CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority of Chinese Patent Application No. 202211642523.7, filed on Dec. 20, 2022, the content of which is incorporated herein by reference in its entirety.
FIELD OF THE TECHNOLOGY
This application relates to the field of semiconductor technology and, specifically, to a three-dimensional (3D) memory device and fabrication method for improved yield and reliability.
BACKGROUND OF THE DISCLOSURE
Not-AND (NAND) memory is a non-volatile type of memory that does not require power to retain stored data. The growing demands of consumer electronics, cloud computing, and big data bring about a constant need of NAND memories of larger capacity and better performance. As conventional two-dimensional (2D) NAND memory approaches its physical limits, 3D NAND memory is now playing an important role. 3D NAND memory uses multiple stack layers on a single die to achieve higher density, higher capacity, faster performance, lower power consumption, and better cost efficiency.
SUMMARY
In one aspect of the present disclosure, a 3D memory device includes a conductor/insulator stack containing a conductive layer and a first dielectric layer alternatingly stacked, a region of memory cells in the conductor/insulator stack, and a gate line slit (GLS) structure extending along a first direction. The GLS structure includes a first section adjacent to the region of memory cells, a second region adjacent to the first section, and a third section adjacent to the second section. The second section is between the first and third sections. The width of the second section is larger than the width of the first section and the width of the third section along a second direction, respectively. The second direction is perpendicular to the first direction.
In another aspect of the present disclosure, a 3D memory device includes a conductor/insulator stack including a conductive layer and a first dielectric layer alternatingly stacked, a region of memory cells in the conductor/insulator stack, and a GLS structure extending along a direction. The GLS structure includes a first section adjacent to the region of memory cells and a second section adjacent to and aligned with the first section. The length of the second section is substantially shorter than the length of the first section along the direction.
In another aspect of the present disclosure, a method for fabricating a 3D memory device includes forming a dielectric stack, forming a channel hole structure extending through the dielectric stack along a first direction, and forming a first opening and a second opening. The dielectric stack includes a first dielectric layer and a second dielectric layer alternately stacked. The first direction is perpendicular to the first and second dielectric layers. The first and second openings are formed for a first section and a second section of a gate line slit (GLS) structure, respectively. The second opening is separated from and adjacent to the first opening. The first and second openings extend through the dielectric stack along the first direction and extend along a second direction that is parallel to the first and second dielectric layers. The length of the second opening is substantially shorter than the length of the first opening along the second direction.
Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a cross-sectional view of a structure of an exemplary 3D array device at a certain stage during a fabrication process according to various aspects of the present disclosure;
FIG. 2 illustrates a top view of the 3D array device shown in FIG. 1 after channel hole structures are formed during the fabrication process according to various aspects of the present disclosure;
FIGS. 3 and 4 illustrate a top view and a across-sectional view of the 3D array device shown in FIG. 2 after openings for GLS are formed according to various aspects of the present disclosure;
FIG. 5 illustrates a across-sectional view of the 3D array device shown in FIG. 4 after the openings for GLS are filled according to various aspects of the present disclosure;
FIGS. 6 and 7 illustrate a top view and a across-sectional view of the 3D array device after the openings for GLS are filled according to various aspects of the present disclosure;
FIGS. 8 and 9 illustrate cross-sectional views of the 3D array device shown in FIG. 7 after openings for the short sections are formed and then filled during the fabrication process according to various aspects of the present disclosure;
FIGS. 10 and 11 illustrate a top view and a cross-sectional view of the 3D array device shown in FIG. 9 after an opening for staircase contact (SCT) is formed according to various aspects of the present disclosure;
FIGS. 12 and 13 illustrate a cross-sectional view and a top view of the 3D array device shown in FIGS. 10 and 11 at a certain stage according to various aspects of the present disclosure;
FIGS. 14 and 15 illustrate cross-sectional views of the 3D array device shown in FIG. 13 at certain stages in the fabrication process according to various aspects of the present disclosure;
FIGS. 16 and 17 illustrate a top view and a cross-sectional view of the 3D array device shown in FIG. 15 after sacrificial stack layers are etched according to various aspects of the present disclosure;
FIGS. 18 and 19 illustrate a cross-sectional view and a top view of the 3D array device shown in FIGS. 16 and 17 after conductive layers are formed according to various aspects of the present disclosure;
FIGS. 20 and 21 illustrate a top view and a cross-sectional view of the 3D array device shown in FIGS. 18 and 19 at a certain stage according to various aspects of the present disclosure;
FIGS. 22 and 23 illustrate a cross-sectional view and a top view of the 3D array device shown in FIGS. 20 and 21 after SCTs are formed according to various aspects of the present disclosure;
FIG. 24 illustrates a cross-sectional view of the 3D array device shown in FIGS. 22 and 23 at a certain stage in the fabrication process according to various aspects of the present disclosure;
FIG. 25 illustrates a cross-sectional view of an exemplary periphery device according to various aspects of the present disclosure;
FIG. 26 illustrates a cross-sectional view of a 3D memory device after the 3D array device shown in FIG. 24 is bonded with the periphery device shown in FIG. 25 according to various aspects of the present disclosure;
FIG. 27 illustrates a schematic flow chart of fabrication of a 3D memory device according to various aspects of the present disclosure;
FIG. 28 illustrates a block diagram of an exemplary system having memory devices according to various embodiments of the present disclosure;
FIG. 29 illustrates a diagram of an exemplary memory card having a memory device according to various aspects of the present disclosure; and
FIG. 30 illustrates a diagram of an exemplary solid-state drive (SSD) having memory devices according to various aspects of the present disclosure.
DETAILED DESCRIPTION
The following describes the technical solutions according to various aspects of the present disclosure with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Apparently, the described aspects are merely some but not all of the aspects of the present disclosure. Features in various aspects may be exchanged and/or combined.
FIGS. 1-24 schematically show a fabrication process of an exemplary 3D array device 100 according to aspects of the present disclosure. The 3D array device 100 is a part of a memory device and may also be referred to as a 3D memory structure. Among the figures, top views are in an X-Y plane and cross-sectional views are in a Y-Z plane or taken along a line in the X-Y plane.
