US20150179498A1 - Nonvolatile memory device and method for fabricating the same - Google Patents
Nonvolatile memory device and method for fabricating the same Download PDFInfo
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- US20150179498A1 US20150179498A1 US14/640,962 US201514640962A US2015179498A1 US 20150179498 A1 US20150179498 A1 US 20150179498A1 US 201514640962 A US201514640962 A US 201514640962A US 2015179498 A1 US2015179498 A1 US 2015179498A1
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- 229910021332 silicide Inorganic materials 0.000 description 5
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- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
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- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
- H10B41/30—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the memory core region
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/764—Air gaps
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/7682—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing the dielectric comprising air gaps
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/408—Electrodes ; Multistep manufacturing processes therefor with an insulating layer with a particular dielectric or electrostatic property, e.g. with static charges or for controlling trapped charges or moving ions, or with a plate acting on the insulator potential or the insulator charges, e.g. for controlling charges effect or potential distribution in the insulating layer, or with a semi-insulating layer contacting directly the semiconductor surface
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66825—Unipolar field-effect transistors with an insulated gate, i.e. MISFET with a floating gate
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/788—Field effect transistors with field effect produced by an insulated gate with floating gate
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/788—Field effect transistors with field effect produced by an insulated gate with floating gate
- H01L29/7881—Programmable transistors with only two possible levels of programmation
Definitions
- Exemplary embodiments of the present invention relate to a nonvolatile memory device and a method for fabricating the same, and more particularly, to a nonvolatile memory device including an air gap formed between gate structures and a method for fabricating the same.
- a nonvolatile memory device maintains data stored therein even though power supply is cut off.
- a NAND flash memory device and the like are widely used.
- a conventional memory device includes a plurality of gate structures each having a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate which are sequentially stacked.
- the floating gate is formed of polysilicon doped with impurities.
- the impurities of the floating gate may not be maintained.
- the impurities of the floating gate may escape during a subsequent heat treatment, or impurities may be implanted into the floating gate during a subsequent ion implantation.
- memory cells may have non-uniform characteristics. In this case, a distribution difference between memory cells may increase.
- Exemplary embodiments of the present invention are directed to a nonvolatile memory device capable of reducing a distribution difference and interference between memory cells and a method for fabricating the same.
- a nonvolatile memory device includes gate structures formed over a substrate, each gate structure including a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate that are sequentially stacked, a protective layer formed on sidewalls of the floating gate, and a second insulating layer covering the gate structures and having an air gap formed between the gate structures, wherein an adhesive strength between the second insulating layer and the protective layer is smaller than an adhesive strength between the second insulating layer and the gate structure.
- a nonvolatile memory device includes a gate structure formed over a substrate and including a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate that are sequentially stacked, and a protective layer formed on sidewalls of the floating gate configured to block impurities from being transferred from or to the floating gate.
- a method for fabricating a nonvolatile memory device includes sequentially forming a tunnel insulating layer, a first conductive layer for a floating gate, an inter-gate dielectric layer, and a second conductive layer for a control gate over a substrate, forming gate structures over the substrate, each gate structure formed by etching the second conductive layer, the inter-gate dielectric layer, and the first conductive layer, and forming a protective layer pattern on at least sidewalls of the etched first conductive layer, the protective layer pattern blocking impurities from being transferred from or to the floating gate.
- FIG. 1 is a plan view illustrating a nonvolatile memory device in accordance with an embodiment of the present invention.
- FIGS. 2 to 6 are cross-sectional views illustrating the nonvolatile memory device and a method for fabricating the same in accordance with the embodiment of the present invention.
- FIG. 7 is a cross-sectional view illustrating a nonvolatile memory device and a method for fabricating the same in accordance with another embodiment of the present invention.
- FIG. 1 is a plan view illustrating a nonvolatile memory device in accordance with an embodiment of the present invention.
- a plurality of active areas ACT are defined in a substrate.
- the plurality of active areas ACT are arranged in parallel to each other and extended in one direction (I-I′ direction).
- a plurality of control gates CG are formed.
- the plurality of control gates CG are arranged in parallel to each other and extended in a direction crossing the active areas ACT.
- a plurality of island-shaped floating gates FG are formed at the respective intersections between the control gates CG and the active areas ACT.
- a tunnel insulating layer (not illustrated) is interposed, and between the floating gates FG and the control gates FG, an inter-gate dielectric layer (not illustrated) is interposed.
- Each of the floating gates FG forms a unit memory cell MC as a charge storing element.
- a structure in which the tunnel insulating layer, the floating gate FG, the inter-gate dielectric layer, and the control gate CG, which are sequentially stacked, will be referred to as a gate structure.
- FIGS. 2 to 6 are cross-sectional views illustrating the nonvolatile memory device and a method for fabricating the same in accordance with the embodiment of the present invention, taken along line of FIG. 1 . First, the fabrication method will be described.
