TWI681552B - Nor flash memory and method of fabricating the same - Google Patents

Abstract

NOR flash memory including three-dimensional memory cells is provided. In the NOR flash memory of the invention, one memory cell includes one memory transistor and one selection transistor. A common source 5 and an active region 3 extending in a vertical direction to electrically connect to the common source 5 are formed over a silicon substrate 9. A control gate 4 of the memory transistor and a selection gate line 2 of the selection transistor are formed to surround a side portion of the active region 3, and a top portion of the active region 3 is electrically connected to a bit line 1.

Description

Anti-or type flash memory and manufacturing method thereof

The invention relates to a NOR flash memory, and to a flash memory with a three-dimensional structure.

In order to improve the accumulation of anti-or type flash memory, virtual grounding method and multi-value method are adopted. In a typical virtual grounding mode, the source/drain of the memory cell is common to the source/drain of the adjacent memory cell in the row direction, and the common source and drain are electrically connected to the bit line. When reading, the ground potential and the read potential are applied to the source of the selected memory cell, and the source/drain of the adjacent memory cell is in a floating state (Patent Documents 1 and 2).

In the multi-value mode, a plurality of thresholds are set for the memory cell to control the charge to reach the floating gate or the charge storage area where the charge is captured. Patent Document 3 discloses a flash memory in the form of mirror bits as a multi-value memory of charge trapping type. This kind of flash memory forms an ONO of oxide film-nitride film-oxide film between the surface of the silicon substrate and the gate electrode, and captures charge at the interface of the oxide film and the nitride film. Instead of applying voltage to the source/drain, the charges are kept on the source side and the drain side of the nitride film (charge storage layer), respectively, and two bits of information are memorized in a memory cell. It has also been proposed that a separate ONO film is formed near both ends of the gate electrode to physically separate the charge storage region.

【Advanced technical literature】 【Patent Literature】

[Patent Document 1] Japanese Patent Laid-Open No. 2003-100092

[Patent Document 2] Japanese Patent Laid-Open No. 11-110987

[Patent Document 3] Japanese Patent Laid-Open No. 2009-283740

In the reverse-type flash memory, there are also problems such as breakdown and short channel effect when the gate length and gate width are reduced. Therefore, it is recognized that the size reduction of the memory cell has reached the limit.

The anti-or type flash memory of the present invention includes: a substrate; a conductive region formed on the surface of the substrate or the substrate; a plurality of columnar portions extending vertically from the surface of the substrate and including an active region; and The memory transistor and the selection transistor are formed to surround the sides of each columnar portion; wherein the control gate is connected to the gate of the memory transistor, and the selection gate is connected to the gate of the selection transistor; the columnar portion One end of is electrically connected to the bit line, the other end of the columnar portion is electrically connected to the conductive area; and a memory cell includes a memory transistor and a selection transistor.

The method for manufacturing the reverse-or-type flash memory of the present invention includes the following steps: forming a conductive region on the surface of the substrate or on the substrate; forming a first conductive layer on the conductive region via a first insulating layer; On a conductive layer, a second conductive layer is formed via a second insulating layer; on the second conductive layer, a A third insulating layer; forming a plurality of openings reaching the conductive region from the third insulating layer; forming an insulating layer for charge storage and an active region of a columnar structure in each opening; and etching the second conductive layer Between the adjacent columnar structures, the second conductive layer is separated; wherein one end of the active area is electrically connected to the conductive area through the open via hole, and the other end of the active area is electrically Connected to the bit line; and one of the first conductive layer and the second conductive layer is the gate of the memory transistor, and the other is the gate of the selection transistor. A memory cell includes a memory transistor and a Select transistor.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an inverted OR flash memory including a memory cell with a three-dimensional structure and a manufacturing method thereof. According to the present invention, by making the memory cell into a three-dimensional structure, the active area of the memory cell can be formed without being restricted by the two-dimensional scaling. In this way, the accumulation of memory cells and high operating current can be achieved at the same time.

