CN108987407A - Three-dimensional memory and its manufacturing method - Google Patents
Three-dimensional memory and its manufacturing method Download PDFInfo
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- CN108987407A CN108987407A CN201810765577.XA CN201810765577A CN108987407A CN 108987407 A CN108987407 A CN 108987407A CN 201810765577 A CN201810765577 A CN 201810765577A CN 108987407 A CN108987407 A CN 108987407A
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/30—EEPROM devices comprising charge-trapping gate insulators characterised by the memory core region
- H10B43/35—EEPROM devices comprising charge-trapping gate insulators characterised by the memory core region with cell select transistors, e.g. NAND
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- H—ELECTRICITY
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- H10B—ELECTRONIC MEMORY DEVICES
- H10B43/00—EEPROM devices comprising charge-trapping gate insulators
- H10B43/20—EEPROM devices comprising charge-trapping gate insulators characterised by three-dimensional arrangements, e.g. with cells on different height levels
- H10B43/23—EEPROM devices comprising charge-trapping gate insulators characterised by three-dimensional arrangements, e.g. with cells on different height levels with source and drain on different levels, e.g. with sloping channels
- H10B43/27—EEPROM devices comprising charge-trapping gate insulators characterised by three-dimensional arrangements, e.g. with cells on different height levels with source and drain on different levels, e.g. with sloping channels the channels comprising vertical portions, e.g. U-shaped channels
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Abstract
The invention discloses a three-dimensional memory and a manufacturing method thereof. Wherein the three-dimensional memory comprises: the grid laminated structure comprises a plurality of layers of grids which are arranged at intervals; the channel structure penetrates through the grid laminated structure and comprises a lower channel column, a conductive connecting layer and an upper channel column which are sequentially arranged along the stacking direction of the grid; the upper channel pillar includes: the lower end of the channel layer extends into the conductive connecting layer and is in contact with the conductive connecting layer; and the memory layer surrounds part of the channel layer and is positioned on the top surface of the conductive connecting layer.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a three-dimensional memory and a manufacturing method thereof.
Background
With the development of science and technology, people live with more and more portable electronic devices, such as digital cameras, MP3, tablet computers, smart phones, and the like. Therefore, the nonvolatile memory market has also grown rapidly. NAND occupies most of the non-volatile memory market due to its numerous advantages of high integration density, low unit bit cost, high reliability, etc.
However, along with the size reduction of semiconductor devices, the reliability and performance of NAND devices are becoming lower, that is, NAND devices face the bottleneck that the two-dimensional structure size cannot be further reduced.
To improve the reliability and performance of NAND, three-dimensional NAND is created. To further increase storage capacity, multi-Channel (e.g., Dual Channel) three-dimensional NAND has also been created.
However, in the related art, in the three-dimensional memory of the multi-channel three-dimensional NAND, there is a limitation in the manufacturing process such that when a voltage is applied to the Word Line (WL), the current ratio of the channel is small, which seriously affects the operation performance of the semiconductor device.
Disclosure of Invention
In order to solve the existing technical problems, embodiments of the present invention provide a three-dimensional memory and a manufacturing method thereof.
The technical scheme of the embodiment of the invention is realized as follows:
an embodiment of the present invention provides a three-dimensional memory, including:
the grid laminated structure comprises a plurality of layers of grids which are arranged at intervals;
the channel structure penetrates through the grid laminated structure and comprises a lower channel column, a conductive connecting layer and an upper channel column which are sequentially arranged along the stacking direction of the grid;
the upper channel pillar includes:
the lower end of the channel layer extends into the conductive connecting layer and is in contact with the conductive connecting layer;
and the memory layer surrounds part of the channel layer and is positioned on the top surface of the conductive connecting layer.
In the above solution, the memory layer has a bottom surface facing the conductive connection layer along the direction, and the bottom surface is not lower than the top surface of the conductive connection layer;
the channel layer also covers the bottom surface.
In the above scheme, the bottom surface is an arc shape recessed in a direction from the lower channel pillar to the conductive connection layer.