As shown in a cross-sectional view in FIG. 1, a structure of the 3D array device 100 includes a substrate 110. In some aspects, the substrate 110 may include a single crystalline silicon layer. The substrate 110 may also include another semiconductor material, such as germanium (Ge), silicon-germanium (SiGe), silicon carbide (SiC), silicon-on-insulator (SOI), germanium-on-insulator (GOI), polysilicon, or a Group III-V compound such as gallium arsenide (GaAs) or indium phosphide (InP). Optionally, the substrate 110 may also include an electrically non-conductive material such as glass, a plastic material, or a ceramic material. When the substrate 110 includes glass, plastic, or ceramic material, the substrate 110 may further include a thin layer of polysilicon deposited on the glass, plastic, or ceramic material. In this case, the substrate 110 may be processed like a polysilicon substrate. As an example, the substrate 110 includes an undoped or lightly doped single crystalline silicon layer in descriptions below.
In some aspects, a layer 132 (e.g., a polysilicon layer) is deposited over the substrate 110. Further, layers 133, 134, and 135 are grown sequentially over the layer 132. The layers 133, 134, and 135 may exemplarily be a silicon oxide layer, a silicon nitride layer, and a polysilicon layer. Optionally, the layers 132-134 may be sacrificial layers and etched away at a certain stage. The layers may be deposited by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or a combination thereof.
Further, a dielectric stack 140 is formed over the layers 132-135. The dielectric stack 140 may be considered as a dielectric stack structure that includes multiple pairs of stack layers, for example, including first dielectric layers 141 and second dielectric layers 142, stacked alternately over each other. Some layers of the dielectric stack 140 are used to form memory cells. In some cases, the layers for fabricating memory cells may include 64 pairs, 128 pairs, or more than 128 pairs of the first and second dielectric layers 141 and 142.
In some aspects, the first dielectric layers 141 and the second dielectric layers 142 are made of different materials. In descriptions below, the first dielectric layer 141 includes a silicon oxide layer exemplarily, which is used as an isolation stack layer, while the second dielectric layer 142 includes a silicon nitride layer exemplarily, which is used as a sacrificial stack layer. The sacrificial stack layer will be subsequently etched out and replaced by a conductive stack layer. The first dielectric layers 141 and second dielectric layers 142 may be deposited via CVD, PVD, ALD, or a combination thereof. Further, a dielectric layer 111 (e.g., a silicon oxide layer) is deposited over the dielectric stack 140 by CVD or PVD.
FIG. 2 shows a schematic top view of the structure of the 3D array device 100 after channel hole structures are formed according to aspects of the present disclosure. Channel hole structures 150 are configured in memory cell regions 112 and 113. Dummy channel hole structures 150A are arranged outside the memory cell regions 112 and 113 and staircase contact (SCT) regions 114 and 115. The SCT regions 114 and 115 are arranged for SCTs. The quantity, dimension, and arrangement of the channel hole structures 150 and dummy channel hole structures 150A as shown in FIG. 2 and in other figures in the present disclosure are exemplary and for description purposes, although any suitable quantity, dimension, and arrangement may be used for the disclosed 3D array device 100 according to various aspects of the present disclosure.
FIGS. 3 and 4 show a schematic top view and a schematic cross-sectional view of the structure of the 3D array device 100 shown in FIG. 2 after openings for GLS are formed according to aspects of the present disclosure. The cross-sectional view shown in FIG. 4 is taken along a line AA′ of FIG. 3. A GLS may also be referred to as a GLS structure. Openings 160-168 are formed for the GLS structures exemplarily. The 3D array device 100 has a great number of channel hole structures 150 arranged in memory planes (not shown). Each memory plane is divided into memory blocks and memory fingers by the GLS structures. For example, the channel hole structures 150 between the openings 160 and 162 may reflect a memory block, which exemplarily includes two memory fingers separated by the opening 161.
The openings for GLS may be formed by, for example, a dry etch process or a combination of dry and wet etch processes. In a horizontal plane or X-Y plane, the openings extend in the X direction, respectively. The openings 160, 161, and 162 are arranged for the main section of GLS and adjacent to the memory cell regions. For example, the memory cell region 112 of FIG. 2 is between the openings 160 and 161, and the memory cell region 113 is between the openings 161 and 162. The openings 163 and 164 are arranged for the side section of GLS and adjacent to the SCT regions. For example, the SCT regions 114 and 115 of FIG. 2 are between the openings 163 and 164 and away from the memory cell regions. The openings 165, 166, 167, and 168 are arranged for the short section of GLS and adjacent to the end of opening 160 or 162. The opening 166 is between the openings 160 and 163, while the opening 168 is between the openings 162 and 164.
Provided the openings 160-162 have a width w1, the openings 163-164 have a width w2, and the openings 165-168 have a width w3. The width is measured along the Y direction. In some embodiments, w1, w2, and w3 may have the same value or similar values. Optionally, w1, w2, and w3 may have different values. For example, w1 and w2 may have the same value or similar values, while w3 may have a value larger than that of w1 and w2. For example, the value of w3 may be at least 20-50% larger than that of w1 and w2. In the X-Y plane, some of the openings, e.g., the openings 160, 163, 165, and 166, may be aligned with respect the Y axis. Alternatively, these openings may not be aligned with respect the Y axis. For example, these openings may have an offset smaller than 10-50% of w1.
Provided the length of the openings 165-168 is s along the X direction. In some embodiments, the value of s may be in a range of w1 to four times of w1. In some cases, the value of s may be substantially smaller than the lengths of the openings 160-164 along the X direction. For example, in some aspects, the value of s may be a thousand times or even ten thousand times smaller than the length of the opening 160 and/or the length of the opening 163. Provided the distance between openings of the main section and short section is d1 in the X direction, and the distance between openings of the side section and short section is d2 in the X direction. The values of d1 and d2 may be the same or similar in some cases. Optionally, the values of d1 and d2 may be different in some other cases. In some aspects, the values of d1 and d2 may be in a range of half w1 to three times of w1.