1. 1-1, 1-2, 1-3, BL1‧‧‧bit line

2. 2-1, 2-2, 2-3, 2-4, 2-j, SG1‧‧‧ select gate line

3‧‧‧ Active area

4‧‧‧ (common) control gate

5‧‧‧ (common) source

5-1, 5-2, 5-3, 5-4 ‧‧‧ source

6, 7, 8, 13, 15, 20, 210‧‧‧‧Insulation

9‧‧‧Si substrate

10‧‧‧Completed etching area

11‧‧‧Region

12‧‧‧ opening

14‧‧‧Insulation layer (charge storage layer)

16, 18‧‧‧ Polysilicon layer (channel area)

19‧‧‧Interval

100‧‧‧P-type well area or P-type silicon substrate

100-1, 100-2, 100-3, 100-4 ‧‧‧P well area

101-1, 101-2, 101-3, 101-4‧‧‧‧N well

110, 110-1, 110-2 ‧‧‧ line selection drive circuit

120, 120-1, 120-2 ‧‧‧ column select drive circuit

200‧‧‧Si substrate

202‧‧‧ Peripheral circuit

220‧‧‧conductive layer

230‧‧‧Memory Cell Array

A, B, MC, MC_1‧‧‧ memory cell

BL, BL1, BL2‧‧‧bit line

CG‧‧‧Control gate

MEM‧‧‧Memory transistor

NWL‧‧‧Non-select character line

SEL‧‧‧Select transistor

SG, SG1, SG2 ‧‧‧ select gate line

SL‧‧‧Source (line)

SWL‧‧‧Select character line

Fig. 1 is a diagram of an equivalent circuit diagram of a memory cell of an inverting type flash memory.

Figure 2 is a cross-sectional view of the memory cell shown in Figure 1.

FIG. 3 is a schematic top view of the memory cell structure of the flash memory according to the embodiment of the invention.

FIG. 4A is a cross-sectional view taken along line A-A of the memory cell structure shown in FIG. 3. FIG.

FIG. 4B is a cross-sectional view showing another embodiment of the A-A line cross section of the memory cell structure shown in FIG. 3. FIG.

Fig. 5 is a sectional view taken along the line B-B of the memory cell structure shown in Fig. 3;

FIG. 6 is a cross-sectional view taken along line C-C of the memory cell structure shown in FIG. 3. FIG.

FIG. 7 is a cross-sectional view taken along line D-D of the memory cell structure shown in FIG. 3. FIG.

Fig. 8 is an equivalent circuit diagram of a memory cell according to an embodiment of the invention.

FIG. 9A is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 9B is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 9C is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 9D is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 9E is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10A is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10B is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10C is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10D is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10E is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10F is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10G is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10H is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 10I is a cross-sectional view of the manufacturing steps of the flash memory of this embodiment.

FIG. 11 is a diagram showing an equivalent circuit of four memory cells of the flash memory of this embodiment.

FIG. 12 is a table showing the bias conditions during the reading operation, programming operation, and erasing operation of the flash memory of this embodiment.

Fig. 13 is a cross-sectional view of a memory cell of a flash memory according to a modification of the present invention.

Fig. 14 is a cross-sectional view of a memory cell of a flash memory according to a modification of the present invention.

Fig. 15A is an explanatory diagram of the relationship between a decoder and a memory cell array according to a modification of the present invention.

Fig. 15B is an explanatory diagram of the relationship between a decoder and a memory cell array according to a modification of the present invention.

16A is a cross-sectional view of a memory cell of a flash memory according to a modification of the present invention.

16B is a cross-sectional view of a memory cell of a flash memory according to a modification of the present invention.

FIG. 17 is a cross-sectional view of a memory cell of a flash memory according to a modification of the present invention.

