1. Field of the Invention
The present invention relates to a semiconductor device. More particularly, the present invention relates to a non-volatile memory (NVM), a non-volatile memory array and a manufacturing method thereof.
2. Description of Related Art
Electrically erasable programmable read only memory (EEPROM) is a type of non-volatile memory that allows multiple data reading, writing and erasing operations. In addition, the stored data will be retained even after power to the device is removed. With these advantages, electrically erasable programmable read only memories have been broadly applied in personal computers and electronic equipment.
A typical flash memory device has a floating gate and a control gate fabricated with doped polysilicon. During an erasing operation by a typical EEPROM device, a critical over-erasure often occurs, leading to a misinterpretation of the data. To prevent such an event from occurring, a select gate is designed on the sidewalls of the control gate and the floating gate and the substrate to form a split gate structure.
Currently, the industry provides a fabrication method for a split-gate memory cell of the AG-AND type of memory array structure as described in U.S. Pat. No. 6,567,315.
Referring to
In the above AG-AND type of memory cell structure, when a memory cell Q1 is performing the programming operation, a bias voltage of 13 volts is applied to the word line, a bias voltage of 1 volt is applied to the auxiliary gate 106a, a bias voltage of 0 volt is applied to the source/drain region 104a, and a bias voltage of 5 volts is applied to the source/drain region 104b for electrons to be injected into the floating gate 108a of the memory device Qm1 to program the memory cell Q1. Since no voltage is applied to the auxiliary gate 106b, the memory cell Q2 is not programmed.
However, in the above AG-AND type of memory cell structure, the source/drain regions (104a, 104b or 104c) are formed in the substrate 100 beside the two sides of the memory cell Q1 (Q2). To prevent the source/drain regions (104a, 104b or 104c) from being too close and the channel underneath the memory cell from being conductive, the source/drain regions need to be parted at a certain distance. Accordingly, the dimension of the memory cell can not be further reduced.
The present invention provides a non-volatile memory device and a non-volatile memory array and a fabrication method thereof. No only the fabrication of the non-volatile memory array is simple, this type of non-volatile memory device can also apply source-side injection (SSI) to perform the programming operating in order to increase the programming speed and to improve efficiency of the memory cell.
The present invention also provides a non-volatile memory, a non-volatile memory array and a fabrication method thereof, wherein the operation voltage of the memory can increase to raise the efficiency of the device.
The present invention further provides a non-volatile memory, a non-volatile memory array and a fabrication method thereof, wherein the memory cell device can be reduced to increase the integration of the device.
The present invention provides a non-volatile memory. The non-volatile memory includes a first row of memory cells, a first source/drain region and a second source/drain region. The first row of memory cells includes a plurality of stacked gate structures, a spacer, a plurality of control gates, a composite dielectric layer. The plurality of stacked gate structures is disposed on the substrate, wherein each stacked gate structure includes a select gate dielectric layer, a select gate and a cap layer, sequentially formed from the substrate. The spacer is disposed on the sidewall of the stacked gate structure. The composite dielectric layer is disposed on the substrate, wherein the composite dielectric layer includes a bottom dielectric layer, a charge trapping layer and a top dielectric layer. A control gate line is disposed above the composite dielectric layer, filling the gaps between every two stacked gate structures. The first source/drain region and the second source/drain region are respectively disposed in the substrate beside the two sides of the first row of memory cells. The above non-volatile memory further includes a second row of memory cells and a third second source/drain region and a third source/drain region disposed on the substrate. The second row of memory cells and the first row of memory cells have similar structures. The second source/drain region and the third source/drain region are disposed in the substrate respectively besides two sides of the second row of memory cells, wherein the first row of memory cells and the second row memory cells share the second source/drain region.
In the structure of the non-volatile memory of the present invention, no isolation structure and no contact are formed between each row of the memory cells. The integration of the memory cell array can thereby increase.
