Nonvolatile selector, and integrated circuit device

Details Nonvolatile selector, and integrated circuit device Nonvolatile selector, and integrated circuit device

2003-04-09

2004-08-24

Le, Thong (Department: 2818)

Static information storage and retrieval

Systems using particular element

Ferroelectric

C365S149000, C365S104000

Reexamination Certificate

active

06781865

ABSTRACT:

TECHNICAL FIELD
The present invention relates to selectors for use in various logic circuits and integrated circuit devices including such circuits and more particularly relates to a selector with a nonvolatile memory function and an IC circuit device including such a selector.
BACKGROUND ART
Multiplexers and demultiplexers are basic logic circuits for MISFETs that have been widely used in recent years. Multiplexers and demultiplexers, also referred to as “selection circuits” and “distribution circuits”, are circuits for selecting input data according to selection signals and circuits for distributing input data according to selection signals, respectively.
FIGS.
14
(
a
) and
14
(
b
) are an electric circuit diagram of a known 4-input multiplexer and a table showing the input-output relation in the multiplexer in accordance with selection signals, respectively. As shown in FIG.
14
(
a
), the known multiplexer includes: four pre-stage-side NMISFETs
1001
through
1004
for receiving four input signals In
1
, In
2
, In
3
and In
4
, respectively; a subsequent-stage-side NMISFET
1005
for receiving outputs from the two pre-stage-side NMISFETs
1001
and
1002
; a subsequent-stage-side NMISFET
1006
for receiving outputs from the two pre-stage-side NMISFETs
1003
and
1004
; an output terminal
1007
for receiving outputs from the two subsequent-stage-side NMISFETs
1005
and
1006
; a pre-stage-side SRAM
1011
for supplying a selection signal D
1
to the two pre-stage-side MISFETs
1001
and
1003
and an inverted selection signal /D
1
to the two pre-stage-side MISFETs
1002
and
1004
; and an SRAM
1012
for supplying a selection signal D
2
to the subsequent-stage-side MISFET
1005
and an inverted selection signal /D
2
to the subsequent-stage-side MISFET
1006
.
As shown in FIG.
14
(
b
), any one of the input signals In
1
through In
4
is uniquely selected as an output signal Out according to the four different combinations of the logical values of the selection signals D
1
and D
2
. In other words, the output signal Out is changed in one-to-one correspondence with the combinations of the selection signals D
1
and D
2
.
A demultiplexer, on the other hand, operates in the opposite input-output relation to the multipleplexer. Specifically, assuming that the input signals In
1
through In
4
are input from the output terminal
1007
, one of the input signals In
1
through In
4
is uniquely output from one of the corresponding input terminals to the input signals In
1
through In
4
shown in FIG.
14
(
a
), according to the four types of data of the selection signals D
1
and D
2
.
Problems that the Invention is to Solve
As has been described, in the known multiplexer, control data is pre-stored in an SRAM (FF) and multiplex operation is carried out according to the content of the pre-stored data. Accordingly, when data in the SRAM is retained, i.e., in the state where power is ON in a circuit, the operation of the multiplexer is carried out in accordance with the stored content in the SRAM. After power has been turned OFF, however, in order to carry out operation of the multiplexer, means for storing data in the SRAM is needed.
It is also possible to store the data that have been stored in the SRAM in a nonvolatile memory such as a flash memory and download the data stored in the nonvolatile memory to the SRAM of the mutiplexer in operating the multiplexer. This, however, additionally requires a nonvolatile memory and a download operation.
As for portable devices that have been widely used in recent years, considering power supply, such as batteries, and power consumption, the function of storing operation in a nonvolatile state is required. If a device is provided with only the function of storing data in a volatile state, data at power-on has to be re-downloaded.
When a circuit such as multiplexer is applied to a neuro device which carries out arithmetic operations and learning using previously processed data, stored contents being volatile also come into question.
Then, the present inventors made attempts to configure a circuit, such as a multiplexer, by using a device with a nonvolatile memory function.
Flash memories and ferroelectric memories (FRAMs) have been out in the market as typical devices having a nonvolatile memory function. Specifically, there have been proposed MFSFETs (metal ferroelectric semiconductor FETs), MFMSFETs (metal ferroelectric metal semiconductor FETs), and MFMISFETs (metal ferroelectric metal insulator semiconductor FETs) (which will be hereinafter referred to as “MFS-type-FETs”) each of which can be obtained by forming a gate insulating film from a ferroelectric film in a MISFET (metal insulator semiconductor field effect transistor). Such a MFS-type-FET is expected to function as a small-scaled nonvolatile memory that is operable at high speed.
The MFS-type-FETs utilize the fact that when a higher voltage than the coercive electric field of a ferroelectric material is applied between the semiconductor substrate and a gate electrode, the polarization of a ferroelectric film is changed and residual dielectric polarization occurs in the ferroelectric film even after the application of a voltage has been stopped. More specifically, a MFS-type-FET turns in a normal ON state or a normal OFF state depending on the direction of the residual dielectric polarization, and then an ON/OFF difference in the FET is stored as information.
However, to cause inversion in polarization in a ferroelectric film, application of a voltage between a gate and a semiconductor substrate is necessary. When 2-value logic values L (0V) and H (supply voltage VDD) for use in regular logic devices are used, application of a reverse field between a substrate and a gate electrode is required in order to reverse the residual dielectric polarization in the ferroelectric film. This results in a problem that the device configuration becomes complex.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a nonvolatile selector which includes a ferroelectric film and utilizes a FET having a simple configuration different from that of a known MFSFET to carry out a nonvolatile operation for selecting a signal, and to provide an integrated circuit device using such a selector.
A nonvolatile selector which includes at least one unit selector and, according to a selection signal and an inverted selection signal, blocks at least one input signal of a plurality of input signals and passes the other signals, characterized in that the unit selector includes: at least one serial capacitor that includes a first capacitor and a second capacitor which are connected to each other in series with an intermediate node located therebetween and at least one of which is a ferroelectric capacitor, and receives the selection signal and the inverted selection signal at both ends, respectively; a first FET including a gate electrode connected to the intermediate node of the serial capacitor, and first and second impurity doped layers functioning as an input section and an output section, respectively; and a second FET including a gate electrode connected to the intermediate node of the serial capacitor, and first and second impurity doped layers functioning as an input section and an output section, respectively, and when the selection signal and the inverted selection signal are received at both ends of the serial capacitor, the potential at the intermediate node is varied according to the logical value of the inverted selection signal so that one of the first and second FETs turns ON and the other turns OFF.
In the unit selector, assume that when the logical value of a selection signal is 1, the first FET and the second FET turns ON and OFF, respectively, according to the potential of the intermediate node. When the logical value of the selection signal is 0, the first FET and the second FET turns OFF and ON, respectively, according to the potential of the intermediate node. Thus, the selector function can be ensured. Since the potential of the intermediate node is maintained

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