[Forms for carrying out the invention]

Fig. 1 is an equivalent circuit of a memory cell array of an inverted OR flash memory, and Fig. 2 is a schematic cross-sectional view of the memory cell. The memory cell A is a programmed memory cell. In the programming operation, in the memory cell A, a voltage of about 10 V is applied to the selected word line SWL, a voltage of about 4 to 5 V is applied to the bit line BL, and the source line is applied. SL supplies GND and injects electrons into the floating gate of memory cell A. Memory cell B is an unprogrammed memory cell adjacent to memory cell A. The non-selected word line NWL of the memory cell B is floating (almost the same as the ground), and a voltage of about 4 to 5 V is applied to the bit line BL, and the source line SL is supplied with GND to a voltage close to GND (in FIG. 2 , The voltage supplied to SL is ~0V). The gate length of the memory cell B must be at least 100 nm in order to suppress the leakage current from the bit line BL to the source line SL, and the gate length cannot be Zoom out further. The gate width cannot be further reduced in order to obtain a high reading current during reading. Because of this, it becomes difficult to increase the degree of accumulation of the NOR flash memory, and it is difficult to reduce the cost per bit.

Next, the embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, an anti-OR flash memory with a three-dimensional structure is exemplified. In addition, it should be noted that the drawings are drawn in order to facilitate the description of the invention, and the size ratio of each part shown in the drawings may not necessarily match the size ratio of the actual device.

【Example】

The inverse OR flash memory of the embodiment of the present invention is different from the traditional memory cell. A memory cell is composed of a selection transistor and a memory transistor. Also, the selection transistor and the memory transistor have a channel region extending substantially perpendicular to the substrate. Fig. 8 shows the equivalent circuit of the memory cell array of this embodiment. Here, a memory array with four rows and two columns is exemplified. A memory cell MC is composed of a selection transistor SEL and a memory transistor MEM. The selection transistor SEL and the memory transistor MEM of each memory cell are connected in series between the bit line 1-1 and the common source 5, and the selection transistor SEL and the memory transistor MEM of each memory cell are on the bit line 1- 2 in series with the common source 5. The selection gate lines 2-1, 2-2, 2-3, and 2-4 are commonly connected electrically to the gate of the selection transistor SEL in the column direction, and the common control gate 4 is commonly electrically connected to each The control gate of the memory transistor MEM of the memory cell MC. The selection transistor SEL has the function of selecting the memory transistor MEM. In the following description, when the bit lines and the gate lines are collectively referred to, bit lines 1 and gate lines 2 are selected.

First, for the memory of the anti-flash memory of this embodiment The details of the cell array construction are explained. As shown in FIG. 3, the bit lines 1-1, 1-2, and 1-3 extend in the X direction, and the select gate lines 2-1 to 2-j that are lower than the bit line 1 extend in the Y direction. An active region 3 extending in the vertical direction is formed in a region where each bit line 1 crosses each selection gate line 2. The active area 3 is a channel area that provides selection transistors SEL and memory transistors MEM.

As shown in FIG. 4A, a common source 5 is formed on the silicon substrate 9. The common source electrode 5 is formed in the entire area where the memory cell array is formed, and is common to all the memory cells in the memory cell array. The common source 5 may be an impurity diffusion region formed by ion implantation of impurities in the silicon substrate 9, or may be a conductive layer formed on the surface of the silicon substrate 9 (for example, conductive polysilicon doped with impurities Floor).

Referring to FIG. 4B, an insulating layer 20 is formed on the silicon substrate 9, and a common source 5 is formed on the insulating layer 20. In this embodiment, on the silicon substrate 9 below the insulating layer 20, circuits of complementary metal-oxide-semiconductor (CMOS) transistors, capacitors, resistors, diodes, etc. may be formed. The present invention can use any of the embodiments of FIG. 4A or FIG. 4B. The following description uses the embodiment shown in FIG. 4A.

On the common source electrode 5, an insulating layer 6, a control gate 4, an insulating layer 7, a selection gate line 2, an insulating layer 8, and a bit line 1 are laminated. At a portion where the bit line 1 and the selection gate line 2 cross, an active area 3 is formed. As shown in FIGS. 4A and 6, the active region 3 including the channel region is formed in a vertical direction relative to the silicon substrate 9. One end of the active area 3 is electrically connected to the common source 5, and the other end is electrically connected to the bit line 1. The insulating layer 6 is formed on the entire surface of the common source electrode 5, and the control gate electrode 4 is formed on the entire surface of the insulating layer 6. Control gate 4 is all memory cells relative to the memory cell array For the sake of common, that is, the control gate 4 is comprehensively formed into one surface.

