS tubes are connected to the second connection end of the first depletion type high-voltage NMOS tube, the gate terminals of the third depletion type high-voltage NMOS tubes are respectively connected to a preset voltage, the numerical values of the preset voltages are gradually increased at this time, and the preset voltage with the largest numerical value is smaller than the preset voltage connected to the gate terminal of the first depletion type high-voltage NMOS tube.

Optionally, the preset voltage connected to the gate terminal of the first depletion type high-voltage NMOS transistor is equal to half of the input high voltage.

Optionally, the threshold voltage of the first depletion type high-voltage NMOS transistor is less than 0, and the threshold voltage of the third depletion type high-voltage NMOS transistor is less than 0.

Optionally, the high voltage functional circuit comprises one of a switching circuit or a level shifting circuit.

As described above, in the memory CMOS circuit of the present application, without modifying the existing high-voltage functional circuit, the auxiliary clamp circuit is only added at the input high-voltage end of the existing high-voltage functional circuit to clamp the voltage of the MOS transistor input to the high-voltage functional circuit to a clamp voltage smaller than the input high voltage at the stage of the output voltage rising, so as to reduce the drain-source voltage of the MOS transistor, reduce the hot carrier injection effect thereof, improve the high-voltage resistance of the circuit, and achieve the purpose of improving the reliability of the circuit with a smaller area cost, thereby improving the performance of the memory.

Drawings

Fig. 1 is a schematic structural diagram of a memory CMOS circuit according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a conventional high-voltage functional circuit.

Fig. 3 (a) shows a waveform diagram of an enable signal EN and an inverted signal thereof, (b) shows a waveform diagram of an output voltage of a conventional high-voltage functional circuit under the enable signal and a waveform diagram of a voltage input to the MOS transistor at a rising stage of the output voltage, and (c) shows a waveform diagram of an output voltage of the memory CMOS circuit under the enable signal and a waveform diagram of a voltage input to the MOS transistor at a rising stage of the output voltage according to the first embodiment.

Fig. 4 is a schematic structural diagram of a memory CMOS circuit according to the second embodiment of the present application.

Description of the element reference numerals

100 high voltage functional circuit

200 auxiliary clamping circuit

Detailed Description

The following description of the embodiments of the present application is provided by way of specific examples, and other advantages and effects of the present application will be readily apparent to those skilled in the art from the disclosure herein. The present application is capable of other and different embodiments and its several details are capable of modifications and/or changes in various respects, all without departing from the spirit of the present application.

Please refer to fig. 1 to 4. It should be noted that the drawings provided in the present embodiment are only schematic and illustrate the basic idea of the present application, and although the drawings only show the components related to the present application and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity and proportion of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.

Example one

As shown in fig. 1, the present embodiment provides a memory CMOS circuit including:

the high-voltage functional circuit 100 comprises at least one MOS transistor, wherein a source terminal or a drain terminal of one MOS transistor M1 is connected with an input high voltage HV; the high-voltage functional circuit 100 is used for realizing that when an enable signal is effective, the output voltage of the high-voltage functional circuit gradually increases and reaches a maximum value HV;

and the auxiliary clamping circuit 200 is arranged between the input high voltage HV and the source end or the drain end of the MOS transistor M1 and is used for clamping the voltage input to the source end or the drain end of the MOS transistor M1 in the output voltage rising stage so as to enable the clamping voltage HV _ clamp to be smaller than the input high voltage HV.

By way of example, the high voltage functional circuit 100 includes one of a switching circuit or a level shifting circuit. In this example, the high voltage functional circuit 100 is a level shift circuit, wherein the level shift circuit includes only three MOS transistors M1-M3, and the drain terminal of the MOS transistor M1 is connected to the input high voltage HV (specifically, as shown in fig. 1); of course, the level conversion circuits of other constituent structures are also applicable to the present example.

Specifically, the MOS transistor in the high-voltage functional circuit 100 may be a conventional MOS transistor (i.e., a non-high-voltage MOS transistor), or may be a high-voltage MOS transistor; when the memory is a conventional MOS transistor, the memory CMOS circuit of the embodiment can be suitable for a high-voltage application scene through the design of the auxiliary clamping circuit 200; when the memory is a high-voltage MOS transistor, the memory CMOS circuit of the present embodiment can be applied to a higher-voltage application scenario through the design of the auxiliary clamp circuit 200.

