Three-dimensional memory device with backside interconnect structure

Abstract

To provide a three-dimensional memory device with a backside interconnect structure.SOLUTION: An embodiment of a three-dimensional memory device and a method for forming the same are disclosed. In one example, the three-dimensional memory device comprises: a substrate; a memory stack including conductor layers and dielectric layers which are alternately arranged above the substrate; a plurality of channel structures each vertically penetrating the memory stack; a semiconductor layer provided above the plurality of channel structures and in contact with the plurality of channel structures; a plurality of source contacts provided above the memory stack and in contact with the semiconductor layer; a plurality of contacts passing through the semiconductor layer; and a backside interconnect layer provided above the semiconductor layer including a source line mesh in plan view. The plurality of source contacts are distributed below the source line mesh and in contact with the source line mesh. A first set of the plurality of contacts is distributed below the source line mesh and in contact with the source line mesh.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to International Application No. PCT / CN2020 / 084600, filed April 14, 2020, entitled "THREE-DIMENSIONAL MEMORY DEVICE WITH BACKSIDE SOURCE CONTACT," and International Application No. PCT / CN2020 / 084603, filed April 14, 2020, entitled "METHOD FOR FORMING THREE-DIMENSIONAL MEMORY DEVICE WITH BACKSIDE SOURCE CONTACT," all of which are incorporated herein by reference in their entireties.

[0002] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to three-dimensional (3D) memory devices and methods for fabricating the same. [Background technology]

[0003] Planar memory cells are being scaled to smaller sizes by improving process technology, circuit design, programming algorithms, and fabrication processes. However, as memory cell feature sizes approach lower limits, planar processes and fabrication techniques become more difficult and costly. As such, the memory density of planar memory cells is approaching an upper limit.

[0004] 3D memory architectures can address this density limitation of planar memory cells. 3D memory architectures include a memory array and peripheral devices for controlling signals to and from the memory array. Summary of the Invention [Means for solving the problem]

[0005] SUMMARY OF THE INVENTION Disclosed herein are embodiments of 3D memory devices and methods for forming the same.

[0006] In one example, a 3D memory device includes a substrate, a memory stack including alternating conductive and dielectric layers above the substrate, a plurality of channel structures each vertically penetrating the memory stack, a semiconductor layer above the plurality of channel structures and in contact with the plurality of channel structures, a plurality of source contacts above the memory stack and in contact with the semiconductor layer, a plurality of contacts through the semiconductor layer, and a backside interconnect layer above the semiconductor layer including a source line mesh in a plan view. The plurality of source contacts are distributed below the source line mesh so as to contact the source line mesh. A first set of the plurality of contacts is distributed below the source line mesh so as to contact the source line mesh.

[0007] In another example, a 3D memory device includes a substrate, a memory stack including alternating conductive and dielectric layers above the substrate, a plurality of channel structures each extending vertically through the memory stack, a semiconductor layer above and in contact with the plurality of channel structures, a plurality of source contacts in contact with the semiconductor layer, and a backside interconnect layer above the semiconductor layer in a plan view including a source line mesh, each of the channel structures below and laterally aligned with a respective one of the source contacts, and a source line mesh above and in contact with each of the source contacts.

[0008] In yet another example, a method for forming a 3D memory device is disclosed. A peripheral circuit is formed on a first substrate. A plurality of channel structures are formed, each vertically penetrating a memory stack on the front side of a second substrate. The first substrate and the second substrate are bonded face-to-face, such that the channel structures are above the peripheral circuit. The second substrate is thinned. A plurality of contacts are formed through the thinned second substrate and a plurality of source contacts are formed in contact with the thinned second substrate. A source line mesh is formed on the back side of the thinned second substrate, the source line mesh overlying and in contact with the plurality of source contacts and a first set of the plurality of contacts.

[0009] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the art to make and use the present disclosure. [Brief explanation of the drawings]

[0010] [Figure 1] 1A-1C are cross-sectional plan views of an exemplary 3D memory device having a central staircase region, according to some embodiments of the present disclosure. [Figure 2A] 1A and 1B are plan views illustrating cross sections of example 3D memory devices with backside interconnect structures according to some embodiments of the present disclosure. [Figure 2B] 1 is a cross-sectional plan view of another exemplary 3D memory device with a backside interconnect structure in accordance with some embodiments of the present disclosure. [Figure 2C] 1A is a cross-sectional plan view of yet another exemplary 3D memory device with a backside interconnect structure in accordance with some embodiments of the present disclosure. FIG. [Figure 3] 1A and 1B are cross-sectional side views of an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. [Figure 4]FIG. 10 is a cross-sectional plan view of yet another exemplary 3D memory device comprising a backside interconnect structure in accordance with some embodiments of the present disclosure. [Figure 5] 1 is a cross-sectional side view of another exemplary 3D memory device with a backside interconnect structure in accordance with some embodiments of the present disclosure. [Figure 6A] 1A-1C illustrate a fabrication process for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. [Figure 6B] 1A-1C illustrate a fabrication process for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. [Figure 6C] 1A-1C illustrate a fabrication process for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. [Figure 6D] 1A-1C illustrate a fabrication process for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. [Figure 7] 1 is a flowchart of a method for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0012] While specific configurations and arrangements are described, it will be understood that this is done for illustrative purposes only. A person skilled in the art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present disclosure. It will be apparent to those skilled in the art that the present disclosure can be employed in a variety of other applications.

[0013] It should be noted that references in the specification to "one embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," etc., indicate that the described embodiment may comprise a particular feature, structure, or characteristic, but that all embodiments may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it will be within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0014] Generally, terms can be understood, at least in part, from their usage in context. For example, the phrase "one or more," as used herein, can be used in a singular sense to describe a feature, structure, or characteristic, or in a plural sense to describe a combination of features, structures, or characteristics, depending at least in part on the context. Similarly, again, articles such as "a," "an," or "the" in English may be understood as conveying singular use or conveying plural use, depending at least in part on the context. Additionally, the phrase "based on" can be understood as not necessarily intended to convey an exclusive series of elements, but instead may permit the presence of additional elements not necessarily explicitly recited, again depending at least in part on the context.

[0015] It should be readily understood that the meanings of "on," "above," and "directly above" in this disclosure should be interpreted in the broadest sense, such that "on" not only means "directly above" something, but can also mean "on top of" something with an intervening feature or layer, and "above" or "directly above" not only means "above" something or "directly above" something, but can also mean "above" something or "directly above" something (i.e., directly above) without any intervening features or layers.

[0016] Spatially relative terms such as "below," "lower," "lower," "above," "upper," and similar terms may be used herein for ease of description in describing the relationship of one element or feature to another, as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be oriented in some other way (rotated 90 degrees or at some other orientation), and the spatially relative descriptors used herein similarly interpreted accordingly.

[0017] As used herein, the term "substrate" refers to a material onto which subsequent layers of material are applied. The substrate itself can be patterned. The material applied onto the substrate can be patterned or left unpatterned. Additionally, the substrate can include a wide range of semiconductor materials, such as silicon, germanium, gallium arsenide, indium phosphide, etc. Alternatively, the substrate can be made from an electrically non-conductive material, such as glass, plastic, or a sapphire wafer.

[0018] As used herein, the term "layer" refers to a portion of material that includes a region having a thickness. A layer may extend across an underlying or overlying structure, or may have an extent that is less than the extent of the underlying or overlying structure. Furthermore, a layer may be a region of a homogeneous or heterogeneous continuous structure having a thickness that is less than the thickness of the continuous structure. For example, a layer may be disposed between the top and bottom surfaces of a continuous structure, or between a pair of horizontal surfaces at the top and bottom surfaces. A layer may extend along a horizontal, vertical, and / or tapered surface. A substrate may be a layer and may include one or more layers therein and / or have one or more layers on, above, and / or below it. A layer may also include multiple layers. For example, an interconnect layer may include one or more conductor layers and contact layers (in which interconnect lines and / or vertical interconnect access (via) contacts are formed) and one or more dielectric layers.

[0019] As used herein, the phrase "nominal / nominally" refers to a desired or target value of a characteristic or parameter for a component or process operation established during the design phase of a product or process, along with a range of values ​​above and / or below the desired value. The range of values ​​may be due to slight variations in the manufacturing process or manufacturing tolerances. As used herein, the term "about" indicates a value of a given quantity that may vary based on a particular technology node associated with the subject semiconductor device. Based on a particular technology node, the term "about" can indicate, for example, a value of a given quantity that varies within 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0020] As used herein, the term "3D memory device" refers to a semiconductor device having vertically oriented strings of memory cell transistors (referred to herein as "memory strings," such as NAND memory strings) on a laterally oriented substrate such that the memory strings extend vertically with respect to the substrate. As used herein, the phrase "vertical" means nominally perpendicular to the outer surface of the substrate.