- a structure in which a tunnel insulating layer 11 and a floating-gate conductive layer 12 are stacked is formed over a substrate 10 .
- Such a structure may be formed by the following process. First, an insulating material for forming the tunnel insulating layer 11 and a conductive material for forming the floating-gate conductive layer 12 are deposited on the entire surface of the substrate 10 . Then, a mask pattern is formed over the conductive material to cover active areas ACT (refer to FIG. 1 ). The mask pattern serving as an etch barrier is used to etch the conductive material and the insulating material. Then, the substrate 10 exposed by the etch process is etched to a predetermined depth to form an isolation trench in the substrate 10 , thereby defining an active area. Subsequently, the isolation trench is filled with an insulating layer to form an isolation layer (not illustrated). As a result of this process, the tunnel insulating layer 11 and the floating-gate conductive layer 12 may have substantially the same plan shape as the active area of the substrate 10 .
- the substrate 10 may include a semiconductor substrate such as silicon.
- the tunnel insulating layer 11 for charge tunneling between the substrate 10 and a floating gate may include oxide, for example.
- the floating-gate conductive layer 12 serves as a charge storing element, and may include a semiconductor material doped with a required impurity such as phosphorus or boron, for example, polysilicon.
- a required impurity such as phosphorus or boron, for example, polysilicon.
- the present invention is not limited thereto.
- control-gate conductive layers 14 may have substantially the same plan shape as the control gates CG of FIG. 1 .
- the inter-gate dielectric layer 13 serves to block charge transfer between the floating-gate conductive layer 12 and the control-gate conductive layer 14 , and may include a triple layer structure such as oxide-nitride-oxide (ONO) layer.
- ONO oxide-nitride-oxide
- the control-gate conductive layer 14 may include impurity-doped polysilicon, for example, but the present invention is not limited thereto.
- a first insulating layer 15 is formed on the surface of the control-gate conductive layer 14 .
- the first insulating layer 15 serves not only to protect the control-gate conductive layer 14 during a subsequent etch process for the floating-gate conductive layer 12 , but also to prevent a protective layer from being formed on the surface of the control-gate conducive layer 14 during a formation process of the protective layer (refer to reference numeral 16 of FIG. 3 ), because the first insulating layer 15 has a poor adhesion characteristic with respect to the protective layer.
- the first insulating layer 15 may include oxide, and may be formed by a dry oxidation process or an atomic layer deposition (ALD) process, but the present invention is not limited thereto.
- the floating-gate conductive layer exposed by the control-gate conductive layer 14 and the first insulating layer 15 is etched.
- a floating gate 12 ′ having an island shape is formed at a position where the control-gate conductive layer 14 and the active area overlap each other.
- a protective layer 16 is formed on the sidewalls of the floating gate 12 ′ to prevent impurities from escaping from the floating gate 12 ′ or impurities from being implanted into the floating gate 12 ′.
- the protective layer 16 may include a material capable of blocking transfer of impurities and having a low adhesive strength with respect to a second insulating layer to be described below (refer to reference numeral 18 of FIG. 6 ).
- the protective layer 16 may include germanium (Ge).
- the protective layer 16 does not adhere to the first insulating layer 15 on the surface of the control-gate conductive layer 14 , the protective layer 16 is not formed on the control-gate conductive layer 14 , but formed on the sidewalls of the floating gate 12 ′ and the tunnel insulating layer 11 . Furthermore, when the adhesion characteristic between the protective layer 16 and the tunnel insulating layer 11 is degraded, for example, when the tunnel insulating layer includes oxide and the protective layer 16 includes Ge, the protective layer 16 may be formed only on the sidewalls of the floating gate 12 ′, but may not be formed on the tunnel insulating layer 11 .
- the protective layer 16 may be formed by ALD, for example, and may have a thickness of several ⁇ .
- the protective layer 16 on the tunnel insulating layer 11 is removed to form a protective layer pattern 16 ′ left only on the sidewalls of the floating gate 12 ′.
- This process is performed to form a junction area in the active area of the substrate 10 between the floating gates 12 ′ and to electrically isolate the floating gates 12 ′ from each other.
- the removal process of the protective layer 16 may be performed by a dry-etch process.
- the process of FIG. 4 may be omitted.
- an ion implantation of impurities such as B or As may be performed to form a junction area in the active area of the substrate 10 between the floating gates 12 ′.
- impurities such as B or As
- the impurities of the floating gate 12 ′ may not escape to the outside.
- the first insulating layer 15 is removed, and a silicide process is performed to transform an upper part of the control-gate conductive layer 14 into a metal silicide layer 17 such as nickel silicide or cobalt silicide, in order to reduce the resistance of the control-gate conductive layer 14 . Accordingly, the control-gate conductive layer 14 and the metal silicide layer 17 may form a control gate. The silicide process may be omitted.