An insulating layer 7 is formed all over the control gate 4, and a plurality of selective gate lines 2-1, 2-2, ..., 2-j extending in the Y direction are formed on the insulating layer 7. An insulating layer 8 is formed on the selection gate line 2, and a plurality of bit lines 1-1 and 1-2 extending in the X direction are formed on the insulating layer 8.

In this way, the memory cell array shown in FIG. 8 is constructed. A memory cell MC is composed of a selection transistor SEL and a memory transistor MEM. The memory transistor MEM includes a control gate 4, a floating gate (charge storage layer) and an active region 3, and stores electrons in the floating gate. The selection transistor SEL includes the selection gate line 2 and the active region 3, and is turned on when a certain positive voltage is applied to the selection gate line 2, making it possible to electrically connect the memory transistor MEM and the bit line 1. In addition, although not shown in FIG. 8, in the memory cell array, the bit line 1, the selection gate line 2, the common control gate 4 and the common source 5 are connected to a decoder for selection and driving, Then, in the reading operation, programming operation, and erasing operation, a suitable bias voltage is applied to each node of the bit line 1, the selection gate line 2, the common control gate 4, and the common source 5 via the decoder.

Next, referring to FIGS. 9A to 10I, a method for manufacturing the memory cell array of the inverted-OR flash memory of this embodiment will be described in detail.

As shown in FIG. 9A, elements for forming an N-type silicon layer such as arsenic (As) or phosphorus (P) are implanted into a P-type silicon substrate 9 by ion implantation, and n+ is formed on the surface of the silicon substrate 9 Common source of high impurity concentration 5. The common source 5 is formed in the entire area where the memory cell array is to be formed. On the silicon substrate 9 including the common source 5, an insulating layer 6 such as a silicon oxide film is formed, and a control gate 4 is formed on the insulating layer 6. The control gate 4 is, for example, a conductive polysilicon layer. Formed on the control gate 4 After the insulating layer 7, a conductive polysilicon layer for selecting the gate line 2 is formed on the insulating layer 7, for example. On the polysilicon layer for selecting the gate line 2, an insulating layer 8 is formed.

Next, as shown in FIG. 9B, the active region 3 extending in a direction perpendicular to the silicon substrate 9 is formed. The detailed manufacturing method for the active area 3 will be described later.

Next, through the photolithography step, the insulating layer 8 and the polysilicon layer for selecting the gate line 2 are simultaneously etched, as shown in FIG. 9C, a plurality of selective gate lines 2 extending in the Y direction are formed, which It is isolated by the etched area 10 in the Y direction.

Next, an insulating layer 20 is deposited over the entire area including the etched area 10, and as shown in FIG. 9D, the insulating layer 20 is left only in the recess of the etched area 10. In some embodiments, in order to form the low-resistance selection gate line 2, the silicide of the selection gate line 2 may be formed through the etched region 10.

Next, a contact hole for exposing the end of the active region 3 is formed in the insulating layer 20, and then a metal material is deposited all over, and the metal material is patterned, as shown in FIG. 9E, a connection to the active region 3 or The bit line 1 at the end of the columnar polysilicon structure.

Next, please refer to FIGS. 10A to 10I to describe the manufacturing steps for forming the region 11 surrounded by the broken line in FIG. 9E. After forming the insulating layer 8, as shown in FIG. 10A, an opening 12 from the insulating layer 8 to the common source 5 is formed. For example, on the insulating layer 8, a mask layer for etching is formed, and a circular opening is formed in the mask layer for etching by the lithography step, which is performed through the mask layer for etching Anisotropic etching forms an opening from the insulating layer 8 to the common source 5.

Next, as shown in FIG. 10B, on the insulating layer 8 including the opening 12, insulating layers 13, 14, and 15 are laminated. For example, the laminated oxide film serves as the insulating layer 13, the nitride film serves as the insulating layer 14, and the oxide film serves as the insulating layer 15. The insulating layer 14 in the center is composed of a silicon nitride film, and has a function as a layer for storing electric charges. For example, the silicon nitride film stores different amounts of electric charges in writing or erasing operations.