[0021] In some 3D memory devices, peripheral circuits and memory arrays are stacked to save wafer area and increase memory cell density. For example, direct bonding techniques have been proposed to fabricate some 3D NAND memory devices (e.g., having 96 or more layers) by connecting peripheral devices and memory arrays face-to-face on different substrates. The memory array substrate is then thinned to form through-silicon vertical interconnects (VIAs), called "TSVs," that run through it to the vertical interconnects, which are padded out with wire bond pads on the backside of the thinned substrate. However, because only wire bond pads and TSVs are formed on the backside of the thinned substrate (i.e., the top surface of the bonded 3D memory device), a substantial amount of area on the backside of the thinned substrate is wasted.

[0022] Various embodiments according to the present disclosure provide 3D memory devices with backside interconnect structures that better utilize the backside area and optimize metal routing. Some or all of the source lines, source select gate (SSG) lines, and power lines can be moved from the front side of the memory array substrate (i.e., the center of the bonded 3D memory device) to the backside of the memory array substrate (i.e., the top surface of the bonded 3D memory device) as a “backside interconnect structure.” In some embodiments, the backside source lines enable source contacts to be formed on the backside of the memory array substrate, which can avoid leakage current and parasitic capacitance between the word lines on the front side and the source contacts through the memory stack. Various backside interconnect structures can be arranged in different layouts, such as meshes (e.g., comb-like shapes) or parallel straight lines, to optimize metal routing and reduce overall resistance based on different memory array structures, further improving the electrical performance of the 3D memory device.

[0023] FIG. 1 illustrates a cross-sectional plan view of an exemplary 3D memory device 100 having a central staircase region, according to some embodiments of the present disclosure. As shown in FIG. 1 , the memory stack of the 3D memory device 100 can include two core array regions 106A and 106B having channel structures 110 therein and a staircase region 104 between the core array regions 106A and 106B in a first lateral direction in the plan view. Note that x- and y-axes are included in FIG. 1 to illustrate two orthogonal directions in the wafer plane. The x-direction is the word line direction, and the y-direction is the bit line direction. The 3D memory device 100, according to some embodiments, includes a central staircase region 104 that laterally separates the memory stack in the x-direction (e.g., word line direction) into two portions, i.e., a first core array region 106A and a second core array region 106B, each of which includes an array of channel structures 110.

[0024] The 3D memory device 100, according to some embodiments, also comprises parallel isolation structures 108 (e.g., gate line slits (GLS)) in the y-direction (e.g., bit line direction), each extending laterally in the x-direction to separate the core array regions 106A and 106B and the array of channel structures 110 therein into blocks 102. The 3D memory device 100 may further comprise parallel drain select gate (DSG) cuts 112 (sometimes also referred to as top select gate (TSG) cuts) in the y-direction in the blocks 102 to further separate the blocks 102 into fingers. It will be understood that the layout of the staircase region and core array region is not limited to the example of FIG. 1 and may include any other suitable layout, such as having side staircase regions at the edges of the memory stack in other examples.

[0025] The cross section of the 3D memory device 100 is of the front side of the 3D memory device 100, where the channel structure 110 is formed. In some embodiments, the 3D memory device 100 is flipped upside down and bonded to another semiconductor device, such as a peripheral device having peripheral circuitry to facilitate operation of the 3D memory device 100. The back side of the 3D memory device 100 thus becomes the top surface of the bonded device and can be used for pad-out. As described in detail below, the area of ​​the back side of the 3D memory device 100 (i.e., the top surface of the bonded device) can be utilized to form various backside interconnect structures in various layouts, in addition to bonding pads, to optimize metal routing and reduce overall resistance, as well as reduce leakage current and parasitic capacitance on the front side of the 3D memory device 100.

[0026] FIG. 2A illustrates a cross-sectional plan view of an exemplary 3D memory device 200 including a backside interconnect structure according to some embodiments of the present disclosure. The 3D memory device 200 may be an example of a 3D memory device 100 after flip-chip bonding, and FIG. 2A illustrates an example of the backside of the 3D memory device 100 after flip-chip bonding. As shown in FIG. 2A , a memory stack of the 3D memory device 200 includes two core array regions 206A and 206B having channel structures (not shown) therein, and a staircase region 204 between the core array regions 206A and 206B in the x-direction (e.g., wordline direction) in the plan view, according to some embodiments. In some embodiments, the 3D memory device 200 further includes a peripheral region 208 outside the core array regions 206A or 206B of the memory stack in the plan view. In the y-direction (e.g., bitline direction), FIG. 2A shows the backside interconnect structure in one block 202 of the 3D memory device 200, which may be repeated any suitable number of times in multiple blocks.

[0027] In some embodiments, the 3D memory device 200 includes, in a plan view, a source line mesh 210. As shown in FIG. 2A , the source line mesh 210 has a comb-like shape, according to some embodiments. For example, the source line mesh 210 may include shaft source lines 214 extending laterally in the y-direction (e.g., bit line direction) in one of the core array regions 206A and 206B. The source line mesh 210 may also include a plurality of parallel tooth source lines 212 each extending laterally in the x-direction (e.g., word line direction) from the shaft source line 214 in one of the core array regions 206A through the staircase region 204 to the other core array region 206B. In some embodiments, the source line mesh 210 is within the core array regions 206A and 206B and the staircase region 204, e.g., extends in the x-direction across the core array regions 206A and 206B and the staircase region 204, but is not in the peripheral region 208.

[0028] The 3D memory device 200 may also include backside source contacts 216 (e.g., in the form of VIA contacts) in the core array regions 206A and 206B, but not in the staircase region 204 or the peripheral region 208. For example, the backside source contacts 216 may be evenly distributed in the core array region 206A or 206B. In some embodiments, the backside source contacts 216 are distributed below and in contact with the source line mesh 210. For example, the backside source contacts 216 may be evenly distributed below and in contact with the source line mesh 210 in the core array region 206A or 206B. That is, the distance (in the x-direction and / or y-direction) between adjacent backside source contacts 216 is the same in the core array region 206A or 206B. In some embodiments, the backside source contacts 216 are distributed below and in contact with the tooth source lines 212 of the source line mesh 210, but not the shaft source lines 214 of the source line mesh 210. It will be appreciated that in some examples, the backside source contacts 216 in the form of VIA contacts may be replaced with one or more source wall-shaped contacts, i.e., interconnect lines.

[0029] The 3D memory device 200 may further include multiple sets of contacts 218, 226, 230, such as through-silicon contacts (TSCs). In some embodiments, the contacts 218 are distributed below and in contact with the source line mesh 210 in the staircase region 204 and portions of the core array regions 206A and 206B. Because the contacts 218 may be TSCs that penetrate the silicon substrate, the contacts 218 are distributed below and in contact with peripheral portions of the source line mesh 210 (including portions of the staircase region 204) to avoid overlapping with the channel structure in the central portion of the source line mesh 210 in the core array regions 206A and 206B, according to some embodiments. For example, as shown in FIG. 2A , the contacts 218 may be distributed below and in contact with the shaft source lines 214 and outermost tooth source lines 212 of the source line mesh 210 in the core array regions 206A and 206B. The contacts 218 may also be distributed below and in contact with each tooth source line 212 of the source line mesh 210 within the staircase region 204 .

[0030] As described in detail below, each backside source contact 216 may be electrically connected to a common source (e.g., array common source (ASC)) of the NAND memory strings in block 202, and the source line mesh 210 electrically connects each backside source contact 216 and is then electrically connected to the common source of the NAND memory strings in block 202. Similarly, each contact 218 may be electrically connected to peripheral circuitry of the 3D memory device 200, and the source line mesh 210 electrically connects each contact 218 and is then electrically connected to the peripheral circuitry of the 3D memory device 200. As a result, the peripheral circuitry is electrically connected to the common source of the NAND memory strings in block 202 and can control and / or sense the common source through metal routing including the contacts 218, the source line mesh 210, and the backside source contacts 216 on the backside of the 3D memory device 200. The layout of the contacts 218, source line mesh 210, and backside source contacts 216, for example, the comb-like shape of the source line mesh 210 and the multiple distributed contacts 218 and backside source contacts 216, can reduce the overall resistance of the metal routing.

[0031] In some embodiments, the 3D memory device 200 includes, in a plan view, another backside interconnect structure—power line mesh 220. As shown in FIG. 2A , the power line mesh 220 has a comb-like shape, according to some embodiments. For example, the power line mesh 220 may include a shaft power line 224 extending laterally in the y-direction (e.g., bitline direction) in the peripheral region 208. The power line mesh 220 may also include a plurality of parallel tooth power lines 222 each extending laterally in the x-direction (e.g., wordline direction) from the shaft power line 224 in the peripheral region 208, through one core array region 206B, through the staircase region 204, and to the other core array region 206A. In some embodiments, the power line mesh 220 is within the peripheral region 208, the core array regions 206A and 206B, and the staircase region 204, e.g., extends in the x-direction from the peripheral region 208 across the core array regions 206A and 206B and the staircase region 204. In some embodiments, the tooth power lines 222 are interleaved with the tooth source lines 212 in the y-direction.