In the above scheme, the channel layer and the conductive connection layer are made of the same material.
In the above scheme, the material is polysilicon.
In the above scheme, the memory layer includes a blocking dielectric layer, a storage dielectric layer, and a tunneling dielectric layer sequentially disposed along a radially inward direction of the upper channel pillar.
The embodiment of the invention also provides a manufacturing method of the three-dimensional memory, which comprises the following steps:
providing a substrate structure, wherein the substrate structure comprises a grid laminated structure, and a lower channel column and a conductive connecting layer which penetrate through part of the grid laminated structure, the grid laminated structure comprises a plurality of layers of grids which are arranged at intervals, and the lower channel column and the conductive connecting layer are sequentially arranged along the stacking direction of the grids;
forming an upper channel hole through a part of the gate stack structure, wherein the upper channel hole penetrates through a part of the surface layer of the conductive connecting layer;
forming a memory material layer at least covering the side wall of the upper channel hole and the top surface of the conductive connecting layer;
etching the memory material layer to remove the memory material layer covering the top surface and the lower end of the side wall so as to form a memory layer, wherein the memory layer is positioned on the top surface;
and forming a channel layer at least covering the memory layer, wherein the lower end of the channel layer extends into the conductive connecting layer and is in contact with the conductive connecting layer.
In the above scheme, the step of etching the memory material layer includes:
forming a sacrificial medium layer, wherein the sacrificial medium layer covers the storage material layer in the upper channel hole, and part of the sacrificial medium layer is positioned on the top surface of the grid laminated structure;
performing first etching to remove the sacrificial medium layer and the memory material layer at the bottom of the upper channel hole;
performing second etching to remove the sacrificial dielectric layer and one end of the memory material layer close to the conductive connecting layer;
a third etch is performed to remove the layer of memory material overlying the lower end of the sidewalls to form the memory layer.
In the above scheme, the step of performing the first etching includes:
performing first etching by adopting a first dry etching process;
or,
sequentially adopting a first dry etching process and a second dry etching process to carry out first etching; wherein,
the second dry etching process uses NH3And NF3Is performed using the fluorine source of (a).
In the above scheme, the step of performing the second etching includes:
performing second etching by adopting a second dry etching process; wherein the second dry etching process uses NH3And NF3Is performed using the fluorine source of (a).
In the foregoing solution, the step of performing the third etching includes:
and performing third etching by using a wet etching process.
In the above scheme, the sacrificial dielectric layer is made of polysilicon.
In the above scheme, the method further comprises: and removing the sacrificial dielectric layer.
In the above scheme, the memory material layer includes a blocking dielectric layer, a storage dielectric layer, and a tunneling dielectric layer sequentially disposed along a radially inward direction of the upper channel hole.
In the above scheme, the conductive connection layer is made of polysilicon.
The three-dimensional memory and the manufacturing method thereof provided by the embodiment of the invention provide a substrate structure, wherein the substrate structure comprises a grid laminated structure, a lower channel column and a conductive connecting layer, wherein the lower channel column and the conductive connecting layer penetrate through part of the grid laminated structure; forming an upper channel hole through a part of the gate stack structure, wherein the upper channel hole penetrates through a part of the surface layer of the conductive connecting layer; forming a memory material layer at least covering the side wall of the upper channel hole and the top surface of the conductive connecting layer; etching the memory material layer to remove the memory material layer covering the top surface and the lower end of the side wall so as to form a memory layer, wherein the memory layer is positioned on the top surface; and forming a channel layer at least covering the memory layer, wherein the lower end of the channel layer extends into the conductive connecting layer and is in contact with the conductive connecting layer, and in the manufacturing process, the formed memory layer is positioned on the top surface of the conductive connecting layer, so that the memory layer does not extend into the conductive connecting layer, namely, no residual insulating layer exists in the upper channel.