The present invention also provides a non-volatile memory cell array. The memory cell array includes a substrate, a plurality of rows of memory cells, a plurality of control gate lines, a plurality of select gate lines, a plurality of source lines and a plurality of drain lines. The plurality of rows of memory cells is arranged into a memory array, wherein the memory array includes a plurality of stacked gate structures disposed on the substrate. Each stacked gate structure includes, sequentially from the substrate, a select gate dielectric layer, a select gate and a cap layer. A spacer is disposed on the sidewall of the stacked gate structure, and the composite dielectric layer is disposed on the substrate. The composite dielectric layer includes a bottom dielectric layer, a charge trapping layer and a top dielectric layer. A plurality of control gates is disposed above the composite dielectric layer between every two stacked gate structures. The source/drain regions are disposed in the substrate respectively beside one side of the two outer stacked gate structures. The plurality of the control gate lines connects the control gates of a same row of the memory cells. A plurality of select gate lines connects the select gates of a same column of the memory cells. A plurality of source lines connects the source regions along a same column, while a plurality of drain lines connects the drain regions along a same column.
The above-mentioned non-volatile memory array can be divided into at least a first memory block and a second memory block. The drain regions of different rows of memory cells in the first memory block are connected through the first drain line, and the drain regions of different rows of memory cells in the second memory block are connected through the second drain line. Further, the first memory block and the second memory block share a source line.
The above-mentioned memory array can apply the source-side injection to inject electrons into the charge trapping layer of a selected memory cell to program the selected memory cell. Further, the above-mentioned memory array can also apply the channel F-N tunneling to eject electrons from the charge trapping layer of the memory cell to the substrate to erase all information from the entire memory cell array.
In the non-volatile memory cell array of the present invention, there is no gap presents in between the memory cell structures. The integration of the memory cell array can thereby increased.
The present invention provides a fabrication method for a non-volatile memory, wherein a substrate is first provided and a plurality of stacked gate structures is already formed over the substrate. Each of the stacked gate structures includes a select gate dielectric layer, a select gate and a cap layer. A source region and a drain region are subsequently formed in the substrate. The source region and the drain region are separated by at least two stacked gate structures. A composite dielectric layer is formed over the substrate, followed by forming a conductive layer over the substrate. The conductive layer is further patterned to form a plurality of connecting control gates that fill the gaps between the stacked gate structures.
During the fabrication method of a non-volatile memory of the present invention, a charge trapping layer (silicon nitride) is used as a charge storage unit. Accordingly, the operating voltage required by an operation can be reduced and the operating speed and efficiency of the memory cell can be improved.
Moreover, using the charge trapping layer (silicon nitride) as a charge storage unit, the process for defining a floating gate when a floating gate is used as a charge storage unit can be omitted. Ultimately, not only the fabrication process is simpler, the integration of the memory array is increased.
Further, no device isolation structure is formed between each row of the memory cells. Therefore, the process is simpler and the integration of the memory array is enhanced.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
Referring to
The rows of memory cells QL1 to QL4 are arranged in a memory array. Each of the control gate lines CG1 to CG4 connects the control gates of the memory cells of a same row. The select gates along a same column of the memory cells are respectively connected by the select gate lines SG1 to SG5. The source line S connects the source regions of a same column of the memory cells and the drain line connects the drain regions of a same column of the memory cells.
The structure of the non-volatile memory cell array of the present invention is illustrated herein with the row of the memory cells QL1.
Referring concurrently to
The substrate 200 is, for example, a silicon substrate. The plurality of stacked gate structures 202a to 202e are disposed on the substrate 200, wherein the stacked gate structures 202a to 202e display, for example, a strip pattern. The thickness of the stacked gate structures 202a to 202e is about 2000 angstroms to 3500 angstroms. The material of the select gate dielectric layer 204 includes silicon oxide, for example, and the select gate dielectric layer 204 is about 160 angstroms to about 170 angstroms thick. The select gate 206, which is about 600 angstroms to about 1500 angstroms thick, is formed with, for example, doped polysilicon. The material of the cap layer 208 includes silicon oxide, and the cap layer 208 is about 1000 angstroms to about 1500 angstroms thick. The spacer 210 is disposed on the sidewall of each stacked gate structure 202a to 202e, wherein the material of the spacer 210 includes but not limited to silicon oxide or silicon nitride.