Next, as shown in FIG. 10C, on the insulating layer 15 including the opening 12, a polysilicon layer 16 is deposited with a certain thickness by chemical vapor deposition (CVD) or the like. Next, as shown in FIG. 10D, the polysilicon layer 16 and the insulating layers 13, 14, and 15 at the bottom of the opening 12 are removed by etching to expose the surface of the common source 5. The polysilicon layer 16 protects the insulating layers 13, 14, 15 including the insulating layer 14 constituting the charge storage layer from etching damage.

Next, on the polysilicon layer 16 including the opening 12, a second polysilicon layer 18 is deposited by chemical vapor deposition or the like, and the opening 12 is filled with the polysilicon layer 18. The polysilicon layer 18 is doped with, for example, boron, and has a P-type. Alternatively, the polysilicon layer 18 is a polysilicon layer containing no impurities such as boron. The polysilicon layer 18 is electrically connected to the common source 5 exposed at the bottom of the opening 12.

Next, as shown in FIG. 10F, the polysilicon layers 16, 18 are planarized or etched back by chemical mechanical polishing (CMP) until the insulating layer 15 is exposed. As a result, only the inside of the opening 12 is left Lower polysilicon layer 16, 18.

Next, as shown in FIG. 10G, the laminated insulating layers 13, 14, 15 and the polysilicon layer for selecting the gate line 2 are etched to form a patterned selective gate line 2. Adjacent selection gate lines 2 are separated by spaces 19 formed by etching.

Next, as shown in FIG. 10H, the insulating layer 20 is fully deposited. The common source 5 is doped with high concentration by N-type impurities such as phosphorus, arsenic, etc., so that N-type impurities are diffused (for example, thermal diffusion) to the bottom of the channel region, and N is formed at the bottom of the channel region Type silicon area. On the other hand, N-type impurities are implanted into the surface side of the channel region by ion implantation, and an N-type silicon region is formed on the surface side of the channel region.

Next, as shown in FIG. 10I, the insulating layer 20 on the active region 3 is etched, and then the bit line 1 is formed. The bit line 1 is electrically connected to the active region 3 through the opening of the insulating layer 20, that is, electrically connected to the channel regions 16, 18.

Next, the operation of the NOR flash memory of this embodiment will be described. In the memory cell array shown in FIG. 11, the memory cell MC_1 is selected, and the other memory cells are set as non-selected. The table shown in Fig. 12 shows the bias conditions during the reading operation, the programming operation, and the erasing operation. In addition, although not shown here, the flash memory includes a finite state machine or a microcontroller for controlling reading operations, programming operations, and erasing operations. These microcontrollers are based on external supply The address, instruction, etc. control the operation of each part.

During the reading operation, the read voltage read1 is biased on the bit line BL1. Read1 is, for example, 1 to 2V. On the selection gate line SG1, a bias voltage of the read voltage read2 is applied. read2 is a voltage higher than the threshold of the selection transistor SEL, for example, 1~3V. At the control gate CG, a bias of the read voltage read3 is applied. Read3 is, for example, 0~3V. Nodes other than the above are GND.

When the threshold Vt of the memory transistor MEM of the memory cell MC_1 is higher than the bias of the read voltage read3, the memory transistor MEM becomes non-conductive, and current does not flow from the bit line BL1 to the source SL, and is recognized as data " 0". Memory cell When the threshold Vt of the memory transistor MEM of MC_1 is lower than the bias voltage of the read voltage read3, the memory transistor MEM is turned on, and current flows from the bit line BL1 to the source SL, which is recognized as data "1".

The range of the threshold Vt of the allowable data "0" and "1" is a range higher or lower than the read voltage read3. On the other hand, in the case of a conventional one-transistor memory cell without selection transistors, the threshold Vt of the data "1" must be lower than the voltage of the control gate CG and must be higher than 0V. Once the threshold Vt of data "1" is lower than 0V, misreading of other memory cells connected to the same bit line will occur.