As shown in FIG. 4, the openings for GLS such as the openings 160 and 163 extend through the dielectric stack 140 and reach the layer 135 in the Z direction or in a direction approximately perpendicular to the substrate 110. As illustrated above, the layer 135 may be a polysilicon layer. In some cases, an oxidation process is performed such that exposed portions of the layer 135 at the bottoms of the openings 160-168 are oxidized and become oxide regions, such as oxide regions 135A and 135B as shown in FIG. 4.
FIG. 4 also shows the channel hole structures 150 that extend in the Z direction or in a direction approximately perpendicular to the substrate 110. The channel hole structures 150 and dummy channel hole structures 150A are formed in channel holes concurrently. The channel holes may be formed by, for example, a dry etch process or a combination of dry and wet etch processes. The channel holes may have a cylindrical shape or pillar shape that extends through the dielectric stack 140, the layer 133-135, and partially penetrates the layer 132. In some aspects, the channel holes may have a taper angle (not shown), and the horizontal dimension of the channel hole may decrease gradually from the top to the bottom. Similarly, the openings 160-168 may also have a taper angle (not shown). For example, the width of the openings 160-168 may decrease gradually from the top to the bottom. After the channel holes are formed, a functional layer 151 is deposited on the sidewall and bottom of the channel hole. The functional layer 151 includes a blocking layer 152 on the sidewall and bottom of the channel hole to block an outflow of charges, a charge trap layer 153 on a surface of the blocking layer 152 to store charges during an operation of the 3D array device 100, and a tunneling layer 154 on a surface of the charge trap layer 153. The blocking layer 152 may include one or more layers that may include one or more materials. The material for the blocking layer 152 may include silicon oxide, silicon nitride, silicon oxynitride, a high-k dielectric material such as aluminum oxide or hafnium oxide, or another wide bandgap material. The charge trap layer 153 may include one or more layers that may include one or more materials. The materials for the charge trap layer 153 may include polysilicon, silicon nitride, silicon oxynitride, nanocrystalline silicon, a high-k dielectric material such as aluminum oxide or hafnium oxide, or another wide bandgap material. The tunneling layer 154 may include one or more layers that may include one or more materials. The material for the tunneling layer 154 may include silicon oxide, silicon nitride, silicon oxynitride, a high-k dielectric material such as aluminum oxide or hafnium oxide, or another wide bandgap material.
Further, a semiconductor channel 155 is deposited on a surface of the tunneling layer 154. The semiconductor channel 155 includes a polysilicon layer in some aspects. Optionally, the semiconductor channel 155 may include an amorphous silicon layer. Like the channel holes, the semiconductor channel 155 also extends through the dielectric stack 140 and layers 133-135, and into the layer 132. The blocking layer 152, the charge trap layer 153, the tunneling layer 154, and the semiconductor channel 155 may be deposited by, e.g., CVD and/or ALD. The structure formed in a channel hole, including the functional layer 151 and semiconductor channel 155, is referred to as the channel hole structure.
After the semiconductor channel 155 is formed, the opening of the channel hole is filled by an oxide material 156 and a conductive plug that connects to the semiconductor channel 155 electrically. In some cases, the functional layer 151 includes an oxide-nitride-oxide (ONO) structure. That is, the blocking layer 152 is a silicon oxide layer, the charge trap layer 153 is a silicon nitride layer, and the tunneling layer 154 is another silicon oxide layer.
Optionally, the functional layer 151 may have a structure different from the ONO configuration. In the following descriptions, the ONO structure is used exemplarily for the blocking layer 152, the charge trap layer 153, and the tunneling layer 154.
After the oxide regions at the bottoms of the openings 160-168 are made, CVD and/or ALD is performed to fill the openings with a material such as polysilicon. The openings 160-168 are filled with filling structures 160A-168A, respectively. For example, the openings 160 and 163 are filled with the filling structures 160A and 163A, as depicted in FIG. 5.
FIGS. 6 and 7 show a schematic top view and a schematic cross-sectional view of the structure of the 3D array device 100 after the filling structures 160A-168A are made according to aspects of the present disclosure. The cross-sectional view shown in FIG. 7 is taken along a line BB′ of FIG. 6 and depicts the filling structure 166A. The filling structures 160A-168A may have the same dimensions as or similar dimensions to that of the openings 160-168. Further, the filling structures 165A-168A are removed by a selective etch, such as a selective wet etch. Openings for the short section of GLS are formed once again after the selective etch.
FIG. 8 shows a schematic cross-sectional view of the structure of the 3D array device 100 after the filling structure 166A is removed and an opening 166B is made. As aforementioned, the width of the opening 166B is w3. Sides of the second dielectric layers 142 are exposed in the opening 166B. In some cases, a timed selective etch (e.g., a selective wet etch) is performed to remove the exposed second dielectric layers 142, leaving cavities (not shown) of a certain depth between the first dielectric layers 141 and surrounding the opening 166B. As the opening 166B is between the filling structures 160A and 163A in the X direction, the timed selective etch may be arranged long enough such that these two filling structures are exposed in the cavities in some aspects. For the same reasons, the filling structures 162A and 164A are exposed in cavities as well.
The openings for the short sections and cavities surrounding the openings are subsequently filled by a dielectric material, such as silicon oxide or nitrogen-doped silicon carbide (NDC) by CVD and/or ALD, forming dielectric filling structures 165C-168C and first filling layers 142A. The first filling layers 142A are made of the dielectric material. The first filling layers 142A and first dielectric layers 141 are alternatingly stacked over each other and surround the filling structures 165C-168C, respectively. In some cases, voids may form in the filling structures. As shown in FIG. 9, the filling structure 166C extends through the dielectric stack 140 and reaches the oxide region in the Z direction. The first filling layers 142A contact the filling structures 160A and 163A along the X direction, respectively, when the two filling structures are exposed in the cavities. The filling structures 165C-168C may be considered as the short sections of GLS in some aspects. In some embodiments, the short section of GLS may include a filling structure (e.g., the filling structure 166C) and the dielectric layers (e.g., the first filling layers 142A and first dielectric layers 141 alternately stacked) surrounding the filling structure. In these cases, the width of the short section of GLS becomes w4. As illustrated in FIG. 9, w4 is larger than w3 in the Y direction. In some aspects, w4 is also larger than w1 and w2 in the Y direction.
