阅读说明：本技术 可编程可抹除的非易失性存储器 (Programmable erasable non-volatile memory ) 是由 许家荣 孙文堂 于 2019-03-22 设计创作，主要内容包括：本发明公开一种可编程可抹除的非易失性存储器,包括：第一选择晶体管、第一浮动栅晶体管、第二选择晶体管与第二浮动栅晶体管。第一选择晶体管的选择栅极与第一源/漏端接收分别接收第一选择栅极电压与第一源极线电压。第一浮动栅晶体管的第一源/漏端与连接至第一选择晶体管的第二源/漏端,第一浮动栅晶体管的第二源/漏端接收第一位线电压。第二选择晶体管的选择栅极与第一源/漏端分别接收第二选择栅极电压与第二源极线电压。第二浮动栅晶体管的第一源/漏端连接至第二选择晶体管的第二源/漏端,第二浮动栅晶体管的第二源/漏端接收一第二位线电压。(The invention discloses a programmable erasable nonvolatile memory, comprising: a first selection transistor, a first floating gate transistor, a second selection transistor and a second floating gate transistor. The selection gate and the first source/drain terminal of the first selection transistor receive a first selection gate voltage and a first source line voltage, respectively. The first floating gate transistor has a first source/drain terminal and a second source/drain terminal connected to the first select transistor, the second source/drain terminal of the first floating gate transistor receiving the first bit line voltage. The selection grid electrode and the first source/drain terminal of the second selection transistor respectively receive a second selection grid electrode voltage and a second source electrode line voltage. The first source/drain terminal of the second floating gate transistor is connected to the second source/drain terminal of the second select transistor, and the second source/drain terminal of the second floating gate transistor receives a second bit line voltage.)

1. A programmable erasable non-volatile memory comprising:

a first select transistor comprising: the selection grid electrode receives a first selection grid electrode voltage, and the first source/drain terminal receives a first source electrode line voltage and a second source/drain terminal;

a first floating gate transistor comprising: a floating gate, a first source/drain terminal connected to the second source/drain terminal of the first selection transistor, and a second source/drain terminal receiving a first bit line voltage;

a second select transistor comprising: the selection grid electrode receives a second selection grid electrode voltage, and the first source/drain terminal receives a second source electrode line voltage and a second source/drain terminal;

a second floating gate transistor comprising: a floating gate, a first source/drain terminal connected to the second source/drain terminal of the second selection transistor, and a second source/drain terminal receiving a second bit line voltage;

wherein the first selection transistor and the first floating gate transistor are formed in a first type well region; the second selection transistor and the second floating gate transistor are manufactured in a second type well area; and the floating gate of the first floating gate transistor is interconnected with the floating gate of the second floating gate transistor.

2. The programmable erasable non-volatile memory of claim 1, wherein said first select transistor and said first floating gate transistor are n-type transistors, said first type well region receives a P-type well region voltage for a P-type well region; and the second selection transistor and the second floating gate transistor are p-type transistors, and the second type well region is an N-type well region for receiving N-type well region voltage.

3. The programmable erasable non-volatile memory of claim 1, wherein said first select transistor and said first floating gate transistor are p-type transistors, said first type well region receives an N-type well region voltage for an N-type well region; and the second selection transistor and the second floating gate transistor are n-type transistors, and the second type well region is a P-type well region for receiving P-type well region voltage.

4. The programmable erasable non-volatile memory of claim 1, wherein the first floating gate transistor has a first channel length; the second floating gate transistor has a second channel length; and the first channel length is less than the second channel length.

5. The programmable erasable non-volatile memory of claim 1, wherein the first floating gate transistor has a first channel width; the second floating gate transistor has a second channel width; and the first channel width is less than the second channel width.

6. The programmable erasable non-volatile memory of claim 1, wherein during a programming operation, a plurality of electrons are injected from a channel region of said first floating gate transistor into said floating gate of said first floating gate transistor.

7. The programmable erasable non-volatile memory of claim 1, wherein during an erase operation, a plurality of electrons are ejected from said floating gate of said first floating gate transistor to said first-type well region.

8. The programmable erasable non-volatile memory of claim 1, wherein during a read operation, said second floating gate transistor generates a read current.

9. The programmable erasable non-volatile memory of claim 8, wherein said second floating gate transistor produces a first read current when said floating gate of said second floating gate transistor stores a plurality of electrons; the second floating gate transistor generates a second read current when the floating gate of the second floating gate transistor does not store the electrons, and the first read current is different from the second read current.