As an example, as shown in fig. 1, the auxiliary clamp circuit 200 includes: a first depletion type high voltage NMOS transistor MN1 and a second depletion type high voltage NMOS transistor MN2, a first connection end of the first depletion type high voltage NMOS transistor MN1 is connected to a first connection end of the second depletion type high voltage NMOS transistor MN2 and is connected to the input high voltage HV, a second connection end of the first depletion type high voltage NMOS transistor MN1 is connected to a second connection end of the second depletion type high voltage NMOS transistor MN2 and is connected to a source terminal or a drain terminal of the MOS transistor M1, a gate terminal of the first depletion type high voltage NMOS transistor MN1 is connected to a preset voltage HV1, and a gate terminal of the second depletion type high voltage NMOS transistor MN2 is connected to an output end of the high voltage functional circuit 100; the preset voltage HV1 is smaller than the input high voltage HV, and the threshold voltage of the second depletion mode high voltage NMOS transistor MN1 is smaller than 0. In practical applications, the first connection end of the first depletion type high voltage NMOS transistor MN1 and the first connection end of the second depletion type high voltage NMOS transistor MN2 may be drain terminals, and the second connection end of the first depletion type high voltage NMOS transistor MN1 and the second connection end of the second depletion type high voltage NMOS transistor MN2 may be source terminals.

Specifically, the preset voltage HV1 is equal to half of the input high voltage HV, so that the memory CMOS circuit of this example can satisfy its own circuit function and improve its reliability as much as possible, so that the memory CMOS circuit of this configuration can satisfy most of the existing application requirements. Of course, in practical applications, the value of the preset voltage HV1 needs to be set according to specific application scenarios, and particularly for some special application scenarios, the value of the preset voltage HV1 may be greater than half of the input high voltage HV or less than half of the input high voltage HV.

Specifically, the threshold voltage of the first depletion type high-voltage NMOS transistor MN1 is less than 0, so that the first depletion type high-voltage NMOS transistor MN1 and the second depletion type high-voltage NMOS transistor MN2 are completely the same, and therefore the first depletion type high-voltage NMOS transistor MN1 and the second depletion type high-voltage NMOS transistor MN2 can be arranged closely in layout design, circuit area can be reduced, and device type selection is facilitated.

Referring to fig. 1-3, the performance of the memory CMOS circuit according to the present embodiment will be described with reference to the conventional high voltage functional circuit.

As shown in fig. 2 and fig. 3 (a), (b), with the conventional level shift circuit, when the enable signal EN is active (i.e., the enable signal EN changes from a low level to a high level), the output voltage Vout thereof gradually increases and reaches the maximum value HV; however, in the rising phase of the output voltage Vout, the voltage Vin input to the drain terminal of the MOS transistor M1 is HV, so the maximum drain-source voltage Vds of the MOS transistor M1 is (HV-Vth _ M1), where Vth _ M1 is the threshold voltage of the MOS transistor M1. It can be seen that, in the rising stage of the output voltage Vout, since the drain-source voltage Vds of the MOS transistor M1 is large, there is a serious hot carrier injection effect, so that the level shift circuit has a reliability problem. It should be noted that, since the drain-source voltage Vds of the MOS transistor M1 will be continuously decreased as the output voltage Vout continuously increases, the problem of circuit reliability caused by hot carrier injection occurs mainly in the first half of the rising period of the output voltage Vout, i.e. the initial period of enabling the enable signal.

As shown in fig. 1 and fig. 3 (a), (c), with the memory CMOS circuit according to the present example, when the enable signal EN is active (i.e., when the enable signal EN changes from a low level to a high level), the output voltage Vout thereof gradually increases and reaches the maximum value HV. In the rising phase of the output voltage Vout, due to the design of the auxiliary clamp circuit 200 in this example, the voltage Vin input to the drain terminal of the MOS transistor M1 is clamped to the clamp voltage HV _ clamp, so the maximum drain-source voltage Vds of the MOS transistor M1 is (HV _ clamp-Vth _ M1); specifically, during the first half of the rising phase of the output voltage Vout, since the output voltage Vout is small, the first depletion type high-voltage NMOS transistor MN1 in the auxiliary clamp circuit 200 clamps the voltage input to the drain of the MOS transistor M1 to (HV1-Vth _ MN 1); in the latter half of the rising phase of the output voltage Vout, that is, after the output voltage Vout approaches the preset voltage HV1, the second depletion type high voltage NMOS transistor MN2 in the auxiliary clamp circuit 200 clamps the voltage input to the drain of the MOS transistor M1 to (Vout-Vth _ MN2), where the clamp voltage HV _ clamp follows the output voltage Vout, but since the auxiliary clamp circuit 200 is controlled by the input high voltage HV, the maximum clamp voltage does not exceed the input high voltage HV, that is, HV _ clamp is min (HV, Vout-Vth _ MN2), and Vth _ MN2 is less than 0; wherein Vth _ MN1 is the threshold voltage of the first depletion mode high voltage NMOS transistor MN1, and Vth _ MN2 is the threshold voltage of the second depletion mode high voltage NMOS transistor MN 2. It can be seen that, at the rising stage of the output voltage Vout, the auxiliary clamp circuit 200 clamps the voltage input to the drain terminal of the MOS transistor M1 to the clamp voltage HV _ clamp smaller than the input high voltage HV, thereby reducing the drain-source voltage Vds of the MOS transistor M1, reducing the hot carrier injection effect thereof, improving the high voltage resistance of the exemplary circuit, achieving the purpose of improving the reliability of the circuit with a smaller area cost, and simultaneously enabling the exemplary circuit to be applicable to an environment with a higher operating voltage. It should be noted that when the output voltage Vout of the high-voltage functional circuit 100 reaches the maximum value HV, the drain-source voltage Vds of the corresponding MOS transistor M1 is very small, and at this time, the auxiliary clamp circuit 200 may be regarded as having no voltage loss; that is, the auxiliary clamp circuit 200 clamps the voltage input to the MOS transistor M1 during the rising phase of the output voltage Vout, and there is no voltage loss after the output voltage Vout reaches the maximum value HV. Moreover, since the auxiliary clamp circuit 200 according to the present example only functions during the rising phase of the output voltage Vout, the delay caused by the auxiliary clamp circuit 200 to the high-voltage functional circuit 100 is small and negligible, i.e., it has little effect on the performance of the high-voltage functional circuit.