As illustrated above, the filling structures 160A-164A and 165C-168C are formed after the channel hole structures 150 are fabricated. Alternatively, these filling structures may be formed before the channel hole structures 150 are made. For example, the openings 160-168 may be etched first. Then the filling structures may be made, respectively. Further, the channel hole structures 150 and dummy channel hole structures 150A may be formed.
FIGS. 10 and 11 show a schematic top view and a schematic cross-sectional view of the structure of the 3D array device 100 after the filling structures 165C-168C and first filling layers 142A are made according to aspects of the present disclosure. The cross-sectional view shown in FIG. 11 is taken along a line CC′ of FIG. 10. The dotted lines as shown in FIG. 10 illustrate the boundary of the short section of GLS in some cases. For example, a dotted line 166D depicts the border line of a first filling layer 142A that surrounds the filling structure 166C and reaches the filling structures 160A and 163A underneath the surface. As aforementioned, the widths of the filling structures 165C-168C and the short section are w3 and w4, respectively.
FIGS. 10 and 11 show an opening 120 arranged for SCT. The opening 120 may be formed by, for example, a dry etch process or a combination of dry and wet etch processes. The opening 120 extends in the X and Y directions horizontally, and penetrates through the dielectric stack 140 and reaches a target second dielectric layer 142 in the Z direction or a direction approximately perpendicular to the substrate 110. The opening for SCT such as the opening 120 may have a circular shape in an X-Y plane in some embodiments. Optionally, the opening for SCT may have another shape (e.g., a square or rectangular shape) in the X-Y plane in some other cases. In descriptions below, the circular shape is used exemplarily. The first and second dielectric layers 141 and 142 are exposed on the sidewall of the opening 120. As aforementioned, the second dielectric layer 142 may be a sacrificial silicon nitride layer. At the bottom of the opening 120, the target second dielectric layer 142 is also exposed. Further, a dielectric material (e.g., silicon oxide or aluminum oxide) is deposited to grow a spacer layer 121A by CVD or ALD. The spacer layer 121A is configured to protect second dielectric layers 142 that are exposed on the sidewall.
An etch, such as a dry etch, is conducted to etch away the spacer layer 121A at the bottom of the opening 120 to expose the target second dielectric layer 142. Further, a selective wet etch is performed to etch out a section of the target second dielectric layer 142. A cavity (not shown) is formed between the first dielectric layers 141. The selective wet etch is conducted for a predetermined etch time to control the depth of the cavity.
Further, a filling material such as carbon is deposited to fill the opening 120 and the cavity by CVD and/or ALD. The opening 120 and the cavity are filled with a filling structure 121 and a second filling layer 121B, respectively. The second filling layer 121B is deposited between adjacent first dielectric layers 141. FIGS. 12 and 13 show a schematic cross-sectional view and a schematic top view after the filling structure 121 and second filling layer 121B are formed. The cross-sectional view shown in FIG. 12 is taken along a line DD′ of FIG. 13.
Further, the methods used for making the opening 120, spacer layer 121A, filling structure 121, and second filling layer 121B are performed repeatedly. More openings for SCT are formed to reach respective second dielectric layers 142 separately. For each opening, a spacer layer is deposited on the sidewall, a cavity is etched between the first dielectric layers 141 at the bottom, and then a second filling layer and a filling structure are deposited by CDD and/or ALD. The spacer layer, second filling layer, and filling structure in each opening contain the same materials as those of the spacer layer 121A, second filling layer 121B, and filling structure 121, respectively. Filling structures 121, 122, 123, and 124 are shown in FIG. 13 exemplarily.
FIG. 14 shows a schematic cross-sectional view of the structure of the 3D array device 100 after the filling structure 163A is etched according to aspects of the present disclosure. When the filling structure 163A is removed in a selective etch (e.g., a selective wet etch), the filling structure 164A is removed concurrently. Etching the filling structure 163A creates an opening 163B. As shown in FIG. 14, sides of the second dielectric layers 142 and the bottom oxide region 135B are exposed in the opening 163B.
Further, a selective etch is performed for a predetermined time period to remove certain sections of the exposed second dielectric layers 142, leaving cavities (not shown) between the first dielectric layers 141. The second filling layers (e.g., the second filling layer 121B) are exposed in corresponding cavities. The opening 163B and the cavities are filled by a material that is the same as that of the second filling layers and filing structures 121-124. A filling structure 163C is formed in the opening 163B, while layers 142B are formed in the cavities, as illustrated in FIG. 15. Concurrently, a filling structure 164C (not shown) is formed that replaces the filling structure 164A. Each of layers 142B is between adjacent first dielectric layers 141 and contacts a corresponding second dielectric layer 142. Some of the layer 142B contact the second filling layers (e.g., the second filling layer 121B), respectively.
FIGS. 16 and 17 show a schematic top view and a schematic cross-sectional view of the structure of the 3D array device 100 at a certain stage according to aspects of the present disclosure. The cross-sectional view shown in FIG. 17 is taken along a line EE′ of FIG. 16. Openings 160B, 161B, and 162B are created, after the filling structures 160A-162A are removed in a selective etch (e.g., a selective wet etch). The oxide regions at the bottoms of the openings and sides of the second dielectric layers 142 on the sidewalls are exposed. Thereafter, the exposed second dielectric layers 142 are removed in a selective etch such as a selective wet etch, creating cavities 143 between the first dielectric layers 141 and changing the dielectric stack 140 into a dielectric stack 144, which is depicted exemplarily in FIG. 17. The layers 142B are exposed in some of the cavities 143, respectively. Further, the filling structures 121-124 and 163C-164C, second filling layers, layers 142B, and spacer layers are etched away in one or more selective wet etches. When the filling structures 121-124 and 163C-164C, second filling layers, and layers 142B are made of carbon, these structures and layers may also be selectively removed by a burning process. Openings are formed by removal of the filling structures 121-124 and 163C-164C and spacer layers. The cavities 143 expand horizontally after removal of the second filling layers and layers 142B.