[0032] In some embodiments, the contacts 226 are distributed in the staircase region 204 and the peripheral region 208 so as to be below and in contact with the power line mesh 220, but not in the core array regions 206A and 206B. Because the contacts 226 may be TSCs that penetrate the silicon substrate, according to some embodiments, the contacts 226 are not in the core array regions 206A and 206B to avoid overlapping with the channel structures in the core array regions 206A and 206B. For example, as shown in FIG. 2A , the contacts 226 may be distributed below and in contact with portions of the shaft power lines 224 in the peripheral region 208 and the tine power lines 222 in the staircase region 204. It is understood that in some examples, the contacts 226 may be distributed in either the peripheral region 208 or the staircase region 204, but not both. That is, the contacts 226 may be distributed in a plan view in at least one of the staircase region 204 or the peripheral region 208 outside the memory array.

[0033] Each contact 226 may be electrically connected to a power line of the peripheral circuitry of the 3D memory device 200, and the power line mesh 220 electrically connects each contact 226 and is then electrically connected to the power line of the peripheral circuitry of the 3D memory device 200. A power source may be electrically connected to the power line mesh 220 through a bonding pad (not shown), and power can be supplied to the 3D memory device 200 through metal routing including the contacts 226 and the power line mesh 220 on the backside of the 3D memory device 200. The bonding pad is part of a backside interconnect structure and can be electrically connected to the power line mesh 220 through the contacts 226. The layout of the contacts 226 and the power line mesh 220, for example, the comb-like shape of the power line mesh 220, and the multiple distributed contacts 226, can reduce the overall resistance of the metal routing.

[0034] In some embodiments, the 3D memory device 200 includes yet another backside interconnect structure in the plan view—multiple SSG lines 228. Each SSG line 228 may extend in the x-direction (e.g., the word line direction) across the two core array regions 206A and 206B and the staircase region 204. In some embodiments, the SSG lines 228 are evenly distributed parallel to each other in the y-direction (e.g., the bit line direction) in the plan view. The SSG lines 228, the tooth power lines 222, and the tooth source lines 212 may be parallel to each other. As shown in FIG. 2A , each SSG line 228 may be sandwiched between two tooth power lines 222 in the y-direction. It is understood that the arrangement of the SSG lines 228, the tooth power lines 222, and the tooth source lines 212 may be different in other examples. For example, the SSG lines 228, the tooth power lines 222, and the tooth source lines 212 may be interleaved with each other in the y-direction.

[0035] In some embodiments, the contacts 230 are distributed in a plan view below and in contact with the SSG lines 228 in the core array regions 206A and 206B, but not in the staircase region 204 and the peripheral region 208. For example, as shown in FIG. 2A , at least one contact 230 in the core array region 206A and at least one contact 230 in the core array region 206B are below and in contact with each SSG line 228. The SSG in the memory stack of the 3D memory device 200 may be disconnected in the staircase region 204, resulting in two disconnected portions in the core array regions 206A and 206B, respectively. Each contact 230 may be electrically connected to a portion of the SSG of the 3D memory device 200 in its respective core array region 206A or 206B. Thus, by extending over the staircase region 204 between the two core array regions 206A and 206B in the x-direction and electrically connecting the contacts 230 in each core array region 206A or 206B, the SSG line 228 can electrically connect two uncoupled portions of the SSG in the core array regions 206A and 206B. That is, the two uncoupled portions of the SSG in the core array regions 206A and 206B can be “bridged” across the staircase region 204 by metal routing including the SSG line 228 and the contacts 230 on the backside of the 3D memory device 200. The layout of the contacts 230 and SSG line 228, for example, multiple parallel SSG lines 228 and multiple distributed contacts 230, can reduce the overall resistance of the metal routing.

[0036] It is understood that the backside interconnect structure is not limited to the example of FIG. 2A and may include any other suitable layout depending on the design of the 3D memory device, such as electrical performance specifications (e.g., voltage and resistance). It is also understood that additional backside interconnect structures may be disposed on the same surface as source line mesh 210, power line mesh 220, and SSG lines 228, as shown in FIG. 2A. For example, bonding pads (not shown) for wire bonding may also be disposed on the backside of 3D memory device 200, such as in peripheral region 208. It is further understood that one or more backside interconnect structures shown in FIG. 2A may not be disposed on the backside of the 3D memory device in other examples, and may be replaced by a counterpart frontside interconnect structure, for example, disposed on the frontside of the 3D memory device.

[0037] FIG. 2B illustrates a cross-sectional plan view of another exemplary 3D memory device 201 including a backside interconnect structure in accordance with some embodiments of the present disclosure. The 3D memory device 201 may be substantially the same as the 3D memory device 200 of FIG. 2A, except that the 3D memory device 201 does not include the SSG lines 228 and contacts 230 of FIG. 2A. FIG. 2C illustrates a cross-sectional plan view of yet another exemplary 3D memory device 203 including a backside interconnect structure in accordance with some embodiments of the present disclosure. The 3D memory device 203 may be substantially the same as the 3D memory device 200 of FIG. 2A, except that the 3D memory device 203 does not include the SSG lines 228, the power line mesh 220, and the contacts 230 and 226 of FIG. 2A. Furthermore, by removing the power line mesh 220, the source line mesh 210 in the 3D memory device 203 can have two parallel-shaft source lines 214 in the core array regions 206A and 206B, respectively.

[0038] FIG. 3 illustrates a cross-sectional side view of an exemplary 3D memory device 300 including a backside interconnect structure according to some embodiments of the present disclosure. The 3D memory device 300 may be an example of the 3D memory devices 200, 201, and 203 of FIGS. 2A-2C. FIGS. 2A-2C may illustrate a cross-sectional plan view of the 3D memory device 300 of FIG. 3 in the AA plane, i.e., within the backside of the 3D memory device 300. In some embodiments, the 3D memory device 300 is a bonded chip including a first semiconductor structure 302 and a second semiconductor structure 304 stacked on the first semiconductor structure 302. The first semiconductor structure 302 and the second semiconductor structure 304 are coupled at a bonding interface 306 therebetween according to some embodiments. As shown in FIG. 3, the first semiconductor structure 302 may include a substrate 301, which may include silicon (e.g., single crystal silicon, c-Si), silicon germanium (SiGe), gallium arsenide (GaAs), germanium (Ge), silicon-on-insulator (SOI), or any other suitable material.

[0039] The first semiconductor structure 302 of the 3D memory device 300 can include peripheral circuitry 308 on a substrate 301. Note that x, y, and z axes are included in FIG. 3 to illustrate the spatial relationships of the components in the 3D memory device 300. The substrate 301 includes two lateral surfaces extending laterally within the xy plane: a surface on the front side of the wafer and a back surface on the back side opposite the front side of the wafer. The x and y directions are two orthogonal directions within the wafer plane: the x direction is the word line direction and the y direction is the bit line direction. The z axis is perpendicular to both the x and y axes. As used herein, whether one component (e.g., a layer or device) is "on," "above," or "below" another component (e.g., a layer or device) of a semiconductor device (e.g., 3D memory device 300) is determined with respect to the substrate (e.g., substrate 301) of the semiconductor device in the z-direction (a vertical direction perpendicular to the xy-plane) when the substrate is positioned at the bottom plane of the semiconductor device in the z-direction. The same concepts for describing spatial relationships apply throughout this disclosure.

[0040] In some embodiments, the peripheral circuits 308 are configured to control and sense the 3D memory device 300. The peripheral circuits 308 may be any suitable digital, analog, and / or mixed-signal control and sensing circuitry used to facilitate operation of the 3D memory device 300, including, but not limited to, page buffers, decoders (e.g., row decoders and column decoders), sense amplifiers, drivers (e.g., word line drivers), charge pumps, current or voltage references, or any active or passive components of the circuitry (e.g., transistors, diodes, resistors, or capacitors). The peripheral circuits 308 may include transistors formed “on” the substrate 301, with the transistors formed in whole or in part within (e.g., below the top surface of) and / or directly above the substrate 301. Isolation regions (e.g., shallow trench isolation (STI)) and doped regions (e.g., source and drain regions of transistors) may also be formed within the substrate 301. The transistors are fast, according to some embodiments, using an advanced logic process (e.g., technology nodes such as 90 nm, 65 nm, 45 nm, 32 nm, 28 nm, 20 nm, 16 nm, 14 nm, 10 nm, 7 nm, 5 nm, 3 nm, etc.). It is understood that in some examples, the peripheral circuitry 308 may further include any other circuitry compatible with the advanced logic process, including logic circuits such as processors and programmable logic devices (PLDs), or memory circuits such as static random access memory (SRAM). In some embodiments, the peripheral circuitry 308 comprises one or more power lines for supplying power (e.g., voltage) to the peripheral circuitry 308.