10. The programmable erasable non-volatile memory of claim 1, wherein the select gate of the first select transistor and the select gate of the second select transistor are connected to each other, and the first select gate voltage is equal to the second select gate voltage.

11. The programmable erasable non-volatile memory of claim 1, further comprising a capacitor, a first end of said capacitor being connected to said floating gate of said first floating gate transistor; and the second terminal of the capacitor receives a certain voltage.

12. The programmable erasable non-volatile memory of claim 11, wherein during an erase operation, a plurality of electrons are ejected from the floating gate of the first floating gate transistor to the first-type well region through the capacitor.

13. A programmable erasable non-volatile memory comprising:

a first type well region;

a first doped region, a second doped region and a third doped region are formed on the surface of the first type well region, wherein the first doped region receives a first source line voltage, and the third doped region receives a first bit line voltage;

a first select gate formed over a surface between the first doped region and the second doped region, the first select gate receiving a first select gate voltage;

a first floating gate formed over a surface between the second doped region and the third doped region;

a second type well region;

a fourth doped region, a fifth doped region and a sixth doped region are formed on the surface of the second type well region, wherein the fourth doped region receives a second source line voltage, and the sixth doped region receives a second bit line voltage;

a second select gate formed over a surface between the fourth doped region and the fifth doped region, the second select gate receiving a second select gate voltage;

a second floating gate is formed over the surface between the fifth doped region and the sixth doped region, and the second floating gate and the first floating gate are in contact with each other.

14. The programmable, erasable non-volatile memory of claim 13, wherein said first type well region receives a P-type well voltage for a P-type well region, said second type well region receives an N-type well voltage for an N-type well region, said first doped region, said second doped region and said third doped region are N-type doped regions; and the fourth doped region, the fifth doped region and the sixth doped region are p-type doped regions.

15. The programmable, erasable non-volatile memory of claim 13, wherein said first type well region receives a N-type well voltage for an N-type well region, said second type well region receives a P-type well voltage for a P-type well region, said first doped region, said second doped region, and said third doped region are P-type doped regions; and the fourth doped region, the fifth doped region and the sixth doped region are n-type doped regions.

16. The programmable erasable non-volatile memory of claim 13, wherein the first-type well region, the second doped region, the third doped region and the first floating gate form a first floating gate transistor, and the second-type well region, the fifth doped region, the sixth doped region and the second floating gate form a second floating gate transistor.

17. The programmable erasable non-volatile memory of claim 16, wherein the first floating gate transistor has a first channel length; the second floating gate transistor has a second channel length; and the first channel length is less than the second channel length.

18. The programmable erasable non-volatile memory of claim 16, wherein the first floating gate transistor has a first channel width; the second floating gate transistor has a second channel width; and the first channel width is less than the second channel width.

19. The programmable erasable non-volatile memory of claim 13, wherein the first select gate and the second select gate are interconnected and the first select gate voltage is equal to the second select gate voltage.

20. The programmable, erasable non-volatile memory of claim 13, further comprising a seventh doped region formed within the first-type well region, the seventh doped region being adjacent to the first floating gate, the seventh doped region being a heavily doped region.

21. The programmable, erasable non-volatile memory of claim 13, further comprising a coupling layer formed adjacent to the first floating gate and the second floating gate.

22. The programmable, erasable non-volatile memory of claim 21, wherein the coupling layer is a polysilicon layer formed beside the first floating gate and the second floating gate.

23. The programmable erasable non-volatile memory of claim 21, wherein the coupling layer is a metal layer formed over the first floating gate and the second floating gate.

Technical Field

The present invention relates to a nonvolatile memory (nonvolatile memory), and more particularly, to a programmable erasable nonvolatile memory.

Background

Referring to fig. 1A to 1D, a conventional programmable and erasable nonvolatile memory is shown, which is disclosed in US patent No. 8941167. FIG. 1A is a top view of a non-volatile memory; FIG. 1B is a cross-sectional view of the non-volatile memory device taken along a first direction (a1a2 direction); FIG. 1C is a cross-sectional view of the nonvolatile memory in a second direction (b1b2 direction); and, FIG. 1D is an equivalent circuit diagram of a non-volatile memory.

As shown in fig. 1A and 1B, the conventional nonvolatile memory includes two serially connected p-type transistors fabricated in an N-well (NW). The N-well NW includes three p-type doped regions 31, 32, 33, and two gates 34, 36 made of polysilicon (polysilicon) are disposed above the surface between the three p-type doped regions 31, 32, 33.