Drawings
FIGS. 1A-1B are schematic cross-sectional views of a three-dimensional memory structure at different stages of fabrication according to an embodiment of the invention;
FIG. 1C is a partial schematic view of the L-shaped bottom of the structure shown in FIG. 1B according to one embodiment of the present invention;
FIG. 2 is a flow chart illustrating a method for fabricating a three-dimensional memory according to an embodiment of the invention;
FIG. 3 is a flowchart illustrating an implementation of step 204 in FIG. 2;
FIG. 4A is a cross-sectional view of a structure formed after depositing a sacrificial dielectric layer according to an embodiment of the present invention;
FIG. 4B is a cross-sectional view of the structure formed after removing the sacrificial dielectric layer at the bottom of the conductive connection layer according to the embodiment of the present invention;
FIG. 4C is a cross-sectional view of a structure formed after a first etch in accordance with an embodiment of the present invention;
FIG. 4D is a schematic cross-sectional view of a structure formed after a second etching in accordance with an embodiment of the present invention;
FIG. 4E is a schematic cross-sectional view of a structure formed after a third etching in accordance with an embodiment of the present invention;
FIG. 4F is a cross-sectional view of the structure formed after removing the sacrificial dielectric layer according to the embodiment of the present invention;
FIG. 4G is a cross-sectional view of a structure formed after deposition of a channel layer in accordance with an embodiment of the present invention;
FIG. 5 is a cross-sectional view of a three-dimensional memory structure formed by a method according to an embodiment of the invention.
Description of reference numerals:
11-a gate; 12-an interlayer insulating layer; 13-upper trench hole; 14-a conductive connection layer; 15-a layer of memory material; 151-barrier dielectric layer; 152 a storage medium layer; 153-tunneling dielectric layer; 16-a channel layer; 17-a sacrificial layer; 18-sacrificial dielectric layer.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
It should be noted that the terms "first," "second," and the like herein are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
To increase the storage capacity, a multi-channel three-dimensional NAND is produced. In the multi-channel three-dimensional NAND, a memory (may also be referred to as a semiconductor device) has a gate stack (may be referred to as a deck) structure. The grid laminated structure comprises a lower laminated structure, a middle medium layer and an upper laminated structure which are sequentially arranged along the vertical direction. The lower channel column penetrates through the lower laminated structure, the conductive connecting layer penetrates through the middle dielectric layer, and the upper channel column penetrates through the upper laminated structure. The lower channel pillar is electrically connected to the upper channel pillar by a conductive connection layer disposed therebetween. The upper and lower stacked structures each include interlayer insulating layers and gates alternately arranged in a vertical direction.
In fabricating the upper channel pillar, as shown in fig. 1A, one embodiment is: after alternately stacking the gate electrode 11 and the interlayer insulating layer 12, forming an upper channel hole 13 passing through the interlayer insulating layer 12 and the gate electrode 11, the upper channel hole 13 passing through a surface layer of the conductive connection layer 14, thereby forming a recess region on the conductive connection layer 14; then, forming a memory material layer 15 (as shown in fig. 1A, including a blocking dielectric layer 151, a storage dielectric layer 152, and a tunneling dielectric layer 153 in sequence from left to right) covering the sidewall of the upper channel hole 13, the recessed region, the overlapped interlayer insulating layer 12, and the top end of the gate 11; then forming a channel layer 16 covering the memory material layer 15; a sacrificial layer 17 is deposited on the channel layer 16, and the structure shown in fig. 1B is formed by an etching process.
As can be seen from fig. 1B, in the structure formed by the above process, part of the memory material layer 15 may remain in the conductive connection layer 14, and specifically, as shown by the dotted circle in fig. 1B, part of the memory material layer 15 may remain in the conductive connection layer 14 at the L-shaped bottom (L-foot), where the position of the L-shaped bottom is shown by the arrow line in fig. 1C.
It has been proved that the residual memory material layer (which is insulating) is difficult to remove by the above etching process, and the conductive connection layer is easily damaged by over etching.