Example two

As shown in fig. 4, the difference between this embodiment and the first embodiment is that the auxiliary clamp circuit 200 of this embodiment further includes: at least one third depletion type high-voltage NMOS tube MN3, a first connection end of the third depletion type high-voltage NMOS tube MN3 is connected with a first connection end of the first depletion type high-voltage NMOS tube MN1, a second connection end of the third depletion type high-voltage NMOS tube MN3 is connected with a second connection end of the first depletion type high-voltage NMOS tube MN1, and the gate end of the third depletion type high-voltage NMOS tube MN3 is connected with another preset voltage HV 2; the preset voltage HV2 connected to the gate terminal of the third depletion mode high voltage NMOS transistor MN3 is less than the preset voltage HV1 connected to the gate terminal of the first depletion mode high voltage NMOS transistor MN 1.

As an example, as shown in fig. 4, when the number of the third depletion type high voltage NMOS transistors MN3 is greater than 1, the first connection terminals of the third depletion type high voltage NMOS transistors MN3 are connected to the first connection terminals of the first depletion type high voltage NMOS transistors MN1, the second connection terminals of the third depletion type high voltage NMOS transistors MN3 are connected to the second connection terminals of the first depletion type high voltage NMOS transistors MN1, the gate terminals of the third depletion type high voltage NMOS transistors MN3 are respectively connected to a preset voltage (HV2-HVn), when the values of the preset voltages (HV2-HVn) gradually increase, and the preset voltage HVn with the largest value is smaller than the preset voltage HV1 connected to the gate terminal of the first depletion type high voltage NMOS transistor MN 1. In practical applications, the first connection end of the first depletion type high voltage NMOS transistor MN1, the first connection end of the second depletion type high voltage NMOS transistor MN2, and the first connection end of the third depletion type high voltage NMOS transistor MN3 may be drain terminals, and the second connection end of the first depletion type high voltage NMOS transistor MN1, the second connection end of the second depletion type high voltage NMOS transistor MN2, and the second connection end of the third depletion type high voltage NMOS transistor MN3 may be source terminals. The purpose of accurately controlling the clamping voltage HV _ clamp can be achieved by the design of at least one third depletion type high-voltage NMOS transistor MN 3; of course, the greater the number of the third depletion type high voltage NMOS transistors MN3 in the design, the higher the control accuracy of the clamp voltage HV _ clamp, i.e., the closer the clamp voltage HV _ clamp is to the true value.

Specifically, the preset voltage HV1 connected to the gate terminal of the first depletion type high voltage NMOS transistor MN1 is equal to half of the input high voltage HV, so that the memory CMOS circuit of this example can satisfy its own circuit function and improve its reliability as much as possible, so that the memory CMOS circuit of this configuration can satisfy most of the existing application requirements. Of course, in practical applications, the value of the preset voltage HV1 needs to be set according to specific application scenarios, and particularly for some special application scenarios, the value of the preset voltage HV1 may be greater than half of the input high voltage HV or less than half of the input high voltage HV.