- a gate structure P is formed, including the tunnel insulating layer 11 , the floating gate 12 ′, the inter-gate dielectric layer 13 , and the control gate 14 and 17 that are sequentially stacked.
- a second insulating layer 18 is formed on the structure shown in FIG. 5 .
- the second insulating layer 18 may include oxide, for example. If the second insulating layer 18 is formed to degrade a step coverage characteristic, for example, if the second insulating layer 18 is deposited by a low pressure (LP) or plasma enhanced (PE) method, the space between the gate structures P may not be filled with an insulating material. In this case, air gaps G 1 and G 2 may be formed between the gate structures P.
- LP low pressure
- PE plasma enhanced
- the size of the air gaps G 1 and G 2 may be increased.
- the size of the lower air gap G 1 between the floating gates 12 needs to be increased.
- the protective layer 16 on the sidewalls of the floating gate IT has a small adhesive strength with respect to the second insulating layer 18 . Therefore, the second insulating layer 18 is not formed on the sidewall of the floating gate 12 ′. Furthermore, the adhesive strength between the second insulating layer 18 and the inter-gate dielectric layer 13 or the control gate 14 and 17 , which is not covered by the protective layer 16 , is larger than the adhesive strength between the second insulating layer 18 and the protective layer 16 .
- the second insulating layer 18 may exist at a predetermined thickness on the sidewalls of the inter-gate dielectric layer 13 and/or the control gate 14 and 17 . Since the protective layer 16 has a small thickness of several A as described above, the protective layer 16 does not have an effect on the size of the lower air gap G 1 . As a result, the size of the lower air gap G 1 between the floating gates 12 ′ may increase.
- the device of FIG. 6 may be fabricated.
- the gate structure P including the tunnel insulating layer 11 , the floating gate 12 ′, the inter-gate dielectric layer 13 , and the control gate 14 and 17 , which are sequentially stacked, is disposed over the substrate 10 .
- the second insulating layer 18 is disposed to cover the gate structure P. At this time, since the second insulating layer 18 has a poor step coverage characteristic, the air gaps G 1 and G 2 are formed between the gate structures P inside the second insulating layer 18 .
- the protective layer pattern 16 ′ is formed to prevent impurity transfer of the floating gate 12 ′.
- the protective layer pattern 16 ′ has a poor adhesion characteristic with respect to the second insulating layer 18 . Therefore, since the second insulating layer 18 is not formed on the protective layer pattern 16 ′, the lower air gap G 1 and the protective layer pattern 16 ′ may be directly contacted with each other. As a result, the size of the lower air gap G 1 between the floating gates 12 ′ may be increased.
- the material forming the protective layer pattern 16 ′ may be properly controlled during the process for forming the protective layer pattern 16 ′ on the sidewalls of the floating gate 12 ′, thereby preventing impurity transfer of the floating gate 12 ′ and increasing the size of the air gap between the floating gates 12 ′. As a result, a distribution difference between memory cells and interference between memory cells may be reduced.
- the protective layer pattern 16 ′ exists on the sidewalls of the floating gate 12 ′ of the gate structure P, but the present invention is not limited thereto.
- the protective layer pattern 16 ′ may also be formed on the other part of the gate structure P excluding the floating gate 12 ′.
- the structure will be described in more detail with reference to FIG. 7 .
- FIG. 7 is a cross-sectional view illustrating a nonvolatile memory device and a method for fabricating the same in accordance with another embodiment of the present invention.
- the gate structure P′ may be formed by the following process: the etch process for forming the inter-gate dielectric layer 13 and the control-gate conductive layer 14 in the process of FIG. 2 is performed and the floating-gate conductive layer 12 is then etched without the process for forming the first insulating layer 15 . That is, the floating gate 120 , the inter-gate dielectric layer 130 , and the control gate 140 may be formed by one etch process using the same mask.
- a protective layer pattern 160 having a small adhesive strength with respect to the second insulating layer 180 is formed on the sidewalls of the gate structure P′ to prevent impurity transfer.
- the protective layer pattern 160 may be formed by depositing a protective layer along the entire surface of the resulting structure having the gate structure P′ formed therein and then performing a dry-etch process to expose the tunnel insulating layer 110 . During the dry-etch process for the tunnel insulating layer 110 , the protective layer deposited on the top surface of the gate structure P′ may be removed. Accordingly, the top surface of the gate structure P′ may be exposed.
- a second insulating layer 180 is formed on the resulting structure having the gate structure P′ and the protective layer pattern 160 formed therein.
- the second insulating layer 180 may be mainly formed over the gate structure P′, and air gaps G 1 ′ and G 2 ′ may be positioned in the entire space between the gate structures P′ to expose the protective pattern 160 .