The first p-type transistor acts as a select transistor with its select gate 34 connected to a select gate voltage (V)_SG) The p-doped region 31 is connected to a source line voltage (V)_SL). Furthermore, the p-type doped region 32 can be regarded as a p-type doped region of the first p-type transistor and a p-type doped region of the second p-type transistor connected to each other. The second p-type transistor acts as a floating gate transistor and includes a floating gate 36 with a p-doped region 33 connected to the bit line voltage (V)_BL). And the N-well (NW) is connected to an N-well voltage (V)_NW)。

As shown in fig. 1A and 1C, the conventional nonvolatile memory further includes an n-type transistor, or an element formed by combining a floating gate 36 and an erase gate region 35. The n-type transistor is formed in a P-type well region (PW). An n-type doped region 38 is included in the P-type well region (PW). In other words, the erase gate region 35 includes a P-type well (PW) and an n-type doped region 38.

As shown in FIG. 1A, the floating gate 36 extends outward and is adjacent to the erase gate region 35. Thus, the floating gate 36 may be considered to be the gate of an n-type transistor, and the n-doped region 38 may be considered to be the n-type source doped region andthe n-type drain doped regions are interconnected. Furthermore, the n-type doped region 38 is connected to an erase line voltage (V)_EL). The P-well (PW) is connected to a P-well voltage (V)_PW). Furthermore, as shown in FIG. 1C, the erase gate region 35 and the N-well (NW) may be separated by an isolation structure 39 (STI), for example, the isolation structure 39 is a Shallow Trench Isolation (STI).

As shown in the equivalent circuit of FIG. 1D, the non-volatile memory includes a select transistor, a floating gate transistor and an n-type transistor. Wherein the selection transistor and the floating gate transistor are both p-type transistors and are formed in an N-type well region (NW), and the N-type well region (NW) receives an N-type well voltage (V)_NW). In addition, the n-type transistor is formed in a P-well (PW) that receives a P-well voltage (V)_PW)。

The select gate terminal of the select transistor receives a select gate voltage (V)_SG) The first source/drain terminal of the selection transistor receives a source line voltage (V)_SL). The first source/drain terminal of the floating gate transistor is connected to the second source/drain terminal of the select transistor, which receives the bit line voltage (V)_BL). The gate terminal of the n-type transistor is connected with the floating gate of the floating gate transistor, the first source/drain terminal of the n-type transistor and the second source/drain terminal of the n-type transistor are connected with each other and receive the erase line voltage (V)_EL)。

Disclosure of Invention

The invention aims to provide a programmable erasable nonvolatile memory with a novel structure.

The invention relates to a programmable erasable non-volatile memory, comprising: a first select transistor including a select gate receiving a first select gate voltage, a first source/drain receiving a first source line voltage, and a second source/drain; a first floating gate transistor including a floating gate, a first source/drain terminal connected to the second source/drain terminal of the first select transistor, and a second source/drain terminal receiving a first bit line voltage; a second select transistor including a select gate receiving a second select gate voltage, a first source/drain receiving a second source line voltage, and a second source/drain; a second floating gate transistor including a floating gate, a first source/drain terminal connected to the second source/drain terminal of the second select transistor, and a second source/drain terminal receiving a second bit line voltage; wherein the floating gate of the first floating gate transistor is interconnected with the floating gate of the second floating gate transistor.

The invention relates to a programmable erasable non-volatile memory, comprising: a first type well region; a first doped region, a second doped region and a third doped region formed on the surface of the first type well region, wherein the first doped region receives a first source line voltage, and the third doped region receives a first bit line voltage; a first select gate formed over the surface between the first doped region and the second doped region, the first select gate receiving a first select gate voltage; a first floating gate formed over the surface between the second doped region and the third doped region; a second type well region; a fourth doped region, a fifth doped region and a sixth doped region formed on the surface of the second type well region, wherein the fourth doped region receives a second source line voltage, and the sixth doped region receives a second bit line voltage; a second select gate formed over the surface between the fourth doped region and the fifth doped region, the second select gate receiving a second select gate voltage; a second floating gate is formed over the surface between the fifth doped region and the sixth doped region, and the second floating gate and the first floating gate are in contact with each other.

In order to better understand the above and other aspects of the present invention, the following detailed description of the embodiments is made with reference to the accompanying drawings, in which:

drawings

Fig. 1A to 1D are known programmable erasable nonvolatile memories.

Fig. 2A and 2B show a programmable and erasable nonvolatile memory according to a first embodiment of the present invention.