Meanwhile, in one embodiment, the material of the blocking dielectric layer and the tunneling dielectric layer may be silicon oxide (also referred to as silicon dioxide or silicon oxide), the material of the storage dielectric layer may be silicon nitride (also referred to as silicon nitride), and in this case, the memory material layer may be described as ONO; in this case, when a voltage is applied to the WL, the ONO remaining in the conductive connection layer cannot invert part of the polysilicon in the channel (form carriers), which causes an excessively large resistance, and thus causes a small channel current, and further causes a small driving current, and the small driving current may affect the normal reading and storing operations of the memory cell, seriously affect the operating performance of the memory device, and may also be understood as reliability.
Based on this, in various embodiments of the invention: in the process of manufacturing the upper laminated structure, after the memory material layer is formed, the memory material layer covering the top surface of the conductive connection layer and the lower end of the side wall of the upper channel hole is removed, so that the formed memory layer is positioned on the top surface of the conductive connection layer.
When the memory material layer covering the top surface of the conductive connecting layer and the lower end of the side wall of the upper channel hole is removed, a thicker sacrificial medium layer can be formed, and then the memory material layer in the conductive connecting layer is directly removed through an etching process, so that the formed memory layer is positioned on the top surface.
In addition, in the process of removing the memory material layer in the conductive connecting layer by utilizing the etching process, as the thicker sacrificial medium layer is deposited, other sacrificial layers do not need to be additionally deposited on the top of the upper laminated structure, and meanwhile, the memory material layer on the side wall of the channel hole is protected in the etching process.
It should be noted that: the gate described in the embodiment of the present invention may be a real gate (the gate is made of a conductive material such as metal, polysilicon, or metal silicide material), or may be a dummy gate (the gate is made of an insulating material such as silicon nitride).
The manufacturing method provided by the embodiment of the invention is described in detail below by taking the materials of the blocking dielectric layer, the tunneling dielectric layer and all the insulating layers as silicon oxides, the materials of the channel layer, the conductive connecting layer and the sacrificial dielectric layer as polysilicon, and the materials of the storage dielectric layer and the gate as silicon nitride as an example. Of course, the above layers may be made of other suitable materials for practical use.
The three-dimensional memory described in the embodiment of the invention has a gate stack structure, and the gate stack structure comprises a lower stack structure, an intermediate dielectric layer and an upper stack structure which are sequentially arranged along a vertical direction. The lower channel column penetrates through the lower laminated structure, the conductive connecting layer penetrates through the middle dielectric layer, and the upper channel column penetrates through the upper laminated structure. The lower channel pillar is electrically connected to the upper channel pillar by a conductive connection layer disposed therebetween. The upper and lower stacked structures each include interlayer insulating layers and gates alternately arranged in a vertical direction.
The manufacturing method of the three-dimensional memory provided by the embodiment of the invention, as shown in fig. 2, includes the following steps:
step 201: providing a substrate structure;
the substrate structure comprises a grid laminated structure, and a lower channel column and a conductive connecting layer which penetrate through part of the grid laminated structure, wherein the grid laminated structure comprises a plurality of layers of grids which are arranged at intervals, and the lower channel column and the conductive connecting layer are sequentially arranged along the stacking direction of the grids.
Here, in practical application, several layers of gate electrodes may be arranged at intervals through the first insulating layer. That is, the upper and lower stacked structures each include first insulating layers and gate electrodes alternately arranged in a vertical direction.
Step 202: forming an upper channel hole through a portion of the gate stack structure;
here, the upper channel hole penetrates through a portion of a surface layer of the conductive connection layer.
Step 203: forming a memory material layer;
here, the memory material layer covers at least sidewalls of the upper channel hole and a top surface of the conductive connection layer.
Step 204: etching the memory material layer to remove the memory material layer covering the top surface and the lower end of the side wall so as to form a memory layer;
here, a memory layer is formed over the top surface.
As shown in fig. 3, the step of etching the memory material layer includes:
step 204 a: forming a sacrificial dielectric layer;
here, as shown in fig. 4A, a sacrificial dielectric layer 18 is formed to cover the memory material layer 15 in the upper channel hole 13, and a portion of the sacrificial dielectric layer 18 is located above the top surface of the gate stack structure. Furthermore, as shown in fig. 4A, the upper channel hole 13 penetrates through a portion of the gate stack structure (through the insulating layer 12 and the sacrificial layer 11), and the upper channel hole 13 penetrates through a portion of the surface layer of the conductive connection layer 14, and a recess region is formed on the conductive connection layer 14.