[0041] In some embodiments, the first semiconductor structure 302 of the 3D memory device 300 further includes an interconnect layer (not shown) above the peripheral circuitry 308 to communicate electrical signals to and from the peripheral circuitry 308. The interconnect layer may include multiple interconnects (also referred to herein as “contacts”), including lateral interconnect lines and via contacts. As used herein, the term “interconnect” may be used broadly to include any suitable type of interconnect, such as middle-end-of-line (MEOL) interconnects and back-end-of-line (BEOL) interconnects. The interconnect layer may further include one or more interlayer dielectric (ILD) layers (also referred to as “inter-metal dielectric (IMD) layers”) in which the interconnect lines and via contacts may be formed. That is, the interconnect layer may include interconnect lines and via contacts in multiple ILD layers. The interconnect lines and via contacts in the interconnect layer may include conductive materials, including, but not limited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al), silicide, or any combination thereof. The ILD layers within the interconnect layer may comprise dielectric materials including, but not limited to, silicon oxide, silicon nitride, silicon oxynitride, low-k dielectrics, or any combination thereof.

[0042] As shown in FIG. 3 , the first semiconductor structure 302 of the 3D memory device 300 can further include a bonding layer 310 at the bonding interface 306 and above the interconnect layer and peripheral circuitry 308. The bonding layer 310 can include a plurality of bonding contacts 311 and a dielectric that electrically isolates the bonding contacts 311. The bonding contacts 311 can include a conductive material, including but not limited to, W, Co, Cu, Al, a silicide, or any combination thereof. The remaining regions of the bonding layer 310 can be formed of a dielectric, including but not limited to, silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric, or any combination thereof. The bonding contacts 311 and the surrounding dielectric within the bonding layer 310 can be used for hybrid bonding.

[0043] Similarly, as shown in FIG. 3 , the second semiconductor structure 304 of the 3D memory device 300 can also include a bonding layer 312 at the bonding interface 306 and above the bonding layer 310 of the first semiconductor structure 302. The bonding layer 312 can include a plurality of bonding contacts 313 and a dielectric that electrically isolates the bonding contacts 313. The bonding contacts 313 can include a conductive material, including but not limited to, W, Co, Cu, Al, a silicide, or any combination thereof. The remaining region of the bonding layer 312 can be formed of a dielectric, including but not limited to, silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric, or any combination thereof. The bonding contacts 313 and the surrounding dielectric within the bonding layer 312 can be used for hybrid bonding. The bonding contacts 313 contact the bonding contact 311 at the bonding interface 306, according to some embodiments.

[0044] As described in detail below, the second semiconductor structure 304 can be bonded face-to-face on top of the first semiconductor structure 302 at a bonding interface 306. In some embodiments, the bonding interface 306 is disposed between the bonding layers 310 and 312 as a result of a hybrid bond (also called a "metal / dielectric hybrid bond"), which is a direct bonding technique (e.g., forming a bond between surfaces without using an intermediate layer such as a solder or adhesive) that can simultaneously obtain a metal-to-metal bond and a dielectric-to-dielectric bond. In some embodiments, the bonding interface 306 is where the bonding layers 312 and 310 come into contact and bond. In practice, the bonding interface 306 can be a layer having a certain thickness that includes the top surface of the bonding layer 310 of the first semiconductor structure 302 and the bottom surface of the bonding layer 312 of the second semiconductor structure 304.

[0045] In some embodiments, the second semiconductor structure 304 of the 3D memory device 300 further includes an interconnect layer (not shown) above the bonding layer 312 to transfer electrical signals. The interconnect layer may include multiple interconnects, such as MEOL interconnects and BEOL interconnects. The interconnect layer may further include one or more ILD layers in which interconnect lines and VIA contacts may be formed. The interconnect lines and VIA contacts in the interconnect layer may include conductive materials including, but not limited to, W, Co, Cu, Al, silicide, or any combination thereof. The ILD layers in the interconnect layer may include dielectric materials including, but not limited to, silicon oxide, silicon nitride, silicon oxynitride, low-k dielectrics, or any combination thereof.

[0046] In some embodiments, the 3D memory device 300 is a NAND flash memory device in which memory cells are provided in the form of an array of NAND memory strings. As shown in FIG. 3 , the second semiconductor structure 304 of the 3D memory device 300 can include an array of channel structures 324 that function as the array of NAND memory strings. As shown in FIG. 3 , each channel structure 324 can vertically penetrate multiple pairs, each including a conductive layer 316 and a dielectric layer 318. The interleaved conductive layers 316 and dielectric layers 318 are part of a memory stack 314. The number of pairs of conductive layers 316 and dielectric layers 318 in the memory stack 314 (e.g., 32, 64, 96, 128, 160, 192, 224, 256, or more) determines the number of memory cells in the 3D memory device 300. It is understood that in some examples, the memory stack 314 can have a multi-deck architecture (not shown) including multiple memory decks stacked on top of each other. The number of pairs of conductive layers 316 and dielectric layers 318 in each memory deck may be the same or different.

[0047] The memory stack 314 may include multiple interleaved conductive layers 316 and dielectric layers 318. The conductive layers 316 and dielectric layers 318 within the memory stack 314 may alternate vertically. In other words, except for those at the top or bottom of the memory stack 314, each conductive layer 316 may be adjacent to two dielectric layers 318 on either side, and each dielectric layer 318 may be adjacent to two conductive layers 316 on either side. The conductive layers 316 may include conductive materials including, but not limited to, W, Co, Cu, Al, polysilicon, doped silicon, silicide, or any combination thereof. Each conductive layer 316 may include a gate electrode (gate line) surrounded by an adhesive layer and a gate dielectric layer. The gate electrode of the conductive layer 316 may extend laterally as a word line and terminate in one or more staircase structures in the memory stack 314. In some embodiments, the top conductive layer 316 functions as an SSG for controlling the source of the NAND memory string. The dielectric layer 318 may comprise a dielectric material including, but not limited to, silicon oxide, silicon nitride, silicon oxynitride, or any combination thereof.

[0048] As shown in FIG. 3 , the second semiconductor structure 304 of the 3D memory device 300 may also include a first semiconductor layer 320 above the memory stack 314 and a second semiconductor layer 322 above and in contact with the first semiconductor layer 320. The dopant type in each semiconductor layer 320 and 322 may be different in different embodiments. The semiconductor layers 320 and 322 may be considered a single semiconductor layer when the semiconductor layers 320 and 322 have the same type of dopant. It is understood that the number of semiconductor layers may be different in other examples and is not limited to the example shown in FIG. 3 .

[0049] In some embodiments, each channel structure 324 includes a channel hole filled with a semiconductor layer (e.g., as the semiconductor channel 328) and a composite dielectric layer (e.g., as the memory film 326). In some embodiments, the semiconductor channel 328 includes silicon, such as amorphous silicon, polysilicon, or single-crystal silicon. In some embodiments, the memory film 326 is a composite layer including a tunnel layer, a storage layer (also referred to as a "charge trapping layer"), and a blocking layer. The remaining space of the channel structure 324 may be partially or completely filled with a capping layer including a dielectric material such as silicon oxide and / or voids. The channel structure 324 may have a cylindrical shape (e.g., a pillar shape). The capping layer, semiconductor channel 328, tunnel layer, storage layer, and blocking layer of the memory film 326 are radially arranged in this order from the center toward the outer surface of the pillar, according to some embodiments. The tunnel layer may include silicon oxide, silicon oxynitride, or any combination thereof. The storage layer can include silicon nitride, silicon oxynitride, silicon, or any combination thereof. The blocking layer can include silicon oxide, silicon oxynitride, a high-k dielectric, or any combination thereof. In one example, the memory film 326 can include a silicon oxide / silicon oxynitride / silicon oxide (ONO) composite layer.

[0050] In some embodiments, the channel structure 324 further includes a channel plug 329 at a bottom (e.g., lower end) of the channel structure 324. As used herein, the “upper end” of a component (e.g., channel structure 324) is the end that is farther from the substrate 301 in the z-direction, and the “lower end” of a component (e.g., channel structure 324) is the end that is closer to the substrate 301 in the z-direction when the substrate 301 is positioned within the bottom-most plane of the 3D memory device 300. The channel plug 329 can include a semiconductor material (e.g., polysilicon). In some embodiments, the channel plug 329 functions as a drain for the NAND memory string.