- a process for silicidizing an upper part of the control gate 140 may be additionally performed before the second insulating layer 180 is formed.
- the device of FIG. 7 may be fabricated.
- the device in accordance with this embodiment of the present invention is different from the above-described embodiment in that the protective layer pattern 160 is positioned on the entire sidewalls of the gate structure P′ including the floating gate 120 .
- the protective layer pattern 160 is formed on the sidewalls of the floating gate 120 , in order to prevent impurity transfer of the floating gate 120 and prevent interference between the floating gates 120 .
- the protective layer pattern 160 may or may not be formed on the other part of the gate structure
- the protective layer pattern 160 may be formed on the entire sidewalls of the gate structure P′.
- the protective layer pattern 160 may be formed on a part of the sidewalls of the gate structure P′, or formed on a part or all of the top surface of the gate structure P′.
- a distribution difference and interference between memory cells may be reduced.
Abstract
A nonvolatile memory device includes gate structures formed over a substrate, each gate structure including a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate that are sequentially stacked, a protective layer formed on sidewalls of the floating gate, and a second insulating layer covering the gate structures and having an air gap formed between the gate structures, wherein an adhesive strength between the second insulating layer and the protective layer is smaller than an adhesive strength between the second insulating layer and the gate structure.
Description
- The present application claims priority of Korean Patent Application No. 10-2012-0096722, filed on Aug. 31, 2012, which is incorporated herein by reference in its entirety.
- 1. Field
- Exemplary embodiments of the present invention relate to a nonvolatile memory device and a method for fabricating the same, and more particularly, to a nonvolatile memory device including an air gap formed between gate structures and a method for fabricating the same.
- 2. Description of the Related Art
- A nonvolatile memory device maintains data stored therein even though power supply is cut off. For example, a NAND flash memory device and the like are widely used.
- A conventional memory device includes a plurality of gate structures each having a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate which are sequentially stacked. Typically, the floating gate is formed of polysilicon doped with impurities.
- However, while a subsequent process is performed after the gate structures are formed, the impurities of the floating gate may not be maintained. For example, the impurities of the floating gate may escape during a subsequent heat treatment, or impurities may be implanted into the floating gate during a subsequent ion implantation. As such, when the impurities of the floating gate are changed, memory cells may have non-uniform characteristics. In this case, a distribution difference between memory cells may increase.
- Recently, as the distance between gate structures decreases with the increase in integration degree of nonvolatile memory devices, interference between memory cells has increased.
- Exemplary embodiments of the present invention are directed to a nonvolatile memory device capable of reducing a distribution difference and interference between memory cells and a method for fabricating the same.
- In accordance with an embodiment of the present invention, a nonvolatile memory device includes gate structures formed over a substrate, each gate structure including a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate that are sequentially stacked, a protective layer formed on sidewalls of the floating gate, and a second insulating layer covering the gate structures and having an air gap formed between the gate structures, wherein an adhesive strength between the second insulating layer and the protective layer is smaller than an adhesive strength between the second insulating layer and the gate structure.
- In accordance with another embodiment of the present invention, a nonvolatile memory device includes a gate structure formed over a substrate and including a tunnel insulating layer, a floating gate, an inter-gate dielectric layer, and a control gate that are sequentially stacked, and a protective layer formed on sidewalls of the floating gate configured to block impurities from being transferred from or to the floating gate.
- In accordance with yet another embodiment of the present invention, a method for fabricating a nonvolatile memory device includes sequentially forming a tunnel insulating layer, a first conductive layer for a floating gate, an inter-gate dielectric layer, and a second conductive layer for a control gate over a substrate, forming gate structures over the substrate, each gate structure formed by etching the second conductive layer, the inter-gate dielectric layer, and the first conductive layer, and forming a protective layer pattern on at least sidewalls of the etched first conductive layer, the protective layer pattern blocking impurities from being transferred from or to the floating gate.
-
FIG. 1 is a plan view illustrating a nonvolatile memory device in accordance with an embodiment of the present invention. -
FIGS. 2 to 6 are cross-sectional views illustrating the nonvolatile memory device and a method for fabricating the same in accordance with the embodiment of the present invention. -
FIG. 7 is a cross-sectional view illustrating a nonvolatile memory device and a method for fabricating the same in accordance with another embodiment of the present invention. - Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention. In this specification, ‘connected/coupled’ represents that one component is directly coupled to another component or indirectly coupled through another component. In addition, a singular form may include a plural form as long as it is not specifically mentioned in a sentence.
- The drawings are not necessarily to scale and in some instances, proportions may have been exaggerated in order to dearly illustrate features of the embodiments. It should be readily understood that the meaning of “on” and “over” in the present disclosure should be interpreted in the broadest manner such that “on” not only means “directly on” something but also include the meaning of “on” something with an intermediate feature or a layer therebetween, and that “over” not only means the meaning of “over” something may also include the meaning it is “over” something with no intermediate feature or layer therebetween (i.e., directly on something).
