This application claims priority for Taiwan patent application no. 108136332 filed on Oct. 8, 2019, the content of which is incorporated by reference in its entirely.
The present invention relates to a memory array, particularly to a single-gate multiple-time programming non-volatile memory array and an operating method thereof.
The CMOS (Complementary Metal Oxide Semiconductor) process has been a normal fabrication method for ASIC (Application Specific Integrated Circuit). Flash memories and EEPROM (Electrically Erasable Programmable Read Only Memory), which features electric programmability and erasability and would not lose its memory after power is turned off, has been widely used in electronic products in the computer and information age.
A non-volatile memory is programmed via keeping charges to vary the gate voltage of the transistor thereof, or not keeping charges to preserve the gate voltage of the transistor. For a non-volatile memory, an erase operation is used to eliminate all the charges kept in the non-volatile memory and restore all the transistors to have the original gate voltages. The flash memory architecture has advantages of small size and low cost. However, the flash memory architecture does not allow erasing or programming a single one-bit memory cell but allows erasing or programming a block of the memory. Therefore, the flash memory architecture is inconvenient in application. The EEPROM architecture supports a “byte write” function. Thus, the EEPROM architecture is more convenient than the flash memory architecture. However, in the conventional EEPROM structure, there are many kinds of control voltages and many memory elements. Therefore, EEPROM occupies larger area than the flash memory. Besides, in bit erasing of EEPROM, the transistors at the unselected positions must be separated. Thus, the cost of using EEPROM is increased.
In order to overcome the abovementioned problems of the conventional technology, the present invention provides a single-gate multiple-time programming non-volatile memory array, and further provides an operating method based on the architecture, so as to perform the bytes writing, erasing and reading operations at the same time.
To achieve the abovementioned objectives, the present invention provides a single-gate multiple-time programming non-volatile memory array, which comprises a plurality of parallel bit lines, a plurality of parallel common source lines and a plurality of sub-memory arrays. The bit lines comprise a first bit line. The common source lines are vertical to said bit lines and divided into a plurality of common source, line groups including a first common source line group, and the first common source line group includes a first common source line and a second common source line. Each sub-memory array is connected with one bit line and one common source line group, and each sub-memory array includes a first memory cell and a second memory cell. The first memory cell is connected with the first bit line and the first common source line. The second memory cell is connected with the first bit line and the second common source line. The first memory cell and the second memory cell are symmetrically arranged at an identical side of the first bit line.
Each of the first and second memory cells functions as an operation memory cell. In selecting one of the operation memory cells as a selected memory cell in carrying out its operations, the operation memory cells, that are connected to the same bit line connecting to the selected memory cell, but not connected to the same common source line connecting to the selected memory cell, are referred to as a plurality of common bit line memory cells; the operation memory cells, that are connected to the same bit line connecting to the selected memory cell, are referred to as a plurality of common word memory cells; and the rest of the operation memory cells are referred to a plurality of unselected memory cells.
The first and second memory cells may both contain an N-type field effect transistor located in a P-type well region or in a P-type substrate. Or, alternatively, they may both contain a P-type field effect transistor located in an N-type well region or in an N-type substrate.
In case of the memory having an N-type field effect transistor, when in operating, performing the following steps are required: applying a substrate voltage Vsubp on a P-type well region or a P-type substrate connecting, to a selected memory cell; applying a first bit voltage Vb1, a first common source voltage Vs1 respectively on a bit line and a common source line, both connecting to each selected memory cell; and applying a second bit voltage Vb2 and a second common source voltage Vs2 respectively on the bit line and the common source line connecting to each unselected memory cell.
As such, in erasing data from the selected memory cell, following conditions have to be satisfied: Vsubp is grounded (0), Vb1 is grounded (0), and Vs1=HV (High Voltage); in writing data into the selected memory cell, the following conditions have to be satisfied: Vsubp is grounded (0), Vb1=MV (medium voltage), and Vs1 is grounded (0); in reading data from the selected memory cell, following conditions have to be satisfied: Vsubp is grounded (0), Vb1=LV (Low Voltage)−2V, and Vs1 is grounded (0); in erasing data from the unselected memory cells, the following conditions have to be satisfied: Vsubp is grounded (0), Vb2 is grounded (0), and Vs2=LV (Low Voltage)−2V; in writing data from the unselected memory cells, the following conditions have to be satisfied: Vsubp is grounded (0), Vb2 is grounded (0), and Vs2=LV (Low Voltage)−2V; and in reading data from the unselected memory cells, the following conditions have to be satisfied: Vsubp is grounded (0), Vb2 is grounded (0), and Vs2=LV (Low Voltage)−2V.