Wherein the memory material layer 15 includes, sequentially arranged in a radially inward direction of the upper channel hole 13: barrier dielectric layer 151, storage dielectric layer 152, and tunnel dielectric layer 153.
In practical applications, a sacrificial layer needs to be deposited on the memory material layer 15, and the sacrificial layer is removed and then a sacrificial dielectric layer 18 covering the memory material layer 15 is formed (i.e., deposited).
It should be noted that: since the material of the top interlayer insulating layer 12 in the upper stacked layer structure is the same as that of the blocking dielectric layer 151, and both materials are silicon oxide, they are not distinguished in the figure.
Meanwhile, since the material of the intermediate dielectric layer is the same as that of the top interlayer insulating layer 12 in the lower stacked structure, and both of them are silicon oxide, they are not distinguished in the drawing.
The Atomic Layer Deposition (ALD) method can precisely control the thickness of a deposited film and has excellent Deposition uniformity and uniformity.
Based on this, in one embodiment, the sacrificial dielectric layer may be deposited using an ALD method.
During deposition, the sacrificial dielectric layer may be thickened compared to the process for manufacturing the structure shown in fig. 1, so as to remove the memory material layer 15, i.e. ONO, in the conductive connection layer 14.
Here, compared with the manufacturing process of the structure shown in fig. 1, in the manufacturing method provided in the embodiment of the present invention, after the sacrificial dielectric layer is formed, the covering silicon dioxide layer (serving as a hard mask) is not deposited, but a subsequent etching process is directly performed, so that in actual application, the sacrificial dielectric layer needs to be thickened, so that the memory material layer (i.e., ONO) located on the sidewall of the upper channel hole can be protected, and the sacrificial dielectric layer can be used as an etching stop layer (which may be expressed in english as a stop layer). Namely, the thickened sacrifice medium layer has two functions, the first function is to protect the ONO positioned on the side wall of the channel hole in the etching process, and the second function is to serve as an etching stop layer, so that the consumption of the hard mask at the top end of the layer structure in the etching process is reduced; meanwhile, a hard mask layer does not need to be deposited, so that a manufacturing process is reduced, the production cost is reduced, and the production time is shortened.
In practical application, the thickness of the sacrificial dielectric layer may be determined according to the thickness of the etching stop layer, for example, 7 to 9 nanometers.
In practical applications, the memory layer may be formed by an etching process.
Step 204 b: performing first etching to remove the sacrificial medium layer and the memory material layer at the bottom of the upper channel hole;
in an embodiment, the first etching may be performed by using a dry etching process. Specifically, the first etching is performed by a first dry etching process, or the first etching is performed by the first dry etching process and a second dry etching process in sequence.
Here, in practical applications, the first dry etching process is generally used to remove a SONO layer (which refers to a silicon Oxide (OX), a silicon nitride (SiN), a silicon Oxide (OX), and an amorphous silicon (Si) thin film layer deposited on the bottom in sequence); the etching method may be specifically one of sputter etching, chemical etching, or high-density plasma etching.
In one embodiment, the second dry etching process is a SiCoNi-R2 etching process.
Here, when the first etching is performed by sequentially using the first dry etching process and the second dry etching process, the sacrificial dielectric layer 18 at the bottom of the upper trench hole 13 is etched by using the first dry etching process, and then a portion of the memory material layer 15 at the bottom of the upper trench hole 13 is further etched, so as to form the structure shown in fig. 4B. A second dry etch process may then be used to etch away the memory material layer 15 at the bottom of the upper channel hole 13, thereby forming the structure shown in fig. 4C.
Of course, when the first etching process is performed only by using the first dry etching process, the sacrificial dielectric layer 18 at the bottom of the upper channel hole 13 and the memory material layer 15 at the bottom of the upper channel hole 13 may be directly etched away by using the first dry etching process, so as to form the structure shown in fig. 4C.