[0051] As shown in FIG. 3 , each channel structure 324 can vertically penetrate the alternating conductive layers 316 and dielectric layers 318 of the memory stack 314 and the first semiconductor layer 320. In some embodiments, the first semiconductor layer 320 surrounds a portion of the channel structure 324 and is in contact with a semiconductor channel 328 comprising polysilicon. That is, the memory film 326, according to some embodiments, is discontinued at a portion of the channel structure 324 abutting the first semiconductor layer 320, exposing the semiconductor channel 328 to be in contact with the surrounding first semiconductor layer 320. In some embodiments, each channel structure 324 can further penetrate vertically into the second semiconductor layer 322. It is understood that the top structure of the channel structure 324 and its relative position with respect to the semiconductor layers 320 and 322 are not limited to the example of FIG. 3 and may vary in other examples.

[0052] 3 , the second semiconductor structure 304 of the 3D memory device 300 can further include insulating structures 330 that each vertically penetrate the alternating conductive layers 316 and dielectric layers 318 of the memory stack 314. Each insulating structure 330 can also extend laterally to separate the channel structures 324 into multiple blocks. That is, the memory stack 314 can be divided into multiple memory blocks by the insulating structures 330, thereby separating the array of channel structures 324 into each memory block. Unlike the slit structures of the existing 3D NAND memory devices described above, which include front-side ACS contacts, the insulating structures 330 do not include contacts therein (i.e., do not function as source contacts) and therefore, according to some embodiments, do not introduce parasitic capacitance and leakage current due to the conductive layers 316 (including word lines). In some embodiments, each insulating structure 330 comprises an opening (e.g., a slit) filled with one or more dielectric materials, including but not limited to silicon oxide, silicon nitride, silicon oxynitride, or any combination thereof. In one example, each insulating structure 330 can be filled with silicon oxide.

[0053] Instead of having a frontside source contact, the 3D memory device 300 may include a backside source contact 332 above the memory stack 314 and in contact with the second semiconductor layer 322. The backside source contact 332 may be one example of the backside source contact 216 of FIGS. 2A-2C. The source contact 332 and the memory stack 314 (and the insulating structure 330 therethrough) may be disposed on opposite sides of the semiconductor layer 322 (the thinned substrate) and may therefore be considered a “backside” source contact. In some embodiments, the source contact 332 penetrates further into the second semiconductor layer 322 and is electrically connected through the semiconductor layers 320 and 322 to the semiconductor channel 328 of the channel structure 324. It is understood that the depth to which the source contact 332 penetrates into the second semiconductor layer 322 may vary in different examples. In some embodiments in which the second semiconductor layer 322 is an N-well, the source contact 332 is also referred to as a backside “N-well pickup.” The source contact 332 may include any suitable type of contact. In some embodiments, the source contact 332 includes a via contact (as the backside source contact 216 in FIGS. 2A-2C). In some embodiments, the source contact 332 includes a laterally extending wall-shaped contact. The source contact 332 may include one or more conductive layers, such as a metal layer (e.g., W, Co, Cu, or Al) or a silicide layer surrounded by an adhesive layer (e.g., titanium nitride (TiN)).

[0054] 3, the 3D memory device 300 can further include a BEOL backside interconnect layer 333 overlying and in contact with the source contact 332 for pad-out, e.g., to transfer electrical signals between the 3D memory device 300 and an external circuit. The backside interconnect layer 333 can also include the example backside interconnect structure described above in FIGS. 2A-2C. In some embodiments, the backside interconnect layer 333 includes one or more ILD layers 334 over the second semiconductor layer 322 and a redistribution layer 336 over the ILD layer 334. The upper end of the source contact 332 is flush with the top surface of the ILD layer 334 and the bottom surface of the redistribution layer 336, according to some embodiments, and the source contact 332 penetrates vertically through the ILD layer 334 into the second semiconductor layer 322. The ILD layer 334 in the backside interconnect layer 333 may comprise a dielectric material including, but not limited to, silicon oxide, silicon nitride, silicon oxynitride, a low-k dielectric, or any combination thereof.

[0055] The redistribution layer 336 in the backside interconnect layer 333 can include conductive materials, including, but not limited to, W, Co, Cu, Al, silicide, or any combination thereof. In one example, the redistribution layer 336 includes Al. Although not shown in FIG. 3 , it is understood that the redistribution layer 336 can be patterned to form various types of backside interconnect structures described herein, such as the source line mesh 210, power line mesh 220, and SSG line 228 of FIG. 2A . In one example, the source contact 332 may be below the source line mesh 210 in the redistribution layer 336 and contact the source line mesh 210. In some embodiments, the backside interconnect layer 333 further includes a passivation layer 338 as an outermost layer for passivation and protection of the 3D memory device 300. A portion of the redistribution layer 336 can be exposed from the passivation layer 338 as a bonding pad 340. That is, the backside interconnect layer 333 of the 3D memory device 300 can also include bond pads 340 for wire bonding and / or bonding to an interposer. Although not shown in Figures 2A-2C, the bond pads 340 can also be part of the backside interconnect structure in some examples.

[0056] In some embodiments, the second semiconductor structure 304 of the 3D memory device 300 further includes contacts 342 and 344 through the second semiconductor layer 322. Because the second semiconductor layer 322 may be a thinned substrate, according to some embodiments, the contacts 342 and 344 are TSCs. The contact 342 may be an example of the contact 218 or 226 in FIGS. 2A and 2B. In some embodiments, the contact 342 penetrates the second semiconductor layer 322 and the ILD layer 334 to contact the redistribution layer 336 (e.g., including the source line mesh 210 and the power line mesh 220). For example, the source of a NAND memory string may be electrically connected to the contact 342 (e.g., as the contact 218 in FIGS. 2A-2C) through the semiconductor layers 320 and 322, the source contact 332, and the redistribution layer 336 (e.g., having the source line mesh 210 in FIGS. 2A-2C). That is, contact 342 (either contact 218 or 226) can be below and in contact with source line mesh 210 or power line mesh 220, respectively, in redistribution layer 336. Although not shown in FIG. 3 , as an example of contact 230 in FIG. 2A , 3D memory device 300 can also include a contact (e.g., an example of contact 230 in FIG. 2A ) that penetrates further into memory stack 314 to contact one of the conductive layers 316 (i.e., SSG) of memory stack 314. The contact (e.g., as contact 230 in FIG. 2A ) can be below and in contact with SSG line 228 in redistribution layer 336.

[0057] In some embodiments, contact 344 penetrates second semiconductor layer 322 and ILD layer 334 to contact bond pad 340. Contacts 342 and 344 may each include one or more conductive layers, such as a metal layer (e.g., W, Co, Cu, or Al) or a silicide layer surrounded by an adhesive layer (e.g., TiN). In some embodiments, at least contact 344 further includes a spacer (e.g., a dielectric layer) to electrically insulate contact 344 from second semiconductor layer 322.

[0058] In some embodiments, the 3D memory device 300 further comprises peripheral contacts 346 and 348, each extending perpendicularly to the second semiconductor layer 322 outside the memory stack 314. Each peripheral contact 346 or 348 can have a depth greater than the depth of the memory stack 314 to extend perpendicularly from the bonding layer 312 to the second semiconductor layer 322 in a peripheral region corresponding to, for example, the peripheral region 208 and the staircase region 204 in FIGS. 2A-2C or the peripheral region of the core array regions 206A and 206B in which the contact 218 is disposed. In some embodiments, the peripheral contact 346 is below and in contact with the contact 342 such that the source line mesh 210 or the power line mesh 220 is electrically connected to the peripheral circuitry 308 in the first semiconductor structure 302. In one example, the sources of the NAND memory strings may be electrically connected to a portion of the peripheral circuitry 308 for controlling / sensing the sources of the NAND memory strings through the redistribution layer 336 (e.g., including the source line mesh 210), the contacts 342 (e.g., as the contacts 218), and the peripheral contacts 346. In another example, a power source may be electrically connected to power lines of the peripheral circuitry 308 for supplying power to the 3D memory device 300 through the redistribution layer 336 (e.g., including the power line mesh 220), the contacts 342 (e.g., as the contacts 226), and the peripheral contacts 346. In some embodiments, the peripheral contacts 348 are below and in contact with the contacts 344, such that the peripheral circuitry 308 in the first semiconductor structure 302 is electrically connected to the pad-out bonding pads 340 through at least the contacts 344 and the peripheral contacts 348. Peripheral contacts 346 and 348 may each include one or more conductive layers, such as a metal layer (e.g., W, Co, Cu, or Al) or a silicide layer surrounded by an adhesive layer (e.g., TiN).