-
FIG. 1 is a plan view illustrating a nonvolatile memory device in accordance with an embodiment of the present invention. - Referring to
FIG. 1 , a plurality of active areas ACT are defined in a substrate. The plurality of active areas ACT are arranged in parallel to each other and extended in one direction (I-I′ direction). Over the substrate, a plurality of control gates CG are formed. The plurality of control gates CG are arranged in parallel to each other and extended in a direction crossing the active areas ACT. Between the control gates CG and the active areas ACT, a plurality of island-shaped floating gates FG are formed at the respective intersections between the control gates CG and the active areas ACT. Between the floating gates FG and the substrate, a tunnel insulating layer (not illustrated) is interposed, and between the floating gates FG and the control gates FG, an inter-gate dielectric layer (not illustrated) is interposed. Each of the floating gates FG forms a unit memory cell MC as a charge storing element. Hereinafter a structure in which the tunnel insulating layer, the floating gate FG, the inter-gate dielectric layer, and the control gate CG, which are sequentially stacked, will be referred to as a gate structure. -
FIGS. 2 to 6 are cross-sectional views illustrating the nonvolatile memory device and a method for fabricating the same in accordance with the embodiment of the present invention, taken along line ofFIG. 1 . First, the fabrication method will be described. - Referring to
FIG. 2 , a structure in which atunnel insulating layer 11 and a floating-gateconductive layer 12 are stacked is formed over asubstrate 10. - Such a structure may be formed by the following process. First, an insulating material for forming the
tunnel insulating layer 11 and a conductive material for forming the floating-gateconductive layer 12 are deposited on the entire surface of thesubstrate 10. Then, a mask pattern is formed over the conductive material to cover active areas ACT (refer toFIG. 1 ). The mask pattern serving as an etch barrier is used to etch the conductive material and the insulating material. Then, thesubstrate 10 exposed by the etch process is etched to a predetermined depth to form an isolation trench in thesubstrate 10, thereby defining an active area. Subsequently, the isolation trench is filled with an insulating layer to form an isolation layer (not illustrated). As a result of this process, thetunnel insulating layer 11 and the floating-gateconductive layer 12 may have substantially the same plan shape as the active area of thesubstrate 10. - The
substrate 10 may include a semiconductor substrate such as silicon. Thetunnel insulating layer 11 for charge tunneling between thesubstrate 10 and a floating gate may include oxide, for example. The floating-gateconductive layer 12 serves as a charge storing element, and may include a semiconductor material doped with a required impurity such as phosphorus or boron, for example, polysilicon. However, the present invention is not limited thereto. - Subsequently, an insulating material for forming inter-gate
dielectric layers 13 and a conductive material for forming control-gateconductive layers 14 are deposited on the resulting structure, and then selectively etched to form a plurality of control-gateconductive layers 14 and inter-gatedielectric layers 13 that extend in a direction crossing the active areas of thesubstrate 10. As a result of this process, the control-gateconductive layers 14 may have substantially the same plan shape as the control gates CG ofFIG. 1 . - The inter-gate
dielectric layer 13 serves to block charge transfer between the floating-gateconductive layer 12 and the control-gateconductive layer 14, and may include a triple layer structure such as oxide-nitride-oxide (ONO) layer. However, the present invention is not limited thereto. The control-gateconductive layer 14 may include impurity-doped polysilicon, for example, but the present invention is not limited thereto. - Then, a first insulating
layer 15 is formed on the surface of the control-gateconductive layer 14. The first insulatinglayer 15 serves not only to protect the control-gateconductive layer 14 during a subsequent etch process for the floating-gateconductive layer 12, but also to prevent a protective layer from being formed on the surface of the control-gateconducive layer 14 during a formation process of the protective layer (refer toreference numeral 16 ofFIG. 3 ), because the firstinsulating layer 15 has a poor adhesion characteristic with respect to the protective layer. The first insulatinglayer 15 may include oxide, and may be formed by a dry oxidation process or an atomic layer deposition (ALD) process, but the present invention is not limited thereto. - Referring to
FIG. 3 , the floating-gate conductive layer exposed by the control-gateconductive layer 14 and the first insulatinglayer 15 is etched. As a result, a floatinggate 12′ having an island shape is formed at a position where the control-gateconductive layer 14 and the active area overlap each other. - Then, a
protective layer 16 is formed on the sidewalls of the floatinggate 12′ to prevent impurities from escaping from the floatinggate 12′ or impurities from being implanted into the floatinggate 12′. At this time, theprotective layer 16 may include a material capable of blocking transfer of impurities and having a low adhesive strength with respect to a second insulating layer to be described below (refer toreference numeral 18 ofFIG. 6 ). When the second insulating layer includes oxide, theprotective layer 16 may include germanium (Ge). Since theprotective layer 16 does not adhere to the first insulatinglayer 15 on the surface of the control-gateconductive layer 14, theprotective layer 16 is not formed on the control-gateconductive layer 14, but formed on the sidewalls of the floatinggate 12′ and thetunnel insulating layer 11. Furthermore, when the adhesion characteristic between theprotective layer 16 and thetunnel insulating layer 11 is degraded, for example, when the tunnel insulating layer includes oxide and theprotective layer 16 includes Ge, theprotective layer 16 may be formed only on the sidewalls of the floatinggate 12′, but may not be formed on thetunnel insulating layer 11. - The