It should be noted that: in practice, as shown in fig. 4C, a portion of the conductive connection layer 14 is usually etched when the first etching is performed.
As can be seen from fig. 4C, after the first etching, the Top (Top) sacrificial dielectric layer 18 is still present, but its thickness is thinner than that during deposition, and the sacrificial dielectric layer 18 on the sidewall of the upper channel hole 13 is also present, and its thickness will typically be greater than 3 nm. As can be seen from fig. 4B, after etching, the deposited sacrificial dielectric layer 18 on the bottom of the recess region (i.e., the bottom of the upper channel hole 13) is removed (i.e., etched away), and a portion of the memory material layer 15 on the bottom is also removed; accordingly, as can be seen from fig. 4C, after etching, the sacrificial dielectric layer 18 on the bottom of the recess region is removed, and the bottom memory material layer 15 is also removed, and at the same time, a portion of the bottom conductive connection layer 14 is also removed.
Step 204 c: performing second etching to remove the sacrificial dielectric layer and one end of the memory material layer close to the conductive connecting layer;
in an embodiment, the second etching may be performed by using a second dry etching process, that is, as described above, the end of the sacrificial dielectric layer and the end of the memory material layer close to the conductive connection layer are removed by using a SiCoNi-R2 etching process, and fig. 4D shows the structure after the end of the sacrificial dielectric layer and the end of the memory material layer close to the conductive connection layer are removed.
As can be seen in fig. 4D, after etching using the SiCoNi-R2 etching process, a portion of the memory material layer 15 deposited on the sidewalls of the recess region is removed.
Among them, the SiCoNi (applied materials corporation) -R2 (second generation) etching process is a silicon and silicide removal etching process. The SiCoNi etch process may use ammonia (NH)3) And nitrogen trifluoride (NF)3) Is performed using the fluorine source of (a).
The SiCoNi etching process is a common cleaning process, and the basic principle of the SiCoNi etching process is NF3/NH3Remote plasma etching and in-situ annealing, both of which are performed in the same chamber. During the etching process, the wafer is placed on a pedestal with a temperature tightly controlled at 35 ℃ and a low power plasma converts NF3 and NH3 into ammonium fluoride (NH)4F) And ammonia difluoride (equation 1). The fluoride condenses on the wafer surface and preferentially reacts with the oxide to form hexafluorosilicone ((NH)4)2SiF6) (equation 2). The silicate may be sublimed in an environment having a certain temperature (e.g., 70 ℃ or higher). In the in-situ annealing process, the wafer is moved to a position close to the heating member, the flowing hydrogen brings heat to the wafer, and the wafer is heated to a higher temperature (for example, above 100 ℃, or above 180 ℃) in a short time, so that the hexa-fluoro-silicone ammonia is decomposed into gaseous SiF4，NH3And HF (equation 3) and are decimated.
Wherein, the reaction equation in the process is as follows:
generation of etchant: NF3+NH3→NH4F+NH4F·HF (1)
Etching process: NH (NH)4F or NH4F·HF+SiO2→(NH4)2SiF6(solid)+H2O (2)
A sublimation process: (NH)4)2SiF6(solid)→SiF4(g)+NH3(g)+HF(g) (3)
High selectivity of oxide and silicon can be achieved with a SiCoNi etch process.
After etching by using the SiCoNi-R2 etching process, as can be seen from fig. 4D, a memory material layer 15 is further deposited on the sidewall of the recessed region (i.e., on the lower end of the sidewall of the upper channel hole 13), and this portion of the memory material layer 15 needs to be removed to enable the conductive connection layer 14 to have no memory material layer 15, i.e., no insulating layer, so that when a voltage is applied to the WL, the current of the channel is normal, and thus the normal reading and storing operations of the memory cell are ensured.
Step 204 d: a third etch is performed to remove the layer of memory material overlying the lower end of the sidewalls to form the memory layer.
In an embodiment, the performing the third etching includes:
and performing third etching by using a wet etching process.