Fig. 3A to 3D are schematic diagrams illustrating the biasing and operation of the first embodiment of the nonvolatile memory in the negative operation.

FIG. 4 is a schematic diagram of the biasing of the first embodiment of the nonvolatile memory in a positive operation.

Fig. 5 shows a second embodiment of a programmable and erasable nonvolatile memory according to the present invention.

Fig. 6A and 6B show a programmable and erasable nonvolatile memory according to a third embodiment of the present invention.

FIGS. 7A to 7D are schematic diagrams illustrating biasing and operation of the nonvolatile memory in the negative operation according to the third embodiment.

FIG. 8 is a schematic diagram of biasing voltages of the nonvolatile memory in a positive operation according to the third embodiment.

Fig. 9A and 9B show a fourth embodiment of a programmable and erasable nonvolatile memory according to the present invention.

Fig. 10A to 10D are schematic diagrams illustrating biasing and operation of the fourth embodiment of the nonvolatile memory in a forward operation.

[ notation ] to show

20. 50, 60, 90: nonvolatile memory

21. 22, 23, 31, 32, 33: p-type doped region

25. 26, 27, 38: n-type doped region

29. 39: isolation structure

34. 36: grid electrode

35: erase gate region

51: coupling layer

Detailed Description

Referring to fig. 2A and 2B, a first embodiment of a programmable and erasable nonvolatile memory is shown. Fig. 2A is a top view of the nonvolatile memory. FIG. 2B is an equivalent circuit diagram of the nonvolatile memory according to the first embodiment.

As shown in FIG. 2A, the nonvolatile memory 20 includes two serially connected P-type transistors fabricated in an N-well (NW) and two serially connected N-type transistors fabricated in a P-well (PW). The N-well (NW) and the P-well (PW) are separated by an isolation structure 29, and the isolation structure 29 can be, for example, a P-type substrate, an N-type substrate, or a deep N-well (DNW).

Three p-doped regions 21, 22, 23 are included in the N-type well NW. Further, a gate SG1 composed of polysilicon (polysilicon) is formed over the surface between the p-type doped regions 21, 22; a gate FG1 composed of polysilicon is formed over the surface between the p-doped regions 22, 23. Wherein the first p-type transistor is used as a first selection transistor with its selection gate SG1 connected to a first selection gate voltage (V)_SG1) The p-doped region 21 is connected to a first source line voltage (V)_SL1). Furthermore, the p-type doped region 22 can be regarded as a p-type doped region of the first p-type transistor and a p-type doped region of the second p-type transistor connected to each other. The second p-type transistor, acting as the first floating gate transistor, includes a floating gate FG1 above it, with the p-type second doped region 23 connected to the first bit line voltage (V)_BL1). And the N-well (NW) is connected to an N-well voltage (V)_NW)。

The P-well PW includes three n-doped regions 25, 26, 27, and two gates SG2, FG2 made of polysilicon (polysilicon) are disposed above the surface between the three n-doped regions 25, 26, 27. Wherein the first n-type transistor is used as the second selection transistor, and its selection gate SG2 is connected to the second selection gate voltage (V)_SG2) The n-doped region 25 is connected to a second source line voltage (V)_SL2). Furthermore, the n-doped region 26 can be considered as an n-doped region of the first n-type transistor and an n-doped region of the second n-type transistor connected to each other. The second n-type transistor is used as a second floating gate transistor and includes a floating gate FG2 above it, with the second n-type doped region 27 connected to a second bit line voltage (V)_BL2). The P-well (PW) is connected to a P-well voltage (V)_PW)。

According to an embodiment of the invention the floating gate FG1 of the first floating gate transistor and the floating gate FG2 of the second floating gate transistor are composed of the same polysilicon, i.e. the floating gate FG1 of the first floating gate transistor and the floating gate FG2 of the second floating gate transistor are interconnected. Further, the channel length (channelling) L1 of the first floating gate transistor is smaller than the channel length L2 of the second floating gate transistor. In addition, the channel width (channel width) w1 of the first floating gate transistor is smaller than the channel width w2 of the second floating gate transistor.

As can be seen from the equivalent circuit of fig. 2B, the nonvolatile memory 20 includes a first selection transistor, a second selection transistor, a first floating gate transistor, and a second floating gate transistor. That is, a memory cell (memory cell) of the nonvolatile memory 20 is composed of four transistors, and the memory cell is connected to two bit lines (bit lines), two source lines (source lines), and two select lines (select lines).