The composite dielectric layer 212 is disposed on the substrate 200. The composite dielectric layer 212 is formed with, sequentially from the substrate 200, a bottom dielectric layer 212a, a charge trapping layer 212b and a top dielectric layer 212c. The material of the bottom dielectric layer 212a includes silicon oxide, for example. Further, the bottom dielectric layer 212a is about 20 angstroms to about 60 angstroms thick. The charge trapping layer 212b is about 30 angstroms to about 70 thick, and is formed with silicon nitride, for example. The material of the top dielectric layer 212c is silicon oxide, for example, and the thickness of the top dielectric layer is about 30 angstroms to about 60 angstroms. The material of the charge trapping layer 212 can also be any other materials that have the charge trapping function.
The plurality of control gates 214a to 214d are disposed on the composite dielectric layer 212, filling the gaps between the stacked gate structures 202a to 202e. Further, the control gates 214a to 214d are connected together by the control gate line 214. The plurality of the control gates 214a to 214d and the control gate line 214 are integrated together, for example. In other words, the plurality of the control gates 214a to 214d extends to above the stacked gate structures 202a to 202e and are connected to the stacked gate structure to form the control gate line 214. The control gate line 214 is substantially perpendicular to the stacked gate structures 202a to 202e, for example. The material of the control gates is doped polysilicon, for example.
The plurality of stacked gate structures 214a to 214d, the spacer 210, the composite dielectric layer 212, the plurality of control gates 214a to 214d constitute a row of the memory cells 220. The source region 218/drain region 216 are respectively disposed in the substrate 200 beside both sides of the row of the memory cells 220. For example, the drain region 216 is disposed in the substrate 200 beside one side of the stacked gate structure 202a of the row of the memory cells 220, while the source region 218 is disposed in the substrate 200 beside one side of the stacked gate structure 202e of the row of the memory cells 220. In other words, the drain region 216 and the source region 218 are disposed in the substrate 200 respectively beside the sides of the two outer stacked gate structures 202a, 202e.
In the structure of the above row of memory cells, each of the control gates 214a to 214d and the composite dielectric layer 212 form the memory cell structure 222a to 222d, respectively, and each of the stacked gate structures 202a to 202d form the memory cell structure 222a to 222d, respectively. The stacked gate structure 202 disposed closest to the source region 218 serves as a switch transistor, for example. Since there is not gap in between the memory cell structures 222a to 222d and the stacked gate structures 202e, the level of integration of memory cells can be increased. Further, the conductive layer 214f and the conductive layer 214e above the source region and the drain region are not used as control gates. The composite dielectric layer 212 disposed above the source region 216 and the drain region 218 can insulate the conductive layer 214f from the drain region 218, and the conductive layer 214e from the source region 216, respectively.
In the above row of memory cells, a charge trapping layer (silicon nitride) is used as a charge storing unit. The required operating voltage for an operation can be lower to enhance the operating speed and efficiency of the memory cell.
Although the above-mentioned embodiments refer to four memory cell structures 222a to 222d connecting together, it is to be understood that these embodiments are presented by way of example and not by way of limitation. In other words, the number of memory cell structures connecting together depends on the actual demand. For example, one common control gate line can connect 32 to 64 memory cell structures.
As shown in
A method for fabrication a memory array according to the present invention is disclosed herein.
Referring to
Referring to
Referring to
Continuing to
In the above row of memory cells, the charge trapping layer (silicon nitride) serves as the charge storing unit. The operating voltage required for an operation can be lower to increase the operating speed and efficiency of the memory cell.
Comparing the process in which a charge trapping layer (silicon nitride) is formed as a charge storing unit with the process in which a floating gate (doped polysilicon) is formed as a charge storing unit, the step for defining the floating gate can be reduced. Accordingly, the process of the invention is simpler and the level of integration is improved.
Although the above-mentioned embodiments refer to four memory cell structures 222a to 222d connecting together, it is to be understood that these embodiments are presented by way of example and not by way of limitation. In other words, the number of memory cell structures connecting together depends on the actual demand. For example, one common control gate line can connect 32 to 64 memory cell structures.
Referring to
Each of the memory cells Q11 to Q44 includes a select gate, a control gate and a charge trapping layer.