Specifically, the threshold voltage of the first depletion type high-voltage NMOS transistor MN1 is less than 0, and the threshold voltage of the third depletion type high-voltage NMOS transistor MN3 is less than 0, so that the first depletion type high-voltage NMOS transistor MN1, the second depletion type high-voltage NMOS transistor MN2, and the third depletion type high-voltage NMOS transistor MN3 are completely the same, and therefore the first depletion type high-voltage NMOS transistor MN1, the second depletion type high-voltage NMOS transistor MN2, the third depletion type high-voltage NMOS transistor MN3, the third depletion type high-voltage NMOS transistor MN2, the third depletion type high-voltage NMOS transistor MN3, the third depletion type high-voltage NMOS transistor MN and the third depletion type high-voltage NMOS transistor MN3 can be closely arranged in layout design, circuit area can be reduced, and device type selection can be facilitated.

To sum up, the memory CMOS circuit of this application, under the condition that need not to change current high-voltage function circuit, only through set up supplementary clamp circuit at current high-voltage function circuit's input high-voltage end to in the output voltage rising stage, the voltage clamp that will input to MOS pipe among the high-voltage function circuit is to being less than the high-voltage clamp voltage of input, thereby reduce the drain source voltage of this MOS pipe, reduce its hot carrier injection effect, improve the high voltage resistance performance of circuit, the realization reaches the purpose that improves the circuit reliability with less area cost, thereby improve the memory performance. Therefore, the application effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles and utilities of the present application and are not intended to limit the application. Any person skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present application. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed in the present application shall be covered by the claims of the present application.

Claims (10)

1. A memory CMOS circuit, the memory CMOS circuit comprising:

the high-voltage functional circuit comprises at least one MOS tube, wherein a source electrode end or a drain electrode end of one MOS tube is connected with input high voltage;

the auxiliary clamping circuit is arranged between the input high voltage and a source end or a drain end of the MOS tube;

wherein the auxiliary clamp circuit comprises: the first depletion type high-voltage NMOS tube and the second depletion type high-voltage NMOS tube are connected in parallel, a first connecting end connected with the first depletion type high-voltage NMOS tube and the second depletion type high-voltage NMOS tube is connected with the input high voltage, a second connecting end connected with the second depletion type high-voltage NMOS tube and the source end or the drain end of the MOS tube are connected, the grid end of the first depletion type high-voltage NMOS tube is connected with a preset voltage, and the grid end of the second depletion type high-voltage NMOS tube is connected with the output end of the high-voltage functional circuit; wherein the preset voltage is less than the input high voltage.

2. The memory CMOS circuit of claim 1 wherein the threshold voltage of the second depletion mode high voltage NMOS transistor is less than 0.

3. The memory CMOS circuit of claim 1 wherein said preset voltage is equal to one-half of said input high voltage.

4. The memory CMOS circuit of claim 1 wherein the first depletion mode high voltage NMOS transistor has a threshold voltage less than 0.

5. The memory CMOS circuit of claim 1, wherein the auxiliary clamp circuit further comprises: the third depletion type high-voltage NMOS tube is connected with the first depletion type high-voltage NMOS tube in parallel, and the grid end of the third depletion type high-voltage NMOS tube is connected with another preset voltage; and the preset voltage connected to the grid end of the third depletion type high-voltage NMOS tube is less than the preset voltage connected to the grid end of the first depletion type high-voltage NMOS tube.

6. The memory CMOS circuit of claim 5, wherein when the number of the third depletion type high voltage NMOS transistors is multiple, the first connection terminals of the third depletion type high voltage NMOS transistors are connected in parallel with the first depletion type high voltage NMOS transistor, the gate terminals of the third depletion type high voltage NMOS transistors are respectively connected to a preset voltage, the value of each preset voltage is gradually increased, and the preset voltage with the largest value is smaller than the preset voltage connected to the gate terminal of the first depletion type high voltage NMOS transistor.

7. The memory CMOS circuit of claim 5 or 6, wherein a preset voltage connected to the gate terminal of said first depletion mode high voltage NMOS transistor is equal to half of said input high voltage.

8. The memory CMOS circuit of claim 5 or 6, wherein the threshold voltage of the first depletion mode high voltage NMOS transistor is less than 0 and the threshold voltage of the third depletion mode high voltage NMOS transistor is less than 0.

9. The memory CMOS circuit of claim 1 wherein said high voltage functional circuit comprises one of a switching circuit or a level shifting circuit.

10. The memory CMOS circuit of claim 9 wherein said level shifter circuit includes a first MOS transistor, a second MOS transistor and a third MOS transistor;

the first MOS tube is connected with the third MOS tube in series, the drain end or the source end of the first MOS tube is connected to the input high voltage, the drain end or the source end of the third MOS tube is grounded, and the gate end of the third MOS tube is used for inputting an inverted enabling signal; and the source end or the drain end of the second MOS tube is used for inputting an enabling signal, the drain end or the source end of the second MOS tube is connected with the grid end of the first MOS tube, and the grid end of the second MOS tube is grounded.

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