Furthermore, the first selection transistor and the first floating gate transistor are both p-type transistors and are formed in an N-well (NW), and the N-well (NW) receives an N-well voltage (V)_NW). In addition, the second selection transistor and the second floating gate transistor are both n-type transistors and are fabricated on a P-type well region (PW), and the P-type well region (PW) receives the P-type well region voltage (V)_PW)。

The select gate terminal SG1 of the first select transistor receives a first select gate voltage (V)_SG1) The first source/drain terminal of the first selection transistor receives a first source line voltage (V)_SL1). The first floating gate transistor has a first source/drain terminal connected to the second source/drain terminal of the first select transistor, and the second source/drain terminal of the first floating gate transistor receives a first bit line voltage (V)_BL1)。

The selection gate terminal SG2 of the second selection transistor receives the second selection gate voltage (V)_SG2) The first source/drain terminal of the second selection transistor receives a second source line voltage (V)_SL2). The first source/drain terminal of the second floating gate transistor is connected to the second source/drain terminal of the second select transistor, and the second source/drain terminal of the second floating gate transistor receives a second bit line voltage (V)_BL2)。

The operation of the non-volatile memory 20 of the present invention is described in detail below.

During a program operation of the non-volatile memory device 20, the first select transistor and the first floating gate transistor are operated such that hot carriers (e.g., electrons) are injected (inject) from a channel region (channel) of the first floating gate transistor into the floating gate FG 1.

During the erasing operation of the nonvolatile memory 20, the voltage difference between the floating gate FG1 and the N-well (NW) of the first floating gate transistor is large, which causes electrons to be ejected (incident) from the floating gate FG1 of the first floating gate transistor to the N-well (NW).

In the read operation of the nonvolatile memory 20, the second selection transistor and the second floating gate transistor are operated such that the second floating gate transistor generates a read current according to the number of electrons on the floating gate FG2, and the storage state of the nonvolatile memory 20 is determined according to the magnitude of the read current.

Fig. 3A to 3D are schematic diagrams illustrating the biasing and operation of the nonvolatile memory in the negative operation (negative operation) according to the first embodiment. When the bias voltage received by the nonvolatile memory 20 has a negative voltage value, the operation is called negative operation.

As shown in FIG. 3A and FIG. 3B, the programming operation can be divided into two time intervals. For example, the programming operation requires 50 μ s, the first time interval is 20 μ s in the initial period, and the second time interval is 30 μ s in the later period.

At the beginning of programming operation, the second selection gate voltage (V)_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) And P-type well voltage (V)_PW) Are all 0V. Furthermore, the first selection gate voltage (V)_SG1) Is 0V, the first source line voltage (V)_SL1) Is 5V, the first bit line voltage (V)_BL1) Is a well voltage (V) of type-2V, N_NW) Is 5V. At this bias, about 0V will couple (couple) to the floating gate FG1 of the first floating gate transistor, thereby turning on the first floating gate transistor. In addition, since the first select transistor is turned on, a programming current Ipgm flows through the first floating gate transistor. Thus, electrons are injected into the floating gate FG1, i.e. from the channel area of the first floating gate transistor.

In the later stage of the programming operation, the second selection gate voltage (V)_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) A ramp voltage (ramp voltage) is provided, for example, 0V is directly raised to 5V. In addition, due to the P-well voltage (V)_PW) At 0V, a voltage of about 5V will be coupled to the floating gate FG2 of the second floating gate transistor. Since the two floating gates FG1, FG2 are connected to each other such that the floating gate FG1 of the first floating gate transistor is also coupled to a voltage of about 5V, more electrons will be injected into the floating gate FG1 of the first floating gate transistor, which may improve the programming efficiency of the non-volatile memory 20.

In addition, in other bias embodiments, the second select gate voltage (V) is supplied_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) The rising voltage of (c) may also be gradually (smooth) from 0V to 5V, or an increment may be provided and gradually raised from 0V to 5V.

As shown in FIG. 3A and FIG. 3C, during the erasing operation, the second selection gate voltage (V)_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) And P-type well voltage (V)_PW) Are all-7.5V. Furthermore, the first selection gate voltage (V)_SG1) A first source line voltage (V)_SL1) A first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) Both are 7.5V. Therefore, the first selection transistor and the second selection transistor are turned off.

Since the floating gate FG2 of the second floating gate transistor may be coupled (coupled) out to a voltage of about-7.5V. At the same time, due to the first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) Both are 7.5V. Thus, the floating gate FG1 of the first floating gate transistor is coupled to the N-well voltage (V)_NW) There is a voltage difference (voltage difference) of about 15V between them, which causes electrons to exit from the floating gate FG1 of the first floating gate transistor to the N-well (NW).