[0059] As shown in FIG. 3 , the 3D memory device 300 also includes various local contacts (also referred to as “C1”) as part of the interconnect structure, in direct contact with structures within the memory stack 314. In some embodiments, the local contacts include channel local contacts 350 each below and in contact with a lower end of a respective channel structure 324. Each channel local contact 350 may be electrically connected to a bit line contact (not shown) for bit line fan-out. In some embodiments, the local contacts further include word line local contacts 352 each below and in contact with a respective conductive layer 316 (including word lines) in the staircase structure of the memory stack 314 for word line fan-out. Local contacts such as the channel local contacts 350 and word line local contacts 352 may be electrically connected to the peripheral circuitry 308 of the first semiconductor structure 302 through at least the bonding layers 312 and 310. Local contacts, such as the channel local contact 350 and the word line local contact 352, may each include one or more conductive layers, such as a metal layer (e.g., W, Co, Cu, or Al) or a silicide layer surrounded by an adhesive layer (e.g., TiN).

[0060] FIG. 4 is a plan view illustrating a cross section of yet another exemplary 3D memory device 400 including a backside interconnect structure, according to some embodiments of the present disclosure. The 3D memory device 400 may be an example of the 3D memory device 100 after flip-chip bonding, and FIG. 4 shows an example of the backside of the 3D memory device 100 after flip-chip bonding. As shown in FIG. 4 , the memory stack of the 3D memory device 400 includes two core array regions 406A and 406B having a channel structure 408 therein and a staircase region 404 between the core array regions 406A and 406B in the x-direction (e.g., word line direction) in the plan view, according to some embodiments. In the y-direction (e.g., bit line direction), FIG. 4 shows the backside interconnect structure in one block 402 of the 3D memory device 400, which may be repeated any suitable number of times in multiple blocks.

[0061] In some embodiments, the 3D memory device 400 includes a source line mesh 410 in a plan view. In some embodiments, the source line mesh 410 is located within the core array regions 406A and 406B and the staircase region 404. As shown in FIG. 4, the source line mesh 410 comprises, according to some embodiments, a plurality of parallel source lines 412 each extending laterally in the x-direction (e.g., word line direction) across the staircase region 404 and the core array regions 406A and 406B in a plan view, similar to the tooth source lines 212 of the source line mesh 210 of FIGS. 2A-2C. Unlike the source line mesh 210 having the single-shaft source line 214 of FIGS. 2A and 2B, the source line mesh 410 may also comprise a plurality of parallel source lines 414 each extending laterally in the y-direction (e.g., bit line direction) in a plan view. The parallel source lines 414 may be disposed within the core array regions 406A and 406B and the staircase region 404, as shown in FIG. 4. It is understood that in some examples, the source lines 414 may not be disposed in the staircase region 404, but only in the core array regions 406A and 406B.

[0062] The 3D memory device 400 may also include backside source contacts 416 (e.g., in the form of VIA contacts) in the core array regions 406A and 406B, but not in the staircase region 404. For example, the backside source contacts 416 may be evenly distributed in the core array region 406A or 406B. As shown in FIG. 4 , each channel structure 408, according to some embodiments, is below and laterally aligned with a respective one of the backside source contacts 416. That is, each channel structure 408 overlaps with a respective backside source contact 416 directly above the channel structure 408, thereby reducing resistance between the source of the NAND memory string and the backside source contact 416. In some embodiments, since the channel structures 408 are arranged in an array having rows and columns, the backside source contacts are also arranged in an array having rows and columns. Each source line 414 or 412 may contact each of the backside source contacts 416 in a row or column of the array in a plan view. In some embodiments, each source line 414 extending in the y-direction can contact each of the backside source contacts 416 in a column. In some examples, each source line 412 extending in the x-direction may contact each of the backside source contacts 416 in a row. In some embodiments, each source line 414 or 412 contacts each of the backside source contacts 416 in two adjacent rows or columns of the array in a plan view. For example, as shown in FIG. 4, each source line 414 extending in the y-direction may contact each of the backside source contacts 416 in two adjacent columns. Similarly, although not shown, each source line 412 extending in the x-direction may contact each of the backside source contacts 416 in two adjacent rows in other examples.

[0063] The 3D memory device 400 may further comprise contacts 418, such as TSCs. In some embodiments, the contacts 418 are distributed below and in contact with the source line mesh 410 in the staircase region 404 and portions of the core array regions 406A and 406B. Because the contacts 418 may be TSCs that penetrate the silicon substrate, the contacts 418 are distributed below and in contact with peripheral portions of the source line mesh 410 (including portions of the staircase region 404) to avoid overlapping with the channel structures 408 in the central portion of the source line mesh 410 in the core array regions 406A and 406B, according to some embodiments. For example, as shown in FIG. 4 , the contacts 418 may be distributed below and in contact with the outermost source lines 412 and 414 in the core array regions 406A and 406B. Contacts 418 may also be distributed below the source lines 414 in the staircase region 404 to contact the source lines 414 .

[0064] As described in detail below, each backside source contact 416 may be electrically connected to the source of a respective NAND memory string, and the source line mesh 410 electrically connects each backside source contact 416 and is then electrically connected to the source of the NAND memory string. Similarly, each contact 418 may be electrically connected to peripheral circuitry of the 3D memory device 400, and the source line mesh 410 electrically connects each contact 418 and is then electrically connected to the peripheral circuitry of the 3D memory device 400. As a result, the peripheral circuitry is electrically connected to the source of the NAND memory string and can control and / or sense the source through metal routing including the contact 418, the source line mesh 410, and the backside source contact 416 on the backside of the 3D memory device 400. Compared to the example of Figures 2A-2C, the layout of contacts 418, source line mesh 410, and backside source contacts 416, e.g., an array of backside source contacts 416 corresponding to the array of channel structures 408, and source lines 414 contacting backside source contacts 416 in two adjacent columns in core array regions 406A and 406B, respectively, can further reduce the overall resistance of the metal routing.

[0065] FIG. 5 illustrates a cross-sectional side view of another exemplary 3D memory device 500 including a backside interconnect structure in accordance with some embodiments of the present disclosure. The 3D memory device 500 may be an example of the 3D memory device 400 of FIG. 4. The 3D memory device 500 is similar to the 3D memory device 300 of FIG. 3, except for the arrangement of the source contacts 502. As shown in FIG. 5, each channel structure 324 is below and laterally aligned (e.g., in both the x- and y-directions) with a respective source contact 502 (e.g., an example of the backside source contact 416 of FIG. 4), which is in contact with the semiconductor layer 322. It is understood that other identical structural details in both the 3D memory devices 500 and 300 will not be repeated for ease of explanation.

[0066] 6A-6D illustrate a fabrication process for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. FIG. 7 illustrates a flowchart of a method 700 for forming an exemplary 3D memory device with a backside interconnect structure according to some embodiments of the present disclosure. Examples of 3D memory devices shown in FIGS. 6A-6D and 7 include 3D memory devices 200, 201, 203, and 400 shown in FIGS. 2A-2C and 4. FIGS. 6A-6D and 7 are described together. It is understood that the operations shown in method 700 are not exhaustive, and that other operations may similarly be performed before, after, or between any of the illustrated operations. Furthermore, some of these operations may be performed simultaneously or in a different order than shown in FIG. 7.

[0067] 7, method 700 begins with operation 702, in which peripheral circuitry is formed on a first substrate. The first substrate may be a silicon substrate. As illustrated in FIG. 6A, peripheral circuitry 604 having a plurality of transistors is formed on a first silicon substrate 602 using a number of processes, including, but not limited to, photolithography, etching, thin film deposition, thermal growth, implantation, chemical mechanical polishing (CMP), and any other suitable process.

[0068] The method 700 continues at operation 704, where a plurality of channel structures are formed on the front side of a second substrate, each of which vertically penetrates the memory stack. In some embodiments, the memory stack comprises two core array regions having channel structures and a staircase region between the two core array regions in a first lateral direction in a plan view. As illustrated in FIG. 6A, an array of channel structures 608, each of which vertically penetrates the memory stack, is formed on the front side of a second silicon substrate 606.

[0069] 7, the method 700 proceeds to operation 706, where the first substrate and the second substrate are bonded face-to-face, such that the channel structure is above the peripheral circuitry. The bonding may include hybrid bonding. As illustrated in FIGS. 6A and 6B, the second silicon substrate 606 and components formed thereon (e.g., channel structure 608) are inverted and bonded face-up, i.e., face-to-face, to the first silicon substrate 602 and components formed thereon (e.g., peripheral circuitry 604), thereby forming a bonding interface 609 between the silicon substrates 602 and 606, according to some embodiments.

[0070] The method 700 continues at operation 708, where the second substrate is thinned, as illustrated in FIG. 7. The thinning is performed from the backside of the second substrate. As illustrated in FIG. 6B, the second silicon substrate 606 (shown in FIG. 6A) is thinned from the backside into the semiconductor layer 610 (i.e., the thinned second silicon substrate 606) using CMP, grinding, dry etching, and / or wet etching.