In case of the memory having a P-type field effect transistor, when in operating, performing the following steps are required: applying a substrate voltage Vsubn on an N-type well region or an N-type substrate connecting to a selected memory cell. As such, in case of the memory having a P-type field effect transistor, in erasing data from the selected memory cell, following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb1=HV (High Voltage), and Vs1 is grounded (0); in writing data into the selected memory cell, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb1−HV is grounded (0), and Vs1=MV (medium voltage)−6V; in reading data from the selected memory cell, following conditions have to be satisfied; Vsubn=HV (High Voltage), Vb1 is grounded (0), and Vs1=LV (Low Voltage)−2V; in erasing data from the unselected memory cells, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb2=LV (Low Voltage)−2V, and Vs2=LV (Low Voltage) or grounded (0); in writing data from the unselected memory cells, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb2=LV (Low Voltage)−2V and Vs2=LV (Low Voltage) or grounded (0); and in reading data from the unselected memory cells, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb2=LV (Low Voltage)−2V, and Vs2=LV (Low Voltage) or grounded (0).
Further, the first memory cell and the second memory cell both include a transistor and a capacitor structure, wherein the transistor and the capacitor structure are disposed in the semiconductor substrate. The transistor comprises a first dielectric layer, a first conduction gate and two highly-conductive ion-doped regions, the first dielectric layer is disposed on the semiconductor substrate, the first conduction gate is stacked on the surface of the first dielectric layer, and the ion-doped regions are respectively disposed at two sides of the first conduction gate and the first dielectric layer to function as a source and a drain and disposed in the semiconductor substrate, wherein the source and the drain have different widths. The edge of the drain is utilized to serve as a capacitor to form the capacitor structure and control a floating gate. A lightly-doped region is located between the drain and the floating gate, and the lightly-doped region and the ion-doped regions are doped with the same type of ions, jointly functioning as a single floating gate of the first memory cell and the second memory cell.
Since the source and the drain of the first and second memory cells are designed to have different widths, the edge of the drain is used to control the floating gate. Thereby, the minimum control voltages and elements during operating are involved to reduce the whole area. Comparing with a conventional single-gate programming non-volatile memory having high cost due to complicated control, the present invention can greatly reduce the amount of the control lines and costs of the non-volatile memory resulting from the simple operations and the least elements.
Below, the embodiments are described in detail in cooperation with the drawings to make easily understood the technical contents, characteristics and accomplishments of the present invention.
Refer to
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The first memory cell 32 further includes an FET 36 (field effect transistor) and a capacitor 38. The FET 36 has a floating gate, a drain connected with the first common source line 23 of the first common source line group 21, and a source connected with the first bit line 11. The edge of the drain is connected with the floating gate. One terminal of the capacitor 38 is connected with the floating gate of the FET 36, and the other terminal of the, capacitor 38 is connected with the first bit line 11 to receive a bias from the first bit line 11. The FET 36 receives a bias from the first bit line 11 and receives a bias from the first common source line 23 so as to write data into, erase or read data in the floating gate.
The second memory cell 34 further includes an FET 40 and a capacitor 42. The FET 40 has a floating gate, a drain connected with the second common source line 24 of the first common source line group 21, and a source connected with the first bit line 11. The edge of the drain s connected with the floating gate. One terminal of the capacitor 42 is connected with the floating gate of the FET 40, and the other terminal of the capacitor 42 is connected with the first bit line 11 to receive a bias from the first bit line 11. The FET 40 receives a bias from the first bit line 11 and receives a bias from the second common source line 24 so as to write data into, erase or read data in the floating gate.
Both the FET 36 and the FET 40 are N-type FETs built in, a P-type substrate or a P-type well region. Alternatively, both the FET 36 and the FET 40 are P-type FETs built in an N-type substrate or an N-type well region. The method for operating a single-gate multiple-time programming non-volatile memory array has different sub-embodiments with respect to the types of FETs. Below the sub-embodiment corresponding to the N-type FETs 36 and 40 is described firstly. In order to understand the ways of operations, the names of various memory cells are first clearly defined as follows.