As shown in FIG. 3A and FIG. 3D, during a read operation, the first select gate voltage (V)_SG1) A first source line voltage (V)_SL1) A first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) Is 2.5V, so that the first select transistor is turned off. Furthermore, the second optionSelect gate voltage (V)_SG2) Is 2.5V, the second source line voltage (V)_SL2) Is 0V, the second bit line voltage (V)_BL2) Is 2.5V, P type well area voltage (V)_PW) Is 0V so that the second select transistor is turned on and the second floating gate transistor generates the read current Iread.

Basically, the magnitude of the read current Iread is determined by whether electrons are stored in the floating gate FG2 of the second floating gate transistor. For example, the floating gate FG2 of the second floating gate transistor stores electrons, which results in the second floating gate transistor being in an off state, producing a read current Iread that is very small at about 0. Conversely, the floating gate FG2 of the second floating gate transistor does not store electrons, which causes the second floating gate transistor to be in an on state, resulting in a larger read current Iread. Therefore, in the read operation, the storage state of the nonvolatile memory 20 can be determined according to the magnitude of the read current Iread.

According to an embodiment of the present invention, the channel length (channel length) L1 of the first floating gate transistor is smaller than the channel length L2 of the second floating gate transistor. In addition, the channel width (channel width) w1 of the first floating gate transistor is smaller than the channel width w2 of the second floating gate transistor. Thus, the first floating gate transistor has better programming efficiency and the second floating gate transistor has better reading efficiency.

In addition, the first embodiment nonvolatile memory 20 may also operate positively (positive operation) in addition to the negative operation. Referring to FIG. 4, a bias diagram of the first embodiment of the non-volatile memory in a positive operation is shown. That is, the bias voltage received by the nonvolatile memory 20 is a voltage value greater than or equal to 0 during the programming operation, the erasing operation and the reading operation. Moreover, the operations of the non-volatile memory 20 during the programming operation, the erasing operation and the reading operation are similar to those in fig. 3B to 3D, and are not repeated here.

Of course, the non-volatile memory 20 of the first embodiment can also be slightly modified to improve the efficiency of the programming operation, the erasing operation and the reading operation. Referring to fig. 5, a programmable erasable nonvolatile memory according to a second embodiment of the present invention is shown.

Compared to the nonvolatile memory 20 of the first embodiment, the nonvolatile memory 50 of the second embodiment is added with a coupling layer (coupling layer)51 and an extension (extension part) sg 2. The extension SG2 is an extension belonging to the select gate SG 2. In addition, the coupling layer 51 can receive a coupling voltage (V)_CP) E.g. coupling voltage (V)_CP) Equal to the second select gate voltage (V)_SG2)。

According to a second embodiment of the invention, a coupling layer 51 is formed near the floating gates FG1 and FG 2. Similarly, extension SG2 of select gate SG2 is also located near floating gates FG1 and FG 2. In addition, the coupling layer 51 is not in contact with the four transistors in the nonvolatile memory 50. For example, the coupling layer 51 may be a polysilicon layer or a metal layer. When the coupling layer 51 is a polysilicon layer, it can be directly fabricated beside the floating gates FG1 and FG 2; when the coupling layer 51 is a metal layer, it can be fabricated over floating gates FG1 and FG 2. The coupling voltage V of the coupling layer 51 is used for programming, erasing or reading_CPMay be coupled to the floating gates FG1, FG2 for improved efficiency.

Referring to fig. 6A and 6B, a programmable erasable nonvolatile memory according to a third embodiment of the invention is shown. Fig. 6A is a top view of the nonvolatile memory. FIG. 6B is an equivalent circuit diagram of a nonvolatile memory according to a third embodiment.

The difference compared to the first embodiment is that in the nonvolatile memory 60, the first selection transistor and the second selection transistor have a common selection gate SG. That is, the select gate of the first select transistor and the select gate of the second select transistor are connected to each other and receive a select gate voltage V_SG。

Of course, changing the connection relationship of the nonvolatile memory 20 of the first embodiment can also accomplish the nonvolatile memory 60 of the third embodiment. For example, in the first embodiment, the selection gate SG1 of the first selection transistor and the selection gate SG2 of the second selection transistor are connected to each other. And, setting a first selectionGate voltage V_SG1Is equal to the second select gate voltage V_SG2。

Fig. 7A to 7D are schematic diagrams illustrating biasing and operation of the nonvolatile memory according to the third embodiment in a negative operation (negative operation).