The source line S and the drain line D extend along the direction of the column of the array. Each row of the memory cells includes four memory cells and a switch transistor connected together. For example, the memory cells Q11 to Q14 and the switch transistor T1 are connected together; the memory cells Q21 to Q24 and the switch transistor T2 are connected together; the memory cells Q31 to Q34 and the switch transistor T3 are connected together; the memory cells Q41 to Q44 and the switch transistor T4 are connected together.
Each of the control gate lines CG1 to CG4 connects the control gates along the same row of the memory cells. For example, the control gate line CG1 connects the control gates of the memory cells Q11 to Q14; the control gate line CG2 connects the control gates of the memory cells Q21 to Q24; the control gate line CG3 connects the control gates of the memory cells Q31 to Q34; the control gate line CG4 connects the control gates of the memory cells Q41 to Q44.
Each of the select gate lines SG1 to SG4 connects the select gates along the same column of the memory cells. For example, the select gate line SG1 connects the select gates of the memory cells Q11 to Q41; the select gate line SG2 connects the select gates of the memory cells Q12 to Q44; the select gate line SG3 connects the select gates of the memory cells Q13 to Q43; the select gate line SG1 connects the select gates of the memory cells Q14 to Q44; the select gate line SG5 connects the gates of the switch transistors T1 to T4 along a same column.
Although the disclosure hereafter refers to certain embodiments for illustrating the operating method of the non-volatile memory of the present invention, it is to be understood that these embodiments are presented by way of example and not by way of limitation.
Memory cell Qn2 is used herein to illustrate the programming operation of the invention. A bias voltage of 5 volts is applied to the source lines. A bias voltage of 1.5 volts is applied to the selected select gate line SG2, while a bias voltage of about 8 volts is applied to the non-selected select gate lines SG1, SG3, SG4. A bias voltage of about 8 volts is applied to the select gate line SG5. A bias voltage of about 7 volts is applied to the selected control gate line CG1, while a bias voltage of about 0 to 2 volts is applied to the non-selected control gate lines CG2, CG3, CG4. The substrate and the drain line are grounded. Source-side injection (SSI) is used to inject electrons into the charge trapping layer of the memory cell to program the memory cell Qn2.
During a reading operation, a bias voltage of about 0 volt is applied to the source line; a bias voltage of about 4.5 volts is applied to the select gate lines SG1 to SG5, respectively; a bias voltage of about 3 volts is applied to the control gate line CG1; and a bias voltage of 2 volts is applied to the drain line. Since the channel of the memory cell is closed and the current is small when the total amount of charges in the charge trapping layer is negative, and the channel is opened and the current is large when the total amount of charges in the charge trapping layer is slightly positive, the opening or closing/large or small current flow at the channel can be used to determine the digital information stored in the memory cell is “1” or “0”.
During the erasing operation, a bias voltage of about −20 volts is applied to the control gate line CG1 and a bias voltage of about 0 volt is applied to the substrate. The channel F-N tunneling is used to pull the electrons from the charge trapping layer of the memory cell to erase the information in the memory cell.
The operation of the memory array includes using the hot carrier effect to program a single memory cell with a single bit as a unit, and the channel F-N tunneling to erase the entire array of the memory cells. Accordingly, the electron injection rate is higher to lower the current flow of the memory cell during an operation. Further, the operating rate is concurrently increased. Therefore, the current consumption is small to effectively lower the power consumption of the entire wafer.
Further, in the above memory array, the charge trapping layer (silicon nitride) is used as a charge storing unit. The operating voltage required for an operation can thereby lowered and the operating speed and efficiency of the memory cell are improved.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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93113274 | May 2004 | TW | national |
94100956 | Jan 2005 | TW | national |
This application claims the priority benefit of Taiwan applications serial no. 93113274, filed on May 12, 2004, and serial no. 94100956, filed on Jan. 13, 2005. This application is a continuation-in-part of a prior application Ser. No. 10/904,478, filed Nov. 12, 2004. All disclosures are incorporated herewith.
Number | Date | Country | |
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Parent | 10904478 | Nov 2004 | US |
Child | 11160104 | Jun 2005 | US |