Here, the wet etching means: the unetched material is dissolved using a chemical solution. Since the dry etch is anisotropic, the layer of memory material overlying the lower end of the sidewall cannot be removed using a dry etch process.
In practical applications, the etch selected for the wet etch process can easily be a phosphoric acid solution with a high etch selectivity, which has a high etch rate for silicon nitride and a nearly zero etch rate for silicon dioxide.
After removing the memory material layer 15 covering the lower end of the sidewall, the structure shown in fig. 4E is formed. As shown in fig. 4E, the memory layer is formed to have a bottom surface facing the conductive connection layer 14 in the direction, and the bottom surface is not lower than the top surface of the conductive connection layer 14.
Wherein, due to the poor anisotropy of the wet etching, the surface thereof exhibits an arc shape, as shown in fig. 4E. That is, the bottom surface of the memory layer in the direction toward the conductive connection layer 14 is an arc shape recessed in a direction from the lower channel pillar toward the conductive connection layer 14.
Step 205: a channel layer is formed overlying at least the memory layer.
Here, a lower end of the channel layer extends into and contacts the conductive connection layer.
In practical application, before the channel layer is formed, the sacrificial medium layer can be removed, and then the channel layer is formed.
Based on this, in an embodiment, the method may further include:
removing the sacrificial dielectric layer;
here, the sacrificial dielectric layer on the sidewall of the upper channel hole may be removed using a wet etching process.
In practical application, when the sacrificial dielectric layer on the sidewall of the upper channel hole is removed by using a wet etching process, an acidic solution with a high selectivity ratio to an oxide can be used.
After removing the sacrificial dielectric layer on the sidewall of the upper channel hole, the structure shown in fig. 4F is formed.
It should be noted that: in the whole etching step (steps 204 a-204 c), the sacrificial dielectric layer plays a role in protection, and can protect the underlying material layer from being etched.
As can be seen in fig. 4F, the sacrificial dielectric layer on the sidewalls of the upper trench hole 13 is removed and the top memory material layer 15 is also removed.
Here, in the case where the channel layer includes polysilicon, in order to prevent the channel layer from being cut or removed, the channel layer may be deposited thicker than a final thickness and then adjusted to a desired final thickness through a correction process (such a process may be referred to as an etch back process) when forming the channel layer.
Based on this, in one embodiment, the step of forming a channel layer at least covering the memory layer includes:
forming a conductive layer covering the memory layer;
and removing a part of the conductive layer through an etching process so as to enable the thickness of the conductive layer to reach a preset thickness, thereby forming the channel layer.
Wherein, in practical application, a conductive layer can be deposited on the memory layer by an ALD method.
After the above steps are completed, the structure shown in fig. 4G can be formed.
As can be seen from fig. 4G, the channel layer 16 and the conductive connection layer 14 are made of the same material, i.e., are polysilicon, and the deposited channel layer 16 covers the top, the sidewalls of the upper channel hole 13, the bottom surface of the memory layer, and contacts the upper surface of the conductive connection layer 14, even covers the recessed region; at the same time, the bottom surface of the memory layer is not lower than the top surface of the conductive connection layer 14, and is isolated from the upper surface of the conductive connection layer 14 by the deposited channel layer 16, so that the memory layer does not extend into the recess region, i.e., into the conductive connection layer 14.
It should be noted that: fig. 5 shows an example in which two gate electrodes 11 are provided. Each gate electrode 11 may correspond to a memory cell transistor, however, in practical applications, the implementation is not limited thereto, for example, in an embodiment, there may be 10, or 20 gate electrodes, etc.
By using the scheme of the embodiment of the invention, the three-dimensional memory structure shown in FIG. 5 can be manufactured. In fig. 5, the gate stack structure includes two stack structures, that is, a lower stack structure, an intermediate dielectric layer, and an upper stack structure, which are sequentially arranged along a vertical direction; meanwhile, the lower channel column penetrates through the lower laminated structure, the conductive connecting layer penetrates through the middle dielectric layer, and the upper channel column penetrates through the upper laminated structure; the lower channel pillar is electrically connected to the upper channel pillar by a conductive connection layer disposed therebetween. Fig. 5 shows an example of a three-dimensional memory in which two stacked structures are provided. However, in practical applications, the embodiment is not limited thereto, for example, in an embodiment, there may be 3, or 5 stacked structures. Wherein the lowermost stack is deposited on the substrate.