Next, the programming operation will be described. On the bit line BL1, a bias voltage of the programming voltage prog1 is applied. prog1 is a voltage below 0V to 1V. On the bit line BL2, a bias voltage of the programming voltage prog2 is applied. prog2 is greater than prog1 and blocks the current from the bit line BL2 to the source SL. At the source SL, a bias voltage of the programming voltage prog4 is applied. prog4 is 4~6V. The control gate CG of the memory cell MC_1 is biased by the programming voltage prog3. prog3 is 5~10V. For the selection gate line SG1, a voltage prog5 higher than the threshold of the selection gate is given; for the selection gate line SG2, a voltage of 0 to lower than the threshold of the selection gate is given.

The lateral electric field on the silicon surface between the control gate CG and the selection gate line SG1 becomes very high, the hot storage electrons are injected into the charge storage layer 14 directly under the control gate CG, and the electrons are stored in the insulating layer 14 by This increases the threshold Vt of the memory transistor MEM of the memory cell MC_1. This programming method is called "source side hot electron injection" because hot electrons are generated in the channel region between the control gate CG and the selection gate line SG. The source side hot electron injection has a small current consumption from the bit line to the source line. Therefore, the majority of tens of bytes Memory cells can be programmed to perform high-speed programming. Since the bias voltage applied to the selection gate line SG2 is below the threshold of the selection gate, the selection transistor SEL connected to the selection gate line SG2 is in an OFF state, and hot electron injection does not occur. Therefore, the memory cells other than the memory cell MC_1 will not shift the threshold Vt in the memory transistor MEM.

Next, the erase operation will be described. There are two methods for erasing. In the erasing method 1, the bit line BL1, the bit line BL2, the selection gate line SG1, and the selection gate line SG2 are made floating (FG), that is, approximately 0V. This is because these nodes are connected to the PN junction side of 0V potential. At the control gate CG, erasing voltage era1 is applied, era1 is -3~-5V. At the source SL, erasing voltage era2 is applied, and era2 is 4~7V. A negative bias is applied to the control gate CG to increase the bias of the source SL, whereby holes are injected into the charge storage layer 14 of the memory transistor MEM from the source SL directly under the control gate CG, or It is to release electrons from the charge storage layer 14 to the source electrode SL, so that the threshold Vt of the memory transistor MEM of the entire memory cell is reduced, which is lower than the read voltage read3.

In the erase method 2, the bit lines BL1, the bit line BL2, the selection gate line SG1, and the selection gate line SG2 have the same bias voltage as the erase method 1. At the control gate CG, an erasing voltage era3 is applied, which is approximately ~0V. At the source SL, erasing voltage era4 is applied, and era4 is 7~10V. As in the case of the erasing method 1, applying a high bias to the source SL reduces the threshold Vt of the memory transistor MEM of the memory cells in the array to become smaller than the read voltage read3.

In order to erase all the memory cells of the selected memory cell array, the above erasing operation is performed, so that the memory transistors MEM of all memory cells are in the state of data "1". Since there is no best memory cell for data "1" Limited by the threshold Vt of a small value, the yield of erasure will become higher than that of the memory cell of a single transistor.

According to this embodiment, the use of transistors having channel regions in the vertical direction can reduce the size of the memory cell. In addition, in the memory cell of this embodiment, the common source is directly connected to the channel region at the bottom of the channel region, so there is no need for an area for source line contact. In addition, in the memory cell of this embodiment, the bit line is directly connected to the channel area at the top of the channel area, so there is no need for the area where the bit line contacts. Also, by forming a circuit under the memory cell array, the area used for this circuit can be reduced, which can also contribute to the reduction in chip size.

When the memory cell is composed of only a single memory transistor, the problem of over erase will reduce the yield. In a certain bit, after the erase operation may be a negative threshold Vt, which may cause other memory cells connected to the same bit line to be misread. In contrast, the memory cell of this embodiment is not only a memory transistor, but also has a selection transistor. Therefore, the problem of excessive erasure does not occur. That is, during the reading operation, the selection gate line of the non-selected memory cell blocks the current of the reading cell of other memory cells connected to the same bit line.

In this embodiment, the source side hot electron injection is used during the programming operation, which can improve the electron injection efficiency. Therefore, most memory cells can be programmed at one time, and high-speed programming can be achieved.