Thereafter, a conductive material such as tungsten (W) is grown to fill the cavities 143, forming conductive layers 145 between the first dielectric layers 141. After the conductive layers 145 are fabricated, the dielectric stack 144 is converted into a conductor/insulator stack 146, as shown in FIG. 18. FIGS. 18 and 19 show a schematic cross-sectional view and a schematic top view of the structure of the 3D array device 100 at a certain stage. The cross-sectional view shown in FIG. 18 is taken along a line FF′ of FIG. 19. FIG. 19 shows openings 160B-162B, 163D-164D, and 121C-124C that are formed by removing the filling structures, respectively. The first and second dielectric layers 141 and 142 are exposed on the sidewalls of the openings 121C-124C. The stack 146 may be considered as a conductor/insulator stack structure that contains the channel hole structures 150, or the functional layers 151 and semiconductor channels 155. The conductor/insulator stack 146 includes the first dielectric layers 141 and conductive layers 145 that are alternatingly stacked over each other. In some aspects, before metal W is deposited in the cavities 143, a dielectric layer (not shown) of a high-k dielectric material such as aluminum oxide may be deposited. Thereafter, a layer of a conductive material such as titanium nitride (TiN) (not shown) is deposited. Further, metal W is deposited to form the conductive layers 145. CVD and/or ALD may be used in the deposition processes. Alternatively, another conductive material, such as molybdenum (Mo), ruthenium (Ru), cobalt (Co), copper (Cu), aluminum (Al), titanium (Ti), tantalum (Ta), tantalum nitride (TaN), doped silicon, or any combination thereof, may be used to form the conductive layers 145.
Referring to FIG. 18, a portion of each functional layer 151 in a channel hole structure 150 is between a portion of one of the conductive layers 145 and a portion of a semiconductor channel 155 in the channel hole structure 150. The conductive layer 145 is configured to connect rows of NAND memory cells in an X-Y plane and configured as a word line for the 3D array device 100. The semiconductor channel 155 formed in the channel hole structure 150 is configured to connect a column or a string of NAND memory cells along the Z direction and configured as a bit line for the 3D array device 100. As such, a portion of the functional layer 151 in the channel hole structure 150 in an X-Y plane, as a part of a NAND memory cell, is arranged between a conductive layer 145 and a semiconductor channel 155, i.e., between a word line and a bit line. The functional layer 151 may also be considered as disposed between the semiconductor channel 155 and the conductor/insulator stack 146. A portion of the conductive layer 145 that is around a portion of the channel hole structure 150 functions as a control gate or gate electrode for a NAND memory cell. The 3D array device 100 can be considered as including a 2D array of strings of NAND cells (such a string is also referred to as a “NAND string”) in the stack 146 or the conductor/insulator stack structure. Each NAND string contains multiple NAND memory cells and extends vertically toward the substrate 110. The NAND strings form a 3D array of the NAND memory cells through the conductor/insulator stack 146 over the substrate 110.
FIGS. 20 and 21 show a schematic top view and a schematic cross-sectional view of the structure of the 3D array device 100 at a certain stage according to aspects of the present disclosure. The cross-sectional view shown in FIG. 21 is taken along a line GG′ of FIG. 20. After the conductive layers 145 are grown in the cavities 143, a dielectric layer (e.g., a silicon oxide layer) is deposited on sidewalls and bottom surfaces of the openings 160B-162B, 163D-164D, and 121C-124C by CVD and/or ALD. Further, a material (e.g., undoped polysilicon or silicon oxide) is deposited to fill these openings by CVD and/or ALD, followed by an optional chemical mechanical polishing (CMP) process. The filling process creates filling structures 160C-162C, 163E-164E, and 121D-124D, as shown in FIGS. 20 and 21. Voids may form in certain filling structures during the filling process.
Referring to FIG. 20, GLS structures 116, 117, and 118 are formed when the filling structures are made. Each GLS structure contains one or more sections extending along a direction (e.g., the X direction). The GLS structure 116 includes the filling structures 160C, 163E, and 165C-166C, corresponding to the main section, side section, and short sections. The GLS structure 117 includes the filling structure 161C, corresponding to the main section. The GLS structure 118 includes the filling structures 162C, 164E, and 167C-168C, corresponding to the main section, side section, and short sections. For the GLS structures 116 and 118, a main section is adjacent to and between two short sections. That is, a short section is adjacent to one end of the main section, while the other short section is adjacent to the other end of the main section. One of the short sections is adjacent to and between a main section and a side section. For the GLS structure 116, in some aspects, the first filling layers 142A and first dielectric layers 141, alternately stacked and surrounding its middle short section, contact its main section and side section along the X direction. In some other cases, the first filling layers 142A around a short section are not made and the second dielectric layers 142 may be replaced by the conductive layers 145. Then, for the GLS structure 116, the first dielectric layers 141 and conductive layers 145, alternately stacked and surrounding its middle short section, contact its main section and side section.
As the sections of the GLS structures are made in the openings 160-168, these sections have certain dimensions of the openings 160-168 with respect to FIG. 3. As such, the main sections have the width w1, the side sections have the width w2, and the short sections have the width w3. In some aspects, w1, w2, and w3 may have the same value or similar values. Optionally, w1, w2, and w3 may have different values. Exemplarily, w1 and w2 may have the same value or similar values, while w3 may have a value larger than that of w1 and w2. Optionally, the value of w3 may be at least 20-50% larger than that of w1 and w2. In an X-Y plane, the sections of a GLS structure (e.g., the GLS structure 116) may be aligned with respect the Y axis. Alternatively, these sections may not be aligned with respect the Y axis. Optionally, these sections may have an offset smaller than 10-50% of w1 with respect to the Y axis.
The length of the sections of the GLS structures is measured along the X direction. The length of the short section is s. Optionally, the value of s may be in a range of w1 to four times of w1 and substantially smaller than the lengths of the main section and side section, e.g., at least ten times smaller. The distance between the main section and short section is d1 in the X direction, and the distance between the side section and short section is d2 in the X direction. The values of d1 and d2 may be the same or similar in some cases. Optionally, the values of d1 and d2 may be different in some other cases. In some cases, the values of d1 and d2 may be in a range of half w1 to three times of w1.
In some aspects, the memory cell regions 113 and 114 each may represent a memory finger, and together may represent a memory block that is between the GLS structures 116 and 118 or between the two main sections of the GLS structures 116 and 118. The memory finger is between the GLS structures 117 and 116 (or 118), or between the main sections of the GLS structures 117 and 116 (or 118).