protective layer 16 may be formed by ALD, for example, and may have a thickness of several Å. - Referring to
FIG. 4 , theprotective layer 16 on thetunnel insulating layer 11 is removed to form aprotective layer pattern 16′ left only on the sidewalls of the floatinggate 12′. This process is performed to form a junction area in the active area of thesubstrate 10 between the floatinggates 12′ and to electrically isolate the floatinggates 12′ from each other. The removal process of theprotective layer 16 may be performed by a dry-etch process. - When the
protective layer 16 is not formed on thetunnel insulating layer 11, for example, when theprotective layer 16 includes Ge and thetunnel insulating layer 11 includes oxide, the process ofFIG. 4 may be omitted. - Then, although not illustrated, an ion implantation of impurities such as B or As may be performed to form a junction area in the active area of the
substrate 10 between the floatinggates 12′. During the ion implantation, since the sidewalls of the floatinggate 12′ are covered by theprotective layer pattern 16′, the impurities such as B or As may not be implanted into the floatinggate 12′. Furthermore, although a subsequent heat treatment process or the like is performed, the impurities of the floatinggate 12′ may not escape to the outside. - Referring to
FIG. 5 , the first insulatinglayer 15 is removed, and a silicide process is performed to transform an upper part of the control-gateconductive layer 14 into ametal silicide layer 17 such as nickel silicide or cobalt silicide, in order to reduce the resistance of the control-gateconductive layer 14. Accordingly, the control-gateconductive layer 14 and themetal silicide layer 17 may form a control gate. The silicide process may be omitted. - As a result of this process, a gate structure P is formed, including the
tunnel insulating layer 11, the floatinggate 12′, the inter-gatedielectric layer 13, and thecontrol gate - Referring to
FIG. 6 , a second insulatinglayer 18 is formed on the structure shown inFIG. 5 . - The second insulating
layer 18 may include oxide, for example. If the second insulatinglayer 18 is formed to degrade a step coverage characteristic, for example, if the second insulatinglayer 18 is deposited by a low pressure (LP) or plasma enhanced (PE) method, the space between the gate structures P may not be filled with an insulating material. In this case, air gaps G1 and G2 may be formed between the gate structures P. Hereinafter, for convenience of description, the air gap G2 disposed between theadjacent control gates gates 12′ is referred to as a lower air gap G1. - Here, in order to prevent interference between memory cells, the size of the air gaps G1 and G2 may be increased. In particular, the size of the lower air gap G1 between the floating
gates 12 needs to be increased. As described above, however, theprotective layer 16 on the sidewalls of the floating gate IT has a small adhesive strength with respect to the second insulatinglayer 18. Therefore, the second insulatinglayer 18 is not formed on the sidewall of the floatinggate 12′. Furthermore, the adhesive strength between the second insulatinglayer 18 and the inter-gatedielectric layer 13 or thecontrol gate protective layer 16, is larger than the adhesive strength between the second insulatinglayer 18 and theprotective layer 16. Therefore, the second insulatinglayer 18 may exist at a predetermined thickness on the sidewalls of the inter-gatedielectric layer 13 and/or thecontrol gate protective layer 16 has a small thickness of several A as described above, theprotective layer 16 does not have an effect on the size of the lower air gap G1. As a result, the size of the lower air gap G1 between the floatinggates 12′ may increase. - Through the above-described fabrication method, the device of
FIG. 6 may be fabricated. - Referring to
FIG. 6 , the gate structure P including thetunnel insulating layer 11, the floatinggate 12′, the inter-gatedielectric layer 13, and thecontrol gate substrate 10. - Over the
substrate 10 having the gate structure P formed thereon, the second insulatinglayer 18 is disposed to cover the gate structure P. At this time, since the second insulatinglayer 18 has a poor step coverage characteristic, the air gaps G1 and G2 are formed between the gate structures P inside the second insulatinglayer 18. - On the sidewalls of the floating
gate 12′, theprotective layer pattern 16′ is formed to prevent impurity transfer of the floatinggate 12′. Theprotective layer pattern 16′ has a poor adhesion characteristic with respect to the second insulatinglayer 18. Therefore, since the second insulatinglayer 18 is not formed on theprotective layer pattern 16′, the lower air gap G1 and theprotective layer pattern 16′ may be directly contacted with each other. As a result, the size of the lower air gap G1 between the floatinggates 12′ may be increased. - In the nonvolatile memory device and the method for fabricating the same in accordance with the embodiment of the present invention, the material forming the
protective layer pattern 16′ may be properly controlled during the process for forming theprotective layer pattern 16′ on the sidewalls of the floatinggate 12′, thereby preventing impurity transfer of the floatinggate 12′ and increasing the size of the air gap between the floatinggates 12′. As a result, a distribution difference between memory cells and interference between memory cells may be reduced. - In this embodiment of the present invention, the
protective layer pattern 16′ exists on the sidewalls of the floatinggate 12′ of the gate structure P, but the present invention is not limited thereto. Theprotective layer pattern 16′ may also be formed on the other part of the gate structure P excluding the floatinggate 12′. Hereinafter, the structure will be described in more detail with reference toFIG. 7 . -
FIG. 7 is a cross-sectional view illustrating a nonvolatile memory device and a method for fabricating the same in accordance with another embodiment of the present invention. - First, the fabrication method will be described, and the duplicated descriptions of the above-described embodiment will be omitted herein.