Both the abovementioned first and second memory cells 32 and 34 are operation memory cells, and one of the operation memory cells can be selected as the selected memory cell to proceed with the operations as required. As to the operation memory cells, that are connected to the same bit line 10 connecting to the selected memory cell, but not connected to the same common source line 20 connecting to the selected memory cell, are referred to as a plurality of common bit memory cells. The operation memory cells, which are connected to the same bit line 10 connecting to the selected memory cell, are referred to as a plurality of common word memory cells. The rest of the operation memory cells are referred to as a plurality of unselected memory cells.
In the following, the operations of the embodiment are described, such that m this way of operation, other unselected memory cells will not be affected, thus operation is related to a specific single memory cell.
When in operating, performing the following steps are required: applying a substrate voltage Vsubp on a P-type well region or P-type substrate connecting to a selected memory cell; applying a first bit voltage Vb1, a first common source voltage Vs1 on a bit line 14, and a common source line 20, both connecting to a selected memory cell; applying a second common source voltage Vs2 on a common source line 20, connecting to each common bit memory cell; applying a second bit voltage Vb2, a first common source voltage Vs1 on a bit line 10, and a common source line 20, both connecting to each common word memory cell; and applying a second bit voltage Vb2, and a second common source voltage Vs2 on the bit line 10, and the common source line 20, both connecting to an unselected memory cell.
In erasing data from the selected memory cell, the following conditions have to be satisfied: Vsubp is grounded (0), Vb1 is grounded (0), and Vs1=HV (High Voltage).
In writing data into the selected memory cell, the following conditions have to be satisfied: Vsubp is grounded (0), Vb1=MV (medium voltage), and Vs1 is grounded (0).
In reading data from the selected memory cell, following conditions are to be satisfied: Vsubp is grounded (0), Vb1=LV (Low Voltage)−2V, and Vs1 is grounded (0).
In erasing data from the unselected memory cells, the following conditions have to be satisfied: Vsubp is grounded (0), Vb2 is grounded (0), and Vs2=LV (Low Voltage)−2V.
In writing data from the unselected memory cells, the following conditions have to be satisfied: Vsubp is grounded (0), Vb2 is grounded (0), and Vs2=LV (Low Voltage)−2V.
In reading data from the, unselected memory cells, the following conditions have to be satisfied: Vsubp is grounded (0), Vb2 is grounded (0), and Vs2=LV (Low Voltage)−2V.
While the FET 36 and the FET 40 are P-type FETs, applying a substrate voltage Vsubn on an N-type well region or an N-type substrate connecting to a selected memory cell.
In erasing data from the selected memory cell, following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb1=HV (High Voltage), and Vs1 is grounded (0).
In writing data into the selected memory cell, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb1 is grounded (0), and Vs1=MV (medium voltage)−6V.
In reading data from the selected memory cell, following conditions are to be satisfied: Vsubn=HV (High Voltage), Vb1 is grounded (0), and Vs1=LV (Low Voltage)−2V.
In erasing data from the unselected memory cells, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb2=LV (Low Voltage)−2V, and Vs2=LV (Low Voltage) or grounded (0).
In writing data from the unselected memory cells, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb2=LV (Low Voltage)−2V, and Vs2=LV (Low Voltage) or grounded (0).
In reading data from the unselected memory cells, the following conditions have to be satisfied: Vsubn=HV (High Voltage), Vb2=LV (Low Voltage)−2V, and Vs2=LV (Low Voltage) or grounded (0).
In the following, a cross section view of a structure, of field effect transistors 36 and 40 and capacitors 38 and 42 of the present invention is described. In this case, an N-type FET is taken as an example for explanation. As shown in
Similarly, in the following, a cross section view of a structure of field effect transistors 36 and 40 and capacitors 38 and 42 of the present invention is described. In this case, a P-type field effect transistor is taken as an example for explanation. As shown in
In the above embodiment, the edge of the drain 114 and 214 of the field effect transistors 36 and 40 is in the middle of the floating gate. The widths of the source 113 and 213 and the drain 114 and 214 are the side lengths along a horizontal axis direction (i.e. the direction parallel to the direction from the source 113 and 213 to the drain 114 and 214, respectively), as shown in
Summing up the above, the single-gate multiple-time programming non-volatile memory array and an operating method thereof according to the present invention is capable of providing a single-gate multiple-time programming non-volatile memory array structure of smaller area at lower cost. Moreover, the present invention can greatly reduce the lengths of control lines, areas and production costs of the non-volatile memory resulting from simple operations and the least elements and the least control voltages.
The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Therefore, any equivalent modification or variation according to the shapes. structures, features, or spirit disclosed by the present invention is to be also included within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 108136332 | Oct 2019 | TW | national |