As illustrated above, the filling structures 163A-164A are removed after the filling structures 165C-168C are made to form the short sections. The short sections may function as a blocking structure. When the filling structures 163A-164A are etched or second dielectric layers 142 are etched through certain openings in regions of the side sections (e.g., the opening 163B), the filling structures 160A and 162A may be shielded from the etch by the short sections. As such, the memory cell regions 113 and 114 may be shielded to a certain extent from the etch in regions of the side sections. Thus, certain fabrication issues may be avoided. The yield and reliability may be improved.
FIGS. 22 and 23 show a schematic cross-sectional view and a schematic top view of the structure of the 3D array device 100 after SCTs are made according to aspects of the present disclosure. The cross-sectional view shown in FIG. 22 is taken along a line HH′ of FIG. 23. After the GLS structures are formed, the filling structures 121D-124D in the SCT regions 114 and 115 are etched away in a selective etch (e.g., a selective wet etch), forming openings (not shown). The dielectric layers coated on the sidewalls are also etched in the etch or another selective etch. A conductive layer 145 is exposed at the bottom of each opening. Sides of certain first and second dielectric layer 141 and 142 are exposed on the sidewall.
Further, a conductive material is deposited by CVD and/or ALD. The conductive material may include a metallic material such as W in some aspects. The deposition creates a conductor layer on the sidewall and bottom of the opening. The conductor layer electrically contacts the exposed conductive layer 145 (i.e., word lines) at the bottom. Optionally, before forming the conductor layer, a conductive material such as TiN may be deposited first to grow a contact and/or barrier layer on the sidewall and bottom of the opening.
After the conductor layer is formed, a dielectric material such as silicon oxide is deposited by CVD to fill the openings with dielectric filling structures 121E-124E. Voids may form in the dielectric filling structures in some cases. Further, a conductive material (e.g., W, Co, Cu, Al, or Ti) is deposited to form SCTs 121F-124F. CVD may be performed in some aspects. The SCTs include the conductor layers, respectively. Each SCT is electrically connected to a corresponding conductive layer 145 through a conductor layer. In some cases, the SCTs each contact and are surrounded by the first and second dielectric layers 141 and 142 alternately stacked over each other.
As shown in FIG. 23, the SCT regions 114 and 115 are between the side sections that correspond to the filling structures 163E and 164E. Each SCT region is adjacent to one of the side sections and away from the main sections and the memory cell regions. Conductive layers 145 in the SCT regions 114 and 115 are electrically and respectively connected to conductive layers 145 in the memory cell regions 112 and 113 by parts of conductive layers 145 around and adjacent to the short sections and side sections. Thus, an SCT in an SCT region is electrically connected to a conductive layer 145 in the memory cell region by a part of a conductive layer 145. The part of the conductive layer 145 is between the SCT region and memory cell region and adjacent to a short section and a side section.
Further, a conductive material such as W, Co, Cu, Al, or Ti is deposited to make vias such as vias 171 and 172. The vias 171 and 172 are aligned with and contact the SCT 121F and the upper end of a channel hole structure 150, respectively. Further, conductor layers (such as metal lines) 173 are deposited for interconnect, and then vias 174 and connecting pads 175-179 are made, as shown in FIG. 24. Conductive materials (e.g., W, Co, Cu, Al, Ti, or a combination thereof) and CVD and/or ALD may be used in the deposition processes. Optionally, a contact/barrier layer (e.g., TiN) may be deposited first before depositing the conductive material. The 3D array structure shown in FIG. 24 may be referred to as the 3D array device 100.
FIG. 25 shows a schematic cross-sectional view of a periphery device 180 according to aspects of the present disclosure. The periphery device 180 is a part of a 3D memory device and may also be referred to as a peripheral structure. The periphery device 180 includes a substrate 181 that may include single crystalline silicon, Ge, SiGe, SiC, SOI, GOI, polysilicon, or a Group III-V compound such as GaAs or InP. Periphery CMOS circuits 182 (e.g., control circuits) are fabricated on the substrate 181 and used for facilitating the operation of the 3D memory device. For example, the periphery CMOS circuits 182 may include metal-oxide-semiconductor field-effect transistors (MOSFETs) and provide functional devices such as page buffers, sense amplifiers, column decoders, and row decoders. A dielectric layer 183 is deposited over the substrate 181 and CMOS circuits 182. Connecting pads (such as connecting pads 184-188) and vias are formed in the dielectric layer 183. The dielectric layer 183 includes one or more dielectric materials such as silicon oxide and silicon nitride. The connecting pads 184-188 are formed to connect with the 3D array device 100 and may include a conductive material such as W, Co, Cu, Al, Ti or a combination thereof.
For the 3D array device 100 and periphery device 180, the bottom side of the substrate 110 or 181 may be referred to as the back side, and the side with the connecting pads 175-179 or 184-188 may be referred to as the front side or face side.
FIG. 26 schematically shows a fabrication process of an exemplary 3D memory device 190 in a cross-sectional view according to aspects of the present disclosure. The 3D memory device 190 includes the 3D array device 100 shown in FIG. 24 and the periphery device 180 shown in FIG. 25. In some embodiments, the 3D array device 100 and the periphery device 180 are fabricated separately and then bonded together to form the 3D memory device 190. Alternatively, the periphery device 180 may be made first, and the 3D array device 100 may be built using the device 180 as a substrate component, forming an integrated 3D memory device.
Provided the 3D array device 100 and periphery device 180 are bonded by a flip-chip bonding method to form the 3D memory device 190, as shown in FIG. 26. In some aspects, the 3D array device 100 is flipped vertically and becomes upside down with the top surfaces of the connecting pads 175-179 facing downward. The two devices are placed together such that the 3D array device 100 is above the periphery device 180. After an alignment is made, e.g., the connecting pads 175-179 are aligned with the connecting pads 184-188, respectively, the 3D array device 100 and periphery device 180 are joined face to face and bonded together. The conductor/insulator stack 146 and the periphery CMOS circuits 182 become sandwiched between the substrates 110 and 181. In some aspects, a solder or a conductive adhesive is used to bond the connecting pads 175-179 with the connecting pads 184-188, respectively. As such, the connecting pads 175-179 are connected to the connecting pads 184-188, respectively.