[0071] The method 700 proceeds to operation 710, as illustrated in FIG. 7, where a plurality of contacts are formed through the thinned second substrate and a plurality of source contacts are formed in contact with the thinned second substrate. The contacts and source contacts are formed from the backside of the thinned second substrate. In some embodiments, each of the channel structures is below and laterally aligned with a respective one of the source contacts. In some embodiments, the source contacts are arranged in an array having rows and columns. As illustrated in FIG. 6C, backside source contacts 612 are formed from and in contact with the backside of the semiconductor layer 610. In some embodiments, each channel structure 608 is below and laterally aligned with a respective backside source contact 612. A plurality of TSCs 614, 616, and 618 can be formed through the semiconductor layer 610 from the backside of the semiconductor layer 610. In some embodiments, the TSC 616 extends further into the memory stack and contacts the SSG within the memory stack.

[0072] The method 700 proceeds to operation 712, as illustrated in FIG. 7, where a source line mesh is formed on the backside of the thinned second substrate, whereby the source line mesh overlies and contacts the plurality of source contacts and the first set of the plurality of contacts. In some embodiments, the source line mesh includes a plurality of parallel source lines, each extending laterally in a plan view. In some embodiments, the source line mesh overlies and contacts each of the source contacts. In some embodiments, each of the source lines contacts each of the source contacts in a row or column of the array in a plan view. In some embodiments, each of the source lines contacts each of the source contacts in two adjacent rows or columns of the array in a plan view. As illustrated in FIG. 6D, a source line mesh 620 is formed on the backside of the semiconductor layer 610, whereby the source line mesh 620 overlies and contacts the backside source contacts 612 as well as the TSCs 614. The layout of the source line mesh 620, backside source contacts 612, and TSCs 614 may vary in different examples, such as the examples shown in FIGS. 2A-2C and 4.

[0073] Method 700 proceeds to operation 714, as illustrated in FIG. 7, where multiple SSG lines are formed on the backside of the thinned second substrate, whereby the SSG lines overlie and contact the second set of multiple source contacts. In some embodiments, each of the SSG lines extends in a first lateral direction across the two core array regions and the staircase region, and the second set of contacts is distributed within the core array region in a plan view. In some embodiments, the SSG lines are evenly distributed in a plan view parallel to a second lateral direction perpendicular to the first lateral direction. As illustrated in FIG. 6D, SSG lines 624 are formed on the backside of semiconductor layer 610, whereby the SSG lines 624 overlie and contact TSCs 616. The layout of SSG lines 624 and TSCs 616 may vary in different examples, such as the example shown in FIG. 2A.

[0074] Method 700 proceeds to operation 716, as illustrated in FIG. 7, where a power line mesh is formed on the backside of the thinned second substrate, whereby the power line mesh is above and in contact with a third set of the plurality of source contacts. In some embodiments, the third set of contacts is distributed in a plan view in at least one of a staircase region or a peripheral region outside the memory array. As illustrated in FIG. 6D, a power line mesh 622 is formed on the backside of semiconductor layer 610, whereby the power line mesh 622 is above and in contact with TSCs 618. The layout of power line mesh 622 and TSCs 618 may differ in different examples, such as the examples shown in FIGS. 2A and 2B. Although operations 712, 714, and 716 are described above as three sequential operations, it will be understood that operations 712, 714, and 716 may be performed in the same fabrication process. For example, one or more of the source line mesh 620, the power line mesh 622, and the SSG lines 624 may be patterned and formed in the same fabrication process.

[0075] According to one aspect of the present disclosure, a 3D memory device includes a substrate, a memory stack including alternating conductive and dielectric layers above the substrate, a plurality of channel structures each vertically penetrating the memory stack, a semiconductor layer above the plurality of channel structures and in contact with the plurality of channel structures, a plurality of source contacts above the memory stack and in contact with the semiconductor layer, a plurality of contacts through the semiconductor layer, and a backside interconnect layer above the semiconductor layer including a source line mesh in a plan view. The plurality of source contacts are distributed below the source line mesh so as to contact the source line mesh. A first set of the plurality of contacts is distributed below the source line mesh so as to contact the source line mesh.

[0076] In some embodiments, the memory stack comprises two core array regions having a channel structure and a staircase region between the two core array regions in a first lateral direction in a plan view.

[0077] In some embodiments, the backside interconnect layer further comprises a plurality of SSG lines in a plan view, and the second set of the plurality of contacts is distributed below and in contact with the SSG lines.

[0078] In some embodiments, each of the SSG lines extends in a first lateral direction across two core array regions and the staircase region, and a second set of contacts is distributed within the core array region in a plan view.

[0079] In some embodiments, each of the second set of contacts penetrates further into the memory stack to contact one of the conductive layers of the memory stack.

[0080] In some embodiments, the SSG lines are evenly distributed in plan view parallel to a second lateral direction perpendicular to the first lateral direction.

[0081] In some embodiments, the backside interconnect layer further comprises a power line mesh in plan view, and a third set of the plurality of contacts is distributed below and in contact with the power line mesh.

[0082] In some embodiments, the third set of contacts is distributed in a plan view in at least one of a staircase region or a peripheral region outside the memory array.

[0083] In some embodiments, the power line mesh has a comb-like shape.

[0084] In some embodiments, the backside interconnect layer further comprises a bond pad electrically connected to the power line mesh through a third set of contacts.

[0085] In some embodiments, the source line mesh has a comb-like shape.

[0086] According to another aspect of the present disclosure, a 3D memory device includes a substrate, a memory stack including alternating conductive and dielectric layers above the substrate, a plurality of channel structures each extending vertically through the memory stack, a semiconductor layer above and in contact with the plurality of channel structures, a plurality of source contacts in contact with the semiconductor layer, and a backside interconnect layer above the semiconductor layer in a plan view including a source line mesh. Each of the channel structures is below and laterally aligned with a respective one of the source contacts. The source line mesh is above and in contact with each of the source contacts.

[0087] In some embodiments, the 3D memory device further comprises a plurality of contacts distributed through the semiconductor layer below and in contact with the source line mesh.

[0088] In some embodiments, the memory stack comprises one or more core array regions having a channel structure, and the contacts are distributed outside the core array regions in a plan view.

[0089] In some embodiments, the source line mesh includes a plurality of parallel source lines, each extending laterally in a plan view.

[0090] In some embodiments, the source contacts are arranged in an array, with each source line contacting each of the source contacts in a row or column of the array in a plan view.

[0091] In some embodiments, each of the source lines contacts each of the source contacts in two adjacent rows or columns of the array in a plan view.

[0092] According to yet another aspect of the present disclosure, a method for forming a 3D memory device is disclosed. A peripheral circuit is formed on a first substrate. A plurality of channel structures are formed, each vertically penetrating a memory stack on the front side of a second substrate. The first substrate and the second substrate are bonded face-to-face, whereby the channel structures are above the peripheral circuit. The second substrate is thinned. A plurality of contacts are formed through the thinned second substrate and a plurality of source contacts are formed in contact with the thinned second substrate. A source line mesh is formed on the back side of the thinned second substrate, whereby the source line mesh is above and in contact with the plurality of source contacts and a first set of the plurality of contacts.

[0093] In some embodiments, the memory stack comprises two core array regions having a channel structure and a staircase region between the two core array regions in a first lateral direction in a plan view.

[0094] In some embodiments, a plurality of SSG lines are formed on the backside of the thinned second substrate, the SSG lines thereby overlying and contacting the second set of the plurality of contacts.

[0095] In some embodiments, each of the SSG lines extends in a first lateral direction across two core array regions and the staircase region, and a second set of contacts is distributed within the core array region in a plan view.

[0096] In some embodiments, the SSG lines are evenly distributed in plan view parallel to a second lateral direction perpendicular to the first lateral direction.

[0097] In some embodiments, a power line mesh is formed on the backside of the thinned second substrate such that the power line mesh overlies and contacts the third set of the plurality of contacts.

[0098] In some embodiments, the source line mesh includes a plurality of parallel source lines, each extending laterally in a plan view.

[0099] In some embodiments, each of the channel structures is below and laterally aligned with a respective one of the source contacts, and the source line mesh is above and in contact with each of the source contacts.

[0100] In some embodiments, the source contacts are arranged in an array, with each source line contacting each of the source contacts in a row or column of the array in a plan view.

[0101] In some embodiments, each of the source lines contacts each of the source contacts in two adjacent rows or columns of the array in a plan view.

[0102] The foregoing description of specific embodiments will clarify the general nature of the disclosure so that those skilled in the art can readily modify and / or adapt such specific embodiments to various uses without departing from the general concepts of the disclosure and without undue experimentation by applying knowledge within the art. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It will be understood that the phraseology or terminology used herein is for the purpose of description and should thus be interpreted by those skilled in the art in light of the teaching and guidance.