As shown in FIG. 7 and FIG. 7B, the select gate voltage (V) is set at the beginning of the programming operation_SG) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) And P-type well voltage (V)_PW) Are all 0V, so that the second select transistor is turned off. Furthermore, the first source line voltage (V)_SL1) Is 5V, the first bit line voltage (V)_BL1) Is a well voltage (V) of type-2V, N_NW) Is 5V. At this bias, about 0V will couple (couple) to the floating gate FG1 of the first floating gate transistor, thereby turning on the first floating gate transistor. In addition, since the first select transistor is turned on, a programming current Ipgm flows through the first floating gate transistor. Thus, electrons are injected into the floating gate FG1, i.e. from the channel area of the first floating gate transistor.

At the end of the programming action, the second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) A rising voltage (ramp voltage) is provided, for example from 0V directly to 5V, so that the floating gate FG2 of the second floating gate transistor is coupled (coupled) out to a voltage of about 5V. Since the two floating gates FG1, FG2 are connected to each other such that the floating gate FG1 of the first floating gate transistor also couples a voltage of about 5V, more electrons will be injected into the floating gate FG1 of the first floating gate transistor, which may improve the programming efficiency of the non-volatile memory 60.

In addition, in other bias embodiments, the second bias voltage is supplied to the second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) The rising voltage of (c) may also be gradually (smooth) from 0V to 5V, or an increment may be provided and gradually raised from 0V to 5V.

As shown in FIG. 7A and FIG. 7C, during the erase operation, the select gate voltage (V)_SG) Is 0V; second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) And P-type well voltage (V)_PW) Are all-7.5V. Furthermore, the first source line voltage (V)_SL1) A first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) Both are 7.5V. Therefore, the first selection transistor and the second selection transistor are turned off.

Since the floating gate FG2 of the second floating gate transistor may be coupled (coupled) out to a voltage of about-7.5V. At the same time, due to the first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) Both are 7.5V. Thus, the floating gate FG1 of the first floating gate transistor is coupled to the N-well voltage (V)_NW) A voltage difference of about 15V will cause electrons to exit from the floating gate FG1 of the first floating gate transistor to the N-well region (NW).

As shown in FIGS. 7A and 7D, during a read operation, the select gate voltage (V)_SG) A first source line voltage (V)_SL1) A first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) Is 2.5V, so that the first select transistor is turned off. Furthermore, a second source line voltage (V)_SL2) Is 0V, the second bit line voltage (V)_BL2) Is 2.5V, P type well area voltage (V)_PW) Is 0V so that the second select transistor is turned on and the second floating gate transistor generates the read current Iread.

Similarly, the magnitude of the read current Iread is determined by whether electrons are stored in the floating gate FG2 of the second floating gate transistor. Therefore, in the read operation, the storage state of the nonvolatile memory 60 can be determined according to the magnitude of the read current Iread.

In addition, the third embodiment nonvolatile memory 60 can also operate positively in addition to the negative operation. Referring to FIG. 8, a biasing diagram of the nonvolatile memory according to the third embodiment during the positive operation is shown. Moreover, the operations of the non-volatile memory 60 during the programming operation, the erasing operation and the reading operation are similar to those in fig. 7B to 7D, and are not repeated herein.

Of course, the nonvolatile memory 60 of the third embodiment can also be slightly modified to improve the efficiency of the programming operation, the erasing operation and the reading operation. For example, a coupling layer is added to the programmable erasable nonvolatile memory of the third embodiment and a coupling voltage is received.

Referring to fig. 9A and 9B, a programmable and erasable nonvolatile memory according to a fourth embodiment of the invention is shown. Fig. 9A is a top view of the nonvolatile memory. FIG. 9B is an equivalent circuit diagram of the nonvolatile memory of the fourth embodiment.

The difference between the first embodiment is that a heavily N-doped region (N +) is formed in the N-well (NW) of the non-volatile memory 90 adjacent to the floating gate FG 1. This results in a capacitor between the floating gate FG1, FG2 and the heavily N-doped region (N +). Basically, the capacitor formed between the floating gate FG1, FG2 and the heavily N-doped region (N +) can form an exit path for electrons during an erase operation. Thus, the electrons have separate moving paths during the programming operation, the erasing operation and the reading operation of the non-volatile memory 90, and the reliability of the non-volatile memory 90 is effectively improved.