Thereafter, other fabrication steps or processes are performed to complete fabrication of the 3D memory device 190. The other fabrication steps and processes are not reflected in FIG. 26 for simplicity. For example, after the flip-chip bonding, the substrate 110 of the 3D array device 100 may be removed from the bottom by a thinning process, such as wafer grinding, dry etch, wet etch, CMP, or a combination thereof. As aforementioned, the layers 132-135 may be polysilicon, silicon oxide, silicon nitride, and polysilicon, respectively. The layer 132 is exposed first and etched. After the layer 132 is removed, the layer 133 and blocking layers 152 become exposed. Then, layers 133-134 and 152-154 are etched out by certain selective etches. The layer 135 and semiconductor channel 155 are exposed. A conductive material or semiconductor material (e.g., doped polysilicon) may be deposited to form a layer that connects with semiconductor channels 155 and functions as an array common source in some cases. Further, additional fabrication steps or processes are performed. Details of the additional fabrication steps or processes are omitted for simplicity.
FIG. 27 shows a schematic flow chart 200 for fabricating a 3D memory device according to aspects of the present disclosure. At 210, a substrate is provided for fabricating a 3D array device. The substrate includes a semiconductor substrate, such as a single crystalline silicon substrate. Sacrificial layers are deposited over a top surface of the substrate. The sacrificial layers may include polysilicon, silicon oxide, and silicon nitride.
Over the sacrificial layers, a dielectric stack is fabricated. The dielectric stack includes a first stack layer and a second stack layer that are alternately stacked. The first stack layer includes a first dielectric layer and the second stack layer includes a second dielectric layer that is different than the first dielectric layer. In some aspects, one of the first and second dielectric layers is used as a sacrificial stack layer.
At 211, channel holes are formed that extend through the dielectric stack and some of the sacrificial layers. A functional layer is deposited on the sidewall and bottom of each channel hole. The functional layer includes a blocking layer, a charge trap layer, and a tunneling layer that are deposited sequentially. Thereafter, a semiconductor channel is deposited on a surface of the tunneling layer. Channel hole structures in memory cell regions are configured to make memory cells. Channel hole structures formed outside memory cell regions are dummy channel hole structures and configured for providing mechanical support when certain cavities are etched. A planarization process may be performed after the channel hole structures are made.
At 212, openings for GLS are formed by etch. Along a direction vertical to the substrate, the openings extend through the dielectric stack. In a horizontal plane, the openings are parallel to each other and extend along the same direction. Some GLS structures have a main section, a side section, and one or more short sections, and are used to divide memory cells into memory blocks. The main, side, and short sections of a GLS structure extend and are positioned along a straight line. Some GLS structures have a main section only and are used to divide a memory block into memory fingers. The short sections are substantially shorter than the main section and side section. The mains sections are adjacent to memory cell regions. The side sections are away from the memory cell regions and adjacent to SCT regions. Optionally, memory cell regions may be memory fingers configured between the main sections. When a GLS structure has a main section, a side section, and a short section, the short section is adjacent to and between the main and a side sections. When a GLS structure has a main section, a side section, and two short sections, the short sections are adjacent to the ends of the main section respectively, and one of the short sections is adjacent to the side section and between the main and side sections. The openings for GLS are filled with first filling structures in a deposition process.
At 213, the first filling structures in regions of the short section are etched away selectively and openings are formed. The sacrificial stack layers exposed on the sidewall of the opening are etched away selectively, creating cavities between the other stack layers. In some cavities, the first filling structures in the main and side sections are exposed. Thereafter, one or more dielectric materials such as silicon oxide are deposited. The openings are filled with a dielectric filling structure and the cavities are filled with first filling layers. In some aspects, the dielectric filling structure is referred to as the short section of a GLS structure. The dielectric filling structure is surrounded the first filling layers. In some cases, when the first filling layers are between regions of a main and side section, these first filling layers are between and contact the first filling structures in the regions.
At 214, an opening for SCT is formed in an SCT region. The opening for SCT reaches a target sacrificial stack layer at the bottom. A dielectric spacer layer is formed on the sidewall of the opening. A section of the target sacrificial stack layer is removed by a selective wet etch, creating a cavity around the bottom of the opening. A deposition process is performed to fill the cavity with a second filling layer and fill the opening with a second filling structure. With similar methods, other openings for SCT are formed respectively, and cavities are etched at the bottoms after removal of target sacrificial stack layers in different depths. These openings and cavities are filled with second filling structures and second filling layers, respectively.
At 215, the first filling structures in regions of the side sections are removed in a selective wet etch. Openings are made and sides of the sacrificial stack layers are exposed on the sidewalls of the openings. The exposed sacrificial stack layers are etched in a timed selective wet etch, creating cavities around the openings. The second filling layers in the SCT regions are exposed in some of the cavities. A deposition process is performed to fill the cavities with third filling layers and fill the openings with third filling structures.
At 216, the first filling structures in regions of the main sections are removed in a selective wet etch, creating openings and exposing sides of the sacrificial stack layers on the sidewalls. The exposed sacrificial stack layers are etched in a selective wet etch, leaving cavities between and around the openings in the dielectric stack. Further, the second and third filling structures and second and third filling layers are removed in one or more selective removing processes. Removal of the second and third filling structures creates openings in the SCT regions and regions of the side sections. Removal of the exposed sacrificial stack layers and second and third filling layers creates cavities extending from the memory cell regions to the SCT regions in the dielectric stack. In some cases, the first filling layers are exposed in the cavities. Thereafter, a deposition process is performed to fill the cavities with conductive materials (e.g., W). Conductive layers are formed in the cavities. The dielectric stack is transformed into a conductor/insulator stack.
At 217, dielectric layers are deposited on the sidewalls and bottom surfaces of the openings. The openings are then filled with dielectric materials or semiconductor materials. Openings in regions of the main and side sections are filled to make the main and side sections of the GLS structures. Openings in the SCT regions are filled with fourth filling structures. When the first filling layers are between a main section and a side section, these first filling layers contact the main and side sections in some cases.