- Referring to
FIG. 7 , a gate structure P′ including atunnel insulating layer 110, a floatinggate 120, an inter-gatedielectric layer 130, and acontrol gate 140, which are sequentially stacked, is formed over asubstrate 100. - The gate structure P′ may be formed by the following process: the etch process for forming the inter-gate
dielectric layer 13 and the control-gateconductive layer 14 in the process ofFIG. 2 is performed and the floating-gateconductive layer 12 is then etched without the process for forming the first insulatinglayer 15. That is, the floatinggate 120, the inter-gatedielectric layer 130, and thecontrol gate 140 may be formed by one etch process using the same mask. - Then, a
protective layer pattern 160 having a small adhesive strength with respect to the second insulatinglayer 180 is formed on the sidewalls of the gate structure P′ to prevent impurity transfer. Theprotective layer pattern 160 may be formed by depositing a protective layer along the entire surface of the resulting structure having the gate structure P′ formed therein and then performing a dry-etch process to expose thetunnel insulating layer 110. During the dry-etch process for thetunnel insulating layer 110, the protective layer deposited on the top surface of the gate structure P′ may be removed. Accordingly, the top surface of the gate structure P′ may be exposed. - Subsequently, a second insulating
layer 180 is formed on the resulting structure having the gate structure P′ and theprotective layer pattern 160 formed therein. In this case, since theprotective layer pattern 160 having a poor adhesion characteristic with respect to the second insulatinglayer 180 is positioned on the sidewalls of the gate structure P′, the second insulatinglayer 180 may be mainly formed over the gate structure P′, and air gaps G1′ and G2′ may be positioned in the entire space between the gate structures P′ to expose theprotective pattern 160. Although not illustrated, a process for silicidizing an upper part of thecontrol gate 140 may be additionally performed before the second insulatinglayer 180 is formed. - Through the above-described fabrication method, the device of
FIG. 7 may be fabricated. - Referring to
FIG. 7 , the device in accordance with this embodiment of the present invention is different from the above-described embodiment in that theprotective layer pattern 160 is positioned on the entire sidewalls of the gate structure P′ including the floatinggate 120. - In short, the
protective layer pattern 160 is formed on the sidewalls of the floatinggate 120, in order to prevent impurity transfer of the floatinggate 120 and prevent interference between the floatinggates 120. However, theprotective layer pattern 160 may or may not be formed on the other part of the gate structure In this embodiment of the present invention, theprotective layer pattern 160 may be formed on the entire sidewalls of the gate structure P′. However, theprotective layer pattern 160 may be formed on a part of the sidewalls of the gate structure P′, or formed on a part or all of the top surface of the gate structure P′. - In accordance with the embodiment of the present invention, a distribution difference and interference between memory cells may be reduced.
- While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
Claims (14)
1-9. (canceled)
10. A method for fabricating a nonvolatile memory device, comprising:
sequentially forming a tunnel insulating layer, a first conductive layer for a floating gate, an inter-gate dielectric layer, and a second conductive layer for a control gate over a substrate;
forming gate structures over the substrate, each gate structure formed by etching the second conductive layer, the inter-gate dielectric layer, and the first conductive layer; and
forming a protective layer pattern on at least sidewalls of the etched first conductive layer, the protective layer pattern blocking impurities from being transferred from or to the floating gate.
11. The method of claim 10 , further comprising forming a first insulating layer on the surface of the etched second conductive layer, after the second conductive layer is etched.