[0103] The embodiments of the present disclosure have been described above with the aid of functional building blocks illustrating implementations of specified functions and their relationships. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of description. Alternative boundaries may be defined so long as the specified functions and their relationships are appropriately performed.

[0104] The Summary and Abstract sections may define one or more, but not all, exemplary embodiments of the present disclosure as contemplated by the inventors, and are therefore not intended to limit the disclosure and appended claims in any way.

[0105] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. [Explanation of symbols]

[0106] 100 3D memory devices 102 blocks 104 Stairs area 106A, 106B Core array area 108 Insulation structure 110 channel structure 200 3D memory devices 201 3D memory device Block 202 203 3D Memory Device 204 Stairs area 206A, 206B Core array area 208 Surrounding Area 210 Source Line Mesh 212 parallel tooth source line 214 Shaft Source Line 216 Backside Source Contact 218, 226, 230 Contact 220 Power Line Mesh 222 Teeth Power Line 224 Shaft Power Line 228 SSG Line 230 Contacts 300 3D memory devices 301 Substrate 302 First Semiconductor Structure 304 Second Semiconductor Structure 306 Joint interface 308 Peripheral Circuits 310 Bonding layer 311 Bonding Contact 312 Bonding layer 313 Bonded Contact 314 Memory Stack 316 Top conductive layer 318 Dielectric Layer 320, 322 Semiconductor layer 324 Channel Structure 326 Memory Film 328 Semiconductor Channels 329 Channel Plug 330 Insulation Structure 332 source contact, backside source contact 333 Backside Interconnect Layer 334 ILD layer 336 Redistribution layer 338 Passivation Layer 340 Bonding Pad 342, 344 Contact 346, 348 Peripheral Contact 350 Channel Local Contacts 352 Word Line Local Contact 400 3D memory devices 402 Block 404 Stairs area 406A, 406B Core array area 408 Channel Structure 410 Source Line Mesh 412 parallel source lines 414 Parallel Source Lines 416 Backside Source Contact 418 Contacts 500 3D memory devices 502 Source Contact 602 First silicon substrate 604 Peripheral Circuit 606 Second silicon substrate 608 Channel Structure 609 Joint interface 610 Semiconductor layer 612 Backside Source Contact 614, 616, 618 TSC 620 Source Line Mesh 622 Power Line Mesh 624 SSG Line 700 methods

Claims

1. 1. A three-dimensional (3D) memory device, comprising: a memory stack including conductive layers and dielectric layers interleaved in a first direction; a channel structure extending vertically through the memory stack in the first direction, the channel structure including a semiconductor channel; a semiconductor layer electrically connected to the semiconductor channel; a source contact electrically connected to the semiconductor layer, the semiconductor layer being between the source contact and the memory stack in the first direction.

2. The 3D memory device of claim 1 , wherein the source contact extends into the semiconductor layer.

3. 2. The 3D memory device of claim 1 , wherein the semiconductor layer comprises a first semiconductor layer and a second semiconductor layer, the first semiconductor layer being between the second semiconductor layer and the memory stack in the first direction, the source contact extending into the second semiconductor layer, and the channel structure extending in the first direction vertically through the memory stack and the first semiconductor layer and vertically into the second semiconductor layer.

4. 2. The 3D memory device of claim 1, wherein the channel structure further comprises a memory film surrounding the semiconductor channel, the memory film abutting the first semiconductor layer being discontinued at a portion of the channel structure, and the semiconductor channel being surrounded by and in contact with the first semiconductor layer.

5. 10. The 3D memory device of claim 1, further comprising a source line mesh in contact with the source contact, the source contact being between the source line mesh and the semiconductor layer in the first direction.

6. further comprising a plurality of interlayer dielectric (ILD) layers; 6. The 3D memory device of claim 5, wherein the ILD layers are between the source line mesh and the semiconductor layer in the first direction, the source contacts extend vertically through the ILD layers, and at least two ILD layers comprise different dielectric materials.

7. 6. The 3D memory device of claim 5, wherein a plurality of source contacts are arranged in rows in a second direction perpendicular to the first direction, the source line mesh including first source lines extending in the second direction, the first source lines contacting the source contacts in the rows.

8. 7. The 3D memory device of claim 6, wherein the plurality of source contacts are arranged in a plurality of rows, and a first source line contacts source contacts in two adjacent rows.

9. 9. The 3D memory device of claim 1, 7, or 8, wherein a plurality of source contacts are arranged in columns in a third direction, the source line mesh further including second source lines contacting the source contacts in the columns, and the third direction is orthogonal to the first direction.

10. 10. The 3D memory device of claim 9, wherein the plurality of source contacts are arranged in a plurality of columns, and the second source line contacts source contacts in two adjacent columns.

11. further comprising an insulating structure extending vertically through the alternating conductive and dielectric layers of the memory stack; 8. The 3D memory device of claim 7, wherein the isolation structures further extend in a third direction, the third direction being orthogonal to the first direction and the second direction.

12. a first contact extending through the semiconductor layer in the first direction; 6. The 3D memory device of claim 5, wherein the first contacts are distributed below the source line mesh so as to contact the source line mesh, and the first contacts are electrically connected to peripheral circuitry of the 3D memory device.

13. 10. The 3D memory device of claim 1, wherein the source contact comprises a plurality of conductive layers including a metal layer and an adhesive layer, a portion of the adhesive layer being between the semiconductor layer and the metal layer.

14. a second contact extending in the first direction in a peripheral region outside the memory stack, a portion of the semiconductor layer extending into the peripheral region, and a depth of the second contact being greater than a depth of the memory stack in the first direction; 10. The 3D memory device of claim 1, further comprising: a third contact extending through the portion of the semiconductor layer in the peripheral region, the third contact electrically connected to the second contact.

15. A substrate; 10. The 3D memory device of claim 1, further comprising peripheral circuitry on the substrate, the peripheral circuitry bonded to the memory stack, the memory stack between the peripheral circuitry and the semiconductor layer.

16. 1. A three-dimensional (3D) memory device, comprising: a memory stack including conductive layers and dielectric layers interleaved in a first direction; a channel structure extending vertically through the memory stack in the first direction, the channel structure including a semiconductor channel; a first semiconductor layer overlying the memory stack in the first direction and electrically connected to the semiconductor channel; a second semiconductor layer overlying the first semiconductor layer in the first direction; a source contact overlying the second semiconductor layer in the first direction, the source contact electrically connected to the semiconductor channel through the first semiconductor layer and the second semiconductor layer.

17. 17. The 3D memory device of claim 16, wherein the channel structure further comprises a memory film surrounding the semiconductor channel, the memory film abutting the first semiconductor layer being discontinued at a portion of the channel structure, and the first semiconductor layer surrounding and in contact with the semiconductor channel.

18. 18. The 3D memory device of claim 17, wherein the source contact extends into the second semiconductor layer in the first direction, and the channel structure extends in the first direction through the memory stack and the first semiconductor layer and into the second semiconductor layer.

19. a plurality of interlayer dielectric (ILD) layers overlying the second semiconductor layer in the first direction; 17. The 3D memory device of claim 16, wherein the source contact extends vertically through the ILD layers, and at least two ILD layers comprise different dielectric materials.

20. 17. The 3D memory device of claim 16, wherein a plurality of source contacts are arranged in rows in a second direction perpendicular to the first direction, and a source line mesh includes first source lines extending in the second direction, the first source lines contacting the source contacts in the rows.

21. 21. The 3D memory device of claim 20, wherein the plurality of source contacts are arranged in a plurality of rows, and the first source line contacts source contacts in two adjacent rows.

22. 22. The 3D memory device of claim 16, 20, or 21, wherein a plurality of source contacts are arranged in columns in a third direction perpendicular to the first direction, and wherein a source line mesh further includes second source lines extending in the third direction, the second source lines contacting the source contacts in the columns.

23. further comprising an insulating structure extending vertically through the alternating conductive and dielectric layers of the memory stack; 21. The 3D memory device of claim 20, wherein the isolation structures further extend in a third direction, the third direction being orthogonal to the first direction and the second direction.

24. a second contact extending in the first direction in a peripheral region outside the memory stack, a portion of the second semiconductor layer extending into the peripheral region, and a depth of the second contact being greater than a depth of the memory stack in the first direction; 17. The 3D memory device of claim 16, further comprising: a third contact extending through the portion of the second semiconductor layer in the peripheral region, the third contact being electrically connected to the second contact.

25. A substrate; 17. The 3D memory device of claim 16, further comprising peripheral circuitry on the substrate, the peripheral circuitry bonded to the memory stack, the memory stack between the peripheral circuitry and the semiconductor layer.

Images