At 218, the fourth filling structures and dielectric layers on the sidewalls in the SCT regions are removed by a selective wet etch, forming openings for SCT. In each opening for SCT, a conductive layer is exposed at the bottom. A conductive material such as W is deposited inside the openings for SCT. Conductor layers are grown on the sidewalls and bottoms. Each conductor layer electrically contacts a corresponding conductive layer (i.e., a word line). The openings are then filled with a dielectric material and conductive top parts that connect to the conductor layers, respectively. The SCTs are formed and they are used as the contacts for word lines. The conductive top part may contain a conductive material such as W, Co, Cu, Al, or Ti.
Further, vias, conductor layers such as metal lines, and connecting pads are formed for interconnect. The vias, metal lines, and connecting pads may contain a conductive material such as W, Co, Cu, Al, or Ti.
At 219, a 3D memory device is fabricated. In some aspects, a flip-chip bonding process is performed to bond the 3D array device and a periphery device to create the 3D memory device. In some other cases, a periphery device is made first. Thereafter, the 3D array device is formed over the periphery device, creating an integrated 3D memory device. Referring to the former scenario, the 3D array device is flipped upside down and positioned above the periphery device. The connecting pads of the 3D array device and the periphery device are aligned and then bonded. Further, the substrate of the 3D array device is removed, and the sacrificial layers are etched. Deposition processes are performed to form vias, conductor layers, and contact pads. The contact pads are configured for wire bonding for connection with other devices.
FIG. 28 shows a block diagram of an exemplary system 300 having a memory device according to various aspects of the present disclosure. The system 300 may be a mobile phone (e.g., a smartphone), a desktop computer, a laptop computer, a tablet, a vehicle computer, a gaming console, a printer, a positioning device, a wearable electronic device, a smart sensor, a virtual reality (VR) device, an argument reality (AR) device, or any other suitable electronic devices having storage therein. As shown in FIG. 28, the system 300 may include a host 308 and a memory system 302 having one or more memory devices 304 and a memory controller 306. The host 308 may be a processor of an electronic device, such as a central processing unit (CPU), or a system-on-chip (SoC), such as an application processor (AP). The host 308 may be configured to send or receive data to or from the memory devices 304.
The memory controller 306 is coupled to the memory devices 304 and host 308 and is configured to control the memory devices 304, according to some implementations. The memory controller 306 may manage the data stored in the memory devices 304 and communicate with the host 308. In some embodiments, the memory controller 306 is designed for operating in a low duty-cycle environment like secure digital (SD) cards, compact Flash (CF) cards, universal serial bus (USB) Flash drives, or other media for use in electronic devices, such as personal computers, digital cameras, mobile phones, etc. In some other embodiments, the memory controller 306 is designed for operating in a high duty-cycle environment, such as solid-state drives (SSDs) or embedded multi-media-cards (eMMCs) used as data storage for mobile devices, such as smartphones, tablets, laptop computers, etc., and enterprise storage arrays. The memory controller 306 may be configured to control operations of the memory device 304, such as read, erase, and program operations.
The memory controller 306 may also be configured to manage various functions with respect to the data stored or to be stored in the memory device 304 including, but not limited to bad-block management, garbage collection, logical-to-physical address conversion, wear leveling, etc. In some implementations, the memory controller 306 is further configured to process error correction codes (ECCs) with respect to the data read from or written to the memory device 304. Any other suitable functions may be performed by the memory controller 306 as well, for example, formatting the memory device 304. The memory controller 306 may communicate with an external device (e.g., the host 308) according to a particular communication protocol. For example, the memory controller 306 may communicate with the external device through at least one of various interface protocols, such as a USB protocol, an MMC protocol, a peripheral component interconnection (PCI) protocol, a PCI-express (PCI-E) protocol, an advanced technology attachment (ATA) protocol, a serial-ATA protocol, a parallel-ATA protocol, a small computer small interface (SCSI) protocol, an enhanced small disk interface (ESDI) protocol, an integrated drive electronics (IDE) protocol, a Firewire protocol, etc.
The memory device 304 may be any memory device disclosed in the present disclosure, such as the 3D memory device 190 shown in FIG. 26. As the 3D memory device 190 may have improved yield and reliability due to the reasons described above, when the device 190 is used, the system 300 may have a lower cost and improved reliability.
The memory controller 306 and one or more memory devices 304 may be integrated into various types of storage devices, for example, be included in the same package, such as a universal Flash storage (UFS) package or an eMMC package. That is, the memory system 302 may be implemented and packaged into different types of end electronic products. FIGS. 29 and 30 exemplarily illustrate block diagrams of a memory card 400 and an SSD 500 according to various aspects of the present disclosure. As shown in FIG. 29, a memory controller 404 and a single memory device 402 may be integrated into the memory card 400. The memory device 402 may be any memory device illustrated above, such as the 3D memory device 190 shown in FIG. 26. The memory card 400 may include a PC card (personal computer memory card international association (PCMCIA)), a CF card, a smart media (SM) card, a memory stick, a multimedia card (MMC, RS-MMC, or MMCmicro), an SD card (SD, miniSD, microSD, or SDHC), a UFS, etc. The memory card 400 may further include a memory card connector 406 configured to couple the memory card 400 to a host (e.g., the host 308 shown in FIG. 28). As shown in FIG. 30, a memory controller 504 and multiple memory devices 502 may be integrated into the SSD 500. The memory devices 502 may be any aforementioned memory device, such as the 3D memory device 190 shown in FIG. 26. The SSD 500 may further include an SSD connector 506 configured to couple the SSD 500 to a host (e.g., the host 308 shown in FIG. 28). In some embodiments, the storage capacity and/or the operation speed of the SSD 500 is greater than those of the memory card 400.
Although the principles and implementations of the present disclosure are described by using specific aspects in the specification, the foregoing descriptions of the aspects are only intended to help understand the present disclosure. In addition, features of aforementioned different aspects may be combined to form additional aspects. A person of ordinary skill in the art may make modifications to the specific implementations and application range according to the idea of the present disclosure. Hence, the content of the specification should not be construed as a limitation to the present disclosure.
Patent Application
20240206162