Next, a modification of the embodiment of the present invention will be described. In the above embodiment, the control gate is formed first, and then the selection gate line is formed, but this is only an example, and the positional relationship may be reversed. At this time, as shown in FIG. 13, a selection gate layer is formed on the insulating layer 6, and the selection gate layer is patterned to form a plurality of gate lines 2 extending in the Y direction. Thereafter, the insulating layer 7 is formed in order The gate 4 and the insulating layer 8 are controlled, and thereafter the steps shown in FIGS. 10A to 10I are performed.

In addition, in the above embodiment, the control gate 4 is formed in the entire memory cell array, so that the control gate 4 is common to all memory cells, but this is only an example, and the control gate can also be divided into a plurality of . At this time, as shown in FIG. 14, after the layer for controlling the gate is formed, this layer is patterned to form a plurality of control gates 4. From the plurality of control gates 4, the control gate related to the selected memory cell is selected, and the selected control gate is biased according to the bias conditions during operation.

Next, the relationship between the memory cell array and the decoder in this embodiment will be described. As shown in FIG. 15A, a P-type well region 100 or a P-type silicon substrate 100 for forming a memory cell array is formed. The row selection drive circuit 110 selects the selection gate line SG based on the row address, and applies a voltage to the selected selection gate line SG according to the bias conditions during operation. When the control gate CG is formed to be common to all the memory cells of the memory cell array, the row selection drive circuit 110 does not select the control gate 4 and applies a voltage to the control gate 4 according to the bias condition during operation. When the control gate 4 is divided into a plurality of rows, the row selection drive circuit 110 selects the control gate 4 according to the row address, and applies a voltage to the selected control gate 4 according to the bias conditions during operation.

In addition, the column selection drive circuit 120 selects the bit line BL based on the column address, and applies a voltage to the selected bit line BL according to the bias condition during operation. In the case where the n+ source 5 on the P-type well region 100 or the P-type silicon substrate 100 is formed to be common to all memory cells of the memory cell array, the column selection drive circuit 120 is operated according to the bias voltage during operation The conditions apply a voltage to the source 5. In addition, as the 15B As shown in the figure, when the source 5 is divided into a plurality of (in the example in the figure, it is divided into four sources 5-1, 5-2, 5-3, 5-4), the column selection drive circuit 120 Then, the source 5 is selected according to the column address, and a voltage is applied to the selected source according to the bias condition during operation.

Fig. 16A shows another modification of the present invention. As shown in the figure, for example, on an N-type silicon substrate, a plurality of P-type well regions 100-1, 100-2, 100-3, 100-4 can also be formed, and independent P-type well regions are formed on each Three-dimensional structured memory cell array.

In addition, FIG. 16B shows a different modification of the present invention. As shown in the figure, P-type well regions 100-1, 100-2 surrounded by a plurality of N-type wells 101-1, 101-2, 101-3, 101-4 can also be formed on a P-type silicon substrate, for example , 100-3, 100-4, and an independent three-dimensional memory cell array is formed on each P-well area. In the examples of FIGS. 16A to 16B, the row selection driving circuit 110-1 is common to the memory cell arrays of the P-type well regions 100-1 and 100-3, and the row selection driving circuit 110-2 is common to the P type. The memory cell arrays of the well regions 100-2 and 100-4 are common, and the column selection drive circuit 120-1 is common to the memory cell arrays of the P-type well regions 100-1, 100-2, and the column selection drive circuit 120-2 It is common to the memory cell arrays of P-type well areas 100-3 and 100-4. However, it is not limited to this, and a row selection drive circuit and a column selection drive circuit may be separately formed in each P-type well region. In this case, the bit line, the selection gate line, the control gate, and the source are independent of the memory cell array in each P-well region.