The manufacturing method of the three-dimensional memory provided by the embodiment of the invention comprises the steps of providing a substrate structure, wherein the substrate structure comprises a grid laminated structure, and a lower channel column and a conductive connecting layer which penetrate through part of the grid laminated structure, the grid laminated structure comprises a plurality of layers of grids which are arranged at intervals, and the lower channel column and the conductive connecting layer are sequentially arranged along the stacking direction of the grids; forming an upper channel hole through a part of the gate stack structure, wherein the upper channel hole penetrates through a part of the surface layer of the conductive connecting layer; forming a memory material layer at least covering the side wall of the upper channel hole and the top surface of the conductive connecting layer; etching the memory material layer to remove the memory material layer covering the top surface and the lower end of the side wall so as to form a memory layer, wherein the memory layer is positioned on the top surface; and forming a channel layer at least covering the memory layer, wherein the lower end of the channel layer extends into the conductive connecting layer and is in contact with the conductive connecting layer, and in the manufacturing process, the formed memory layer is positioned on the top surface of the conductive connecting layer, so that the memory layer does not extend into the conductive connecting layer, namely, no residual insulating layer exists in the upper channel.
In addition, when the memory material is etched, a sacrificial medium layer is formed firstly, the sacrificial medium layer covers the memory material layer in the upper channel hole, and part of the sacrificial medium layer is positioned on the top surface of the grid laminated structure; then, carrying out first etching to remove the sacrificial medium layer and the memory material layer at the bottom of the upper channel hole; performing second etching to remove the sacrificial medium layer and one end of the memory material layer close to the conductive connecting layer; and finally, carrying out third etching to remove the memory material layer covering the lower end of the side wall, and completely removing the residual insulating layer in the upper channel by three etching processes. In addition, in the whole etching process, the sacrificial dielectric layer plays a role in protection and can protect the material layer below from being etched, so that a silicon dioxide layer used as a hard mask does not need to be deposited, a manufacturing process of the three-dimensional memory is reduced, the production cost is reduced, and meanwhile, the production time is shortened.
Based on the foregoing method, and with reference to fig. 4G, an embodiment of the present invention further provides a three-dimensional memory, including:
the grid laminated structure comprises a plurality of layers of grids 11 which are arranged at intervals;
the channel structure penetrates through the grid laminated structure and comprises a lower channel column, a conductive connecting layer 14 and an upper channel column which are sequentially arranged along the stacking direction of the grid;
the upper channel pillar includes:
a channel layer 16 having a lower end extending into the conductive connection layer 14 and contacting the conductive connection layer 14;
a memory layer surrounding a portion of the channel layer 16 and located on a top surface of the conductive connection layer 14.
Wherein, in one embodiment, the memory layer has a bottom surface facing the conductive connection layer 14 along the direction, the bottom surface not being lower than the top surface of the conductive connection layer 14;
the channel layer 16 also covers the bottom surface.
More specifically, the bottom surface may be an arc shape recessed in a direction from the lower channel pillar toward the conductive connection layer 14.
In one embodiment, the memory layer includes a blocking dielectric layer 151, a storage dielectric layer 152, and a tunneling dielectric layer 153 sequentially disposed along a radial inward direction of the upper channel pillar.
In one embodiment, the channel layer 16 and the conductive connection layer 14 are the same material. For example, the material may be polysilicon or the like.
It should be noted that: the technical schemes described in the embodiments of the present invention can be combined arbitrarily without conflict.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (15)
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| CN111180463A (en) * | 2020-01-03 | 2020-05-19 | 长江存储科技有限责任公司 | Three-dimensional memory and method of making the same |
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| CN113035883A (en) | 2021-06-25 |
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