Since the N + region is connected to the N Well (NW), the N + region also receives the N well voltage (V)_NW). As shown in FIG. 9B, one end of the capacitor is connected to the floating gate FG1, FG2, and the other end of the capacitor receives the N-type well voltage (V)_NW)。

Referring to fig. 10A to 10D, bias voltages and operation diagrams of the fourth embodiment of the nonvolatile memory in a positive operation are shown.

As shown in FIG. 10A and FIG. 10B, at the beginning of the programming operation, the second select gate voltage (V)_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) Are all 3V. Furthermore, the first selection gate voltage (V)_SG1) Is 3.5V, the first source line voltage (V)_SL1) Is 7V, the first bit line voltage (V)_BL1) Is a well voltage (V) of type 0V, N_NW) Is 7V and P-type well region voltage (V)_PW) Is 0V. Under this bias, the first select transistor is turned on and a programming current Ipgm is generated to flow through the first floating gate transistor. Thus, electrons are injected into the floating gate FG1, i.e. from the channel area of the first floating gate transistor.

At the later stage of the programming action, secondSelect gate voltage (V)_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) A rising voltage, for example from 0V directly to 6V, is provided so that the floating gate FG2 of the second floating gate transistor is coupled (coupled) out to a voltage of about 6V. Since the two floating gates FG1, FG2 are connected to each other such that the floating gate FG1 of the first floating gate transistor is also coupled out to a voltage of about 6V, more electrons will be injected into the floating gate FG1 of the first floating gate transistor, which may improve the programming efficiency of the non-volatile memory 90.

In addition, in other bias embodiments, the second select gate voltage (V) is supplied_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) The rising voltage of (c) may also be gradually (smooth) from 0V to 6V, or an increment may be provided and gradually raised from 0V to 6V.

As shown in FIG. 10A and FIG. 10C, during the erasing operation, the second selection gate voltage (V)_SG2) A second source line voltage (V)_SL2) Second bit line voltage (V)_BL2) And P-type well voltage (V)_PW) Are all 0V. Furthermore, the first selection gate voltage (V)_SG1) A first source line voltage (V)_SL1) A first bit line voltage (V)_BL1) Both are 7.5V. N-type well voltage (V)_NW) Is 15V.

Since the floating gate FG2 of the second floating gate transistor may be coupled (coupled) out to a voltage of about 0V. Meanwhile, the N-type heavily doped region (N +) receives an N-type well voltage (V) of 15V_NW). Thus, a voltage difference of 15V between the floating gate FG1 and the heavily N-doped region (N +) of the first floating gate transistor will cause electrons to exit from the floating gate FG1 of the first floating gate transistor through the capacitor to the heavily N-doped region (N +) and into the N-well region (NW).

As shown in FIGS. 10A and 10D, during a read operation, the first select gate voltage (V)_SG1) A first source line voltage (V)_SL1) A first bit line voltage (V)_BL1) And N-type well voltage (V)_NW) It was 2.5V. Furthermore, a second select gate voltage (V)_SG2) Is 2.5V, the second source line voltage (V)_SL2) Is 0V, the second bitLine voltage (V)_BL2) Is 2.5V, P type well area voltage (V)_PW) Is 0V so that the second select transistor is turned on and the second floating gate transistor generates the read current Iread.

Basically, the magnitude of the read current Iread is determined by whether electrons are stored in the floating gate FG2 of the second floating gate transistor. Therefore, in the read operation, the storage state of the nonvolatile memory 90 can be determined according to the magnitude of the read current Iread.

Similarly, the nonvolatile memory 90 of the fourth embodiment can be slightly modified to improve the efficiency of the programming operation, the erasing operation and the reading operation. For example, a coupling layer is added to the fourth embodiment programmable erasable nonvolatile memory and a coupling voltage is received.

Furthermore, in the above embodiments, the p-type select transistor and the p-type floating gate transistor are used to perform the programming operation and the erasing operation; and the reading operation is performed by using the n-type selection transistor and the n-type floating gate transistor. Of course, the present invention is not limited thereto, and those skilled in the art can also use the n-type selection transistor and the n-type floating gate transistor to perform the programming operation and the erasing operation; and a reading operation is performed by using the p-type selection transistor and the p-type floating gate transistor.

As is apparent from the above description, the present invention provides a programmable and erasable nonvolatile memory. The non-volatile memory can be programmed or erased by a positive or negative operation, and the storage state of the non-volatile memory is determined by a read operation.

While the present invention has been described with reference to the above embodiments, it is not intended to be limited thereto. Various modifications and alterations may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention is subject to the scope defined by the appended claims.