Fig. 17 shows another modification of the present invention. This modified example is an example in which a memory cell array 230 having a three-dimensional structure is provided on a silicon substrate 200. On the silicon substrate 200, the periphery of the decoder, booster circuit, sensing circuit, etc. is formed Circuit 202. An insulating layer 210 is formed on the silicon substrate 200, a conductive layer 220 is formed on the insulating layer 210, and a memory cell array 230 is formed on the conductive layer 220. The conductive layer 220 provides a common source for the memory cell array 230. The conductive layer 220 is, for example, an N-type polysilicon layer or is formed by laminating a metal layer and an N-type polysilicon layer. The three-dimensional memory cell array 230 is formed on the conductive layer 220 using the manufacturing steps described in FIGS. 4 to 10. In this way, forming a peripheral circuit on the silicon substrate 200 and laminating a memory cell array thereon can reduce the two-dimensional area of the semiconductor chip.

The preferred embodiments of the present invention have been described in detail above, but the present invention should not be limited to specific embodiments. Various modifications and changes can be made within the scope of the invention described in the patent application. change.

1‧‧‧bit line

2‧‧‧Select gate line

3‧‧‧ Active area

4‧‧‧ (common) control gate

5‧‧‧ (common) source

6, 7, 8, 13, 15, 20 ‧‧‧ insulation layer

9‧‧‧Si substrate

14‧‧‧Insulation layer (charge storage layer)

Claims (10)

An anti-or type flash memory includes: a substrate; a conductive area formed on the substrate; a plurality of columnar portions extending vertically from the surface of the substrate and including an active area; and a plurality of memory transistors and A plurality of selection transistors surround the sides of each columnar portion, the memory transistors and the selection transistors form a plurality of memory cells; wherein the gate of the memory transistor is connected to the control gate, and the above selection transistor The gate of the crystal is connected to the selection gate; one end of the columnar portion is electrically connected to the bit line, and the other end of the columnar portion is electrically connected to the conductive area; and each of the memory cells includes one A memory transistor and a selection transistor, and each memory cell contains its own selection transistor. The reverse-or-type flash memory according to item 1 of the patent application scope, wherein a plurality of insulating layers are formed between the control gate and the columnar portion, and a charge storage layer is provided between the plurality of insulating layers. The reverse-OR flash memory as described in item 1 of the patent application, wherein the columnar portion is made of silicon, and a plurality of insulating layers surround the silicon columnar portion and the control gate, and the plurality of There is a silicon nitride film between the insulating layers. The reverse-or type flash memory as described in item 1 of the patent application, wherein the columnar portion is made of silicon, and the silicon column is surrounded by a plurality of insulating layers A silicon nitride film is provided between the plurality of insulating layers between the shape portion and the control gate and between the silicon pillar portion and the selection gate. The anti-flash memory as described in any one of claims 1 to 4, wherein the control gate is common to all memory cells of the memory cell array. The anti-flash memory according to any one of items 1 to 4 of the patent application range, wherein the conductive region is common to all memory cells of the memory cell array. The reverse-or-type flash memory according to any one of the items 1 to 4 of the patent application, wherein the flash memory further includes a control device, and the control device controls the gate of the selected memory cell during programming operation Applying a first programming voltage and applying a second programming voltage to the conductive region cause the selection transistor to be turned on via the selection gate. A method for manufacturing an inverted or flash memory includes the following steps: forming a conductive region on a substrate; forming a first conductive layer on the conductive region via a first insulating layer; on the first conductive layer, Forming a second conductive layer via a second insulating layer; forming a third insulating layer on the second conductive layer; forming a plurality of openings from the third insulating layer to the conductive region; forming charges in each opening Insulation layer for storage and active area of columnar structure; and Etching the second conductive layer to separate the second conductive layer between adjacent columnar structures; wherein one end of the active region is electrically connected to the conductive region via the open via hole, The other end of the active area is electrically connected to the bit line; and one of the first conductive layer and the second conductive layer is the gate of the memory transistor, and the other is the gate of the selection transistor, each memory The cell contains a memory transistor and a selection transistor, and each memory cell contains its own selection transistor. The method for manufacturing a reverse-or-type flash memory as described in item 8 of the patent scope further includes forming a contact hole exposing the conductive region by etching the charge storage insulating layer at the bottom of the opening . The method for manufacturing a reverse-or-type flash memory as described in item 9 of the patent application scope, wherein a protective film is formed on the charge storage insulating layer when the charge storage insulating layer is etched.

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