12. The method of claim 11 , wherein an adhesive strength between the first insulating layer and the protective layer pattern is smaller than an adhesive strength between the protective layer pattern and the first conductive layer.
13. The method of claim 11 , wherein the twilling of the first insulating layer is performed by a dry-oxidation process or atomic layer deposition (ALD) process.
14. The method of claim 10 , wherein the forming of the protective layer pattern comprises:
forming a protective layer on sidewalls of the etched first conductive layer and the tunnel insulating layer; and
removing the protective layer on the tunnel insulating layer through a dry-etch process.
15. The method of claim 10 , wherein the protective layer pattern is further formed on a part or all of the gate structure excluding the etched first conductive layer.
16. The method of claim 10 , wherein an adhesive strength between the tunnel insulating layer and the protective layer pattern is smaller than an adhesive strength between the protective layer pattern and the first conductive layer.
17. The method of claim 10 , wherein the protective layer pattern comprises Ge.
18. The method of claim 11 , further comprising removing the first insulating layer, after the forming of the protective layer pattern.
19. The method of claim 11 , wherein the first insulating layer or the tunnel insulating layer comprises oxide.
20. The method of claim 10 , further comprising forming a second insulating layer covering the gate structures and having an air gap formed between the gate structures, after the forming of the protective layer patterns.
21. The method of claim 20 , wherein an adhesive strength between the second insulating layer and the protective layer patterns is smaller than an adhesive strength between the second insulating layer and the second conductive layer or an adhesive strength between the second insulating layer and the inter-gate dielectric layer.
22. The method of claim 20 , wherein the second insulating layer comprises oxide.
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KR1020120096722A KR20140029055A (en) | 2012-08-31 | 2012-08-31 | Semiconductor device and method for fabricating the same |
US13/718,732 US9006813B2 (en) | 2012-08-31 | 2012-12-18 | Nonvolatile memory device and method for fabricating the same |
US14/640,962 US20150179498A1 (en) | 2012-08-31 | 2015-03-06 | Nonvolatile memory device and method for fabricating the same |
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KR20130072670A (en) * | 2011-12-22 | 2013-07-02 | 에스케이하이닉스 주식회사 | Method of manufacturing a semiconductor device |
US9859151B1 (en) * | 2016-07-08 | 2018-01-02 | Asm Ip Holding B.V. | Selective film deposition method to form air gaps |
CN108281426B (en) * | 2017-01-06 | 2020-11-27 | 中芯国际集成电路制造(上海)有限公司 | Memory and forming method thereof |
CN108346663B (en) * | 2017-01-23 | 2020-12-18 | 中芯国际集成电路制造(上海)有限公司 | Semiconductor device, manufacturing method thereof and electronic device |
US10985051B2 (en) * | 2019-07-24 | 2021-04-20 | Nanya Technology Corporation | Semiconductor device with air spacer and method for forming the same |
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US5424233A (en) * | 1994-05-06 | 1995-06-13 | United Microflectronics Corporation | Method of making electrically programmable and erasable memory device with a depression |
US5780350A (en) * | 1997-01-30 | 1998-07-14 | Lsi Logic Corporation | MOSFET device with improved LDD region and method of making same |
US20120146125A1 (en) * | 2010-12-13 | 2012-06-14 | Samsung Electronics Co., Ltd. | Non-volatile memory devices and methods of fabricating the same |
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JP2001250926A (en) * | 2000-03-03 | 2001-09-14 | Hitachi Ltd | Semiconductor integrated circuit device |
KR20080035915A (en) | 2006-10-20 | 2008-04-24 | 삼성전자주식회사 | Non-volatile memory device and method of fabricating the same |
US7557008B2 (en) * | 2007-01-23 | 2009-07-07 | Freescale Semiconductor, Inc. | Method of making a non-volatile memory device |
KR101778287B1 (en) * | 2010-08-30 | 2017-09-14 | 삼성전자주식회사 | Semiconductor memory devices and methods for fabricating the same |
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2012
- 2012-08-31 KR KR1020120096722A patent/KR20140029055A/en not_active Application Discontinuation
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US5424233A (en) * | 1994-05-06 | 1995-06-13 | United Microflectronics Corporation | Method of making electrically programmable and erasable memory device with a depression |
US5780350A (en) * | 1997-01-30 | 1998-07-14 | Lsi Logic Corporation | MOSFET device with improved LDD region and method of making same |
US20120146125A1 (en) * | 2010-12-13 | 2012-06-14 | Samsung Electronics Co., Ltd. | Non-volatile memory devices and methods of fabricating the same |
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US20140061755A1 (en) | 2014-03-06 |
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US9006813B2 (en) | 2015-04-14 |
CN103681685B (en) | 2018-05-25 |
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